The technology used to monitor the health of structures isn't new. It was used even before the mid-'70s when monitoring devices were built for specific job locations and installed to track certain events. Technicians then visited the structure periodically to record data, evaluate it, and produce reports for the owner. But today there's a wide range of "off-the-shelf" sensors, hardware, and software available. Thanks to the Internet, cell phone technology, miniaturized computers, and PDAs, information can be transferred more conveniently. Sensing devices can be installed either during construction or anytime after. Today several companies install and report data in this way.

Tom Weinmann is the manager for the Sensors and Diagnostics Group at Construction Technology Laboratory (CTL), Skokie, Ill. His department uses a wide variety of readily available sensing devices to help keep owners apprised of the physical condition of their structures. Sensors quickly and easily provide information about the effect of wind forces, temperature, seismic events, tilts and rotations of structural members, corrosion of steel, vibrations, acoustic emissions, deflections, and settlement of structures. "Response values can be assigned to each sensor. In the event that a response value is exceeded, an alarm can be activated and initiate an automated dial-out modem to call personnel with voice messages," adds Weinmann.