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Engineering Structures (18737323)340
This study presents an innovative approach for deconstructable external semi-rigid composite beam-to-column joints (DECJs) under cyclic loading featuring friction-grip bolted shear connectors, central reinforcing bars, and prefabricated geopolymer concrete slabs. The proposed design aimed to enhance deconstructability and sustainability by inserting central reinforcing threaded bars through column flanges, allowing for the disassembly of joint elements after their service life. Five full-scale external steel-concrete composite joints were designed and tested under cyclic loading to assess their seismic performance, focusing on failure modes, slip, moment-rotation responses, ductility, stiffness, energy dissipation, and strength degradation. The variables are the reinforcement ratio for central reinforcing bars, the diameter of bolted shear connectors, and the presence of steel fiber in geopolymer concrete (GPC) slabs. The experimental results showed that the use of bolt shear connectors, central threaded bars, and steel fiber-reinforced GPC slabs in DECJs significantly enhances the rotation capacity approximately 2–2.7 times higher than that provided by EC4. The proposed DECJ enhances the moment capacity and ductility of the joints, making them suitable for seismic applications. Moreover, it provides joint deconstructability, reduces the carbon footprint of the system, and effectively predicts the moment capacity of specimens, aligning with observed failure modes. Finally, a simple design model for estimating the moment capacity of the joints is proposed using the component-based modeling approach. © 2025 Elsevier Ltd
Journal of Constructional Steel Research (0143974X)235
This study offers a 3D finite element modeling (FEM) and parametric analysis of a novel extended endplate beam-to-column semi-rigid deconstructable external composite joint (DECJ) under cyclic loading. This innovative DECJ is created by connecting the precast geopolymer concrete slab to the top flange of a steel beam using bolted shear connectors, and inserting threaded central reinforcing bars into the column flanges to enhance the demountability of the entire system. The FEM was developed using ABAQUS software and verified against the experimental study results to analyze the structural behavior and failure modes of the proposed DECJ system. The study investigates the effect of various parameters, including the diameter of bolted shear connectors, the degree of shear connection, the ratio of central reinforcing bars, the thickness of the endplate, the thickness and strength of the geopolymer concrete slab, and the bolt diameters of the connection zone. The findings suggest that to prevent the failure of bolted shear connectors, the optimal shear connection degree of approximately 73 %–90 % and the concrete slab thickness of 80-120 mm should be maintained. Additionally, the central reinforcing bar ratio is preferred to be around 0.98 % to avoid the failure of shear connectors and reinforcing bars. Furthermore, the ratio of endplate thickness to connection zone bolt diameter should be between 0.64 and 0.82 to reduce the fracture risks of connection zone bolts. Finally, a new predictive equation is proposed to determine the plastic moment capacities of DECJs with precast concrete slabs, demountable bolted shear connectors, and demountable central reinforcing bars under cyclic loading. © 2024
Case Studies in Construction Materials (22145095)22
The significance of finding industrial waste solutions in the construction industry plays a crucial role in the quest for environmental conservation. To reduce the carbon footprint, this research has focused on developing solutions. This study assesses the mechanical properties of water-cured alkali-activated slag concrete (AASC) prepared using a one-part activator, where the dry alkali activator is pre-mixed with slag before water addition. The mix is then reinforced with three types of steel fibers, namely deformed steel fibers (DSF), recycled tire steel fiber (RTSF), and hybrid steel fiber (HSF) at varying volume fractions (0.5 %, 0.75 %, and 1.0 %). Numerous characteristics, including workability, compressive strength, flexural strength, splitting tensile strength, flexural toughness, and SEM observations in short-term, and stress-strain response under uniaxial compression, modulus of elasticity, peak strain and energy absorption in long-term were assessed. According to the test results, compressive strength was largely unaffected by fiber addition, with DSF at 1 % volume (DSF1) achieving the highest strength (58.51 MPa at 28 days). Conversely, optimal compressive strength for RTSF was observed at 0.5 % volume. On the other hand, the concrete mixes' splitting tensile, and flexural strengths increased with the addition of steel fibers achieving maximum values at 1 % DSF. The addition of steel fibers transformed the stress-strain response of one-part AASC mixes from brittle to ductile, with HSF specimens at 1 % volume (HSF1) exhibiting a 50 % increase in strain related to peak stress compared to the reference. Remarkably the HSF1 mix achieved a 421 % increase in toughness at 365 days compared to the reference mix. The DSF1 mix at 28 days and HSF1 at 365 days achieved the highest energy absorption capacity. Overall, the inclusion of 1 % DSF, RTSF, and HSF fibers enhanced the mechanical properties of one-part AASC, with DSF providing the most significant improvements at 28 days. © 2024 The Authors
Composite beams consisting of precast concrete slabs and steel beams connected by deconstructable high-strength friction-grip bolts (HSFGB) have recently attracted much research attention due to their compatibility with sustainable construction. However, studies on the behavior of these composite beams have been entirely deterministic, with no consideration for uncertainty in the governing parameters, especially for the bolted shear connector varieties. In this paper, a three-dimensional finite element model is developed to investigate the behavior of this type composite beam considering the nonlinearities of the geometry, materials, and component interfaces. Nonlinear springs with zero length are utilized to model the HSFGB shear connectors, and then the complete beam model is embedded in a Monte Carlo-based probabilistic assessment approach. The results show that the simplified spring model is reliable in predicting the behavior of composite beams while being efficient in terms of computational efficiency and time savings for conducting probabilistic analyses. The probabilistic analysis finds that Monte Carlo simulation is a useful method for identifying probabilistic trend behaviors with acceptable accuracy to quantify the effect of structural parameter uncertainties. The composite beam with a partial shear connection shows a greater variety of beam responses than the composite beam with a full shear connection. © 2025 Institution of Structural Engineers
Steel and Composite Structures (15986233)56(1)pp. 49-65
The combination of precast concrete slabs and steel beams connected by deconstructable high-strength friction-grip bolts has emerged as a promising solution for sustainable construction. However, the lack of design guidelines and r egulations has restricted its widespread use. This study aims to conduct a reliability analysis to evaluate the flexural resistance factor (φ) for composite beams with HSFGB shear connectors, as the AISC Specifications incorporate the shear connector resistance factor as part of the overall resistance factor of the composite beam. To analyze the behavior of the composite beam, a three-dimensional finite element model was developed and validated. Additionally, a sensitivity analysis was performed to investigate the impact of various parameters on the flexural strength of the composite beam. The flexural resistance factor for this type of composite beam with varying degrees of connection was evaluated providing an acceptable level of safety. The variability and uncertainty in connectors were determined based on existing push-out tests using statistical analysis. A reliability study found that the reduction factor of flexural resistance for this type of composite beam is dependent on the degree of shear connection. Additionally, using the flexural resistance factor recommended for conventional composite beams with welded shear connectors in the AISC code is unconservative for deconstructable composite beams. © 2025 Techno-Press, Ltd.
