major maintenance repair-2

*REPAIR OF BRIDGE EXPANSION JOINT, BEARING and PROTECTION WORK

REPLACEMENT OF EXPANSION JOINT

Description of Repair Method

The quality and maintenance of the expansion joints are very important for the behavior of bridges and the durability. Especially the expansion joints which should be waterproof as well as resistant to leakage.After water leakage happens to the expansion joints, the dirt, soil, gravel and water are collected on the Bearing seat position. The corrosion of steel member like steel bearing, lower flange of steel girder shall occurs easily and seriously under the damp condition. This repair method is adopted for Steel type and Rubber type expansion joint which should be adopt water-proof type expansion joint.*

The damaged expansion joint shall be dismantled by concrete chipping using electric jack hammer. Before applying the jack hammer, the concrete cutter shall be applied to cut both side of concrete surface to make straight cutting line. The new expansion joint shall be installed to keep same height finishing. The non-shrink concrete/grout shall be poured, finishing and curing.

Photo 8-4 Sample of water-proof type expansion joint*

Application Criteria

The replacement of steel expansion joint may be adapted to the damages ranked with Bad in Condition Rating Criteria as below;

For Water Leakage: Detected area > 50%For Abnormal space/noise: DetectedFor Difference in elevation: Difference in elevation is >30mm at expansion gapFor Displacement: Pourable joint sealant maybe almost completely lostFor Cracking: Cracking on primary members especially in welded parts*

The replacement of rubber expansion joint may be adapted to the damages ranked with Bad in Condition Rating Criteria as below;Water leakage: detected area >50%Abnormal Space/ Noise: DetectedDifference in Elevation: >30mm at expansion gapRuptur: Rubber seal dislodge or pell Water leakage: detected area >50%Abnormal Space/ Noise: DetectedDifference in Elevation: >30mm at expansion gapDeteriorated Sealant: Pourable joint sealant maybe almost completely lost. off from location*

Work Sequence

1.Dismantle the existing expansion joint

At first both side of concrete surface shall be cut by concrete cutter in transverse direction.The damaged expansion joint shall be dismantled by chipping concrete.*

2.Chipping concrete of both side of the expansion joint

The chipping work shall be continued until final surface for new expansion joint. The existing rebar shall be remained to keep strength.*

3.Set up new expansion joint

The new expansion joint with water-proof device shall be installed. The re-bars shall be fixed by mechanical anchor. D16 re-bars are laid in transverse direction.

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4.Pouring non-shrink concrete

After checking measurement, the none-shrink concrete shall be poured and cured to be completed.

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Required Materials and Tools/Equipment

Material Requirement

Steel Angle and Steel cover plateNon-shrink mortal/concreteFlexible AsphaltPhoto 8-3 Sample Asphalt Rubber material*

Required Materials

Concrete CutterElectric impact hammer/small jackhammerElectric concrete vibratorGas burnerAsphalt mini cookerSurface finisherTamping machine

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REPLACEMENT OF BEARING


Proper service life of the elastomeric bearings will be estimated at 15 25 years. As aging of the material after a certain period of service, rubber bearings have severe Bulging or cracking. It is time to replace the elastomeric bearing. Replacement of new bridge bearings should be performed strictly in accordance with the relevant technical requirements and recommendations given normally by the bearings manufacturers. Installation should be performed by highly experienced staff and adequately supervised.

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Photo 9-1 Sample of Replacement Bearing Fig. 9-1 Rubber Bearing

Usually the Jack-up girder technique shall be performed to replace bearings. It is referred to 9-3 Jack-up Girder. During replacement of bearing, the traffic may be opened but restriction of passing speed is necessary for safety. The girder shall be jacked up around 5mm to 10mm at one jack stroke. *


The replacement of bearing shall be applied to the old rubber bearing which has severe crack, abnormal bulge and old steel bearing which has loose connection. This repair method is a combination with method of Jack-up girder described in Section 9-3.The capacity of new rubber bearing should be the same as old bearing capacity approved by the Engineer.

