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Portland, OR, United States

Hocker B.,David Evans and Associates Inc. | Wardwell N.,JOA Surveys LLC
23rd International Technical Meeting of the Satellite Division of the Institute of Navigation 2010, ION GNSS 2010 | Year: 2010

Under a charting contract with the National Oceanic and Atmospheric Administration (NOAA), David Evans and Associates, Inc. (DEA) was tasked to evaluate the VDatum model in addition to mapping large portions of Chesapeake Bay. The VDatum software was developed by NOAA to vertically transform geospatial data among a variety of tidal, orthometric and ellipsoidal vertical datums. The goal of the evaluation was the Mean Lower Low Water (MLLW) datum model as applied to convert GNSS determined ellipsoid heights to chart datum. Using a buoy outfitted with GNSS and a tilt sensor, tidal datums were computed at three locations bounding the project area in 2009 and work continues in 2010. Data was collected at each location for a minimum of 30-days to maximize the accuracy of the datum computation. Post-Processed Kinematic (PPK) methodologies were used to process the GNSS data from the buoy and compute time-tagged antenna heights. These heights were then corrected by the antenna offset to the water line and the buoy's tilt sensor data was analyzed. Corrected ellipsoid water levels were filtered and the datums were computed using the Tide-by-Tide method of simultaneous comparisons using a control station. Final results were compared with existing shore-based tide stations, GNSS water levels computed on two survey vessels and the VDatum model. Source


Higgins C.,Oregon State University | Amneus D.,Group Makenzie | Barker L.,David Evans and Associates Inc.
Sustainable Bridge Structures - 8th New York City Bridge Conference, 2015 | Year: 2015

A visually distressed vintage conventionally reinforced concrete deck girder (RCDG) bridge was identified by routine inspection. Subsequent investigation showed the distress was due to a poorly detailed splice location for the flexural steel and the ratings determined the girders to be significantly understrength. The bridge was shored to allow it to remain in service until it could be strengthened. The bridge was strengthened using near-surface mounted (NSM) titanium alloy bars. Round titanium alloy bars with a unique deformation pattern were specially developed for this application. Experimental research was conducted to evaluate the behavior of the as-built poorly detailed girder and then to evaluate the performance of the strengthening approach. Realistic full-scale girder specimens were constructed, instrumented, and tested to failure. The specimens mimicked the in situ materials, loading interactions, and geometry. The as-built strength was verified to be very low and the distress observed in the tests priot to failure and were similar to those observed in the field. Two specimens were strengthened with NSM titanium alloy bars and exhibited much higher strength and deformation capacity. The observed strengths of the specimens with NSM titanium enable the bridge to carry legal and permit loads without restriction. The member strength was shown to be well predicted using the analysis program Response 2000 and was conservatively predicted using AASHTO-LRFD design methods. The approach and materials were applied to the actual bridge, and the bridge was restored to service without the need for shoring or posting. The first ever application of titanium alloy bars to a reinforced concrete bridge was completed at a 30% cost savings compared to alternatives. © 2015 Taylor & Francis Group, London. Source


Barbosa A.R.,Oregon State University | Link T.,David Evans and Associates Inc. | Trejo D.,Oregon State University
Journal of Bridge Engineering | Year: 2016

This paper presents the results of a testing program developed to assess the performance of circular RC bridge columns constructed with ASTM A706 Grade 80 [550] high-strength steel (HSS) reinforcement. Two pairs of columns were tested (four columns in total). The columns were subjected to lateral cyclic loading to determine the effects of steel reinforcement grade (yield strength) and of moment-shear span ratio on column performance. Each pair consisted of one column constructed with Grade 80 [550] HSS reinforcement and a control column constructed with Grade 60 [420] reinforcement. The first pair had a moment-shear span ratio of six (6), and the second pair had a moment-shear span ratio of three (3). All four columns were designed to have similar nominal bending-moment capacities. Results indicate that the columns constructed with Grade 80 [550] HSS reinforcement achieve similar resistance, similar maximum lateral displacements, and similar curvature ductility values when compared with the control columns constructed with Grade 60 [420] reinforcement. However, columns constructed with Grade 80 [550] reinforcement exhibited lower hysteretic energy dissipation than the control columns. Results also indicate that, independently of the steel grade, as the moment-shear span ratio decreases, the maximum drift ratio decreases, despite an increase in the displacement ductility. © 2015 American Society of Civil Engineers. Source


Eidswick J.,Montana State University | Steinholtz P.,David Evans and Associates Inc.
Transportation Research Record | Year: 2011

Land managers can benefit from each other's successes and lessons learned through existing alternative transportation system (ATS) deployment efforts. For this reason, the Paul S. Sarbanes Transit in Parks Technical Assistance Center assembled a set of four case studies to document those successes and examine those lessons. The case studies focused on the partnerships that allowed the ATS to be implemented, integrated with other ATSs, and operated and, in some cases, to remain financially sustainable. The four partnership case studies were the Santa Ana National Wildlife Refuge, the North Moab Recreation Area, the Cape Cod National Seashore, and the Grand Island National Recreation Area. The objective of this study was to share the ATS model and partnership lessons learned from each of the four partnering endeavors. Although each of the four case studies had its own unique ATS and set of partners, the partnership lessons learned had some major common themes, including choosing partners carefully, clearly identifying partners' roles and responsibilities, meeting with partners on a regular basis, and making ongoing communication a priority. The ATS lessons learned also had some major common themes, including identifying support for the ATS both in the community and with national land management agency leaders and creating detailed financial plans and vehicle specifications. Source


Byrne W.,David Evans and Associates Inc. | Upchurch J.,Grand Canyon National Park
ITE Journal (Institute of Transportation Engineers) | Year: 2011

Some of the significant improvements had resulted in improved visitor experiences and much less congestion at Grand Canyon National Park's South Rim. These results were expected to have implications for plans to address congestion and entrance station delays at other recreation areas. The general management plan envisioned that most of the travel needs for visitors to the South Rim was to be met by a significantly expanded transit system, including a shuttle system connecting the South Rim to a major parking facility to the south of the park boundary and an internal system of transit routes serving the major destinations in and near Grand Canyon Village. The primary components of the plan included added service lanes at the south entrance station and implementation of stacked fee collection stations to allow multiple vehicles to be served simultaneously in two of the lanes and Realignment of the main park access road away from the canyon rim to allow pedestrians to move between the newly developed areas. Source

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