Thin-Walled Structures (02638231)199
Cold-formed steel composite beams are known for their unique advantages, like being lightweight and ease of installation. The use of profiled steel sheeting in cold-formed composite beams reduces construction time and costs by acting as a permanent formwork in the composite beams. The current study presents a 3D finite element model of cold-formed steel composite beam specimens comprising a cold-formed double-lipped channel section, profiled steel sheeting, concrete slab, and bolted shear connector. Employing bolted shear connectors, structural components can be deconstructed and replaced after their service life expires or if they are damaged. The characteristics of the materials obtained from an experimental program were assigned to the finite element model. Geometric characteristics, material nonlinearities, and loading procedures were attentively simulated, and a dynamic explicit procedure was employed for the numerical analyses. A comparison of the results obtained from the finite element models and the available experimental results validated the precision of the models. Then, numerical studies were conducted to investigate the effects of various parameters, including compressive strength of concrete, thickness of concrete slab, height and grade of cold-formed steel section, thickness of profiled steel sheeting, number and diameter of shear connectors, on the behavior of the composite beam. The results showed that the height and grade of the cold-formed steel section and compressive strength and thickness of the concrete slab have a significant effect on increasing the capacity of the composite beam. © 2024 Elsevier Ltd
Arabian Journal for Science and Engineering (21914281)49(4)pp. 5447-5466
The lack of a code for preparing one-part geopolymer concrete (GPC) is one of the major obstacles to its wide use. This study adopted one of the most common methods for preparing ordinary concrete, the ACI method, taking into account the most important variables affecting this method and then modified it to suit one-part GPC. Three different sizes of aggregates and four water-to-binder ratios (W/B) were used in preparing the concrete mixtures in this study. In addition, three different proportions of sodium metasilicate were used as the activator, which ultimately resulted in a total of 36 mix designs. Specimens were subjected to various tests, including setting time, workability, and compressive strength. In addition, the material's behaviour was studied using X-ray diffraction and scanning electron microscope. The results indicate that the ACI method is generally applicable for designing geopolymer concrete mixtures with minor adjustments. Consequently, the table used for predicting concrete strength based on a specific water/cement ratio has been replaced with relevant figures that depict the relationship between compressive strength and the water-to-binder ratio. In addition, a step-by-step flowchart has been presented that explains how to design one-part geopolymer concrete. Conducted experiments indicated that the properties of geopolymer concrete are greatly affected by the ratio of W/B and the size of aggregate used in preparing the concrete mixture. Furthermore, the quantity of activators has significant effects on concrete's workability and compressive strength. Results of the experiment suggest that one-part GPC can provide greater compressive strength than ordinary concrete. © King Fahd University of Petroleum & Minerals 2023.
Almohammad-albakkar m., ,
Behnamfar, F.,
Ataei, A. Journal of Constructional Steel Research (0143974X)216
An innovative grooved gusset plate damper (GGPD) is further developed in this study by conducting cyclic tests and numerical analysis. The proposed damper is installed in X-Concentrically Braced Frames (X-CBFs) for enhancing the seismic performance and energy dissipation of such a system. To investigate the performance characteristics of the system, three 2/3-scale specimens are constructed that are different only in the details of the damper. The damper consists of a gusset plate in which a number of slits are cut around the diagonal braces. The steel between the slits undergoes large plastic deformations under in-plane double curvature, which provides a good level of ductility and energy dissipation. Low cycle fatigue is observed at drift ratios over 1.5% in the first specimen. Thickness of the middle part of the gusset plate is increased in the third specimen as a remedy which turns out to be successful to postpone degradation of stiffness and strength to the drift ratios larger than 3%. Furthermore, a detailed nonlinear 3D finite element model is developed and validated against the results of laboratory tests. The nonlinear finite element model is shown to be successful in predicting failure and fracture due to low cycle fatigue and showing the superiority of the modified specimens in preserving the stable shapes of the hysteresis loops and the cyclic energy dissipation. © 2024 Elsevier Ltd
Bolted shear connectors have recently been introduced and studied as a convenient and demountable alternative for shear studs in steel-concrete composite beams. The major problem of welded studs is their undeconstructability. Bolted shear connectors make it possible to deconstruct and reuse the connection after its service life. In this study, the cyclic behavior of embedded bolted shear connectors in steel-concrete composite beams was investigated. The specimens included prefabricated concrete slabs with a square hole, which was filled with grout after assembling the concrete slab and steel section. Eight specimens were fabricated and tested to examine the effect of the bolt's diameter and strength on the cyclic behavior. To determine its behavior characteristics force-slip curves were applied. Ductility, strength degradation, and energy dissipation were the primary parameters investigated in this study. The results showed that the bolt's diameter and strength significantly influenced the cyclic behavior of composite beams. Increasing the bolt's diameter and strength improved the connection's ductility and energy dissipation. Furthermore, doubling the bolt's cross-section increased the connection's ultimate strength by more than twice. © 2024 Institution of Structural Engineers
Journal of Constructional Steel Research (0143974X)222
Modern construction necessitates eco-friendly structures that minimize carbon dioxide emissions and are designed for easy disassembly, facilitating the reuse of structural components with minimal effort and cost. Facilities employing geopolymer concrete designed for disassembly serve as an exemplary model for such construction. In this research, four full-scale interior demountable steel-concrete composite beam-to-column joints having precast geopolymer concrete slab were conceived, produced, and subjected to cyclic loading tests. A comprehensive examination was conducted on the structural behaviors of interior demountable steel-concrete composite beam-to-column joints, encompassing crack patterns, failure modes, moment-rotation responses, force-displacement curves, strain distributions, shear connector slippage, and energy dissipation. The research examined how the structural behavior of interior demountable composite joints is affected by the diameter of bolted shear connectors and the reinforcement ratio of precast concrete slabs. The results indicated that increased reinforcement in the slab enhances the rotation of the connection, the initial rotational stiffness, the bearing capacity of the joint, and the joint's over-strength. The dissipation of energy is impacted by both the dimensions of the reinforcement in the slab and the diameter of the shear connectors. The joint's stiffness was assessed through an analysis of the bending moment-rotation curve, following the guidelines outlined in Eurocodes 3 and 4. The deformability meets the minimum rotation capacity requirement (0.03 rad) specified by these codes. In summary, bolted shear connectors enable controlled slippage, ensuring a smooth response to applied loads and making this joint well-suited for withstanding cyclic loads, such as those associated with earthquakes. The test results also show that the composite beam to column joints having precast concrete slab and bolted shear connectors can be deconstructed easily at the end of their service life. © 2024 Elsevier Ltd
Results in Engineering (25901230)24
A comprehensive understanding of the engineering characteristics of one-part slag-based geopolymer concrete (SBGC) is instrumental in promoting its widespread adoption and optimized design, improving construction practices, and advancing sustainability in the built environment. This study examined the workability, development of compressive strength, tensile strength, modulus of elasticity, and stress-strain behavior of one-part SBGC. The long-term compressive strength of SBGC, under both ambient curing and water curing conditions, has also been examined. Multiple combinations of mixtures were assessed, accounting for diverse factors such as activator ratio, aggregate size, water-to-binder ratio, curing conditions and activator types. This research also proposes new equations for predicting tensile strength and modulus of elasticity for one-part SBGC. The findings reveal that water-cured specimens demonstrate up to 43 % higher compressive strength and 52 % higher tensile strength compared to those cured under ambient conditions. Increasing the activator proportion in the mixture notably accelerates the early-stage development of compressive strength and SBGC's modulus of elasticity. Furthermore, one-part SBGC exhibits a long-term strength development that surpasses conventional concrete by over 20 %. In addition, the stress-strain behavior of SBGC reveals its inherent fragility, marked by near-perfect linear elasticity that abruptly transitions to complete and sudden collapse, distinguishing it from ordinary concrete. Microstructural analyses indicate that elevating the activator ratio reduces the presence of unreacted GGBFS particles and quartz in the mixture, thereby promoting the formation of gel. © 2024 The Author(s)
Journal of Building Engineering (23527102)95
Composite cold-formed steel (CFS)-concrete structures have been widely used due to their benefits such as more ultimate strength, stiffness, and postponement of lateral buckling compared to bare CFS steel. Appropriate shear connectors should be used in order to establish composite performance between the CFS section and the concrete component. Traditional welded-stud connectors cannot be used due to the low thickness of the CFS members. Therefore, in this paper, a novel composite connection consisting of bolted-shear connectors embedded in grout is proposed and its performance is investigated by numerical models of push-out tests. A three-dimensional finite element model of the composite connection considering the non-linearities of the material and geometry, interfaces, and interactions between the components and materials are developed and verified against the results of the experimental study. After that, an extensive parametric study is carried out and the effects of different parameters, such as bolt strength and diameter, CFS section thickness, concrete compressive strength, and pretension load on the structural behavior of this type of composite connection are investigated and discussed in detail. It is concluded that the behaviour of the composite connection is significantly influenced by bolt strength and diameter, CFS section thickness and strength. The available design models provided in different provisions, including AISI, EC4 and AISC that predict the shear load capacity of connections with preload bolted shear connectors are reviewed and assessed. The results show that the ultimate shear load capacity values predicted by these provisions were found to be relatively less accurate. Finally, a new and more accurate design equation based on the results of this study is then proposed. © 2024 Elsevier Ltd
Mechanics Based Design of Structures and Machines (15397742)52(2)pp. 628-649
Due to the low thickness of cold-formed steel (CFS) sections, welding of traditional studs on them is not recommended; and there is a need to use shear connectors suitable for this type of sections. In this paper, the behavior of U-shaped shear connectors as connectors compatible with CFS composite beams has been investigated, to offer practical relationships for predicting the ultimate strength of this type of connectors. Accordingly, after the development of finite element (FE) models with the ability to predict the ultimate strength of U-shaped connectors, their performance against experimental results was validated. Then, an extensive parametric study, consisting of 216 numerical samples, was accomplished to provide a reliable database. As the main and most important of this study, two methods of artificial neural networks and stepwise regression were developed, and practical formulations were proposed to predict the ultimate strength of U-shaped shear connectors in CFS composite beams. Finally, in addition to evaluating the accuracy of the proposed formulas, a comparison was made between them and the relationships proposed by AISI, AS/NZS and EC3 codes for CFS screw connections. The relationships presented in this paper can be used by practical engineers in the design process of CFS composite beams. © 2022 Taylor & Francis Group, LLC.
