Glulam beams reinforced with FRP externally-bonded: theoretical and experimental evaluation

The glued- laminated lumber (glulam) technique is an efficient process for the rational use of wood. Fiber-reinforced polymer (FRPs) associated with glulam beams provide significant improvements in strength and stiffness and alter the failure mode of these structural elements. In this context, this paper presents guidance for glulam beam production, an experimental analysis of glulam beams made of Pinus caribea var. hondurensis species without and with externally-bonded FRP and theoretical models to evaluate reinforced glulam beams (bending strength and stiffness). Concerning the bending strength of the beams, this paper aims only to analyze the limit state of ultimate strength in compression and tension. A specific disposal was used in order to avoid lateral buckling, once the tested beams have a higher ratio height-to-width. The results indicate the need of production control so as to guarantee a higher efficiency of the glulam beams. The FRP introduced in the tensile section of glulam beams resulted in improvements on their bending strength and stiffness due to the reinforcement thickness increase. During the beams testing, two failure stages were observed. The first was a tensile failure on the sheet positioned under the reinforcement layer, while the second occurred as a result of a preliminary compression yielding on the upper side of the lumber, followed by both a shear failure on the fiber-lumber interface and a tensile failure in wood. The model shows a good correlation between the experimental and estimated results.

Fiberglass-reinforced glulam beams: Mechanical properties and theoretical model

The glued-laminated lumber (glulam) technique is an efficient process for making rational use of wood. Fiber-Reinforced Polymers (FRPs) associated with glulam beams provide significant gains in terms of strength and stiffness, and also alter the mode of rupture of these structural elements. In this context, this paper presents a theoretical model for designing reinforced glulam beams. The model allows for the calculation of the bending moment, the hypothetical distribution of linear strains along the height of the beam, and considers the wood has a linear elastic fragile behavior in tension parallel to the fibers and bilinear in compression parallel to the fibers, initially elastic and subsequently inelastic, with a negative decline in the stress-strain diagram. The stiffness was calculated by the transformed section method. Twelve non-reinforced and fiberglass reinforced glulam beams were evaluated experimentally to validate the proposed theoretical model. The results obtained indicate good congruence between the experimental and theoretical values.

Theoretical model and experimental analysis of glulam beam reinforced with FRP

This work present a study of glulam beams reinforced with FRP. It was developed a theoretical model that calculates strength and stiffness of the beams. The model allows for the calculation of the bending moment, the hypothetical distribution of linear strains along the height of the beam, and considers the wood has a linear elastic fragile behavior in tension parallel to the fibers and bilinear in compression parallel to the fibers, initially elastic and subsequently inelastic, with a negative decline in the stress-strain diagram. The stiffness was calculated by the transformed section method. Twelve non-reinforced and fiberglass reinforced glulam beams were evaluated experimentally to validate the proposed theoretical model. The results obtained indicate good congruence between the experimental and theoretical values.

Influence of storage period of pieces in stiffness of pinus elliottii Glulam Beams

This study aimed to investigate the influence of storage time (0, 48 hours) of Pinus elliottii pieces and the tests to obtaining modulus of elasticity (static bending and transversal vibration) in glued laminated timber beams, produced with resorcinol based adhesive and 0.8 MPa compaction pressure. After pieces were properly prepared, part of them was used in immediate three manufacturing glulam beams, tested after adhesive cure, and part stored for 48 hours under a roof with a temperature of 25°C and relative humidity of 60% for subsequent manufacturing and testing three other glulam beams. Results of analysis of variance (ANOVA) revealed that the storage period was significant influence in modulus of elasticity obtained in static bending test (8% reduction from 0 to 48 hours). This not occurred with modulus of elasticity obtained by transversal vibration test (no significant influence). ANOVA results showed equivalence of means in both test procedures. New researches ire needed to better understand the investigated phenomenon, using new wood species, other storage conditions and a great number of samples.

