Structural evaluation and design procedure for wood beams repaired and retrofitted with FRP laminates and honeycomb sandwich panels

© 2015 Elsevier Ltd. All rights reserved. As compared to other structural applications of polymeric composites, limited information is available on structural behavior of wood members strengthened with polymer composites. The focus of this paper is to evaluate the structural performance and practical use of wooden beams repaired and retrofitted with fiber-reinforced-polymeric (FRP) composites. The paper presents a summary results of an experimental study on the behavior of both Douglas Fir and Glulam wood beams repaired and retrofitted with different composite strengthening systems. In addition, the paper presents a simplified design procedure to predict the capacity of timber beams strengthened with FRP composites. Two types of composites; wet layup laminates and sandwich panels, and two lamination schedules; unidirectional and bidirectional, and two lamination geometries; U-laminate and flat laminates were evaluated. For "flexure/shear" wood beams repaired and retrofitted with bidirectional, carbon/epoxy U-shaped wet layup laminates, a total of eight Douglas Fir (Dug Fir) Larch # 1 wood beams were tested to failure. For "flexure-only" wood beams retrofitted with flat unidirectional laminates, both wet layup and precured sandwich honeycomb composites were evaluated. Experimental results indicated that the use of composites as external repair and rehabilitation elements resulted in an appreciable increase of both strength and stiffness. A practical case study is also presented that provides a step-by-step procedure for analyzing and designing a polymeric composite system for repair of partially damaged wood girders by fire

Structural evaluation and design procedure for wood beams repaired and retrofitted with FRP laminates and honeycomb sandwich panels

© 2015 Elsevier Ltd. All rights reserved. As compared to other structural applications of polymeric composites, limited information is available on structural behavior of wood members strengthened with polymer composites. The focus of this paper is to evaluate the structural performance and practical use of wooden beams repaired and retrofitted with fiber-reinforced-polymeric (FRP) composites. The paper presents a summary results of an experimental study on the behavior of both Douglas Fir and Glulam wood beams repaired and retrofitted with different composite strengthening systems. In addition, the paper presents a simplified design procedure to predict the capacity of timber beams strengthened with FRP composites. Two types of composites; wet layup laminates and sandwich panels, and two lamination schedules; unidirectional and bidirectional, and two lamination geometries; U-laminate and flat laminates were evaluated. For "flexure/shear" wood beams repaired and retrofitted with bidirectional, carbon/epoxy U-shaped wet layup laminates, a total of eight Douglas Fir (Dug Fir) Larch # 1 wood beams were tested to failure. For "flexure-only" wood beams retrofitted with flat unidirectional laminates, both wet layup and precured sandwich honeycomb composites were evaluated. Experimental results indicated that the use of composites as external repair and rehabilitation elements resulted in an appreciable increase of both strength and stiffness. A practical case study is also presented that provides a step-by-step procedure for analyzing and designing a polymeric composite system for repair of partially damaged wood girders by fire

Impact of hygrothermal aging on rotational behavior of web-flange junctions of structural pultruded composite members for bridge applications

his paper presents the results of the second part of a multi-phase study focused on hygrothermal behavior of pultruded fiber reinforced polymer (PFRP) web-flange junction for bridge applications. The information reported herein focuses on hygrothermal effect on the rotational stiffness and strength of web/flange junctions (WFJs) of typical pultruded profiles commonly used in general construction applications and in bridge decks in particular. Experimental results extracted from a total of twenty-seven as-built (unexposed) and seventy-six pultruded WFJs specimens exposed to fresh water and artificial seawater environments at temperatures of 40℃, 60℃and 80℃. The study evaluated the rotational characteristics of six different web-flange junctions and hygrothermal aging effects on one of such junctions. The experimental results indicated that the moment capacity and associated rotational stiffness of J1 junction group specimens was the largest among the junction “J” groups evaluated in this study. In addition, it was concluded that the moment capacity of AJ2-M1 adhesively-bonded junctions was the largest; however, the rotational stiffness of specimens AJ3-M1 and AJ3-M2 were the highest among the “AJ#-M1” group and “AJ#-M2” group, respectively. A general conclusion was reached, based on the experimental results, that is both the WFJ moment capacity and associated rotational stiffness are proportional to the size of three elements: (i) web thickness, (ii) fillet radius, and (iii) flange thickness of the pultruded profile. Results also showed that: (1) the difference in ultimate moment capacity degradation due to hygrothermal effects for WFJs exposed to fresh water and artificial seawater environments at temperatures of 40℃ and 80℃ is relatively small, however, the ultimate moment capacity degradation of specimens exposed to artificial seawater was relatively higher as comparted to those exposed to fresh water environments at a temperature of 60℃; (2) in general, exposure to higher temperatures, results in a relatively higher strength degradation, except for the case of fresh water exposure at a temperature range between 40℃and 60℃