Mechanics Based Design of Structures and Machines (15397742)52(7)pp. 4284-4311
In recent years, the high-strength friction-grip bolt (HSFGB) shear connectors in steel-concrete composite beams as deconstructable connectors are of great research interest since they are aligned with sustainable construction. However, the design strength equation for this type of connector has not yet been provided by the design codes such as AISC and Eurocode 4. In this paper, with regard to the reliability aspect, the design strength equation of HSFGB shear connectors is investigated which is projected into a partial safety factor according to Eurocode 4. Accordingly, the three-dimension finite element (FE) push-out model of the composite connection is developed and verified via experimental results to predict the load-slip behavior and failure modes in this type of bolted shear connector. Then One-Factor-at-a-Time (OFAT) method as a sensitivity analysis and Plackett-Burman (PB) design method as a screening analysis are utilized to identify the effective factors of the ultimate strength of HSFGB connectors. Finally, based on a complete database of all existing experimental findings, the results obtained from 55 three-dimension finite element models conducted in this paper, and appropriate statistical analysis, a high-precision equation for predicting ultimate strength is provided. Then the value of the partial safety factor is determined through a reliability study in accordance with EN1990, which provides an acceptable level of safety for the proposed design equation based on Eurocodes. Reliability analysis found that a partial factor of 1.52 was justified for the design strength of HSFGB connectors, which differed from the partial factor of 1.25 stated in the EC for welded stud shear connectors. © 2023 Taylor & Francis Group, LLC.
International Journal Of Civil Engineering (17350522)22(6)pp. 1099-1116
This study presents an experimental study on cold-formed steel (CFS) composite beams with profiled steel sheeting. Four full-scale composite beam specimens comprising cold-formed double-lipped channel sections, profiled steel sheeting, concrete slabs, and bolted shear connectors were examined. The results show that profiled steel sheeting behaves like tensile reinforcement beside the concrete slab. Of particular interests were thickness and height of CFS beams. The results showed that for higher steel thickness, the failure mode was concrete crushing before CFS beam reached its yielding point. Besides, no failure occurred in the shear connections. By increasing the thickness of CFS from 1.25 to 2 mm, the ultimate loading capacity of composite beams increased almost 45%. This was due to the presence of the profiled steel sheeting and the strong connectors, which prevented sudden slip between the CFS beam and the concrete slab. A comparison between code-calculated and experimentally evaluated degree of shear connection shows that the results are so close. Furthermore, a 3D finite element model was established, and the numerical models were verified against experimental results and the behavior of structures were accurately simulated. © The Author(s), under exclusive licence to the Iran University of Science and Technology 2024.
Thin-Walled Structures (02638231)192
Although cold-formed steel (CFS) members have been widely used in structures, their application is limited due to the buckling and instability of these members. To enhance their strength and stiffness, they are often combined with other materials like concrete or timber. One of the main challenges in composite structures is ensuring proper connection between different components to facilitate safe shear load transfer. This is achieved through various types of shear connectors. Bolted shear connections are preferred over headed shear studs because they offer greater strength and can be easily dismantled. Headed shear studs welded onto a steel section are unsuitable for CFS members due to their low thickness. In this paper, we propose a novel demountable composite connection specifically designed for prefabricated CFS structures. The behavior of this connection was evaluated through fifteen push-out test specimens, with key variables including CFS section thickness and bolt diameter/strength. The ultimate load, stiffness, ductility, and failure modes of all specimens were determined. The results revealed that specimens with a higher thickness of CFS members experienced bolt fracture, exhibiting superior effective stiffness, strength, and ductility. Conversely, specimens with a lower thickness of CFS members failed due to distortional buckling of the CFS members. The test results underscore the importance of carefully designing and providing a proportionate CFS section thickness to ensure shear connectors fracture before the CFS members. This significantly improves the shear strength capacity of the composite connection with CFS sections and precast concrete slabs. Furthermore, the deconstructability of the connection at the end of its service life was investigated. The steel–concrete composite connection with precast concrete slabs and demountable bolted shear connections was also modeled using a 3D finite element method. The numerical model's accuracy in simulating the observed structural behavior was confirmed against experimental data. Finally, appropriate and straightforward formulations for predicting the ultimate load of the CFS-concrete composite connection were proposed. It was concluded that the predictions of ultimate shear load capacity values by EC4, AISC, and AISI provisions for this composite connection are significantly less accurate. © 2023 Elsevier Ltd
Engineering Applications of Artificial Intelligence (09521976)118
In recent years, the use of artificial intelligence-based methods in engineering problems has been expanded. In the current study, the method of artificial neural networks (ANN) has been employed to predict the ultimate strength of bolted shear connectors in cold-formed steel (CFS) composite beams. For this purpose, multilayer perceptron (MLP) networks with a hidden layer were used. Three parameters affecting the performance of these networks, including the training algorithm, the activation function in the hidden layer, and the number of neurons in the hidden layer, were examined and the most accurate network was selected. The input and target data for training the network were provided by conducting an extensive numerical study on the behavior of bolted shear connectors in CFS composite beams. Consequently, using ABAQUS software, finite element (FE) models validated with experimental results were first developed. Then, 216 models with different characteristics were analyzed and a reliable database was provided for the development of neural networks. Moreover, in order to prove the high accuracy of the ANN method, the stepwise regression (SR) method was also developed as one of the powerful regression-based methods, and the performances of these two methods were compared. Finally, the most important purpose of this study is to propose an accurate ANN-based formulation in order to predict the ultimate strength of bolted shear connectors in CFS composite beams. Due to the fact that so far no relationship has been proposed to predict the resistance of shear connectors in CFS composite beams, the formula presented in this paper can be helpful in the design process of this type of beams. © 2022 Elsevier Ltd
Thin-Walled Structures (02638231)184
The concurrent use of concrete slab, and cold-formed steel section as a composite beam improves strength and stiffness, thus preventing local and lateral buckling of the beam. The composite action could be fulfilled by suitable shear connectors, though the codes do not prescribe any equation to determine the shear capacity, and design rule of these connectors. The friction-grip bolted shear connectors were introduced and their mechanical performance was studied via the experimental tests and finite element modeling. At first, ANSYS software was used for the 3D finite element modeling of these connections. The obtained results were verified by experimental results. It can be shown that the proposed model can estimate the behavior of friction-grip bolted shear connectors in composite beams with cold-formed steel section. Then, extensive parametric studies with 72 specimens were carried out and the effect of diameter and strength of the bolts, thickness and strength of cold-formed steel sections, clearance between the bolt and concrete hole and pretension force on the behavior of these connectors were evaluated. The effect of each parameter on the shear capacity of the connection was evaluated. Some equations were proposed for figuring out the shear capacity and load–slip curve of these connections based on the experimental and 3D finite element results. © 2023 Elsevier Ltd
Journal of Building Engineering (23527102)74
Nowadays, composite beams consisting of steel beams and concrete slabs are widely used in the construction industry. In this research, an experimental study was carried out to investigate the performance of friction-grip bolted shear connectors in composite beams with cold-formed steel sections. For this purpose, 17 full-scale push-out tests were examined according to EC4 in order to investigate the performance of this connection. Of particular interests were load-slip curves, the maximum shear capacity, ultimate slip (ductility) and failure modes. Experimental results show that the behavior of this connection is different from that of headed-stud shear connector. The diameter and strength of bolt and thickness of cold-formed steel section have the most critical effects on the shear capacity and ductility of these connections. Furthermore, 3D finite element modeling was performed and validated against experimental results. The results reveals that numerical models can estimate the capacity of friction-grip bolted shear connectors with acceptable accuracy. The results also highlight that the predominant failure mode in all specimens is bearing. Thus, the use of AISI equations to determine the bearing capacity of the screw holes as the shear capacity of friction-grip bolted shear connectors is recommended. It is also concluded that this connection possesses the necessary ductility according to the EC4 (= 6 mm) and is suitable for use in composite beams with cold-formed steel sections. © 2023
