Hyuk-Chun Noh

Investigation into Central-Difference and Newmark’s Beta Methods in Measuring Dynamic Responses

Studies in the structural systems include two main approaches, design and analysis, which require response evaluation of structures to the external loads including live and dead loads. Structures behave statically and dynamically for static and dynamic loads, respectively. One of the most important dynamic loads acting on a structure is earthquake force. In order to find responses of structures subjected to earthquake, several schemes of direct integration can be used. This study deals with two methods of calculating dynamic responses of a single-degree of freedom oscillator, i.e., central difference method (CDM) and Newmarks beta method (NBM), using recorded ground acceleration for 60seconds. The maximum relative acceleration is obtained to determine maximum relative displacement by which estimation of quality and quantity of failure occurred to a structure for a given earthquake is provided. Firstly both CDM and NBM are discussed. Second, for a specific damping ratio dynamic responses are evaluated for periods of range in between 0.1sec to 1.5sec to evaluate the effects of period on responses of system. Third, the effects of damping on dynamic responses of SDOF system are evaluated by considering different damping coefficients from ζ=0 to 0.5. The results are compared and discussed to investigate the range of periods and damping factors where methods can provide a better estimation of responses.

Uncertain Out-of-Plane Behavior of Composite Plates due to Spatially Random Material Properties

This paper deals with the evaluation of response variability of composite plates due to randomness in the Poisson’s ratio in particular for the out-of-plane behavior. To this end, we adopt the weighted integral stochastic finite element (SFE) scheme and derive a SFE formulation employing Taylor’s expansion on the random Poisson’s ratio and displacement vector as well. In case of composite plates, the stiffness of the structure is affected by the stacking scheme of individual layers. This means that even the plates subjected only to in-plane loading can show out-of-plane behavior. In order to investigate this phenomenon, we chose two example plates with symmetric and asymmetric stacking scheme. A detailed explanation on the results is addressed for the plates under consideration.

Effect of Random Material Parameter in the Shell Structures

The random nature of structural parameters is to affect the behavior of the structure which cannot be detected in the context of deterministic analyses. Taking into account the randomness in the material parameter, we evaluate probabilistic behavior of the shell structures made of isotropic material. Specifically, the elastic modulus is taken to be random since the parameter plays an utmost important role in the behavior of structures. The results of the proposed scheme are compared with those based on Monte Carlo simulation. It is observed that the proposed scheme is in good agreement with the MCS, which shows the adequacy of the proposed scheme.