102 - Bridge Design Submission Requirements: Difference between revisions

From Delaware DOT Bridge Design Manual
Jump to navigation Jump to search
mNo edit summary
mNo edit summary
Line 176: Line 176:


=== 102.4 Construction Schedule ===
=== 102.4 Construction Schedule ===
A detailed construction schedule shall be prepared for each bridge project. Preparation of the construction schedule must be coordinated with Engineering Support. Specific requirements related to the development of the construction schedule, including historic production rates for various construction activities, are located on the ''DRC – Cost Estimating & Project Timing Tab''.
For Department-designed projects, the designer should request the preparation of a Critical Path Method (CPM) schedule from Engineering Support. For consultant-designed projects, the consultant is responsible for the preparation of the Critical Path Method schedule, which must be submitted for review by Engineering Support. A draft CPM schedule should be included with the Semi-Final and Final Plan submissions and finalized for the Timing Statement for the PS&E submission.
=== 102.5 Bridge Design Procedures ===
==== 102.5.1 Quality Assurance and Quality Control ====
In designing bridges and other highway structures, the designer’s mission is to prepare safe, durable, and economical design solutions, produce a quality set of plans that meet the project requirements, and use details that are consistent with DelDOT practices and suitable for bidding and construction.
The development of all bridge projects should adhere to the requirements of DelDOT’s ''Quality Assurance/Quality Control Plan'' (2009) and the ''Plan Development Process'' (2010), both of which can be found on the ''DRC – Project Management Tab.'' The plan development checklists are also a vital element of DelDOT’s Quality Assurance / Quality Control (QA/QC) process and should be utilized for each submission. The checklists include:
* Plan Submission Checklist – ''DRC – Project Management Tab''
* Concrete Girder Bridge Plan Checklist – ''DRC – Bridges and Structures Tab''
* Steel Girder Bridge Plan Checklist – ''DRC – Bridges and Structures Tab''
* Precast Concrete Arch or Rigid Frame Bridge Plan Checklist – ''DRC – Bridges and Structures Tab''
* Precast Concrete Box Culvert – ''DRC – Bridges and Structures Tab''
In accordance with the ''Quality Assurance/Quality Control Plan,'' consultants must submit a project-specific QA/QC Plan prior to commencing work on a project. The consultant QA/QC plan will be reviewed by and mutually agreed upon by DelDOT’s project manager and the consultant.
==== 102.5.2 Designed-In Value ====
===== 102.5.2.1 ''Alternatives Analysis'' =====
For structures requiring a TS&L submission as outlined in ''Section 102.6.5.1 – Type, Size, and Location Submission Requirements'', the designer should evaluate several alternative bridge types. This will aid in the selection of the most appropriate structure type. At least three bridge types that pass the logical selection process should be submitted in the alternatives study included with the TS&L submission, together with a preliminary first cost/construction cost or life-cycle cost analysis (LCCA) and a final recommended bridge type.
For major and complex bridges, as defined in ''Section 101 – Introduction'' herein, a minimum of two bridge types should be studied for each: a steel and concrete alternate design. One bridge type may be accepted if a reasonable explanation is provided.
===== 102.5.2.2 Life-Cycle Cost Analyses =====
For beam-type structures and structures that require a TS&L submission as outlined in ''Section 102.6.5.1 – Type, Size, and Location Submission Requirements'', the selection of a recommended structural alternative shall be based on a first cost / construction cost or LCCA. For most structures, a first cost / construction cost analysis is used. An LCCA is used for major and complex bridges, as defined in ''Section 101 – Introduction'' herein, or as directed by the Bridge Design Engineer.
LCCAs shall be performed for bridge projects or project elements to assist in determining the best alternative. An LCCA should be included with the TS&L submission to compare the costs of each considered alternative. The following should be considered:
* Design costs
* Construction costs
* Right-of-way costs
* Routine maintenance costs
* Periodic maintenance and rehabilitation costs
* Service life (typically 100 years)
* Operating costs
* Accident costs
* User costs
An LCCA shall be performed in studying alternate design concepts to compare the benefits and costs at different times in a bridge structure’s life span. Future benefits and costs over the proposed time span of each alternative should be evaluated. A long-term perspective should be considered in programming improvements and selecting among alternative design, maintenance, rehabilitation, and reconstruction strategies in designing bridge structures. Refer to FHWA publication ''Life-Cycle Cost Analysis Primer'' (2002) available from the Office of Asset Management for more information (http://www.fhwa.dot.gov/infrastructure/asstmgmt/lcca.cfm).
