Fire analysis of timber composite beams with interlayer slip

The purpose of this paper is to model the behaviour of timber composite beams with interlayer slip, when simultaneously exposed to static loading and fire. A transient moisture-thermal state of a timber beam is analysed by the Luikov equations, and mechanical behaviour of timber composite beam is modelled by Reissner's kinematic equations. The model can handle layers of different materials. Material properties are functions of temperature. The thermal model is validated against the experimental data presented in the literature. Generally, the model provides excellent agreement with the experimental data. It is shown that the material properties of timber play an important role in the fire resistance analysis of timber structures when exposed to fire

Modelling of timber joints in traditional structures

Original unstrengthened timber connections and the effects of different strengthening techniques have been evaluated experimentally with tests on full-scale birdsmouth joints. Experimental results show that structural response of traditional timber connections under cyclic loading cannot be represented by common constraint models, like perfect hinges or rigid joints, but should be using semi-rigid and friction based models. A research program has investigated the behaviour of old timber joints and examined strengthening criteria. The main parameters affecting the mechanical behaviour of the connection have been singled out. A synthetic model of cyclic behaviour has been adapted on the basis of experimental results

Technical Note: Probabilistic Failure Analysis of a Solid Timber Column

In this paper, a reliability evaluation of a solid timber column of square cross section subjected to axial and lateral loading in accordance with the design requirements of Eurocode 5 is reported. The First Order Reliability Method (FORM 5) which was written in FORTRAN language was used in the reliability estimation. The results obtained showed that both load and slenderness ratio have eects on the reliability of a solid timber column. It was also shown that the safety of such a column can be enhanced if adequate and suitable dimensions are chosen to have a lower slenderness ratio.Keywords: reliability evaluation, solid timber column, Eurocode, axial loading, slenderness rati

Numerical approaches for the analysis of timber frame walls

A numerical approach to simulate the behaviour of timber shear walls under both static and dynamic loading is proposed. Because the behaviour of timber shear walls hinges on the behaviour of the nail connections, the force-displacement behaviour of sheathing-to-framing nail connections are first determined and then used to define the hysteretic properties of finite elements representing these connections. The model nails are subsequently implemented into model walls. The model walls are verified using experimental results for both monotonic and cyclic loading. It is demonstrated that the complex hysteretic behaviour of timber shear walls can be reasonably represented using model shear walls in which nonlinear material failure is concentrated only at the sheathing-to-framing nail connections

Physical and mechanical behaviors of thermally modified rubberwood glulam beam under sustained and cyclic loading

This study evaluated the effect of thermal modification on the physical and mechanical properties of rubberwood glued laminated (glulam) timber. The flexural creep property and cyclic loading behavior were also investigated. The obtained results indicated that the MC and specific gravity of thermally modified rubberwood decreased with an increase in modification temperature. Moreover, the flexural strength of the rubberwood glulam timber at modification temperatures of 180 and 220oC was 8.57% and 46.72%, respectively, which was less than that of the control rubberwood dried at 90oC. However, the MOE between the thermally modified rubberwood glulam timber and control specimens was not significantly changed. The flexural creep test indicated that the maximum relative creep of the thermally modified rubberwood timber equaled 0.31, which was lower than that of other natural timber and tended to decrease when increasing the stress level. Various mathematical models were also proposed, and the best-fitted model was found to be the Bailey-Norton power law model. Nevertheless, the cyclic loading results also proved that thermal modification temperature had a direct effect on the ductility index and energy dissipation of rubberwood glulam timber, but it had no significant effect on the impairment of strength.   

Experimental investigation of in-plane loaded timber-framed rammed earth panels. Part II: cyclic shear-compression tests

Preliminary indications about the timber-framed rammed earth panel (TREP) stiffness and load bearing capacity have been obtained from a first experimental study that has been expressively set up and performed to investigate the TREP in-plane static behavior. The present part II, together with the foregoing part I (companion paper), illustrates and discusses the key experimental results obtained from the compression-shear loading tests performed on rammed earth panels reinforced by a contouring timber frame. In the present part II of the paper, the cyclic loading tests on two TREP elements and one bare timber frame are carefully analyzed, the results are discussed, in terms of load capacity and ductility, and the detected damage modes are explained. The results seem to show that the reinforcing timber frame provides a substantial benefit enabling the development of an effective “strut-and-tie” resisting mechanism that effectively exploits the compressive strength of the rammed earth panel and promotes a ductile failure mode.(undefined

Experimental Assessment on the Hysteretic Behavior of a Full-Scale Traditional Chinese Timber Structure Using a Synchronous Loading Technique

In traditional Chinese timber structures, few tie beams were used between columns, and the column base was placed directly on a stone base. In order to study the hysteretic behavior of such structures, a full-scale model was established. The model size was determined according to the requirements of an eighth grade material system specified in the architectural treatise Ying-zao-fa-shi written during the Song Dynasty. In light of the vertical lift and drop of the test model during horizontal reciprocating motions, the horizontal low-cycle reciprocating loading experiments were conducted using a synchronous loading technique. By analyzing the load-displacement hysteresis curves, envelope curves, deformation capacity, energy dissipation, and change in stiffness under different vertical loads, it is found that the timber frame exhibits obvious signs of self-restoring and favorable plastic deformation capacity. As the horizontal displacement increases, the equivalent viscous damping coefficient generally declines first and then increases. At the same time, the stiffness degrades rapidly first and then decreases slowly. Increasing vertical loading will improve the deformation, energy-dissipation capacity, and stiffness of the timber frame

Preliminary performance-based design of a post-tensioned glue-laminated timber frame

Post-tensioned timber joints have been studied at the ,nstitute of Structural Engineering at the ETH =urich. A post-tensioned beam-column timber joint has been developed using glued laminated timber with local hardwood reinforcement. 2nly a single straight tendon is placed in the middle of the beam and post-tensioned to restrain the rotation of the joint. 1o additional steel elements are used. The developed joint is characterised by a high degree of pre-fabrication and easy assembly on site. The glue-laminated timber moment-resisting frame featuring this joint shows great potential for timber frame structures especially for multi-storey buildings. Robust performance-based design criteria are a necessity for a s uccessful market implementation of the proposed system. A simplified analytical model was developed in order to predict the structural performance of the post-tensioned timber connection and facilitate preliminary performance-based design. This model was implemented in 2penSees using a bi-linear rotational spring approach. The model was verified against an analytical model and validated against tests on a post-tensioned timber joints under gravity loading and under horizontal loading. Moreover, a complex numerical model was developed using 2penSees to check the accuracy of the proposed preliminary design model. The preliminary design model was used to design fictitious moment-resisting post-tensioned glue-laminated timber frame structures using the loads prescribed in the Swiss code. The design process showed that neither the gravity loads nor the seismic load controlled the design. The design was governed by the lateral deformations due to wind. Based on this finding it is recommended to focus further research on increasing the connection stiffness or on adding additional structural elements to address the seismic performance of post-tensioned timber frames in regions of high seismicity

Multi-scale analysis of timber framed structures filled with earth and stones

This paper deals with the seismic analysis of timber framed houses filled by stones and earth mortar using a multi-scale approach going from the cell to the wall and then to the house. At the scale of the elementary cells, experimental results allow fitting the parameters of a new versatile hysteretic law presented herein through the definition of a macro-element. Then, at the scale of wall, the numerical simulations are able to predict its behavior under quasi-static cyclic loading and is compared to experimental results allowing validating the macro-element model