[GEORGE WASHINGTON BRIDGE MAJOR DECK REPLACEMENT PROJECT 1977-78]

[Music] [Music] the George Washington Bridge is the most heavily traveled bridge in the world since it was opened in 1931 over 1 b600 million vehicles have crossed it the Port Authority of New York and New Jersey was given the responsibility to plan develop and operate terminal and transportation facilities and to Advan projects that promote and protect the Commerce of the New York New Jersey Port District the George Washington Bridge provides a northern bypass Route Around Manhattan and is a vital Link in the metropolitan transportation system in an effort to El minate the increasing repairs to the existing bridge deck and the resulting inconvenience to motorists the Port Authority has undertaken a 37 million project to replace the upper level deck in 1931 the bridge carried six Lanes of traffic today's Bridge structure carries 14 Lanes of traffic eight on the upper level and six on the lower level approximately 80 million Vehicles cross the bridge each year maintaining service was the greatest challenge of the upper level deck replacement project the original Builders of the bridge anticipated the great influx of vehicular traffic the towers cables and other primary members were designed to attain the full ultimate carrying capability of the bridge in order to replace the upper level deck Port Authority Engineers had to pay particular attention to the structural design of the bridge film taken during the original construction shows some of the daring skills required of the steel workers although today's safety precautions have eliminated many of these hazards the method of constructing suspension bridges has remained essentially the same after erecting the towers and spinning the cables the structure was ready for the roadway floor system to be installed a coordinated effort between workmen on the structure and on barges in the Hudson River was necessary to install these main floor beams the Expansion Joints of the roadway slabs correspond to the 60t spacing the suspender ropes and the main floor beams this segmented construction is the key to a deck replacement plan that keeps all lanes open to traffic during rush hours the existing deck is an 8 and 1/2 in thick reinforced concrete slab with a 3/4 in Asphalt itic surface the main reinforcement consists of 6in bulb T's 15 in on Center riveted to the top flanges of the secondary floor beam top reinforcement is the grid of 1/2 in diameter reinforcing bars for 46 years the reinforced concrete deck on the upper level has with stood not only the Incredible volume of traffic but also the effects of weather deicing sauce tire chains and studded snow tires since 1961 when the first major repairs were made an estimated 50% of the upper level deck has either been patched or completely replaced the rate of deterioration almost doubled in the 70s and by 1976 the annual repair cost averaged $500,000 consequently early in the 1970s studies made of the deck's condition concluded that full deck replacement was warranted [Music] accordingly the following criteria were established for this program the new deck must have an improved wearing surface it must be long lasting and require as little maintenance as possible the new deck must provide a minimum service life of 20 years all work must be completed within a 2-year construction period use of all 14 Bridge Lanes must be provided during Peak traffic hours and during off peak hours a minimum of 10 traffic Lanes must be provided four on the upper level and six on the lower level opposing traffic flows must be separated by a median barrier in May of 1974 the Port Authority launched a full scale test program to evaluate the most promising full deck replacement alternative in it a 60x 44t section of the main span of the upper level deck was to be removed and replaced with various pre fabricated orthotropic steel panels during the removal operations a major finding of the deck studies was verified a delamination in the concrete along the top of the buob teas was clearly visible the orthotropic panels basically consisted of flat thin steel plates stiffened underneath by longitudinal ribs after the panels were installed different asphaltic wiring courses were to be applied a subsequent test program was initiated by Port Authority Engineers to determine if the steel panels could be preped the success of both test programs culminated in the final design of a prepa orthotropic module which could be installed in one night each module is designed to replace 160x 44t Bay of the existing deck adjacent bays are not Disturbed during the replacement process this concept is feasible because the deck was constructed in segments to allow for movement in the bridge and differential expansion and contraction of the [Music] steel pre-formed neoprene compression seals are used to seal joints between modules along the curb and along the median barrier each module is comprised of four 60t long orthotropic panels which are separately installed and feel bolted together along three longitudinal joints each orthotropic panel consists of a paved 5/8 in thick deck plat stiffened by 7in T's the te's are welded to the deck plate at 15 in on Center where adjacent panels meet 7in angles are welded to the edge of each panel so that they can be bolted back to back strap plates 8 in wide