Experimental assessment of damping factors in concrete housing walls

thin walls having low concrete strength, minimum web steel ratios and web shear reinforcement made of welded wire meshes are commonly used in low-rise concrete housing. the damping factor commonly used for code-based dynamic analysis was evaluated based on seismic response measured during shake table tests of six low-rise concrete walls. the variables studied were the type of concrete (normal and lightweight), the web steel shear ratio (0.125% and 0.25%), the type of web shear reinforcement (deformed bars and welded wire meshes) and the effect of openings (doors and windows). dynamic properties were evaluated considering the advantages of frequency-domain system identification, using the dynamic transfer function amplitude fitting method. the effect of failure mode on damping factor is discussed. an equation for estimating damping associated with a particular vibration period value is also proposed. it was observed that a 5% damping factor (assumed for dynamic analysis of concrete housing in the range of lineal elastic behaviour) was consistent with the values measured here.