Bridge Type Study DPcomments accepted...Bridge Replacement Type And Construction Impact Study...

BRIDGE REPLACEMENT TYPE AND

CONSTRUCTION IMPACT STUDY

Performed for the New York State Department of Transportation In Support of the

Draft Environmental Impact Statement For the Kosciuszko Bridge Project

Kings County and Queens County, NY

September 2006

DRAFT

Kosciuszko Bridge Project

New York State Department of Transportation

Kosciuszko Bridge Project 1 September 2006

A. INTRODUCTION

This study consists of two major topics: bridge concepts for replacing the Kosciuszko Bridge and an assessment of construction impacts on the local community and businesses.

The bridge type study discusses several alternatives considering design efficiency, construction ease and impact, traffic staging, and future maintenance. This report also proposes the most reasonable construction methods for new bridge structures.

The impact study contains the methods and procedures for dismantling the existing structures, including the steel truss superstructures, and the foundations. The study of new bridge construction includes adjusting column locations to avoid or minimize conflicts with existing buildings, roads and bridge foundations, and to determine the approximate dimensions of the foundations. It also includes a preliminary plan of the staging areas for temporary storage of precast segments and demolition debris. Finally, the construction schedules and the cost estimates for these alternatives are provided.

This study was performed using Alternatives BR-3 and BR-5 as the basis. Portions of these alternatives are applicable to the other alternatives. The eastbound Long Island Expressway (LIE)-bound bridge and Westbound Brooklyn Queens Expressway (BQE) bridges of Alternative BR-3 are similar to the new eastbound bridge of Alternative RA-5 and new westbound bridge of Alternative RA-6, respectively. The eastbound LIE-bound bridge of Alternative BR-3 and both the eastbound BQE-bound and westbound bridges of Alternative BR-5 are similar to bridges required for Alternative BR-2.

B. REPLACEMENT STUDY

B.1. Constraints

The replacement bridge must consider the following constraints:

Three roadways:

o 3-lanes eastbound for LIE-bound traffic (EB-3), o 2-lanes eastbound for BQE-bound traffic (EB-2), and o 4-lanes westbound (WB-4).

Each roadway consists of two to four 3.66 m (12 ft) wide traffic lanes, a 1.22 m (4 ft) left shoulder, and a 3.05 m (10 ft) right shoulder.

A 4 m (13 ft) wide bikeway/walkway is planned on the same level as the roadway deck. The main span must clear the 40 m (130 ft) wide by 27 m (90 ft) high navigation channel.

(Note: the existing 38 m (125 ft) vertical clearance is expected to be reduced.) Main span piers adjacent to Newtown Creek should be located on land to preclude

marine vessel impact. Where possible, the foundations for the new piers should not interfere with the existing

foundations. Although new piers should not be placed on existing roads, some local street re-

alignment is possible. Impact of construction on local businesses and residences should be minimized. Three lanes in each direction must be maintained at all times during construction.

Bridge Replacement Type And Construction Impact Study


B.2. Roadway Configurations

The first two bridges built parallel to the existing bridge must carry at least three 12 ft lanes of traffic. Lane configurations during and after construction are shown in Figure 1 for Alternatives BR-3 and BR-5.

For Alternative BR-3 the most efficient and cost effective construction method would be to build the first two bridges (EB-3 and WB-4) with their final roadway arrangement. However, constructing the WB bridge in this manner would require extending the bridge over the cemetery. Because this is unacceptable, WB-4 would be constructed in two stages. EB-3 would be erected first, and then, after the demolition of the existing bridge, the remaining 2-lane bridge EB-2 and the remaining portion of WB-4 would be erected.

For Alternative BR-5 the EB-3 and EB-2 would be constructed first, with WB-4 constructed after demolition of the existing bridge. Minor re-striping will be necessary to convert the temporary westbound roadway to its final EB-2 configuration.

For both Alternatives BR-3 and BR-5, the most efficient and cost effective construction would result in three independent structures. The advantage of separating the structures is that no additional stages for closure pours are necessary. Furthermore, it eliminates construction cold joints which have the potential to leak and avoids the need for a temporary barrier.

B.3. Approach Span Bridge Types

There are a number of bridge types that would be appropriate at the site. Both short and long span options are considered, with either a steel or concrete superstructure.

