•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.
AbstractThe prestressed-laminated timber (Pres-Lam) system is an innovative low-damage wood-hybrid system that utilizes post-tensioned (PT) mass timber components, e.g., laminated veneer lumber ...(LVL), glued laminated timber (glulam), and cross laminated timber (CLT), along with various types of energy dissipators, e.g., axial energy dissipators (also called fuses) and U-shaped flexural plates (UFPs). Previous tests carried out on this system focused on scaled (one-third or two-thirds) LVL specimens, whereas limited studies have been conducted on the Pres-Lam system with CLT which has mechanical properties and composition different from LVL. Through comprehensive tests, the lateral-load response of PT-only and Pres-Lam CLT shear walls was investigated in this study. A total of 14 different full-scale PT-only and Pres-Lam CLT walls in four configurations were tested under monotonic and reversed cyclic loading. A user-friendly fuse was designed and adopted in the Pres-Lam CLT wall specimens. PT-only and Pres-Lam CLT shear walls had bilinear elastic and elastic-plastic behavior, respectively, with a stretching point corresponding to the state at which the PT force started to increase. With energy dissipators, Pres-Lam CLT shear walls had higher resistance, maximum lateral drift and energy dissipation compared to PT-only walls. The influence of the initial PT force, the fuse spacing, and the number of UFPs on the stiffness, resistance, maximum lateral drift and energy dissipation of the wall specimens was discussed. The test results also show that the behavior of the Pres-Lam CLT shear walls can be decoupled and a superposition rule can be applied to obtain the stiffness and resistance of such systems. Yielding and buckling of the fuses occurred at the early stage of loading as designed, and localized crushing of wood at the end of panels happened when the lateral drift was at or beyond 2.5%. The test results gave a valuable insight into the structural behavior of the PT-only and Pres-Lam CLT shear walls under in-plane lateral loads.
► The increase in the load capacity of reinforced beams is significant, amounting to as much as 79%. ► The strengthening is acceptable from the point of view of conservation doctrine. ► The use of ...CFRP strips is an effective way of strengthening historic beams.
The paper presents the results of studies proposing to use carbon fibre reinforced polymer (CFRP) strips to reinforce beams with defects (biological corrosion, inclusions, slope of grain, cracks) in order to restore their load-bearing capacity. The proposed solution, consisting in bonding CFRP strips into the cross section, is suitable for restoration work in historic buildings. Moreover, owing to the fact that the reinforcing inserts are situated inside the cross section, the possibility that the adhesive strip–wood bond will delaminate is reduced and the fire resistance of the element is increased. The increase in the load-bearing capacity of the tested beams amounted from 21% to over 79%. The results of an analysis of the static behaviour of the reinforced cross sections, carried out using numerical modelling and the finite element method, are presented.
In recent decades, there is a trend in Scandinavian countries to build multi-storey residential houses using prefabricated timber modules. It is a highly efficient construction process with less ...environmental impact and less material waste. A significant building element in the timber modules is the light-frame timber wall, which has to be carefully analysed and optimized in this process. This paper presents a new parametric Finite Element (FE) model that can simulate both in-plane and out-of-plane deformations in the light-frame walls. A new and flexible (Eurocode based) approach to define the properties of the mechanical connections is introduced. A numerical model is presented through simulations of several walls that were verified with full-scale experiments. The results indicate that the numerical model could achieve fairly reasonable accuracy with the new approach. Furthermore, several parametric studies are presented and discussed from global and local points of view, to investigate the effects of certain parameters that are not considered in the design method according to Eurocode 5.
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