Machine Foundation Design: Experimental and Analytical Soil Structure Interaction

A comprehensive dynamic testing program has been undertaken to establish the dynamic characteristics of existing fan foundations in order to evaluate their suitability to support new variable speed fans. The dynamic testing program encompassed two sets of tests: pull tests and steady-state vibration test. In addition, dynamic soil-structure interaction analyses were performed to evaluate the response of the foundation to the dynamic operating loads of the new fans

Vibration of Synchrotron Foundation Due to Ground-Transmitted Excitation

The Canadian Light Source (CLS) is a third generation synchrotron that will be capable of generating a wide spectrum of electromagnetic radiation used in the study of the atomic and sub-atomic structure of materials. The CLS facility will feature a 50 m diameter vacuum storage ring used to contain a highly focused stream of electrons. The accuracy required in aiming the electron beam and resulting radiation necessitates very stringent operational tolerances on foundation vibrations, with peak dynamic displacements being limited to less than 0.35 μm. To assess the level of seismic excitation at the site due to traffic on an adjacent roadway, an extensive “green field” ground vibration monitoring program was carried out. The analytical model used to calculate the dynamic characteristics of the foundation system is described. A Fourier analysis approach was used to predict the response of the foundation to the ground-induced vibrations. The results of the analysis showed that the proposed foundation system would perform satisfactorily

Review of Available Methods for Evaluation of Soil Sensitivity for Seismic Design

Sensitivity describes the effect of soil disturbance/remoulding on shear strength. Cyclic stresses during seismic events may lead to varying levels of disturbance and remoulding of brittle sensitive clays. The Canadian Foundation Engineering Manual (CFEM) recommends site-specific evaluation of the seismic hazard, including site response analysis, for sites that have quick or highly sensitive clays. Different levels of soil sensitivity have been shown in different versions of CFEM and their errata. The current manual CFEM (2006) classifies clay as highly sensitive if its sensitivity is greater than 40 (classified as Class F soil). However, there is considerable variation within the literature with respect to descriptions of sensitivity and more importantly, the related seismic risks that different soil states represent. This can have a significant impact on determination of the appropriate seismic forces on supported structures according to the seismic provisions of the current National Building Code of Canada, NBCC (2005). This paper reviews the different methods used to evaluate soil sensitivity and the sensitivity classifications in the literature. Based on this review, suggestions are provided for improvements of this approach to seismic design

Seismic landslide hazard mapping for Greater Vancouver, British Columbia

The lower Mainland of southwest British Columbia (BC) hosts about 3.5 million people and significant infrastructures of national importance. Southwestern BC has the highest seismic risk in Canada with significant potential to cause earthquake-induced hazards including tsunamis, liquefaction and landslides. A Cascadia mega-thrust (MW 9) earthquake is predicted to generate $75 billion Canadian dollars in losses. This damage can be resulted from ground shaking or its secondary phenomena like landslides; ground shaking during earthquakes may trigger landslides that can damage or destroy buildings, bury roads and highways and kill and injure people. In Canada, during the past century and a half, landslides have caused more fatality than all other natural hazards combined. Seismic hazard mapping for landslides integrates topographic, geotechnical and seismological information to develop the earthquake-induced slope displacements map which is indicator of seismic landslide potential. In this study we use a pseudo-probabilistic Newmark displacement analyses for regional landslide susceptibility mapping and its application will be illustrated with developing earthquake induced landslide hazard map for the quadrangle in Greater Vancouver area. The predicted displacements are assigned to the defined grids to come up with the final seismic landslide hazard map. The seismic landslide hazard map predicts very low hazard level (displacementcm) for the selected region which is in agreement with the observations in our field survey in July 2018 where no signs of deformation were recorded (e.g. cracks, settlements, previous landslides, scarps)

Impact of Ground Motion Duration and Soil Non-Linearity on the Seismic Performance of Single Piles

Pile foundations strongly influence the performance of supported structures and bridges during an earthquake. In case of strong earthquake ground motion, soft soils may be subjected to large deformation manifesting aspects typical of the non-linear behaviour such as material yielding, gapping and cyclic degradation. Therefore, nonlinear soil-pile interaction models should be able to capture these effects and improve the prediction of the actual seismic loading transferred from the foundation to the superstructure. In this paper, a beam on nonlinear Winkler foundation (BNWF) model is used, which can simulate cyclic soil degradation/hardening, soil and structural yielding, slack zone development and radiation damping. Incremental Dynamic Analyses (IDAs) are performed to evaluate the effects of Ground Motion Duration (GMD) and soil non-linearity on the performance of single fixed-head floating piles. Various homogeneous and bilayer soil profiles are considered, including saturated clay and sand in either fully dry or saturated state and with different levels of compaction. In order to evaluate the effect of nonlinearity on the response, the results of the nonlinear analyses are compared with those obtained from linear soil-pile analysis in terms of bending moment envelope. Results show the relevance of considering the GMD on the performance of the single pile especially when founded on saturated soils. For low intensities and dry sandy soils, the linear soil-pile interaction model can be used for obtaining reliable results

Insights into the role of natural products in the control of the honey bee gut parasite (Nosema spp.)

The honey bee is an important economic insect due to its role in pollinating many agricultural plants. Unfortunately, bees are susceptible to many pathogens, including pests, parasites, bacteria, and viruses, most of which exert a destructive impact on thousands of colonies. The occurrence of resistance to the therapeutic substances used against these organisms is rising, and the residue from these chemicals may accumulate in honey bee products, subsequently affecting the human health. There is current advice to avoid the use of antibiotics, antifungals, antivirals, and other drugs in bees, and therefore, it is necessary to develop alternative strategies for the treatment of bee diseases. In this context, the impact of nosema diseases (nosemosis) on bee health and the negative insults of existing drugs are discussed. Moreover, attempts to combat nosema through the use of alternative compounds, including essential oils, plant extracts, and microbes in vitro and in vivo, are documented.Plan of High end Foreign Experts of the Ministry of Science and Technology | Ref. G2022016009

The numerical and empirical evaluation of structural performance of elevated tanks considering soilstructure interaction effects

Water tanks are an essential lifeline whose continuing availability and serviceability immediately after earthquake events are crucial for providing undisrupted emergency services. Their seismic performance is, therefore, of paramount importance. The seismic response of an elevated liquid tank situated on a soft soil deposit was studied by means of field vibration tests and numerical simulations. The ambient and forced vibration tests were conducted to identify the soil-structure interaction (SSI) effects on the small strain dynamic behavior of the structure. A series of time domain numerical analyses were performed to evaluate the seismic performance of these structures from a performance based design point of view. The results showed that consideration of SSI increased the displacement demand significantly. Thus, the calculated maximum displacement demand for supporting frame components of the tank may be underestimated significantly when the SSI effects are neglected. In addition, the seismic induced shear forces considering SSI effects were much smaller than the seismic shear forces for the fixed based case. For some soil types, the effect of this reduction on the overall response may become more prominent than the structural ductility mechanism. This resulted in the failure mechanism being initiated by a coupled compression - bending moment effect, rather than shear failure. Finally, the sloshing response is significantly increased due to the SSI