B.3.a. Short span option

Typical approach spans are 46 m (150 ft) or less. For a 46 m (150 ft) straight girder span, as shown in Figure 2, the roadway curvature causes a variation in the deck overhang at the fascia girders of 0.884 m (2.9 ft) for the tightest radius of 533 m (1,750 ft).

This means that for such spans the girders can be straight with a constant spacing. Also span by span segmental construction (erecting a full span of segments from an overhead launching gantry) can be used. The alignment offset is modest and the 46 m (150 ft) span is a usual span for this type of construction. It may be possible to use a gantry fabricated for another project, as opposed to custom building a new gantry. For this option the main piers can be V-shaped in order to decrease the main span length while keeping the foundations on land (see Figure 3).

STEEL GIRDER BRIDGE WITH COMPOSITE CONCRETE DECK (GIRDER ERECTION)

Each bridge is continuous over 23 spans ranging from 41 m (135 ft) to 82 m (270 ft) (see Figure 3) and consists of 4 to 6 I-girders supporting a reinforced concrete slab acting compositely. The slab can either be precast or cast in place.

The girders are lifted into place from ground level using a crane at each end. For the main span, the girders would have to be steel due to the length of the main span but could be precast concrete girders for the typical spans. This requires a 30 m (100 ft) wide construction area parallel and adjacent to the bridge for crane installation and trucks. This would result in a



number of impacts to local streets and private property as shown in Figure 4. Table 1 lists the roadways and properties that would be closed and vacated as each span is erected. For Alternative BR-3, the final bridge is located between the first two bridges constructed (EB-3 and WB-4), and construction of the final bridge (EB-2) would require short-term closure of one or both of the operating BQE bridges while girders are lifted into place.

TABLE 1: CONSTRUCTION CONFLICTS WITH EXISTING LAND USE – STEEL PLATE GIRDER (SHORT SPAN OPTION)

Physical Conflict Crane Position East Side West Side

A1 Close Anthony Street Close Thomas Street Mid Span Close Anthony Street Close Thomas Street P1 Close Anthony Street Close Thomas Street Mid Span Close Anthony Street Close Thomas Street P2 Close Anthony Street Close Thomas Street and Stewart Street Mid Span Close Anthony Street and Stewart Avenue Close Thomas Street and Stewart Street

P3 Close Anthony Street Conflict with building at Lot 2814-6

Close Thomas Street Conflict with building at Lot 2207-05

Mid Span Conflict with buildings at Lots 2824-6, 2824-10. Close Thomas Street Conflict with building at Lot 2207-10

P4 Conflict with buildings at Lots 2824-10, 2824-18. Close Thomas Street Conflict with building at Lot 2207-10

Mid Span Close Gardner Avenue Conflict with building at Lots 2814-18, 2815-3.


P5 Close Gardner Avenue Conflict with building at Lots 2814-10, 2814-18.


Mid Span Close Gardner Avenue Conflict with building at Lot 2815-3. Close Thomas Street and Gardner Avenue

P6 Close Cherry Street Close Thomas Street and Gardner Avenue Mid Span Close Cherry Street Close Thomas Street

P7 Close Cherry Street Close Thomas Street Conflict with building at Lot 2802-1

Mid Span Close Cherry Street Close Thomas Street Conflict with building at Lot 2802-1

P8 Close Cherry Street and Scott Avenue Close Thomas Street Conflict with building at Lot 2802-1

Mid Span Close Scott Avenue Close Thomas Street Conflict with building at Lot 2802-1

P9 Close Thomas Street Conflict with building at Lot 2809-01

Close Townsend Avenue and Scott Avenue Conflict with building at Lot 2802-1

Mid Span Close Thomas Street Conflict with building at Lot 2809-01 Close Scott Avenue and Townsend Street

P10 Close Cherry Street Close Townsend Street Conflict with building 2799-1

Creek P11 Stop LIRR service Mid Span Stop LIRR service Stop LIRR service P12 Stop LIRR service. Mid Span P13 Close Laurel Hill Boulevard and 56 Road Mid Span Close Laurel Hill Boulevard P14 Close 56th Road Close Laurel Hill Boulevard



Physical Conflict Crane Position East Side West Side

Mid Span Close Laurel Hill Boulevard

P15 Close Laurel Hill Boulevard Interfere with Calvary Cemetery

Mid Span Close Laurel Hill Boulevard Interfere with Calvary Cemetery

P16 Conflict with buildings at Lots 2519-29, 2519-35 Close Laurel Hill Boulevard Interfere with Calvary Cemetery

