Economic circumstances of Native people in selected metropolitan centres in western Canada

Report : 95 p

A Validation Study of a Seismically Induced Ground Strain Model Using Strong Motion Array Data

This study concerns ground strains that result from spatially variable ground motions unrelated to ground failure. Prior empirical work shows a dependence of peak ground strain (PGS) on peak ground displacement (PGD) but is applicable only for weak motions (PGD \u3c 10 cm). Prior semi-empirical work, in which strains were evaluated from simulated ground motions that preserve the coherency, Fourier amplitude variability and wave passage observed in array recordings, found a similar dependence of PGS on PGD but also a significant dependence on separation distance of observation points. Here we describe a procedure to calculate PGS between pairs of stations in an array to test the separation dependence of PGS. The Lotung LSST array was selected due to its closely spaced stations (6 to 85 m) and large number of recordings. The PGS estimated from station pairs from 11 events illustrate that the distance dependence of PGS is statistically significant, with PGS increasing as separation distance decreases

Uncertainties and Residuals in Ground Motion Estimates at Soil Sites

For a given seismic source, ground motions at soil sites can be estimated using either soil attenuation relationships, or ground response analyses with input motions scaled to match spectral ordinates from rock attenuation relationships. Ground response analyses are performed with the expectation that accounting for nonlinear sediment response improves the accuracy and reduces the uncertainty in estimated motions. Discussed here are the benefits of ground response analyses as a function of site condition. This is accomplished by preparing statistical predictions of ground motions at 36 strong motion recording sites on soil. Two predictions are made, one using a modified soil attenuation relationship, the other using ground response analyses with a large suite of carefully selected and scaled input motions. Predictions from both methods are compiled as 5% damped spectral ordinates, and are expressed as medians and standard errors. These quantities can then be compared to the spectra of the recorded motion to evaluate the residuals of the estimates. For periods, T\u3c 1 s, ground response analyses are found to improve the accuracy of ground motion predictions relative to soil attenuation. However, a positive bias in median ground response estimates is found that indicates a systematic underprediction of ground motion

Active Reward Learning for Co-Robotic Vision Based Exploration in Bandwidth Limited Environments

We present a novel POMDP problem formulation for a robot that must autonomously decide where to go to collect new and scientifically relevant images given a limited ability to communicate with its human operator. From this formulation we derive constraints and design principles for the observation model, reward model, and communication strategy of such a robot, exploring techniques to deal with the very high-dimensional observation space and scarcity of relevant training data. We introduce a novel active reward learning strategy based on making queries to help the robot minimize path "regret" online, and evaluate it for suitability in autonomous visual exploration through simulations. We demonstrate that, in some bandwidth-limited environments, this novel regret-based criterion enables the robotic explorer to collect up to 17% more reward per mission than the next-best criterion.Comment: 7 pages, 4 figures; accepted for presentation in IEEE Int. Conf. on Robotics and Automation, ICRA '20, Paris, France, June 202

Modular analytical solutions for foundation damping in soil-structure interaction applications

Foundation damping incorporates combined effects of energy loss from waves propagating away from a vibrating foundation (radiation damping) and hysteretic action in supporting soil (material damping). Foundation damping appears in analysis and design guidelines for force- and displacement-based analysis of seismic building response (ASCE-7, ASCE-41), typically in graphical form (without predictive equations). We derive closed-form expressions for foundation damping of a flexible-based single degree-of-freedom oscillator from first principles. The expressions are modular in that structure and foundation stiffness terms, along with radiation and hysteretic damping ratios, appear as variables. Assumptions inherent to our derivation have been employed previously, but the present results are differentiated by: (1) the modular nature of the expressions; (2) clearly articulated differences regarding alternate bases for the derivations and their effects on computed damping; and (3) completeness of the derivations. Resulting expressions indicate well-known dependencies of foundation damping on soil-to-structure stiffness ratio, structure aspect ratio, and soil damping. We recommend a preferred expression based on the relative rigor of its derivation.</jats:p

Preliminary Test Results for Full Scale Drilled Shaft Under Cyclic Lateral Loading

Preliminary results are presented of a field testing program for a full-scale, large diameter cast-in-drilled-hole (CIDH) shaft/column under cyclic lateral loading. The shaft was extensively instrumented to enable high precision, redundant section curvature measurements, measurements of pressure at the soil-shaft interface around the shaft perimeter, and in situ measurements of concrete quality. The principal objective of the testing was to characterize the soil-shaft interaction across a wide displacement range to gain insight into the adequacy of existing design guidelines (which are based principally on the testing of small diameter piles) for the large diameter shafts commonly used to support highway bridges in California. Also of interest is the failure mechanism of the shaft-column, since most previous tests of large-diameter shaft-columns do not test the column to large levels of ductility. This testing was only recently completed, and reduction and interpretation of the data is ongoing as of this writing. This paper presents preliminary results of the overall specimen performance across the full range of tested displacements. Details of the soil-shaft interaction remain under study, and are not presented here

Recent Advances in Terrestrial Lidar Applications in Geotechnical Earthquake Engineering

During the past five years, geotechnical earthquake engineering and ground deformation research has benefited from the advent of terrestrial LIDAR technology, a revolutionary tool for characterizing fine-scale changes in topography. For ground deformation research, LIDAR is particularly useful for characterizing the dimensions of failures and for monitoring subtle deformations through time. Tripod mounted LIDAR systems have accuracies of approximately 0.4-2.0 cm, and can illuminate targets up to one kilometer away from the sensor. During several minutes of LIDAR scanning, millions of survey position points are collected and processed into an ultra-high resolution terrain model. During earthquake reconnaissance efforts, the detailed failure morphologies of landslides and liquefaction sites can be measured remotely and in a way that is either impractical or impossible by conventional survey means. The ultra-high resolution imagery of the complex surface morphology of ground failures allows the exploration and visualization of damage on a computer in orientations and scales not previously possible. Detailed understanding of the ground surface morphology allows for better numerical modeling of potential failure modes, deformation patterns, and morphologies. Finally, LIDAR allows for the permanent archiving of 3-D terrain models. In this paper, we present the evaluation of the accuracy, bias and dispersion of LIDAR data under controlled experimental conditions. Field applications of LIDAR-damage visualization and analysis are presented from data gathered during the 2004 Niigata Chuetsu (M6.6) earthquake and the 2007-2008 PARI-Ishikari, Hokkaido blast-liquefaction experiment

Functional changes in gut microbiota during hematopoietic stem cell transplantation for severe combined immunodeficiency

[Editorial letter