Assessment of existing steel railway bridges

A series of dynamic tests, acceleration measurements, evaluation, finite element model simulations and safety index calculations were performed on existing steel railway bridges giving service on railway network. Dynamic tests were fulfilled by using a special test train on these bridges to obtain the dynamic parameters and these parameters were then used to refine the finite element models of the bridges. Once the models have been updated to represent the actual condition, safety indices were calculated for structural components of the bridges for each proposed loading condition. These safety indices were used to calculate failure probabilities of structural members. As the final step, system reliability of the bridges was evaluated based on proposed system models of the bridges. It is believed that this study will provide a reliable background for proposed heavier axle loads resulting from new freight trains by realizing the current condition of bridge structures.     

Present condition of highway bridges in Vietnam: an analysis of current failure modes and their main causes

This paper reports on research conducted to evaluate the current status of highway bridges in Vietnam. The adopted approach included literature reviews to identify common failure modes and causes, together with site inspections to ascertain their validity. Interviews were also conducted with the various stakeholders to further understand the current condition of the inspected bridges. Results show an overall picture of existing bridges in poor physical condition, thus providing poor service to users. Defects that have previously been identified in the literature include corrosion, settlement, fatigue damage, obsolescence, scouring and aging. New problems identified were human invasions and missing elements. Previous literature identifies traffic overload and jams, collision, adverse environmental conditions and poor maintenance as causes for these problems. Additionally, this paper considers war, improper data retention and other country-specific causes. The authors suggest that maintenance efforts should be prioritized to remedy and eliminate serious failures. Properly trained maintenance crews need to be established and further research carried out to establish adequate bridge maintenance systems.     

Application of new damage indicator-based sequential law for remaining fatigue life estimation of railway bridges

Miner’s rule is generally accepted as the fatigue criteria for life estimation of railway bridges. Similarly, it has always been acknowledged as a simplification that is easy to use in design where detailed loading history is unknown. But in the case of existing railway bridges where the detailed loading history is known, Miner’s rule might provide incorrect results because of its omission of load sequence effect. Recently, a new damage indicator-based sequential law has been proposed to capture the load sequence effect more precisely. However, application of this sequential law to estimate the remaining fatigue lives of existing railway bridges has not been properly studied. Therefore, the major objective of this paper is to estimate the remaining fatigue life of a railway bridge using the sequential law and hence introduces a new approach to estimate remaining fatigue life of riveted railway bridges. This approach is specially based on combination of real stress histories, sequential law and fully known Wöhler curve. The practice of sequential law to obtain the remaining fatigue lives due to both uniaxial and multiaxial stresses are described by estimating remaining life of a considered railway bridge. Further, the obtained fatigue lives are compared with Miner’s estimations. Hence it could be concluded that it is advisable to apply the sequential law for assessment of remaining fatigue lives of riveted railway bridges, where the detailed stress histories are known.     

Fragility analysis of track-on steel-plate-girder railway bridges in Korea

More than 40% of the bridges in conventional Korean railway lines are track-on steel-plate-girder (TOSPG) bridges. They are characterized by a superstructure consisting of railway tracks sitting directly on steel plate girders without any ballast system. Most of these bridges have been designed with little or no consideration given to seismic loading. In this paper, seismic fragility curves of TOSPG bridges in Korea are developed. Fragility curves are developed first for the components, by using the probabilistic seismic demand model. The developed component fragility curves show that the bearings are the most vulnerable components of the TOSPG bridges against seismic loading. On the other hand, the piers are much less vulnerable, although they contain no reinforcing bars. This is because the superstructure mass is very light, and therefore horizontal loading transferred from the superstructure to the piers is minimal. A generic damage measure is introduced for measuring the system-level damage of structures out of the component-level damages. The system fragility curves are then developed, using the generic damage measure. Finally, representation of seismic risk in terms of expected seismic losses is demonstrated. This demonstration shows how the fragility analysis is utilized for risk assessment and support in decision-making.     

