Compression capacity of boundary elements of RC slender shear walls confined with pre-fabricated rectangular continuous hoops

초록

Current seismic design codes require complicated lateral confinement details for the boundary elements of reinforced concrete (RC) slender shear walls to secure the deformation capacity, which leads to deterioration of the workability and economy. In this study, pre-fabricated rectangular continuous hoops (PRCHs) were used as alternative lateral confinement details for wall boundary elements. As PRCHs are manufactured in factories, it is possible to enhance their workability and economy significantly compared with conventional lateral confinement details. To evaluate the compression capacity of the wall boundary elements confined with PRCHs, 10 specimens were tested under cyclic and monotonic axial loading. The type of lateral confinement, vertical and horizontal spacing of the PRCHs, and loading methods were addressed as test parameters. The test results showed that the boundary elements with PRCHs showed an equivalent ultimate deformation capacity compared with the boundary elements with special seismic details specified in the current design codes. Decrease of the vertical spacing of PRCHs from 75 mm to 50 mm increased effective confined compressive strength (f(cc)') by 13 % and the ultimate confined concrete strain (epsilon(cu,c)) by 26 %. In addition, increase of the net horizontal spacing between PRCH modules from 0 to 100 mm decreased f(cc)' by 8 %-13 % and epsilon(cu,c) by 5 %-12 %. To accurately evaluate the concrete confinement effect of PRCH, a modified stress-strain model was suggested based on the Mander's confinement model. Using the proposed method, the strength and deformation capacity of walls with confined by PRCHs were quantitatively compared to those of unconfined walls and walls with special seismic details.

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