Thomas T. Baber

Bio: Thomas T. Baber is an academic researcher from University of Virginia. The author has contributed to research in topics: Random vibration & Monte Carlo method. The author has an hindex of 9, co-authored 12 publications receiving 1024 citations.

Random vibration of hysteretic degrading systems

Abstract: A differential equation model for hysteretic systems with strength, stiffness or combined degradation is presented. Solution under white noise, Kanai filtered white noise and temporally modulated filtered white noise is obtained by equivalent linearization, without recourse to the Krylov-Bogoliubov approximation typically required for hysteretic systems. Resulting zero time lag covariance response matrices agree well with simulated solutions at all excitation levels. First passage predictions are nonconservative, because of the non-Gaussian character of the response.

Random Vibration of Degrading, Pinching Systems

Abstract: A differential equation model to describe pinching, degrading response of hysteretic elements is presented. The model consists of a nonpinching hysteretic element, in series with a “slip-lock” element. Zero mean response statistics for a single degree of freedom oscillator whose stiffness is described by the series model, computed by equivalent linearization and by Monte Carlo simulation, are compared. The model response statistics are seen to be reasonable estimated by equivalent linearization.

Modeling General Hysteresis Behavior and Random Vibration Application

Abstract: A simple constructive technique for the development of rate-type hysteresis models for general nonlinear system is presented. The technique is used to develop hysteresis models to incorporate time history-dependent postyield restorting forces, and general pinching behavior in smoothly varying deteriorating models. Applications of these models to random vibration analysis modeling via simulation and equivalent linearization techniques under Gaussian noise excitation is presented.

Modeling and random vibration analysis of SDOF systems with asymmetric hysteresis

Abstract: This study focuses upon SDOF systems having non-linear, hysteretic stress-strain behavior which is asymmetric about the initial linear elastic relationship Differences between tensile and compressive strength witnessed in various materials, particularly in the unique stress-strain properties of the shape-memory alloy Nitinol, motivate the need for mathematical models capable of simulating asymmetric response Two models are presented, and the specific capabilities of each are explored Both models follow the rate-type format of the Bouc-Wen model, and offer previously unavailable stress-strain relationships Response statistics under Gaussian White Noise input are obtained using the method of equivalent linearization For asymmetric systems, a need for non-zero-mean analysis is evident, even under zero-mean input

Deterioration Modeling of Steel Components in Support of Collapse Prediction of Steel Moment Frames under Earthquake Loading

Abstract: Reliable collapse assessment of structural systems under earthquake loading requires analytical models that are able to capture component deterioration in strength and stiffness. For calibration and validation of these models, a large set of experimental data is needed. This paper discusses the development of a database of experimental data of steel components and the use of this database for quantification of important parameters that affect the cyclic moment-rotation relationship at plastic hinge regions in beams. On the basis of information deduced from the steel component database, empirical relationships for modeling of precapping plastic rotation, postcapping rotation, and cyclic deterioration for beams with reduced beam section (RBS) and other-than-RBS beams are proposed. Quantitative information is also provided for modeling of the effective yield strength, postyield strength ratio, residual strength, and ductile tearing of steel components subjected to cyclic loading.

The Hysteresis Bouc-Wen Model, a Survey

Abstract: Structural systems often show nonlinear behavior under severe excitations generated by natural hazards. In that condition, the restoring force becomes highly nonlinear showing significant hysteresis. The hereditary nature of this nonlinear restoring force indicates that the force cannot be described as a function of the instantaneous displacement and velocity. Accordingly, many hysteretic restoring force models were developed to include the time dependent nature using a set of differential equations. This survey contains a review of the past, recent developments and implementations of the Bouc-Wen model which is used extensively in modeling the hysteresis phenomenon in the dynamically excited nonlinear structures.

Seismic Damage Analysis of Reinforced Concrete Buildings

Abstract: Experiences from past strong earthquakes, such as the 1968 Miyakiken-Oki earthquake in Japan and the 1971 San Fernando earthquake in California, have shown the vulnerability of reinforced concrete buildings to strong ground shakings. For economic reasons, however, some level of damage should be expected and permitted in the aseismic design of structures, particularly of low-rise buildings. In spite of this recognition, the potential seismic damage of structures and the associated aseismic provisions are based largely on qualitative engineering judgment. In order to assess the seismic safety of reinforced concrete buildings, the quantitative analysis of structural damage under random earthquake excitations needs to be improved.