Prefabricated Bridge Elements and Systems

Slide 1. ABC/PBES Specifications, Contract Drawings and Details

by
Mary Lou Ralls, P.E., Principal
ralls-newman@sbcglobal.net
512-422-9080

Slide 2. Learning Outcomes

• Identify resources for examples of various ABC/PBES
  
• Acquire specifications, contract drawings, and details for various ABC/PBES projects
  
• Describe issues concerning regional and national details and standards
  
• Describe seismic considerations and research

Slide 3. Resources for ABC/PBES Specifications, Contract Drawings, and Details

FHWA prefabricated bridges website HfL projects website ABCT website ACTT website ABC Center PBES Connection Details Manual PBES Cost Study

State DOT bridge websites FHWA SPMT Manual UDOT ABC SPMT manual & guide NCHRP domestic scan report NCHRP & other research ABC Manual SHRP2 R04 Final Report

Speaker Notes:

While there is no one source to obtain a compilation of ABC/PBES specifications, contract drawings, and details, a number of resources are available to acquire examples used in previous ABC/PBES projects. The intent of acquiring these specifications, contract drawings, and details is to have a starting point for a new project to take advantage of lessons learned from a similar previously constructed project.

Slide 4. Resources for ABC/PBES Specifications, Contract Drawings, and Details (Cont’d)

http://www.fhwa.dot.gov/bridge/prefab/projects.cfm

Speaker Notes:

The first resource to be discussed is the FHWA prefabricated bridges "Innovative Projects" website. A screen shot of the home page for this website is shown.

Slide 5. FHWA Prefabricated Bridges Website 50+ Projects

View Projects

• All projects
• By Specific Elements or Systems:
• Partial-Depth Deck Panels
• Full-Depth Deck
• Panels Beams: More Efficient Shapes
• Pier Cap, Column, and/or Footing
• Abutment Wall, Wingwal, and/or Footing
• Superstructure
• Substructure
• Total Bridge

Speaker Notes:

Over 50 PBES projects from around the country are included in this website. Only completed projects are included. The projects are categorized by specific element or system type as shown in the slide.

Slide 6. FHWA Prefabricated Bridges Website 50+ Projects

Location State Completion Date Contact Person Description

Project Photo ABC/PBES Type Advantages Related Documents

Speaker Notes:

The information provided for each project includes the location, the state, the year built, the contact person, a brief description of the project, and a project photo. Also included for each project is the PBES type (for example, deck), the advantages of using PBES for the project, and related documents.

Slide 7. FHWA Prefabricated Bridges Website Related Documents

• Contract Drawings
  
• Detail Sketches
  
• Construction Photos
  
• Construction Process Description

http://www.fhwa.dot.gov/bridge/prefab/projects.cfm

Speaker Notes:

Related documents may include contract drawings, detail sketches, construction photos, and a description of the construction process. Currently only a limited number of projects have related documents posted on the website.

Slide 8. FHWA Prefabricated Bridges Website Contract Drawings

Speaker Notes:

Various contract drawings included in the contract documents are available for download in pdf format. This example is a plan sheet for precast caps used in a Texas project.

Slide 9. FHWA Prefabricated Bridges Website Contract Drawings

Speaker Notes:

As shown here, some of the contract drawings have extensive construction notes.

Slide 10. FHWA Prefabricated Bridges Website Contract Drawings

Precast Bent Cap Construction Notes – Examples:

• Identify which construction specification items to build in accordance with;
  
• Describe how caps are to be handled;
  
• Specify concrete mix design and grouting requirements;
  
• Specify construction process, with note that says what contractor must do if deviating from those requirements

Speaker Notes:

For this precast bent cap project, the construction notes include such details as which construction specification items to build in accordance with, how the caps are to be handled, concrete mix design requirements, grouting requirements, and the required construction process. A note is also provided that says what the contractor must do if deviating from those requirements.

Slide 11 FHWA Prefabricated Bridges Website Detail Sketches

NHDOT Epping Bridge

Speaker Notes:

Related documents may also include detail sketches, as shown here for the New Hampshire Epping prefabricated bridge.

