Papers by Ayman S MOSALLAM
Construction and Building Materials, Dec 10, 2018
The performance of shear connectors embedded in RPC is evaluated by push-out tests. Load-strain r... more The performance of shear connectors embedded in RPC is evaluated by push-out tests. Load-strain responses for the shear connectors using RPC under push-out load are discussed. The shrinkage effect of RPC material on performance of shear connectors is analyzed. The applicability of existing predicting equations to PBL using RPC with shrinkage effect is assessed.
Residual mechanical properties of triaxial CFRP laminates after thermal cycling and ultraviolet radiation exposure of composite bridge members
Structures, Apr 1, 2021
Abstract Environmental processing, such as thermal cycling and ultraviolet (UV) exposure contribu... more Abstract Environmental processing, such as thermal cycling and ultraviolet (UV) exposure contribute to mechanical properties degradation of polymer composites. This paper focused on assessing the mechanical properties of triaxial carbon/epoxy (CFRP) composite laminates used in fabricating light-weight composite bridges when exposed to both thermal cycling and ultraviolet radiation. In this study, five test series with a total of 39 specimens were performed to evaluate such exposure effects on tensile, compressive, and shear behavior of CFRP laminates. The experimental program was divided into five groups, including (i) Pre-exposure (baseline) test group tests; (ii) Unstressed thermal cyclic aging where unloaded specimens are exposed to fifty thermal cycles from 71 °C to –33 °C; (iii) Tension thermal cyclic test group where specimens are pre-tensioned to 30% of the baseline ultimate tensile strength and are exposed to fifty thermal cycles from 71 °C to –33 °C; (iv) Compression thermal cyclic test group where specimens are subjected to 30% of the baseline ultimate compression strength while exposed to fifty thermal cycles from 71 °C to –33 °C; (v) UV radiation test group where unstressed specimens are continuously exposed to 313 UVB ultraviolet radiation for 750 h. Experimental results indicated that thermal cycling effects on both tensile and compressive moduli are larger than its effect on tensile and compressive strengths of the triaxial composite laminates. In addition, the effect of thermal cyclic exposure on specimens loaded in tension has a larger impact on laminate tensile properties. It was also found that thermal cycling effects on shear strength are larger than its effect on the laminate shear modulus and that the effect of thermal cycling of pre-compressed laminates has a major influence on the CFRP composite laminate shear properties. Results also indicated that exposure to ultraviolet radiation has a large effect on both tensile strength and modulus, as well as the compressive strength of CFRP laminates. However, it has a negligible effect on compressive and shear moduli, as well as laminate shear strength.
Design Basis for Creep in Composites Structures
Infrastructure: New Materials and Methods of Repair, 1994
Composites Part B-engineering, Jul 1, 2007
In this paper, a stress-strain model for concrete confined by fiber reinforced polymer (FRP) comp... more In this paper, a stress-strain model for concrete confined by fiber reinforced polymer (FRP) composites is developed. The model is based on the results of a comprehensive experimental program including large-scale circular, square and rectangular short columns confined by carbon/epoxy and E-glass/epoxy jackets providing a wide range of confinement ratios. Ultimate stress, rupture strain, jacket parameters, and cross-sectional geometry were found to be significant factors affecting the stress-strain behavior of FRP-confined concrete. Such parameters were analyzed statistically based on the experimental data, and equations to theoretically predict these parameters are presented. Experimental results from this study were compared to the proposed semi-empirical model as well as others from the literature.
