Hybrid composite glulam timber reinforced using deformed steel bars and epoxy resin adhesive (RGTSB), was significantly developed in Kagoshima University. In this paper, a beam-to-beam connection for RGTSB and experimental data on the connection are presented. Two 2:3-scaled simply-supported beams under four-point flexural bending in short-term loading, connection elements under short and long-term tension loading were tested. The connection for RGTSB beam performed on bending behaviour such as non-connection RGTSB beam, especially better on ductility.
In this paper a novel and efficient structural system, that comprises steel beams and prefabricated timber slabs is developed and tested under short-term service and ultimate limit state loading conditions. In the proposed steeltimber composite (STC) system, bolt and coach screws are employed to transfer shear between steel beam and prefabricated timber slab and provide a composite connection. A series of experimental push-out tests were carried out on cross-banded LVL-Steel and CLT-Steel hybrid specimens to investigate the behaviour of different connection types. Furthermore, the load-deflection response of full-scale STC beams was captured by conducting 4-point bending tests on STC beams. The failure modes of connections and composite beams have been monitored and reported. The results illustrate advantages of using timber panels in conjunction with steel girders in terms of increasing strength and stiffness of composite beams
In this study, the duration-of-load and size effects on the rolling shear strength of CLT manufactured from MPB-afflicted lumber were evaluated. The study of the duration-of-load effect on the strength properties of wood products is typically challenging; and, additional complexity exists with the duration-of-load effect on the rolling shear strength of CLT, given the necessary consideration of crosswise layups of wood boards, existing gaps and glue bonding between layers.
In this research, short-term ramp loading tests and long-term trapezoidal fatigue loading tests (damage accumulation tests) were used to study the duration-of-load behaviour of the rolling shear strength of CLT. In the ramp loading test, three-layer CLT products showed a relatively lower rolling shear load-carrying capacity. Torque loading tests on CLT tubes were also performed. The finite element method was adopted to simulate the structural behaviour of CLT specimens. Evaluation of the rolling shear strength based on test data was discussed. The size effect on the rolling shear strength was investigated.
The results suggest that the rolling shear duration-of-load strength adjustment factor for CLT is more severe than the general duration-ofload adjustment factor for lumber, and this difference should be considered in the introduction of CLT into the building codes for engineered wood design.
An analysis of glued composite timber-concrete systems is presented. Experimental data obtained from laboratory tests under short-term loading are compared with the analytical calculation and the design procedure for fully composite beams given in the EN 1995-1-1 standard. Numerical linear 2D finite element modelling and an analytical solution assuming linear elastic behaviour of glue and the interlayer slip are also conducted and validated. The effect of composite action in the three mentioned approaches is assessed by comparison of midspan deflections. In this way, a parametric study of the glue-line properties and the interlayer slip stiffness on load-carrying capacity and serviceability of glued composite beams exposed to short-time loading is easily performed.
This paper deals with laminated timber-concrete (LTC) composite beam members, for applications in sustainable building structures, in which the interlayer connection is achieved with adhesives, similarly to the glued laminated timber beams, instead of the classically used shear connectors (e.g. mechanical connectors or notches). Only a small number of studies of this type of high-performance members are available. The strength and stiffness of the LTC under short-term static ramp-loading were studied on new and retrofit (joist-type) floor members, through laboratory tests and non-linear finite element modelling. In the initial tests the typical failure mode observed was the failure of the wood in tension. Consequently, a carbon fibre reinforced polymer (CFRP) layer was added to the tension side of the timber layer, forming a multi-composite member. The research results indicate that the structural performance in terms of efficiencies and strength for the LTC beams exceeds the corresponding performance of similar classical timber-concrete beams with shear connectors due to the different shear transfer and failure modes. By adding the CFRP reinforcement to the tension fibres of the timber layer, the failure mode changed again, allowing for further increase in strength and stiffness.
This PhD research provides a detailed procedure for designing and investigating the short term static behaviour of a proposed long span timber floor system for non-residential applications that meets serviceability and ultimate limit design criteria, with the use of timber as the only structural load bearing part of the system. In this study the behaviour of two types of LVL are investigated through a number of experimental and analytical tests. As a result of the tension and compression tests, a suitable constitutive law is developed which can accurately capture the stress-strain relationship and the failure behaviour of LVL, and it can also be incorporated into FE analysis of any LVL beam with similar structural features to the tested specimens. Further, the results of the full scale four point bending tests on LVL sections are used to identify the behaviour of LVL up to the failure point and to develop a finite element model to capture the behaviour and failure of LVL. Moreover, after investigating the long span timber floors, one system is proposed to be fabricated for the extensive experimental and numerical investigation. The results of the full scale experimental tests together with the numerical investigation provide a robust model for predicting the performance of any timber beams with similar structural features to the proposed system while the dimensions and spans can be varied according to special requirements such as dynamic performance or fire resistance requirements.
A timber-concrete composite (TCC) combines timber and concrete, utilising the complementary properties of each material. The composite is designed in such a way that the timber resists combined tension and bending, whilst the concrete resists combined compression and bending. This construction technique can be used either in new build construction, or in refurbishment, for upgrading existing timber structures. Its use is most prolific in continental Europe, Australasia, and the United States of America but has yet to be widely used in the United Kingdom. To date, the topping upgrades used have been 40mm thick or greater. Depending on the choice of shear connection, this can lead to a four-fold increase in strength and stiffness of the floor. However, in many practical refurbishment situations, such a large increase in stiffness is not required, therefore a thinner topping can suffice. The overarching aim of this study has been to develop a thin (20mm) topping timber-concrete composite upgrade with a view to improving the serviceability performance of existing timber floors. Particular emphasis was given to developing an understanding of how the upgrade changes the stiffness and transient vibration response of a timber floor. Initially, an analytical study was carried out to define an appropriate topping thickness. An experimental testing programme was then completed to: characterise suitable shear connectors under static and cyclic loads, assess the benefit of the upgrade to the short-term bending performance of panels and floors, and evaluate the influence of the upgrade on the transient vibration response of a floor. For refurbishing timber floors, a 20mm thick topping sufficiently increased the bending stiffness and improved the transient vibration response. The stiffness of the screw connectors was influenced by the thickness of the topping and the inclination of the screws. During the short-term bending tests, the gamma method provided a non-conservative prediction of composite bending stiffness. In the majority of cases the modal frequencies of the floors tested increased after upgrade, whilst the damping ratios decreased. The upgrade system was shown to be robust as cracking of the topping did not influence the short-term bending performance of panels. Thin topping TCC upgrades offer a practical and effective solution to building practitioners, for improving the serviceability performance of existing timber floors.
Timber-steel hybrid beams have been proposed, tested and analyzed for their use in multi-storey buildings. After the first concepts and tests were presented in the WCTE 2014, two whole testing series are finished and their results globally presented and analyzed. The beams fulfilled all the expectations and therefore can be presented as a reliable possibility for future proposals of timber-based frame multi-storey buildings. The present paper presents a summary of the part regarding hybrid beams inside the research project “Timber based mixed systems for dense construction in urban areas” carried out by the Institute of Structural Design and Timber Engineering of the Vienna University of Technology.