Reply to the discussion by Fellenius on “Comparison of Canadian Highway Bridge Design Code and AASHTO LRFD Bridge Design Specifications regarding pile design subject to negative skin friction”

2021 ◽  
pp. 1-1
Author(s):  
James R. Bartz ◽  
James A. Blatz
Keyword(s):  
Skin Friction ◽  
Highway Bridge ◽  
Design Code ◽  
Bridge Design ◽  
Negative Skin Friction ◽  
Design Specifications ◽  
Pile Design ◽  
Aashto Lrfd

Comparison of Canadian Highway Bridge Design Code and AASHTO LRFD Bridge Design Specifications regarding pile design subject to negative skin friction

2020 ◽  
Vol 57 (7) ◽  
pp. 1092-1098
Author(s):  
James R. Bartz ◽  
James A. Blatz
Keyword(s):  
Skin Friction ◽  
Drag Force ◽  
Limit State ◽  
Highway Bridge ◽  
Ultimate Limit State ◽  
Design Code ◽  
Bridge Design ◽  
Negative Skin Friction ◽  
Design Specifications ◽  
Aashto Lrfd

Negative skin friction acting on piles has long been included in the design of bridge foundations subject to ground settlement. However, currently there are inconsistencies in how negative skin friction and drag force are incorporated into the calculation of the geotechnical ultimate limit state (ULS), partly due to differences in the design codes. The latest editions of the Canadian Highway Bridge Design Code and AASHTO LRFD Bridge Design Specifications are compared with the analysis of a hypothetical steel H-pile, driven through a settling clay layer into a dense, nonsettling layer. The results show that foundation designs can be significantly more conservative and costly when adhering to the AASHTO code because this code includes the drag force in the geotechnical ULS. It is concluded that adhering to the CHBDC can result in a reduced foundation system by considering the actual force distribution in the pile.

Updating the AASHTO LRFD Movable Highway Bridge Design Specifications

2021 ◽  
Author(s):  
Jeffrey Newman ◽  
Kevin Johns ◽  
Thomas Murphy ◽  
Maria Lopez ◽  
Zolan Prucz ◽  
...  
Keyword(s):  
Highway Bridge ◽  
Bridge Design ◽  
Design Specifications ◽  
Aashto Lrfd

Live-Load Response of Alabama’s High-Performance Concrete Bridge

2003 ◽  
Vol 1845 (1) ◽  
pp. 115-124 ◽  
Author(s):  
Robert W. Barnes ◽  
J. Michael Stallings ◽  
Paul W. Porter
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Highway Bridges ◽  
Live Load ◽  
Bottom Flange ◽  
Actual Behavior ◽  
Bridge Design ◽  
Design Specifications ◽  
Special Procedure ◽  
Aashto Lrfd

Results are reported from live-load tests performed on Alabama’s high-performance concrete (HPC) showcase bridge. Load distribution factors, deflections, and stresses measured during the tests are compared with values calculated using the provisions of the AASHTO LRFD Bridge Design Specifications and AASHTO Standard Specifications for Highway Bridges. Measured dynamic amplification of load effects was approximately equal to or less than predicted by both specifications. Distribution factors from both specifications were found to be conservative. Deflections computed according to AASHTO LRFD Bridge Design Specifications suggestions matched best with the measured deflections — overestimating the maximum deflections by 20% or less. Bottom flange stresses computed with AASHTO distribution factors were significantly larger than measured values. AASHTO LRFD Bridge Design Specifications provisions suggest a special procedure for computing exterior girder distribution factors in bridges with diaphragms. When two or more lanes were loaded, this special procedure did not reflect the actual behavior of the bridge and resulted in very conservative distribution factors for exterior girders. Further research is recommended to correct this deficiency.

Equivalent area of voided slabs

1998 ◽  
Vol 25 (4) ◽  
pp. 797-801 ◽  
Author(s):  
Leslie G Jaeger ◽  
Baidar Bakht ◽  
Gamil Tadros
Keyword(s):  
Simple Expression ◽  
Technical Note ◽  
Axial Stiffness ◽  
Highway Bridge ◽  
Slab Thickness ◽  
Design Code ◽  
Bridge Design ◽  
Equivalent Thickness ◽  
Simple Alternative ◽  
Equivalent Area

In order to calculate prestress losses in the transverse prestressing of voided concrete slabs, it is sometimes convenient to estimate the thickness of an equivalent solid slab. The Ontario Highway Bridge Design Code, as well as the forthcoming Canadian Highway Bridge Design Code, specifies a simple expression for calculating this equivalent thickness. This expression is reviewed in this technical note, and a simple alternative expression, believed to be more accurate, is proposed, along with its derivation. It is shown that the equivalent solid slab thickness obtained from consideration of in-plane forces is also applicable to transverse shear deformations, provided that the usual approximations of elementary strength of materials are used in both cases.Key words: axial stiffness, equivalent area, shear deformation, transverse prestressing, voided slab, slab.

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