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RFID in Constructio






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RFID in Constructio RFID in Constructio Document Transcript

  • Radio Frequency Identification (RFID) and Building Information Modeling (BIM); Integrating the Lean Construction Process J. Mark Taylor, Ph.D., JD Auburn University Auburn, Alabama Stephen A. Coady, MBC Candidate Auburn University McWhorter School of Building Science Jon Chesser Atlas RFID Solutions, Inc. Birmingham, Alabama Abstract Radio Frequency Identification (RFID) is an emerging technology that is beginning to receive attention in the construction industry. From asset and progress management, to the locating of underground and in-wall utilities/objects, to the integration of RFID with building information modeling (BIM), the potential benefits of RFID to the construction industry will be a topic that receives more and more attention in the future. RFID, in conjunction with BIM, shows great promise in the promotion of lean construction techniques in the construction industry. As the technology becomes more readily accessible and the cost of implementation decreases, this will be used on more and more construction projects. Once contractors start adventuring into the potential that RFID has, the greater the construction industry will benefit. Keywords: Radio Frequency Identification, RFID, Building Information Modeling, BIM, Lean Construction, Technology, Construction Technology. 1 Introduction Profitability in the construction industry takes exceptional execution at every stage of a construction project, from the initial planning and design phases, to the closing out, and signing of the final contracts. The unique complexities and 1
  • unpredictable nature of projects in the construction industry make successful management a very valuable asset, but an extremely difficult chore. According to statistics in 2006, more than half of construction firms fail within their first four years in business [1]. The importance of productivity improvements within the construction industry has been generating a significant amount of interest [2]. Efficient management of assets may be considered a serious contributor to profit margins in almost every form of business. Technological advancements have provided companies in many different industries with more effective means for tracking and managing their assets. One such technology is Radio Frequency Identification (RFID). Among the many possible uses, it can be used for identification and data storage of objects, animals, and people. 1.1 Radio Frequency Identification (RFID) Radio Frequency Identification (RFID) refers to an automatic identification technology which utilizes radio frequencies, or waves, to capture and transmit data [3]. Data can be gathered and stored regarding an array of tagged items such as objects/components, people, and animals. There is currently a vast range of uses for the technology outside of construction including, but not limited to, product tracking for retail chains, library usages, inventory and supply chain management, animal tracking, health care, access and security systems, postal environment, airport baggage management, usages in automobile keys, and toll-collection (EZ-Pass). RFID technology uses a tag (also known as a transponder), and a reader (sometimes referred to as an interrogator), to successfully communicate and transmit data. The data gathered through tag and reader communication is transferred to a host system, such as a personal computer, or connected to a business’s enterprise system. The tag is attached to, or embedded into the object for which data is being gathered. Tags are comprised of a micro-chip and an antenna, which are encapsulated in a protective covering. RFID tags can have many different shapes, sizes and protective housings. Generally RFID transponders are considered either passive, or active. Active tags are those that have an internal power supply (a battery). Passive tags, on the other hand, do not contain a battery [4]. Some general characteristics of passive and active tags, as well as some pictures of each, are shown in Figures 1 and 2. Since passive tags do not have an internal power supply, they can only successfully transmit data when they absorb the power emitted by a reader. Since active tags have an internal battery source, they can actively emit a signal to the reader in order to communicate and transmit data. Active tags, therefore, have longer reading ranges. Active tags can also be “always on”, or programmed to “wake up” at determined time increments (every minute, 5 minutes, 10 minutes etc.), in order to communicate with a reader. However, long term use of the active tag is limited by the life of its battery, a problem that can limit its usefulness in facilities management. 2
  • Passive Tag Characteristics: No internal power supply Mostly read only (data cannot be re-written) Unlimited life Usually smaller/lighter than active tags Generally cheaper than active tags Limited read range Less data storage capability than active tags. Figure 1. Examples and Characteristics of Passive RFID Tags Active Tag Characteristics: Contains internal power supply (battery) Typically read/write (data can either be fixed or changed) Limited life (can be up to about 10 years) Usually larger/heavier than passive tags Generally more expensive than passive tags Longer reading range than passive Increased data storage capability Figure 2. Examples and Characteristics of Active RFID Tags Electronic reading devices are used to communicate with tagged objects and acquire data regarding those items. RFID readers or scanners can be portable (handheld) or stationary. The readers also contain an antenna for transmitting signals to the desired tags. The distance that a reader can read a tag will vary from one system to another. The reading range depends more so on the reader than the tag [5]. Some sample pictures of RFID readers are shown in Figure 3. 3 View slide
