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Understanding and predicting the durability of timber structural components of buildings can lead to a more reliable and efficient use of this material in constructions. The work described herein presents a methodology to assess the life-expectancy of wall-foundation details in timber buildings based on the estimation of the durability of the timber structural element. Risk classes were defined starting from the inputs from the most relevant standards addressing the durability of timber available in Europe. The attribution of a risk class to the wall-foundation detail requires decision trees that consider the key aspects that affect the durability of this construction detail in the case of fungal attack. The methodology was then applied to three case studies and the results were compared to the observations from onsite inspections carried out on the decayed structural timber elements. The present work represents the first step towards the development of a tool capable of predicting the durability of timber components within the building structure. The work reported herein was carried out within the framework of the TSafe project.

Steel–timber hybrid construction systems, in particular structures with steel frames, composite steel–timber floors and shear walls with Cross-Laminated Timber (CLT) sheets, combine the industrialized construction technology typical of steel systems with the advantages offered by CLT panels, namely lightness and in-plane stability. The paper proposes some original engineered solutions for joining CLT panels with steel elements. Specifically, it examines connections which allow both prefabrication of the components in the factory and their quick assembly on site. Experimental tests performed on a number of different connections will be presented and discussed. The first Part of the paper addresses some fundamental aspects and potentialities of steel–timber hybrid prefabricated systems. Two innovative steel–timber hybrid components to build floors and shear walls will be described in detail in the companion paper (Part II).

This paper deals with the static and dynamic seismic analysis of light timber-frame buildings. Through the use of the UNITN-model proposed in a previous work, the study is here extended to full-scale buildings. An iterative procedure to properly distribute a horizontal load to the shear-walls, considering the coupled action of the vertical-load and the hold-downs state, is developed; three methods for the application of the response spectrum analysis are proposed as well. These methods may be used to predict the seismic-behaviour and to design non-regular timber shear-walls buildings. A numerical example illustrates the application of the procedures.

In European seismic areas timber structures are found as building frames, in combination with masonry infills, in bridges, but most frequently in roof structures and floor slabs of traditional buildings. Seismic strengthening of existing structures should provide a well-defined and simple path to seismic forces, maintain timber members elastic, and develop as much as possible the post-elastic behaviour of joints. Provisions must be adopted to avoid sudden loss of capacity and brittle failure, and to foster ductility. Different criteria for seismic strengthening of floor slabs and of carpentry joints are presented.

This paper presents the results of the ongoing work on the revision of the provisions for the seismic design of timber buildings in Europe included within Chapter 8 of Eurocode 8. The most recent research results and technical developments regarding both wood-based materials and structural systems have been implemented into the proposed new version together with the application of the capacity design to each structural system. The main objectives are to update the few and incomplete provisions included in the current version to the current state-of-the-art and to correct some misleading rules. This manuscript represents the authors’ point of view on the basis of a scientific research background and the design common practice regarding different key aspects in the seismic design of timber structures.

Shake table tests were carried out on a 7 m × 5 m three-story, timber light-frame building (7.5 m height) at the TreesLab laboratory (Eucentre) in Pavia. The aim of the research was to evaluate the seismic behavior of a typical Italian prefabricated timber building and to study the interaction between the individual structural components tested in quasi-static manner in a previous experimental study. The 1979 Montenegro Earthquake ground motion, recorded at the Ulcinj-Hotel Albatros station, was selected as the ground motion for seismic tests. The maximum peak ground acceleration was scaled to 0.07 g, 0.27 g, 0.5 g. 0.7 g, and 1 g in order to evaluate the building’s performance at different levels of seismic input. More than 100 instruments were used to monitor the behavior of the building during seismic tests measuring acceleration, displacement, and forces. The visual inspection shows that the building did not show any damage during all seismic tests. However the data analysis (dynamic identification, c...

