Rene D. Gabbai

Bio: Rene D. Gabbai is an academic researcher from The Catholic University of America. The author has contributed to research in topics: Wind engineering & Vortex-induced vibration. The author has an hindex of 9, co-authored 13 publications receiving 726 citations. Previous affiliations of Rene D. Gabbai include Rutgers University & National Institute of Standards and Technology.

Wind-induced tall building response: a time-domain approach

Abstract: Estimates of wind-induced wind effects on tall buildings are based largely on 1980s technology. Such estimates can vary significantly depending upon the wind engineering laboratory producing them. We describe an efficient database-assisted design (DAD) procedure allowing the realistic estimation of wind-induced internal forces with any mean recurrence interval in any individual member. The procedure makes use of (a) time series of directional aerodynamic pressures recorded simultaneously at typically hundreds of ports on the building surface, (b) directional wind climatological data, (c) micrometeorological modeling of ratios between wind speeds in open exposure and mean wind speeds at the top of the building, (d) a physically and probabilistically realistic aerodynamic/climatological interfacing model, and (e) modern computational resources for calculating internal forces and demand-to-capacity ratios for each member being designed. The procedure is applicable to tall buildings not susceptible to aeroelastic effects, and with sufficiently large dimensions to allow placement of the requisite pressure measurement tubes. The paper then addresses the issue of accounting explicitly for uncertainties in the factors that determine wind effects. Unlike for routine structures, for which simplifications inherent in standard provisions are acceptable, for tall buildings these uncertainties need to be considered with care, since over-simplified reliability estimates could defeat the purpose of ad-hoc wind tunnel tests.

Effect of woven fabric architecture on interlaminar mechanical response of composite materials: an experimental study

Abstract: Woven fabrics are usually selected for the reinforcement phase in laminated composite materials due to their balanced in-plane mechanical and thermal properties and their relatively simple handling during the composite fabrication process. One of the questions that usually arise in the design of laminated composites is the selection of the woven fabric architecture. It is well known the effect that this architecture plays in the in-plane elastic and ultimate composite properties under either in-plane tensile or shear loading. However, the effect of the woven fabric architecture on the mechanical response of composites under interlaminar shear loading is not well established. An experimental study was conducted to determine the role of the woven fabric architecture and its geometrical parameters on the interlaminar shear response of laminated composites. A set of composite materials with the same epoxy matrix and carbon fiber were prepared with five different woven fabrics of similar areal density and fibe...

Modelling vortex-induced fluid-structure interaction

Abstract: The principal goal of this research is developing physics-based, reduced-order, analytical models of nonlinear fluid–structure interactions associated with offshore structures. Our primary focus is to generalize the Hamilton’s variational framework so that systems of flowoscillator equations can be derived from first principles. This is an extension of earlier work that led to a single energy equation describing the fluid–structure interaction. It is demonstrated here that flow-oscillator models are a subclass of the general, physical-based framework. A flow-oscillator model is a reduced-order mechanical model, generally comprising two mechanical oscillators, one modelling the structural oscillation and the other a nonlinear oscillator representing the fluid behaviour coupled to the structural motion. Reduced-order analytical model development continues to be carried out using a Hamilton’s principle-based variational approach. This provides flexibility in the long run for generalizing the modelling paradigm to complex, three-dimensional problems with multiple degrees of freedom, although such extension is very difficult. As both experimental and analytical capabilities advance, the critical research path to developing and implementing fluid–structure interaction models entails — formulating generalized equations of motion, as a superset of the flow-oscillator models; and — developing experimentally derived, semi-analytical functions to describe key terms in the governing equations of motion. The developed variational approach yields a system of governing equations. This will allow modelling of multiple d.f. systems. The extensions derived generalize the Hamilton’s variational formulation for such problems. The Navier–Stokes equations are derived and coupled to the structural oscillator. This general model has been shown to be a superset of the flow-oscillator model. Based on different assumptions, one can derive a variety of flowoscillator models.

Experimental Investigation of Vortex-Induced Vibration in One and Two Dimensions With Variable Mass, Damping, and Reynolds Number

Abstract: Measurements are made of vortex-induced vibration of an elastically supported circular cylinder in water with reduced velocity (U/f n D) from 2 to 12, damping factors (ξ) from 0.2% to 40% of critical damping, mass ratios (m/ρD 2 ) from π/2 to π/17, and transverse, inline, and combined inline and transverse motions at Reynolds numbers up to 150,000. Effects of mass, damping, Reynolds number, and strakes on vortex-induced vibration amplitude, frequency, entrainment, and drag are reported.