Superstructure orthorhombicII (OII) phase in polycrystalline samples of YBCOx was observed by using synchrotron in-situ high resolution powder diffraction (HRPD) techniques at 300˚C. Rietveld method (RM) refinement was employed to analyse the collected diffraction data under proper oxygen partial pressure atmospheres. Our study indicates that by oxygen uptake, the samples undergo structural pha...

Abstract—The solution of the nonlinear dynamic equilibrium equations of base-isolated structures adopting a conventional monolithic solution approach, i.e. an implicit single-step time integration method employed with an iteration procedure, and the use of existing nonlinear analytical models, such as differential equation models, to simulate the dynamic behavior of seismic isolators can requir...

This paper investigates the response of pile foundations to deep-excavations. An elastoplastic two-stage model is used study groups (with free- or rigidly capped-heads) and piled structures (grade beams bearing walls), considering piles embedded in either uniform layered ground. The validated using results analytical solutions, as well data from centrifuge tests real case histories. Then, a par...

This paper presents a nonlinearly parameterized controller for the adaptive control of base-isolated buildings subjected to a set of near-fault earthquakes. The control scheme is based on discrete direct adaptive control, wherein the system response is minimized under parameter uncertainties. Stable tuning laws for the controller parameters are derived using the Lyapunov approach. The controlle...

The first phase of the seismically excited base-isolated benchmark building was received well by the structural control community, culminating in the March 2006 journal special issue. The special issue contained contributions from over dozen participants world-wide. While the focus of the Phase I effort was on linear isolation systems, Phase II attempts to galvanize research efforts on control ...

This work considers improving the heat recovery of an existing heat exchanger network (HEN) while minimizing the total annualized cost of the retrofit design. The focus is on stepwise approaches that generate, starting from the base case network, a candidate retrofit HEN at each step in order to sequentially retrofit the HEN topology while permitting user intervention during the resolution proc...

Base isolation is an increasingly applied earthquake-resistant design technique in highly seismic areas. Examination of the actual performance of isolated structures in real earthquake has become a critical issue. In this paper, a new computational method for system identification is proposed for obtaining insight into the linear and nonlinear structural properties of based-isolated buildings. ...