Study On The Behavior Of Prestresseed Steel Truss Reinforced Concrete Deep Beam

Steel truss reinforced concrete deep beam have good mechanical performance.Under thecondition of the same parameters，the capacity of steel truss reinforced concrete deep beamincreased by about30%-40%than ordinary reinforced concrete deep beam(Shear capacityimprovement is particularly significant), the rigidity increased by30%-50%, while avoidingthe brittle failure form of reinforced concrete deep beam， showing very goodplasticity.Significant superiority of deep beam component of this type used in the sectionheight close to or even exceed-storey transfer beam，which have good applicationprospect.However, previous experimental research found that the concrete tensile strength,shear strength，limit elongation is small，brittle，when subjected to external load, bendingcracks and shear cracks appear earlier，and the crack width may exceed the crack limit in theserviceability limit state，before the high bearing capacity and rigidity of the beam can befully developed, therefore，how to control the development of the outsourcing of cracks inconcrete is the issue to be examined.In this paper，the prestressing technique is used to controlthe development of the cracks in steel truss reinforced concrete deep beam to withstand heavyload, in order to improve the cracking load and control the development of crack，layoutprestressed steel strand along the tie direction based on strut-and-tie model.Prestresseed steel truss reinforced concrete deep beam is a new component type， whichcomplex internal structure，it is necessary to do a detailed research on mechanical behavior ofsuch component in order to promote the popularization and application of this component.Themain contents and results of the paper were summarized as follows.(1)In order to do a research on mechanic behavior of prestresseed steel truss reinforcedconcrete deep, large scale model tests of the component are carried out. The experimentsshowed that layout prestressed steel strand at the bottom of the component could improve its’capacity and rigidty，improving the cracking load greatly，reducing the maximum crack width，controlling the development of cracks very well，making crack width may not exceed thecrack limit in the serviceability limit state under large load, and the component in line with thestrut-and-tie force model.(2)The nonlinear finite element method was applied to carry out the whole processsimulations of the mechanic behavior of the prestresseed steel truss reinforced concrete deepbeam，the finit element method analysis results are very satisfavtoty by comparison with the experimental results，so that the finite element model used to analyze the components of thistype of load-displacement relations and stress distribution is feasible.(3)Capacity of the components are calculated according to Chinese code、American code、Modified strut-and-tie model based on Mohr-Coulomb failure criterion and sotfenedstrut-and-tie model, the calculated results are compared with the experimental results. Theresults show that，too conservative to apply the Chinese code； in accordance with Americancode calculation results do not match with the experimental； in accordance with sotfenedstrut-and-tie model calculation results are slightly conservative by comparison with theexperimental results，but the calculations require multiple iterations，the process is complex，not suitable for practical engineering design； in accordance with Modified strut-and-tie modelbased on Mohr-Coulomb failure criterion calculation results seemed somewhat conservativeby comparison with the experimental results，and the formula is simple，easy to understandand grasp，recommend using this method in practical engineering design.