Prefabricated Bridge Elements and Systems

Slide 1. Connection Details for Prefabricated Bridge Elements and Systems

by
Michael P. Culmo, P.E.
Vice President of Transportation and Structures
CME Associates, Inc., East Hartford, CT

Slide 2. Learning Outcomes

After completing this Module, you will be able to:

• identify roadblocks to accelerated bridge construction
• identify the resources for locating Connection Details for PBES
• describe features of PBES that improve the quality of the finished product
• recognize a typical construction schedule for a bridge built with PBES
• recall ways to save money by using ABC and PBES

Slide 3. Roadblocks to Accelerated Construction

The primary concerns that owner agencies have with respect to adopting accelerated construction techniques are:

Need for Quality Details Durability Design Methodologies and Training Construction Methodologies

Speaker Notes:

FHWA has polled transportation agencies in the past to determine the roadblocks to using ABC. The responses are as shown.

Slide 4. "Connections Details for Prefabricated Bridge Elements and Systems"

• FHWA has developed this manual
• This publication is intended to provide information that will go a long way to answering all four of the previous concerns.
• Focus on details that have been used in the past.

Speaker Notes:

In response to the concerns from agencies, FHWA developed a manual that focused on connection details that have been successfully used in the past.

Slide 5. "Connections Details for Prefabricated Bridge Elements and Systems", cont’d.

Project Goals:

• Gather details of Connections that have been used on accelerated bridge construction projects
• Investigate transfer of technology from other markets into the bridge market
• Parking Garages
• Stadiums
• Buildings

Speaker Notes:

The details were gathered from transportation agencies and other industries, which turned out to be a key component of the work. Accelerated construction is also used in vertical construction. Many of the details used in this industry are transferable to bridge construction.

Slide 6. "Connections Details for Prefabricated Bridge Elements and Systems", (Cont’d.)

All details need to pass a critical test before being published in the document:

• Does the connection result in a rapid construction process?
• Does the connection transmit the forces between elements effectively?
• Is the connection durable?
• Is it cost effective and easy to construct?
• If a process or connection is proprietary, is there more than one supplier?

Speaker Notes:

It is imperative that all detail pass these critical test in order to ensure proper performance and a 75 year service life.

Slide 7. Sources of Data

• State DOT’s
  • Questionnaires sent via e-mail
• Federal Agencies
• Researchers (previous and current)
• Producers/Fabricators

Speaker Notes:

The connection details were gathered from the following sources.

Slide 8. Manual Organization

Speaker Notes:

The manual is organized so that users can easily find details. The sections are divided by parts of the bridge that are defined in AASHTO. Superstructure, Substructure and Foundations.

Slide 9. Connection Data Sheets

Speaker Notes:

Detail data sheets were developed that are similar to materials cut sheets. Users can gather enough information to complete a structure type study. Contact information and detail performance are included. Users can contact the agency that submitted the details and find out more information as their project proceeds.

Slide 10. Precast Cantilever Abutments

Speaker Notes:

Samples of details included in the manual: Precast cantilever abutment connections.

Slide 11. Precast Integral Abutments

Speaker Notes:

Samples of details included in the manual: Precast integral abutment connections.

Slide 12. Precast Piers

Speaker Notes:

Samples of details included in the manual: Precast pier bent connections.

Slide 13. Precast Piers, cont’d.

Speaker Notes:

Samples of details included in the manual: Precast pier cap connection.

Slide 14. Precast Decks on PS Beams

Speaker Notes:

Diagrams of Precast deck connections on concrete beams.

Slide 15. Precast Decks on Steel Framing

Speaker Notes:

Photo of precast deck connections on steel beams.

Slide 16. Precast Decks

Speaker Notes:

Samples of details included in the manual: Precast deck connections on steel beams.

Slide 17. FRP Decks

Speaker Notes:

Samples of details included in the manual: FRP deck connections on steel beams.

Slide 18. Total Bridge Element Prefabrication

Speaker Notes

Everything shown in this graphic can be prefabricated and connected.

Slide 19. Complete Bridge Element Prefabrication

New Hampshire Project How fast can we build a bridge? Experimental project All components prefabricated 115 foot span Precast cantilever abutments Clock started after old bridge was removed Roadway open to traffic in 8 days Time Lapse Video on YoutubeTM Search "Epping Bridge Construction"

Speaker Notes:

This is an example of a totally prefabricated bridge in Epping, NH. All details used in this project are included in the manual.

Slide 20. Manual Distribution

Availability Published June 2009 Is available through FHWA Highways for LIFE website www.fhwa.dot.gov/hfl/

Speaker Notes

The manual is complete and available for use. A web-site is under development that will include the details in the manual. Other details will be added to the website as they become available

Slide 21. Other Sources for Details

Utah DOT ABC Website www.udot.utah.gov (search ABC) Piers, abutments, walls, decks PCI Northeast www.pcine.org (Bridge resources) MassDOT Working on new ABC manual NCHRP Report 681 Development of a Precast Bent Cap System for Seismic Regions Web search "NCHRP Report 681"

Speaker Notes

There are other sources of details for ABC connections.