Impact of hygrothermal aging on rotational behavior of web-flange junctions of structural pultruded composite members for bridge applications

his paper presents the results of the second part of a multi-phase study focused on hygrothermal behavior of pultruded fiber reinforced polymer (PFRP) web-flange junction for bridge applications. The information reported herein focuses on hygrothermal effect on the rotational stiffness and strength of web/flange junctions (WFJs) of typical pultruded profiles commonly used in general construction applications and in bridge decks in particular. Experimental results extracted from a total of twenty-seven as-built (unexposed) and seventy-six pultruded WFJs specimens exposed to fresh water and artificial seawater environments at temperatures of 40℃, 60℃and 80℃. The study evaluated the rotational characteristics of six different web-flange junctions and hygrothermal aging effects on one of such junctions. The experimental results indicated that the moment capacity and associated rotational stiffness of J1 junction group specimens was the largest among the junction “J” groups evaluated in this study. In addition, it was concluded that the moment capacity of AJ2-M1 adhesively-bonded junctions was the largest; however, the rotational stiffness of specimens AJ3-M1 and AJ3-M2 were the highest among the “AJ#-M1” group and “AJ#-M2” group, respectively. A general conclusion was reached, based on the experimental results, that is both the WFJ moment capacity and associated rotational stiffness are proportional to the size of three elements: (i) web thickness, (ii) fillet radius, and (iii) flange thickness of the pultruded profile. Results also showed that: (1) the difference in ultimate moment capacity degradation due to hygrothermal effects for WFJs exposed to fresh water and artificial seawater environments at temperatures of 40℃ and 80℃ is relatively small, however, the ultimate moment capacity degradation of specimens exposed to artificial seawater was relatively higher as comparted to those exposed to fresh water environments at a temperature of 60℃; (2) in general, exposure to higher temperatures, results in a relatively higher strength degradation, except for the case of fresh water exposure at a temperature range between 40℃and 60℃

Experimental and Numerical Evaluation of Perfobond Rib Shear Connectors Embedded in Recycled Aggregate Concrete

In this paper, the use of recycled aggregate concrete (RAC) for the upper slabs in steel-concrete composite beams is proposed. Perfobond rib connector (PBL), a relatively new type of shear connectors, has been widely used to ensure composite action between the steel and concrete elements in composite beams. For the past decades, several studies on assessing the performance of PBLs have been conducted, but very few focused on the PBLs that are embedded in RAC slabs. This paper presents results of an experimental and numerical simulation study that focused on characterizing the behavior of PBL fabricated using RAC. In the experimental program, a total of six standard push-out specimens, divided into three groups, were fabricated and loaded to failure. Test results indicated that the ductility of the PBLs using RAC materials decreased as the perforated steel plate thickness decreased, while the PBL ultimate strength increased by 4.3% and 12.8% for steel plate thicknesses of 10.0 mm and 12.0 mm, respectively, as compared to specimens with 8.0 mm steel plate thickness. Finite element (FE) models for PBLs embedded in RAC were developed, and numerical results were validated by corresponding experimental results. An extensive parametric numerical analysis was conducted to assess the effects of different parameters such as transverse steel rebar diameter and perforated steel plate strength and thickness on the performance of such connectors. Numerical simulation results showed that the PBL ultimate strength obtained based on the perforated plate fracture failure mode increases linearly as the steel rebar diameter increases. Also, numerical results indicated that as steel plate strength and thickness increase, failure mode changes from steel plate fracture to rupture of reinforced concrete dowels. Furthermore, existing published analytical formulas for predicting behavior of PBLs were assessed via a comparison with experimental and numerical results developed in this study. The outcomes of this study contribute in providing fundamental knowledge in a new sustainable application of PBL in steel-concrete composite beams with RAC slabs

Experimental and Numerical Evaluation of Perfobond Rib Shear Connectors Embedded in Recycled Aggregate Concrete

In this paper, the use of recycled aggregate concrete (RAC) for the upper slabs in steel-concrete composite beams is proposed. Perfobond rib connector (PBL), a relatively new type of shear connectors, has been widely used to ensure composite action between the steel and concrete elements in composite beams. For the past decades, several studies on assessing the performance of PBLs have been conducted, but very few focused on the PBLs that are embedded in RAC slabs. This paper presents results of an experimental and numerical simulation study that focused on characterizing the behavior of PBL fabricated using RAC. In the experimental program, a total of six standard push-out specimens, divided into three groups, were fabricated and loaded to failure. Test results indicated that the ductility of the PBLs using RAC materials decreased as the perforated steel plate thickness decreased, while the PBL ultimate strength increased by 4.3% and 12.8% for steel plate thicknesses of 10.0 mm and 12.0 mm, respectively, as compared to specimens with 8.0 mm steel plate thickness. Finite element (FE) models for PBLs embedded in RAC were developed, and numerical results were validated by corresponding experimental results. An extensive parametric numerical analysis was conducted to assess the effects of different parameters such as transverse steel rebar diameter and perforated steel plate strength and thickness on the performance of such connectors. Numerical simulation results showed that the PBL ultimate strength obtained based on the perforated plate fracture failure mode increases linearly as the steel rebar diameter increases. Also, numerical results indicated that as steel plate strength and thickness increase, failure mode changes from steel plate fracture to rupture of reinforced concrete dowels. Furthermore, existing published analytical formulas for predicting behavior of PBLs were assessed via a comparison with experimental and numerical results developed in this study. The outcomes of this study contribute in providing fundamental knowledge in a new sustainable application of PBL in steel-concrete composite beams with RAC slabs