This dissertation discusses the research, development, and design considerations used to produce a Structural Information System (SIS) capable of characterizing the behavior of reinforced concrete structures in real time. The SIS consists of a collection of surface mounted and/or embedded sensors connected to a portable computer. The work includes theoretical arguments, polymer concrete mixture design, concrete testing, reinforcement selection and placement, sensor selection and placement, and structural testing and analysis.
Since a concrete reinforced structure is typically over-reinforced, such that failure occurs within the concrete, efforts are focused on the development of embedded sensors designed to monitor strain in the reinforcement. This is accomplished by mounting strain gages within hollow carbon fiber tendons. The embedded gages are protected from the surrounding environment and measurements are insensitive to lead wire effects because the strain gage wires are free from contact with the concrete.
Tests conducted on an adaptive structure, designed to resist reverse loadings, demonstrate how the approach can be used to identify significant changes that affect structural integrity. The primary objective is to insure that the stress in the materials remains within the elastic range so that damage does not occur. However, the ability to characterize failure, once it occurs, is also demonstrated by analyzing data obtained from displacement-controlled tests.
Results indicate that splices, incorporated into the reinforcing tendons to facilitate strain gage placement, not only help to prevent sudden failure but allow the structure to withstand relatively high service loads despite appreciable deformation. This observation may be very important in situations where significant damage results from an earthquake, hurricane, collision, impact, or terrorist attack. The ability to monitor the sensors in real time during field operations will result in significant cost savings especially because corrective action need only be taken if and when problems are detected.
Results show that when a finite element model is developed to accurately characterize the structural response, a complete distribution of displacement, strain, and stress can be obtained with a SIS consisting of a single embedded sensor. Guidelines for improving the design of the embedded system are given along with recommendations for future research.
The work represents an extension of prior, pioneering research performed by the author in the area of Strategically Tuned Absolutely Resilient Structures (STARS) and is unique in that I) a SIS is developed to characterize the structural response of a reinforced concrete structure, 2) sensors are placed within hollow carbon fiber tendons, 3) expansion joints are incorporated into the primary reinforcement, 4) a STAR structure is investigated, and 5) a hybrid approach is suggested.