Mid Span Conflict with buildings at Lots 2519-29, 2519-35 Close Laurel Hill Boulevard Interfere with Calvary Cemetery

P17 Conflict with buildings at Lots 2519-29, 2519-35, 2519-34

Close Laurel Hill Boulevard Interfere with Calvary Cemetery

Mid Span Close 55th Avenue Close Laurel Hill Boulevard Interfere with Calvary Cemetery

P18 Close 55th Avenue and 43rd Street Close Laurel Hill Boulevard Interfere with Calvary Cemetery

Mid Span Close 43rd Street Conflict with building at Lot 2517-25


P19 Close 54th Drive and 43rd Street Conflict with building at Lot 2517-25


Mid Span Close 54th Drive and 43rd Street Close Laurel Hill Boulevard Interfere with Calvary Cemetery

P20 Close 43rd Street Conflict with buildings at Lots 2516-13, 2516-28


Mid Span Close 43rd Street Conflict with buildings at Lots 2516-13


P21 Close 54th Road and 43rd Street Conflict with building at Lot 2515-28


Mid Span Close 43rd Street Conflict with building at Lot 2515-25


P22 Close 43rd Street Conflict with building at Lot 2515-22


Mid Span Close 43rd Street and 54th Ave Close Laurel Hill Boulevard and 54th Avenue Interfere with Calvary Cemetery

A2 Close 54th Avenue Close Laurel Hill Boulevard and 54th Avenue Interfere with Calvary Cemetery

CONCRETE SEGMENTAL BRIDGE (SPAN-BY-SPAN CONSTRUCTION)

Each bridge is continuous over 23 spans with the same span arrangement as the steel girder option, ranging from 41 m (105 ft) to 82 m (270 ft) and consists of a single precast post-tensioned concrete box girder. For the typical spans the segments are erected on a self-launching, span-by-span gantry and are delivered from the completed portion of the deck. For the main span the segments are erected with the balanced cantilever method using a crane on the completed portion of the deck with the segments supplied from the deck. This minimizes construction impact on the ground. Alternatively, a steel main span could be lifted in one piece from the channel.

B.3.b. Long span option

Typical approach spans are 61 m (200 ft) or more. For a 61 m (200 ft) span, the alignment offset from the span chord is 0.884 m (2.9 ft) for the tightest radius of 533 m (1,750 ft). For 76 m (250 ft) it would be 1.372 m (4.5 ft), which would require an excessive cantilever for the deck, therefore curved girders are required. Also span-by-span segmental construction would not be



possible due to the span length and curvature. The superstructure would either consist of curved steel box girders with a concrete deck or precast segmental concrete box girders erected in the balanced cantilever method (see Figure 5).

STEEL BOX GIRDER BRIDGE WITH COMPOSITE CONCRETE DECK (GIRDER ERECTION)

Each bridge is continuous over 15 spans ranging from 30 m (100 ft) to 122 m (400 ft) and consists of two or three steel box girders supporting a reinforced concrete slab acting compositely. The slab can either be precast or cast in place. The width of each girder is limited to about 4.6 m (15 ft) for transportation.

As shown in Figure 4, the girders are erected in two elements: a hammerhead over the pier and a central portion connecting to the hammerhead of the previous pier. All segments are lifted into place from ground level using a crane at each end. This requires a 30 m (100 ft) wide construction area parallel and adjacent to the bridge for crane installation and trucks. This would result in a number of impacts to local streets and private property as shown in Figure 6. Table 2 lists the roadways and properties that would be closed and vacated as each span is erected. For Alternative BR-3, the final bridge is located between the first two bridges constructed (EB-3 and WB-4), and construction of the final bridge (EB-2) would require short-term closure of one or both of the operating BQE bridges while girders are lifted into place.

A solution with V-shaped main piers is also possible in order to decrease the maximum length of the girders to 91 m (300 ft).

TABLE 2: CONSTRUCTION CONFLICTS WITH EXISTING LAND USE – STEEL BOX GIRDER (LONG SPAN OPTION)

Physical Conflicts Crane Position East Side West Side

A1 Close Anthony Street Close Thomas Street MID SPAN Close Anthony Street Close Thomas Street P1 Close Anthony Street Close Thomas Street MID SPAN Close Anthony Street Close Thomas Street

P2 Close Stewart Avenue and Anthony Street Conflict with building at Lot 2814-6

Close Thomas Street and Stewart Street Conflict with building at Lot 2207-05

MID SPAN Conflict with buildings at Lots 2814-6, 2814-10

Close Thomas Street Conflict with buildings at Lots 2207-05, 2207-10

P3 Conflict with buildings at Lots 2814-10, 2814-18.