Ataei, A.,
Chiniforush, A.A.,
Bradford m.a., M.A.,
Valipour h.r., H.R.,
Ngo, T.D. Journal of Building Engineering (23527102)54
This paper concerns the cyclic behaviour of embedded bolted shear connectors in steel-timber composite joints. The effect of the strength and size of the shear connector and the orientation of the cross-laminated timber panels with respect to the direction of the load on the cyclic behaviour of this type of composite connection were investigated through an extensive experimental study. In total, eleven steel-timber composite connections having a steel section and mechanical shear connectors embedded in grout were tested under a low-cycle, high-amplitude loading regime. The equivalent viscous damping, ductility, strength impairment, energy dissipation and the failure modes of all composite connections were assessed in detail to characterise the behaviour of a mechanical shear connector under cyclic loading conditions. The experimental results show that embedded bolted shear connectors have high energy-dissipating capacity and ductility if adequate edge distances of the bolts and shear pockets are provided. In addition, a finite element model of the composite connection considering the non-linearities of the geometry, and interfaces between the components and materials is developed and verified against the results of the experimental study. Based on the results obtained from the simulation, it can be demonstrated that the developed FE model is able to predict the behaviour of the composite connection at the local and global level. © 2022 Elsevier Ltd
Chiniforush, A.A.,
Ataei, A.,
Valipour h.r., H.R.,
Ngo, T.D.,
Malek s., Construction and Building Materials (09500618)356
The paper presents a comprehensive experimental–numerical study on dimensional stability of spruce CLT panels and provides new insights into understanding the effect of mechanical properties of wood layers on moisture-induced strains. Deformations in Norway spruce CLT as well as their wood layers were studied in two orthogonal planes under sorption and desorption cycles. Coefficients of Moisture Expansion (CME), Coefficient of Moisture Contraction (CMC), as well as Coefficient of Thermal Expansion (CTE) were determined using dimensional measurements at 15° and 50℃. A 3-D nonlinear finite element (FE) model was developed to better understand the effect of glue and wood mechanical properties, as well as their CME and CTE on two CLT cross-sections. Unlike previous studies, the glue layers have been modelled as thin physical layers bonding wood layers. Hence, the effect of glue lines on the performance of CLT panels can be elucidated quantitatively. Results demonstrated good agreement between the FE model predictions of moisture-induced strains and the experimental data under both sorption and desorption isotherms when the wood moisture content is below fibre saturation point (FSB). Discrepancies between experiments and the model were noted at moisture contents above FSB. Such discrepancies may be attributed to measurement inaccuracies at small scale, the annual ring patterns, uncertainties in material properties, glue penetration into wood cell walls, as well as imperfect bonding at the glue lines. Results highlighted the significant effect of the mismatch between CTE and CME (or CMC) of wood in different directions on the development of stresses and consequently delamination, and perpendicular to grain failure in CLT panels subjected to extreme humidity levels. © 2022 Elsevier Ltd
Journal of Constructional Steel Research (0143974X)198
A three-dimensional finite element modelling and parametric analysis of a composite connection having prefabricated concrete slabs and preload bolted shear connectors are presented in this study. The load-slip relationship for this type of shear connection subjected to monotonically loading with the effect of different parameters including bolted shear connector size, bolt grade, hole size in precast concrete slab and steel beam top flange, concrete strength, and bolt preloading force is studied by means of ABAQUS software. A finite element model of the composite connection considering the non-linearities of the geometry, interfaces between the components, and materials is developed and verified against the results of the experimental study. An extensive parametric study is conducted, and the influences of different parameters on the structural behaviour of demountable steel-concrete composite shear connection are discussed in detail. In addition, a comparison of the estimated values obtained from design equations proposed by current standards, including EC4 and AISC for headed stud shear connectors, and the design recommendations provided in other studies for bolted shear connectors are conducted. According to the calculation result, the accuracy of different design methods is evaluated. Finally, a regression analysis of the data produced by the FE analysis has been employed to propose a new design equation to determine the ultimate strengths for the post-installed preload bolt shear connectors. It is concluded that the ultimate shear load capacity values predicted by EC4 and AISC provisions for composite connections having prefabricated concrete slabs and preload bolted shear connectors found to be relatively less accurate but conservative. © 2022 Elsevier Ltd
Thin-Walled Structures (02638231)177
The use of concrete slab in cold-formed steel (CFS) beams can not only increase the ultimate resistance, but also can prevent their lateral buckling. Since the formation of composite action in this type of beams requires the use of appropriate shear connectors, in this paper, an extensive numerical study was conducted to investigate the behavior of 8.8 grade bolted connectors in CFS composite beams. For this purpose, at the first, advanced numerical models of concrete-CFS section connections were developed. Geometric details, material nonlinearities, material damage models and loading protocols were carefully simulated. Next, the results obtained from the numerical models were validated in detail against the experimental results. It was proved that the developed models have the ability to simulate the behavior of the 8.8 grade bolted connectors in these connections. At the end, an extensive parametric numerical study consisting of 216 connections was conducted. The examined parameters included CFS thickness, CFS ultimate strength, concrete compressive strength, embedded bolt's height and bolt diameter. Consequently, the effect of each of these parameters on the ultimate strength, ductility as well as the failure modes of the bolted shear connectors was carefully investigated. © 2022 Elsevier Ltd
Structures (23520124)29pp. 519-533
An experimental study according to EC4 on deconstructable steel-concrete composite bolted shear connectors is carried out to investigate the effect of various bolt size, concrete strength, bolt strength and clearance size between the precast concrete slab and bolt on the static behaviour of this type of composite connection. Shear load capacity for the first bearing, average major slip at the first bearing, maximum shear load capacity per bolt, slip corresponding to the maximum shear load capacity, maximum average slip between the precast concrete slab and steel beam and failure modes are assessed. A total of 12 composite specimens were tested according to EC4 with different parameters using deconstrcutable bolted shear connectors. In addition, two steel-concrete composite connection specimens using welded headed stud shear connectors were tested as control specimens to determine the influence of prefabricated concrete panels and deconstructable friction-grip bolted shear connectors on the performance of the steel-concrete composite connection. The experimental results show that deconstrcutable steel-concrete composite bolted shear connectors have completely different behaviour compared to welded headed stud shear connectors. Furthermore, a 3D finite element model of the steel-concrete composite connection having precast concrete slabs and deconstructable bolted shear connectors was performed. Numerical model was verified against experimental results, and was shown to accurately simulate their observed structural behaviour. © 2020 Institution of Structural Engineers
Engineering Structures (18737323)249
Since few studies have focused on the shear connectors in the composite cold-formed steel beams so far, this paper studies the behavior of the U-shaped shear connectors which can be used in the composite beams comprising cold-formed steel beam and concrete slab. Accordingly, ten full scale push-out tests were conducted to investigate the ultimate load, failure modes, ductility and stiffness of the U-shaped shear connectors. For this purpose, four types of shear connectors by different screw diameters and orientation of U-shaped shear connectors with respect to the direction of the load were considered; and utilized by two types of cold-formed steel beams with thickness of 1 and 2 mm. The results have shown that change of the screws’ diameter from 4.8 to 6.3 mm, leads to an increase of the ultimate load about 25% and 40% for 1 mm and 2 mm thick specimens, respectively. It is also concluded that transverse shear connectors have a better performance than longitudinal ones considering both ultimate load and ductility. The main observed failure mode of all specimens was tilting and bearing in shear connectors except for two specimens which was incorporated with pull-over mode. Moreover, ductility of the shear connectors was examined according to EC4 code. The results show that except for two specimens, the other U-shaped shear connectors used in this study can be accounted ductile. © 2021 Elsevier Ltd