==== 102.5.3 Documentation of Design ====
The design of each bridge must be documented to provide a permanent reference for future use. Documentation of the design should follow the requirements of the DelDOT ''Quality Assurance/Quality Control Plan'', which is available on ''DRC – Project Management Tab'' and, at a minimum, should include the following:
* Design computations
* Specific references to specifications
* Assumptions
* Specific design criteria
* Hydraulic and hydrologic reports
* Foundation reports
* Quantity calculations
* Material properties
* Computer printouts, if the design was prepared using a computer (include the input, output, and the name and version of the software used)
* Design checklists
* Plan submission checklists
* Any design exceptions and/or design variances
The above noted items are in addition to those materials required for inclusion in the “Design Document Binder” as defined by DelDOT’s ''Quality Assurance/Quality Control Plan''.
The documentation should be kept in notebooks or folders for permanent storage in the contract file (alternatively, electronic files, in PDF format, may be retained). Each plan submission must include a copy of the design computations and printouts for review; they must include the date and the name/initials of the designer who performed the computations and the person who checked them on each sheet. The date and the name/initials of the DelDOT reviewer will be added following review of the computations. The cover sheet for the calculations shall have signature lines for the designer, checker, and reviewer to recommend what is contained therein. In the final plan submission, consultant designers should submit all of the original documentation to the Bridge Design Engineer. Any changes to the documentation should be submitted by the time construction is completed.
==== 102.5.4 Design Exceptions and Design Variances ====
Typically, designs will meet or exceed the minimum Department-governing criteria and AASHTO new construction criteria for the 13 Controlling Design Elements. Occasionally, unusual conditions may warrant consideration of a lower standard. The need for design exceptions and design variances must be identified early in the design phase, so approval or denials do not delay completion of the design or require extensive redesign. In such cases, the proposed design must be thoroughly documented for review and approval by the Department and, if required, by FHWA.
Sufficient detail and explanation must be provided to build a strong case to those reviewing design exception and design variance requests. The 13 Controlling Design Elements are considered safety related and the strongest case must be made to accept a reduction in the stated standards. At some point, this justification may be required to defend the Department’s and/or the designer’s design decisions. All deviations must be uniquely identified, located, and justified. Blanket approvals will not be granted.
Generally, a design exception or design variance can be justified if it can be shown that:
* The required criteria are not applicable to the site specific conditions.
* The project can be as safe by not following the criteria.
* The environmental or community needs prohibit meeting criteria.
Most often a case for approval of a design exception or design variance is made by showing the required criteria are impractical and the proposed design wisely balances all design impacts. The impacts usually compared are:
* Operational impacts
* Impacts on adjacent section
* Level of service
* Safety impacts
* Long term effects
* Costs
* Cumulative effects
A justification should not be made solely on the basis that:
* The Department can save money.
* The Department can save time.
* The proposed design is similar to other designs.
The Design Exception and Design Variance Request Forms (Figure 102‑1 and Figure 102‑2) shall be used to document requests for deviations. The designer must provide all the supporting rationale (e.g., the necessary design criteria, figures, calculations, cost analyses, accident records, mitigation costs, photographs, plan sheets) for each request in sufficient detail to document the request. The Project Design Control Checklist Form (Figure 102‑3) and the Design Criteria Form (Figure 102‑4) should be included in the documentation, if applicable. The Design Criteria Form applies to new construction or 4R projects. A project note shall be included in the plans listing the items that have approved design exceptions and/or design variances.

