Showing papers by "An Chen published in 2012"
TL;DR: In this paper, a 1:3 scaled FRP deck bridge model was tested with an FRP sandwich honeycomb deck connected to steel girders using the prototype shear connector and it was shown that the shear connection was able to provide partial composite action of about 25%, and sustain a cyclic fatigue loading equivalent to 75-year bridge service life span.
21 citations
TL;DR: In this paper, the authors describe a synthesis of findings pertaining to rehabilitation of concrete T-beam bridges with externally bonded fiber-reinforced polymer composites from a Pennsylvania Department of Transportation District 3 (PennDOT D3) project, with the purpose of answering common questions of concern mainly by state DOT engineers and officials.
Abstract: This paper describes a synthesis of findings pertaining to rehabilitation of concrete T-beam bridges with externally bonded fiber-reinforced polymer (FRP) composites from a Pennsylvania Department of Transportation District 3 (PennDOT D3) project, with the purpose of answering common questions of concern mainly by state DOT engineers and officials. A method for selecting applicable candidate bridges for suitability of repair with externally bonded FRP composites is described. Three levels of repair are identified, Level 1 (contract), Level 2 (contract/department force), and Level 3 (department force). From this classification, a candidate bridge was selected for a contract repair project. Field and laboratory testing of existing bridge materials is described. Prerepair tests included ultrasonic pulse velocity and rebound hammer on beam concrete, compressive strength tests on deck concrete cores, carbonation tests for both beam and deck concrete, scanning electron microscope–energy dispersive X-ray spectroscopy (SEM-EDX) analyses for beam and deck concrete, and tension tests of the extracted reinforcing steel. Structural analysis was on the basis of AASHTO specifications. Finite-element (FE) modeling was performed to determine existing capacity, and the FE model was calibrated by testing of the bridge by using applied truck-loads. The FRP design was based on strengthening the bridge to sustain an HS-20 AASHTO truck loading. The FRP-repair system was designed on the basis of current American Concrete Institute design guidelines. Repair work and post construction load testing were completed. Supporting full-scale lab studies were conducted to evaluate the most effective concrete substrate repair method and FRP strengthening scheme for laboratory damaged concrete beams by accelerated corrosion, to assure better long-term performance under static and fatigue loads. Results from the rehabilitated bridge and supporting testing were used to develop draft PennDOT design standards and construction specifications and to apply lessons learned to the design and constructability of nearly 1,000 concrete T-beam bridges in Pennsylvania.
12 citations
11 Jul 2012
TL;DR: An analytical approach based on energy method to characterize flexural-torsional (lateral) buckling of cantilever composite wood I-beams with sinusoidal web geometry is presented in this paper.
Abstract: Due to the efficiencies and lightweight, wood I-beams have been extensively used for long-span applications in civil engineering. Buckling is the most likely mode of failure before material failure. This paper presents an analytical approach based on energy method to characterize flexural-torsional (lateral) buckling of cantilever composite wood I-beams with sinusoidal web geometry. The accuracy of this analytical model is verified through good correlations with existing Finite Element and testing results for I-beams with flat and sinusoidal webs.
12 citations
11 Jul 2012
TL;DR: In this paper, the authors explored the long-term behavior of FRP-concrete interface under Mode II loading condition through a combined accelerated ageing test and a prediction model based on Arrhenius relation.
