Collapse test and moment capacity of the Ruytenschildt reinforced concrete slab bridge

A large number of existing reinforced concrete solid slab bridges in the Netherlands are found to be insufficient for shear upon assessment. However, research has shown additional sources of capacity in slab bridges, increasing their total capacity and possibly changing their failure mode. Previous testing was limited to half-scale slab specimens cast in the laboratory. To study the full structural behaviour of slab bridges, testing to failure of a bridge is necessary. Research on load testing is carried out in order to develop load testing guidelines. In August 2014, a bridge was tested in two spans. The bridge was load tested, and additional cycles until yielding occurred in the reinforcement were added to the experiment. Though calculations with current design provisions showed that the bridge could fail in shear, the field test showed failure in flexure before shear. The unity check for flexure was determined. The experiment shows that the methods for rating of existing reinforced concrete slab bridges are conservative.     

Diagnostic load testing and assessment of existing bridges: examples of application

Load testing method is a significant tool in the assessment of bridge safety. One type of load tests is diagnostic load testing, the aim of which is to establish a comparison between real bridge behaviour and analytical calculation. It can be used either as acceptance test of the structures or as an estimation tool for the load carrying capacity of the already existing structures that have been in service for some time. This article presents diagnostic load tests and three examples of their application to various bridge structures and emphasises their diagnostic potential for assessment. In the majority of cases of diagnostic load tests presented in the literature, the experimental results (deflections, strains, etc) are very close or lower than the predicted ones and for this reason, such tests are expected to validate the existing structure. However, in the cases presented here, it is shown how the experimental results differ considerably from the expected ones. Since the theoretical and the experimental results of all three examples did not match, it was highly recommended to keep the matter under close investigation. A deep insight into the bridges showed serviceability and safety concerns and in some cases a repair/strengthening was necessary.     

A hybrid experimental-numerical approach for load rating of reinforced concrete bridges with insufficient structural properties

This article presents a non-destructive approach for load rating of reinforced concrete bridges without structural plans. The approach is found on a hybrid method, which employs vibration and live load testing coupled with numerical simulation and model updating techniques, to converge on estimate of unknown structural parameters. The material properties of bridge and the amount of reinforcing steel for calculating the bending capacity of a bridge are determined through model updating results and nondestructive approaches. The updated model is then employed to determine load effects for calculating load rating factors, and these results are combined with live load test result to arrive at the bridge capacity, and ultimately the load rating. The method is validated by testing a skewed reinforced concrete slab bridge for load rating purposes. The bridge was instrumented with accelerometers and strain gages, and the responses of the bridge under vibration and quasi-static tests were measured. Results demonstrated that the proposed method is capable of determining the bridge capacity and load rating factor with good accuracy, and not only can be used for load rating of concrete bridges without structural information, but also can be useful in condition assessment of existing concrete bridge with available as-built information.     

Proof load testing for bridge assessment and upgrading

Bridge deterioration with time and ever increasing traffic loads raise concerns about reliability of aging bridges. One of the ways to check reliability of aging bridges is proof load testing. A successful proof load test demonstrates immediately that the resistance of a bridge is greater than the proof load. This reduces uncertainty in the bridge resistance and so increases the bridge reliability. The paper considers a reliability-based calibration of intensities of proof loads for aging bridges to verify either an existing or increased load rating taking into account possible bridge deterioration. Intensities of proof loads are calibrated based on a consistent target reliability index. The influence of test risk, dead to live load ratio, and uncertainties associated with dead and live loads and bridge resistance is considered. The results presented in the paper relate to short and medium span bridges.     

桥梁检测技术综述

通过对桥梁检测试验的综合叙述,说明了桥梁检测的主要项目以及各自所要达到的目的,并简要介绍了荷载试验的注意事项和试验方法,从而达到完善桥梁检测技术和确保桥梁安全的目的.     