Slide 12. FHWA Prefabricated Bridges Website Ongoing Updates

• Contact information updated
• Recent projects added
• More project details included, e.g.:
  
  • Specifications
  • Contract Drawings
  • Contracting Strategies
  • Costs

http://www.fhwa.dot.gov/bridge/prefab/projects.cfm

Speaker Notes:

The website is currently being updated. Contact information is being checked and updated as needed. Recent projects are being added, and other related information is being added. In addition to specifications and contract drawings, contracting strategies, costs, bid tabs, and schedule are being added as available. These updates will be posted as available, so check the website periodically for updates.

Slide 13. FHWA Prefabricated Bridges Website Ongoing Updates

Highways for LIFE demonstration projects website

Speaker Notes:

Another resource is the Highways for LIFE demonstration projects website. A screen shot of the home page for this website is shown.

http://www.fhwa.dot.gov/hfl/projects.cfm

Slide 14. FHWA Prefabricated Bridges Website Ongoing Updates

HfL Project Summaries

http://www.fhwa.dot.gov/hfl/summary/projects_summary.cfm

Speaker Notes:

HfL project summaries can be accessed from the HfL home page. Shown here are several of the HfL-sponsored ABC/PBES projects. A final report can be downloaded for each of these projects.

Slide 15. FHWA Prefabricated Bridges Website Ongoing Updates

Accelerated Bridge Construction Technology (ABCT) website

http://www.fhwa.dot.gov/bridge/accelerated/index.cfm

Speaker Notes:

Another resource is the Accelerated Bridge Construction Technology (ABCT) website. A screen shot of the home page for this website is shown. As you can see, reports and presentations can be downloaded from this website.

Slide 16. FHWA Prefabricated Bridges Website Ongoing Updates

Accelerated Construction Technology Transfer (ACTT) website

http://www.fhwa.dot.gov/construction/accelerated/

Speaker Notes:

The Accelerated Construction Technology Transfer (ACTT) website is another resource that provides links to various articles and reports on ABC projects. A screen shot of the home page for this website is shown.

Slide 17. Center for Accelerated Bridge Construction at Florida International University

http://www.abc.fiu.edu/

Speaker Notes:

The Center for Accelerated Bridge Construction at Florida International University is a new ABC resource that is available to you. The purpose of the Center is to promote and expand the use of ABC by being the place to go to get information and support to design and build projects using ABC technologies and techniques in a cost-effective manner. The Center will also identify needed research and resources, and develop new technologies. A screen shot of the "Upcoming Events" page shows details about the Center’s kickoff webinar. This website is currently being populated with ABC information. You may access the website at the link shown at the bottom of the slide.

Slide 18. Center for Accelerated Bridge (Cont’d)

General Topics Superstructure Connections Substructure Connections Foundation Connections Connection Design Examples Proprietary Products Sample Construction Specrifications Case Studies

http://www.fhwa.dot.gov/bridge/prefab/if09010/

Speaker Notes:

Another resource is the Connection Details Manual. It includes connection details used across the US. Sample construction specifications and case studies are also included. A module will be presented on this manual.

Slide 19. Center for Accelerated Bridge (Cont’d)

Cost-competitive projects Reduced onsite construction time Construction cost less than engineer’s estimate Project details Project owner contacts Other contacts, e.g.: Contractor Design Engineer Prefabricator

http://www.fhwa.dot.gov/bridge/prefab/successstories/091104/

Speaker Notes:

Another resource is the 2006 FHWA PBES Cost Study that was discussed in the previous module.

Slide 20. FHWA PBES Cost Study

Case studies of nine projects

• Project description
  
• Project size / dimensions
  
• ABC/PBES types
  
• Fabrication/construction details
  
• Construction photos
  
• Contract requirements
  
• Cost – engineer’s estimate vs. bid
  
• Contact information

http://www.fhwa.dot.gov/bridge/prefab/successstories/091104/

Speaker Notes:

In addition to a discussion of the costs for each of the nine case studies, a project description includes project size and dimensions, ABC/PBES types, fabrication and construction details, construction photos, contracting strategies, and contact information.

Slide 21. State DOT Websites – UDOT

http://www.udot.utah.gov/main/f?p=100:pg:0:::1:T,V:1991,

Speaker Notes:

State DOT bridge websites are another resource for PBES specifications, contract drawings, and details. Shown here is the Utah DOT’s ABC home page. As you can see, a number of resources are available for download.

