Flexural behavior of assembled monolithic long-span composite beams with CIP reinforced concrete layer atop precast hollow core slabs

Abstract

Steel-concrete composite beams (CB) with precast hollow-core slabs (HCSs) have been widely used in long-span structures for its high bending capacity, good ductility, lightweight, and fast construction. A novel assembled monolithic CB with a cast-in-place (CIP) reinforced concrete layer poured on the precast HCSs (CBCH) was proposed in this study. Eight full-scale flexural tests were conducted majoring in the parameters of span (L = 6.0 m and 8.4 m), degree of shear connection (λDS = 100%, 70%, and 30%), width of CBCH (B = 2100 mm and 1800 mm), and thickness of CIP concrete layer (hCIP = 60 mm and 20 mm). Three typical failure modes were observed: i.e. flexural failure, longitudinal shear failure in the shear span, and peeling failure occurring between the precast HCS and CIP concrete layer. The results indicate that the λDS and hCIP can significantly affect the failure modes, flexural capacity, and ductility; the B has a slight influence on the bending behavior of CBCH. In addition, an extensive parametric study was conducted according to the test results. To elevate the bending capacity of CBCH, relative formulas are proposed, and agree well with the results of test and parametric study. Based on the theoretical and FE analysis, the partial shear specimens with λDS ≥ 85% can achieve almost the same performances as the full shear specimens (λDS = 100%). However, a λDS = 100% and the minimum hCIP = 60 mm are recommended to ensure the integrity of the CBCH in engineering practice.