Design Memorandum



TO:                  All Design Section Staff

FROM:            Bijan Khaleghi
DATE:             December 6, 2007
SUBJECT:       LRFD General Notes - Pile Foundation


This design memorandum supersedes the Design Memorandum issued on September 17, 2002.

Recent communications with the WSDOT Geotechnical Services Branch have resulted in establishing the following procedure for pile foundation design and modification to LRFD General Notes:

The pile ultimate bearing resistance included in the General Notes shall be taken as the maximum factored pile loading from the applicable service, strength, and extreme-event limit states divided by the applicable resistance factor for pile bearing as specified in the geotechnical report.

A table of all pile loadings and tip elevations, and a pile layout shall be submitted to the geotechnical engineer for the project for review as soon as the foundation design is completed. The submittal to the project geotechnical engineer shall also include the factored service load per pier to check group settlement. The project geotechnical engineer needs to submit to bridge designer an overdrive estimate to be includes in the Bridge Special Provision for overdriving.


Background:

To be consistent with the requirements of the WSDOT Geotechnical Design Manual article 8.12.2.6.3, the Geotechnical Services Branch recommends that only pile ultimate bearing resistance shall be shown in the General Notes. The ultimate pile bearing resistance shall be taken as the maximum pile loading from the applicable service, strength and extreme-event limit states.

The designer shall submit a separate table showing all pile loadings and tip elevations, and pile layout plan view to the geotechnical engineer for the project prior to the completion of the project.

If you have any questions regarding these issues, please contact Chyuan-Shen Lee at 705-7441 or Bijan Khaleghi at 705-7181.

cc:   Mohammad Sheikhizadeh, Bridge Construction - 47354

       F. Posner, Bridge and Structures 47340



Example for GENERAL NOTES

Piles shall be driven to an Ultimate Bearing Resistance as follows:

Pier No.

Ultimate Bearing Resistance

1

==== tons

4

==== tons


 

Example for Pile Design Data Sheet

The following tables including pile foundation layout and loading shall be submitted to the geotechnical engineer for the project at the early stage of design for their review.

                   Factored Pile Loads (tons) *

 

 

Pier No.

Service-I Limit State

Strength Limit State

Extreme Event-I
Limit State

Ultimate
Bearing
Resistance
***

Compression **

Tension

Compression **

Tension

Compression **

Tension

1

====

====

====

====

====

====

====

2

====

====

====

====

====

====

====

3

====

====

====

====

====

====

====

4

====

====

====

====

====

====

====

* Values in this table are per pile and are the maximum values at the pier. If no piles go into uplift, enter 0.0 for uplift loading.

** Include loading due to downdrag but does not include the effect of loss of friction.

***Ultimate bearing resistance is the maximum factored compression load divided by the resistance factor.


 

Pile Foundation Data

Minimum/Estimated Tip Elevation

(ft)

Pier No.

Pile Size/

Type

Total Number
of Piles

Factored Service Load (tons per Pier)

Pile Spacing (ft)

Pile Cap Dimensions(ft)

Parallel To Centerline of Pier

Normal To Centerline of Pier

Length

(Parallel To Centerline of Pier)

Width

(Normal To Centerline of Pier)

Thickness

1

====

====

====

====

====

====

====

====

== / ==

2

====

====

====

====

====

====

====

====

== / ==

3

====

====

====

====

====

====

===

====

== / ==

4

====

====

====

====

====

====

====

====

== / ==