Condition of Prestressing of the Ft. Lauderdale- Hollywood Airport Deconstructed Segmental Bridges Luis M. Vargas Beiswenger Hoch and Associates

Tendon ducts Recent evidence of voids along duct tendons Tendon ducts of Bridge I-75/I-595 interchange are currently being repaired Tendons grouting is essential in PT durability  Protect the prestressing steel from intrusion of contaminants  Provide necessary bond of strands consistent with design assumptions

Forensic Inspection of Segmental Bridges FLL expansion program (Task 2)  Reconfigure interchange access to airport  Construction of 6 segmental bridges  Deconstruction of 3 existing segmental bridges -- First time in North America Provided a unique opportunity to examine the condition of the prestressing

Deconstructed Segmental Bridges Airport A K D

US-1 Airport D A K

Deconstructed Ramp D

Bridge Deconstruction Three precast concrete segmental curved bridges built in the Mid-80’s Bridge were erected in balanced cantilever with bonded internal tendons Bridge span arrangement D (7 spans): 87’ ’-123.5’ ’ ’-142.2’ A (9 spans): K (4 spans): Total precast segments: 250

Deconstructed Bridge

Condition of Prestressing of Deconstructed Bridges Objective: Assess the condition of prestressing of deconstructed bridges Methodology: Examine the bridge remains prestressing tendons anchorages

Precast Segmental Bridges in FDOT-D4 By the end of 2003 FDOT-D4 will have 36 bridges 86% (31) with internal tendon, 14% (5) with internal/external tendons FLL Deconstructed bridges are typical of medium span bridges with internal tendons First full scale precast segmental bridge whose remains are examined

Post-tensioning Characteristics Transverse tendons have flat metal ducts tendons with cement-water grout PT anchorage is 5” off segment face, with blockout at deck Transverse tendons are 42 ft. long – representative of two lane box girders Longitudinal tendons have round metal ducts tendons with cement-water grout Longitudinal PT is 176 ft. long, maximum

Transverse Tendons: Examination of Remains Saw cutting deck & Crushing of concrete allowed examination of transverse PT 29 segments had deck saw cut longitudinally (total 549 ft.) 156 tendons were severed (34% of Bridge D)

Ramp D: Transverse tendons 3-0.6” Strands

Transverse tendons surface corrosion due to exposure to environment

Transverse tendons inspection All transverse tendons examined were fully grouted Prestressing steel, anchors and ducts were in excellent condition No indication of any corrosion activity

Longitudinal Tendons: Examination of Remains Segments that were Saw-cut and Wire-cut permitted examination of longitudinal PT 123 precast segments examined (~50% of all segments);  Bridge D: 19 segments (22% of Bridge)  Bridge A: 60 segments (44% of Bridge)  Bridge K: 44 segments (100% of Bridge) Tendons 9-0.6” Strands

common in about 50% of top tendons: max ½” in size Bleed water lens

Top tendons fully grouted

Top tendon partially grouted

Fully grouted Partially grouted

Bottom tendons fully grouted

Void size in tendons Only voids in grout greater than ¾” were accounted for Voids < ¾” in size and fully encapsulated in grout were considered not to be detrimental to tendon protection

Results of longitudinal tendons inspection Bridge D Top tendons :  Endemic bleed water lens at top of duct—  ~60% of ducts exhibit 1/4” ~ 1/2” small void  Grout encapsulated tendon completely  35 voids (9.9%) out of 354 test locations Bottom tendons :  Tendons were fully grouted  0 voids in 124 test locations Overall voiding in ducts is 7.3% of tested locations No signs of corrosion

Results of longitudinal tendons inspected Bridge A Top tendons :  Endemic bleed water lens at top of duct—  ~50% of ducts exhibit 1/4” ~ 1/2” small void  Grout encapsulated tendon completely  79 voids (7.7%) out of 1020 test locations Bottom tendons :  Tendons were mostly fully grouted  18 voids (4.2%) out of 426 test locations Overall voiding in ducts is 6.7% of tested locations No signs of corrosion

Results of longitudinal tendons inspected Bridge K Top tendons :  Endemic bleed water lens at top of duct—  ~50% of ducts exhibit 1/4” ~ 1/2” small void  Grout encapsulated tendon completely  62 voids (9.2%), 672 test locations Bottom tendons :  Tendons were mostly fully grouted  18 voids (8.1%) out of 222 test locations Overall voiding in ducts is 8.9% of tested locations No signs of corrosion

Anchorages All anchors were found in good condition

Anchorages Tendon

Joints All joints found in good condition. During split, segments always fail at concrete section and never at epoxied joint.

Joints

Conclusions of Forensic Study These bridges are representative of medium span bridges Tendon protection (grouting) and PT hardware are representative of 1980’s technology Transverse tendons were found fully grouted Bleed water lens at upper side of top tendons appears to be endemic in these bridges Longitudinal tendon voiding is limited to 7.5% of all tested locations (2818 points-- top and bottom)