Experimental Research And Nonlinear FEA On Seismic Behavior Of Reinforced Concrete Dual Coupling Beams With Floor Slabs

As important components of shear walls, frame-shear wall structure andframework-core tube structure,The seismic behavior of coupling beams had importantinfluence on the whole structural seismic behavior. Coupling beams yield in advance ofcoupling walls to play the role of reducing effectively the destruction of main structurethrough absorbing and consuming the earthquake energy under horizontal earthquakeaction.On account of functional requirements and structural design needs, smallspan-to-depth ratio coupling beams are common throughout these structures.In order toavoid brittle shear failure in the earthquake, Researchers at home and abroad haveproposed a great many different reinforcement schemes to improve seismic behavior ofsmall span-to-depth ratio coupling beam so that the ductility factors of them subjectedto shear failure can meet the ductility requirement of coupling beams in shear wallstructure subjected to vertical earthquake action.Although these ways have good seismicperformance,they have some problems such as difficulty in constructing.Currently, there is a new method to improve the seismic behavior of deep couplingbeams by designing a slot down the middle of them and forming two small couplingbeams with twice span-to-depth ratio than the original beams.If we neglect the influenceof the concrete slabs on dual coupling beams,the method has to be reasonable intheory.But the impacts of position of the slot on dual coupling beams with slabs have tobe studied further because coupling beams and slabs are usually cast in place in the realprojects. Furthermore, lacks of enough experimental validation of seismic behavior ofthe dual coupling beams reawaken our consciousness of the necessity of furtherresearch on them.In order to meet national requirement for industry and civil products as4saving1environment protected.China has advocated actively the use of high-strength steel in ourcountry’s construction industry. Code for Design of Concrete Structures(GB50010-2010)has actually promote500Mpa grade steel as main bearing reinforcement.To this end, theauthors completed three tests of conventionally reinforced dual coupling beams withfloor slabs with500MPa grade steel, the paper’s main contents as follows:①Completed three experiments on conventionally reinforced dual coupling beamswith floor slabs with span-to-depth ratio of2.0aiming to investigate the seismic behavior of them under medium and above shear-compression ratio.②Currently, dual coupling beams usually are formed by designing the slot in themiddle of beams.but floor slabs may bring about discrepancy in stiffness,failure modesand bearing capacity between newly formed dual beams. The paper attempts to pursuethe reasonable position of slot so that dual coupling beams perform favourable seismicbehavior.③Through above-mentioned tests,we researches and compares seismicperformances of syntheses diagonal reinforcement coupling beams,diagonalreinforcement coupling beams and general coupling beams which previously completedwith dual doupling beams with500Mpa steel under conditions of same span-depth ratio,similar shear-compression ratio and characeristic value for providing stirrup.④The paper takes the finite element software(ABAQUS) to analysis and simulatethe nonlinear behaviour of these three specimens under monotonic loading, and thencompares analytical results with experimental results, including the development ofconcrete damage and stress distribution of bars and the load-displacement curve.After these studies mentioned, the preliminary conclusions as follows:①When the shear-compression ratio of conventionally reinforced dual couplingbeams with a span-depth ratio of2.0is around0.20, their displacement ductility factorsapproximately meet requirement which displacement ductility factors is no less than3.5for Grade I earthquake-resistance coupling beam, which means their seismicperformance is not as what is originally expected.②Influences of floor slab on seismic behavior of conventionally reinforced dualcoupling beams can not be neglected in the design. Floor slabs have impacts ondevelopment of cracks and failure mode of dual coupling beams. In addition,steel infloor slabs make contribution to coupling beams in tension.According to the comparisonresults of specimen CB-K5and CB-K8,we suggest designing the slot in the middle ofbeams with shear-compression ratio of0.2when considering influences of floor slab onseismic behavior of conventionally reinforced dual coupling beams.③Comparing with small span-depth ratio coupling beams previously completedwith different reinforced schemes, lower stiffness of dual coupling beams with floorslabs at the early stage lead to greater yield displacement. With increasing drift angle ofbeams, speeds of them with floor slabs are much slower than that of the commoncoupling beams. The displacement ductility factors of them will decreased and absolutedeformation capability of them will increased during failure compared with the common coupling beams.