钢板桩在铁路桥梁深基坑支护中的应用

通过杭甬客专某水中墩深基坑工程的设计与施工,介绍了钢板桩在深基坑支护工程中的应用,从钢板桩的长度计算、支撑和围檩的结构检算以及钢板桩、围檩、支撑的安装要点等方面进行了系统的叙述,通过实践证明,板桩式基坑支护具有良好的工程性能和可重复利用的特性,在满足支护结构强度、刚度要求的同时还具有较好的经济效益,是一种较为合理的支护形式。     

#br# 我国钢管混凝土拱桥应用现状与展望

共收集到截止2015年1月的已建和在建的钢管混凝土拱桥413座（跨径不小于50m）。统计分析表明,钢管混凝土拱桥在我国修建的数量不断增多、跨径不断增大。从行业分布来看,在公路、城市桥梁中的应用仍是主体,在铁路尤其是高速铁路中的应用不断增多。在结构体系方面,上承式、中承式、拱梁组合式、飞鸟式和下承式刚架系杆拱5大类,仍为主要应用的桥型,占总数的85%。在截面形式方面,以圆钢管混凝土为基本单元组成的单圆管、哑铃形和桁式是应用的主流。提篮拱被应用于各种桥型,尤其是大跨度铁路桥。无风撑拱主要应用于120m跨径以下的桥梁,且以斜靠拱和拱梁组合桥为主,截面多采用横向刚度较大的形式。拱肋的材料强度不断地提高,钢管以Q345钢为主,混凝土以C40、C50为主。虽然对桥面系强健性的重视在不断提高,然而强健性好的整体式和具有加劲纵梁的悬吊桥面系的应用还不够普及。钢管拱的架设方法仍以支架法、悬臂法和转体法3种为主,其中悬臂拼装法应用最多,适用跨径最大范围也最广。     

A multi-level strategy for successively improved structural analysis of existing concrete bridges: examination using a prestressed concrete bridge tested to failure

This paper describes a multi-level strategy with increased complexity through four levels of structural analysis of concrete bridges. The concept was developed to provide a procedure that supports enhanced assessments with better understanding of the structure and more precise predictions of the load-carrying capacity. In order to demonstrate and examine the multi-level strategy, a continuous multi-span prestressed concrete girder bridge, tested until shear failure, was investigated. Calculations of the load-carrying capacity at the initial level of the multi-level strategy consistently resulted in underestimated capacities, with the predicted load ranging from 25% to 78% of the tested failure load, depending on the local resistance model applied. The initial assessment was also associated with issues of localising the shear failure accurately and, consequently, refined structural analysis at an enhanced level was recommended. Enhanced assessment using nonlinear finite element (FE) analysis precisely reproduced the behaviour observed in the experimental test, capturing the actual failure mechanism and the load-carrying capacity with less than 4% deviation to the test. Thus, the enhanced level of assessment, using the proposed multi-level strategy, can be considered to be accurate, but the study also shows the importance of using guidelines for nonlinear FE analysis and bridge-specific information.     

Structural details of steel girder–abutment joints in integral bridges: An experimental study

Integral bridges, which have integrated superstructures and substructures, should essentially maintain the rigid behavior and structural safety of the various existing joints. Especially temperature sensitive, girder-abutment joints for integral steel bridges are steel–concrete composite structures and require sufficient rigid behavior. Yet, various design guidelines and standards do not state these specific designs or construction methods. This study proposes structural details of girder-abutment joints in integral steel bridges for enhanced rigid behavior and load-resisting and crack-resisting capacity. Thus, this study additionally suggests various joints that apply stud shear connectors and perfobond rib shear connectors to existing empirically constructed girder-abutment joints. This study verifies the performance and evaluates the behavior of the proposed steel girder-abutment joints through experimental loading tests of empirically constructed joint specimens and specimens of the proposed joints. Also, this study performs FE analysis (non-linear structural analysis), which applies contact interaction of the interface of the steel–concrete composite joints. As a result of the experimental loading test, all the existing empirical joints and the proposed joints demonstrated sufficient rigidity and crack-resisting capacity under required design and yield load and are applicable as girder-abutment joints for integral steel bridges. Moreover, the proposed joints are judged to be structurally superior to the empirically constructed joints by the results of analysis for load-displacement relationships, crack-propagation behaviors, and load-strain relationships. Like the proposed girder-abutment joints in this study, joints with improved rigid behavior and load-resisting and crack-resisting capacity may resolve and properly control durability and serviceability issues of integral bridges.     

