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George Bogdan Nica

Abstract

The explosion of bombs near buildings generally yields severe damages to the structures. Explosion resistant standards and requirements are constantly being developed and upgraded. This paper focuses on the damages which occur toa RC slab due to blast action. The numerical model replicates a ¼ scale experiment. The analysis is conducted using a software based on the recently developed Applied Element Method. This numerical method is able to model accurately all the structural behavior stages up to failure. The results are compared to experimental data available in the literature. The analysis reveals that the slab failure due to uplift pressures may be avoided by some simple reinforcing details, as they are listed in the Romanian National Annex – accidental loads of the Eurocode EN 1991-1-7.

Open access

George Bogdan Nica and Florin Pavel

Abstract

This paper focuses on the collapse analysis of a planar RC frame. This research is based on an experimental study presented in the literature. The analyses are conducted using a dedicated software based on the Applied Element Method. This numerical method is able to model accurately all the structural behaviour stages leading up to the collapse itself. A very good match between the experimental and numerical results is observed. The numerical investigation highlights several behaviour stages for the model RC frame. Moreover, the contribution of the RC slab and the impact of the concrete strength on the overall collapse mechanism is discussed and evaluated through numerical investigation.

Open access

George Bogdan Nica and Andrei Gheorghe Pricopie

Abstract

Pounding effects during earthquake is a subject of high significance for structural engineers performing in the urban areas. In this paper, two ways to account for structural pounding are used in a MATLAB code, namely classical stereomechanics approach and nonlinear viscoelastic impact element. The numerical study is performed on SDOF structures acted by ELCentro recording. While most of the studies available in the literature are related to Newmark implicit time integration method, in this study the equations of motion are numerical integrated using central finite difference method, an explicit method, having the main advantage that in the displacement at the ith+1 step is calculated based on the loads from the ith step. Thus, the collision is checked and the pounding forces are taken into account into the equation of motion in an easier manner than in an implicit integration method. First, a comparison is done using available data in the literature. Both linear and nonlinear behavior of the structures during earthquake is further investigated. Several layout scenarios are also investigated, in which one or more weak buildings are adjacent to a stiffer building. One of the main findings in this paper is related to the behavior of a weak structure located between two stiff structures.

Open access

George Bogdan Nica, Vasile Calofir and Ioan Cezar Corâci

Abstract

In recent years, the pounding effect during earthquake is a subject of high significance for structural engineers. In this paper, a state space formulation of the equation of motion is used in a MATLAB code. The pounding forces are calculated using nonlinear viscoelastic impact element. The numerical study is performed on SDOF structures subjected by 1940 EL-Centro and 1977 Vrancea N-S recording. While most of the studies available in the literature are related to Newmark implicit time integration method, in this study the equations of motion in state space form are direct integrated. The time domain is chosen instead of the complex one in order to catch the nonlinear behavior of the structures. The physical nonlinear behavior of the structures is modeled according to the Force Analogy Method. The coupling of the Force Analogy Method with the state space approach conducts to an explicit time integration method. Consequently, the collision is easily checked and the pounding forces are taken into account into the equation of motion in an easier manner than in an implicit integration method. A comparison with available data in the literature is presented.