Chapter 3: Advanced Planning

Section 1: General Considerations

New Bridges

There are many factors that should be considered in advanced planning for new bridge projects, including:
  • Superstructure type - span lengths, superstructure depth
  • Vertical clearance
  • Horizontal geometry
  • Substructure
  • Hydraulics
  • Speed of construction
  • Need for detours or phased construction
  • Aesthetics
  • Economics
  • Accelerated Bridge Construction (ABC)

Modification of Existing Structures

Modifications such as widening, strengthening, or raising a structure are often required to meet increasing traffic demands at existing bridges. Modifications of bridge projects funded by any category of funding may occur only after an analysis of the following:
  • Field Assessment by District personnel that have completed
    the TxDOT inspection training, Safety Inspection of In Service Bridges,
     to verify the current condition of the structure
    -or-
  • signed and sealed appraisal of the structural adequacy and condition of the existing structure by a professional engineer licensed in the State of Texas.
    Approval of all proposed work is required from Bridge Division prior to developing plans for modifying an existing structure
  • An economic study of replacement versus modification
  • A study of the method and handling of traffic during construction

Appraising the Existing Structure

Use the following procedure to determine the structural adequacy and condition of the existing structure:
  • Perform a load rating
    in accordance with the Bridge Inspection Manual for all structures in Fair or Good condition or if the bridge plans indicate a design less than HL-93, and provide a signed and sealed copy of the load rating to the District to be added to the Bridge Inspection Management System
    . At a minimum, the bridge must
    have a Rating Factor of 1.0 at the Operating Rating level for Specialized Hauling Vehicles, Emergency Vehicles, Design load of HS-20 or HL-93 design load, and any other truck loads added to the TxDOT Bridge Inspection Manual,
    and must have condition ratings as follows:
    • Item 58 (Deck)
      –
       Rating greater than or equal to 4
    • Item 59 (Superstructure)
      –
       Rating greater than or equal to 5
    • Item 60 (Substructure)
      –
       Rating greater than or equal to 5
    • Item 62 (Bridge-class Culvert)
      –
       Rating greater than or equal to 5
      Do not widen and/or rehabilitate a bridge if load posting would still be required after work is completed, except for the historically significant bridges discussed later in this chapter.
  • Perform a field assessment. The field assessment must be performed by a person who has successfully completed the bridge inspection training.
  • Submit the field assessment
    report, after it has been signed and sealed by a registered professional engineer in the State of Texas,
     to the Bridge Division project manager. The Bridge Division Field Operations Section Director will also consider the following factors in determining whether to rehabilitate or replace a structure:
    • Load Rating
    • Condition of the bridge as determined by the
      Field Assessment
    • Type of structure
    • Intended use (average daily traffic, percent of truck traffic, location, etc.)
  • Updated hydrologic and hydraulic analyses, including a scour analysis, are required for all bridge widening, bridge replacement, and roadway profile modifications that may adversely affect the flood plain, even if no structural modifications are necessary
Plan development can continue only if the Bridge Division concurs with the scope of work proposed in the field assessment form. These criteria apply to all bridge types, including bridgeclass culverts. Replace bridges with a load capacity that cannot be economically strengthened to
a Rating Factor of
 1.0 –
Operating Rating, for all load rating trucks in the TxDOT Bridge Inspection Manual

Field Assessment

The field assessment form and associated site visit are required to determine all structural deficiencies that prohibit a reasonable service life with normal maintenance. Inspect the condition of the foundation, substructure, and components of the superstructure. Starting this process with a desk review of the files located in AssetWise is recommended before performing the site visit.
The desk review is not a substitute for visiting the bridge and performing a thorough inspection to identify the scope of work and most importantly to determine accurate quantities related to each type of repair
.
  • While at the bridge check for the following deficiencies:
    • Settlement of the foundation
    • Spalling, cracking, or deterioration of the concrete and corrosion of the reinforcing steel in the substructure.
    • Deterioration in steel protective systems (paints or coatings) and corrosion/section loss in the structural steel elements.
    • Movement or rotation of the abutments due to approach slab or pavement movement.
    • Any damage or defects of the beams or girders and bearings
    • Unsound concrete, cracking, delamination, efflorescence
      ,
       and corrosion of the reinforcing steel in the top and bottom of the deck.
    • Deterioration of the overlay due to defects or damage in the underlying concrete.
  • Photographs of the following:
    • Bridge ends
    • Bridge elevations
    • Bridge approaches
    • Problem areas
      (
      Take a few
       pictures
      showing
      each type of
      deficiency/
      repair
      location
       that will be referenced in the Working Drawings/Plan
      s
      . There is no need to include a picture of every location in the field assessment form.)
    • Views upstream and downstream, if applicable
  • After Completing the field assessment:
    • A review and analysis of the extent of the deficiencies and the feasibility of repair.
    • Replacement
      at some point in the future
      is usually recommended if a 20-year
      remaining
      service life cannot be predicted.
      • (future = once the bridge becomes eligible for replacement)
    • A review of the hydraulic adequacy, if applicable
      .
    • If there are concerns of whether to repair or replace the deck, Bridge Division is available to help with Non-Destructive Testing (NDT) to help determine the extent of the damage, repair quantity calculations, and the associated cost estimate.