  • Figure 3. Examples of RFID Readers The frequency level at which an RFID system operates is also a key contributor to a system’s characteristics and performance. Higher frequency levels will increase the system’s reading range, as well as increase the speed at which data is transmitted from the tag to the reader and the host computer. On the other hand, lower frequency levels will decrease the reading range, as well as the speed of data transfer to the reader and rest of the system [5]. The frequency bands in which RFID systems operate is determined by each country’s respective regulatory body. The Radio Frequency (RF) section of the electromagnetic spectrum generally spans from 3Hz (Very Low Frequency) to 300GHz (Extremely High Frequency) (Table 1). Generic Band Name Frequency Range Comment Low Frequency (LF) 120 - 135 kHz Short range inductive applications. High Frequency (HF) 13.56 MHz Worldwide common frequency, smart cards and labels. Ultra High Frequency 433 MHz Active low power tags. (UHF) 860 - 960 MHz Band with major supply chain development activity. Microwave 2450 MHz Active tag technology gives range and fast data rates. Table 1. Radio-Frequency Identification Device Frequency Ranges There are many different varieties of RFID readers and tags which have different performance levels for certain criteria and purposes of use. This makes it difficult to analyze costs and historical trends. However, Niemeyer, Pak, and Ramaswamy [6] analyzed and forecasted the downward trend in average RFID tags and readers in a McKinsey Quarterly Report (Figure 4.) This downward trend should help facilitate increased adoption in the future. 4 View slide
  • Figure 4. Average cost per RFID tag and reader, Niemeyer et al, 2003 1.2 Lean Construction Lean construction results from the application of a new form of production management to construction. Essential features of lean construction include a clear set of objectives for the delivery process, aimed at maximizing performance for the customer at the project level, concurrent design of product and process, and the application of production control throughout the life of the product from design to delivery [7]. The highly competitive nature, combined with stringent time and cost budgets that are common in construction, require participants within the industry to constantly seek improvements in productivity [2]. Productivity can be measured in many ways, but is often defined as a measurement of the quality and/or quantity of output, in relation to the input required to produce that output. Among the many aspects critical to achieving better productivity, is a company’s ability to manage its assets and resources successfully. The efficient allocation, supervision, and motivation of on-site employees may be an important aspect of management for construction companies that employ a large number of craft workers. Effective management of building materials both throughout the supply chain, and while on- site, may be considered another important task for construction projects. The knowledge regarding the whereabouts of important tools and equipment on large- scale projects can affect productivity. The demand for increasing productivity and safety throughout project delivery has stimulated the exploration of new technologies that may be implemented to improve productivity of construction work. Many other industries have utilized 5
  • RFID technology for multiple purposes, perhaps most often for the tracking of products, and inventory systems management [8]. Currently, the prospective opportunities for RFID within construction are quite vast. Areas of lean management that can potentially utilize RFID technology and implementation include: Tracking and tracing of components vehicles, parcels etc Inventory Management Product ID - using the right component and device Maintenance of service systems Track recording of components Incorporating RFID into design The number of studies and experiments that have looked at different uses of the technology has significantly increased recently. From asset and progress management, to the locating of underground and in-wall objects and utilities, the outlook for potential benefits in productivity through the implementation of RFID in the construction industry is starting to look positive [9]. Organizations such as FIATECH, CICA, ERA Build, and the Construction Industry Institute (CII), have analyzed the technology’s potential within the construction industry through various pilot studies, demo applications, journal articles and papers, in an attempt to map out key processes and functions that could possibly benefit from RFID. ERA Build’s Final Report on RFID in Construction [8] noted the following as the main drivers for the construction industry: Tracking and tracing of components, vehicles, parcels etc. Supply Chain Management and Logistics - efficiency Product ID - using the right component and device Maintenance of service systems Track recording of components Although interest in RFID in the construction industry has increased significantly over the past decade, the number of companies that have adopted the technology for continued use within their operations remains somewhat stagnant. According to the same ERA Build Report [8], some of the main preventers of widespread construction industry adoption include: Immature application of advanced logistics systems and the absence of information and identification systems in the construction industry. Lack of awareness of RFID's potential in the construction industry. Low RFID-knowledge and awareness in the construction sector Lack of robust RFID-initiatives in the construction industry Lack of successful RFID-implementation cases that thoroughly shows its potentials The traditionally less industrialized construction industry and its relatively negative attitudes toward new innovations and technology A National Institute of Standards and Technology (NIST) white paper entitled Smart Chips in Construction, noted recommendations for further research that is needed before advances are to be made in implementing RFID in the construction 6
  • project life cycle. Among other requirements, the paper calls for increases in RFID pilot studies within construction. For increased promotion of RFID solutions in the construction industry, ERA Build’s final report [8] stated that “the primary need is for exchange of knowledge and project RFID sampling to increase contractor and owner awareness of the potential savings.” It will become increasingly important to continue to evaluate different reasons for RFID adoption, and the implementation processes that are undertaken by those companies which utilize the technology. 