A few days ago, the Zhuhai Municipal Bureau of Housing and Urban-Rural Development issued the "Notice on Strengthening the Control of the Thickness of the Protective Layer of Concrete Reinforcement", which pointed out that the steel bar at the bottom of the slab and the longitudinal steel bar at the bottom of the beam should be fully tied with the stirrups.
The competent departments of housing and urban-rural construction of the preparatory group of all districts (functional areas) and Hezhou New District, the municipal construction project quality monitoring station, the construction project quality supervision institutions of all districts, and the construction, design, construction and supervision units:
In order to strengthen the supervision of concrete structure engineering in our city and ensure the bearing capacity and durability of concrete structures, the relevant matters related to strengthening the thickness control of concrete reinforcement protective layer are hereby notified as follows:
1. Strengthen design disclosure
Before the start of construction, the construction unit organizes the design and other units to make the design disclosure, clarify the thickness requirements of the reinforcement protective layer of different parts, and confirm the "Confirmation Table of the Thickness of the Concrete Reinforcement Protective Layer" (see Annex 1 for details).
2. Strengthen structural measures
(1) The steel bar at the bottom of the slab and the longitudinal steel bar at the bottom of the beam should be fully tied with the stirrups.
(2) Formulate special construction plans and strictly implement them. The scheme should clarify the material, quantity, spacing and fixing method of the point cushion block to ensure that the positioning deviation of the reinforcement conforms to the provisions of the current national standards.
3. Strengthen process management
The construction and supervision unit should strengthen the process quality management of weak parts such as the bottom of the basement beam, the bottom of the bathroom slab, and the side beam, and be equipped with special personnel and self-inspection instruments for timely self-inspection. In the self-inspection of each layer, each type of weak part should not be less than 2% of the number of components and not less than 3 components. Problems found in the self-test should be handled through normal procedures until closure, and corrective measures should be taken to avoid recurrence of similar problems. The results of the self-inspection should be counted and filled in the "Statistical Table of Self-inspection of the Reinforcement Protective Layer" (see Annex 2 for details), which is included in the main acceptance inspection data.
This notice shall be implemented as of the date of issuance.
Attachment 1: Confirmation table of the thickness of the protective layer of concrete reinforcement
Note: 1. Article 4.1.6 of the "Technical Code for Waterproofing of Underground Engineering" stipulates that the thickness of the protective layer of the reinforcement on the surface of the waterproof concrete structure shall not be less than 50mm. 2. The basement and toilet should be classified as Class IIA.
Appendix 2: Statistical table of self-inspection of reinforcement protective layer
Note: 1. Statistics are made by unit projects, and statistics are carried out separately in the basement. 2. The self-inspection part must include the bottom of the basement beam, the bottom of the toilet slab, the bottom of the toilet beam, the side beam, etc.
Further discussion:
How is it stipulated in the code about the full and jump tie of the reinforcement?
In the on-site construction management, we have to speak with the basis for the question of which reinforcement bindings must be fully tied and which can be jumped, where the basis comes from, drawings, atlases, national specifications and the construction plan that has been prepared and approved. Of course, the drawings and construction plans of each project are different and cannot be the same. Today, I will mainly talk about whether the intersection of the reinforcement mesh must be fully tied in the "Building Construction Manual" and "Construction Code for Concrete Structure Engineering", which are common in most areas.
One
Building Construction Manual
(1) The provisions on steel bar binding in the fourth part of the "Building Construction Manual" are as follows:
(1) The intersection of the steel bar must be firmly tied with iron wire.
(2) The reinforcement mesh of the plate and the wall, in addition to the intersection points of the two rows of steel bars on the periphery, the intersection points of the middle part can be staggered and fastened apart, but it must be ensured that the stressed steel bars do not displace. The steel mesh sheets that are stressed in both directions must be firmly rooted.
(2) Article 21 of the "Building Construction Manual" stipulates the following on steel bar binding:
Except for the main reinforcement in the column reinforcement and the beam reinforcement with welded joints, the rest of the stress reinforcement and stirrups are connected by binding. The reinforcement is tied on site, with 20 gauge iron wire. The stirrups of columns and beams are vertically arranged with the stressed reinforcement, and the overlapping of stirrup hooks should be staggered along the direction of the stressed reinforcement. The intersection points of the two rows of reinforcement on the periphery of the reinforcement mesh of the plate and the whole pouring layer should be tied firmly at each point, and the intersection points of the middle part can be staggered and fastened apart, but it must be ensured that the stressed steel bar will not be displaced. In short, the binding should be done: the position of the steel bar is accurate, the binding is firm, the position of the steel bar joint, the lap length, the thickness of the protective layer, etc. meet the requirements, and the construction is strictly in accordance with the drawing.
Two
Code for construction of concrete structure engineering
5.4.9 of the Code for the Construction of Concrete Structures stipulates as follows:
The detailed structure of the reinforcement binding shall comply with the following provisions:
(1) The binding lap joints of the steel bar should be tied with iron wire in the center and at both ends of the joint;
(2) The intersection points of the reinforcement mesh of each vertical plane in the reinforcement skeleton of walls, columns and beams should be firmly established; The intersection of the upper part of the reinforcement mesh of the plate should all be firmly fastened, and the bottom reinforcement mesh can be staggered and fastened at intervals except for the edge part.
To sum up, in strict accordance with the requirements of the specification, only the reinforcement reinforcement at the bottom of the plate has staggered binding at intervals (and must be a one-way plate), and the reinforcement mesh of the shear wall wall is stressed in both directions, so the reinforcement of the shear wall should also be fully tied.
The raft is full of boats
The wall panels are fully reinforced
Of course, in the case of clear requirements in the drawings, it must be subject to the design requirements, and there are different regulations in various places, and many regions and enterprises are required to carry out full binding no matter what the situation.