Effective stiffness of non-rectangular reinforced concrete structural walls and engineering beam-truss models in seismic design and analysis

When reinforced concrete walls are subjected to severe earthquakes, damage and cracking will appear throughout the structure. As a consequence, this will result in a reduction of the walls stiffness. Most of design codes propose to apply a reduction factor between 0.35 and 0.5 on the uncracked wall stiffness for evaluating the effective stiffness. These reduction factors were based on studies made on rectangular cross-section walls. However, design codes still allow using these factors for assessing the effective stiffness of non-rectangular cross-section walls. The present work aims at verifying if the reduction factors proposed by design codes are overestimated or underestimated when dealing with non-rectangular cross-section walls. For this purpose, 14 different cross-section shapes of walls will be numerically modeled by means of beam-truss model. The reduction factors of each wall will then be derived from the numerical results by applying different procedures. Finally, the numerically obtained factors can be compared to the ones proposed by design codes.