Triage methodology of bridges for infrastructure management: empirical analysis of road networks in municipalities with declining populations and increasing debts

The population of Japan peaked in 2010 and has since entered a depopulation period. On the other hand, there are many bridges that were constructed in the past, especially during the period of high economic growth. Their deteriorating state is becoming increasingly evident. It is expected that maintenance and management costs of the development and maintenance of urban infrastructure for bridges will increase. It is necessary to respond to the ageing of the national land stock. This study verifies urban infrastructure methodology to develop and maintenance using a road network of a municipality whose population actually decreases. This methodology makes use of the basic data held by the municipality such as the population and the length of the road. More specific, the authors propose a methodology for applying the triage to the decision-making processes involving bridges such as road bridges, similar to how it is applied when providing medical care to those with injuries caused by large-scale disasters. The proposed methodology is useful for municipal bridge management strategy and can be applied to other countries around the world that may face decreasing population and/or rising debt in the future.     

Stakeholder impact analysis of infrastructure project management in developing countries: a study of perception of project managers in state‐owned engineering firms in Vietnam

Construction projects can involve a diverse range of stakeholders and the success of the project depends very much on fulfilling their needs and expectations. It is important, therefore, to identify and recognize project stakeholders and develop a rigorous stakeholder management process. However, limited research has investigated the impact of stakeholders on construction projects in developing countries. A stakeholder impact analysis (SIA), based on an approach developed by Olander (2007), was adopted to investigate the stakeholders’ impact on state‐owned civil engineering projects in Vietnam. This involved the analysis of a questionnaire survey of 57 project managers to determine the relative importance of different stakeholders. The results show the client to have the highest level of impact on the projects, followed by project managers and the senior management of state‐owned engineering firms. The SIA also provides suggestions to project managers in developing and evaluating the stakeholder management process.     

非加劲与防屈曲钢板剪力墙性能及设计理论的研究现状

钢板剪力墙已被证明是高烈度区优秀的抗侧力构件,但设计方法不够成熟,阻碍了钢板剪力墙的推广应用。为服务设计,基于非加劲和防屈曲钢板剪力墙的研究历史和现状,总结出二者在性能和设计理论方面的主要研究成果,特别是对其力学性能、使用性能、工作机理、等代模型及边缘框架设计作了重点阐述。其中,最近新提出的等代模型(非加劲和防屈曲钢板剪力墙),可适用于钢框架内嵌任意厚度钢板(厚板、中厚板及薄板)的结构分析。同时,指出当前设计方法的不足之处在于不能体现钢板剪力墙延性和耗能的优势,定量反映钢板剪力墙性能优势是今后研究工作中要解决的关键理论问题。此外,对于非加劲钢板剪力墙与框架施工顺序进行了初步分析,对同步施工时非加劲钢板剪力墙受剪承载力应予以折减。图33参39     

Behaviour and design of restrained steel column in fire, Part 3: Practical design method

This paper presents a practical design method for calculating the buckling and failure temperatures of restrained steel column under axial load or combined axial load and bending moment based on the results of extensive numerical parametric studies. Design equations for unrestrained columns in fire are adopted to calculate the buckling temperature of a restrained column by including the additional compression axial force due to restraint thermal elongation. The cross-section yield axial strength-plastic bending moment interaction curve is employed when calculating the failure temperature of restrained column. Results from the proposed method are compared with ABAQUS simulation for different cases. For the restrained column under axial load only, the buckling and failure temperatures calculated by the simplified method agree well with predictions by ABAQUS. For the restrained column under combined axial force and bending moment with realistic parameters, the buckling and failure temperatures predicted by the proposed method also agree well with ABAQUS predictions.     

Study of ground vibrations induced by railway traffic in a 3D FEM model formulated in the time domain: experimental validation

In this paper, a three-dimensional numerical model is applied for studying railway vibrations. The numerical model is based on finite element method formulated in the time domain with an implicit scheme of integration. In the first part of the paper the numerical approach is briefly described. An uncoupled scheme is applied: (i) firstly the train loads are calculated taking into account dynamic excitation with a 2D vehicle-track model; (ii) the computed loads on each sleeper are introduced into a 3D numerical model, developed in the commercial code Plaxis, which is used to simulate the wave propagation in the ground. In the second part of the paper a real case study, located in Portugal, is presented, being used for the experimental validation of the proposed model. The numerical results of ground vibrations show an acceptable agreement with real measurements. Therefore, the proposed approach can be used as a reliable prediction tool based on PLAXIS software, which allows simulating railway vibrations in some specific cases such as soft soils, inhomogeneous geometries in the longitudinal direction of the track and transition zones.     

