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SUMMARY
SCOPE
IMPLEMENTATION
TECHNOLOGY TRANSFER
RESEARCH TEAM
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1. Introduction
2. Prevention of Ice Formation Using Geothermal Heat
2.1 Passive Geothermal Deck Heating Systems
2.2 Active Geothermal Deck Heating Systems
2.3 OSU Smart Bridge Research
2.4 OSU Mesonet Research
2.5 OSU ITS Research
2.6 OSU Ground Source Heat Pump Research
2.7 OSU Related Controls Research
2.8 OSU Related Corrosion Research
3. Developing a "Smart" Geothermal Deck Heating System
4. Proposed Scope
4.1 Simulation and Design Software
4.2 System Design and Installation Guidelines
4.3 Control Systems and Strategies
4.4 Life Cycle Economic Analysis
4.5 Technology Transfer
4.6 Experimental Work
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1.1 The Problem of Bridge Deck Icing
Travel is hazardous in the late fall, winter, and early spring, during periods of snow, sleet and freezing rain. Perhaps the greatest danger along this line is the frequent occurrence of preferential icing of bridges, where bridge decks become icy and slick while adjacent roadways remain clear. Some drivers crossing preferentially iced bridges lose control of their vehicles. Single or multiple vehicle accidents often result. The risk of mishap is worse when other non-ideal conditions exist such as during low visibility conditions and bridge/roadway maintenance operations. It is of high priority that preferential icing be prevented.
1.2 Conventional Responses to Bridge Deck Icing
By far, the most frequent responses to bridge deck icing are the applications of salt and/or sand or other gritty material. Salt applied to a bridge deck prior to icing can prevent preferential icing. But salt and sand are usually spread only once ice is already present on a bridge. Money is wasted if salt or sand is distributed too early and then later found unnecessary (Malloy, 1994). Therefore, salt/sand applications generally do not stop preferential icing.
There are other problems with salt. Sodium chloride (rock salt) is the most popular salt due to its low cost (Fleeg, 1990; Malloy, 1994). But ice will not be melted by salt if temperatures fall below about 25°F("Deicing," 1991). Calcium chloride is another popular salt and is effective at lower temperatures. It is considerably more expensive, though("Deicing," 1991), and more corrosive (Trost et al., 1987) than rock salt.
The corrosive influence of salt is a major disadvantage of its use. Water in which salt is dissolved is splashed onto vehicles and bridges, and seeps through cracks in bridge decks (Fleeg, 1990). While steel (and concrete, for that matter) is not chemically attacked directly by salt, water in which salt is dissolved evaporates less rapidly. Metal surfaces in contact with salt water stay wet and rust for a longer period of time ("Deicing," 1991).
Corrosion of reinforcing steel bars in bridge decks has been a major problem in the past. When the reinforcing steel corrodes, strength is greatly reduced, and bridge deck failure can occur. Preventive measures taken include the use of galvanized bars, epoxy-coated bars, greater concrete cover on top of the top layer of steel, concrete surface treatments, and other techniques (Babaei and Hawkins, 1987; "Thruway," 1994). Some controversy still exists over the effectiveness of epoxy-coated bars (Korman, 1992; Collins, 1994; "Thruway," 1994) but their use and effectiveness have generally been embraced by the engineering community. Some alternative noncorrosive liquid substances are being developed (Fleeg, 1990; Trost et al., 1987). However, at this point, these are greatly more expensive than currently available salts.
Salt has also been thought harmful to the environment by some. Little risk exists, however, if deicing salts are stored and handled correctly and roadway drainage is directed properly. Salts even promote the health of some vegetation (Priebe, 1990).
1.3 Alternative Responses to Bridge Deck Icing
The first alternative to bridge deck icing would use advanced weather prediction technology to more efficiently manage conventional responses to bridge deck icing. Bridges and roadways may be fitted with an appropriate number of weather sensing devices. These devices, along with information from other weather stations, may be used to create a "thermal map" of the state or region, and icing conditions may be predicted much more accurately. Salt/sand applications are planned and conducted much more efficiently. The costs involved in installing and maintaining the sensors more than offset the savings realized. With such a system, some of the more effective but more expensive deicing chemicals may be considered for use (Malloy, 1994).