Revision as of 14:40, 17 November 2021

102.1 Plan Presentation

102.1.1 Drafting Standards

Standard line widths, lettering sizes, fonts, and symbols have been established to promote uniformity in the preparation of bridge design plans. Refer to the CADD Standards Manual (Wiki Format) for Department drafting standards. Example plans are located on the DRC – Example Plans Tab and demonstrate proper application of the Department’s drafting standards and plan presentation.

Drawings must be concise and without repetitious notes, dimensions, and details. Plans, sections, elevations, and details must be drawn accurately to scale. Scales must be large enough to show clearly all dimensions and details necessary for construction of the structure. Preferably, plans, sections and elevations should be drawn to a scale not less than ¼"= 1'-0" and details to a scale not less than 3/8"= 1'-0".

A north arrow symbol should be placed on all plan views.

When describing directions or locations of various elements of a highway project, the construction baseline and stationing should be used as a basis for these directions and locations. Elements are located either left or right of the construction baseline and near and far with respect to station progression (e.g., near abutment, left side, right railing, left far corner).

Elevation views of piers and the far abutment should be shown looking forward along the stationing of the project. The near abutment should be viewed in the reverse direction. Near and far abutments should be detailed on separate plan sheets for staged construction projects or for other geometric conditions that produce asymmetry between abutments.

For each substructure unit, the skew angle should be shown with respect to the construction baseline or, for curved structures, to a reference chord. See Section 103 – Bridge Geometry and Structure Type Selection for the definition of bridge skew.

In placing dimensions on the drawings, sufficient overall dimensions must be provided so it is not necessary for a person reading the drawings to add up dimensions in order to determine the length, width, or height of an abutment, pier, or other element of a structure.

In general, the designer should avoid showing a detail or dimension in more than one place on the plans. Duplication is usually unnecessary and always increases the risk of errors, particularly when revisions are made.

If a view or a section must be placed on another sheet, both sheets should be clearly cross-referenced.

When misinterpretation is possible, the limits of pay items must be clearly indicated on the corresponding details of a structure.

Abbreviation of words should generally be avoided. Abbreviations, unless they are common use, may cause uncertainty in interpreting the drawings. If abbreviations are used, they should be defined on the notes sheet.

102.1.2 Plan Sheet Sequence

Bridge project plans shall be assembled in the following order:

  • Title sheet
  • Index of sheets
  • Addenda and revisions sheet
  • Legend sheet
  • Notes sheet
  • Roadway detail and geometry sheets
  • Construction details
  • Bridge sheets
  • Environmental compliance sheets
  • Erosion control plan sheets
  • Traffic control plan sheets
  • Traffic sheets
  • Utility sheets (if applicable)
  • Right-of-way sheets (if applicable)
  • Quantity sheets (as required)

Quantity sheets must provide a separate quantity summary for each bridge as well as a total project quantity summary. Quantity sheets are used when a bridge or bridges are incorporated into a project development project or when multiple bridges are included in one bridge project. When bridges are part of a project development project, a separate quantity summary for each bridge is required.

Bridge sheets are assembled in the order of construction as follows:

  • Bridge notes, including bridge quantities and index of bridge sheets
  • Bridge plan, section, and elevation (including key plan where applicable)
  • Lay-out plan
  • Foundation layout
  • Pile details
  • Abutment details
  • Pier details
  • Bearing details
  • Framing details
  • Beam details
  • Diaphragm details
  • Camber details
  • Moment and shear diagrams (required for complex bridges or as directed by the Bridge Design Engineer)
  • Deck and bridge railing details
  • Finished deck elevations
  • Expansion joint details
  • Approach slab details
  • Miscellaneous details
  • Reinforcing bar list
  • Soil borings

It is preferred that sheets be combined on smaller projects to reduce the number of sheets.

102.1.3 Bridge Sheet Preparation

In preparing bridge plans, the designer should fully implement the plan development checklists, which are available on the DRC – Bridges and Structures Tab and Project Management Tab. Bridge sheets should generally be arranged in the order the bridge will be constructed.

The number of bridge sheets will vary with the size and complexity of the structure. At a minimum, the bridge sheets must show:

  • A general plan view and elevation view
  • Typical bridge sections
  • Substructure details
  • Superstructure details
  • Bearing details
  • Railing and parapet details
  • Reinforcement and reinforcement schedules
  • Soil borings

A separate sheet is typically used for each abutment and pier. Where piles are used, a pile layout should be provided for each substructure unit.

In addition, as appropriate, the bridge sheets should show the following:

  • Deck details including grades
  • Joint details
  • Camber diagrams
  • Deck placement sequence
  • One feasible bridge erection scheme (as applicable for major and/or complex structures)
  • Other details necessary for constructing the bridge

General instructions for completing specific bridge sheets are presented below.