and 1/2 in thick are welded to the underside of the tee flanges at the existing secondary floor beam locations these strap plates have oversized holes 1 1/2 in in diameter to ensure a matchup of a bolted connector with the existing 3/4 in diameter rivet holes of the secondary floor beams the fabrication phase of the replacement project begins at the plant of Carl cotch erecting company in Carterette New Jersey kotch has the $18.5 million contract for fabrication and installation of the new deck fabrication began in early March 1977 with completion in August of 1978 the upper level deck over 400,000 s ft requires an approximate 9,000 tons of steel a588 weathering steel was selected because of its high strength and maintenance-free characteristics fabrication is organized in assembly line fashion with each particular phase taking place on a separate area of the [Music] shop first the 5/8 in thick plate is lifted into position with a device called a vacuum pad the vacuum pad has 12 36-in circular vacuum pads capable of lifting 20 tons the contractor designed and constructed this apparatus especially for this job it enables him to individually lift a nton deck plate from the top of a stack without requiring a chocked space between plates for change of straps the orthotropic design did not permit holes in the deck plate [Music] next the ribs are placed on top of the deck plate so that the panel can be pulled by winch along the rails to a jig the contractor decided to fabricate the panel separately on single panel jigs in order to meet the strict tolerances tolerances were specified for overall dimensions and squareness of each four panel module as well as for plate flatness and straightness of the ribs in order to facilitate welding the Tails were designed to permit complete Fabrication in an upside down position the ribs are tack welded to the deck plate as the panel is pulled through the jig panels are then moved to an automatic welding machine this machine helps the contractor accomplish the nearly 200 mil of welding required for this project after the panel is hydraulically secured into position workmen align the heads of the welding apparatus the welding machine then mov moves over the panel along a track at 44 in per minute it automatically feeds eight wires through four heads Each of which lays down a 1/4 thick fillet Weld and covers it with flux the machine also has an automatic flux Recovery Unit which vacuums up the flux and recycles [Music] it one of the less glamorous operations is hole punching for the thousands of holes that must be punched in the strap plates the contractor uses an automatic machine [Music] in the next stage of assembly the strap plates are placed in a position that matches the 5'2 in spacing of the Bridge's secondary floor beams the straps are then welded to the flanges of the teas using fillet [Music] Wells panels are then moved to the milling machine here a rotating 10-in diam cutting head with 20 tungsten carbide bits grinds down the edge of the panel as the entire machine moves down a track at 3 ft per minute the contractor selected Milling as the method to meet the tight tolerances along the longitudinal [Music] joints after Milling the panel is moved to the finishing section here a number of activities are performed first the ends of each panel must be burned off to bring it down to its 60t length [Music] next if the panel requires a drainage Inlet a cutout is made and a frame is welded on the inlets were designed to utilize the existing Bridge drainage system because flexible Pavements must be constrained along that perimeter to prevent flow 1 and 1/2 in end dams are called for along the curved median barrier and it Expansion Joints here here the contractor uses a self-propelled apparatus which lays down a 3/8 in fillet weld along one of the longitudinal end dams after the panels have been inspected they are trucked Outdoors to a Paving jig The Jig is 6 1/2 ft above the ground and approximately 70 ft wide by 175 ft long The Jig can accommodate four modules of four panels each a total of 16 panels the bed of The Jig is designed to simulate the inplace support conditions of the bridge in order to ensure that all panels are within tolerance and to check bolt hole alignment prior to installation contractor uses a variety of balance beam hookups to lift the panels depending on the stage of construction during each lift predetermined values for deflection of the panel cannot be exceeded the steel surface is abrasive blasted with a machine called a wheel abater this machine bombards the steel surface with recycled metal shot to remove any far material which might inhibit the bond and to roughen the steel surface to increase the bond if the pavement is to adhere to the steel deck during handling installation and throughout its service life is essential to create a strong bond between it and the steel deck hand sand blasting methods are used along the side bands shortly after the panels or abrasive blasted a distributed truck sprays a hot asphalt cement tack coat on the steel surface this tack code is applied at approximately a tenth of a gallon per square yard and acts as a glue between the steel and pavement the results of the test programs were instrumental in the choice of a specially designed 1 and 1/2 in thick asphalt concrete pavement asphalt concrete is a widely