Behavior of High Strength Reinforced Concrete Wide Beams Under Bending and Torsion Effects

Abstract

The research includes experimental study for behavior of HSC wide beams under bending and torsion moments.  Nine  beams of 1200×220×110 mm were tested. Parameters of the study were torque to bending moments ratio (T / M), longitudinal and transverse reinforcement ratios (ρ_L & ρ _t). The results indicated that presence of torsion combined with bending moment significantly reduces the ultimate moment capacity (M_u) and results in changing beam failure from flexural mode to torsional or flexural-torsional mode. Also torsion effect results in reducing cracking moment capacity and propagation of inclined cracks combined to vertical cracks. These influences for torsion increase with increasing T / M ratio and ρ_L and with decreasing ρ_t. Increasing ρ_L results in significant increase in Mu especially when T / M decreases, while increasing ρ_t results in slight increase in M_u and its effect decay as T / M decreases. Increasing T / M ratio makes Moment-deflection response softer especially in case of high ρ_L. Increasing ρ_L makes this response stiffer especially in case of pure bending whereas increasing ρ_t slightly stiffens this response in advanced loading stages for high values of T / M. Torque-rotation response is stiffer as T / M ratio increases. Also, increasing ρ_L makes the responses stiffer for all values of T / M while increasing ρ_t makes it slightly stiffer in advanced loading stages. Mathematical expression for calculation of ultimate moment capacity for this type of beams was proposed and give results that have good agreement with experimental results.

Keywords: wide beam, high strength concrete, bending, torsion, deflection, rotation.

DOI: 10.7176/CER/12-12-05

Publication date: December 31^st 2020