Miroslav Bajer

Ventilated façade systems are being increasingly used in energy-efficient building envelopes due to their configurational flexibility and potential to reduce thermal bridging. This study focuses on the experimental evaluation of anchoring components used in such systems, specifically examining the effect of various thermal insulation pads and internal inserts on the system’s mechanical, thermal, and fire performance. A series of laboratory tests was carried out to assess the static behavior of aluminum brackets under both tensile (suction wind load) and compressive (pressure wind load) forces. The results demonstrate that the use of thermal pads and inserts does not lead to any significant degradation of the mechanical capacity of the anchoring brackets, confirming their structural reliability. Additional thermal testing revealed that the use of insulating materials significantly reduces heat transfer through the brackets. Fire resistance tests were conducted to compare the performance of different types of insulation pads under elevated temperatures. The findings indicate that the choice of pad material substantially influences both fire integrity and thermal performance. This study confirms the potential of incorporating optimized insulating pads and inserts into façade brackets to enhance the thermal and fire performance of ventilated façades without compromising their structural behavior.

The analysis presented in this paper is focused on problems of bond strength as an overall bond quality parameter of industrial adhesives for structural anchoring. In the first part, the problem of bond strength as the most important parameter influencing the final anchor resistance to tension load is described. Further in the text, a new methodology of simplified testing of the strength parameters of adhesives is described. Special test specimens made from steel are repeatedly used in this methodology. Additionally, results of these tests on some new recipes for adhesive are presented. Especially, epoxy resins with special fillers, such as carbon fibres, carbon nanotubes or graphene, were tested. The use of these adhesives in temperatures close to zero degrees Celsius was also tested.

The goal of the research presented in this paper is the experimental and theoretical analysis of cross‐section which can be asymmetric. Particularly, there are experimental tests of several beams of selected cross‐section shapes described and analysed. The main idea of those experiments was to observe the differences in behaviour between monosymmetric cross‐section and the asymmetric one. Currently used design methods for a solution of lateral‐torsional buckling are based on critical moment approach. This solution is also implemented in design codes but it is limited for use of double and monosymmetric cross‐sections.Another part of the paper is focused on the numerical evaluation of transversally loaded beam of one monosymmetric and four asymmetric cross‐section shapes susceptible to lateral‐torsional buckling. Several analytic methods used for evaluation of the beam bending resistance in design software were evaluated.This paper presents the comparison of numerical and experimental results of transversally loaded beams with monosymmetric and asymmetric cross‐sections. Stresses in selected parts of the cross‐section are evaluated and compared together. This comparison shows that the normal stress on both (monosymmetric and asymmetric) cross sections is the subject of the same rules – a combination of stresses inflicted by bending and torsion caused by an eccentricity between the point of load application and the centre of shear.

The paper presents experimental and numerical research of strengthening of columns under load using welded plates. Three sets of three columns each were tested. All columns were 3 m long. The load from loading cylinders was transmitted through knife-edge bearings, which ensured pinned boundary condition perpendicular to the weaker axis. Set (A) comprised columns with welded T shaped cross-section. Set (B) comprised columns with welded monosymmetric I shaped cross-section. Both sets (A) and (B) had been loaded monotonically until collapse occurred. Set (C) contained columns with T shaped cross-section with the same dimensions as the columns in set (A). The columns from set (C) were first loaded to 70 kN. The force was being held constant and the second flange was being welded to the web under load. After the welding process was finished and the specimen cooled, the column was loaded to failure. The average forces at collapse of column sets (A), (B) and (C) were 143 kN, 308 kN and 323 kN, respectively. It was unexpected that the columns strengthened under load (C) had higher average resistance than the columns welded without preload (B). It could be caused by the residual stress and distortion caused by welding. The study includes the results of finite element models of the problem created in ANSYS software. The results from the experiments and numerical simulations were compared.

The topic of this paper is the glue-concrete interface of bonded anchors loaded by tension force. The paper is closely focused on bond strength experiments using high strength concrete up to class C50/60 or higher together with pure epoxy resin and fibre-reinforced resin. The goal of this research is to find the limits of the effective use of such glue types in high performance concrete, and also to verify the most commonly used design methods for bonded anchors. The presented research includes experimental analysis of the glue-concrete interface and the influence of its parameters on anchor behaviour. The presented analysis shows some problems of the 'separated failure modes' approach and also presents experimentally verified bond strength values obtained for the currently most widespread glue types. Results of fibre reinforced epoxy resin are also presented in this paper.

This paper summarizes the results of pilot experimental research focused on determination of the behaviour and bond strength limits of currently most widespread industrial glues used for anchor bonding. The goal of this research is to find the limits of the effective use of such glue types in high performance concrete, and also to verify the most commonly used design methods for bonded anchors. The progress and configuration of the experiments are described. The goal of this research is to find the limits of effective use of these glue types in high performance concrete and also verification of mostly used design methods. The article is closely focused on bond strength experiments using high strength concrete up to class C50/60 or higher together with pure epoxy resin and FRP reinforced resin).

This paper refers to behaviour and capacity of axially loaded columns strengthened under load using welded steel plates. This method of strengthening is fast, simple and widely used but no universal and reliable analytical solution has been presented yet. In the paper, focus is put on flexural buckling. The approach using cross-section properties of strengthened member and the modified buckling reduction factor was used to calculate the ultimate resistance. In buckling theory, the resistance of column subjected to compression load is reached when the most stressed fibres start to yield. However, some researchers allow certain amount of yielding for base material of columns strengthened under load. In the paper, the new modified buckling reduction factor based on Eurocodes is derived. Two types of column strengthening under various preload magnitudes are investigated using finite element study in ANSYS code and transient analysis type. Birth and death of elements is used to simulate strengthening welded plates. The results are compared with analytical solutions.

Composite slabs with prepressed embossments present an effective solution for horizontal load bearing structures. Sheeting serves as a formwork in construction stage and as a tension bearing member after hardening of concrete. There is no need for additional tensile reinforcement in case of sufficient longitudinal shear bearing capacity of the embossments. Longitudinal shear bearing capacity is not precisely determined when designing according to nowadays standards. Full scale bending tests of the slabs are used to determine characteristics for m – k method or partial connection method. Bending tests are expensive and space demanding. Alternatively small-scale shear tests can be used to determine shear characteristics of the sheeting. However, shear tests cannot include all the effects affecting the bearing capacity of bended slab, such as effect of curvature or distribution of load. Therefore, related design method has to be used to determine load bearing capacity of the slab in bending. This paper extends achievements presented by the authors in contribution in CRRB 2013. The results of small-scale tests are compared with results of numerical models of the slab in shear. Numerical models are created in two different finite element codes. Setting of steel-concrete interface properties in the models is validated using data from literature.

The loadbearing capacity of steel‐concrete composite slabs using thin‐walled steel sheeting with prepressed embossments is in most cases determined by their resistance in longitudinal shear. The design of composite slabs still requires full‐scale laboratory bending tests to be performed. Small‐scale shear tests cannot include all of the influences affecting the bent slab. However, by using an appropriate procedure, the shear characteristics obtained from such tests can be used to determine the bending capacity of the slab. Two such procedures are compared in this paper.End restraints effectively increase the loadbearing capacity of the composite slabs. Two different types of easily assembled additional end constraints are also tested and compared in this paper. Small‐scale tests are used to obtain their shear bearing characteristics and to predict the loadbearing capacity of bent slabs using these restraints.