Ice prevention or removal of Veteran's Glass City Skyway cables

Transcription

1 The University of Toledo The University of Toledo Digital Repository Theses and Dissertations 2013 Ice prevention or removal of Veteran's Glass City Skyway cables SeyedAli ArbabzadeganHashemi The University of Toledo Follow this and additional works at: Recommended Citation ArbabzadeganHashemi, SeyedAli, "Ice prevention or removal of Veteran's Glass City Skyway cables" (2013). Theses and Dissertations This Thesis is brought to you for free and open access by The University of Toledo Digital Repository. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of The University of Toledo Digital Repository. For more information, please see the repository's About page.

2 A Thesis entitled Ice Prevention or Removal of Veteran s Glass City Skyway Cables by SeyedAli ArbabzadeganHashemi Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Civil Engineering Dr. Douglas K. Nims, Committee Chair Dr. Cydnee L. Gruden, Committee Member Dr. Terry Ng, Committee Member Dr. Victor J. Hunt, Committee Member Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo December 2013

3 Copyright 2013, SeyedAli ArbabzadeganHashemi This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author.

4 An Abstract of Ice Prevention or Removal of the Veteran s Glass City Skyway Cables by SeyedAli ArbabzadeganHashemi Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Civil Engineering The University of Toledo December 2013 The Veteran s Glass City Skyway (VGCS) is a large cable stayed bridge with single pylon crossing over Maumee River in Toledo, Ohio. This structure was put into service in the summer of 2007 and carries three lanes of traffic in each direction. Under some weather conditions, ice forms on the stays of VGCS. Ice accumulation can exceed one half inch and accumulated ice may persist on the stays for several days. As the stays warm, ice falls from stays and posing a potential a hazard for motorists and requiring lane closures. Lane closure cause inconvenience to public travelling and economic losses. To assist the Ohio Department of Transportation in developing ice hazard mitigation strategies and providing information to assist ODOT in managing the VGCS during icing events, several studies have been carried out. This thesis will address four aspects of ice hazard mitigation on the VGCS. 1) Icing experiment station which was designed, built, and successfully operated 2) Outdoor experiments on the full scale specimens 3) Report the test results 4) Selection of sensors to obtain required information iii

5 5) Design of the anchorage for self-supporting tower. To help the Ohio Department of Transportation, a study which includes an analysis, assessment, and preliminary validation tests of the most viable technologies for anti-icing/deicing of the VGCS stays has been performed. Information for developing an anti-icing/deicing strategy was gathered during outdoor experiments on the full scale sheath specimens. Sensors which give a better understanding of the microclimate of the VGCS before, during, and after of icing events were chosen. A self-supporting instrumentation tower was selected and installed on the median of the VGCS to gather data from sensors, and improve the performance of the dashboard. Typical double-nut anchorage system based on AASHTO sign specification was designed to support the instrumentation tower on the median of the VGCS. iv

6 Acknowledgements I take this opportunity to express my thanks and acknowledge to my advisor Dr. Douglas K. Nims for his encouragement and continuous support during my master study. I would like to thank Dr. Ng for his support and directions during my research. I also would like to thank Dr. Gruden and Dr. Hunt for being on my committee. I thank University of Toledo students Mr. Owjan Hashtroodi, Mr. Hamed Ghaedi, and Mr. Nutthavit Likitkumchorn for their assistance in setting up the Scott Park Campus icing experiments. I also would like to thank University of Cincinnati graduate students Mr. Jason Kumpf and Mr. Biswarup Deb for their efforts in development of dashboard and installation of bridge sensors. This project was sponsored by the Ohio Department of Transportation. The author gratefully acknowledges their financial support for both this study and also installation of instrumentation tower. The author also would like to thank ODOT personnel Mr. James Bradley and Mike Gramza for their support in tower design and overall supervising during this project. v

7 Contents Abstract... iii Acknowledgements... v Contents... vi List of Tables... viii List of Figures... ix List of Abbreviations... xii 1 Introduction Statement of the Problem Bridge General Information Stay Description Objective Overview Chapter History of Icing Events on the VGCS Lessons Learned from the past Icing Events Literature Review Technology Matrix Most Viable Technologies for VGCS vi

8 3 Managing Icing Events Background Ice Fall Dashboard Sensors Available Sensors Additional Sensors Self-Supporting Instrumentation Tower Tower design Anchorage System Design Design Outdoor Experiments on the Full Scale Specimens Data Acquisition System and Sensors Icing Simulation Experiments Chemical Experiments Coating Experiments Conclusion and Future Work Conclusion Future Work References A Anchorage Design Calculations B Rohn Calculation vii

9 List of Tables 2.1 Ice Accumulation Weather Condition Ice Falling Weather Conditions Most Viable Solution Ice Accumulation and Ice Shedding Criteria Uncertainties that Need to be Resolved List of Thermistors Abbreviations..34 viii

10 List of Figures 1-1 Ice Accumulation on the East Side of the VGCS Ice on the Pylon and the VGCS Glass Large Piece of Almost Ice Hitting a Car Veteran s Glass City Skyway Schematic of Stay Cable Cross-Section Ice Accumulation Pattern, Febrarury 20 th, Ice Accumulation Patten, February 23rd, Weather Summary for the Week of 2011 Icing Event Solar Radiation, February 24th, Application of Hydrophobic Coating on the Surface DC Bias Deicing where Electrolysis forms Bubbles Pulse Electro Thermal Deicing (PETD) Ice Being released using Dielectric Heating Navy Vertical Launch Systems with Electrically Heated Door Edges Infrared heaters above CRREL Entrance Aviation Facility using Infrared Radiant System Photonic deicer for deicing of power lines Process Diagram ix

11 3-2 Dashboard Readout for February 21, Goodrich Ice Detector Leaf Wetness Sensor Location of Thermistors on VGCS (Stay 8 and 20) Themistors on the VGCS Crack on the Ice Layer with Liquid Water Thermistors Block Stay Temperature 16 th to 17 th of January Stay Temperature 2013 Minor Icing Event Stay Temperature 15 th to 16 th of May Sunshine Sensor Campbell Scientific Rain Gage Installation of Rohn Tower on Median of the VGCS Tower Anchorage System Google Earth Shot of Scott park Experiments Setup Sensors on South-faced Specimen Data Acquistion System Spraying a Mist of water on North-faced Specimen Pattern of Ice Accumulation on Outdoor Tests Water Beneath the Ice Layer before Shedding Ice Shedding Steps Stay s Behaviour in Icing Test 2/15 to 2/ x

12 4-10 Stay s Behavior in Icing Test 2/20 to 2/ Formation of Ice in Chemical Anti-icing Test Drip Tube System used in Chemical Deicing Test Hydrobead Sprayed on the half of Specimen Water Droplets due to Hydrobead Specimen s Behavior in Coating Test xi

13 List of Abbreviations AASHTO American Association of State Highway and Transportation Officials ACI.American Concrete Institute AISC..American Institute of Steel Construction ASD Allowable Stress Design CRREL Cold Region Research Laboratory EEDS..Electro-expulsive Deicing Systems HDPE...High Density Polyethylene LRFD..Load and Resistance Factor Design LWS Leaf Wetness Sensor ODOT...Ohio Department of Transportation PETD...Pulse Electro Thermal Deicing RWIS..Roadway Information System TEO Thermistor East Outer TES Thermistor East Sheath TLS.Thermistor Lower Sheath TUO Thermistor Upper Outer TUS Thermistor Upper Sheath TWS...Thermistor West Sheath VGCS...Veteran s Glass City Skyway xii

