Seattle University

Structural Design Package for the Replacement of a County Bridge

The project abstract is below. For the indepth project description, click here to download a PDF.

Abstract

All engineering students of our university are required to complete a year-long, industrially-sponsored senior design project prior to graduation. In the project described below, a team of four students worked under the supervision of two liaison engineers from a local county and a university faculty advisor on the design of a bridge requiring replacement. In fall quarter, the students prepared a written proposal for the county outlining the project, scope and plan of work, project deliverables, schedule and budget. The design was done in winter and spring quarters and culminated in a report describing the design methods, engineering drawings, calculations and recommendations. The team made oral presentations to the county at the end of fall, outlining the project approach, and in spring quarter, describing their final design.

A local county identified one of its bridges as structurally deficient and not in compliance with current standards for lane width and pedestrian access. In addition, the bridge had several design challenges: the center support and abutment had experienced severe scouring and erosion; the site had a high pressure artesian aquifer located 48 feet below the road surface; the roadway profile had both a horizontal and vertical curve.

The county requested the student team to submit a structural design package for a single span, pre-stressed concrete bridge superstructure, substructure and roadway approach slab. In response, the team designed a 70 ft long, 49 ft wide bridge superstructure using decked bulb tee girders. The bridge has two-12ft vehicle lanes, two-5ft bike lanes and two-5 to 7ft sidewalks. The substructure consists of 18” diameter cast-in-place concrete piles. The team also designed the abutment consisting of sheet pile walls.

The student team prepared a structural design package for the client consisting of structural plans and details using AutoCAD 2007, construction specifications including special provisions, a construction sequence memo, construction cost estimate and design calculations. The team submitted 30%, 60%, 90% and 100% submittals to the county.

During the academic year the student team met with the faculty advisor weekly and with the liaison engineer biweekly or weekly, to discuss team progress. Because the sponsor was located 30 miles away from the university, some of the sponsor meetings were held via videoconferencing. Each team member served as the project manager during the year, running team meetings, setting agendas, assigning tasks to members and following up on action items. The project strengthened the team’s ability to apply their technical knowledge to a practical problem, to work as a team, to communicate effectively, to learn and practice project management and leadership skills and to meet the clients’ needs.

The county submitted the preliminary design package to the state department of transportation in the summer of 2008 requesting funding. This was the only bridge within the county approved for full replacement.