A second alternative response is a deck heating system installed within the bridge. Preferential icing is prevented without the disadvantages of conventional responses as discussed in the previous section. Bridge deck heating systems may use either embedded electric resistance wire or embedded hydronic tubing. Bridge deck heating systems which used embedded electric resistance wire have tended to be extremely expensive to operate (Blackburn et al., 1978).
Hydronic bridge deck heating systems circulate a heated fluid through tubing in the bridge deck. The heating might be provided by either a boiler, directly from the ground, or by a ground source heat pump system. Systems using heat from the ground ("geothermal"), either directly, or through a heat pump, are discussed in the next section.
Hydronic bridge deck heating systems can be operated remotely without extra input from people, machines or materials. This represents an advantage over using the sensor-thermal map method, described above, of optimizing the conventional responses to icing.
Research in Wyoming, Oklahoma, West Virginia, and Japan has demonstrated that a "heat pipe" deck heating system eliminates preferential icing of bridges (Witwer & Sommers, 1974; Long & Baldwin, 1980; Tanaka, 1981; Nydahl et al., 1984; Lee et al., 1986). As shown in Fig. 1, an evaporator pipe or set of pipes is embedded into the ground near a bridge and filled with liquid, usually ammonia. The liquid is evaporated by the heat of the earth and the vapor travels upward into condenser pipes installed in the bridge deck. The vapor then gives up its heat to the deck, condensing in the process. Finally, the condensed liquid flows by gravity back down into the evaporator(s) to complete the cycle.
Figure 1. Schematic Arrangement of "Heat Pipe" Bridge Deck Heating System (from Nydahl et al., 1984, p. 16)
This system is passive in that it operates without need of pumps, control systems, external power, or any human intervention. The evaporation-condensation cycle is in operation whenever the bridge deck is cooler than the earth. Heat is removed from the earth even when ice wouldn't form anyway. This extra removal of heat is not a problem from the standpoint of operating costs—there are none. But the pipe size and/or depth of bury must be increased to compensate for the excessive heat loss.
The inside of each heat pipe must be carefully cleaned. Plumbing in the bridge deck must have just enough slope so that condensed liquid flows back to the evaporators. Because of the complications of preparing and constructing, the installation cost of the heat pipes may be prohibitive— in a study by Nydahl, et al. (1984) the heating system accounted for 59% of the cost of the combined bridge and heating system.
Furthermore, it is likely that one or a few ondenser pipes may end up being installed without the required slope. Also, it may happen that not all plumbing is correctly cleaned (Nydahl et al., 1984). In both these circumstances, ice will form on the bridge near the problem pipe(s). The heating system cannot be repaired without tremendous cost and effort (e.g., tearing up the bridge deck or digging up the surrounding earth).
In the Wyoming studies cited, it was demonstrated that there is enough geothermal heat available to eliminate preferential bridge deck icing—even in relatively cold climates. Therefore, a cost effective heat delivery system would have broad applicability throughout the United States. Active geothermal deck heating holds the promise of being economical. The term "active" means the heat system is controlled. Heat is conserved and any operating costs of conveying heat to the deck are minimized.
An active geothermal system for heating roadways (not bridge decks) was tested in Trenton, New Jersey in the early 1970’s (Winters, 1977). The system utilized pipe buried underneath the roadway horizontally at depths between 3 and 13 feet. The system proved to be workable and melted the snow during five major snowstorms. While the system was not aimed at keeping bridge decks ice free, it does illustrate the general concept.
A simple active heating system, as schematically shown in Fig. 2, would be composed of an electric-powered pump that circulates earth-heated fluid through piping to the deck. It is expected that installation would be less costly than the heat pipe system. The conduits would not have to be specially prepared to ensure extreme cleanliness so plastic pipe could be used rather than steel. Fluid flow would be pressurized so careful construction to enable gravity flow would not be required.
