Railway Concrete Bridge Research Articles

Fragility estimate of railway bridges due to concrete fatigue

Railway concrete bridges are prone to fatigue collapse, being subjected to multiple cyclic loads during their lifetime. This paper proposes a probabilistic procedure for assessing the fatigue life of concrete railway bridges. The procedure includes the uncertainties related to the concrete fatigue model and the concrete strength by highlighting the relevant uncertainty of existing fatigue models. Therefore, it proposes an enhancement of the fatigue model proposed by the Fib Code 2010 to reduce the modelling error possibly. The model has been calibrated on an extensive data set of normal-strength concrete samples following a Bayesian approach. Parallelly, the parameters have been reduced using a Bayesian step-wise deletion process. The paper uses the proposed probabilistic model to estimate the fragility curves in general cases by considering appropriate ranges for the train velocity, stress ratios and the number of cycles per year. In the second step, the paper applies the procedure to the fragility estimate of a typical prestressed-concrete railway bridge. The bridge response has been estimated using a finite-difference (FD) model. The FD model, simulating train–track–bridge interaction, has been calibrated on the measured displacement response. The analyses have been referred to different scenarios when suitable ranges of train velocities and cycles per year are considered.

Seismic performance assessment of concrete bridges with traffic-induced fatigue damage

This paper proposes a universal analytical method for the seismic performance assessment of concrete bridges with initial fatigue damage caused by traffic loads. Load modeling is firstly performed, and random models of traffic load and seismic loads are established using stochastic processes. Subsequently, the theoretical approach for deterministic seismic response analysis of concrete bridges with initial traffic-induced fatigue damage is established by a combination of the micro-meso stochastic damage constitutive models and the finite element numerical method. In this manner, the seismic damage and failure mechanism of concrete bridges with initial fatigue damage can be elucidated. Further, considering the randomness of loads, the stochastic seismic analytical framework of concrete bridges damaged by traffic loads is put forward, in accordance with the probability space partition-based random load combination method and the probability density evolution theory. In such a way, the seismic reliability and safety of existing damaged concrete bridges can be well evaluated. Finally, a railway concrete bridge, as a practical engineering application, is investigated to validate the applicability of the proposed method.

Changes and Prospects of Maintenance Technologies for the Railway Concrete Bridges

Changes and Prospects of Maintenance Technologies for the Railway Concrete Bridges

Determination of Load-Carrying Capacity of Railway Concrete Bridges According to New Guideline

The handbook "Determination of load-carrying capacity of railway bridges" [1] has grown up due to updating of old Slovak guideline [2] taking into account Eurocodes. In the case of railway bridges, there are about 2300 bridges in Slovakia and about 78 % of them are from concrete or masonry. About 28 % of bridge total number is older than 77 years and about 18 % of them are even older than 100 years. Therefore, there is need to make regular inspections, recalculate them – determine of load-carrying capacity and then to decide, which of them should be repaired or reconstructed [3,4]. The paper presents general concepts and basic assumptions for determining the load-carrying capacity of reinforced and prestressed concrete railway bridges. In contrast to design of a new bridge, additional data related to existing bridge condition and its behaviour like information from regular inspections and real state of degradation can be taken into account. Special recommendation and allowances for global analysis of existing concrete superstructures for the purpose of the load-carrying capacity estimation are discussed, as well.

Prediction of the Environmental Noise Level of Railway Cars Crossing a Concrete Bridge

In the conventional model for the prediction of the railway environmental noise, one used an empirical formula of the total noise level at specific distances. Only a function of the distance to the source was also used to calculate the noise level near the railway bridges. However, the noise varies depending on the position of the receiver as well as the distance from the source especially at concrete bridges. In this paper, a noise propagation model in the railway concrete bridge was derived by considering the diffraction at the bridge deck and the ground effect and applying the ISO 9613-2 noise propagation model. We compared the predicted and measured values of environmental noise at a high-speed railway bridge, and it was confirmed that this prediction model gives relatively small errors.

Theoretical Calculation and Experimental Research of Shrinkage of High Strength Concrete an High-Speed Railway Bridges

Concrete bridges on high-speed railway are usually constructed with high strength concrete. Because of shrinkage of concrete, large stress and deformation always appear in construction and operation process of bridges. It even leads to concrete cracking. So as to guarantee the safety of structures and smoothness of tracks, correct calculation of concrete shrinkage effect must be done. Concrete shrinkage effect is a very complex non-stress strain problem which is influenced by numerous factors and difficult to calculate. According to the factors considered from different emphasis aspects, a variety of patterns or specifications are formed based on different domestic and foreign models of concrete shrinkage calculation. Combined with the construction of Jiangshan Harbor Bridge (75+2×135+75) m prestressed concrete continuous beam bridge on Hangzhou-Changsha high-speed railway, concrete shrinkage field tests and measurements were carried in which the same mix of high strength concrete as that of the bridge was used. The results of tests and measurements were compared with results of different theoretical models. The effects of high strength concrete shrinkage on high-speed railway concrete bridges were studied and some useful conclusions were obtained.