• Structural Engineering and Mechanics
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• 제49권1호
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• pp.65-80
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• 2014

This paper reports on the development of a minimum cost design model and its application for obtaining economic designs for reinforced High Strength Concrete (HSC) T-sections in bending under ultimate limit state conditions. Cost objective functions, behavior constraint including material nonlinearities of steel and HSC, conditions on strain compatibility in steel and concrete and geometric design variable constraints are derived and implemented within the Conjugate Gradient optimization algorithm. Particular attention is paid to problem formulation, solution behavior and economic considerations. A typical example problem is considered to illustrate the applicability of the minimum cost design model and solution methodology. Results are confronted to design solutions derived from conventional design office methods to evaluate the performance of the cost model and its sensitivity to a wide range of unit cost ratios of construction materials and various classes of HSC described in Eurocode2. It is shown, among others that optimal solutions achieved using the present approach can lead to substantial savings in the amount of construction materials to be used. In addition, the proposed approach is practically simple, reliable and computationally effective compared to standard design procedures used in current engineering practice.

• Structural Engineering and Mechanics
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• 제11권2호
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• pp.151-170
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• 2001

With increasing competition, the engineering industry is in need of optimization of designs that would lead to minimum cost or weight. Recent developments in Genetic Algorithms (GAs) makes it possible to model and obtain optimal solutions in structural design that can be put to use in industry. The main objective of this paper is to illustrate typical applications of GAs to practical design of structural systems such as steel trusses, towers, bridges, reinforced concrete frames, bridge decks, shells and layout planning of buildings. Hence, instead of details of GA process, which can be found in the reported literature, attention is focussed on the description of the various applications and the practical aspects that are considered in Genetic Modeling. The paper highlights scope and future directions for wider applications of GA based methodologies for optimal design in practice.

• Computers and Concrete
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• 제19권5호
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• pp.589-597
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• 2017

Strut-and-tie modeling method, which evolved on truss-model approach, has generally been preferred for the design of complex reinforced concrete structures and structural elements that have critical shear behavior. Some structural members having disturbed regions require exceptional detailing for all support and loading conditions, such as the beam-column connections, deep beams, short columns or corbels. Considering the general expectation of exhibiting brittle behavior, corbels are somewhat dissimilar to other shear critical structures. In this study, reinforcement layout of a corbel model was determined by the participation of structural optimization and strut-and-tie modeling methods, and an experimental comparison was performed against a conventionally designed model.

• Structural Engineering and Mechanics
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• 제56권5호
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• pp.707-726
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• 2015

There is a growing trend of considering uncertainty in optimization process since last few decades. In this regard, Robust Design Optimization (RDO) scheme has gained increasing momentum because of its virtue of improving performance of structure by minimizing the variation of performance and ensuring necessary safety and feasibility of constraint under uncertainty. In the present study, RDO of reinforced concrete folded plate and shell structure has been carried out incorporating uncertainty in the relevant parameters by Monte Carlo Simulation. Folded plate and shell structures are among the new generation popular structures often used in aesthetically appealing constructions. However, RDO study of such important structures is observed to be scarce. The optimization problem is formulated as cost minimization problem subjected to the force and displacements constraints considering dead, live and wind load. Then, the RDO is framed by simultaneously optimizing the expected value and the variation of the performance function using weighted sum approach. The robustness in constraint is ensured by adding suitable penalty term and through a target reliability index. The RDO problem is solved by Sequential Quadratic Programming. Subsequently, the results of the RDO are compared with conventional deterministic design approach. The parametric study implies that robust designs can be achieved by sacrificing only small increment in initial cost, but at the same time, considerable quality and guarantee of the structural behaviour can be ensured by the RDO solutions.

• Computers and Concrete
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• 제21권4호
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• pp.441-449
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• 2018

FE models for complex or large-scaled structures that need detailed modeling of structural components are usually constructed using commercial analysis softwares. Updating of such FE model by conventional sensitivity-based methods is difficult since repeated computation for perturbed parameters and manual calculations are needed to obtain sensitivity matrix in each iteration. In this study, an FE model updating procedure avoiding such difficulties by using response surface (RS) method and a Pareto-based multiobjective optimization (MOO) was formulated and applied to FE models constructed with a commercial analysis package. The test building is a low-rise reinforced concrete building that has been seismically retrofitted. Dynamic properties of the building were extracted from vibration tests performed before and after the seismic retrofits, respectively. The elastic modulus of concrete and masonry, and spring constants for the expansion joint were updated. Two RS functions representing the errors in the natural frequencies and mode shape, respectively, were obtained and used as the objective functions for MOO. Among the Pareto solutions, the best compromise solution was determined using the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) procedure. A similar task was performed for retrofitted building by taking the updating parameters as the stiffness of modified or added members. Obtained parameters of the existing building were reasonably comparable with the current code provisions. However, the stiffness of added concrete shear walls and steel section jacketed members were considerably lower than expectation. Such low values are seemingly because the bond between new and existing concrete was not as good as the monolithically casted members, even though they were connected by the anchoring bars.

