Experimental And Capacity Study On Bending Behavior Of C80Steel Reinforced Concrete Beams At Early Age

Early age concrete structures has obvious time variability, which have an important impact on the durability of the construction and safety of service period. Through bending experiments and finite element simulation the paper studied the mechanical properties and the calculation method of C80steel reinforced concrete beams. The main work is as follows:(1) This experimental study on bending behavior of1,3,7,28,90d of8high strength steel reinforced concrete beams(SRCL),their failure modes, the deflection, strains and cracks developments were recorded. Mechanical properties such as the ultimate moment and the section stifness were focused on. The influence on the long-term performance was assessed by the early loaded beam(50%of compressive strength) after ld,3d,7d and nature conservancy after28d.The results show that the cracking load are substantially independent of the impact of age after1d,yield load and ultimate load at early age (before7d) phase increases with increasing age;50%static load on the beam during early age had little effect on the long-term performance, but decreased the ductile behavior of beams.(2) Based the material testing, by ABAQUS for C80steel reinforced concrete beam finite element analysis, the effects of different steel ratio and the thickness of the protective layer on the ultimate bearing capacity of the beam. The results show that ABAQUS can simulate beam ultimate load and yield load, but there is a large error in the simulation of deformation; ultimate bearing capacity of the steel beam increases with the steel rate increase, but not significant; increasing large thickness of the protective layer would greatly reduce the ultimate bearing capacity of the beam.(3)"Technical Specification for Steel-Reinforced Concrete Structures"(YB9082-2006) is calculated without considering the interaction of the beam section bending steel and concrete so that the calculated results are too conservative,"Technical specification for steel reinforced composite structures"(JGJ138-2001) in fact is only suitable for C60and the following grade concrete and steel requirements and shaft located web region, which exceeds the webs and shaft, the formula does not suitable, so it has obvious limitations. This paper presents the case of five kinds of steel reinforced concrete beams with broad applicability of normal section bending capacity is calculated by.