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International Journal of Steel Structures (20936311) 25(2)pp. 449-461
Cold-formed steel C-shaped connectors are one of the most commonly used components in a connection e.g. track-to-stud connections which may be exposed to various destructive failure modes. This paper presents a detailed experimental study of 78 specimens to investigate the pull-out ultimate strength and force–displacement responses of C-shaped connectors subjected to tensile loading conditions. Effects of various design parameters were considered including plate thickness, screw diameter size, distance between the screw rows and formed corner of the C-shaped sections, number and arrangement of the screws, and internal screw rows. Then, a developed pull-out strength equation with a resistance reduction factor was proposed and the obtained results were compared against existing design standard equations. From the comparisons, the proposed equation can accurately predict the screw pull-out strength in C-shaped connectors’ webs. The results of this equation can be applied to analytical methods as mechanical characteristics of the component of C-shaped section’s web in tension or bending. © Korean Society of Steel Construction 2025.
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
Considering the importance of cold-formed steel clip angles in light-weight structures, this paper presents an experimental investigation into the behavior of cold-formed steel clip angles when one leg is connected to a thin-walled member and the other leg is subjected to tension forces. Of particular interests were ultimate tensile and shear resistances, as well as different potential failure modes, such as pull-out, pull-through, and bearing/tilting. Effects of various design parameters were investigated, including number of screws, size of screws, thickness of the member connected to the screw head, thickness of the member connected to the screw threads, ratio of the distance between the clip angle's corner and the bolt row to the distance between the corner and the screw row, and screw installation direction. The data obtained from experimental tests were compared to those obtained from current design standards’ equations. Subsequently, new design equations were proposed for the pull-out and bearing strengths as the dominant failure modes in order to overcome the overestimation and the underestimation of existing equations. © 2024 Institution of Structural Engineers
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.
While cold-formed steel structures have been extensively studied for seismic-resistant construction, existing regulations, and implementation guidelines do not comprehensively address the impact of key design parameters on the seismic behavior of CFS strap-braced shear wall systems. This study investigates the lateral resistance and seismic behavior factor of strap-braced shear walls and compares them with code values, and tries to fully understand the effect of different design parameters on the seismic R-factor of these systems. The effect of parameters such as the strap cross-sectional area, aspect ratio, and distance between the studs is studied using ANSYS finite element software to create datasets for various configurations. The pushover analysis results obtained from this analysis are utilized to perform incremental dynamic analysis, under a set of 22 ground motion records, to evaluate the seismic response modification factor for different residential buildings. For this purpose, one to four-story residential buildings are designed based on four seismic hazard zones: low, moderate, high, and very high and then, they are analyzed. Results of pushover analysis show that increasing the strap cross-sectional area and aspect ratio increases capacity, but changing the distance between studs does not have a significant effect, and the R factor presented by codes is conservative. Incremental dynamic analysis results also indicate that the behavior of studied buildings varies depending on the structure and selected record and the suggested R factor by codes for diagonal straps braced cold-formed steel structures is acceptable for buildings up to three stories in low, medium, and high seismic zones, and for buildings up to two stories in very high seismic zones. Overall, this study shows that strap-braced cold-formed steel shear walls have the potential to achieve higher seismic R-values in comparison to design codes. © 2024 Institution of Structural Engineers
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
Australian Journal of Structural Engineering (13287982) 24(2)pp. 173-189
In this paper, cold-formed steel C-shaped connectors, as one of the most commonly used components in steel wall/framing systems, were investigated under the pull-out failure modes using a detailed numerical study. Finite element models were validated using the data obtained from an experimental program; and the results were compared with the current design equations. Finally, a new pull-out strength equation was proposed based on the critical parameters affecting the behaviour of C-shaped connectors. In addition, initial bending stiffness of C-shaped connectors was studied using a simplified analytical approach; and the results obtained from the proposed new stiffness equation were compared with the initial slope of experimental and numerical force-displacement curves. These comparisons confirm the accuracy of the new strength and stiffness equations in order to apply to the analytical methods such as component-based method in future works. © 2022 Engineers Australia.
Archives of Civil and Mechanical Engineering (16449665) 23(1)
Nowadays, cross-arm truss structures made by cold-formed steel sections are used in power distribution networks. Although cold-formed steel structures have some advantages such as being lightweight and fast operation, they suffer from relatively low resistance against heat. This paper investigates the effect of elevated temperature on structural performance of cross-arm cold-formed steel structure based on experimental studies and additional numerical modeling. Furthermore, temperature-time curves of the structures were compared against thermal loading standards ISO834 and ASTM E119. For this purpose, the temperature-rotation curve of the structures and the effect of the initial vertical load before thermal loading on this curve were investigated. Also, temperature-rotation curves obtained in the laboratory as well as numerical modeling were studied and compared against each other. © 2023, Wroclaw University of Science and Technology.
