•Two mechanics-based analytical models were developed for predicting the deflection and resistance of balloon-type CLT shear wall system.•The developed analytical models were capable of reasonably ...predicting the deflection and resistance of single- and coupled-panel balloon-type CLT shear walls tested under in-plane lateral loads.•The influence of the vertical load, wall aspect ratio, and vertical joint on the structural performance of the balloon-type CLT shear walls was successfully investigated using the verified elastic-base model.
Besides platform-type construction method, a rarely investigated balloon-type method, in which the walls are continuous for the entire height of the building and the floor panels are attached to the walls at each floor, can also be used to construct Cross Laminated Timber (CLT) buildings. The balloon-type method endures several key advantages to the CLT buildings, such as reducing connections and avoiding accumulating compression perpendicular to grain in the floors, thus being a viable solution for high-rise buildings. In this paper, two mechanics-based analytical models (rigid- and elastic-base models) were developed for predicting the deflection and resistance of balloon-type CLT shear wall system. The developed analytical models incorporate the contribution of the wall bending and shear deformation, as well as contribution from the wall rocking and sliding, and the slip in the vertical joints between panels, on the overall wall deflection. The resistance of this system was assumed to be governed by the hold-downs, shear connectors, and vertical joints, if present. The analytical models were validated against the test results of four balloon-type CLT shear walls in two configurations tested under monotonic or cyclic load. The verified analytical models were used to investigate the influence of vertical load, wall aspect ratio, and vertical joint on the structural performance of the balloon-type CLT shear wall. The developed analytical models provide a mechanics-based approach for researchers and engineers to predict the structural performance of balloon-type CLT shear walls. The wall test results and the parameter analysis results gave a valuable insight into the structural behavior of the balloon-type CLT shear walls.
This paper presents the experimental results on the fire resistance of traditional timber mortise-tenon joints with looseness, decay and cracking in the jointing area. Static loading test and fire ...resistance tests were conducted on six full scale joint specimens. The development of the temperature, the charring depth and rate, and the degradation of the rotational stiffness of the joints with fire exposure time was quantified. It was found that the service damage can have significant influence on the fire resistance of the traditional timber mortise-tenon joints. The charring rate calculated from the beam and column cross-sections is close to the recommended value in design code for softwood. The displacement of the damaged joints with wood decay and cracking increased by 69% and 90%, respectively, with respect to that of the undamaged joint after 30 min of dire exposure. The rotational stiffness of a damaged joint after 30 min of fire exposure can drop down to 11.4% of the initial rotational stiffness of a sound joint at ambient temperature. The influence of the stiffness degradation of joints on the moment redistribution and fire endurance of neighbouring beams and columns is worth of further investigation.
The recent energy and environmental crises and corresponding regulations have increased interest in replacing conventional materials with sustainable materials in construction. Due to the outstanding ...properties of wood, such as recyclability, reusability and natural renewability, it is considered a sustainable material. In addition, wood has a high strength-to-weight ratio and outstanding acoustic and thermal insulation properties, which make it an appropriate construction material in numerous applications, including in main structural members such as beams, columns and flooring systems as well as in non-structural members, such as windows, doorframes and insulating envelopes. Recent advancements in the production of engineering wood and efficient adhesives have made the fabrication of structural members with large cross sections, long spans and structural properties comparable to steel and reinforced concrete, feasible and cost-effective. As a result, interest in long-span timber buildings has increased greatly. In this paper, a comprehensive review of research studies investigating various aspects of long-span timber structures, including material properties, structural performance and sustainability, are presented. In particular, over 100 research papers were systematically reviewed to study the constructability of long-span flooring systems. The techniques and methodologies available for the fabrication, analysis and experimental investigations of structural flooring systems are also reviewed in detail. Overall, this comprehensive review helps to achieve a greater understanding of structural static and dynamic responses of long-span timber flooring systems, and undertaking the challenges and opportunities presented in this paper could significantly contribute to the improvement of the structural design to reach optimised, sustainable, and constructible systems.
•Recent studies on long-span timber flooring systems were reviewed.•Structural performance, design criteria, constructability and sustainability aspects were presented.•Current challenges and limitations were introduced.•Research gaps and recommendations for future works were presented.
•In historical structures, wooden elements are often degraded by superficial insect attacks.•Neglecting the contribution of degraded areas to the load bearing capacity of the beam can be an ...over-conservative approach.•A reduction coefficient of degraded wood is defined based on theoretical calculation and experimental investigation.•The reduction coefficient can be applied to the mechanical properties of degraded areas so to include them in structural calculation.•A value of n = 5 is proposed for the reduction coefficient.
Existing timber structures are often affected by peripheral degradation due to insect attack. The contribution of the degraded areas of the beam cross-section to the load bearing capacity is usually neglected, leading to an over-conservative approach to the structural verification of historic wooden constructions. This work analyses timber elements dismantled from a nineteenth century building by means of a comprehensive geometrical survey, the evaluation of the degraded portion of the cross-section and by destructive bending tests. An iterative procedure based on the linear elastic theory of composite beams was set up to define a reduction coefficient of the mechanical properties of degraded wood, in order to include the contribution of the degraded parts during the structural calculation. The analytical procedure proved to be effective only for timber elements without localised major defects or anomalies, such as woodworking or internal decay, which may alter the linear elastic flexural behaviour of the beam. The values obtained of the reduction coefficient ranged from 1.7 to 5.0 and were successfully verified by numerical models.