available lowcost material with good wearing characteristics and is easy to maintain modifications were made to the standard asphalt concrete mixture to reduce the void content and to increase its plasticity the reduction in void content protects the Integrity of the underlying steel deck by making the pavement more impervious to water and chemicals The increased plasticity gives the pavement added flexibility to accommodate both the deflection the panels undergo during handling and changes in panel Dimensions which occur during temperature variations two 10-ton rollers were used to compact the pavement a three-wheel roller was used for breakdown and initial compaction and the tandem roller was used for smoothing and final [Music] compaction after a 12-hour cooling off period the pavement is ready to be saw cut over the longitudinal steel joints of each panel a cut is made with a double-bladed saw cutting machine that runs along a channelized track after the cut is made it must be routed out so that the panels can be separated the resulting 3/4 in gap will eventually be filled in with a cold tar epoxy mortar material after the panels have been installed the entire fabrication and Paving operation for one four panel module has taken approximately 2 days since fabrication runs well ahead of installation the contractor stores the panels in his yard until the day they are due to be installed each panel is then individually trucked to a waiting area at the bridge installation of modules is essentially divided into two routine day and night work sequences day work is performed during off peak hours from 10:00 a.m. to 3:00 [Music] p.m. after Port Authority Personnel Clos two lower level traffic Lanes these vehicles used for debris removal and scaffold relocation proed to the job [Music] site day work revolves around a series of five Bays of scaffolding suspended beneath the upper level deck the scaffolding consists of Steel decking welded to a steel frame here laborers on top of the scaffolding shovel debris from the previous night's deck demolition into a truck for removal each day one Bay of scaffolding is has moved to a new location to do this the contractor equipped a truck bed with hydraulic lifts capable of lowering and raising sections of scaffolding into new positions the scaffolding serves as both a work platform and as an enclosure to protect the lower roadway from debris the scaffolding is designed to withstand the impact of a 100lb weight drop 6 ft hanger clamps are used to fasten and unfasten the scaffolds to the existing Bridge [Music] framing workers on top of one of the Bays of scaffolding ready the underside of an existing slab for removal and replacement their objective is to completely free the Bay from the secondary floor beams to do this riveted connections between the bul beams and the slab and the secondary floor beams are broken with the two-man rivet [Music] Buster meanwhile in another Bay workers are busy installing and tightening the remaining bolts of last night's orthotropic module installation tightening of the high strength bolts is checked with a torque wrench by far the most fascinating aspect of this project is the nightly activities required to install the new deck construction was planned so that eastbound Lanes would be installed in 1977 and Westbound Lanes in 1978 it was essential to the 2-year construction schedule that at least 160x 44t Bay be replaced during each night's 10 hour our work Shi to do this all four lanes in the roadway being replaced had to be closed to safely accommodate a nighttime two-way traffic flow on the remaining roadway a New Jersey type median barrier was installed at the start of each construction season 30ft long concrete sections were installed on plastic foam bedding and since no anchoring holes were permitted in the new bridge deck the sections were interconnected to fully develop their dead weight resistance to vehicle impacts the barrier once installed remained in place for the entire construction season separating the opposing Lanes of traffic during nighttime work hours re-rooting of traffic requires a coordinated effort between Port Authority personnel and the contractor's work Crews the object is to safely interrupt the flow of traffic and to redirect it from the roadway being replaced while Port Authority police momentarily stop traffic a work crew moves barricades to divert eastbound motorists into the westbound roadway for the two-way traffic operation this bypass will be kept operational throughout the 10hour work shift through use of strategically placed traffic control [Music] signals once the bypass is operational the traffic is then led by control vehicles through the barricade configuration in about 20 minutes a full two-way operation is underway the concept for the actual deck replacement involved four work phases while the contractor varied sizes of units the basic concept remained in effect first each existing roadway Lane will be saw cut and jackhammered into manageable sections eight sections are shown here the contractor elected to use only two per Lane next the brakes and the slab were covered with joint plates bolted in place and designed to support traffic across the deck slab the the following night deck sections would be removed if for some reason an entire Lane was not removed prep paved temporary deck plates