| Steel concrete special-shaped column refers to the cross-sectional shape of "T" shape,"L" shape and 10-shaped concrete column,the interior is mainly based on steel as a special composite component of the skeleton.This kind of structure combines the advantages of reinforced concrete special-shaped column and steel concrete column,and can significantly improve the defects such as insufficient bearing capacity of reinforced concrete special-shaped column,poor earthquake resistance and difficult construction of beam and column joints.Because its limb thickness can be the same width as the wall,so it can make the room does not appear column edges,improve the effective use of space,but also make the building graphic design has a greater space for play.With the rapid development of civil engineering in China,the components such as steel concrete special-shaped columns have been widely used in multi-storey and high-rise buildings.Therefore,the tectonic forms of steel concrete special-shaped columns are of great significance to the structural optimization of high-rise buildings in China and to the improvement of the seismic performance of the whole structure.The steel bearing rate of steel concrete structure is much higher than that of reinforced concrete structure,and if fire occurs,fire damage has a great influence on the mechanical properties of the structure itself.In this paper,the temperature field analysis,the failure process and the final failure form,the test data analysis and so on of 1 unaffected steel concrete cross-column specimens and 3 high temperature naturally cooled steel concrete cross-column specimens are carried out,and the following conclusions are drawn:(1)The concrete color of the cylindrical surface after high temperature is dark red,showing bright color at the inner corner of some limbs,darker in the boundary,and the whole column is covered with small cracks with cracked shape,the vertical crack cracks of the specimen are usually present in the limbs of the limbs and at the distance of 15 cm at the end of the limb.(2)When the temperature of the concrete inside the specimen reaches 100 ?,the slope of the temperature change curve of the concrete will become smaller,similar to the "Temperature platform segment",and the time of the temperature platform will be delayed as the measuring point gradually progresses into the core area concrete,but its duration will be longer.(3)In the current test into the constant temperature phase of 100 minutes,the temperature difference of the concrete inside the specimen increased,after entering the constant temperature stage 100 minutes,the temperature difference of the concrete inside the specimen decreased.(4)With the increase of constant temperature,the axial displacement value with upward is increasing,but the speed of the increase of displacement value is decreasing continuously.(5)The temperature field of steel concrete cross column can be simulated well by using the finite element software ABAQUS,but there are some differences with the test,which is considered to be caused by the failure to consider the influence of water vapor on the temperature field.(6)Compared with the test piece XGS-01,the load of the specimen XGS-03 and XGS-04 to yield decreased by 6.37% and 14.71% respectively,and the ultimate bearing capacity decreased by 10.82% and 19.5% respectively.It is indicated that the high temperature damage obviously reduces the yield strength and ultimate bearing capacity of the cross column of steel-shaped concrete.(7)The yield load decreased by 8.9% and the ultimate bearing capacity decreased by 9.75% compared with the XGS-03 of the specimen XGS-04.It is shown that the yield strength and ultimate bearing capacity of the specimen decrease continuously with the increase of the constant temperature.(8)Compared with the XGS-01 of the specimen,the plasticity of the specimen XGS-03 and the XGS-04 decreases,that is,the safety reserve of the shaped steel concrete special column is reduced,which indicates that the high temperature damage significantly reduces the plasticity and safety reserve ability of the cross column of the steel concrete,and decreases with the increase of the high temperature time,but the decrease is smaller.(9)For the XGS-01 of the test piece,the ductility of the specimen XGS-03,XGS-04 decreased by 2.4% and 2.6% respectively.This shows that the high temperature damage significantly reduces the displacement ductility of the specimen.(10)The displacement ductility coefficient of the XGS-03,XGS-04 of the comparison,although the ductility coefficient of the XGS-03 is greater than the ductility coefficient of the XGS-04,but the difference is very small,which shows that with the increase of the constant temperature,the ductility of the cross column of the steel concrete has little effect.(11)Through the analysis of the stiffness degradation of the specimen,it is explained that the initial stiffness of the cross column of steel concrete is obviously reduced by the high temperature damage,the initial cut line stiffness of the component XGS-03 is reduced by 12.06%,and the initial XGS-01 stiffness of the component XGS-04 is 26.46% lower than that of the component cut line.When the steel concrete cross column reaches yield,although the stiffness is decreasing,the effect is not obvious.Before the yield of steel concrete special-shaped column,with the increase of constant temperature,the initial stiffness decreases obviously,the initial cut line stiffness of component XGS-04 ratio component XGS-03 is reduced by 15.7%,and the length of constant temperature increases after the specimen reaches yield,although the stiffness decreases but the effect is not obvious.(12)Through the analysis of the strength degradation of the specimen,it is more inclined to brittle failure for unaffected high temperature specimens.Constant temperature duration is not very obvious for the effect of strength degradation.(13)High temperature damage has little effect on the energy dissipation performance of steel concrete special-shaped columns,that is,after high temperature damage,the steel concrete cross column still has good energy dissipation performance. |
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