聚丙烯混凝土板柱结构抗火性能研究

The fire behavior polypropylene fiber(PPF) reinforced concrete slab-column structures is studied by means of the standard real scale fire tests, consisting of 14 slab-column connections and 8 plates. During the tests the experimental phenomena and temperature distributions as well as high temperature deformations will be recorded, meanwhile the crack development and the failure mechanism of the slab-column connections and the plates with various edge conditions are studied. The influence of the length and proportion of PPF on cracking and spalling, temperature distributions and high temperature deformations is also discussed and compared with the results obtained from the precious tests.. Based on the fine thermo-mechanical coupled model the key parameters, such as the lengths and contents of PPF, various boundary constraints and so on, to the fire behavior of PPF concrete slab-column structures will be studied. The calculation methods of ultimate capacity of PPF concrete slab-column connections and plates can be deduced separately by means of experimental and theoretical data. The concise methods can be used in the fire resistant design of PPF concrete slab-column structures conveniently.

本项目拟利用火灾试验炉开展聚丙烯纤维(PPF)混凝土板柱结构的标准抗火试验研究，包括14个足尺板柱节点抗火试验和8个足尺平板抗火试验，试验详细记录各种试验现象、板柱构件温度变化以及高温变形情况，考察不同约束条件下PPF混凝土板柱构件的裂缝开展、破坏模式，给出PPF长度与掺量对板柱构件高温开裂及爆裂、内部温度场和高温变形影响的规律，并与已有普通混凝土板柱结构抗火试验进行对比分析。. 基于精细化有限元模型对板柱结构进行热-力耦合分析，研究PPF长度与掺量、边界约束等关键参数对PPF混凝土板柱结构抗火性能的影响规律。结合试验和理论数据分别给出PPF混凝土板柱节点和平板的高温极限承载力计算方法，便于PPF混凝土板柱结构的抗火设计。

申请人首先对常温下和高温后PPF混凝土的材料性能开展研究，发现常温下PPF混凝土的峰值应力、弹性模量均高于基准混凝土，而峰值应变和泊松比则与PPF掺量和长度相关。其中PPF长度为3mm、掺量为1.0kg/m3时峰值应力最大。高温后，PPF混凝土的应力-应变全曲线相似，其质量损失率、峰值应力、峰值应变、弹性模量和泊松比的变化主要取决于PPF高温融解和气化对混凝土截面的削弱和温度应力释放两个方面。随着经历温度的升高，峰值应力和弹性模量逐渐减小，峰值应变和泊松比先降后增。数据对比表明PPF长度为9mm，掺量为0.5kg/m3时，高温后性能最优。基于回归分析，建立了高温后PPF混凝土单轴受压应力-应变的分段式本构方程，并结合电镜扫描结果分析了低坍落度PPF混凝土的微观结构和破坏机理。同时申请人开展了PPF混凝土板和板柱节点的抗火性能试验研究，试验考查PPF掺入对混凝土力学性能的影响。在PPF混凝土板的抗火试验中考查受火时板的裂缝开展规律和破坏模式，获得炉温、受火全过程的板内温度场变化规律以及板的平面内与平面外变形规律。在板柱节点抗火试验中测量了板柱节点的位移，并记录了高温时和高温后板柱节点裂缝的扩展情况，得到PPF混凝土板柱节点的裂缝扩展规律。通过ABAQUS对火灾下PPF混凝土板柱节点进行有限元分析，并将模拟结果和试验结果进行对比分析，包括混凝土截面温度、钢筋温度以及关键点位移-时间变化等，试验模型均吻合较好，为下一步参数分析奠定了基础。