【作者】 白丽丽；

【导师】 王振清；

【作者基本信息】 哈尔滨工程大学 ， 固体力学， 2008， 博士

【摘要】 受火后钢筋混凝土构件的力学性能复杂,例如,钢筋和混凝土材料强度和弹性模量等力学性能的衰减、钢筋与混凝土粘结强度的退化,导致结构构件截面承载力相应降低,从而使其综合抗力水平降低。因此,在正常使用荷载作用下,结构构件的综合抗力水平低于总体荷载效应,结构构件的可靠性水平就不能满足规范要求。某些受火后钢筋混凝土构件经修复加固可以继续使用,在修复加固前要以一定的理论计算为基础。所以对火灾受损钢筋混凝土结构构件进行可靠性分析,能为火灾后钢筋混凝土结构的破损评估、维修加固及寿命预估提供理论基础,从而确定合理的维修加固方案、提高结构构件的综合抗灾能力、降低维修费用等。本文在前人研究的基础上,对目前国内外火灾工程研究概况进行了系统分析和总结,同时还在以下各方面作了一些尝试,主要内容如下:1.进一步完善受火后钢筋混凝土构件剩余承载力的计算方法,提高其计算精度。针对受火后构件材料力学性能衰减和截面尺寸减小,分别给出分层法和等效截面缩减法对受火后钢筋混凝土构件剩余承载力计算方法进行了初步的探讨。给出受火后构件抗力折减系数,为构件在一定条件下的可靠性分析提供理论基础。2.讨论了火灾后钢筋混凝土构件可靠性的影响因素。一方面考虑火灾过程中钢筋混凝土构件组成材料的钢筋和混凝土的力学性能劣化导致构件抗力的衰减;另一方面考虑将火灾作用过程中的钢筋混凝土构件受力改变等效成一种荷载—等效火灾荷载作用到结构构件上,使组成极限状态方程的荷载作用效应增加。从不同影响因素的角度考虑,建立了不同的受火后钢筋混凝土构件的功能函数,分析了火灾后构件剩余抗力的统计特性。3.引入时变可靠性理论,对长期使用后又遭受火灾作用的钢筋混凝土构件的可靠性进行了分析。即考虑了火灾前抗力随时间的衰减,又考虑了火灾后高温作用对结构构件抗力有所折减,同时又考虑了两个过程抗力的相关性,进而推导出火灾前和火灾后抗力相关性的公式。算例分析表明,使用时间和高温作用对结构构件的可靠性都有一定的影响,将火灾前抗力随时间变化的可靠性问题和火灾后抗力随温度折减的可靠性问题结合起来考虑,同时引入两个过程相关性是符合实际的。4.建立了四面受火后钢筋混凝土轴心受压柱的抗力模型和极限状态方程。分析了受火时间、钢筋和混凝土强度、配筋率、截面尺寸、长细比等不同影响参数对受火后钢筋混凝土柱可靠性指标的影响。5.给出受火后偏心受压柱可靠性分析方法。在综合考虑受火后偏压柱的轴力和弯矩相关性和独立性的情况下,对偏压柱进行了可靠性分析,并将两种情况下的可靠性分析结果进行了全面比较,揭示其差异性。比较结果表明,该方法对受火后钢筋混凝土偏心受压柱进行可靠性分析时比只考虑单一因素(轴力或弯矩)更符合真实情况。更多还原

【Abstract】 Mechanical performance of reinforcement concreter (RC) member after fire duration is complicated, For example, materials strength and elastic modulus of reinforcement and concrete and bond strength between reinforcement and concrete deteriorate significantly, which result in the decrease of load bearing capacity of member, so the resistance decrease. Under the action of regular service load, the reliability of structural member fails to meet the criterion of current code if the resistance is lower than the total load effect.Some RC members post- fire can continue to serve after they are repaired and strengthened, all which are based on some theoretic calculations. So reliability analysis can supply some theory basis to damaged assessment, maintenance-strengthening and life forecast of RC member after fire exposure, and the reasonable maintenance-strengthening method can be determined, the synthesized ability of disaster resistance is increased, the maintenance costs are decreased. Based on the previous research results, besides systematic analysis and conclusions are made other studies in this thesis are included as the following:1. The calculation method of residual bearing capacity of RC member post-fire was perfected in order to improve calculate precision. Against to degeneration on mechanical performance of materials and reduction on section dimension of RC member post-fire, primarily discussion was carried out on the calculation method of residual bearing capacity, such as stratification and equivalent cross-section economization. Resistance reduced coefficient of member was given. All which provide theory basis for reliability analysis of RC member post-fire under some condition.2. Influence factors of reliability of RC member post-fire were discussed .On the one hand, degeneration of member resistance was considered, which was caused by degeneration of mechanical performance of reinforcement and concrete materials. On the other hand, equivalent fire-load was considered, which is caused due to change of stress under fire duration and is equivalent as fire load, so the load effect made up to limit state equation increase. Performance function of RC member post-fire was established and digital character of member resistance was analyzed.3. Time-dependent reliability was introduced, the reliability of RC member subject to fire after long-time serve was analyzed. Degeneration of resistance with active time was considered before fire; Degeneration of resistance under high temperature was also considered after fire. Correlation of resistance between the two procedure was considered simultaneously, and formula of the resistance correlation was deduced. The numerical example indicated that it is more suitable for engineering case to consider the change of resistance fore-fire with active time and the change of resistance post-fire with temperature were considered generally, simultaneously introduce the correlation of resistance between the two course.4. The resistance model and limit state equation of axial compression columns subjected to four-side fire are established .The influences on reliability of RC member after fire exposure are analyzed , which is caused by different parameters such as fire duration, strength of reinforcement and concrete, ratio of reinforcement, section dimension and slenderness ratio and so on.5. Reliability analysis method of eccentric compression column after fire exposure was given. Under the situation that correlation and independence between axis and moment were considered comprehensively, reliability of the eccentric compression column after fire exposure was analyzed, analysis results of the two conditions were compared comprehensively and the difference was disclosed. Results indicate that the method of reliability analysis on eccentric compression column after fire exposure is more coincident with real case than only the single factor of axis or moment is considered.更多还原