The strengthening and stiffening of traditional timber floors with the addition of timber planks and the use of dry connections falls into the category of “traditional” repair methods. Nevertheless, a high degree of innovation and scientific/industrial research is implicit in some modern applications of this type of intervention. If newly developed systems are to be satisfactorily adopted to repair ancient structures, their effectiveness and reliability need to be adequately evaluated. The study highlights the importance of investigation actions for the design, calibration, and control of intervention in the restoration of heritage structures. On the occasion of the adoption of an innovative timber-to-timber strengthening technique for the rehabilitation of a traditional timber floor in a mediaeval castle in Italy, a thorough investigation was carried out. Tests were performed in situ on the structural elements, in both the original and the repaired condition, and the results were compared with those obta...

This paper aims at applying a direct displacement-based method to assess the seismic vulnerability of existing multi-storey wooden buildings. This procedure is consistent with Priestley’s direct methodology firstly developed for reinforced concrete structures. The distinctive characteristic of the proposed method is that the system response is quantified through the use of displacements instead of equivalent elastic strengths, according to the traditional force-based approaches. Consequently, in comparison to common force-based procedures, this method cannot only be considered as a rational alternative but also as a new seismic philosophy to design or assess structures. A representative timber construction system commonly used in Italy was selected as case study. The construction system illustrated in this work was analysed in detail, with special attention given to the mechanical connections typically used. The typical failure mechanisms and the energy dissipation capacity of the structure or of its members were identified on the basis of the mechanical properties of structural parts and connections, as well as of their geometry. In the proposed direct displacement-based assessment approach, the seismic intensity that would cause the limit state to be exceeded can be calculated by means of simple formulas. Therefore, the capacity to demand ratio can be simply derived. The procedure could be used to gauge the likelihood of losses, by combining it with simple loss models to account for probabilistic aspects.

In refurbishment operation of existing timber floors could prove of some interest the possibility of hogging the existing timber beams, in case of the presence of excessive permanent midspan deflections. In the case of sagged timber floors which cannot be buttressed due to heritage issues, the possibility of cambering a timber beam by simply putting another wooden beam on the top of it and inserting screws inclined at 45° relative to the beam axis has been experimentally investigated, with some promising result. The cambering procedure has proved to be more effective when the fastener are inserting starting from the internal part of the beam, permitting to obtain significant values of upward deflection (it has been observed an upward deflection of about one three-hundredth of the total beam length): the values could possibly be increased by reducing the screw spacing or by using fasteners able to generate a greater pressure. The effectiveness of this method is based on the capability of self-tapping screws to induce internal stress in timber element during the drilling procedure: the horizontal component of the resultant pressure yielded by the inclined screws is directly related to the possibility to hog the composite system. The aim of the experimental campaign described in this paper was to investigate the values of the internal stress induced by different type of fasteners during the drilling procedure, studying the influence of different parameters such as screw angle with respect to the grain direction, initial pressure, head penetration length, threaded part length, connector typology, wood density, time-dependence.

An analytical model is proposed to estimate the seismic displacement capacity, at serviceability and ultimate limit states, of timber portal frame structures with dowelled joints. The predictions from the simplified formula are compared with the results of numerical analyses carried out on a sample of representative cases. These cases result from a simulated design procedure, consistent with Eurocode 8, and are generated via Monte Carlo sampling, with varying sizes, materials and load conditions and also uncertainties in these parameters. Based on the outcome of the analysis we propose a set of practical formulas which allow prediction of the displacement with a given percentile of overestimates. In addition, it is shown that these equations for displacement capacity can be used to generate fragility curves for performance-based earthquake engineering applications. Prescription of an overstrength factor in code provisions is recommended to avoid brittle failure.

The paper illustrates recent research on timber joints assembled with traditional and innovative dowel-type connectors. The experimental results are presented in terms of force–displacement relationships for specimens tested under a monotonic procedure and hysteretic diagrams for specimens tested under the cyclic procedure. The aim is to determine some quantitative values from the experimental data in order to characterise the ductility and dissipation capability of timber joints while taking account of design standards for earthquake-resistant structures. The paper presents and discusses procedures for the analysis of experimental data proposed in test standards and the scientific literature, the purpose being to evaluate the ability of current procedures to mechanically characterise a joint's behaviour as a function of different kinds of connector – traditional dowel-type systems or innovative self-tapping screws inserted with different inclinations with respect to the shear plane. For some cases, alternative more robust procedures are proposed, especially where a lack of consistency in the current standard procedures was noted.