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
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
Journal of Construction Engineering and Management (19437862) 148(6)
Worksite accidents in the construction and infrastructure industries result in cost overruns and schedule downtimes. Previous research has analyzed cost and schedule deviations caused by worksite accidents within these industries. However, a quantitative analysis of accidents at the subsector level and comparisons at the organizational level have yet to be undertaken. Toward this aim, worksite accident data are collected across different industry subsectors and organizations of different sizes, and an integrated risk register is constructed to capture cost and schedule deviations caused by worksite accidents. The findings indicate that structural and installation services are the main contributors to workplace accidents in terms of cost and time deviations. Moreover, organizational size is an important factor in the impact analysis of worksite accidents. Large organizations in the structural services were found to make a significant impact on cost overruns and schedule downtimes. They are followed by small organizations in the installation services subsector and medium/large organizations in the heavy and civil engineering subsector. The findings in this study reveal that improvements and investments in safety training and workplace communications are needed for efficient accident prevention. © 2022 American Society of Civil Engineers.
Archives of Civil and Mechanical Engineering (16449665) 21(2)
Civil engineering projects deal with different risks over their life-cycle. Generally, risk sources are categorized into three types of cost, time, and project quality. The Modified Advanced Programmatic Risk Analysis Model (MAPRAM) is one of the leading approaches in this field that can assess the risks of the project on its whole life cycle. Electricity transmission lines have always been one of the most costly and time-consuming infrastructure projects. The costs of these projects play a significant role in a country's development budget. Given the considerable time and cost of constructing the foundations for power transmission towers, providing an economical design will significantly help in reducing duration and budget of these projects. In this study, using MAPRAM, first, different types of foundations of power transmission lines were studied; then the optimal foundations were introduced for a specific place as a case study, shaping a general framework to appoint the optimal foundation for power transmission lines in different areas. The foundations studied in this study included: pad & chimney foundation, auger foundation, steel grillage foundation, concrete piles, and helical piles. Initially, different types of foundations were designed, and then, the costs of each foundation in a whole life-cycle were estimated. Next, the risks and probability of their occurrence were identified for each type of foundation. Finally, the appropriate foundation was determined for the studied soil samples by performing an optimization process. © 2021, Wroclaw University of Science and Technology.
Khouzani, M.A. ,
Zeynalian dastjerdi, M. ,
Hashemi esfahanian, M. ,
Mostofinejad, D. ,
Farahbod, F. ,
Shahadifar, M. Journal of Building Engineering (23527102) 44
Several roofing systems have been proposed given their significance in concrete structures, in terms of time and resources. A biaxial voided slab system is introduced to improve the solid slab system's performance by creating voids in the concrete and removing ineffective material. In this study, the bending behavior of voided slabs is investigated numerically. For this purpose, a numerical ABAQUS model is presented and then verified using available experimental results. Then, a parametric study was carried out focusing on the plastic balls and their spacing, steel cages, and the position of plastic balls relative to the slab height. As shown in this paper, the presence of plastic balls improves the flexural capacity, because of steel cages. However, the spacing between plastic balls and their position have not a significant effect on flexural behavior. Finally, the numerical results were compared with the ultimate moment capacities from ACI 318-19, AS 3600-18, EC2 2004, and CSA A23.3-19, and were shown that considering steel cages have better consistencies with numerical results. © 2021 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
Journal of Civil Engineering and Management (18223605) 27(3)pp. 149-161
Various risks significantly influence pricing of bids and a wide range of factors impact bid pricing risks. Of these, client’s reputation and the record of projects owned by a client have vital contribution on the issue. Current practices however fail to capture the impacts of client-related factors. There is a need for developing a practical quantitative approach, which enables estimators to process bid risk allocation easily. Through reliability analysis, the developed method proposed in this study enables practitioners to make informed bid/no-bid decisions based on estimating the probabilities of schedule and cost overruns. Estimating the probability of project failure enables estimators to quantify the risk element of bid price. In addition, schedule and cost overrun cumulative probability distributions can be used to estimate the expected value of these variables. The practicability of this proposed method is tested by empirical data obtained from 40 university construction projects of one client, for estimating the bid price of a low-rise building. For researchers, findings provide illuminating insight into the potential of using reliability analysis as a valuable tool for bid decision-making practices. So too, the proposed method offers a blueprint for estimating and calculating time and contingency – and managing associated risks – in planning construction projects. The contribution of this study for the world of practice lies in providing a simple, rapid and cost-effective method for bid decision-making processes. © 2021 The Author(s). Published by Vilnius Gediminas Technical University.
