锈蚀钢筋混凝土保护层锈胀开裂时间的预测模型

由钢筋锈蚀引起的混凝土保护层锈胀开裂是混凝土结构耐久性极限状态的重要标志,是决定结构使用寿命的重要因素。以钢筋均匀锈蚀为前提,考虑锈蚀产物的变形特性以及锈胀裂缝开展过程中锈蚀产物进入裂缝的实际情况,借助弹性力学和Faraday腐蚀定律,建立混凝土保护层锈胀开裂时刻的钢筋锈蚀率以及锈胀开裂时间计算公式。针对影响混凝土保护层锈胀开裂时间各主要因素的分析表明,增大钢筋的混凝土保护层厚度、减小钢筋直径、提高混凝土强度以及控制锈蚀产物的体积膨胀率都有利于混凝土结构耐久性的提高。与已有试验结果的对比分析可知,对于加速锈蚀和长期锈蚀情况,计算公式的预测结果均较为理想,可用于由钢筋均匀锈蚀引起的混凝土保护层锈胀开裂时间的预测分析。     

Probabilistic service life of reinforced concrete structures with randomly distributed corrosion-induced cracks

This paper proposed a probabilistic service life prediction method for reinforced concrete (RC) structures with randomly distributed chloride corrosion-induced cracking. In the proposed method, spatial randomness of environmental, geometric and physical factors was considered that influence corrosion process and crack propagation of RC structures at the material level. Karhunen–Loéve (KL) expansion method was utilised for modelling the spatial random fields. Four limit state functions were proposed based on four deterioration events (corrosion initiation, surface crack initiation, modulus degradation and exceedance of repair limit). Then, time-dependent reliability analyses of an RC bridge slab were conducted using the proposed method. Finally, sensitivity analysis of the statistical parameters including mean, variance, correlation length as well as the truncation number for KL expansion method were conducted to determine the effects of those parameters to the service life.     

钢筋混凝土锈胀开裂及对腐蚀反作用影响研究

在阅读分析大量国内外研究文献和总结对比欧盟、挪威及中国相关土木规范的基础上,深入系统的综述了腐蚀环境下钢筋混凝土锈胀开裂、裂缝宽度和裂缝对腐蚀影响三方面的研究现状,分析表明已有的大量锈胀开裂研究中未能深入考虑混凝土内部实际初始缺陷;目前尚缺乏锈胀裂缝宽度的理论分析;且未从锈胀裂缝动态发展对腐蚀进程时变影响的角度研究裂缝与腐蚀的关系。相关研究的随机分析在国际上仍处于起步阶段,而针对我国具体环境特征的研究依然十分缺乏,由此对未来研究趋势进行了展望。     

碳化引起混凝土锈胀开裂前钢筋锈蚀量的研究

在分析碳化引起的钢筋混凝土构件中钢筋腐蚀机理和已有钢筋锈蚀量预测模型的基础上。建立了全面考虑氧气浓度、温度、相对湿度、保护层厚度、钢筋直径和混凝土强度的多因素钢筋锈蚀量预测模型，且进行了实际工程的验证，可为混凝土结构耐久性评估、可靠性鉴定提供科学的依据。     

荷载作用下开裂钢筋混凝土梁锈胀开裂模式及锈蚀分布研究

为提高混凝土结构的服役性能,对混凝土保护层的锈胀开裂过程进行研究。对荷载作用下锈蚀18个月的内掺氯盐钢筋混凝土梁的截面锈胀裂缝分析发现：环向裂缝宽度沿径向呈指数函数变化;锈胀裂缝的开裂模式、锈蚀产物与钢筋混凝土受力状态、骨料及裂缝的相对位置均密切相关;保护层破坏以层状破坏为主。通过研究提出,在对锈蚀钢筋混凝土梁进行承载力分析时,建议剪压区不考虑受压混凝土保护层的作用,对剪拉区和弯拉区钢筋与混凝土之间的黏结性能要进行折减。     

Accurate cover crack modelling of reinforced concrete structures subjected to non-uniform corrosion

Abstract

Concrete cover cracking caused by reinforcement corrosion is a significant durability problem of reinforced concrete (RC) structures. Extensive research has been carried out in the last few decades while most were focused on corrosion of a single reinforcing bar. Very little research has examined the whole cover cracking of RC structures due to multiple reinforcement corrosion. This article develops a numerical model to predict the structural failure of the whole cover of concrete induced by corrosion of multiple reinforcing bars. Moreover, a non-uniform corrosion model is established based on experimental results, in contrast to conventional uniform assumption. Two typical cover failure modes under the non-uniform corrosion of multiple reinforcing bars are identified and discussed. The effects of cover thickness, reinforcement spacing, fracture energy of concrete, etc., on cover cracking patterns and crack width are also investigated. The derived numerical model is verified by comparing the results with those from experiments in literature. Accurate prediction of concrete cover cracking can allow timely maintenance of existing structures and rational design for new buildings which prolongs the service life of the RC structures.     