Slide 22. Schematic Design of a Prefabricated Bridge

Speaker Notes:

This is an example of how to use the FHWA manual to prepare a structure type study for an ABC project.

Slide 23. Case Scenario

• 4 lane bridge over an expressway
• Existing bridge has deteriorated beyond repair
• Heavy traffic on both roadways
• A temporary bridge or staged construction is an option
• The local business will accept a short term closure with the detour
• As opposed to a long term staged project
• Establish the detour and accelerate the bridge construction to less than 30 days

Speaker Notes:

This hypothetical bridge was chose to represent typical deficient highway overpasses throughout the country.

Slide 24. Existing Bridge

Speaker Notes:

The existing bridge layout is as shown.

Slide 25. Existing bridge issues

Speaker Notes:

Major issues include deterioration of substructures caused by leaking joints and spray attack from passing vehicles. The clearance is also substandard.

Slide 26. Proposed Bridge Type

After a formal study, the owner opted for the following structure criteria:

• Continuous steel girders (weathering steel)
• Reduce to a two span bridge
• Increase clearance by raising approach grades (3’)
• Use integral abutments (no deck joints)
• Composite concrete deck
• Membrane waterproofing and Bituminous wearing surface
• Open steel railings (galvanized)

Speaker Notes:

The proposed bridge is a conventional composite stringer bridge with the following criteria.

Slide 27. Proposed Bridge

Speaker Notes:

The layout was chosen to improve the geometry of the roadway under the bridge and eliminate the problems at the site. The new substructures are located at different location to facilitate construction. The new substructures can be built at the same time the existing substructures are demolished, thus saving time.

Slide 28. Sources of details

• FHWA Connections manual:
  "Connection Details for Prefabricated Bridge Elements and Systems"
  1. Review Chapter 1
     • Investigate connection types, materials, tolerances
  2. Search applicable sections of other chapters for details
• NCHRP Report 681
  "Development of a Precast Bent Cap System for Seismic Regions"
  
  
• Utah DOT ABC Standards

Speaker Notes:

Before the connections are chosen form the manual. Designers should review chapter 1 to become familiar with ABC concepts.

Slide 29. Connection Types Chosen

• The owner chose the following connection types
  – Grouted reinforcing splice couplers
  • Quick, proven system
  • Can develop full bar strength
  • Simplifies the design process (same as CIP)
  – Grouted PT Ducts
  • Provides significant adjustability at cap connection
  – Grouted Voids
  • Corrugated metal pipe voids for integral abutments
  • Small blockouts for pinned connections (approach slabs)
  – Concrete Closure pours between precast elements
  • Use for a limited number of connections (slower)

Speaker Notes:

The design in this case chose three different types of connections for the bridge

Slide 30. Grouted Reinforcing Splice Couplers

Emulates a reinforcing steel lap splice Multiple companies – non-proprietary Used in precast parking garages, stadiums and bridges Installation video on youtube – Search "Georgia Pier Construction"

Speaker Notes:

Grouted reinforcing splice couplers are an example of a connection that migrated from the vertical construction industry.

Slide 31. Grouted Reinforcing Splice Connectors

Speaker Notes:

The couplers can be used where ever a construction joint would normally be placed in a conventional bridge. This facilitates the design of the bridge because it can be designed as a cast-in-place structure. The couplers replace the normal lap splices. The only design change is the depth of the reinforcing cage in order to get proper cover over the couplers.

Slide 32. NCHRP Report 681 Detail

Grouted PT Duct

Similar to grouted sleeves Used in several states Tested for high seismic regions Significant adjustability Details, specifications and design information available

Speaker Notes:

The NCHRP study was for high seismic regions, however the connections are good for all locations.

Slide 33. Footing to Sub-grade Connection

Speaker Notes:

The connection of the footings to the sub-grade is made with a simple grout pour. Flowable fill can also be used. The data sheet from the manual is shown.

Slide 34. Footing to Footing Connection

Use CIP Closure Pour

• Cast closure pour during structure erection
• Design precast for structure DL
• Design continuous footing for total loads

Speaker Notes:

The connection of the footings is a simple closure pour. The closure pour can be placed as the remainder of the bridge is erected. No need to wait for concrete to cure.

Slide 35. Footing to Column Connection

Speaker Notes:

The connection of the footings to the column is made with grouted couplers. The data sheet from the manual is shown.

Slide 36. Column to Cap Connection

Use details from NCHRP Report 681

Speaker Notes:

The connection of the columns to the pier cap is made with grouted PT ducts.

Slide 37. Completed Pier

Speaker Notes:

This is a graphic showing the pier connections chosen.

Slide 38. Abutment Details

Integral Abutment to piles     – Section 3.2.3.1 Precast Integral Abutment to Piles Corrugated metal pipe voids     – Place over pile and fill with concrete Detail developed by Iowa DOT     – Used in other states also Reduces element weight Has large capacity to transfer pile loads    – Shear transfer via shear friction

Speaker Notes:

Corrugated metal pipes are an inexpensive and structurally sound connection. The voids can be used to reduce element weight as well.

