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Recent Projects

Featured Projects

Naval Air Station

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shim_trans  Summery
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shim_trans  Objective
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shim_trans  Project Background
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shim_trans  Scope of Work
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shim_trans  Bravo 25 Description
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shim_trans  Overview
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shim_trans  Crane Rail Removal
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shim_trans  Loss of Transverse
 Negative Moment
 Capacity over the
 Outboard Crane Rail
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shim_trans  Concrete Repair
 Materials
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shim_trans  Top Deck
 Repair Procedure
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shim_trans  Under Deck Repairs
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shim_trans  Cathodic Protection
 System
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shim_trans  Cathodic Protection
 System Installation
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shim_trans  Grout Resistivity
 Measurements
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shim_trans  Reinforcing Steel
 Lead Wire Installation
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shim_trans  Upgrade Reinforcement
 Introduction
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shim_trans  Analysis of Bravo-25
 Load Response
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shim_trans  Calculation of
 Bravo 25 Resistence
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shim_trans  Modes of Failure
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shim_trans  Bravo 25
 Upgrade Design
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shim_trans  Concrete Surface
 Preparation
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shim_trans  Embedded
 Reinforcement
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shim_trans  Wet Lay-up
 Composite Laminate
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arrow_right  Proof Tests using
 Impact Load Method
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shim_trans  Costs
 Acknowledgements
 References
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Turbine Deck Load Capacity Restored


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Home > Recently Completed Projects > Featured Project > Pearl Harbor

Featured Project

 

Proof Tests using Impact Load Method

To demonstrate and quantify Bravo 25 upgrade performance, NFESC engineers applied proof loads in excess of 130 kips (580 kN) to crucial areas of the deck. Measured pier responses included the deflected shape of the pier deck and strain in the upgrade reinforcement at critical locations. Strain response was measured at points of maximum stress at the edge of pile girders, at the edge of transverse girders, at midspan of center slabs, at midspan of the track slabs, and at midspan of curb slabs. Test spans were selected that were free of obstructions. The spans between the following bents were tested:

181 – 182
184 - 185
185 –186
187 – 188
218 – 219
219 – 220

as well as Bent 23 adjacent to the curb.

NFESC used a falling weight deflectometer (FWD) and the Impact Load Method (ILM) that was developed to quantify structural performance for condition assessment. The FWD is a trailer-mounted, computer-controlled load-testing device that applies an impact load whose magnitude exceeds all wheel loads that are encountered on Navy piers (Figures 76 through 78). The FWD was specifically built to apply loads up to 130 kips (580 kN) on a 12-inch (30 cm) diameter platten. The length of the load pulse is approximately 30 milliseconds. The FWD has built-in sensors to measure and record histories of the load and displacement in the vicinity of the load.

 

The FWD data processor digitized (at 10,000 samples per second) and converted the analog signals. A portable computer monitored the test progress and stored the digitized load pulse and pier deflection responses. Peak values were selected for comparison with finite element model analysis. All data was stored in computer files compatible with the spreadsheet program, EXCEL©. Each test generated over 3,000 data values.

 

Deflection data was recorded at 12 locations along two orthogonal transducer beams that project from the load point. One transducer beam was aligned with the longitudinal axis of the FWD trailer while the other was transverse. Deflection sensors were positioned along the longitudinal transducer beam at 13 inches (33 cm) aft of the load point, at the load point, and at 16.5, 24, 36, 48.5, and 60 inches (42, 61, 91, 123, and 152 cm) forward of the load point. Displacement sensors were positioned at 13, 24.5, 37, 48, and 60.5 inches (33, 62, 94, 122, and 159 cm) along the transverse transducer beam. The longitudinal transducer beam was normally oriented along the longitudinal direction of the wharf (perpendicular to the transverse bent girders) except at curbside load points where the longitudinal transducer beam orientation was rotated 90 degrees or parallel to the transverse bent girders. Peak deflections from each sensor time history determined the deflected basins that characterize the stiffness of the structural members in the vicinity of the load application.

 

Strain gauges were positioned at crucial locations. NFESC attached 1/2-inch foil strain gauges to carbon rods prior to embedment at the edges of transverse girders and outside rail girder. Five-inch wire gauges were mounted in the epoxy saturate between laminate layers at midspan. Strain response was measured and recorded using a Campbell data logger. The strain under the load point, in neighboring spans and adjacent structural elements was measured. The sample rate was 2,000 data points per second for each gage. Many of the laminate strain gauges were inoperative before the tests began. The probable cause was not obtaining isolation of the wire strain element from the carbon fibers during installation. Strain elements must be electrically isolated from the carbon fibers by complete epoxy encapsulation in future installations.