Chiniforush, A.A.,
Ataei, A.,
Bradford m.a., M.A. Journal of Constructional Steel Research (0143974X)183
An experimental study of deconstructable steel-concrete shear connectors using bolts under a low-cycle high-amplitude loading protocol is undertaken to investigate the effect of the concrete compressive strength, bolt size and its grade and size of clearance between the precast concrete slab and bolt on the load-slip response. To characterise the cyclic performance of the shear connectors, the ductility, strength degradation and absorbed energy are evaluated for all specimens. The experimental campaign includes twelve deconstructable shear connector specimens which were constructed and tested to failure. The failure modes involved severe concrete crushing, fracture of the bolt connectors, bolt bending and fracture, and bolt bending. In addition, three separate specimens were constructed and tested under monotonic loading and the results were compared with their cyclic test counterparts. The results obtained from the experiments show that the ultimate shear load capacity of the deconstructable steel-concrete shear connectors under cyclic loading was considerably less than that under monotonic loading. A structural model comprising of two parallel springs is also described and fitted to the experimental results to represent the load-slip response of the examined shear connectors. © 2021 Elsevier Ltd
Thin-Walled Structures (02638231)164
Composite beams comprised of steel sections and concrete slabs, are one of the most widely used beams due to their advantages such as improving stiffness and strength compared to bare steel or reinforced concrete beams. Moreover, another important advantage of such beams is to prevent buckling of steel section by placing it under tension, which is especially important for low-thickness steel sections such as cold-formed steel (CFS) sections. Although the use of CFS sections in combination with concrete slabs can increase the efficiency of such sections, their low thickness makes it difficult to weld traditional studs as shear connectors on their top flanges. The current paper presents an experimental investigation about the behavior of bolted shear connectors in the composite cold-formed steel beams as a suitable alternative to welded shear studs. To do so, three main parameters including thickness of CFS sections, and size and strength of bolts were taken into account. Fifteen full-scale push-out specimens were constructed and tested. The ultimate load, ductility, stiffness and failure mode of all specimens were then assessed; and their results were reported and precisely discussed. Based on the results, depending on the size and strength of bolts, the ultimate load per shear connector for 1 mm thick CFS sections’ specimens is found between 6.2 and 8.6 KN, while this value for specimens by 2 mm thick CFS sections, is found between 15.6 and 26.8 KN. Moreover, based on EC4, the ductility of shear connectors was examined; the results indicate that all bolted shear connectors in this study can be assumed ductile and can be used in partial shear connections. © 2021 Elsevier Ltd
Chiniforush, A.A.,
Valipour h.r., H.R.,
Ataei, A. Construction and Building Materials (09500618)303
Push-out experiments on cross-laminated timber (CLT) panels connected to laminated veneer lumber (LVL) were carried out and load vs slip response of the CLT-LVL composite joints were obtained and stiffness, peak load, and ductility of the timber-timber composite (TTC) connections were evaluated and reported. Moreover, full scale 6.0 m long CLT-LVL beams with the tested shear connectors were fabricated and tested under four-point bending set up and the load vs mid-span deflection as well as load vs end slip graphs of the TTC beams were provided. Furthermore, the failure mode, service stiffness and load-carrying capacity of the CLT-LVL beams were studied. The main variables in the experimental program were the type of shear connectors (i.e. single or double threaded screws, dowels embedded in cementitious grout or epoxy pocket), size and installation angle of the screws, CLT panel thickness and orientation of the load with respect to CLT panels (i.e., loaded parallel || or perpendicular ⊥ to the outermost timber lamellae). A continuum-based finite element (FE) model for the TTC beams was developed and analysed using ABAQUS software. It was shown that the FE models can capture the load–deflection and peak load of the TTC beams with reasonable accuracy. The validated FE model was employed to conduct a parametric study and investigate the effect of CLT slab segmentation on the stiffness and load-carrying capacity of the CLT-LVL composite beams. Lastly, the adequacy of the existing simple analytical model for predicting stiffness and load-carrying capacity of the TTC connections and beams was demonstrated. © 2021 Elsevier Ltd
Ataei, A.,
Chiniforush, A.A.,
Bradford m.a., M.A.,
Valipour h.r., H.R. Journal of Constructional Steel Research (0143974X)161pp. 328-340
Feasibility and acceptable performance of the steel-timber composite (STC) system as a sustainable alternative to conventional steel-concrete composite have been demonstrated through recent static push-out and bending tests. But, structural behaviour and energy dissipation capacity of the STC connections subjected to cyclic loads have not been investigated yet. This study investigates the cyclic behaviour of STC connections with mechanical shear connectors. In total, twelve STC joints were fabricated by connecting the cross-laminated timber (CLT) panels to the flanges of a steel profile and the joints were subjected to low-cycle high-amplitude loading regime. Effects of the shear connector type (i.e. screw, high strength bolt), shear connector size and the orientation of CLT panels (outer lamellas parallel and/or perpendicular) with respect to the direction of the load were considered in the experimental program. The ductility, strength impairment and equivalent viscous damping which characterise the performance of a mechanical shear connector under cyclic loading conditions in steel-timber composite connections were assessed. The results of the cyclic tests demonstrated the high ductility and energy dissipating capacity of the steel-timber composite connections. A simple hysteretic model was proposed for steel-to-CLT composite connections with bolt and screw shear connectors and the model was calibrated against the results of laboratory experiments. © 2019 Elsevier Ltd
Engineering Structures (18737323)198
An experimental study of the cyclic behaviour of steel-concrete composite connections using mechanical shear connectors subjected to a low-cycle high-amplitude loading regime is presented in this study. The ductility, strength degradation and absorbed energy which characterise the performance of a mechanical shear connector under cyclic loading conditions in steel-concrete composite connections are assessed. Nine steel-concrete composite connection specimens were designed and tested in order to investigate the cyclic behaviour of the proposed composite connections, and to elucidate the structural behaviour of the demountable bolt shear connectors between the precast concrete panels and steel beams. In addition, three monotonic tests on steel-concrete composite connection were conducted to evaluate the yield slip, yield load, ultimate slip, and ultimate shear strength capacity. The size of the bolted shear connector and the strength of the bolted shear connectors are the main variables in this study. The preparation and construction of the specimens, the testing procedure, the test set-up, and the instrumentation used are described and the results of the monotonic and cyclic tests are reported in detail. © 2019 Elsevier Ltd
Ataei, A.,
Valipour h.r., H.R.,
Bradford m.a., M.A.,
Chiniforush, A.A. Construction and Building Materials (09500618)226pp. 636-650
This study presents the results of laboratory push-down tests conducted on one pure steel and four steel-timber composite (STC) cruciform subassemblies to assess the failure characteristics, stiffness, flexural resistance and ductility of the extended end plate STC beam-to-column connections subjected to negative (hogging) bending moment. In the proposed composite system, the cross -laminated timber (CLT) panels were connected to the top flange of steel girders using coach screws and the steel beams were connected to the steel columns by bolted extended end plates. Moreover, the two juxtaposed CLT slabs (subject to tension) were connected by the mechanically anchored threaded rod and/or surface spline joints with steel plates. The experimental results showed that the extended end plate STC connection have enough rotation capacity to provide for plastic analysis/design of the STC beams. Furthermore, it was shown that the composite action in conjunction with continuity of timber slab can increase the bending moment capacity of the connection more than 50% of that for a pure steel connection. © 2019 Elsevier Ltd
Bradford m.a., M.A.,
Ataei, A.,
Valipour h.r., H.R. pp. 127-135
A three-parameter power model is developed for quantifying the moment-rotation characteristics of a blind bolted flush end plate joint system that connects a composite beam to a Concrete-Filled Steel Tube (CFST) column in a steel framed building structure. A detailed 3-D non-linear continuum-based finite element model of the connection region including the composite beam, flush end plate, blind bolts and the CFST is developed, which can capture the pertinent physical, geometrical and contact non-linearities. The model is validated against test results, and is used to provide valuable empirical modelling in the computer design of framed structures within a paradigm of “advanced analysis”. © 2018 Taylor & Francis Group, London.
