Experimental Study On Aseismic Performance Of Reinforced Concrete Piers With Local Ductile Concrete

Steel fiber reinforced concrete(SFRC)is a new compound material produced by adding moderate steel fiber into based cementitious composites,with advantage of high strength,high ductility and strong impact resistance.This thesis researches basic mechanical properties of SFRC with water cement ratio,sand ratio,content of fly ash and volume content of steel fiber variating by orthogonal tests.Then SFRC with compression strength more than 50MPa and flexural strength up to 12 Mpa was produced when volume-ratios of steel fiber is 2%,which has the characteristics of high fluidity and uniform distribution of fibers.Applying this material in the potential plastic hinge region of bridge piers locally to make five SFRC bridge piers and one formal reinforced concrete bridge pier.The pseudo-static tests on aseismic performance of these specimens under combined compression,flexure,shear and torsion,were conducted to explore the effects of local application of SFRC,stirrup ratio in the potential plastic hinge and length of SFRC.The failure modes and seismic performances of the piers specimens including load-displacement hysteretic curves,skeleton curves,torsional capacity,stiffness degeneration,ductility,and energy dissipation were analyzed to study the aseismic capacity of them.The results indicate that:1、Applying SFRC in the potential plastic hinge region of piers locally avoids the damage to the plasticity hinge of piers which has complex structure stress,makes the cracks develop rapidly and the load reache the peak pressure in a short time,and slows the degeneration of bearing capacity.Initial stiffness of piers could grow rapidly and increase up to 30%,and torsion loading capability is improved by 14%at least.2、The differences in length of SFRC in the specimens had limited effects on torsion loading capability in the experiment.Longer SFRC in the specimens produce a milder degeneration of bearing capacity.3、Reducing stirrup by half in the region where replacing formol concrete with SFRC has not weakened the torsion loading capability of specimens and had little effect on degeneration of torsional rigidity,but lowered torsional rigidity around 10%.Reducing the stirrup ratio to 0.343%aggravated the degeneration of bearing capacity.4、The torsion failure of the specimen was verified by the global global deformations and steel strain of specimen.The results indicate that SFRC with high elastic modulus and the stirrup work in synergy together,reducing the stress and strain of torsional stirrup.