14 Chapter 1 Introduction 1.1 Statement of the Problem The Veteran s Glass City Skyway is a large cable-stayed bridge with a single pylon crossing over Maumee River in Toledo, Ohio. The VGCS is owned by Ohio Department of Transportation and is considered as the most expensive project ever undertaken by ODOT (Wikipedia, 2013). Under some winter conditions, ice forms on the stay cables of VGCS. Ice accumulation can exceed one half inch and accumulated ice may persist for several days on the stays. As the stays warm, ice sheds from the stays in cylindrical sheets. The sheets may fall over 250 feet to the roadway and can be blown across several lanes of traffic. Ice sheds from the stays in less than a minute. The potential of falling sheets requires lane closure for the duration of the ice persistence. The VGCS, which is an important connector for multimodal transportation and economic development, has thousands of vehicles crossing daily. Lane closures cause inconvenience to traveling public and loss to economic activities. Falling ice is a safety hazard to motorist and determining ice 1

15 presence remotely is problematic. Determining ice presence manually puts ODOT personnel in harm s way. At this time, there is no existing anti-icing/deicing technology that appears to be practical for mitigating the icing problem on the VGCS. This means the solution may be a combination of existing technologies or completely a new approach. The Ohio Department of Transportation has contracted The University of Toledo to design and develop a viable anti-icing/deicing solution for VGCS icing problem. This study is the phase two of an extended icing contract with Ohio Department of Transportation. Figures 1-1 and 1-2 show ice accumulation on the stays and pylon of VGCS in the 2011 icing event. Figure 1-1: Ice Accumulation on the East Side of VGCS 2

16 Figure 1-2: Ice on the Pylon and the VGCS Glass Figure 1-3, which was captured during 2011 ice fall event, shows a large piece of ice falling into the third lane of traffic while vehicles are still crossing over the bridge. Red circle shows a piece of ice which nearly hit a car (Belknap, 2011). Figure 1-3: Large Piece of Ice Almost Hitting a Car (Belknap, 2011) 3

17 1.2 Bridge General Information Veteran s Glass City Skyway, previously known as the Maumee River Crossing, is a large cable stayed bridge crossing over Maumee River on Interstate 280 in Toledo, Ohio. The VGCS is one of two installations of a new cradle system which eliminates the anchorage system on the pylon by carrying the stays from one side of the bridge deck to another side. The construction of this structure began in 2001 and the bridge was put into service in the summer of VGCS carries three lanes of traffic in each direction. The entire project consists of 8,800 feet of approaches and main span. The main span is cablestayed type bridge with a single pylon of approximately 216 feet above the bridge deck and two approaches on each side. The north bound approach is approximately 4,000 feet and south bound approach is approximately 3,350 feet. Figure 1-4 shows VGCS s main span on Maumee River and part of the approaches. Figure 1-4: Veteran's Glass City Skyway 4

18 1.3 Stay Description The VGCS stays consist of a sheath and epoxy coated strands. The sheaths are made of 316L stainless steel. The VGCS stays have 82 to 156 strands depending on their location. The outer diameter of the stays is either 18 or 20 depending on number of strands inside of them. The thickness of the sheath is 1/8. The stay sheaths of the VGCS serve no structural function. They cover and protect the epoxy coated prestressing strands. Brushed stainless steel was chosen for its low life cycle cost and aesthetic qualities rather than conventional high density polyethylene (HDPE). Figure 1-5 shows a schematic of the sheath resting on the epoxy coated strands at mid-height of a long stay. Figure 1-5: Schematic of Stay Cable Cross-Section 5

19 There are several unique features of the VGCS stays which make them susceptible to ice accumulation and shedding process. The VGCS stays are made of stainless steel. It is hypothesized that heat properties of stainless steel may affect how ice accumulates or sheds on stays. The stainless steel transmits heat faster than the conventional HDPE. The VGCS stays have larger diameters compared to other cablestayed bridges. Larger diameter causes the formation of larger pieces of ice. The stays have a brushed surface for reflecting the light from pylon and the sun. Brushed surface may influence the way ice accumulates on the stay. 1.4 Objective The objective of this work were 1) To build an icing experiment station which should replicate the ice accretion and shedding behavior of the VGCS, 2) Conduct experiments that evaluate if the icing experiment station could be used to experiment on techniques for control of icing including coating, deicing chemicals and internal heating of the stays and serve as a test bead for instruments used to monitor icing, 3) Report the test results for the work on coating, chemicals, and internal heating 4) Selection of sensors to obtain required information 5) anchorage design of the instrumentation tower. 1.5 Overview The overall objective of this phased project is to help ODOT in implementing an anti-icing/deicing strategy for the VGCS and manage icing events. The goal is that the VGCS will have the same level of reliability during icing events as the other ODOT transportation systems. No existing ice prevention or removal strategy seems to be 6

20 practical of VGCS. Thus, the solution may be the combination of existing active and passive technologies or completely new one. The first phase of this study focused on the review of all identified technologies without regard to practicality, a background study which included weather conditions for the past icing events on VGCS, an assemblage of a comprehensive data base of existing solutions, a study of the advantages and disadvantages of technologies, on-site observation and collecting data from the 2011 icing event (Nims, 2010). The work documented here is part of the second phase of this study. The work completed includes: 1) Icing experiment station which was designed, built, and successfully operated during icing season of ) Outdoor experiments on the full scale specimens to begin resolving several uncertainties for designing an effective anti-icing/deicing technology 3) Report the test results 4) Selection of sensors to obtain required information to manage ice events 5) Design of the anchorage for self-supporting tower which supports the sensors. 7

21 Chapter History of Icing Events on the VGCS Five icing events have occurred on the VGCS. Kathleen Jones, CRREL expert and research team member, has prepared a report which describes the first four icing events and the conditions which caused them (Jones, 2010). The last event which occurred in February 2011 was documented by the University of Toledo graduate students. The icing events and basic features are listed in Table 2-1 and Table 2-2. Table 2-1: Ice Accumulation Weather Conditions Ice Event December 2007 March 2008 December 2008 January 2009 February 2011 Precipitation Event Freezing rain and Fog Snow, rain, and fog Snow and fog; freezing rain and fog Freezing rain and fog Freezing rain, clear 8

22 Table 2-2: Ice Falling Weather Condition Ice Event December 2007 March 2008 Ice Fall Weather Rain with temperature above freezing Sun with temperature above freezing December 2008 January 2009 Rain, gusty winds and temperatures above freezing Gusty winds, temperature above freezing February 2011 Light wind, overcast, and temperature above freezing Freezing rain has happened four times in the icing events and is considered as the most probable cause for icing events. Freezing rain requires cold air below freezing at ground level, warm air aloft, a high pressure to hold the cold air in the place, and precipitation of liquid water. The duration of an icing event depends on how long the high pressure stays in the place and liquid precipitation rather than ice pellets falls. It is also possible for wet snow to accumulate on the stays and cause an ice event. This snow can turn to ice when the air temperature is above freezing. That means, an ice event can begin with the atmospheric temperature above freezing. Icing on the cables of VGCS may also occur in super cooled clouds or fog. The ice accumulation may increase with decreasing visibility in the fog. 9