We introduce a direct Displacement-Based Design methodology for glued laminated timber portal frames with moment-resisting doweled joints. We propose practical expressions to estimate ultimate target displacement and equivalent viscous damping, and we demonstrate that these expressions provide prior values that are close to those obtained a posteriori using a more refined model. Applied to case studies, the method yields base-shear forces lower than those obtained using the force-based approach of Eurocode 8. This is due to the high dissipation capacity of the specific connection technology, which apparently is conservatively accounted for in the q-factor of Eurocode 8.

This paper presents a non-invasive technique that can extract an accurate geometrical description of growth layer surfaces in wood. The method has been validated for sawn spruce elements (Picea Abies Karst.). The aim is to implement a procedure to model domain geometry in the numerical analysis of wooden elements, taking into account the intrinsic variability of the material. The approach presented by the authors avoids internal imaging and achieves a digital 3D model of growth layers, using, as input data, images of the ring pattern, which represents the growth surface boundary curves, visible on all the cut faces of the wooden element.

Synthetic methods for the diagnosis of structures and particularly for their vulnerability assessment rely on simplified calculations and visual inspection. Their effectiveness strongly depends on an accurate calibration of the procedure by which data are collected. A recent methodology for the seismic vulnerability assessment of timber roofs in historical buildings has been applied to the Thun Castle during a study for its rehabilitation. The purpose was twofold: testing and calibrating the procedure on a heritage structure and estimating the capability of the roof structure to resist seismic action, as required in a zone of low but not negligible seismicity.

In this paper an investigation campaign, carried out in occasion of the restoration of a timber floor in the Belasi Castle (Trentino, Italy), is reported. In order to validate a testing procedure for the calibration and control of an innovative wood-wood strengthening technique, results of tests performed in situ on the structural elements, in both the original and the repaired condition, have been compared with those obtained in laboratory on some dismantled beams. For the characterization of the material decay, both local mechanical and global vibrational testing have been carried out. For the mechanical characterization of the beams, before and after repair, direct static bending tests have been performed, with distributed loads, on site, and according to standard four-points loading schemes, in laboratory.

The aim of this paper is to propose a method for calculating the load-bearing capacity and stiffness of screws placed in an inclined position with respect to the shear plane and subjected to shear–compression load, to shear–tension load or to a combination due to their crossed X-position. At the same time, the authors also wish to highlight how the current method indicated by Eurocode 5 is partially unsuitable for describing the experimental results of strength and stiffness for these particular configurations. To this regard, push-out tests were carried out and the analysis of the resulting load–displacement curves has led to the definition of the main parameters describing the mechanical behaviour of the connections: strength, stiffness, effective number, ductility. The experimental values of strength and stiffness were then compared with the theoretical ones obtained using the Eurocode 5 calculation method and the calculation method proposed in this paper.

This work intends to assess the accuracy of the methodology proposed in the Eurocode 5 for laterally loaded nailed timber-to-concrete connections. First, the adequacy of the methodology proposed by Eurocode 5 for the dowel-type fasteners is analyzed and discussed, using timber elements from Pinus pinaster Ait. Square and round smooth nails have been used, initially on push-out tests of single and double shear dowel-type connections. Later, a similar investigation is carried out on timber-concrete connections, using the same kind of fasteners (nails), in single shear, wood species and experimental procedure. The use and the influence of permanent formwork are also investigated. As a result, comparisons between the values obtained for the load-carrying capacity and the slip modulus using the analysis provided by the Eurocode 5, when existing, and the experimental results are presented.