Figure 2. Schematic Diagram of a Simple Active Bridge Deck Heating System
Should additional heat be necessary or desirable, a heat pump could be incorporated into the system. Ground source heat pump systems have been developed through pioneering research at Oklahoma State University (OSU) over the past 20 years. This thermal system has been used in many residential and commercial applications in the last decade and is even in use at the Oklahoma State Capitol. A ground-coupled heat pump can heat a home for about 35% of the cost of an electrical resistance system. Pipe liquid may be heated to as high as 110°F. In a bridge deck heating system, this level of heat would allow for a reduction in the amount of piping required.
Fluid could also be circulated on some hot days in the summer. The sun's radiant heat would be transported from the deck to "recharge" the ground (Katsuragi et al., 1989). Heat removed during the previous cold season would be replaced.
As part of a small experimental project, researchers at OSU developed a small-scale bridge deck with a ground-source heat pump heating system. This is described most fully in an M.S. thesis supervised by Dr. Spitler (Wadivkar 1997). The bridge deck was operated over part of one winter. During that time, a number of individual tests were made under freezing weather conditions, while introducing "artificial precipitation" (water misted from a spray bottle). A three-dimensional finite difference model of the bridge deck was developed. In addition to conduction heat transfer inside the bridge deck, convection, solar radiation, and thermal radiation boundary conditions were incorporated. The model was calibrated based on the data from the tests. It was able to predict the surface heat flux reasonably well; the surface temperature could be predicted within a few degrees Fahrenheit, but a higher degree of accuracy is needed to predict the occurrence of icing conditions that are only marginally below freezing.
Subsequently, additional models have been developed and implemented in both a stand-alone fashion, and as a component model for TRNSYS. TRNSYS is a transient, modular, component-based system simulation program aimed at thermal systems. In such an environment, the bridge deck model can be hooked to models of a heat pump, ground loop heat exchanger (Yavuzturk and Spitler 1999), circulating pump, controller, etc. Then, various control strategies and operating strategies can be tested with different ground loop heat exchanger configurations in different climates. Computer simulation of the bridge deck and other components is a quite powerful technique, allowing quick and inexpensive investigations that could only be done experimentally over a very long term at a cost of millions of dollars. However, additional refinement and validation of the component models are needed in order to confirm and validate the results.
Also, several of the investigators have been involved in a project to build the first full-scale "smart" bridge heated with a ground source heat pump system. This will be implemented on a bridge near Weatherford, Oklahoma, on I-40. Currently, the engineering contractor is being negotiated. It is anticipated that construction will start sometime in the spring of 2000, and operation of the heating system should begin either in the early months of 2001 or late fall of 2001.
The Oklahoma Mesonet (Brock, et al. 1995; http://okmesonet.ocs.ou.edu) is a unique, statewide network of 115 automated monitoring stations (average station spacing is approximately 19 miles). At each site, a comprehensive set of weather and soil variables is measured by a set of instruments located on or near a 10-meter-tall tower (Elliott, et al. 1994). The measurements are packaged into "observations" every 5 minutes, and transmitted to a central facility every 15 minutes, using the Oklahoma Law Enforcement Telecommunications System. Within minutes after the observations are acquired, these Mesonet data and related value-added products are available to a large and diverse user community. Examples of Mesonet data and products can be found at the following URL: http://okmesonet.ocs.ou.edu/sample.
Oklahoma State University and the University of Oklahoma have been full partners in the planning, design, installation, operation, and maintenance of the Mesonet. Throughout this process, Dr. Elliott (a co-PI on this proposal) has served as OSU’s lead representative to the Mesonet. He is intimately familiar with the network and its operation, and has established close working relationships with weather and climate professionals at the University of Oklahoma. This meteorological expertise will be made available to the Smart Bridge project via a subcontract.
The Mesonet has been in full operation since early 1994. During this time, over 99.9% of all possible data observations (now approximately 15 million per month) have been successfully collected and archived. An extensive program of data quality assurance is in place (Arndt, et al. 1998). The quantity and quality of the data stream that the Mesonet can provide for the Smart Bridge research effort is unparalleled in the U.S. and probably the world. Recognizing that other areas of the country currently can not match the spatial and temporal resolution of Mesonet data, our investigations will include various subsets of Mesonet data as well as other sources of weather data that are readily available nationwide.