Evaluation of perforated steel plates as connection in glulam-concrete composite structures

This paper shows the results of an experimental investigation carried out on a connection element of glulam and concrete composite structures, through double-sided push-out shear tests. The connection system was composed of perforated steel plates glued with epoxy adhesive. Five specimens were made and tested under shear forces. This innovative connection system showed an average initial slip modulus equivalent to 339.4 kN/mm. In addition, the connection system was evaluated by means of numerical simulations and the software ANSYS was used for this purpose. The numerical simulations demonstrated good agreement with the experimental data, especially in the regime of elastic-linear behavior of materials. (C) 2011 Elsevier Ltd. All rights reserved.

Experimental Study of Interfacial Stress Distribution of Bonded-in BFRP Rod Glulam Joints Using Fibre Optic Sensors (FOS)

In this study, fibre optic sensors (FOS) were used to investigate the interfacial stress-strain behaviour of bonded-in basalt fibre reinforced polymer (BFRP) rods loaded into glulam members. Pull-out tests were conducted to examine the effect of bonded length and load-to-grain direction on the distribution of stress at the BFRP rod/adhesive zone. It was observed that the stress concentration at the loaded end of the BFRP rod of the samples was significantly the highest while the unloaded end showed the lowest. Increasing the bonded length at the same loading configuration resulted in a decrease in stress concentration at the loaded end. The stress concentration at the loaded end of the perpendicular to the grain samples was relatively higher than that of the corresponding parallel to the grain samples.

Pontes pedonais em madeira lamelada colada:caracterização, dimensionamento, patologia e conservação

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Edificações

Projecto de estruturas de uma passagem superior em madeira

Este projecto visa um estudo de uma solução para uma ponte pedonal de Madeira Lamelada Colada (MLC) entre o Hospital Pedro Hispano e o Norte-Shopping, localizada na Senhor da Hora. Inicialmente foram analisadas diversas variantes, com vários tipos de sistemas, sendo adoptada uma ponte formada por dois arcos, que se aproximam à medida que se afastam dos encontros unidos por contraventamentos em cruz. O tabuleiro encontra-se suspenso por tirantes e apoiados dos dois lados nos encontros. Foi realizado uma pequena introdução histórica da utilização da madeira enquanto material de construção, a sua fabricação e os vários tipos de pontes pedonais em MLC. O uso da madeira em estruturas fez com que a abordagem do Eurocódigo 5 (EC5) tivesse uma maior importância. A estrutura é modelada no programa de cálculo “DLUBAL ” através de um modelo de barras tridimensional de modo a efectuar uma análise estática e dinâmica global, recorrendo-se para tal a normas e princípios gerais de verificação de segurança dos regulamentos Europeus, nomeadamente os Eurocódigos das várias especialidades. Apresentam-se em anexo vários desenhos da ponte, desenhos das peças de ligação, o mapa de trabalhos e quantidades, ideias preliminares, dimensionamento e a escolha dos ligadores e por fim os diagramas de esforços dos elementos aos Estados-limite Último.

Sahatavarasta valmistetun pienpalkin tuotekehityksen esiselvitys

Työn tavoitteena oli selvittää markkinalähtöiset mahdollisuudet erään puurakentamisen tuoteperheen kehittämiseksi pienpuusta valmistettavalla palkilla. Työssä käsiteltiin Suomen puupalkkimarkkinoita. Lisäksi työn tavoitteena oli tuoteperheen muiden kehittämismahdollisuuksien tutkiminen ja siinä käytettävän brändin käyttömahdollisuuksien pohtiminen. Ensiksi työssä tutustuttiin nykyiseen tuoteperheeseen. Tämän jälkeen kartoitettiin käytössä olevien puupalkkien ominaisuuksia ja kilpailukykyä. Sekä kirjallisten että puhelinhaastattelujen perusteella työssä perehdyttiin puupalkkien markkinoihin, markkinointiympäristön erityispiirteisiin ja etsittiin uudelle puupalkille kilpailukykyisiä ominaisuuksia. Brändien käyttömahdollisuuksia kartoitettiin perustuen lähinnä julkisiin kirjallisiin lähteisiin. Työssä tehdään esitys tuoteperheen täydentämiseksi pienpalkilla. Tulevaisuudessa sekä teollinen että yksityinen puurakentaminen ovat siirtymässä erilaisten rakentamisjärjestelmien käyttöön. Rakentamisen laatuvaatimukset ovat kiristymässä. Tämä johtaa rakentamisen tuotteiden ja tuotantomenetelmien kehittämiseen. Tuoteperheiden käyttö on lisääntymässä ja niiden merkitys kaupankäyntikokonaisuuden osana kasvaa myös puutuotteiden osalla.