Slide 22. State DOT Websites – UDOT

• Full-Depth Precast Concrete Deck Panels Manual
  
• Precast Approach Slab Manual
  
• Precast Box Culvert Manual
  
• Precast Bulb Tee Girder Manual
  
• Precast Substructure Elements Manual
  
• SPMT Process Manual and Design Guide
  
• Master Process for Bridge Moves Using SPMTs

http://www.udot.utah.gov/main/f?p=100:pg:0:::1:T,V:2090,

Speaker Notes:

For example, included are ABC manuals on full-depth precast concrete deck panels, precast approach slabs, precast box culverts, precast bulb tee girders, precast substructure elements, and SPMT bridge moves.

Slide 23. State DOT Websites – TxDOT

http://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/bridge-e.htm

Speaker Notes:

The Texas DOT also has an extensive bridge website. Shown here is a contract drawing for the Texas partial-depth precast concrete deck panels downloaded from the TxDOT bridge standards website.

Slide 24. State DOT Websites – TxDOT

Example Standard included in Guide to Bridge Standard Drawings: Decked Slab Beam (ABC) 20-in. & 23-in. depth 6.5-ft, 7-ft, & 8-ft width 30-ft to 60-ft span lengths

To access TxDOT bridge standards & guide: http://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/bridge-e.htm, or Google "TxDOT Bridge Standards"

Speaker Notes:

Also available for download from the TxDOT bridge standards website is their Guide to Bridge Standard Drawings. It provides guidance for several of TxDOT’s bridge standards, including the decked slab beam that they consider one of their ABC standards.

Slide 25. TxDOT Guide to Bridge Standard Drawings

Description of Component Standard Drawing Location Standard Drawing Features Standard Drawings Needed for Bridge Details

Additional Drawings Needed to Complete Bridge Details Restrictions on Use of Standard Drawings Special Considerations Specific Bridge Layout Requirements

To access TxDOT bridge standards amp; guide: http://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/bridge-e.htm, or Google "TxDOT Bridge Standards"

Speaker Notes:

The TxDOT Guide to Bridge Standard Drawings includes a description of a number of its standard bridge types and for each provides guidance such as the website location that the standard can be found, features of the standard, and drawings that need to be included for a bridge project.

Slide 26. TxDOT Guide to Bridge Standard Drawings

http://www.fhwa.dot.gov/bridge/pubs/07022/

Speaker Notes:

The 2007 FHWA Manual on Use of Self-Propelled Modular Transporters to Remove and Replace Bridges is another ABC/PBES resource. It is available for download electronically at the FHWA prefabricated bridges website, or in print from the FHWA Office of Bridge Technology.

Slide 27. FHWA Manual on Use of SPMTs to Remove & Replace Bridges

Appendices

• App. A: Example User Cost Model Spreadsheet
• App. B: Example Plan Sheet Details for Cast-in-Place Deck Closure Pour Option to Facilitate Span Fit-Up
• App. C: Example Calculations for Comparing Total Bridge Weight and Estimated Cost Premium for Normal-Weight Concrete and Lightweight Concrete Bridge
• App. D: Example Specification for SPMT Equipment
• App. E: Example Plan Sheet for Contractor Alternatives
• App. F: Example Specification for Lightweight Aggregate
• App. G: Example Specification for Incentive/Disincentive and Bonus Used in Conjunction with App. E

Speaker Notes:

The manual includes 15 appendices with various example specifications, contract drawings, details, and other information.

Slide 28. FHWA Manual on Use of SPMTs to Remove & Replace Bridges

Appendices, cont’d.

• App. H: Example Specifications for Incentive/Disincentive
• App. I: Example Specifications for Bonus
• App. J: Example Specifications for Lane Rental
• App. K: Example Specification for Value Engineering
• App. L: Examples of Partnering Provisions
• App. M: Example Plan Sheets for Traffic Control Plans
• App. N: Example Specification for Settlement Report for Temporary Shoring on Shallow Foundations
• App. O: Example Diagrams for Path and Motion

http://www.fhwa.dot.gov/bridge/pubs/07022/

Speaker Notes:

These examples are intended to serve as a starting point  for new projects.