The origins of ITS research at OSU can be traced back to the early 1980’s when ITS technologies were confined largely to conceptual developments and small-scale deployments by few researchers who recognized the potential impacts of ITS on the delivery of transportation services. The research program at OSU involved the development of real-time incident detection algorithms, incident management, ramp metering, and traveler information systems. Dr. Samir Ahmed’s work in these areas is well documented in the ITS literature. These early developments continue to be reflected in today’s ITS components of advanced traffic management in metropolitan areas.
Currently, researchers at OSU are involved in planning ITS deployment projects in the Oklahoma City area (e.g., the Oklahoma City MPO incident management project). In addition, researchers at OSU are partnering with their colleagues in the region to plan a Mid-continent International Trade Corridor ITS/CVO.
Like other ITS deployment projects, the smart bridge technology should conform to national architecture and applicable standards and protocols. On December 21, 1998, interim guidance on consistency with national ITS architecture and standards was issued in the Federal Register (63 FR 70443). Although the specific technologies and institutional arrangements used in any particular deployment are left to the discretion of the individual agencies and organizations involved, conformance to the national architecture and standards is required to promote interoperability, efficiency and interconnectivity of the different ITS components.
Oklahoma State University has been known for sometime as the center for research and development of ground source heat pump systems in the world. Experiments involving single and multiple-pipe vertical ground heat exchangers began under the direction of Dr. Jim Bose at Oklahoma State University in the early 1980s. Since then, numerous experimental and computational research projects have been performed, including:
Study of single and multiple-pipe horizontal heat exchangers followed in the mid-1980s. These studies reduced the length of the required trench from approximately 400 feet to 125 feet with comparable performance. In the early 1990s, a newly developed circular or "Slinky" heat exchanger resulted in rapid industry acceptance of horizontal trenches as short as 65 feet.,
Guidance for designers in the form of design software. The design software will allow state departments of transportation designers as well as private industry designers to determine required ground loop heat exchanger size and configuration, heat pump sizing, circulating pump sizing, the effects of various control and operating strategies, energy consumption, electricity costs, approximate first costs, life cycle costs, and anticipated bridge deck life extension, and projected cost/benefit ratios.
Backfill studies and design performance studies.
Recommended weather sampling, forecasting, control strategies, and operating strategies,
Research into the effects of grout type on vertical ground heat exchangers.
Development of an in situ ground thermal property measurement apparatus and analysis techniques.
Development of two different commonly used software design tools, the CLGS and GLHEPRO programs.
Development of short time step models of vertical ground heat exchangers, heat pumps, and other related components.
Research into shallow heat rejecters, e.g. shallow ponds and heated pavement systems for rejecting excess heat from the ground loop.
Not only has this research been conducted at OSU, it has also been transferred, primarily through the International Ground Source Heat Pump Association. The International Ground Source Heat Pump Association (IGSHPA) was established in 1997 to advance geothermal heat pump technology on local, state, national, and international levels. Headquartered on the campus of Oklahoma State University, IGSHPA utilizes state-of-the-art facilities for conducting geothermal research and geothermal heat pump (GHP) system installation training.
IGSHPA designs and produces promotional brochures, case studies, fact sheets, and a bi-monthly newsletter. Training workshops are a big part of IGSHPA’s function in the geothermal industry. The association pioneered training in GHP installation and created the manuals currently used in the industry. IGSHPA has developed programs and training materials including course curricula, manuals, videotapes, and a train-the-trainer program. This program allows regional training sites to be developed where personnel in diverse locations can receive industry training that helps ensure a high quality of future GHP installations.
IGSHPA holds two annual conferences, one focused primarily on technical advances and research results, and the other on marketing strategies and product development. More recently, IGSHPA has developed a web site comprised of over 1400 separate pages of consumer and industry information, including brochures, case studies, and a free on-line database listing contact information for hundreds of GHP professionals.
Twelve faculty in five different departments in the College of Engineering, Architecture, and Technology are actively involved in control system research. There are a total of seventeen graduate level control courses available with a number of additional control related courses offered through the Departments of Computer Science and Statistics. Because controls is an area of recognized strength, a proposal to create a Control Systems Engineering M.S. degree-granting program at OSU has been submitted and is currently under review. This would be a new, interdisciplinary program targeted for both on-campus and non-traditional, off-campus students.
