BEHAVIOR AND STRENGTH OF COMPOSITE PUSH ـ OUT SEGMENTS WITH DEMOUNTABLE STUD SHEAR CONNECTORS

Abstract

The present study is an attempt to determine the mechanical properties of the demountable headed studs used as shear connectors in steel-concrete composite systems through evaluating the behavior of such systems. The work is exposed to experimental investigation on the behavior of standard push-out prototypes provided by demountable headed studs of various states and fashions in comparison with the behavior of a standard push-out prototype furnished by the traditional base-welded headed stud. For this purpose, eight push-out prototypes are manufactured to conduct the test program up to failure. The observed responses are the types of the fracture patterns commencing and extending during monotonous loading up to failure and the established failure modes, while the calculated responses are the load-slip relationships and the shear stiffness patterns. The effects of five parameters covered by the eight push-out prototypes are examined in this work. They are the degree of rigidity of the junction interconnecting the stud and the attaching steel element, the size of thread in the shank bottom of the demountable headed stud, the distribution of the demountable headed studs, removal of the head of the demountable stud, and using LWAC for the concrete block. Test results indicate that the degree of the attachment rigidity at base of the demountable headed stud plays the major role in weakening and softening the composite system with the condensing the pattern of fracture mechanism due to the new colonizing brittle shear fracture at the stud base. On replacing the welded headed – stud base by a nut and washer – tightening technique a 16% decrease of the ultimate load carrying capacity has taken place.

However, the value of relative slip at failure has suffered 17% decrease with that replacement, thus indicate the new brittle fracture component represented by the shear failure at the demountable – stud base. Other parameters also prove to have active diversified effects on the studied responses but of variable subservient degree. Finally the way to further experimental and analytical work on the performance of composite systems with demountable shear connectors has, thus, become accessible.