Dowel-laminated timber (DLT) elements consist of lamellae arranged side-by-side that are connected with beech dowels. Due to the glue-free DLT element layup, joints and shear walls potentially suffer from considerable reduction of stiffness and load carrying capacity as metal fasteners inserted perpendicular to the element plane may be placed in gaps between the single lamellae. Tests on typical joints showed that, depending on the fastener diameter, the remaining load carrying capacity of joints in DLT in comparison to joints in solid wood may be only 25%. Tests on DLT shear walls with different sheeting proved that the use of DLT structures as shear walls is only possible if at least one-sided sheeting is used. Cyclic tests on DLT shear walls demonstrated that the DLT construction typology has energy dissipation properties similar to traditional timber frame construction. Analogously, preliminary behaviour factors for DLT buildings evaluated with numerical models were also similar to those for timber frame buildings.
This paper summarises parts of the research outcomes of a university-government collaborative project aiming at determining the capacity and reliability of veneer-based structural products manufactured from early to midrotation (juvenile) hardwood plantations logs. Two species planted for solid timber end-products (Eucalyptus cloeziana and Corymbia citriodora) and one species traditionally grown for pulpwood (Eucalyptus globulus) were studied for the manufacture of the new products. Focus of this paper is on LVL beams. To cost-effectively determine the nominal design bending strengths of the new beams, a numerical model was developed. The model was found to accurately predict the strength of LVL beams with an average predicted to experimental ratio of 1.00 with a low coefficient of variation of 0.10. Using an established probabilistic database of the material properties of the veneered resources as model input, Monte-Carlo simulations were then performed. The design strength of the new LVL beams was established and found to be comparable to, and in some cases up to 2.5 times higher than, the ones of commercially available softwood products. Recommendations are also made in the paper on the appropriate capacity factors to be used for various service categories of structures. The proposed capacity factors were found to be 5% to 12% lower than the ones currently used in Australia for beams manufactured from mature softwood logs
Glued-in-rods (GiR) represent a class of joints being used in timber engineering that are mostly used to transfer axial loads in structural members with Glass Fibre Reinforced Polymers (G-FRP) increasingly being considered as rod material. The primary objective of the research presented herein was to apply a probabilistic capacity prediction method to timber joints with G-FRP GiR. The experimental campaign was specific in two ways: firstly, G-FRP rods were bonded into both ends of the timber block with both ends being tested to failure; and secondly, as opposed to most previous studies exhibiting stiff adhesives, a ductile Polyurethane with markedly non-linear behaviour was used. All material characterisation was performed with methods that can be reproduced by any standard laboratory equipment, to provide parameters for the subsequent numerical analyses. Based thereupon, a probabilistic method was used and provided reasonably accurate predictions of the joint capacities of 25 different geometrical GiR configurations. The probabilistic method was extended for realistic estimations of the experimental capacity scattering in form of upper and lower quantiles.
In this work the behaviour of hybrid multi-storey buildings braced with Cross-Laminated-Timber (CLT) cores and shear-walls is studied based on numerical analyses. Two procedures for calibrating numerical models are adopted and compared to test data and application of provisions in current design codes. The paper presents calibration of parameters characterising connections used to interconnect adjacent CLT panels and building cores, and attach shear-walls to foundations or floors that act as eleveted diaphragms. Different case studies are analysed comparing the structural responses of buildings assembled with „standard" fastening systems (e.g. hold-downs and angle-brackets), or using a special X-RAD connection system. The aim is to characterize behaviours of connections in ways that reflect how they perform as parts of completed multi-storey superstructure systems, rather than when isolated from such systems or their substructures. Results from various analyses are presented in terms of principal elastic periods, base shear forces, and uplift forces in buildings. Discussion addresses key issues associated with engineering analysis and design of buildings having around five or more storeys.