Slide 29. FHWA Manual on Use of SPMTs to Remove & Replace Bridges
FDOT I-4/Graves Avenue Case Study

• Project Description
  
• Bridge Removal with SPMTs
  
• Bridge Construction and Erection with SPMTs
  
• Time Savings
  
• Initial Construction Costs
  
• Delay-related User Cost Savings
  
• Net Cost Savings from Use of New Technology
  
• Participants
  
• Post-Installation Interviews – Contractor & Subcontractor
  
• Lessons Learned

Speaker Notes:

The manual also has an extensive case study of the 2006 FDOT I-4 / Graves Avenue bridge project. It provides a project description, details on the removal of the existing bridge and construction of the new bridge in the staging area, erection of the new bridge with SPMTs, and the onsite construction time savings.

The case study also discusses construction costs, delay-related user cost savings, and the net cost savings from use of SPMTs. It also includes post-installation contractor and sub-contractor interviews and lessons learned.

Slide 30. Accelerated Bridge Construction SPMT Process Manual and Design Guide

http://www.udot.utah.gov/main/f?p=100:pg:0:::1:T,V:2090,

The Utah DOT has developed a more detailed manual on the use of SPMTs to move bridges. The Accelerated Bridge Construction SPMT Process Manual and Design Guide can be downloaded from the UDOT website.

Slide 31. Preconstruction Process

http://www.udot.utah.gov/main/f?p=100:pg:0:::1:T,V:2090,/

Speaker Notes:

Also available from the UDOT website to assist an owner with SPMT bridge moves is a pre-construction process flowchart that defines the responsibilities of the owner, contractor, and engineer of record.

Slide 32. Example of UDOT Responsibilities

This is an enlargement of the previous flowchart to show some of UDOT’s responsibilities.

Slide 33. Example of Engineer of Record Responsibilities

Speaker Notes:

This enlargement shows some of the Engineer of Record responsibilities.

Slide 34. Construction & Transport Process

http://www.udot.utah.gov/main/f?p=100:pg:0:::1:T,V:2090,

Speaker Notes:

Another flowchart in the manual shows the construction and transport process.

Slide 35. Example of Contractor Responsibilities

Speaker Notes:

This enlargement shows some of the contractor’s responsibilities related to construction and transport.

Slide 36. NCHRP Domestic Scan Program

Domestic Scan on Best Practices in Accelerated Construction Techniques
March 2009

http://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP20-68A_07-02.pdf

Speaker Notes:

The National Cooperative Highway Research Program (NCHRP) domestic scan program sponsored a scan on best practices in accelerated construction techniques. The 2009 final report on that scan can be downloaded from the TRB website.

Slide 37. National Cooperative Highway Research Program

Projects Related to ABC

No.	Title	Status
12-65	Full-Depth, Precast-Concrete Bridge Deck Panel Systems	Report 584
12-69	Design and Construction Guidelines for Long-Span Decked Precast, Prestressed Concrete Girder Bridges	Final Report on web
12-74	Development of a Precast Bent Cap System for Seismic Regions	Report 681
10-71	Cast-in-Place Concrete Connections for Precast Deck Systems	Web-Only Document 173

Speaker Notes:

NCHRP has several recently completed research projects related to ABC. Those include topics related to full-depth deck panels, long-span decked precast prestressed concrete girder bridges, precast bent cap connections for seismic regions, and cast-in-place connection details for precast deck systems. Each of these research projects includes design details and proposed design and construction specification language for consideration by the AASHTO Subcommittee on Bridges and Structures.

Full-Depth Deck Panels per NCHRP 12-65

TxDOT Live Oak Creek Bridge – 2008 86 full-depth, full-width deck panels, totaling 22,400 sq ft View shows blockouts for shear studs & transverse connection rebar

Panels designed per NCHRP 12-65 – no post-tensioning or overlay Erection of deck panels over shear studs on beams

Speaker Notes:

Bridge owners use the details developed in the research projects. As shown here, the Texas DOT built a bridge deck using the details from NCHRP 12-65.

