预应力连续钢-混组合梁抗火性能

Fire resistance of prestressed continuous steel-concrete composite beams

为研究预应力连续钢-混组合梁在火灾高温下的耐火性能,以通用有限元程序ABAQUS为平台,提出了模拟预应力连续钢-混组合梁火灾高温下非线性全过程受力行为的有限元模型。通过分析组合梁跨中挠度、拉索张力以及跨中与中间支座处弯矩随温度变化的规律,研究了荷载比、预应力比、拉索相对截面面积、跨高比4个参数对预应力连续钢-混组合梁抗火性能的影响。结果表明:荷载比对预应力连续钢-混组合梁的抗火性能有负面影响,荷载比越大,升温初期阶段拉索张力随温度升高而降低的速率越慢,且临界温度越低,达到临界状态时的挠度也越小,预应力比的影响主要在火灾升温的初始阶段,在这一阶段,预应力比越大,挠度增长越慢;随着温度进一步升高,不同预应力比条件下挠度-温度曲线接近重合;具有不同拉索截面面积的预应力连续组合梁,其跨中弯矩随着温度升高先降低,在150℃时达到最低值,之后随着温度升高弯矩不断增大;中间支座处负弯矩升温初期先增大,达到峰值后,随温度升高而逐渐降低;临界状态下预应力连续钢-混组合梁中间支座弯矩逐渐减小;具有不同跨高比的预应力连续钢-混组合梁,在荷载比相同时,其临界温度相差较小,挠度值接近;对于跨高比大于10的预应力连续钢-混组合梁,可以忽略跨高比对其抗火性能的影响。

To study the fire resistance of prestressed continuous composite beams (PCCBs) under fire, a finite element model for simulating the nonlinear performance of PCCBs during fire exposure was investigated by numerical simulation using the ABAQUS software. The Fire resistance effects of the load ratio, prestress ratio, ratio of cross-sectional area of the external tendons, and ratio of span to height on the deflection of the beams were studied, by analyzing deflection at mid-span and the tension in the external tendons and the moment with temperature at the mid-span and middle support of the PCCBs. The results show that the load ratio has a negative impact on the fire resistance of the PCCBs. The greater is the load ratio, the slower the tension in the external tendons decreases with increasing temperature, the lower is the critical temperature, and the smaller is the deflection at the critical state of PCCBs. The effect of the prestress ratio on the composite beam is mainly in the initial stages of the fire exposure. At the early stage, the larger is the prestress ratio, the slower is the rate at which the deflection increases. The deflection temperature curves under different prestress ratios tend to coincide at the critical stage. For PCCBs with different ratios of cross-sectional areas of the external tendons, the moment at the mid-span of PCCBs gradually decreases with an elevated temperature. After reaching the minimum at 150 ℃, the moment increases with the increase of temperature. Relatively, the moments at middle support increase with an elevated temperature at the initial stage. After reaching the maximum value, they gradually decrease with increasing temperature. In the critical state, the moment of middle support of the PCCBs is very small. Critical temperatures for PCCBs with different span and high ratio have a small difference in critical temperature when the load ratio is the same, and their deflection values are very close. When the span high ratios are greater than 10, the effect on performance of PCCBs can be ignored.