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The topic of this paper is experimental and numerical analysis of the impact strength of unreinforced concrete slabs. Impact strength of concrete is significant in case of some accidental loads during exploitation. Impact strength can be determined experimentally, using Drop-weight test, Charpy test, Projectile impact test, Explosive test, etc. In this research, a numerical model for determining the impact strength of concrete slabs based on Finite element method (FEM) and high-end engineering software has been proposed. Modelling approach to this problem was applying the Explicit dynamics FEM analysis. Thereat, two different existing material models for concrete were enforced: Concrete damage plasticity model – CDP (implemented in ABAQUS/Explicit software), and the Riedel-Hiermaier-Thoma model – RHT (implemented in ANSYS Workbench software). Analysis parameters for both material models, necessary as input data, have been determined through a series of FEM analyses and validated by performed experiments, using drop-weight test. Results of the numerical analyses have been compared with the experimental ones, as well as mutually. Advantages and drawbacks of both material models are highlighted, as well as the reliability of the proposed numerical models. The proposed numerical FE models, confirmed by experiments, can be successfully used for determining impact strength of concrete slabs in further research.

During rehabilitation of residential buildings built in the first half of the 20th century, it is necessary to strengthen timber floors so they can fulfill the requirements of strength and serviceability according to contemporary regulations. Floors made of monolithic timber girders can be most easily strengthened by forming a composite structure with a reinforced concrete slab supported on a trapezoidal steel sheeting, with appropriate connections between different materials. In the paper, the procedure of calculation of nails used as shear connectors for composite action of timber and concrete is presented. The procedure is based on equations given in Eurocode 5, and besides that, a calculation applying FEM has been conducted, and a comparison of results is presented.

Steel-timber composite structures have numerous advantages compared to steel only and timber only structures. One of the most important parts of a composite structure is the composite connection. Object of this research was a steel-CLT composite connection consisting of a steel profile, a cross-laminated timber (CLT) panel and a bolt with nut and washer. Aim of the research was to develop an efficient finite element (FE) model of a bolted steel-CLT composite connection and to validate it experimentally. The research process consisted of several steps: experimental testing of the considered connection using asymmetrical push-out test, numerical modelling and analysis of the connection using Finite Element Method (FEM), validation of the numerical model using experimental results, and parametric study of the proposed numerical model. For numerical analysis, an innovative method for timber modelling has been proposed. The comparison between the experimental and numerical research results demonstrated that the proposed numerical model was convenient for practical application in structure analyses. The parametric study showed that, in some cases, atypical failure modes of the connection occurred. Based on registered behavior, a recommendation is given to calculate the load capacity of the connection integrally, taking into account both the primary (Johansen’s) and the secondary (rope effect) part of the connection strength, instead partially, as proposed by EN standards.

Profiled sheets are widely used in modern steel structures, either as cladding or as casing in composite structures. Their strength calculation represents a complex task because one must deal with thin-walled structures that have complicated cross-section shape. Manufacturer’s catalogues provide data about their strength, mostly for continuous surface load. These data are mostly obtained by testing. EUROCODE EN 1993-1-3, i.e., its Annex A2, regulates the testing procedures for profiled sheets, allowing two main approaches regarding load application: uniformly distributed load and equivalent line load (in four locations). In addition, the mentioned code proposes roller supports that simulate pinned joints at the ends, neglecting the fastening conditions, which unavoidably are present with these structures. Aim of this research was to prove if the two proposed load patterns produce identical results, and to reveal how fastening devices affect the structural strength. In this research, the Finite Element Method (FEM) analysis with geometrical and material nonlinearity and contact analysis in the support zones were applied for the strength calculation of one typical profiled steel sheet. The analysis was conducted for ultimate load strength and for maximum load at standard deflection of L/200. In order to provide the testing conditions as real as possible, the support conditions were set in two ways: a) with support width B=40 mm and N=2 fasteners at the support, i.e., one fastener in each outer trough; b) with support width B=200 mm and N=8 fasteners at the support, i.e., two fasteners per every trough. The first support case is intended to simulate behavior close to a simply supported beam, and the second should simulate a beam fixed at its ends. The analysis encompassed the two load patterns provided by EUROCODE standard, and the results were compared. The results reveal that the surface load approach gives higher strength values than the four-point-load, both for ultimate load and for maximum load at deflection of L/200. This stands for both analyzed support conditions. The results of the research indicate that the codes should much more precisely define the testing conditions for such structures and make them closer to reality, for the purpose of more reliable and economic design.