Electronic communications regulation in Europe: An overview of past and future problems

For many years, electronic communications has been one of the most important areas of policy intervention for the EU. Liberalization and privatization of the telecommunications industry were very important topics of policy debate in the two decades from 1990 to 2010. In these years, the EU developed a sophisticated regulatory framework that aspired to the principle of favoring the entrance of new players in the sector, and characterized by a strong pro-competition flavor. However, more recently the necessity of mobilizing important investments for the creation of new next-generation networks, capable of delivering all the benefits of the digital revolution to European citizens, has cast doubts on the validity of the established framework. This article discusses the solutions adopted during the liberalization process, and summarizes some of the key future challenges to the existing regulatory framework.     

火车站区域整体开发与城市转型——荷兰恩斯赫德城市设计及启示

该文通过对荷兰恩斯赫德市火车站区域城市设计的研究,探讨了火车站区域的规划建设对于城市转型发展的作用,以及火车站区域的城市设计对土地利用、空间环境整治、城市交通系统整合、景观环境塑造等综合发展方面的积极意义。     

An overview of domestic energy consumption in the UK: past,present and future

Global contribution from domestic sector towards energy use is quite remarkable, accounting for 20–40% of total primary energy consumption in developed countries. Current predictions indicate that the domestic energy consumption will steadily increase as a consequence of notable growth in world population, everlasting technological developments, growing demand for building services and rising comfort levels. In this respect, an accurate understanding and interpretation of energy consumption data in domestic sector is of vital importance for further amendments in energy policies at the global scale. Within the scope of this paper, an overview of the trends and some key drivers that have affected domestic energy consumption in the UK from 1970 to present is presented. Energy consumption by fuel type and end use, average domestic gas and electricity use in recent years, energy consumption per household and per person are illustrated in a comparable way.     

Renovation of existing office buildings in regard to energy economy: An example from Ankara,Turkey

Unit energy consumption of existing buildings in Turkey is excessive. While average energy consumption of residential buildings in Europe is 100 kWh/m² per year, it is about 200 kWh/m² per year in Turkey. The principle reason for this, is that there was not any regulation on thermal insulation issues until recent years. However, the fiscal value of total energy consumption in residential buildings is about $2.5 billion. Recent research has shown that 40% of this energy consumption could be saved, provided that using energy efficiently. Furthermore, every reduction in energy-usage has a significant influence on environmental protection and CO₂ emissions. This study has focused on energy efficiency in a building of public sector that had been inaugurated in 1988 in Ankara. During the pre-investigative step, it has been determined that 47% of total energy consumption of the building could be saved.     

Transport and mobility in sub-Saharan African cities: An overview of practices,lessons and options for improvements

Urban mobility is increasingly becoming one of the planning and development issues for cities in the sub-Saharan Africa (SSA) region. Sub-Saharan cities are growing fast, outstripping the current transport infrastructure. Despite the population and spatial growth, many cities are defined by inadequate planning, rapid urbanisation and deteriorating transport infrastructure and services. In most sub-Saharan African countries, modes of urban mobility are highly dependent on income. Transport options are limited. In fact, walking and cycling are often the main means available for the majority of city commuters. Little effort is made to develop a range of transport options or to improve bike or walking paths. Combined with traffic jams, poor governance and the increasing cost of living, public transport mobility in sub-Saharan cities is having a tremendous impact on their liveability and citizens development aspirations. This paper argues that inclusive and broad ranging transport planning must be prioritised in SSA cities to improve the capacity of citizens to participate in work opportunities as well as to fulfil their daily domestic needs. Using observations and comparing progress in other countries and regions, we note that the majority urban poor, women in particular, are often bearing the brunt of inadequate planning and transport provision. We note that urban planning and transport infrastructure should therefore be (re) designed with particular focus on the wellbeing of the poor. The paper thus ends with a range of suggestions on what planning, design and policy options might be available to better integrate various commuting modes into urban planning infrastructure. In doing so, the paper notes that safety and security are critical elements of improving urban and spatial transport planning in the sub-Saharan Africa region.     

Regulating sanitation services in sub-saharan africa: An overview of the regulation of emptying and transport of faecal sludge in 20 cities and its implementation

Onsite sanitation is widely used in Sub-Saharan African (SSA) cities. Safe transportation and emptying of the resulting faecal sludge are essential for healthy cities. Typically provided by an informal and unmonitored private sector, these services are being increasingly regulated. This research provides an overview of the regulatory mechanisms in place in 20 cities across SSA, their implementation and emerging common trends. Findings highlight the diversity of tools, mechanisms, and capabilities. We conclude that incremental and pragmatic change is needed to achieve fully regulated services, with adequate implementation particularly facilitated by support and incentive mechanisms, and participation of all stakeholders.