预制混凝土结构的应用与研究进展

对预制混凝土结构的特点、应用及研究进行了必要的阐述,分析了我国预制混凝土体系发展受阻的原因,指出了在我国发展和应用预制混凝土结构所需解决的三个问题。     

Critical issues,condition assessment and monitoring of heavy movable structures: emphasis on movable bridges

In this paper, a relatively less studied class of structures is presented based on the research conducted on Florida's movable bridges over the last several years. Movable bridges consist of complex structural, mechanical and electrical systems that provide versatility to these bridges, but at the same time, create intermittent operational and maintenance challenges. Movable bridges have been designed and constructed for some time; however, there are fewer studies in the literature on movable bridges as compared to other bridge types. In addition, none of these studies provide a comprehensive documentation of issues related to the condition of movable bridge populations in conjunction with possible monitoring applications specific to these bridges. This paper characterises and documents these issues related to movable bridges considering both the mechanical and structural components. Considerations for designing a monitoring system for movable bridges are also presented based on inspection reports and expert opinions. The design and implementation of a monitoring system for a representative bascule bridge are presented along with long-term monitoring data. Various movable bridge characteristics such as opening/closing torque, bridge balance and friction are shown since these are critical for maintenance applications on mechanical components. Finally, the impact of environmental effects (such as wind and temperature) on bridge mechanical characteristics is demonstrated by analysing monitoring data for more than 1000 opening/closing events.     

高精度预制混凝土技术在我国的应用与研究

作为现代混凝土工程技术的重要组成部分之一,高精度预制混凝土技术的研究与应用得到了很大的发展,本文描述了高精度预制混凝土技术在我国的研究与应用现状,并提出了目前高精度预制混凝土技术存在的问题和今后的研究方向.     

Ultimate strength of continuous composite box-girder bridges with precast decks

In order to apply precast decks to continuous composite bridges, several experiments and analytical studies were performed. From many previous studies, design criteria for crack controls in transverse joints of prefabricated slabs were confirmed. These considerations were needed for serviceability. The bridges which satisfy service limit states, also, should be evaluated for ultimate strengths to define limit states. In this paper, experimental and analytical studies of two-span continuous composite bridges with open box girder section were conducted. Cracking, yielding and ultimate loads were evaluated and compared with the test results for design of continuous composite bridges with precast decks. To evaluate yielding loads of continuous bridges, an uncracked section method considering moment redistribution which is defined in EUROCODE 4, was considered. In calculation of ultimate strengths, full or partial shear connection and sectional classes which were defined in EUROCODE or AASHTO LRFD specifications were considered. Also, through numerical analysis considering material nonlinearities, moment-curvature relationship and moment redistributions were estimated.     

Updating and validation of the dynamic model of a railway viaduct with precast deck

This study describes the calibration and experimental validation of the dynamic model of a railway viaduct with precast deck. Global modal parameters of the structure and local modal parameters of the upper slab of the deck are identified based on a dynamic test. The calibration of the numerical model is done using a genetic algorithm that allows obtaining optimal values of 11 parameters of the numerical model. The inclusion of local modal parameters proved to be crucial, as various parameters of the numerical model do not have significant influence on global modal parameters. Mode pairing between numerical and experimental vibration modes is performed using a recent technique based on modal strain energy. The experimental validation of the calibrated numerical model is done by the comparison between numerical responses and experimental responses obtained in a dynamic test under railway traffic. This dynamic test shows the existence of a nonlinear behaviour of the viaduct's supports. There is an excellent correlation between numerical and experimental responses for different train speeds with the adjustment of the longitudinal supports stiffness of the calibrated model.     

预制混凝土结构的应用与住宅产业化

分析了我国住宅产业化的现状,提出发展预制混凝土结构是实现住宅产业化的途径,同时指出发展预制混凝土结构还可以有效实现建筑节能,从而进一步推广预制混凝土结构的应用。     

对国外混凝土预制构件试验研究工作的思考

简要叙述了国外混凝土预制构件的发展情况,重点介绍了几个典型预测混凝土构件试验研究的实例,建议我国混凝土行业应加强试验研究工作。     

GPS monitoring of a steel box girder viaduct

Structural performance monitoring of bridges has increased as major infrastructure ages and is required to sustain loads that are significantly greater than those predicted during design. Structural stiffness and/or mass distribution can change over the lifespan of a bridge structure. Resulting changes in profile or resonant frequency provide key indicators of change, and may identify structural defects. Field tests using GPS for monitoring relatively small deformations were carried out on a steel box girder viaduct bridge in the UK. The configuration consisted of five GPS receivers located at key locations on the viaduct and two reference GPS receivers. GPS data was collected at either 10 Hz or 20 Hz and post-processed using proprietary software, along with appropriate filtering and spectral analysis. Three main frequencies were clearly detected by the GPS in the vertical component. A previously reported frequency of approximately 0.56 Hz was identified along with two other frequencies. The peak vertical deflections lie in the range of ± 50 mm, while lateral and longitudinal deflections of much smaller magnitude – in the order of a few mm – are also measured. The use of GPS leads to readily obtained and useful engineering data for continued monitoring of structures.     