MID SPAN Close Gardner Avenue Conflict with buildings 2814-18 and 2815-3 Close Gardner Avenue and Thomas Street

P4 Close Thomas Street and Gardner Avenue Conflict with building at Lot 2802-1

MID SPAN Close Cherry Street Conflict with building at Lot 2802-1

P5 Close Scott Avenue Conflict with building at Lot 2809-01

Close Townsend Street Conflict with building at Lot 2802-1

MID SPAN Conflict with building at Lot 2809-01 Close Scott Avenue and Townsend Street

P6 Close Thomas Street. Close Townsend Street Conflict with building at Lot 2799-1

CREEK P7 Stop LIRR service MID SPAN Stop LIRR service Stop LIRR service



Physical Conflicts Crane Position East Side West Side

P8 Conflict with building at Lot 2520-30 MID SPAN Close 56 Road. Close Laurel Hill Boulevard and 56th Road P9 Close Laurel Hill Boulevard

MID SPAN Close Laurel Hill Boulevard Interfere with Calvary Cemetery

P10 Conflict with buildings at Lots 2519-29, 2519-35


MID SPAN Conflict with buildings at Lots 2519-29, 2519-34, 2519-35


P11 Close 55th Avenue and 43rd Street Close Laurel Hill Boulevard Interfere with Calvary Cemetery

MID SPAN Close 43rd Street Conflict with building at Lot 2517-25


P12 Close 54th Road and 43rd Street Conflict with buildings at Lot 2516-24, 2516-28


MID SPAN Close 43rd Street Conflict with buildings at Lots 2516-23, 2516-24, 2516-13


P13 Close 43rd Street And 54th Road Conflict with building at Lot 2516-13


MID SPAN Close 43rd Street Conflict with buildings at Lots 2515-28, 2515-25, 2515-22


P14 Close 43rd Street Conflict with building at Lot 2515-22


MID SPAN Close 54th Avenue and 43rd Street Close Laurel Hill Boulevard and 54th Avenue Interfere with Calvary Cemetery

A2 Close 54th Avenue and 43rd Street Close Laurel Hill Boulevard and 54th Avenue Interfere with Calvary Cemetery

CONCRETE SEGMENTAL BOX GIRDER BRIDGE (BALANCED CANTILEVER CONSTRUCTION)

Each bridge is continuous over 15 spans ranging from 30 (100 ft) to 122 m (400 ft) and consists of a single precast post-tensioned concrete box girder.

Figure 7 shows the construction sequence for concrete segmental girder bridge. The spans 91.5 m (300 ft) or less are erected using an overhead self-launching gantry. The segments can be delivered from the deck to minimize impact on the local streets. Spans greater than 91.5 m (300 ft) are erected using the balanced cantilever method since the span is too long to use a gantry. Segments are hoisted into place using a beam and winch system, with segments installed on alternating sides to balance the cantilevers. The segments can be brought to the site by barges on Newtown Creek.

B.3.c. Conclusion

The bridge site is very congested with businesses and it is important to minimize ground level impacts. Longer spans result in fewer columns on the ground, which is favorable. Overhead construction such as concrete segmental construction using a launching gantry will also reduce ground level impacts, since construction with cranes would require businesses and local streets to be closed while girders were lifted into place. Overhead construction with girder launching



(constructing bridge segments at one end and progressively pushing the bridge across the pier tops) is impractical since the bridge alignment includes three tangent (straight) and two curved sections.

B.4. Main Span Bridge Type

Each of the Build Alternatives present unique challenges for creating an efficiently-constructible and aesthetically pleasing main span. To provide background for the following discussion, the five DEIS alternatives are briefly described in Table 3.

TABLE 3: SUMMARY OF ALTERNATIVES

Alternative Description

RA-5 Rehabilitation of the existing bridge with four westbound lanes and –two eastbound lanes, and a new parallel bridge with –three eastbound lanes plus a bikeway/walkway at the eastbound side of the new bridge.

