In this study, the binary bat algorithm (BBA) for structural topology optimization is implemented. The problem is to find the stiffest structure using a certain amount of material and some constraints using the bit-array representation method. A new filtering algorithm is proposed to make BBA find designs with no separated objects, no checkerboard patterns, less unusable material, and higher structural performance. A volition penalty function for topology optimization is also proposed to accelerate the convergence toward the optimal design. The main effect of using the BBA lies in the fact that the BBA is able to handle a large number of design variables in comparison with other well-known metaheuristic algorithms. Based on the numerical results of four benchmark problems in structural topology optimization for minimum compliance, the following conclusions are made: (1) The BBA with the proposed filtering algorithm and penalty function are effective in solving large-scale numerical topology optimization problems (fine finite elements mesh). (2) The proposed algorithm produces solid-void designs without gray areas, which makes them practical solutions that are applicable in manufacturing.
In this study, the optimum design of a three-dimensional framed steel structure subjected to blast loading is considered. The main idea of this research is to develop a practical formulation for the design optimization problem and to study the effect of including blast loads in the design process. The optimization problem is formulated to minimize the total weight of the structure subjected to American Institution of Steel Construction (AISC) strength requirements and blast design displacement constraints. The design variables for beams and columns are the discrete values of the W-shapes selected from the AISC tables. A car carrying 250 lbs of Trinitrotoluene with a 50 ft standoff distance from the front face is modeled as the source of the blast loading. Pressure-time histories are calculated on the front, sides, roof, and rear faces of the structure. Since the problem functions are not differentiable with respect to the design variables, the gradient-based optimization algorithms cannot be used to solve the problem. Therefore, metaheuristic algorithms are used to solve the optimization problem. Linear and nonlinear dynamic analyses are carried out in the optimization process. The problems are solved using metaheuristic optimization with the equivalent static loads method (MOESL). In MOESL, the dynamic load is transformed into equivalent static loads (ESLs) then the linear static analysis is carried out in the optimization process. The problems are 4-bay×4-bay×3-story frames under serviceability and blast loading. It is shown that a penalty on the optimum structural weight is substantial for designing structures to withstand blast loads.
This experimental research aims to study the use of wire mesh–epoxy composite (WMEC) as a shear-strengthening technique for reinforced concrete (RC) beams by focusing on the following parameters: (1) presence of shear reinforcement in the shear span; (2) type of strengthening technique (U-jacketing, vertical U strip, or inclined strip); and (3) number of wire mesh layers (three or six layers). Nine simply supported rectangular RC beams were tested under two monotonic point loads. The testing specimens were divided into two groups: (1) five beams without shear reinforcement and (2) four beams with shear reinforcement. Load–deflection relationship, shear ductility index, beams’ stiffness, energy absorption, crack propagation, mode of failure, and strain were studied for all testing specimens and compared with those of the control beams to measure the improvement from WMEC addition. Results showed that all WMEC types enhanced the shear capacity. Among the three shear-strengthening types, the continuous U-jacket scheme had a higher effect, increasing the shear capacity between 33.4 and 95.9% and the shear ductility index by 23% relative to those of the reference specimens. The shear capacity improvement by WMEC for the beams without shear steel reinforcement was greater than that for the beams with shear reinforcement under the same shear-strengthening configuration. When the number of wire mesh layers was doubled, the ultimate load was further increased from 33.4 to 57.8%. This research showed that WMEC is a practical and excellent shear-strengthening technique for RC beams. Doi: 10.28991/CEJ-2022-08-06-09 Full Text: PDF
An explosion is characterized as a sudden release of large energy over a very short duration. As the blast wave travels parallel to a surface, it creates a side-on pressure and when it hits a surface perpendicularly or at an angle, it creates a reflected pressure. Side-on pressure and reflected pressure are much higher than service loads for the structure. Thus, when a blast happens near a building that is not designed to withstand blast loads, it can cause catastrophic damage. The objective of this study is to present a formulation for the design optimization of framed steel structures subjected to blast loads. Also, a formulation is presented for the design optimization of structures that can withstand some possible damage due to blast loads. To this end, an optimization procedure that includes definitions of design variables, cost function, constraints, and structural analyses is discussed. The design variables for beams and columns are the discrete values of the W-shapes selected from American Institute of Steel Construction (AISC) tables. The optimization problem is to minimize the total structural weight subjected to AISC strength requirements and blast design displacement constraints. Linear static, linear dynamic, and nonlinear dynamic analyses are incorporated in the optimization process and optimum designs are compared. Due to design variables and some constraints discontinuity, gradient-based optimization algorithms cannot be used to solve the optimization problem. Therefore, metaheuristic algorithms are used that require only simulation results to solve problems with discrete variables and non-differentiable functions. Since the number of simulations and robustness to obtain good designs are important for the class of problems discussed in this research, a new hybrid optimization algorithm based on Harmony Search (HS) and Colliding Bodies Optimization (CBO) is developed and examined. The algorithm is named Hybrid Harmony Search-Colliding Bodies Optimization (HHC). Also, a novel design domain reduction technique viii TABLE OF CONTENTS LIST OF TABLES .
This article investigates the use of Harris Hawks Optimization (HHO) to solve planar and spatial trusses with design variables that are discrete. The original HHO has been used to solve continuous design variables problems. However, HHO is formulated to solve optimization problems with discrete variables in this research. HHO is a population-based metaheuristic algorithm that simulates the chasing style and the collaborative behavior of predatory birds Harris hawks. The mathematical model of HHO uses a straightforward formulation and does not require tuning of algorithmic parameters and it is a robust algorithm in exploitation. The performance of HHO is evaluated using five benchmark structural problems and the final designs are compared with ten state-of-the-art algorithms. The statistical outcomes (average and standard deviation of final designs) show that HHO is quite consistent and robust in solving truss structure optimization problems. This is an important characteristic that leads to better confidence in the final solution from a single run of the algorithm for an optimization problem.
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