【正文】 ensile strength of sample shall yet be equal to tome of the actual tensile strength of the mother material. When actual strength is being calculated, the actual cross section area of the steel bar shall be adopted. Site test of joints shall be per batches for checking acceptance. Joint of same type, same size and same class in the same batch under the same construction condition shall be arranged in one batch of 500 joints for checking acceptance. The final batch, if less than 500 pieces, will be considered as one batch for checking acceptance. For each batch checked for acceptance, 3 samples shall be taken at random for onedirection tensile test and then be inspected and evaluated in accordance with class designed.When all the 3 onedirection tensile test results meet requirement of strength, that batch is considered as qualified.If one of the samples is unqualified, other 6 sample shall be taken for retest。 if there is still one of the samples is unqualified, the batch will be considered as unqualified. 10 batches will be tested at site for inspection, if all the onedirection tests are qualified, quantity of joint for each batch may be increased by twice.Construction and acceptance specification of concrete structure engineering project GB 5020492 Tying steel bars shall meet the following rules:I．Cross points of bars shall be tied firmly.II．For steel bar net of board and wall, in addition to the cross points of the two rows of bars that are at the outside edges shall all be tied firmly, partial crossing points in middle may be tied every other point in a staggering way, but it should be guaranteed that position of steel bars with no deviation。 steel bars bearing load from both directions shall all be tied firmly.III．For tying steel bars of beams and columns, except for that designed specially, shall be perpendicular to the steel bars that is load bearing. At the place where the hooks of tying bars are piling up one another, they should be arranged in a staggering way along the direction of load bearing steel bars. joint of steel bars shall meet the following rules:I．Overlapping length from the end to the bending point shall not be shorter than 10 times of diameter of the bar.II．In tensile loading zone, the end of a steel bar of class I shall have a bend hook.III．Length of overlapping of steel bars that is of class I and is bearing pressing load with diameter under 12mm, and any steel bar bearing load and in the structure that is bearing pressing load shall not be shorter than 35 times of diameter of the steel bar. IV．At location of overlapping, the steel bar shall be tied firmly at both ends and the middle.V． For length of overlapping of tensile steel bar joint with tying wire shall meet requirement in table . , and that of pressing load bearing bars shall be time of the former. length of overlapping joint of bars with tying wire table type of steel barstrength class of concreteC20C25higher than C25class I steel bar35 d30 d25 dcrescent veinsclass II steel bar45 d40 d35 dclass III steel bar55 d50 d45 dcold drawn lowcarbon steel wire300 mmNote:(1) When diameter of steel bars of class I and class II d=25mm, overlapping length of tensile steel bar shall be the value in the table plus 5d.(2) When diameter of screw thread steel bar is no bigger than d=25mm, overlapping length shall be the value in the table minus 5d.(3) When the load bearing steel bar is likely to be disturbed during curing period, length of overlapping shall be increased accordingly.(4) In any case, overlapping length of steel bars that are loaded with tensile along longitudinal direction shall not be shorter than 300mm。 that loaded with pressing force shall not be shorter than 200mm.(5) Overlapping length of steel bar tied with wire and is in light aggregate shall be longer than that in mon concrete by 5d: for colddrawn steel bar 50mm shall be increased.(6) When strength of concrete is lower than C20, overlapping length of class I and class II steel bars shall be the value of C20 in the table plus 10d.(7) Overlapping length of load bearing steel bars of class I and class II that are required for antiearthquake capability shall be increased by 5d.(8) When two pieces of steel bars with different diameters, overlapping length shall be based on the thinner. Reinforced concrete structure engineering projectConstruction and acceptance specification of concrete structure engineering project GB 5020492 Class, category and diameter of steel bars shall be adopted according to design. When substitution is needed, it should be agreed by the design institute. Shape and size of processing steel bars shall meet requirement of design. Surface of steel bar shall be clean without damage, oil spot, painting dirt and rust. Steel bars with pellet rust or scale are not allowed to use. Thickness concrete protective layer of load bearing steel bar shall meet requirement of design. If design has no significant requirement, it shall be smaller than diameter of load bearing steel bar and meet the regulation in table . Thickness of concrete protection layer of steel bars table environment and conditionname of structure memberclass of concrete strengthlower than C25C25 and C30higher than C30normal indoor ambientboard, wall and shell15beam and column25outdoor or indoor high humid environmentboard, wall and shell352515beam and column453525with paved cushion layerfoundation35without paved cushion layer70Note: (2) For prefabricated structure members in normal factory indoor environment, when the strength is not lower than C20 and if construction work quality is assured, thickness of concrete protection layer may be reduced from the value listed in the table by 5mm, but that of prestressed reinforcing bar shall not be thinner than 15mm. Those at out