| Steel reinforced concrete special-shaped columns are not only be arranged flexiblyand use of large area, but also have high bearing capacity and good seismicperformance.Predictably, steel reinforced concrete special-shaped columns will be moreand wider application in multistory and high rise buildings in the future. Compared withreinforced concrete special-shaped columns’ study, steel reinforced concretespecial-shaped columns of fire resistance research in China is still in at an primarystage.Because of the irregularity of the cross section shape, calculation of the normalsection bearing capacity calculation of Steel reinforced concrete special-shaped columnsis more complicated than the rectangular section columns.In order to guarantee thesafety of columns under fire and understand the mechanical properties of special-shapedcolumn under high temperature, this paper investigates the mechanical properties ofSRC special-shaped column (including cruciform, T-shaped, L-shaped with equal legsand inequiaxial L-shaped) under the fire from the experimental study, ABAQUSsimulator, MATLAB programming and simplified calculation of bearing capacity ofSRC special-shaped columns. In this paper, the main work and results are as follows:1. This article designed nine cruciform, eight T-shaped, nine L-shaped with equallegs (DL-shaped) and nine inequiaxial L-shaped (BL-shaped) steel reinforced concretespecial-shaped columns with the help of team members. For each cross section forms ofspecial-shaped columns, eight root (T-shaped column for7) was carried out fireexperiment under the standard temperature curve, as a contrast,1root for axialcompression test under normal temperature to get cross section temperature fielddistribution; carrying out static loading test on the specimen after the fire, analyzing theeffects of eccentricity and load angle on residual bearing capacity at the same time. Theexperimental results showed that:(1) The closer point is away from the fire surface, thehigher the temperature is and the greater the increase is; conversely, the temperature islower, temperature range is more gentle. Measuring points of the cross section core areais warming lesser and basically under200℃.(2) The load Angle and eccentricity has agreat influence on the mechanical performance of special-shaped columns. Whateverthe cross-section form special-shaped columns is, at other changeless conditions, theresidual bearing capacity decreases with the increase of eccentricity, bearing capacity of 0degree load angle is higher than bearing capacity of45degree load angle.(3) Nomatter what kind of cross section the steel reinforced concrete special-shaped columnsare, the vertical displacement and lateral displacement experienced three stages whichare gentle deformation, speed deformation and sharp increase. In the point of the abilityto resist deformation, a cross column is better than that of t-shaped column, BL-shapedcolumn is superior to the DL-shaped column, t-shaped column is superior to theDL-shaped column, at other changeless conditions.(4) The bearing capacity of crosscolumn is1.15to1.5times as large as the t-shaped cross section column, the bearingcapacity of BL-shaped1.06to1.17times as large as the DL-shaped cross sectioncolumn and the load resistance performance of DL-shaped cross section column isbetter than the T-shaped section column.2. With the help of engineering simulation of the finite element software ABAQUS,This article carry out temperature field analysis under fire and mechanical performanceanalysis field of steel reinforced concrete special-shaped columns. The results showedthat:(1) simulation value calculated by ABAQUS is good agreement with the testresults, which can basically reflect the general rules of cross section of warming.(2)The lateral displacement curve of the test and the lateral displacement curve calculatedby ABAQUS is almost the same, that is, with the increase of eccentricity, the lateraldisplacement of X direction and Y direction present an increasing tendency, and thevertical lateral displacement changes little.(3) The resistance ability of bend of thesection increases at first then decreases with the increase of axial force. Test the limitsof eccentricity and the limits of using ABAQUS to calculate eccentricity. The balancedeccentricity get by the test is consistent with the balanced eccentricity calculated byABAQUS.3. According to the principle of plane section assumption and numerical analysis, Icompiled MATLAB program to calculate normal section bearing capacity of hightemperature steel reinforced concrete; we can get N-M curves, Mx-Mycurves and theposition of the neutral axis of the limit damage of special-shaped column by theprogram, and analyze the effect of load Angle and eccentricity, concrete strength gradeand shaped steel ratio on normal section bearing capacity of steel reinforced concretespecial-shaped column under standard temperature. The conclusion was as follows:(1)It is difficult to solve the problem by general mathematical analytical method due to theapplication of the nonlinear, and it is quick and efficient to gain a convergent solution by Quasi-Newton method.(2) The abaqus value and matlab value of balanced eccentricityagree well with test value.(3) The load Angle, shaped steel ratio and concrete strengthgrade has important effects on the ultimate bearing capacity of steel reinforced concretespecial-shaped columns (including cruciform, T-shaped, L-shaped with equal legs andinequiaxial L-shaped). At other changeless conditions, the ultimate bearing capacity ofthe component increases with the shaped steel ratio increases, and is in proportional tothe concrete strength grade; and decreases with the increase of eccentricity.(4) Thechange law of N-M curves and Mx-Mycurves of Steel reinforced concrete special-shapedcolumn under fire after1hour is similar to reinforced concrete special-shaped column,and the increase of the shaped steel ratio can increase the bearing capacity ofspecial-shaped columns.4. According to the experimental data, the simulation data of this article, I putforward equivalent section method which is suitable for calculating the normal sectionbearing capacity of steel reinforced concrete special-shaped columns under hightemperature, and used this method to calculate the test component in this paper to verifythe reliability of this method. The calculation results show that:(1) The method ofequivalent is more safe for cross section, T-shaped, BL-shaped and DL-shaped underthe small eccentricity.(2) The calculated value of four kinds of algorithms of bearingcapacity agree well. |
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