混凝土结构锈胀裂缝中铁锈分布的试验研究

混凝土结构锈胀开裂是导致混凝土结构耐久性失效的主要原因.在锈胀开裂过程中,铁锈是否填充到锈胀开展的裂缝中,是影响锈裂模型预测结果准确与否的重要因素之一.对人工气候环境下加速劣化的混凝土试块进行切片研究,采用数码显微镜观察了混凝土锈胀开裂裂缝中铁锈分布的情况,由此分析随裂缝开展铁锈发展的过程.试验研究认为,对于外裂裂缝,在裂缝开展到保护层表面之前,铁锈对裂缝的填充可忽略不计;只有在裂缝贯通到保护层表面后,铁锈才会逐渐填入钢筋附近的裂缝之中,并能在较远位置的裂缝边缘观察到铁锈的吸附.而对于内裂裂缝,钢筋锈蚀到一定程度后,也会有少量的铁锈填入裂缝中,但填充过程要缓慢得多.铁锈发展的这一特性,对混凝土结构锈裂过程的分析和合理锈裂模型的建立具有非常重要的指导意义.     

Coupled reliability model of biodeterioration, chloride ingress and cracking for reinforced concrete structures

Maintaining and operating civil infrastructure systems has been recognized as a critical issue worldwide. Among all possible causes of safety reduction during the structural lifetime, deterioration is particularly important. Structural deterioration is usually a slow time-dependent process controlled by safety and operation threshold specifications. This paper presents a model of RC deterioration by coupling biodeterioration (i.e., chemical, physical and mechanical action of live organisms), steel corrosion, and concrete cracking. The final purpose of the model is to compute the reduction of the concrete section and the area of steel reinforcement in order to assess the change of structural capacity with time. Given the uncertainties in both the parameters and the model, the probabilistic nature of loads, the material properties and the diffusion process are taken into account to evaluate structural reliability. The model is illustrated with an example where the inelastic behavior of a pile subject to random loading is considered. The results of the analysis have shown that the effect of biodeterioration on the structural performance is significant and can cause an important reduction of its lifetime. On the whole, the paper states that modeling the effects of biodeterioration in RC structures should be included as part of infrastructure planning and design, especially, when they are located in aggressive environments.     

混凝土结构锈裂形态试验研究及数值模拟

混凝土结构服役后期会出现保护层剥落的情况,混凝土保护层剥落与内部锈胀裂缝的分布情况密切相关。通过对不同尺寸与配筋情况的混凝土试块进行内部锈胀裂缝开展与分布研究,采用改进通电加速锈蚀方法加速试块劣化,通过切片观测锈蚀后试块内部锈胀裂缝形态,研究箍筋、保护层厚度、钢筋间距对内部锈胀裂缝开展的影响。研究结果表明：箍筋显著改变了内部锈胀裂缝开展与分布情况;混凝土保护层厚度较小或钢筋间距较大时,钢筋锈胀裂缝表现为单根锈胀开裂形式,反之则表现为钢筋之间的水平贯通裂缝。基于黏聚力单元建立了有限元分析模型,将钢筋锈胀变形作为位移加载依据,对试块锈裂过程进行数值分析,模拟结果与试验结果吻合较好。     

浅论钢筋混凝土结构抗火设计

现就钢筋混凝土结构抗火性能的研究进行了综合述评，分析了火灾下钢筋混凝土力学性能的劣化过程，针对现阶段的研究状况，对需要深入探讨的课题提出了建议。     

钢筋混凝土屋面井字梁裂缝的分析与处理

结合工程实例,对钢筋混凝土屋面井字梁出现裂缝的原因分析,采取相应的处理措施。     

混凝土工程裂缝预防与控制

对混凝土结构受力裂缝，及对混凝土温降、气干变形在外部、内部约束下引发的各不同的收缩裂缝，作了简明的开裂机制分析；在此基础上，针对各不同的致裂要素，从配置钢筋与混凝土的材料选配、施工技术、分段设缝等几个方面阐释了裂缝防控技术要点也简介了对传统控温防裂做法有所补充发展的新概念——“致裂温度”：为配合做好混凝土裂缝防控工作提供启迪、参考。     