2 Background Literature on RFID and its potential within the construction industry has mainly arisen within the last decade or so. The Construction Industry Institute (CII) conducted a workshop regarding RFID and possible implementations in construction in 1998 [3]. The workshop divided into four groups consisting of material management, engineering/design, maintenance, and field operations. Each group identified many potential RFID applications within their delegated areas of concentration. A lengthy report was written in 2006 regarding RFID and construction [8]. Contents of that report include: a brief introduction into RFID technology; the uses and benefits found in other industries; Applications to the construction industry, as well as a list of cases and pilot studies that have been performed globally; and the driving forces for RFID, and challenges faced that may deter or delay industry-wide acceptance. There have also been a number of brief articles written recently which express RFID’s lurking presence within the construction industry. The prospects for improved productivity through its implementation, and some problems that have hindered its adoption into construction are also addressed in those articles [9, 10]. The positives and potential negatives of RFID uses for supply chain management are assessed in articles by Wang [11] and Santosh [12], which explore new management processes, as well as the legal aspects and concerns for confidentiality of supply chain processes information, resulting from uses of RFID. Actual data producing research and experimental testing of RFID utilizations for improved efficiency in construction processes have been performed predominantly over the last few years. One significant study has been done through a collaborative research method performed jointly by Samsung Corporation, Sungkyunkwan University, and Doalltech Corporation [13]. The study concentrated on RFID and 4D CAD (Computer Aided Design) technologies for improved progress management of structural steel work on high-rise buildings in Seoul, Korea. RFID was implemented from the beginning steel manufacturing phase, and tracked throughout the delivery and receiving of materials phases. Invoicing practices and on-site management of the steel inventory, from receiving and storing, to the actual erection of the pieces, were tracked and analyzed for three projects. Two of the three projects implemented the new technologies, whereas the other followed current methods and practices for managing the supply chain and construction processes of structural steel components. Although there were plenty of positives resulting from the study, some apparent signs of the immaturity of the 7
  • technology were reported. A lack of confidence in the technology was expressed by those who were unfamiliar with RFID. Manufacturers of the steel were the most reluctant to adopt the process because of the added work of attaching the RFID tags and a lack of benefits on their end. On the positive side, increases were reported in productivity for time spent inputting data, unloading steel, time spent in stockyards of factory and construction site, and the general contractor and subcontractor’s daily reports. An overall process time with the new technologies was shown to have 17% more time efficiency than the conventional process for supplying and erecting the steel [13]. A materials tracking field test that was sponsored by the Construction Industry Institute was performed by professors and graduate students from The University of Texas at Austin, University of Kentucky, and University of Waterloo, along with the collaborative help of local industry partners, and RFID solutions vendors. The studies were done on two projects: A $750 million power plant in Rockdale, TX, constructed by Bechtel; and a 550 megawatt Portlands Energy Center in Toronto, Canada, contracted by SNC-Lavalin Constructors Inc. Both of these studies also produced positive data and worker feedback regarding RFID implementation [9]. Through comparing the time it took to locate materials with the old method, to the automated method with RFID/GPS technology, the study found that the average time to locate materials with the manual method was 36.8 minutes, and the time it took with the automated method was 4.6 minutes. In an ENR article, Paul Murray, the site manager on the Canadian project noted “Instead of having a $75-per-hour pipefitter go out and look for [a component], we had a $14-per-hour student intern ID it, and then they would go out and get it” [9]. Murray also commented on the performance of the technology and implementing it full time: “We had two identical boilers…Once we saw the use of it we weren’t going to let one boiler fall behind” [9]. Research on the use of RFID in the concrete curing processes has also developed over the past fifteen years. In 1995, an article in the Journal of Construction Engineering and Management proposed three potential uses for the technology within the construction industry [5]. The concepts developed in that article pertained to concreting operations; cost coding for labor and equipment; and material control. The article mentioned the potential ability of RFID to take incremental temperatures, but for the most part concentrated on proposed systems for tags to be externally applied to concrete trucks and concrete test cylinders in order to locate and identify them. Another article discusses external applications of RFID to concrete was recently written in the past two years [14]. The article analyzes the tracking of engineered-to-order components such as precast concrete members throughout the supply chain with RFID. The article harps on the automated data collection that RFID provides which workers try to avoid, as well as the durability of the technological equipment, but still only mentions external attachment to objects, as the cheaper passive tags better suited their budget. A study regarding the implementation of RFID tags inside concrete specimens was performed by Wang et al. [11]. One goal of the study was to develop a web- based quality inspection and management system for improving the availability and 8
  • communication of inspection data results to those involved in the construction process. The quality management system that developed was designed to quickly gather data in material test lab areas and relay that data, via the internet, to other parties of interest such as the owner, consultant firm, customers, suppliers and contractors. Another important goal of the study was to determine through field tests, whether the insertion of an RFID tag inside concrete would influence the strength of a specimen. Proper placement within a specimen was also discussed. Conclusions regarding the web based system claimed that it “enhanced the construction quality inspection and management performance in…working efficiency, reduction of operation cost, customer satisfaction enhancement, and time saving in inspection operation and management progress” [11]. The study also found that the placement of RFID tags inside concrete specimens did not influence the strength of those specimens. An important note to add is that the research expressed the importance of the insertion position of the tags within the concrete because if the tag were too deep, it would be unreadable [11]. The Michigan Department of Transportation (MDOT) performed another study and Dr. Andrew J. DeFinis wrote a white paper on the research entitled “Concrete Maturity Testing in Michigan”, in February of 2004 [15]. The test was performed because the MDOT wanted to develop a provision that would allow contractors in Michigan to use maturity testing to approximate the strength development of concrete pavements. The maturity concept estimates the strength development of concrete by taking into account the combined effects of temperature, and the time a specimen was poured. Data on time and temperature, gathered through RFID wireless tags located within the concrete, was entered into an equation known as the Nurse-Saul equation. The Nurse-Saul equation is used to estimate the strength of concrete in pounds per square inch. Standard concrete cylinders were also tested and the compressive strength was compared to the maturity estimates. The study concluded that the Concrete Maturity Monitoring System measurement results were within 4-11% of the concrete cylinders. Differences in results were expected to be reduced if adjustments could be made to the method of curing the concrete cylinders. Every RFID tag placed on the project worked. Currently a study is underway which will utilize RFID tags for concrete curing information on the construction of the Freedom Tower in Manhattan, which is being erected on the location where the World Trade Center towers once stood [16]. The tags are being utilized on almost every major concrete pour including footings, core walls, elevator shafts, stairs wells, and all mechanical spaces. Identec Solutions AG, Lustenau, Austria is providing the tags, and the article reports that approximately 20,000 active RFID tags will be used throughout the 1,776-foot tall tower and its surrounding structures. Research regarding the monitoring of labor inputs, and uses of new technologies to compose real-time assessments and make necessary adjustments to labor force allocations, has become an increasingly attractive topic in construction [17]. Studies performed by Navon and Goldschmidt in 2002 explored possible technologies that could be used for automated location measurement. RFID played a significant role in their design of a performance measurement system, which proposed to determine 9
  • worker’s locations at certain time intervals, and then measure the amount of work completed at those locations, or “work stations”, to establish a metric of productivity [17]. In 2003, Navon and Goldschmidt put their performance measurement system through a series of smaller, preliminary field experiments, in order to analyze the systems accuracy in measuring worker efficiency. The results determined that the “prototype successfully measured the time workers spent performing their tasks with an accuracy level of plus or minus 10-20%” [18]. The study also mentioned the uses of RFID technology for determining employee locations after accidents have occurred on a site. The amount of literature pertaining to RFID and the employments to the construction industry has significantly increased since the year 2000. There are numerous reports that explain the current uses in other industries, and anticipate that possible applications within construction will increase in the future. A handful of data producing experiments have been performed for asset tracking and management, particularly for materials, equipment labor and concrete curing, with hopes of determining potential improvements in the project delivery process. 3 Case Study This specific case study pertaining to RFID applications within the construction industry was performed on a power plant expansion project being constructed by Bechtel Corporation in the Northern United States. The expansion project consists of two coal-fired steam-turbine generating units, as well as supporting facilities, and related civil work. The contractor’s scope of work consists of engineering, procurement, construction, and start up. The project will cost an estimated $2.15 billion dollars, with construction scheduled from 2005 to 2010. Of the two units, one is scheduled to begin operation in 2009, and the second is scheduled to begin operation in 2010. 3.1 Site Layout and Material Lay-Down Yard The original project site utilization plan for the project delineated one large area of the site to act as the lay-down yard for construction materials as they were brought onto the site. A substantial amount of site work was necessary in order to prepare the land for construction of the new expansion facilities. The earth removed from the shoreline area where the new expansion project was to be constructed was placed on the proposed materials lay-down area. Afterwards, it was found that there were issues with the underpinning soils and the majority of the land would not suffice for material storage. Approximately 60 acres of land intended for material storage was determined to be unusable. As the original material lay-down yard was unsuitable, the construction management team was forced to reorganize and utilize alternative land for the necessary material storage for the project. Through arrangements with landholders to the south of the construction site, additional land was acquired for material 10
  • storage needs for the duration of the project. The yards now stretched from North to South and the distance between the two farthest most yards was approximately three miles. 3.2 Materials Management Process without RFID The materials management process for the project is comprised of a series of activities or processes that ultimately lead to the installation of a component into the facility. A majority of the steel and piping for the project was received on site via truck. Some components for the project were shipped by boat. As materials are delivered to the site, they came with a packing list, which detailed the contents of the shipment, including where it came from, contact information, date of shipment, etc. Each component of material comes with its own specific material identification code for the project. The material ID codes are written on the surface of the components, and are comprised of a series of numbers and letters (Figure 5). The entire receipt process and the entry of items into the materials management database was performed with a paper based Figure 5. Material ID code manual method. The materials are accounted for and manually entered into the materials management database system, so that construction activities could be coordinated depending on the availability of materials. The components are then taken to the lay-down yards and placed within a specific grid. Caldas et al. [19] refer to this stage as “Sorting.” The