Thin-Walled Structures (02638231) 164
Pull-out failures are one of the common failures in load bearing cold-formed steel clip angles causing catastrophic damages, where plate and screw fastener are dislocated. Thus, a detailed experimental study was first conducted to investigate the pull-out failures in cold-formed steel clip angles under tensile loading conditions. Then, since experimental tests are time-consuming and expensive, the ability of finite element modeling in the ABAQUS software environment was used to predict the pull-out behavior of the clip angles. The force–displacement behavior, ultimate strengths, and failure modes were compared with those obtained from experimental tests to validate the finite element models. The results were compared with those obtained from current design equations. Then, new design equations associated with numerical and both numerical and experimental results were provided by considering all geometrical and mechanical parameters to accurately predict the pull-out failure loads of the clip angles. © 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
International Journal of Steel Structures (20936311) 20(5)pp. 1465-1481
On the structural analysis, connection effects should be evaluated in terms of rotational stiffness and ultimate strength; this makes it possible to obtain realistic behavior of the structure. In this research, a simple analytical evaluation is carried out to predict the behaviors of the connections as a bi-linear curve. Mechanical properties of the initial and the second parts of this curve are obtained by component-based method and a suggested classification method, respectively. The component-based method represents a joint by using a combination of rigid and flexible components. Each of the components is modeled by means of specific stiffness and strength values and they are assembled together to obtain the initial mechanical properties of the joint. The suggested classification method classifies all the components in a connection into three groups based on comparing the ultimate and the design moment strength of each component with those of the connection. By considering this procedure, a new equation is proposed to determine joint post-limit rotational stiffness. This simple and fast method is applicable to any type of joints regardless of profile type and applied loading. The proposed method is applied to a bolted angle, an end-plate to rectangular hollow section column and two bolted end-plate beam-to-column connections. The results are compared with those obtained from some other analytical, numerical and experimental methods. The outputs confirm that the proposed method is simpler, more accurate and less time consume than the other methods. © 2020, Korean Society of Steel Construction.
Journal of Constructional Steel Research (0143974X) 166
Load bearing cold-formed steel clip angles are one of the commonly used connectors in lightweight cold-formed steel structures. These connectors may fail at their screw connections due to pull-out failure when the screw pulls out of the plate under tension loading conditions. These localized connection failures can cause undesirable failures by dislocating both clip angle and sub-plates. Therefore, a detailed experimental study was carried out to investigate the pull-out failures of load bearing cold-formed steel clip angles considering different parameters such as clip angle configuration, clip angle thickness, screw diameter size, screw thread pitch, number of screws and screw location. This paper presents the test results conducted in this study and compares them with existing pull-out design standard equations. Also, a design equation with a resistance reduction factor is developed and suggested in order to accurately determine the pull-out strength of the cold-formed steel clip angles. © 2020
Structural Concrete (14644177) 21(1)pp. 291-302
In some of biaxial voided slabs, spherical or ellipsoidal plastic balls enclosed in steel cages are used to eliminate ineffective concrete. To investigate the bending and shear behavior of this system, five full-scale specimens were cast including two bending specimens for investigating bending capacity and cracking distribution as well as three shear specimens used to study the shear capacity, cracking distribution, and concrete casting effect on the shear behavior. Moreover, the effects of the steel cage rods were studied on the bending and shear capacity. It was found that while both solid and biaxial voided specimens exhibited almost similar failure mode, both the bending and shear capacity of biaxial voided specimens were affected by the steel cages. In contrast, the voided specimens exhibited a significantly lower shear capacity than the solid ones while the different concrete casting methods had no effects on the capacity and behavior of biaxial voided specimens. Finally, a comparison was made with experimental results and ACI 318-14, MC 2010, and Eurocode 2 recommendations. © 2019 fib. International Federation for Structural Concrete
Structures (23520124) 24pp. 791-803
In this paper, a numerical and analytical study was carried out in order to develop a new initial stiffness equation for thin-walled steel plate in bearing component. In this regard, effects of different design variables and curling occurrence on initial stiffness of this component were investigated. A set of parametric studies was performed on experimentally validated finite element models restraining curling occurrence to investigate the effect of geometrical parameters on initial stiffness of thin-walled steel plates. These design parameters included plate thickness, end distance, and edge distance and number of bolts. Effect of curling occurrence on initial stiffness was also considered using an analytical study. Finally, a new initial stiffness equation was proposed and compared with Eurocode3 design standard equation of hot-rolled steel plates. This new equation can be used in component-based modeling to calculate initial stiffness of thin-walled steel plate in bearing component. The outputs obtained by new equation showed better agreement with validated finite element results than those of old equation. © 2020 Institution of Structural Engineers
Structures (23520124) 25pp. 256-267
