Alternative Refinement Update. Policy Advisory Group December 10, 2007

Transcription

1 Alternative Refinement Update Policy Advisory Group December 10, 2007

2 Alternative A

3 Alternative B

4 Alternative C

5 Alternative D

6 Alternative E

7 Draft EIS Alternatives

8 Bridge Type Selection Policy Advisory Group December 10, 2007

9 Bridge Type versus Design Types are named according to the principal load carrying structure. This selection establishes the overall character of the bridge. Types are evaluated in the draft EIS. Design is defining the proportions, shapes, and features for the bridge type. Design is an iterative process dealing with a wide array of engineering and aesthetic features. It is developed following selection of a preferred alternative.

10 Selection of Bridge Types Aim is to select both moderately-priced and higherpriced bridge types (to get more detailed cost and impact information from draft EIS analysis) Not each bridge type is suitable for each alternative

11 Bridge Types Under Consideration Moderately-Priced Box Girder Delta Frame Stress Ribbon (bike/ped bridge only) Higher-Priced Deck Arch Through Arch Cable-Stayed Extradosed Suspension (bike/ped bridge only)

12 Box Girder

13 Box Girder Examples

14 Delta Frame

15 Delta Frame Examples

16 Deck Arch

17 Deck Arch Examples

18 Cable-Stayed

19 Cable-Stayed Examples

20 Extradosed

21 Extradosed Examples

22 Through Arch

23 Through Arch Examples

24 Bicycle/Pedestrian Bridge Options Stress Ribbon (left) Suspension (right)

25 Key Attributes Moderate- Priced Bridge Types Higher-Priced Bridge Types Notes A Rehab with new bicycle/pedestrian bridge Box Girder Delta Frame Stress Ribbon Deck Arch Cable-Stayed Extradosed Through Arch Suspension B Rehab N/A N/A No new bridge C D Replacement with double deck Replacement with staged construction N/A Box Girder Delta Frame Cable Stayed Through Arch Deck Arch Only two bridge types work with double deck due to river clearance Only three bridge types work with staged construction E Replacement on new alignment Box Girder Delta Frame Deck Arch Cable-Stayed Extradosed Through Arch

26 Bridge Type Working Group Expert volunteer group convened by County to advise staff and CTF Members include: Bruce Johnson - Chief Bridge Engineer, ODOT Gil Kelley - Portland Planning Bureau Robert Perron -Perron Collaborative Scott Thayer - Ankrom Moisan Architects Paddy Tillett - Zimmer Gunsul Frasca Architects Sharon Wood-Wortman Bridge Historian Met four times to develop, refine, and evaluate candidate bridge types

27 Bridge Type Working Group Key Attributes Harmony with landscape and setting Scale in the landscape view of the City and nature Distinctive character Iconic presence identity that anchors bridge to place State-of-the-art in bridge engineering design Elegance and craftsmanship Structural honesty and uniqueness Gateway to Portland and Sellwood Opportunity for accent lighting-architectural presentation Variety of bridges on the Willamette Historic reference

28 Bridge Type Working Group Key Attributes Sense of place/user experience Awareness of bridge structure denotes place on bridge Awareness of river beneath Amendable to bike/ped as well as auto/trucks Place for bikes and peds connection to trail loops Experience dependent on direction of travel Flexibility to accommodate existing and future uses Facilitate future streetcar opportunities Anticipate future increased bike/ped use Accommodate future changes in cross-section Integrate approaches with main bridge and connectors

29 Bridge Type Working Group Key Attributes Minimize river and land use impacts Minimum impacts to river for signing, recreation, boating... minimize piers in water Adapt bridge to position in channel Minimize right-of-way impacts at touchdown points Life long utility and durability Seismic performance Minimize long term maintenance Lightness of touch

30 Who is the CTF? A group of about 20 volunteers representing diverse constituencies associated with the Sellwood bridge Neighborhoods Businesses Commuters Freight Transit Bicyclists Pedestrians Natural resources River users Historic Aesthetics

31 CTF Bridge Type Activities October 15 CTF discussion of bridge type concepts and attributes suggested by Bridge Type Working Group (BTWG), requests for additional information Mid-October newsletter mailing to 22,000 households October 28 posting of on-line survey November 12 CTF discussion of refined concepts with BTWG November 28 open house, closing of on-line survey December 3 December 3 CTF consideration of open house and survey results, open discussion, recommendation

32 Preferences and Recommendations Working Group Open House (69 participants) On-line Survey (1,600 responses) CTF A (bike/ped only) C (double deck) * M-Stress ribbon H-Suspension Suspension Cable-stayed M-Stress ribbon H-Cable-stayed H-Cable-stayed H-Through arch H-Through arch H-Through arch D (staged construction) ** M-Delta frame H-Deck arch M-Delta frame H-Deck arch M-Delta frame H-Deck arch M-Delta frame H-Deck arch E (new alignment) M-Box girder H-Through arch M-Delta frame H-Through arch M-Delta frame H-Through arch M-Box girder H-Through arch M = moderately-priced H = higher-priced * Moderately-priced bridge types do not work for double-deck structure due to river clearance ** Deck arch is only higher-priced type that can be constructed in stages

33 Alternative A: Recommendation Rationale Stress Ribbon Most economical Light touch Distinctive character--not duplicated elsewhere in Portland Ease of construction--could keep bike/ped connection across river during construction Cable-Stayed Avoids massive anchorage structure on each bank required by Suspension bridge Distinctive character--not duplicated elsewhere in Portland PAG suggestion of a signature bike-ped bridge

34 Alternative C: Recommendation Rationale Through Arch Through Arch Public opinion survey and open house preferences Broader appeal than Cable-Stayed Elegant, classic bridge form

35 Alternative D: Recommendation Rationale Delta Frame Public opinion survey and open house preferences More distinctive than Box Girder Narrow cross-section--piers will not seem too wide from oblique viewpoints Triangular appearance recalls the appearance of existing Sellwood Bridge trusses Deck Arch Deck Arch Public opinion survey and open house preferences Only higher-priced option that works with staged construction

36 Alternative E: Recommendation Rationale Box Girder Most economical Appearance is lighter from some angles compared to Delta Frame Appropriate to longer bridge structure Through Arch Through Arch Public opinion survey and open house preferences- -broad public appeal Elegant, classic bridge form