Authors: Yang Jun Luo, Xiao Xiang Wu, Alex Li

Abstract: For generating a more reasonable initial layout configuration, a three-dimensional topology optimization methodology of the steel-concrete composite structure is presented. Following Solid Isotropic Material with Penalization (SIMP) approach, an artificial material model with penalization for elastic constants is assumed and elemental density variables are used for describing the structural layout. The considered problem is thus formulated as to find the optimal material density distribution that minimizes the material volume under specified displacement constraints. By using the adjoint variable method for the sensitivity analysis, the optimization problem is efficiently solved by the gradient-based optimization algorithm. Numerical result shows that the proposed topology approach presented a novel structural topology of the simply-supported steel-concrete composite beam.

886

Authors: Xian Bao Duan, Fu Cai Qian, Ya Qin Guo

Abstract: Formulations and numerical results for optimal shape design of a body located in the incompressible Stokes fluid flow are presented. The study is based on an optimal control theory. The optimal state is defined by the reduction of drag forces subjected to the body. The cost functional should be minimized satisfying the Stokes equations. The Shape sensitivity analysis of the cost functional was derived based on the adjoint method. For the numerical study, the optimal shape of the body which has a circular shape as an initial state can be finally obtained as the streamlined shape.

303

Authors: Yu Samizo, Mutsuto Kawahara

Abstract: This paper presents a method to control a flow behavior using the first-order adjoint equation method. A flood causes large-scale and extensive damage to the human property. It is expected that the damage can be suppressed to minimum if the water level or velocity of the river can be controlled. Therefore, the optimal control of a water flow is carried out in this study. In the control theory, the performance function which is defined by the square sum of the discrepancy between the computed and the objective water elevation at the target points is used. The extended performance function is given by the performance function and the state equation. The first-order adjoint equation can be derived by the condition that the first variations of the extended performance function and constraint condition are zero. The gradient of the extended performance function is obtained by solving the first-order adjoint equation. As the minimization technique, the weighted gradient method is applied. The shallow water equation based on the water velocity and elevation is used as a state equation. As the spatial discretization, the stabilized bubble function is employed. As the temporal discretization, the Crank-Nicolson method is applied. In numerical studies, the optimal control of water elevation in the Ikari dam lake is carried out. In this research, the optimal water velocity sent by the pump to minimize the water rise in the Ikari dam lake is computed. The inflow boundary conditions are presupposed as sinusoidal wave water elevation. The results of optimal control is performed effectively.

466

Authors: Hisaki Sawanobori, Mutsuto Kawahara

Abstract: The purpose of this study is to determine the optimal angle of wings which is attached to an oscillating body located in an incompressible flow. At present, there are some bridges with wings to prevent oscillation by the wind. The angle of the wing is very important so as to minimize the oscillation of bridge. In this study, the angle to minimize the oscillation is presented by optimal control theory. In order to minimize the oscillation, the performance function which is expressed by the displacement of body is introduced. The performance function should be minimized satisfying state equation. This problem can be transformed into the minimization problem by the Lagrange multiplier method. As a minimization technique, the weighted gradient method is applied. For the discretization, the arbitrary Lagrangan-Eulerian(ALE) finite element method is applied to solve the FSI problem. The optimal control of an oscillating bridge is shown as numerical study.

5102

Authors: Julien Waeytens, Veronique le Corvec, Philippe Lévèque, Dominique Siegert, Frederic Bourquin

Abstract: Reinforced concrete beams are widely employed in civil engineering structures. To reduce the maintenance financial cost, structure damages have to be detected early. To this end, one needs robust monitoring techniques. The paper deals with the identification of mechanical parameters, useful for Structural Health Monitoring, in a 2D beam using inverse modeling technique. The optimal control theory is employed. As an example, we aim to identify a reduction of the steel bar cross-section and a decrease of the concrete Young modulus in damaged areas. In our strategy, the beam is instrumented with strain sensors, and a known dynamic load is applied. In the inverse technique, two space discretizations are considered: a fine dicretization (h) to solve the structural dynamic problem and a coarse discretization (H) for the beam parameter identification. To get the beam parameters, we minimize a classical data misfit functional using a gradient-like algorithm. A low-cost computation of the functional gradient is performed using the adjoint equation. The inverse problem is solved in a general way using engineer numerical tools: Python scripts and the free finite element software Code_Aster. First results show that a local reduction of the steel bar cross-section and a local decrease of concrete Young modulus can be detected using this inverse technique.

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