Analysis of Total Deflection of Reinforced Concrete Box Beams Under Repeated Loading


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Title: Analysis of Total Deflection of Reinforced Concrete Box Beams Under Repeated Loading

Author(s): Yew-Chaye Loo and Yen Wen Wong

Publication: Journal Proceedings

Volume: 81

Issue: 1

Appears on pages(s): 87-94

Keywords: box beams; creep properties; cyclic loads; deflection; live loads; moments of inertia;reinforced concrete; static loads; structural analysis.

Date: 1/1/1984

A simple, computational procedure is presented for the prediction of the total deflection of singly-reinforced concrete box beams under repested loading. The total deflection is obtained by summing the instantaneous live load deflection and the accumulated dead load deflection. The latter may be computed as the product of the intial dead load deflection and intensive creep factor. Following a comparitive study, the most suitable method is chosen from well-known procedures for the computation of the intial dead load deflection. Based on the experimental data on 30 under-reinforced box beams (tested under 100,000 cycles of load), an empirical formula for the intensive creep factor is derived. Parallel to the logarithmic time-creep equation, the formula is considered to be more realistic than an alternative hyperbolic method. For computing the instantaneuos live load deflection of any loading cycle, a new equation for the equivilant moment of interia is proposed. This equation is shown to be superior to existing formulas. All equations recommended for use are simple and explicit. Comparisions with the test results indicate that the proposed computational procedure is generally accurate.