The longitudinal shear bond behavior of an innovative laminated fiber reinforced composite slab

Highlights

• A new laminated pouring technique using both LWAC and FRLWAC is proposed.

• A new type of laminated concrete-profiled steel sheeting composite slab is proposed.

• The height of plastic neutral axis is a suitable lamination thickness.

• The validities of rational modifications for assessing τ_u of LFRCSs are confirmed.

Abstract

Composite slabs with ordinary concrete and typical profiled steel sheeting are widely used in construction industry due to their obvious advantage in casting as well as in structural performance. This paper proposes a new laminated pouring technique, and presents a series of full-scale tests conducted on a new type of composite slab produced using both lightweight aggregate concrete and polymer fiber reinforced lightweight aggregate concrete with a closed-type (non-embossed dovetailed) steel sheeting profile (LFRCS). A total of 12 simply supported specimens were tested to investigate the structural behavior of this new type of composite slab with special emphasis on the lamination thickness. Test results were used to obtain an effective range for the laminated pouring technique. It was observed that plane cross-sections remain plane in LFRCSs but the longitudinal shear bond strength dominates the failure mode regardless of lamination thicknesses. In addition to linear regression methods and PSC based methods that are typically used for accessing the longitudinal shear bond strength for composite slabs with normal weight and lightweight concretes, rational modifications and relevant formulas for the specified LFRCS configurations including the effects of tensile reinforcement have been proposed. Results predicted using the proposed analytical techniques were compared those obtained experimentally, and the comparison showed good agreement.

Introduction

Composite slab floor systems consisting of structural concrete and cold-formed profiled steel sheeting are widely used in steel framed buildings due largely to the reduction of self-weight and simplification of the construction process. The profiled steel sheeting acts as a permanent formwork before casting and as tension reinforcements after casting; the standard scaffolding and propping systems are, hence, not required [1]. The composite action between concrete and steel sheeting interface is crucial, and often controls the failure mode. The longitudinal shear bond failure is reported to be the most common failure mode in composite slabs; significant end slips are reported to occur between concrete and profiled steel sheeting interfaces well ahead of reaching its ultimate bending capacity [2], [3], [4], [5].

Lightweight aggregate concrete (LWAC) is now considered as a useful construction material. It is widely used in tall buildings, long-span structures and, in general, large-size structures due to significant reduction in self-weight. This type of concrete is also reported to provide better performance in fire resistance as well as in thermal and acoustic insulation when compared with normal weight concrete (NWC) [6], [7], [8]. Nevertheless, its physical and mechanical properties are largely affected by the strength of aggregates. The brittleness of LWAC is higher than the same strength-grade NWC which makes it susceptible to cracking, and results in some durability issues [9].

Using extra fibers, such as steel fiber and polymer fiber, as an additional material to produce a relatively ductile fiber reinforced lightweight concrete (FRLWAC) is considered as an effective solution; this technique improves a number of properties of the concrete matrix such as tensile strength, ultimate load carrying capacity, toughness, post-failure ductility and crack control ability. Fibers used in such concrete carry redistributed tensile stresses and limit the propagation of cracks [10], [11].

Therefore, the concept of fiber reinforced concrete in combination with profiled steel sheeting composite slab has recently been proposed and examined by a number of researchers. Gholamhoseini et al. [12] indicated that despite using fiber reinforcements, the longitudinal shear bond failure dominated the strength of steel fiber reinforced concrete composite slabs; all tested slabs failed with remarkable interface and end slips, and experienced significant post-cracking and post-slip strength as well as showing significant improvement in crack control. Similar research was also conducted by Wollmann et al. [13] and Abas et al. [14]. However, there has been no research reported in literature to date to examine the possibility of combining the beneficial features of fiber reinforced light-weight concrete and profiled steel sheeting in composite slab construction.

Use of additional fibers may help to achieve improved structural performance but will increase costs and self-weight of constructions, especially addition of steel fibers. In this study, a new type of polymer fiber was used, and an innovative laminated pouring technique was proposed to achieve an optimum balance from material aspect i.e. minimizing the amount of expensive material for achieving maximum structural performance [11]. On the basis of previous consideration, the aim of this study was to investigate the physical and the mechanical properties of the proposed new laminated fiber reinforced composite slabs (LFRCS). Obtained experimental results were used to analyze and discuss the stress distribution patters, a suitable lamination thickness for the considered technique, observed failure modes and the crack control ability of the considered slabs. The effects of tensile reinforcement were investigated, and rational modifications to existing design equations have been proposed to access the longitudinal shear bond strength for LFRCS.