Investigation of the degree of composite action in composite beams with precast concrete hollow core slabs

Due to its economic and structurally efficient design benefits, steel-concrete composite structures are widely employed, particularly in the construction of multistory long-span structures. Composite structures incorporating precast concrete hollow core (PCHC) slabs offer advantages such as reduced weight, enhanced fire resistance, improved soundproofing, and increased sustainability compared to traditional solid concrete slabs. While previous studies have investigated the composite action between steel beams and solid concrete slabs, there has been a limited focus on understanding the composite behaviour between composite steel beams and PCHC slabs. This oversight in current building codes during the design phase may contribute to the specification of smaller steel beam sections. This paper aims to investigate the degree of composite action between steel beams and PCHC slabs by performing two full-scale flexural tests. The specimens feature PCHC slabs with depths of 203- and 254 mm connected to steel beams through 19-mm diameter shear connectors. The monitoring of concrete crack formation, failure modes, and deflections was conducted using instrumentation and a data acquisition system. The degree of composite action (DCA), a crucial parameter for describing the structural behaviour of composite beams, was determined using displacement, load, and strain methods. Additionally, the digital image correlation (DIC) technique was applied to track the location of the neutral axis within the composite beam during testing. DIC results were subsequently employed to validate the neutral axis position obtained from the experimental data based on the results of the earlier performed push-out tests on composite beams with PCHC slabs. A novel methodology was proposed to enhance the design process for composite beams employing hot-rolled sections with PCHC slabs. This innovative approach takes into account the degree of composite action, thereby offering a valuable framework for the structural design of such composite structures. • Degree of composite action (DCA) in composite steel beams with PCHC slabs is calculated. • Full-scale flexural tests were performed on composite beams with PCHC slabs. • Neutral axis position (N.A.P.) in composite PCHC systems is obtained from push-out tests. • Steel beam web deformation and neutral axis displacement are monitored using DIC. • Experimental bending moments are compared to values from push-out test results.