Bolted shear connectors vs. headed studs behaviour in push-out tests Marko Pavlović a, ⁎, Zlatko Marković a , Milan Veljković b , Dragan Buđevac a a Faculty of Civil Engineering, University of Belgrade, Serbia b Luleå University of Technology, Sweden abstract article info Article history: Received 8 February 2013 Accepted 4 May 2013 Available online 2 June 2013 Keywords: Steel–concrete composite beams Prefabricated structures High strength bolts Headed studs Shear connector height Parametric study Push-out tests Finite element analysis Damage plasticity Prefabrication of concrete slabs reduces construction time for composite steel–concrete buildings and brid- ges. Different alternatives for shear connectors (bolts and headed studs) are analysed here to gain better in- sight in failure modes of shear connector in order to improve competiveness of prefabricated composite structures. Casting of high strength bolted shear connectors in prefabricated concrete slabs offers the higher level of prefabrication comparing to a standard method of grouting welded headed studs in envisaged pockets of concrete slabs. In addition, bolted shear connectors can easily be dismantled together with the concrete slab thus allowing the improved sustainability of the construction, simpler maintenance, and devel- opment of modular structural systems. Bolted shear connectors have been rarely used in construction, actu- ally just for rehabilitation works, because there is a lack of design recommendation. The first step towards the design recommendation is to understand the difference between the headed shear studs and the bolted shear connectors in a push-out test. Push-out tests, according to EN1994-1-1, using 4 M16 — grade 8.8 bolts with embedded nut in the same layout and test set-up as for previously investigated headed studs were performed. Finite element models for both shear connectors were created, and good match with experimen- tal data was obtained. Basic shear connector properties such as: shear resistance, stiffness, ductility and fail- ure modes have been compared and discussed in detail by using experimental and FE results. Parametric FE analyses of shear connector's height are carried out and shear resistance reduction factor has been proposed for bolted shear connectors. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction Steel–concrete composite beams have been used in buildings and bridges for decades. In-situ casted concrete requires often temporary supports and formwork which leads to a longer construction time compared to, recently established, prefabricated concrete slabs. Pre- fabrication of concrete slabs is a good way to reduce the construction time and optimize construction process. Composite action between a steel profile and a concrete slab is most commonly established by grouting grouped headed studs welded to a flange of steel section in envisaged openings (pockets) of prefabricated concrete slabs. Moreover, if the replacement of concrete slabs is required either for structural reasons (maintenance) or practical reasons (end of the life time), bolted shear connectors has big advantages because of easier dismantling. Prefabricated composite deck structures with bolted shear connec- tors may be used in residential and commercial buildings, car parks and modular building systems. They can also be competitive for short span overpass bridges and modular temporary bridge systems. Dry as- sembling and faster erection process are obtained by casting bolts in prefabricated concrete slabs and by on-site assembling into predrilled flange of steel section part of composite member. In this case, low fabri- cation tolerances of prefabricated elements need to be achieved so as to ensure assumed composite action of the structure. Tolerances for the concrete slabs in prefabricated bridges are rather strict and very good state of the art on the requirements, achieved toler- ances and costs are provided in Hällmark licentiate thesis [1]. Reference is made to a match casting technique in order to get sufficient precision. This technique means that the first element can be cast in an ordinary formwork, but from the second element and further, the previous cast element should be used as formwork on one side of the next element. By using this match-casting technique it has been shown that it is pos- sible to keep the mean joint-gap ≤ 0.4 mm as achieved in the single span L = 28 m, prefabricated composite road bridge AC 1684 built in 2002 in Norrfors, Sweden. The total cost of the prefabricated bridge was smaller than the in-situ cast bridge, in spite of such small execution tolerances achieved. The construction costs with use of bolted shear connectors are expected to be higher when compared to traditional headed studs. Still, the faster erection and life cycle cost analysis may lead, for cer- tain applications, that the total economy of the precast structures be- comes competitive. However, bolted shear connectors in composite structures are rarely used. One of the possible reasons could be the lack of detailed research and design rules concerning their specific Journal of Constructional Steel Research 88 (2013) 134–149 ⁎ Corresponding author. Tel.: +381 641471748. E-mail address: marko@imk.grf.bg.ac.rs (M. Pavlović). 0143-974X/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcsr.2013.05.003 Contents lists available at SciVerse ScienceDirect Journal of Constructional Steel Research