Abstract: Rehabilitating and retrofitting concrete structural members using externally bonded Fiber Reinforced Polymer (FRP) strips has been gaining steadily use in recent years because of its many advantages. An important design issue with significant performance and safety implications is the debonding of externally bonded FRP strips in flexural members, where the delamination is primarily due to Mode-II facture. Although extensive research has been conducted on Mode II fracture of CFRP-concrete interface, only limited studies are available on durability. This paper explores the long-term behavior of FRP-concrete interface under Mode II loading condition through a combined accelerated ageing test and a prediction model based on Arrhenius relation. Mode-II single shear test was adopted in the accelerated ageing test, where specimens were subjected simultaneously to two environmental conditioning effects: (1) immersed in deionized water varying from 0 to 13 weeks; and (2) controlled temperatures varying from 25°C to 60°C (77°F to 140°F) of samples while immersed in water. The Energy Release Rate (ERR) determined before and after conditioning was considered a measure of the durability performance of the specimens. Based on the short-term data from the accelerated aging test, a detailed procedure is developed using Arrhenius relation to predict the long-term performance of the CFRP-concrete interface. It can be concluded that the accelerated ageing test and the prediction procedure used in this study can be a useful tool to evaluate the durability of the CFRP-concrete interface.
3 citations
TL;DR: Honeycomb fiber-reinforced polymer sandwich panels with sinusoidal core geometry have been shown to be successful both for new construction and rehabilitation of existing bridge decks as mentioned in this paper.
Abstract: Honeycomb fiber-reinforced polymer sandwich panels with sinusoidal core geometry have shown to be successful both for new construction and rehabilitation of existing bridge decks. This investigatio...
3 citations
11 Jul 2012
TL;DR: In this paper, a composite wood I-joist was evaluated under torsion, cantilever buckling, and four-point bending, and a finite element analysis was performed to evaluate specific properties of these beams.
Abstract: 3 Benedum Distinguished Teaching Professor, CEE-WVU. 4 Research Associate Professor, CEE-WVU. ABSTRACT This study presents a combined experimental and finite element analysis of composite wood I-joists under torsion, cantilever buckling, and four-point bending. Wood I-joists are long, slender structural members designed for long-span joist and rafter applications. Theses members are composed of thin-walled webs with relatively low stiffness and relatively thick flanges. Due to the nature of the web, these beams will likely fail in buckling before ultimate load is reached. Recently at West Virginia University, a new structural wood composite panel has been developed using discarded veneer-mill residues (McGraw 2009). This unidirectional composite panel was manufactured with two specific geometries, a flat and a sinusoidal configuration with equivalent volumes, to be used as web material in prefabricated wood I-joists. The web panels were joined in length using a finger joining technique and a tongue-and-groove joint was used connect the web to the laminated veneer lumber (LVL) flanges. These beams were evaluated at two different depths, each with flat and sinusoidal webs. Three tests were performed to evaluate specific properties of these joists. First, these beams were tested in torsion to evaluate their stiffness and torsional response, following the procedure outlined in Davalos et al. (2009). An evaluation of the flexural-torsional buckling response was performed using a cantilever test as presented in Qiao et al. (2003). Finally, a four-point bending test was performed to determine the elastic moduli of the beams. A finite element analysis was performed for each of the different tests, showing good correlations.
2 citations
11 Jul 2012
TL;DR: In this paper, a two-step composite model was used to find the shrinkage of mortar from the paste and then the range of concrete shrinkages was determined using the shrinkages of the mortar and the Hashin-Shtrikman bounds with the corresponding elastic modulus.
Abstract: Partial replacement of Portland cement by industrial by-products such as fly ash and silica fume (collectively known as mineral admixtures) in the normal concrete diverts the deposition of those by-products from landfills, reduces CO2 emissions, and produces durable and sustainable concrete. Shrinkage strain is a major parameter for concrete durability. No systematic data are available to predict the shrinkage of concrete containing mineral admixtures from paste properties to coupon level. In this study, composite modeling was developed from paste level to coupon level for 10 concrete mixtures containing fly ash, and, silica fume, individually as well as in combination, at two different w/cm ratios. Then a two-step composite model was used; firstly to find the shrinkage of mortar from the paste and then the range of the concrete shrinkages was determined using the shrinkage of the mortar and the Hashin-Shtrikman bounds (1963) with the corresponding elastic modulus. The prediction model agreed well with experimental data. The predicted shrinkages from the ACI 209R and CEB M90-99 were computed and the predicted model was found to be in close agreement with the experimental results.
1 citations