The current research investigated the delamination process of adhesively bonded hardwood (European beech) elements subject to changing climatic conditions. For the study of the long-term fracture mechanical behavior of gluedlaminated components under varying moisture content, the role of moisture development, time- and moisture-dependent responses are absolutely crucial. For this purpose, a 3D orthotropic hygro-elastic, plastic, visco-elastic, mechano-sorptive wood constitutive model with moisture-dependent material constants was presented in this work. Such a comprehensive material model is capable to capture the true historydependent stress states and deformations which are essential to achieve reliable design of timber structures. Besides the solid wood substrates, the adhesive material also influences the interface performance considerably. Hence, to gain further insight into the stresses and deformations generated in the bond-line, a general hygro-elastic, plastic, visco-elastic creep material model for adhesive was introduced as well. The associated numerical algorithms developed on the basis of additive decomposition of the total strain were formulated and implemented within the Abaqus Finite Element (FE) package. Functionality and performance of the proposed approach were evaluated by performing multiple verification simulations of wood components, under different combinations of mechanical loading and moisture variation. Moreover, the generality and efficiency of the presented approach was further demonstrated by conducting an application example of a hybrid wood element.
The paper presents a numerical study conducted on a seven storey cross-laminated (X-lam) buildings equipped with translational Tuned Mass Dampers (TMD’s), as a technique for reducing the notoriously high drifts and maximum seismic accelerations of these types of structures. The building was modelled in the finite element software package Abaqus using 2D elastic shell elements and non-linear springs, which were implemented as an external user subroutine and properly calibrated to simulate the cyclic behavior of connectors in X-lam buildings. The used TMD device is linear, and placed on the top of the building. Time-history dynamic analyses were carried out under natural earthquake ground motions. Several comparisons between the response of the structure with and without TMD are presented, and the effectiveness and limits of these devices to improve the seismic performance of X-lam buildings are critically discussed.
This paper presents a finite element modeling case study of three different designs of hybrid timber-steel 6-story buildings. One of the buildings is composed by steel frames and timber diaphragms while the other two cases consist of the initial design with timber shear walls added in different dispositions, one with outer walls and the other...
This thesis discusses the development of a new innovative reinforced concrete hybrid structure. The hybrid structure consists of reinforced concrete frame incorporated with Cross Laminated Timber (CLT) and metallic damper connections. The seismic design of this proposed system was carried out with the displacement-based design framework and the design was successfully verified. First, this study focused to numerically model the conventional metallic (steel slit) damper and validated with the experimental result using the Abaqus finite element program. Then, to minimize the drawbacks of the conventional damper specimen, a parametric study has been carried out by changing the shape parameters of the damper using the factorial design of experiments. The purpose of conducting a parametric study is to find the appropriate configuration of the damper which can perform well with the proposed hybrid system. Further, the importance of the shape parameter and their interactions in the final response was studied using the response surface method. Secondly, the proposed hybrid system with the metallic damper connection was modeled in Extended Three Dimensional Analysis of Building Systems (ETABS) and then the overall behavior of the system was investigated. In addition, a direct displacement-based design framework was developed for the seismic design of this proposed system. To verify the proposed framework, a 2D six storey hybrid structure was modeled using ETABS. Then, a nonlinear time history analysis was conducted for the modeled structure using 50 set of ground motions to evaluate its performance. The results indicate that the proposed design framework is effective in controlling the displacement of the hybrid system under seismic excitation.
The paper discusses experimental and numerical seismic analyses of typical connections and wall systems used in cross-laminated (X-Lam) timber buildings. An extended experimental programme on typical X-Lam connections was performed at IVALSA Trees and Timber Institute. In addition, cyclic tests were also carried out on full-scale single and coupled X-Lam wall panels with different configurations and mechanical connectors subjected to lateral force. An advanced non-linear hysteretic spring to describe accurately the cyclic behaviour of
connections was implemented in ABAQUS finite element software package as an external subroutine. The FE model with the springs calibrated on single connection tests was then used to reproduce numerically the behaviour of X-Lam wall panels, and the results were compared with the outcomes of experimental full-scale tests carried out at IVALSA. The developed model is suitable for evaluating dissipated energy and seismic vulnerability of X-Lam structures.
This research investigated the fire performance of unprotected timber floors, focussing on composite joist floors, composite box floors and timber-concrete composite floors. The study of these floors was conducted using the finite element software ABAQUS using a thermo-stress analysis in three dimensions, and with experimental fire tests of floor assemblies. The major goal of this research was to develop a simplified design approach for timber floors, validated against the numerical and experimental work.
Four furnace tests were conducted on unprotected timber floor systems in the full-scale furnace at the BRANZ facilities in New Zealand. A sequentially coupled thermal-stress analysis was conducted to determine the effects of a fire on floor assemblies under load. The thermal modelling predicted the charring damage of the floors tested in the experiments to within a few millimetres of precision, and the simplified assumptions made in relation to fire inputs, boundary conditions, mesh refinement and effective material parameters were accurate to the desired level of precision. A sensitivity study was conducted comparing different mesh sizes, time step sizes, material model approaches and software suites to determine any shortfalls which may be encountered in the analysis. It was found that a material model adopting a latent heat approach was the most adequate for modelling timber in fires using these effective values, and mesh sizes of up to 6 mm produced relatively precise results.
The structural modelling predicted the displacement response and failure times of the floors to within 20% of the experimental data, and the simplified assumptions made in relation to fire inputs, boundary conditions, mesh refinement and effective material properties were once again accurate to the desired level of precision. A modification to the reduction in tension strength at elevated temperatures was proposed to better predict the observed behaviour. A sensitivity study concluded that the material model definition plays a vital role in the output of the modelling. Non-standard fire exposures were also modelled for completeness.
A simplified design method to estimate the fire resistance of unprotected floor assemblies was also developed. The method uses a bi-linear charring rate the assumption of a zero strength layer in the timber. The method was compared to the experimental data from this research and others around the world. The results were also compared to other charring rate methodologies from around the world.
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 inplane and out-of-plane