既有混凝土桥梁加宽改造设计的基础理论研究

Many highways, especially those expressways finished before and during the 1990s in China can not meet the present traffic demands and need reconstruction of widening transformation, a large number of bridges in the highways and expressways,especially those concrete bridges that take up more than 95% of the total, will undoubtedly become the controlling projects. But so far, the basic theoretical system and the corresponding code system about the designing of the existing bridges widening and reconstruction have not been established at home and abroad. present design referring to the new bridge design specifications and experience for the widening of the existing bridge is clearly lack of scientific background. In this research proposal, systematic research will be conducted on the basic theoretical problems in designing of the existing bridge widening and reconstruction, such as the reasonable determination of design reference period, objective reliability and design loadings;evalution method of reliability, durability and ultimate bearing capacity; the reasonable determination of the concrete shrinkage, creep effects as well as the force transfer mechanism and reasonable structure between old and new bridges for the widening of existing bridges. The final propose are to develop and improve the basic theory in designing of the existing bridges widening and transforming, develop the corresponding rational design methods and establish a reliable basis for the preparation of specifications on existing bridge widening design. the relative research conclusions also can be as the reference to the design of existing bridge strengthening.

我国公路特别是上个世纪90年代中早期以前修建的高速公路已有众多不能满足现在的交通需求而迫切需要进行加宽改造，沿线大量桥梁，特别是占总数95%以上混凝土桥梁的加宽改造无疑成为其关键的控制性工程。但国内外迄今尚未建立有关既有桥梁加宽改造设计的基本理论体系及相应的规范体系，设计人员现在多参照新建桥梁设计规范及经验进行既有桥梁的加宽改造设计，显然缺乏科学性。本申请项目将对既有混凝土桥梁加宽改造设计的基础理论问题，诸如既有桥梁加宽改造设计时设计基准期、目标可靠度及设计荷载的合理确定；加宽改造桥梁的可靠度、耐久性及极限承载能力的分析评定方法；加宽改造桥梁混凝土收缩、徐变效应的合理确定以及新旧桥梁连接的传力机理和合理构造等进行较为系统的理论与试验研究，发展和完善既有桥梁加宽改造设计的基础理论，提出相应的合理设计方法，为桥梁拓宽改造相关设计规范的编制提供可靠依据，其研究成果亦可为既有桥梁的加固设计提供参考

本项目对既有混凝土桥梁加宽改造设计的基础理论进行了研究，提出了相应的设计方法，可供相关设计规范的编制时参考。项目研究共完成论文36篇，其中博士学位论文4篇、硕士学位论文7篇，期刊论文25篇；申请发明专利1项。主要成果如下：.（1）建立了包括结构可靠度基本参数（设计基准期、目标可靠度、设计荷载等）确定方法、结构抗力退化模型、体系时变可靠度计算理论等在内的加宽改造混凝土桥梁上部结构时变可靠度分析体系。.（2）提出了适合混凝土桥梁拼接状态的混凝土自由收缩和新旧混凝土约束收缩预测模型。.（3）提出了不同上部结构形式（实心板、空心板、T梁、箱梁）桥梁加宽改造时收缩徐变效应的计算方法及减小收缩徐变效应的措施。.（4）建立了考虑随机性、模糊性以及信息不完整性的加宽改造混凝土桥梁耐久性评定体系。.（5）提出了基于超声脉冲法和冲击回波法测定RPC弹性模量的简便方法。.（6）提出了解析表达的混凝土疲劳应变的粘-弹-塑性预测模型以及混凝土力学性能的尺寸效应律。.（7）研发了采用超高性能活性粉末混凝土RPC灌注的混合梁钢-混结合段PBL剪力键和采用RPC强化再生骨料的再生骨料混凝土材料。.（8）对预应力孔道注浆状态无损检测方法中的冲击回波法和超声波层析成像法开展了系统的试验和理论研究。研究了实际结构各参数对检测效果的影响规律，提出了预应力孔道无浆孔道处冲击回波厚度频率的计算公式以及一种超声波层析成像正演模拟中的线性走时插值射线追踪综合改进算法（综合改进LTI算法），可用于桥梁拼宽时既有桥梁状态检测与评定。.（9）建立了不同壁厚箱形墩在寒流降温作用下的负温差分布模式，提出了适合长江中游地区超宽分离式混凝土箱梁在日照辐射和寒流降温作用下的竖向温度梯度模式。.（10）提出了混凝土箱梁顶板在局部荷载作用下的极限荷载和塑性横向受力有效分布宽度的计算公式。