Analysis of light gage steel shear diaphragms

A method is presented for the elastic analysis of shear diaphragms composed of standard light gage steel panels. A finite element approach is adopted, in which the mechanical properties of the diaphragm components are incorporated in an analytical model of the assemblage, using the direct stiffness method of matrix structural analysis. Results are compared against experimental values

Non-linear finite element analysis of light gage steel shear diaphragms

SUMMARY Shear diaphragm action of properly designed light gage steel panels used for floors, roofs, and walls in steel buildings increase the stiffness and strength of such buildings. Considerable savings in weight and cost can be realized if full account of this action is taken in design. To make good use of the diaphragm action, detailed knowledge on diaphragm response to loading is essential. An efficient computer program has been prepared to analyze light gage steel shear diaphragm behavior in the linear and nonlinear ranges of response, up to collapse. The program uses figinite element concepts for analysis, and has routines to deal with the beams, purlins, panels, and connections. Beams and purlins are modeled by conventional flexural elements with three degrees of freedom at each node. Panels are represented by rectangular orthotropic plane-stress plate elements. Two different models for corrugated panels are proposed. One model makes use of an average effective shear modulus along the entire panel length, while in the other two different shear moduli are attributed to the end and central regions of the panel. The connections are modeled by spring elements, and, according to location, several different models utilizing these spring elements are used. The non-linear analysis is based on experimental evidence that, in general, the connections are the only important source of non-linearity up to collapse. For this reason, only the connection behavior is represented by a non-linear function. All other components of the diaphragm assembly are assumed to remain elastic throughout the loading range. The connectors can be either welds, used for heavily-stressed shear diaphragms, or screw fasteners, used for more lightly loaded installations. In both cases, the non-linear force-displacement relation used for the connection is a multi-linear approximation of the load-displacement curve obtained from a shear test of the connection and the small region around it. The program uses a frontal routine for the solution of the stiffness equations. The non-linear analysis is done by the residual force method, which utilizes the original elastic stiffnexx matrix at every stage of the analysis, and which arrives at the correct solution for each load increment through an iterative procedure. A modified Aitken accelerator is used to speed the convergence. In order to reduce the task of preparing input data, a mesh generator has been written. This mesh generator requires only simple basic data for the generation of the complete finite element mesh, for most practical diaphragms. The computer program has been employed to analyze diaphragms for which test results are available. Both linear analyses up to the elastic limit, and non-linear analyses up to and beyond the elastic limit have been conducted. For three of the four diaphragms analyzed, very good agreement between numerical and experimental results have been obtained. For a standard corrugated diaphragm, numerical results in the non-linear range show a more flexible behavior than in test. Detailed analysis indicates that this is most probably due to unavailability of correct connection test data for use in analysis. The force distribution in the diaphragms, overall diaphragm deflections, and seam slips are found at different ranges of response. As a result of the analyses, it is confirmed that connection non-linearity is the most important factor in the nonlinear range of diaphragm response, differences in shear modulus being only of secondary importance. It is concluded that the computer program developed is an efficient and dependable tool for research and design

Analysis of light gage steel shear diaphragms

INTRODUCTION: It has long been recognized by structural engineers, that light gage steel cladding floor and roof decking systems have a considerable stiffening and strengthening effect on building frameworks. The beneficial contribution of these diaphragm systems is most pronounced when the structure as a whole is subjected to loads which result in an in-plane shear action of the cladding. This occurs, for example, when the rigidity of a floor or roof diaphragm acting as a membrane is utilized to transmit lateral forces to stiff end walls. Another example of diaphragm action is found in pitched roof portal sheds under vertical and lateral loads. In such cases the membrane strength and rigidity of the cladding can be used to restrict the tendency of intermediate frames to sway, by transfering the load to end walls and resulting in substantial economy in the design of the frames. Specific utilization of the in-plane shear strength and stiffness of panelling was suggested more than 18 years ago, but unless this effect could be calculated in advance no practical use could be made. In order to take this contribution to stiffness and strength into account in engineering design, it was necessary to develop means for predicting the effective shear rigidity and ultimate strength in shear of the steel panel diaphragm. Because of the complexity of such diaphragm systems, up to now, engineers have relied upon tests of full-scale-panel assemblies, in which the performance of specific combinations of panels, marginal framing members and connections have been studied on a strictly ad hoc basis. While much has been learned using this approach, and valuable design information was obtained, no rational theory to describe and predict structural behavior has resulted. On the other hand, testing of large full scale diaphragm installations is expensive and time consuming, and tests results are applicable only to identical assembly using the same panels as tested, with directly equivalent fastening systems. The need for a general method of analysis is clear

