两跨预应力混凝土连续梁抗火性能试验与分析

为研究预应力混凝土连续梁的抗火性能,进行了9根两跨有粘结预应力混凝土连续梁抗火试验.通过布置于试验梁内的热电偶,获得了试验梁截面的温度场分布.布置于试验梁上的位移传感器测试结果表明,火灾下连续梁变形增长速度在受火过程中增长速度大体上是一致的.各试验梁边支座反力实测结果表明,受火10 min以内,试验梁边支座反力快速减小,受火10~40 min,边支座反力变化平缓,受火40 min以后,边支座反力又快速恢复.试验梁在受火过程中试验梁背火面经历了水分溢出、水蒸气形成和发展、溢出水干涸及水蒸气消失的过程.基于试验结果,拟合出了考虑各关键参数影响的火灾下两跨连续梁边支座反力与梁跨中变形的计算公式.

Experiment and analysis on fire resistance of two-span bonded prestressed concrete continuous beams

Experiment on fire resistance of nine two-span bounded prestressed concrete(PC) continuous beams is completed. Temperature distribution along section of the beams was obtained by embedded thermocouples in the beams. Test result measured by displacement sensors on the beams indicate that the increase speed of the deflection of the beams remain the same in fire. Test result measured by load cells at the side supports indicates that side supports reaction decreases rapidly in 10 minutes heating; when undergoing fire after10 minutes till 40 minutes, side supports reaction changing slightly; after that the side supports reaction begins to recover rapidly. During fire, the whole process of water overflowing, vapor appearing and developing, and water drying, vapor disappearing occurs on unexposed surface. Analysis of temperature distribution and deflection of test slabs is carried out using ANSYS software. Calculation formula of side support reaction and deflection in the mid-span of beams subjected to fire were obtained by fitting curve of experimental data of different specimens at different time with the number of 1080, deflection in the mid-span of the beam at normal temperature, elastic calculated value of side support reaction at normal temperature, ratio of concrete cover of prestressing steel to span of beams, load level, global reinforcing index of the middle support being taken into account.