Fatigue properties of concrete floor slab

The fatigue characteristics of the overall structure of the concrete floor slab are the key to determining the service life of the pavement. Many materials with better fatigue properties do not extend the service life of the pavement layer when used in bridge deck pavement structures. Through the fatigue test of the composite beam of double-layer asphalt pavement structure and the three-layer composite structure of "cement concrete slab + double-layer asphalt mixture paving", the fatigue performance of the composite structure of cement concrete bridge deck pavement is studied. At the same time, the influence of the waterproof bonding layer between the layers is considered. The results show that when the micro-strain is 700με, the fatigue life of “epoxy asphalt concrete + SMA” structure is 1.4 times that of other types of pavement structures; the fatigue life of “cement concrete slab + epoxy asphalt concrete + SMA” three-layer composite structure It is 2.1 times that of other types of paving structures. The conclusion shows that the "epoxy asphalt + SMA" composite pavement structure is suitable for cement concrete bridge deck pavement.

Reinforcement of building structures is a complex task and there are many factors to consider. The reinforcement method should be selected from the aspects of convenient construction, no influence on production, reasonable economy and good effect. The general principles are as follows:

(1) Reinforcement should be as close as possible to production or less production, because the loss of production is often several times or several times the cost of reinforcement. Whether it can be re-reinforced under load depends on the stress-strain state of the structure. If the internal stress of the general component is less than 80% of the design strength of the steel, and the damage and deformation of the component are not too serious, the load non-stop production reinforcement method may be employed.

(2) The reinforcement scheme should be easy to manufacture, construct and easy to inspect.

(3) Structural manufacturing assembly should be carried out outside the production area as much as possible.

(4) Reinforcement should be made of high-strength bolts or welding as much as possible. Concrete manufacturer

When high-strength bolts are used for reinforcement, the bearing capacity of the drilled section shall be checked. When welding is used, the original bar stress generated by the actual load is preferably less than 60% of the steel design strength, and the limit shall not exceed 80%. Otherwise, it shall be taken. The corresponding measures can be applied.

The distributed steel bars are mainly used to uniformly transfer the load on the plate surface to the stressed steel bar; resist the tensile stress generated by the four temperature changes and the concrete shrinkage in the direction perpendicular to the span of the plate; The skeleton prevents the displacement of the stressed steel bar when the concrete is poured.

1. The cross-sectional area of the steel bar distributed per unit length in the unidirectional plate shall not be less than 15% of the cross-sectional area of the stressed steel bar per unit width, and shall not be less than 0.15% of the cross-sectional area of the directional plate; the spacing of the distributed steel bars shall not be greater than 250 mm, and the diameter shall not be less than 6mm.

For the case of large concentrated load, the cross-sectional area of the distributed steel bars should be appropriately increased, and the spacing should not exceed 200 mm.

2. In the area of the cast-in-place plate with large temperature and shrinkage stress, the spacing of the steel bars should be 150-200mm, and the temperature-shrinking steel bars should be arranged on the surface of the plate. The reinforcement ratio of the upper and lower surfaces of the plate in both the longitudinal and transverse directions should not be less than 0.1%.

The temperature shrinkage steel bar can be arranged through the original steel bar, or a structural steel mesh can be separately set, and the original steel bar is overlapped with the requirements of the tensile steel bar or anchored in the peripheral member. Kunshan Jianguo Concrete

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