预应力耐火钢⁃混凝土连续组合梁抗火性能研究

Investigation on Fire Resistance of Prestressed Fire⁃resistant Steel⁃concrete Continuous Composite Beams

采用有限元软件对耐火钢预应力连续组合梁在高温下的抗弯性能进行参数研究,引入了材料非线性、几何非线性以及钢梁初始几何缺陷,考察了预应力组合梁在高温下的破坏形态,耐火极限,跨中挠度随温度及时间变化的曲线,分别得到了不同受火工况与耐火钢使用截面位置对组合梁高温下抗弯性能的影响规律。结果表明:不同受火工况对普通组合梁和耐火钢组合梁的抗火性能有较大影响,组合梁在双侧受火工况下其挠度下降的幅度明显大于单侧受火工况下挠度下降的幅度,耐火时间也明显减短;在同一受火工况下,其他部分使用普通钢条件下,钢梁下翼缘使用耐火钢比腹板使用耐火钢更能有效提高组合梁在高温下的抗弯能力和耐火极限;当组合梁中钢梁下翼缘与腹板同时使用耐火钢时能显著提高组合梁的抗火性能,并达到与钢梁全截面使用耐火钢时同样的效果;仅在钢梁跨中区段内下翼缘和腹板上使用耐火钢时,耐火钢布置区段越长,则组合梁跨中挠度下降幅度越小,临界温度也越高。

Flexural properties of fire-resistant steel-concrete prestressed continuous composite beams at high temperatures were numerically investigated.Material nonlinearity,geometric nonlinearity and initial geometric defect of the composite beam were introduced.Effects of fire condition cases and dis⁃tributed location of fire-resistant steel along the longitudinal axis of composite beams were obtained,by analyzing failure modes,fire resistance,and the variation of mid-span deflection with temperature or with time.The results show that:different fire scenarios have great influence on the fire resistance performance of both regular and fire-resistant steel-concrete composite beams,the mid-span deflection of composite beams under a combination of fire condition decreases faster than the beams under onesided fire conditions,and the critical time is significantly shortened;Under the same fire scenario,it is found that composite beams with refractory steel flanges and regular steel webs have excellent flexural capacity and larger critical duration than composite beams with regular steel webs and flanges under high temperature;Composite beams made of refractory steel bottom flanges and webs and regular steel upper flanges have the same fire resistance as composite beams made of refractory steel;When refractory steel is used only as the lower flange and web in the vicinity of mid-span of the steel beam,the longer the distribution region of refractory is,the smaller the deflection is and the higher the criti⁃cal temperature is.