Flange effects on seismic performance of reinforced concrete squat walls with irregular or regular openings

• Effects of irregular or regular openings on seismic performance of RC walls.
• Test results of two series of RC walls with or without flanges were presented.
• Reliability of existing strut-and-tie model to predict the strength of walls was evaluated.
• Design suggestions are given to improve existing strut-and-tie models.

A series of six one-third scaled reinforced concrete (RC) structural walls with irregular or regular openings were tested to investigate the effects of size, arrangement, and irregularities of the openings on the seismic behaviour of RC walls. The crack pattern development, failure mechanism, and hysteretic responses of tested specimens are presented. The stiffness deterioration and equivalent hysteretic damping (energy absorption capacity) of tested specimens are compared and discussed. Another series of six rectangular walls with openings, which are tested by Yanez et al., are also introduced for quantification of the flange effects on seismic behaviour of RC walls with openings. It is found that flanges could significantly increase ultimate strength but reduce deformation capacities. Moreover, flanges may change the failure mode of rectangular walls from ductile flexural failure to brittle sliding shear failure. Flanges may aggravate the concrete crushing, spalling as well as buckling and fracture of vertical reinforcements. However, concrete crushing and rebar fracture is mainly concentrated in the flanges.