Performance of structural composite slab with partial and full interaction

Abstract

Composite concrete slab with steel decking profile as permanent formwork is gaining wide acceptance in structural construction of large scale buildings. The strength and behaviour of composite slabs are governed by the shear interaction between the concrete and the steel deck. The loss of interaction between the two materials is the main reason of the failure of composite slabs before reaching the maximum bending capacity. Technical information to strengthen the bonding and interaction in composite slab is still lacking. This study presents a new method for strengthening composite slab by an innovative U-bolts shear connectors and conventional headed studs shear connectors (HSSC). The study comprises of three components; experimental, theoretical and numerical works. The experimental work consists of eight full-scale composite slab specimens. The first specimen was made without any shear connection. The second specimen was constructed with one line of shear studs welded to the support beam while the third, fourth and fifth specimen was constructed with two lines of shear studs. The sixth specimen was constructed with U-bolts shear connectors that were fixed through the steel sheets profile. The seventh specimen was constructed with one line of shear studs with the U-bolts shear connectors. The eighth specimen was constructed with two lines of shear studs and the U-bolts shear connectors. The theoretical work consists of modifying existing stiffness method to analyse the composite slab with the U-bolts shear connectors and end anchorages. A calculation procedure was also developed to study the shear bond stress versus end slip relationships (shear bond property) from four-point bending test. Finally, three-dimensional finite element software, ANSYS, was used to determine the accuracy of the elastic stiffness method. Experimental results of composite slab tests show that the shear connectors had more efficiency for increasing the stiffness and strength of the composite slab compared with composite slab without shear connectors. Also, it was observed that the U-bolts shear connectors are strong and ductile enough to provide full composite action between the profile steel plate and concrete slab. Composite slabs with the U-bolts shear connectors show that the best performance is achieved compared to composite slab with HSSC shear connectors. The bending resistance of the proposed composite slab was improved up to 500% compared to conventional composite slab. The theoretical results show that the modified elastic stiffness method is successful to analyse partial and full composite slab. The theoretical values show a good agreement compared to the results of full-scale slab test. Good agreement was recorded between the results from finite element modelling, experimental and the modified stiffness method at linear elastic stage. It is concluded that the proposed composite slab is strong enough to be used in large scale structure.