Experimental and numerical investigation of a cold-formed steel system used to restore old buildings floor

This paper presents a novel configuration of built-up cold-formed steel (CFS) flooring system in the shape of a box section. A new technique is applied to produce the components of the flooring system, which are fastened by self-drilling screws. This box section consists of a cast-in-situ concrete slab, trapezoidal steel decking, two sigma section, steel plate and stiffening equal angles. The main objectives of this system is to enable rapid construction and decrease the time, requirements, and cost. As a result, the proposed system is designed to use the decking in a longitudinal direction. Many old buildings have sturdy structures but their floors were ruined due to being fabricated from timber. This flooring system will be implemented to increase their quality of life and be reused. The loading experiments of four specimens were carried out. The failure modes of the CFS flooring system, load-deflection relation curves, longitudinal strain distribution at different heights were obtained. The experimental results show that the flooring system has high stiffness and flexural performance and can reach ultimate strength without local buckling failure. The failure occurs due to distortion at the end supports. Then, the capacity of the flooring system was calculated theoretically. Then, the practical and theoretical results were compared. The calculated results agree well with the test results. A three-dimensional finite element model is also established to investigate structural performance of the proposed system.