23 2.2 Lessons Learned from the past Icing Events To have a better understanding of icing events, nature of ice formation and ice falling, and what happens during ice storms, a brief summary and lessons learned from past icing events on the VGCS is presented below. Jones report describes the first four icing events and weather conditions which preceded them (Jones, 2010). The last icing event, February 2011, was captured and documented by the University of Toledo graduate students (Belknap, 2011). December 2007: First record showed that ice shed from the VGCS stays on December 12 th. The data from Toledo Express Airport and Metcalf Field showed freezing rain and freezing fog on December 9 th 10 th caused ice accretion on the stays. Rainfall with temperature above freezing triggered the ice shedding from stays. March 2008: The formation of ice on the stays was observed with temperature above freezing on March 28 th. Weather data showed a snow and rain with temperature below freezing, concurrent with a fog which caused ice formation on the stays. Clear sky and air temperature above freezing on the March 28 th were considered as shedding triggers. December 2008: on December 17 th, ice was first observed on the stays. The icing event took 7 days until the ice fell off the stays on December 24 th with temperature above freezing. Data gathered from Toledo Express Airport, Metcalf Field, and Toledo Blade showed that freezing rain, snow, and fog were the conditions which caused ice accretion on the stays. 10

24 January 2009: Ice first was observed on January 3 rd and fell on January 13 th. The data from airport weather stations showed that freezing rain accompanied by fog caused accumulation of ice on the stays. Temperature rising above freezing on January 13 th caused ice to fall from the stays. February 2011: This icing event was observed and recorded from ice formation on the evening of February 20 th through the ice shedding on the morning of February 24 th. On February 20 th s night, the RWIS station on the bridge reported freezing rain, then a drop in temperature. The wind was from the east side and clear ice with few air bubbles (glaze ice) was deposited by the freezing rain. By the morning, the ice on top of stay cable was ¼ inch thick, on the east side about ½ inch thick, on the bottom there were small icicles and ice was about ½ inch thick. On the west side, the stay was bare except some frozen rivulets. Figure 2-1: Ice Accumulation Pattern, February 20th, (Belknap, 2011) 11

25 The ice remained on the stays on February 21 st. On February 22 nd, the temperature started at 15 F and rose to 21 F by afternoon then dropped to 10 F again. Although the air temperature was below freezing, the sun was out and solar radiation was 575 watts m 2 and causing the presence of liquid water between the ice layer and stay sheath. Even when the temperature is below freezing, a greenhouse effect causes a layer of water to exist between the ice layer and stainless steel sheath. This water layer can trigger ice falling when the sun is bright. Ice fall was imminent, however, the ice did not fall before the temperature dropped and the liquid water refroze at the end of the day. The ambient temperature was below freezing on February 23 rd and overcast. UV radiation penetrated the clouds and warmed up the stay sheath. The resulting infrared radiation could not escape the interstice between the sheath and the ice in the interstice got warmer than ambient temperature and causing the presence of liquid water. Figure 2-2: Ice Accumulation Pattern, February 23rd, (Belknap, 2011) 12

26 Ice fall event happened at the morning of Thursday February 24 th. Ice fall event started at 8:30am. Ice would begin to fall somewhere along a stay. Then all the ice on that stay would unzip. An entire stay would be clear of ice in less than a minute. Most of the ice fell straight to the pavement., but if there was a breeze or a piece of ice caught the air falling down it could blow over the side of the bridge (see Figure 1-3). Traffic was stopped at 9:30am. The ice continued to fall until 11 am. At that time 80% of the ice had already fallen. Some pieces of ice remained on the pylon glass and stays at the pylon. Weather conditions at the time of the ice fall were air temperature above freezing, overcast, and light wind coming out from the west. The bridge was closed for the rest of the day. Start of Ice Shedding Figure 2-3: Weather Summary for the Week of 2011 Icing Event. (Belknap, 2011) 13

27 Start of Ice Shedding Figure 2-4: Solar Radiation, February 24th, (Belknap, 2011) In Jones report (Jones, 2010), the common factor for shedding for all previous events was temperature above freezing which accompanied by rain, wind, or sunshine visibility. For this last ice event, the temperature was above freezing, a light wind came from east, and the sky was cloudy. 2.3 Literature Review Icing is a worldwide problem for large bridges and other industrial facilities in cold climates; therefore, a broad literature on anti-icing/deicing technologies was reviewed. The main literature sources are two reports and a paper on icing for off-shore oil industry written by Charles C. Ryerson, CRREL expert and research team member (Ryerson, 2008, 2011, and 2013). Ryerson in his reports addresses 16 different technologies which would be applicable in oil industry. Wind turbines have experienced the same icing problems like VGCS. Parent has a review which was addressing critical techniques for anti-icing/deicing of wind turbines (Parent, 2011). Chemicals are considered as both deicing and anti-icing technologies. They are widely available commercially and are used in several industries such as aviation, off- 14

28 shore oil industry, transportation departments, and marine structures. Chemicals can be applied as both dry and wet applications. In anti-icing, chemicals are either used to reduce the adhesion strength between ice layer and the substrate or prevent from the formation of ice. In deicing technology, chemicals are usually used to melt ice layers during or after ice storms. The most widely used chemicals are calcium chloride, magnesium chloride, potassium chloride, calcium magnesium acetate, urea, and agricultural based chemicals. The concerns about chemicals are environmental, corrosion issues and application persistence. Coating is another technology which is an active subject of development and testing. Coating is a passive anti-icing technology which means they are applied to the surfaces to reduce the adhesion strength of ice to the surfaces and prevents the formation of ice on the surfaces (Ryerson, 2008). Kulinich in his work evaluated ice repellency of rough hydrophobic coating in different materials with different surface topographies (Kulinich, 2011). New approach of this technology would be the development of super hydrophobic material which causes water to bead into small droplets. Menini developed new coating with ice phobic characteristics on aluminum alloys which is widely used for several industries such as transmission lines, aircraft wings, and fuselage (Menini, 2011). Fig. 2-5 shows water droplets on the surface which is covered by hydrophobic coating. 15

29 2008). Figure 2-5: Application of Hydrophobic Coating on the Surface (Ryerson, Concerns with coatings are efficacy in preventing of ice formation on the surfaces and their persistence through the winter. New designs, materials, and details can be considered for new cable-stayed bridges in cold climates to prevent ice accumulation on their stays. Recently, innovative deicing technologies have been developed which use electricity as a technique to melt ice. These techniques cause ice to melt at the ice/substrate layer and using some external forces to remove the ice from the substrate. Electrical techniques have developed in three fundamental subcategories. These techniques are 1) application of a DC bias voltage to the ice/substrate interface, 2) pulse electro-thermal deicing, and 3) ice dielectric heating (Ryerson, 2008). In the first technique, small DC current is applied to the ice/substrate interface through conductors to reduce the adhesion strength. Figure 2-6 shows the presence of bubbles in the interface which helps in removing the ice. 16

30 Figure 2-6: DC Bias Deicing where Electrolysis forms Bubbles (Ryerson, 2008) In pulse electro thermal deicing, a thin film conductor is used in the interface which melts the thinnest ice layer and external energy, wind or gravity, is used to remove the ice. The best reference of that technology is a paper which was written by Petrenko (Petrenko, 2011). In this paper, Petrenko presents the pulse electro thermal deicing (PETD) method, its theory, results of computer simulations, and extensive data from laboratory tests as well as several large-scale implementations. One of the promising features of this method would be the low energy for deicing. Figure 2-7 shows a thin metal-foil heater which is used in the ice/substrate interface to melt the ice layer. 17

