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The effect of multiple vehicles on a bridge's dynamic amplification is a complex problem. Previously authors have examined multiple vehicle presence by constructing elaborate finite element models or undertaking field tests. Although both these methods give valuable information regarding the magnitude of dynamic amplification, the results tend to be site-specific and give limited insight into how large amplifications occur. This paper examines the dynamic amplification factor of a simply supported bridge being crossed by two loads traveling in both the same and opposing directions. Simple numerical point load models are used to determine the critical load velocities and load positions that result in high amplifications. An experimentally validated finite element model is used to examine the applicability of the conclusions to real bridge/vehicle systems.

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Learning the lessons from structural failure necessarily involves investigating the organisational and technical causes of failure, and ensuring these lessons are disseminated to the wider structural engineering profession to prevent reoccurrence. Yet despite the obvious benefits of such an approach, individuals and organisations are generally reluctant to disclose or acknowledge failure, and these psychological reactions can dominate their ability to learn the critical lessons. Understanding the role these psychological reactions play in inhibiting learning is a key step in developing practical methodologies for ensuring the lessons of past failures are not forgotten. This paper reviews and discusses some of the unique aspects of anticipating, responding to, and learning from all forms of failure, not only those of a structural nature. The paper reviews the barriers to learning, the challenges of identifying and analysing failure, the importance of 'near-misses' in anticipating failure, and explores how these insights can provide guidance to the structural engineering profession on how best to ensure effective learning occurs.