K-shaped bracing is one of the lateral load resisting systems used in Cold-Formed Steel structures. Recently, some researches have been conducted to obtain further information about the seismic performance of the CFS using K-shaped bracings under monotonic and cyclic loads. In this research, the seismic performance factor of this structural system is under study. To determine the proper value of this factor, a non-linear finite element model of this structural system is developed using OpenSees software, and the cyclic behavior of this model is verified with previous experimental results. Several structures designed in accordance with Iranian seismic code were modeled using the verified model, and incremental dynamic analysis is performed on these structures. The analysis was performed according to FEMA P695 procedures using a ground motion set consisting of 22 earthquake records. Eventually, the studies showed that the seismic performance factor of 2 is a proper value for the cold-formed steel frames with K-shaped bracings. Also, as another result, the increase in the number of stories and the site's seismic risk will increase the structure's collapse probability. Furthermore, the height limitation proposed by seismic codes for this system seems to be somewhat conservative and it can be concluded that usage of the K-shaped bracing system is possible for taller structures in zones with low seismicity risk. Finally, it can be concluded that the K-shaped bracings might not have a suitable performance due to ductility issues. © 2020 Institution of Structural Engineers
Thin-Walled Structures (02638231) 150
Load bearing cold-formed steel clip angles are commonly used in various connections, subjected to different loading conditions. This numerical parametric study was performed in order to investigate the effect of various parameters on pull-through strength of fasteners on the anchored leg of cold-formed steel clip angles. In this regard, a finite element analysis is conducted, using ABAQUS program, to model the specimens subjected to tension forces. The finite element modeling is verified, using the existing tested clip angles and the ability of the validated finite element models in predicting the pull-through strength of other clip angle cases is evaluated, by comparing the obtained results with the experimental results. This parametric study provides a detailed information on the effect of any effective parameters, such as clip angle geometry, basic mechanical properties, and screw fastener head or washer sizes on the pull-through failures of bearing clip angles. According to the results, although the effects of parameters, such as screw fastener head or washer sizes and mechanical properties, on the pull-through strength are significant, the effect of clip angle geometry can be neglected. Finally, a suitable design equation is proposed to calculate the pull-through failure of load bearing clip angles. Moreover, a new equation is presented to calculate elastic stiffness of cold-formed steel clip angles, using a simple analytical model. The results obtained from this equation are in a proper agreement with the initial slope of force-displacement curves. © 2020 Elsevier Ltd
Structures (23520124) 27pp. 1075-1085
The numerous advantages of solid slabs, including adequate rigidity, appropriate fire resistance, and sound insulation, have further extended the system's applications. The main disadvantage of this system is, however, its extreme weight, especially in long spans. Since concrete is not involved in bearing in the tensile zone, its removal can lower the weight without affecting the load bearing of the slab. In a number of systems, named biaxial voided slabs, ellipsoidal or spherical sacrificial plastic balls are used to create voids within the concrete. As this system has just been introduced, considerable uncertainties have been raised about one-way and two-way shear behaviors of the system. Accordingly, four full-scale specimens were built in order to investigate these behaviors. Two one-way and two two-way full-scale shear specimens with dimensions of 3500 × 1200 × 200 mm and 2300 × 2300 × 200 mm (length × width × height) were constructed, respectively. These specimens were used to compare the shear capacity, cracking distribution, and deflection in solid and biaxial voided specimens. Also, the effect of vertical rods of steel cages on the shear behavior was investigated. The results show the steel cages clearly contributed to shear bearing; and although the shear capacity of voided specimens was less than solid ones, the failure mode of all specimens was shear. Finally, a new method was proposed to predict the ratio of shear capacity of biaxial voided slabs to solid slabs. Hence, the proposed method can predict the ratio of biaxial voided capacity to solid slab capacity with an adequate precision. © 2020 Institution of Structural Engineers
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
International Journal Of Civil Engineering (17350522) 16(6)pp. 671-680
This study introduces a mathematical model to represent the hysteresis behavior of structural systems. Compared with some of the analytical models currently in use, this model (which considers different structural phenomena, including pinching, stiffness degradation, strength deterioration, and sliding) yields more precise responses. This model is based on Mostaghel’s well-known model, although some essential modifications and sliding effects are also considered. The model is developed based on a simple single-degree-of-freedom multi-linear mechanical system and on the development of partial differential equations. The proposed model includes the basic characteristics of the hysteresis cycles that can be easily measured through experimental tests. To demonstrate the degrading phenomena of the hysteresis behavior of the structures, several examples of different actual structural systems are presented, to show that the proposed analytical model can provide realistic descriptions of the structural hysteretic performances. In addition, comparisons between the outputs of this model and some hysteretic curves of other models are presented to show the high capability and accuracy of the proposed model. © 2017, Iran University of Science and Technology.
