Experimental Study On Seismic Performance Of Axially-restrained Concrete Short Columns After Fire

It is likely to have an impact to the seismic performance after fire ofreinforced concrete columns when holding charge or axially-restrained in fire.But the influence of the degree of regularity and literature has been rarelyreported. Therefore, an experimental study is carried out in this article onseismic performance after fire of concrete short column when holding chargeor axially-restrained in fire. Meanwhile a numerical simulation is made byusing the finite element software to the fire-damaged concrete short column inone-way napped process. Based on this, calculation formulas of shear bearingcapacity after fire of concrete columns are recommended that the all-around infire and three-side by the fire. In this paper, the main work and conclusionsare as follows:A pseudo static test on the concrete short column is carried out, ten ofwhich are heated one hour in fire, while the other two are compared in roomtemperature. In the experimental study, the influence law is analyzed on theaxial constraint, the axial compression ratio, shear span ratio and other factorsto the damage form, the shear bearing capacity, stiffness, ductility andhysteretic characteristics of concrete short columns. Results show that:(1)concrete short columns by the shear span ratios1.5~1.9, the shear bearingcapacity decreased by24.7%~26.4%when exploded to fire for one hour.(2)The shear bearing capacity of the concrete short column is slightly improved whenhigh temperature with axial pressure ratio0.2corresponding high temperature afterfire without loading specimen.(3) In general, after high temperature under axialconstraint, the shear capacity of reinforced concrete short column is reduced, theshear bearing capacity after fire of concrete short column with axial constraint underthe high temperature is89.9%~100.4%of the corresponding high temperaturewithout the constraints.(4) The axial compression ratio is a key factor on the shearproperties of the concrete short column after fire, When the axial compression ratio increased from0.1to0.2,0.3, the shear span ratio of1.5after the fire resistance ofconcrete short column shear bearing capacity is increased by6.4%,10.9%, shear spanratio of1.9after the fire resistance of concrete short column shear bearing capacity isincreased by4.2%,26.1%.Based on the finite element analysis software ABAQUS, numerical analysismodel is established on the concrete short column under high temperature. ThePython language is used for the programming post-processing to obtain a temperaturefile in which data of highest temperate of every node during heating and coolingphases is stored. Then the file is imported to the model after fire to calculate theperformance of the one-way napped process. By using the model of group9root oftemperature and shear bearing capacity of reinforced concrete short column withnumerical calculation, proposed model analysis parameters. Established finiteelement model can better simulate the fire within the cross section under the action ofeach measuring point temperature development course and the shear capacity ofreinforced concrete short column after the fire, but the whole process of load-displacement curve simulation accuracy remains to be further improved.Using numerical analysis model systematically analyzes the influence law ofconcrete short column shear bearing capacity when changed in the axial pressure ratio,sectional dimension and stirrup spacing on all—sides by the fire and on three—sidesby the fire. Then a calculating formula of the concrete short column shear bearingcapacity that the three sides by the fire after is suggested.