Cracking in Large-Sized Long-Span Prestressed Concrete AASHTO Girders

摘要

An investigation was conducted to study a cracking problem associated with theproduction of large-sized long span prestressed concrete AASHTO girders. During the production of these girders in the prestressing plant, vertical cracks often develop near the mid-third of the span after the girders have been cured overnight on the casting bed and before the prestressing strands are detensioned. The cracks would extend across the top flange of the girder transversely and penetrate vertically down through the girder web, reaching toward the bottom flange. The objective of the investigation was to identify the causes of the problem, and to develop and recommend its remedies. The research included a national survey of prestressed concrete producers to assess the status of the problem, a literature review of relevant issues, a series of laboratory and field studies to determine the condition of concrete and tendon force during the curing period, and an analysis of the girder under restrained thermal contraction.