Behaviour of continuous deep beams with unsymmetrical web openings

Abstract

It is important to understand that deep beams behave differently from normal beams. Due to their dimensions, deep beams are predominantly controlled by shear strength. Precise analytical study on reinforced concrete deep beams has always been a complex issue and the presence of web openings in continuous deep beams exacerbates the situation. Thus far, no code provisions are available for the evaluation of such beams. Besides, there are very few investigations performed on continuous deep beams with web openings.

This paper presents the testing of four continuous deep beams with unsymmetrical web openings to cater to various configurations of web reinforcement. All deep beams tested had an identical cross-section of 180 mm × 750 mm and a total length of 4600 mm. Test parameters including the crack observations, load-deflection responses, diagonal displacement of webs and strain measurements for the steel reinforcing bars were conducted to assess the behaviour of the deep beams. It was concluded that the configurations of the steel reinforcement had a significant influence on the structural behaviour of these deep beams. The capacity of the deep beams with web openings was enhanced when reinforcing bars were provided at the top and bottom of the web openings.

A parametric study using the concept of the strut-and-tie model (STM) was also carried out. In the present report, an STM was proposed to predict the failure load of the deep beams without web openings. Comparisons were made between the results obtained from the experimental approach and analytical study to validate the proposed STM. In summary, the proposed STM was able to demonstrate a reasonable correlation with the crack patterns and predict the failure load of the deep beam without web openings.