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Participant

Join Date: Apr 2012
Posts: 2

# Limit of the Horizontal Deflection for a Bridge Pier Design

04/02/2012 11:57 PM

I am designing a high bridge column with column height about 110 ft. Calculated horizontal deflection on the top of column is 4 inches. All forces and stresses are OK but I connot find the limitations for the horizontal deflection from AASHTO LRFD. Could anybody give me a clue to find the limit on any design Codes?

Thanks

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Guru

Join Date: Apr 2010
Location: Trantor
Posts: 4844
#1

### Re: Limit of the horizontal deflection for a bridge pier design

04/03/2012 7:25 AM

Is this for a real bridge? Where is it being built?

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Guru

Join Date: May 2009
Location: Red Hook, New York (Mid-Hudson River Valley)
Posts: 4291
#2

### Re: Limit of the Horizontal Deflection for a Bridge Pier Design

04/03/2012 9:39 AM

This horizontal deflection appears to be too excessive IMO, even with a column height of 110 feet.

IF you're in the USA as I assume you are, then you have to work within the framework of the Federal Highway Administration and state guidelines, not just the AASHTO LFRD Bridge Design Manual. Also, you have to apply sound engineering judgement during the design process.

Q: What design force is producing this horizontal deflection value, seismic or wind?

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Guru

Join Date: May 2009
Location: Red Hook, New York (Mid-Hudson River Valley)
Posts: 4291
#3

### Re: Limit of the Horizontal Deflection for a Bridge Pier Design

04/03/2012 9:58 AM

You should read this Forensic Engineering report prepared by the NYSDOT regarding the failure of a pier for the Dunn Memorial Bridge that spans over the Hudson River between Albany and Rensselaer New York

https://www.dot.ny.gov/divisions/engineering/structures/repository/manuals/dunn_failure_report_10-05.pdf

You need to provide us with some additional details of this bridge. Is this a REAL bridge or a hypothetical one? Homework? Also, the type of bridge that this pier supports? Girder support types for this pier and adjacent piers? Is this horizontal deflection measured longitudinally or transversely in relation to the bridge span axis? Type of pier and configuration? Have thermal stresses and loads been included in the design calculations? How was the design loads and subsequent designs arrived at, by manual computation or computer analysis and design?

So far, you have not given us much to go on....

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Participant

Join Date: Apr 2012
Posts: 2
#5

### Re: Limit of the Horizontal Deflection for a Bridge Pier Design

04/03/2012 7:25 PM

Thank you for quick responses!

It is a real direct connection bridge in a big five levels interchange. Superstructure consists of several concrete I girder simple spans (110' to 120' span length) with elastomeric bearings. The bridge on a R=800 ft horizontal curve. Bridge width is 38 ft and each pier with two columns. Column size is between d=7' to 10'. Leap RC-Pier program was used to design and analysis. AASHTO LRFD was used. The deflections come from braking force, wind load and centrifugal force. P-delta method was used with a 0.4 reduced factor for moment of inertia. The outputs from the program look ok for the design. The top of column horizontal deflections are between 1" to 4" (85% in longitudinal direction) I cannot find in AASHTO talking about the limit for the deflections.

Guru

Join Date: May 2009
Location: Red Hook, New York (Mid-Hudson River Valley)
Posts: 4291
#4

### Re: Limit of the Horizontal Deflection for a Bridge Pier Design

04/03/2012 10:10 AM

Here's something for you written by the Wyoming DOT regarding the BRASS PIER (LRFD) program. It may be very useful for your design....

http://www.dot.state.wy.us/files/content/sites/wydot/files/shared/Bridge/BRASS/Pier%28LRFD%29%20V2.1.2%20Technical%20Manual.pdf

I cannot do the design for you....but I can sort of point you in the right direction.

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Anonymous Poster #1
#6

### Re: Limit of the Horizontal Deflection for a Bridge Pier Design

04/04/2012 6:36 PM

consider throwing your designs in the trash and starting over. the colomn is obviously under design.

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Anonymous Poster (1); Bridgema (1); CaptMoosie (3); Usbport (1)

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