Experimental Response of RC Walls With Openings Under Cyclic Loading

Abstract eng:
The Mw 8.8 earthquake in 2010 in Chile damaged several reinforced concrete (RC) structures, where many walls elements failed. This type of element is the preferred option used in residential buildings. According to the Chilean design practice, these walls usually have complex geometry and discontinuities in height, mainly in the first story or the first underground floor where architectural requirements impose openings at the base or present hanging walls. Nowadays, the Chilean codes do not provide special provisions for any kind of discontinuities. This paper shows the results of an experimental study of walls specimens with an opening at the base, where inelastic deformation is expected. The main objective is giving design recommendations for modeling and detailing. In particular, information will be provided regarding evaluation of the maximum compressive strain, which is used currently for detailing using a displacement-based procedure for continuous (non-perforated) walls. Four walls are constructed with the same dimensions (2.65 m height, 0.9 m large and 0.15 m thickness) and different shapes of the opening (15% and 30% of the length, and 11% and 22% of the wall height) –always at the base- and tested under constant axial load of about 0.07f’cAg, while cyclic lateral pseudo-static loading is applied at the top of the wall. The walls were made using typical materials in the common practice (concrete strength of 25MPa and steel yield stress of 420 MPa). One of the specimens presents slab elements at the base to be able to capture their influence in the wall response. The results indicate that the lateral strength is similar in all cases, which implies that flexural yielding is achieved for all specimens that presented similar longitudinal reinforcement. However, displacement capacity varies with opening size. All specimens with openings have less ductility, where the specimen with wider and taller opening reduced its displacement capacity by about 30% compared to the continuous wall. The width of the opening was more influential than the height in the displacement capacity. The slab presented a beneficial effect in the displacement capacity.

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