Dynamics of structures

The dynamic behavior of rigid-block structures resting on a rigid foundation subjected to horizontal harmonic excitation is examined. For slender structures, the nonlinear equation of motion is approximated by a piecewise linear equation. Using this approximation for an initially quiescent structure, safe or no-toppling and unsafe regions are identified in an excitation amplitude versus excitation frequency plane. Furthermore, several possible modes of steady-state response are detected, and analytical procedures are developed for determining the amplitudes of the predominant modes and for performing stability analyses. It is shown that the produced stability diagrams can be beneficial to assessing the toppling potential of a rigid-block structure under a given amplitude-frequency combination of harmonic excitation; in this manner the integration of the equation of motion is circumvented.

Closure of "Rocking of Rigid Blocks Due to Harmonic Shaking"

SynOptics Communications Inc.

Written by a leader on the subject, Introduction to Geotechnical Engineering is first introductory geotechnical engineering textbook to cover both saturated and unsaturated soil mechanics. Destined to become the next leading text in the field, this book presents a new approach to teaching the subject, based on fundamentals of unsaturated soils, and extending the description of applications of soil mechanics to a wide variety of topics. This groundbreaking work features a number of topics typically left out of undergraduate geotechnical courses.

Geotechnical Engineering: Unsaturated and Saturated Soils

Automatic detection of atrial fibrillation using stationary wavelet transform and support vector machine

In the companion paper (I-Problem Statements of the Current Seismic Design Code), the current Korean seismic design code is required to be modified considering site characteristics in Korea for the reliable estimation of site amplification. In this paper, three site classification methods based on the mean shear wave velocity of the top 30m , fundamental site periods and bedrock depth were investigated and compared with each other to determine the best classification system. Not enough of a difference in the standard deviation of site coefficients to determine the best system, and neither is the difference between the average spectral accelerations and the design response spectrum of each system. However, the amplification range of RRS values based on were definitely concentrated on a narrow band than other classification system. It means that sites which have a similar behavior during earthquake will be classified as the same site category at the site classification system based on . The regression curves between site coefficients and described the effect of soil non linearity well as the rock shaking intensity increases than the current method based on . Furthermore, it is unambiguous to determine sue category based on when the site investigation is performed to shallower depth less than 30m, whereas the current is usually calculated fallaciously by extrapolating the of bedrock to 30m. From the results of this study, new site classification system based on was recommended for legions of shallow bedrock depth in Korea.

Development of Site Classification System and Modification of Design Response Spectra considering Geotechnical Site Characteristics in Korea (II) - Development of Site Classification System

The role of physical modeling in design of geotechnical systems

Development of Electrical Resistivity Survey System for Geotechnical Centrifuge Modeling

In order to investigate the soil disturbance induced by anchor-shoe for PVD installation and the anchoring mechanism, a new two dimensional testing system was developed. By using the developed testing system, 1g and centrifuge model tests were performed, simulating the driving-retrieval process of both conventional symmetric anchor shoe and new asymmetric anchor shoe. Various size anchor-shoes were simulated and the results were compared. The images recorded during the installation were analyzed by image processing technique. The results of the image analysis presented the clay disturbance depending on the size and type of anchor shoe. In addition, from the retrieval process, the anchoring mechanism was revealed and the holding capacity was measured. As results, the size of anchor shoe influences the soil disturbance and holding capacity. The new asymmetric anchor shoe reduces the soil disturbance and improves anchoring performance.

/pdf/two-dimensional-model-testing-system-for-analysis-of-pvd-1wcwgxifje.pdf

Two-dimensional Model Testing System for Analysis of PVD Installation and Soil Disturbance

In order to verify that the recently proposed two-parameters site classification system and the corresponding site coefficients are suitable for the local geological conditions in Korea, a comparison was conducted with current Korean seismic code, Eurocode-8, NYC DOT seismic code. The design spectrum of the current Korean seismic code is significantly amplified in the long-period range, whereas the other response spectra, including the proposed two-parameters approach, are significantly amplified in the short-period range, which is a typical geological condition in Korea. In addition, based on the results of site response analyses in the specific 10km×10km area of Gyeongju, spatial distributions of site coefficients from site-specific seismic response analyses were compared with the proposed site coefficients, as well as those specified in the current Korean seismic code. The site coefficients (Fa and Fv) from the current Korean seismic codes show significantly high spatial error distributions compared with those specified by the two-parameters site classification system. Therefore, the proposed system is suitable for regions of shallow bedrock including the Korean peninsula.

Verification of 2-Parameters Site Classification System and Site Coefficients (I) - Comparisons with Well-known Seismic Code and Site Response Characteristics

Dong-Soo Kim

Papers

Development of Site Classification System and Modification of Design Response Spectra considering Geotechnical Site Characteristics in Korea (II) - Development of Site Classification System

The role of physical modeling in design of geotechnical systems

Development of Electrical Resistivity Survey System for Geotechnical Centrifuge Modeling

Two-dimensional Model Testing System for Analysis of PVD Installation and Soil Disturbance

Verification of 2-Parameters Site Classification System and Site Coefficients (I) - Comparisons with Well-known Seismic Code and Site Response Characteristics