Recent Advances in Non-Linear Site Response Analysis

Studies of earthquakes over the last 50 years and the examination of dynamic soil behavior reveal that soil behavior is highly nonlinear and hysteretic even at small strains. Non-linear behavior of soils during a seismic event has a predominant role in current site response analysis. The pioneering work of H. B. Seed and I. M. Idriss during the late 1960’s introduced modern site response analysis techniques. Since then significant efforts have been made to more accurately represent the non-linear behavior of soils during earthquake loading. This paper reviews recent advances in the field of non-linear site response analysis with a focus on 1-D site response analysis commonly used in engineering practice. The paper describes developments of material models for both total and effective stress considerations as well as the challenges of capturing the measured small and large strain damping within these models. Finally, inverse analysis approaches are reviewed in which measurements from vertical arrays are employed to improve material models. This includes parametric and non-parametric system identification approaches as well as the use of Self Learning Simulations to extract the underlying dynamic soil behavior unconstrained by prior assumptions of soil behavior

District Superintendent and School Board President Perceptions Regarding Leadership Characteristics for Superintendents of Texas Schools

ABSTRACT District Superintendent and School Board President Perceptions regarding Leadership Characteristics for Superintendents of Texas Schools. (December 2009) Kenneth Lee Groholski, B.S., Sam Houston State University M.Ed., Tarleton State University Chair of Advisory Committee: Dr. John R. Hoyle The purpose of this study was to compare the perceptions of Texas Public School superintendents and school board presidents on the importance of leadership characteristics of the superintendency. The questionnaire used in this study was developed by Dr. Douglas D. Wilson and modified by the researcher. Responses to a Likert Scale instrument and a nominal ranking of ten leadership characteristics were solicited from superintendents and school board presidents of Texas public schools. The population was superintendents and school board presidents from Texas Public Schools. The population was divided into large school districts (>10,000 students) and small school districts (<10,000 students). Data was then generated regarding the respondent’s perceptions of leadership characteristics. Descriptive statistics and Mann-Whitney Tests for differences were used to determine if possible significant differences exist in the data. Results were reported using the Statistical Package for Social Sciences (SPSS 14.0). Major findings of the study suggest: 1. Superintendents may view the importance of instructional leadership, prior work experience in education, and effective school board relations significantly higher than school board presidents. 2. Superintendents of small schools may view the importance of instructional leadership, prior work experience in education, and effective school board relations significantly higher than school board presidents of small schools. Conversely, school board presidents of small schools may view the focus on professional development significantly higher than superintendents of small schools. 3. Superintendents of large schools may view the importance of instructional leadership, comfort with media relations and politics, and effective school board relations significantly higher than school board presidents of large schools. 4. Regardless of school size, superintendents and school board presidents appeared to be in agreement concerning the three least important superintendent leadership characteristics

Seismic site response analysis and extraction of dynamic soil behavior and pore pressure response from downhole array measurements

Seismic site response analysis is commonly used to predict ground response due to local soil effects. Advancements in the knowledge of shear-induced excess pore pressure generation has led to the development and implementation of pore pressure response models for site response analysis with effective stress consideration. This thesis chiefly regards the further development of an inverse analysis procedure to extract dynamic soil behavior and pore pressure response from downhole array measurements. Downhole arrays are increasingly being deployed to measure motions at the ground surface and within the soil profile, with some arrays instrumented to measure the pore pressure response throughout the soil profile. The measurements from these arrays provide valuable data to validate site response analysis models and also to reveal the coupled soil behavior and pore pressure response during seismic excitation. However, the current approaches do not fully benefit from the downhole array measurements. Once the prediction is different from the measurements, site response analysis models cannot be readily calibrated to match field measurements. Early developments in inverse analysis schemes allowed for the identification of soil properties from downhole array measurements, but the identified parameters could not be readily integrated into a material constitutive model for future use in site response analysis. Recent development of an inverse analysis algorithm, Self-learning Simulations (SelfSim), integrated field measurements with site response analysis to capture the measured ground response while extracting the underlying soil behavior under total stress consideration. This research extends the SelfSim inverse analysis algorithm to effective stress consideration by including measurements of both motions and pore pressure response from downhole arrays. The extended framework is able to gradually capture the measured global iii response while simultaneously extracting the underlying soil behavior and pore pressure response. When used in site response analysis, the resulting soil model and pore pressure response model provide correct ground motion and pore pressure response throughout the soil profile. The extracted soil behavior and pore pressure response can be enhanced using additional field measurements. The algorithm is verified with four synthetic downhole array recordings and is also applied to downhole array recordings from the Imperial Valley Wildlife Liquefaction Array. The extracted soil behavior is compared with laboratory measurements and is used to identify the effects of excess pore pressures, number of loading cycles, and loading rate on soil behavior. The extracted pore pressure response is compared with current pore pressure response models employed in seismic site response simulation to assess the validity of such models

The Right to Representation by Counsel in University Disciplinary Proceedings: A Denial of Due Process of Law

This comment argues that university students who face suspension or expulsion for disciplinary reasons, as opposed to academic dismissal, are entitled to have retained legal counsel represent them as an element of procedural due process. The article begins with a general discussion of the jurisprudence that has developed concerning the Fourteenth Amendment's Due Process Clause. Utilizing both federal and state court decisions, the comment then demonstrates that university students hold protected liberty and property interests in their collegiate educations or degrees such that the procedural protections of the Due Process Clause are triggered when students face disciplinary suspension or expulsion. The article then proceeds to examine the present state of the law and the rationale which courts have articulated in concluding that students generally have no right under the Due Process Clause to have retained legal counsel represent them at disciplinary hearings conducted by public universities. Finally, applying the established factors for determining the scope of procedural protection to be accorded a person when a protected interest is jeopardized, the author argues that due process commands that legal counsel be permitted to represent students at university disciplinary hearings because of the enormous importance of education and the existence of a substantial risk that students may be erroneously suspended or expelled when not represented by counsel

Simplified Model for Small-Strain Nonlinearity and Strength in 1D Seismic Site Response Analysis

Commonly used simplified one-dimensional nonlinear seismic site response analyses employ constitutive models based on a variation of the hyperbolic model to represent the initial stress-strain backbone curve. Desirable features of the backbone curve include provision of (1) an initial shear modulus at zero shear strain, (2) a limiting shear stress at large shear strains, and (3) flexible control of the nonlinear behavior between those boundary conditions. Available hyperbolic models have combinations of two of these features. A new general quadratic/hyperbolic (GQ/H) model is developed from the bivariate quadratic equation to provide all desired features. Nonlinear behavior is controlled by a shear-strain-dependent curve-fitting function. The model&apos;s unload-reload rules and coupling with pore-water pressure generation are also presented. Several total-stress site response analyses are presented to demonstrate the performance of the GQ/H model relative to a commonly used hyperbolic model in which the maximum shear stress cannot be defined. The analyses show the importance of properly representing the maximum shear stress in the constitutive model because it may lead to underestimation or overestimation of the computed site response.ope