Concrete composite floor technology?

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4.3, concrete composite floor technology

4.3. 1, technical content

Concrete composite floor technology is to divide the floor into two parts along the thickness direction, with precast floor at the bottom and concrete composite layer at the top. The precast floor with bottom reinforcement is used as a part of the floor, as a template for the post-cast concrete composite layer, to bear the load in the construction stage and form an integral composite concrete member with the post-cast concrete layer.

According to the specific stress state, concrete composite floor can be divided into one-way composite slab and two-way composite slab. Precast floor can be divided into "awned reinforcement" and "awnless reinforcement" according to whether there are cantilever reinforcement or not; Flat joint can be divided into separate joint (that is, "close joint" between the bottom plates) and integral joint (with post-pouring belt between the bottom plates) according to the connection mode.

Precast floor can be divided into precast concrete floor and precast prestressed concrete floor according to the types of reinforced bars: when precast concrete floor adopts non-prestressed steel bars, truss reinforced concrete floor is often used to enhance stiffness; Precast prestressed concrete floor slab can be prestressed concrete flat slab, prestressed concrete rib slab and prestressed concrete hollow slab.

When the span is more than 3m, the precast slab should adopt truss reinforced concrete slab or prestressed concrete slab; When the span is more than 6m, prestressed concrete ribbed slab and prestressed concrete hollow slab should be used for precast slab; When the thickness of composite slab is greater than 180mm, prestressed concrete hollow composite slab should be adopted.

The key to the design of precast concrete composite floor slab is to ensure that the concrete on the upper and lower sides of the composite surface bears the same load and coordinate the stress, which is generally realized by the roughness of the composite surface and the shear structural reinforcement at the interface.

Whether reliable supports are set in the construction stage determines the design and calculation method of composite slab. Reliable supported composite slabs shall be set up so that the precast members will not deform under the weight of post-poured concrete and construction load, and the design and calculation shall be based on the whole flexural member; For unsupported composite slab, the internal force and deformation of the member are affected by the weight of the secondary concrete and the construction load, and the design and calculation should be carried out according to the composite member with two-stage stress.

4.3.2, technical indicators

(1) The design and construction requirements of precast concrete composite floor slab shall meet the relevant requirements of current national standards: Code for Design of Concrete Structures (GB500 10), Technical Specification for Assembled Concrete Structures (JJ1) and Technical Standard for Assembled Concrete Buildings (GB/T 51). The fabrication, construction and short-term design of precast slabs should meet the relevant requirements of Code for Construction of Concrete Structures (GB 50066). Construction acceptance shall comply with the relevant requirements of Code for Acceptance of Construction Quality of Concrete Structure Engineering (GB 50204).

(2) The design atlas of relevant national building standards includes truss reinforced concrete composite slab (60mm thick bottom slab) 15G366- 1, precast ribbed slab concrete composite slab 14G443 and prestressed concrete composite slab (50mm and 60mm solid bottom slab) 06SG439-659.

(3) The concrete strength grade of precast concrete floor slab should not be lower than C30；; The concrete strength grade of precast prestressed concrete floor slab should not be lower than C40 and C30；; The concrete strength grade of post-cast concrete overlay shall not be lower than C25.

(4) The thickness of precast slab should not be less than 60mm, and the thickness of concrete composite layer of post-cast strip should not be less than 60mm.

(5) The joint surface of precast floor slab and post-cast concrete composite layer shall be provided with rough surface, the area of which shall not be less than 80% of the joint surface, and the concave-convex depth shall not be less than 4 mm; Set the prefabricated bottom plate of truss reinforcement and set the natural rough surface.

(6) When the span of precast slab is more than 4m, or when the longitudinal reinforcement of the upper part of cantilever slab and adjacent cantilever slab is anchored in the cantilever layer, truss reinforcement or other forms of shear structural reinforcement shall be set.

(7) When precast prestressed floor slab is used, reliable measures should be taken to control inverted arch.

4.3.3, scope of application

The floor structure in various houses is especially suitable for residential buildings and various public buildings.

4.3.4, engineering case

Beijing Vanke New Mile, Jinyu Huafu, Baoye Wanhuacheng, Shanghai Urban Construction Pujiang Base Phase V Affordable Housing, Hefei Shushan Public Rental Housing, Shenyang Metro Huisheng New Town, Shenzhen-Hong Kong New Town Industrial Housing, etc.

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