Study On Seismic Behavior And Retrofit Of Low-Slenderness Reinforced Concrete Coupling Beams

The coupled shear wall structure is a lateral load resisting system through couplingbeams to hold two or more pieces of shear wall together. The reasonable design methods forshear wall structure have to comply with the concept of multiple seismic fortification lines,follow the guidelines of strong shear wall and weaken coupling beams together with strongshear capacity and weak bending capacity. Dissipation of seismic energy is mainly throughthe end of the coupling beam and the bottom of the shear wall limb yield in earthquake.Inaddition, coupling beams,as the chief component to anti-earthquake in the shear wallstructure to insure the security of the main structure of wall,should yield firstly,to keepbuildings away from collapse.To meet the functional requirements and architectural design needs,coupling beamsoften appear in small-span-to-depth-ratio in structures such as shear wall structure,frame-wall structure, frame-corewall structure etc. Shear failure constantly arose in couplingbeams in Wenchuan Earthquake in2008. As a consequence, the capacity of ductility andenergy dissipation is too poor to satisfy the seismic requirement. So far, domestic andoverseas researchers have not yet found out an effective way to make the low-slendernesscoupling beams done easily. Therefore, it is rather significant to do some research on seismicperformance of low-slenderness coupling beams.In order to improve the seismic behaviors of RC coupling beams including ductility andseismic energy, not only some researches about the new reinforcement arrangement schemeof low-slenderness coupling beams through the low cyclic loading test have been made, butalso some discussions about the retrofit methods for existing reinforcement arrangement havebeen done in this thesis on the basis of numberous references. The preliminary conclusionsare as follows:1）Three kinds of low-slenderness coupling beams with new reinforcement scheme areput forward. Compared with ordinary reinforcement coupling beam, the results show thatconcrete coupling beams with cross steel and three rings of stirrup adding diagonal barsimprove not only the beam’s deformability, ductility and energy dissipation greatly, but alsothe beam’s shear intensity and stiffness and slow down the increase of its degradation.Hence,the two forms of reinforcement can improve the seismic performance of RC couplingbeams.2）Seismic behavior of RC low-slenderness coupling beams strengthened with CFRP isstudied and the impact of CFRP together with anchor bars on the seismic performance of beam is analyzed. In this section, four specimens’ tests of ordinary reinforced coupling beamsin which the span-to-depth radio is1.5are completed. They are reinforced by three ways withCFRP according to the current regulations and construction code. Through the low cyclicloading test, the results show that coupling beam with CFRP have higher bearing capacityand better behavior of the ductility and seismic energy, but the bearing capacity and stiffnessdegradation velocity are not slow down. It also demonstrates that inserting CFRP anchorreinforcement into concrete can enhance not merely the joint between CFRP and concrete,butalso the seismic performance of coupling beams through the CFRP share the beam bearingcapacity and energy dissipation.