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EXPERIMENTAL INVESTIGATIONS ON FLEXURAL STRENGTHENING OF OLD WOOD MEMBERS IN HISTORICAL BUILDINGS WITH GFRP Y. Batebi Motlagh¹*, Y. Gholipour²,Gh Ebrahimi³, M. Hosseinalibeygi 4 (1) PhD Student, school of civil engineering, Univ. of Tehran, Faculty of civil eng., Technical Univ. of Babol (2) Associate Professor, school of civil engineering, University of Tehran. Email: ygpoor@ut.ac.ir (3) Professor, Faculty of natural resources, University of Tehran. Email: ebrahimi@nrf.ut.ac.ir Abstract The aim of this paper is to describe a new innovative technology for strengthening old wood members in historical buildings, which had lost part of their strength due to heavy loads, loading time factor, effects of fungal or insect attacks. Most of the ancient buildings throughout Iran have been constructed mainly using wooden members. Some of the structural members in such valuable buildings are partially defective and, therefore, they seriously need to be repaired or rehabilitated, in order to maintain appropriate strength. Present research is focused on strengthening the old wood beam members with glass fiber reinforced polymer (GFRP) composite materials, sampling from non-essential sections of historical buildings. A three-point loading test was used to study the behavior of the beam subjected to gradual static load under different configurations of reinforcement. The load-displacement response, ultimate strength, modulus of elasticity and the mode of failures were evaluated. The experimental results have shown an improvement in load capacity, strength and stiffness of the hybrid samples in comparison with un-reinforced ones. At the end, the experimental and analytical results were compared with each other. Keywords: GFRP, rehabilitation, retrofit, stiffness, strength, wood. 1. Introduction Before the era of steel and concrete technology wood was the most common structural material in residential, public and industrial buildings throughout Iran, particularly in the Northern provinces which own commercial forest. The majority of existing ancient buildings in this country are over one century old; some of them are registered as historical heritage and are still standing in a good functioning shape. At present, conservation and restoration of these valuable buildings are the main concern of Iran's office of historical heritage. Inappropriate rehabilitation of the defective structural elements in historical buildings has had a great influence on their beauty and dignity, See Fig. 1. Fig. 1. Replacement of old stringers with new material . Over the past 40 years both fiber reinforced polymer (FRP) and non-FRP materials have been used to reinforce wooden structural members. * E-mail: y.batebi@nit.ac.ir Joseph Gril (edited by), Wood Science for Conservation of Cultural Heritage –Braga 2008: Proceedings of the International Conference held by COST Action IE0601 (Braga - Portugal, 5-7 November 2008, ISBN 978-88-6453-157-1 (print) ISBN 978-88-6453-165-6 (online) © 2010 Firenze University Press
WOOD SCIENCE FOR CONSERVATION OF CULTURAL HERITAGE During the last two decades, a special prefabricated fiber reinforced polymer (FRP) composite was developed to repair and retrofit wooden elements in the field. The advantages of these reinforcing materials lie in their low weight, high tensile strength and resistance to corrosion. According to recent investigations, FRP materials have been successfully used to strengthen existing structural members. Svecova and Eden (2004) tested timber beams reinforced with GFRP dowel bars as shear reinforcement as well as flexural bars to avoid the tension failures observed in some of the specimens [1]. Amy and Svecova (2004) presented an economical rehabilitation scheme to strengthen creosotetreated timber beams in both flexural and shear with glass fiber reinforced polymer bars [2]. Borri et al. (2005) presented a method for flexural reinforcement of old wood beams with CFRP materials. Mechanical tests on the reinforced wood showed that external bonding of FRP materials may increase flexural stiffness and bending capacity [3]. Corradi et al. (2006) presented in-plane shear reinforcement of wood beam floors with FRP [4]. Buell et al. (2005) presented an investigation on reinforcement timber bridge beams with a single Carbone-FRP (CFRP). A 69% increase of bending strength was reported when compared with control beam and a compression failure mode [5]. Calderoni et al. (2006) presented an evaluation of flexural and shear behavior of ancient chestnut beams under both experimentally and theoretically. The results have shown that the simplified methods commonly used to evaluate the bearing capacity of wooden beams can be safely applied to ancient structural members [6]. Dagher (2005) introduced current state of the art of reinforced wood technology, new products, codes and specifications [7]. Corradi and Borri (2007) presented a study on Fir and Chestnut timber beams reinforced with GFRP pultruded elements and the tests showed that the reinforcement with GFRP beams produced significant increase in flexural stiffness and bending capacity [8]. The purpose of this study is to present a new innovative technology, based on glass fiber reinforced polymer composite (GFRP) sheets, for the on-site rehabilitation of the old wooden members in historical buildings, through testing of small size wooden members and comparing the experimental results with numerical calculation. 3. Materials and methods 3.1. Wood Materials This experimental test is based on more than 50 specimens of ancient Zelkova serrata (Celtic Occidentalis) which is a hardwood. These specimens have been obtained from newly replaced and crushed structural elements of a historical building, located in the town of Babol, near the Caspian Sea, built up almost 150 years ago. Because of the limitation of obtaining enough old wood for testing and also because of major defects present in the main wood, like longitudinal splitting, cracking, degraded zones and holes due to nailing and insects attack, the samples were obtained in size of 25× 25× 410 mm, and tested according to ASTM D143 for small clear specimens of reinforced timbers [9]. 3.2. GFRP Materials In recent years FRP has been used as a compatible reinforcement material for timbers and plywood. The physical/mechanical/chemical properties of the FRP are very versatile. The FRP may be engineered to match and complement the orthotropic properties of wood; consequently, incompatibility problems between the wood and the reinforcing FRP are minimized. A unidirectional pultruded glass fiber-reinforced-polymer (GFRP) sheet with a thickness of 0.16 mm in size of 25× 410 mm was used, having the physical and mechanical characteristics reported in Table 1, as provided by the producer. 3.3. Resins The adhesive used in this test was Mac epoxy glue, which consisted of two parts, resin and hardener, mixed in the ratio of 3:1 by volume volume. The mechanical properties of the epoxy resin are reported in Table 1. 303
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Proceedings e report 67
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Wood science for conservation of cu
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SUMMARY Introduction ..............