31 Figure 2-7: Pulse Electro Thermal Deicing (PETD) (Petrenko, 2011) One of the implementations of PETD is the Uddevalla Bridge in Sweden (Petrenko, 2011). A system in current usage was installed on one cable which is over 200m in length and 25cm in diameter and one pylon. The system is not used anymore on Uddevalla Bridge. The third electrical technique is ice dielectric heating. That method uses high frequency excitation from 60 khz to 200 khz to melt ice layer. Figure 2-8 shows ice layer releasing from electrical transmission cable using ice dielectric heating method. 18

32 2008) Figure 2-8: Ice Being Released using Ice Dielectric Heating (Ryerson, The next technology which is considered as new technology, 20 years old, is electro-expulsive deicing systems (EEDS). EEDS uses a variety of technologies to create small amplitude and short duration pulses to remove the ice from the substrate. The most common one is an electrically actuated system which was designed and developed by NASA Ames (Ryerson, 2008). There are several technologies which use heat as a method to deice or anti-ice structures. The most applicable ones are electrothermal, hot air, and water deicing. Electrothermal heating is using electrical resistance as a source in deicing or antiicing. In electrothermal heating, heating of substrates occurs as a result electricity conducted through wires such as nichrome wires or carbon layers. That method is 19

33 considered as the most efficient heating system due to fact that all of energy conducted through the wires is converted to heat. An example of this method is the heating of the automobile windows. Figure 2-9 shows an application of heating cables to prevent icing of hatches and bulk-head doors which is used by Navy. Figure 2-9: Navy Vertical Launch Systems with Electrically Heated Door Edges (Ryerson, 2008) Another source of heat for deicing and anti-icing is hot air. The example of this technology is the automobile windshield defroster. Hot air is used widely in the aviation industry. The U.S. Air Force used jet engines mounted on the trucks as a source of energy to blow warm air across the wings of iced aircraft (Ryerson, 2008). for deicing. The last category of heating technology is using hot water as a source of energy 20

34 Hydraulic and steam system is another technology which uses the high pressure water jets to remove ice from surfaces. The Navy considers this technology to be viable and less expensive for deicing of ships (Ryerson, 2008). The efficiency of hydraulic system is dependent to variety of factors such as: nozzle size, flow rate, wind, and distance. Another technology which is considered as a unique technology is infrared deicing. This method is a kind of remote technology which heats the objects through absorption of infrared energy. There are still additional experimental and analytical needs to understand the deicing process using infrared heaters (Koeing, 2011). Figure 2-10 shows using electric infrared heaters to deice door entrance at Cold Region Research Laboratory (CRREL) facility. Figure 2-11 also shows the application of infrared deicing in the aviation industry. 2008) Figure 2-10: Infrared heaters above CRREL Entrance (Ryerson, 21

35 Figure 2-11: Aviation Facility using Infrared Radiant System (Ryerson, 2008) Millimeter wave technology is another technology for deicing and detecting the presence of ice on the surfaces. The ice naturally absorbs microwave energy and heats. That technology is applicable to any situations where water is available to absorb microwave energy and heat the surfaces (Ryerson, 2008). Cables especially transmission and power lines have significant experiences from icing problems. Due to the nature of that problem, a broad range of studies either deals with the ice accretion mechanism or removal strategies have in that area. Generally several technologies can be applied to keep the cable from ice accumulation. Dalle had a study which summarized accumulation mechanism of wet snow on overhead lines(dalle, 2011). Couture introduced the smart power line concept and using photonic deicer to melt accumulated ice on power lines (Couture, 2011). 22

36 2011) Figure 2-12: Photonic deicer for deicing of power lines (Couture, 2.4 Technology Matrix The objective of literature review was to assemble a comprehensive list of all solutions for VGCS. To reach that goal, a technology matrix which has a description of the technology, a discussion of its advantages and disadvantages, a rough estimate of the cost of each technology, and the status was developed (Belknap, 2011). The technology matrix lists 75 potential technologies in 13 different categories. The categories of technologies include: 1- Chemical and chemical distribution: Anti-icing/deicing chemicals such as salt or agricultural base products and practical systems to distribute them. 2- Coatings: A layer applied to the surface of the sheath which prevents ice accretion on surfaces. 3- Design: Changing the shape of stays sheath to prevent ice accumulation. 23

37 4- Electrical deicing systems: Using repelling forces between conductors to produce an explosive force that ejects ice from the sheath. 5- Pneumatic expulsive deicing systems: That is the system which inflatable boot covers the stays. When the boot is inflated, the ice cracks and falls down. 6- Heat: Use of thermal systems to prevent formation of ice or remove accumulated ice. 7- Infrared radiant heat: Use of radiant infrared heating to warm up the stays to prevent ice accumulation or remove accumulated ice. 8- Heating the ice-substrate interface: Applying heat directly to the interface between the ice and sheath. This reduces energy demand. 9- High-velocity water, air, or steam: Use of a high velocity stream of fluid to force the ice to fall off from stays. 10- Manual deicing methods: Chip or scrape ice off the stays. 11- Piezoelectric: Attach a piezoelectric actuator to the sheath surface to break the bond of ice to the stay and ice falls off the stairs. 12- Vibration or covers: Using vibration to break the ice-surface bond or covering the stays to prevent ice formation. 13- Ice detection: Sensors can monitor ice accumulation or detect the presence of ice. 24

38 2.5 Most Viable Technologies for VGCS Solving icing problem of the VGCS is considered as an applied research instead of basic research. Due to this fact, a technology selection meeting was held in June The notes for advantages and disadvantages of the technology matrix are available in a report which was submitted to ODOT, Innovation, Research and Implementation Section (Nims, 2010). Table 2-3 summarizes the most viable technologies which seem to apply for the icing problem of VGCS. Table2-3: Most Viable Solution for VGCS Category Specific Technology Chemicals Coating Sodium Chloride Agricultural Products Beet Heat Calcium Chloride Hydrobead Internal Heating Heat - Forced air - Air with piccolo tube - Steam heating element 25

39 Chapter 3 Managing Icing Events 3.1 Background Managing of ice events requires information on the microclimate of the VGCS. ODOT Roadway Weather Information System (RWIS) and Meteorological Aviation Reports (METAR) from local airports have been used by research team members and ODOT personnel to monitor potential icing events. This chapter describes the additional sensors which have been selected to have a better understanding of the microclimate of the VGCS and the design of self-supporting tower which supports them. For this data to be actionable, the sensor output must be easily used by the bridge operators. The translation of raw data to readable information is handled on the VGCS by the ice dashboard (Kumpf, 2012). 3.2 Ice Dashboard A virtual inference system with a web-based dashboard was developed and implemented by the research team to help ODOT s personnel in managing upcoming icing events. This program also allows team member researchers to monitor conditions 26

40 when ice accumulation is possible, conditions of ice persistence, and conditions when an ice fall is more likely (Kumpf, 2012). Figure 3-1 shows the diagram of entire process of dashboard (Agrawal, 2011). Figure 3-1: Process Diagram (Agrawal, 2011) Jones study of the past icing events on VGCS lead to dashboard criteria for ice accumulation and ice falling (Jones, 2010). Table 3-1 summarizes ice accumulation and falling criteria. Table 3-1: Ice Accumulation and Ice Shedding Criteria Criteria Ice Accumulation Description - Air temperature below freezing and precipitation type is rain - Air temperature below freezing and fog - Air temperature above freezing and precipitation type is wet snow Ice Fall - Air temperature above 32 F (warm air) - Clear sky (solar radiation) 27

