【Haichuan Construction Technology】What are the five inspection items for the main structure?
Thread Content
The main structural system of a building refers to the load-bearing structural framework that, based on the foundation, bears and transfers all the loads from the upper parts of the building, resists lateral forces, and ensures the overall stability of the building. If a building is compared to a person, then its core structure is the building’s “skeleton”; the quality of this core structure directly affects the overall safety and service life of the building. Controlling the quality of construction projects relies on scientific and rigorous testing methods; when it comes to the testing of the main structure, five specific types of tests are essential. Inspection of the main structure of construction projects includes testing the compressive strength of concrete, the thickness of the rebar protection layer, the thickness of floor slabs, the distribution of rebar, and the pull test for rebar installed later – what is commonly referred to as the five types of inspections. 1 Testing of concrete compressive strength: The compressive strength of concrete is a key indicator for evaluating the reliability of concrete structures, as it directly affects the structure’s load-bearing capacity and seismic performance. The main testing methods include the rebound method, core drilling method, and ultrasonic-rebound composite method. In engineering practice, the rebound method is primarily used. The rebound method involves striking the concrete surface with a rebound hammer, measuring the distance the hammer bounces back, and using this rebound value to estimate the strength of the concrete. This is a surface non-destructive testing method that relies on the correlation between the hardness and strength of the concrete surface to determine the compressive strength of the concrete.
2 Detection of the thickness of the rebar cover layer: The thickness of the rebar cover layer has a direct impact on the durability and fire resistance of reinforced concrete structures. An overly thin protective layer can cause the rebar to rust prematurely, while an overly thick one may lead to cracks. The thickness of the rebar cover is generally tested non-destructively using electromagnetic principle detection methods. By emitting electromagnetic signals from the probe, a secondary induced magnetic field is generated in the rebar surrounding the protective layer; this field is detected by the probe. After processing by the instrument, a measurement of the thickness of the rebar’s protective layer is obtained. In accordance with GB50204-2023 \"Code for Acceptance of Construction Quality of Concrete Structures\" and JGJ/T152-2019 \"Technical Specification for Testing Steel Bars in Concrete\", the sampling principle for the steel bar cover thickness is as follows: for beam and slab elements, 2% of the total number of such elements, with a minimum of 5 elements, should be sampled for testing. For cantilever beams, the number of components to be sampled shall be no less than 5% of the total, and at least 10 pieces. For cantilever slabs, the number of components to be sampled shall be no less than 10% of the total, and at least 20 pieces. Allowable deviation: (1) For beam elements, the allowable deviation in the thickness of the protective layer is +10mm and -7mm. (2) For slab elements, the allowable deviation in the thickness of the protective layer is +8mm and -5mm. A pass rate of 90% or higher for all thickness inspections of the protective layers is considered acceptable ； If it is between 80% and 90%, double sampling can be performed for re-evaluation.
Inspection of floor slab thickness: The thickness of floor slabs is related to the stiffness and load-bearing capacity of the structure. Insufficient thickness can lead to vibration of the floors, poor sound insulation, and even safety hazards. Non-destructive testing is carried out using the electromagnetic principle detection method. The transmitting probe and the receiving probe are placed on the surface and bottom of the floor slab to be tested, respectively. The transmitting probe emits electromagnetic signals, while the receiving probe captures the attenuated magnetic field signals; after processing by the instrument, the thickness of the floor slab is determined. High-rise buildings should use reinforced concrete structures with cast-in-place floor slabs, whose standard thickness is 10 cm; cast-in-place floor slabs in ordinary buildings that are less than 8 cm thick are considered substandard. The thickness of floor slabs in general floors should not be less than 80 mm; when concealed pipes are embedded in the slab, it should not be less than 100 mm ； The thickness of the top floor slab should not be less than 120 mm. In accordance with GB50204-2023 \"Code for Acceptance of Construction Quality of Concrete Structural Engineering\", the sampling principle for floor slab thickness is: select 1% of the representative rooms, with a minimum of 3 rooms ； For large-scale structural elements, the inspection surfaces can be divided along the longitudinal and transverse axes; 10% of them should be inspected randomly, with a minimum of 3 surfaces ； For 6 floors or less, no fewer than 3 floor slabs shall be sampled; for 6 floors or more, no fewer than 6 floor slabs shall be sampled. No less than 5 measurement points should be taken from each floor slab for testing. When the designed thickness of a cast-in-place floor slab is ≤150mm, the allowable deviation is +8mm/-5mm. Over 90% of the measurement points should fall within the allowable deviation range.
Testing time: The age of the steel bars bonded with adhesive must meet the specified requirements; for anchor bolts that use chemical bonding, the bonding material must have reached the required level of curing at the time of testing. The above are the main aspects of the five tests for the main structure, with non-destructive testing being the primary method and destructive testing used as a supplement. Different regions may have varying requirements for the five inspection items related to the main structure; in some areas, inspections for structural dimension deviations and structural deformation are added. In practical engineering applications, it is necessary to follow the requirements set by the local housing and construction authorities.
【History of Haichuan Chemical】Born for the defense chemical industry, Hualu Engineering Company has achieved remarkable development over 60 years https://bbs.hcbbs.com/thread-5704223-1-1.html (Source: Haichuan Chemical Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】2791-2025: Fuda Zijin Hydrogen Energy unveils China’s first 1,000-kilogram-class commercial ammonia decomposition hydrogen production and hydrogen refueling station https://bbs.hcbbs.com/thread-5704209-1-1.html (Source: Haichuan Chemical Industry Forum)
【Haichuan Construction Technology】How to Prepare and Manage Project Quality Management Plans https://bbs.hcbbs.com/thread-5704329-1-1.html (Source: Haichuan Chemical Industry Forum)
【Ten Years of Rapid Development in Chemical Equipment】2792-2025: Breaking Monopolies! Huayou Gongjian Company’s self-developed \"bending pipe tool\" proves useful in East African projects https://bbs.hcbbs.com/thread-5704226-1-1.html (Source: Haichuan Chemical Industry Forum)