• 한국전산구조공학회논문집
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• 제30권3호
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• pp.265-274
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• 2017

본 연구는 콘크리트 구조설계기준을 만족시키면서 내재에너지와 이산화탄소 배출량을 최적화할 수 있는 철근 콘크리트 기둥에 대한 지속가능 설계법을 제시한다. 지속가능 설계법은 기존의 비용절감 중심의 강도설계법에서 벗어나 철근 콘크리트 구조물의 환경 및 에너지 소비에 대한 부하를 최소화할 수 있게 해준다. 철근 콘크리트 기둥의 파괴모드는 가해지는 축력과 휨의 비율에 따라 인장지배와 압축지배로 나누어지기 때문에 각각의 지배모드에 대한 최적화 해석을 수행하였다. 다양한 단면형상과 철근량에 대해 비용, 내재에너지, 이산화탄소 배출량을 최적화시킨 단면을 산출하고 그 특성을 비교 분석하였다. 최적화 해석결과에 대한 분석을 통해 비용을 약 10% 증가시킬 때 내재에너지는 약 25% 그리고 이산화탄소 배출량은 약 55%까지 감소시킬 수 있음을 보였다. 특히, 기둥이 인장지배 상태인 경우 압축지배 상태인 경우보다 내재에너지와 이산화탄소 배출량을 더 큰 폭으로 감소시킬 수 있음을 보였다. 결과적으로 지속가능 설계법은 비용의 최소화 외에도 강도설계법에서 고려하지 않았던 내재에너지나 이산화탄소 배출량을 감소 또는 최적화하는 설계를 가능케 하여 지속가능개발의 개념을 철근 콘크리트 구조물 설계에 도입할 수 있도록 해주는 것을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.479-484
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• 2000

In this study, optimal design of reinforced concrete piers under seismic load is numerically investigated. Object function is the area of the concreate-section. Design variables are the total area of reinforcement and concrete-section dimension(Circular section diameter). Constraints of the design strength of the column, longitudinal reinforcement ratio and lower and upper bounds on the design variables are imposed. The reinforcement concrete column is analysed and designed by the Ultimated Strength Design method and load combination involving dead, live, wind and seismic load is used. For numerical optimization, ADS(Garret N, Vanderplaats_ routine is used. From the result of numerical examples, the concrete-section dimension was reduced, but longitudinal reinforcement was not changed. The results show that confinement reinforcement was reduced and confinement reinforcement spacing is increased. The higher strength of reinforcement used, the more concrete-section area was reduced.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.212-218
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• 1999

In this study , Computer programs for the optimum and automation desgin of reinforced concrete box culvert were developed. It was shown that even though the strarting points and optimization method are different the objective function and optimum design variables converge to a value within a close range respectively, and consequently the optimum design program developed in the study is reliable and stron. 3D-design drawing can be drawn using automation desgin computer program developed in this study.

• Geomechanics and Engineering
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• 제24권3호
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• pp.237-251
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• 2021

The main purpose of this study is to investigate the performance of the proposed hybrid teaching-learning based optimization algorithm on the optimum design of reinforced concrete (RC) cantilever retaining walls. For this purpose, three different design examples are optimized with 100 independent runs considering continuous and discrete variables. In order to determine the algorithm performance, the optimization results were compared with the outcomes of the nine powerful meta-heuristic algorithms applied to this problem, previously: the big bang-big crunch (BB-BC), the biogeography based optimization (BBO), the flower pollination (FPA), the grey wolf optimization (GWO), the harmony search (HS), the particle swarm optimization (PSO), the teaching-learning based optimization (TLBO), the jaya (JA), and Rao-3 algorithms. Moreover, Rao-1 and Rao-2 algorithms are applied to this design problem for the first time. The objective function is defined as minimizing the total material and labor costs including concrete, steel, and formwork per unit length of the cantilever retaining walls subjected to the requirements of the American Concrete Institute (ACI 318-05). Furthermore, the effects of peak ground acceleration value on minimum total cost is investigated using various stem height, surcharge loads, and backfill slope angle. Finally, the most robust results were obtained by HTLBO with 50 populations. Consequently the optimization results show that, depending on the increase in PGA value, the optimum cost of RC cantilever retaining walls increases smoothly with the stem height but increases rapidly with the surcharge loads and backfill slope angle.

• Smart Structures and Systems
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• 제20권1호
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• pp.53-60
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• 2017

Reinforced concrete shear wall is one of the most common structural forms for high-rise buildings, and seismic energy dissipation techniques, which are effective means to control structural vibration response, are being increasingly used in engineering. Reinforced concrete-mild steel damper stiffness-tandem energy dissipation coupling beams are a new technology being gradually adopted by more construction projects since being proposed. Research on this technology is somewhat deficient, and this paper investigates design principles and methods for two types of mild steel dampers commonly used for energy dissipation coupling beams. Based on the conception design of R.C. shear wall structure and mechanics principle, the basic design theories and analytic expressions for the related optimization parameters of dampers at elastic stage, yield stage, and limit state are derived. The outcomes provide technical support and reference for application and promotion of reinforced concrete-mild steel damper stiffness-tandem energy dissipation coupling beam in engineering practice.