As indicated in the task description for "Integrated Control Strategies," the proposed work does not require breakthroughs in the well-developed fields of systems and control theory, but novel integration of existing control concepts. The Smart Bridge controls PI, Dr. Whiteley, is actively investigating fuzzy reasoning and neural networks in combination with traditional control strategies. Most importantly, Dr. Whiteley's research group has expertise in real-time systems programming, a critical need to ensure Smart Bridge technology transfer and utilization.
To accurately predict the life span and effective life cycle cost of a heated concrete bridge deck, the rates of salt penetration and corrosion must be determined. Researchers in Dr. Knobbe’s group have been funded for more than 3 years by the US DoD to utilize electrochemical corrosion detection methods to detect corrosion and assess corrosion prevention characteristics of metal surface treatments. The corrosion research program, housed in OSU’s Department of Chemistry, includes Professor Knobbe, three postdoctoral research fellows, and two Ph.D. graduate students. In addition to the OSU team, Dr. Knobbe is a member of several collaborative corrosion research groups, including affiliations with the Air Force Research Laboratory-Materials Directorate (AFRL/ML, Wright Patterson AFB), the Oklahoma City Air Logistics Center (OC-ALC) Technology Center (Tinker AFB), the NavAir Materials Laboratory (NAWC-AD; Patuxent River NAS), and the NSF-funded Coatings and Surface Treatment Collaborative Research Consortium at North Dakota State University.
The proposed research subtask will include the implementation of remote corrosion detection methods to promote in-situ quantitation of metal loss in deck modules. This approach will leverage previous work sponsored by US DoD and US DOT in the area of remote corrosion detection. Results of the in-situ measurements, used to calculate internal reinforcing steel corrosion rates, will serve as the basis for determination of the service lifetime of conventional and heated bridge modules under comparable service conditions. Service lifetime and life cycle cost assessment will be performed by a assistant professor to be hired by the OSU CEAT.
An active, "smart" bridge deck ice prevention system, taking full advantage of the current heating and control technologies available, as described above, is highly desirable. Travel would be safer; resources would be used more efficiently; and damage to bridge, vehicles, and, the environment would be reduced.
It should be noted that, if cost is no object, a workable bridge deck heating system could be built and operated today. However, such a system would not be "smart" and more to the point, it would not be cost-effective to build or operate. Therefore, a very important part of this project is aimed at optimizing the design and the control and operating strategies to minimize the first cost and the operating costs.
The mission of this project is to"Research, design, and demonstrate technically feasible, economically acceptable, and environmentally compatible Smart Bridge systems to enhance the nation’s highway system safety and to reduce its life cycle cost."
Accordingly, the proposed project is organized around establishing the technical feasibility, optimizing the design to reach economically acceptable first costs and operating costs, predicting the increase in bridge deck lifetime due to reduced application of salt, and quantifying the economic benefits due to increased bridge deck life, improved safety, and reduced maintenance. In addition, a substantial effort will be made to transfer the technology throughout the U.S. wherever preferential icing is a problem. The proposed approach to the problem is outlined in the next section.
As described in section 3, the project is organized around the following five objectives:
stablishing the technical feasibility,
Optimizing the design to reach economically acceptable first costs and operating costs,
Predicting the increase in bridge deck lifetime due to reduced application of salt,
Quantifying the economic benefits due to increased bridge deck life, improved safety, and reduced maintenance, and
Transferring the technology.
The five objectives are addressed by work in six categories and further broken down into a set of tasks. The first three categories, simulation and design software, system design and installation guidelines, and control systems and strategies are aimed primarily at establishing the technical feasibility and reaching economically acceptable first costs and operating costs. However, several of the tasks are cast with an eye towards technology transfer. In particular, the design software will be an important feature of transferring the technology – the software will contain the design procedure and economic analysis, and will be delivered along with training to other state departments of transportation.
The fourth category, bridge life and life cycle economic analysis, is aimed at predicting the increase in bridge deck life and quantifying the economic benefits. The fifth category, technology transfer, is included because of the importance of providing this technology to the eventual end users. Finally, the sixth category, experimental work, will involve construction, instrumentation, operation and monitoring of a working heated bridge deck system. The system will serve to provide data for validation and serve as a testbed for control and operating strategies.
