Research on Engineering Structures and Materials

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.