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Structural Health Monitoring of the First Geosynthetic Reinforced Soil – Integrated Bridge System in Hawaii

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Structural Health Monitoring of the First Geosynthetic Reinforced Soil – Integrated Bridge System in Hawaii STRUCTURAL HEALTH MONITORING OF THE FIRST GEOSYNTHETIC REINFORCED SOIL – INTEGRATED BRIDGE SYSTEM IN HAWAII A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI‘I AT MĀNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN CIVIL ENGINEERING MAY 2014 By Joseph Brandin Lawrence Thesis Committee: Phillip Ooi, Chair Person Horst G. Brandes Peter G. Nicholson ABSTRACT Geosynthetic reinforced soil is defined as closely-spaced (≤ 12 inches; typically 8 inches) alternating layers of geosynthetic reinforcement and compacted soil. A geosynthetic reinforced soil - integrated bridge system (GRS-IBS) consists of three main components; a reinforced soil foundation (RSF), a GRS abutment, and an integrated approach. GRS-IBS is being promoted by the Federal Highway Administration (FHWA) where GRS abutments are used to support single span bridge superstructure in their Everyday Counts Initiative, which is focused on accelerating implementation of proven, market-ready technologies. There are many advantages of GRS abutments over traditional concrete abutment walls but two of the more notable ones are: (1) elimination of the need to form, pour and wait for the concrete to cure resulting in accelerated construction and significant cost savings; and (2) reduced carbon footprint with less concrete and hence cement (production of 1 ton of cement releases 1 ton of CO2 into the atmosphere) utilized in the abutment walls. The first GRS-IBS in Hawaii was recently constructed in Lahaina, Maui. The superstructure was instrumented with strain gages to measure the effects of concrete shrinkage and the GRS abutments were instrumented to measure footing vertical pressures, lateral pressures behind the end wall and the GRS facing, bridge footing settlement and lateral displacement of the GRS facing. All gages were monitored remotely with the aid of a data acquisition system. From the recorded data, it was observed that (1) the bridge superstructure continually undergoes thermal expansion and contraction; (2) overall the superstructure compressive strains tend to increase and the end wall lateral pressures tend to decrease with time, which is an indication of superstructure concrete shrinkage; (3) the total footing settlement did not exceed 0.9 inch at the time of writing; (4) the measured pressures underneath the footing are consistent with the estimated stress from the superstructure; during construction and (5) the footing cyclically undergoes rotation about a transverse axis causing the vertical pressures to fluctuate cyclically while the lateral pressures behind the bridge end wall are also undergoing pressure cycles consistent with the effects of thermal loading. A finite element analysis was performed to compare results with the measured field data. The analysis yielded nearly identical trends for footing settlement and facing lateral pressure. This helped verify that the observed trends and measured values are reasonable. ACKNOWLEDGMENTS The author would like to thank the Federal Highway Administration (FHWA) for sponsoring this research through their Innovative Bridge Research and Deployment program. Input from Mr. Michael Adams (FHWA) on the design of the instrumentation system was invaluable, for which the author is greatly indebted. The author would also like to thank Ms. Melia Iwamoto for helping with installation and data collection throughout the project. Lastly, Professor Ooi for his advice and support throughout the entire investigation The author acknowledges KSF Inc. for designing the GRS-IBS over the Kauaula Stream. The assistance and coordination provided by the contractor Goodfellow Brothers Inc. with installation and protection of the instruments is invaluable and greatly appreciated. Geokon Inc. helped troubleshoot the data acquisition system, for which the author is most grateful. The review of this work by the thesis committee consisting of Professors Phillip Ooi, Horst Brandes, and Peter Nicholson is also greatly appreciated. Table of Contents Abstract ......................................................................................................................................................... ii AcknowleDgments ....................................................................................................................................... iii 1 Introduction ........................................................................................................................................... 1 1.1 Overview ....................................................................................................................................... 1 1.2 Benefits ......................................................................................................................................... 1 1.3 Objectives ..................................................................................................................................... 4 1.4 Organization .................................................................................................................................. 5 2 Literature Review .................................................................................................................................. 6 2.1 Material ......................................................................................................................................... 6 2.1.1 Facing Elements .................................................................................................................... 6 2.1.2 Backfill Material ................................................................................................................... 9 2.1.3 Geosynthetics ...................................................................................................................... 10 2.2 Lateral Earth Pressure on Wall Facing ....................................................................................... 11 2.2.1 Wu (2007) ........................................................................................................................... 12 2.2.2 Soong and Koerner (1997) .................................................................................................. 13 2.2.3 German Geotechnical Society (2011) ................................................................................. 14 2.3 Mechanically Stabilized Earth versus Geosynthetic Reinforced Soil ......................................... 15 2.3.1 Reinforcement spacing ........................................................................................................ 15 2.3.2 Reinforcement Length ......................................................................................................... 15 2.3.3 Vertical Capacity................................................................................................................. 16 2.3.4 Deformations ....................................................................................................................... 17 2.3.5 Reinforcement Rupture ....................................................................................................... 19 2.3.6 Reinforcement Pullout ........................................................................................................ 20 2.3.7 Connection Requirement ..................................................................................................... 20 2.3.8 Limiting Eccentricity .......................................................................................................... 20 2.4 Case Studies of Monitored Bridges on GRS Abutments ............................................................ 21 3 Kauaula Stream Bridge ....................................................................................................................... 31 3.1.1 Project Overview................................................................................................................. 31 3.1.2 Subsurface Stratigraphy ...................................................................................................... 35 3.1.3 GRS Abutment Materials .................................................................................................... 35 3.1.4 Construction Sequence ........................................................................................................ 39 iv 4 Instrumentation ................................................................................................................................... 51 4.1 Pressure Cells .............................................................................................................................. 51 4.1.1 Vertical Earth Pressure Cells .............................................................................................. 55 4.1.2 Nano concrete tiles .............................................................................................................. 57 4.1.3 Lateral Earth Pressure Cells ................................................................................................ 61 4.2 Inclinometer ................................................................................................................................ 64 4.3 Strain Gage .................................................................................................................................. 71 4.4 Deformation Meter ...................................................................................................................... 77 4.5 PVC pipe and
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