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Durability testing of reinforced concrete beams under fatigue loading in a simulated marine environment
Title
Durability testing of reinforced concrete beams under fatigue loading in a simulated marine environment.
Creator
Ahn, Woo-Suk., Florida Atlantic University, Reddy, Dronnadula V.
Abstract/Description
This thesis addresses the evaluation of the durability of reinforced concrete marine structures subjected to fatigue loading. The laboratory investigation was carried out on full and half size reinforced concrete specimens with three different water cement ratios (0.3, 0.4, and 0.56), static and fatigue loading conditions, and epoxy-coated and regular black steel reinforcements; a mineral admixture (silica fume), and a corrosion inhibitor (calcium nitrite) were used for specimens made with...
Show moreThis thesis addresses the evaluation of the durability of reinforced concrete marine structures subjected to fatigue loading. The laboratory investigation was carried out on full and half size reinforced concrete specimens with three different water cement ratios (0.3, 0.4, and 0.56), static and fatigue loading conditions, and epoxy-coated and regular black steel reinforcements; a mineral admixture (silica fume), and a corrosion inhibitor (calcium nitrite) were used for specimens made with water/cement ratio 0.4 concrete. The marine tidal zone was simulated by alternate filling and draining of the tank (wet and dry cycles), and a galvanostatic corrosion technique to accelerate corrosion of rebar was introduced. Half-cell potentials and changes of crack width were measured periodically during the exposure and followed by ultimate strength testing. The significant findings include adverse effect of fatigue loading, existence of an explicit size effect, poor performance of epoxy coated steel, and negative effect of the increasing water/cement ratio.
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Date Issued
1995
PURL
http://purl.flvc.org/fcla/dt/15178
Subject Headings
Concrete beams--Fatigue, Underwater concrete construction, Reinforced concrete--Fatigue, Seawater--Corrosion
Format
Document (PDF)
experimental and analytical investigation of viscoelastic pipe-soil interaction
Title
An experimental and analytical investigation of viscoelastic pipe-soil interaction.
Creator
Ahn, Woo-Suk., Florida Atlantic University, Reddy, Dronnadula V., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
An overview of the current issues of HDPE pipe-soil systems is followed by a comprehensive literature review addressing current specifications, design methods, and relevant research projects. The following experimental tasks are described: (i) environmental stress cracking resistance (modified AASHTO M294), (ii) creep (10,000 hour parallel plate loading at super ambient temperatures), (iii) performance of buried pipes, subjected to live loading in a soil chamber, and (iv) field monitoring....
Show moreAn overview of the current issues of HDPE pipe-soil systems is followed by a comprehensive literature review addressing current specifications, design methods, and relevant research projects. The following experimental tasks are described: (i) environmental stress cracking resistance (modified AASHTO M294), (ii) creep (10,000 hour parallel plate loading at super ambient temperatures), (iii) performance of buried pipes, subjected to live loading in a soil chamber, and (iv) field monitoring. The findings include (i) satisfactory short-term environmental stress cracking resistance, (ii) temperature-dependency of the flexural modulus, (iii) the evidence of transition between slow crack growth and rapid crack propagation due to imperfect installation, and (iv) high load carrying capacity for the properly installed pipe in uniform backfill, showing an over-deflection failure mode with top flattening. The analytical investigations are as follows: (i) Bidirectional shift-constructed master curve, based on accelerated creep test values for long-term modulus prediction that showed good agreement with the Arrhenius equation-based analysis, (ii) Development of a seven-degree Voigt-Kelvin viscoelastic model based on the bidirectional shift-constructed master curve for analytical prediction of the long-term modulus, (iii) Comparison of two-dimensional and three-dimensional harmonic FEM analyses with the measured response of pipe-soil interaction, that demonstrated the analytical predictability of the pattern of deformation and stress distribution, and (iv) Determination of axial stress distribution along the pipe in non-uniform backfill condition, evaluated by approximate analysis based on finite differencing the deflection profile obtained from the assembly of individual finite segments/sections. This overcomes the limitation of the harmonic FEM analysis for pipe-soil interaction involving non-uniform soil conditions longitudinally and/or varying soil thickness circumferentially. The findings include (i) importance of axial stress contribution at failure, (ii) top flattening failure mode due to over-deflection preceding buckling or yielding, and (iii) critical adverse effect of the non-uniform backfill condition that can lead to joint opening, localized buckling, liner tearing/debonding, or cracking. The work has "spin off" applications to the coastal and offshore environments for sewage outfalls, marine pipelines etc.
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Date Issued
1998
PURL
http://purl.flvc.org/fcla/dt/12550
Subject Headings
Soil-structure interaction, Pipe, Plastic--Testing, Underground pipelines
Format
Document (PDF)