components are grouped within grids according to characteristics and material identification code. Different groups of materials are assigned a color scheme. Specific colors and twisted combinations of colored flags are attached to the respective groups of materials for future identification and locating purposes. Materials are stored in the lay-down yard until needed for installation. When a construction crew or trade is prepared to construct a certain section of the facility, the necessary materials have to be retrieved from the lay-down yard. For this, a superintendent coordinated with a field engineer and communicated the plans for assembling a certain area of the facility. The field engineer would generate a material withdrawal request (MWR), which listed all of the necessary materials that the superintendent’s crew needed in order to complete the specified scope of work. The MWR is sent to the Materials Management staff, where they develop a “pick ticket”. The pick ticket lists the materials needed, along with the respective lay- 11
  • down yard and grid location of the component. The Materials Management team then gives the pick ticket to the respective staff so that they can locate the materials. Workers would take the pick ticket to the lay-down yards and visually locate the materials that were needed for installation. Once located, the components were flagged, organized, and staged so that the pick-up process of those materials would be easier and more efficient. The materials would be loaded and taken to the construction area where they were turned over to the construction team. Once the materials had been turned over to the construction team, the receiving foremen would sign off on the materials to assure that they have received them. The sequence of activities in the materials management process for this project was similar to the one described in the pilot test performed by Caldas et al. [19], in which the impacts of utilizing Global Positioning Systems (GPS) for the locating of materials was measured (Figures 6 and 7). Figure 6. Material Management Process [2]. 3.2.1 Problems Presented With the Manual System The issues presented for materials management on Bechtel’s power plant expansion revolve around the ability of personnel to locate and flag specific material items (Flagging), so they may be organized for convenient pick-up and transporting. When materials required for installation are not ready at the time they are needed, installation crews may become idle and nonproductive, which can increase craft labor hours up to 16-18% [20]. The sheer volume of materials required on the construction site presented the materials management team with several problems. The $2.15 billion power-plant 12
  • Superintendent Materials are loaded •Ready to construct up, taken to site, and workers sign off Communicates to on receipt Field Engineer. Trade Workers Field Engineer •Take ticket and locate, •Develops MWR (list of flag, and organize/stage needed materials) materials for pick-up Sends MWR to Sends pick ticket to Materials Mgmt. respective trade staff. staff. Materials Management •Develops pick ticket Figure 7. Responsibilities and Paperwork for On-site Material Management Process project is comprised of an incredibly large number of intricate components of steel, piping, and other structural and functional components. Individual piping pieces can become very difficult to identify when they are closely stacked together in areas of what can be thousands of square meters per lay-down grid. Additionally, there is a limited number of colors that flagging comes in, and it can become difficult for the picking crew to decipher which materials are for their specific load if there are multiple loads marked with the same colored flagging (Figure 8). Figure 8. Piping and structural steel lay-down yards 13
  • The arrangement of the material yards is also a factor which can contribute to decreased efficiency in the flagging process, as well as the rest of the material management process. The farthest lay-down yard was almost three miles from the construction site. Therefore, minimal time spent at the storage yard was desired since it took a significant amount of travel time to get there and back. Another factor affecting the material management process was the weather conditions. Extremely cold temperatures, combined with rain and snowfall, were the main areas of concern regarding severe weather that could affect construction productivity. The flagging process was made much more difficult after heavy snowfall for the obvious reason that the materials would get covered in snow and the material ID codes must be uncovered, with shovels or by hand, in order to properly identify. Snowfall could complicate and delay the delivery of materials to the construction site further if a significant amount of snow was received after the flagging crew had already located and flagged the necessary materials. The flagging process must essentially be repeated by either the flagging crew or by the picking team when they come to load the items for transportation to the construction site. 3.3 Experience with Automated Systems, Lean Construction, Six Sigma, and Decision to Implement Due to the problems associated with the manual tracking system, the decision was made by management to implement a full scale RFID/GPS based system for the entire on-site materials management process. ERA Build [8] noted that long implementation time and difficulty in obtaining the skills and knowledge on the technology can be key operational and technical barriers that face companies in adopting the technology. This was the company’s first full scale application of the technology. The big decision to invest and employ the technology on a large scale was made less difficult, in large part, due to the company’s previous participation and involvement in pilot tests. Bechtel hosted an academic study pertaining to RFID technology on one of its construction sites in 2005. Bechtel’s field test was performed over approximately three months on a twin- boiler project in Rockdale, Texas. Chief sponsors of the pilot were the Construction Industry Institute (CII) and FIATECH, and the research team was comprised of about two dozen individuals representing universities, construction firms, institutes, and technology vendors [9]. The field tests compared the times of the typical paper based manual method of locating steel items, to the RFID/GPS based automated method for tracking down components in the lay down yards. The trial results found that the average time taken to locate a specific component with the manual process was 36.8 minutes. The average time taken to locate materials with the automated method was 4.6 minutes. Also, when using the manual method, 9.52% of material components “were not immediately found,” compared to the 0.54% of the automated method. The research team regarded the success rate of the automated system to be quite significant considering the fact that the failure to locate critical items can lead to costly slowdowns, and sometimes even re-procurement [9]. 14