 

Each load test series consisted of at least four impact load applications at increasing load levels preceded by a small load to set the load platen. Peak loads were approximately 30 kips (135 kN) at Level 1; 55 kips (245 kN) at Level 2; 90 kips (400 kN) at Level 3; and 130 kips (580kN) at Level 4. Increasing load levels provide an opportunity to check the linear load-deflection response of the structure.

 

Example load, deflection, and strain data is presented for the curb slab area, rail slab, and center slab. Figures 79 through 98 have load-, deflection-, and strain-time histories, deck deflection distributions, load-deflection responses, and load-strain responses. The maximum measured response in the external composite reinforcing was less than 600 microstrain (18 ksi (125 mPa) carbon fiber stress). The maximum measured strain in the carbon composite rods was less than 200 microstrain (9 ksi (62 mPa) carbon fiber stress). Except at the center slab span, non-linear behavior was not encountered. The concrete cracking strength of the center slab was exceeded so there was a stiffness change from the first load level to the second, however, the stiffness was constant from the second level to the fourth. NFESC coupled ILM response with finite element analyses (FEA). Analysts compared ILM deflections with those generated by the FEA using the same loading. The finite element model results are in the same order of magnitude (+/-100 percent). The actual structural response is shaped by specific and localized crack networks in the deck that were not modeled. The FEA models provide an accurate representation of the service limits of the pier by precise modeling of the support conditions of the piles, pilecaps and beams.

 

The center slab and the curb slab are crucial areas of the wharf and limit the outrigger loads. The beam and column elements of the utility loop below the curb slab at every bent add little strength and stiffness to the curb slab that cantilevers out from the pile girder. The structural responses are well below the service limit of the composites and should be satisfactory for supporting outrigger loads up to 125 kips (555 kN).

 

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Figure 76. FWD positioned to apply
load to the midspan of the
“Outside Rail Slab”.
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Figure 77. FWD positioned on “Center Slab” to apply load to the middle of the deck between bents and between rail slabs.
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Figure 78. FWD positioned on “Curb Slab” (219-220) to apply load to crucial point at the edge of the wharf.
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Figure 79. Load impulse applied to the midspan of rail slab between Bents 184 and 185.
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Figure 80. Deflection response to impact load at midspan of rail slab between Bents 184 and 185.
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Figure 81. Strain histories of carbon rods measured at Bent 184 for load applied rail slab midspan.
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Figure 82. Strain history of carbon laminate measured below the load point at midspan 184-185.
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Figure 83. Linear load-deflection response of midspan rail slab.
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Figure 84. Linear load-strain response of midspan laminate and carbon rod over Bent 184.
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Figure 85. Deflection distribution about load point at rail slab midspan between Bents 184-185.
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Figure 86. Load impulse applied to the midspan of rail slab between Bents 184 and 185.
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Figure 87. Deflection response of midspan of rail slab to load applied between Bents 184 and 185.
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Figure 88. Strain history of carbon rod measured adjacent to Bent 184 with load at midspan 184-185.
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Figure 89. Load-deflection response of curb slab between Bents 219 and 220.
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Figure 90. Load-strain response of transverse carbon rod between Bents 219 and 220.
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Figure 91. Deflection distribution of curb slab between Bents 219 and 220.
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Figure 92. Load impulse applied to midspan of center deck slab.
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Figure 93. Deflection response at the midspan of the center deck slab between Bents 184 and 185.
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Figure 94. Deflection distribution of load applied midspan of center Deck slab.
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Figure 95. Linear load-deflection response of center deck slab between Bents 184 and 186.
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Figure 96. Center slab midspan laminate load-strain response between Bents 184 and 185.
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Figure 97. Load-deflection response of the “Curb Slab” at Bent 223 (above the utility loop).
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Figure 98. Deflection distribution about load point on curb slab at Bent 223.

 

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ACE Restoration & Waterproofing, Inc.
620 E. Walnut Ave.
Fullerton, CA 92831
714.526.7366
Fax: 714.526.7965

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  ACE Restoration and Waterproofing Quick Service Overview:
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  by ACE Restoration and Waterproofing.

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