Composite Structures, Jun 1, 2015
This paper presents and evaluate the performance of a novel, non-conventional fiber-reinforced-po... more This paper presents and evaluate the performance of a novel, non-conventional fiber-reinforced-polymeric (FRP) composite system for repair strengthening reinforced concrete (RC) beams. This strengthening system is in the form of thin sandwich FRP panels that are bonded/bolted to concrete. In evaluating this innovative system, experimental and numerical assessment were conducted. In the experimental phase of this study, service and ultimate flexural behavior of three groups of RC beams were evaluated. The three beam specimens of the first group were designated as control specimens and their performance was used as baseline for comparison to the performance of the other two strengthened RC beams groups. The second and third groups comprised of three beam specimens for each group that were externally strengthened with bolted/bonded carbon/phenolic sandwich panels. A nonlinear finite element analysis was performed using LS-DYNA code to simulate and predict the flexural behavior of all RC beam specimens. A numerical parametric study was performed for different simulated cases to assess the effect of several parameters. Numerical results agreed well with the experimental results and test observations. The results of this study indicated that the FRP sandwich panel strengthening systems are effective in enhancing flexural behavior of the strengthened RC beams.
Structures, 2020
Design optimization of fiber-reinforced polymeric (FRP) composite products is essential to facili... more Design optimization of fiber-reinforced polymeric (FRP) composite products is essential to facilitate their applications in engineering structures. For bridge structures, the main design optimization goals are the reduction of FRP material consumption and the structure weight, which aim to reduce the initial construction cost and achieve a longer bridge span. Compared with conventional steel-concrete composite bridges, FRP-steel composite bridges possess more design variables and more complex design process, which necessitate the simplified optimization models. This paper aims to propose a two-scale design optimation method for FRP bridge deck on the steel girder. The macro behavior of the pultruded FRP composite bridge deck is analyzed. Regarding the micro level, the equivalent properties of pultruded GFRP lamination are calculated by combining micromechanics and classical lamination theory (CLT). The above-mentioned macro pultruded GFRP bridge level and the micro fiber/resin level were bridged based on the assumption that the micro-component effective homogenized strain equals to the corresponding macro strain. The two-scale lamination optimization of pultruded GFRP bridge deck is finally achieved by finding optimized two-scale design variables that can achieve the minimum bridge weight or the lowest initial construction cost with all listed constraint requirements satisfied. A pultruded FRP deck supported on equally-spaced steel girders was selected as a case study to show how to obtain
Engineering Structures, Mar 1, 2017
This paper aims at examining the structural behavior of perfobond strip (PBL) connectors for stee... more This paper aims at examining the structural behavior of perfobond strip (PBL) connectors for steelconcrete joint of hybrid girders with ultra-high performance concrete (UHPC) as grout for such connectors. Twenty-four push-out specimens fabricated according to the design used for the connectors in the steel-concrete joint in a hybrid cable-stayed bridge have been investigated. Effects of several parameters such as (i) the interface bond between perforated plate and concrete, (ii) dowels inside the holes in the plate, and (iii) volume of steel fibers in the UHPC on the behavior of PBL were discussed in depth. Experimental results indicated that the use of a 2% volume fraction of steel fibers in the UHPC, increased the average bond strength at the plate/concrete interface and the shear resistant-capacity of concrete dowel by 82% and 50%, respectively, as compared to UHPC specimens without the fibers. The concrete dowel played an important role in developing the desired loading resistant-capacity of the PBL, and about 34-41% of the overall resistance of a standard PBL embedded in UHPC were supplied by the concrete dowel surrounding transverse rebar. The source of the achieved ductility of PBL was mainly determined by the action of transverse rebars, and the ductility in the specimens having transverse rebars was about eleven times the ductility of similar specimens without the rebars. Furthermore, the experimental ultimate strength values of PBL were compared with available equations in literatures published recently, and an analytical model for PBL/UHPC was developed and appropriate parameters were derived from present data and used to provide reliable prediction of ultimate resistant-capacity of PBL in the hybrid girders' steel-concrete joints.
