| High performance concrete has the advantages that are high workability,high volume stability and high durability,so that is widely used in various civil engineering.At the same time,in the case of sudden high temperature caused by fire,under the influence of internal vapor pressure,thermal strain and temperature stress,high performance concrete is prone to bursting and spalling due to its dense internal structure,which sharply declines the concrete structure's bearing capacity,even leads to collapse that will seriously threaten the safety of people's lives and property.Therefore,it is of great practical and socio-economic significance to study the damage degradation mechanism of high performance concrete components under high temperature-load coupling,and attempt to reveal the high temperature burst mechanism of high performance concrete and to improve the fire resistance performance of high performance concrete structures.Based on the National Natural Science Foundation of China(51478290),this paper takes C80 high-performance concrete simple-supported beam as the research object,and studies the change process of thermal strain in high-performance concrete simple-supported beam under high temperature-load coupling action with fire temperature through vibration string strain gauge.By comparing the changes of thermal strain in the trabecular specimens with 0% and 0.2% PP fiber content,the effect from PP fiber on the thermal strain in the high performance concrete simply supported beams under the coupling action of high temperature-load was studied.The temperature field,thermal stress,thermal strain and displacement of high performance concrete simply supported beam under high temperature-loading were simulated by ABAQUS software,and the simulation results were compared with the experimental results.Provide experimental and theoretical references for high-performance concrete structures to improve fire resistance,post-fire assessment,reinforcement design,and related specification development.The main research contents are as follows.?.Experimental study on mechanical properties of C80 HPC.The elastic modulus test and the splitting tensile test were carried out on C80 HPC specimens with 0% and 0.2% PP fiber content after high temperature action.The test results show that the elastic modulus and splitting tensile strength of C80 HPC specimens continue to decrease with the fire temperature is gradually increasing.When the fire temperature is less than 250?,the elastic modulus of C80 HPC specimens with PP fiber is greater than the elastic modulus of C80 HPC specimens without fiber;under the same temperature,the tensile strength of C80 HPC specimens with PP fiber is greater than that of C80 HPC specimens without fiber.?.High temperature(resistance furnace)no load thermal strain test study.The C80 HPC trabecular specimens were heated by electric resistance furnace to study the changes of thermal strain at different depths of high-performance concrete simply supported beams under high temperature.The test results show that the closer the fire surface is to the bottom of the C80 HPC trabecular specimen,the smaller the variation of the strain value is.The farther away from the fire surface of the C80 HPC trabecular specimen is,the larger the strain value is.For the same depth,the strain value of the fiber-filled C80 HPC trabecular specimen is much smaller than that of the plain C80 HPC trabecular specimen.?.Thermal strain test study of high temperature(open flame)and load coupling.The C80 HPC trabecular specimens were heated by a self-made open flame furnace to study the thermal strain changes of high-performance concrete simply supported beams at different depths under high temperature-load coupling.The test results show that the transverse strain value of the C80 HPC trabecular specimen is larger than that of the longitudinal strain at the same depth.The PP fiber can effectively restrain the thermal strain inside the C80 HPC simply supported beam under high temperature-load coupling.?.Thermal strain simulation of simply supported beams under the coupling of high temperature and load.The temperature field,thermal stress,thermal strain and displacement of C80 HPC simply supported beam under high temperature-load coupling were simulated by ABAQUS software,and the simulation results were compared with the experimental results.The results show that when the fire time is the same,the closer to the fire surface of the C80 HPC simply supported beam,the higher the temperature;when the fire temperature is the same,the farther away from the fire surface of the C80 HPC simply supported beam,the greater the stress value;The variation trend of the strain values in the simulated C80 HPC simply supported beam is basically the same as the strain in the high temperature(open flame)-load coupling test.PP fiber can reduce the temperature value,stress value,strain value and displacement of C80 HPC simply supported beam under high temperature and load coupling. |
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