Scientia Iranica (23453605) 25(3A)pp. 1015-1024
Since the proper use of construction machinery in infrastructure projects is important, it is essential to employ an optimum selection of machinery in these projects. Advanced Programmatic Risk Analysis and Management model (APRAM) is one of the recently developed methods that can be used for risk analysis and management purposes considering schedule, cost, and quality, simultaneously. In this paper, the APRAM method is first introduced and then modified in order to consider environmental risks. This method can consider potential risks that might occur over the entire life cycle of the project, and can be employed as an efficient decision-support tool for construction managers selecting machinery for an infrastructure project where various alternatives might be technically feasible. A case study of 3 possible combinations of excavation machines is then discussed. All project risks related to cost, time, quality, and environment are identified considering the capital costs which should be spent on each combination. Finally, some graphs, which are derived from the method, are taken into account in order to decrease the risks of each combination and optimize the selection of excavating machinery. The outcomes highlight the efficiency of the APRAM model for the optimal selection of machinery in construction projects. © 2018 Sharif University of Technology. All rights reserved.
Advanced Steel Construction (1816112X) 14(4)pp. 562-588
An experimental study on the behavior of cold formed steel (CFS) strap bracing connections is presented in this paper. 75 cold-formed steel strap bracing connections were examined. The connections maximum load capacity and the load-deformation behavior as well as the failure modes of the connections are investigated. The strap bracing connections included 0.55mm and 0.75mm cold-formed G550 steel and four different types of steel strap material. The connections behaviors are discussed and the design capacities calculated from different CFS design standards are compared to the experimental results of the connections. The results show that generally the monotonic tested connections capacities are lower than the cyclic capacities. Also, it is found that although the design provisions predict some of the behaviours of screwed connections, they are not fully suited to accurately predicting the ultimate behaviour of the strap bracing connections. Therefore, the recommended capacities for the strap bracing connections are based on the experimental results. © 2018, Hong Kong Institute of Steel Construction. All rights reserved.
Journal of Construction Engineering and Management (19437862) 144(2)
Maintenance cost optimization and performance prediction of bridge structures have become important challenges in bridge management systems. The performance of bridge structures should be carefully monitored, especially in severe climatic conditions. The objective of this study is to develop a rational method that predicts the most cost-effective intervention schedule for bridges, where the structural safety is maintained with the minimum possible lifecycle cost. The framework functions through (1) a central database that contains the asset inventory along with the maintenance actions list, (2) a biquadratic system reliability-based deterioration model, (3) an intervention effect model that simulates the effect of undertaking various intervention scenarios on the bridge superstructure performance, (4) a financial model that computes the lifecycle costs throughout the planning horizon, and (5) an optimization model that utilizes a genetic algorithms engine to compare the different intervention scenarios and selects the most cost-effective one. This method is applied to a simply supported bridge superstructure case study, designed in accordance with Canadian highway bridge design standards. The results indicate that undertaking less costly minor repair actions may considerably reduce the lifecycle costs as a result of decreasing the number of costly major interventions. The optimum scenario resulted in an equivalent uniform annual cost of US8,277 per year, which shows 4.5 times cost saving as compared with the conventional scenario where only major repairs are performed. This innovative combination of reliability analysis, nonlinear finite-element modeling, and genetic algorithms optimization supports asset managers in long-term planning and ensures undertaking rational and objective decisions. © 2017 American Society of Civil Engineers.
International Journal Of Civil Engineering (17350522) 16(11)pp. 1643-1653
In this paper, the seismic performance of cold formed steel shear walls sheathed by fiber cement boards (FCB) is investigated. Of particular interest is the seismic response modification factor of FCB shear walls. Nonlinear incremental dynamic analyses of multi-story cold formed steel framed structures were carried out following an approach adopted by FEMA-P695 on the description of building seismic behavior. Different scaled earthquake records in three different earthquake prone regions located on low, medium and high seismic risk zones in Iran were taken into account. One, two and three story CFS archetype buildings were analyzed using models created in OpenSees software to predict structural performance of the buildings. Nonlinear dynamic time history analyses were carried out employing OpenSees software utilizing 2D models of a FCB braced wall tower. A stick model was created whose behavior was fitted to the lateral resistance versus deformation of each story that braced elements in the model. The elements were defined via material Pinching4 to construct a uniaxial material exhibiting pinched load-deformation response and demonstrate degradation under cyclic loading. The results show that most relevant codes which suggest the value of seismic response modification factor equal to 2 for cold formed steel shear walls sheathed by FCB are acceptable only for up to three story buildings in low seismic risk zone, up to two story in medium seismic zone and one story in high seismic risk zone. © 2018, Iran University of Science and Technology.
