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

Nigdeli, Sinan Melih,Bekdas, Gebrail Techno-Press 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.

Optimum Design of RC Continuous Beams Considering Unfavourable Live-Load Distributions

Sinan Melih Nigdeli,Gebrail Bekdas 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.4

The cross-sections of Reinforced Concrete (RC) members are assumed in the preliminary design. With optimization, optimum dimensions of cross-sections providing required security measures can be obtained. Although, the area of the reinforcement bars is a computable value according to the cross-section, the amount and size of bars are also design variables in order to ensure the placement of bars providing adherence and other physical conditions. In this paper, the optimum design of RC continuous beams is presented by considering design constraints given in ACI-318 (Building Code Requirements for Structural Concrete). The most critical stress resultants of continuous beams are computed for all live load distribution patterns using three moment equations and were used in the analysis of continuous beam. A Random Search Technique (RST) is developed in order to minimize the material cost of the continuous beam. The RST is employed in different stages of optimization process such as cross-section and reinforcement bar optimization. The approach is effective to find the detailed optimum design of RC continuous beams with minimum cost.

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.

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.

Optimum Tuned Mass Damper Design in Frequency Domain for Structures

Sinan Melih Nigdeli,Gebrail Bekdas 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.3

The design of tuned mass dampers for reduction of seismic vibrations in multiple degree of freedom structures is also a complex problem and the optimization of design parameters of tuned mass damper are needed for the best reduction of structural responses. In the optimization process, frequency or time domain solutions can be iteratively used. In this paper, a frequency based optimization technique is presented to find design variables such as mass, period and damping ratio of tuned mass damper on the top of a structure. A music inspired metaheuristic algorithm called harmony search is employed to reach the optimum solution. The optimum results were obtained for two 10-story and one 40-story structures. According to comparisons with time domain based method, frequency domain based methods is effective to reduce maximum values and to obtain a steady stead response for critical excitations.

Metaheuristic Optimization of Reinforced Concrete Footings

Sinan Melih Nigdeli,Gebrail Bekdaş,Xin-She Yang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11

The primary goal of an engineer is to find the best possible economical design and this goal can be achieved by considering multiple trials. A methodology with fast computing ability must be proposed for the optimum design. Optimum design of Reinforced Concrete (RC) structural members is the one of the complex engineering problems since two different materials which have extremely different prices and behaviors in tension are involved. Structural state limits are considered in the optimum design and differently from the superstructure members, RC footings contain geotechnical limit states. This study proposes a metaheuristic based methodology for the cost optimization of RC footings by employing several classical and newly developed algorithms which are powerful to deal with non-linear optimization problems. The methodology covers the optimization of dimensions of the footing, the orientation of the supported columns and applicable reinforcement design. The employed relatively new metaheuristic algorithms are Harmony Search (HS), Teaching-Learning Based Optimization algorithm (TLBO) and Flower Pollination Algorithm (FPA) are competitive for the optimum design of RC footings.

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.

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).