Pull rod: generally located at the longitudinal joint of pavement skeleton; When the temperature rises, the concrete pavement expands and extends to both sides. When the temperature drops, the concrete pavement slab will shrink. If there is no tie rod, it will stay on the original extension line, so that inappropriate cracks will appear on the road surface. The tie rod is used to pull back the extended concrete pavement slab.
Dowel: As the name implies, it plays the role of transmitting force. When the vehicle load acts on the concrete pavement slab, the stress on the veneer is great. If there are plates at both ends of the plate to help, the plate acting on the load will be much less stressed. Just like a person picking things, if two people lift a pair of shoulder poles at both ends of the pole, then the person picking things will feel very hard. Therefore, thicker steel bars are arranged at both ends of the pavement slab as dowel bars.
Application of tie rod and dowel bar;
The joints of pavement mainly include longitudinal joints and transverse joints. The longitudinal joints are divided into longitudinal contraction joints and longitudinal construction joints, and the longitudinal joints of the slab are parallel to the road centerline. The longitudinal contraction joint spacing is the width of the plate. When a paving width is greater than 4.5m, longitudinal contraction joints shall be set. The longitudinal contraction joint adopts the form of false joint, and a pull rod is arranged in the center of the thickness of the plate. ? When a paving width is less than the pavement width, longitudinal construction joints should be set. Longitudinal construction joints can be divided into flat joints and tongue-and-groove joints. A tie rod should be added in the longitudinal seam. ? Transverse joints can be divided into expansion joints, transverse contraction joints and transverse construction joints. Transverse joints should be arranged perpendicular to longitudinal joints, and transverse joints of adjacent plates should be aligned, and staggered joints are not allowed.
The purpose of setting expansion joints is to provide space for the expansion of concrete pavement and avoid excessive hot pressing stress. At the expansion joint, the concrete slab is completely disconnected, so it is called true joint. Considering the construction and use, expansion joints should be set as little as possible or not. The telescopic part is provided with a sliding dowel bar, which is parallel to the board surface and the road center line. Expansion joints should be set at the intersection of adjacent bridges or other fixed structures or other roads. The distance between transverse contraction joints is the length of slab, which should be determined according to local climate conditions, slab thickness, subgrade stability and experience. It is generally believed that the plate length should be about 25 times of the plate thickness, so the plate length is generally 4~5m, and the maximum is not more than 6 m. And the length-width ratio of the plate is 1: 1.3. The shrinkage joint is in the form of false joint, the joint width is 3~8mm, the joint depth is 1/5~ 1/4, and the concrete at the lower part of the slab remains connected. Generally, there is no dowel bar at the transverse contraction joint. At the end of daily construction or when concrete pouring is interrupted, transverse construction joints must be set. ?
So flat seam is aimed at tongue-and-groove seam. True joints are aimed at false joints. Generally, tie rods are set in the longitudinal joints of cement concrete pavement. The so-called longitudinal joint is the middle joint between two cement pavements, and the pull rod is generally made of steel bars, which plays a traction role on the left and right cement concrete pavements. That is to say, they are arranged in the middle, at a certain interval, connecting the left and right pavements? Set steel dowel at contraction joint and expansion joint, apply round steel bar, half of which is coated with asphalt, allowing sliding. Expressway needs to set expansion joints at regular intervals.