| Compared with the common reinforced concrete (RC)special-shaped columns，thesteel reinforced concrete(SRC) special-shaped columns have larger capacity, higheraxial compression ratio limits and better seismic performance because its contain moresteel. However, the areas under fire of SRC special-shaped columns are more than thecommon section columns. After fire, the proportions of damage areas are large. Thesteel will increase heat exchange and cause more serious damage. High temperatureswill weaken the mechanical properties of the steel. But, the investigations on the fireresistance performance of SRC special-shaped columns are blank at home and abroad.This paper designs4SRC L-special-shaped columns in order to study the fireresistance performance from the aspect of experiment, numerical simulation andmechanical characteristics of section. The main work and conclusions include asfollows：1. Four full-scale SRC columns with special-shaped cross section wereexperimentally investigated in fire following IS0834standard heating process. Thesection temperature field, the vertical and lateral deformations, apparent phenomenonand cracks distributions under fire were got. The experimental results show that:(1)temperature is higher when the points closer to the fire, conversely, the temperature islower. The highest temperature was600℃. The temperature rise on the symmetry axisof cross section was small than200℃. The temperature at two flange of steel weredifferent and the difference of middle section of columns were217℃for an average.(2)The crack distributions were all same and most wide cracks were horizontal anddiagonal.2. According to the fire damage column, the compression test was implemented toget the strains, deformation law, bond slips and residual limit bearing capacities. Theexperimental results show that (1) whether big or small eccentric loading, its finaldestruction was the concrete crushed or flake; the compressed channel steel can yield,the tension channel steel usually do not have to yield;(2) bond slips between concreteand steel were small which indicates that concrete and steel can work together (3) Inthe load, the SRC columns with special-shaped cross section will occur two-waybending, the average of relative of lateral displacement were6.41mm, which explain that after fire the columns still has quite big the lateral stiffness;3. Using finite element analysis software ANSYS, analyzed the temperature fieldafter fire, and then used the injury model, analyzed the axial and bias compression test.From the test we can find that (1)The temperature field calculated by ANSYS were ingood agreement with test can reflect the general rule of cross section temperature (2)deformations of columns calculated by ANSYS were in good agreement with testbecause ANSYS ignore the transient thermal strain and other factors.(3) it is necessaryto develop a special computer program to simulate the mechanical behaviors of SRCspecial-shaped cross section columns at elevated temperature due to the timeconsuming of numerical simulation using solid element．4. The characteristics of temperature field．generalized neutral axis position,ultimate bearing capacity, position of point corresponding to maximum bearingcapacity, N-M envelop diagram and M-M envelop diagram for cross section ofspecially-shaped SRC columns subjected to fire were investigated．Studies show：(1)the area of N-M envelop diagram of SRC special-shaped cross section columns arelarger than the RC special-shaped cross section columns as well as ultimate bearingcapacity and ultimate flexural capacity.(2) With the increase of eccentricity, thelocation of the neutral axis is offset continuously from tension to compression zone.When the load angle was45degrees, the location of the neutral axis and perpendicularto the bending effect plane, but when the load angle was0and90, they were notperpendicular.(3) The influence of time and the way by fire on special-shapedcolumn’s temperature field more obvious.(4) the assumption of plane section in the L-shaped steel reinforced concrete special-shaped column still usefull. |
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