Ataei, A.,
Chiniforush, A.A.,
Valipour h.r., H.R.,
Bradford m.a., M.A.
An experimental study of the cyclic behaviour of composite steel-timber panel connections using different mechanical shear connectors subjected to a low-cycle high amplitude regime is presented in this study. Twelve steel-timber composite connection specimens were designed and tested in order to investigate the cyclic behaviour of the proposed composite connections, and to characterize the structural behaviour of demountable bolt/screw shear connectors between Cross-Laminated Timber (CLT) panels and steel beam. Six types of mechanical shear connectors including coach screws (12, 16 and 20 mm), dog screws (16 and 19 mm) and Grade 8.8 bolts (16 mm) were used to connect the CLT timber to the steel beam. In addition to the type of shear connectors, the direction of the load application with respect to panel orientation (perpendicular and parallel to the grain) is also one of the main variables in this study. The paper also outlines the preparation and construction of the specimens, the testing procedure, the test setup and the instrumentation used to measure the response during the tests. The test results indicate high ductility and energy dissipating capacity for steel-timber composite connection. © WCTE 2018 Committee.
Ataei, A.,
Bradford m.a., M.A.,
Valipour h.r., H.R.,
Chiniforush, A.A.
An experimental study of four full-scale cruciform sub-assemblages of beam-to-column steel-timber composite joints with extended end plates was conducted to simulate the behaviour of an internal joint in a semi-rigid steel-timber frame. In this system, the Cross-Laminated Timber (CLT) panels were attached compositely to the steel beam using coach screws to achieve the shear connection and the steel-CLT composite beams were connected to the steel columns by bolted extended end plates. In addition, one specimen without a CLT slab was constructed and tested as a control with which to assess the influence of the CLT panels on the performance of the joint. The structural behaviour of this type of joint which requires the connection of the two juxtaposed CLT panels subjected to tension near the column was explored. The test results show that these novel composite joints have credible rotation and moment capacities and provide a viable alternative to their steel-concrete counterparts within a paradigm of reduced carbon emissions in the construction sector. © WCTE 2018 Committee.
Ataei, A.,
Moradi, M.,
Valipour h.r., H.R.,
Bradford m.a., M.A. Journal of Constructional Steel Research (0143974X)151pp. 204-215
This paper investigates the enhanced loading capacity and structural behaviour of a transversely confined precast reinforced concrete (RC) deck slab with deconstructable post-installedfriction-grip bolted (PFGB) shear connectors. A detailed 3D non-linearcontinuum-based finite element (FE) model of the deconstructable composite deck with external confining systems (i.e. cross-bracings or ties) and PFGB shear connectors is developed and analysed using the commercial software ABAQUS. The non-linearity of the contacts/interfaces, geometrical and material non-linearities are considered in the FE models. The developed FE models are validated against experimental results and it is shown that the proposed FE model can adequately predict the enhancing effect of arching action in a transversely confined deconstructable precast RC deck slab. Lastly, a parametric study is carried out and effect of different parameters such as compressive strength of concrete, yield strength and proportion of reinforcing bars, clearance between concrete slab and PFGB shear connectors and pretension stress in the PFGB shear connectors on the stiffness and strength enhancement provided by the arching action are evaluated and discussed. © 2018 Elsevier Ltd
Chiniforush, A.A.,
Akbarnezhad, A.,
Thakore, P.,
Ataei, A.
Long-term behavior of engineered wood species was investigated under tensile loading in variable outdoor climatic conditions. Sustained tensile loads parallel to the grain were applied to specimens of Spruce Pine, Pacific Teak, Laminated Lumber Veneer, and Cross-Laminated Timber. Tests were conducted at three different stress levels simultaneously and temperature and relative humidity of the environment were monitored continuously throughout the loading period. A constitutive fiber finite element model was developed to simulate the experimental data. Complementary data for free shrinkage and swelling as well as diffusion coefficient from the same samples were measured in three orthogonal directions and the generated model was calibrated. The developed constitutive model considers the effect of viscoelastic and mechano-sorptive creep, shrinkage and swelling, thermal and moisture inelastic deformation, and deformation due to Young's modulus changes. There is a good correlation between the numerical and experimental results. © WCTE 2018 Committee.
Journal of Constructional Steel Research (0143974X)129pp. 75-92
This paper presents a three-dimensional finite element modelling of an innovative flush end plate semi-rigid beam-to-column composite joint comprising deconstructable post-installed friction-grip bolted shear connectors. The moment versus rotation relationship for these prototype joints subjected to a hogging bending moment with the influence of partial shear connection is investigated using ABAQUS software. This relationship is an indicator of the ductility of a composite joint and is a necessity for a semi-rigid frame analysis. A detailed finite element model of the connection region including the precast concrete slab, steel beam, flush end-plate, bolted shear connectors and the steel column is developed in the paper. Material and geometrical non-linearities as well as the non-linearity of the interfaces are incorporated in the model. The accuracy and reliability of the numerical formulation are verified against experimental data reported elsewhere. In addition, a composite joint with partial shear connection is constructed and tested in this study, and the numerical predictions are compared with the test results. An extensive parametric study is then conducted, using several parameters that include the degree of shear connection, reinforcement ratio, thickness of the precast concrete slab, spacing of bolted shear connectors, size of the bolts in the connection zone, thickness of the flush end plate, steel grade for the beam, column and end plate and the column flange thickness. Finally, moment versus rotation models for deconstructable flush end plate beam-to-column composite joint are proposed, and it is demonstrated that the design models developed can also be used for composite joints with high strength steel components. © 2016 Elsevier Ltd
Engineering Structures (18737323)130pp. 282-296
Composite beams comprising of concrete slabs and steel beams joined by conventional headed stud shear connectors are commonly used in modern steel-framed building construction. However, because the headed stud shear connectors are welded onto the top flange of the steel beam and cast into the in situ concrete slab, deconstruction of the composite beam and the reuse of its components at the end of structural life in defence to demolition is virtually impossible, which is at odds with the increasing demands placed on improving the sustainability of building infrastructure. As an alternative, an innovative sustainable composite beam and slab system is proposed, in which precast geopolymer concrete panels are attached to the steel beams using high-strength friction-grip bolts instead of cast in situ floors with pre-welded headed stud connectors. The advantages of a low-carbon design, both by the use of geopolymer concrete elements and system deconstructability, can be achieved in this proposed system. In this paper, a three-dimensional finite element model is developed to investigate the structural behaviour of the proposed sustainable composite beam and slab system. Material non-linearities and the interaction of the structural components are included in the model. The accuracy and reliability of the finite element formulation developed are validated by comparisons with experimental results. Extensive parametric studies are conducted to elucidate the effects of the change in the concrete panel configuration, the number and diameter of the bolts, the type and strength of the concrete and the grade of the steel beam on the behaviour of the system. The use of modified rigid plastic analysis is assessed, and a modification is suggested to predict the flexural strengths of the composite beams and slab system. © 2016 Elsevier Ltd
A 3-D finite element modelling of flush end plate semi-rigid beam-to-column composite joints is described. The joints comprise of deconstructable post-installed friction-grip bolted shear connectors. The moment-rotation characteristics for these prototype joints subjected to a hogging bending moment with the influence of partial shear connection is investigated using ABAQUS, including material and geometric non-linearities. The accuracy and reliability of the numerical formulation are verified against experimental data, and a parametric study is conducted. Momentrotation models for deconstructable flush end plate beam-to-column composite joints are proposed from these results. © 2020, American Institute of Steel Construction, AISC. All rights reserved.
