Peter K. K. Lee

Temperature monitoring of steel bridges

The temperature monitoring of Tsing Ma Bridge is performed by the Wind and Structural Health Monitoring System on the Lantau Link as one of its functions. The system consists of over 90 platinum resistance type detectors on Tsing Ma Bridge installed at 4 selected cross-sections. Since May 1997, temperature measurements have been continuously recorded. The University of Hong Kong has been assisting in the analysis of these field measurements. This paper describes the instrumentation and data analysis related to the study. In parallel with this, experimental segmental steel sections under the influence of solar radiation have been set up on the university campus and temperature measurements have been recorded since 1993. Correlation results of observed data have shown that the temperature of steel sections mainly depends on the solar intensity and shade air temperature. Based on the theory of heat transfer, finite element models for different structural components of the bridge deck have been developed for prediction of temperature distribution. Good agreement with field data was observed. Comparison of positive temperature gradients among different structures has shown that they can generally be classified into two categories depending on the number of web faces exposed to the environment.

Design, Fabrication, and Assembly of a Large Oedometer

A typical Casagrande-type oedometer cell is 76 mm in diameter and 19 mm high. It may perform satisfactorily in the measurements of consolidation parameters of homogeneous fine-grained soil specimens up to a maximum applied vertical stress of approximately 3 MPa. However, when it is required to evaluate the load-deformation characteristics of soil specimens containing relative large-diameter grain particles and/or at a considerably higher stress level, the existing apparatus is evidently inadequate. Therefore, an oedometer of 425 mm in internal diameter was designed, fabricated, and assembled at The University of Hong Kong. The consolidation stress that can be applied is up to 13.5 MPa. Specimen preparation and measurement procedure have to be developed to cope with the new apparatus. The design, fabrication, and assembly of the large oedometer are documented and discussed in this paper. Moreover, experimental procedure developed and measurement data demonstrating the applicability of the new apparatus are presented.

Semi-active damping device for vibration control of buildings using magnetorheological fluid

Publisher Summary This chapter proposes a new shear mode damping device using magnetorheological (MR) fluid. The proposed damping device consists of two 10mm thick steel plates placed parallel to each other with a gap of 15mm in between. This gap is filled with MR fluid. Another steel plate, which can slide freely between the two parallel plates, is immersed in the fluid to a depth of about 30mm. The width of the sliding plate in contact with the MR fluid is 50mm. The design of electromagnetic circuit requires the optimization of magnetic field energy in the fluid gap and minimization of the magnetic flux loss in other areas of the circuit. There should be adequate steel areas so as to keep the magnetic field intensity low. The electromagnetic circuit design and the configuration of the MR damping device have been verified using the finite element computer program, COSMOS/M. Results of the two-dimensional finite element analysis indicate that there are losses and nonuniform distribution of fluxes at junctions and boundaries, especially at the parallel steel plates.

4th-order spline wavelets on a bounded interval

The4th-order spline wavelets on a bounded interval are constructed by the4th-order truncated B-spline functions. These wavelets consist of inner and boundary wavelets. They are bases of wavelet space with finite dimensions. Any function on an interval will be expanded as the sum of finite items of the scaling functions and wavelets. It plays an important role for numerical analysis of partial differential equations, signal processes, and other similar problems.