Experimental Investigation On Mechanical Properties After The Fire Of L-special-shaped Steel Reinforced Concrete Columns

The steel reinforced concrete special-shaped column configuration not only hassteel, also contain the right amount of stirrup, so its carrying capacity and aseismiccapacity has increased significantly and the axial compression ratio limit may beextended appropriately. The current domestic and foreign research of steel reinforcedconcrete special-shaped columns mainly focus on the normal temperature case.However,the research of fire performance is almost blank stage and has not yet formeda set of calculation theory and design method of the system. This article carried out theL shaped steel reinforced concrete special-shaped columns after fire mechanicalproperties research.It not only can better improve the fire resistance designspecifications and regulations, also provides the basis for fire damage assessment andrepairment after the reinforcement work. Full text from the experimental research,numerical simulation and sectional characteristic three aspects are studiedsystematically, The main work and conclusions include the following four aspects:Firstly,8l-shaped steel reinforced concrete special-shaped columns under ISO834standard heating curve on both sides of the fire test, the measured cross-sectiontemperature distribution and axial and lateral displacement, and fire-damaged crackdistribution. The results are as follows:(1)temperature rising curve with basicallyISO834standard heating curve;(2)Distance from the fire panel, the higher thetemperature, the highest measured temperature reaches500degrees C, warming curveat15min to20Min in a more gentle, and then rate-of-temperature-rise faster.(3)Axialdisplacement maximum value near6mm, the minimum value is only1.1mm.Secondly, static loading test of specimen to room temperature, measured itsultimate bearing capacity, concrete and steel strain, axial and lateral displacement andthe bond between concrete and steel column slip. The results are as follows:(1)Lshaped steel reinforced concrete special-shaped column compression process is dividedinto elastic, working with cracks and damage three stages;(2)By fire after1h,45°Angle relative to0°Angle load, eccentricity of60mm,100mm,180mm,240mm, its bearing capacity was reduced by20.3%,20.8%,35.2%and20.3%respectively(3)Regardless of the axial displacement of specimen at the initial and late stages, thedisplacement value maintained in (10±2) mm, column section in the maximum bondslip between concrete and steel a little less than2mmThirdly,using general finite element software ABAQUS to specimen model oftemperature field analysis and structure analysis of damage, to get the cross-sectionaltemperature distribution and cross-sectional limit load, the calculation results ofdeformation and strain.The calculation results are as follows:(1)The calculated crosssection temperature curve and the corresponding point test value of temperature curveis almost the same;(2)Column1~9ultimate bearing capacity of error between thecalculated value and experimental value, respectively,7.7%,0.57%,11.2%,15.17%,15.08%,7.3%,9.9%,8.06%,9.9%;(3)Axial displacement is similar with the changingrule of the lateral displacement curve, along the direction of0°Angle when loading,specimen of lateral displacement, in the Y direction is about1/2of the X axis.Finally, Analysis of generalized neutral axis location, the average response,section properties, such as the Nu-e curve Nu-Mu curve to further reveal itsmechanical properties after fire, in addition to its sections at different time in firedamage assessment. The calculation results are as follows:(1)From an average sense ofstrain, plane-section assumption of l-shaped steel reinforced concrete special-shapedcolumn after fire still apply(2)The Nu-Mu related curves can be seen, the0degreesangle when the loading of the curve and the Axis Between the envelope is larger than45degrees angle when trying to load the envelope size.(3)Serious injury in depth theedge section, similar to the arc-shaped" distribution, and test specimen from the fire1H,1.5H,2H,3H, and after serious damage the maximum depth:30MM,36MM,46mm and65mm, and seriously damage the size of the Area, are:17.68%and20.05%and25.75%and36.91%.