Yuichi Sato

Recent progress in finite element analysis aids the simulation of seismic vibration of an entire reinforced concrete (RC) building structure and indicates that drying shrinkage cracks affect seismic resistance performance. Polypropylene fiber-reinforced concrete (PFRC) is a promising material since the fibers will reduce the cracks and strains under drying shrinkage. This paper attempts to quantify the vibration characteristics of PFRC walls by means of a drop-weight test and finite element analyses. Four wall specimens having the same geometry and bar arrangement are prepared. After a one-year drying shrinkage period, the walls are subjected to impact loading of a constant collision velocity of 5 m/s, using a steel drop weight of 398.8 kg. Shear cracks are observed in the restrained wall made of plain concrete, while cracks are insignificant in the PFRC wall. Three-dimensional (3D) nonlinear finite element analyses are conducted to simulate all behaviors from drying shrinkage cracking up to the time of impact loading, and to estimate the vibration characteristics. The analysis results indicate that the polypropylene fiber content reduces the elongation of the natural period by an average of 13.7%.

This paper describes the effect of spanwise interval synthetic jets on the reduction of aerodynamic noise radiated from a pantograph head for a high speed train. Noise measurement results indicate that the ejection of synthetic jets in parts of spanwise area of full-scale panhead model is more effective than in the whole spanwise area for the reduction of aeolian tone. In addition, this method makes it possible that actuation noise can be reduced.

An acoustic noise prediction system has been developed to reduce acoustic noise of electric equipment such as servers. The system can accurately predict the noise in frequency-domain without an actual prototype by coupling two acoustic simulation methods, which are: (1) a boundary elements method (BEM) for low-frequency prediction, and (2) a combined method of both statistical energy analysis (SEA) and geometrical acoustics for high-frequency prediction. The prediction accuracy in high-frequency has been improved by considering higher-order diffractions of an exterior space. We show that our system predicts acoustic pressure of the equipment precisely enough and leads to a good coincidence with actual measured values.

Fifty-four bond specimens were subjected to cyclic bond tests to obtain the bond stress–slip relationships between the fiber reinforced polymer (FRP) sheets and concrete. The specimens were prepared in accordance with Japan Concrete Institute recommendations (in 1998). The tests were conducted using three experimental variables: (1) type of FRP (aramid, carbon, and polyacetal); (2) sheet layers (single layered and double layered); and (3) loading hysteresis. The bond stress–slip model was developed on a Popovics base envelope and consisted of seven empirical parameters: The maximum bond stress τmax , the corresponding slip smax , the curve characteristic constant a , the unloading stiffness K , the ultimate slip su , the friction stress τfp , and negative friction stress τfn . Numerical analyses using the model compared well overall to the experimental cyclic responses of the specimens.