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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
© Copyright Post-Tensioning Institute all rights reserved. Page 1 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 2 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 3 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 4 of 16
I‐35 Extension, Duluth, MN
• Retained (and improved) pedestrian access to Lake Superior
• Roadway below is completely unnoticeable to those in the park
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 5 of 16
Natchez Trace, Tennessee
• PT, segmental arch
• Open views
• Built in balanced cantilever for minimal valley disruption
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 6 of 16
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?
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 7 of 16
LEED Categories
• Sustainable Sites (SS)
• Water Efficiency (WE)
• Energy & Atmosphere (EA)
• Materials & Resources (MR)
• Indoor Environmental Quality (EQ)
• Innovation in Design (ID)
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 8 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 9 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 10 of 16
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)
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 11 of 16
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.
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 12 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 13 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 14 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 15 of 16
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
2009 PTI Technical Conference Sustainable Post-Tensioned Bridge ConstructionJeffery S. Volz Andrea J. Schokker, LEED AP
© Copyright Post-Tensioning Institute all rights reserved. Page 16 of 16