1,015 research outputs found
Equivalent linearization of bridges with bilinear isolation systems
No full textAlthough maximum displacement demands of bridges can be obtained through non-linear time history analysis, many approximate methods have been proposed in recent codes to reduce the required computational time distinctive of non-linear approaches. Among these methods, equivalent linearization method is best known. This paper evaluates the accuracy of equivalent linearization method adopted in AASHTO through comparison of non-linear and linear time history analysis. The isolation system is characterized by bilinear hysteretic behavior and the bridge is simplified to be a single-degree-of-freedom (SDOF) system. A comprehensive parametric study is performed using a program developed by MATLAB in combination with OpenSees. Results show that the predicted maximum displacement is significantly underestimated by AASHTO method when the strain hardening ratio and ductility ratio are relatively small. To improve the estimation accuracy of equivalent linearization technique, a new equation of equivalent damping ratio is proposed by modifying AASHTO method. © 2014 Taylor & Francis Group
Equivalent damping of bilinear hysteretic SDOF system considering the influence of initial elastic damping
No full textThe premise of equivalent linearization method is that the peak response of an inelastic system can be estimated as the peak response of a linear elastic system having reduced stiffness and increased damping. Different approaches have been used to determine the properties of the equivalent linear system, in particular the equivalent damping ratio. In general, equivalent damping is specified as the sum of elastic and hysteretic component, where the former is assumed to be constant, and the latter depends on the ductility and hysteresis model. It is found that, however, many studies only focus on the definition of hysteretic damping and omit the influence of elastic damping on the prediction accuracy of equivalent linearization method. Motivated by this limitation, comprehensive parametric analysis is performed in this paper based on bilinear hysteretic SDOF systems to identify the influence of elastic damping. Results show that elastic damping has significant influence on the estimation accuracy of equivalent linearization method. To improve the estimation accuracy of equivalent linearization method, improved method of equivalent damping is proposed by considering the influence of elastic damping. It is found that the proposed method is able to provide accurate and conservative values of equivalent damping for practical design of base isolation systems
Synthesis and structure of bis[2,6-bis(2-pyridylamino)pyridinium] tetrachlorocadmiumate(II)
No full textImproved equivalent viscous damping model for base-isolated structures with lead rubber bearings
No full textNowadays, seismic isolation system has been widely applied in the world to mitigate damage risk of structures. Although maximum displacement demand can be obtained through nonlinear time history (NLTH) analysis, many approximate methods are frequently recommended in structural specifications to reduce the required computational time. One of the best-known methods is the equivalent linear (EL) method, in which the nonlinear response of isolator can be adequately modeled using a fictitious viscously damped elastic structure. In this paper, a comparison between existing expressions supplying the state of research is carried out and then, an improved expression is presented for equivalent linearization of structures supported on lead rubber bearings (LRB). Based on the concept of secant stiffness, the optimal damping ratios, which minimize the errors of maximum displacement between EL analysis and NLTH analysis, are calculated and averaged over 12 ground motions. Then, a rational model to estimate equivalent damping ratio is derived through statistic analysis of the optimal damping ratios. To examine the prediction accuracy of the proposed model, mean ratios of approximate to exact maximum displacement and root mean square error for different isolated period are calculated as evaluation indicator. Compared with other EL models, the newly proposed model predicts a displacement that is in better agreement with the one obtained through NLTH analysis. © 2014 Elsevier Ltd
Simulation parameters for the QL, ABSQL and DSRABSQL algorithms.
No full textSimulation parameters for the QL, ABSQL and DSRABSQL algorithms.</p
A new shift of the QL algorithm for irreducible symmetric tridiagonal matrices
No full textAbstractA new shift in the QL algorithm for symmetric tridiagonal matrices is described. The shift is a combination of the Rayleigh quotient shift and Wilkinson's shift. It is shown that QL is globally convergent with this shift and that the asymptotic rate is always cubic
PiCO QL: A software library for runtime interactive queries on program data
No full textAbstractPico ql is an open source c/c++ software whose scientific scope is real-time interactive analysis of in-memory data through sql queries. It exposes a relational view of a system’s or application’s data structures, which is queryable through sql. While the application or system is executing, users can input queries through a web-based interface or issue web service requests. Queries execute on the live data structures through the respective relational views. pico ql makes a good candidate for ad-hoc data analysis in applications and for diagnostics in systems settings. Applications of pico ql include the Linux kernel, the Valgrind instrumentation framework, a gis application, a virtual real-time observatory of stellar objects, and a source code analyser
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