  • 3.3.1 Six Sigma Management Strategies Bechtel utilizes Six Sigma management strategies throughout their business processes and construction projects. Six Sigma is a quality based business strategy which aims to decrease the amount of defects, or errors, or failures that a company might encounter throughout its business processes. Defects are known as anything that may lead to customer dissatisfaction. Six Sigma aims to develop quantifiable business improvements via statistical analysis of data. The process can be described as: “Six Sigma methodology of problem solving integrates the human elements (culture change, customer focus, belt system infrastructure, etc.) and process elements (process management, statistical analysis of process data, measurement system analysis, etc.) of improvement.” The experience gained through the field study proved to be valuable for Bechtel, in regards to developing future applications. Not only did the field studies produce valuable data for statistical analyses, but the relationship that was gained with the technology vendor during the field tests, was able to be continued, and developed into a business relationship for their full scale implementation. 3.3.2 Technological Specifications: Tags and Readers The tags utilized in this full scale implementation were active RFID tags. These active tags continually “wake up” and send out their ID information at pre- configured intervals (i.e. every 1 second, every 2 seconds, every 10 seconds, etc.). The active tags are Ultra High Frequency (UHF), and they operate on a 915MHz frequency level. The lifespan of the tags is generally five years. The physical dimensions of the tags measure about 5 x 1 x .85 inches and weigh about 50 grams. Tags with these characteristics and reading ranges cost approximately $25(US) each. The reading units utilized in this application were a combination of RFID reader and Global Positioning System (GPS) receiver. The readers were mobile, handheld computers, or personal digital assistants (PDA), suitable for field readings. The readers’ operate with Microsoft Windows. Approximately six handheld readers were utilized on the entire project; usually a team (i.e. iron-workers) would have its own reader which was designated for them each day. RFID/GPS readers such as those utilized in this study currently cost approximately $5,000(US). The automated materials management process also used barcode scanners for association purposes. The scanners were mobile, handheld devices that utilize Bluetooth technology. The scanners operate on High Frequency (HF) radio waves at a 13.56 MHz frequency level. The scanners are rechargeable. The physical dimension of the barcode scanner is about 4.8 x 2 x 1.3 inches and weighs 132 grams (about 0.3 pounds). These barcode scanners currently cost around $450- $500(US). (Figure 9). Server software is also required for the system and it can cost approximately $35,000 - $50,000(US) depending on the software and the vendor. 15
  • Figure 9. System Hardware 3.4 Implementing the RFID/GPS Based System The RFID/GPS based materials management process was not implemented from the beginning of the project. It was only after the problems mentioned above arose, that the decision to implement the automated tracking system was made. At that time, around 65-75% of the materials for construction had already been delivered to the site. Having the majority of the materials on site meant that the materials management process would have to be retro-fitted with the technology. Roughly 6-10 employees were assigned the task of attaching tags to materials in the lay down yards, and associating those tags to the specific material piece in the management system. This project tagged 20,000+ unique material components with RFID. Approximately 12,000 tags were utilized for this project, as tags are reusable. 3.4.1 Attaching and Associating RFID Tags to Materials RFID tags were attached to the material components with plastic zip ties. The holes present on the RFID tags make this a simple process and the tags can attach to materials through anchor bolts in the materials, or by simply wrapping two ties around the materials and pulling tightly (Figure 10.). Once the tags are attached, they must be associated with the respective material to which they are attached, for future tracking purposes. Some materials arrived on site with a barcode label that indicated the component’s material ID. Others did not have barcodes attached, and their material ID would be written on the exterior of the component. If the material component had been delivered with a barcode label, then the association process becomes very simple and almost instant. The barcode label on the material component is simply scanned along with the barcode label on the RFID tag attached to it. The barcode scanner is able to instantly transmit the material ID and RFID tag’s ID into the RFID reading device wirelessly via Bluetooth technology. Once the material ID and tag ID had been input into the RFID reader, 16
  • the worker could hit “associate” on the RFID reader to initiate communication with the tag while next to it, and that specific RFID tag’s ID would then be linked to the material component on which it was attached. Once the tag was associated, the workers would hit the “locate” button on the RFID/GPS reader, and the component’s latitude and longitude is stored in the reader. The tag had been associated to the specific material component and now that specific material component was ready to be tracked. When items arrived with barcode labels, the association process, after the tag had been attached, was very simple, and completely automated. The association process takes approximately 10 seconds. Figure 10. Associating materials with and without barcodes ID When material components did not have an attached barcode label, the association process was changed slightly. Workers would still scan the barcode on the tag to input the tag ID into the RFID reader, but had to type in the material’s unique material ID, which was stamped or written on the exterior of the item, into the RFID reader. The worker hits “associate” on the RFID reading device so that the material component would now be linked to the tag (Figure 10). Again, the worker would hit “locate” to assign the material a latitude and longitudinal position. When employees typed the material ID into the handheld devices manually, the elements of human error become possible. Problems such as entering the material product ID incorrectly were more prone to happen in this case. 3.4.2 GPS Mapping and RFID Tag Locations Before the system was implemented, the lay-down yards throughout the site were geo-coded, mapped and entered into a geographic information system (GIS), which divides the yards into their respective coordinated grids. As Torrent and Caldas [20] explained, GPS receivers can be set to transform collected systems into a coordinate system. The default latitude and longitude degrees for a global system 17