In order to assess the safety of old timber structures and eventually to select appropriate strengthening strategies, the evaluation of mechanical properties of the material is of key importance. Visual strength-grading coupled with the use of nondestructive in situ testing allows these properties to be determined. Nowadays, the definition of both nondestructive testing (NDT) procedures and criteria for the results interpretation are almost exclusively in charge of the producer. In Italy, effort has been made to develop codes for grading timber on-site, and also by means of NDT. The aim of this paper is to highlight the difficulties and shortcomings that still occur in the assessment of traditional timber members following the criteria established by the legislation in force in Italy. The presented results can be helpful for the building surveyor who is in charge of the inspection of existing timber structures. Indeed, the paper gives some indications on the effectiveness of the grading criteria applied on historical timbers, as well as on the level of accuracy of some nondestructive methods.

This paper aims at the development of multi-storey prefabricated modular buildings. Particularly, this document deals with a novel versatile construction system in which the main structural members, made by combining timber with steel, are highly engineered and can be produced in the factory. The research demonstrates the potential of steel–timber hybrid structures in terms of sustainability, providing lightweight modern seismic-resistant constructions. This document presents the results of a comprehensive experimental campaign, including tests on several innovative connections, and of the numerical FEM analyses of the structural components. The paper also provides prototypes of new highly-industrialized steel–timber hybrid shear wall and floor components.

Conservative restoration principles developed for the protection of monuments are currently applied in the structural upgrading of traditional existing buildings in order to preserve their cultural heritage. Timber structures, typically, present in these buildings to support roofs and floors, had for long been substituted when buildings were upgraded, often using new and different materials, and sometimes yielding unsatisfactory results in terms of structural behavior. The current conservation trend requires developing criteria for interventions and implementing operative procedures complying with modern structural safety requirements and satisfying conservative restoration principles. Research progress is also being made in understanding the behavior of traditional timber joints and elements in service conditions and at the limit state under exceptional actions, as well as the effectiveness of different types of reinforcement. Actual cases of restoration of buildings that included conservation of the timber structures have proven to be economically competitive with the choice of substitution.

In case of exceptional or accidental destructive events (e.g., earthquakes, floods, fire), the advisability of completely reconstructing a vanished artifact may be questionable. Among the possible approaches for reconstruction, the so-called philological method allows the complete reading of the whole building. Analogous to the study of literary texts, this method is based on the analysis of the “architectural language” of a building that is its form and its technical characteristics as well as its structural behavior. This case study concerns reconstruction of the timber roof of the Church of the Pieve in Cavalese (Italy), destroyed during a fire on March 29, 2003, for which the philological approach has been chosen. The design process consisted of two important phases: first the determination of the precise form of the original roof, by considering different kinds of evidence, then the introduction of necessary modifications, to meet the present-day structural standards. Such design choice, far from bei...

This paper describes a shaking-table experimental programme performed on four different multi-storey timber houses within the transnational Seismic Engineering Research Infrastructures for European Synergies (Series) project at the National Laboratory of Civil Engineering in Lisbon, Portugal. The aim of the Series project was to promote cooperation between main European research centres by giving access to their facilities. Under the timber buildings research programme within the Series framework, four real-scale three-storey buildings of plan dimension 7 × 5 m were assembled and tested: two timber-frame houses, one log house and one cross-glued laminated timber house. This paper describes the common parts of the various tests undertaken, such as the test set-up and the measurement layout. The tests themselves are described in a series of companion papers by the authors.

The rehabilitation of old historic buildings often requires retrofitting traditional timber connections. Experimental and numerical methods were used in this work to study the elastic and postelastic behavior of the birdsmouth joint, which is used with great frequency in old timber roof structures, especially in the Mediterranean and Alpine regions. After a preliminary inspection of several buildings to acquire data on existing assemblages, an experimental program of testing full-scale samples under monotonic and cyclic loads was undertaken. Different configurations with parameters related to geometry, loading, and material properties were studied using a finite-element model of the connection; the results were calibrated with experimental results. The behavior of various joints was also investigated using a simplified physical model. The leading roles of friction, axial compression, and joint dimensions in determining the joint capacity and postelastic behavior have been highlighted and quantified. Diffe...

