Estimation of Shrinkage with Creep Effects on R.C. Multi-storey Buildings in Accordance with the Code of Practice for the Structural Use of Concrete 2004

摘要

The problem of cracking in concrete floor structures due to shrinkage and creep is common in reinforced concrete construction, especially in floor structures of long spans and/or under strong lateral restraints. The Code of Practice for Structural Use of Concrete 2004 of Hong Kong has provisions to account for the effects. Formulation of the 1-dimensional problem based on floor structures simulated as hinged bar members under restraints has been carried out by Liu et al. (2006). This paper adopts similar principle and derives a detailed approach to calculate stress in single storey single bay floor structures to the Code of Practice for Structural Use of Concrete 2004 that can be simply worked out by hand calculations or simple spreadsheets. Design charts for general use have also been prepared. Furthermore, the authors have also extended the approach to multi-storey and multi-bay structures. Rapid decrease in stresses in the upper storeys in normal multi-storey buildings has been identified and discussed. Demonstration that stress due to shrinkage and creep of floor structures in multi-storey structures can be conservatively estimated by prepared charts for single storey single bay floor structures has also been carried out.