【作者】 张凯；

【导师】 朱虹；

【作者基本信息】 东南大学 ， 结构工程， 2018， 硕士

【摘要】 纤维增强复合材料(Fiber Reinforced Polymer,FRP),亦称纤维增强塑料(Fiber Reinforced Plastics)或先进的复合材料(Advanced Composites Materials,ACMs)具有高比强度和耐疲劳性能优越等突出的力学性能,密度低和抗腐蚀性强等显著的物理性能。其在土木工程的应用可分为两大领域:一类为应用FRP作为结构修复材料加固既有结构,另一类是应用FRP作为结构增强材料在新建结构中替代部分传统钢筋直接使用。虽然FRP材料在土木工程中的应用日益扩大,但是目前对于火灾或高温下研究很缺乏,并且已有文献中以直接暴露于高温所测得的性能数据并不适合作为实际结构中FRP材料的性能指标的依据,而这些性能指标通常并不乐观,且离散性较大,这些问题已成为了FRP材料推广应用的主要瓶颈问题。针对此,本文重点开展了带包覆层BFRP筋的高温及拉伸加载试验,通过设置包覆层模拟FRP筋在结构中的实际情况,对结构中FRP筋高温下和高温后的残余力学性能进行研究。论文优先选出高温下抗开裂性能良好的包覆层材料,开展了在相同的环境温度下不同预制裂缝宽度(最大裂缝宽度为2.5mm)对包覆层试件内部温度场的影响。试验结果表明在本试验的温度环境中(以100℃/min的速率升至400℃),短切玄武岩纤维增强水泥砂浆包覆层具有优良的高温抗开裂性能,裂缝对试件温度场的影响较小。为了解决高温下带包覆层试件内部BFRP筋应变数据的采集难点,采用基于光纤BOTDA(布里渊散射)技术制备自传感BFRP筋从而获取应变数据。而这一方法需要进行高温工况中光纤传感性能的试验研究,为此详细讨论了对光纤传感性能有重要影响的两个关键参数——温度系数和应变系数,并在不同情况下标定了系数的大小,从而为后续数据的可靠性提供了保证。在上述研究的基础上依次开展了高温下/后带包覆层试件(预制不同的裂缝宽度)BFRP筋残余力学性能试验,并将其与高温下FRP裸筋或高温后BFRP裸筋的力学性能进行对比分析。试验结果表明,不同预制裂缝宽度包覆层试件BFRP筋(直至裂缝宽度达到2.0mm)的高温下的力学性能随着裂缝宽度的变化较小,且优于筋材表面温度场和高温作用时间相同情况下FRP裸筋的残余力学性能,带包覆层BFRP筋高温后的力学性能受包覆层细小裂缝(<2.0mm)宽度的影响较小,但包覆层整体的作用明显,带包覆层BFRP筋在400℃下的高温后力学性能显著优于BFRP裸筋。最后总结和对比文献中FRP裸筋残余力学性能公式,分别对本文试验情况下带包覆层BFRP筋高温下/后残余抗拉强度和弹性模量进行拟合,提出火灾高温时及高温后结构中FRP筋残余力学性能建议公式,从而为FRP增强/加固混凝土构件耐高温性能的设计提供可靠的参考和支撑。更多还原

【Abstract】 Fiber Reinforced Polymer(FRP)or fiber-reinforced plastics,advanced composites materials(ACMs)has the excellent mechanical performance of high specific stiffness and specific strength,superior fatigue endurance,and has the physical advantages of low density and excellent corrosion resistance.Its application in the civil engineering structure can be divided in two major fields: one is to apply FRP as a structural restoration material to strengthen existing structures,and the other is to use FRP as a structural reinforced material to replace a part of traditional steel bars in a new structure.Although the application of FRP is increasing,there is a lack of research under high temperatures,and more attention has been focused on the performance indicators of FRP directly exposed to high temperatures,which is not suitable in paractical structures.Morevoer,the performance indicators mentioned above are not optimistic and discrete.These aspects have impeded the wide acceptance and use of these materials.Thus the experimental study of the residual mechanical properties of BFRP bars with cladding layer,which is to get close to the practical situation,during and after temperatures,is more reasonable and practical.Firstly,the cladding layer with good resistance to crack was selected.Results from the tests indicates that cement mortar reinforced with chopped basalt fiber can avoid cracks under the heating rate of 100℃/min up to 400℃.Based on that,the influence of prefabricated crack width on the temperature filed of the cladding layer member was investigated.Through the comparison of the results,the effect of crack width is less important.Secondly,to solve the difficulty of acquiring the strain of BFRP bars with cladding layer,an optical sensing technology,i.e.,BOTDA(brillouin optical time domain analysis),is utilized.And the two key parameters,i.e.,the temperature coefficient and the strain coefficient,are calibrated under different conditions,which provides guarantee for the reliability of the subsequent data.Then,the mechanical properties of BFRP bars with cladding layer,during or after high temperatures,were investigated.For the experiment during high temperatures,the results indicated that the influence of crack width(up to 2.0mm)on the FRP mechanical properties is not significant.And compared with bare BFRP bars after the same high temperatures,its strength and modulus is higher.For the experiment after high tempertures,the results indicated that the influence of crack width(<2.0mm)is less important.And compared with bare BFRP bars at 400℃,its strength and modulus is obviously higher.Finally,data from the experiments was utilized to proposed empirical relations for variation of tensile strength and modulus of BFRP bars that with cladding layer with temperatures.更多还原