简直转连续斜箱梁桥单梁静载试验分析

单梁静载试验是检验桥梁在正常运营期间能否保证桥梁正常运营的一个重要手段,通过对单梁静载试验,检测单梁的结构性能是否达到设计文件和规范要求,保证成桥后桥梁的安全。结合某预应力混凝土斜箱梁实例,介绍预应力钢筋混凝土简直转连续单梁静载试验的检测内容、试验步骤和试验结果分析。总结单梁静载试验结果,对预应力钢筋混凝土简直转连续梁桥作出正确的质量评估,为以后的试验提供理论依据。     

东莞东部快速路广深铁路跨线桥动载试验研究

以广深铁路跨线桥动载试验为例，介绍了动载试验的测试内容、测试原理和测试结果及试验结论，为该桥的竣工验收提供技术依据，并为类似桥梁的动载试验提供经验。     

Structural adequacy assessment of a disused flat bottom rail wagon as road bridge deck

This paper presents half of a full scale experimental testing technique for assessing the structural adequacy of a disused flat bottom rail wagon (FBW) for low volume, heavy axle load road bridge applications. The aim of this ongoing research project is to develop sufficient knowledge required for achieving significant economy and safety of the heavy axle transportation system in regional government council roads. In the absence of such knowledge, the viability of replacing/rehabilitating the ageing bridges could not be economically justified, mainly due to low volume traffic and the costs of alternate solutions using new materials for heavy axle load demands.This study describes a comprehensive laboratory testing of half of a single lane, single span bridge deck and an associated three dimensional finite element modeling. The novel idea in the paper is to enforce the transverse continuity conditions along the longitudinal edge of the half of full scale bridge so that the single FBW tested will mimic the behaviour of a double FBW deck for a single lane road bridge under heavy axle design loads. Several serviceability and ultimate load tests, conforming to the Australian bridge design traffic loads applied at critical locations of the FBW system are reported in the paper. The test results demonstrate that the FBW possesses sufficient structural strength and can service the required design traffic loads.     

昆明二环路系统桥梁结构荷载等级的分析

昆明市主城二环路系统是由高架系统和地面系统构成的双层系统。分析了影响桥梁结构荷载等级的主要因素:相关规范规定、交通功能及服务对象、既有桥梁的利用与否、拟利用的既有桥梁的原设计荷载等级、投资控制、技术措施及运营期的管养等,得到了桥梁结构的汽车荷载等级的合理结论。     

浅析3×20m连续梁桥检测技术

桥梁检测主要包括外观检测和荷载试验。桥梁外观技术状况主要依外观检查和无损检测数据进行评定;桥梁荷载试验分为静荷载和动荷载试验。本文针对连续梁检测技术,结合某3x20m钢筋混凝土连续箱梁工程,阐述了连续梁桥外观检查、荷载试验的主要程序,及等效荷载作用下桥梁结构的应力、挠度及动态效应。     

桥梁逆作承台–群桩复合基础应用与现场实测研究

为进一步研究逆作复合基础在桥梁工程中的适用性,开展了桥梁逆作承台–群桩复合基础的实桥应用研究,针对有水和无水的施工环境,分别提出了桩与承台间预留孔采用带剪力连接键的钢护筒和收口网模板的构造设计与连接施工工艺,并通过12组接头承载性能试验验证了工艺方案的可靠性。通过现场实测,揭示了桥梁逆作承台–群桩复合基础受力机理,测试结果表明:采用逆作方案,先施工桩基和预留桩孔的承台,待盖梁施工完成后再封桩,使桩与承台形成整体共同参与受力,能够使封桩前承台底土承担上部荷载,有效发挥浅层地基土的承载能力;封桩后,基础沉降增量和承台底土压力增量均明显减缓,继续增加的上部荷载主要由桩基承担,能够有效控制封桩后桥梁沉降。     

Development of performance assessment tools for a highway bridge resulting from controlled progressive monitoring