Journal of Constructional Steel Research (0143974X) 147pp. 53-61
This paper presents a detailed investigation of the lateral characteristics of cold-formed steel truss structures used in electric power substations. Five full-scale specimens were tested, and their responses were recorded under monotonic and cyclic loading regimes. Of particular interest were the specimens' maximum lateral load capacities and deformation behaviours. A rational estimation of the seismic response modification factor, R, of the truss structures is also provided. In addition, different types of stiffened sections were employed in order to examine the impact of the presence of stiffeners and lips on seismic behaviour, as well as on the lateral resistance of the structure. Detailed comparisons between relevant code methods, finite element modelling and an experimental study were then conducted to suggest an appropriate value for the R factor. A financial evaluation was also performed, to highlight the advantages of employing cold-formed steel trusses in the electric power substation industry. The results show that the cold-formed steel structural system is a reasonable alternative to the currently used hot-rolled steel structures, and that its use decreases the cost of the structures by almost 50%. © 2017 Elsevier Ltd
Archives of Civil and Mechanical Engineering (16449665) 18(3)pp. 863-876
This paper presents an experimental study on structural performance of concrete poles used in electric power distribution network (EPDN). Three full scale 12-m concrete poles were tested; and a numerical study on a 7-span distribution line was also carried out in order to investigate lateral behavior of the network under severe weather conditions, as it is believed EPDN has a vital role on sustainability of power transmission from the power planet to the consumers which might be hundreds kilometers far away. One of the main issues in EPDN is concrete poles’ collapse under simultaneous wind and ice loads in some unreachable snow covered areas. However, the results show that the prescribed loading regimes by standards do not induce any damage into the distribution network nevertheless some unforeseen loads like gust wind load in heavy weather conditions cause the poles’ failure. Therefore, a non-linear pushover analysis was carried out to find out the weakest part of the distribution network; and finally some suggestions for increasing the EPDN's sustainability are made. © 2018 Politechnika Wrocławska
Australian Journal of Structural Engineering (13287982) 19(3)pp. 222-233
Cold-formed steel shear walls are commonly used in the housing industry. Generally, the wall stud connections play an important role in the seismic performance of these structures as they should be capable to dissipate the induced energy via the plastic deformation of the shear wall components. The riveted connection between the studs and the tracks is one of the most important components that dictates the behaviour and strength of such panels. In this paper, details of an experimental study on the behaviour and strength of two types of rivets which are applied in riveted wall stud connections under tension and compression monotonic loading are presented. Twenty-four full-scale specimens were taken into account. Two dominant failure modes are identified: rivet head failure and buckling failure of the section away from the connection in tension and compression tests, respectively. The results show that the second rivet type (type O) possesses a higher capacity in both tension and compression; and therefore is recommended to use by CFS designers. In addition, the design capacities of the connections were calculated based on some design codes and compared with the experimental results. It is shown that the codes are too conservative and can be improved considerably. © 2018, © 2018 Engineers Australia.
Australian Journal of Structural Engineering (13287982) 18(2)pp. 113-124
Non-linear finite element analyses were carried out to evaluate the seismic characteristics of steel-sheathed cold-formed steel (CFS) shear walls using the finite element analysis software ANSYS. The numerical models presented here were verified based on experimental tests considering different structural characteristics including: material non-linearity, geometric imperfection residual stresses, connection non-linearity and perforations. A total of 15 models with various structural characteristics were investigated. Based on the results, it was concluded that the lateral performances of the walls are significantly affected by structural characteristics of the walls including: the thickness of frame members and sheathing plates, edge screw spacing stud spacing and height and span width of the frame. Investigating the research outcomes shows that American Iron and Steel Institute (AISI) standard, considered as the most comprehensive design code amongst the available CFS provisions, only takes into account the wall’s aspect ratio and the fastener spacing in order to prescribe the nominal shear strength of the walls, while the effects of the other structural characteristics are neglected. This brings to a conclusion that the codes and standards, including AISI, should be revised considering various ranges of structural parameters which are being employed in currently-in-use steel-sheathed shear walls in housing industry worldwide. © 2017 Engineers Australia.
Canadian Journal of Civil Engineering (03151468) 43(12)pp. 1034-1043
This study presents a methodology that utilizes a new combination of two compressed damage indices as input data of an artificial neural network (ANN) ensemble to detect multi-damages in the braces of cold formed steel shear walls. To identify an efficient input data for ANN, first, three main groups of damage indices are considered: modal parameter-based damage indices; frequency response functions (FRFs)-based damage indices and time series-based damage indices. Furthermore, principal component analysis (PCA) technique is applied to reduce the dimensions of FRFs and time series-based input pattern. By a sensitivity study, two suitable damage indices of PCA-compressed time series data and PCA-compressed FRFs are identified and then combined to produce a new efficient input data for a hierarchy of ANN ensembles. The numerical results show that the ANN ensemble-based damage detection approach with the proposed collection of two damage indices is effective and reliable. © 2016, Canadian Science Publishing. All rights reserved.
