Experiment alinvestigation of thein-plane cyclic response of infilled reinforced concrete frames and their possible retrofit measures

Abstract

..In the present study, an extensive experimental laboratory investigation has been carried out to study the comparative in-plane cyclic behavior of brick infilled, isolated brick infilled and bare reinforced concrete (RC) frames and to find an appropriate retrofit measure for those frames against earthquakes. Bangladesh is recognized to be an earthquake prone region where multistoried masonry infilled reinforced concrete framed buildings are commonly seen. Burnt clay bricks are the most common infill materials used as partition walls in those RC framed structures. Lack of knowledge on the mechanical properties of the clay brick infills prevents the local structural engineers from idealizing the seismic performances of such buildings in Bangladesh. In this context, present study focuses on the experimental investigation of the comparative in-plane cyclic response of the bare RC frames and the locally available brick infilled RC frames. Moreover, in-plane cyclic behavior of a newly proposed construction method of brick infilled RC frames where the infill is isolated from the surrounding RC frames have also been evaluated and compared with the bare and the conventional brick infilled RC frames. In the present research, the increasing in-plane reverse cyclic loads in increasing magnitude have been applied on six single bays, single story ½ scale models comprising two bare RC frames; two brick infilled RC frames and two isolated brick infilled RC frames till their ultimate capacities were reached accompanied by substantial deformation and propagation of cracks. Behaviors of these frames were evaluated through the observed strength and deformation characteristics along with hysteretic energy dissipation capacity and ductility. Later, the damaged specimens were repaired with FC laminates and tested following the same procedures as for the original frames. The experimental results proved three times larger shear capacity as well as lower ductility of brick infilled RC frames in comparison to bare RC frames. While, the isolated brick infilled RC frames exhibited 40% lower shear capacity and comparatively large energy dissipation capacity as compared to the brick infilled RC frame. Furthermore, repair or retrofitting with ferrocement laminates confirmed improved performances of all the damaged frames regarding shear capacity, stiffness degradation and energy dissipations. Eventually more than the original strengths were achieved by repairing the damaged frames with ferrocement laminates.