RA-6 Rehabilitation of the existing bridge with –two westbound lanes and –four eastbound lanes, and a new parallel bridge with three eastbound lanes. A bikeway/walkway can not be carried on the new bridge without impacting Calvary Cemetery, and the existing bridge can not carry an added bikeway/walkway without major reconstruction, therefore no bikeway/walkway is included in this alternative.

BR-2 Three new parallel bridges with a –four-lane westbound bridge plus bikeway/walkway, a three-lane eastbound bridge, and a two-lane eastbound bridge constructed after demolition of the existing bridge.

BR-3 Three new parallel bridges with a four-lane westbound bridge plus bikeway/walkway, a three-lane eastbound bridge, and a two-lane eastbound bridge constructed after demolition of the existing bridge. Construction of the westbound bridge would be done in two stages, since the proximity of Calvary Cemetery to the existing bridge does not allow the full width of the bridge to be constructed until the existing bridge is demolished.

BR-5 Three new parallel bridges with a three-lane eastbound bridge, a two-lane eastbound bridge and a four lane westbound bridge plus bikeway/walkway constructed after demolition of the existing bridge.

B.5. Main Span Bridge Type

The main span over Newtown Creek could conceivably be almost any bridge type. The shoreline is basically open ground, so the main span could be largely fabricated off site, barged to the site and lifted into place. Bridge types that were specifically studied for this project are concrete segmental, extradosed (see Figure 8), and cable stayed bridges. A cable stayed main span would add to the cost, but since the main span is a small portion of the total project, the percentage increase in cost may not be great if an economical design is used. Final bridge type will be determined during the final design phase.

A signature span would likely visually clash with the existing bridge for the Rehabilitation with Auxiliary Lanes (RA) Alternatives, so only a concrete segmental bridge has been considered for the RA Alternatives. A rendering of the main span of Alternative RA-5 is shown in Figure 9.



FIGURE 9: RENDERING OF ALTERNATIVE RA-5 WITH NEW CONCRETE SEGMENTAL BRIDGE ADJACENT TO THE EXISTING BRIDGE.

Figures 10, 11 and 12 show the BR Alternatives as concrete segmental, extradosed and cable stayed, respectively. As shown, each has the potential to be aesthetically pleasing.



FIGURE 10: RENDERING OF CONCRETE SEGMENTAL BR ALTERNATIVE

FIGURE 11: RENDERING OF EXTRADOSED BR ALTERNATIVE



FIGURE 12: RENDERING OF CABLE STAYED BR ALTERNATIVE

Construction staging of the Bridge Replacement (BR) Alternatives has a significant impact on which bridge type is appropriate for the main span. The following sections evaluate the three bridge types for each of the BR Alternatives.

B.5.a. Alternative BR-2

Alternative BR-2 is constructed with a new temporary bridge on the westbound side and new EB-3 bridge on the eastbound side as shown in Figure 13. After the existing bridge is demolished, WB-4 and EB-2 are constructed as shown in Figure 14.

FIGURE 13: ALTERNATIVE BR-2, CONSTRUCTION STAGE 1



FIGURE 14: ALTERNATIVE BR-2, FINAL CONDITION

The Alternative BR-2 main span could consist of either two or three parallel extradosed or cable stayed bridges as shown in Figures 15 through 18, however, with two parallel bridges the width differs significantly, which is aesthetically displeasing.

FIGURE 15: ALTERNATIVE BR-2, 3 PARALLEL EXTRADOSED BRIDGES




FIGURE 17: ALTERNATIVE BR-2, 3 PARALLEL CABLE STAYED BRIDGES




B.5.b. Alternative BR-3

Alternative BR-3 is constructed with WB-4 and EB-3 on the eastbound and westbound sides as shown in Figure 19. WB-4 can not be completely constructed in Stage 1 since the existing bridge is in close proximity to Calvary Cemetery. After the existing bridge is demolished, WB-4 is completed and EB-2 is constructed in the center as shown in Figure 20.



It would be very impractical to construct an extradosed or cable stayed bridge in stages as would be required for WB-4 with Alternative BR-3, so this concept is dismissed. The center bridge could be constructed as a cable stayed bridge as shown in Figure 21.



FIGURE 21: ALTERNATIVE BR-3, 2 CONCRETE SEGMENTAL BRIDGES WITH CENTER CABLE STAYED BRIDGE

B.5.c. Alternative BR-5

Alternative BR-5 is constructed with EB-2 and EB-3 on the eastbound side as shown in Figure 22. After the existing bridge is demolished, WB-4 is constructed as shown in Figure 23.





