Showing papers by "Mohamed A. ElGawady published in 2018"

Shaking Table Testing of Segmental Hollow-Core FRP-Concrete-Steel Bridge Columns

Abstract: This article presents dynamic tests of three damage-resistant segmental hollow-core bridge columns with posttensioned unbonded strands. One column was constructed without energy dissipaters...

Behavior of Hollow-Core FRP-Concrete-Steel Columns under Static Cyclic Flexural Loading

Abstract: This paper presents the seismic behavior of hollow-core fiber-reinforced polymer (FRP)-concrete-steel (HC-FCS) columns comparable with the conventional RC column. The typical HC-FCS column ...

Effect of Curing Temperatures on Zero-Cement Alkali-Activated Mortars

Abstract: Three alkali-activated mortars (AAM), or what is called geopolymer, mix with different fly ashes sources were tested during the study. X-ray fluorescence was carried out on AAM samples to determine their chemical composition. Flowability and setting times of the AAMs were tested. Compressive strength was analyzed for five different temperatures of 30, 40, 55, 70, and 85 °C under five different time intervals of 4, 8, 16, 24, and 48 h. The compressive strength results indicate that the calcium content and ratio of silica to alumina played a pivotal role in the optimum curing conditions for each of AAMs.

Leaching Assessment of Eco-Friendly Rubberized Chip Seal Pavement:

Abstract: Companies in the United States need to mine billions of tons of raw natural aggregate each year. At the same time, billions of scrap tires are stockpiled every year. As a result, replacing the natu...

Effect of Different Class C Fly Ash Compositions on the Properties of the Alkali-Activated Concrete

Abstract: Class C fly ashes from two different coal-fired power plants were used to manufacture alkali-activated concrete. The workability and the compressive strength were studied in this paper. The workability was measured by the slump test. The compressive strengths at different ages of 1, 7, and 28 days were measured. Three different curing regimes including elevated heat curing at 70 °C, laboratory ambient curing at 23 ± 2 °C, and moist curing in the moisture room at 23 ± 2 °C were applied to identical mixtures to investigate the curing regime effects. Both types of fly ashes showed high slump of 212.5 and 225 mm. The results revealed that the compressive strength of the specimens that cured at the ambient or moist conditions increased with increasing the calcium content in the fly ash. However, the compressive strength of the specimens that were cured at 70 °C decreased when increasing the calcium content of the fly ash. The compressive strength of the concrete based on fly ash having higher calcium content at 28 days reached to 34.78, 36.62, and 51.46 MPa for oven-, ambient-, and moist-cured specimens, respectively. Furthermore, the compressive strength of the concrete based on fly ash having relatively lower calcium content at 28 days reached to 36.43, 30.79, and 47.45 MPa for oven-, ambient-, and moist-cured specimens, respectively.

Field Implementation of Rubberized Chip Seal

Abstract: This section was monitored for its texture, skid resistance, and aggregate dislodge over a period of one year. The MTD increased significantly with an increase in the rubber content where the MTD of rubberized chip seal with 50% replacement ratio was increased by 77% compared to the conventional chip seal. Raveling distress was also observed due to snowplowing actions. No damage or any sort of distress was observed in the wheel paths due to traffic loads.

Resilient civil infrastructure under dynamic loadings 2020

Abstract: 1School of Natural and Built Environments, University of South Australia, Adelaide, SA, Australia 2Department of Civil and Environmental Engineering, The University of Auckland, Auckland, New Zealand 3Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO, USA 4Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong

Inelastic Response Evaluation of Precast Composite Columns under Seismic Loads

Abstract: This paper presents a non-linear finite element analysis of large-scale hollow-core fiber-reinforced polymer-concrete-thin walled steel (HC-FCS) precast columns under reversed cyclic loading. The HC-FCS columns provide an economical and efficient alternative to conventional concrete bridge columns. The precast HC-FCS column consists of a concrete shell sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner thin-walled steel tube. The steel tube diameterto thickness (Di/ts) ratio was 254. The proposed FEA model was developed using LS_DYNA multipurpose software and was verified by experimental results performed in this study. The FE model was used to investigate some important phenomena such as thin-walled steel tube cyclic local buckling and to determine where and when steel tube yielding and damage initiation occurs. The comparison and analysis of the proposed model to predict local damages, failure patterns, and hysteretic curves were in reasonable accuracy with the experimental outcomes. 1 Graduate Research Assistance and PhD student, Dept. of Civil, Architectural, and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO. 65401; mma548@mst.edu 2 Benavides Associate Professor, Dept. of Civil, Architectural, and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO. 65401; elgawadym@mst.edu §Corresponding author Inelastic response evaluation of precast composite columns under seismic loads Mohanad M. Abdulazeez1; and Mohamed A. ElGawady2§, PhD, M. ASCE

