Concrete-encased composite structure exhibits improved strength, ductility and fire resistance compared to traditional reinforced concrete, by incorporating the advantages of both steel and concrete materials. A major drawback of this type of structure is the bond slip introduced between steel and concrete, which directly reduces the load capacity of the structure. In this paper, an active sensing approach using shear waves to provide monitoring and early warning of the development of bond slip in the concrete-encased composite structure is proposed. A specimen of concrete-encased composite structure was investigated. In this active sensing approach, shear mode smart aggregates (SAs) embedded in the concrete act as actuators and generate desired shear stress waves. Distributed piezoceramic transducers installed in the cavities of steel plates act as sensors and detect the wave response from shear mode SAs. Bond slip acts as a form of stress relief and attenuates the wave propagation energy. Experimental results from the time domain analysis clearly indicate that the amplitudes of received signal by lead zirconate titanate sensors decreased when bond slip occurred. In addition, a wavelet packet-based analysis was developed to compute the received signal energy values, which can be used to determine the initiation and development of bond slip in concrete-encased composite structure. In order to establish the validity of the proposed method, a 3D finite element analysis of the concrete-steel bond model is further performed with the aid of the commercial finite element package, Abaqus, and the numerical results are compared with the results obtained in experimental study.
In this paper, we introduce the concept and architecture of agent grid. Agent grid is an intelligent platform that enables the independent operating entities (agents) to interact with one another to form dynamic services on the Grid. Under this view, we built an agent grid platform named AGrIP that includes four layers and several useful toolkits.With the platform support, we implemented the flood decision support system which combines the wireless sensor network for data acquisition and software agent technology for legacy system integration. Additionally, we developed a toolkit for programmers to visually develop software agents which makes the development process easier.Besides, the MWAC model proposed is for sensor network to save power which can transit the information for long distance.This system is now applied as a module in the City Emergency Interact Project.
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