大跨径混凝土箱梁桥有效温度与应变的实测分析

基于苏通大桥辅助航道桥运营期两年内实测的温度、气象和应变数据,对混凝土箱梁的有效温度与应变进行了分析。结果表明:箱梁的尺寸越小,有效温度变化的范围越大,设计基准期为100年的墩顶梁和跨中箱梁的有效温度范围分别为(-4.3℃,37.3℃)和(-6.1℃,42.2℃);大气前3天的最高(低)平均温度与箱梁有效温度的相关性系数高达0.97,通过回归分析得到的箱梁有效温度与大气前3天平均最高(低)温度的关系式,可用来对箱梁有效温度进行预测。最后提出了修正混凝土收缩、徐变效应的方法,并使用箱梁有效温度对主墩墩底混凝土的竖向相对应变和支座截面箱梁顶板混凝土的纵向相对应变进行了预测。     

基于MRD与LRB混合控制的隔震连续梁桥地震响应

为了研究磁流变阻尼器(MRD)与铅芯橡胶支座(LRB)混合控制对桥梁结构地震响应及隔震效果的影响,以典型三跨连续梁桥为背景,采用平行板模型模拟MRD的本构关系,采用Bouc-Wen模型模拟LRB的力-位移非线性行为,通过对结构的离散建立无控制、LRB单独控制、MRD与LRB混合控制的多种控制工况有限元计算模型,运用有限单元方法建立系统的动力特性矩阵,并采用瞬时最优控制算法对其进行了非线性时程对比分析.分析结果表明:采用MRD与LRB混合控制工况与LRB单独控制工况相比,前者的结构地震响应明显降低,隔震效果得到明显提高;在桥墩、桥台处均安装MRD与仅在桥墩或桥台处安装MRD的LRB隔震桥梁相比,前者对结构地震响应的控制效果更好.     

Estimating extreme temperature differences in steel box girder using long-term measurement data

The extreme temperature differences in fiat steel box girder of a cable-stayed bridge were studied.Firstly,by using the long-term measurement data collected by the structural health monitoring system installed on the Runyang Cable-stayed Bridge,the daily variations as well as seasonal ones of measured temperature differences in the box girder cross-section area were summarized.The probability distribution models of temperature differences were further established and the extreme temperature differences were estimated with a return period of 100 years.Finally,the temperature difference models in cross-section area were proposed for bridge thermal design.The results show that horizontal temperature differences in top plate and vertical temperature differences between top plate and bottom plate are considerable.All the positive and negative temperature differences can be described by the weighted sum of two Weibull distributions.The maximum positive and negative horizontal temperature differences in top plate are 10.30 ℃ and -13.80 ℃,respectively.And the maximum positive and negative vertical temperature differences between top plate and bottom plate are 17.30 ℃ and-3.70 ℃,respectively.For bridge thermal design,there are two vertical temperature difference models between top plate and bottom plate,and six horizontal temperature difference models in top plate.     

大跨径钢箱梁在温度影响下的振型分析

近年来,大跨径钢箱梁桥得到了飞速的发展,同时,在施工中发现温度对它的影响不容忽视．钢箱梁桥在太阳照晒下,箱梁顶部与底部会产生较大的温差,由此而产生的温度应力,会给该桥梁带来初始缺陷,并影响钢箱梁桥的振型变化．自振频率是桥梁结构动力特性的模态参数,也是评价桥梁动力性能的重要依据．以大跨度连续刚箱桥为例,进行建模分析,得出在温度荷载影响下的振型变化情况,对桥梁的设计与施工具有一定的参考价值．     

多跨系杆拱桥极限承载力影响因素

为求得多跨系杆拱桥的稳定系数和安全储备,建立了多跨系杆拱桥的空间有限元模型.通过特征值屈曲分析,得到了成桥状态各工况的稳定系数,并分析了横撑刚度和数量对稳定系数的影响.考虑材料非线性和几何非线性的极限承载力分析,得到了成桥状态的活载稳定系数和恒载稳定系数,并分析了风荷载、温度作用、荷载布置和初始缺陷对稳定系数的影响.分析结果表明,特征值屈曲分析可以提供结构极限承载力的合理估计,横撑刚度对结构稳定系数的影响较横撑数量的影响要大;极限承载力分析过程中主拱四分点部位和跨中部位首先进入塑性状态,静风荷载对结构稳定系数的影响较温度作用和初始缺陷的影响要大.     

