Audronis Kazimieras Kvedaras

Load‐bearing capacity of concrete‐filled steel columns

Abstract This paper represents the analysis of 1303 specimens of CFST experimental data. Test results are compared with EC4 provided method for determining the load‐bearing capacity of these composite elements. Several types of CFSTs were tested: both circular and rectangular cross‐sections with solid and hollow concrete core with axial load applied without and with moment, with sustained load and preloading. For circular cross‐section columns there is a good agreement between the test failure load and the EC4 calculation for both short and long columns with and without moment. For rectangular cross‐section columns the agreement is good except when the concrete cylinder strength was greater than 75 MPa, when many tests failed below the strength predicted by EC4. Preloading the steel tube before filling with concrete seems to have no effect on the strength. This paper also presents the stress distribution, confinement distribution and complete average longitudinal stress‐strain curves for concrete‐filled s...

BEHAVIOUR OF HOLLOW CONCRETE-FILLED STEEL TUBULAR COMPOSITE ELEMENTS

Abstract Behaviour of composite steel‐concrete elements in various loading stages is quite well analysed by theoretical investigations and experiments. Concrete‐Filled Steel Tube (CFST) is one of many composite elements used at present in civil engineering. Different approaches and design philosophies were adopted in different design codes for it. But for hollow CFST elements, which are more effective than ordinary CFST, any code does not provide information about how to design these elements. Further investigations of hollow composite CFST elements are needed. In loading stage, when a particular level of stresses exists, an interaction between steel tube and concrete core appears and therefore a complex stress state of element takes place, which increases the load‐bearing capacity of the whole composite element. This interaction between components of CFST elements is reached because of different material properties, such as Poissons ratio, elasticity modulus etc. In this article reasons of the above‐men...

Research and practice of concrete-filled steel tubes in Lithuania

Abstract The research and practice of concrete-filled steel tubular members in Lithuania are described. Attention is especially paid to more effective super-thin and thin-walled concrete-filled steel tubes incorporating hollow concrete cores formed by centrifugal force. The fundamentals of behaviour and structural analysis with substantiation of principles of the design methods for such members as tubular columns, beam-columns, beams and trusses, as well as for their connections are presented. It is shown that, because of loading, an interaction occurs between these two traditional materials—steel and concrete—located in the external shell and internal core, and that this also significantly increases the resistance of hollow structural members. Attention is paid to projects that utilize hollow concrete-filled steel tubular structures, incorporated in various buildings, which prove their great technical and economical efficiency, safety and reliability.

Behaviour evaluation of “sleeved” connectors in composite timber‐concrete floors

Abstract The paper presents the structural solution to the joisted floor when the timber joist of composite cross‐section and the concrete slab are interconnected via a special semi‐rigid connection and form a timber‐concrete joisted floor composite element. Tensioned bottom flange is formed of a solid timber joist, the web is of oriented strand boards (OSB) and the compressive top flange is of a concrete slab into which a part of the web is let in. Studies were carried out on the “sleeved” connector in this part of the web between OSB and concrete slabs that should increase the stiffness of this connection. Theoretical and experimental researches on inter‐behaviour of connection of the sub‐components of composite timber I beam‐concrete were carried out, the obtained results are presented and evaluated.

Centrifugally manufactured hollow concrete‐filled steel tubular columns

Abstract Hollow concrete‐filled steel tubular elements (H‐CFSTs) represent a type of composite steel‐concrete elements. These elements are usually produced by spinning. During this process wet concrete mix in the steel tube is displaced and compacted by centrifugal force and the concrete core so formed achieves better physical and mechanical properties in comparison with other compaction methods. These improvements are related to concrete density, Youngs modulus, Poisson’ s ratio, compressive strength, deformability as well as to a more uniform distribution of fine and coarse aggregates and binding particles along the thickness of the hollow concrete core formed by multi‐layering centrifugation process. The peculiarities of the spinning process, recommendations for proportioning the components for the specimens manufacture, spinning time needed for displacement and compaction of concrete mix, preparation of specimens for testing and testing methods used are presented in this paper.

Bending Behavior of Structural Glass Laminated With Different Interlayers

Experimental results on the bending strength of structural laminated glass are presented. Three different interlayer laminates were used: polyvinyl butyric (PVB), ethylene vinyl acetate (EVA), DuPont SentryGlas Plus (SGP), and a 6-mm-thick tempered soda-lime-silica glass. Four-point bending tests up to failure were carried out on test specimens according to the EN 1288-3 standard and deflections at the midspan of the specimens and the sliding displacement between their two structural glass sheets with different types of interlayer laminates were measured. A comparison between experimental results for the resistances of glass composite panels with various interlayers and monolithic glass sheets is presented too.

Evaluation of long‐term behaviour of composite timber‐concrete structures according to EC

Abstract The objective of this work is the investigation of long‐term behaviour of composite timber‐concrete beams. Both ultimate and serviceability limit states have to be satisfied according to modern design codes, such as Eurocode 5. Because of the rheological phenomena such as creep, time‐dependent (viscoelastic) creep, mechano‐sorptive (moisture change) creep and shrinkage/swelling that occur in the component materials, stress and strain distribution changes in time. The rheological phenomena have to be taken into account for long term verifications. This paper presents the review of the evaluation of long term behaviour of composite timber‐concrete beams according to European design codes EC5 and EC2.

Experimental investigation into fire resistance of HC‐FST columns under axial compression

Abstract A certain amount of analytical methods for determining fire resistance of concrete filled steel tubular columns are developed. Mostly those methods refer to or have as an origin the data about the results of real experiments. The research work on this kind of composite column behaviour under fire conditions with a wide range of different parameters measuring was performed. The behaviour of 16 axially loaded HC‐FST (hollow concrete filled steel tubular) columns without fire protection under conditions similar to ISO‐834 fire and under normal conditions was experimentally investigated and the results are presented in this paper. The experimental values of fire resistance were measured and the failure mode was determined for 4 axially loaded columns. And for the comparison of test parameters, 4 axially loaded HC‐FST columns were tested under normal conditions. In addition, 8 hollow concrete‐filled steel tubular stub columns and 4 hollow concrete tubular stub columns under normal conditions were test...

Investigation of rational depth of castellated steel I‐beams

Abstract There are many methods to calculate castellated steel beams; however, neither of these methods determines the rational cross‐section selection. Selecting the rational cross‐section induces a significant reduction in the quantity of steel. A new algorithm for selecting the rational dimensions of the castellated beams is presented in this paper. In future works it may be adopted and used for design. 12 m long beams, web thickness 6–12 mm and web depth 500–1000 mm are analysed in this paper. Opening size used varies from half of the web depth to the total web depth minus 100 mm. The chosen cross‐sectional area of two flanges is equal to the cross‐sectional area of the web. The thickness of the flanges is twice as big as the thickness of the web. The finite element method was used for geometrical and physical non‐linear analysis of the castellated beams under a uniformly distributed load. The upper flanges of the beams are restrained out of the plane. The results are presented in relevant charts.

Innovative structural system of steel roofs

Abstract A novel lightweight roof structural system consisting of strut-framed beams and flexible decking is discussed. Two types of upper chord of the strut-framed beam, continuous beam or pinned beam have been studied. The peculiarities of behaviour of these structures under load and the possibilities of optimal adjustment of stresses have been investigated. Comparative analysis of the two types of upper chord at a different number of intermediate supports and slenderness of the chords is presented. Evaluation of technical and economical efficiency of the strut-framed beams and flexible decking is presented.