G. Gazetas

Bio: G. Gazetas is an academic researcher. The author has contributed to research in topics: Pile & Kinematics. The author has an hindex of 1, co-authored 1 publications receiving 182 citations.

Dynamic pile‐soil‐pile interaction. Part II: Lateral and seismic response

Abstract: SUMMARY A simplified three-step procedure is proposed for estimating the dynamic interaction between two vertical piles, subjected either to lateral pile-head loading or to vertically-propagating seismic S-waves. The starting point is the determination of the deflection profile of a solitary pile using any of the established methods available. Physically-motivated approximations are then introduced for the wave field radiating from an oscillating pile and for the effect of this field on an adjacent pile. The procedure is applied in this paper to a flexible pile embedded in a homogeneous stratum. To obtain analytical closed-form results for both pile-head and seismic-type loading pile-soil and soil-pile interaction are accounted for through a single dynamic Winkler model, with realistic frequency-dependent ‘springs’ and ‘dashpots’. Final- and intermediate-step results of the procedure compare favourably with those obtained using rigorous formulations for several pile group configurations. It is shown that, for a homogeneous stratum, pile-to-pile interaction effects are far more significant under head loading than under seismic excitation.

Kinematic pile bending during earthquakes: analysis and field measurements

Abstract: The passage of seismic waves through the soil surrounding a pile imposes lateral displacements and curvatures on the pile, thereby generating ‘kinematic’ bending moments even in the absence of a su...

Cumulative Seismic Damage of Reinforced Concrete Bridge Piers

Abstract: This report describes a comprehensive experimental study to investigate cumulative damage in reinforced concrete circular bridge piers subjected to a series of earthquake excitations. Twelve identical quarter-scale bridge columns were tested. They were designed and fabricated in accordance with current AASHTO specifications. Testing was in two phases. Phase I testing consisted of benchmark tests to establish the monotonic force-deformation envelope and the energy capacity under standard cyclic loads; and constant amplitude tests to determine the low-cycle fatigue characteristics of the bridge column. Phase II testing was composed of a series of analytically predicted displacement amplitudes representing the bridge response to typical earthquakes. Test observations indicate two potential failure modes: low cycle fatigue of the longitudinal reinforcing bars; and confinement failure due to rupture of the confining spirals.

Experimental and analytical investigation of seismic retrofit of structures with supplemental damping : Part.1 - Fluid viscous damping devices

Abstract: This report, the first in a series, presents the evaluation of fluid viscous dampers used as additional braces in reinforced concrete frame structures. This is part of a larger experimental investigation of different damping devices being carried out at the University at Buffalo. A series of shaking table tests of a 1:3 scale reinforced concrete frame incorporating a variety of damping devices were performed after the frame was damaged by prior severe (simulated) earthquakes. An analytical platform fro evaluation of structures integrating such devices was developed and incorporated in IDARC Version 3.2. The experimental and analytical study shows that the dampers can reduce inelastic deformation demands and, moreover, reduce the damage, quantified by an index monitoring permanent deformations.

Kinematic soil-structure interaction from strong motion recordings

Abstract: Earthquake strong motion recordings from 29 sites with instrumented structures and free-field accelerographs are used to evaluate variations between foundation-level and free-field ground motions. The focus of the paper is on buildings with surface and shallowly embedded foundations. The foundation/free-field ground motion variations are quantified in terms of frequency-dependent transmissibility function amplitude uHu. Procedures are developed to fit to uHu analytical models for base slab averaging for the assumed conditions of a rigid base slab and a vertically propagating, incoherent incident wave field characterized by ground motion incoherence parameter k. The limiting assumptions of the model are not strictly satisfied for actual structures, and the results of the identification are apparent k values ~denoted k a) that reflect not only incoherence effects, but also possible foundation flexibility and wave inclination effects. Nonetheless, a good correlation is found between k a values and soil shear wave velocity for sites with stiff foundation systems. Based on these results, recommendations are made for modifying free-field ground motions to estimate base slab motions for use in response analyses of buildings.