International Journal of Optimization in Civil Engineering
Volume:7 Issue: 4, Autumn 2017

Optimization techniques can be efficiently utilized to achieve an optimal shape for arch dams. This optimal design can consider the conditions of the economy and safety simultaneously. The main aim is to present an applicable and practical model and suggest an algorithm for optimization of concrete arch dams to enhance their seismic performance.
To achieve this purpose, a preliminary optimization is accomplished using PSO procedure in the first stage. Capabilities of Ansys Parametric Design Language (APDL) are applied for modeling the Dam-Foundation-Reservoir system. In the second stage with training the neural network, Group Method of Data Handling (GMDH) and replacement of Ansys analyst, optimal results have been achieved with the lowest error and less number of iteration respectively. Then a real world double-arch dam is presented to demonstrate the effectiveness and practicality of the PSO-GMDH. The numerical results reveal that the proposed method called PSO-GMDH provides faster rate and high searching accuracy to achieve the optimal shape of arch concrete dams and the modification and optimization of shape have a quite important role in increasing the safety against dynamic design loads.

Graph theory based methods are powerful means for representing structural systems so that their geometry and topology can be understood clearly. The combination of graph theory based methods and some metaheuristics can offer effective solutions for complex engineering optimization problems. This paper presents a Charged System Search (CSS) algorithm for the free shape optimizations of thin-walled steel sections, represented by some popular graph theory based methods. The objective is to find shapes of minimum mass and/or maximum strength for thin-walled steel sections that satisfy design constraints, which results in a general formulation for a bi-objective combinatorial optimization problem. A numerical example involving the shape optimization of thin-walled open and closed steel sections is presented to demonstrate the robustness of the method.

In this paper a Guided Tabu Search (GTS) is utilized for optimal nodal ordering of finite element models (FEMs) leading to small profile for the stiffness matrices of the models. The search strategy is accelerated and a graph-theoretical approach is used as guidance. The method is evaluated by minimization of graph matrices pattern equivalent to stiffness matrices of finite element models. Comparison of the results with those of some powerful methods, confirms the robustness of the algorithm.

This paper presents a Cuckoo Optimization Algorithm (COA) model for the cost optimization of the one-way and two-way reinforced concrete (RC) slabs according to ACI code. The objective function is the total cost of the slabs including the cost of the concrete and that of the reinforcing steel. In this paper, One-way and two-way slabs with various end conditions are formulated as ACI code. The two-way slabs are modelled and analyzed using direct design method. The problems are formulated as mixed-discrete variables such as: thickness of slab, steel bar diameter, and bar spacing. The presented model can be applied in design offices to reduce the cost of the projects. It is also the first application of the Cuckoo Optimization Algorithm to the optimization of RC slabs. In order to demonstrate the superiority of the presented method in convergence and leading to better solutions, the results of the proposed model are compared with the other optimization algorithms.

Offshore jacket-type towers are steel structures designed and constructed in marine environments for various purposes such as oil exploration and exploitation units, oceanographic research, and undersea testing. In this paper a newly developed meta-heuristic algorithm, namely Cyclical Parthenogenesis Algorithm (CPA), is utilized for sizing optimization of a jacket-type offshore structure. The algorithm is based on some key aspects of the lives of aphids as one of the highly successful organisms, especially their ability to reproduce with and without mating. The optimal design procedure aims to obtain a minimum weight jacket-type structure subjected to API-RP 2A-WSD specifications. SAP2000 and its Open Application Programming Interface (OAPI) feature are utilized to model the jacket-type structure and the corresponding loading. The results of the optimization process are then compared with those of Particle Swarm Optimization (PSO) and its democratic version (DPSO).

In this paper the factor of safety (FS) and critical line-segments slip surface obtained by the Alternating Variable Local Gradient (AVLG) optimization method was presented as a new topic in 2D. Results revealed that the percentage of reduction in the FS obtained by switching from a circular shape to line segments was higher with the AVLG method than other methods. The 2D-AVLG optimization method is a new topic for finding critical line-segments slip surface which has been addressed in this paper. In fact, the line-segments slip surface is a flexible slip surface. Examples proves the efficiency and precision of the 2D-AVLG method for obtaining the line-segments critical slip surface compared to the circular and circular-line slip surfaces.