41 Dashboard speedometer gauge consists of four sections. Green part means there is no ice on the stays. Yellow part shows ice accumulation process on the stays. If 80% of the total records (gathering data from available sensors, section 3-2) meet any or a combination of ice accumulation criteria, then the dashboard reports formation of ice on the stays in one timing cycle. Orange part shows ice persistence on the stays. This section monitors ice accumulation and shedding criteria simultaneously and considered as a transition part. The last part of speedometer gauge is red. This part monitors ice shedding on the stays. If 80% of total records meet ice fall criteria, then the dashboard reports the possibility of falling of ice in one timing cycle. The performance of dashboard during 2011 icing event was proved to be successful especially in determining ice accumulation and persistence. Figure 3-2 shows the readout of dashboard for the ice accumulation and persistence of 21 st of February, 2011 icing event. Figure 3-2: Dashboard Readout for February 21,

42 3.3 Sensors Available Sensors There are some sources of information which are used to understand the weather conditions before, during, and after of icing storms. The main local source is the ODOT roadway information system (RWIS) which was installed on the VGCS. The following information can be collected from this station (Nims, 2010). 1- Wind speed and direction. 2- Air temperature, dew point, and relative humidity. 3- Type of precipitation, intensity, and visibility. 4- Traffic count, vehicle length, and speed. Additional weather information can be collected from Toledo Express Airport, Toledo Executive Airport. Temperature, dewpoint, wind speed and direction, cloud cover and heights, visibility, barometric pressure, precipitation amount, lightning can be collected from airport stations (Agrawal, 2011) Additional Sensors Presently, the information on icing events is from limited direct observation on the bridge and limited local weather conditions at either RWIS or Airport stations. There is insufficient information concerning the ice accumulation conditions, ice falling 29

43 conditions, and microclimate of the VGCS before, during, and after icing events. This information is necessary to develop some types of anti-icing/deicing technologies, to help ODOT to anticipate the icing events and take the necessary action to inform the public and keep them safe, and improve the performance of the dashboard for managing the icing events. Table 3-2 summarizes the required information for managing upcoming icing events which eliminates the need for ODOT personnel to manually check icing conditions. Table 3-2: Uncertainties that Need to be Resolved Required Information Presence of Ice Stay Temperature Sky Solar Radiation Local Weather Conditions Visual records of icing conditions Uncertainties that need to be resolved It is difficult to be certain when ice accumulates on the stays except field observation. Ice thickness also triggers the criteria in falling conditions The temperature of the VGCS stays during icing events is unknown. This temperature is considered as one of the reasons for falling conditions Solar radiation can cause the sheath surface temperatures to go above freezing even if the ambient temperature is below freezing. This can trigger shedding of ice off the stays The VGCS has its own climate. Type and amount of precipitation, wind speed and direction need to be determined Observation of the stays condition during icing events can be valuable 30

44 Below are detailed descriptions of the sensors selected to gather the information recommended in Table Goodrich Ice Detector: There is no record of ice presence on the VGCS stays other than field observation which has been made during past icing events. Ice presence is indicative of ice falling possibility. Ice also can leave the stays through sublimation instead of shedding. The rate of ice accumulation is another uncertainty. This rate can dictate response lead time for an active anti-icing/deicing system. The Goodrich ice detector detects ice accumulation on an ultrasonic axially vibrating tube. It also measures precipitation transitions between liquid and solid condition (Goodrich, 2009). One of the unique features of this sensor is that it differentiates rain from freezing rain. Figure 3-3 shows Goodrich ice detector which is tested during baseline ice simulation experiment at Scott Park. Figure 3-3: Goodrich Ice Detector 31

45 2- Leaf Wetness Sensor: Leaf wetness is a parameter which is used to describe the amount of dew or precipitation left on the surface. This sensor is widely used for agricultural purposes to detect the presence of moisture on foliage and calculate the duration of wetness. The LWS has a potential to detect if water is liquid or frozen. The LWS is using dielectric constant to detect the difference between water or ice on its upper surface. Figure 3-4 shows LWS with a light coating of ice which was installed on the full scale specimen to Scott Park to detect the presence of ice. Figure 3-4: Leaf Wetness Sensor 3- Thermistors: Ice accumulation and ice falling directly depend on stays behavior before, during, and after icing storms. The history of the VGCS sheath s temperature is unknown. To have a local measurement of stay temperature during events to design an accurate anti-icing/deicing strategy, an array of thermistors was installed on VGCS stays. Figure 3-5 shows the location of thermistors on the bridge on stay 20 (span 7) and stay 8 (span 28). 32

46 Figure 3-5: Location of Thermistors on VGCS (Deb, 2013) The thermistors arrangement, which is shown on figure 3-6, was selected to monitor the temperature at the stay sheath. East Figure 3-6: Thermistors on the VGCS Table 3-3 summarizes a list of abbreviations which was used on figure

47 Table 3-3: List of Thermistors Abbreviation Abbreviation TUO TUS TEO TES TLS TWS Description Thermistor Upper Outer Thermistor Upper Sheath Thermistor East Outer Thermistor East Sheath Thermistor Lower Sheath Thermistor West Sheath Upper and east facing thermistor blocks report both the ambient and the sheath (surface) temperatures. This arrangement was selected due to the field observation of 2011 icing event. On 22 nd of February of 2011, solar radiation raised the sheath s temperature above freezing which caused the presence of liquid water below ice layer. That water reduced the adhesion strength between sheath and ice which increased the probability of ice shedding even if the ambient temperature was below freezing. Figure 3-7 shows crack in the ice on the sheath with liquid water below the ice layer. Figure 3-7: Crack on the ice layer with liquid Water 34

48 West and lower blocks report the sheath temperature. Custom design Geokon thermistors which fit with the existing data acquisition system were chosen to report the VGCS s sheath temperature. Figure 3-8 illustrates the cross section design drawing of the Geokon thermistors, details of the mounting block and an overview of the temporary installation of a thermistor at the Scott Park. Figure 3-8: Thermistors block Data from three days was selected to monitor the performance of thermistors on the VGCS stays. The first data which is shown in figure 3-9 illustrates the VGCS stay s temperature of 16 th to 17 th of January As shown in the figure, all of thermistors have a consistence performance after sunset to the next sunrise. Solar radiation after rising of the sun causes a dramatic increase in upper and east faced thermistor s 35

49 temperature. Later in a day, the west faced thermistor s temperature is increasing gradually until the sunset which again all of thermistors report the consistent temperatures. Temperature (F ) /15/ :31 1/16/2013 4:19 1/16/2013 9:07 1/16/ :55 1/16/ :43 1/16/ :31 1/17/2013 4:19 1/17/2013 9:07 1/17/ :55 1/17/ :43 1/17/ :31 TUO TUS TEO TES TWS TLS Time Figure 3-9: Stay Temperature - 16 th to 17 th of January 2013 The next data shows the February 26 th, 2013 minor icing event. In the afternoon, ice accumulation on the stays was reported. At 3:30 pm, the thickness of ice ranged up to ¼ inch. Later in the evening, the ambient temperature rose up above freezing which caused the stays to became clear of ice. The ice melted and ran down the stays without shedding. Figure 3-10 shows the temperature of the VGCS sheaths during this icing event. 36

