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ODOT Office of Structural Engineering
Welcome to the ODOT Office of Structural Engineering LRFD Frequently Asked Questions Website. The purpose of this site is to provide the sole source for answers to all LRFD related questions.
Please make sure to review all FAQ’s prior to submitting questions to avoid duplications. The Office of Structural Engineering staff will review each question and post a response in a timely manner.
All questions and comments regarding LRFD issues are important to us. This forum will allow our office to address oversights and errors and to provide clarifications to design policies in a formal and uniform manner.
Please DO NOT contact individual OSE staff members by phone or email regarding LRFD issues. |
Frequently Asked Questions & Answers Click on the arrows to expand () or collapse () a category. |
LRFD Implementation |
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How do I determine if my project should be LRFD or not? |
The required design specification for a project is based upon project classification (e.g. Local-Let, Major, Minor or Minimal) and the project milestone dates. For more specific information, please see the cover letter for the release of the ODOT Bridge Design Manual, July 2007 available for download at:
http://www.dot.state.oh.us/se/BDM/BDM2007/Cover%20Letter_07-20-07.pdf | |
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How do I know which Standard Bridge Drawings are applicable for LRFD projects? |
Our office is currently evaluating each of the Standard Bridge Drawings, Design Data Sheets and Plan Insert Sheets for compliance with the AASHTO LRFD Bridge Design Specifications. Upon completion of this evaluation, each drawing will be modified to clearly indicate whether it is compliant with the Standard Specifications for Highway Bridges, 17th Edition; the LRFD Bridge Design Specifications, 4th Edition; or both. Until this is evaluation is complete, designers may make direct reference to the following drawings with LRFD projects: AS-1-81, BR-1, BR-2-98, DBR-2-73, DS-1-92, EXJ-2-81, EXJ-3-82, EXJ-4-87, EXJ-5-93, EXJ-6-95, PCB-91, SBR-1-99, TST-1-99, and VPF-1-90. The remaining current drawings not listed above shall be analyzed for compliance with the LRFD specifications prior to their use.
New LRFD versions of the single-span slab drawing, continuous-span slab drawing, prestressed concrete box beam drawing, and prestressed concrete box beam design data sheets are under development for release in the near future . | |
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Will PDF copies of all of the course manuals from the 2006/2007 ODOT LRFD courses be posted on the Web? |
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Does the Department plan to hold future LRFD training courses? |
The Department currently has no plans to provide any additional LRFD training courses. | |
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ODOT Bridge Design Manual, July 2007
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Section 200 |
Why was the vertical clearance requirement for grade separation structures to remain in BDM Section 207.1 eliminated? |
The July 2007 edition of the manual applies only to new structures as noted in BDM Section 101 and as defined in BDM Section 400. For information regarding all rehabilitation projects, including vertical clearance requirements, refer to the January 2004 edition of the Bridge Design Manual. |
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Section 300 |
If there is no shear key, what is ODOT's policy on inclusion of passive pressure in front of the footing face to check the sliding for retaining wall footings on soil? |
As stated in BDM Section 303.4.1.2, it is ODOT policy to use passive earth pressure acting only on a footing key for sliding resistance. The unstated intent of this policy is that passive earth pressure acting at the front of the footing above undisturbed in-situ soils should be ignored. |
What load factors should be applied to a bearing’s nominal resistance when applying this force as a loading as specified in BDM Section 301.4.5? |
The nominal resistance of the bearing shall be applied as a Friction Force (FR) with the corresponding load factor. |
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AASHTO LRFD Bridge Design Specifications
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Section 2 |
The Commentary for "Optional Criteria for Span-to-Depth Ratios", AASHTO LRFD C2.5.2.6.3 states that the ratios "contained in previous editions of the AASHTO Standard Specifcations for Highway Bridges..." are provided "...with some modifications." These modifications can produce significantly deeper section requirements for continuous steel superstructures. Does ODOT intend to use the LRFD modified span-to-depth ratio or the original Standard Specification ratio? |
In addition to the span-to-depth criteria for curved steel girder systems specified in LRFD 2.5.2.6.3, designers shall use the following criteria in lieu of those shown in Table 2.5.2.6.3-1:
1. When variable depth members are used, values may be adjusted to account for changes in relative stiffness of positive and negative moment sections.
2. The ratios shown for Precast I-Beam and Adjacent Box Beam superstructures shall apply only to members made continuous with full length longitudinal post-tensioning. Otherwise, use ratios shown for simple spans.
3. S = slab span length, in ft. For slabs not built integrally with their supports, S shall be the clear span plus the depth of the slab but need not exceed the distance between centers of supports. For slabs built integrally with their supports, S shall be the clear span.
4. L = span length, in ft. For continuous and rigid frame members, L shall be the distance between the Strength I Limit State dead load contraflexure points.
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LRFD Frequently Asked Questions |
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