This paper proposed a distributed seismic damage sensing network using PZT-based smart aggregates for RC building
structures, aiming to monitor the structural local seismic response. The stress history and the crack patterns of the
structure under earthquake load in positions of interest are the two key issues to be monitored. The concept of the
seismic damage mechanism monitoring by means of direct piezoelectric effect and stress wave propagation evaluation is
proposed. The proposed smart aggregates consist of PZT sensing element and the stone holding matrix. Its senssitivity
for dynamic compressive stress induced by earthquake load and the influence of pre-stress from dead load of building
structures after embedment are discussed. It is shown that the proposed smart aggregates suits for seismic stress
monitoring and the static pre-stress has no significant influence on its performance.
Debonding failure has been reported as the dominant failure mode for FRP strengthening in flexure. This paper explores
a novel debonding monitoring method for FRP strengthened structures by means of OTDR-based fiber optic technology.
Interface slip as a key factor in debonding failures will be measured through sensing optic fibers, which is instrumented
in the interface between FRP and concrete in the direction perpendicular to the FRP filaments. Slip in the interface will
induce power losses in the optic fiber signals at the intersection point of the FRP strip and the sensing optic fiber and the
signal change will be detected through OTDR device. The FRP double shear tests and three-point bending tests were
conducted to verify the effectiveness of the proposed monitoring method. It is found that the early bebonding can be
detected before it causes the interface failure. The sensing optic fiber shows signal changes in the slip value at about
36~156 micrometer which is beyond sensing capacity of the conventional sensors. The tests results show that the
proposed method is feasible in slip measurement with high sensitivity, and would be cost effective because of the low
price of sensors used, which shows its potential of large-scale applications in civil infrastructures, especially for bridges.
Determination of structural seismic damage mechanisms and post-seismic damage assessment remains a major challenge
for civil engineers. One of the main reasons is that traditional sensors cannot serve for such a long term to capture a
destructive earthquake and the seismic damage cannot definitely be predicted in advance. In this paper, a smart
distributed fiber optic monitoring method based on OTDR technology is developed for steel structure seismic damage
identification. Geopolymer is used as a "smart material" to couple the sensing optic fiber with the structure of interest. It
not only functions as the adhesive for bonding the optic fiber to the structure and protecting it, but also works as the
sensing material by forming cracks when the pre-defined damage state occurs, which introduce optic power loss into the
optic fiber. The power loss is able to be monitored through optic time domain reflectrometry (OTDR). Tentative tests are
conducted to decide the composition of geopolymer. It is found that the Si/Al ratio of 3.8 provided cracking strains of
about 1300 micro strain, which is desirable for monitoring the yielding of steel. Monotonic, cyclic and buckling loading
tests on steel specimen were conducted to verify the efficiency of the proposed system in monitoring seismic damage
Determination of the actual nonlinear inelastic response mechanisms developed by civil structures such as buildings and bridges during strong earthquakes and post-earthquake damage assessment of these structures represent very difficult challenges for earthquake structural engineers. One of the main reasons is that the traditional sensor can't serve for such a long period to cover an earthquake and the seismic damage location in the structure can't be predicted in advance definitely. It is thought that the seismic damage of reinforced concrete (RC) structure can be related to the maximum response the structure, which can also be related to the cracks on the concrete. A distributed fiber optic sensor was developed to detect the cracks on the reinforced concrete structure under load. Fiber optic couples were used in the sensor system to extend the sensor system's capacity from one random point detection to more. An optical time domain reflectometer (OTDR) is employed for interrogation of the sensor signal. Fiber optic sensors are attached on the surface of the concrete by the epoxy glue. By choosing the strength of epoxy, the damage state of the concrete can be responded to the occurrence of the Fresnel scattering in the fiber optic sensor. Experiments involved monotonic loading to failure. Finally, the experimental results in terms of crack detection capability are presented and discussed.