Dynamic Nonlinear Analysis of an Irregular Office Building

The common analysis methods of structural building include the response spectrum, static nonlinear analysis (pushover) and dynamic nonlinear analysis method. Meanwhile, for the analysis of irregular structures, dynamic nonlinear analysis method could accurately simulate the seismic response of structure under rare earthquake. In this paper, the dynamic nonlinear analysis was carried out to evaluate the seismic performance of an office building with irregular in plan and in elevation. The simulation results show that the maximum inter story-drift angle can satisfy the requirement in the nation code. Few shear walls exceeded the concrete yield compressive stress and most of the shear walls remained in the elastic stage. Most frame columns were within the component acceptance criterion of IO. By the above analysis results, it can be judged that the seismic capacity of the building structure can reach the seismic performance objectives in the code.

Dynamic Nonlinear Analysis of Semi-Rigid Steel Frames Based on the Finite Particle Method

The Finite Particle Method (FPM), based on the Vector Mechanics, is a new structural analysis method. This paper explores the possibility of the proposed method being applied in the dynamic nonlinear analysis of semi-rigid steel frames. Taking the two dimensional beam element as an example, the formulations of the FPM to calculate the dynamic and geometric nonlinear problems are derived. Spring model with zero-length is adopted to simulate the relationship between internal forces and deformations of the semi-rigid steel connections. The nonlinear strengthen spring model is used to analyze the nonlinear behavior of the semi-rigid connection. Explicit time integrations are used to solve equilibrium equations. Comparing to traditional Finite Element Method, iterations and special modifications are not needed during the dynamic nonlinear analysis, which is more advantageous in structural complex behavior analysis. Two numerical examples are presented to analyze the behaviors of rigid and semi-rigid steel frames, and behaviors of linear and nonlinear semi-rigid connections, which demonstrate the accuracy and applicability of this method in dynamic nonlinear analysis.

STUDY ON RELATION BETWEEN INELASTIC AND ELASTIC DISPLACEMENT FOR VRANCEA EARTHQUAKES

At present, Romanian code for seismic design P100 is in a process of assimilation of the requirements from the equivalent European code, EN-1998-1. However, the unique characteristics of the Vrancea earthquakes require additional adjustment for some relations. One of these relations regards the simplified calculation of inelastic displacements and represents the main objective of this article. The paper uses dynamic nonlinear analysis performed on single degree of freedom systems as the main investigation tool. For all the analyses, two hysteretic models are used: Takeda and kinematic hardening. In the beginning, the paper presents the influence of overstrength on inelastic displacements for several behaviour factors. Next, the overstrength-period diagram is proposed based on a case study. Finally, the spectrum of c, the ratio between inelastic and elastic displacement is calculated. The main result of the study is the simplified equations proposed for c factor, relations that can be successfully used in current design.

Effects of Attached Body on Biomechanical Response of the Helmeted Human Head Under Blast

The results of a computational study on the effect of the body on biomechanical responses of a helmeted human head under various blast load orientations are presented in this work. The focus of the work is to study the effects of the human head model boundary conditions on mechanical responses of the head such as variations of intracranial pressure (ICP). In this work, finite element models of the helmet, padding system, and head components are used for a dynamic nonlinear analysis. Appropriate contacts and conditions are applied between different components of the head, pads and helmet. Blast is modeled in a free space. Two different blast wave orientations with respect to head position are set, so that, blast waves tackle the front and back of the head. Standard trinitrotoluene is selected as the high explosive (HE) material. The standoff distance in all cases is one meter from the explosion site and the mass of HE is 200 grams. To study the effect of the body, three different boundary conditions are considered; the head-neck model is free; the base of the neck is completely fixed; and the head-neck model is attached to the body. Comparing the results shows that the level of ICP and shear stress on the brain are similar during the first five milliseconds after the head is hit by the blast waves. It explains the fact that the rest of the body does not have any contribution to the response of the head during the first 5 milliseconds. However, the conclusion is just reasonable for the presented blast situations and different blast wave incidents as well as more directions must be considered.