Design and performance of precast concrete structures

A precast concrete structural system offers many advantages over in-situ casting. For example, greater control over the quality of materials and workmanship, improved health and safety (with casting carried out at ground level rather than at height) and cost efficiency (with standard forms continually re-used) are all realised through the off-site production of structural elements. As a result, a large body of research has been conducted into their performance, with many national codes of practice also devoting specific sections to design and detailing. However, contemporary design practice has been shown to not always correctly reflect the findings of published experimental studies. Concrete technology is continually evolving, as is the industry s knowledge of how to model and predict the behaviour of the resulting structural components. Using such understanding to design and justify the more efficient, cost-effective or flexible manufacture of precast components can offer a key commercial advantage to a precast manufacturer. In this context, the numerical and experimental investigations undertaken as part of this study have been specifically focussed on quantifying the advantages of utilising beneficial alternatives. Specifically the research has looked at improvements in concrete mixes, lightweight aggregates and reinforcing strategies, for precast structural elements required to transfer loads both vertically and horizontally. However, because of the non-standard solutions considered, different approaches have been used to demonstrate their suitability. Towards this goal, an alternative assessment strategy was devised for slender precast concrete panels with central reinforcement. The procedure was found to lead to design capacities that are in good agreement with actual experimental findings and should thus result in future manufacturing efficiency. The method can also be used for alternative concrete types and reinforcement layouts. Fresh and early-age material characteristics of self-compacting concrete mixes with a partial or complete replacement of traditional gravel and sand constituents with lightweight alternatives were investigated. This was done to demonstrate the feasibility of their use for the manufacture of large scale structural components, with clear benefits in terms of lifting and transportation. A computational push-down procedure was utilised to demonstrate the potential unsuitability of current tying regulations for avoiding a progressive collapse event in precast framed structures. The findings are considered to be of particular significance for these structures due to the segmental nature of the construction and the associated inherent lack of structural continuity.