Ataei, A.,
Bradford m.a., M.A.,
Valipour h.r., H.R. pp. 168-178
This paper investigates the structural behaviour of an innovative beam-to-column composite semi-rigid joint with deconstructable post-installed friction-grip bolted shear connectors and Grade S690 high strength steel flush end plates. Non-linear continuum-based finite element models are developed and validated against the results of four full-scale laboratory tests of this innovative joint. The validated finite element models are used for conducting an extensive parametric study in which the effects of the reinforcement ratio, thickness of the precast concrete slab, degree of shear connection, size of the bolts in the connection zone and thickness of the flush end plate on the structural behaviour of a composite joint with deconstructable post-installed friction-grip bolted shear connectors and Grade S690 high strength steel flush end plates are investigated. © ASCE.
Engineering Structures (18737323)114pp. 1-13
Traditional steel-concrete composite beams are known to exhibit excellent structural characteristics, in terms of their stiffness and strength, when compared with bare steel or reinforced concrete beams. However, within current paradigms of lowering carbon emissions and enhancing the possibly of material recycling, such traditional composite beams cannot be deconstructed easily and their elements are not recyclable because they rely on welded headed stud connectors that are encased within cast in situ concrete to achieve the necessary shear connection. This paper presents the detailed results of quasi-static tests conducted on full-scale composite beams as part of a novel deconstructable and sustainable structural system. For this system, precast concrete slabs are attached to a steel beam using tensioned high-strength friction-grip bolts in clearance holes as the elements to provide the shear connection. The precast slabs are made using geopolymer concrete in lieu of concrete made from ordinary Portland cement, whose manufacture is a major contributor to anthropogenic CO2 emissions worldwide, thereby enhancing the low-carbon attributes of the structural system. The test results demonstrate the very significant ductility of the beams, with substantial interface slips being developed and sustained at loads close to the ultimate strength limit state. The tension induced in the bolts provides sufficient frictional resistance between the precast slabs and steel beams to ensure that the composite system has full shear interaction throughout the range of service loading. It is also confirmed that composite beams with bolted shear connectors can be deconstructed easily at the end of their service life, with the slabs, steel beams and bolts being reusable in other structural applications. © 2015 Elsevier Ltd.
Structures (23520124)7pp. 43-58
Composite steel-concrete floor systems represent a ubiquitous structural steel framing system for commercial and industrial buildings in the developed world, which exploit the strengths of reinforced concrete and structural steel both symbiotically and in a complementary fashion. However, as attention is being focused increasingly towards minimising emissions and maximising recycling, these composite systems are problematic for many reasons. This paper describes the results of tests on three full-scale sustainable flush end plate semi-rigid beam-to-column joints and three push-out tests with deconstructable tensioned bolted shear connectors, needed to establish the strength of the shear connection in order to design the joints. For this system, precast concrete slabs having a reduced content of ordinary Portland cement are attached compositely to the steel beam using post-tensioned high-strength friction-grip bolts that are unbolted readily at the life-cycle end of the building. This innovative connection system is proposed to circumvent the high-carbon attributes associated with the demolition of conventional steel-concrete composite framing systems. The push-out tests show that the behaviour of specimens with post-installed bolts in clearance holes is significantly different to that of members with stud shear connectors in slabs cast in situ, and the bolted connectors provide reliable and adequate shear connection to composite beams and joints with precast concrete slabs. The test results show that these composite joints have credible rotation and moment capacities within the recommendations of EC3 and EC4, and that fracture of the joint occurs after substantial rotational deformations had been achieved. © 2016
Ataei, A.,
Bradford m.a., M.A.,
Valipour h.r., H.R.,
Liu, X. Engineering Structures (18737323)123pp. 124-140
The design of engineering structures for deconstructability can reduce the energy and cost required for their demolition and for the disposal of their construction waste, and it also enhances the sustainability of a building by allowing for easy dismantling and the reuse or recycling of structural components and construction materials at the end of the service life of the building. In addition, using high performance materials such as high strength steel can improve the sustainability of a structure by providing for higher design stresses and accordingly reducing the self-weight of the structure. This paper describes the results of four full-scale beam-to-column deconstructable composite joints with high strength steel S690 flush end plates. The structural behaviour of the new system in conjunction with application of post-installed friction-grip bolted shear connectors for developing deconstructable composite floors is investigated. The test results show that the proposed composite beam-to-column joints can provide the required strength and ductility according to Eurocode 3 and Eurocode 4 specifications, and that the system can be easily deconstructed at the end of the service life of the structure as a proof of concept. © 2016 Elsevier Ltd.
Ataei, A.,
Bradford m.a., M.A.,
Valipour h.r., H.R. Finite Elements in Analysis and Design (0168874X)122pp. 16-38
High-strength steel has a higher yield strength, greater corrosion resistance and superior toughness compared to mild steel, and its use can contribute to the sustainability of a steel structure by increasing its structural life whilst reducing steel usage and maintenance. In addition, using deconstructable steel-concrete composite floors can facilitate component recycling and reuse and can improve the sustainability of the building industry significantly by reducing energy consumption and construction waste at demolition. This paper investigates the structural behaviour of an innovative beam-to-column composite semi-rigid joint with deconstructable post-installed friction-grip bolted shear connectors and grade S690 high strength steel flush end plates. Non-linear continuum-based finite element models are developed and validated against results of four full-scale laboratory tests of this innovative joint. The validated finite element models are used for conducting an extensive parametric study in which the effects of the reinforcement ratio, thickness of the precast concrete slab, degree of shear connection, number of bolted shear connectors, size of the bolts in the connection zone, size of the steel beam and thickness of the flush end plate on the structural behaviour of a composite joint with deconstructable post-installed friction-grip bolted shear connectors and grade S690 high strength steel flush end plates are investigated. A simple analytical model is proposed to predict the moment capacity and rotation capacity of this type of composite joint. © 2016 Elsevier B.V.
Structures (23520124)8pp. 130-143
This paper describes a three-dimensional finite element modelling of an innovative flush end plate semi-rigid composite joint, to a concrete-filled steel tubular column, using high strength blind bolts. This innovative composite joint is formed by connecting a precast concrete slab to the top flange of a steel beam using post-installed friction-grip bolted shear connectors to facilitate the deconstructability of the entire system. A finite element model is developed using ABAQUS software to study the structural behaviour and failure modes of these prototype joints. Both geometrical and material non-linearities, as well as the non-linearity of the contacts and interfaces, are incorporated in the model. Four full-scale laboratory test specimens having deconstructable flush end plate composite semi-rigid joint to CFST columns using bind bolts are tested, with the results then used for validation of the finite element model. The proposed numerical models developed are used for conducting an extensive parametric study, in which the effects of the reinforcement ratio, thickness of the precast concrete slab, degree of shear connection, number of bolted shear connectors, size of the blind bolts in the connection zone and thickness of the flush end plate on the structural behaviour of the composite joint to concrete-filled columns are investigated. A design recommendation in the form of an empirical equation is then formulated. © 2016 Elsevier B.V.
Ataei, A.,
Bradford m.a., M.A.,
Valipour h.r., H.R. Procedia Engineering (18777058)145pp. 1153-1160
As attention is being focused increasingly towards minimising carbon emissions and enhancing the possibly of material recycling in the construction industry, traditional composite systems are recognised as being problematic on several counts. Composite action between the conventional concrete slab and steel beam is provided typically by stud shear connectors welded to the top flange of the steel beam, and the demolition of such members requires a considerable amount of time and energy, as well as being environmentally intrusive and creating much waste. In addition, existing composite systems mostly utilise conventional concrete made from ordinary Portland cement whose production is attributed to a large portion of carbon emissions worldwide. As an alternative, it is proposed that precast concrete slabs be attached to a steel frame with semi-rigid bolted connections using high-strength friction grip bolts as the elements to provide the shear connection. Moreover, the use of geopolymer concrete in the casting of the slabs eliminates the use of ordinary Portland cement entirely. The paper reports tests undertaken on full-scale beams and on full-scale joints in this sustainable and deconstructable system. This study shows that both the joints and beams demonstrate very significant ductility, with large rotations, deformations and interface slips being developed and sustained during the testing. © 2016 The Authors.