钢筋混凝土结构中钢筋机械锚固技术研究进展

以钢筋混凝土结构中钢筋机械锚固技术为研究对象,分析了国内外学者对钢筋机械锚固技术的研究现状和一些工程应用实例,进一步提出了椭圆形钢筋锚固装置的研究思路,以期能够缓解钢筋拥挤,为今后钢筋混凝土结构的研究提供理论依据。     

混凝土保护层锈胀开裂条件的弹性力学分析

混凝土中钢筋锈蚀是混凝土结构耐久性研究的重要内容,研究混凝土中的钢筋锈蚀,并建立混凝土保护层锈胀开裂时钢筋锈蚀量估计模型,是分析现有结构性能退化及耐久性评估的关键工作,对于准确预测结构的使用寿命与剩余寿命具有十分重要的意义.采用弹性力学分析方法,对混凝土保护层锈胀开裂全过程进行了建模,借助一些合理的假设,得到了混凝土保护层锈胀开裂条件的理论计算公式,该公式不仅可以应用普通混凝土结构,也可应用于其他类型混凝土结构.最后并对公式进行了验证,表明理论计算公式具有较好的实用性.     

施工期钢筋混凝土结构的安全性

介绍了施工期建筑结构安全分析的内容,分别阐述了钢筋混凝土结构施工期荷载,抗力及可靠度的特点,并对目前国内外施工期建筑结构的安全分析研究进展进行了总结和展望,以期促进施工期钢筋混凝土结构安全性分析。     

锈蚀钢筋混凝土保护层破坏模式

本文采用弹性力学及有限元方法，分析钢筋锈蚀产物体积膨胀在周围混凝土中的应力分布。提出了混凝土保护层四种破坏模式：直角破坏、楔形破坏、垂直方向顺筋开裂及整层破坏。工程调查结果与本文提出的四种破坏模式吻合较好。     

考虑材料耐久性的在役混凝土结构可靠度研究

基于近年来大量的相关研究文献，从混凝土结构的材料耐久性和在役结构的荷载特点出发，按结构可靠性分析的常规步骤，对在役混凝土结构可靠性研究的成果和应用作了概括性介绍，并对不同的方法做了比较分析，以期为在这方面的进一步应用和发展提供参考。并指出基于信息更新的在役结构可靠性研究将是该领域今后一个新的研究方向。     

In-situ condition monitoring of reinforced concrete structures

Performance of concrete structures is significantly influenced and governed by its durability and resistance to environmental or exposure conditions, apart from its physical strength. It can be monitored, evaluated and predicted through modeling of physical deterioration mechanisms, performance characteristics and parameters and condition monitoring of in situ concrete structures. One such study has been conducted using Non-destructive testing equipment in the city of Bhopal and around located in India. Some selected parameters influencing durability of reinforced concrete (RC) structures such as concrete cover, carbonation depth, chloride concentration, half cell potential and compressive strength have been measured, for establishing correlation among various parameters and age of structures. Effects of concrete cover and compressive strength over the variation of chloride content with time are also investigated.     

Dynamic analysis of reinforced concrete frame-wall structures

The nonlinear response and failure mechanism of reinforced concrete frame-wall systems is investigated through the employment of a mathematical model. The mathematical model is composed of two mechanical models: a concentrated spring model used for the flexural behaviour of beam and column type members and a multiple spring model used for the response of the wall system. Both account for inelastic behaviour of reinforced concrete.The mathematical model is applied to a ten-storey frame-wall system. The constituent members are replaced by one of the mechanical models whose stiffness characteristics reflect the inelastic properties and hysteresis tendencies of the member. The resulting equations are solved by a step by step time integration procedure. Computed results are compared with experimental results obtained from a structure tested on the Illinois earthquake simulator. The correlated results are then used to define the significant response characteristics.     

核心型钢混凝土组合结构体系应用前瞻

主要介绍了核心型钢混凝土组合结构体系在高层住宅建筑中的应用前景和性能优势,分析了核心型钢混凝土组合结构体系在国内外的研究现状,并探讨了核心型钢混凝土组合结构目前存在的主要问题.对21个不同配钢形式的核心型钢混凝土柱试件进行截面非线性分析.分析结果表明,各种形式核心配钢均能有效提高柱截面在较高轴压比下的曲率延性系数.介绍了2个核心型钢混凝土组合结构工程实例.在综合分析基础上,提出了核心型钢混凝土组合结构体系的抗震设计建议和深入研究思路.