Desempenho estrutural de vigas em madeira laminada colada armada

The objective of the present work was to evaluate Pinus’ glued laminated timber (glulam) beams and steel reinforced glulam beams, using PU mono-component adhesive in lamination step and epoxy adhesive to bond steel bars. The mechanical performance was verified through bending test, and the adopted method based on homogenized section, to considerate the differences between wood and steel mechanical properties. The homogenization section method proved itself effective in obtaining the stiffness of the parts in MLCA. The stiffness of reinforced beams increased 91% in comparison with glulam beams, differing only 5.5 % from value of stiffness calculated

Pasarela peatonal sobre el río Ulla, provincia de Lugo (Galicia)

Se trata de un proyecto de pasarela peatonal colgante sobre el río Ulla, de aproximadamente 36 metros de luz. La especial belleza del área natural en que se situará llevó a la opción de un diseño claro y sencillo para lograr su integración en el lugar. Se busca que la pasarela pase lo más desapercibida posible y deje el protagonismo para el entorno, el río y la naturaleza misma. La difícil accesibilidad de la zona condicionó el diseño y los procedimientos constructivos a adoptar. Se optó por una tipología de pasarela colgante de cables de acero, tablero de madera de castaño y soportes de madera laminada cilíndrica, sobre unos estribos de hormigón armado parcialmente ocultos gracias a su integración en la topografía del lugar. El diseño modular del tablero, construido a base de piezas prefabricadas de madera de castaño que se ensamblan entre sí, permite el montaje en seco mediante avance del tablero sin necesidad de cimbra. Su diseño con dos capas cruzadas de entablado solidarizadas proporciona al conjunto un comportamiento estructural similar al de una placa maciza de madera. This is the project of a suspension footbridge over the Ulla River. It has a span of about 36 meters. The beauty of the natural surroundings where it is located guided the design to the option of a clear and simple proposal with the aim of achieving an integrated project for the area. The footbridge tries to be as invisible as possible with the purpose of maintaining the natural quality of the river and its surroundings. The difficult access to the area conditioned the design and the construction procedures chosen. A suspension footbridge with stainless steel cables, chestnut timber deck and cylindrical glulam piles was designed in the end. The reinforced concrete abutments are partially concealed thanks to their integration in the topography of the area. The deck is built of prefabricated chestnut timber modules that can be joined together at the construction site and can be assembled without the necessity of scaffolding over the river. The design of the deck, with two crossed layers of chestnut boards screwed down together, permits a structural behaviour similar to a solid wooden slab.

Desarrollo metodológico mediante análisis experimental de la valoración de la degradación en situación de incendio de uniones carpinteras en estructuras de madera laminada encolada