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Work Sequence

1.Jack-up Girder

The work Sequence without New bearing installation is as same process as 9-3 Jack-Up Girder process. Replacement Bearing process shall be described in this article. The surface of expansion joint shall be cured to keep safety for passing traffic during jacking up. The height difference between surface of abutment and girder shall be below 10mm to be kept the safety of passing traffic.*

2.Dismantle Existing Bearing and Chipping Bearing Base

After jacking-up, proceed to dig or chip of bearing base concrete for removing existing bearings.*

3.Making New Bearing Seat and Set up New Bearing

If the new bearing seat shall be finished chipping and arranging rebar, the new bearing shall be set up on right position and height. The height shall be considered to add as compressive displacement of elastic rubber bearing. After inspection, non-shrink mortal/concrete shall be poured then cured for several days.*

4.After Cutting, Jack Down Girder

Several days curing mortal/concrete, the girder shall be jacked down to be supported by the new rubber bearing. Finally position and height of the new bearing shall be measured to be approved by the Engineer.*

5.Dismantle Jacks and Temporary Supports for the Final Work

After replacement of the new rubber bearings are accomplished, jack device and temporary supports shall be dismantled. Steel surfaces shall be painted, if found necessary.*


1. Required Materials

The materials for the Elastomeric bearing pads are referred to ITEM 412-ELASTOMERIC BEARING PADS of DPWH standard. RebarNon-shrink mortal/concrete

2. Required Tools/equipment

Hydraulic JackElectrical JackhammerTrowel

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Specification

1. Materials Requirement

Bearing PadsElastmeric bearing pads shall conform to AASHTO M251.The Bearing pads shall consist of alternative laminations of elastmer and metal bonded togther, and shall conform to the following design requirements:(Durometer Hardness 53)Bearing stress:5.0-10.0 N/mm2Shearing Modulus:0.69 N/mm2Bulk Modulus:2,000 N/mm2

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The elastomer portion of the elastomeric compound will be 100 percent virgin chloroprene meeting the requirements of Min. 2,500 psi in tensile strength, 400% in ultimate elongation and 50 5 in hardness.Laminates shall be rolled mild steel sheets embedded by a minimum of 3.2 mm of elastomer.

Other Materials

For Re-bar, refer to ITEM710- REINFORCING STEEL AND WIRE ROPE.

For bearing base mortar, refer to the non-shrink mortar described in Section 5-4-5.

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2. Construction Requirement

Jack up girder

The contractor should submit the shop drawing of jack up girder to be approved by the Engineer. The jack capacity shall be designated by the Engineer under considering dead load and live load during replacement work.

Making New Bearing Seat and Set up new Bearing

The contractor should submit shop drawing of new bearing seat to be approved by the Engineer before making the new Bearing Seat by chipping concrete. After supporting the girder by the temporary support near the bearing portion, the old bearing shall be dismantled. *

After Curing, jack down girder

Non-shrink mortar/concrete shall be cured to get enough strength for support the reaction. The contractor should submit test result of specimen strength which is same curing days as in actual to be approved by the Engineer. If the test result shall be approved, the jack down girder shall be applied as release the jack reaction. If the reaction shall be transferred from jack to new Bearing during jack down motion, the jack shall be able to dismantle from the underneath of the girder. Dismantle Jacks for the final this work

The jacks shall be jacked down by taken safe step. The reaction is supported by new bearings already at above step. Temporary support materials and jacks shall be dismantled safely.*

PROTECTION WORKS

SLOPE PROTECTION WITH FOUNDATION SUPPORTED BY PILES


Slope protection around the abutment is often brokered due to scouring, river flow, and inadequate construction manner as shown in Photo 10-1. In most defect cases, foundation of slope protection is neglected so that movement of protection due to sliding or scouring could not be retained. Repair method of slope protection is to provide an appropriate foundation.

