钢筋混凝土连续梁火灾下及火灾后的抗剪性能研究

Continuous reinforced concrete beam is an important element of structure, the fire resistance of continuous reinforced concrete beam had significant effect on the fire safety of the whole structure. Compared with simply supported beam, the structural behavior of continuous reinforced concrete beam with both sagging moment and hogging moment is more complex. At present, most of the studies about the fire behavior of continuous reinforced concrete beam have been focused on the flexural behavior of RC beam, and a limited number of studies on shear behavior of continuous reinforced concrete beam have been carried out. According to the program, theoretical and experimental investigation of full-scale continuous reinforced concrete beam specimens will be conducted. The shear behavior of two-span and three-span continuous reinforced concrete beams with various parameters including boundary conditions, shear span to depth ratios, stirrup ratios and fire case in fire will be studied. The shear behavior of two-span and three-span continuous reinforced concrete beams after various fire time will be explored. Moreover, the theoretical analysis of the beam specimens will be accomplished via nonlinear finite element analysis software. Influences of the parameters on shear behavior of continuous reinforced concrete beam will be analyzed. A simplified model will be developed for calculating the shear capacity of continuous reinforced concrete beam. The research results of the program will provide the basis for performance-based fire safety design, damage assessment and repair after fire of the reinforced concrete structures.

钢筋混凝土连续梁是建筑工程中应用最广泛的梁构件形式，其抗火性能对整个结构的火灾安全影响巨大。与简支梁相比，连续梁由于具有正负两个方向的弯矩，受力更复杂，剪力传递机理明显不同于简支梁。目前针对钢筋混凝土连续梁火灾行为的研究大多为抗弯性能研究，而对于抗剪性能研究较少。本项目拟采用足尺钢筋混凝土连续梁试件进行试验和理论研究，在不同边界条件、剪跨比、配箍率及受火工况下，对钢筋混凝土两跨、三跨连续梁在火灾下及不同受火时间火灾后的抗剪性能进行研究，建立非线性有限元分析模型并进行计算，分析各重要参数对火灾下及火灾后钢筋混凝土连续梁抗剪性能的影响规律，提出火灾下及火灾后钢筋混凝土连续梁斜截面承载力的实用计算方法。研究成果将为建筑结构的抗火性能化设计以及火灾后结构的损伤评估和加固修复提供依据。

钢筋混凝土连续梁是建筑工程中应用最广泛的梁构件形式，其抗火性能对整个结构的火灾安全影响巨大。与简支梁相比，连续梁由于具有正负两个方向的弯矩，受力更复杂，剪力传递机理明显不同于简支梁。目前针对钢筋混凝土连续梁火灾行为的研究大多为抗弯性能研究，而对于抗剪性能研究较少。基于此，项目组开展了足尺钢筋混凝土连续梁火灾下的抗剪性能试验以及火灾后的残余抗剪性能试验，并建立了连续梁的非线性有限元分析模型，研究了具有不同荷载比、剪跨比、混凝土保护层厚度、配箍率及受火工况的钢筋混凝土连续梁火灾下及火灾后抗剪性能，分析了受火时间及冷却方式对梁高温后残余抗剪承载力的影响，并与简支梁进行了对比。通过研究，主要得到以下结论：（1）减小剪跨比和荷载比能显著提高火灾下钢筋混凝土梁的抗剪性能。（2）与常温下混凝土保护层厚度增加使梁有效截面高度减小，进而导致梁抗剪承载力下降不同，火灾下混凝土保护层厚度增加后，混凝土对箍筋的保护作用增强，钢筋混凝土连续梁的抗剪能力显著提高，混凝土保护层厚度每增加10mm，梁的耐火极限约提高28%。（3）与单跨受火工况相比，两跨同时受火的连续梁耐火极限降低。高温下连续梁由于发生了内力重分布，其抗剪性能优于简支梁。（4）配箍率对钢筋混凝土连续梁火灾后的抗剪性能有较大的影响，增大配箍率能够较好地约束混凝土，提高梁的抗剪承载力。与自然降温方式相比，采用淋水冷却降温方式的梁受火后残余抗剪性能显著降低。. 本项目的研究成果可以为建筑结构的抗火性能化设计以及火灾后结构的损伤评估和加固修复提供依据。