This study presents spatial vibration modelling of steel–concrete composite beams. Structures of this type are commonly used as elements of composite floors and primary carrying girders in bridge structures. Two-dimensional models used to date did not enable analysis of all eigenmodes, specifically torsional, flexural horizontal, and distortional. A discrete computational model was developed in the convention of the rigid finite element method, the so-called RFEM model. It was assumed that the concrete slab and the steel I-section would be modelled separately. This approach realistically reflects the actual performance of the connection, comprising studs connecting the concrete slab and the steel section. The model was used to analyse two steel–concrete composite beams with different connector spacings. The paper presents the results of experiments conducted on the two composite beams. Their dynamic characteristics, including frequency and vibration modes, were determined with impulse response methods. Based on experimental research, identification of connection parameters with substitute longitudinal moduli of elasticity of reinforced concrete was conducted. A comparison of experimental results with those calculated with the model confirmed their good agreement.

In this paper, the results of dynamic laboratory tests of four laminated veneer lumber (LVL) slabs of different thicknesses, widths, and types were presented. In three of the tested slabs, LVL with all veneers glued lengthwise was used (LVL R). In one LVL slab, a fifth of the veneers were glued crosswise (LVL X). Laminated veneer lumber slabs are engineering wood products with several important performance characteristics, making them a sustainable and preferred solution in civil engineering. To ensure the safe operation of a building with LVL structural elements, it is important to know their dynamic properties. The basic dynamic characteristics of the slabs obtained from experimental tests made it possible to validate the numerical models of the slabs. The slab models were developed in the Abaqus program using the finite element method. The elastic and shear moduli of laminated veneer lumber used in the four slabs were identified through an optimization process in which the error between the analyzed frequencies from the laboratory tests and the numerical analyses was minimized. In the case of slabs that possess the same thickness and are composed of different LVL types, the elastic modulus of LVL R in the longitudinal direction was 1.16 times higher than the elastic modulus of LVL X in the same direction. However, the elastic moduli of LVL R in tangential and radial directions were lower than the elastic moduli of LVL X in the same directions. The above was the result of the fact that the 45 mm LVL X slab had 3 out of 15 veneers glued crosswise. In the case of slabs possessing different thicknesses but the same width and type, the elastic modulus of the thicker panel was 1.13 times higher than that of the thinner panel. After validating the models, the numerical analyses yielded results consistent with the experimental results. The numerical models of the LVL slabs will be used to develop numerical models of composite floors with LVL panels in future research. Such models will allow for the analysis of floor dynamic characteristics and user-generated vibrations, which is required when verifying the serviceability limit state.

The paper presents changes of modal parameters such as natural frequencies, damping ratios and energy transfer ratios (ETR) following damage of the connection of a steel-concrete composite beam. Sensitivity analysis of the parameters is conducted both for numerical simulation and experimental results. The energy transfer ratio ETR is determined: i) for the whole beam – as a global parameter which can be used for damage detection, ii) for segments of the beam – as a local parameter which can be used for damage localisation.

This paper presents parameter estimation of a mathematical model regarding natural vibrations of a reinforced concrete slab. Parameter estimation is based on experiments conducted on a real reinforced concrete slab. Estimated parameters include: substitute longitudinal modulus of elasticity of the reinforced concrete slab, which takes into account longitudinal reinforcement, effective thickness of the reinforced concrete slab and coefficient of damping. Using appropriate criteria during, the process of parameter estimation of the reinforcement concrete slab models has a great impact on obtaining precise results. The estimation criteria are selected in order to achieve consistency of natural vibration frequencies along with the Frequency Response Function measured during experiments with those calculated with the mathematical model. The model and all the calculations have been made using MATLAB programming environment.

Steel–timber composite beams are a relatively new type of composite structure. They have many important advantages, owing to which they may be considered a sustainable solution. Their connectors may be demountable, which makes it possible to separate steel girders from LVL panels at the end of their service life. After disassembly, the structural elements can be recycled. One of their advantages is that they are lighter than steel–concrete composite beams. However, this may result in the poor performance of floors with steel–timber composite elements subjected to dynamic loadings. For this reason, the dynamic characteristics of floors should be investigated to verify the serviceability limit state of human-induced vibrations. In this study, the dynamic response of the three steel–timber composite beams with varying screw spacing was captured and used to validate their numerical models. The frequencies obtained from the numerical analyses correspond to the experimental results. A very high agreement between the vibration mode shapes was obtained because the MAC index values were close to 1. The validated numerical model of a single steel–timber beam may be used in future studies to create a complex numerical model of a steel–timber composite floor.

This paper presents a preliminary evaluation of the load-bearing capacity of steel-timber composite beams with cold-formed omega girders and laminated veneer lumber slabs. These structural elements may be used as ceiling beams. The finite element models of the analysed composite beams were created in ADINA and Abaqus. The theoretical estimations of the resistance to bending were based on the elastic analysis (elastic resistance to bending) and the rigid-plastic theory (plastic resistance to bending). The elastic load-bearing capacity obtained in the numerical simulation in ADINA was identical to the one from the theoretical analysis. The elastic load-bearing capacity from the numerical analysis in Abaqus was 1.02 times higher than the one from the theoretical analysis. The plastic bending resistance obtained from the theoretical analysis was 1.08 times higher than the one from the numerical simulation in ADINA and 1.03 times higher than the one from the numerical simulation in Abaqus. In part 2 of the paper, a modification to the cross-section and a reinforcing method were proposed.