  • can be transformed into a “local projected system” so that it “simplifies the implementation of the localization mechanisms by providing coordinates in fundamental units of length, such as meters [20]. An image of the digital lay down yard on an office desktop easily identifies the material and its location in the lay- down yard (Figure 11). Figure 11. Digital map of lay down yards with grids 3.4.3 Tag Item Location with RFID/GPS System Because of costs and other issues, attaching individual GPS receivers to each piece of material, when there are mass amounts of material items, has been deemed an infeasible option for the purposes of locating construction materials [20]. Therefore, the project in this study utilized six RFID reading devices that were equipped with GPS receivers, and the material components were tagged with RFID tags. The GPS receivers are able to determine their own location at any given time. The active RFID portion of the reader could then be utilized with localization methods, which are algorithmic based location projections based on strength of signal and reader location, as described by Torrent and Caldas [20], for the projected locations of the RFID tagged components that were within reading range of the reader. Periodic updates are made in order to update the projected locations of materials. To perform a periodic update on a lay down yard, an employee would either walk or drive around the perimeter of the lay down yards with an RFID/GPS handheld very slowly, in order to allow the reader to pick up all tags within the yard. Once the updates are complete, the RFID readers are brought back to the materials 18
  • management office and placed in their “dock” (Figure 12). When placed in a dock, the handheld reader automatically transfers new data, gathered by field activity, into the main materials management database. Figure 12. Docked RFID/GPS Readers in Office 3.4.4 Automated Locating Process With the RFID/GPS system in place, the goal is to make the material locating (flagging) process much easier and faster. With the automated system in place, after the Engineer has developed a material withdrawal request (MWR), the materials management office staff generates a pick ticket packet which included a list of the required materials and each item’s specific yard and grid, as well as a supplemental image, which would give the workers the approximate location of each component within their respective grid, assigned by the GPS/RFID localization methods (Figure 13). The workers go to the correct lay down yard and grid, and go approximately to where the printed map had indicated the material’s location to be within that grid. Once in the area, the workers utilize the RFID/GPS reader to narrow in and find the component. The reader could pull up two different modes for finding the items. The map view utilizes the GPS portion of the reader. The digital map of the yard can be displayed on the handheld screen and the GPS receiver will show where the 19
  • Figure 13. Pick ticket list and map of projected locations employee is standing, and the projected location of the material. The employee’s positioning on the screen is represented by a blue dot, and the material component is represented by a red dot (Figure 14). Another method was to set the reader into what was referred to as the Geiger counter mode. A Geiger counter is an instrument that can detect and measure radioactivity [21]. The Geiger counter mode of the reader allows the worker to communicate only with the specific tag that is desired. The Geiger counter can be utilized within 150ft proximity from the tagged components. As the worker moves with the reader, the GPS receiver determines and gathers information on the location of the reader. The RFID portion communicates with the desired tag, and the reader utilizes localization methods based on the positions of the reader (gathered by GPS), and the received strength of signal from the desired tag at those positions (gathered by RFID). A compass pointed the employee in the direction of the tag with which the reader was communicating (Figure 14). The reader also emits audible “beeps” that becomes more rapid and in closer intervals as the reader gets closer to the tag, and the signal strength increases. When the reader is within a couple of meters from the tag, the compass would change to a cross-hair and display the words “WITHIN RANGE” (Figure 14). Once the reader is held next to the correct tag/material, the blue column bars fill the graphing area displayed on the screen (Figure 14). The worker then examines the material and the material ID, which is written on the exterior of the component, to assure that the material ID on the item matched the material ID listed in the pick ticket. As before, once the materials had been located, they could be organized, 20
  • prepared for loading and transported to the construction area. The construction crew would sign off on the materials to assure that they had been received for installation. After materials were delivered, the tags would be removed from the material and placed in a steel bucket. The tags could then be recycled back to the material management office, where they would be disassociated from the material to which they were originally attached, and stored for possible reuse. Figure 14. Reader in Geiger, Map, and Within Range 3.4.5 Performance of the System The performance of the technology was satisfactory and it was noted that there were very few malfunctions. One issue of concern was whether or not the technology would perform in very cold temperatures. They found that the system worked down to -26 degrees Fahrenheit. Also, it was mentioned that at extreme temperatures below that mark, the readers were affected by the cold before the tags, so workers would warm the readers by means such as holding the readers inside their coats. Tags could easily be read through a couple of feet of snow. Although the tags were durable, moving materials or placing heavy materials on top of each other can sometimes damage the tags. It was proven that if the outer shell of the tag has been damaged, but the internal battery and antenna device had not been affected, the tag maintained its readability function. For assurance measures on this project, tags that were damaged in any way were replaced, and new tags were attached and associated to the material. During the initial stages of implementing the RFID system, a few tags were left attached to their respective material components after the materials were installed in the facility. When readings were attempted on the installed materials from inside the facility, workers found that the surrounding structure, which was comprised of mass amounts of steel, did not facilitate successful communication between tag and reader. Therefore, management decided to remove the tags for recycling once the materials had been received and signed for by the receiving foreman. 21