Ataei, A.,
Bradford m.a., M.A.,
Valipour h.r., H.R. Engineering Structures (18737323)99pp. 616-630
This paper presents the results of static tests conducted on four full-scale flush end plate semi-rigid beam-to-column joints in a novel deconstructable and sustainable structural frame system. In this system, precast concrete slabs that are associated with reduced CO2 emissions during their manufacture are attached compositely to a steel beam using a novel method of shear connection that takes advantage of post-installed friction-grip bolted shear connectors and the composite steel beams are connected to concrete-filled steel tubular columns using flush end plates with blind bolts. The proposed structural system can be deconstructed at the end of its service life so that demolition waste is minimised and component recycling is maximised. In addition, application of precast slabs instead of cast in situ conventional concrete slabs can improve the quality of construction, reduce construction time and labour costs and lower the carbon footprint of the structure. The structural response of the beam-to-column joints is assessed under a monotonically increasing static load and the influence of the type of precast concrete slab and bolted shear connectors, as well as degree of shear connection, on the structural performance of this structural system are investigated. The test results show that these novel composite joints have credible rotation and moment capacities according to the recommendations of EC3 and EC4, and fracture of the joints occurs after development of substantial rotation. © 2015 Published by Elsevier Ltd.
Ataei, A.,
Bradford m.a., M.A.,
Valipour h.r., H.R. Journal of Structural Engineering (07339445)141(9)
This paper develops both a three-parameter power model and a Ramberg-Osgood model for quantifying the moment - rotation characteristics of a blind-bolted flush end-plate system that connects a composite beam to a concrete-filled steel tubular (CFST) column in a steel framed building structure. By default, these connections are semirigid, and accurate analyses of structures including them necessitate quantitative knowledge of their moment-rotation response. A detailed three-dimensional (3D) nonlinear-continuum-based finite element model of the connection region including the composite beam, flush end-plate, blind bolts and the concrete-filled steel tube is developed in this paper. This sophisticated FE model can capture the pertinent physical, geometrical, and contact nonlinearities, and its accuracy is verified against experimental data reported elsewhere in the literature. The calibrated FE model is then employed for a parametric study in which the effects of the slab reinforcement ratio, the thickness of the slab, the degree of the shear connection, the diameter of the blind bolts as well as the pretension force in them and their yield stress, the depth of the beam, and the thickness of the flush end-plate are investigated. The results of the parametric study are employed to calibrate moment-rotation relationships, which are proposed in a convenient analytic form. It is shown that the proposed model predicts the moment-rotation response of blind-bolted flush end-plate composite beam-to-CFST column connections with good accuracy, and it provides a valuable empirical modeling that can be used in the computer design of composite framed building frames in the new paradigm of design by advanced analysis. © 2014 American Society of Civil Engineers.
Applied Mechanics and Materials (discontinued) (16627482)553pp. 588-593
A semi-rigid beam-to-column composite blind bolted connection is modelled using ABAQUS software. The mechanics of this innovative joint considered in the paper requires careful consideration in order to capture the response accurately using computational techniques. The composite beam is connected to a concrete-filled square column using blind bolts, and the model simulates a connection in hogging bending moment. Partial shear connection is considered, as well as the non-linear material properties and geometry of all of the constitutive components. All connection components were taken as being the same size as used in the experiments against which the method is calibrated, and furthermore the model does not need recourse to empirical push-out test data. The technique can be used to model the connections easily, resulting in rapid and reliable solutions. Using the numerical model which is calibrated accurately against experimental test results, a parametric study is carried out to investigate the pertinent parameters such as the reinforcement ratio, axial loading in the column, thickness of the concrete slab, degree of the shear connection, diameter of the blind bolts and the pretension force in them on the structural behaviour of this innovative type of joint. Based on the parametric studies, recommendations for the design of this kind of structural joint are given. © (2014) Trans Tech Publications, Switzerland.
Applied Mechanics and Materials (discontinued) (16627482)553pp. 557-563
Composite construction is a popular and effective method of construction, exploiting the strengths of both reinforced concrete and structural steel in building construction in a complementary fashion. Within paradigms related to minimisation of emissions and maximisation of product recycling, these composite systems are problematic on a number of fronts. Firstly, common and traditional composite systems utilise ordinary Portland cement, which is known to be a very large contributor to atmospheric CO2 emissions. Secondly, for typical construction practices for steel-concrete composite systems, casting of the concrete onto profiled steel decking and conventional reinforcement placing are undertaken on-site, which is time consuming and labour intensive, and which can increase the cost of construction. Thirdly, composite action between the steel beam and the concrete slab is usually achieved by using headed shear studs. The headed shear studs connect these two elements permanently, which leads to much waste at the end of the service life of the building when it is demolished. This paper models a sustainable semi-rigid beam-tocolumn composite blind bolted connection with deconstructable bolted shear connectors using ABAQUS finite element (FE) software. In this "green" system, precast geopolymer concrete (GPC) slabs are attached compositely to the steel beam via pretensioned bolted shear connectors and the composite beam is connected to GPC-filled square columns using blind bolts. Non-linear material properties and non-linear geometric effects are considered in the simulation of a connection in hogging bending. Based on the FE modelling, using pretensioned bolts as shear connectors with GPC can improve the behaviour of semi-rigid flush end plate composite joints in terms of ductility and load capacity. Moreover, the behaviour of the bolted shear connectors should be considered in composite joint design as being very different to headed stud connectors. © (2014) Trans Tech Publications, Switzerland.
A semi-rigid beam-to-column composite blind bolted connection is modelled using ABAQUS software. The composite beam is connected to the concrete-filled square column using blind bolts, and the model simulates a connection in hogging bending moment. Partial shear connection is considered, as well as the non-linear material properties of all constitutive components. All connection components were taken as roughly the same size as used in the experiments against which the method is calibrated, and the model does not need recourse to empirical push test data. The technique can be used to model connections easily, resulting in rapid and reliable solutions. © 2013 Taylor & Francis Group, London, UK.
Composite construction is a popular and effective method of construction, exploiting the strengths of both reinforced concrete and structural steel in building construction in a complementary fashion. Within paradigms related to minimisation of emissions and maximisation of product recycling, these composite systems are problematic on a number of fronts. Firstly, common and traditional composite systems utilise ordinary portland cement, which is known to be a very large contributor to atmospheric CO2 emissions. Secondly, for typical construction practices for steel-concrete composite systems, casting of the concrete onto profiled steel decking and conventional reinforcement placing are undertaken on-site, which is time consuming and labour intensive, and which can increase the cost of construction. Thirdly, composite action between the steel beam and the concrete slab is usually achieved by using headed shear studs. The headed shear studs connect these two elements permanently, which leads to much waste at the end of the service life of the building when it is demolished. This paper models a sustainable semi-rigid beam-to-column composite blind bolted connection with deconstructable bolted shear connectors using ABAQUS finite element (FE) software. In this "green" system, precast geopolymer concrete (GPC) slabs are attached compositely to the steel beam via pretensioned bolted shear connectors and the composite beam is connected to GPC-filled square columns using blind bolts. Non-linear material properties and non-linear geometric effects are considered in the simulation of a connection in hogging bending. Based on the FE modelling, using pretensioned bolts as shear connectors with GPC can improve the behaviour of semi-rigid flush end plate composite joints in terms of ductility and load capacity. Moreover, the behaviour of the bolted shear connectors should be considered in composite joint design as being very different to headed stud connectors. © ASCE.
