2018 STATEWIDE CONFERENCE ON LOCAL BRIDGES · STAFFORD BRIDGE REHABILITATION October 23-25, 2018...

STAFFORD BRIDGE REHABILITATION

October 23-25, 2018

2018 STATEWIDE CONFERENCE

ON LOCAL BRIDGES

Matt Hunt, PE, Associate, Project ManagerSteve Hagy, PE, Project Engineer

Introduction

• Stafford Bridge Rd (CR 67) over Fish Creek,

Saratoga County

• Bridge rehabilitation including deck replacement

• Locally Administered Federal-Aid (LAFA) Project

• Owner/Sponsor: Saratoga County

• Design & CI Consultant: Creighton Manning

• Contractor: New Century Construction

Presentation Objectives

• Walk through the bridge rehabilitation process

• Gain insight into identifying solutions to various challenges associated with rehabilitations

• Provide recommendations to accommodate unknowns that may surface during construction

• Generally speaking, the girders were in very good condition

Evaluation of existing bridge

• Evidence of ponding on the deck at the pier

Evaluation of existing bridge

• Various pot holes and cracking of the asphalt wearing surface

Evaluation of existing bridge

• 6 concrete deck cores

Evaluation of existing bridge

Modeling the bridge

Defining the Alternative

• Project originally scoped as a rehab including deck replacement• Evaluated and dismissed a deck repair with overlay

alternative• Removing the deck provides access to make steel repairs

• Full deck replacement accommodated Geometry and Structural improvements

Defining the Alternative

• Geometry improvements• Eliminated one of the seldom used sidewalks to widen

the roadway to include 5ft shoulders to accommodate cyclists

Defining the Alternative

• Structural improvements• Originally intended to simply fix the deterioration by

plating the beam webs individually

• Completed steel repairs by retrofitting the beams to be continuous for deck dead load and live load

• Replaced all bearings and made the pier bearings fixed

• Eliminated joint at the pier

• Jointless abutment details

Design

• Create new AASHTOware models to assess both stages of construction and the final condition• Stage 1 – keep traffic on the existing deck supported

by 3 girders

• Stage 2 – move traffic to new deck supported by 2 retrofit girders made continuous for deck dead load and live load

• 2 Girder section required balance, stability, and torsional analysis

Stage IStage 2

Design

• Beam splices• Splices designed for stresses caused by non-composite

deck dead load, composite superimposed dead load, and live load

• Splices are not designed for steel dead load because those stresses are already “locked in” to the girders for the erected simple spans

Design

• Check pier for seismic considerations and longitudinal load• FHWA Seismic Retrofitting Manual for Highway

Structures

• Existing reinforcement at pier footing and stem interface sufficient to resist seismic load

Design

• Deck haunch calculations to set roadway profile• Used original AASHTOware model to calculate

theoretical dead load deflections

• Used roadway profile from topographical survey to determine the original over-camber of the beams

• Used new AASHTOware model to calculate the anticipated dead load deflections for the proposed bridge

• Applied new deflections to over-cambered beams

• Set the proposed roadway profile to ensure a minimum 2” haunch

• Also used the calculations to provide reinforced haunch limits in the plans

Design

• Bearings• Steel laminated elastomeric

• Changed configuration to fix the continuous beams at the pier

Construction

• Temporary traffic signal

Construction

• Stage 1 deck removal

Construction

• Substructure modifications

Construction

• Steel repair and girder retrofit

Construction

• Anticipated tall haunches to obtain desired profile due to excess camber in the girders discovered during design

• Haunches up to 9”

Construction

• Pouring the deck

Project wrap-up

• Engineer’s Estimate: $1.94M

• Contractors bid: $2.294M

• Final construction cost: $2.322M

• Began construction: May 2015

• Construction Complete: November 2015

Lessons Learned

• Do not underestimate effort and cost to make girders continuous; requires as-built geometry to be near perfect to be cost effective

• Superstructure replacement would have been a better value given final construction cost; project was under funded because it began as a simple deck replacement with minor steel repairs

Recommendations for Rehabs

• Include additional quantity for unanticipated deterioration (steel, field drilling, etc)

• If possible, EIC or one of the inspectors should be experienced in bridge rehabs

• Include enough Construction Support hours to allow the design engineer to go to the site and assess unanticipated conditions

PDH Question #1

The yield Strength of ASTM A441 steel is:

a) 40ksi

b) 42ksi

c) 46ksi

d) 50ksi

e) Can be any of the above depending on the structure steel shape and/or thickness

PDH Question #2

The difference between the design for a retrofit to make two simple spans continuous for deck dead load and live load and a conventional continuous beam design is that the steel dead load stresses are calculated for the simple span configuration.

a) True

b) False

PDH Question #3

To eliminate the “double hump” caused by over-cambering the original beams, the design team:

a) Relied on the contractor to propose a solution during construction

b) Made an assumption and hoped for the best

c) Calculated the theoretical camber of the original beams based on the topographical survey and AASHTOware model and set the proposed profile to ensure a minimum 2” haunch in consideration of the proposed deflections