Derivation of energy-based base shear force coefficient considering hysteretic behavior and P-delta effects

A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom（MDOF） system is approximated by using the modal energy-decomposition. Energybased base shear coefficients are verified by means of both pushover analysis and nonlinear time history（NLTH） analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation.

A Numerical Study on the Mechanisms Producing Forces on Cylinders Interacting with Stratified Shear Environments

A three dimensional(3D)numerical wave flume is used to investigate carefully the ISWs(Internal solitary wave)forces acting on cylinders interacting with a stratified shear environment.Using the Large-Eddy Simulation(LES)approach and analyzing the distribution of shear stress and pressure along the surface of the cylinder,the differential pressure resistance and the viscous force are obtained.The method of multiple linear regression analysis is adopted and a comprehensive influence coefficient is determined accordingly to account for the dimensionless forces acting on the cylinder.Results show that the differential pressure resistance on a square cylinder is 1.5 times higher than that on a circular cylinder in the upper layer,while the differential pressure resistance on a square cylinder is 3.5 times larger than that on a circular cylinder in the lower layer.The viscous force is 1–2 orders of magnitude smaller than the differential pressure resistance,which means that the viscous force could be ignored.The comprehensive influence coefficient shows positive correlation with the relative wave height and negative correlation with upper and lower water depth ratio.

Study on Viscoelastic Property of Nanometer SiO_2 Doped Rare Earth Carboxylate Grafting Poly-Silicone Liquid ERF

Nano-SiOdoped with rare earth carboxylate grafting continuous component of functional poly-silicone liquid, a kind of subsidence high-resistance. Electrorheological fluid (ERF) was synthesized. And its viscoelastic properties were investigated experimentally. The special polarization effect of rare earth in the ERF was also discussed. The forced oscillating behavior was obtained using a rheometer. The variation of the shear modulus of ERF subjected to various stress amplitude and frequency were investigated. The complex shear modulus and storage modulus of ERF were also given at different electric field intensities. Meanwhile, the creep and recovery characteristics of ERF were also measured. The equilibrium compliance Jc and the steady state recoverable compliance JR were investigated as a function of electric field strength and ratio of reactant, and the effect of ERF′s structure was analyzed. With increasing in electric field strength at fixed ratio of reactant, the plastic response diminishes, and the elastic behavior rose.

ASYMPTOTIC BEHMIOR OF SOLUTIONS OF FORCED NONLINEAR NEUTRAL DIFFERENTIAL EQUATIONS

The purpose of this paper is no investigate the asymptotic behavior of soluti- ons of the fored nonlinear neutral diffierential equationsOur rosults, as a special case, improve and extend the corresponding results in[1] and [2].