50 :54:14 13:06:14 14:18:14 15:30:14 16:42:14 17:54:14 19:06:14 20:18:14 21:30:14 22:42:14 Temperature (F ) TUO TUS TEO TES TWS TLS RWIS Time Figure 3-10: Stay Temperature Minor Icing Event As shown in figure 3-10, ambient temperature after 5:45 pm increased above freezing which caused the melting of ice layer on the stays. The difference between the RWIS station and other sensors shows how RWIS does not adequately represent the stays temperature for anticipating shedding or in this event, melting conditions. The last data monitors the stay s temperature from 15 th to 16 th of May The stay shows a consistent behavior same as the first data. The stay s temperature increased to 110 F during day time and drops to 60 F during night time. Figure 3-11 shows the sheath temperature during this period. 37

51 /14/ :31 5/15/2013 7:14 5/15/ :58 5/15/ :42 5/16/2013 6:25 5/16/ :09 5/16/ :53 Temperature (F ) TUO TUS TEO TES TWS TLS RWIS Time Figure 3-11: Stay Temperature 15 th to 16 th of May Sunshine Sensor: It has been observed that solar radiation on the VGCS stays is a condition that can trigger ice shedding. On 22 nd of February of 2011, solar radiation raised the sheath s temperature above freezing which caused the presence of liquid water below the ice layer. That liquid water is considered as condition which triggers the ice shedding. Sunshine sensor measures global and diffuse radiation. This sensor also measures sunshine duration. Sunshine sensor uses photodiodes with a computer generated shading pattern for measuring solar radiation (Delta-T Devices, 2002). 38

52 Figure 3-12: Sunshine Sensor 5- Electrically Heated Rain and Snow Sensor: It is an electrically heated precipitation gage which provides year-round measurement of rain and snow. It has been observed that ice accumulation and ice persistence depend on the rate and amount of precipitation. This sensor also uses wind screen to minimize the effect of wind on the rain measurement (R. M. Young, 2011). Figure 3-13: R. M. Young Rain Gage (Deb, 2013) 39

53 6- Weatherproof Camera: The goal of having active weatherproof camera on the self-supporting instrumentation tower is to observe the unquantifiable aspect of icing events and track the performance of dashboard. Reviewable visual record of icing events gives valuable information before, during, and after storms. 3.4 Self-Supporting Instrumentation Tower Tower design VGCS. The ROHN self-supporting tower was chosen to support the instruments on the Figure 3-14: Installation of Rohn Tower on Median of the VGCS Tower design is in accordance with national standard ANSI/EIA-222-F and ANSI/TIA-222G. In Rohn design report, tower elements were analyzed as three 40

54 dimensional beam models. Beam element is considered as two nodes element with three degree of freedom at each nodes (Two translations and one rotation). Calculations for anchorage system are based on maximum factored reactions, maximum download reaction: 21.3 kips - Maximum uplift reaction: 20.4 kips - total shear reaction: 1.73 kips and over turning moment: kips-ft. Rohn self-supporting tower is divided equally to three sections, 45GSR for upper and middle sections and 45GSRH for lower section which has stiffer diagonal and horizontal sections. The Rohn design assumed the base of the tower was 120 feet above the ground. Following design criteria: 360 degree wind orientation per 30 degree increment, Basic wind speed (no ice) = 90 mph, Basic wind speed (with ice) = 40 mph, Design ice thickness = 1.0", Exposure category = C, Structure classification = II, Topography category = 1. Maximum compressive and tensile forces in legs are 20.4 kips and 19.6 kips. Considering governing compressive capacity, 44.4 kips, and governing tensile capacity, 51.7 kips, the demand to capacity ratio of 0.46 shows the tower has capacity beyond the design loads to accommodate future instrumentation. The demand to capacity ratios of 0.29 for the 45GSRH diagonal and 0.24 for horizontal sections shows this standard tower design is not being pushed to the limit (Rohn, 2011). Rohn tower has been installed on the east side of the VGCS. As shown on figures 2-1 and 2-2, typically most of the ice accumulates on the east side of the stays. On the west side, stays are usually bare except for occasional frozen rivulets. This reflects the conditions during the most likely icing event. 41

55 3.4.2 Anchorage System Design The original design of the metrological tower supporting from the parapet was found to be unsuitable and a through-the-deck bolt design was developed and approved. The basic design specification used for this anchorage system was AASHTO Standard Sign Support Specification. This specification is the most appropriate because it addresses our mounting and general tower concerns. However, this is an Allowable Stress Design (ASD) specification and the Rohn loads are maximum load envelopes in a Load and Resistance Factor Design (LRFD) format so it was necessary to formulate the loads in an ASD format. When possible, nominal strengths are computed in an LRFD format and compared to the required strengths. When AASHTO Sign did not provide guidance in designing of the tower, AISC 14 th, and ACI-318 were used. A typical double nut connection was chosen as the anchorage system. Design loads were based on the ROHN report which considered strength and service limit states. Following failure modes were considered for design criteria: bolt failure, tensile strength of concrete, base plate failure, fatigue failure of base plate and anchor bolt, failure of plate washer, and bearing strength of concrete. The anchorage design calculations are presented in the appendix. The tower was installed in the spring of 2013 and the instruments were installed shortly thereafter. The instruments will be operational in the icing season. 42

56 Figure 3-15: Tower Anchorage System 3.5 Design The best way to manage icing events would be to obviate them by design. This method is not practical for existing bridges, but would a solution for new cable-stayed bridges. First consideration is to eliminate superstructure, pylon and cable stays, as much as possible. Second is having a single plane of stays with wider lanes of traffic. The traffic is not trapped by stays if considering one plane instead of several planes. The third one is having smaller stays to eliminate formation of large ice sheets. 43

57 Chapter 4 Outdoor Experiments on the Full Scale Specimens For designing an effective long term anti-icing/deicing technology for VGCS, more information needed to be gathered. The information required includes data about efficacy of chemicals on the stays, and information about coating. Performing these experiments on the bridge is inefficient and dangerous. An icing experiment station was designed, built and initially operated during the winter of Three full scale sheathing specimens 10ft long with the same diameter, material, and reflective brushed surface as the VGCS stays have been set up on the outdoor concrete pad at University of Toledo Scott Park campus. Figure 4-1 shows a screen shot of concrete pad at Scott Park which is taken from Google Earth. 44

58 Scott Park s Concrete Pad Figure 4-1: Google Earth Shot of Scott Park Figure 4-2: Experimental Setup On the bridge the stays have 82 to 156 prestressing epoxy coated structural strands depending on the location of stays. In the test set up, 120 un-tensioned strands were used. As shown in figure 1-5, on the bridge at mid-span, the epoxy coated strands are at top of the cross-section. In the test configuration, the strands rest at the bottom of the specimen for safety reasons. As shown in figure 4-2, the experimental setup contains 45

59 north facing, south facing, and horizontal specimens oriented north-south to simulate the bridge conditions as realistically as possible. 4.1 Data Acquisition System and Sensors The specimens were instrumented with designed thermistors to get the temperature at the sheath surface (Figure 3-8), a consisting of an array of flat thermocouples which are installed outside and one inside to get surface temperature of specimen, in addition, we used photo sensors to track sun location, a probe thermocouple for getting the inside temperature of specimen at different locations, an array of ice detectors to determine the difference between liquid water and ice, and a local weather station to collect the ambient temperature, wind speed, wind direction, and amount of rain and snow. Figure 4-3 shows several sensors which were installed on the upper part and east side of the specimen to monitor icing behavior of specimen. Leaf Wetness Sensor Goodrich Ice Detector Photo Sensor Figure 4-3: Sensors on South-faced Specimen 46

