Evaluation of Concrete Bridge Behavior through Load Testing – International Perspectives
|Publication Date:||1 May 2018|
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.
In recent years, both researchers and practicing engineers worldwide have been refining load testing methods to balance accuracy, cost, effort, and time, and have been addressing increasingly complex structures and situations. To exchange international experiences among a global group of researchers and compare load testing methods used internationally, ACI Committee 342 organized two sessions titled "Evaluation of Concrete Bridge Behaviour through Load Testing - International Perspective" at the 2017 ACI Fall Convention in Anaheim, CA. This Special Publication contains several technical papers from experts who presented their work at these sessions, in addition to papers submitted for publication only.
This Special Publication combines contributions from different regions of the world, and in particular from Denmark, Germany, the Netherlands, Poland, Spain, Sweden, and from different regions in the United States. The technical papers consider both theoretical and practical aspects of load testing, discuss different levels of bridge behaviour assessment such as visual inspections, modelling, and load testing. They introduce the reader to the codes and guidelines that may only be available in some countries. The impact of differences in live loads, design codes, reserve capacities, age of structures, construction practices between Europe, and North America on assessment of concrete bridges is reflected by case studies. Recent developments with regard to codes and standards around the world for load testing are discussed, and open questions for future developments are highlighted by the authors.
The wide variety of concrete bridge structures investigated included shortspan reinforced concrete slab bridges, older reinforced concrete earth-filled arch bridges, bridges that have been damaged and/or retrofitted, and modern prestressed concrete bridges with new materials. Reasons why load testing is required also vary and include apparent damage, opportunities created by decommissioned bridges, necessity to carry super heavy vehicles, use of unique materials or geometry, and absence of design plans. Results of testing bridges under static or dynamic service loads create knowledge on expected service
performance and allow load ratings, while testing decommissioned bridges to near collapse or collapse reveals true capacity and the level of conservatism in design assumptions. Several papers highlight vehicles or rigs designed specifically for reuse in standardized load testing. Others use recent technology such as 3-D scanning or digital image correlation to collect data, in addition to traditional methods such as strain gauges. As such, this Special Publication provides a global perspective on strategies for assessing the in-service performance of concrete bridges, and an overview of the state-of-the-art with regard to load testing internationally.
Overall, in this Special Publication, authors from different backgrounds and geographical locations share their experiences and perspectives on load testing and its impact on understanding concrete bridge behaviour. The coeditors, Dr. Pinar Okumus and Dr. Eva Lantsoght, are grateful for the contributions of the Special Publication authors and sincerely value the time and effort of the authors in preparing the papers in this volume.