In seismically active regions, the resistance of buildings against earthquakes must be improved. Post-installed anchors are generally used to connect retrofitting members to existing concrete members of a structure. However, research on the mechanical behavior of post-installed anchors subjected to combined shear and tensile stress is insufficient. Therefore, in this study, loading tests were conducted on anchor bolts by applying cyclic shear loading and constant tensile forces. Additionally, a mechanical model was constructed to evaluate the experimental results. In this model, the shear force was equal to the sum of the bending resistant force at the plastic hinge, the supporting stress of the concrete, and the shear component of the tensile stress of the anchor bolt. The results demonstrate that, with increasing tensile force, the shear force decreases and the joint separation increases. In addition, the proposed model was shown to reasonably replicate the shear load and slip relationship determined from experimentation results.

Introduction

In seismically active regions, seismic retrofits are often used to improve the resistance of buildings against earthquakes. Commonly, retrofitting is achieved by connecting strengthening members to existing members of a structure by using post-installed anchors. During an earthquake, these anchors distribute the shear stress by dowel action and catenary action in the reinforced concrete structures [1], therefore post-installed anchors are very vital elements. Although the retrofitting members are typically internally connected within an existing structure, the method of externally connecting them is gaining popularity. Fig. 1 shows an image of an external seismic retrofit. The main advantage of an externally connected seismic retrofit, as opposed to its internally connected counterpart, is that the construction will not obstruct the internal functions of the building. At the joints of such structures, a tensile force is caused by bending moments acting between the existing and expanding frames. Therefore, the joints of the structures with externally connected retrofits are subjected to both shear and tensile forces. However, it is thought that the vertical loading slightly affects the shear strengths of the post-installed anchors, but this paper focuses on the shear behaviors as an early step in the investigation of the anchors.