Three-Dimensional Numerical Analysis of Hollow-Core Composite Building Columns

Abstract: This paper presents a numerical study on the behavior of hollow-core fiber-reinforced polymer-concrete-steel (HC-FCS) columns with square steel tubes under combined axial compression and flexural loadings. The investigated HC-FCS column consisted of an outer circular fiber-reinforced polymer (FRP) tube, an inner square steel tube, and a concrete wall between them. Three-dimensional numerical models were developed using LS-DYNA software for modeling large-scale HC-FCS columns. The finite element (FE) models were designed and validated against experimental results gathered from HC-FCS columns tested under cyclic lateral loading. The FE results were in decent agreement with the experimental backbone curves. These models subsequently were used to conduct a parametric FE study investigating the effects of the confinement ratio and buckling instabilities on the behavior of the HC-FCS columns. In general, the HC-FCS columns with square steel tube failed by steel tube local buckling followed by FRP rupture. The obtained local buckling stresses that result from the FE models were compared with the values calculated from the empirical equations of the design codes. Finally, based on the FE model results, an expression was proposed to predict the square steel tubes local buckling stresses of HC-FCS columns.

Flexural Rigidity Evaluation of Seismic Performance of Hollow-Core Composite Bridge Columns

Abstract: This paper investigates experimentally the seismic behavior of two hollow-core fiber-reinforced polymer-concrete-steel (HC-FCS) columns under cyclic loading as a cantilever. The typical precast HC-FCS member consists of a concrete wall sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner steel tube. The FRP tube provides continuous confinement for the concrete wall along the height of the column. Five large-scale HC-FCS columns were investigated during this study to estimate the effective flexural (which is an important factor to define the buckling capacity and deflection of such columns) and the effective structural stiffness of the composite columns. These columns have the same geometric properties; the only difference was in the thickness of the inner circular steel tubes and the steel tube embedded length into the footing. A three-dimensional numerical model has been developed using LS-DYNA software for modeling these large-scale HC-FCS columns. The nonlinear FE models were designed and validated against experimental results gathered from HC-FCS columns tested under cyclic lateral loading and used to evaluate the effective stiffness’s results. The estimated effective stiffness results that were obtained from the experimental work were compared with the FE results. This study revealed that the effective flexural and the effective structural stiffness for the HC-FCS columns need more investigation to be addressed in the standard codes, since the embedded hollow core steel tube socket connections cannot reach the fully fixed end condition to act as a cantilever member subjected to a lateral load with a fully fixed end condition. Moreover, the effective stiffness results were found to be highly sensitive to the steel tube embedded length and slightly to the unconfined concrete strength.

Probabilistic Seismic Demand Analysis of a Bridge with Unbonded Post-Tensioned Concrete Filled Frp Tube Columns

Abstract: Ground motions at sites close to a fault are sometimes affected by forward directivity, where the rupture energy arrives at the site in a form of a very short duration pulse. These pulses impose a heavy demand on structures located in the vicinity of the fault. In this research a probabilistic seismic demand analysis (PSDA) for a self-centering bridge is carried out. The bridge columns consisted of unbonded post-tensioned concrete filled fiber reinforced polymer tubes. A bridge model was developed and non-linear time history analyses were performed. Three different methodologies that use spectral accelerations to predict structural response was used and a time domain approach was used for PSDA. In addition to the three approaches, a time domain PSDA methodology was also used. The results of the PSDA from the four approaches are compared, and the advantages of using the time domain methodology are discussed. The results of the PSDA showed that for a site located very close to the fault (6 km in this study) even the smaller magnitude earthquakes can have significant contribution to the hazard because the periods of pulses generated by small magnitude earthquake coincide with the period of the bridge. Since the small magnitude events occur with greater frequency than large magnitude events they can have high contribution to the hazard. 1 PhD Candidate, The Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech., manishar@vt.edu 2 Professor, Civil, Arch. and Environmental Eng. Dept., Missouri University S&T, Rolla, MO, United States, E-mail: elgawadym@mst.edu (Corresponding Author) 3 Professor, The Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech., E-mail: adrianrm@vt.edu Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 17 September 2018 doi:10.20944/preprints201809.0311.v1 © 2018 by the author(s). Distributed under a Creative Commons CC BY license. 2

The Influences of Mechanical Load on Concrete-Filled FRP Tube Cylinders Subjected to Environmental Corrosion

Abstract: Fiber-reinforced polymer (FRP) has been introduced into civil engineering since last century and finds tremendous applications in retrofitting and constructing infrastructures. Numerous studies have been done on its durability performance; however, most of the test specimens were not applied with mechanical loads while subjecting to environmental conditions, which didn’t reflect the actual service load in a real application. This paper aims to investigate the influence of mechanical loads on concrete-filled FRP tube (CFFT) cylinders while they are under harsh environmental conditions. Both loaded and unloaded specimens were put into an environmental chamber and exposed to freeze/thaw cycles, wet/dry cycles, and heating/cooling cycles for 72 days. Compression tests and split-disk tensile tests were conducted on the CFFT cylinders and the outer FRP tubes, respectively, after the conditioning was completed. Experimental results showed slight reduction on the stress, but considerable decrease on the strain for loaded CFFT when comparing to unloaded specimens.