Mechanical Analysis Of The Shear Behavior Of Steel Fiber Reinforced Concrete Coupling Beams With Small Span-depth Ratio

The coupling beam is an important component in the shear wall structure and a force transmission link between shear walls.It can consume the earthquake energy to become the first line of the defense in building structure aseismatic.The mechanical properties of the coupling beam have an important effect on the seismic performance of the shear wall structure.The study of small span-depth ratio coupling beam have demonstrated that the structure design based on the "strong shear weak bending" concept of the traditional small span ratio reinforcement beam is difficult to avoid premature shear failure even distribute a large number of stirrups.It can not meet the seismic design requirements of high ductility and high energy consumption.In order to improve the seismic performance of the small span-depth ratio coupling beam,domestic and foreign scholars have done a lot of research and analysis.The current "concrete structure design code"(GB50010-2010)in China suggested that the small span-depth ratio coupling beam can be used in new forms of reinforcement(such as concentrated diagonal reinforcement,diagonal brace reinforcement).But there are some difficulties in the practical construction,which affect the popularization and application of this method.The addition of steel fibers to the small span-depth ratio reinforced concrete coupling beam can improve various aspects performance of the beam obviously,and domestic and foreign scholars have done some experiment research.However,there are few studies on the mechanism analysis,failure mode,and shear bearing capacity calculation method for steel fiber reinforced concrete coupling beam with small span-depth ratio.Based on the low cycled reversed loading experiment for 16 steel fiber reinforced concrete coupling beams(span-depth ratio from 1.0 to 2.5,concrete strength from C30 to C80,the volume fraction of steel fiber from 0% to 2.5%),this paper summarizes the development of cracks,the failure mode and the stress characteristics of reinforcements of the coupling beams and analyze the shear mechanism and the deformation factors of the small span-depth ratio steel fiberreinforced concrete coupling beam.It also analyze the influence factors of the shear capacity of the small span-depth ratio steel fiber reinforced concrete coupling beam,such as span-depth ratio,concrete strength and the volume fraction of steel fiber.Then,on the basis of the above analysis,this paper proposes a calculating formula for the ultimate displacement angle,a calculating formula for shear strength based on the Chinese code and a calculation method for shear capacity based on softening strut-and-tie model for the small span-depth ratio steel fiber reinforced concrete coupling beams.