Failure Mode Study Of Frame-shear Wall Structure Subject To Strong Earthquake Loads

The frame-shear wall structure is able to form spacious areas due to its flexibilityon structural arrangement and provide high lateral stiffness by the shear walls. Hence,it has already been widely adopted in industry. Because of the interaction between shearwall and frame in the frame-shear wall structure, the stress state of its frame is distinctfrom frame structure. There are few studies have been carried out to investigate thefailure modes of the frame-shear wall structures under the strong earthquake loads,while most of them are based on the multi-line defense method. Therefore, it’snecessary to further study the failure modes of frame-shear wall structure subject tostrong earthquake loads.This study analyzes the force mechanism of the frame-shear wall structure toobtain the factors that affect the failure modes. According to different arrangements ofthe shear wall and the different stiffness characteristic values, establish the3D FEMmodes were established to carry out the elastic-plastic dynamic time-history analysis,and investigate their influences on the failure mode.Based on the comparison study, the following conclusions were gained：①By means of analyzing the storey shearing force distribution proportions underthe small earthquake, large earthquake and ultra earthquake loading, it shows that as theearthquake intensity improves, the destruction of the wall limb aggravates, and theproportion of the shear force in the frame increases. The earthquake loads willre-distribute in the wall limb and the frame, and the shear force in the upper storey willbe larger than the total shear force of the storey. Therefore, it’s better to consider theeffects on the capacity of the frame when the plastic development causes are-distribution of the internal force during the design of the frame-shear walls.②The differences of the arrangements of the shear wall will affect the failuremode under the strong earthquake loads. When the bending resistance of the wall limbwas quite strong caused by the specific arrangement of the structure, it was found thatthe failure of the wall limb was severe. When the shear wall arrangement forms a coretube, the destruction of the bottom of the tube is severe under the same earthquakeaction, and the plastic failure of the wall limb is earlier than the frame. The status ofdamage on the frame is much lighter that made the frame become the second defenseline. When the arrangement of the shear wall forms a coupled shear wall, the beams fail first. With the continuous earthquake loading, the wall limb fails badly, and the bothends of the frame beam become plastic hinges, but the whole frame still retains certaincarrying capacity.③As the stiffness characteristic value increases, the damage degree of thestructure will be higher under the same earthquake action. When the stiffnesscharacteristic value is small, the hinges will yield in the shear wall limb due a largewall-column ratio. As the ground motion continues, the shear wall limb yields andunloads, and the earthquake action on the frame would be increased, which causesplastic hinges appear in each components of the frame. If the stiffness characteristicvalue of the frame-shear wall structure is high and the specific gravity of the frame isheavy, the frame will fail before the limb will under the earthquake action due to a smallnumber of shear walls. This means that there’s no hinge failure at the bottom of theshear wall limb until the plastic hinges in the frame have unloaded. The analysis aboveshows that when the stiffness characteristic value is low and earthquake strikes, thestructure system would make the shear wall limb become the first defense line and theframe the second. When the characteristic value is high, the frame fails before the shearwall limb, and in this case, the frame would be the first defense line of the structuresystem and the shear wall limb would be the second.④By using the failure assessment index to evaluate each failure mode,it wasfound there were some differences in the results for each assessment index, but thesedifferences were quite small. The evaluation results are consistent with the structuraldamage phenomenons.