Slide 39. Abutment to Pile Connection

Speaker Notes:

The connection of the piles to the abutment cap is made with a simple grouted void. The data sheet from the manual is shown.

Slide 40. Abutment Cap to Cap Connection

Use Utah DOT Details Concreted key Use integral diaphragm to link caps together

Speaker Notes:

The abutment cap to cap is made with a simple concreted shear key combined with the integral diaphragm that is case after the superstructure is in place. 2+ Piles per cap element are recommended.

Slide 41. Approach Slab Connection

Speaker Notes:

The connection of the approach slab to the abutment cap is made with a simple grouted void. The data sheet from the manual is shown. The connection of the backwall to the abutment stem is made with grouted couplers.

Slide 42. Completed Abutment

Speaker Notes:

This is a graphic showing the abutment connections chosen.

Slide 43. Beam to Deck Connection

Speaker Notes:

The connection of the precast deck to the steel beam is made with a simple grouted void. The data sheet from the manual is shown. Note the age of this detail and its corresponding performance.

Slide 44. Deck to Deck Connections

Speaker Notes:

The connection of the precast deck to deck connection is made with a simple grouted key. The data sheet from the manual is shown. Note the age of this detail and its corresponding performance.

Slide 45. Deck to Deck Connections, cont’d.

Speaker Notes:

The transverse connection of the precast deck is completed with longitudinal PT. The data sheet from the manual is shown. Note the age of this detail and its corresponding performance.

Slide 46. Deck to Deck Connections, (Cont’d.)

Speaker Notes:

A connection of the precast deck to deck is made with a closure pour at the roadway crown. This is done to reduce the handling size of the elements and account for the deck geometry. It is not required on every bridge. The data sheet from the manual is shown.

Slide 47. PC Deck Connection Details

Speaker Notes:

This is a graphic showing the deck connections chosen.

Slide 48. Superstructure to Abutment Connection

Use CIP Closure Pour Utah DOT Detail Allows for significant adjustability Provides connection between abutment stem elements

Speaker Notes:

This detail shows the integral abutment elements and connections. This detail is not included in the FHWA manual. It was taken from the Utah DOT ABC standards.

Slide 49. Completed Superstructure

Speaker Notes:

This is a graphic showing the superstructure connections chosen.

Slide 50. Complete Bridge

Speaker Notes:

This is a graphic showing the entire bridge.

Slide 51. Estimated Construction Schedule

Speaker Notes:

The schedule shown is based on real-world experience on ABC projects. This should be considered a minimum timeframe for a typical prefabricated element project.

Slide 52. Costs

Typical New Bridge (Cost=$175/sf)	=	$2,200,000
Premium for ABC (assume 20%)	=	$440,000
Temporary Bridge (Cost=$50/sf)	=	($620,000)
Net Savings	=	$180,000

Note: These prices will vary greatly by region.

Speaker Notes:

The costs shown are relative. ABC can cost more than conventional construction for the structural elements, however there are other non-structure savings that can be realized, including the cost of a temporary bridge.

Slide 53. Other Cost Savings

• Ways to reduce bid prices with ABC
  • Standardization
  • Programmatic (not one of a kind)
  • Reduced project site costs (trailers, etc.)
  • Reduced maintenance of traffic costs
  • Inflation
• Other Non- Bid Savings with ABC
  • Fewer police details
  • Reduced agency costs during construction (staff time)
• User Costs
  • Plus: $$ can be significant
  • Minus: $$ not in the budget

Speaker Notes:

There are other non-structure related cost savings that can also be realized.

Slide 54. Quality

• FL has had very good success with precast piers in very harsh environments
• CT has had Precast full depth decks in place for over 20 years
  • Crack Free Deck
  • Excellent condition
• Integral abutments eliminate deck joints

Speaker Notes:

The FHWA manual demonstrates that the details chosen can be exposed to harsh environments with great success.

Slide 55. Old Adage

By elimination of temporary bridges or costly stage construction schemes, and accounting for reduced agency costs

Speaker Notes:

Based on the information discussed in this presentation, it is possible to get high quality, low overall project costs and rapid construction.

Slide 56. Conclusions

• It is possible to build a complete bridge in 30 days (or less)
• The FHWA manual provides a starting point for a complete bridge prefabrication project
• New details are coming on line all the time
  • NCHRP Report 681, Utah DOT, PCI Northeast (www.pcine.org)
• You do not need to sacrifice quality to get rapid construction
• You can save money on an accelerated bridge project by:
  • Reducing construction time
  • Eliminate temporary bridges or staging

Speaker Notes:

In conclusion: It is possible to replace a bridge in 30 days using prefabricated bridge elements.  The FHWA manual is a great starting point for planning an ABC project. ABC does not necessarily mean higher overall project costs.

Slide 57. Module Conclusions

You should now be able to:

• identify roadblocks to accelerated bridge construction
• identify the resources for locating Connection Details for PBES
• describe features of PBES that improve the quality of the finished product
• recognize a typical construction schedule for a bridge built with PBES
• recall ways to save money by using PBES

Slide 58. Questions

culmo@cmeengineering.com