五等跨连续梁模态分析试验及冲击系数

分析计算五等跨连续梁的固有频率和振型,探讨连续梁桥冲击系数与其固有频率和振型的关系,并进行了连续梁振动试验,试验模型采用槽型梁,支撑方式采用钢锟轴支撑,试验结果运用DASP模态分析软件进行处理,得到五等跨连续梁的前5阶振型及频率。利用Midas有限元分析软件对连续梁进行有限元分析,将其计算结果与试验结果进行对比,证实振型变化的真实性。经过试验分析,连续梁的前5阶振型最大曲率位置被确定,结合规范讨论计算冲击系数时结构固有频率的选取。结果表明:当计算跨中正弯矩效应时,冲击系数宜按照《桥规》采用基频计算;当计算中支座负弯矩效应时,冲击系数应采用第3阶频率。     

基于视频图像技术的两不等跨连续梁振动研究

针对两不等跨连续梁的试验模型,通过视频采集设备录制梁的振动视频,并采用Matlab软件将其振动视频分解成图像,对一系列的图像运用多项式拟合法进行亚像素边缘检测,对由视频得到的梁边缘时域信号进行模态分析,得到连续梁的前三阶振型和频率。将得到的结果与Midas建立的有限元模型分析结果及传统检测结果比对表明,基于视频图像技术的振动分析有较高的精确性。结合规范讨论了计算冲击系数时的频率选择。结果表明:当计算跨中正弯矩效应时冲击系数应该按照《桥规》采用基频计算,在计算中支座负弯矩效应时冲击系数应采用第2阶频率进行计算。     

4等跨连续梁模态试验分析及冲击因数研究

为了研究连续梁桥冲击因数与其固有频率和振型的关系,分析计算了4等跨连续梁的固有频率和振型,并进行了4等跨连续梁振动试验;通过分析和试验,确定梁的前四阶振型最大曲率位置,结合规范讨论了计算冲击因数时结构固有频率的选取。结果表明:当计算4等跨连续梁桥的正弯矩效应时,冲击因数计算采用基频是合理的;当计算负弯矩效应时,不应采用基频,应采用第2阶频率。     

不同跨径组合的三跨连续梁的模态分析试验

分析计算三跨等截面等跨连续梁的固有频率和振型,探讨不同跨径组合三跨连续梁振型的区别,并讨论冲击系数的取值。用Midas有限元软件进行分析计算,采用槽型梁作为连续梁模型,以钢辊轴作为支承,为并用DASP模态分析设备对试验模型进行模态分析,得到不同跨径组合下连续梁的前三阶频率及其振型,并将试验结果与Midas计算结果进行对比,证实振型变化的真实性。结果表明,第二、三阶振型随着跨径组合的变化会出现转折,支座处振型的曲率发生变化;考虑跨中支座正弯矩效应时,冲击系数按照《桥规》采用基频计算;考虑中支座负弯矩效应时,冲击系数应采用第二或第三阶频率计算。     

黑山湖特大桥跨兰新铁路零号块临时固结计算

连续梁桥墩和梁存在支座,是铰接关系。而连续梁桥采用悬臂施工在没有合拢前是悬臂状态,为了保证挂篮施工过程的安全性,必须对连续梁桥墩和梁进行临时固结处理。因此临时固结成败直接关系着连续梁悬臂施工的安全和稳定。本文结合黑山湖跨兰新铁路立交特大桥,分析连续梁桥临时固结的设计计算。     

四不等跨连续梁振动试验分析及冲击系数探讨

分别讨论并比较在不同跨径比下的连续梁的固有频率及振型的变化规律和异同点。试验梁采用槽型梁,除了对模型进行固有振动分析和理论计算外,还采用有限元软件分别对各个跨径比下的试验模型进行有限元计算分析和计算。以有限元的计算结果作为参考,同传统检测试验得到的结果进行对比分析,论证振型变化规律的真实性。结果表明:对于不同跨径的对称四跨连续梁,支座对称移动时,前3阶振型始终对于中支座是对称或者反对称的,并且中支座在2阶振型中首先出现反弯点。当计算跨中正弯矩效应时,冲击系数按照《桥规》采用基频计算;当计算中支座负弯矩效应时,冲击系数应采用第2阶频率进行计算。     

连续梁0#梁段施工分析

本文针对锦州市某大桥悬臂连续梁工程,对连续梁0#梁段施工进行了分析,包括临时支墩施工分析、0#块满堂支架搭设及预压分析、模板、钢筋工程施工分析.通过对殷陈特大桥悬臂连续梁0#梁段施工分析,为广大施工一线人员提供借鉴.     