Journal of Constructional Steel Research (0143974X) 127pp. 176-186
This paper presents an experimental study on the behaviour of cold formed steel truss connections. Eighteen full scale cold-formed steel truss connections were tested. Of particular interests are the specimens maximum load capacity and the load-deformation behaviour. The study also looks at the failure modes of the connections. The behaviours exhibited by the connections are discussed and the design capacities calculated from the current CFS design standards are compared to the experimental results of the connections. This study investigates the main factors contributing to the ductile response of the CFS truss connections in order to suggest recommendations for connection designs, and improvements so that the connections respond plastically with a significant drift and without any risk of brittle failure. Also, a number of alternative fasteners are chosen and investigated for comparison with those that are currently specified for trusses' connections. © 2016 Elsevier Ltd
Advances in Structural Engineering (13694332) 18(11)pp. 1819-1829
This paper presents a non-linear finite element analyses in order to investigate the seismic performances of steel sheathed cold formed shear walls. The numerical models presented here are verified based on experimental tests considering different structural characteristics including: material nonlinearity, geometrical imperfection, residual stresses and perforations. A comparison between the numerical simulations and the test results shows a good agreement proves that the finite element analysis can be used effectively to predict the ultimate capacity of steel sheathed CFS shear panels. A total of 15 models with different structural parameters are investigated. Of particular interests were the specimens' maximum lateral load capacity and deformation behaviour in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the seismic characteristics of steel sheathed CFS shear walls and the corresponding dimensions and configuration.
Journal of Constructional Steel Research (0143974X) 107pp. 1-11
This paper presents an experimental study of cold formed steel frames sheathed by fibre-cement boards (FCB) under cyclic lateral loading. Four full scale fibre-cement shear walls were tested. Of particular interests are the specimens maximum lateral load capacity and the load-deformation behaviour as well as a rational estimation of the seismic response modification factor, R factor. The study also looks at the failure modes of the systems and investigates the main factors contributing to the ductile response of the CFS shear walls in order to suggest improvements so that the FCB sheathed walls respond plastically with a significant drift and without any risk of brittle failure such as connection failure or fibre-cement board fracture. Both double-sided and single-sided FCB shear panels as well as a new proposed configuration were studied. The study shows that while the overall performance of the currently in-use FCB sheathed lateral resistant system under cyclic loads is not satisfactory with a small average R factor of 2.5, the proposed FCB lateral resistant system can be considered as a reliable system with a much higher value of R factor of 5. © 2015 Elsevier Ltd. All rights reserved.
Advances in Structural Engineering (13694332) 16(2)pp. 245-257
This paper presents a detailed investigation of the lateral performance of X-strap braced cold-formed steel shear walls and their response modification factor, R. Four full-scale 2.4 × 2.4 m specimens with different configurations were tested, and their responses recorded under a standard cyclic loading regime. Of particular interest were the specimens' maximum lateral load capacity and deformation behaviour as well as a rational estimation of the seismic response modification factor. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of the cold formed steel (CFS) shear walls in order to suggest improvements so that the shear steel walls respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling. The walls tested have different number of strap elements with different angles, and brackets. The study shows that the performance of this kind of CFS lateral resistant system under cyclic loads is satisfactory; and can be considered reliable. A discussion on the calculated response factors in comparison to those suggested in the relevant codes of practice is also presented.
Journal of Construction Engineering and Management (19437862) 139(1)pp. 51-59
The advanced programmatic risk analysis and management model (APRAM) is one of the recently developed methods that can be used for risk analysis and management purposes considering schedule, cost, and quality risks simultaneously. However, this model considers those failure risks that occur only over the design and construction phases of a project's life cycle. While it can be sufficient for some projects for which the required cost during the operating life is much less than the budget required over the construction period, it should be modified in relation to infrastructure projects because the associated costs during the operating life cycle are significant. In this paper, a modified APRAM is proposed, which can consider potential risks that might occur over the entire life cycle of the project, including technical and managerial failure risks. Therefore, the modified model can be used as an efficient decision-support tool for construction managers in the housing industry in which various alternatives might be technically available. The modified method is demonstrated by using a real building project, and this demonstration shows that it can be employed efficiently by construction managers. The Delphi method was applied in order to figure out the failure events and their associated probabilities. The results show that although the initial cost of a cold-formed steel structural system is higher than a conventional construction system, the former's failure cost is much lower than the latter's. © 2013 American Society of Civil Engineers.
Thin-Walled Structures (02638231) 60pp. 229-238
This paper presents a non-linear finite element analyses in order to optimize the seismic characteristics of strap-braced cold formed steel shear walls enhanced with brackets in the four interior corners of the wall. The numerical models presented here are verified based on experimental tests considering different structural characteristics including: material nonlinearity, geometrical imperfection, residual stresses and perforations. A comparison between the numerical simulations and the test results shows a good agreement proves that the finite element analysis can be used effectively to predict the ultimate capacity of strap-braced CFS shear panels. A total of 16 models with different variants of bracket length are investigated. Of particular interests were the specimens' maximum lateral load capacity and deformation behavior in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the optimum seismic characteristics of strap-braced CFS shear walls and the corresponding dimensions and configuration. © 2012 Elsevier Ltd.