En situación de incendio, los elementos estructurales de madera laminada encolada (?MLE?) sufren una degradación térmica que les lleva a una pérdida de sección portante. El Código Técnico de la Edificación cuantifica esta pérdida en 0,55 - 0,70 mm/min por cada cara sometida a carga, según especie y densidad, pero no propone una metodología específica para el cálculo de uniones carpinteras en situación de incendio. Para conocer el comportamiento de este tipo de uniones en situación de incendio, la Plataforma de Ingeniería de la Madera Estructural (PEMADE) de la Universidad de Santiago de Compostela, el Instituto de Ciencias de la Construcción Eduardo Torroja y el Centro Tecnológico CIDEMCO-Tecnalia han realizado conjuntamente una serie de ensayos experimentales sobre probetas ensambladas con unión carpintera del tipo cola de milano. Se han sometido las probetas a cargas térmicas variantes en el tiempo siguiendo la norma ISO 834-1, tal y como indica el CTE. Se registró usando termopares la variación de la temperatura a lo largo de la duración del ensayo. En este trabajo se expone en detalle la metodología desarrollada para realizar los ensayos, así como los primeros resultados obtenidos. In a fire event, glued laminated timber ("GLULAM") elements suffer a thermal degradation that produces in them a decrease of bearing section. Spanish technical building normative (?CTE?) quantify this decreasing from 0.55 to 0.70 mm / min according to species and density, but does not propose a specific methodology for calculating carpenter joints in a fire situation. In order to understand the behavior of such joints in a fire situation, the Platform for Structural Timber Engineering (PEMADE) of University of Santiago de Compostela; Institute of Science Construction Eduardo Torroja and Technology Center CIDEMCO-Tecnalia conducted together a series of experimental tests on glulam specimens assembled with a carpenter union type called ?dovetail?. Specimens were subjected to thermal loads varying in time according to ISO 834-1, as indicated by the CTE. Thermocouples were inserted in the specimens, recording the temperature variation along the length of the test. This paper details the methodology developed for the test and the first results.

Évaluation d’une nouvelle méthode de calcul des assemblages en bois à l’aide de connecteurs de petits diamètres

Les charpentes en bois doivent inévitablement inclure des assemblages pouvant transférer les charges entre les éléments de façon adéquate pour assurer l’intégrité de la structure. Les assemblages sont une partie critique des structures en bois puisque dans la plupart des cas, ce sont ceux-ci qui permettent de dissiper l’énergie et d’obtenir un mode de rupture ductile sous les charges sismiques. Ce mode de rupture est préférable, puisqu’il donne lieu à une grande déformation avant effondrement, permettant ainsi une évacuation des occupants en toute sécurité lors de tremblement de terre. Les assemblages à petits diamètres tels que les clous, les rivets et les vis sont fréquemment utilisés dans les constructions en bois et on suppose qu’ils amènent une rupture ductile bien qu’il soit impossible pour les concepteurs de prédire exactement le mode de rupture à l’aide de la méthode de calcul actuelle. De plus, les rivets ont une application très limitée dû au fait que la méthode de calcul utilisée actuellement s’applique à des configurations, essences et types de produits de bois très spécifiques. L’objectif de ce projet est d’évaluer une nouvelle méthode de calcul proposée par des chercheurs de Nouvelle-Zélande, Zarnani et Quenneville, pour les assemblages à rivets, mais adaptable pour les assemblages de bois à attaches de petits diamètres. Elle permet au concepteur de déterminer avec précision le mode de rupture des assemblages de différentes configurations avec différents produits de bois. Plus de 70 essais sur les assemblages à rivets et à clous résistants à des charges variant de 40kN à 800kN ont été effectués dans le cadre de ce projet de recherche afin de valider l’utilisation de cette méthode avec le produit du bois lamellé-collé canadien Nordic Lam et la comparer avec celle présentement utilisée au Canada. Les modes de rupture ductile, fragile et mixte ont été prévus avec l’emphase sur le mode fragile puisque c’est celui-ci qui est le plus variable et le moins étudié. Les assemblages en bois lamellé-collé Nordic Lam étaient cloués ou rivetés selon différentes configurations variant de 18 à 128 clous ou rivets. Les résultats démontrent une bonne prédiction de la résistance et des modes de rupture des assemblages à clous et à rivets. Pour quelques configurations des assemblages à rivets, les prédictions de la nouvelle méthode sont plus élevées qu’avec la méthode actuelle. Les assemblages à clous ont démontré des ruptures de la tige de clous au niveau du plan de cisaillement lors de tous les essais effectués, ce qui ne correspond pas à un mode ductile ou fragile prévue par la méthode de calcul.