  • 3.4.6 Results and Future Plans Jim Rogers, the Six Sigma Black Belt for the project, commented on the current standing of the automated system and the effects that Six Sigma and RFID/GPS have had on the project: “We used all the (RFID) tools, and the application of LEAN to eliminate a wasteful flagging step…We now send the loading crew straight to the material rather than having another pair of people go ahead to make sure they can find the material, flag or identify it with colored ribbon, in order to optimize the loading crew’s time, and that of the crane. The quantified savings were centered on eliminating the flaggers, although many other benefits are known, e.g. schedule, supply chain risk, staging space savings.” The RFID/GPS based system utilized on the project described in this case study will continue to be used by the company for upcoming projects of similar type. Two new projects will utilize the same technology are recently getting underway in Ohio and Illinois. In this case study, the automated system was retrofitted to the existing materials already on site and in the lay down yards, however, future applications will aspire to implement the system so that the materials will be tagged with RFID before they arrive on the project site. When commenting on further developments of RFID based solutions, and the processes that will be impacted and changed, Rogers noted: “The whole supply chain, from engineering through procurement, field material management, construction, and some selected components (that need maintenance) by the customer. We started with the greatest need, with a compelling business case, and we will build from there.” The future goals will be to track different components throughout the entire supply chain, as well as while on site, and selected components that will need maintenance in the future, could also remain tagged with RFID after installation to facilitate easier identification for maintenance. To do this, it will require increased cooperation and coordination with suppliers, customers, and others involved in the supply chain process. 4 Conclusions Although RFID technology solutions for the construction industry are still in the early stages of development, case studies are showing that custom solutions can be proven beneficial for some construction companies’ processes. Solid business cases for RFID based solutions that can be uniformly applied across the construction industry remain to be seen. This may be in large part due to the fact that each construction project will be unique to a certain degree, whether it is by size, complexity, life-cycle, geographic location, etc. Also, depending on the size and structure of a construction company, it may or may not be able to accommodate, and assign overseers for the adoption of a new technological system. Those companies that remain curious and open minded towards the technology will be more likely to realize potential benefits. If construction companies are willing and able to put forth the effort and investment of time that might be necessary to familiarize themselves with the technology (different variations and combinations), then those companies will be the ones that begin to realize the potential for applications within their own 22
  • processes and project delivery methods. The experience a company gains with the technology through sponsored academic studies proves to be valuable for both statistical data, as well as for developing a working relationship with the technology vendor. These experiences, combined with the companies’ excellent ability to self- analyze and pinpoint weaknesses within their current processes, ultimately led to a full scale implementation of an RFID/GPS automated system, which was aimed at completely eliminating an entire step within the materials management process. Another technology that may facilitate the transition from tracking field materials to in-place materials is in the area of building information modeling (BIM). As more and more projects are becoming BIM based, a natural progression will be to link the RFID solution to the BIM solution. This would mitigate the problems currently encountered with reading tags of in-place materials and the loss of data once a battery ceases to operate. If the owner receives an as-built model, the facilities management process can eventually be streamlined. This is truly in line with the lean construction philosophy. References [1] Ganaway, N. (2006). Construction Business Management: A Guide to Contracting for Business Sources. Butterworth-Heinemann [2] Park, H. (July, 2005). Benchmarking of Construction Productivity. Journal of Construction Engineering and Management, 131(7), 772-778. [3] Jaselskis, E., El-Misalami, T. (2003). Implementing Radio Frequency Identification in the Construction Process. Journal of Construction Engineering and Management. 129(6), 680-689. [4] Roberts, C.M. (2006). Radio Frequency Identification (RFID). Computers and Security, 25(01), 18-26. [5] Jaselskis, E., Anderson, M., Jahren, C., Rodriguez, Y., Njos, S. (1995, June). Radio-Frequency Identification Applications in Construction Industry. Journal of Construction Engineering and Management. 06(1995), 189-196. [6] Niemeyer, A., Pak, M. H., Ramaswamy, S. E. (2003). Smart tags for your supply chain. The McKinsey Quarterly, 4. Retrieved May 1, 2009 from http://www.mckinseyquarterly.com [7] Howell, Gregory A. (1999). What is Lean Construction. IGLC-7 Proceedings, University of California, Berkeley, CA, July 26-28, 1999. [8] ERA Build. (2006). Review of current state of radio frequency identification (RFID) technology, its use and potential future use in construction. 23
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