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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.

ABSTRACTIn 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.

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.

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.

ABSTRACTCold-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.

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.

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.

AbstractNon-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.

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.

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.