Experimental Research On Seismic Behavior Of Small-Span-to-Depth-Ratio Dual Coupling Beams With HRB500Bar

Coupling beams in reinforced concrete coupled sheer walls are the key componentsto guarantee a good seismic performance. Small-Span-to-depth-ratio coupling beams（l/h_b≤2.5） are usually used if required in construction. Experiment results showthat when the shear stress is above average(V/f_cbh_b0≥0.20), the coupling beams withthe seismic design of the conventional frame beam cannot meet the ductilityrequirements of the integral structure under the action of earthquake. By applying thecross oblique tendon scheme （dark hold） and common integrative diagonalreinforcement scheme specified in the Code for Design of Concrete Structures（GB50010-2012）, the seismic performance of the coupling beams is dramaticallyimproved. But due to the certain width requirements and complex structures of thecoupling beams, it is hard to be applied in construction, thus affecting its use in practicalengineering. In recent years a new scheme proposed in engineering design to improvethe seismic performance of the small-span-to-depth-ratio coupling beams works byinstalling a whole-length gap in the middle of the beam to divide it into twobigger-span-to-depth-ratio coupling beams designed with the common reinforcementscheme, which is also applied in some high-rise buildings. With most high-risebuildings designed with cast-in-place slabs, problems like the following ones should beanswered before practice: how is the seismic performance of thesmall-span-to-depth-ratio dual coupling beams? How would the position of slabinfluence the seismic performance of the coupling beams? etc. Taking this intoconsideration, this project conducts the experiments of the seismic performance of thesmall-span-to-depth-ratio slotted coupling beams with cast-in-place slabs and comparesit with that of other small-span-to-depth-ratio coupling beams of common reinforcementscheme.The newly revised Code for Design of Concrete Structures （GB50010-2012）introduced the use of500MPa high strength bars. In order to test the seismicperformance of the small-span-to-depth-ratio dual coupling beams with500MPa barunder same condition, three experimental studies are conducted. The project mainlyfocuses on the following aspects:①Analyze the force and seismic performance of the specimen with HRB500barsof different span-to-depth ratios. ②Compare the seismic performance of the dual coupling beams, diagonal obliquecoupling beams and multiple oblique coupling beams with HRB500bars, and that withHRB335, both of which are of the same span-depth ratio, sheer stress and stirrupcharacteristic value.The conclusions drawn from this project are as follows:①With the same span-to-depth ratio, close sheer stress and stirrup characteristicvalue, the dual coupling beams with HRB500bars have a bigger yield displacement andultimate displacement, a lower stiffness, almost the same displacement ductilitycoefficient and bigger displacement angles compared with the coupling beams of otherreinforcement schemes. When the lateral stiffness of the whole structure can beguaranteed, the seismic performance of such small-span-to-depth-ratio slotted couplingbeams can meet the requirements.②It is necessary to take the effect of flange into account while designing thesmall-span-to-depth-ratio dual coupling beam reinforcement.③It is appropriate to put the slot in the middle of the small-span-to-depth-ratiocoupling beams when applying the dual coupling beam scheme and the other couplingbeams can be designed with the common scheme.