lessons learned - bridge concepts (part 1 of 3) · directive from brian blanchard, assistant...

Lessons Learned - Bridge Concepts(Part 1 of 3)

Tom Andres P.E.

Assistant State Structures Design Engineer

This Presentation has been endorsed by FDOT Executive Management

FDOT

Directive From Brian Blanchard,Assistant Secretary for Engineering and Operationsto give this Presentation

Brian’s Statement:

The Department is leader in the use of the Design-Build method of project procurement. Reportedly we have done more projects since 1998 than the rest of the state agencies combined with nearly 500 projects totaling more than $13B. The program has been enormously successful but not without its challenges.

As we develop transportation projects to address the growing concern for congestion in our urban areas we are faced with some of the most difficult projects with the highest volume of traffic in highly constrained areas. These factors lead to complex designs which in turn have led to a growing concern regarding the departure, in some cases, from transparent designs, best practices and sound engineering that has historically made us successful.

I fully support this first of its kind presentation to share our concerns and frustration with our partners to improve the process. I know Tom’s presentation will come as no surprise to anyone involved with these significant structures. The department is concerned with the trend we are seeing and ask that each and everyone involved in the design of our infrastructure have the department’s goal in mind to provide safe and efficient facilities for the traveling public.I fully support this effort and ask that you designers join in supporting our goals.

Brian Blanchard

Lessons Learned - Bridge ConceptsGeneral Trends – Design-Build Process

Bridge Design Innovation/

Efficiency-Cost Managing Measures

ProjectCosts

Design ComplexityAnd Depth of

Required Design Calculations

Lessons Learned - Bridge Concepts

Design-Build:The Tendency is to Sharpen Designs to a Razors Edge –Resulting in Less Structural Reserve Capacity

- COST SAVINGS MEASURES-

Lessons Learned -Bridge ConceptsDesign-Build:Trend Towards More Complexity to save a Buck

“Intent of Code Compliance” and “Good Engineering” when Code and Contract (SDG etc.) do not directly address an issue.

Lessons Learned -Bridge ConceptsDesign-Build:Cutting Corners to Save a Buck

VS

Developing an Innovative Comprehensive Design Solution that saves Millions of Dollars

Cutting Corners Vs Innovative Comprehensive Design Solutions

Lessons Learned -Bridge ConceptsDesign-Build:

- Designer Allegiance has Changed.

- The Black Hat - Hot Potato Game.

Lessons Learned -Bridge ConceptsDesign-Build:

- Designer Allegiance has Changed.

- The Black Hat - Hot Potato Game.

FDOT

Independent Peer Review of Category 2 Bridges

The peer review is intended to be a comprehensive, thorough independent verification of the original work. An independent peer review is not simply a check of the EOR’s plans and calculations; it is an independent verification of the design using different programs and independent processes than what was used by the EOR.

Independent Peer Review of Category 2 Bridges

Going forward, we are considering that for design-build Category 2 component reviews, that the Peer Reviewer be given access to the Department’s ERC comments and that the Certification Letter(s) include a statement that the Department’s ERC comments have been accounted for in the independent assessment.

The Most Important Step in a

Successful Bridge Design is

Developing the Bridge Concept

Lessons Learned - Bridge ConceptsCase Studies

Design Complexity – C-Pier/ Footing Connection ①

①Design-Build Detail Traditional Transparent

REF: Standard Plans Instructions

Index 462-000 Series


① Design-Build Detail


①

REF: Standard Plans Instructions

Index 462-000 Series

Steel Curved Ramp Slab Thickness ②

②

13’-0”Typ. 8

½ “

Dec

k

Steel Curved Ramp Slab Thickness ②

②

Wide Two Box Curved

Ramp w/ Substringer

Deck System③

③

59’

26’

Wide Two Box Curved Ramp w/ Substringer

Deck System③

During Deck Pour, Screed Rails Raise Up as Boxes Rotate Inward Due to Unbalanced Section

③

Wide Two Box Curved Ramp w/ Substringer

Deck System③

③ 59’

26’

If Shear Connection, Potential Cracking at Cope Radius

Is Redundancy Factor of 1.2 Adequate?

