Seismic behaviour of assembled monolithic concrete coupling beams through tests of two-story coupled shear walls

Abstract

In the prefabricated concrete shear wall structure, in order to further improve the construction efficiency, the underwindow wall and the wall pier on both sides are often prefabricated as a whole. Therefore, the assemble integral coupling beam is composed of a prefabricated under-window wall, a cast-in-place strip and a prefabricated upper-window wall. The failure mode of this type assemble integral coupling beam under cyclic loading has not been reported. Because the wall under the window is also merged into the coupling beam, the length-to-depth ratio of the coupling beam is further reduced. However, the upper and lower walls are prefabricated standard walls with opening, which cannot be configured with inclined bars, which is a common way for cast-in-place coupling beams with relatively small length-depth ratio. In addition, how to connect the upper and lower prefabricated walls is also a key problem that affects the seismic performance. Six, two-story, full-scale assembled monolithic coupled concrete shear walls were tested to investigate the seismic behaviour of the new assemble integral coupling beam and the role of coupling beam aspect ratio (1.5, 1.85, 2.4) and connecting method (with and without grouted sleeves) between prefabricated panels on seismic performance. Two specimens were tested for each beam aspect ratio, one with a single row of grouted sleeves in the under-window panel used to splice reinforcement between the two precast panels and the other without sleeves. Test results indicate that damage in specimens with beam aspect ratios of 1.5 and 1.85 resulted from flexural yielding of beam reinforcement followed by diagonal cracking of the coupling beams, whereas damage in the specimen with larger aspect ratio (2.4) was primarily due to flexural hinging at the ends of the coupling beams. The connection details greatly affect the type and degree of damage, and more concentrated damage was observed in specimens without grouted sleeves along the interface between the precast under-window panel and cast-in-place strip. However, whether the grouted sleeve connection was used had little effect on the load capacity, deformation and stiffness of the specimens. Drift ratios at 15% drop in the peak strength ranged from 1.1% to 1.6%. The flexural capacity of the assembled integral coupling beam can be calculated as one beam according to the formula of the conventionally CIP concrete coupling beam.