Title: Deflection Calculation for Reinforced Ultra-High- Performance Concrete Beams Based on Effective Moment of Inertia

Author(s): Fei Peng, Zhi Fang, and Song Cui

Publication: Structural Journal

Volume: 119

Issue: 4

Appears on pages(s): 263-275

Keywords: beam; deflection; effective moment of inertia; tension stiffening; ultra-high-performance concrete (UHPC)

DOI: 10.14359/51734523

Date: 7/1/2022

Abstract:
Due to the bridging effect of steel fibers in ultra-high-performance concrete (UHPC), reinforced UHPC beams exhibit much higher post-cracking stiffness and smaller deflection compared with conventional reinforced concrete beams. This paper attempts to develop a mechanics-based yet simplified method for determining the instantaneous deflection of reinforced UHPC beams at serviceability limit state. First, a validated numerical procedure is developed to predict the moment-curvature behavior of reinforced UHPC sections under serviceability conditions. Then, the tension stiffening in the beam is evaluated. It is found that the moment-curvature response of the UHPC section at the stabilized microcracking stage is almost parallel to that of the fully cracked section, with a nearly full tension-stiffening response. On this basis, a design equation for the effective moment of inertia is derived for calculating the deflection of reinforced UHPC beams. It is found that the proposed approach can provide reasonably conservative deflection predictions, with a mean value of the predicted-to-measured deflection ratio of 1.21 and a standard deviation of 0.309, by comparing its predictions with available experimental results of 82 flexural tests.