Miloš Milić

The second generation of Eurocode 5 is in preparation and has not yet been adopted, so the calculation of the load-carrying capacity of timber-steel connections is based solely on the rules of the first generation. Currently, load-carrying capacity is determined using expressions for thin or thick steel plates. For cases in between, linear interpolation is used. The thickness and mechanical properties of the steel plate significantly influence the behaviour of the timber-steel connection, which is why research in this field focuses on improving the expressions for the connection capacity. The aim is to define the failure modes more precisely and determine the connection capacity more accurately. This paper shows how Johansen’s expressions for timber-timber connections can be adjusted for steel-timber connections by accounting for the previously mentioned parameters.

This paper presents the development of an innovative steel-cross laminated timber (steel-CLT) shear connector designed for efficient shear transfer. The structural performance and mechanical behaviour of the proposed system were comprehensively evaluated through experimental testing and numerical modelling. Push-out tests were conducted to evaluate the load-carrying capacity, stiffness, and failure modes under static loading. Additionally, a three-dimensional finite element model was developed to simulate the nonlinear response, material behaviour, and contact mechanics between the steel components and timber layers. The numerical model was validated against experimental results, showing strong agreement in terms of load-displacement behaviour and ultimate capacity. The findings demonstrate that the proposed connection achieves high strength and ductility, offering a promising solution for composite steel-timber structures. 

The increasing demand for sustainable and resource-efficient buildings has intensified the need for comprehensive environmental assessment tools in the construction sector. Construction materials play a crucial role in determining the environmental performance of buildings throughout their life cycle, influencing energy consumption, resource depletion, waste generation, and greenhouse gas emissions. As the construction industry seeks to reduce its environmental footprint and support sustainable development goals, Life Cycle Assessment (LCA) has emerged as a widely accepted methodology for evaluating environmental impacts and supporting informed decision-making. This review paper examines the application of Life Cycle Assessment (LCA) to the evaluation of construction materials, with a particular focus on their environmental performance and recent developments in sustainable construction. The study reviews the life cycle impacts of commonly used materials, including concrete, steel, timber, aluminium, glass, and other structural and non-structural materials. The findings demonstrate that no construction material is environmentally superior in all situations and emphasize the importance of context-specific material selection based on comprehensive life cycle assessment. Integrating environmental, technical, and functional considerations through LCA can support more sustainable decision-making and contribute to the development of low-carbon, resource-efficient buildings and infrastructure.

This paper presents a condition assessment and an analysis of the degradation causes for the road bridge over the Nišava River near the village of Vrandol, in the municipality of Bela Palanka. The structure represents a specific modification of the „Karpoš“ precast system, where steel wagon-type beams were utilized for the superstructure alongside standard substructure elements – specifically, precast piles. Through field investigation and macroscopic inspection, a critical structural condition was identified, primarily caused by the loss of stability in the substructure. Due to the impact of debris and ice, significant deviations from the vertical alignment were observed in the reinforced concrete conical piles. These geometric imperfections induced substantial parasitic stresses within the columns and main girders. Coupled with evident corrosion of the steel elements and degradation of the deck slab due to inadequate drainage, the bridge’s load capacity has been reduced below safety limits. This paper categorizes the recorded damages and proposes urgent rehabilitationl measures, while recommending a temporary traffic ban to prevent structural collapse.

In civil engineering, high-profile sheets (HPS) are widely used. They are used as loadbearing elements in a system of stacked roofs, for covering large-span structures or as permanent formwork when casting concrete slabs. Determining the load-bearing capacity of these elements is a complex task, and designers take this data from the manufacturer's catalog. Data on the load-bearing capacity are usually given depending on the serviceability limit state (SLS), without special consideration of the support conditions. For these reasons, this paper presents an in detail methodology for determining the load-bearing capacity of a standard type of HPS, using an experimental method. The research was carried out on a sheet panel with a span of 6000 mm of a simple beam static system. The length of the support on the purlin was 200 mm and it was secured with eight bolts. The load to failure test was conducted according to the SRPS U.M1.047 standard using the method of applying an equally distributed gravitational load. The experimentally obtained results were compared with the catalog values provided by the manufacturers. The test showed that the applied support conditions (length of contact with the purlin, number and arrangement of connecting means in the connection) have a positive effect on increasing the load-bearing capacity and cost-effectiveness of the HPS.

The paper shows the reconstruction of the supporting structure of the main hall of the Leskovac Fair. The specifics of the construction with a roof structure in the form of a network of orthogonal cables were analyzed. The significance of the building is reflected in the innovative system applied to the roof and in the architectural achievement of Yugoslav architecture in the mid-20th century. In this period, only a few buildings with this design were built in the world. In terms of historical heritage, the Fair building is the embodiment of former economic development and a witness to the industrial and cultural life of Leskovac and its surroundings. The paper presents the measures aimed at rehabilitating the building. The reconstruction design envisaged the addition of two floors with commercial function along with the conversion of the building into a shopping center. The newly designed part of the structure is subtly incorporated into the existing reinforced concrete structure. The design provided for maximum preservation of the authenticity of the external appearance of the hall.

The paper shows the reconstruction of the supporting structure of the main hall of the Leskovac Fair. The specifics of the construction with a roof structure in the form of a network of orthogonal cables were analyzed. The significance of the building is reflected in the innovative system applied to the roof and in the architectural achievement of Yugoslav architecture in the mid-20th century. In this period, only a few buildings with this design were built in the world. In terms of historical heritage, the Fair building is the embodiment of former economic development and a witness to the industrial and cultural life of Leskovac and its surroundings. The paper presents the measures aimed at rehabilitating the building. The reconstruction design envisaged the addition of two floors with commercial function along with the conversion of the building into a shopping center. The newly designed part of the structure is subtly incorporated into the existing reinforced concrete structure. The design provided for maximum preservation of the authenticity of the external appearance of the hall.

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.

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.