Short and long-term deflection behaviour of steel reinforced concrete shallow beams
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Date
2013
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University of New Brunswick
Abstract
Current methods of computing the short and long-term deflection of reinforced concrete
members are empirical and have been found to be inaccurate for some cases. The
present research will examine the deflection behaviour of reinforced concrete members
to explore whether a rational approach for computing short and long-term deflection can
be developed.
Fourteen steel reinforced shallow beams were cast and used to perform both short and
long-term tests. Both traditional and more recent approaches to predict short-term
deflection were investigated. Results indicated that selecting an appropriate cracking
load has a significant impact on predicting the short-term response. In addition, a
rational approach to compute the residual deflection after unloading was developed.
Long-term deflection multipliers were computed from the experimental investigation
and the results were compared to the CSA A23.3-04 reported values. The long-term
deflection multipliers for beams tested at an early age, correspond well with the
published values. However, for beams tested at a late age, CSA A23.3-04 long-term
deflection multipliers significantly overestimate deflection, as expected. A rational
approach to compute long-term deflection has been developed based on theoretical
studies of axial members. This approach has been extended to flexural members and the
predicted results agree well with the experimentally observed deflections.