混凝土预制桩打桩质量要求与问题的分析

介绍了混凝土预制桩打桩质量要求 ,分析了混凝土预制桩打桩中遇到的问题 ,对常见的问题提出了处理措施 ,满足了设计要求 ,保证了工程质量。     

SP预应力空心板在居住建筑中的应用和发展

分析现浇板和传统预制板的特点和弱点,提出发展SP板和SP叠合板是住宅实现大开间、灵活隔断的有效途径之一,也是建筑施工实现现代化的重要内容之一。     

高墩连续刚构桥线形控制分析

以某连续刚构桥为工程背景,建立该桥的有限元模型,并采用灰色预测控制系统对其进行线形控制,通过对线形控制的理论预测值和实测值比较分析,说明灰色预测控制系统能较好地应用于此类桥梁的线形控制。     

Structural performance evaluation of a precast prefabricated bridge column under vehicle impact loading

In this study, the numerical analysis method was proposed to analyse the structural behaviour of bridge columns under various impact loading conditions. A parametric study of vehicle impact simulation was carried out to determine the impact loading-time functions. According to the impact simulation results, five-point piecewise linear approximation is proposed and validated. The proposed loading function was applied to the material nonlinear finite element analyses of two different types of bridge piers, the cast-in-place reinforced concrete bridge columns and the prefabricated bridge columns, which were designed under the same loading conditions. The dynamic performances of the considered bridge piers are compared using the results of dynamic numerical analyses. Also, the static design loadings of a vehicle crash defined in the Korean bridge design code and AASHTO LRFD Bridge Design Specifications were applied to analyse the results of the dynamic analyses of the piers.     

外壳预制核心现浇装配式RC梁的预制外壳抗弯承载力的试验研究

介绍了一种可用于多、高层房屋建筑的新型装配整体式RC结构体系——外壳预制核心现浇装配整体式RC结构,进行了该结构体系的RC梁的预制U形外壳的抗弯承载力试验,考察了装配整体式U形外壳的破坏模式、开裂荷载、极限承载力等力学性能及其计算方法,为实际工程应用提供了参考。     

预制梁板施工中主要质量问题的分析与处治

结合侯运、新原、长晋、沈彰等多条高速公路的施工实践,针对预制梁板施工中较常出现的一些质量问题,对其产生的原因进行了较为详细的分析与探讨,并提出了具体的处治措施及建议。     

预制装配式剪力墙结构节点抗震性能试验研究

为促进建筑工业化和住宅产业化,进行预制装配式剪力墙结构中间层边节点的抗震性能试验研究。对2个现浇试件和3个预制装配试件进行低周反复荷载试验,试验结果表明预制装配试件具有与现浇试件相当的抗震性能。结合ANSYS进行理论分析,考虑到有限元方法的局限性,分析采用正向单调加载模式来近似评价节点在低周反复荷载作用下的抗震性能。有限元分析结果与实测结果能较好地吻合,可用来评价其抗震性能。最后,基于有限元模型探讨节点连接钢筋构造。通过系列工作,为今后预制装配式剪力墙结构的深入研究及推广提供试验及理论基础。     

钢纤维喷射混凝土支护长期效应的数值模拟

用有限元方法模拟坑道钢纤维喷射混凝土支护的长期效应,研究钢纤维喷射混凝土支护的可行性。     

桥梁预制板梁混凝土底模施工与脱模技术

公路桥梁预制钢筋混凝土板梁施工中,底模的制作及脱模是关键,根据对板梁底面的质量要求,阐述在底模施工时的场地选择,底模测量及浇筑,脱模技术几方面主要应考虑的注意事项,并介绍几种常见的脱模技术,指出其各自的施工要点及优缺点,并进行了比较。     

预制混凝土支护管桩在深基坑工程中的应用

先张法预应力预制混凝土支护管桩作为一种新型的基坑支护桩,具有桩身质量好、强度高和成桩可靠等特点值得推广与应用。基于基坑位移计算方法,分析了采用预应力预制混凝土支护管桩进行基坑支护,影响其位移变化的参数,并结合南京邮电大学科研综合楼基坑工程实例,介绍了支护桩的布置方式,对比了基坑位移的理论计算值与实测值,结果表明：计算位移变化平缓,最大值约在17.0～23.2 mm之间;现场实测的最大水平位移值在16.10～21.50 mm之间,二者数值接近,变化规律基本一致,证实了预应力预制混凝土支护管桩用于基坑支护的可靠性和有效性,值得在同类工程中参考。     

黄土地区井筒式地下连续墙基础的长期监测与分析

以山西某在建拱桥为依托,对其采用的井筒式地下连续墙基础进行长期监测,研究了在不同工作状态下,井筒式地下连续墙各片墙所承受的轴力与侧摩阻力的分布规律,特别在正常工作荷载下,闭合墙基础的承载性状类似于端承摩擦墙。并结合土压力盒所测墙周土体作用于工程墙的土反力值,分析了承台与土芯之间的作用并不显著,且在运营阶段,墙内土芯对闭合墙的水平承载力贡献小,而外侧的上部表层土和浅层土对工程墙基础的水平承载力影响很大。     

Reliability assessment of cable-stayed bridges based on structural health monitoring techniques

This paper presents the reliability analysis approach of long-span cable-stayed bridges based on structural health monitoring (SHM) technology. First, the framework of structural reliability analysis is recognised based on SHM. The modelling approach of vehicle loads and environmental actions and the extreme value of responses based on SHM are proposed, and then models of vehicle and environmental actions and the extreme value of inner force are statistically obtained using the monitored data of a cable-stayed bridge. For the components without FBG strain sensors, the effects and models (extreme values) of dead load, unit temperature load, and wind load of the bridge can be calculated by the updated finite element model and monitored load models. The bearing capacity of a deteriorated structure can be obtained by the updated finite element model or durability analysis. The reliability index of the bridge's critical components (stiffening girder in this study) can be estimated by using a reliability analysis method, e.g. first order reliability method (FORM) based on the models of extreme value of response and ultimate capacity of the structure. Finally, the proposed approach is validated by a practical long-span cable-stayed bridge with the SHM system. In the example, reliability indices of the bridge's stiffening girder at the stage after repair and replacement after 18 years of operation, and the damaged stage are evaluated.