Introduction, specifications, installation process, corrosion causes of anchor bolts

2022-02-19 /News

anchor screw

Anchor bolts are screw rods used to fasten equipment, etc. on concrete foundations. It is generally used in infrastructures such as railways, highways, electric power enterprises, factories, mines, bridges, tower cranes, large-span steel structures and large buildings. Has strong stability. 

Specification

Anchor bolts generally use Q235 and Q345, which are round. It seems that I have not seen the use of threads, but if the force requires it, it is not a bad idea. Rebar (Q345) is strong, and the thread of the nut is not as easy to be round. For light round anchor bolts, the burial depth is generally 25 times its diameter, and then a 90-degree hook with a length of about 120mm is made. If the bolt diameter is large (such as 45mm) and the buried depth is too deep, a square plate can be welded at the end of the bolt, that is, a large head can be made (but there are certain requirements). The burial depth and hook are all to ensure the friction between the bolt and the foundation, so as not to cause the bolt to be pulled out and damaged. Therefore, the tensile capacity of the anchor bolt is the tensile capacity of the round steel itself, and the size is equal to the cross-sectional area multiplied by the design value of the tensile strength (140MPa), which is the allowable tensile bearing capacity at the time of design. The ultimate tensile capacity is to multiply its cross-sectional area (which should be the effective area at the thread) by the tensile strength of the steel (Q235 tensile strength is 235MPa). Since the design value is on the safe side, the tensile force at the time of design is less than the ultimate tensile force. 

Installation process

The installation of anchor bolts is generally divided into 4 processes.

1. The verticality of the anchor bolts

The anchor bolts should be installed vertically without inclination.

2. Laying of anchor bolts

During the installation of the anchor bolts, the secondary grouting of the dead anchor bolts is often encountered, that is, when the foundation is poured, the reserved holes for the anchor bolts are reserved in advance on the foundation, and the anchor bolts are put on when the equipment is installed. bolts, and then pour the anchor bolts to death with concrete or cement mortar.

3. Anchor bolt installation - tighten

4. Make construction records for the installation of corresponding anchor bolts

During the installation process of the anchor bolts, the corresponding construction records should be made in detail, and the type and specifications of the anchor bolts should be truly reflected, so as to provide effective technical information for future maintenance and replacement.

Generally, the pre-embedded parts with higher installation accuracy should be made into ground cages (the pre-embedded steel plates that have been punched through the bolt holes should be worn first, and nuts should be installed to press them down. Before pouring, the pre-embedded parts should be tied to the formwork and fixed. The installation size of the foot bolts can be guaranteed. If you want to save materials, you can also use steel bars to weld and fix them. After the welding is completed, you need to check the geometric dimensions. At this point, the foot bolt installation is truly completed. 

standard

Countries have different specifications and standards, such as British, legal, German, Australian standard, and American standard.

Corrosion Causes

(1) The reason for the medium. Although some anchor bolts are not in direct contact with the medium, for various reasons, the corrosive medium is likely to be transmitted to the anchor bolts, causing the anchor bolts to corrode.

(2) Environmental reasons. Carbon steel bolts will corrode in wet environments.

(3) The reason for the bolt material. In the design, although the anchor bolts are selected according to the regulations, they often only consider the strength of the bolts and do not consider that under special conditions, the anchor bolts will be corroded during use, so corrosion-resistant materials such as stainless steel are not used.

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