Combined with the k-ε turbulence model of general application, a refined finite element model of a utility tunnel’s gas compartment filled with the methane/air mixture is developed. A series of analyses are made by using the powerful industry-leading computational fluid dynamics (CFD) software flame acceleration simulator (FLACS) to study the shock wave propagation rule in the gas compartment. The longitudinal and transversal distribution laws of the explosion shock wave are gained taking into consideration the spatial characteristics of the gas compartment. The influences of a few parameters, such as initial conditions and section size of the gas compartment, on the shock wave propagation rule are further discussed. The basic procedure for predicting the peak pressure of the blast wave is provided by considering the initial conditions and the gas compartment, and the corresponding injury effect of the explosion wave on the living beings is assessed. The investigation demonstrates that the peak pressure by the coupled effect between the initial conditions is significantly influenced, especially at the upper and lower gas explosion limits. The peak pressure increases gradually as the width or height increases, and both basically meet the linear relation. The proposed method can forecast the peak pressure of the explosion shock wave in the gas compartment accurately. According to the peak pressure longitudinal and transversal distributions of the blast wave, the peak pressure is far greater than the killing pressure threshold in the underground and closed space; consequently, it is not safe for the living beings in the gas compartment.
In this study, to satisfy the base isolation demand of large-scale building structures under different earthquake records, a new bidirectional variable curvature friction pendulum bearing (BD-VCFPB) is proposed. The VCFPB is designed in detail based on the basic principle of a friction pendulum system. Moreover, the sliding interface function, gap between the slider and the sliding interface, and polytetrafluoroethylene (PTFE) plate stress are studied. Finally, a dynamic cyclic test is conducted to study the influence of the slider size, contact pressure on the PTFE plate, and loading frequency on the hysteretic behavior of the VCFPB. The results indicate that the hysteretic curves of the horizontal force and the displacement are regular, symmetrical, stable, and full, and clearly reflect the variable curvature convex and concave characteristics and the excellent behavior of energy dissipation of the BD-VCFPB. The sliding friction coefficient varies significantly with the contact pressure on the PTFE plate and the loading frequency; however, it has little relation with the slider size. A hysteretic model is proposed based on the results of a unidirectional test, and it is in good agreement with the hysteretic curves of the horizontal force and the displacement from a bidirectional test. VCFPB PTFE Bidirectional loading test Hysteretic model Long-period ground motions CORRESPONDENCE Shu-Chao Lin
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