12-EXPANSION JOINTS

EXPANSION JOINTS

1. GENERAL

This section deals with the expansion joints in bridge structures in accordance with the details shown in the Drawings and conforming to the requirements of MoRTH Specifications and IRC: SP-69 or as directed by the Engineer.

The types of expansion joints generally adopted in bridge construction are:

i) Buried joint.

ii) Filler joint.

iii) Asphaltic plug joint.

iv) Compression seal joint.

v) Single strip/box seal joint.

vi) Reinforced elastomeric joint etc.

Since single strip/box seal joint and compression seal joint are the commonly used expansion joints in bridges by the department, these types of joints alone are mentioned under this section. For details of other type of joints, IRC: SP-69 shall be referred to.

2. SINGLE STRIP/BOX SEAL JOINT

Single strip/box seal expansion joint consists of two edge beams with anchorages and an elastomeric sealing element held firmly in the housings of edge beams that guarantee the water tightness of the joint. The maximum gap between the edge beams at road surface when the joint fully opens due to maximum contraction of deck shall be limited to 80 mm for the comfortable passage of the traffic. The edge beams protect the adjacent edges of bridge deck from damage due to vehicular impact and also transfer the vehicular load to the deck structure through robust anchorage system. Typical single strip seal joint is shown in figure.

                                                         

                                             

Fig. : Typical cross section of single strip joint and arrangement.

2.1 Components

1. The edge beam shall be either extruded or hot rolled steel section including continuously shop welded section with suitable profile to mechanically lock the sealing element in place throughout the normal movement cycle. Further, the configuration shall be such that the section has a minimum thickness of 10 mm all along its cross section (flange and web). Thickness of lips holding the seal shall not be less than 6 mm. The minimum height of the edge beam section shall be 80 mm. The minimum cross sectional area of the edge beam shall be 1500 mm2.
2. The edge beams of single strip/box seal joints shall be anchored in the concrete with rigid loop anchorage. The anchor loops shall be connected to the edge beam by means of anchor plate welded to the edge beam. Total cross sectional area of anchor loop on each side of the joint shall not be less than 1600 mm2 per metre length of the joint and the centre to centre spacing shall not exceed 250 mm. The thickness of anchor plate shall not be less than 0.7 times the diameter of anchor loop or 12 mm whichever is higher. The anchor loop at the edge profiles should be at right angles to the joint. Planned deviations of this direction are allowable only for the range of 90°±20°. The anchoring reinforcement of the construction must lie parallel to the anchor loops.
3. The sealing element shall be a preformed/extruded single strip of such a shape as to promote self-removal of foreign material during normal joint operation. The seal shall possess high tear strength and be insensitive to oil, gasoline and ozone. It shall have high resistance to ageing. The specially designed proprietary type of locking system of seal in the housing of edge beam shall be such as to ensure 100% water tightness as well as ease of installation and replacement. Mechanical fastening of sealing element with edge beam shall not be permitted. Sealing element shall be continuous over the entire joint. The working movement range of the sealing element shall be at least 80 mm with a maximum of 100 mm at right angles to 'the joint and ± 40 mm parallel to the joint. Minimum gap for inserting the Chloroprene seals in the expansion joint shall be 25 mm.
4. The steel for edge beams shall conform to any of the steel grade equivalent to RST 37-2 or 37-3 (DIN), S235JRG2 or S355K2G3 of EN10025 (DIN 17100), ASTM A 36 or A 588, CAN/CSA Standard G40.21 Grade 300 W and Grade B of IS: 2062. For subzero condition, material for steel shall conform to Grade C of IS: 2062.
5. The sealing element shall be made of Choloroprene Rubber (CR). The properties of CR shall be as specified in table 4100-1.
6. Anchorage steel shall conform to Grade B of IS: 2062 or equivalent standard.