NCHRP 12-74 Project Objectives

Develop design methodologies, connection details, and design and construction specifications for precast bent cap systems in all seismic regions

• Systems and methodologies for entire U.S.
• Practical, cost-effective connection details
• Design examples
• Design and construction specifications with commentary in AASHTO LRFD format

Source: Eric Matsumoto, California State University, Sacramento

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_681.pdf

Speaker Notes:

NCHRP 12-74 is a recently completed research project that developed precast cap-to-column connection details. The final report includes design examples and proposed design and construction specification language with commentary in AASHTO LRFD format, for consideration by the AASHTO Subcommittee on Bridges and Structures to include in the LRFD design and construction specifications.

Slide 40. Grouted Duct and Cap Pocket Details

Grouted Duct	Section	Isometric View of Joint	Elevation
Cap Pocket	Plan	Cap Pocket, Full Ductility (CPFD) Elevation	Cap Pocket, Limited Ductility (CPLD) Elevation

Speaker Notes:

The research project developed details for both a grouted duct connection and a cap pocket connection. These were selected because they were the most commonly used connections for precast caps as identified in the project’s literature search.

Slide 41. NCHRP 12-74 Lateral Load-Displacement for All Specimens

Source: Eric Matsumoto, California State University, Sacramento

Speaker Notes:

The research tests showed excellent lateral load-displacement behavior, comparable to a conventional cast-in-place cap-to-column connection.

Slide 42. NCHRP 12-74 Hysteretic Response

Speaker Notes:

The hysteretic response under seismic loading was also comparable to conventional cast-in-place construction.

Slide 43. NCHRP 10-71 – Precast Composite Slab Span System (PCSSS) based on French Poutre Dalle System  from 2004 FHWA International Scanning Tour

Span to Depth: 1/28 - 1/30 Span lengths 20 to 60 ft (45 ft span – 20 in depth) Minimum CIP depth 6 in Place ~12 beams in 4 hours Reference: NCHRP 10-71, C. French, C. K. Shield, Univ of Minnesota; & Z. J. Ma, Univ of Tenn - Knoxville

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w173.pdf

Speaker Notes:

NCHRP 10-71 is a recently completed research project that developed connection details for the precast composite slab span system (PCSSS) that is based on the Poutre Dalle system seen in France on the 2004 prefabricated bridges international scan.

Slide 44. NCHRP 10-71 PCSSS Initial Implementation

Speaker Notes:

The research team evaluated various reinforcement patterns and other details in their development of connection details that perform well.

Slide 45. NCHRP 10-71 Construction

Speaker Notes:

These are construction photos of a bridge in Iowa that was constructed with the details developed in the research project.

Slide 45. Longitudinal and Transverse Joints in DBTs and Precast Deck Panels

Reference: NCHRP 10-71, C. French, C. K. Shield, Univ of Minnesota; & Z. J. Ma, Univ of Tenn - Knoxville

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w173.pdf

Speaker Notes:

Also developed in the NCHRP 10-71 project are connection details for longitudinal and transverse cast-in-place concrete joints to transfer moment and shear between decked bulb tees and between precast deck panels.

Slide 47. 7-day and Overnight Cure Closure Pour Materials

Ref.: NCHRP10-71

Speaker Notes:

In addition, closure pour materials for the joints were evaluated. Closure pour materials for a 7-day cure and an overnight cure were subjected to various durability tests to ensure good long-term performance.

National Cooperative Highway Research Program
Projects that Facilitate the Use of ABC

No.	Title	Status
18-12	Self-Consolidating Concrete for Precast Prestressed Concrete Bridge Elements	Report 628
18-14	Evaluation and Repair Procedures for Precast/Prestressed Concrete Girders with Longitudinal Cracking in the Web	Report 654
18-15	High-Performance/High-Strength Lightweight Concrete for Bridge Girders and Decks	Research in progress
24-31	LRFD Design Specifications for Shallow Foundations	Report 651

Speaker Notes:

NCHRP also has several research projects that facilitate the use of ABC. Three relatively recent projects included evaluation of self-consolidating concrete for precast elements, evaluation and repair procedures for precast prestressed concrete girders with longitudinal cracking in the web, and LRFD design specifications for shallow foundations. An ongoing research project is evaluating the use of high-strength, high-performance lightweight concrete for bridge girders and decks.

