Jeffery S. Volz Sustainable Post-Tensioned Bridge … Convention... · 2009 PTI Technical...

Sustainable Post-Tensioned Bridge Construction

Jeffery S. VolzAssistant Professor

Missouri University of Science & Technology

Andrea J. Schokker, LEED APProfessor and Head of Civil Engineering

University of Minnesota Duluth

2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP

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Sustainability

• Commonly used definition:“…meets the needs of the present without compromising the ability of future generations to meet their own needs”

Cardboard bridge (Japan)…not so good in the wet season

• Sustainability includes impact on society, environment, and economy



Presenter

Presentation Notes

Sustainability is often simply called “green” with the false assumption that it only involves environmental impacts – societal and economic impacts also play a major role Just because it’s recycled doesn’t make it sustainable (cardboard bridge – an artistic display in Japan for a pedestrian bridge that was removed when the wet season started)

Inherent benefits with PT

• Durability / life‐cycle– Typically crack free at service– Multiple levels of protection for the steel

• Efficient use of materials– Slender members– Longer spans– Multiple use of forms

• Local products– Precast near site or CIP

• Waste products (pozzolans)• Reuse

– Recycled aggregate, etc• Potential for minimal environmental disturbance



Presenter

Presentation Notes

All the usual suspects – we’ve been doing these for years under the titles of durability and economy (picture is the Wabasha bridge in Minneapolis – illustrates the bulleted items on the slide plus it has pedestrian features like a walkway and lookout points) These are key aspects to sustainability, but the full picture incorporates energy usage, quality of living, etc.

5th Street Bridge, Atlanta

• Connects GA Tech main campus with bookstore, restaurants, etc. over 12 lanes of traffic

• Park atmosphere in urban Atlanta

• Bike and pedestrian paths



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Presentation Notes

Not PT (that I know of), but an example of some of the sustainability considerations outside of material usage

I‐35 Extension, Duluth, MN

• Retained (and improved) pedestrian access to Lake Superior

• Roadway below is completely unnoticeable to those in the park



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Presentation Notes

Another example of creative usage to consider in special situations. Here’s some background from the web for you (the old 35 ended in the middle of town and this extended it far enough from downtown to ease the traffic flow at the end): The opening of the Leif Erickson Tunnel in Duluth, MN, on October 28, 1992, completed I-35 (Duluth to Laredo, TX). The Duluth segment began as a conventional freeway that would have cut off access to the shoreline and eliminated historic properties. With the help of a Citizens Advisory Committee, the Minnesota Department of Transportation (Mn/DOT) redesigned I-35 to include cut and cover tunnels, architectural design treatments, and extensive landscaping. (AJS note: you can’t tell there’s a road below you in this park and it’s a huge benefit for access from downtown to Lake Superior – lots of green space and it encourages walking and biking from downtown to the Lake front boardwalk)

Natchez Trace, Tennessee

• PT, segmental arch

• Open views

• Built in balanced cantilever for minimal valley disruption



Rating System

• Most well‐known is LEED for buildings– Leadership in Energy and Environmental Design

– Points given toward building certification for sustainable efforts in specific areas

– Innovation points

How would a system like LEED be changed for concrete bridges?



Presenter

Presentation Notes

Not meaning to imply a LEED converted for bridges is the way to go, but the exercise of using LEED and seeing how each aspect does (or doesn’t) apply to bridges is good for getting in the right mindset (picture is of the Proximity Hotel in North Carolina, LEED Platinum – note the use of concrete as the finished interior surface)

LEED Categories

• Sustainable Sites (SS)

• Water Efficiency (WE)

• Energy & Atmosphere (EA)

• Materials & Resources (MR)

• Indoor Environmental Quality (EQ)

• Innovation in Design (ID)



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LEED for New Construction Pictures: The Aldo Leopold Foundation Headquarters, Wisconsin, LEED Platinum, carbon neutral, produces 15% more energy than it uses Project 7Ten House, LEED Platinum, Los Angeles

Sustainable Sites

• Construction pollution prevention

• Site selection, brownfield sites

• Location that encourages walking/biking/public transit

• Protect habitat, preserve open space

• Stormwater quality and quantity control

• Reduce heat island effect

• Light pollution reduction



Presenter

Presentation Notes

Considering the first LEED Category… this is a glimpse at the kind of items that can receive points

Sustainable Sites Bridges

• Construction pollution prevention – Runoff, construction material disposal

• Site selection, brownfield sites– Minimize environmental impact (piers in water or sensitive environmental

areas, etc)• Location that encourages walking/biking/public transit

– Pedestrian and bike trails integrated with bridge• Protect habitat, preserve open space

