[jianjianjiantong] master the key points of steel bar supervision, and pass the steel bar construction acceptance easily!


I

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2

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Before formal welding, the welder must be supervised to carry out welding performance test under site conditions, and formal production can only be carried out after passing the inspection

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Anchorage length correction coefficient (a) should be taken according to table 4

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3

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For centralized processing of steel bars, the processing unit shall issue the factory certificate and steel bar factory certificate or steel bar test sheet approval (copy), but the seal of the processing unit shall be stamped

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See Table 3 for anchorage length La and seismic anchorage length Lae of tensile reinforcement

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raw material control of steel bar (I) steel bar 1

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4

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The steel strand shall not have broken, transverse cracks and intersecting steel wires, and the surface shall not have lubricants, oil stains and slight floating rust Generally, chemical analysis is not carried out for building steel bars, but chemical composition inspection shall be carried out when brittle fracture, poor welding performance or significantly abnormal mechanical properties are found in the processing of steel bars, or when there is no factory certificate, unknown steel grade or imported steel bars with welding requirements

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The longitudinal load-bearing reinforcement of axial tension and small eccentric tension members shall not adopt binding lap joint

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La =? A * lablae =? AE * La Table 4 anchorage length correction factor of tensile reinforcement? Anchorage conditions? A – nominal diameter of ribbed reinforcement is greater than 251.10? Epoxy resin coated ribbed reinforcement 1.25? Reinforcement easily disturbed during construction 1.10? Protective layer thickness of anchorage zone 3d0.8 note: in Interpolation is used in the interval

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Note: 1

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Table 3 non seismic anchorage length La and seismic anchorage length Lae of tensile reinforcement

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When mechanical joints are set at places with large stress, the area of steel bars with joints within the same joint shall not be more than 50% of the total area of steel bars, and the section of adjacent joints shall not be less than 35d and 500mm apart (D is the larger direct area of stressed steel bars)

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Mechanical connection or welding shall be adopted for the connection of frame beam, concealed column longitudinal bar of seismic wall and steel bar with diameter ≥ 22; 2

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The supervision engineer shall check the welder’s qualification certificate (retest every two years)

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Binding and overlapping connection can be adopted for other steel bars; 3

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Where the diameter of longitudinal reinforcement is d ≥ 25 mm or the span of beam is greater than 8 m, straight thread connection shall be adopted, binding lap joint shall not be adopted, and the joint performance shall not be lower than grade II

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(2) Methods of steel bar connection: 1

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6

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Welding rod: E43 welding rod is used to weld hpb300 reinforcement and hpb400 reinforcement; E55 welding rod is used to weld HRB400 reinforcement

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The raw materials of reinforcement and the connection of reinforcement shall be witnessed by the supervisor, and the sampling test shall be kept for record to verify the test results of the contractor; the re test results of reinforcement shall be inspected according to the type of reinforcement

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If there is more than one item, it can be calculated by multiplication, but it should not be less than 0.63 and (AE) is seismic anchorage The length correction factor is 1.15 for the first and second seismic grade, 1.05 for the third seismic grade and 1.00 for the fourth seismic grade

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The reinforcement without retest or unqualified in retest shall not be used in the project

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The design requirements of the project: (1) the ratio of the measured tensile strength to the measured yield strength of the reinforcement shall not be less than 1.25; (2) the ratio of the measured yield strength to the standard strength of the reinforcement shall not be greater than 1.3; (3) the measured total elongation of the reinforcement under the maximum tensile force shall not be less than 9% (4) the HRB400 grade reinforcement shall be used for the embedded reinforcement, and the cold processed reinforcement shall not be used; (5) The hanging bar shall be made of HRB400 steel bar (2) welding rod and flux 1

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Anchorage length of longitudinal reinforcement at the bottom of cast-in-place concrete slab: the longitudinal reinforcement at the bottom of slab shall extend to the middle line of beam, and shall not be less than 10 days and 100 mm

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After entering the construction site, the reinforcement shall be subject to appearance inspection, retest according to the batch (generally the same specification), and witness sampling according to 100% quantity

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2、 Anchorage of reinforcement 1

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Welding joint is strictly prohibited for the connection of cold-rolled ribbed steel bars; (3) overlapping length of longitudinal tensile steel bars (see general description of structural design for details); 1

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La should not be less than 2002

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Unless otherwise indicated in the drawing, the thickness of lap weld is 0.3d, the width of weld is ≥ 0.8d, the length of weld is 11d for single side weld and 6D for double side weld.

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D is the diameter of anchorage bar

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5d0.7 note: (1) 180 ° hook shall be made at the end of hpb300 reinforcement, and the length of straight section after bending shall not be less than 3D; (2) when the thickness of protective layer of anchorage reinforcement is not more than 5D, transverse structural reinforcement shall be set within the length range of anchorage reinforcement, and its diameter shall not be less than D / 4 (D is the maximum diameter of anchorage reinforcement); the spacing between beams, columns and other components shall not be more than 5D, and the spacing between slabs, walls and other components shall not be large (D is the minimum diameter of anchorage reinforcement) 3

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If there are bumps, the height and depth of other defects shall not be greater than the allowable deviation of the position

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4

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Connection of reinforcement (1) the general specification of structural design stipulates that the connection of reinforcement can be divided into two categories: binding and lapping; mechanical connection or welding

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2

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2

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The appearance inspection requirements (see Table 1) table 1 steel bar type: no cracks, scabs and folds on the surface of hot-rolled steel bar

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The basic Anchorage Length Lab and lab of tensile reinforcement are shown in Table 2

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Steel bar shall have factory quality certificate or test report

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Table 2 basic anchorage length of tensile steel bar lab, type of labe steel bar seismic grade concrete strength grade c20c25c30c35c40c45c50c55 ≥ c60hpb300 class I and II (labe) 45d39d35d32d32d29d28d25d24d class III (labe) 41d36d32d29d26d25d24d23d22d class IV (labe) non seismic lab39d34d30d28d25d24d23d22d21dhrb335hpbf335 class I and II (labe) 44d38d33d33d31d29d26d25d24d class III (labe) 40d 35d31d28d26d24d23d22d22d grade 4 (Lab) non seismic lab 38d33d29d27d25d23d22d21d21dhrb400hpbf400rrb400 grade 1 and 2 (Lab) — – 46d40d37d33d32d31d30d29d grade 3 (Lab) — – 42d37d34d30d29d28d27d26d26d grade 4 (Lab) non seismic lab — 40d35d32d32d29d28d27d26d25dhrb500hpbf500 grade 1 and 2 (Lab) — – 55d49d45d41d41d39d37d36d35d grade 3 (Lab) — – 50d45d41d41d38d36d33d32d grade 4 Labe non seismic lab — 48d43d39d36d34d32d31d30d3

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5

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In consideration of the large amount of reinforcement, the dense reinforcement of structural nodes, and the complex intersection, and the simplified design method, the actual layout of reinforcement at nodes (sample) shall be drawn according to the engineering situation, or the node template shall be made, so as to reasonably arrange the reinforcement and arrange the reinforcement crossing sequence

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Mechanical connection of longitudinal stressed steel bars The joints should be staggered with each other

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The welding rod and flux shall have factory certificate, and shall be consistent with the welding type, base metal type or the variety and specification required by the design

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The supervisor will urge the construction unit to do this work according to the requirements

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2

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