2.2 Fabrication

1. Rolled steel profiles for edge beams shall be long enough to cater for the full carriageway width. These shall be cut to size as per actual requirements. Alignment of the steel profiles shall then be made on work tables in accordance with the actual bridge cross-section. For this purpose, the contour of bridge cross-section shall be sketched on the tables. After the steel profiles are aligned, these will be fixed to the tables by means of screw clamps and tacked by arc welding.
2. Anchor plates shall be cut to the required size by gas cutting. These shall be welded to the edge beams.
3. Anchor loops shall be bent to the required shape and welded to anchor plates.
4. All steel sections shall be protected against corrosion by either hot dip galvanizing with a minimum thickness of 150 micron or by epoxy coating.
5. All surfaces of the steel inserts and anchorage including the surfaces to be in contact with or embedded in concrete shall be given treatment as per MoRTH specification.
6. The finally assembled joints shall then be clamped and transported to the work site.

2.3 Installation

Expansion joints shall be installed as per approved Drawing. The procedure for installation of various components shall be as follows:

1. The width of the gap to cater for movement due to thermal effect, prestress, shrinkage and creep, superstructure deformations (if any) and substructure deformations (if any) shall be determined and intimated to the manufacturer.
2. Depending upon the temperature at which the joint is likely to be installed, the gap dimension shall be preset.
3. Immediately prior to placing the joint, the pre-setting shall be inspected. In case the actual temperature of the structure is different from that taken for pre-setting, suitable correction shall be done. After adjustment, the brackets shall be tightened again.
4. Rolled up neoprene strip seal shall be cut to the required length and inserted between the edge beams by using a crow bar pushing the bulb of the seal into the steel grooves of the edge beams.
5. The carriageway surfacing shall be finished flush with the top of the steel sections. The actual junction of the surfacing/wearing coat with the steel edge section shall be formed by a wedge shaped joint with a sealing compound. The horizontal leg of the edge beam shall be cleaned beforehand.
6. It is particularly important to ensure thorough and careful compaction of the surfacing in order to prevent any premature depression forming in it.

3. COMPRESSION SEAL JOINT

Compression seal joint shall consist of steel armoured nosing at two edges of the joint gap suitably anchored to the deck concrete and a preformed chloroprene elastomer or closed cell foam joint sealer compressed and fixed into the joint gap with special adhesive binder. The seal is supposed to remain in continual compression due to pressing of the seal wall against joint faces throughout the service life to ensure that the joint remains water tight and capable of rebelling debris. The maximum gap when the joint fully opens due to maximum contraction of deck shall be limited to 40 mm. A typical compression seal joint is shown in figure.

                                              

                                                 

Fig: Typical cross section of compression seal joint and arrangement.

3.1 Components

1. The steel nosing shall be of angle section ISA 100x100. The thickness of legs shall not be less than 12 mm. The top face of the angle shall be provided with bleeder holes of 12 mm diameter spaced at maximum 100 mm centres so as to ensure that there are no voids in the concrete beneath the angle.
2. The steel nosing shall be anchored to the deck by headed shear studs or anchor plates cast in concrete or a combination of anchor loops. Anchor bars shall engage the main structural reinforcement of the deck and in case of anchor plates and anchor loops, transverse bars shall be passed through them. The minimum thickness of anchor plates shall be 12 mm. Total cross sectional area of bars on each side of the joint shall not be less than 1600 mm2 per metre length of the joint and the centre to centre spacing shall not exceed 250 mm for loop anchors and 150 mm for headed shear studs. The ultimate resistance of each anchorage shall not be less than 600 in kN/m any direction. Steel shall conform to Grade B of IS: 2062. For sub-zero condition, material for steel shall conform to IS: 2062 Grade C.
3. The sealing element shall be a preformed continuous chloroprene/closed cell foam seal with high tear strength, insensitive to oil, gasoline and ozone. It shall have high resistance to ageing and ensure water tightness. The seal should be continuous for the full length of the joint required for carriageway, kerbs and footpaths, if any. The seal shall cater for a horizontal movement up to 40 mm and vertical movement of 3 mm.
4. The steel for nosing and anchorage shall conform to weldable structural steel as per IS: 2062 Grade B.
5. The physical properties of chloroprene/closed cell foam sealing element shall conform to the following:

1. Chloroprene seal shall be preformed extruded multi-web cellular section of chloroprene of such a shape as to promote self removal of foreign material during normal service operations. Chloroprene of joint seal shall satisfy the properties stipulated in MoRTH Specifications.
2. Closed cell foam seal shall be of preformed non-extruded non-cellular section made from low density closed cell, cross linked ethylene vinyl acetate, polyethylene copolymer that is physically blown using nitrogen. The material shall have properties as indicated in the table.