Numerical Evaluation of Channel-Beam Railway Bridge with Hollow Section Concrete Deck
Springer eBooks, 2022
Shear behavior of flexible-sleeve perfobond strip connectors: Experimental and analytical studies
Engineering Structures, Aug 1, 2022
Long-term exposure of fiber-reinforced polymer (FRP) profile to harsh in-service environment will... more Long-term exposure of fiber-reinforced polymer (FRP) profile to harsh in-service environment will lead to irreversible degradation of mechanical properties. Understanding the exposure "aging" effects on pultruded FRP composites is important for their application in bridge structures. The moisture diffusion process plays a very important role to understand material degradation of GFRP laminations exposed to hydrothermal environment. In this paper, the moisture diffusion process with focusing on pultruded GFRP composites used in bridge applications is numerically simulated. The parameters of moisture diffusion are calibrated by gravimetric tests of thin plates.
Experimental Study on Flexural Performance of HSS-UHPC Composite Beams with Perfobond Strip Connectors
Journal of Structural Engineering-asce, Jun 1, 2022
Numerical Simulation of Non-Fick Moisture Diffusion of Pultruded Composite GFRP Bridge Deck Plates
Journal of Performance of Constructed Facilities, Dec 1, 2021
Composites Part B-engineering, Feb 1, 2017
In terms of the unidirectional characteristics of the majority of unstiffened open-web pultruded ... more In terms of the unidirectional characteristics of the majority of unstiffened open-web pultruded fiber reinforced polymer (PFRP) composites profiles, local failure of matrix-rich web/flange junctions (WFJ) are inescapable due to lack of fiber continuity at WFJs. Strength and stiffness of WFJ, greatly affect PFRP structure's overall strength, its buckling and post-buckling
Experimental and numerical investigation on in-plane compression and shear performance of a pultruded GFRP composite bridge deck
Composite Structures, Nov 1, 2017
Abstract The in-plane compression and shear performance plays a significant role in achieving an ... more Abstract The in-plane compression and shear performance plays a significant role in achieving an optimum and reliable design of pultruded glass fiber-reinforced polymer (GFRP) bridge deck supported on steel girders that have been used in bridge decks retrofit application or new construction in the past decade. This paper presents a summary of several laboratory experiments that were performed on a pultruded GFRP bridge deck for pedestrian or light vehicular loading in order to evaluate both the deck’s in-plane compression and shear properties. The experimental results showed that the average web thickness has a relatively larger influence on the in-plane shear behavior than the in-plane compressive behavior. Three-dimensional finite element models utilizing the Hashin’s theory laminate failure, adhesive layers failure via cohesive element and initial geometry imperfections by using limited critical eigenmodes multiplied by empirical coefficient were employed to numerically simulate both the deck’s in-plane compression and shear ultimate capacity and stiffness based on elastic engineering constants obtained from micromechanics. The numerical results agreed well with experimental results that could provide a reference for the design and construction of such type of pultruded composite bridge decks.