The Alternative BR-5 main span could consist of either two or three parallel extradosed or cable stayed bridges as shown in Figures 24 through 26. The width of WB-4 is similar to the width of EB-2 and EB-3 combined, so two parallel bridges look compatible.






Based on this evaluation, the following bridge types are considered appropriate for consideration:

Alternative RA-5: concrete segmental

Alternative RA-6: concrete segmental

Alternative BR-2:

o Three concrete segmental spans

o Three extradosed spans

o Three cable stayed spans

Alternative BR-3:


o One center cable stayed span, two outer concrete segmental spans

Alternative BR-5:


o Two extradosed spans



o Three extradosed spans

o Two cable stayed spans

o Three cable stayed spans

C. IMPACT STUDY

The most important premise in this study is to develop methods and procedures for the demolition and construction work which will minimize the impact to local communities and minimize the use of local roads for construction purposes. After concrete segmental construction was selected for the approach spans as the least disruptive to the local businesses, a detailed conceptual design was performed to determine physical impacts of bridge construction. The physical impacts for the high level portions of the bridge are defined by column locations and footing construction.

C.1. Refining Span Lengths

The original bridge plans were reviewed from the standpoint of alleviating conflicts between new foundations and the existing bridge footings. The revised plans, elevations and sections for Alternatives BR-3 are shown in Figures 27 and 28, and Figures 29 and 30 for Alternative BR-5 . Span lengths vary from 30.4 m (100 ft) to 122 m (400 ft), and they were adjusted to minimize conflicts with businesses and local roads as much as practical. The depth of the girder is 3.4 m (11 ft) for bridges up to 61-m (200 ft) span length, and is increased at piers to 5.2 m (17 ft) for 91.4 m (300 ft) spans and 6.7 m (22 ft) for 122 m (400 ft) spans.

Figure 31 shows the extradosed bridge option for 122 m (400 ft) spans over the Newtown Creek. The depth of the girder is shallower than a concrete segmental bridge with a depth of 3.35 m (11 ft) and 4 m (13 ft) at piers. The girder consists either of a concrete box girder or steel box girder. The steel box girder may be used for a 50 m (160 ft) center portion of the main span over the Newtown Creek, and the prefabricated steel segment may be lifted up by winches and joined with the concrete deck. The height of the pylon above the deck is approximately 12.2 m (40 ft).

C.2. New Foundations

The type and size of the new foundations were determined based on the geotechnical data surveyed along the existing foundations. Generally, the area is covered with fill from 3 m to 6 m (10 ft to 20 ft) thick. Although the blow counts recorded during standard penetration testing shows wide variance of the depth of the fill, the records show nearly 100 blow counts below 60 m (196 ft) deep from the ground surface, indicating dense soil suitable for supporting the bridge foundations.

A large diameter drilled pile foundation was considered for all the new foundations, since the soil condition is generally of silty sand with some silty clay layers, which is favorable for this type of construction. The diameter of the drilled piles considered in this study are 1.83 m (6 ft), and the maximum pile length will be approximately 22 m (73 ft). Drilled pile construction will generate less noise and vibration than driven piles, but may be difficult to install if boulders are encountered. Additionally, there is widespread soil contamination in the area, and contaminated soil and water extracted while drilling would need to be collected, treated and

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disposed of properly. 0.46 m (18 inch) driven pipe piles were also considered, and it was determined that the foundation size would be similar using either pile type.

The piles were designed primarily for axial bearing capacity in soil. The maximum axial forces under the service load condition for the completed bridge were used for the pile design. The effect of unbalanced conditions anticipated during the cantilever construction was considered in the pile design. Seismic analysis will be performed in final design.

Figures 28 and 30 show the cross sections of typical foundations for Alternatives BR-3 and BR-5 respectively. Note that the westbound bridge of Alternative BR-3 consists of 2 boxes constructed in separate stages. This is because there is not enough room between the existing bridge and Calvary Cemetery to construct this bridge in a single stage. As shown in the figure, this would require a second set of columns.

C.3. Demolition and New Construction Procedure

It is preferable to perform demolition of the existing bridge using overhead construction techniques, similar to the new bridge construction, to avoid closing businesses and local streets while lifting bridge sections with large cranes. A detailed conceptual demolition study was performed, and it was confirmed that overhead construction techniques are feasible and economical.

