Rasim Temür

Space applications of tensegric structures

Tensile integrity (tensegrity, tensegric) structures are suggested for possible use in outer space and on space bodies because of their minimal need for structural materials, ease of transfer and mounting. Structurally their behavior is non-linear. It has been shown here that their structural analysis can successfully be performed by total potential optimization using meta-heuristic algorithms (TPO/MA). The named method is an emerging technique that combines minimum energy principle of mechanics with metaheuristic algorithms. The technique thus defined has been shown to be very efficient, accurate and robust in analyzing structures. The success of the technique is especially profound for non-linear structures. In this study the named technique is applied to tensile integrity (tensegrity, tensegric) structures which are known to be highly nonlinear, thus difficult to analyze.

Geometrically Nonlinear Analysis of Trusses Using Particle Swarm Optimization

Particle swarm optimization (PSO) algorithm is a heuristic optimization technique based on colony intelligence, developed through inspiration from social behaviors of bird flocks and fish schools. It is widely used in problems in which the optimal value of an objective function is searched. Geometrically nonlinear analysis of trusses is a problem of this kind. The deflected shape of the truss where potential energy value is minimal is known to correspond to the stable equilibrium position of the system analyzed. The objective of this study is to explore the success of PSO using this minimum total potential energy principle, in finding good solutions to geometrically nonlinear truss problems. For this purpose analyses are conducted on three structures, two plane trusses and a space truss. The results obtained show that in case of using 20 or more particles, PSO produces very good and robust solutions.

Computation of Nonunique Solutions for Trusses Undergoing Large Deflections

Determination of nonunique configurations of structures is a problem which cannot be treated readily using classical methods of analysis. In the literature, these kinds of problems are tackled for some simple problems, like trusses with a small number of joints and members, and with specially designed approaches. The recent method of analysis called Total Potential Optimization using Metaheuristic Algorithms (TPO/MA), on the other hand, provides an efficient tool for dealing with these kinds of problems, practically without recourse to any special arrangement. In this analysis, using Harmony Search as the metaheuristic algorithm, large truss structures with linear elastic members are investigated under large deflections as to the existence of more than one solution. The results have shown that for the two examples investigated, a tower truss with 25 members and a dome truss with 24 members, nonunique configurations do exist at quite unexpected levels of loads, and that only one of them can be found with normal applications of the well-known Finite Element method.

Grey wolf optimizer for optimum design of reinforced concrete cantilever retaining walls

In this study, optimum design of cantilever reinforced concrete cantilever retaining walls is investigated under static load conditions. A methodology based on a recently developed metaheuristic algorithm called grey wolf optimizer was proposed. As the objective function, the total cost of the retaining wall including concrete, steel, labor, transportation etc. is considered. The eleven design variables such as heel and toe projections, stem thickness at the top and bottom of the wall, slab thickness, diameters and spacing of reinforced bars in critical sections are considered in the optimization process. During the optimization, totally twenty-nine design constraints including overturning stability, sliding stability, bearing capacity (maximum and minimum soil stresses), flexural moment and shear capacities of the section, minimum and maximum reinforcement ratio, development length of the bars, spacing limits of the bars (maximum and minimum spacing) are checked for the security of the wall. The requirem...

Düşey Yük Etkisi Altındaki Kazık Gruplarının Bozkurt Optimizasyon Algoritması ile Optimizasyonu

Yumusak/gevsek zeminler uzerine insa edilecek temeller, geoteknik muhendisligi acisindan buyuk sorunlara neden olmaktadir. Temelden aktarilan dusey yukler, yumusak/gevsek zeminde gocmeye ve/veya asiri oturmalara neden olabilmektedir. Bu tur problemlerin onlenebilmesi icin ilave geoteknik tedbirlerin alinmasi zorunlu olmaktadir. Temel alti kazik imalati, gunumuzde siklikla kullanilan tedbirlerden biridir. Kaziklar, saglam zemin icindeki soket boylarina bagli olarak, uc kazigi veya surtunme kazigi olarak tanimlanmaktadir. Genellikle, temellerin altinda meydana gelecek farkli oturmalarin ve dis merkezlik etkisinin azaltilmasi icin temel altinda birden fazla kazik imal edilmektedir. Bu kaziklarin birbirleriyle etkilesimi “grup etkisi” olarak tanimlanmaktadir ve bu etkilesim kaziklarin yuk tasima kapasitelerinde azalmaya neden olmaktadir. Guvenli ve ekonomik bir tasarim icin, tek bir kazigin tasima kapasitesinin hesaplanmasi ve kazik grubundaki optimum kazik sayisinin belirlenmesinde optimizasyon yapilmasi gerekmektedir. Bu calisma kapsaminda, Bozkurt Optimizasyon algoritmasinin dusey yuk etkisi altindaki kazik gruplarinin optimizasyon problemleri icin gecerliliginin arastirilmasi amaclanmistir. Bu amacla karsilastirma yapilabilmesi icin Parcacik Surusu Optimizasyon algoritmasi ve Gelistirilmis Harmoni Arama algoritmasi kullanilmistir. Incelenen yontemlerin, dusey yuk altindaki kazik gruplari icin hizli, guvenli ve ekonomik tasarimlar yapilmasi konusunda muhendislere yardimci olmasi amaclanmaktadir. Yumusak/gevsek zeminler icinde imal edilecek fore kaziklarin tasima kapasiteleri ve optimizasyonu ele alinmistir.

Rijit Döşeme Varsayımının Perde Duvarlarda Oluşan Kesme Kuvvetlerine Etkisi

Bu calismanin amaci; rijit doseme varsayiminin bina turu yapi sistemlerindeki perde duvarlarda olusan kesme kuvvetleri uzerine etkilerini arastirmaktir. Bilgisayarlarin gelismesine kadar kullanilan el hesaplarinda sadece sinirli sayida denklemle analiz yapilabilmekteydi. Bu sebeple islem hacmini kucultmek icin bazi basitlestirme yontemleri gelistirilmistir. Bina turu yapilarin analizinde dosemelerin duzlemlerinde sonsuz rijit modellenmesi bu varsayimlardan biridir. Buna gore her kat dosemesi agirlik merkezinde, kendi duzleminde iki oteleme ve duzlemine dik bir acisal yer degistirme olmak uzere toplam uc serbestlik derecesi ile tanimlanmaktadir. Bu calismada dosemeler rijit diyafram ve elastik diyafram olarak modellenmis ve dogrusal elastik analiz yapilmistir. Analiz sonuclari karsilastirmali olarak sunulmustur. Bu sonuclara gore rijit doseme varsayimi sonucu, esnek doseme modeline oranla insaat maliyeti daha yuksek ancak yapisal guvenligi daha dusuk yapilarin tasarlanmasi soz konusu olabilmektedir. The purpose of this study is to establish the effects of rigid floor assumption on shear forces that occurs on shear walls of building type structural systems. Before the advent of computers only limited number of equations could be solved manually. Thus, simplification methods have been developed to reduce the total processes. In the structural analysis of buildings, rigid floor assumption is one of these methods. At the mass center of each rigid floor, there is a master node having three degrees of freedom to represent the two in-plane translations and one out of plane rotation. In this study, the linear elastic design analysis is carried out modeling floors as rigid diaphragm and flexible diaphragm. Results of the analysis are presented comparatively. According to these results, as a consequence of rigid floor assumption, it can be an issue to get designed such buildings those construction costs are higher but structural safety is lower in comparison with flexible floor model.