Development of computational software for analysis of curved girders under construction loads

The analysis of horizontally curved, trapezoidal steel girders presents a variety of computational challenges. During the erection and construction stages before a concrete deck is available to form a closed section, these girders are weak in torsion and susceptible to warping. Considering the design of an entire bridge system, current design approaches favor the use of a grid analysis methodology. While the use of a grid analysis procedure offers the advantage of computational efficiency, it is unable to capture girder stresses and brace member forces with sufficient accuracy, particularly during the critical erection and construction stages. In this paper, we present an alternative analysis approach based on the finite element method. The developed software has been designed to be computationally efficient and easy to use for bridge designers.     

单拱面预应力混凝土系杆拱桥极限承载力分析

本文将系杆拱桥的拱肋离散为空间圆弧梁单元,基于拖带圆柱坐标推导格林应变张量,用平截面假定及三次插值函数描述圆弧梁单元位移模式,采用加权残值配点法消除剪力和薄膜力闭锁;现吊杆为二力杆单元。对于多室箱形梁系杆离散为梁段单元,考虑箱形梁翘曲、畸变、横向弯曲等。基于连续介质力学U．L．列式法建立系杆拱桥的平衡方程并考虑材料的非线性。根据分析模型编制了相应的计算程序,计算结果与实验结果一致,同时分析了单拱面系杆拱桥极限承载力的影响因素,并计算了一座实桥的极限承载力。     

Practical crack control during the construction of precast segmental box girder bridges

Cracks that occurred in the bottom slab of a precast segmental bridge were investigated through a construction sequence analysis, which revealed that the cracks were caused by excessive deformation during temporary post-tensioning while joining the segments. In addition, a parametric study was performed to evaluate the effects of the prestressing sequence, bottom slab thickness, and position of the prestressing anchors. The structural behavior of the girder sections was greatly affected by the thickness of the bottom slab and the position of prestressing anchors, but not by the prestressing sequence. Based on the results, a construction method that prevents the cracks is proposed.     

大件运输中增设辅助桥墩加固法分析

随着我国现代化工业建设的发展,大件运输己日趋频繁,这些大件运输车辆具有总重和轴重大、通行次数少及行车速度慢等特点。从大件车辆及桥梁的考虑,依据大件运输中桥梁加固工程的特点,结合云南省某工程案例,针对大件运输车辆在中小跨径桥梁的通行要求,采用辅助桥墩法,运用有限元软件对加固前后的桥梁内力进行计算分析,结果表明辅助桥墩法能显著降低由活载作用产生的内力。     

大梁不同工作位置的精确定位在低姿态伸缩梁岸桥中的应用

当前许多国家和地区均对码头提出了明确的限高要求,如PORT EVERGLADES便将码头限高设置为53 m。因此,项目设计人员选择使用伸缩结构来代替以往的仰起结构,从而达到规定的限高标准。在设计工作中,因低姿态伸缩梁岸桥内部空间有限,且在定位安装方面的难度较高,各缠绕和机构安装工作需要技术人员具备更高的精度水平,工作量也更大,难以像以往岸桥一样在车间完成所有的排装工作。需要科学规划安装的实施步骤,全面分析可能出现的情况,并在现场单独完成各项工序。基于此,结合相关实践经验,主要就关于大梁不同工作位置的精确定位在低姿态伸缩梁岸桥中的应用进行了分析和探讨。