102.1.3.1 General and Project Notes

General notes include items that are applicable to all projects. Standard general notes and legend sheets are available on the DRC – CADD Tab. The most recent versions of these sheets shall be used on all projects. General notes include such items as:

  • Design specifications
  • Standard construction specifications
  • Other notes not addressed by the Standard Specifications

Project notes include items that are specific or unique to the project. Bridge project notes include:

  • Index of bridge sheets, including sheet titles and numbers
  • Design criteria
  • Design loading (e.g., special dead loads specific to the bridge, metal deck form dead loads, future wearing surface dead loads)
  • Live load distribution method
  • Vertical and horizontal datum
  • Hydraulic and scour data (including information as noted in Section 104 –Hydrology and Hydraulics) for structures draining an area of ½ square miles or greater
  • Structural steel specification and grade
  • Welding specification and information
  • Painting and protective coatings specification and direction
  • Portland cement concrete class and/or strength
  • Reinforcing steel specification and grade
  • Prestressing steel specification and grade
  • Foundation information
  • Removal items
  • Utilities
  • Traffic control references
  • Other specific project-related notes
102.1.3.2 Bridge Plan and Elevation

The bridge plan and elevation sheet generally serve as a record document, which contains critical information regarding the structure and project site and is referenced throughout the life of the structure. The following essential information shall be shown on the bridge plan and elevation sheet. If all of the following items cannot be accommodated on the bridge plan and elevation sheet, they may be shown on the next or succeeding sheets with proper reference.

  1. Plan: Outlines of substructure above ground and superstructure; length of spans along profile grade of roadway, skew angle(s), stations, and grade elevations at intersections of profile grade with centerline bearing at abutment and centerline piers; designation of piers, abutments, and wingwalls (e.g., Pier 5, Near Abutment, Wingwall A); horizontal distance between profile grade lines in the case of dual structures; contours for existing and final ground lines; location of points of minimum actual and required vertical clearances, scuppers, and lighting poles; minimum actual and required horizontal clearances between underpassing highways or centerline of railroad tracks and faces of adjacent parts of substructure; and normal horizontal clearances between faces of substructure for drainage structures.
  2. Elevation: Rate and direction of roadway grade, spacing of railing posts, spacing and mounting heights of lighting poles, protective fence location, finished ground line and approximate original ground line along centerline of bridge, Ordinary High Water (OHW) and design storm elevation, bottom of footing elevations, estimated pile tip elevations, and required and provided minimum vertical clearances together with the elevations that define the clearances provided. The type of joint and movement classification for each joint must be shown on the plans. The fixity at each substructure unit must be shown. For definition and requirements for highway vertical clearance, see Section 103 – Bridge Geometry and Structure Type Selection. For drainage structures, the minimum vertical clearance is the maximum unobstructed design flow depth under a bridge.
  3. Typical Normal Section(s) of Superstructure: Roadway width between curbs or sidewalks, overall dimensions, out-to-out faces of barriers, shoulder width, cross slopes of roadway, minimum slab thickness, girder spacing, girder type, girder size, and overhang. All applicable cross sections shall be shown on the bridge plan and elevation sheet.
  4. Grade Data: Horizontal and vertical alignment data, superelevation, run-in/run-out data, and points of rotation in accordance with the Road Design Manual.
102.1.3.3 Lay-Out Plan

A lay-out plan is essential to correctly convey the geometry of the bridge. The lay-out plan shall be prepared in accordance with the following direction.

