bent (pier) protection guide

2020 Virtual Short Course October 13, 2020

Bent (Pier) Protection GuideEdgar F. Cuellar, E.I.T.

October 13, 2020


Table of contents

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5-6

7-31

3-4Introduction.

When and Where will the Guide posted.

What is covered in the Guide.

1

2

3


What is the Bent (Pier) Protection Guide?


Introduction

§ The Bent (Pier) Protection Guide was conceived due to the need of guidance for protection of columns and bents from collapsing due to vehicular collision.

§ The guide does not contains “How-To” guidance, instead it guides the users to AASHTO and Bridge Design Manual articles to find the information that can be used for the protection of bents.

§ This guide focuses in the protection of piers. This guide does not contain information about traffic safety which focuses on the protection of drivers against obstacles in the road.

§ The Bent (Pier) Protection Guide does not contain information for railroad and vessel collision.

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When and Where can the guide be accessed?


When and Where is the Guide posted.

§ The Pier Protection Guide is expected to be posted next year.§ Guide will be posted in the TxDOT’s Bridge Division Publications external site.

https://www.txdot.gov/business/resources/consultants-contractors/publications/bridge.html

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What is coveredin the Guide?


What is covered the Guide

§ The main topics covered by the guide are:– Design Considerations– Load Redirection– Structural Resistance– Widenings

§ The guide also has some examples in the appendices.– Vehicle Deflection Wall Example– Column Jacketing Example

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Column Repair

Vehicle Deflection Wall

Column Design


Design Considerations



§ A Flow chart is included in Appendix “A” as an aid to help the Engineer decide whether Pier Protection is required.

10

Dimension between Column and Edge of

Travel way less than 30'?

NoYes

What type of roadway is this?

Do adjacent roadways have the potential to cause vehicular

impact to columns?

NoYes

Undivided in tangent and horizontally

curved

Divided curvedsections

Divided tangent sections

Use:PHBP = 3.457 x 10 -9

Use:PHBP = 2.184 x 10-9

Use:PHBP = 1.090 x 10-9 No further action

needed

Evaluate if vehicular collision protection is needed using:

AFHBP = 2(ADTT) (PHBP)365 > 0.0001 (Critical or Essential Bridges)

AFHBP = 2(ADTT) (PHBP)365 > 0.001 (Typical Bridges)

Consider using Roadside protection devices. For

more information refer to AASHTO Roadside

Design Guide

Is AFHBP Satisfactory?Yes No

No further action is needed.

Pier Protection is required.

This flow chart is mainly used when Bents are being evaluated

routinely, however, a more direct approach can be taken by reviewing crash data and decide to add Pier Protection based on

crash data alone.

OptionalEvaluate if

AFBC is Satisfactory

Yes No



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Actual Dimension: 10’ – 20’

Minimum: 30’


Design Considerations (Flow chart “No” Path)

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No


impact to columns?



13



impact to columns?

NoYes


curved



Use:PHBP = 3.457 x 10 -9

Use:PHBP = 2.184 x 10-9

Use:PHBP = 1.090 x 10-9

No further action needed



Design Guide



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Design Considerations (Flow chart “Yes” Path)

15



Yes




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impact to columns?

NoYes


curved



Use:PHBP = 3.457 x 10 -9

Use:PHBP = 2.184 x 10-9

Use:PHBP = 1.090 x 10-9

No further action needed



Design Guide



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Evaluate if vehicular collision protection is needed using:

AFHBP = 2(ADTT) (PHBP)365 > 0.0001 (Critical or Essential Bridges)

AFHBP = 2(ADTT) (PHBP)365 > 0.001 (Typical Bridges)

Is AFHBP Satisfactory?Yes No

No further action is needed.

Pier Protection is required.

OptionalEvaluate if

AFBC is Satisfactory

Yes No


Load Redirection


Load Redirection

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§ An embankment, such as a soil slope sloping away from the columns. (Drilled shafts in this case)


Load Redirection

§ A test level (TL-5) structurally independent, crashworthy ground mounted 54.0-in. high barrier, located within 3.25 ft. from the component being protected.

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Load Redirection

§ A test level (TL-5) structurally independent, crashworthy ground mounted 42.0-in. high barrier, located between 3.25 ft. to 10 ft. from the component being protected.

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Load Redirection

§ A TL-5 42.0-in. high barrier located at between 10ft. and 30ft. from the component being protected.

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T80SS SSCB


Load Redirection

§ A split rail can be used where space is a constraint like in Highway corridors.

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Split Rail Guidance (See Two Side T80PP Traffic Rail (T80PP-TS) standard.)


Structural Resistance



§ 600 kip force.§ Between 2 to 5 feet above ground.§ 0 to 15 degrees from the direction of traffic.§ Shear, Flexure, and the connections.

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15 deg15 deg

ELEVATION PLAN

600 kip2’

-0” t

o5’

-0”

(AASHTO LRFD 3.6.5)



§ Repair– Concrete repair + jacketing– Concrete repair + add a deflection wall– Partial removal + replace with a bigger column– Refer to the TxDOT’s Concrete Repair Manual

§ Preemptive– Deflection Wall

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Column Repair

Larger Column

Column Jacketing



§ Sample Details for VDW located in Appendix “B” of the guide.

§ Example failure modes for the Yield Analysis method are included in Appendix “C”.

§ VDWs Need to be tailored for specific project.§ Analysis required for VDWs.

• Changes in wall width and column spacing will affect capacity.• Changes in skew of bent relative to the lower

roadway affects required capacity.• VDW distributes the force to all the columns of the

bent, so each column will see only a portion of the load.

§ Sample Details for Column Jacketing located in Appendix “B” of the guide.

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Widenings


Widenings

§ Same design practice for New Columns of the widening.

§ Use constraints that are consistent with the details used to connect to the existing structure.

– If there is a gap between new and existing bents they will be considered independent.

– If the bents are connected is the connection a Full Moment connection or Pin Connection.

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Temp Reinf. Splices = *

Bent Cap Bott. Main Reinf. Splices = *

Bent Cap Top MainReinf. Splices = *

* For Epoxy-Coated bars multiply values shown by a factor of 1.5


Widenings

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Widenings

§ For the existing elements of the widening:– Can the bent resist the load as is?. – Does a vehicle deflection wall need to be

added to increase the capacity of the bent/columns?.

– Consider the roadside safety concerns.

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Column Repair


Questions?

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bent (pier) protection guide

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