Maintaining Traffic During Construction

Identify the traffic control needs of the project prior to the development of the bridge layouts. Communication between the engineer responsible for traffic control and the design engineer is critical during the preparation of the bridge layouts and during development of the construction sequencing process.
The District’s desired approach (ABC, phased, detour/temporary crossing structures, or temporary bridge structures) must be submitted in writing as part of the Preliminary Bridge Layout Review (PBLR). Although the need to maintain traffic can often by justified, full closure with ABC should generally be considered as the first option. Category 6 funding will be used to cover the additional costs for options other than ABC, only with written approval from the Bridge Management Section Director. It is crucial that these discussions occur early in the planning of a project.
  • Accelerated Bridge Construction
     – Accelerated bridge construction techniques should be considered for every bridge project. Accelerated bridge construction can be a more cost-effective option with less disruption to traffic than lengthy detours or temporary construction.
    • Projects using Accelerated Bridge Construction techniques require early coordination between traffic control engineers and bridge designers to ensure an appropriate balance between cost and acceptable closure times.
  • Phased Construction
     – Replacing an existing bridge with a new bridge may require phased construction. Keeping lanes of the existing bridge open during the first phase of construction of the new bridge can be a cost-effective means of maintaining minimum traffic needs. Use of phased construction must be identified early in plan development and have a written justification showing that it is justified in lieu of ABC.
  • Detour/Temporary Crossing Structures
     –
    If a project must maintain traffic during
    a
    bridge replacement
    project, detours will only be allowed where an economic justification shows that
    Accelerated Bridge Construction (ABC)
     is more expensive and neither ABC nor phased construction are feasible.
  • Temporary bridge structures are
    not
     a common element in most bridge projects
    . Careful coordination between the bridge designer,
    t
    raffic control engineer, environmental coordinator, and the bridge project manager should occur early in the process to properly design these structures.
  • Category 6 funding for temporary structures or detours must be approved by the Bridge Management Section
    . Economic justification, including consideration of accelerated bridge construction techniques is required as an alternative to temporary detours.
If the project allows the contractor to provide the temporary bridge for a project, the plans
must
include certain items:
  • The required number and width of traffic lanes and the required design loading
    .
  • The alignment of the temporary structure
    .
  • Any special requirements, such as limits on fill, right-of-way, or other environmental restrictions.

Environmental Concerns

FHWA is responsible for assuring that the projects it funds do not have significant environmental
i
mpacts
,
 or if they do, that appropriate action is taken. The following Environmental Affairs Division assessments, listed in order of investigative detail from least to most, may be requested:
  • Categorical Exclusion (CE)
  • Environmental Assessment (EA)
  • Finding of No Significant Impacts (FONSI)
  • Environmental Impact Statement (EIS)
The Environmental Affairs Division (ENV) supports the
District
 environmental coordinator. The environmental coordinator conducts assessments and works closely with the Bridge Division project manager when evaluating environmental concerns. This coordination should occur as early as possible in the project development process. The Environmental Permits, Issues, and Commitments (EPIC) sheet is initiated in the
District,
 in the preliminary project development stage, to ensure that all environmental issues are addressed. To obtain information concerning access to the Texas Environmental Compliance Oversight System (Texas ECOS) and EPIC, contact ENV. Such concerns may include the following:
  • Proximity to Hazardous Sites
  • Hazardous Paint Asbestos
  • Hydraulic Impacts
  • Wetlands Impact Storm Water Runoff Mitigation of Environmental Impacts. Historically Significant Bridges, Property, and Archeological Coordination. Accessibility/ADA Considerations