基于视频图像法的两跨连续梁振动研究

针对两跨连续梁实验模型,通过采集连续梁振动视频,再将视频转化为数字图像的方法,运用多项式拟合法作为视频图像边缘检测技术中亚像素精度图像边缘识别的算法,对每幅图像进行亚像素边缘识别检测,获取各时刻梁边缘各点位置,经Matlab程序读取整个振动过程梁边缘数据,即可得到梁边缘各点的振动时间历程,进而通过DASP系统对测得数据进行模态分析,得到连续梁前二阶频率和振型。对比采用传统加速度传感器识别连续梁振动信号分析结果表明,两者模态参数识别结果具有一致性,基于视频图像边缘检测技术的连续梁振动测试是可行的。     

数字图像技术在三等跨连续梁振动分析中的运用

为了论证视频图像法实测三等跨连续梁固有频率和振型的可靠性及精确性,使用视频录制设备录制三等跨连续梁的振动视频,通过Matlab将其分解成一系列图像,并运用多项式拟合程序将边缘精确到其亚像素级别,得到梁上各点的时间历程,最后进行模态分析。将得到的梁的前3阶频率和振型和通过传统检测方法测得的结果,分别与有限元软件建立模型进行模态分析所得到的结果进行误差对比。结果显示视频图像法对测量三等跨连续梁的固有频率及振型是有效可靠的,而且比传统桥梁检测方法更接近理论计算结果。     

两等跨曲线连续梁模态试验及有限元分析

为了得到曲线连续梁的固有频率和振型,以便为桥梁检测提供校核依据;有机地结合了有限元模态分析方法和试验模态分析方法,对某两等跨曲线连续梁进行了模态分析,得到曲梁的前4阶频率及振型,并将试验结果与有限元计算结果进行对比。结果表明:除去一阶频率误差较大外,第2~4阶相对误差均小于4%,振型基本吻合;一阶固有频率受扭转影响较大,第2~4阶频率受扭转影响依次减小;曲梁前4阶频率均小于等跨直梁。     

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part Ⅱ: Analytical study

Strengthening reinforced concrete (R. C.) beams using prestressed glass fiber-reinforced polymer (PGFRP) was studied experimentally as described in Part Ⅰ of this paper (Huang et al., 2005). In that paper, R. C. beams, R. C. beams with GFRP(glass fiber-reinforced polymer) sheets, and R. C. beams with PGFRP sheets were tested in both under-strengthened and over-strengthened cases. The test results showed that the load-carrying capacities (ultimate loads) of the beams with GFRP sheets were greater than those of the beams without polymer sheets. The load-carrying capacities of beams with PGFRP sheets were greater than those of beams with GFRP sheets. The objective of this work is to develop an analytical method to compute all of these load-carrying capacities. This analytical method is independent of the experiments and based only on the traditional R. C.and P. C. (prestressed concrete) theory. The analytical results accorded with the test results. It is suggested that this analytical method be used for analyzing and designing R. C. beams strengthened using GFRP or PGFRP sheets.     

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part I： Experimental study

INTRODUCTION The aging or deterioration of existing R. C.(reinforced concrete) or P. C. (prestressed concrete)structures is one of the major problems that modernengineers have to face. If the flexural or shear strengthof R. C. or P. C. structures is not sufficient to maintaintheir service functions, strengthening of these struc-tures becomes necessary. To date, steel plates havebeen used to strengthen concrete members. Usingcomposite plates to strengthen R.C. or P.C. structures…     

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part II:Analytical study

INTRODUCTION When the flexural load-carrying capacities of existing R. C. or P. C. structures are not sufficient for the service loads, structural strengthening becomes necessary. Using steel plates to strengthen concrete members is a traditional method (Raithby, 1980) and is still an important and popular way at the present time. Fiber-reinforced polymer (FRP) sheets and plates have been used recently as an alternative to steel plates for strengthening concrete structures be-cause th…     

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part Ⅰ: Experimental study

This work is aimed at studying the strengthening of reinforced concrete (R. C.) beams using prestressed glass fiber-reinforced polymer (PGFRP). Carbon fiber-reinforced polymer (CFRP) has recently become popular for use as repair or rehabilitation material for deteriorated R. C. structures, but because CFRP material is very stiff, the difference in CFRP sheet and concrete material properties is not favorable for transferring the prestress from CFRP sheets to R. C. members. Glass fiber-reinforced polymer (GFRP) sheets with Modulus of Elasticity quite close to that of concrete was chosen in this study. The load-carrying capacities (ultimate loads) and the deflections of strengthened R. C. beams using GFRP and PGFRP sheets were tested and compared. T- and ⊥-shaped beams were used as the under-strengthened and over-strengthened beams. The GFRP sheets were prestressed to one-half their tensile capacities before being bonded to the T- and l-shaped R. C. beams. The prestressed tension in the PGFRP sheets caused cambers in the R. C. beams without cracks on the tensile faces. The PGFRP sheets also enhanced the load-carrying capacity. The test results indicated that T-shaped beams with GFRP sheets increased in load-carrying capacity by 55% while the same beams with PGFRP sheets could increase load-carrying capacity by 100%. The ⊥-shaped beams with GFRP sheets could increase load-carrying capacity by 97% while the same beams with PGFRP sheets could increase the loading-carrying capacity by 117%. Under the same external loads, beams with GFRP sheets underwent larger deflections than beams with PGFRP sheets. While GFRP sheets strengthen R. C. beams, PGFRP sheets decrease the beams' ductility, especially for the over-strengthened beams (⊥-shaped beams).     

