RFID Helps Control and Organize Construction Sites

By Rhea Wessel

Germany's University of Wuppertal has developed a hardware and software platform that provides managers with up-to-the-minute information regarding materials, tools and individuals entering and leaving job sites.

Constructions sites are beehives of activities, with vehicles dropping off materials, workers arriving and leaving, and tools being dropped off and picked up when they are no longer required. Activities must take place in carefully timed sequences to ensure each part of a project is completed as the next begins. Orchestrating all of this activity is difficult and time-consuming, but the Construction Management and Industry Department of Germany's University of Wuppertal believes radio frequency identification can help.

Researchers have combined several RFID applications into a single "control center" designed to monitor and document personnel and materials as they enter and exit construction sites. The so-called RFID Construction Logistics Control Center combines RFID hardware, software and related computer systems within a freight container designed to be placed at the entrances and exits of construction sites.

Manfred Helmus, chair of the Construction Management and Industry Department

The functions available via the control center allow construction managers to have accurate and up-to-date information regarding the materials, tools and personnel within a construction site's boundaries. Passive tags on people, tools and materials identify them as they enter the job site, so that managers know the times of arrival and departure. The control center also includes an RFID-based application to ensure that construction workers are actually wearing their required protective gear.

Manfred Helmus, the chair of the Construction Management and Industry Department, says the control center will soon be commercially available. Development began in March 2008 and lasted until February 2010, when a two-month testing period of the project's single prototype was completed at a construction site in Essen. The university is currently in negotiations with the project's partners about producing and selling the containers. According to Helmus, each RFID system in a container functions independently of the others, and users can customize the combination of applications they need.

A fully equipped control center container can be used for four types of people-tracking RFID applications, as well as three that track goods. People-tracking applications include an RFID-based access-control system for the construction site, restricted areas within that site, an RFID-based system for tracking the work hours of employees and contractors, and another that ensures workers wear the proper protective clothing. The control center monitors the delivery of materials by recording when trucks arrive and leave the site, and tracks the tools workers carry into the site. In addition, RFID is the basis of an automatic, self-service kiosk at which employees can purchase small amounts of missing supplies, upon demand, on the construction.

Construction-site managers must oversee dozens—and sometimes hundreds—of contractors on a single construction site every day. In order to know who is on the construction site at any given time, as well as the amount of time spent on the construction site, managers must track who enters and leaves. With the control center in place, a worker must present his RFID-enabled ID card at one of two RFID-enabled turnstiles in the container, and have the fingerprints on each hand read in order to validate that individual's identity before entry is permitted.

According to Helmus, due to the high number of illegal workers in the construction sector, the fingerprint reader is important for ensuring that workers do not share a badge. He and his team designed the system to work with two fingerprint readings instead of one to increase the system's accuracy, since initial tests showed that it was occasionally difficult to get an accurate fingerprint reading for those with dirty hands or scarred fingers. Once an employee is identified, the turnstile opens and the system begins tracking the time spent on the construction site. The information can be used by employers for calculating pay for workers.

Such information is also extremely useful in case of an accident. The data collected via RFID shows a construction site manager immediately which workers are on site. Since the unique ID number on the EPC Gen 2 tag used in each ID is linked to that person's job description—such as a roofer or an electrician—managers can also infer where on the construction site the person might be working.

In addition, the system monitors the use of protective gear. While a worker is being identified with a badge and fingerprints, the readers mounted near the turnstiles check to make sure the employee is wearing the necessary protective gear. The system does this by comparing the actual gear worn with information stored in a database regarding the equipment a specific worker is required to wear.

Each turnstile has one UHF reader from FEIG Electronics with three antennas. One antenna reads the tag inside a worker's helmet, another does the same for the tag attached to a safety vest, and a third mounted close to the ground is used for reading tags attached to a worker's boots above the shoestrings. If a positive ID is made and the worker is wearing all necessary gear, he will see a green light and be able to pass the turnstile.

Construction managers who set up other readers at key points on the construction site, such as at offices or entrances to dangerous areas, can utilize the same access-control system to allow only authorized workers into a particular area.

Material Tracking

Helmus and his team also tested the control center system's ability to track incoming and outgoing RFID-tagged goods with handheld and mobile readers. According to Helmus, the system makes this much easier by turning records that are often still kept by hand today—a site's daily log—into digital records.

Construction-site managers and subcontractors frequently struggle to maintain accurate inventories of their on-site equipment. If all items were tagged, an RFID reader at the construction site entrance could be used to mark the entry and exit of all tools and materials onto the site.

The system includes material-logistics software accessible through a Web portal. Helmus and his team designed it so that suppliers could produce their own RFID tags to be attached to delivery notices, if suppliers had RFID printers. For instance, a company operating on a construction site could log on, order insulation panels or other supplies, and receive an electronic notice indicating when the supplies are expected to be delivered.

When a driver arrives with the goods and an RFID-tagged delivery notice, he or she approaches the construction site entrance, the tag is read, and the driver is then allowed to enter the site. If all the goods in the payload are tagged, RFID could also be used to compare delivery notices with actual goods delivered. Agnes Kelm, an engineer who worked on the project, says this idea was tested with bar codes only, since participating suppliers did not have RFID printers.

RFID could also be used to track construction tools and equipment. If these items are tagged, those tags could be read at the control center using a handheld reader. Feasibility tests were performed with an Intermec IP 30 reader.

By using the system, managers would have accurate, up-to-date lists about their property, which could greatly reduce the amount of equipment that gets lost, misplaced or mistakenly taken by other companies operating on the construction site. In addition, by combining tool information with employee IDs, businesses could record which worker used which tool, and when. Such information is valuable, Helmus explains, in case a company must retrace the steps made during construction for legal or regulatory reasons.

A third material-tracking application that the university integrated into software used to run its control center system is a standalone RFID-application from Gradwohl. The company has developed a freight-container-sized rental system that is unmanned and can be placed on construction sites. Workers who need to rent a tool or purchase a few missing screws can enter the container, use their RFID-based badge for identification, select their materials on a touch screen and then retrieve materials from a drawer that pops open, or a locker accessible with a key.

"The RFID Construction Logistics Control Center is a major piece in the puzzle for making construction processes more transparent, efficient and controllable," Helmus says, adding, "The system can also save lives by ensuring that workers wear the assigned protective equipment."

The project, led by the university's Construction Operation and Construction Industry Teaching and Research Area, is part of ARGE RFIDimBau, a research cluster focused on the use of RFID in the construction sector that is part of the ZukunftBAU project. ZukunftBAU is an initiative of the country's Federal Ministry for Transport, Building and Urban Affairs and the Federal Office for Building and Regional Planning.

Industrial partners for the project include Streif Baulogistik, Cichon Stolberg, Klebl, Züblin, ALHO, ThyssenKrupp Real Estate and Gradwohl. Streif Baulogistik, a specialist in construction logistics, contributed know-how, while Cichon Stolberg and PCO provided software for the RFID application.