Full-scale Slab Specimens Research Articles

Structural behaviour of steel fibre-reinforced concrete floor system for modular construction

Steel fibre-reinforced concrete (SFRC) slabs are ideal for modular construction owing to the shorter span of slab in standardised modules. To investigate the structural behaviours of SFRC floor system designed for modular construction, nine full-scale slab specimens were tested both at ambient temperature and under fire conditions. The crack pattern, failure mode, concrete spalling phenomenon, deformation capacity, load-carrying capacity and fire resistance time of the SFRC slabs are reported and compared with those of conventional steel rebar-reinforced concrete slabs. The experimental results showed that SFRC slabs achieved sufficient load carrying-capacity and fire resistance time for the application in modular buildings. A fibre-element model is proposed for computing the temperature distribution and cross-sectional moment resistance of SFRC slabs under fire conditions. Based on the experimental findings, design recommendations are provided to determine the fire resistance of SFRC floor system in modular construction.

Effect of Stirrups on the Behavior of Semi-Precast Concrete Slabs

A semi-slab of precast concrete (or half-slab) is a structural system that consists of concrete at the bottom half of a slab and concrete cast in situ at the top. To avoid traditional formwork and minimize the bottom half of the slab, this section can function as formwork and reduce the thickness of precast slabs, which makes their transportation easy. The interface between precast and overtopping concrete is effective for the slab system's performance. To improve the half-slab floor system, it is needed to have a shear connector (stirrups). Therefore, to better understand the behavior of this slab system, six full-scale slab specimens (2×7.5 m) with different shapes of the stirrups and spacing between them were constructed for this study. One specimen was produced with no connections and served as a reference specimen, while the other employed stirrups to connect slab units. The tests found that the distribution and type of stirrups affect the structural performance of the semi-precast concrete slab. The maximum load capacity of slabs with rectangular or triangular connections was nearly more significant than reference slabs, reaching 136.11 and 86.11%, respectively. The maximum load increased by 81.4 % for rectangular connections and 54.9% for triangular connections when the distance between the connectors was reduced from 600 to 300 mm. Furthermore, stirrups in semi-precast slabs could improve the cracking behavior, stiffness, and ductility. Doi: 10.28991/CEJ-2022-08-08-09 Full Text: PDF

Strengthening of Concrete Element with Precast Textile Reinforced Concrete Panel and Grouting Material.

Textile reinforced concrete (TRC) has widely been used for strengthening work for deteriorated reinforced concrete (RC) structures. The structural strengthening often requires accelerated construction with the aid of precast or prefabricated elements. This study presents an innovative method to strengthen an RC slab-type element in flexure using a precast panel made of carbon TRC. A total of five RC slabs were fabricated to examine the flexural strengthening effect. Two of them were strengthened with the precast panel and grouting material and another set of two slabs was additionally strengthened by tensile steel reinforcement. The full-scale slab specimens were tested by a three-point bending test and the test results were compared with the theoretical solutions. The results revealed that the ultimate load of the specimens strengthened with the TRC panel increased by at least 1.5 times compared to that of the unstrengthened specimen. The application of the precast TRC panel and grouting material for the strengthening of a prototype RC structure verified its outstanding constructability.

Flexural Strengthening of Concrete Slab-Type Elements with Textile Reinforced Concrete.

This paper deals with flexural strengthening of reinforced concrete (RC) slabs with a carbon textile reinforced concrete (TRC) system. The surface coating treatment was applied to a carbon grid-type textile to increase the bond strength. Short fibers were incorporated into the matrix to mitigate the formation of shrinkage-induced cracks. The tensile properties of the TRC system were evaluated by a direct tensile test with a dumbbell-type grip method. The tensile test results indicated that the effect of the surface coating treatment of the textile on the bonding behavior of the textile within the TRC system was significant. Furthermore, the incorporation of short fibers in the matrix was effective to mitigate shrinkage-induced crack formation and to improve the tensile properties of the TRC system. Six full-scale slab specimens were strengthened with the TRC system and, subsequently, failure tested. The ultimate load-carrying capacity of the strengthened slabs was compared with that of an unstrengthened slab as well as the theoretical solutions. The failure test results indicated that the stiffness and the ultimate flexural capacity of the strengthened slab were at least 112% and 165% greater, respectively, than that of the unstrengthened slab. The test results further indicated that the strengthening effect was not linearly proportional to the amount of textile reinforcement.

Load-deflection behaviour of concrete slab-type elements casted on stay-in-place TRC formwork

This paper presents the design and experimental validation of a durable textile reinforced concrete (TRC) panel that can be used to furnish a stay-in-place (SIP) formwork and a protective layer over the outer surface of the reinforced concrete (RC) elements, which require high durability and long service life. The objectives of this study are to increase the flexural capacity and to improve the durability of the RC elements by employing an SIP TRC formwork panel. A durable binder system was designed to offer excellent durability performance in a chloride-rich environment. Six full-scale RC slab-type specimens were casted on the SIP TRC formwork. The load-deflection behaviour of the full-scale slab specimens was compared with the analytical solutions. The results of a full-scale flexural failure test indicated that the ultimate flexural capacity of the slab specimens with the TRC formwork was at least 141% greater than that of the RC slab without the TRC formwork.

Short-term behaviour of reinforced and steel fibre–reinforced concrete composite slabs with steel decking under negative bending moment

An experimental study was conducted on reinforced and steel fibre–reinforced concrete composite slabs with steel decking under negative bending moment to quantify the ultimate behaviour, loading capacity and crack width under short-term loading. Eight full-scale slab specimens were cast with different types and amounts of reinforcement in the concrete (e.g. mesh, steel fibre or normal reinforcing bars) but with the same type of steel decking. Each slab was simply supported and tested in four-point bending under increasing load until failure. The deflections at mid-span and under the applied point loads were monitored together with the end interface slip. The crack widths were obtained for each slab for different levels of applied load. It was found that the end slip was quite negligible and complete interaction on the steel decking–concrete slab interface existed at service loads and ultimate limit states. Compared to the slab with 20 kg/m3 steel fibre, the application of steel fibre in excess of 60 kg/m3 increased the rotational capacity and ultimate load by 60% and 80%, respectively. Moreover, the higher dosage of steel fibres resulted in improved crack control, as for the same level of applied load, the crack width was often reduced by 75%. However, the slabs with conventional high-strength ductile reinforcements had the greatest ultimate load and rotational capacity and exhibited the best degree of crack control with finer and more distributed cracks.