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Photo 10-1 Broken Slope Protection*


Appropriate masonry type will be selected from the wet masonry such as stone masonry, grouted riprap and concrete masonry. The foundation should be concrete structure with wooden pile as shown in Figure 10-1. Wooden piles are basically driven in minimum 2.0m. The foundation is provided at the level below 1.0m from river bed.

This criterion is only applied as a standard repair for the damaged protection of small and medium river less than 500 m3/sec of maximum discharge.

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Figure 101 Foundation Supported by Pile for Slope Protection*

Work Sequence

1.Excavation of Scoured Area

The broken existing slope protection shall be removed and the scoured area is excavated in accordance with the line and depth in the drawings. The limit of removal of the existing slope protection is marked on the existing protection. After excavation, the bed surface is compacted by lightweight mechanical or vibratory compactor.*

2.Placing Concrete for Foundation

Wooden piles are driven at the interval of 1.5m. In case that the pile is not driven, the pile top is possible to cut. The foundation concrete is provided rebar in minimum and then placing concrete in the formwork. If river water is flowed, cofferdam is provided with sand bags.*

3.Compaction of Gravel Filling

Gravel filling for base of the masonry is compacted by lightweight mechanical or vibratory compactor after surface preparation compacted on the slope. More than 300mm base in the thickness may be divided into 2 layers.*

4.Placing Masonry

Appropriate masonry type will be selected from the wet masonry such as stone masonry, grouted riprap and concrete masonry. *

5.Installation of Gabion mattress and Backfill

After filter fabric sheet is spread tight on the bed, gabion mattress is installed in front of the concrete foundation to protect local scouring and the foundation movement. Finally, the excavation area and voids around the protection structure are backfilled by cobble stone up to the level of river bed.*



Gabion Mattress Filling RockWooden PileFilter Fabric Sheet (under Gabion mattress)Backfilling Materials

2. Required Tools/Equipment

Vibratory CompactorBackhoe

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Specification


All materials required for the gabion mattress are in accordance with DPWH Standard Specifications, Item 505-Grouted Riprap, Item 506-Stone Masonry and Item-510-Concrete Slope protection.


Construction requirements for the slope protection are in accordance with DPWH Standard Specifications, Item 505-Grouted Riprap, Item 506-Stone Masonry and Item-510-Concrete Slope protection.

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GABION MATTRESS


Local scouring around the pier is often occurred due to strong steam flow velocity and riverbed materials and type of pier as shown in Photo 10.2.1. The most defect case, pier is settled down and then are subject to undermine and failure. The protection of local scouring is to eliminate or minimize future damage.Photo 10.2.1 Local Scouring around Pier*


Gabion mattress will be selected for protecting local scouring around pier as a simple and effective repair method. The scoured area should be excavated at minimum 1.0m for gabion mattress installation. The width of the mattress is more than 2 times for upper layer and 3 times for lower layer of scouring depth from the end of pier shaft in transversal and longitudinal as shown in Figure 10-2. The filter fabric sheet should be laid under the mattress.

This criterion is only applied as a standard repair for the damaged protection of small and medium river less than 500 m3/sec of maximum discharge.

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Figure 102 Application Requirement of Gabion Mattress*

Work Sequence

1.Excavation of Scoured Area

The scoured area around pier is excavated in accordance with the line and depth in the drawings. The excess scoured under the depth shown in drawing is filled with selected material. After excavation, the bed surface is compacted by lightweight mechanical or vibratory compactor.*

2.Filter Fabric Sheet Placing

The filter fabric sheet shall be spread tight and pegged by material approved by the Engineer. The filter fabric sheet shall be placed with lapping of minimum 30 cm.*

3.Installation of Gabions

The filling shall be carried out by placing individual stone material into the gabion by hand. When the mattresses are filled, the cover panels shall be closed and the selvages bound with binding wire as in the assembly process. On completion the mattress shall be completely tight and square.*