Timber-concrete composite (TCC) structure system is most frequently used in large-span structures. Recently, a performance-based fire safety design method named improved travelling fires methodology ...(iTFM), which is suitable for long-span structures, has been developed. In this article, an energy-based time equivalent method (EBTEM) is proposed, while its effectiveness is experimentally verified. The proposed method can be used to evaluate the fire resistance of the TCC structures subjected to iTFM fires. The results indicated that the damage degree at different spatial positions of the TCC structure under the same fire size was different, and the location with the least and most serious damages occurs towards the beginning and middle of the fire path, respectively. The results show that this difference in damage degree mainly depends on the fire size, and the difference becomes less pronounced as the fire size increases. Concomitantly, it can be obtained that the damage degree under the different fire sizes was different, and the smaller the fire size, the greater the damage degree. Hence, when the EBTEM is adopted to design the TCC structures exposed to iTFM fires, the setting of fire protection target is largely determined by the actual fire size.
When dealing with timber structures, the characteristic strength and stiffness of the material are made highly variable and uncertain by the unavoidable, yet hardly predictable, presence of knots and ...other defects. In this work, we apply the sparse grids stochastic collocation method to perform uncertainty quantification for structural engineering in the scenario described above. Sparse grids have been developed by the mathematical community in the last decades, and their theoretical background has been rigorously and extensively studied. The document proposes a brief practice-oriented introduction with minimal theoretical background, provides detailed instructions for the use of the off-the-shelf Sparse Grid Matlab kit (freely available online and straightforward to use) and discusses two preliminary examples inspired from timber engineering problems that highlight how sparse grids exhibit superior performances compared to the plain Monte Carlo method.
•An Uncertainty Quantification methodology is applied to timber-like structures.•IGA collocation is used for solving the equilibrium equations.•Smolyak and adaptive sparse grids are used for managing random parameters.•This methodology requires no coding effort and outperforms Monte Carlo.
•The mechanical and physical properties of whole timber are discussed.•New digital survey, design, and fabrication techniques are reviewed.•Non-destructive evaluation techniques are ...reviewed.•Structural systems and connection types are reviewed.•Future research priorities for whole timber construction are identified.
Forests worldwide are overstocked with small-diameter trees, putting them at increased risk of disease, insect attack, and destructive high-intensity wildfires. This overstocking is caused primarily by the low market value of these small-diameter trees, which are generally unsuitable for sawn timber production and yield low prices when sold for biomass fuel, paper, or fibre-based engineered timber products. Considerable research in recent decades has demonstrated the potential for these small-diameter trees to be used in minimally processed round segments as structural elements in buildings, bridges, towers, and other infrastructure. Recent structures have also demonstrated the use of trees with major curvature and branching, which are also of low market value, in their round form as primary structural elements. Such “whole timber” construction serves as a low-cost, low-impact building system while providing revenue to forest owners to conduct harvests of low-value trees as required for sustainable forest management. This paper reviews developments in whole timber construction, presenting new non-destructive evaluation techniques, digital survey, design and fabrication methods, new processing technologies, and a diverse range of novel connection types and structural systems. It is shown that the key materials characterisation, processing, and design challenges for whole timber construction have been largely addressed, and that whole timber has the potential to be an important complement to other timber products in construction globally in the coming decades. It is recommended that future work focus on exploiting new digital technologies and scaling whole timber structural applications through increased prefabrication.
•Predict the decay in timber balconies.•Importance of a targeted monitoring plan to prevent disastrous failures.•Analysis of case studies and incipient collapses.
The aim of this paper is the ...prediction of the life expectancy of timber balconies to minimise their risk of failure. The life expectancy is estimated considering the effects of fungal attacks on the timber structural elements. The prediction of life expectancy of timber components is set up through (i) the analysis of the state of the art, (ii) the definition of risk classes and decision trees, (iii) the prediction of the decay, (iv) the definition of an inspection procedure, and (v) the development of an adaptive monitoring plan. The the state-of-the-art analysis of the construction details that most affect durability allows for defining the risk classes and decision trees that address all the possible scenarios where water can penetrate the construction detail. The decision trees associate one of the risk classes to the detail under analysis providing a straightforward indication about the exposure of the timber structural elements to decay due to fungal attack. The allocation to a risk class allows the evaluation of the main parameters of a decay prediction model based on functions for estimating the decay rate that are available in the literature. The decay predicted and the inspection results provide the input data to the adaptive motoring plan, defining an efficient program of inspections. Case studies were selected to validate the results of the decay prediction on the outcomes of onsite inspections and to provide sample data for setting the monitoring plan.
•High performance dampers: key components in seismic-resistant CLT structures.•Tests on three semi-rigid fastening solutions for a steel damper.•Change of properties of the whole connection due to ...semi-rigid nature of fastenings.•Replaceability of the damper confirmed for all fastenings.•Minimal stiffness ratio of fastenings should be provided by capacity design rules.
High performance dampers are a key component in low-damage earthquake-resistant timber structures and they should be designed according to displacement-based design criteria. In this case, a well-defined non-linear force vs displacement relationship of the connection is to be known by the designer (e.g., to evaluate inter-storey drifts), underlying the importance of their careful experimental characterization. In this study, the cyclic shear response of a panel-to-panel joint, fastened to the wooden elements with three alternative solutions, was experimentally tested. Results showed that, although fulfilling the capacity design criteria and allowing an easy replacement of the damper, the semi-rigid nature of fastenings produces important modifications to the mechanical properties of the whole connection type, such as elastic stiffness, yielding point, ductility and equivalent viscous damping.
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