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part Ⅱ： Analytical study

Strengthening reinforced concrete （R. C.） beams using prestressed glass fiber-reinforced polymer （PGFRP） was studied experimentally as described in Part I of this paper （Huang et al., 2005）. In that paper, R. C. beams, R. C. beams with GFRP （glass fiber-reinforced polymer） sheets, and R. C. beams with PGFRP sheets were tested in both under-strengthened and over-strengthened cases. The test results showed that the load-carrying capacities （ultimate loads） of the beams with GFRP sheets were greater than those of the beams without polymer sheets. The load-carrying capacities of beams with PGFRP sheets were greater than those of beams with GFRP sheets. The objective of this work is to develop an analytical method to compute all of these load-carrying capacities. This analytical method is independent of the experiments and based only on the traditional R. C. and P. C. （prestressed concrete） theory. The analytical results accorded with the test results. It is suggested that this analytical method be used for analyzing and designing R. C. beams strengthened using GFRP or PGFRP sheets.     

钢筋混凝土连续梁受弯承载力可靠性分析

由于钢筋混凝土连续梁的作用荷载、材料、几何特征等具有随机性,使其荷载效应、抗力也具有随机性。针对钢筋混凝土连续梁受弯承载力可靠性,采用Monte-Carlo （蒙特卡洛）法抽样进行计算,定性分析了荷载效应比、材料强度、楼面荷载类型等对钢筋混凝土连续梁受弯承载力可靠度指标的影响。研究结果表明：随荷载效应比增大,连续梁可靠指标减小;随材料强度增加,连续梁的可靠指标变化不明显;楼面活荷载类型对连续梁可靠指标有影响。     

Ultimate stress increase in unbonded tendons in prestressed concrete beams

Since the assumption of plane sections cannot be applied to the strain of unbonded tendons in prestressed concrete beams subjected to loadings,a moment-curvature nonlinear analysis method is used to develop analytical programs from stress increases in unbonded tendons at the ultimate limit state.Based on the results of model testing and simulation analysis,equations are proposed to predict the stress increase in tendons at the ultimate state in simple or continuous beams of partially prestressed concrete,considering the loading type,non-prestressed reinforcement index βp,prestressing reinforcement index βs,and span-depth ratio L/h as the basic parameters.Results of 380 beams studied here and test results for 35 simple beams obtained by the China Academy of Building Research were compared with those from prediction equations given in codes and other previous studies.The comparison reveals that the values predicted by the proposed equations agree well with experimental results.     

外包钢-混凝土组合梁正截面极限抗弯承载力的试验研究

基于外包钢混凝土组合梁的试验研究和塑性理论,按照钢梁和混凝土塑性中和轴相对位置的不同,分别推导了完全剪切连接和部分剪切连接的外包钢混凝土组合梁的正截面极限抗弯承载力的计算公式,并对外包钢混凝土组合梁进行了非线性有限元分析,分析中重点考虑了材料非线性和接触非线性.8根完全剪切连接和3根部分剪切连接试件的正截面极限抗弯承载力的计算结果及有限元分析结果与试验结果吻合良好.     

基于ANSYS程序的钢筋混凝土梁非线性数值模拟

采用商用程序ANSYS对不同配筋率的钢筋混凝土梁进行非线性数值分析，以考察不同配筋率对钢筋混凝土梁受弯性能的影响。结合数值模拟分析过程，详细介绍了基于ANSYS程序的钢筋混凝土构件非线性数值分析的关键技术，分析了对不同配筋率的钢筋混凝土粱的刚度变化、破坏特征、截面应力分布、裂缝发展和钢筋、混凝土应力及应变发展过程。     

玻璃纤维布加固的钢筋混凝土梁试验研究与抗弯承载力计算

对9根玻璃纤维布加固的钢筋混凝土梁和3根对比梁进行了抗弯性能试验研究. 试验中考虑了配筋率、加固量、剪跨比与混凝土强度等级4个参数. 试验结果表明, 经玻璃纤维布加固的钢筋混凝土梁抗弯承载力有显著提高; 混凝土强度、配筋率、加固量对极限荷载有显著影响; 剪跨比对加固梁的破坏形态有影响. 根据不同的破坏模式, 提出了抗弯承载力计算方法.