How to calculate the lap length of frame reinforcement

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According to the new code, it is impossible to have specific values, and academic research should be rigorous, not only based on experience, but also to find the source of experience.

make a summary explanation:

explain, use ll to express a lap length (including seismic LLE), The calculation of ll and seismic LLE is shown in the atlas (i.e. the attached drawings)

below, the new version of G101 atlas is used to explain from the non common parts to the common parts

1. If the lap joint structure is adopted, the lap joint section must be 100%, that is, the width of the lap joint zone should not be less than 800mm

2. For slab lap joint, take one ll, and the crack resistance slab reinforcement should be 150mm.

3. The horizontal reinforcement of shear wall is usually not lap joint, The vertical reinforcement is overlapped by ll, and the same part is overlapped by 1.2ll

4. The reinforcement mesh of strip foundation slab is overlapped by 150 mm

5. Generally, the main beam does not use binding and overlapping link. When the binding joint is unavoidable for the whole length reinforcement of the main beam, lap by ll, and pay attention to the staggered reinforcement (two purposes of staggering, 1. Save the reinforcement according to the concrete specification, or the whole reinforcement is easy to meet the specification, 2. It is convenient for pouring and vibrating concrete), and the erection bars are overlapped by 150 mm

(Note: when the new code has 8 m clear span and the main beam is overlapped by binding, the whole length after 9 m calculation does not meet the requirements of the code for overlapping and anchoring, please also note)

6. In Chapter 8.4 of the concrete code, the longitudinal tensile reinforcement is not less than 300, and the longitudinal compressive reinforcement is not less than 200

3. The erection bar is mainly set up for fixing the reinforcement framework, and it does not participate in the stress calculation. Therefore, the lap length is 150 mm. The lap length you said is not 150 mm, but calculated according to the lap length LLE of the tensile reinforcement. It is not the erection bar, but the upper full-length bar, This situation generally occurs when the specification of the negative reinforcement of the bearing is inconsistent with the specification of the full-length reinforcement in the centralized marking, LLE (small diameter) is used instead of 150 mm. See page 79 of 11g101-1 for details.

4. 1. The overlapping length of erection reinforcement and bearing negative reinforcement is 150 mm. Because the erection bar is mainly set up to fix the reinforcement framework and does not participate in the stress calculation, the lap length is 150 mm
2. Erecting reinforcement refers to the positioning reinforcement set to meet the structural or construction requirements. The erection reinforcement is set on both sides of the outer edge of the compression area of the beam to fix the stirrup and form the reinforcement framework. If the compression zone is equipped with longitudinal compression reinforcement, the erection reinforcement can no longer be provided. The diameter of erecting reinforcement is related to the span of beam
3. Erecting reinforcement can literally play the role of erecting. For example, for a beam, only tensile reinforcement and shear stirrups need to be arranged at the lower part of the beam, and the concrete strength in the compression area of the upper part of the beam is sufficient, so there is no reinforcement. When making the reinforcement framework, there is no longitudinal reinforcement at the upper part of the beam, and the upper corner of the hoop reinforcement can not be fixed. Therefore, two 14 or 16 reinforcements are generally used to distribute at the upper two corners, This is the erection bar, which is not subjected to any force in calculation, but it is also subject to compression in practice. Later, it can be used for positioning without calculation, while the vertical reinforcement of structural frame needs to be calculated. The bearing capacity of the beam can be improved to a certain extent e to the compression of the steel bars.

5. Erecting reinforcement plays the role of positioning between two layers of reinforcement, also known as positioning reinforcement. Because it does not participate in the force, so the specification does not make detailed provisions. If spot welding is not considered for the erection reinforcement, it is binding fixation. There is no requirement for lap length. As long as it can be supported stably, it is the same to keep long and short.

6. 150 mm is the lap length. If it is double-sided welding, it can be 5 times the diameter of reinforcement, that is 5 × 14 = 70mm, 75mm meets the specification requirements; If it's not double-sided welding, it's wrong.