4.Backfilling

The Backfill shall be brought up evenly on all sides of the structure as appropriate, and each layer shall be extended to the limits of excavation or to natural ground.*



Gabion Mattress Filling RockFilter Fabric Sheet Backfilling Materials

2. Required Equipment

Vibratory CompactorBackhoe

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Specification


All materials required for the gabion mattress are in accordance with DPWH Standard Specifications, Item 511-Gabions and Mattresses


Excavation and Backfilling

The foundation of gabions shall be excavated and the back area of gabion structure shall be backfilled after completion of gabions in accordance with DPWH Standard Specifications. Each layer of backfill shall be compacted using an acceptable lightweight mechanical or vibratory compactor.*

Filter Fabric Sheet Placing

The ground where the filter fabric sheet is to be placed shall be thoroughly cleaned of debris, wood or any other material other than the material of the ground prior to spreading of the filter fabric sheet. The filter fabric sheet shall be spread tight and pegged by material approved by the Engineer. The filter fabric sheet shall be placed with lapping of minimum 30 cm.

Installation of Gabion

Where mattress are being assembled in position in a revetment, the binding of the edges of each mattress in the assembly process and the binding together of adjacent mattress may be carried out in the same operation. The vertical corners shall be kept square and to full dimension by inserting a steel bar of at least 20 mm diameter at each vertical corner, maintaining it in the correct final position throughout the filling process, the selvages of the mattress panels shall be bound to the selvages of adjacent mattress with binding wire. *

The filling shall be carried out by placing individual stone material into the gabion by hand. In this case, the stones shall be bedded on each other and packed as in dry random rubble masonry. No loose stones shall be tipped into the mattress and the practice of coursing and packing the outer layer and filling the interior with waste stones shall not be permitted. When the mattresses are filled, the cover panels shall be closed and the selvages bound with binding wire as in the assembly process. On completion the mattress shall be completely tight and square, true to dimensions, line and level as shown on the Drawings.

Backfilling

Backfill for Gabion Mattress shall be in accordance with DPWH Standard Specifications Item 103.2.6. The Backfill shall be brought up evenly on all sides of the structure as appropriate, and each layer shall be extended to the limits of excavation or to natural ground.*

SLOPE PATCHING


Slope protection around the abutment is often damaged partially due to inadequate compaction of slope basement, strong stream flow velocity and inadequate rain drain. Although visible damage on the slope protection is limited, the large void under the protection will be occurred due to the basement failure. The wide area of slope protection including the damaged portion should be removed for the patching repair.*

Photo 10-3. Partially Damaged Protection*


Slope patching will be applied for protecting the limited damages on the masonry in early damage stage and effective repair method. The damaged area should be widely removed at minimum 500mm extra in transversal and longitudinal direction for new protection. The protection bed should be excavated in 600mm in depth from masonry surface as shown in Figure 10-3. New masonry patched into the excavated area is composed with gravel filling of 300mm and wet masonry of 300mm which is selected from stone masonry, grouted riprap and concrete masonry as shown in Figure 10-4.

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Figure 103 Typical Damaged Slope ProtectionFigure 104 Slope Protection After Repair*

Work Sequence

1.Removal of Damaged Protection

The broken existing slope protection shall be removed and the scoured area is excavated in accordance with the line and depth in the drawings. The limit of removal of the existing slope protection is marked on the existing protection. After excavation, the bed surface is compacted by lightweight mechanical or vibratory compactor.*

2.Compaction of Gravel Filling

Gravel filling for base of the masonry is compacted by lightweight mechanical or vibratory compactor after surface preparation compacted on the slope. More than 300mm base in the thickness may be divided into 2 layers.*

3.Patching Masonry

Appropriate masonry type will be selected from the wet masonry such as stone masonry, grouted riprap and concrete masonry.*

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major maintenance repair-2

Documents

damaged expansion joint

expansion joints

expansion gapruptur

rubber type expansion

existing expansion jointat

expansion gapfor displacement

concrete chipping

chipping concrete