Structural Damage Caused by the 1976 Guatemala Earthquake

National Science FoundationResearch Grant ATA 74 2296

Effect of Magnitude and Type of Damping on Soil Amplification

Soil Amplification studies conducted to obtain site specific seismic motions at the free surface of a soil deposit or at any other elevation (convolution process), or to determine compatible base motions at a given depth for soil structure interaction analyses (deconvolution) assume, when performed in the frequency domain simulating nonlinear soil behavior through an iterative linear analysis, that the internal soil damping is of a linear hysteretic nature. This tends to filter out excessively the high frequency components of motion for convolution studies and leads to eventual instability of the solution at a given depth (function of the soil properties) when performing deconvolution. In this paper, the results obtained using constant frequency independent, linear proportional and inverse proportional damping in the iterative solution are compared to those provided by true nonlinear analyses using consistent soil models

Dynamic Characteristics of Comares Palace in the Alhambra

This paper describes the geotechnical investigations that have been conducted to characterize the static and dynamic properties of the ground, the foundation and the structure\u27s material of the Comares tower in the Alhambra palace. The Gmax values of the different materials were determined using seismic refraction, P-wave transmission tomography, cross-hole and down-hole tests. To obtain the variation of the shear moduli with strain amplitude surface wave and cyclic horizontal plate loading tests were performed in several trenches excavated in the immediate neighborhood. The analysis of the structure response to M = 5 earthquakes recently recorded at the top and the bottom of the Tower allowed to check the dynamic properties of the materials estimated previously

Comparison among SASW, ReMi and PS-logging techniques: Application to a railway embankment

Results obtained by SASW and PS-logging (in-hole) seismic techniques are compared with the relatively new ReMi (Refraction microtremor) method at a common site with a well-known soil profile: a recently constructed high-speed railway embankment. PS-logging is the most accurate technique in identifying the soil profile of the embankment followed by Re-Mi and SASW. Mean shear wave velocity estimations are also higher for PS-logging, followed by SASW and ReMi, while mean deviation is similar in each technique. The ReMi technique has provided very accurate results in the study of the embankment profile, which in addition to its high operability and its fast data processing, makes it a very convenient technique for extensive geotechnical survey

Axial kinematic response of end-bearing piles to P waves

Kinematic pile-soil interaction under vertically impinging seismic P waves is revisited through a novel continuum elastodynamic solution of the Tajimi type. The proposed model simulates the steady-state kinematic response of a cylindrical end-bearing pile embedded in a homogeneous viscoelastic soil stratum over a rigid base, subjected to vertically propagating harmonic compressional waves. Closed-form solutions are obtained for the following: (i) the displacement field in the soil and along the pile; (ii) the kinematic Winkler moduli (i.e., distributed springs and dashpots) along the pile; (iii) equivalent, depth-independent, Winkler moduli to match the motion at the pile head. The solution for displacements is expressed in terms of dimensionless transfer functions relating the motion of the pile head to the free-field surface motion and the rock motion. It is shown that (i) a pile foundation may significantly alter (possibly amplify) the vertical seismic excitation transmitted to the base of a structure and (ii) Winkler moduli pertaining to kinematic loading differ from those for inertial loading. Simple approximate expressions for kinematic Winkler moduli are derived for use in applications. © 2013 John Wiley & Sons, Ltd

On soil-structure interaction in large non-slender partially buried structures

This paper addresses the seismic analysis of a deeply embedded non-slender structure hosting the pumping unit of a reservoir. The dynamic response in this type of problems is usually studied under the assumption of a perfectly rigid structure using a sub-structuring procedure (three-step solution) proposed specifically for this hypothesis. Such an approach enables a relatively simple assessment of the importance of some key factors influencing the structural response. In this work, the problem is also solved in a single step using a direct approach in which the structure and surrounding soil are modelled as a coupled system with its actual geometry and flexibility. Results indicate that, quite surprisingly, there are significant differences among prediction using both methods. Furthermore, neglecting the flexibility of the structure leads to a significant underestimation of the spectral accelerations at certain points of the structure