would be dropped into the gaps in the deck finally when all sections of a lane were removed a new orthotropic panel would be installed by 8:00 each night fully mobilized Crews begin their tasks once at the site laborers must remove volted roadway plates from three longitudinal saw cuts and from trenching alongside the Cur curb and median barrier they also remove a black top patch from a 6-in wide saw cut trench which divides the 60ft bay into 20x 40t lengths saw cutting and trenching was performed the night before to speed up the removal of the existing deck these Cuts divide the bay into eight sections 4 11t x 20t sections and 4 11t x 40t [Music] sections a 125 ton crane with the 90t Boom is then set into a predetermined position replacement of a single Bay does not require crane repositioning because of the Crane's weight special shoes are attached to the Outriggers to distribute the load safely to the bridge deck what seems at sometimes to be utter chaos is actually well orchestrated use of various trades each activity is planned to allow for maximum utilization of men and machines in the limited time and space available to remove the eight sections of deck workers must first burn through all of the reinforcing steel exposed in the jackhammered trenches they must also break out four lifting ports in each slab the portable scaffolding protects lower roadway traffic from [Music] debris while workmen are busy attaching the Crane's lifting apparatus other men on the scaffolding below try to Jack free the first 11x 20t slab once freed from the supportive steel the section of deck is easily loaded onto a truck for removal work Crews concentrate their efforts on removing 2 11x 20t slabs along an expansion joint these slabs must be removed first because the work required to install a new support chair at the expansion joint is time consuming the procedure used to remove the first concrete slab is repeated to remove the second 11x 20t slab even though the heads of the rivets have been removed beforehand a considerable amount of force is still required to release the panels when the rivet Shanks the combination of tension exerted by the crane and the force applied during jacking are eventually enough to free the panel after these two small slabs of freed the steel must be thoroughly clean of all loose scale slag rust or any other delerious substance that might inhibit welding and later painting after cleaning the workers weld on a new support chair at the expansion [Music] joint at the other end of the work area the first of the 40ft slabs is ready to be removed although twice as heavy as the 20ft slabs handling is no real problem the use of the large capacity crane proved to be especially valuable during these operations permitting removal of large deck sections quickly and [Music] easily as the removal of these slabs progresses steel surfaces exposed for the first time in 46 years must be refinished the top flanges of the secondary floor beams are cleaned of rust and scale and coated with an epoxy paint for protection the expansion joint area is primed with red lead [Music] paint with the existing deck removed in two lanes and the supporting steel painted and inspected the first prefabricated panel is unloaded from a flatbed truck and set into position this panel is normally installed between 11:30 p.m. and midnight almost 4 hours after the start of the operation from this point on the pace increases as work proceeds simultaneously on the installation of new panels and the removal of the existing [Music] deck meanwhile two-way traffic is Flowing freely on the adjacent roadway unaffected by the heavy construction a second orthotropic panel is installed within minutes of the first lifting hooks are attached at the panel's fifth points to minimize deflection throughout the first Year's construction deflections were so tightly controlled that none of the 312 panels installed suffered pavement separation or other damage the lifting hooks are designed so that they can be easily slipped out from underneath when the second panel has been jacked into position against the first workers on the scaffolding begin bolting as the remaining two panels are being placed other crews are busy providing the final touches to some of the orthotropic panels already installed at the median barrier extra space was allowed to simplify installation of the last panel Workman now w a closure angle into place thus only a 3/4 in gap remains to be filled with a preformed neoprene compression seal [Music] on another portion of the new deck the longitudinal pavement joints must be filled after debris in the joint is routed out a masking tape is applied to the bottom of the joint to eliminate a stress inducing bond between the steel joint and the filler then after an epoxy tack cat is applied to the sides of the asphalt a colar epoxy mortar is hand Trel into the gap the success of this system is due primarily to the compatibility of the epoxy mortar with the asphalt concrete the last panel is usually set by 4:30 a.m. the work area is then cleaned up and the lanes reopen to traffic by 6:00 a.m. the success of the deck replacement of the George Washington Bridge offers a viable alternative to other replacement methods this project has demonstrated that heavily traveled roadways can be repl placed without inconveniencing the [Music] public for