Research On Seismic Performance Of Reinforced Concrete Short-limb Shear Walls After Fire

Reinforced concrete (RC) short-pier sheer wall has been widely used in high-risebuildings because of its good architectural functions.Now, The RC short-limb shearwalls studied were mainly focused on the mechanical behaviors at room temperature.However, the performances of short-limb shear walls which all-around in firesituations have rarely been reported. In addition, the tensile strength of concretewould directly affect inclined section bearing capacity of short-pier sheer walls. Theresidual strength of concrete exposed to elevated temperature have been studied bymany researchers. But about research into a tensile strength of concrete was a bitpremature.So this paper investigates the tensile strength of concrete after fire and theseismic behavior of the RC short-limb shear walls after exposed to fire, thencalculation it. The main work and conclusions include as follows：1. The splitting tensile strength of62groups of concrete standard cubic specimenswas investigated. The effects of temperature, cooling mode, curing age and standingtime on the failure pattern of splitting section and the tensile strength of concrete werediscussed, and the related calculation formula of the tensile strength were proposed indifferent conditions. The results show that,there is a great influence of temperature onsplitting sectional failure pattern and tensile strength of concrete after exposed to hightemperature. The splitting section is smooth lower than300℃and then becomesrough with higher temperature, and it is almost along the hardening cement pastewhere the coarse aggregates are nearly undamaged exceeding600℃. The tensilestrength of the concrete after fire with spray cooling is smaller than that with naturalcooling. The shorter the curing age is, the lower the tensile strength of the concreteafter fire is. With an increase in standing time, the tensile strength of the concreteafter fire decreases at first and then decreases, and it is smallest standing for28days.2. Based on the pseudo-static tests of six concrete short-limb shear walls after fireand one contrastive specimen at ambient temperature, the effects of fire exposuretime, axial load ratio, concealed column and concealed bracing on the failure mode,bearing capacity, stiffness, ductility ratio, skeleton curve and hysteretic energy were analyzed. A calculation formula for the shear capacity of concrete short-limb shearwall after exposed to fire on all sides was proposed according to the calculationmethod at ambient temperature specified in code. The results show that the hystereticrules and the hysteretic characteristics of concrete short-limb shear wall after fire aredifferent to the one at ambient temperature. The strength of short-limb shear wall isdecreased with an increasing in fire exposure time. The axial load ratio has a positiveinfluence on the improvement of bearing capacity of short-limb shear wall after fire,but it is not convenient for stiffness. The stiffness and dissipated hysteretic energy ofshort-limb shear wall after fire can be increased by concealed column and X-shapedconcealed bracing. The residual capacity can not be improved by the former one, butit can be enhanced by the latter one.3.Use the finite element analysis software ABAQUS to analyse the test results, thedisplacement-load curve of shear walls are obtained, which are closed to the results oftest, within error limit of10%. Then use software ABAQUS to calculate the bearingcapacity of T-shaped Short-limbed shear Wall within the effects of fire exposuretime, axial load ratio and flange width. The results show that: The residual strength ofT-shaped short-limbed shear wall with an axial load ratio of0.2decreases9.31%and44.10%after exposed to fire for60min and120min, respectively. After exposed tofire for60min, the peak stress of T-shaped short-limb shear wall is linear increasedwith the axial load ratio.When the flange width less than275mm, With the increaseof flange width, the residual strength of T-shaped of the same. The residual strengthof T-shaped short-limbed increased with the Wing wall width, When the flange widthgreater than300mm.