OPTIMUM REDUCTION OF FLEXURAL EFFECT OF AXIALLY SYMMETRIC CYLINDRICAL WALLS WITH POST-TENSIONING FORCES

Gebrail Bekdaş,Sinan Melih Nigdeli 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.7

Post-tensioning of axially symmetric cylindrical walls has been used to prevent cracking and serviceability failures. In the case ofaxially symmetric cylindrical walls used for storing water, post-tensioning improves impermeability by reducing the tension loadsgenerated by fluid loads. However; achieving these improvements in axially symmetric cylindrical walls requires determination of asuitable design for post-tensioning loads. By optimizing the locations and intensities of the post-tensioning loads, the effects onaxially symmetric cylindrical walls can be minimized. In this study, four metaheuristic algorithms such as harmony search (HS),flower pollination algorithm, bat algorithm and teaching-learning based optimization are investigated for optimum design of posttensionforces on axially symmetric cylindrical walls. The design involves the location and intensity of the post-tensioning cables. Inthe optimization process, analyses of cylindrical walls are conducted by a developed module using the superposition method (SPM). According to the analyses results, the optimization methods investigated are effective in reducing maximum longitudinal momentson cylindrical walls, but major difference in performance of the methods are seen.

Optimum design of axially symmetric cylindrical reinforced concrete walls

Gebrail Bekdaş 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.3

The main aim of this paper is to investigate the relationship between thickness and height of the axially symmetric cylindrical reinforced concrete (RC) walls by the help of a meta-heuristic optimization procedure. The material cost of the wall which includes concrete, reinforcement and formwork, was chosen as objective function of the optimization problem. The wall thickness, compressive strength of concrete and diameter of reinforcement bars were defined as design variables and tank volume, radius and height of the wall, loading condition and unit cost of material were defined as design constants. Numerical analyses of the wall were conducted by using superposition method (SPM) considering ACI 318-Building coderequirements for structural concrete. The optimum wall thickness-height relationship was investigated under three main cases related with compressive strength of concrete and density of the stored liquid. According to the results, the proposed method is effective on finding the optimum design with minimum cost.

Optimum design of axially symmetric cylindrical reinforced concrete walls

Bekdas, Gebrail Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.3

The main aim of this paper is to investigate the relationship between thickness and height of the axially symmetric cylindrical reinforced concrete (RC) walls by the help of a meta-heuristic optimization procedure. The material cost of the wall which includes concrete, reinforcement and formwork, was chosen as objective function of the optimization problem. The wall thickness, compressive strength of concrete and diameter of reinforcement bars were defined as design variables and tank volume, radius and height of the wall, loading condition and unit cost of material were defined as design constants. Numerical analyses of the wall were conducted by using superposition method (SPM) considering ACI 318-Building code requirements for structural concrete. The optimum wall thickness-height relationship was investigated under three main cases related with compressive strength of concrete and density of the stored liquid. According to the results, the proposed method is effective on finding the optimum design with minimum cost.

Active structural control via metaheuristic algorithms considering soil-structure interaction

Serdar Ulusoy,Gebrail Bekdaş,Sinan Melih Nigdeli 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.2

In this study, multi-story structures are actively controlled using metaheuristic algorithms. The soil conditions such as dense, normal and soft soil are considered under near-fault ground motions consisting of two types of impulsive motions called directivity effect (fault normal component) and the flint step (fault parallel component). In the active tendon-controlled structure, Proportional–Integral–Derivative (PID) type controller optimized by the proposed algorithms was used to achieve a control signal and to produce a corresponding control force. As the novelty of the study, the parameters of PID controller were determined by different metaheuristic algorithms to find the best one for seismic structures. These algorithms are flower pollination algorithm (FPA), teaching learning based optimization (TLBO) and Jaya Algorithm (JA). Furthermore, since the influence of time delay on the structural responses is an important issue for active control systems, it should be considered in the optimization process and time domain analyses. The proposed method was applied for a 15-story structural model and the feasible results were found by limiting the maximum control force for the near-fault records defined in FEMA P-695. Finally, it was determined that the active control using metaheuristic algorithms optimally reduced the structural responses and can be applied for the buildings with the soil-structure interaction (SSI).

Teaching learning-based optimization for design of cantilever retaining walls

Rasim Temür,Gebrail Bekdaş 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.57 No.4

A methodology based on Teaching Learning-Based Optimization (TLBO) algorithm is proposed for optimum design of reinforced concrete retaining walls. The objective function is to minimize total material cost including concrete and steel per unit length of the retaining walls. The requirements of the American Concrete Institute (ACI 318-05-Building code requirements for structural concrete) are considered for reinforced concrete (RC) design. During the optimization process, totally twenty-nine design constraints composed from stability, flexural moment capacity, shear strength capacity and RC design requirements such as minimum and maximum reinforcement ratio, development length of reinforcement are checked. Comparing to other nature-inspired algorithm, TLBO is a simple algorithm without parameters entered by users and self-adjusting ranges without intervention of users. In numerical examples, a retaining wall taken from the documented researches is optimized and the several effects (backfill slope angle, internal friction angle of retaining soil and surcharge load) on the optimum results are also investigated in the study. As a conclusion, TLBO based methods are feasible.

