This paper describes the test program of glued-in deformed bar timber joint conducted in pull-pull configuration, which aims to investigate the bond behavior of glued-in deformed bar systems in glulam. The varying parameter are bar slenderness ratio and glue-line thickness. In order to obtain the bond stress distribution along the anchorage length, special deformed bar with strain gauges attached internally were designed. Test results show that both the bar slenderness ratio and glue-line thickness have obvious influence on withdrawal strength and bond behavior of glued-in deformed bar joint. Failure modes of specimens are also analyzed in this paper. Ductile failure modes of glued-in rod timber joint could be realized with reasonable design.
The introduction of Cross-laminated Timber (CLT) as an engineered timber product has played a significant role in the considerable progress of timber construction in recent years. Extensive research has been conducted in Europe and more recently in Canada to evaluate the fastening capacity of different types of fasteners in CLT. While ductile capacities calculated using the yield limit equations are quite reliable for fastener resistance in connections, however, they do not take into account the possible brittle failure modes of the connection which could be the governing failure mode in multi-fastener joints. Therefore, a stiffness-based design approach which has already been developed by the authors and verified in LVL, glulam and lumber has been adapted to determine the block-tear out resistance of connections in CLT by considering the effect of perpendicular layers. The comparison between the test results on riveted connections conducted at the University of Auckland (UoA) and at the Karlsruhe Institute of Technology (KIT) and the predictions using the new model and the one developed for uniformly layered timber products show that the proposed model provides higher predictive accuracy and can be used as a design provision to control the brittle failure of wood in CLT connections.
International Conference on Performance-based and Life-cycle Structural Engineering
December 9-11, 2015, Brisbane, Australia
Tall timber building designs have utilized cross-laminated timber (CLT) significantly over the past decade due the sustainable nature of timber and the many advantages of using an engineered mass timber product. Several design methods have been established to account for the composite action between the orthogonally adhered timber plies. These methods assume perfect bonding of the adjacent plies by the adhesive. CLT designs methods for timber in fire have also been formulated. These methods rely on the relatively constant charring rate of timber to calculate a sacrificial layer to be added onto the cross-sectional area. While these methods focus on the timber failure mode of reduced cross section by charring, the failure mode of ply delamination is often overlooked and understudied. Due to the reduction of shear and normal strength in the adhesive, the perfect bond assumption can be questioned and a deeper look into the mechanics of CLT composite action and interfacial stress needs be conducted. This paper seeks to highlight the various design methods for CLT design and identify the failure mode of delamination not present in the current design codes.
An experimental study was conducted to elucidate the effects of thermal penetration on delamination and the potential changes in failure mode of CLT. The first test series studied thermal penetration depths at various heat fluxes. The second test series consisted of single lap shear tests at homogeneous elevated temperatures followed by a...
The design of multiple bolted connections in accordance with Appendix E of the National Design Specification for Wood Construction (NDS) has incorporated provisions for evaluating localized member failure modes of row and group tear-out when the connections are closely spaced. Originally based on structural glued laminated timber (glulam) members made with all L1 Douglas fir-Larch laminating lumber, the NDS provisions were confirmed by additional analysis, which indicates the applicability of the provisions to glulam with reduced design shear values. Due to the similarity to glulam in the grain orientation and layup strategy, laminated veneer lumber (LVL) is subject to similar failure modes. As a result, a study was initiated by APA – The Engineered Wood Association and the LVL industry, in collaboration with the Forest Products Laboratory (FPL) of the U.S. Department of Agriculture (USDA) to evaluate if a reduced design shear stress is necessary for LVL under similar multiple bolted connection configurations. This paper describes the test results obtained from the study, which indicate that an adequate load factor exists for LVL multiple bolted connections without a reduction in the LVL design shear stress when designed in accordance with Appendix E of the NDS.
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