Bridge Instability in Wind and Spatial Flutter Analysis

Uwe Starossek 대한토목학회 1998 대한토목학회 학술발표회 논문집 Vol.1998 No.1

Numerical analyses of the force transfer in concrete-filled steel tube columns

Starossek, Uwe,Falah, Nabil,Lohning, Thomas Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.2

The interaction between steel tube and concrete core is the key issue for understanding the behavior of concrete-filled steel tube columns (CFTs). This study investigates the force transfer by natural bond or by mechanical shear connectors and the interaction between the steel tube and the concrete core under three types of loading. Two and three-dimensional nonlinear finite element models are developed to study the force transfer between steel tube and concrete core. The nonlinear finite element program ABAQUS is used. Material and geometric nonlinearities of concrete and steel are considered in the analysis. The damage plasticity model provided by ABAQUS is used to simulate the concrete material behavior. Comparisons between the finite element analyses and own experimental results are made to verify the finite element models. A good agreement is observed between the numerical and experimental results. Parametric studies using the numerical models are performed to investigate the effects of diameterto-thickness ratio, uniaxial compressive strength of concrete, length of shear connectors, and the tensile strength of shear connectors.

Experimental and numerical identification of flutter derivatives for nine bridge deck sections

Starossek, Uwe,Aslan, Hasan,Thiesemann, Lydia Techno-Press 2009 Wind and Structures, An International Journal (WAS Vol.12 No.6

This paper presents the results of a study into experimental and numerical methods for the identification of bridge deck flutter derivatives. Nine bridge deck sections were investigated in a water tunnel in order to create an empirical reference set for numerical investigations. The same sections, plus a wide range of further sections, were studied numerically using a commercially available CFD code. The experimental and numerical results were compared with respect to accuracy, sensitivity, and practical suitability. Furthermore, the relevance of the effective angle of attack, the possible assessment of non-critical vibrations, and the formulation of lateral vibrations were studied. Selected results are presented in this paper. The full set of raw data is available online to provide researchers and engineers with a comprehensive benchmarking tool.

Progressive Collapse of Bridge : Aspects of Analysis and Design 해석 및 설계적 고찰

Starossek, Uwe Korean Group of IABSE;Korea wind Engineering Resea 2006 Proceedings of the International Symposium on Sea- Vol.2006 No.-

In this shown that current design method are inadequate to prevent progressive collapse. Definitions for the terms collapse resistance and robustness are proposed. An approach for designing against progressive collapse is suggested and a set of corresponding design criteria is presented. These include requirements, design objectives, design strategies, and verification procedures. In addition to the better-Known design method providing specific local resistance or alternate load paths, an approach base on isolation by compartmentalization is presented and discussed. It is found that the terms continuity, redundancy, and robustness should be carefully distinguished. the general concepts and findings presented here are applied to bridges. 이 논문에서는 현재 사용되는 설계 방법이 연속적인 붕괴를 방지하는데 부적절함을 보인다. 붕괴 저항성이나 강인성과 같은 용어에 대한 정의를 제안한다. 연속적인 붕괴에 저항 항 수 있는 설계 방법과 해당 설계 기준을 제안한다. 이 설계 기준에는 요구조건, 설계 목표, 설계 전략 및 검증 절차가 포함된다. 특정 국부 저항이나 힘 경로 조절과 같은 상대적으로 잘 알려진 방법이외에, 구체화에 의한 격리 (isolation by compartmentalization) 개념에 바탕을 둔 새로운 접근론을 제안한다. 또한 연속성, 여용성, 강인성과 같은 용어들이 신중하게 구분되어야 함을 밝히며, 이 개념들을 교량에 적용한다.

Numerical analyses of the force transfer in concrete-filled steel tube columns

Uwe Starossek,Nabil Falah,Thomas Löhning 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.2

The interaction between steel tube and concrete core is the key issue for understanding the behavior of concrete-filled steel tube columns (CFTs). This study investigates the force transfer by natural bond or by mechanical shear connectors and the interaction between the steel tube and the concrete core under three types of loading. Two and three-dimensional nonlinear finite element models are developed to study the force transfer between steel tube and concrete core. The nonlinear finite element program ABAQUS is used. Material and geometric nonlinearities of concrete and steel are considered in the analysis. The damage plasticity model provided by ABAQUS is used to simulate the concrete material behavior. Comparisons between the finite element analyses and own experimental results are made to verify the finite element models. A good agreement is observed between the numerical and experimental results. Parametric studies using the numerical models are performed to investigate the effects of diameterto-thickness ratio, uniaxial compressive strength of concrete, length of shear connectors, and the tensile strength of shear connectors.

