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Vibration performance of a one-way simply supported timber-concrete composite (TCC) floor section has been studied using analytical as well as numerical methods. Focal points have been verification and validation of results from analytical and numerical calculations of vibration response based on experimental data. For the analytical calculations, floor bending stiffness and vibrational response are determined from methods proposed in the current and revised versions of Eurocode 5. The numerical calculations based on the finite element (FE) method are done using 3D solid elements with orthotropic material parameters. When comparing the results of the FE analysis, better agreement with the experimental data is reached for the fundamental frequency when 3D solid elements are used rather than 3D beam elements. Furthermore, better agreement with the experimental data is reached for RMS acceleration by FE analysis rather than the method based on Eurocode 5. For detailed analysis, the authors suggest performing dynamic FE analysis and calculating vibration response from the TCC floor's modal responses as eigenmodes and natural eigenfrequencies below 40 Hz. For future studies, it is recommended that the verification of vibration response may be accomplished by applying standard EN 16929.

This paper summarizes the findings of two full-scale blasts tests on a steel braced frame structure with composite floor slabs, which are representative of a typical office building. The aim of this research study was to experimentally characterize the behavior of conventionally designed steel braced frames to blast loads when enclosed with conventional and blast-resistant façade. The two tests involved a three-story, steel braced frame with concentrical steel braces, which are designed to resist typical gravity and wind loads without design provisions for blast or earthquake loads. During the first blast test, the structure was enclosed with a typical, non-blast-resistant, curtainwall façade, and the steel frame sustained minimal damage. For the second blast test, the structure was enclosed with a blast-resistant façade, which resulted in higher damage levels with some brace connections rupturing, but the building did not collapse. Observations from the test program indicate the appreciable reserved capacity of steel brace frame structures to resist blast loads.

A two-dimensional interface finite element capable of associating flat shell elements positioned one above the other was developed. The implemented interface element can physically simulate the contact between the flat shell elements and connect the reference planes of the shell elements above and below it. The formulation presented allows consideration of nonlinear behavior for the deformable connection as well as for the concrete and steel materials that make up the shell structure. One of the practical applications analyzed in this research is the numerical simulation of composite floors formed by a reinforced concrete slab connected to steel beams through a deformable connection. In this case, the concrete slab and the steel beams are discretized by flat shell elements and the deformable connection is discretized by two-dimensional interface elements. Experimental and numerical results from literature were used to validate the implemented elements. In the two examples analyzed, the results obtained for the displacements were close, with the difference, in the first case, being associated with uncertainties during the experimental test and in the second, the difference in theories used in the formulation of the implemented elements.

Desert sand foamed concrete (DSFC), which offers advantages, such as fire resistance, sound insulation, construction convenience, and environmental benefits, has not been used in cold-formed steel (CFS) composite floors. In this study, four full-scale specimens were designed and tested under four-point bending to investigate the effect of foamed concrete filling and holes. The load–deflection curves and strain distribution at mid-span were measured and analyzed. The experimental results indicated that the failure modes of the CFS composite floors were local buckling at the top flange for specimens without holes and tensile failure at the bottom flange for specimens with holes, respectively, which differed from the web crippling observed in non-composite floors. Moreover, due to the presence of foamed concrete, the flexural stiffness was significantly improved by 117.6% and 73.6% for the specimens without holes and with holes, respectively, while ultimate capacity increased by 224.9% and 121.8%, respectively. Through the nonlinear finite element models validated against experimental results, it was found that the flexural behavior was improved with the increase in CFS thickness and foamed concrete strength. The impact of the holes was not obvious for specimens infilled with holes.

The present paper deals with composite steel-concrete floor with headed shear studs welded onto a flat steel plate. In bridges applications, which are the focus of the paper, very thick steel plates are often combined with a moderate layer of concrete. And, in some wide slab applications, the most performant lay-out for the shear studs could lead to them being welded on top of an existing butt weld between steel plates. Presently, we are ignorant about the shear resistance of the weld-to-weld interface and its possible detrimental effect on the overall resistance of the system. In addition, the ultimate behaviour of the system combines the flexural resistance of a composite cross-section followed by, when the concrete is cracked, the development of a compressed arch anchored in these headed shear studs, emphasising the importance of such connections. Both questions are addressed in the paper and, based on experiments, an in-depth analysis on the system’s behaviour at ultimate limit state is provided. Two types of tests are performed: pure shear tests complying to the push-out tests of Annex B of EN 1994-1-1 and beam tests with four-point loading where the studs in the shear spans are loaded with longitudinal shear. For each pair of tests, the reference specimen was made with a steel plate without a butt weld or comprising a butt weld directly under the line of shear studs. Typical floor dimensions from bridge applications are studied. No difference in shear capacity, stiffness or failure mode could be observed. However, it was noticed that the classic design rules provided in EN1994-1-1 cannot accurately predict the failure load of the chosen configuration. Based on assumptions made following the observations of the failure mechanisms, the authors propose a theoretical evaluation of the capacity of the system. ispartof: Engineering Structures vol:197 status: published

Connecting timber panels to steel girders using mechanical fasteners (e.g. screws and bolts) is an attractive and novel method for developing a fully prefabricated and sustainable hybrid steel-timber composite (STC) floor that can also facilitate future dismantling and recycling of the structural components. This study concerns the short-term behaviour of innovative STC floors comprising of cross-laminated timber (CLT) and/or laminated veneer lumber (LVL) panels connected to steel girders by various mechanical fasteners and/or glue. The mechanical characteristics of STC connections play an essential role in the safe and economical design of hybrid STC structures and floor systems. Accordingly, at the first stage of this research project, short-term behaviour of STC connections has been investigated. Push-out tests on different types of STC lap joints with coach screws (with and without a reinforcing nail plate), high-strength bolts and a combination of glued and screwed connectors are reported, and the load-slip behaviour, stiffness, strength and failure modes of the STC connections are characterised. At the second stage, short term behaviour of STC system was investigated through four-point bending tests. The results of four-point bending tests performed on full-scale STC beams are reported and the structural behaviour (i.e. the load-deflection response, short-term stiffness, and peak load capacity and failure modes) of the proposed STC system are studied. At the last stage of the project, extensive non-linear 1D and 2D finite element (FE) analyses of STC beams are carried out and the numerical results are verified against the test results. It is shown that 1D and 2D FE models can adequately capture the structural response of the STC beams. Using the FE and experimental results, the composite efficiency of STC beams that can significantly influence their structural behaviour beams is determined. In addition, the mechanical behaviour of lap STC connections was investigated through using a nonlinear 3D continuum-based FE model. In the FE models developed, the non-linear behaviour and failure of the timber is captured by a stress-based failure criterion formulated in the framework of continuum-damage mechanics. Yielding of the steel plates and fasteners (i.e. coach screws and bolts) is captured by an elastic-hardening plastic constitutive law. These FE models are validated against experimental (push-out) tests conducted on LVL and Steel-CLT composite lap connections. It is shown that the FE models developed can adequately predict the load-slip response and failure mode of the hybrid steel-timber composite connections tested. The validated FE model is used to undertake a parametric study that elucidates the influence of the yield strength and the length of the fasteners and the post-tensioning force in the bolts on the stiffness, load carrying capacity and load-slip behaviour of hybrid steel-timber composite connections.