As highway bridges continue to deteriorate given the increased service life, increase in vehicle demand and exposure to harsh environmental climates, new methods of monitoring their in situ performance are of high priority. Damage within the structure can alter various load demand and capacity characteristics, affecting the overall integrity of the bridge. Discussed in this paper is the monitoring of a simple span bridge superstructure under various induced damage states. Strain measurements were recorded at the midspan and north abutment of each girder. Six levels of damage progression were implemented at a rocker bearing and various diaphragms to girder connections. Transverse load distribution factors (DFs) and neutral axis (NA) locations were measured for each damage case and evaluated against the baseline undamaged response. These measurements serve to provide a possible method of damage detection using load-testing parameters already employed by various transportation agencies. Next, a performance index (PI) is developed for this stringer/multi-girder bridge utilising the NA and DF response from the steel girder system and the allowable stress design load-rating data. The ratio of NA to DF was compared to the inventory load rating for each girder at each damaged state. The data were fitted with a power regression model to form the PI. Furthermore, a 95% prediction interval was used around the predicted response to capture all the data from the testing. The model was applied to the damaged structure as well as two additional stringer/multi-girder bridges. The objective of the PI is to complement existing qualitative assessment protocols with quantitative results for improving the condition assessment process.     

Bridge performance indicators based on traffic load monitoring

The assessment of the existing road bridges as a part of bridge management networks has been a subject of several European research projects and actions in the last few decades. Bridge management includes a series of activities, interconnected in order to achieve optimal balancing of required costs, potential risks and overall bridge performance. This paper discusses a valuable link between a specific indicator (traffic load information calculated using Bridge Weigh-in-Motion measurement data) and the corresponding structural performance (reliability of existing bridge). It is shown that implementation of weigh-in-motion measurements in the probabilistic assessment of existing road bridges can reveal hidden bridge reserves and predict bridge reliability development over the required lifetime. Consequently, such approach can yield an unrestricted use of the bridge over a much longer remaining service life. Broader advantages lie in an improved road network management, road bridges in particular, and in a more sustainable development of infrastructure network and greater satisfaction of road users and owners.     

某双曲拱桥的动静力测试及承载能力评估

本文以某双曲拱桥的承载力评估为例,在总结几种有限元模型离散方法的基础上,结合双曲拱桥的结构形式,提出采用梁板结合的模拟方法,用大型通用有限元软件ANSYS进行了双曲拱桥的模型建立.同时,阐述了双曲拱桥的动载及静载试验的试验方法与过程,包括用等代荷载的方法确定荷载车辆、各种工况的分级加载、动载及静载试验测点的布置.依据有限元分析结果与动静力荷载结果的对比分析,对工程实例桥的承载能力进行了评估分析,得出了该桥当前的结构性能和状况.结果表明,正确的计算模型是评定双曲拱桥承载能力的关键,有限元法中的板梁法结合双曲拱桥的结构形式,是双曲拱桥结构空间分析的一种有效方法,以有限元理论分析和动静力荷载试验相结合的方法能较为全面地评定双曲拱桥的承载能力,可为同类桥梁计算分析及承载能力评定提供参考.     

大跨高墩曲线连续刚构桥荷载试验

与常规直线桥梁荷载试验不同,曲线连续刚构桥梁荷载试验有其独特的特点。结合某高速公路上一座大跨高墩曲线连续刚构桥的工程实例,介绍了荷载试验内容、试验方法和静、动载的理论计算,分析对比试验结果,并对该桥的结构性进行了评价,得出满足《大跨径混凝土桥梁试验方法》规定的结论。对同类曲线连续刚构桥梁荷载试验具有参考价值。     

Methodology for development of live load models for refined analysis of short and medium-span highway bridges

Abstract

The accuracy of bridge system safety evaluations and reliability assessments obtained through refined structural and finite element analyses depends not only on the accuracy of the structural model itself but also on the proper modelling of the maximum traffic loads. While current code-specified live load models were calibrated to properly reflect the safety levels of bridge structures analysed using the simplified methods adopted in bridge design and evaluation manuals, these load models may not lead to accurate results when implemented during refined structural analysis procedures. This paper describes a method to calibrate appropriate live load models that can be used for advanced analyses of bridges. The calibration procedure is demonstrated using actual traffic data collected at a representative weigh-in-motion station in New York State. The proposed calibration methodology is applicable for developing live load models for different bridge service periods, bridge types and design/assessment codes or standards. Live load models obtained using the proposed calibration procedure are readily implementable for deterministic refined analyses of highway bridges to produce similar results to those of complex traffic load simulations. Examples are presented that describe how results of such calibrated live load models would be used in engineering practice.     