              Table: Properties of closed cell form seal

 Chemical tests shall be performed on specimens of elastomer and the properties of elastomer shall conform to the values/standards indicated in table.

 

6.  The type and application of lubricant cum adhesive material used in bonding the preformed joint seal to the steel nosing and concrete shall be as recommended by the manufacturer/supplier of the seal system.
7. All steel sections shall be protected against corrosion as stated by hot clip galvanizing or any other approved anticorrosive coating with a minimum thickness of 150 micron.
8. The dimension of the joint recess and the width of the gap shall conform to the approved Drawing.
1. Anchoring steel shall be welded to the main reinforcement in the deck maintaining the level and alignment of the joint.
10. The width of the recess shall not be less than 300 mm on either side of the joint. Care shall also be taken to ensure efficient bonding between already cast/existing deck concrete and the concrete in the joint recess.
11. At the time of installation, joint shall be clean and dry and free from spalls and irregularities, which might impair a proper joint seal.
12. The lubricant cum adhesive shall be applied to both faces of the joint and joint seal prior to installation in accordance with the manufacturer's instructions.
13. The joint seal shall be compressed to the specified thickness for the rated joint opening and ambient temperature at the time of installation which shall be between 5°C and 35°C.
14. The joint seal shall be installed without damage to the seal. Loose fitting or open joints shall not be permitted.

4. WORKMANSHIP

1. Expansion  joints shall be  installed under close supervision ofthe manufacturer's /supplier's Engineer. Detailed Installation Manual shall be supplied by the manufacturer/ supplier.
2. The dimensions of the recess in the deck shall be established in accordance with the Drawings or design data of the manufacturer, taking into account the width of gap for movement of the joint.
3. The pre-setting of expansion joint shall be done by means of an auxiliary construction.
4. The road surfacing/wearing coat shall be laid before commencing installation of joint. Before laying wearing coat, the recess portion shall be filled with sand and wearing coat shall be laid in a continuous manner over the deck slabs and recess portion. Prior to installation of the joints, portion of wearing coat over the recess shall be removed by a suitable method such as saw cutting and the infill sand shall also be removed.
5. The size and form of recess shall suit the geometry of the expansion joint. However, the width shall not be less than the specified value for a particular type of joint. In order to avoid difficulties during installation, the points to be checked and considered are:

1. Dimension of recess.
2. Levels.
3. Skew and slope.
4. Designed gap between bridge deck and abutment and/or between adjoining decks.
5. Existing structural reinforcement according to the Drawings.

6. Reinforcing bars that would obstruct the installation of expansion joint shall be bent to accommodate the expansion joint anchorages. Cutting off or removal of interfering reinforcing bars shall only be done after consultation with the Engineer. The recess shall be cleaned thoroughly. If necessary, the surface should be roughened. All loose dirt and debris shall be removed by wire brushing, air blowing and dried with hot compressed air.
7. Shuttering must be used to seal the space between the underside of the joint and the vertical face of the recess. The shuttering must be fitted in such a way that it forms an appropriate seal against the edge of the recess. The recess shall be shuttered in such a way that dimensions shown on the Drawing are maintained. The formwork shall be rigid and firm.
8. Level marks shall be set next to the recess. This enables a controlled levelling of the expansion joint. Lowering the expansion joint/joint construction/insert into the recess shall be done in such a way that the entire length of the joint is evenly lowered into the recess. Thereafter, the joint/joint construction/insert is precisely levelled and adjusted in the longitudinal, transverse and vertical planes. If required, the joint must also be adjusted to the gradient of the final surface level.
9. The expansion joint/joint construction/insert shall be installed preferably in the early morning when the temperature is distributed almost uniformly over the whole bridge. Immediately before the installation, the actual temperature of the bridge shall be measured. If it is not within the considered tolerance, the preset adjustment shall be corrected. The joint/joint construction/insert shall be lowered in a predetermined position. Following placement of the joint/joint construction/insert in the prepared recess, the joint/joint construction/insert shall be levelled and finally aligned and the anchorage steel on one side of the joint welded to the exposed reinforcement bars of the structure. Upon completion, the same procedure shall be followed for the other side. With the expansion joint/joint construction/insert finally held at both sides, the auxiliary brackets shall be released, allowing it to take up the movement of the structure. After carrying out the final fixing, the protection against corrosion shall be completed.
10. For fully assembled joints with one end fixed and other end movable e.g. modular strip/box seal joint, connection shall be as detailed below:

