Alfredo M. P. G. Dias

A non-linear 3D FEM model to simulate timber-concrete joints

This paper, presents 3D non-linear FEM models developed to predict the mechanical behaviour of timber-concrete joints made with dowel-type-fasteners. They consider isotropic behaviour for steel and concrete and orthotropic behaviour for timber, all the materials are modelled with non-linear mechanical behaviour. Besides, the interaction between materials is modelled using contact elements associated with friction. The results obtained in the numerical simulations are evaluated and compared with results obtained in laboratory shear tests. The model developed showed the capacity to simulate the behaviour of the joints if the materials used are properly modelled. Nevertheless further research is still necessary to improve the modelling of the materials particularly timber.

Assessment of Timber–Concrete Connections Made with Glued Notches: Test Set‐Up and Numerical Modeling

The aim of this study is to analyze the mechanical behavior of timber—concrete connections established through glued notches, as well as the parameters that may affect it, specifically in the experimental shear test procedure. With these objectives in mind, a database based on a literature survey was created, identifying different shear test set-ups. In addition, a numerical approach was also adopted, based on experimental results. A numerical finite element method model was developed in order to describe the behavior of this type of connection. To validate the model, three sets of experimental tests were used, differing according to the notch material, the concrete class and the set-up’s geometry. Using this model, parametric studies were developed to analyze the effects of the material and geometrical parameters and support conditions. The database showed that double-shear tests were the most common experimental test set-up. The numerical modeling allowed a good approximation to a connection’s linear-elastic behavior. Parametric studies showed that the parameter with the greatest effect on a connection’s stiffness was the modulus of elasticity of timber, in contrast with the support conditions. The locations chosen to measure displacements on timber and concrete elements were also shown to affect the calculated connection stiffness.

Modal Frequencies of a Reinforced Timber-Concrete Composite Floor: Testing and Modeling

AbstractThe reinforcement of a timber floor with a concrete layer properly connected to produce a composite system represents not only an improvement in the stiffness but also a foreseeable change in the modal frequencies of the floor. In order to assess that change, a typical timber floor, which was subsequently reinforced with a concrete layer to produce a composite, was tested at both stages in the research reported in this paper. Additionally, composite beams taken from the original floor were also tested. The results showed a significant decrease (44%) in the fundamental frequency after the reinforcement. In order to obtain the mode shapes and frequencies of the floor, finite-element (FE) models of the floors and beams were created. The FE models accurately matched the experimental results. Having validated the model, a parametric study was carried out to compare the results provided by the proposed FE model with a numerical model from the bibliography and to understand the influence of the most rele...

X-Lam Panels in Swimming-Pool Building – Monitoring the Environment and the Performance

The cross-laminated timber panels (X-Lam panels) are produced for structural use in Service Classes 1 and 2 conditions, in accordance with what is established on Eurocode 5 [. Timber boards are glued together on orthogonal layers, allowing the panel to perform two important characteristics: good dimensional stability and loading in two-way directions. The influence of wood moisture content on the feasibility of cross-laminated timber is described in this paper regarding the dimensional stability of the panels when applied in high moisture locations. Several European Technical Approvals, state the low importance of the dimensional variations with moisture content of this type of panel, but some reference values can be found in other technical documents. The French Avis Technique [[[1 reference the value of 0.01mm/m for in-plane deformation (per percentage of timber moisture variation) and the TRADA Wood Information Sheet, WIS 2/3-62 [1, refers the maximum value of 0.02mm/m for the same conditions.The use of the X-Lam panels in Service Class 3 can not be used, concerning the high level of stressing in glue lines, and no producer has yet certified it for this Service Class. Moreover, the French Avis Technique doesnt allow the use of X-Lam panels in swimming-pools due to high hygrometry, even for conditions corresponding to Service Class 2.Cross laminated timber panels are widely used across Europe but are giving the first steps in Portugal at the moment. The first big project was finished in spring 2012 in Almada, comprising a building integrating a 25 meter in-door swimming-pool and a gym. In order to assess the behavior of the timber structure, due to the non-conventional using of the X-Lam panels, a monitoring program was started immediately after building construction. The results obtained are presented and discussed in this paper.