60 For collecting data, a wireless sensor monitoring system with three nodes and one base station was used. Figure 4-4: Data Acquisition System 4.2 Icing Simulation Experiments In unique microclimate of the VGCS, some major factors cause ice accumulation and shedding which was mentioned in table 3-1. Formation of ice would be a long process which would take at least 8 to 10 hours. The type of accumulated ice highly depends on weather conditions. On the other hand, ice shedding would be a fast process. In the last icing event, 90 percent of ice shed in 45 minutes (Nims, 2010). The goal of laboratory icing experiments was simulation of the icing occurrences on the VGCS and tracking the icing behavior of the sheathing. The experiments were conducted outdoors in cold weather. Icing was simulated by spraying a mist of water with a temperature of approximately 34 F at constant intervals. 47

61 Figure 4-5: Spraying a Mist of Water on North-faced Specimen The water was applied slowly enough that the water and latent heat of transformation did not raise the specimen temperature above freezing. Figure 4-6 shows the ½ inch thick accumulated ice on the north facing specimen. Figure 4-6: Pattern of Ice Accumulation on Outdoor Tests Shedding simulation was trickier than formation. The target was to simulate ice falling in a fashion like happens on the bridge. Based on the past reports of (Belknap, 2011), (Jones, 2010), and (Nims, 2010), ice shedding is more likely to happen when air 48

62 temperature is above freezing and with a clear sky such that solar radiation warms up the specimens. The experiments have been done to prove falling criteria, and create a baseline of specimens behavior before, during, and after shedding. Solar radiation would make a dramatic difference between specimen and ambient temperature and cause creation of liquid water under the ice on the specimen. Presence of liquid water before shedding Figure 4-7: Water beneath the Ice Layer before Shedding As the ambient temperature increases above freezing and due to gravity load, ice falls in large curved chunks. Icing experiments shows that at least 1/4 thickness is required for shedding of ice layer. This is consistent with observed icing event of 2011 (Section 3.3.2). Figure 4-8 shows shedding steps of a large chunk of ice on the stay during simulation experiments. A video of this shedding experiment is on the VGCS website. 49

63 Figure 4-8: Ice Shedding Steps 50

64 Figure 4-9 shows the temperature monitoring of south-faced specimen from 15 th to 18 th of February As shown in that figure, the specimen accurately simulates the icing behavior as it occurs on the VGCS. Temperature ( F) Top Bottom West East Top Inside 0 2/15/ :28 2/15/ :52 2/15/ :16 2/16/2013 1:40 2/16/2013 4:04 2/16/2013 6:28 2/16/2013 8:52 2/16/ :16 2/16/ :40 2/16/ :04 2/16/ :28 2/16/ :52 2/16/ :16 2/17/2013 1:40 2/17/2013 4:04 2/17/2013 6:28 2/17/2013 8:52 2/17/ :16 2/17/ :40 2/17/ :04 2/17/ :28 2/17/ :52 2/17/ :16 2/18/2013 1:40 2/18/2013 4:04 2/18/2013 6:28 2/18/2013 8:52 2/18/ :16 Time Figure 4-9: Stay s Behavior in Icing Test 2/15 to 2/18 51

65 Temperature ( F) A B C D 2/20/ :14 2/20/ :02 2/21/2013 3:50 2/21/2013 8:38 2/21/ :26 2/21/ :14 2/21/ :02 2/22/2013 3:50 2/22/2013 8:38 2/22/ :26 2/22/ :14 2/22/ :02 Time Figure 4-10: Stay s Behavior in Icing Test 2/20 to 2/22 Top Bottom West East Top Inside Figure 4-10 monitors the second simulation test which was done during 20 th to 21 st of February Part A of this figure focuses on ice accumulation scenario. The small thickness of ice layer started to accumulate on the specimen at 21:10. Increasing ice thickness was difficult due to the latent heat which was caused by additional water freezing. Water spray was controlled during the accumulation process to prevent ice layer from washing away instead of accumulating. The sudden increase and decrease of temperature in part A illustrates the change in specimen temperature when water is applied. Part B of the graph illustrates ice persistence behavior of specimen. The outdoor weather temperature was 21 F during the night and stayed below freezing during the day. 52

66 Part C shows ice shedding process. The temperature of the top and east surface of the specimen increased dramatically at sunrise. The sun was out and solar radiation caused the presence of liquid water between ice layer and specimen. Ice shedding happened at 13:25. Part D again shows ice accumulation scenario of the specimen. There is a coincidence between part A and D. This demonstrates the consistency of the icing behavior of the specimen. 4.3 Chemical Experiments Chemicals are considered as a second anti-icing/deicing strategy for the VGCS. There is a concern about the efficacy and the effect on the stay appearance from the chemicals. It was desired to conduct experiments with a typical deicing chemical to establish the procedure for testing chemicals at the icing experiment station. Antiicing/deicing experiments to determine the efficacy and behavior of chemicals were conducted with Beet Heat. Beet Heat is an organic based material and made of refined molasses carbohydrate, NaCl, CaCl2, KCl, and MgCl2 (Trademarkia, 2011).This chemical was selected for this trial which was proved by ODOT to deice of pavements which means no bio hazard and readily available. In the first test, the Beet Heat concentrate was applied with manual sprayer on half of the specimen and the baseline icing test was conducted to see the efficacy of that anti-icing strategy. Figure 4-15 shows how ice accumulates on the specimen with the presence of chemical. 53

67 Figure 4-11: Formation of Ice in Chemical Anti-icing Test As shown in Figure 4-11, the chemical first melts lower layers of ice to water but; since the water does not roll off the sheath, accumulated water suddenly turns to ice again. In the deicing chemical test, baseline icing test was conducted for formation of 1/8 inch thick of ice on the specimen, then a drip tube system was used to flow the Beat Heat on the ice layer. As shown in Figure 4-12, the chemical just melts a narrow rivulet through the ice due to low viscosity. 54

68 Figure 4-12: Drip Tube System used in Chemical Deicing Test Beet Heat was used as a chemical in preliminary anti-icing/deicing tests. Beet Heat showed unpromising performance during anti-icing/deicing experiments. It is suggested to use a chemical with design characteristics for having a better performance in deicing test or add detergent to have more viscosity. Drip tube system is supposed to mount on the VGCS stays for distributing the chemicals in anti-icing strategy. This system can affect the aerodynamics of the stays which also needs to be considered before installation. 4.4 Coating Experiments Coatings are supposed to reduce the adhesion strength of ice to the stay surface and are often considered as an anti-icing or passive technology. To investigate the efficacy of a coating for icing problem of VGCS, a revolutionary type of coating was tested. The coating is considered as a surface treatment which can make surfaces extremely water repellant and ice phobic. 55

69 The specimen was instrumented by thermocouples to the see the thermal behavior of stainless steel sheath with the presence of coating. Hydrobead was sprayed to one side of the specimen, and then baseline icing experiment was conducted to see the efficacy of this super hydrophobic coating (Hydrbead,2013). Figure 4-13: Hydrobead Sprayed on the half of Specimen Hydrobead caused water to bead into small droplets. Due to brushed surface of sheath, small water droplets did not roll off the coated surface and suddenly turned to ice. Figure 4-14: Water Droplets due to Hydrobead Figure 4-15 shows the behavior of sheath which is covered half by hydrobead and half without hydrobead in coating test. Ice started to accumulate on the specimen by 56