The 1st side: The fixed side of the assembled joint (either the abutment or the bridge deck side) is designated the 1st side for connecting the joint. The preliminary fixing is made by evenly placing and welding of reinforcing bars over the entire length between the anchor loops and the deck reinforcement. To facilitate concreting, the gap between recess and shuttering is sealed by a grout seam. The seam must be left to dry prior to final concreting. After this, additional reinforcing bars are welded until all anchor loops are firmly connected to the deck reinforcement. The expansion joint shall be considered sufficiently fixed when no vibration is noted when it is lightly tapped. The expansion joint shall not be subjected to any loads that could in any way displace the precise location of this fixing.

10. 2. The 2nd side: Depending on the size of the expansion joint and the expected movement during installation, the most suitable time must be determined for fixing of the 2nd (moveable) side. Usually this is the early morning hours with the smallest temperature deviations. The procedure is identical to that for the 1st side. The joint shall be provisionally fixed to the reinforcement as fast as possible.

    3. Immediately afterwards, the fixation brackets shall be removed. Thereafter, the gap between recess and shuttering shall be sealed with grout seam and the remaining reinforcing bars welded as described previously.

    4. Prior to final concreting, the position of the joint/joint construction/insert must be recorded. The Engineer must give written confirmation of the correct position of the joint and recess concreting. The recess shall be thoroughly watered. Before pouring the concrete the joint construction should be protected by a cover.

    5. Controlled concrete having strength not less than that in superstructure subject to a minimum of M35 shall be filled into the recess. The water cement ratio shall not be more than 0.4. If necessary, admixtures may be used to improve workability. The concrete must exhibit low shrinkage. The concrete shall be finished flush with the carriageway surfacing. The concrete shall be kept damp until it has cured in order to avoid fissures caused by drying too fast. After the concrete has cured, the movable installation brackets and shuttering still in place shall be removed.

    6. For modular strip seal joint, the space beneath the joint boxes shall be completely filled with concrete so that traffic loads are safely transmitted into the structure.

    7. As soon as the concrete in the recess has become initially set, a sturdy ramp shall be placed over the joint to protect it from traffic at site. Expansion joint shall not be exposed to traffic loading before completion of carriageway surfacing.

    8. The elastomeric sealing element may be field installed. For strip seal and modular strip seal joints, the sealing element shall be in continuous lengths spanning the full carriageway width. Proper fit of the seal of the sealing element must be ensured. The seal shall be installed by suitable methods in such a way that it is not damaged.

5. SAMPLING AND TESTING

5.1 Routine tests

This include tests for materials conforming to specifications, carried out by the original manufacturer i.e., in case of imported joints by the foreign manufacturer as part of their quality control procedure for all joints to be supplied by them. Detailed documentation of all the tests and inspection data as per complete quality control procedure shall be supplied by the original manufacturer in the form of Quality control report. Routine tests shall primarily include:

1. Raw materials inspection: Test on all raw materials used for the manufacturing of joints as per relevant material standard shall be carried out by the manufacturer.

1. Confirmation of the grade of steel: Grade of the steel for the edge beam shall be confirmed by conducting tests for yield stress, tensile strength and elongation.
2. Tests for steel for the anchorage shall conform to IS: 2062.
3. Chloroprene seal shall be checked for hardness, tensile strength, elongation at fracture, tear propagation strength, residual compressive strain, change in hardness, change in tensile strength, change in elongation at fracture, ageing in ozone and swelling behaviour in oil. The manufacturers/suppliers shall have in-house testing facilities for conducting these tests.

