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
2.2 Fabrication
Property |
Code |
Specified value |
Hardness |
DIN 53505 ASTM D 2240* |
63+5 Shore A. 55+5 Shore A. |
Tensile strength |
DIN 53504 ASTM D 412* |
Min 11 MPa. Min 13.8 MPa. |
Elongation at failure |
DIN 53504 ASTM D 412* |
Min 350%. Min 250%. |
Tear propagation strength longitudinal transverse |
DIN 53507 ASTM D 624*(Dia C) |
Min 10 N/mm. Min 10 N/mm. |
Shock elasticity |
DIN 53512 |
Min 25%. |
Abrasion |
DIN 53516 |
Max 220 mm2 . |
Residual compression strain (22 hours/70?C/30% strain) |
DIN 53517 ASTM D 395* (Method B) |
Max 28%. |
Ageing in hot air (14 days/70°C): |
DIN 53508 |
|
Change in hardness Change in tensile strength Change in elongation at fracture |
|
Max +7 Shore A. Max -20%. Max -20%. |
Ageing in ozone (24 h/50 pphm/25°C/20% strain) |
DIN 53509 |
No cracks. |
Swelling behavior in oil: (168 hours/25°C) |
DIN 53521 |
|
ASTM oil No.1 Volume Change Change in hardness |
|
Max +5%. Max -10 Shore A. |
ASTM oil No.3 Volume Change Change in hardness |
|
Max +25%. Max -20 Shore A. |
Cold hardening point |
ASTM D 1043 |
Min -35°C. |
2.3 Installation
Expansion joints shall be installed as per approved Drawing. The procedure for installation of various components shall be as follows:
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
Table: Properties of closed cell form seal
Property |
Code |
Specified value |
Density |
|
41.7 - 51.3 kg/m3 . |
Compression set on 25 mm |
ASTM D 3575 |
50% compression samples for 22 hours at 23°C, 2 hour recovery; 13% set. |
Working temperature |
|
-70°C to +70°C |
Water absorption (Total immersion for 3 months) |
ASTM D 3575 |
0.09766 kg/m2 . |
Tensile strength |
|
0.8 MPa. |
Elongation at break |
ASTM D 3575 |
195±20%. |
Chemical tests shall be performed on specimens of elastomer and the properties of elastomer shall conform to the values/standards indicated in table.
Property |
Code |
Specified value |
Adhesion strength |
IS: 3400 Part-14 |
7 kN/m. |
Low temperature stiffness |
ASTM D 797 |
Young’s modulus: 70 N/mm2 (Max). |
Ash content |
IS: 3400 Part-22 |
5%. |
Polymer identification test (Infrared spectro- photometry) |
ASTM D 3677 |
Comparison of spectra with reference to sample of polychloroprene. |
4. WORKMANSHIP
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.
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.
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.
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.
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.
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.
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.
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:
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
Performance evaluation tests |
Compression seal joint |
Single strip/ Box seal joint |
Cyclic motion |
Applicable |
Applicable |
Ponding |
Applicable |
Applicable |
Debris expelling |
Applicable |
Applicable |
Pull-out test |
Not applicable |
Applicable |
Vehicular braking/ Traction test |
Not applicable |
Applicable |
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).
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