Structures, Oct 1, 2020
Design optimization of fiber-reinforced polymeric (FRP) composite products is essential to facili... more Design optimization of fiber-reinforced polymeric (FRP) composite products is essential to facilitate their applications in engineering structures. For bridge structures, the main design optimization goals are the reduction of FRP material consumption and the structure weight, which aim to reduce the initial construction cost and achieve a longer bridge span. Compared with conventional steel-concrete composite bridges, FRP-steel composite bridges possess more design variables and more complex design process, which necessitate the simplified optimization models. This paper aims to propose a two-scale design optimation method for FRP bridge deck on the steel girder. The macro behavior of the pultruded FRP composite bridge deck is analyzed. Regarding the micro level, the equivalent properties of pultruded GFRP lamination are calculated by combining micromechanics and classical lamination theory (CLT). The above-mentioned macro pultruded GFRP bridge level and the micro fiber/resin level were bridged based on the assumption that the micro-component effective homogenized strain equals to the corresponding macro strain. The two-scale lamination optimization of pultruded GFRP bridge deck is finally achieved by finding optimized two-scale design variables that can achieve the minimum bridge weight or the lowest initial construction cost with all listed constraint requirements satisfied. A pultruded FRP deck supported on equally-spaced steel girders was selected as a case study to show how to obtain
Investigation on structural performance of perfobond strip connector group in steel-concrete joints
Engineering Structures, Sep 1, 2021
Abstract The use of an innovative type of perfobond rib (PBL) shear connector in steel–concrete j... more Abstract The use of an innovative type of perfobond rib (PBL) shear connector in steel–concrete joints of hybrid girder bridges has gained wide popularity among bridge engineers. For a PBL group with multi-row PBLs in tandem arrays, comprehensive interactions exist among the connectors. However, the current design approaches assume that the force transferred by each row of PBL is uniform, resulting in an overestimated shear resistance of the connector group. The main objective of this paper is to introduce a mathematical approach, which accounts for the bonding-friction effects (BF) at the perforated steel plate/concrete slab interfaces and the reinforced concrete dowel (RD) effects by the perfobond hole, to assess the ultimate resistance of PBL group under the RD fracture failure mode. In this study, six push-out specimens for different PBL groups, with varying connectors’ quantity, were evaluated experimentally to determine the key parameters for the proposed analytical model. The experimental results revealed the significant reduction in average resistance of single PBL in a connector group as connector number increased. The proposed approach is validated by an experimental database that includes push-out test results obtained from the previously published studies and afterwards converted to the design load level, which can be extensively applied to the PBL group using normal concrete and ultra-high performance concrete (UHPC). The proposed analytical approach provides an efficient tool for analyzing and designing of PBL group in steel–concrete joints of hybrid girder bridges.
Probabilistic Fatigue Stiffness Degradation of Frp Laminates Considering Stress Ratio Effects
Social Science Research Network, 2023
Journal of Reinforced Plastics and Composites, Sep 27, 2017
Premature local failure of web/flange junctions of the majority of unstiffened commercially produ... more Premature local failure of web/flange junctions of the majority of unstiffened commercially produced pultruded fiberreinforced polymer composites profiles is inescapable due to lack of fiber continuity at the resin-dominated junction zones. This paper focuses on evaluating both short-and long-term behavior of such junctions when subjected to axial tensile stresses. In this study, the axial mechanical behavior of web/flange junctions of pultruded bridge deck components before and after hygrothermal aging effect is investigated. In the experimental phase, axial tensile tests were performed on six different types of pultruded web-flange junctions to assess axial characteristics of each web/flange junction type. In order to evaluate the hygrothermal behavior of such junctions, axial tensile tests were conducted on web/flange junction specimens that were exposed to both fresh water and artificial seawater environments at temperatures of 40 C, 60 C, and 80 C. Several controlling parameters affecting both strength and stiffness of pultruded fiber-reinforced polymer junctions were identified and discussed that include: (i) Junction's web and flange thicknesses, (ii) fillet radius, and (iii) variation of hygrothermal exposure environments. Results of this study indicated that the axial tensile capacity of a pultruded profiles is increased as the thickness of both web and flange increases. Also, it was found that the larger fillet radius of the pultruded fiber-reinforced polymer profile may contribute to a larger axial tensile capacity of pultruded profiles. However, due to variable size and geometry of the resin-rich junction zones and the common manufacturing defects in the form of folded fabric and other fibers misalignment effects, it is difficult to generalize the preceding results. Experimental results also showed that the degradation of web/flange junctions axial tensile strength increases when junctions are exposed to higher temperatures. Also, it was found that the axial tensile characteristics for junctions specimens exposed to freshwater environment are slightly different than those that were exposed to artificial seawater environments.
Evaluating the high-temperature endurance of FRP-strengthened concrete using an innovative insulation system: Experimental investigation
Journal of Building Engineering
Investigation on interfacial anti-sliding behavior of high strength steel-UHPC composite beams
Composite Structures
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Papers by Ayman S MOSALLAM