– Construction method (balanced cantilever segmental, etc)• Stormwater quality and quantity control

– Pervious concrete where possible on site– Environmentally friendly deicers

• Reduce heat island effect– Light colored materials = concrete

• Light pollution reduction– Minimize lighting trespass into the

surrounding area



Presenter

Presentation Notes

If a system were set up for bridges, it would likely require reorganization from this model (and different heading titles), but to keep things simple, we’ll consider the “bridge version” of what each of these building focused point areas would be 1. Consider runoff, concrete disposal, and any other possible pollution or disturbance 2. Site selection for least environmental impact (not likely brownfield); include selection of bridge type to minimize piers in sensitive areas, etc 3. Welcoming to non-autos when possible – anything that reduces auto/truck use helps (a bit tricky in the bridge business!) 4. Construction methods, footprint of the bridge and approaches, etc 5. Decrease runoff, quality of runoff (no harmful deicer use – not an easy problem to solve, but some products are available) 6. And don’t paint the bridge rusty brown to match the steel bridge next to it! 7. Lighting as needed (safety, etc), but consider fixtures that focus light where needed

Water Efficiency Bridges

• Limit or eliminate potable water use for landscaping– Native plants with lower water requirement

– Use of captured rainwater

• (The other WE topics are directed at occupant use)



Presenter

Presentation Notes

(Jeff – I’ve put in slides for each of the categories, but feel free to skip or just show briefly if time is a problem)

Energy & Atmosphere Bridges

• This category focuses on energy use by the occupants whereas bridges would focus more on energy savings during construction and through durable designs– Efficient use of materials, life‐cycle energy use– Quick/prefab construction (get in, get out, stay out)

• Energy generation– Solar, wind, etc.



Presenter

Presentation Notes

I call the left picture “crazy architects” Clearly this is not the intent for a standard bridge, but is certainly “outside the box”. This particular project is in Copenhagen, Denmark and was design as the city’s waterfront gateway. The bridge is a skywalk for pedestrians between the two skyscrapers. The right picture shows a the Vincent Thomas bridge (Los Angeles) that uses solar power for the LED lighting (LED lighting was also used on the new PT bridge on I-35 W in Minneapolis)

http://www.inhabitat.com/2008/11/10/copenhagen-gateway-by-steven-holl/

Materials & Resources Bridges

• Construction waste management– Redirect concrete/steel for recycling elsewhere or onsite

• Reduce, reuse, recycle– Minimize virgin material use– Reuse if possible (barriers, precast units, forms, etc)

– Recycled aggregate– Pozzolans

• Local (minimize transport energy)– Local ready‐mix or precaster

• Renewable– Local certified lumber forms or reusable forms



Presenter

Presentation Notes

This is the big category for PT concrete bridges (and concrete in general) – many of the inherent sustainability items for PT bridges fall into this category

Air Quality Bridges

• LEED focuses on indoor environmental air quality (ventilation, low emitting materials, light/heat comfort for occupants)

• For Bridges this is more focused on safety (construction workers, end users) and comfort (end users)– Low VOC paint, coatings, sealers

• Minimize unnecessary use of paint

– Minimize use of hazardous chemicals– Safe and comfortable integration of modes of travel– Environmentally friendly deicers



Presenter

Presentation Notes

LEED focuses on indoor environmental air quality, so the case for bridges is different, however, many of the same principles apply for safety of workers during construction and users of the bridge

Innovative Design Bridges

• Innovation in design– New approaches and new materials that have not yet been considered

• Accredited professional (LEED AP)– Accreditation or training in applying sustainable concepts to bridges



Presenter

Presentation Notes

Light activated, pollution “devouring” concrete (or self-cleaning) on the memorial sculpture on the I-35W replacement bridge – a potential future innovation in structural concrete being tried in a low risk situation Accreditation – if we don’t lead the effort, someone else will and we will end up conforming to their rating system with little input (like concrete in LEED)

http://projects.dot.state.mn.us/35wbridge/images/IMG_4794.jpg

Conclusions

• The sustainability movement is here to stay • PT concrete bridges have inherent advantages that have long been utilized

• To be on the forefront we need to continue sustainable practices and be innovative in new ways to encompass all of sustainability: society, economy and environment

• We need to move quickly to help lead the effort for concrete bridges – we have the expertise



Presenter

Presentation Notes

LEED focuses on indoor environmental air quality, so the case for bridges is different, however, many of the same principles apply for safety of workers during construction and users of the bridge

Jeffery S. Volz Sustainable Post-Tensioned Bridge … Convention... · 2009 PTI Technical...

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