Influence of high sustained loads and longitudinal reinforcement on long-term deformation of reinforced concrete beams

Abstract

The objective of the study is to examine the influence of high sustained loads and longitudinal reinforcement on the long-term deformation of concrete beams. First, the influence of high sustained loads on the creep of reinforced concrete beams was investigated using five beams with load levels (ratio of sustained load to failure load) of 0.3, 0.4, 0.5, 0.6, and 0.7. A load level of 0.3 is the service load for a comparative analysis, and load levels of higher than 0.3 are considered high loads. The influence of the longitudinal reinforcement on the creep of the reinforced concrete beams was then studied using four beams with a ratio of longitudinal reinforcement of 0.81%, 1.55%, 2.14%, and 2.72%, respectively. Furthermore, the influences of the load levels and longitudinal reinforcement on the curvature creep, creep of the concrete at the edge of the compressive zone, and the mid-span deflection creep were analysed. Moreover, a comparison between the test data and the existing calculation model of the deformation of a beam was conducted, and the existing model used to predict the long-term deflection of reinforced concrete beams with high sustained loads within a wide range of longitudinal reinforcement ratios was modified. Finally, post-creep tests of the beams were conducted and the calculated formulas of the total strain (the sum of the initial strain, creep strain, and increased strain after creep) of the concrete at the compression edge of the beams was obtained through a regression analysis.