Analysis of light gage steel shear diaphragms

INTRODUCTION It has long been recognized by structural engineers, that light gage steel cladding floor and roof decking systems have a considerable stiffening and strengthening effect on building frameworks. The beneficial contribution of these diaphragm systems is most pronounced when the structure as a whole is subjected to loads which result in an in-plane shear action of the cladding. This occurs, for example, when the rigidity of a floor or roof diaphragm acting as a membrane is utilized to transmit lateral forces to stiff end walls. Another example of diaphragm action is found in pitched roof portal sheds under vertical and lateral loads. In such cases the membrane strength and rigidity of the cladding can be used to restrict the tendency of intermediate frames to sway, by transfering the load to end walls and resulting in substantial economy in the design of the frames. Specific utilization of the in-plane shear strength and stiffness of panelling was suggested more than 18 years ago, but unless this effect could be calculated in advance no practical use could be made. In order to take this contribution to stiffness and strength into account in engineering design, it was necessary to develop means for predicting the effective shear rigidity and ultimate strength in shear of the steel panel diaphragm. Because of the complexity of such diaphragm systems, up to now, engineers have relied upon tests of full-scale-panel assemblies, in which the performance of specific combinations of panels, marginal framing members and connections have been studied on a strictly ad hoc basis. While much has been learned using this approach, and valuable design information was obtained, no rational theory to describe and predict structural behavior has resulted. On the other hand, testing of large full scale diaphragm installations is expensive and time consuming, and tests results are applicable only to identical assembly using the same panels as tested, with directly equivalent fastening systems. The need for a general method of analysis is clear

Analysis of light gage steel shear diaphragms

INTRODUCTION: It has long been recognized by structural engineers, that light gage steel cladding floor and roof decking systems have a considerable stiffening and strengthening effect on building frameworks. The beneficial contribution of these diaphragm systems is most pronounced when the structure as a whole is subjected to loads which result in an in-plane shear action of the cladding. This occurs, for example, when the rigidity of a floor or roof diaphragm acting as a membrane is utilized to transmit lateral forces to stiff end walls. Another example of diaphragm action is found in pitched roof portal sheds under vertical and lateral loads. In such cases the membrane strength and rigidity of the cladding can be used to restrict the tendency of intermediate frames to sway, by transfering the load to end walls and resulting in substantial economy in the design of the frames. Specific utilization of the in-plane shear strength and stiffness of panelling was suggested more than 18 years ago, but unless this effect could be calculated in advance no practical use could be made. In order to take this contribution to stiffness and strength into account in engineering design, it was necessary to develop means for predicting the effective shear rigidity and ultimate strength in shear of the steel panel diaphragm. Because of the complexity of such diaphragm systems, up to now, engineers have relied upon tests of full-scale-panel assemblies, in which the performance of specific combinations of panels, marginal framing members and connections have been studied on a strictly ad hoc basis. While much has been learned using this approach, and valuable design information was obtained, no rational theory to describe and predict structural behavior has resulted. On the other hand, testing of large full scale diaphragm installations is expensive and time consuming, and tests results are applicable only to identical assembly using the same panels as tested, with directly equivalent fastening systems. The need for a general method of analysis is clear

Analysis of multistory frames with light gauge steel panel infills

PREFACE This report was originally presented as a thesis to the Faculty of the Graduate School of Cornell University in partial fulfillment of the requirements for the degree of Doctor of Philosophy, conferred in August 1972. The author wishes to thank Professor Arthur H. Nilson, Project Director, and Professor Robert G. Sexsmith, Principal Investigator, for the help and guidance that made this work possible. This investigation was supported by the American Iron and Steel Institute