  1. A lay-out sketch shall be shown, preferably on the first or second sheet of the structure drawings. There should be ample open space outside of the sketch to allow wing and barrier line extensions for lay-out point recordings. Frequently, exaggerations of curvature, angle, or other are necessary to show the information clearly.
  2. The sketch shall be as simple as possible, but as complete as possible so that the structures will be constructed according to the plans.
  3. All necessary tie-in dimensions between highway alignment, working points, lines of structure, and other control points shall be shown in feet to two decimal places on the sketch.
  4. A table of coordinates for all working points, a table of coordinates for the baseline, and coordinates to four decimal points must be provided. The following note should be included: Four place coordinates are for computational purposes only and do not imply a precision beyond two decimal points.
  5. The sketch shall show the baseline and the shape of the exterior face of the substructure (abutments and wingwalls). All corners shall be referenced by showing working points and station/offset referenced to the baseline. Wingwall angles to the front face of abutments shall be referenced. Working point coordinates may be shown on the plan.
  6. At intermediates piers, the skew angle between the centerline of the pier and the baseline is required. The location of the intersection of the pier centerline with the baseline shall be tied to other parts of the substructure by baseline dimensions. The distance from the baseline to the centerline of roadway along the centerline of the pier shall be provided. The station of the intersection points at the baseline shall be shown. Distances between the outside faces of each barrier shall be shown.
  7. For multi-level structures, each level shall be sketched separately, but referenced to the same baseline.
  8. The lay-outs sketch for box culverts shall include inside faces of walls, ends of the culvert, and the front face of the wingwalls. Reinforced concrete arch culverts, concrete rigid frames, and metal culverts shall be treated similarly.
102.1.3.4 Other Plans

The following shall be followed by the designer in the development of specific plan types that may be required:

  1. Proprietary Retaining Walls: When proprietary retaining walls are included in a project, provisions must be included in the contract documents to guide the suppliers of the walls. The contract documents will illustrate the general lines and grades of the proposed retaining wall along with any dead, live and earth loading which the wall design must support as well as geotechnical properties of the fill material and foundation material. During construction, the contractor will submit, through the shop drawing review process, the completed drawings and calculations of the wall design for review by the designer.
  2. Reinforcement Bar Schedules: A reinforcement bar schedule must be prepared whenever reinforcement is required on the project. The reinforcement bar schedule will be prepared in sufficient detail by the designer such that it can be directly utilized for construction without need for additional detailing efforts by the contractor. The preparation of the schedule shall utilize the Department’s Bridge Rebar Sheet Program (BR-10-001, 2010), which is located on the DRC – Bridges and Structures Tab. Bar marks should not be repeated. For bar marks that cover varying lengths of bar, the minimum and maximum lengths of bar shall be denoted in the schedules, along with the varying distance per number of bars. For example: S601, 9'-0" to 12'-0", vary 2 EA. by 6".
  3. Soil Boring Logs: The soil boring log sheet shall be prepared using the DelDOT Bridge Boring Log Program (BO-01-001, 2012). Further instructions on the use of the program are located on the DRC – Bridges and Structures Tab.

102.1.4 Bridge Number

The bridge number is a unique identification number assigned to each bridge (e.g., 1-393-441, 3-152-13A). The bridge number is assigned by the Bridge Management Engineer. The bridge number consists of the county identification number (1 = New Castle County, 2 = Kent Count, and 3 = Sussex County), the unique bridge number, and finally the roadway designation number. For a new bridge, the designer should request the bridge number from the Bridge Management Engineer at the time of the TS&L submission. On bridge plans, the bridge number may omit the roadway designation number for a shorter presentation.

102.2 Special Provisions Development

Special provisions should be used to pay for an item of work if:

  1. There is no standard specification that covers the type of work; or
  2. The work is substantially different from the Standard Specifications and the differences will have a cost effect.

The use of special provisions should be minimized. Efforts should first be made to use a standard specification. However, the use of a special provision is appropriate when introducing new products or construction techniques.

The DelDOT Engineering Support is responsible for maintaining standard or modified specifications. Any special provisions needed for bid items not covered by standard or previously prepared special provisions must be prepared by the designer. The designer must coordinate the preparation and use of all project special provisions with Engineering Support.

Prior to the Semi-Final Construction Plans submission, the designer must transmit electronic drafts (in MS Word format) of all project special provisions to the Bridge Design Engineer, who will determine whether special provisions are needed or if the work can be specified via notes while using standard pay items. The Bridge Design Engineer will forward the approved special provisions to Engineering Support. Engineering Support will review the draft special provisions; correct format, context and language; and compile the special provisions book. Engineering Support will circulate the special provisions book to DelDOT Design and Construction at the time of the Semi-Final Plans Submission. Once comments received following the Semi-Final Construction Plans review are incorporated into the special provisions book by the designer, as assisted by Engineering Support, the special provisions are considered final.

