Load testing of concrete bridges is a practice with a long history. Historically, and particularly before the unification of design and construction practices through codes, load testing was performed to show the travelling public that a newly built bridge was safe for use. Nowadays, with the aging infrastructure and increasing loads in developed countries, load testing is performed mostly for existing structures either as diagnostic or proof tests. For newly built bridges, diagnostic load testing may be required as a verification of design assumptions, particularly for atypical bridge materials, designs, or geometries. For existing bridges, diagnostic load testing may be used to improve analysis assumptions such as composite action between girders and deck, and contribution of parapets and other nonstructural members to stiffness. Proof load testing may be used to demonstrate that a structure can carry a given load when there are doubts with regard to the effect of material degradation, or when sufficient information about the structure is lacking to carry out an analytical assessment.

Current codes often underestimate the capacity of existing bridges. The purpose of the tests presented here has been to assess the real behaviour and capacity of three types of bridges in order to be able to utilize them in a more efficient way. The three studied bridges are: (1) Lautajokk – A one-span trough bridge tested in fatigue to check the shear capacity of the section between the slab and the girders; (2) Övik – A two span trough bridge strengthened with Near Surface Mounted Reinforcement (NSMR) of Carbon Fibre Reinforced Polymers (CFRP) tested in bending, shear and torsion; and (3) Kiruna – A five-span prestressed three girder bridge tested to shear-bending failures in the girders and in the slab. The failure capacities were considerably higher than what the code methods indicated. With calibrated and stepwise refined finite element models, it was possible to capture the real behaviour of the bridges. The experiences and methods may be useful in assessment and better use of other bridges.

The state of West Virginia is home to a substantial population of bridges that are in service well past their initial design lives. As these bridges have aged, and inevitably deteriorated, management has become a challenge. In 2006, The West Virginia Division of Highways (WVDOH) enlisted the help of Drexel University to develop an approach to managing these structures, with a particular focus on reinforced concrete bridges with little to no documentation. One such structure was the Barnett Bridge, located near Parkersburg, WV. This filled concrete arch bridge was built in 1929 with a 90 foot (27.4m) single span over a small creek. The bridge was posted due to challenges in accurately load rating the structure with only minimal historical documentation. Working side by side with WVDOH, and through a combination of load testing, repairs, and targeted long-term monitoring, the bridge was left in service. This paper presents the case study of the Barnett Bridge, from when it appeared in the local newspaper in 2008 as one of the bridges in the state with the lowest sufficiency rating, to present day where it still serves the surrounding area, with a focus on the proof load test that served as the cornerstone for the revitalization of this structure.

A large subset of the Dutch bridge stock consists of reinforced concrete slab bridges, for which assessment often results in low ratings. To prioritize the efforts of the bridge owner, more suitable assessment methods for slab bridges are necessary. Research efforts over the past years resulted in the development of several methods, at levels requiring increasing costs, time, and effort for increasing accuracy. The last option, when an analytical assessment is not possible due to uncertainties, is to use proof load testing to evaluate the bridge directly. To develop recommendations for the proof load testing of reinforced concrete slab bridges for the Netherlands, different methods are combined: pilot proof load tests on bridges with and without material damage, a collapse test, tests on beams taken from an existing bridge and new beams with similar dimensions cast in the laboratory, and an extensive literature review. The result of this study is a set of recommendations that describe how to prepare and execute a proof load test, and how to analyze the results. This paper summarizes the research program about proof load testing from the Netherlands and gives an overview of the currently developed recommendations and topics for further research.

Nowadays, finite element analyses provide information about the performance of a structure, but they are more or less simplified. Therefore, load tests are the only way to find the “real” behavior of an existing bridge subjected to the rating process. In this paper, the state-of-the-art concerning load tests of concrete road bridges is presented, and the problems of the execution of such tests are specified. It is pointed out that only load tests accompanied with current finite element analyses may result in a proper assessment of the level of safety of the bridge. The authors’ procedure of complex assessment of such bridges combines in-situ examination of the structure, load testing, and finite element modeling. The paper discusses the following topics: aims and fundamentals of static diagnostic and proof load tests; the load application method according to different codes and specifications; the basis for proper assessment of the target load: reliability index, partial factors approach, global rating factor approach; establishing the load allowable on the bridge, based on the applied proof load; and the proposed procedure of assessment of existing concrete road bridges by load testing.