A series of monotonic and cyclic tests were performed on unstrengthened specimens, in order to characterize the original behavior of connections, representative of traditional timber trusses. Subsequently, connections strengthened with metal devices were tested under monotonic and cyclic loading. Test data of original connections has been gathered with the purpose of characterizing their behavior, in particular, the post-elastic response and the failure mode. Observing the behavior of strengthened connections under cyclic loading gave straight indications on the positive and negative characteristics of the different strengthening techniques analyzed., Fundação para a Ciência e a Tecnologia (FCT)

The misunderstanding of the overall behaviour of traditional timber trusses can result in incorrect strengthening interventions or, frequently, on their replacement. Timber roof structures need a more concise knowledge of the real behaviour to determine internal loads and control the load transfer. For that, laboratory tests on scaled or full-scale specimens of members, connections and trusses are needed. In this paper, an accurate geometric and mechanical evaluation of the timber elements of two King-post timber trusses, based on grading results with data gathered from non-destructive tests (NDT), including mechanical evaluation of the modulus of elasticity in bending (MoE), followed by full-scale carrying tests were performed. The trusses were reassembled in laboratory and submitted to a series of symmetric and non-symmetric cyclic tests, according to the Limit States. Strengthening techniques evaluated in precedent research steps were used in a second phase of the load-carrying tests.

The static and dynamic behavior of timber structures largely depends on their connections. In traditional timber construction, elements are usually connected with carpentry joints based on contact pressure and friction, often with only minor reinforcement generically intended to avoid disassembling. In current practice, interventions for the upgrading of carpentry joints are mainly based on empirical knowledge according to tradition. Often they produce a general strengthening of the connection, but are not specific for the case of seismic action. Strengthening on heuristic bases may be only partially effective or possibly disproportioned. The behavior of the carpentry joints most used in roof structures is examined. The birdsmouth joint, connecting rafters to the tie beam, has been studied first, characterizing its behavior numerically and experimentally in monotonic and cyclic conditions. Other forms of the rafter‐to‐tie connection, the double notch joint and the case of parallel rafters, are discussed. Some general criteria for the seismic strengthening of these joints are presented.

The seismic quality of traditional timber structures, as those supporting roofs in old buildings, mostly depends on the condition of their connections. A research program has investigated the behavior of old timber joints and examined retrofitting criteria. The main parameters affecting the mechanical behavior of the connection have been singled out and their effects quantified by means of experimentation and numerical analysis. A synthetic model of the cyclic behavior has been formulated, implemented in a finite element format, and used in the analysis of timber structures in seismic conditions. The model has been verified with full-scale experimentation on a roof truss. Different reinforcing methods have been compared on the basis of experimental observation and calculated structural response. The study has shown that a satisfactory post-elastic response, comparable to that of new structures, may be reached for suitably retrofitted structures.

The reported research aims to provide means to improve the performances of timber structures, particularly when brittle behavior of timber elements can represent an obstacle in adopting timber structures. Several technological approach solutions are under investigation within the frame of a threeyear national research project: the first solution analyzed is the mixed glulam beam manufactured coupling laminations of different wood species, featuring a better performance as far the global ductile behavior is concerned. A numerical iterative approach has been adopted to determine the moment-curvature relationship in the plastic field up to failure. The tests performed so far confirm the expected behavior on the basis of the numerical analysis. NOMENCLATURE

The monitoring of timber structures exposed to natural climate fluctuations during their service life is an important topic for both their serviceability and safety. Numerical methods based on the recent advances in hygro-thermal modelling of wood can integrate the usual sensor-based monitoring techniques by reducing the maintenance costs for timber structures. In this paper, a 3D full coupled analysis based on the multi-Fickian theory with sorption hysteresis of wood is implemented in Abaqus FEM code by defining a new finite element in a user subroutine. To verify the method, the hygro-thermal behaviour of a glulam beam tested in laboratory under variable humidity within a previous research is analysed and the numerical values of moisture content are found to be in agreement with the experimental data. Furthermore, a numerical case-study of a glulam cross section under real climate variations is presented and the related results show the capability of the method to predict the moisture states in each points of the glulam member under continuously variable humidity and temperature.