Ahmet Demir

Field Test of Circular Footings on Reinforced Granular Fill Layer Overlying a Clay Bed

The ultimate bearing capacity and settlement of a circular shallow rigid plate on compacted granular fill layer with and without geogrid reinforcement overlying on natural clay deposit exhibiting low bearing capacity and large settlement have been investigated. A total of 15 field tests were carried out using a circular model rigid plate with a diameter of 0.90 m. This study has been initially directed to evaluate the beneficial effects of the compacted granular fill layer on natural clay deposit for the shallow rigid plate performance. Then, the reinforcing effect of the top granular fill layer with horizontal layers of welded geogrid reinforcement on the bearing capacity and settlement has been studied. Parameters of the testing program include granular fill thickness, depth of first reinforcement, vertical spacing of reinforcement layers, and number of reinforcement layers. Bearing capacity ratio (BCR) and percentage reduction in settlement (PRS) were defined to evaluate improvement performance. Based on the test results, the effect of the granular fill and welded geogrid reinforcement on the bearing capacity and settlement are discussed. The results indicate that the use of granular fill layers over natural clay soils has considerable effects on the bearing capacity and settlement characteristics. The construction of granular fill layer with welded geogrid reinforcement over clay deposit helps in redistributing the applied load to a wider area. It has been observed that the use of welded geogrid reinforcement in granular fill layer provides additional improvement of bearing capacity and provides reduction in settlement of the rigid plate up to 80 and 60 %, respectively.

Experimental and numerical studies of metallic powders subjected to cold isostatic pressing

Abstract The cold isostatic pressing behaviour of aluminium and iron powders was analysed, both experimentally using a cold isostatic pressing unit, and numerically using a nonlinear finite element program. The pressing unit, which can withstand up to 650 MPa pressure was designed and constructed in this study. Aluminium and iron powders, having different hardness values and almost the same particle sizes, have been pressed in the pressure unit and the mechanical behaviours of these powders were investigated in the 100−500 MPa pressure range. Attained densities were about 98% for aluminium and 88% for iron powders. Pressing resulted in significant increases in microhardnesses of the aluminium and iron powders. Light and scanning electron microscopy examinations revealed that severe plastic deformation took place in the powders of aluminium and iron. The densification behaviour of aluminium and iron powders under the cold isostatic pressing was also analysed using the finite element method, in which an ela...

Kum Zemine Gömülü Çan Tipi Ankrajların Deneysel Çalışmalar ve Sayısal Analizler ile İncelenmesi

Temeller genellikle basinc yuklerine maruz kalmaktadir. Fakat ruzgar yuku vb. gibi yanal yuklere maruz kalan yuksek binalar, elektrik uretmek icin kullanilan ruzgar tribunleri vb. gibi yapilarin temelleri cekme yuklerine maruz kalmaktadir. Bu tip yuklere maruz yapilarin temelleri tasarlanirken bu cekme kuvvetinin etkisini incelemek gerekmektedir. Bu calismada kum zemine gomulu can tipi ankrajlarin cekme kapasitesi deneysel calismalar ve numerik analizlerle incelenmistir. Deneysel calismalarda ve sayisal analizlerde taban capi 50, 100 ve 150 mm olan can tipi ankrajlar kullanilmistir. Can tipi ankrajin egimli yuzeyinin acisi, gomulme derinligi ve gomuldugu kum zeminin sikiligi gibi parametrelerin cekme kapasitesine etkisi arastirilmistir. Ayrica helisel ve dairesel ankrajlarin cekme kapasiteleri deneysel olarak bulunarak can tipi ankrajlarin cekme kapasiteleri ile kiyaslanmistir. Bu calismanin sonucunda gorulmustur ki, cekme kapasitesi ankraj acisinin degisiminden cok fazla etkilenmemektedir ve cekme kapasitesi ankraj acisi arttikca az bir miktar azalmaktadir. Ayrica, can tipi ankrajin capi, gomulme derinligi ve gomuldugu kumun rolatif sikiligi arttikca cekme kapasitesi artmaktadir.