Also, as discussed in section 2, a number of the tasks here will make use of information gained in the Weatherford bridge deck implementation.
Each task is briefly described in this section. Also, the responsible investigators are listed for each task described below.
4.1.1 Develop and Validate Advanced Modeling Software
Modeling software can be used to evaluate the operation of a specific configuration of bridge deck and heating system in a specific climate in lieu of building and operating the bridge deck. This is the only feasible way to evaluate a range of system configurations, operating strategies and control strategies, in various climates.
This will build on work already done using existing component-based dynamic modeling software (TRNSYS and HVACSIM+). We have developed component models that allow us to simulate the ground loop heat exchanger, heat pump, bridge deck, and circulating pumps. New component models of controllers will need to be developed. The bridge deck model needs further refinement and experimental validation. The experimental validation will be done using the experimental facilities described below in Section 4.6.
This task will involve further refinement of the bridge deck model by improving its convection and conduction models, and validation against experimental data collected as part of Task 4.6. The chief deliverable product of this project will be the advanced modeling software.
Investigators: Spitler, Rees, Fisher
4.1.2 Develop Design Software
The software described above is suitable for use by researchers – it is highly flexible and has a correspondingly complex user interface. This task involves the development of software that could be used by practicing engineers (i.e. not just by researchers). This would combine the advanced modeling software with a "simplified" user interface and some searching/optimizing features. The software will be distributed to state highway departments and other interested parties as part of the technology transfer activities.
Investigators: Spitler, Delahoussaye, Fisher
4.2.1 Further Refinements to Ground Loop Heat Exchanger Design & Alternative Designs
This task will involve the investigation of further refinements to the ground loop heat exchanger design and studies of alternatives to the standard closed-loop system. The refinements to be investigated (thermally-enhanced grout, controlled U-tube spacing, storage vs. extraction field designs) are oriented towards making the most of a storage system. Possible alternative systems include an open-loop system and a hybrid closed-loop-open-loop system. The goal is to reduce both the first cost and operating cost of the system. This task is experimental and computational.
Investigators: Smith, Spitler
4.2.2 Investigate Integration of Smart Bridge with ITS Systems
The primary objective of this task is to develop a model for integrating the smart bridge deck heating technology into other ITS systems and services based on the national ITS architecture and the emerging standards and protocols. The national architecture defines how the ITS systems and components can be linked together, whereas the standards and protocols (data, communications, messages, performance, etc.) ensure compatibility and interoperability.
In addition, this task will explore the issues of liability, technology constraints, integration strategies, and implementation options related to the smart bridge technology.
Investigators: Ahmed
Development of a "smart" control system which guarantees ice-free bridge deck conditions at all times while minimizing both the first cost (because the ground loop heat exchanger size depends on the annual load) and the operating cost is one of the defining components of the project. The control system and strategies to be developed will support varying degrees of measurement and weather information availability. That is, the Smart Bridge technology can be utilized in regions lacking Oklahoma's sophisticated Mesonet weather monitoring system.
4.3.1 Control System
A unique bridge deck heating control system will be developed that meets the conflicting demands of ice-free bridge conditions with minimal capital and operating costs. The control system will utilize regional weather measurements and National Weather Service forecasts to provide proactive or feedforward control. Bridge temperature measurements and other local conditions will be used to provide feedback control and guarantee avoidance of icing conditions. The composite control system will utilize a combination of models (weather, bridge, heating system, other) with ability to learn with experience how to optimize bridge deck heating. Task 4.3.1. will be subdivided into the following tasks:
4.3.1.1 Weather Inputs
Bridge deck icing is of course highly dependent on the weather. To be "smart" and economically optimized, control systems and strategies must incorporate and react to information on past, current, and future weather conditions. In addition to identifying the most relevant weather variables influencing bridge icing, this task will quantify the value of on-site weather data, spatially distributed data from a real-time weather network, and National Weather Service forecasts. The methodologies for data integration and forecasting will recognize that the available weather information can vary considerably from one location/region to another.