Existing Pier

Pier Reconfiguration Case Study ④

④

Existing Bearing Typ.

New Footing ExtensionAnd Pier

OPTION 1: MOVE PIER


New Steel Straddle PierCap

OPTION 2: CONSTRUCT NEW STEEL STRADDLE PIER CAP

Existing Steel Boxes and Ramp to Remain

Existing Hammerhead Pier to be Removed

StiffnessComparison


Steel SIP Box Form w/ PT’ed ConcreteStraddle PierCap Infill

OPTION 3: CONSTRUCT NEW CONCRETE STRADDLE PIER CAP INSIDE

SIP STEEL BOX FORM DESIGNED FOR TEMPORARY CONDITION ONLY

Existing Steel Boxes and Ramp to Remain

Existing Hammerhead Pier to be Removed

StiffnessComparison


OPTION 3: CONSTRUCT STEEL SIP FORM w/ NEW CONCRETE

STRADDLE PIER CAP

OPTION 2: CONSTRUCT NEW STEEL STRADDLE PIER CAP

OPTION 1: MOVE PIER

Would Require Major Strengthening of the SuperstructureChanges the Boundary Conditions of the Unit Due to the Change in Support Location

Would Require Major Strengthening of the SuperstructureChanges the Boundary Conditions of the Unit Due to the More flexible Cap Element

Would Likely Not Require Major Strengthening of the Superstructure Does Not Appreciably Changes the Boundary Conditions of the UnitPost-tensioning of Cap for both Strength and Clamping ForceSelect a PT Profile that Balances the LoadsProvide Shear Connectors at Existing Box/Cap Interface


Pier Reconfiguration Case Study ⑤

⑤ Existing Ramp

At-Grade Roadway

New RampWidening


Existing Ramp

At-Grade Roadway

New RampWidening

OPTION 1: CONSTRUCT NEW FRAMED STEEL STRADDLE

PIER CAP TO SUPPORT WIDENING


Existing Ramp

At-Grade Roadway

New RampWidening

K1(hard)

K1K1K1K2(soft)

K3(soft)

Concern is overstressing existing girder



Concern is overstressing deck


Existing RampNew RampWidening

Other Potential Challenges:

Hammerhead cap strengthening to resist couple;

Through-bolt:- conflicts with stirrups;- local bearing loads;- bearing load distribution and

concern with interface surface softening over time;

Dual girder straddle cap to pier column moment connection details and execution

Load distribution across widening interface associated with temperature gradients of straddle cap.





OPTION 2: CONSTRUCT NEW NON-INTEGRAL NON-FRAMED

STEEL STRADDLE PIER CAP

NewColumn Cap

New Dual Steel Girder Cap



NewColumn Cap






NewColumn Cap


4’ BearingSpacing

Longitudinal Loads

Cap overturning due loading as well eccentric loads due to cap twisting and bending from thermal gradients, fabrication tolerances, bearing placement tolerance, dynamic affects etc.




OPTION 3: CONSTRUCT NEW CONCRETE STRADDLE PIER CAP


New Concrete Post-Tensioned

Cap

New bearing

Shear Studs

Typ.

PT Tendons Typ.

OPTION 3: CONSTRUCT NEW CONCRETE STRADDLE PIER CAP

INSIDE SIP STEEL BOX FORM DESIGNED FOR TEMPORAY

CONDITION ONLY

OPTION 2: CONSTRUCT NEW NON-INTEGRAL STEEL STRADDLE

PIER CAP

OPTION 1: CONSTRUCT STEEL I-GIRDERS STRADDLE


Stiffness differences between the existing fairly stiff cap carrying the existing girders and the fairly flexible steel cap carrying the widening would require more loads to be shed to the existing girders overstressing them.

Would Require Major Strengthening of the Existing SuperstructureChanges the Boundary Conditions of the Unit Due to the More flexible Cap Element

Would Likely Not Require Major Strengthening of the Superstructure Does Not Appreciably Changes the Boundary Conditions.


Two Ramp Straddle Pier ⑥

⑥

Steel Box Straddle Pier


⑥

Transmitting Compression

due to Flexure

CONCEPT


⑥

lessons learned - bridge concepts (part 1 of 3) · directive from brian blanchard, assistant...

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