Experimental and numerical identification of flutter derivatives for nine bridge deck sections

Uwe Starossek,Hasan Aslan,Lydia Thiesemann 한국풍공학회 2009 Wind and Structures, An International Journal (WAS Vol.12 No.6

This paper presents the results of a study into experimental and numerical methods for the identification of bridge deck flutter derivatives. Nine bridge deck sections were investigated in a water tunnel in order to create an empirical reference set for numerical investigations. The same sections, plus a wide range of further sections, were studied numerically using a commercially available CFD code. The experimental and numerical results were compared with respect to accuracy, sensitivity, and practical suitability. Furthermore, the relevance of the effective angle of attack, the possible assessment of noncritical vibrations, and the formulation of lateral vibrations were studied. Selected results are presented in this paper. The full set of raw data is available online to provide researchers and engineers with a comprehensive benchmarking tool.

Progressive Collapse of Structures: Nomenclature and Procedures

Informa UK (TaylorFrancis) 2006 Structural engineering international Vol.16 No.2

Optimized Topology Extraction of Steel-Framed DiaGrid Structure for Tall Buildings

이동규,Uwe Starossek,신수미 한국강구조학회 2010 International Journal of Steel Structures Vol.10 No.2

This study presents an optimal angle and a topology extraction of diagonal members in a DiaGrid structural system for tall buildings. The angle and topology of diagonal members are achieved by using a computer-oriented SIMP topology optimization. The objective function for the design optimization is to both maximize Eigenfrequency for resisting dynamic responses and minimize mean compliance for static responses. Relative densities subjected to SIMP penalty law are used for both optimization design variables and material properties, and then finite element analysis is carried out by using the relative element density. Frequency and mean compliance sensitivities with respect to relative density are straightforwardly derived by discrete sensitivity formulations. Based on the design sensitivity analysis, an initial topology with a given fixed support is shifted toward a final topology charged by almost voids (0) and solids (1) during every optimization procedure. An optimal DiaGrid topology with the highest stiffness is finally determined to resist both static and dynamic behaviors. Numerical examples with varied fixed support models are studied to find out optimal angles and topologies of diagonal members for a DiaGrid system design.

Topological optimized design considering dynamic problem with non-stochastic structural uncertainty

이동규,Uwe Starossek,신수미 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.1

This study shows how uncertainties of data like material properties quantitatively have an influence on structural topology optimization results for dynamic problems, here such as both optimal topology and shape. In general, the data uncertainties may result in uncertainties of structural behaviors like deflection or stress in structural analyses. Therefore optimization solutions naturally depend on the uncertainties in structural behaviors, since structural behaviors estimated by the structural analysis method like FEM need to execute optimization procedures. In order to quantitatively estimate the effect of data uncertainties on topology optimization solutions of dynamic problems, a so-called interval analysis is utilized in this study, and it is a well-known non-stochastic approach for uncertainty estimate. Topology optimization is realized by using a typical SIMP method, and for dynamic problems the optimization seeks to maximize the first-order eigenfrequency subject to a given material limit like a volume. Numerical applications topologically optimizing dynamic wall structures with varied supports are studied to verify the non-stochastic interval analysis is also suitable to estimate topology optimization results with dynamic problems.

Vertical Building Collapse Triggered by Loss of All Columns in the Ground Story−Last Line of Defense

Nikolay Lalkovski,Uwe Starossek 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.2

In multi-story buildings, one of the worst collapse types in terms of structural damage and loss of life is the pancake-type collapse, where some or all floors end up lying on top of each other like the layers of a pancake, with the floor contents crushed between them. Mostly observed after strong earthquakes, such collapses are triggered by loss of some or all vertical load bearing elements in some story−often the ground story. Once this occurs, the building part above the lost vertical elements− still intact−starts gaining downward velocity until it meets resistance from below. The ensuing impact forces often lead to collapse progression ending in total collapse. However, there are some examples of buildings in which the columns of an entire story failed and the collapse remained arrested after the subsequent impact. Such cases were observed in the 1995 Kobe earthquake and in the 1985 Mexico City earthquake. There have also been some failed controlled demolition attempts in which the intended total vertical collapse did not occur after letting a building collide with the ground by explosive removal of the vertical load bearing elements in the lowest stories. In an attempt to determine the factors which play the main role in arresting vertical collapse once initiated at the ground level, this paper studies the behavior of vertically falling multi-story building structures impacting a rigid surface representing the ground. A simplified analytical model of the problem is presented. Depending on the structural properties, several possible energy dissipation mechanisms, and−in case the collapse cannot be arrested at impact−collapse modes, are identified.