Performance of a Three-Substep Time Integration Method on Structural Nonlinear Seismic Analysis

In this work, a study of a three substeps’ implicit time integration method called the Wen method for nonlinear finite element analysis is conducted. The calculation procedure of the Wen method for nonlinear analysis is proposed. The basic algorithmic property analysis shows that the Wen method has good performance on numerical dissipation, amplitude decay, and period elongation. Three nonlinear dynamic problems are analyzed by the Wen method and other competitive methods. The result comparison indicates that the Wen method is feasible and efficient in the calculation of nonlinear dynamic problems. Theoretical analysis and numerical simulation illustrate that the Wen method has desirable solution accuracy and can be a good candidate for nonlinear dynamic problems.

A Novel Framework to Assess Soil Structure Interaction (SSI) Effects with Equivalent Fixed-Based Models

Soil structure interaction (SSI) effects have been extensively studied with advanced numerical simulations even if these approaches are time consuming and require much effort to perform. In particular, when SSI models are compared with fixed based ones, two main effects need to be considered: period elongation and damping increase. The paper proposes numerical models to build fixed based models calibrated on these two parameters and perform complex SSI analyses. A new framework that may be used to assess SSI with equivalent fixed-based models is herein presented and validated with non-linear dynamic numerical simulations. Opensees was performed to reproduce non-linear numerical simulations by considering hysteretic materials and advanced soil models.

Heavy Water Lengthens the Molecular Circadian Clock Period in the Suprachiasmatic Nucleus of Mice In Vitro

Heavy water lengthens the periods of circadian rhythms in various plant and animal species. Many studies have reported that drinking heavy water lengthens the periods of circadian activity rhythms of rodents by slowing the clock mechanism in the suprachiasmatic nucleus (SCN), the mammalian circadian center. The SCN clock is stable and robust against disturbance, due to its intercellular network. It is unclear whether this robustness provides resistance to the effects of heavy water. Here, we report that heavy water lengthened the rhythm period of clock gene expression of the SCN and peripheral tissues in vitro using a PERIOD2::LUCIFERASE bioluminescence reporter. Our results show that the period-elongation rate of the SCN is similar to those of other tissues. Therefore, the intercellular network of the SCN is not resistant to the period-elongation effect of heavy water.

An Improved Sub-Step Composite Time Integration Formulation With Enhanced Performance on Linear and Nonlinear Dynamics

An improved time integration scheme is proposed for linear and nonlinear dynamics. The proposed scheme has two free parameters which control numerical dissipation and accuracy effectively. Basic properties including spectral stability, algorithmic accuracy, algorithmic damping, period elongation and overshooting behavior are investigated. The influences of algorithmic parameters on these properties are quantified. The effectiveness of the proposed scheme for linear and nonlinear dynamics is evaluated through some numerical examples. Analytical and numerical results demonstrate that the proposed scheme has the following significant characteristics: (1) desirable accuracy can be obtained for various linear and nonlinear problems, when compared with other effective schemes; (2) for nonlinear problems, new scheme also shows good performance; (3) the proposed scheme has simple formulation and good compatibility for various dynamic problems, and thus, is a promising candidate for practical analysis.

A Method of Improving Time Integration Algorithm Accuracy for Long-Term Dynamic Simulation

This paper aims to improve the accuracy of time integration algorithms (TIAs) for long-term simulation of structural dynamics. To this end, a new method of reducing the period elongation (numerical dispersion) was proposed by utilizing the mass scaling matrix. Firstly, the period elongation of explicit Gui-[Formula: see text] algorithm as a representative was analyzed, and the strategy of enhancing the algorithm accuracy was investigated. Subsequently, the period elongation was reduced by introducing a parameter to change the mass matrix, which is weighted by the original mass matrix and stiffness matrix. The bisection method is utilized to determine the parameter according to the formulation of period elongation. Since just the mass matrix of original algorithm is changed slightly, the convergence rate of original TIA remains unchanged and the proposed mass scaling method imposes little influence on the stability condition of original algorithm. Moreover, this method has few modifications to the computer program of TIA and is easy to implement. Finally, both linear and nonlinear long-term dynamic response analyses for multiple-degree-of-freedom systems indicated that the proposed mass scaling method is effective and convenient to reduce the period elongation for several typical TIAs.

Effect of Secondary Raw Material on the Change of Single Extensive Elongation of Non-Woven Fabrics

The article describes research studies in the laboratories of the departments of "Spinning Technology" and "Silk Technology". For this purpose were taken samples of cotton fiber and silk waste from the carding machine in the spinning process, 100% cotton fiber waste, 50% cotton fiber, 30% silk, 20% mulberry bark fiber, 70% cotton fiber, 15% silk, 15% mulberry bark fiber, non-woven fabrics were produced from 75% cotton fiber 10% silk 15% mulberry bark fiber blends. The single-period elongation deformation of the obtained non-woven fabrics was determined using the device "Stoyka".

A spectral-acceleration-based combination-type earthquake intensity measure for high-rise stack-like structures

Ground motion intensity measures are of great importance for the seismic design of structures. A well-chosen intensity measure will reduce the detailed ground motion record selection effort for the nonlinear dynamic structural analyses. In this article, a spectral-acceleration-based combination-type earthquake intensity measure is presented. This intensity measure considers the higher modes effect and period elongation effect due to nonlinear deformation at the same time. The modal mass participation factors are determined to take weighting coefficients and the product of elastic first-mode period T1 and a constant C is expressed to represent the elongated period. Therefore, the proposed intensity measure is a combination of earthquake ground motion characteristics, elastic structural responses, higher modes participation, and the period elongation effect due to inelastic structural behaviors. Four three-dimensional models of reinforced concrete stack-like structures including a 240 m-high chimney, a 180 m-high chimney, a 120 m-high chimney, and a 42.3 m-high water tower are established and analyzed in ABAQUS to investigate the correlation between the intensity measure and the maximum curvatures under 44 far-field ground motions and 28 near-fault ground motions with a pulse-like effect. With the optimal vibration modes and the proper period elongation coefficient, the efficiency of the introduced intensity measure is compared with the other 15 intensity measures. The results indicate that the proposed intensity measure is believed to be a good choice for high-rise stack-like structures, especially under the near-fault ground motions with pulse-like effect.