混凝土结构裂缝控制的安全度设置水平研究

发布时间：2018-04-02 12:28

本文选题：钢筋混凝土构件　切入点：钢衬钢筋混凝土压力管道　出处：《武汉大学》2013年博士论文

【摘要】：混凝土结构的裂缝控制是关系到混凝土结构能否满足耐久性与适用性要求的重要研究课题之一,但目前各国混凝土结构设计规范的裂缝控制标准和设计方法仍未及达成共识,裂缝控制标准与混凝土结构耐久性关系的研究还不够完善。本文主要从荷载作用下的裂缝宽度计算值的保证率以及基于耐久性的裂缝控制标准的模糊可靠度分析入手,对普通钢筋混凝土构件的裂缝控制标准以及钢衬钢筋混凝土压力管道外包混凝土结构轴向裂缝的控制标准的安全度设置水平进行了较为深入的研究,相关研究成果可供国内混凝土结构设计规范今后修订时借鉴和参考。主要研究成果如下。 (1)提出了不同荷载组合下裂缝宽度计算值的等效保证率的概念。以频遇组合或准永久组合下的裂缝宽度计算值与标准组合下调整短期裂缝宽度扩大系数后的裂缝宽度计算值相等效为原则,提出了不同荷载组合下裂缝宽度计算值的等效保证率的概念。利用等效保证率的概念,可以定量比较不同荷载组合下裂缝宽度计算值的安全度设置水平。针对当前正常使用极限状态的可靠度研究尚不够充分的条件下,本文所提出的不同荷载组合下裂缝宽度计算值的等效保证率指标作为一种合理的尝试,避开了较为繁琐的可靠指标计算,为裂缝控制的安全度设置水平提供了定量分析手段,为定量分析普通钢筋混凝土构件裂缝控制标准的安全度设置水平开辟了一条新途径。 (2)建立了计算单根构件裂缝宽度最大值的随机模型。利用短期裂缝宽度计算值的保证率与短期裂缝宽度扩大系数的关系,将短期裂缝宽度扩大系数视为随机变量,建立了计算单根构件裂缝宽度最大值的随机模型。 (3)建立了裂缝引起构件耐久性损伤的综合隶属函数模型。基于裂缝对混凝土结构耐久性损伤影响的研究成果,以裂缝宽度最大值与保护层厚度之比以及裂缝宽度平均值与保护层厚度之比作为控制指标,建立了裂缝引起构件耐久性损伤的综合隶属函数模型。 (4)建立了裂缝控制标准与混凝土结构耐久性之间的定量关系。根据已建立的裂缝引起构件耐久性损伤的综合隶属函数模型,利用Monte-Carlo法对GB50010-2010规范钢筋混凝土构件裂缝控制标准基于耐久性的可靠指标进行了计算分析,建立了裂缝控制标准与混凝土结构耐久性之间的定量关系。 (5)利用不同荷载组合下裂缝宽度计算值的等效保证率的概念和GB50010-2010规范钢筋混凝土构件裂缝控制标准基于耐久性的可靠度分析结果,对我国现行规范的裂缝控制标准提出了以下修订建议,可供我国现行规范今后修编时借鉴和参考： 1)宜采用荷载频遇组合计算计算钢筋混凝土构件的裂缝宽度,短期裂缝宽度计算值保证率仍宜保持为95%左右。 2)当保护层厚度c80mm时,裂缝宽度限值[Wmax]可取为保护层厚度c的线性函数,即取[Wmax]=kc。对于潮湿大气环境,可取k=0.005；对于氯离子侵蚀环境,可取k=-0.0035。当保护层厚度c80mm时,对于潮湿大气环境[Wmax]可取为0.40mm；对于氯离子侵蚀环境[Wmax]可取为0.30mm。 (6)利用本文所提出的等效保证率概念,对我过现行电力行业标准DL/T5141-2001《水电站应力钢管设计规范》钢衬钢筋混凝土压力管道外包混凝土结构轴向裂缝宽度计算公式的安全度设置水平进行了分析比较,进而从保证裂缝宽度计算公式具有一定的计算精度和符合一定的安全度设置水平的要求出发,对我国现行电力行业标准DL/T5141-2001关于钢衬钢筋混凝土压力管道外包混凝土结构轴向裂缝的控制标准提出了以下修订建议,可供我国现行电力行业标准DL/T5141-2001今后修编时借鉴和参考： 1)宜采用荷载标准组合计算钢衬钢筋混凝土压力管道外包混凝土结构的轴向裂缝宽度,同时提出了两套计算钢衬钢筋混凝土压力管道外包混凝土结构轴向裂缝宽度的建议公式,相应的裂缝宽度计算值的保证率约在85%-90%之间。 2)关于最大裂缝宽度的限值,采用本文建议公式一时,最大裂缝宽度限值可取为0.3mm;采用本文建议公式二时,最大裂缝宽度限值可取为0.35mm。
[Abstract]:Concrete structure crack control is related to the concrete structure can meet one of the important research topics in durability and applicability, but the cracks in concrete structure design specification at present national standards and design methods and control has not yet reached a consensus on the crack control standard and concrete structure durability is not perfect. This paper mainly from the crack the width of loading of the calculated value of the guarantee rate and durability based on crack control standard of fuzzy reliability analysis of reinforced concrete crack control standard and control standard of axial concrete structure crack of reinforced concrete penstock outsourcing the safety level is studied. The research results can for the revision of the code for design of concrete structures and the reference. The main research results are as follows.
(1) the equivalent value calculation of crack width under different combined loads. The concept of guaranteed rate value is equivalent to the principle of calculation of crack width with frequent combination or quasi permanent combination of crack width calculation value and standard under the combination of short-term adjustment after the expansion of the crack width coefficient, the equivalent value calculation of crack width in different load under the combination of the concept of guaranteed rate. Using the equivalent guarantee rate concept, value calculation of crack width can be quantitatively compared under different load combinations the safety level. In view of the current research on reliability of serviceability limit state is still not sufficient conditions, the equivalent value calculation of crack width in different load combinations is proposed under the guarantee index as a reasonable attempt to avoid the tedious calculation of reliability index, provides a quantitative analysis method for the safety level of crack control, fixed A new way is opened up to analyze the level of safety of the crack control standard of ordinary reinforced concrete members.
