Research on Engineering Structures and Materials

53-71

Authors: İffet Feyza Çırak, Hasan Kaplan, Salih Yılmaz, Özlem Çalışkan Değirmenci, Nihat Çetinkaya

Retrofit of the existing seismically deficient buildings is a common need especially in earthquake prone regions. Chemical anchors are widely used to connect existing and newly added structural elements, such as shear walls. Therefore, modelling the behaviour of anchors which transfer axial and shear forces to the added members is important for design and analyses. There is no anchor model present in the current literature accounting shear behaviour. Therefore, a new model is established using results of a comprehensive experimental study conducted at Pamukkale University Earthquake and Construction Technology Research Laboratory. In this study, mentioned shear model is tested using two- story, one-bay RC frame specimens strengthened with external shear walls. In analyses of the models, SAP 2000 software is used and nonlinear shear behaviour of anchors is represented by NLLink elements. It is concluded that, suggested anchor shear model may be used for modelling external shear wall anchor behaviour.

81-97

Authors: Ahmed. M. Hashem, Rasha. S. El-Tawil, Mohamed Abutabl, Ali. E. Eid

Layered LiNi1/3Mn1/3Co1/3O2 (NMC) positive materials were synthesized by efficient, low cost and easy manageable methods such as oxalate co-precipitation and sol-gel processes. Preliminary electrochemical results show that sol-gel sample provide better results than co-precipitated samples. With the aim to improve the properties of the co-precipitated samples these were coated with carbon and alumina bearing in mind the co-precipitated method is suitable for large scale production. The subsequently performed local structure investigations revealed well crystallized layered cathode materials with α-NaFeO2-type structure (R-3m space group). Sample tests using both the scanning electron microscope (SEM) and the transmission electron microscope (TEM) showed submicron particles with a slight tendency to agglomerate and furthermore the existence of a thin film that encapsulates the oxide particles. 7Li magic angle spinning nuclear magnetic resonance (7LiMAS NMR) measurements were carried out for pristine and coated samples to compare the cation arrangement in the transition metal layers. Finally, electrochemical tests revealed a remarkable improvement in capacity retention of the coated oxides compared to the parent compounds.

109-120

Authors: Bengi Gözmen, Hüseyin Akıllı

This paper investigates the effects of permeable cylinder on vortex shedding downstream of the permeable cylinder in deep water flow by PIV technique. In order to reveal the effect of porosity β on the vortex shedding, the permeable cylinder having four different porosities (β = 0.4, 0.5, 0.6 and 0.7) with a diameter of 45 mm have been used. During the experiments, the free-stream velocity is U∞= 156 mm/s, which corresponds to the Reynolds number of Re=5000 based on the solid cylinder diameter. The experiments show that the permeable cylinder is effective on the suppression of vortex shedding in the wake region for all porosities and in terms of the inner cylinder-outer permeable cylinder arrangement, it is understood that the inner-outer cylinder arrangement having the diameter ratio of D/d=1.5 is not effective on the attenuation of vortex shedding downstream of the inner cylinder-outer cylinder arrangement as expected. The inner and outer permeable cylinders behave like an impermeable cylinder having the diameter of D=45 mm for the porosities of β = 0.4, 0.5 and 0.6. The suppression of the large scale vortices is weak. On the other hand, for the porosity β = 0.7, the peak value of Reynolds shear stress drops to 0.0368 which is less than that of the bare cylinder. The reduction of is approximately 10%.

1-10

Authors: Gökhan Özdemir, Beyhan Bayhan

Cyclic motion of lead rubber bearings (LRBs) leads to increasing temperature in lead core initiating the reduction in strength of LRB. This reduction results in a deteriorating bi-linear force deformation relation for LRB. In this study, response of LRBs (with deteriorating hysteresis loops due to temperature change) subjected to near-field ground motions with distinct pulse-type behavior is studied. Ground motions are applied bi-directionally and LRBs are modeled with due consideration of coupled behavior in the two orthogonal horizontal directions. Response of LRBs with deteriorating hysteresis is compared with that of non-deteriorating ones by considering bounding analyses (upper and lower bound). Thus, nonlinear response history analyses are performed for each selected ground motion record. Bounding analyses result in over predicted displacement demands for LRBs compared to results obtained by implemented deteriorating bi-linear LRB model. By means of new deteriorating model, engineers may come up with more efficient isolation system designs.

35-37

Authors: Şeref Doğuşcan Akbaş

In this paper, free vibration and static bending analysis of functionally graded (FG) beams resting on Winkler foundation are investigated within Euler-Bernoulli beam theory and Timoshenko beam theory. Material properties of the beam change in the thickness direction according to power-law distributions. The governing equations and the related boundary conditions are derived using the principal of the minimum total potential energy. The Navier-type solution is used for simply-supported boundary conditions, and exact formulas are proposed for the static deflections and the fundamental frequencies. In order to establish the accuracy of the present formulation and results, the natural frequencies are obtained, and compared with the published results available in the literature. Good agreement is observed. Numerical results are presented to investigate the influences the different material distributions, foundation stiffness, and shear deformation on the bending and free vibration behavior of FG beams.