Grouped headed studs may be successfully utilized to achieve the longitudinal shear connection between prefabricated slabs and steel beams. The behaviour of the studs and the ultimate resistance of the group were analysed using the results of experimental push tests and by employing advanced FE analyses. Different arrangements of studs in the group were investigated, focusing on minimal distance between the studs. It is demonstrated that the full shear resistance of a group of headed studs is achieved even when the distances between the studs are less than the minimum requirement according to EN 1994-1-1. Concrete class C30/37 is the minimum that should be used. Furthermore, the paper presents a new model for calculating the shear resistance of grouped headed studs. The proposed design model is based on an equivalent stud diameter and can be used for various arrangements of headed studs in a group. The shear resistance formula and the requirements for ductility are consistent with the existing Eurocodes. Fatigue loading is not considered in this paper, so the proposed recommendations are valid for buildings including multi-storey car parks.

Friction connections with long open slotted holes have been proven to be a competitive alternative to the conventional flange connections in steel tubular towers for wind energy converters. As full-scale tests are not available, results of Finite Element Analysis (FEA) of the real-scale tower geometry are used in this paper to investigate the influence of tower cross section shape, execution tolerance (gap between the shells) and length of the connection on the bending resistance. Buckling behaviour of the shell in the vicinity of the friction connection in circular and polygonal towers is compared. The friction connection is thoroughly examined and recommendations for execution tolerances are given. The influence of two types of the execution tolerances on the connection strength is considered: inward bended “fingers”, leading to inclined gaps, and a parallel gap created by different tower diameters.

The RFCS project SIROCO (2014–17) included research on the further development and optimization of double shear connections with injection bolts to achieve slip- and creep-resistant bolted connections considering various influencing parameters. The type of resin, the curing condition of the resin, the geometrical and mechanical characteristics of the connection and the type of loading were studied. Results showed, for example, that of the five epoxy resins investigated, only RenGel SW404 + HY2404 (Araldite) fulfils the requirements given in Eurocode 3. A bearing stress of 175 MPa is safely allowable in the long-term without exceeding imposed deformation limits.

Currently, onshore wind turbines are economical for 2.5 mega-watt inland installation [1]. One of the alternatives to achieve the higher power capacity in onshore wind turbines is to go to higher altitude, which increases the wind speed and has more uniform wind pressure, leading to higher possible annual energy production and relatively lower maintenance costs due to wind shear induced vibrations. This paper deals with a predesign of a new type of tower that should overcome known disadvantages of steel tubular towers for heights over 150 meters. This first part of the paper addresses the viability of a hybrid support structure in respect of ultimate limit states and structural dynamics as part of the requirements in exploring the feasibility of the hybrid tower concept. The hybrid wind turbine tower concept consists of a lattice (lower) structure and a tubular tower for the higher tower segment. The study cases found in literature were designed with maximum height of 160m and the 2.5MW wind turbine. Moreover, they used commercial "L" sections which leads to high number of connections and bolts. The project that supports the present paper aims at using optimally design hollow cross sections, to reduce the number of connections, and low maintenance type bolts. The developed study case is made for 220m tower height and using 5MW wind turbine.

The prefabrication of concrete slabs reduces construction time and the total life cycle cost of composite steel-concrete buildings and bridge decks. Using bolts as shear connectors embedded in prefabricated concrete slabs enables reuse and easy replacement of slabs as structural members suitable for a circular economy construction concept. The results of static push-out experiments on M16 and M24 bolts, grade 8.8, are shown here. The focus is on the validation of advanced finite element (FE) modelling by experiments. Damage material models for bolt and concrete slab were used and the most realistic preloading of the bolts modelled with threads was achieved by turning the nut in the FE model. An explicit dynamic solver with mass scaling function was used for quasi-static analysis including fracture. Two failure modes obtained in experiments – bolt shear and concrete crushing – were realistically modelled by the FEA, which shows that the model is suitable for a parametric study leading to theoretical models of failure modes and slip capacity of the shear connection. Results indicate that the bolts with nuts on both sides of the steel flange can be successfully used as demountable shear connectors.

A steel hybrid structural solution for onshore wind turbine towers was proposed in the European project SHOWTIME. This solution is used in the lattice structure for the lower portion of the tower. Recently, a procedure for fatigue life estimation of steel half-pipes bolted connections applied in global structural models using multiaxial Smith-Watson-Topper (SWT) criteria was proposed by Öztürk et al. In this paper a procedure for design S-N curve modelling of steel half-pipes bolted connections is proposed. This procedure is based on a local approach using multiaxial fatigue criteria together with an elastoplastic analysis using the finite element method. The materials to be used in this analysis are the S355 and S690 steels. This evaluation to be performed is calibrated with experimental results of fatigue tests of the connection under consideration.

Since the partial collapse of the Ronan Point building in London in 1968, requirements for the avoidance of disproportionate collapse are addressed in the design codes. Despite these prescriptive requirements, the ability of steel connections to sustain large tensile forces whilst undergoing significant rotations has been questioned by recent studies and real evidences (as for example, the collapse of the World Trade Center in 2001).This paper describes the non-linear behaviour of a T-stub joint exposed to impact loads, by exploring a finite element model developed in ABAQUS software. The numerical model is validated against experimental results considering quasi-static loading and dynamic loading. A ductile failure criterion is implemented in the model, and the strain rate effect on the material behaviour is demonstrated in the enhancement of the force-displacement response. Finally, parametric studies, concerning the load magnitude, load application time and T-stub flange thickness, are performed. The results show that different dynamic loads have minor effect on the force displacement response, whilst the load application time has a larger effect. Moreover, it is also concluded that the force-displacement enhancement is less prominent for stiffer T-stubs.

This paper is the second part of the study on the cold-formed high strength steel circular and polygonal sections intended to be used in tubular wind towers. Results from 32 numerical finite element analysis (FEA) models were compared with and calibrated against results of the tests on 32 corresponding specimens. The FEA results agreed well with the experimental results in terms of resistances and load-displacement curves. Further investigations on the numerical models were performed. Yield stress used in the FEA significantly affected the resistances of the numerical models. Using 0.2% proof stress leaded to higher resistance than the experimental results. Corners significantly influenced buckling behaviour in the polygonal section models. Analyses of an oval opening in the tubular specimens showed that peak stresses around the opening were considerably higher in the polygonal section models than in the circular section models. Finally, investigation of sensitivity to geometrical imperfections indicated that failure modes of numerical models with geometrical imperfections according to EC3 significantly differed from those of tested specimens and numerical models with geometrical imperfections obtained from the 3D scans.