Cyclic Behavior of Interfaces for Seismically Retrofitted RC Buildings

Abstract

In seismically retrofitted reinforced concrete (RC) structures, new members are connected to existing members using interfaces with roughened surfaces and post-installed dowel bars. During an earthquake, the interfaces are subjected to cyclic shear and normal stresses. Therefore, the structural design of interfaces is essential. In a previous study, normal and shear loads were applied to interface specimens. Moreover, a shear strength estimation method was proposed; however, the cyclic behavior was not discussed. This paper presents a cyclic model of the roughened surface in retrofitted RC structures. First, an envelope model was constructed using the previous shear strength estimation method and Saenz model, a constitutive law of concrete. Subsequently, the cyclic rules were modeled. Moreover, a previous dowel model was incorporated into the proposed cyclic model to estimate the test results. Finally, the proposed model provided reasonably estimated test results; the average ratio of the test results to the model results was 1.04. In addition, as δ increased, the effect of the dowel bar intensified in terms of shear.

Modified Cyclic Model Of Interfaces With Roughened Surface And Dowel Bar Subjected To Normal And Shear Stresses

“…As mentioned in the previous paper [2], when dd was smaller, the opening was wider; therefore, for the specimen with dd = 13 mm, the previous model overestimated the test results. Fig.…”

“…In the previous study [2], the authors constructed the original model for the roughened surface. The original model can be applied to the specimens subjected to the tensile and shear stresses.…”

“…Gb0 and δcp are set to 6.9 N/mm 2 /mm and = 0.50 mm, respectively. [2] In the Saenz model [18], β = 2 was employed. In this study, to express the stress-softening behavior of the roughened surface, the modified β was used as follows.…”

“…[10] Moreover, the authors studied a roughened surface by a hammer and post-installed dowel bars. [1][2][11][12][13][14][15][16]. In the studies, the interfaces and the post-installed dowel bars were subjected to the tensile and shear stresses.…”

“…Furthermore, the shear strength formula was proposed. [2] In the equation, the uneven surface was considered as a cone; and, with based on the previous study, the shear strength τmax was expressed by vertical projection area of the uneven surface and the value of the exponent of fc. Then, the value of τmax,p, that is the maximum shear stress on the positive side, is calculated by the following equation:…”