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WOOD SCIENCE FOR CONSERVATION OF CU
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INTRODUCTION These proceedings of a
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(A) MATERIAL PROPERTIES
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SORPTION OF MOISTURE AND DIMENSIONA
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VIBRATIONAL PROPERTIES OF TROPICAL
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CREEP PROPERTIES OF HEAT TREATED WO
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MEASUREMENT OF THE ELASTIC PROPERTI
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ELASTIC PROPERTIES OF MINUTE SAMPLE
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4. Results Young's modulus (10^4 Mp
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PREDICTION OF LINEAR DIMENSIONAL CH
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DIMENSIONAL CHANGE OF UNRESTRICTED
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DIMENSIONAL CHANGE OF UNRESTRICTED
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AGEING OF WOOD - DESCRIBED BY THE A
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90 30 0 3,0E-03 - 2,0E 2,0E-03 - 1,
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4. Application HYGRO-LOCK INTEGRATI
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RESEARCH ON THE AGING OF WOOD IN RI
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RESEARCH ON THE AGING OF WOOD IN RI
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Xylarium Database RESEARCH ON THE A
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AGING WOOD FROM CULTURAL PROPERTIES
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AGING WOOD FROM CULTURAL PROPERTIES
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STRENGTH AND MOE OF POPLAR WOOD (PO
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STRENGTH AND MOE OF POPLAR WOOD ACR
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STRENGTH AND MOE OF POPLAR WOOD ACR
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PHOTODEGRADATION AND THERMAL DEGRAD
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ROMANIAN WOODEN CHURCHES WALL PAINT
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DISINFECTION AND CONSOLIDATION BY I
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3. Results and discussion WOOD SCIE
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FUNGAL DECONTAMINATION BY COLD PLAS
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STUDIES ON INSECT DAMAGES OF WOODEN
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TERMITE INFESTATION RISK IN PORTUGU
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BIODETERIORATION OF CULTURAL HERITA
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4. Causes of biodeterioration WOOD
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DEGRADATION OF MELANIN AND BIOCIDES
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MOULD ON ORGANS AND CULTURAL HERITA
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RESEARCH STUDY ON THE EFFECTS OF TH
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4. Methodology WOOD SCIENCE FOR CON
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NON DESTRUCTIVE IMAGING FOR WOOD ID
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METHODS OF NON-DESTRUCTIVE WOOD TES
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MEASUREMENT AND SIMULATION OF DIMEN
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IN THE HEART OF THE LIMBA TREE (TER
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3. Conclusions WOOD SCIENCE FOR CON
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2. Materials and methods WOOD SCIEN
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3. Chemometrics WOOD SCIENCE FOR CO
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3. Results and discussion WOOD SCIE
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NIR SPECTROSCOPIC MONITORING OF WAT
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NUMERICAL SIMULATION OF THE STRENGT
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3. Methods and models WOOD SCIENCE
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SIMPLE ELECTRONIC SPECKLE PATTERN I
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5. Conclusions WOOD SCIENCE FOR CON
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Average r adiated presure field (dB
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EXPERIMENTAL AND NUMERICAL MECHANIC
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EFFECT OF THERMAL TREATMENT ON STRU
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The aims of this work are to: WOOD
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ultramarine [bad] titanium white [m
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4. Conclusions chrome yellow WOOD S
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Fig. 7 - A soaked lamella clamped i
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(D) CONSERVATION
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Page 296 and 297: THE CONSEQUENCES OF WOODEN STRUCTUR
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Page 337 and 338: 3. Results and discussions WOOD SCI
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