SEMI-PRECAST SEGMENTAL BRIDGE CONSTRUCTION METHOD: POST-TENSIONING OF THIN-WALLED BOX GIRDERS

Abstract

In an ongoing research project at the Institute of Structural Engineering of TU Wien, thin-walled, pre-fabricated concrete elements are used for the development of segmental box girder bridges. The indi-vidual components of the box girder are assembled on-site using steel parts to form individual bridge segments. These segments are then joined together by means of post-tensioning to form a bridge girder. Due to the use of thin-walled elements with a slab thickness of about 70-100 mm, conventional methods of post-tensioning reach their limits. In standard bridge girders, thick-walled webs and slabs are normally available in the area of force application, thus bending moments can be safely borne and sufficient anchorage lengths can be provided for stirrups. This is no longer the case in the thin-walled segments. New approaches are therefore necessary to ensure the safe introduction of post-tensioning forces into the box girder. The general assembly of segments consisting of thin-walled, prefabricated elements is described, fol-lowed by the approach for the construction of blisters or other types of elements in those thin-walled segments for the introduction of post-tensioning forces, presenting a precast variant as well as an in-situ-concrete method. Failure mechanisms, that can occur during the post-tensioning of thin-walled segments, as well as measures to ensure the force transmission into the thin-walled elements with the help of external steel members are discussed. Finally, a comparison of non-linear finite element simu-lations to experimental results is presented. The results of the research show that post-tensioning forces can be safely introduced into the thin-walled box girder segments using the new approach. In the paper, encountered problems are illustrated and proposed solutions presented.