Thin-Walled Structures (02638231) 51pp. 64-75
Experimental investigations were conducted to evaluate the lateral seismic characteristics of light-weight knee-braced cold-formed steel structures. In all, four full-scale 2.4×2.4 m2 specimens with different configurations were tested under a standard cyclic loading regime. This paper focuses on the specimens maximum lateral load capacity and deformation behavior and provides a rational estimate of the seismic response modification factor, R, of knee-braced walls. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of CFS walls. That is in order to suggest improvements so that the shear steel walls respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling. A discussion on the calculated response factors in comparison to those suggested in the relevant codes of practice is also presented. © 2011 Elsevier Ltd.
Journal of Engineering Mechanics - ASCE (07339399) 138(11)pp. 1381-1387
A differential model is presented to show the behavior of general hysteretic systems considering all relevant structural characteristics, including pinching, stiffness degradation, load deterioration, and sliding. This model is generated based on Mostaghel's model, which already includes all of these characteristics except sliding. Thus, an attempt is made to develop the model to also cover sliding. A single-degreeof- freedom system is used to develop the hysteretic model by writing a system of ordinary differential equations. The proposed model captures the key features of the hysteretic cycles of any structure using some measurable system parameters through tests. A few examples of bilinear systems excited by harmonic loads are provided to show that the descriptions of the force-displacement performance of general hysteretic systems are realistic. © 2012 American Society of Civil Engineers.
Journal of Constructional Steel Research (0143974X) 77pp. 23-31
Detailed investigation of the lateral performance of K-braced cold-formed steel structures and their response modification coefficients, R factor, are presented in this paper. A total of 12 full-scale 2.4 × 2.4 m specimens of different configurations are considered, and the responses investigated under a standard cyclic loading regime. Of particular interest are the specimens' maximum lateral load capacity and deformation behavior as well as a rational estimation of the seismic response modification factor. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of the CFS walls in order to suggest improvements so that the shear steel walls respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling. A discussion on the calculated response factors in comparison to those suggested in the relevant codes of practice is also presented. Crown Copyright © 2012 Published by Elsevier Ltd. All rights reserved.
In this paper the performance of steel sheathed cold-formed steel shear walls is evaluated by testing seven full scale walls under cyclic and monotonic loading. Of particular interest are the specimens' maximum lateral load capacity and deformation behaviour. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of the CFS walls in order to suggest improvements so that the steel shear walls respond plastically with a significant drift and without any risk of brittle failure, such as failure in the connections. The walls tested are of different configurations possessing different structural characteristics including: stud's thickness, width of the walls, and loading pattern. The test outcomes show that the common failure mode of the walls is an undesirable anchorage failure. Considering that there are very few criteria in the code which clarify the design of anchorage for steel sheathed systems, the study signifies the need and the importance of further research in this area.
Thin-Walled Structures (02638231) 49(12)pp. 1517-1525
Non-linear finite element analyses were carried out to evaluate and optimize the seismic characteristics of knee-braced cold formed steel shear walls using software ANSYS. Different structural characteristics including: material nonlinearity, geometric imperfection, residual stresses and perforations are taken into account. The numerical models were verified based on experimental tests. Agreement of the numerical simulations and the test results showed that finite element analysis can be used effectively to predict the ultimate capacity of knee-braced CFS shear panels. A total of 12 models with a various ranges of knee-elements lengths were investigated. Of particular interests were the specimens maximum lateral load capacity and deformation behavior in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the optimum seismic characteristics of knee-braced CFS shear walls and the corresponding dimensions and configuration. © 2011 Published by Elsevier Ltd.
Light weight Steel Framed structures currently in use in Australia, are normally braced using face mounted thin straps, cross braces that are of the same shape as studs, or compressed cement boards screwed to the face of the walls. While these are found adequate in low seismic regions of Australia, an investigation into the earthquake resistance properties of LSF have led authors to investigate alternative bracing types that may present a more favourable ductility. Knee braces that are specially designed for this purpose are introduced in the paper and studied in a specially designed testing rig. The tests are on four full scale walls of 2.4 m x 2.4 m and are of a cyclic nature. Of particular interest are the specimens maximum lateral load capacity and the load-deformation behaviour. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of the LSF walls in order to suggest improvements so that the shear steel walls respond plastically with a significant drift and without any risk of brittle failure such as connection failure or stud buckling. The walls tested have different length of Knee-elements with or without brackets which have same length of Knee-elements. The study shows that although the performance of this kind of LSF lateral resistant system under cyclic loads is satisfactory, its shear strength is significantly lower than those LSF lateral resistant systems which are currently in use in Australia. In regions with medium to high seismic activity, the use of these braces would not be sufficient purely as to the lateral resistance.
