Five steel-concrete composite beams are tested under low reversed cyclic loading. The failure patterns, hysteretic characteristics, hysteretic model, deformation restoring capacity, ductility, energy dissipation capacity, stiffness degradation and slips of the prestressed composite beams are discussed. Attention is paid to the effects of partial prestress ratio and degree of shear connection on the seismic performance of these beams. Studies show that the prestressed composite beams behave in a relatively ductile manner. Ductility of the composite beams decreases as the partial prestress ratio and the degree of shear connection increase. It was also observed that the applied prestressing is favourable for energy dissipation during downwards loading. Slips between concrete slabs and steel beams have adverse effects on energy dissipation in positive moment regions of composite beams. Tests also show that the effects of partial prestress ratio and the degree of shear connection are negligible to degradation of stiffness in composite beams.
For the advantages such as clean and environmental,the gas has been frequently used in human production and living.However,the gas explosion also becomes the major threaten for the production safety,the casualties caused by which is mainly due to the buildings collapse.This paper studies the deflagration venting of the buildings.First,by combining the research home and abroad,we analyze the impacts of vent area on the explosion pressure. We Compare different countries' specification of explosion venting area, and obtain the general conclusions about discharge area.Then,by taking domestic present status into account,we introduce the inertial venting system and light friable system of the buildings,and analyze the current problems existing in the venting system.Finally,we put forward the future development direction for the venting system of buildings.
ABSTRACT:The merits of high performance concrete (HPC) and fiber reinforced polymer (FRP) could be combined for using in the concrete structures to improve the structural mechanical behavior. Six beams cast with HPC and prestressed with Carbon FRP (CFRP) strands were tested and discussed in this paper. Test variables included partial prestressing ratio (PPR) of CFRP strands and material of reinforcements (steel and Glass FRP). Test results indicated that all the beams failed in two modes, i.e., compression failure mode and tension failure mode. The ultimate deflection of all the beams reached 1/70-1/41 of the spans and the ductility coefficients of the steel reinforced beams were higher than 3.5 (except the one with the highest steel reinforcement ratio), indicating good deformability and ductility. An increase in partial prestressing ratio (PPR) had a positive effect on ductility. The ductility of Glass FRP reinforced beam was much lower than that of steel reinforced beams while the deformability was quite similar.
In order to study the flexural performance of high strength reinforced concrete beam, through the loading test of six groups of specimens, investigate its force deformation characteristic. Test shows that the high-strength steel has very notable significance to improve the bearing capacity of the beam. The yield deflection and breakage load of the beam are also gradually increased with the continuous enhancement of the steel strength. Calculate the periodical value of load and deflection of the concrete beams according to the code and simplified M N calculation method. After the comparative analysis of the test results, amend the calculation formula for the deflection of yield and breakage of high strength reinforced concrete beam. And the calculation results coming from the amended formula are in good agreement with the experimental results.
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