Slide 49. National Cooperative Highway Research Program
2011 Project Related to ABC

No.	Title	Status
12-88	Synthesis of System Performance of Accelerated Bridge Construction (ABC) Connections in Moderate-to-High Seismic Regions	Report 698 *

* Funded as a synthesis project to review related past & ongoing research, define what is missing, & make recommendations for future research as a "Program of Work."

Speaker Notes:

A recently completed research project that was funded as a synthesis project identified additional ABC connection details that need to be tested for use in moderate-to-high seismic regions.

Slide 50. National Cooperative Highway Research Program

Speaker Notes:

The extreme events research facility MCEER at the University of Buffalo recently conducted the first-ever shake table test of a precast segmental post-tensioned bridge. The FHWA-sponsored tests proved adequate system performance under seismic loading.

Slide 51. Coming Soon!
ABC Manual

Overview of ABC techniques & practices currently in use App. A: Design Examples App. B: Standard Products App. C: Sample Construction Specifications App. D: Erection and Transportation Equipment

Speaker Notes:

A resource that will be available in 2011 is the FHWA-sponsored ABC Manual. This manual will provide an overview of ABC techniques and practices currently in use around the country. Appendices will include design examples and sample construction specifications.

Slide 52. Coming in 2011!

SHRP2 R04 Final Report

Innovative Bridge Designs for Rapid Renewal

Objective:
To develop standardized approaches to designing, constructing & reusing (including future widening) complete bridge systems that address rapid renewal needs and efficiently integrate modern construction equipment

Speaker Notes:

A resource that will also be available in 2011 is the Strategic Highway Research Program 2 (SHRP2) final report for Research Project R04, "Innovative Bridge Designs for Rapid Renewal." The project’s objective is to develop standardized approaches to designing, constructing , and reusing (including future widening) complete bridge systems that address rapid renewal needs and efficiently integrate modern construction equipment.

Slide 53. Regional versus National Standards
Considerations

• State DOT Bridge Standards
• Prefabrication Plants
  • Precasters
  • Steel Fabricators
• Local Contractor Means & Methods

Speaker Notes:

One would expect that economy could be achieved by developing national ABC/PBES shapes. However, a number of issues should be considered.

First, many state DOTs have developed their own ABC/PBES shapes and their construction industries have geared their operations to build bridges with those shapes. Similarly, prefabrication plants have bought forms for those shapes, and local contractors have developed their processes to use them.

Slide 54. Regional versus National Standards
Consideration, cont.

• County Initiatives, e.g.,
  • Alabama precast low-volume bridge standards
  • Collier County, Florida initiative
• Regional Initiatives, e.g.,
  • PCINE Northeast Extreme Tee (NEXT) beam being used in the northeast US
  • PCI Zone 6 FAST/Task Team to develop standards for spliced U-beams and curved U-beams to be used in the southeast US

Speaker Notes:

Also, there are initiatives at the county level to use specific shapes. For example, for over 40 years counties in Alabama have been using precast bridge superstructure and substructure standards developed by the Alabama DOT for its low-volume roads.

There are regional initiatives as well. Regional initiatives include the PCINE Technical Committee’s development of the Northeast Extreme Tee (NEXT) beam, which is now being used by several northeastern states. Also, PCI has created a team to develop standards for spliced U-beams and curved U-beams for use in southeastern states.

Slide 55. ABC/PBES Seismic Considerations

• ABC/PBES are being used in seismic regions
• Research confirms adequate seismic performance of connection details, e.g.,
  • Cap to column
  • Precast segmental post-tensioned bridge
• Research on additional connection details for seismic regions is ongoing
• More research is planned

Speaker Notes:

Seismic issues should also be considered for ABC/PBES projects. ABC/PBES details are being used in seismic regions. Research now confirms the adequate seismic performance of some ABC/PBES connection details, for example, cap-to-column details and total bridge system details as discussed earlier in this module. Research on additional connection details for seismic regions is ongoing, and more research is planned. Verified connection details are currently available, and more will become available in the future.

Module Conclusion

You should now be able to:

• Identify resources for examples of various ABC/PBES
• Acquire specifications, contract drawings, and details for various ABC/PBES projects
• Describe issues concerning regional and national details and standards
• Describe seismic considerations and research

QUESTIONS?

Mary Lou Ralls, P.E.
ralls-newman@sbcglobal.net
512-422-9080