International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 09 Issue: 07 | July 2022
p-ISSN: 2395-0072
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BRIDGE DECK CRACKING Aysha S1, S Nabeel2 (Structural Engineering), APJ Abdul Kalam Kerala Technological University (Construction Engineering and Management), APJ Abdul Kalam Kerala Technological University ---------------------------------------------------------------------***--------------------------------------------------------------------2. BRIDGE DECK CRACKING Abstract - A crack is a complete or incomplete separation of 2M.Tech
1M.Tech
concrete into two or more parts produced by braking or fracturing. If the induced tensile stresses are higher than the limiting tensile strength of the concrete, the concrete will crack. The biggest problems affecting bridge decks are the deterioration of concrete. Cracks in the deck create a path for water and salts to reach the steel, often leading to corrosion of the reinforcement. The causes of early age cracking are varied but are primarily attributed to effects such as plastic shrinkage, temperature effects and drying shrinkage. This paper discusses about various variables that contribute to bridge deck cracking, evaluation of cracking and methods of repair in detail.
Based on the orientation of cracking in bridge decks, cracks are commonly characterized into five major categories transverse, longitudinal, diagonal, pattern or map, and random. 2.1 TRANSVERSE CRACKING Transverse cracks are the most commonly observed type and typically run perpendicular to the bridge girders but may also appear parallel to the skew near the abutments. These cracks are usually full depth. Cracks widths often exceed 0.002 inch and can reach widths of 0.025 inch, leading to an increased probability of water and chloride ion penetration. The major cause of transverse cracking has been shown to be restrained shrinkage.
Key Words: Plastic shrinkage, bridge deck cracking, evaluation of cracking
1.INTRODUCTION
2.2 LONGITUDINAL CRACKING
1.1 GENERAL
Longitudinal crack run parallel to the bridge girders and generally form directly above the edges of the girders. This type of cracking in ordinary girder type bridges is thought to be due to the presence of steel angles at these locations that are used to secure stay-in-place metal deck pans and cause a stress concentration.
The biggest problems affecting bridge deck is the deterioration of concrete. The causes of early age cracking are varied but are primarily attributed to effects such as plastic shrinkage, temperature effects and drying shrinkage. The cracking of bridge decks not only creates unsightly aesthetic condition but also greatly reduces durability, leads to a loss of functionality, loss of stiffness, and ultimately the loss of structural safety, resulting in aesthetic conditions that require the premature need for rehabilitation or replacement.
2.3 DIAGONAL CRACKING Diagonal cracks are commonly associated with bridges with skew, as the cracks are generally observed in areas of the deck with acute angles.
If the volumetric change of concrete due to shrinkage and thermal stresses is restrained, tensile stresses will develop in concrete. If the induced tensile stresses are higher than the tensile capacity of the concrete, the concrete will crack. A crack is a complete or incomplete separation of concrete into two or more parts produced by braking or fracturing. Cracks in the deck create a path for water and salts to reach the steel, often leading to corrosion of the reinforcement.
2.4 MAP CRACKING Pattern or map cracking is a very common form of cracking seen on all types of decks and bridges. Map cracks are often attributed to improper curing. As the deck cures, surface moisture is allowed to evaporate too quickly and volumetric change through shrinkage is incited.
3. VARIABLES CONTRIBUTING TO CRACKING
The basic problem of bridge deck cracking lies in the heating, hydrating, and expanding of young concrete next to older concrete and or fixed members that are cooling and shrinking at different rates which results in cracks in the young concrete. The cracks can be influenced by the material characteristics, casting sequence, formwork, climate conditions, and geometry all of which are time dependent.
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3.1 MATERIAL PROPERTIES 3.1.1 Cement In general, the studies have shown that the maximum amount of cement used should be limited to 356 Kg/m3 (of concrete), which correlates to at 28- 13 day unconfined
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