The steel bar splicing specification ensures the s

2022-07-22
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Steel bar overlapping refers to the connection method that two steel bars have a certain overlapping length with each other and are bound with binding wires, which is suitable for the connection of steel bars with smaller diameters. Generally used for reinforcing mesh in concrete, longitude and latitude are evenly arranged, without welding, but only fixed by iron wire. There are four common connection methods for steel bar connection: binding rolling connection, welding connection, cold pressing connection and spiral connection. Except for some cases (such as open flame is not allowed), welding connection should be used as far as possible to ensure quality, improve efficiency and save steel

when we walk through the construction site, we can always see the flashing welding. When we overlook the construction site, we can also see many people working together to bind and lap the reinforcement. In fact, whether it is welding or lapping the reinforcement or connecting the reinforcement with the help of equipment, it belongs to the reinforcement lapping work. For the reinforcement lapping work, our country also has strict standards for the reinforcement lapping specification. Today, let's learn about the relevant knowledge of the steel bar splicing specification

Introduction to the specification of steel bar splicing

China has corresponding laws and regulations for the specification of steel bar splicing, and the following common points can be learned from the code for design of concrete structures:

for the steel bars that are subject to longitudinal force under axial tension and small eccentric tension rod, due to the physical characteristics, it is not suitable to use binding and splicing. If the diameter of the tensile reinforcement is greater than 25mm, the diameter of the compression reinforcement is generally more than 28mm. At this time, it is best not to use the binding lap joint, so what kind of reinforcement diameter is suitable for binding lap? The new "code for design of concrete structures" published by the state in 2010 has made accurate requirements for this data, that is, 25mm and 38mm

generally speaking, there is another “ Lap length ” For those who are not familiar with it, this parameter is often regarded as the length of the weld when the reinforcement is welded. Next, we will provide you with some other main parameters in the reinforcement lapping work:

reinforcement type concrete strength grade is: c15c20 ~ c25c30~c35≥ C40。 For those rebars that need the welding joint of the upper bar, if the diameter of the upper bar is consistent with that of the main bar, we can use low-level upper bar rebars, and whether it is the lap welding joint of the rebar or the welding joint of the upper bar, their weld thickness value can not be less than 0.4 times of the diameter of the main bar, and the weld width can not be less than 0.6 times of the diameter of the main bar, This has a great impact on the safety of the main reinforcement

with the development of the times, there are still many hot-rolled steel bars with a diameter greater than 10mm in the market, and their joints are best overlapped by arc welding

requirements for reinforcement lap length

the lap length of reinforcement generally refers to the lap length of reinforcement binding connection, and it also refers to the weld length of reinforcement welding

here are some regulations on binding and connection for your reference

minimum lap length of longitudinal tensile reinforcement

c15 C20 ~ C25 C20 C35 &ge~ C40

plain round reinforcement HPB (I) grade 45d 35d 30d 25d

ribbed reinforcement HRB (II) grade 55D 45d 35d 30d

reinforcement lap length

HRB400 (III) grade

rrb400 (III) - 55D 40d 35d 35d

note: this table is applicable to the situation that the binding joint area percentage of longitudinal tensile reinforcement is not greater than 25%

when the area percentage of binding joint is between 25% and 50%, the value in the table is multiplied by the coefficient 1.2

when the area percentage of binding joint is greater than 50%, the value in the table is multiplied by the coefficient of 1.35

when the minimum lap length is the lap length of two bars with different diameters, it is calculated by the diameter of the thinner bar

how much is the overlapping length of reinforcement mesh suitable

why should reinforcement mesh be overlapped? It is also mentioned above that the size of reinforcement mesh cannot meet the size of the whole area of the construction site, so it is necessary to overlap. At the same time, there may be a question. Isn't it the same to put two ends directly without overlapping? Either in fact or in theory, this method is not feasible, because the parts that are not overlapped after the construction will cause cracks or fractures in the pavement or building due to the separation of nets

what is the proper length of mesh lap? The purpose of mesh lapping is to prevent the construction body from cracking, and the density (length) of lapping is too small, which will also cause cracks or fractures due to imperfect construction. Generally, the lap length should be 3-5 mesh holes, which not only ensures the perfect splicing of reinforcement mesh, but also ensures the perfect construction of the building

anchorage of the upper reinforcement of the beam

when the cross-section size of the column is large enough, the straight-line anchorage method shall be adopted, the anchorage length shall not be less than LA, and the extension beyond the center line of the column shall not be less than 5d&mdash& mdash; This is because considering that the frame analysis is based on the axis of beam and column, the formation of this anchoring form is more effective for force transmission from an empirical point of view. At the same time, from the force transmission mechanism forming the node “ Truss mechanism ”, It should not be too short

when the cross-section size of the column is not large enough to place the straight-line anchor length of the beam reinforcement, 90 DEG is used; Bend the anchoring method of the tail section. At this time, the longitudinal reinforcement of the beam should extend to the opposite side of the node and bend downward, and the length of the horizontal projection section should not be less than 0.4la, and the length of the vertical projection section should be 15d. (it is no longer required that the total anchorage length should not be less than the tensile anchorage length LA) &mdash& mdash; The test shows that the main anchoring capacity of this anchoring method is provided by the bonding effect of the horizontal anchoring section from the drawing end to the beginning of the bending arc, and the anchoring capacity of the vertical section only works when the slip deformation of the horizontal section is large. When the horizontal anchoring section is long enough, the bending arc and the subsequent tail section are basically not tensioned (only considered as a backup measure)

editor's summary: having said so much, I believe you have a certain understanding of the relevant knowledge of the steel bar splicing specification. For daily use, these specifications can not only regulate our steel production and construction, but also ensure the safety of constructors to a certain extent

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