courthouse wash pedestrian bridge moab, utah - utah … · utah state university (usu). the team...
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Arches Engineering (AE) is a team of four civil engineering students at Utah State University (USU). The team has selected to work in conjunction with Jones & DeMille Engineering (JDE) to design a pedestrian bridge over Courthouse Wash in Moab, Utah. After analyzing the conditions, AE determined a prefabricated steel bridge with a modified bowstring truss style would best suit the 130-foot crossing.
A modified bowstring truss has a relatively low cost, is aesthetically pleasing, and is simple to construct. AE specifies to use a prefabricated bridge to reduce cost and simplify on-site construction. A drilled shaft foundation would best support the bridge over Courthouse Wash. This recommendation is due to the depth of the bedrock and the poor soil conditions. The design phase is anticipated to take 12 weeks and cost approximately $66,500.
COURTHOUSE WASH PEDESTRIAN BRIDGEMOAB, UTAH
PROPOSAL SUMMARY
ALTERNATIVES
CRITERIA & DECISION MATRIX DESIGN
SPECIAL THANKS
SELECTED ALTERNATIVE
Table 1 shows a Pugh Matrix comparing the design criteria to the four alternatives. Scores are assigned for how alternatives meet the design criteria. A score of 0, 1, or 2 represents an alternative poorly meets, somewhat meets, or best meets a design criterion, respectively. The bridge has a total score of 9. The do nothing, stair crossing, and highway crossing alternatives have scores of 3, 4, and 5, respectively. Therefore, the pedestrian bridge alternative best meets the design criteria.
Table 1. Pugh Matrix
Decision Factors Highway Crossing Stair Crossing Do Nothing Bridge
Average Pedestrian Walking Time 0 1 0 2Overall Cost 1 1 2 0
Environmental Impacts 1 0 1 1Client’s Needs 1 1 0 2
Impacts to Property 1 1 0 2Aesthetics 1 0 0 2
Total Score: 5 4 3 9
John Spendlove, PE Jones and DeMille Engineering
Professor Austin Ball, SEUtah State University
Professor Joe Caliendo, PhD, PE Utah State University
As shown in Table 1, the alternative that best fit the criteria was the pedestrian bridge. Building a bridge will best meet the design criteria for the site. The estimated total cost of construction and installation for Alternative 4 is $444,875, as shown in Table 2. The cost for building the pedestrian bridge is three times more than the next most expensive alternative; however, the other alternatives do not satisfy the design criteria. Therefore, constructing a pedestrian bridge spanning Courthouse Wash is the recommended alternative.
Table 2. Estimated Construction Costs for Bridge Alternative
DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING – WYATT HANSEN, L. KADE FLAKE, JOSH KERKVLIET, TRYGVE McCREA
The goal of AE is to implement a cost-effective option to shorten the pedestrian travel time between the Fairfield Inn and future businesses separated by Courthouse Wash. Currently, pedestrian traffic has no constructed option to cross the wash.
Pedestrians must walk farther to future businesses by crossing the bridge on Highway 191. AE considered four alternatives based on the following criteria: pedestrian walking time, overall cost, environmental impact, client’s need, property impact, and aesthetic appeal.
In addition to some alternate routes AE also evaluated other bridge types which included:
● Thrust Arch Bridge● Beam Bridge ● Truss Bridge
Figure 1. Routes of alternatives
Figure 2. Image of Courthouse Wash in Moab, Utah
Figure 4. Courthouse Wash delineated watershed
Figure 3. AutoCAD drawings of proposed bridge spanning Courthouse Wash
Figure 5. Arches Engineering team members
FAIRFIELD INN
HIGHWAY 191
COLORADO RIVER
COURTHOUSE WASH
Item No. Description Quantity Unit Unit Price Total Amount1 Mobilization 1 LS $20,000 $20,0002 Clear and Grub 55000 SF $0.25 $13,7503 Excavation 30 CY $12 $3604 Dust Control 1000 kGal $30 $30,0005 Geotechnical Analysis 1 LS $10,000 $10,0006 Concrete 12 CY $600 $7,2007 Steel Reinforcement 2400 LB $1.60 $3,8408 Superstructure 1 LS $177,950 $177,9509 Install Superstructure 1 LS $25,000 $25,000
10 Concrete Bridge Deck 13 CY $800 $10,40011 Reclamation Seeding 0.6 ACRE $7,000 $4,200
Subtotal $302,700Contingency - 25% $75,675
Design Fees $66,500Total $444,875
Superstructure (Figure 3):• A prefabricated steel bridge ensures
reduced construction time and cost.• Designed according to AASHTO LRFD
Bridge Design Specifications, 2007.• A modified bowstring style truss with
a weathering finish compliments other pedestrian bridges in the area.
• A concrete deck provides a long service life with little to no maintenance.
Substructure (Figure 3):• A drilled shaft foundation rests the
weight of the bridge and traffic on the bedrock 30 feet below.
• The abutment, wing wall, and approach slab are designed to AASHTO LRFD Bridge Design Specifications, 2007.
● Suspension Bridge● Cable-Stayed Bridge● Timber Bridge
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