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This paper aims to experimentally study static responses of bridge longitudinal truss, and the distribution rules of the structural and local stresses were analyzed. The results of the analyses on experimental data show that the typical details in the longitudinal truss concentrate to a limited area on the toe of a dominate weld at the intersection among the upper chord or bottom chord, diagonal and the gusset plates; with boundary conditions being strengthened, stress distribution of the tested specimen became flat and the monolithic tress level decreased relatively. Based on obtained test information, the results are used for updating and validating this kind of structural model, and determining the parameters of finite element model.

Acoustic fibers are potential candidates for developing sensors used in nondestructive evaluation (NDE) and process monitoring of composite materials. Acoustic fibers, like optical fibers, are easily embedded into polymeric composite materials. Because of the mechanical nature of the acoustic wave, acoustic fibers have direct sensing abilities on the variation of mechanical properties of their surrounding materials. Two experimental fiber acoustic sensors are developed. One is applied to detect the changes of properties of cured RHO-C rubber with temperature. Another is used to monitor the curing process of epoxy. Test results show the feasibility of applying the fiber acoustic sensors to NDE and process monitoring for polymeric materials.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this paper, a geometrical acoustics method has been presented to describe acoustic wave propagation in a fiberacoustic waveguide in which the acoustic velocity varies continuously in the radial direction. Based on the acoustic wave equation, a WKBJ approximate method has been used to analyze the propagation and cutoff characteristics of guided acoustic modes in this waveguide. It is believed that this acoustic fiber can transmit acoustic and optical signals at the same time when the refractive index of the core material is greater than that of the cladding material and the acoustic velocity of the core material is less than that of the cladding material. Furthermore, this type of acoustic fiber is suitable because of low loss and hence long distance transmission paths.

This paper presents a discussion of multimode optical fibers used for acoustic wave (2–10 MHz) propagation. The optical fiber acts as a connecting rod between two piezoelectric transducers (PZT) that are attached at each end (dumbbell arrangement). This device is then completed by encapsulation of a solid epoxy or a strengthened composite. One piezoceramic is excited and generates an elastic wave to propagate along the optical fiber and into the other piezoceramic. An alteration of the steady‐state signal thus is indicative of an impact and/or random pressure disturbances upon the composite. Additionally, environmental temperature changes are also detectable. Experimental measurement and related theories are demonstrated.