Additional guidance on the preparation and formatting of special provisions is located on the DRC – Project Management Tab.

102.3 Quantities and Cost Estimates

The calculation of quantities and creation of a cost estimate is required at every stage of the design process. The project cost drives numerous decisions during the development of the design and quantity calculations and cost estimates must be prepared in a diligent manner with accurate results.

The calculation of project quantities should be developed in accordance with the DelDOT Quantity Calculations Guidelines, which is located on the DRC – Cost Estimating & Project Timing Tab. This document provides guidance on the calculation of several standard items that are commonly encountered on DelDOT projects.

DelDOT also maintains a unit cost history for all bid items that should be referenced in the development of cost estimates. Unit costs from the DelDOT history can be used as a starting point and should be adjusted to reflect project-specific characteristics, such as quantity size, project location, and site conditions. The unit cost history can be obtained on the DRC – Cost Estimating & Project Timing Tab.

102.4 Construction Schedule

A detailed construction schedule shall be prepared for each bridge project. Preparation of the construction schedule must be coordinated with Engineering Support. Specific requirements related to the development of the construction schedule, including historic production rates for various construction activities, are located on the DRC – Cost Estimating & Project Timing Tab. For Department-designed projects, the designer should request the preparation of a Critical Path Method (CPM) schedule from Engineering Support. For consultant-designed projects, the consultant is responsible for the preparation of the Critical Path Method schedule, which must be submitted for review by Engineering Support. A draft CPM schedule should be included with the Semi-Final and Final Plan submissions and finalized for the Timing Statement for the PS&E submission.

102.5 Bridge Design Procedures

102.5.1 Quality Assurance and Quality Control

In designing bridges and other highway structures, the designer’s mission is to prepare safe, durable, and economical design solutions, produce a quality set of plans that meet the project requirements, and use details that are consistent with DelDOT practices and suitable for bidding and construction.

The development of all bridge projects should adhere to the requirements of DelDOT’s Quality Assurance/Quality Control Plan (2009) and the Plan Development Process (2010), both of which can be found on the DRC – Project Management Tab. The plan development checklists are also a vital element of DelDOT’s Quality Assurance / Quality Control (QA/QC) process and should be utilized for each submission. The checklists include:

  • Plan Submission Checklist – DRC – Project Management Tab
  • Concrete Girder Bridge Plan Checklist – DRC – Bridges and Structures Tab
  • Steel Girder Bridge Plan Checklist – DRC – Bridges and Structures Tab
  • Precast Concrete Arch or Rigid Frame Bridge Plan Checklist – DRC – Bridges and Structures Tab
  • Precast Concrete Box Culvert – DRC – Bridges and Structures Tab

In accordance with the Quality Assurance/Quality Control Plan, consultants must submit a project-specific QA/QC Plan prior to commencing work on a project. The consultant QA/QC plan will be reviewed by and mutually agreed upon by DelDOT’s project manager and the consultant.

102.5.2 Designed-In Value

102.5.2.1 Alternatives Analysis

For structures requiring a TS&L submission as outlined in Section 102.6.5.1 – Type, Size, and Location Submission Requirements, the designer should evaluate several alternative bridge types. This will aid in the selection of the most appropriate structure type. At least three bridge types that pass the logical selection process should be submitted in the alternatives study included with the TS&L submission, together with a preliminary first cost/construction cost or life-cycle cost analysis (LCCA) and a final recommended bridge type.

For major and complex bridges, as defined in Section 101 – Introduction herein, a minimum of two bridge types should be studied for each: a steel and concrete alternate design. One bridge type may be accepted if a reasonable explanation is provided.

102.5.2.2 Life-Cycle Cost Analyses

For beam-type structures and structures that require a TS&L submission as outlined in Section 102.6.5.1 – Type, Size, and Location Submission Requirements, the selection of a recommended structural alternative shall be based on a first cost / construction cost or LCCA. For most structures, a first cost / construction cost analysis is used. An LCCA is used for major and complex bridges, as defined in Section 101 – Introduction herein, or as directed by the Bridge Design Engineer.