Optimum tuned mass damper design for preventing brittle fracture of RC buildings

Sinan Melih Nigdeli,Gebrail Bekdas 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.12 No.2

Brittle fracture of structures excited by earthquakes can be prevented by adding a tuned mass damper (TMD). This TMD must be optimum and suitable to the physical conditions of the structure. Compressive strength of concrete is an important factor for brittle fracture. The application of a TMD to structures with low compressive strength of concrete may not be possible if the weight of the TMD is too much. A heavy TMD is dangerous for these structures because of insufficient axial force capacity of structure. For the preventing brittle fracture, the damping ratio of the TMD must be sufficient to reduce maximum shear forces below the values proposed in design regulations. Using the formulas for frequency and damping ratio related to a preselected mass, this objective can be only achieved by increasing the mass of the TMD. By using a metaheuristic method, the optimum parameters can be searched in a specific limit. In this study, Harmony Search (HS) is employed to find optimum TMD parameters for preventing brittle fracture by reducing shear force in additional to other time and frequency responses. The proposed method is feasible for the retrofit of weak structures with insufficient compressive strength of concrete.

Analysis of trusses by total potential optimization method coupled with harmony search

Toklu, Yusuf Cengiz,Bekdas, Gebrail,Temur, Rasim Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.2

Current methods of analysis of trusses depend on matrix formulations based on equilibrium equations which are in fact derived from energy principles, and compatibility conditions. Recently it has been shown that the minimum energy principle, by itself, in its pure and unmodified form, can well be exploited to analyze structures when coupled with an optimization algorithm, specifically with a meta-heuristic algorithm. The resulting technique that can be called Total Potential Optimization using Meta-heuristic Algorithms (TPO/MA) has already been applied to analyses of linear and nonlinear plane trusses successfully as coupled with simulated annealing and local search algorithms. In this study the technique is applied to both 2-dimensional and 3-dimensional trusses emphasizing robustness, reliability and accuracy. The trials have shown that the technique is robust in two senses: all runs result in answers, and all answers are acceptable as to the reliability and accuracy within the prescribed limits. It has also been shown that Harmony Search presents itself as an appropriate algorithm for the purpose.

Analysis of trusses by total potential optimization method coupled with harmony search

Yusuf Cengiz Toklu,Gebrail Bekdaşa,Rasim Temur 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.2

Current methods of analysis of trusses depend on matrix formulations based on equilibrium equations which are in fact derived from energy principles, and compatibility conditions. Recently it has been shown that the minimum energy principle, by itself, in its pure and unmodified form, can well be exploited to analyze structures when coupled with an optimization algorithm, specifically with a meta-heuristic algorithm. The resulting technique that can be called Total Potential Optimization using Meta-heuristic Algorithms (TPO/MA) has already been applied to analyses of linear and nonlinear plane trusses successfully as coupled with simulated annealing and local search algorithms. In this study the technique is applied to both 2-dimensional and 3-dimensional trusses emphasizing robustness, reliability and accuracy. The trials have shown that the technique is robust in two senses: all runs result in answers, and all answers are acceptable as to the reliability and accuracy within the prescribed limits. It has also been shown that Harmony Search presents itself as an appropriate algorithm for the purpose.

A novel harmony search based optimization of reinforced concrete biaxially loaded columns

Sinan Melih Nigdeli,Gebrail Bekdaş,김상훈,김종우 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.6

A novel optimization approach for reinforced concrete (RC) biaxially loaded columns is proposed. Since there are several design constraints and influences, a new computation methodology using iterative analyses for several stages is proposed. In the proposed methodology random iterations are combined with music inspired metaheuristic algorithm called harmony search by modifying the classical rules of the employed algorithm for the problem. Differently from previous approaches, a detailed and practical optimum reinforcement design is done in addition to optimization of dimensions. The main objective of the optimization is the total material cost and the optimization is important for RC members since steel and concrete are very different materials in cost and properties. The methodology was applied for 12 cases of flexural moment combinations. Also, the optimum results are found by using 3 different axial forces for all cases. According to the results, the proposed method is effective to find a detailed optimum result with different number of bars and various sizes which can be only found by 2000 trial of an engineer. Thus, the cost economy is provided by using optimum bars with different sizes.

Resource Constrained Project Scheduling by Harmony Search Algorithm

Omer Giran,Rasim Temur,Gebrail Bekdaş 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.2

The construction industry is nonhomogeneous and also managing construction projects are more difficult in today's world. Construction projects are huge and contractors want to accomplish them within a short time in this fast changing era. Therefore, the time and resource have to be managed for a successful construction project management. Resource leveling is one of the primary tools used for managing resources. The target is leveling the resources within a minimum time period to complete the project successfully. Resource constrained project scheduling problems (RCPSP) are a Non-deterministic Polynomial-time hard (NP-hard) problem therefore heuristic methods can be used to solve it. This paper presents a harmony search method for solving the RCPSP. In order to compare the performance of the developed software three examples were chosen from the literature. Computational results indicate that the harmony search method is more effective, rapid and suitable for the RCPSP than existing solutions.