(2) establish a stochastic model to calculate the maximum value of a single component. The crack width calculated with short-term crack width and crack width rate guarantee short-term expansion coefficient, short-term crack width expansion coefficient as random variables, stochastic model is established to calculate the maximum value of a single component crack width.
(3) establish a comprehensive membership function model of cracks caused by component durability damage. The effect of the crack on the durability of reinforced concrete structure based on the maximum crack width and the protective layer thickness ratio and average crack width and thickness of the protective layer is used as control index, established the cracks caused by the integrated component membership the function model of durability damage.
(4) to establish the quantitative relationship between the crack control standard and the durability of concrete structures. According to the established fracture caused by the integrated component membership function model of durability damage of reinforced concrete members, the GB50010-2010 specification standard of crack control durability based on reliability index were calculated and analyzed by using Monte-Carlo method, established a quantitative relationship between the crack the control standard and the durability of concrete structures.
(5) calculated using equivalent crack width under different load combinations to ensure the concept and specification of GB50010-2010 reinforced concrete structure crack control standard reliability analysis results based on durability rate of cracks in the current specification of the control standard and put forward the following suggestions, for our current standard in the future revision of reference:
1) the crack width of reinforced concrete members should be calculated by the combination of load frequency, and the guarantee rate of the short term crack width should remain about 95%.
2) when the protective layer thickness of c80mm, maximum crack width [Wmax] desirable as a linear function of the thickness of the protective layer of C, which is [Wmax]=kc. to the humid atmosphere, desirable for environmental k=0.005; chloride ion erosion, desirable k=-0.0035. when the protective layer thickness of c80mm, the wet atmospheric environment [Wmax] can be 0.40mm; for chloride ion erosion the environment [Wmax] can be 0.30mm.
(6) using the equivalent proposed the concept of guaranteed rate, safety level of the current power industry standard of DL/T5141-2001< hydropower station should be axial concrete structure crack of reinforced concrete penstock width specification design capacity of steel pipe outsourcing formula is analyzed and compared, and then from that crack width calculation formula has a certain accuracy and meet certain safety level requirements, the power industry standard in China DL/T5141-2001 on the axial wall of steel lined reinforced concrete penstocks concrete structure cracking control standard put forward the following suggestions, for our standard DL/T5141-2001 current power industry in the future revision of reference:
1) should adopt the combination of standard axial load calculation of crack width of reinforced concrete penstock concrete structure at the same time, two sets of calculation of steel lined reinforced concrete penstocks axial crack width formula is proposed, calculation of crack width of the corresponding guarantee rate is about 85%-90%.
2) about the limit of the maximum crack width, the maximum crack width limit can be 0.3mm when using the recommended formula in this paper. When the formula two is recommended in this paper, the maximum crack width limit can be 0.35mm..

【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU375

【参考文献】