Reinforcement of Timber Floors-Transversal Load Distribution on Timber-Concrete Systems

In this paper the transversal load distribution in timber-concrete systems is analysed and discussed. The analysis is based on experimental and numerical results obtained for real scale timber-concrete systems. Two situations are considered: a timber-concrete floor for a multi-storey building with dimensions of 3.39mx3.48m in plan view and a road bridge deck with dimensions of 5mx14m also in plan view. In both situations the systems were designed to the loads required by the European codes. The effect of the transversal load distribution was experimentally assessed by imposing concentrated loads in various locations, eccentric to both transverse and/or longitudinal direction. Additionally, FEM models were developed to describe the mechanical behaviour of the two composite timber-concrete systems. The results obtained with both methodologies are presented and discussed. Based on this discussion conclusions are drawn regarding the amount of transversal distribution that can be expected in this type of reinforcement solution.

Structural Connections for Small-Diameter Poles

AbstractIn Portugal, given the large proportions of natural regeneration pine stands, a large amount of young trees must be removed from the forest, to assure the quality of mature trees and to decrease the risk of fire. With this problem in mind, a national study was launched to investigate the use of maritime pine small-diameter poles in structural applications. The study had two different tasks. The first task comprised the determination of mechanical properties and the establishment of visual and mechanical strength grading procedures and is already completed. The second task concerns the development of connections. This paper presents results within the second task. Three types of connections, regarding failure load and stiffness, were studied: connections using central plates; glued-in rods; and dowel nuts. The glued-in rods showed the highest mean failure load and, especially, stiffness. Indeed, the glued-in rods showed a mean stiffness around six times higher than the one obtained for the other st...

Sustainability and Lifecycle Assessment of Timber-Concrete Composite Bridges

AbstractOver the last few years there has been a renewed interest on the use of timber-concrete composite (TCC) structures in bridge decks, possibly because of their cost competitiveness and environmental friendliness. Accordingly, this paper investigates the sustainability of TCC bridge decks under a threefold environmental, economic, and sociocultural perspective. Two different types of decks, which represent the overall characteristics of TCC bridges constructed around the world, are first described. Next, the paper presents a comparative sustainability assessment of two existing concrete bridges and their TCC deck potential alternatives (of the types previously mentioned); a lifecycle methodology, based on standards from the International Organization for Standardization (ISO) and other publications, is followed. The main conclusions are that, when compared with concrete decks, TCC solutions cause less environmental impact and are cost-competitive. Regarding sociocultural impacts, this analysis reveal...

Bending Strength and Stiffness of Portuguese Maritime Pine Utility Poles

Abstract The Civil Engineering Department of the University of Coimbra set up a project with the purpose of grading and characterizing Portuguese maritime pine utility poles. To achieve the aim of this project, 64 utility poles that met the requirements of Comite Europeen de normalization EN14229 were collected in the central coastal region of Portugal. The utility poles were characterized according to various anatomic and geometric characteristics: the number of knots, the amount of taper, the nominal diameter, and the rate of growth. Each utility pole was also tested in bending. From these tests, the bending strength and modulus of elasticity were determined. The results obtained were in line with previously published results for utility poles from other species. In addition to this, wood samples were collected from each specimen to determine the moisture content and density. The correlation coefficients between the bending strength and modulus of elasticity were determined, as were the coefficients bet...

Grading of Portuguese Maritime Pine Small-Diameter Roundwood

AbstractThis paper presents work carried out with the aim of characterizing the mechanical behavior and developing visual and machine-strength grading systems for Portuguese maritime pine roundwood for structural applications. Two samples of forty maritime pine logs each were collected, one in a northern region of Portugal and another in an interior central region. After drying, the logs were visually graded and subjected to nondestructive tests, using vibration and ultrasounds, for determination of dynamic modulus of elasticity. The logs were then subjected to destructive tests for determining bending and compression strength and bending modulus of elasticity. These results were analyzed in order to identify the features to be considered in the strength grading process. From this analysis, a proposal was developed to visually grade Portuguese maritime pine roundwood in two strength grades. According to the European strength class standard for solid timber, the upper grade has similar mechanical propertie...

Damage Detection on Timber Floors’ Supports through Dynamic Analysis

ABSTRACT The dynamic changes in a traditional layout of a short-span timber floor due to deterioration on supports were investigated experimentally and numerically. The floor was evaluated for its normal situation (undamaged) and for simulated situations of total support degradation. The experimental dynamic parameters were obtained by an operational modal analysis technique and comprised the undamped frequencies, damping ratios, as well the mode shapes. A finite-element model was then developed in a software package and validated with experimental results. The comparison of numerical and experimental results revealed that damage location at supports is easily detectable by a qualitative comparison of mode shapes with the ones of the undamaged situation.