Full scale testing of old steel truss bridge

As part of an investigation to comprehend behavior of old steel truss bridges, ultimate load tests were carried out on a steel truss bridge that was transported to the structural laboratory. The first ultimate load test consisted of testing the bridge in its existing configuration without any retrofit. The failure mode was by sudden rupture of a forged diagonal tension member. The mode of failure was ‘brittle’ in nature and there was no warning. The failed member, together with other forged tension members, was retrofitted and an additional ultimate load test was conducted. The retrofitted bridge failed in a more ductile manner. The failure took place gradually and there was ample warning before the failure.A major conclusion from ultimate load tests was that in inspecting old steel truss bridges one should pay very close attention to tension members that use forging.This paper presents a brief overview of the ultimate load tests conducted. More detailed information on the complete scope of the project is presented in Azizinamini et al., Final report, STPB-STWD(13), (1997); 479 pp.     

A new accelerated-replacement method and full-scale test of a new superstructure for existing OSPG railway bridges

Existing open-steel-plate-girder (OSPG) railway bridges in Korea are so old that they can no longer provide the desired ride quality when trains pass over them due to loss of integrity. In addition, existing bridges do not have ballast, thus impacts from passing trains are delivered directly to piers and abutments. The damage that accumulated is one of the main causes of cracks in pier concrete. To cure this problem, replacement of the existing bridges is required. However, since they are still in service, conventional construction methods cannot be used for their replacement. A new method is necessary to quickly replace the existing bridges in a way that does not disturb the existing train schedule. In this study, a new accelerated-replacement method is proposed using a newly developed crane-vehicle which possesses cranes able to lift a replacement bridge, and which is able to travel on existing train tracks. This study also addresses the design and manufacture of a new bridge deck appropriate for accelerated-replacement construction. Finite element analyses and experimental tests were conducted to estimate the performance of the new bridge deck. The analyses included a static load case and dynamic analysis at various train speeds. The experimental tests included static loading and modal tests to capture the fundamental natural frequency and damping ratio of the bridge deck, and a dynamic amplification test. The results of this study can be used for practical replacement of aged existing open-steel-plate-girder bridges and to improve the integrity and ride quality of railway bridges in Korea.     

Shear failure analysis on ultra-high performance concrete beams reinforced with high strength steel

A new deck system for moveable bridges was developed that makes use of ultra-high performance concrete (UHPC) reinforced with high strength steel (HSS) rebar to achieve the light weight and high strength requirements in moveable bridge applications. However, the typical deck strips of this deck system failed predominantly due to shear cracks in simply supported beam proof tests. This paper investigates the mechanism of the deck strip shear failure experimentally and analytically. Experimental studies were performed at several scales, including material characterization, bond strength tests, small-scale prism tests, and full-scale beam tests. Specimens with traditional shear strengthening techniques were also tested. Several existing formulas were utilized to predict the shear strength, and the results were compared to the experimental results. The accuracy and limitations of these formulas are discussed. The shear failure of UHPC-HSS beams is not characterized by brittle response or catastrophic load reduction as with normal reinforced concrete. Therefore, this particular shear failure mode is regarded as acceptable. However, the additional shear resistance caused by the localized deformation of the longitudinal reinforcement is not recommended to be considered for design capacity formulas.     

三跨预应力连续梁桥动载试验分析

对现有桥梁在动荷载下的受力参数与理论计算的参数相比,得出了该桥梁的实际使用状态,通过模拟实际桥梁,分析了各种不利荷载作用下桥梁的受力响应,该动荷载试验分析结果为箱形连续梁桥的动荷载控制设计提供了数据支持。