Ayhan Nuhoglu

A practical approach for nonlinear analysis of tensegrity systems

Tensegrity systems are lightweight structures composed of cables and struts. The nonlinear behavior of tensegrity systems is critical; therefore, the design of these types of structures is relatively complex. In the present study, a practical and efficient approach for geometrical nonlinear analysis of tensegrity systems is proposed. The approach is based on the point iterative method. Static equilibrium equations are given in nodes for subsystems, thus the maximum unknown displacement number in each step is three. Pre-stress forces in the system are taken into account in a tangent stiffness matrix, while similar calculations are carried out for each node in the system which has a minimum of one degree of freedom. In each iteration step, the values found in previous steps are used. When it reaches permissible tolerance of calculation, final displacements and internal forces are obtained. The structural behavior of the tensegrity systems were evaluated by the proposed method. The results show that the method can be used effectively for tensegrity systems.

Identification of Historical Veziragasi Aqueduct Using the Operational Modal Analysis

This paper describes the results of a model updating study conducted on a historical aqueduct, called Veziragasi, in Turkey. The output-only modal identification results obtained from ambient vibration measurements of the structure were used to update a finite element model of the structure. For the purposes of developing a solid model of the structure, the dimensions of the structure, defects, and material degradations in the structure were determined in detail by making a measurement survey. For evaluation of the material properties of the structure, nondestructive and destructive testing methods were applied. The modal analysis of the structure was calculated by FEM. Then, a nondestructive dynamic test as well as operational modal analysis was carried out and dynamic properties were extracted. The natural frequencies and corresponding mode shapes were determined from both theoretical and experimental modal analyses and compared with each other. A good harmony was attained between mode shapes, but there were some differences between natural frequencies. The sources of the differences were introduced and the FEM model was updated by changing material parameters and boundary conditions. Finally, the real analytical model of the aqueduct was put forward and the results were discussed.

Investigation of structural safety of existing masonry healthcare facilities in Turkey

Masonry healthcare facilities in Turkey are investigated in the current research. The structural assessment of the healthcare facilities has become very important for increasing building safety. A large amount of the existing healthcare facilities are generally old buildings, constructed before engineering practices were developed making most buildings vulnerable to severe structural damage. Since healthcare facilities are costly buildings to replace, structural and non-structural assessments have economical importance. Even non-structural behavior can be more critical than structural behavior as ground vibrations can cause severe damage to these types of facilities. Different ground vibrations and soil types are employed in the analyses to investigate structural and non-structural behavior of these types of facilities.

Interactive search algorithm: A new hybrid metaheuristic optimization algorithm

Abstract In this paper, a new hybrid optimization algorithm, called “Interactive Search Algorithm (ISA)” is proposed for the solution of the optimization problems. This algorithm modifies and combines affirmative features of two developed metaheuristic methods called Integrated Particle Swarm Optimization (iPSO) and Teaching and Learning Based Optimization (TLBO). ISA consists of two separate paradigms: (i) Tracking and (ii) Interacting. Tracking paradigm utilizes the information stored in the current agent’s memory and two other important agents, the weighted and best agents, to guide the colony. On the other hand, interacting paradigm provides a pairwise interaction between agents to share their knowledge with each other. Each agent based on its tendency factor employs one of these two paradigms in each cycle of ISA to explore the search space. Additionally, rather than conventional penalty approach, ISA utilizes the improved fly-back approach to handle problem constraints. The search capability of the proposed method is tested on the number benchmark mathematical functions and constrained mechanical design problems as the real-world examples. Consequently, the achieved numerical results demonstrate that the proposed method is competitive with other well-established metaheuristic methods.

Rize Merkez Kurşunlu Camisi’nin deprem davranışının incelenmesi

Tarihi yapilarin mevcut yuklere ve ileride olabilecek zorlanmalara karsi yapisal davranislarinin belirlenmesi, korunmasi, saglamlastirilmasi, restorasyon ve muhendislik acisindan oldukca onemlidir. Bu kapsamda, tarihi yapilar bilgisayar programlari ile modellenerek analizleri yapilmakta ve davranislari belirlenmektedir. Bu calismada, SAP2000 programi kullanilarak Rize Merkez’de bulunan ve 1570 yilinda Iskender Cafer Pasa tarafindan yaptirilan Kursunlu Camisi uzerinde Cape Mendocino, Duzce ve Landers depremleri uygulanarak, zaman tanim alaninda dinamik analizler gerceklestirilmistir. Yigma tasiyici sisteme sahip olan tarihi yapida her bir ivme kaydi icin ortaya cikan yer degistirme ve gerilme degerleri elde edilmis ve analiz sonuclari dogrultusunda bir degerlendirme yapilmistir.

Protection of Archaeological Remains in the Yortanli Dam Reservoir in Turkey

This study discussed conflicts in a large-scale development project realized in an archaeological area. The dam reservoir of Yortanli constructed as a part of a contemporary irrigation project in Western Turkey conflicted with the antique settlement of Allianoi, which had developed in the same area around a natural thermal spring in the 2nd century ad. The aim was to present the protection decisions and implementations related with the archaeological site of Allianoi in the Yortanlı Dam Reservoir so that monitoring and criticism of its consequences can be possible in the future. The tools of the three disciplines, hydraulic engineering, structural engineering and conservation, were emphasized. The following conclusions were derived: The understanding of the protection-development conflict of archaeological heritage-dam relations in the case of Allianoi-Yortanlı necessitates the evaluation of its legal, administrative, technical, and managerial aspects with all related governmental and non-governmental parts. The presented evaluation provides an opportunity for the discussion of the validity of the protection intervention, which is reburial of the remains prior to water retention in the dam, within an international framework. The presentation of the details of the protection process may facilitate the monitoring and criticism of its consequences in the future.