Is external post-tensioning an effective solution for shear strengthening of bridge elements?

Abstract

[Abstract]: Retrofitting of existing concrete structures has become an important issue nowadays in the construction industry. Such necessity had been caused by several factors, especially when concrete is subjected to severe environmental and loading conditions. In such situations, the remedy is either to demolish the existing structure and construct a new one or to retrofit the existing structure by an appropriate strengthening methodology. In this regard, external post-tensioning has been proven to be effective in flexural strengthening of bridge elements such as main girders, transverse girders and headstocks. There have been some attempts to use the external post-tensioning technology to increase the shear strength of bridge elements such as headstocks. One of the issues that need careful consideration is the presence of existing shear cracks in such structural elements. Recent experimental investigations using model specimens revealed that the strength enhancement by external prestressing is highly influenced by the existence of shear cracks in the concrete member. It was found that the external post-tensioning is only effective when the shear cracks are properly repaired by a suitable technique such as epoxy injection of cracks. This paper presents the results of the investigation, discussing the effectiveness of external posttensioning in shear strengthening of concrete bridges, with a case study of Tenthill Creek Bridge in Queensland, Australia.