Lessons from incidents attributable to the uncertainties in bridge launching illustrated by a case study

Abstract

Like other competitive bridge erection techniques, incremental launching is a highly vulnerable process that entails considerable risks to persons. In steel and composite bridges, in particular, patch loading and other mechanisms that induce instability must be avoided. Considerable uncertainties are associated with both resistances and support reactions during launch operations due to the broad range of factors involved. Nonlinear finite element (FE) analysis is very useful for the explicit verification of both local and overall system stability during steel structure launching. Monitoring, in turn, may be a very powerful tool for reducing the risks associated with such operations. Further research is needed both to establish safety levels for temporary structures and on-site activities and to develop a suitable design format for nonlinear FE analysis. However, in everyday practice, engineers and builders must deal with much more basic problems, often related to the interaction between the structure under construction and the ancillary resources used, as exemplified in the case study described in this contribution. The lessons learnt from such incidents are extremely useful for improving the strategies presently in place to reduce construction-related risks.

Analysis of height difference between three trusses of a steel truss bridge during incremental launching

“…Granata [12] studied adjustable prestressing for the construction stages of incrementally launched bridges. The second research direction is finite element analysis [13], [14], [15], [16]. Mohamed Marzouk [13] simulated the construction process by using numerical simulations.…”

“…Zhang and Luo [15] studied the path loading of a steel box girder during incremental launching by using numerical analysis and provided solutions. Tanner [16] studied the overall stability and local stability during incremental launching. The third research direction is experimental study [17], [18], [19].…”

Learning from incidents during bridge erection

“…Many of the problems that must be dealt with in everyday practice are more elementary, however [1]. An analysis of a number of incidents and accidents occurring over a fairly short period of time in recent Spanish bridge construction history, for instance [2], shows that they are often related to human error, which, on closer analysis, can be traced back to flawed organisation. On many an occasion, the origin of such flaws lies in the singularities inherent in the auxiliary elements used in construction.…”

Requisitos de seguridad estructural basados en los riesgos para las personas

“…− Análisis del material: ¿conlleva la capacidad de combustión, la toxicidad, el carácter explosivo o la falta de durabilidad de los materiales constitutivos empleados o de los productos finales un potencial para causar eventos no deseados? − Análisis de interfaces: muchas amenazas están relacionadas con la transferencia de materiales, fuerzas, información o responsabilidades [Schneider 1994, Tanner 2013b, por lo que la pregunta adecuada versa sobre ¿cómo se salva una determinada interfaz?…”

“…Para muchos de los casos recopilados, las fuentes de información disponibles se limitan a diferentes medios de comunicación ya que no todos los países siguen la tradición anglosajona de publicar los informes de ingeniería forense [Tanner 2013b]. Además, en los medios generalistas estos accidentes suelen ser noticia en los primeros días después de su ocurrencia, cuando la información a menudo es confusa.…”