13.2
Exemple de conception : joints dans les chaussées en béton
Les joints de chaussée pour béton sont essentiels pour maintenir l'intégrité structurelle et la longévité de la chaussée en contrôlant où et comment l…
L’extension d’une chaussée existante en béton ordinaire est proposée pour la construction à l’aide de dalles de béton, assurant une fissuration minimale de la chaussée.
Un ingénieur de chaussée décide de fournir des joints de construction, d’expansion, d’isolation et de contraction pour contrôler la fissuration de la chaussée.
Les joints de construction sont des espaces prévus entre la nouvelle dalle et une dalle existante pour permettre d’éventuels mouvements dans la nouvelle dalle. Des chevilles encastrées dans le béton relient les dalles adjacentes entre elles.
Les joints de dilatation sont des espaces prévus entre les dalles adjacentes pour permettre la dilatation thermique du béton.
Sa construction consiste à disposer des goujons en rangées dans le sens transversal de la chaussée et à couler du béton sur les barres.
L’espace laissé est ensuite rempli de charges compressibles et de produits d’étanchéité.
Des joints d’isolation sont prévus à l’endroit où la chaussée rencontre un trou d’homme. Un joint d’un demi-pouce de large autour du trou d’homme, rempli d’un matériau compressible, forme le joint d’isolation.
Enfin, le joint de contraction est assuré par le sciage d’une rainure dans la chaussée en béton récemment durci orientée perpendiculairement au sens de la circulation.
Cela permet de localiser et de contrôler la formation de fissures pendant la contraction du béton.
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Q1: What are the main types of joints used in concrete pavement design?
Concrete pavements use four primary joint types: construction joints, which connect new and existing slabs; expansion joints, which accommodate thermal expansion; isolation joints, which separate pavement from fixed objects like manholes; and contraction joints, which are saw-cut grooves that control crack formation. Each joint type serves a specific function in managing pavement movement and preventing random cracking.
Q2: How do construction joints work in concrete pavement extensions?
Construction joints are gaps between new and existing concrete slabs that allow movement in the new slab during curing. Dowel bars embedded in the concrete tie adjacent slabs together, transferring loads while permitting controlled movement. This design prevents stress concentration at the interface between old and new pavement sections.
Q3: Why are expansion joints necessary in concrete pavements?
Expansion joints accommodate concrete's thermal expansion, preventing high compressive forces that can cause joint spalling or structural failure. These joints are created by arranging dowel bars in transverse rows and filling the gap with compressible fillers and sealants. This allows adjacent slabs to expand independently without damaging the pavement structure.
Q4: What is the purpose of contraction joints in concrete pavements?
Contraction joints are saw-cut grooves made perpendicular to traffic flow in recently hardened concrete. These joints create a weakened vertical plane that localizes and controls crack formation during concrete's contraction, directing cracks to predetermined locations rather than allowing random cracking across the slab.
Q5: How are isolation joints designed around pavement obstacles?
Isolation joints are provided where pavement encounters fixed objects like manholes. A half-inch wide joint filled with compressible material surrounds the obstacle, allowing the pavement and adjacent structures to move independently. This prevents stress transfer between the pavement and the fixed object.
Q6: What materials are used to fill concrete pavement joints?
Concrete pavement joints are filled with compressible fillers and sealants that accommodate movement while maintaining structural integrity. These materials allow adjacent concrete sections to expand and contract independently while preventing water infiltration and debris accumulation in the joint spaces, ensuring long-term pavement durability.
Q7: How do dowel bars function in concrete pavement joints?
Dowel bars are embedded in concrete to tie adjacent slabs together while facilitating controlled movement. In construction joints, they connect new and existing slabs; in expansion joints, they're arranged in transverse rows to transfer loads. This design maintains load transfer capacity while allowing thermal and contraction movements.