SYSTEM REDUCTION IN SPACE FOR DYNAMIC FINITE ELEMENT ANALYSIS OF BEAM-COLUMNS ASSEMBLIES AGAINST EARTHQUAKES

True behaviour of structural systems is nonlinear and dynamic. For the analysis, a conventional approach is to discretize in space (by finite elements) the partial differential equations describing the behaviour, and then integrate in time the resulting ordinary initial value problem. Despite advances in finite elements and time integration, computational effort is still an important concern. Every new day, along with improvements in CPU, RAM, and hardware, the size and complicatedness of structural systems increase. Accordingly, new improvements are being suggested for efficient analysis, in order to prevent or lessen the excessive computational effort. This is a main purpose of reduction methods (Besselink et al., 2013). The main attention in this paper is on reduction in space and simplifying models to be analyzed with less number of the degrees of freedom. The structures are limited to structural systems consisted of beam-columns, the discretization in space is considered by simple two-node beam-column element, and the method for dynamic analysis is time history analysis using a time integration method. In 2008, a technique was proposed for reducing the time history analysis against digitized excitations (Soroushian, 2008). The reduction obviously differs from the objective here, i.e. reduction in space. However, in view of the mathematical basis of the technique (Soroushian, 2008) and the successful past experiences (Table 1) (Garakaninezhad & Moghadas, 2015; and Zarabimaensh, 2017), the technique is recentlyadapted to finite element static analysis of assemblies of beam-columns (Farahani et al., 2017). The results were successful with computational effort reductions more than the original application, i.e. time history analysis.

Keywords:

Structural dynamic analysis , Finite element analysis , Reduction in space , Accuracy , Computational effort