LCCAs shall be performed for bridge projects or project elements to assist in determining the best alternative. An LCCA should be included with the TS&L submission to compare the costs of each considered alternative. The following should be considered:

  • Design costs
  • Construction costs
  • Right-of-way costs
  • Routine maintenance costs
  • Periodic maintenance and rehabilitation costs
  • Service life (typically 100 years)
  • Operating costs
  • Accident costs
  • User costs

An LCCA shall be performed in studying alternate design concepts to compare the benefits and costs at different times in a bridge structure’s life span. Future benefits and costs over the proposed time span of each alternative should be evaluated. A long-term perspective should be considered in programming improvements and selecting among alternative design, maintenance, rehabilitation, and reconstruction strategies in designing bridge structures. Refer to FHWA publication Life-Cycle Cost Analysis Primer (2002) available from the Office of Asset Management for more information (http://www.fhwa.dot.gov/infrastructure/asstmgmt/lcca.cfm).

102.5.3 Documentation of Design

The design of each bridge must be documented to provide a permanent reference for future use. Documentation of the design should follow the requirements of the DelDOT Quality Assurance/Quality Control Plan, which is available on DRC – Project Management Tab and, at a minimum, should include the following:

  • Design computations
  • Specific references to specifications
  • Assumptions
  • Specific design criteria
  • Hydraulic and hydrologic reports
  • Foundation reports
  • Quantity calculations
  • Material properties
  • Computer printouts, if the design was prepared using a computer (include the input, output, and the name and version of the software used)
  • Design checklists
  • Plan submission checklists
  • Any design exceptions and/or design variances

The above noted items are in addition to those materials required for inclusion in the “Design Document Binder” as defined by DelDOT’s Quality Assurance/Quality Control Plan.

The documentation should be kept in notebooks or folders for permanent storage in the contract file (alternatively, electronic files, in PDF format, may be retained). Each plan submission must include a copy of the design computations and printouts for review; they must include the date and the name/initials of the designer who performed the computations and the person who checked them on each sheet. The date and the name/initials of the DelDOT reviewer will be added following review of the computations. The cover sheet for the calculations shall have signature lines for the designer, checker, and reviewer to recommend what is contained therein. In the final plan submission, consultant designers should submit all of the original documentation to the Bridge Design Engineer. Any changes to the documentation should be submitted by the time construction is completed.

102.5.4 Design Exceptions and Design Variances

Typically, designs will meet or exceed the minimum Department-governing criteria and AASHTO new construction criteria for the 13 Controlling Design Elements. Occasionally, unusual conditions may warrant consideration of a lower standard. The need for design exceptions and design variances must be identified early in the design phase, so approval or denials do not delay completion of the design or require extensive redesign. In such cases, the proposed design must be thoroughly documented for review and approval by the Department and, if required, by FHWA.

Sufficient detail and explanation must be provided to build a strong case to those reviewing design exception and design variance requests. The 13 Controlling Design Elements are considered safety related and the strongest case must be made to accept a reduction in the stated standards. At some point, this justification may be required to defend the Department’s and/or the designer’s design decisions. All deviations must be uniquely identified, located, and justified. Blanket approvals will not be granted.

Generally, a design exception or design variance can be justified if it can be shown that:

  • The required criteria are not applicable to the site specific conditions.
  • The project can be as safe by not following the criteria.
  • The environmental or community needs prohibit meeting criteria.

Most often a case for approval of a design exception or design variance is made by showing the required criteria are impractical and the proposed design wisely balances all design impacts. The impacts usually compared are:

  • Operational impacts
  • Impacts on adjacent section
  • Level of service
  • Safety impacts
  • Long term effects
  • Costs
  • Cumulative effects

A justification should not be made solely on the basis that:

  • The Department can save money.
  • The Department can save time.
  • The proposed design is similar to other designs.

The Design Exception and Design Variance Request Forms (Figure 102‑1 and Figure 102‑2) shall be used to document requests for deviations. The designer must provide all the supporting rationale (e.g., the necessary design criteria, figures, calculations, cost analyses, accident records, mitigation costs, photographs, plan sheets) for each request in sufficient detail to document the request. The Project Design Control Checklist Form (Figure 102‑3) and the Design Criteria Form (Figure 102‑4) should be included in the documentation, if applicable. The Design Criteria Form applies to new construction or 4R projects. A project note shall be included in the plans listing the items that have approved design exceptions and/or design variances.