Investigators: Elliott, Whiteley, Spitler, OU Meteorology Personnel
4.3.1.2 Surrogate Bridge Freezing Sensors
Between three and five surrogate bridge freezing sensors will be developed, fabricated, installed at various locations throughout the state, and monitored. Surrogate bridge freezing sensors are small (approximately two feet in diameter) instrumented concrete slabs. The surrogate bridge freezing sensors can be used to approximately determine whether or not a bridge deck in the same location would freeze, if untreated. The sensors will be used to provide training data for some of the control strategies which will be investigated as part of the next sub-task.
Investigators: Spitler, Fisher
4.3.1.3 Integrated Control Strategies
A modular control system with capability to function with varying levels of input will be developed ensuring flexibility, reliability, and ease of maintenance. The system will be hierarchical with multiple control modules running in parallel. While the individual control components are available, integration to meet the Smart Bridge performance requirements will require innovation. Because the control system will rely heavily on predictive models, autonomous procedures to update critical model parameters will be provided. A software simulator will be developed to facilitate design and evaluation of different control system strategies.
Investigators: Whiteley, Elliott, Spitler
4.3.2 Investigating Summer Recharge Strategies
These would involve circulating fluid through the bridge deck, to the ground loop heat exchanger during the summer to replenish the energy extracted during the winter. Again, the goal of this task is to reduce both the first cost and the operating cost. Ultimately, it may be possible to completely eliminate the heat pump, using stored energy from the ground directly to heat the bridge deck. Failing that, it might be possible to replace the heat pump with a small electric, propane, or natural gas booster heater. Eliminating the heat pump would result in a significant reduction in both first cost and operating cost.
Investigators: Spitler
4.4.1 Corrosion Assessment and Control
This portion of the project focuses on the effectiveness of bridge deck heating toward corrosion reduction within the deck structure. Studies will include in situ and ex situ corrosion measurements on reinforcing steel elements using a parallel series of test bridge modules. Nondestructive in situ measurements will be conducted using integrated corrosion sensors, while destructive ex situ observations will be periodically performed on sacrificial modules to verify sensor reporting accuracy and to calibrate sensor output in terms of total metal loss and corrosion type. Life span assessment and life cost cycle analyses will be performed and will serve as a basis of comparison between heated and conventional deck types.
Investigators: Knobbe, new CEAT faculty
4.4.2 Overall Life-cycle Economic Analysis
Perform life-cycle economic analysis of alternative winter maintenance technologies of bridge decks, and develop a computer program which can be used by practicing engineers to evaluate the life-cycle cost and economics of a particular bridge. The computer program should complement the design software described in Task 4.1.2 and can be integrated with it into a "Smart Bridge Design and Analysis Software". A life-cycle economic analysis will be conducted on the Weatherford bridge on Interstate 40 to determine the net present value of the specific de-icing technology applied.
Investigators: Ahmed., Holmes
The objective of this task is to raise the transportation community’s awareness and understanding of the "smart" geothermal bridge deck heating system and to promote the adoption of this technology through information exchange, training, and professional capacity building. The technology transfer process will involve market planning (identifying the target audience), technical information packaging, promotion, delivery, and technical assistance to provide ongoing help with specific problems. Tools of technology transfer will include print media (papers, research & implementation reports, newsletters, manuals), presentations (conferences, workshops, training courses), demonstration projects, the Internet, university transportation centers, LTAP centers, teleconferencing, and partnering with industry associations.
Two experimental projects will support the above tasks. They will be used for model validation, physical testing of salt penetration, and testing of control strategies. However, it is anticipated that only the first task can be funded as part of this project. Additional funding will be sought for the second task. The tasks are as follows:
4.6.1 Testing of a Medium-Scale Bridge Deck Heating System
This task will involve the construction, instrumentation, operation, and analysis of a medium-scale (24’x24’) bridge deck and ground source heat pump-based bridge deck heating system.
4.6.2 Testing of Bridge Deck Sections in a Climate Controlled Chamber
This will be used both for validation of the heat transfer models, and possibly in conjunction with a highway simulator, to study salt penetration and corrosion. However, additional funding will be sought, and the success of these efforts cannot be predicted.
Oklahoma State University
College of Engineering, Architecture & Technology
Oklahoma Transportation Center
