Investigation on behavior of prefabricated double-channel composite beams with web openings in modular buildings under sagging moment

Abstract

Innovative prefabricated composite beams are continuously being introduced to enhance structural performance while minimizing costs and construction time. The prefabricated double-channel composite beam is a new section that offers improved structural performance, facilitates rapid assembly, and helps reduce construction time and costs. However, previous research on such beams has overlooked the importance of incorporating web openings for the installation of building services. Therefore, this paper aims to investigate the influence of web opening depth, length, and spacing on the behavior of prefabricated double-channel composite beams (DCCP). Static bending tests were carried out on a beam with circular web openings and three beams with varying elongated web opening lengths. Then, a finite element (FE) models of DCCPs with varying depth, length, spacing of web openings, sections and bolt pitch were performed to investigate their influence on the behavior of DCCP under sagging moment. The experimental and finite element (FE) results revealed that beams with elongated web openings experienced failure due to the Vierendeel mechanism, while the beam with circular web openings failed due to C-channel yielding and concrete crushing at midspan. The depth, length, and spacing of the web openings significantly influenced the ultimate capacity of the beams. As the size of the web openings increased, the ultimate capacity decreased, whereas an increase in the spacing of the openings led to a 3–5% increase in the ultimate capacity. A theoretical model was developed to calculate the ultimate capacity of DCCPs, and its predictions aligned with the experimental and FE results.