Dynamics of structures

Seismic Rehabilitation of Existing Buildings

A computer program is a series of coded instructions for the computer to obey and represent a method of processing data. Programs can't be written in English. They must first be written using a special language called a programming language. A PROGRAMMING LANGUAGE (e.g. BASIC, PASCAL, and C+) consists of a set of codes and rules which can be used to construct commands for the computer. These commands are read and translated into electronic pulses needed to make the computer work. Programs are written by programmers. A computer language is a set of instructions used for writing computer programs. There are THREE (3) levels of languages: 1. MACHINE LANGUAGE – this was the first language available for programming. It varies from one computer to another, but the basic principles are the same. MACHINE LANGUAGE PROGRAMS are written using a series of 0's and 1's i.e. using a BINARY SYSTEM. All programs written today must be translated into machine language before they can be executed (used) by the computer. EXAMPLE: 110110001 2. ASSEMBLY LANGUAGE / LOW LEVEL LANGUAGE – these were developed to replace the 0's and 1's of machine language with symbols that are easier to understand and remember. Like with machine language, Assembly language varies form one make of computer to another so that a program written in one assembly language will not run on another make of computer. EXAMPLE: LDA 300 ADD 400 STA 500 3. HIGH LEVEL LANGUAGE – these differ from low level languages in that they require less coding detail and make programs easier to write. High level languages are designed for the solution of problems in one ore more areas of the application and are commonly described as application-oriented or problem-oriented languages. High level languages are not machine dependant. Programs written in a high level language must be translated to a form which can be accepted by that computer, i.e.

The computer program

System identification analyses are used to evaluate soil-structure interaction effects for 77 strong motion data sets at 57 building sites that encompass a wide range of structural and geotechnical conditions. Kinematic interaction effects on the \"input\" motion at the bases of structures are found to be relatively modest in many cases, whereas inertial interaction effects on the structural response to these motions can be significant. To quantify inertial interaction effects, fixed- and flexible-base modal vibration parameters are used to evaluate first-mode period lengthening

Closure of "Seismic Soil-Structure Interaction in Buildings. II: Empirical Findings"

Seismic soil–foundation–structure interaction observed in geotechnical centrifuge experiments

Equivalent linear and nonlinear site response analysis for design and risk assessment of safety-related nuclear structures

During an earthquake, the flexibility of the near-surface soil affects the dynamic response of the supported structure. This dynamic interaction is termed soil-structure interaction (SSI). Soil-structure interaction is important for performance-based design, which has seen increasing use in earthquake engineering in the United States in the last decade. Soil-structure interaction analysis is preceded by siteresponse analysis, which is the process of calculating the response of a soil profile to rock motion at depth. Soil flexibility also results in the interaction of adjacent structures through intermediate soil. This interaction is termed structure-soil-structure interaction (SSSI), which can be important for the performance assessment of buildings, especially those constructed in dense, urban areas. The studies presented herein share the common goal of a better understanding of the phenomena of site response, SSI and SSSI, and advancing the numerical tools that simulate these phenomena. The state-of-the-art in site-response and SSI analysis of buildings and nuclear structures involves the use of linear or equivalent-linear numerical methods that function in the frequency domain. However, nonlinear time-domain methods may be more appropriate for cases involving intense earthquakes that result in highly nonlinear soil and foundation response. Such nonlinear methods are available but rarely used due to the higher computational requirements and lack of experience with analysts and regulators. This report assesses industry-standard equivalent linear and nonlinear site-response and SSI analysis programs, and provides practical guidelines on their usage. The assessment includes benchmarking the time-domain programs against frequency-domain programs for analyses involving almost linear soil response, and a comparison of the predictions of these programs for analyses involving highly nonlinear soil and foundation response. The assessment also identifies the various pitfalls that can be expected when using these programs and suggests workarounds. Structure-soil-structure interaction has been rarely studied, mainly due to the lack of experimental or field-based case-studies that demonstrate its effects on structural response. The US National Science Foundation funded a research project titled ‘Seismic Performance Assessment of Buildings in Dense Urban Environments’ to understand the significance of SSSI in buildings through a series of centrifuge experiments and numerical simulations. The experiments involve small-scale building models with commonly-found superstructure and foundation configurations. This report describes some of these centrifuge experiments, and their numerical simulations, which are comprehensive and performed using both equivalent-linear and nonlinear SSI analysis programs. The numerical and experimental results show that wave-based SSSI does not significantly affect the global response of the buildings considered in this study.

Chandrakanth Bolisetti

Papers

Equivalent linear and nonlinear site response analysis for design and risk assessment of safety-related nuclear structures

Site response, soil-structure interaction and structure-soil-structure interaction for performance assessment of buildings and nuclear structures

Linear and nonlinear soil-structure interaction analysis of buildings and safety-related nuclear structures

Time-domain soil-structure interaction analysis of nuclear facilities

Using seismic isolation to reduce risk and capital cost of safety-related nuclear structures