Growing tendency for Urbanization and rapid development of the cities has resulted in urban neighborhoods obstructing the access of each other to the natural sources e.g. solar energy, natural ventilation. Sunlight as the main part of input energy in urban energy balance equation and natural lighting is of vital importance. This paper attempts to achieve an optimum morphology for residential blocks in urban area with the highest exposure to the sunlight. To reach this goal a pilot area in Tabriz’s downtown was selected and regarding solar angle, local street regulations and the width of surrounding streets 3 different scenarios for the buildings blocks were defined. Using a three-dimensional microclimate model, ENVI-met, solar access of defined scenarios was calculated for the longest and the shortest day of the year. Results showed that Type C2 (highest, more open spaces) is a more efficient style for winter times as it receives more of the sun’s energy and also the amount of sun it gets during a day and type B2 (medium open space and height) is the better for summer as it gets less energy from the sun and it is exposed to sunlight less than other types in a hot summer day.

Impulsive and convective frequencies are one of the most important subjects for evaluation of the seismic behavior of tanks. These two frequencies are defined by Housner and used for obtaining Rayleigh damping in time history analysis. ACI 350 and NZSEE standards have suggested some analytical solutions for finding convective and impulsive frequencies. These frequencies can also extract from modal analysis by finite element (FE) software. In current study, these frequencies are extracted by using FE software and performing modal analysis. Also these modes are compared with analytical methods from ACI and NZSEE standards. Based on the results, convective frequencies obtained from FE and ACI and NZSEE methods are so close together, with just two percent variation between FE and analytical codes, while there are significant differences among these methods for impulsive frequencies. Furthermore, this study shows that the wall thickness has no effect on the convective frequencies, while it is completely opposite for impulsive frequency. When the wall thickness rises by 1.5 times, impulsive frequencies increase by 1.75, 1.55 and 1.48 times for finite element, NZSEE and ACI methods, respectively. In addition, based on the observations, when the liquid height is low, NZSEE method presents high values of impulsive frequency.

Reinforced concrete (RC) slabs exhibit complexities in their structural behavior under load due to the composite nature of the material and the multitude and variety of factors that affect such behavior. Current methods for determining the load-deflection behavior of reinforced concrete slabs are limited in scope and are mostly dependable on the results of experimental tests. In this study, an alternative approach using Artificial Neural Network (ANN) model is produced to predict the load-deflection behavior of a two-way RC slab. In the study, 30 sets of RC slab specimens of sizes 700mm x 600mm x 75mm were cast, cured for 28days using the sprinkling method of curing and tested for deflection experimentally by applying loads ranging from 10kN to 155kN at intervals of 5kN. ANN model was then developed using the neural network toolbox of ANN in MATLAB version R2015a using back propagation algorithm. About 54% of the RC specimens were used for the training of the network while 23% of the sets were used for validation leaving the remaining 23 % for testing the network. The experimental test results show that the higher the applied load on the slab, the higher the deflection. The result of the ANN model shows a good correlation between the experimental test and the predicted results with training, validation and test correlation coefficients of 0.99692, 0.98921 and 0.99611 respectively. It was also found that ANN model is quite efficient in determining the deflection of 2-way RC slab. The predicted accuracy of performance value for the load-deflection set falls at 96.67% of the experimental load-deflection with a 0.31% minimum error using the Microsoft spreadsheet model. As such the comprehensive spreadsheet tool created to incorporate the optimum neural network. The spreadsheet model uses the Microsoft version 2013 excel tool software and can be used by structural engineers for instantaneous access to the prediction if any aspect of a concrete slab behavior given minimal data to describe the slab and the loading condition.

Offshore pipelines are an effective tool for transportation of oil and gas which are usually assembled by the use of girth welds. Since flaws may naturally exist at such welds, fracture assessment of girth welded offshore pipelines is substantial. Current fracture assessment procedures like BS 7910 consider identical material properties for the weld and the base metals. However the strength difference between weld and base materials has significant effect on fracture assessment results. This effect is magnified greatly for pipelines which are operated in deep waters and are subjected to large plastic loads. In this paper 3D nonlinear elastic-plastic finite element analyses using the ABAQUS software are performed in order to investigate the effect of weld mismatching at various crack geometries on fracture assessment of pipeline’s girth weld. It is noteworthy that such a quantitative study on the effect of weld mismatching condition at different crack geometries on ECA analysis has not been performed so far. Based on simulation performed, a new optimized formula is proposed for fracture analysis of girth welded pipeline with surface cracks considering the effect of weld mismatching conditions at plastic strains. The results show that comparison of proposed formula results with those available experimental data reveals a great agreement. Furthermore, it is observed that the effect of strength difference between the base and the weld materials is insignificant for short cracks whereas mismatching plays a more dominating role in long cracks. Also, with increasing the crack heights the effect of weld mismatching raises meaningfully. In addition, ECA analysis results with and without weld mismatching effect are compared.