Modified Softened strut and tie model for predicting shear strength of Squat walls with different aspect ratio openings

Abstract

Reinforced concrete squat wall is the prime lateral resisting structure in middle to low rise buildings which experience shear forces. In majority cases, due to occupant needs, ventilation and architectural requirements, openings needs to be provided in these squat walls which can have different shape/aspect ratio as per type and architectural look of buildings. This research considered and looked in to the problem of finding out, which aspect ratio opening is best to worst if provided in squat walls. The approach adopted in this research is an analytical approach, which is modified softened STM modeling in order to know the peak shear strength of various aspect ratio openings in squat wall. The novelty of proposed model is that, the said model incorporates the softening effect by considering a uniform triangular distribution of transverse stresses on struts as a result of tie linked with it and consequently producing a shear strength formula which will produce accurate results for each change in aspect ratio of openings in a wall which was verified by two methods. First experimentally, for that 1:2(B/H) aspect ratio opening squat wall was casted and tested under quasi static lateral loadings and the results were accurate with analytical ones upto 93.32 %. Secondly FEM model of 2:1(B/H) aspect ratio opening squat wall was analyzed in Abaqus software, and the results were accurate upto 93.89 % with analytical results. The validation proved the proposed model valid and accurate for any aspect ratio opening in squat wall. This research will provide benefit to the designers and architects for choosing best shape/aspect ratio of openings in lateral resisting reinforced squat walls.