C.3.a. Demolition Schemes

Two schemes were considered and compared. The first scheme is to start the demolition of the existing structures from the Brooklyn end and move towards the Queens end. The second scheme is to start the demolition at two fronts, starting from Newtown Creek and moving toward the Brooklyn and Queens ends simultaneously.

DEMOLITION SCHEME 1 (ONE-FRONT DEMOLITION)

The demolition begins from the lowest point of the Brooklyn end and proceeds towards the Queens end. Demolished superstructure materials are transported across the bridge to the Queens end, trucked to the Newtown Creek shoreline and shipped out by barges. The last truss span in Queens (Span 100) would be removed from ground level. Pier demolition would be performed from ground level. Figure 32 shows these typical demolition sequences for the Scheme 1.

DEMOLITION SCHEME 2 (TWO-FRONTS DEMOLITION)

Another scheme for the demolition of the existing structures is to start from the truss spans adjacent to the main span (Spans 88 and 90) and simultaneously proceed toward each end. The last truss spans in Brooklyn and Queens (Spans 79 and 100) would be removed from ground level. Pier demolition would be performed from ground level. Figure 33 shows these typical demolition sequences for the Scheme 2.

C.3.b. Demolition Methods

DEMOLITION OF TRUSS SPANS



The truss spans consist of 21 simply supported truss bridges, 10 in Brooklyn and 11 in Queens, with spans ranging from 37.5 m (180 ft) to 70.7 m (232 ft).

The demolition sequence for an individual truss span is shown on Figure 34. Most of the deck, crossbeams and stringers would be demolished, with the exception of a 6 m (20 ft) section at the center. A temporary cable-stay support system would be installed to support the truss span as it is being demolished, and the adjacent truss span will be used to counterbalance the truss span being demolished. Temporary cable stay posts will be installed on the pier between the adjacent spans. The top and bottom chords between the adjacent truss spans will be connected by tie plates to resist the horizontal thrust from the stay cables. The expansion bearings will be fixed to resist the horizontal thrust. Stay cables will be attached to the temporary posts and will be connected to pin plates on the upper truss chords at the panel points.

After the preparatory work as described above is completed, a hydraulic crane on rubber tires sitting on timber mats supported on the remaining center portion of the existing bridge deck will begin dismantling the truss member by member. The removed members will then be transported by trucks to the temporary storage before being shipping out by barge.

DEMOLITION OF MAIN SPAN (SCHEME 2)

Scheme 2 demolishes the Main Span by lowering the truss onto a barge in Newtown Creek. The demolition procedure is shown on Figure 35. Prior to the demolition of the main span truss, the concrete filled steel grid floor, crossbeams, stringers and sidewalk brackets would be removed to reduce the weight.

The two truss panels at each end will be used to support a winch and pulley lowering system. The remaining 61 m (200 ft) long steel truss will be supported by the lowering system before the upper and lower chords at each end are cut to lower the truss onto a barge. The remaining two truss panels at each end will be demolished by using a crane on the ground.

D. CONCLUSION

A long span concrete segmental bridge using overhead construction techniques is recommended for the Kosciuszko Bridge to minimize the impact of construction. Other alternatives such as a steel girder bridge would require closing businesses and local roads while large cranes lift girders into place.

Alternatives for the Main Span over Newtown Creek, which could be a "signature span", include an extradosed or cable stayed bridge, although almost any bridge type could be erected since the area around the main span is fairly open, and barge access allows large prefabricated bridge sections to be barged to the site. A signature span would likely be inappropriate for the RA Alternatives since the new span would be adjacent to and lower than the existing span, which would be visually incompatible.

Construction staging constrains what would be reasonable for the main span with the BR Alternatives. Three parallel bridges are appropriate for Alternative BR-2. Two concrete segmental spans with a signature span between them is appropriate for Alternative BR-3. Two parallel spans are appropriate for Alternative BR-5. The main span bridge type will be determined during final design.



Demolition methods and procedures for the existing truss bridge using overhead demolition techniques have been developed. A temporary cable stay support system is considered for demolition of typical truss spans in which the truss is dismantled without the use of a crane on the ground. The main span segment can be demolished using the temporary cable stay system, or by lowering the main span truss down onto a barge by a winch and pulley lowering system.

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