2. Process inspection: Process inspection including inspection of all manufacturing processes adopted to manufacture the joints e.g., welding, corrosion protection, clamping, pre-setting, greasing, bonding by adhesives and riveting, as appropriate, shall be carried out by the manufacturer.
3. Complete dimensional check: Complete dimensional check of all components of joint as well as the assembled joint with respect to the approved Drawings and tolerances as per specifications.

5.2 Acceptance tests

In addition to the routine tests, the manufacturer as well as the local supplier in case of imported joints shall have complete in-house testing facilities for the following tests. The Engineer shall insist upon these tests before acceptance of the joint. The applicability of the acceptance tests shall be as per table.

Cyclic motion: Cyclic motion test may be carried out once on one complete joint assembly or one meter sample piece selected at random from the entire lot of supply for each type of joint irrespective of movement capacity. The test sample shall be subjected to 5000 expansion and contraction cycles at minimum 30 cycles per hour. The test movement shall be 10% more than the design expansion/contraction movement. Any sign of distress or permanent set of any component or the assembly due to fatigue, will lead to rejection of entire lot of supply.

Ponding: Prior to acceptance, 25% of the completed and installed joints, subject to a minimum of one joint, shall be subjected to water tightness test. Water shall be continuously ponded along the entire length for a minimum period of 4 hours for a depth of 25 mm above the highest point of deck. The width of ponding shall be at least 50 mm beyond the anchorage block of the joint on either side. The depth of water shall not fall below 25 mm anytime during the test. A close inspection of the underside of the joint shall not reveal any leakage.

Debris expelling test: Debris expelling test shall be carried out on one metre sample piece selected at random from the entire lot of supply. The fully open gap shall be filled flush with granular debris and cycled 25 times for full opening and closing. The mass of debris repelled after 25 cycles shall be expressed as the percentage of initial mass. The percentage expelled shall not be less than 75.

Pull-out test: Pull-out test shall be carried out on one meter sample piece selected at random from the entire lot of supply. The joint shall then be stretched until the sealing element slips off from its housing. The minimum stretching of the joint before slip-off shall be least 150% of the rated movement capacity of the seal.

Vehicular braking/traction test: This is the only initial acceptance (in-house) test. This test may be carried out once on one complete joint assembly or one metre sample piece selected at random from the entire lot of supply for each type of joint irrespective of movement capacity. The test sample shall be installed between two blocks of concrete in its mean position. A truck wheel load of 40 kN shall be drawn across the specimen with an engaged ratchet with wheel locked to simulate locked brakes and then rolled back. The cycle shall be repeated for 50,000 times with a period of 2 seconds.                                                                                     
Table: Applicability of acceptance tests

 

 RELATED CODES:

1.IRC: SP-69:-Guidelines and Specifications for Expansion Joints.

2.ASTM D 395:-Standard test methods for rubber property - compression set.

3.ASTM D 412:-Standard test methods for vulcanized rubber and thermoplastic elastomers - Tension.

4.ASTM D 624:-Standard test method for tear strength of conventional vulcanized rubber and thermoplastic elastomers.

5.ASTM D 1043:-Standard test method for stiffness properties of plastics as a function of temperature by means of a torsion test.

6.ASTM D 2240:-Standard Test Method for Rubber Property—Durometer Hardness.

7.DIN 53508:-Accelerated ageing of rubber.

8.DIN 53509:-Determination of resistance of rubber to ozone cracking under static strain.

9.DIN 53512:-Determining the rebound resilience of rubber using the schob pendulum.

10.DIN 53516:-Testing of rubber, elastomers; determination of abrasion resistance.

11.DIN 53517:-Testing of rubber and elastomers; determination of compression set after constant strain.

12.DIN 53521:-Determination of the behaviour of rubber and elastomers when exposed to fluids and vapours.

13.MoRTH:-Specifications for road and bridge works (5th revision).

*****