Experimental Study On Seismic Performance Of Prestressed High Strength Concrete Frame Beam

According to “the four energy saving and one environmental protection” requirements, the use of high-strength reinforcement and high-strength concrete is promoted. The relevant provisions of 500 MPa hot-rolled ribbed steel bars have been put into the "Code for design of concrete structures"(GB50010-2010). Promoting the use of high-strength reinforcement and high-strength concrete can save the amount of steel and concrete, reduce engineering costs and give a huge economic benefit. In this paper, experimental study on seismic performance of prestressed concrete beams with high-strength reinforcement(500MPa) and high strength concrete(C60) has been done to provide basic data on the application of prestressed structures with high-strength reinforcement and high strength concrete.In this paper, quasi-static tests have been carried out to study the seismic performance of prestressed frame beams with 500 MPa high strength reinforcement and high-strength concrete. Comparison analysis of prestressed frame beams and non-prestressed frame beams with the same converted reinforcement ratio(2.6%) has been used to study seismic performance of prestressed frame beams with high-strength reinforcement and high-strength concrete; The seismic performance tests have been carried out on specimens of different converted reinforcement ratio(2.6%?3.1% and 3.6%) to determine the reasonable value of the maximum converted reinforcement ratio;effects of high-strength stirrups constraints on seismic performance can be concluded by the prestressed frame beams of 3.6% converted reinforcement ratio;effects of prestressing intensity ratio on seismic performance can be concluded by specimens with prestressing intensity ratio(?=0.8) which is higher than limits in the specification.The results show that, with the increase of the converted reinforcement ratio and the height of the concrete compression zone, pinching occured in the hysteresis loops of prestressed frame beams, falling section of carrying capacity was steepened and ductility and energy dissipation capacity were decreased gradually. When the converted reinforcement ratios are 2.6% to 3.1%, the displacement ductility factors are greater than 3.0,which can meet the general requirements(3~4) for ductility failure; When the converted reinforcement ratio is 3.6%, the displacement ductility factor is 2.82,which shows slightly lower ductility, When the converted reinforcement ratio is 3.6% in prestressed concrete beams with high-strength stirrups, displacement ductility factor is 3.36, which shows that ductility and energy dissipation capacity improve significantly. With the same converted reinforcement ratio and the same other factors, improvement of the prestressing intensity ratio do not change seismic performance of the beams significantly. Seismic performances of non-prestressed frame beams are better than the prestressed frame beams in hysteretic behavior, ductility and energy dissipation capacity.For prestressed concrete structures, with rational design and proper structural measures, they can have good seismic performance, which would be conducive to the development and application of prestressed concrete.