预应力活性粉末混凝土梁抗火性能与抗火设计

Spalling and mechanical properties deterioration of Reactive Powder Concrete (RPC) at elevated temperature will result in serious damage and collapse to the building structures. For this reason, spalling of RPC beams in high heating rate environment and high stress level will be studied, an expression for the top envelope line of the concrete spalling will be presented by taking the concrete water content at ambient temperature as the x-axis, and the normal stress level of concrete extreme fiber in the pre-compression zone of beams at elevated temperature as the y-axis, spalling prevention method of reasonable fiber type and amount, type and thickness of smearing rationally tunnel fire resistant coating will be put forward, taking as estimate and control method for spalling of RPC beams. Experimental study on prestressed RPC beams subjected to fire will be carried out, the refined model for fire resistance analysis will be studied by taking the effect of high temperature creep strain of prestressing steel tendons, thermal stress coupling and spalling of RPC. The effect of load level and concrete cover thickness on fire resistance of prestressed RPC beams will be considered. Experimental study on mechanical behavior of prestressed RPC beams after fire will be carried out, calculation methods of section bearing capacity, stiffness and crack width for prestressed RPC beams after fire will be put forward. The effect of fire duration time, concrete cover thickness and initial load level on mechanical behavior will be studied. Damage mechanism and failure mode of prestressed RPC beams subjected to fire and after fire will be revealed. Fire safety design, assess damage and repair method after fire of prestressed RPC beams will be put forward.

火灾下活性粉末混凝土（简称RPC）的爆裂和力学性能退化将导致结构的毁损，甚至倒（坍）塌。为此，试验研究高升温速率、高应力状态下足尺RPC梁的爆裂性能，得到以正应力水平为纵坐标、以含水率为横坐标的RPC爆裂的上包络线，作为RPC梁爆裂判别与控制的依据；提出抑制RPC梁高温爆裂的纤维种类及掺量、防火涂料类型及涂置厚度等措施。开展预应力RPC梁抗火性能试验研究，建立考虑预应力钢筋高温蠕变、混凝土热-力耦合效应与高温爆裂影响的抗火分析精细化模型，研究荷载水平和保护层厚度等因素对其抗火性能的影响规律。开展火灾后预应力RPC梁力学性能试验，提出火灾后预应力RPC梁剩余承载力、刚度和裂缝宽度的计算方法，研究受火时间、保护层厚度和初始荷载水平等因素对其火灾后力学性能的影响规律。揭示火灾下和火灾后预应力RPC梁的损伤机理和破坏模式，提出预应力RPC梁抗火设计方法和火灾后损伤评估与修复方法。

新型超高性能混凝土-活性粉末混凝土（RPC）具有超高强度和高耐久性，在大跨度结构、超高层建筑和服役环境恶劣的结构中有明显优势，在土木工程领域具有广阔的应用前景。RPC与高强预应力筋结合，形成以预应力RPC梁，能够充分发挥两者材料性能。预应力RPC梁在火灾下的爆裂及承载性能尚不清楚，成为制约其广泛应用的科学技术壁垒。本项目以预应力RPC梁的抗火性能为研究对象，开展了以下工作。. （1）完成了160个RPC试件高升温速率下的爆裂性能试验，结果表明，单掺2%钢纤维RPC在120℃干热养护后，采用ISO834标准升温曲线升温时未发生爆裂，提出了RPC结构构件防火灾高温爆裂的技术措施。. （2）完成了8个预应力RPC梁抗火性能试验，建立了预应力RPC梁抗火性能精细化仿真模型，通过试验和扩参数分析，摸清影响预应力RPC梁抗火性能的关键参数和各关键参数的影响规律，结果表明，荷载水平和保护层厚度对预应力RPC梁抗火性能影响显著，给出了不同耐火极限对应的抗火设计方法和构造措施。. （3）完成了8个预应力RPC梁火灾后承载性能试验，建立了预应力RPC梁火灾后承载性能精细化仿真模型，通过试验和扩参数分析，摸清影响预应力RPC梁火灾后承载性能的关键参数和各关键参数的影响规律，结果表明，受火时间、保护层厚度对预应力RPC梁火灾后剩余承载性能影响显著，给出了预应力RPC梁火灾后剩余承载力的计算方法和加固修复措施。. （4）以试验数据和理论为基础，提出了预应力RPC梁抗火设计建议，为工程设计应用奠定基础。