Korhan Ozgan

Dynamic analysis of thick plates including deep beams on elastic foundations using modified Vlasov model

Dynamic analysis of foundation plate-beam systems with transverse shear deformation is presented using modified Vlasov foundation model. Finite element formulation of the problem is derived by using an 8-node (PBQ8) finite element based on Mindlin plate theory for the plate and a 2-node Hughes element based on Timoshenko beam theory for the beam. Selective reduced integration technique is used to avoid shear locking problem for the evaluation of the stiffness matrices for both the elements. The effect of beam thickness, the aspect ratio of the plate and subsoil depth on the response of plate-beam-soil system is analyzed. Numerical examples show that the displacement, bending moments and shear forces are changed significantly by adding the beams.

Application of the Modified Vlasov Model to the free vibration analysis of thick plates resting on elastic foundations

The Modified Vlasov Model is applied to the free vibration analysis of thick plates resting on elastic foundations. The effects of the subsoil depth, plate dimensions and their ratio, the value of the vertical deformation parameter within the subsoil on the frequency parameters of plates on elastic foundations are investigated. A four-noded, twelve degrees of freedom quadrilateral finite element (PBQ4) is used for plate bending analysis based on Mindlin plate theory which is effectively applied to the analysis of thin and thick plates when selective reduced integration technique is used. The first ten natural frequency parameters are presented in tabular and graphical forms to show the effects of the parameters considered in the study. It is concluded that the effect of the subsoil depth on the frequency parameters of the plates on elastic foundation is generally larger than that of the other parameters considered in the study.

Optimum Design of Braced Steel Space Frames including Soil-Structure Interaction via Teaching-Learning-Based Optimization and Harmony Search Algorithms

Optimum design of braced steel space frames including soil-structure interaction is studied by using harmony search (HS) and teaching-learning-based optimization (TLBO) algorithms. A three-parameter elastic foundation model is used to incorporate the soil-structure interaction effect. A 10-storey braced steel space frame example taken from literature is investigated according to four different bracing types for the cases with/without soil-structure interaction. X, V, Z, and eccentric V-shaped bracing types are considered in the study. Optimum solutions of examples are carried out by a computer program coded in MATLAB interacting with SAP2000-OAPI for two-way data exchange. The stress constraints according to AISC-ASD (American Institute of Steel Construction-Allowable Stress Design), maximum lateral displacement constraints, interstorey drift constraints, and beam-to-column connection constraints are taken into consideration in the optimum design process. The parameters of the foundation model are calculated depending on soil surface displacements by using an iterative approach. The results obtained in the study show that bracing types and soil-structure interaction play very important roles in the optimum design of steel space frames. Finally, the techniques used in the optimum design seem to be quite suitable for practical applications.

YAPI ZEMİN ETKİLEŞİMİNİN BETONARME YAPILARIN TASARIMINA ETKİSİ

Betonarme yapilarin tasarimi sirasinda genellikle temel zemini rijit bir ortam olarak dikkate alinarak tabanda kolonlarin ankastre oldugu kabulu ile yapi-zemin etkilesimi ihmal edilmektedir. Oysaki zemin, ust yapidan aktarilan yukler altinda sekil degistiren, gerilmelere maruz kalan ve maruz kaldigi etkilere karsi tepki olusturan bir ortamdir. Bu nedenle zemin etkileri dikkate alinmadan yapilan bir ust yapi tasariminin eksik kalabilecegi soylenebilir. Bu calismada, yapi-zemin etkilesiminin betonarme yapilarin tasarimina etkisi incelenmektedir. Bu amacla daha once literaturde incelenmis olan 8 katli bir yapi ornegi dikkate alinmistir. Yapinin oturdugu zemin, rijit yapi-zemin kabulunun yaninda Winkler ve Gelistirilmis Vlasov Modelleri de kullanilarak modellenmistir. Sayisal sonuclar SAP2000 paket programi ile MATLAB’te kodlanan bir yazilimin es zamanli kullanilmasiyla elde edilmistir. Bu sayede SAP2000 paket programina kendi icerisinde var olmayan Gelistirilmis Vlasov Modeli ile cozum yapma kabiliyeti kazandirilmistir. Cozumden elde edilen periyot, taban kesme kuvveti, kolon normal kuvvetleri, kolon egilme momentleri ve kolonlarin boyuna donati oranlari her bir zemin modeli icin karsilastirilmistir. Calismanin sonunda yapi-zemin etkilesiminin betonarme yapilarin tasarimina etkisinin ihmal edilemeyecek duzeyde oldugu gorulmustur