Tested versus code capacity of existing bridges - Three examples

Selected Scientific Papers - Journal of Civil Engineering, 2012

In the paper, the actual condition of several existing concrete railway bridges with encased steel beams is discussed. This structural type represents relatively often solution for small span railway bridges in Slovakia. The main conclusions from inspections and in-situ diagnostics are published together with the results of the loadcarrying capacity calculation on the basis of new European codes. Despite of well-known disadvantages, the bridges with filler-beam decks are still demanded by railway authorities because of their big stiffness and small construction depth.

Procedia Engineering, 2015

In frame of global European standardization and in consequence of new knowledge concerning existing bridge reliability, the need for revision of the service handbook "Determination of the railway bridges loading capacity" had started up. The new guideline has been worked up by the collective of the Department of Structure and Bridges from the University of Zilina in cooperation with Slovak Railways and other cooperators among academicians and designers. In the presented paper, the attention is paid to the general concept and basic assumptions of the new guideline for determining the railway bridge loading capacity.

Civil and Environmental Engineering

The article describes general principles and basis of evaluation of existing railway bridges based on the concept of load-carrying capacity determination. Compared to the design of a new bridge, the modified reliability level for existing bridges evaluation should be considered due to implementation of the additional data related to bridge condition and behaviour obtained from regular inspections. Based on those data respecting the bridge remaining lifetime, a modification of partial safety factors for actions and materials could be respected in the bridge evaluation process. A great attention is also paid to the specific problems of determination of load-caring capacity of steel railway bridges in service. Recommendation for global analysis and methodology for existing steel bridge superstructure load-carrying capacity determination are described too.

Practice Periodical on Structural Design and Construction, 2003

The paper discusses a few issues related to capacity rating of existing bridges using field test results. The principles of proof and diagnostic load tests for capacity evaluation are presented through discussing the rating formulas for both tests. The proof load rating is proven a lower bound method. The diagnostic rating is proven the same as linear extrapolation, meaning an upper bound approach in nature. Two different methods used in the literature in calculating load distribution factors are discussed. The two methods are proven theoretically equal in an ideal case, but could be significantly different for field bridges due to the effects of many field factors. To distinguish the two methods, one is defined as load distribution factor ͑LDF͒ and the other as girder distribution factor ͑GDF͒. An example is used to demonstrate the discussions. The results indicate that, on one hand, the measured LDF, though calculated from measured strains, cannot fully reflect the capacity conditions of field bridges. It reflects only a relative load distribution among girders. On the other hand, the GDF approach may overestimate the bridge capacity, because it includes all the beneficial effects. Some beneficial effects may not be reliable for ultimate capacity and thus need to be removed from the capacity rating.

Engineering Structures, 2006

A systematic study of a historic railway steel truss bridge, still in use, is presented. The study includes static and dynamic field measurements as well as laboratory tests. The tests have been conducted to develop a validated analytical model, which in turn is employed to assess the capacity of the bridge to carry heavier train loads as well as seismic and wind loads, as specified by current codes. Members that require strengthening or replacement are identified, strengthening schemes are proposed and the remaining fatigue life of the bridge in its present condition and after the suggested strengthening is predicted.

Structure and Infrastructure Engineering, 2017

Full-scale failure tests of bridges play an important role in the better understanding of the behaviour of bridges and in the development of assessment methods. Such experiments are challenging and often expansive and, thus, are rare. This paper provides a review of failure tests on concrete bridges with a focus on the learning outcomes from the tests. In total, 40 failure tests have been identified for 28 bridges. Various types of bridges have been studied, involving bridge decks composed of slabs, girders and combinations thereof. There are examples of both reinforced concrete (RC) and prestressed concrete (PC) decks. In general, the tests indicated conservative estimates of the load-carrying capacity using theoretical calculations based on methods traditionally used for design and assessment. It can also be concluded that almost a third of the experiments resulted in unexpected failures, mainly shear instead of flexure. It also seems that inaccurate representation of geometry, boundary conditions and materials often explains the differences between the theoretical and the tested capacity.

2012

Abstract: This paper presents an overview of the in–service performance assessments of a steel–concrete composite (SCC) short–span railway bridge superstructure. A field load testing and visual inspections for the assessments of the SCC bridge durability under an actual service environment were conducted. The test result indicates that the SCC bridge superstru cture has no structural problems and is structurall y performing well in–service as expected. The results may provide a baseline data for future field SCC bridge load bearing capacity assessments and also s erve as part of a long–term performance of SCC bridge superstructure.

2008

The paper summarises the work on concrete bridges performed in the EU project Sustainable Bridges. The work provides enhanced assessment methods that are able to prove higher loadcarrying capacities and longer fatigue lives for existing concrete railway bridges, and is implemented in a Guideline . Methods for determination of in-situ material properties and advanced methods for structural analysis were developed. One main focus was non-linear analysis, since these provides the greatest potential for discovering of additional sources for load-carrying capacity. Furthermore, methods to assess the remaining structural resistance of deteriorated concrete bridges with respect to corrosion and fatigue were developed.

High Tech Concrete: Where Technology and Engineering Meet, 2017

Three Swedish concrete bridges have been tested to failure and the results have been compared to assessment using standard code models and advanced numerical methods. The three tested and assessed bridges were: (1) Lautajokk, a 29 year old one span (7 m) concrete trough bridge tested in fatigue to check the concrete shear capacity. (2) Ӧrnskldsvik, a 50 year old two span trough bridge (12 + 12 m) strengthened to avoid a bending failure. (3) Kiruna Mine Bridge, a 55 year old five span prestressed concrete road bridge (18 + 21 + 23 + 24 + 20 m) tested in shear and bending of the beams and punching of the slab. The main results in the paper are the experiences of the real failure types, the robustness/weakness of the bridges, and the accuracy of different codes and models. In all three cases the bridges had a considerable hidden capacity.