SUNSHINE SKYWAY BRIDGE Retrofit of the Post-Tensioned Precast Transition Pier Columns on the Sunshine Skyway Bridge Presented by: Antonio Ledesma, P.E. May 7, 2012
SUNSHINE SKYWAY BRIDGE, FLORIDA
Presentation Outline 1. INTRODUCTION 2. SKYWAY STRUCTURAL SYSTEM 3. SKYWAY CONSTRUCTION METHODS 4. PREVIOUS REHABILITATION OF HIGH-LEVEL APPROACH COLUMNS 5. PRECAST SEGMENTAL TRANSITION PIERS 6. REPAIR OPTIONS 7. CONSTRUCTION
Introduction The Sunshine Skyway Bridge is located on the west central coast of Florida. Part of I-275 linking Tampa/St. Petersburg to Bradenton/Sarasota across Tampa Bay. In May 1980, a major ship impact caused the collapse of the southbound main span. Sunshine Skyway Bridge St. Petersburg
Sunshine Skyway Bridge NORTH LOW LEVEL TRESTLE SPANS (4283 ) NORTH HIGH LEVEL APPROACH (2430 ) MAIN SPAN (4000 ) SOUTH HIGH LEVEL APPROACH (2430 ) SOUTH LOW LEVEL TRESTLE SPANS (8738 ) Total Bridge length: 4.14 miles
High Level Approaches and Main Span Unit
Structural System High Level Approaches HIGH LEVEL APPROACH HIGH LEVEL APPROACH Total length: 4,860 ft Post-Tensioned Precast Segmental Box Girders (Span-by-Span) Post-Tensioned Precast Segmental Columns
Structural System Main Span Unit MAIN SPAN UNIT Total length: 4,000 ft Post-Tensioned Precast Segmental Box (Balanced Cantilever)
Precast Segmental Substructure Bearing pad PT anchorage Column cap Transition point External Tendon Segment joint (typ) Internal tendon Precast footing shell Grout pad Cast-in-place concrete Precast concrete strut Tremie seal concrete
Previous Rehabilitation of Approach Piers PE Duct Couplers Poor detail of vertical tendon couplers
Column 133 NB SE Tendon September 2000 Corroded strands in the zone of 2 ft below the column cap (11 out of 17 0.5 strands were failed)
Failed strands as a result of severe corrosion
Previous Rehabilitation of Approach Piers
Previous Rehabilitation of Approach Piers
Previous Rehabilitation of Approach Piers Core holes in footing and grout PT bars in place Top of Footing Place reinforcing
Previous Rehabilitation of Approach Piers Concrete pumped from top of deck Placing concrete inside column
Transition Piers Between HLA and Main Unit
Transition Piers 106 (6 S) and 117 (6 N)
Expansion Joint Segment at Transition Pier
As-Built Transition Columns Tie-Down Tendons Hollow Columns Filled with Concrete for Vessel Impact
Transition Pier Analysis Do we need to repair the transition pier columns? How to repair columns with concrete already placed inside segments? What is the purpose of the tie-down tendons Vessel Impact Load Case Hurricane Wind Load Case Impact of vessel impact risk analysis Repair options
Transition Column Inspection Column 117 SB Top view of interior column
Transition Column Inspection Column 106 SB Poorly done duct couplers
Transition Column Inspection Column 117 SB
Transition Column Inspection Column 117 NB Tendon T4 E (spiral cracked duct)
Transition Column Inspection Column 106 SB Cracked PE duct in 6 gap beween top of pier cap and transition segment
Transition Column Inspection Column 117 SB View at column transition point
Transition Column Inspection Column 117 SB Void
Transition Column Inspection Column 117 SB View of T1 W (cracked duct and void)
Purpose of Tie-Down Tendons 4 looped tendons (8 vertical tendons) 2-17x0.5 Tendons extend into superstructure EOR used tie-down tendons for vessel impact and hurricane wind analysis 2 4 2 Tie-Down Tendons
EOR Original Design Scenario 2100 k 1900 k Vessel Impact Load - 4000k Design Load Pier cannot withstand full force; inelastic scenario was used to satisfy requirement
Vessel Impact Risk Analysis 3*LOA = 2310 ft CL Channel Limit analysis to 3*LOA limit as specified in AASHTO (piers outside of limit are designed for minimum vessel impact) 8 piers on either side of the channel
Aerial View of Sunshine Skyway Bridge First two piers are very well protected, eliminate from risk analysis Conservatively ignore protection of remaining piers
Vessel Impact Risk Analysis 1350 k 2000 k Transition Pier 4000 k Protected
Wind Load on Bridge Wind Pressure Service Level Ultimate Strength 80 psf 177 mph 250 mph 60 psf 153 mph 217 mph
Check Uplift at Bearings Service Level Wind (153 mph) No Uplift at Bearings Tie-Down Tendons Not Required M top Wind Ultimate Wind defined as 1.6 x Wind @ 80% of Ultimate Strength M u = 1.6 x Moment / 0.8 M top = 7725 kip-ft M base = 15125 kip-ft M base
Analysis Summary Proposed Vessel Collision Load = 2000 k Actual Column and Foundation Capacity = 2250 k Collapsed Column Scenario would not be required Tie-down tendons not required for vessel collision or hurricane wind load cases
Transition Pier Repair Potential Options for Lower Column Repair Option 1: Repair the columns from the inside (coring 55 deep concrete) Option 2: Repair the columns from the outside (using a cofferdam)
How do you repair the columns? Hollow Columns Filled with Concrete for Vessel Impact
Repair Option 1: Core Holes Inside Column Lower Column Repair: Core 5 φ holes through filled column and footing 28-1 ¾ φ unstressed PT bars Grout bars in place
Repair Option 2: Core Holes Outside Column 1 Concrete Shell 1 Concrete Shell Cofferdam
Repair Option 2: Core Holes Outside Column Steel Cofferdam (need split form for repair) Precast Dumb-Bell Precast Concrete Strut Precast Dumb-Bell And Steel Cofferdam During Construction
Repair Option 1 Chosen: Core Holes Inside Column Column Buttresses Upper Column: 24-1 ¾ φ Bars 5 φ Cored Holes Lower Column: 28-1 ¾ φ Bars
Upper Column Repair: Reinforced Column Buttresses Upper Column Repair: Core 5 φ holes through 2 thick lower segments and pier cap 4 column buttresses 24-1 ¾ φ unstressed PT bars
Upper Column Repair: Remove External Tendons Upper Column Repair: After column buttresses in place, strip external ducst, add anchorage plates to tendons and encapsulate in concrete to form an anchorage block Cut and remove external tendons Lower tendons to remain and will provide redundancy to lower column repair PT bars connecting pier cap to transition segment added at Department s request
Cost Estimate Option 1: Repair from inside (coring concrete) Estimated Total: $ 3 million Option 2: Repair from outside (w/ cofferdam) Estimated Total: $ 4 million Construction Time : 9 months to 12 months. Original Contract Amount: $2.2 million Original Construction Time: 1 year Unforseen conditions will increase total dollar amount and contract time.
Construction Photos Core Drill 5 diameter, 5 long steel tubing
Construction Photos Cleaning out core holes for lower column repair Core holes in thickened section For upper column buttress bars
Construction Photos Preparing and finishing column buttresses
Construction Photos Removal of external tendon ducts and addition of anchorage clamps
Removal of external PT tendon tie-down and installation of PT bar tiedown Construction Photos
Current Project Status 2 columns completed, 2 ongoing Estimated completion: Summer, 2012
Thank you. Contact: Antonio Ledesma, P.E. ledesma@pbworld.com