70 spraying mist of water with the temperature approximately 34 F. Ambient temperature was 23.4 F. The graph starts with a sudden raise in the specimen s temperature due to latent heat which caused by freezing water and drops smoothly. On the right side of the figure, the gap shows that hydrobead moves the freezing water away from the sheath Specimen Temp Temperature ( F) Specimen Temp w Hydrobead 5 0 3/3/13 3:46 3/3/13 4:07 3/3/13 4:29 3/3/13 4:50 3/3/13 5:12 3/3/13 5:34 3/3/13 5:55 3/3/13 6:17 3/3/13 6:38 3/3/13 7:00 3/3/13 7:22 3/3/13 7:43 Time Figure 4-15: Specimen s Behavior in Coating Test The efficiency of the super ice phobic coating was evaluated during outdoor tests on the stainless steel and HDPE specimens. Hydrobead caused the water to bead into small droplets and ice built up on the specimen. Hydrobead also changed the ice structure and build up rate on the stainless steel specimen. Overall, for this test hydrobead did not significantly impede the buildup of ice and it raised durability concerns in long term. Other concerns with this water repellant and ice phobic coating are: discoloration of the shiny surface of the VGCS stays, attraction of dirt, maintenance cost, and 57

71 renovation after ice events. After approximately of one month, the hydrobead had a gummy appearance on the stays. 58

72 Chapter 5 Conclusion and Future Work The Veteran s Glass City Skyway, formerly known as the Maumee River Crossing is a cable-stayed bridge on Interstate 280 in Toledo, Ohio which is owned by Ohio Department of Transportation. Since the VGCS has been in service, five times ice formed on the stays. Ice shedding from the stay poses a hazard to public safety, and results in economic loss due to lane closure. The VGCS stays have unique features which cause them to be more susceptible in icing problems. These characteristics are that the stays are stainless steel, larger diameter, having brushed finishing, may contribute to the icing problem. The objectives of this work were to build an icing experiment station which should replicate the ice behavior of the VGCS. Conduct experiments that evaluated if the icing experiment station could be used to evaluate techniques for control of icing including coating, deicing chemicals and internal heating of the stays and serve as a test bead for instruments used to monitor icing. Report the test results for the work on coating, chemicals, and internal heating. Development of sensors to gather required information. Anchorage design for self-supporting instrumentation tower to support sensors. 59

73 5.1 Conclusion Tasks which have been completed are: design, construction, and performing of full scale laboratory station to simulate the practical technologies in much more controlled fashion environment, outdoor experiments to track the sheath responses during the selected tests to resolve several uncertainties, Report the test results during experiments, selection of additional sensors to gather more information concerning the ice accumulation conditions, ice shedding conditions, and track the microclimate of the VGCS during icing events, and design of the anchorage for self-supporting tower which supports the sensors. The icing experiment station was used to conduct several icing simulation tests to reproduce reliable ice accretion and reasonable shedding on the 10 ft long stainless steel specimens. The same icing behavior of the VGCS stays which was observed during February 2011 icing event was achieved. During full scale outdoor test, important aspects of the behavior of the ice on the stays were validated such as approximately ¼ thick ice layer is required for shedding of ice layers. Controlling water temperature more closely during ice accretion is proposed as an improvement. The feasibility of using the experiment station to conduct anti-icing/deicing experiments using chemicals was demonstrate by performing experiments with Beet Heat. In anti-icing test, Beet Heat did not significantly influence the ice buildup on the stays. In deicing test, Beet Heat also did not sheet, but rather cut a narrow path through the ice layer. Adding detergent to the Beet Heat may improve the sheeting behavior. 60

74 The experiment station was successfully used to conduct a coating experiment. In the coating test, ice formed on the stainless steel specimen with a significant thickness. Hydrobead also discolored the shiny surface of specimen and collected some dirt. 5.2 Future Work Based on the preliminary findings, next step of this project would focus on more refined experiments, and thermal analysis for the refinement of the sensor system. Three steps have been suggested to develop a process for finding the most practical technology for the next phase of this study. They include: 1) Testing in the University of Toledo icing tunnel to identify candidate methods for future development, 2) Testing on the full scale specimens to verify the results from icing tunnel, and 3) Field testing at the VGCS. 61

75 References ACI , 2011, Building Code Requirements for Structural Concrete. AASHTO LRFD, 2010, AASHTO LRFD Building Design Specifications, 5 th Edition with 2010 Interims. AASHTO Signs, 2011, AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals, Fifth Edition 2009, 2011 Revisions. Agrawal, S., 2011, Automated Ice Monitoring System for the Veteran s Glass City Skyway. School of Electronics and Computing Systems of the University of Cincinnati. Belknap, J.W., 2011, Designing Ice Management System for the Veteran s Glass City Skyway. University of Toledo. Couture, P., 2011, Smart Power Line and Phobic De-icer Concepts for Transmission-line Capacity and Reliability Improvement. Cold Region Science and Technology, Vol. 65, pp, Dalle, B., and Admirat, P., 2011, Wet Snow Accretion on Overhead Lines with French Report of Experience. Cold Region Science and Technology, Vol. 65, pp, Deb, B., 2013, Continued Weather Monitoring System for the Veteran s Glass City Skyway. School of Electronics and Computing Systems of the University of 62

76 Cincinnati. Decagon LWS, 2010, Leaf Wetness Sensor. Brochure, Delta-T Devices, 2002, Sunshine Sensor. Brochure, Goodrich, 2009, Ice Detector Model 0872F1. Brochure, Hydrobead, 2013, Jones, K. F., 2010, Toledo Weather Conditions Associated with Ice Accumulation on the Skyway Stays (Draft). Cold Regions Research and Engineering Laboratory, Hanover, NH Koenig, G. G., and Ryerson, C. C., 2011, An Investigation of Infrared Deicing through Experimentation. Cold Region Science and Technology, Vol. 65, pp, Kilinich, S. A., and Farzaneh, M., 2011, On Ice-releasing Properties of Rough Hydrophobic Coatings. Cold Region Science and Technology, Vol. 65, pp, Kumpf, J., Helmicki, A., Nims, D. K., Hunt, V., Agrawal, S,. 2012, Automated Ice Inference and Modeling on the Veteran s Glass City Skyway Bridge. Journal of Bridge Engineering, ASCE, Thecnical Note. Menini, R., Ghalmi, Z., Farzaneh, M., 2011, Highly Resistant Icephobic Coating on Aluminum Alloy. Cold Region Science and Technology, Vol. 65, pp, Nims, D. K., 2010, Ice Prevention or Removal on the Veteran s Glass City Skyway Cables (Draft Interim Report). Ohio Department of Transportation Office of Research and Development, State Job Number Parent, O., Ilinca, A., 2011, Anti-icing and De-icing Techniques for Wind Turbines: Critical Review. Cold Region Science and Technology, Vol. 65, pp,

77 Petrenko, V. F., Sullivan, C. R., Kozlyuk, V., Petrenko, F. V., Veerasamy, V., 2011, Pulse Electro-thermal De-icer (PETD). Cold Region Science and Technology, Vol. 65, pp, R. M. Young, 2011, Electrically Heated Rain and Snow Gage. Brochure, Rohn, 2011, Self-Supporting Towers. Brochure, Ryerson, C. C., 2011, Ice Protection of Offshore Platforms.. Cold Region Science and Technology, Vol. 65, pp, Ryeson, C. C., 2008, Assessment of Superstructure Ice Protection as Applied to Offshore Oil Operations Safety. Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire Ryerson, C. C., 2013, Icing Management for Coast Guard Assets. Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire Trademarkia, 2011, Wikipedia, 2013, -Glass-City-Skyway. 64

78 Appendix A Anchorage Design Calculation 65

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