Over 5 million m 3 of engineered wood products (EWPs) are produced in the EU annually and the market is rising. However, EWPs have a high degree of petrochemical use in their manufacturing. In addition, throughout the life span of these EWP products from manufacture to disposal, they emit formaldehyde and other volatile organic compounds (VOCs), which makes recycling very difficult. In this paper, preliminary experimental work on Adhesive Free Engineered Wood Products (AFEWPs) is presented, which covers (1) manufacture of compressed wood (CW) dowels, (2) fabrication of adhesive free laminated beams and connections, (3) structural testing of AFEWPs. Also, the finite element models are being developed to assist designing of AFEWPs in terms of size of compressed wood dowel and dowel patterns in order to maximise their stiffness and load carrying capacities.
This research investigates the fire behaviour of laminated veneer lumber elements and cross-laminated timber panels. The study focused on some research questions regarding the fire resistance of unprotected and protected timber structural elements, the possibility to predict accurately the fire behaviour of timber elements through numerical modelling, and the accuracy of analytical estimations of fire resistance using simplified design methods.
Experimental tests of small and large specimens exposed to fire on one or more sides and subjected to different types and levels of load were performed. The results highlight the good performance of timber structural elements in fire conditions. The collected data were used to validate two- and three-dimensional models implemented in the general purpose finite element code Abaqus. Thermal and mechanical analyses were carried out to estimate the temperature distribution within unprotected and protected cross-sections of different sizes, the fire resistance and the displacement of timber elements loaded in-plane and out-of-plane. Further, parametric studies assuming different timber properties-temperature relationships were also performed. The proposed numerical modelling can be used to investigate the fire behaviour of timber members made of other wood-based products and subjected to different loads and fire conditions.
Experimental and numerical results were compared with analytical predictions obtained by using simplified design methods proposed by current codes of practice and recent research proposals. Numerical and analytical methods provide overall acceptable estimations of fire behaviour of timber members, especially considering the high variability that characterizes the wood material and the experimental tests, in particular the fire tests.
Cross-laminated timber (CLT) is an innovative wood technology currently gaining popularity in Canada. However, there is little published information available regarding its performance in fire. The focus of this research is on a series of eight medium-scale, fire-resistance CLT floor tests. Parameters such as charring rate, temperature profile, deflection, gypsum protection and adhesive performance, as well as the overall fire resistance of the floors when subjected to both standard and non-standard fire exposures were evaluated. The results, which compare favourably to past standard fullscale CLT floor tests, were used to develop a numerical model capable of predicting the performance of various CLT floor configurations exposed to any possible fire or load. The experiments demonstrate that CLT panel constructions can be designed to possess a fire-resistance that complies with building code requirements. The additional fire performance data provided from the results of these tests will help facilitate the incorporation of CLT into design standards and building codes.
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 presents the direct displacement-based design (DDD) procedure, structural modelling method, and structural performance calibration for post-tensioned CLT shear wall structures (PT-CLTstrs). Numerical models of the post-tensioned (PT) CLT shear walls were developed and calibrated with the experimental results. Based on the developed shear wall models, parametric analysis were conducted to investigate the lateral performance influencing factors. Then, a DDD procedure was developed and demonstrated by the design examples of a set of 8-, 12-, and 16-storey PT-CLTStrs. The corresponding simplified structural models were developed, and then a series of pushover and time-history dynamic analysis were conducted to calibrate the calculated structural performance objectives with the design targets of the DDD procedure. Finally, the empirical cumulative distribution functions (CDFs) of the maximum inter-storey drift (MaxISDR) were constructed. It is found that when the width of the PT CLT shear walls increases from 1.8 m to 3.0 m, the base shear at the drift of 2.0 % increases by twice accordingly. When the diameter of the PT strand increases from 15.2 mm to 34.6 mm, the base shear at the drift of 2.0% increases by up to five times. Additionally, the MaxISDR limitation of the PT-CLTStrs is recommended as 2.2% under the collapse prevention (CP) hazard level. The study results can serve as guidelines for the development of engineering design methods for the PT-CLTStrs.
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