High Load Damage Repair on Through Truss Bridges – Case Study

Ming Jiao, M. Eng., P. Eng.Manager, Transportation - Bridges

CASE #1:

Nice opening, But the road appears to be blocked!

CASE #2:

Surprise!More Surprises!!

Through Truss DamageCase 1 – Portal DamageCase 2 – Vertical and Diagonal Member Damage

OUTLINES

Emergency Inspection and DesignWorking ProceduresIssues and Concerns

Woer

ConstructionWorking ProceduresIssues and Concerns

Woer

Background Info:

Damaged by an over height load (a large metal oilfield type tank) on November 20, 2014.

• Portal member torn off

• Batter posts – cracks and broken

• Top chord – cracks• Vertical members –

cracks• Bracing - Bent

The bridge was closed

Emergency Initial Site Inspection

November 21, 2014

Risk Assessment and Damage Evaluation

Risk Assessment?

Ensure Public Safety

Structural Stability & Capacity

Recommendations

Damage Report with Repair Alternatives

Inspection Results Including Damage Details, Recommendation and Priority Levels for Each Member

Emergency Repairs;

Permanent Repair Design and Tender

• Reference Drawings (A Drawings) were Received and Reviewed

• Second Site Visit to Measure and Conform member type and sizes

Emergency Repairs

Consideration

Quick

Meets Basic Requirement

Easy – Can be Constructed by Local Contractors

Short-Term Solution

Does not Conflict with Future Repair

Safe! Safe! Safe!- Load Restriction- Time Period- Inspection

Design Drawings

Contents

Plan / Elevation

Material List

Sections

Connection Details

Temporary Support Loading Requirement

Notes

Construction – Temporary Support

• Showing Vertical Load on the Design Drawings;

• Temporary Support Procedure Review and Discussion

• Construction Working Procedure Review and Discussion

• On-site Inspection

• Safety Concerns

Damage Repair for Connections at U2

Damage Repair for Connections at U1

Damage Repair for Connections at U1

Damage Repair for Connections at U1

Damage Repair for Connections at U1

Construction Cost: $200,000

Repair Design Consideration

GENERAL REPAIR APPROACHES— Full Member Replacement – Pro and Con— Partial Member Replacement — Reinforcing – Cover Plates— Heat Straightening — Grinding

CONSTRUABILITY AND COST— Bolt Holes— Environmental Concern – Paint— Tolerance Requirements— Construction Procedure Review— Temporary Support— Insurance – Scope of Work

Background Info:

One Part of our Three-Year Contract with AT Central Region

General Truss Repair –Mainly Grinding

Site Visit – The First SurpriseNew Wide Damage on Batter Post

Changed our Scope of Work a Little

Partial Section Replacement

Tender Prepared;One Drawing Included

Tender was out in January 2018

Surprise # 2:

Received Phone Call from a Contractor

Emergency Site Visit – Emergency Inspection Report

Tender Addendum # 1 – Postpone the Closing Date

Ensure Public Safety

Structural Stability & Capacity

Recommendations

Damage Report with Repair Alternatives

Inspection Results Including Damage Details, Recommendation and Priority Levels for each Member

Emergency Repairs

Permanent Repair

Design and Tender

Emergency Repairs

Consideration

Quick

Basic Requirement

Easy

Short-Term Solution

Does not Conflict with Future Repair

Safe! Safe! Safe!- Evaluate

Structural Loss- Focus on

Compression Members and Members with big Portion loss

- Speed Control

Member Repair Design

MembersFull Replacement vs Section Replacement vs Heat Straightening

Member Full Replacement – Temporary Support Required

Partial Replacement – Local Temporary Support

Reinforcing – Cover Plates

Heat Straightening – Time Consuming – no Support Required

Grinding – Loses Capacity; only can be used for Minor Defects

ConnectionsCapacity Design

Member Strength; Load Capacity from A Drawings; and Load Rating – Csi Bridge

Bolt Patens – Bridge Code 10.18.4 – min / max Spacing and min / max end Distance -

Bolt Holes – Shop Drill and Field Drill

Construction –Temporary Support

• Temporary Support Under each Vertical;

• A Jump Span to Cover Last two Panels over the River

• Construction Working Procedure Review and Discussion

• On-site Inspection

• Safety Concerns

Damage Repairs: 1. Member Replacement2. Section Replacement

Section Replacement:

Lessons Learned – Time Consuming and Costly

Section Replacement:

Lesson and Learn – Local Temporary SupportRisks: Deflection Control - Can not meet tolerance

Heat Straightening:

Lessons Learned– Time Consuming and Costly

Heat Straightening:

Tolerance Requirements

Painting - Temporary Control

Thank you!

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