Thread Content
300 Core Technical Issues in Reinforcement Engineering (I) 1. What is the reinforcement cover? Answer: The distance from the outer edge of the stress-reinforcing steel to the concrete surface. The rebar cover is the distance from the outer edge of the outermost rebar to the concrete surface. The distance from the outer edge of the outermost rebar to the concrete surface. 2. Are the stirrups inside or outside the beam and column cover? Answer: Inside. 3. What should be the thickness of the cover layer for the longitudinal reinforcement in frame beams? Answer: It should be 30 millimeters rather than 25 millimeters. The thickness of the concrete cover for the longitudinal reinforcement in frame beams is not necessarily 25; it varies depending on the environmental category. One type of environment, with a beam cover thickness of 20 mm ； Class IIa environment, beam cover thickness 25mm ； Class IIb environment, beam cover thickness 35 mm ； Class 3A environment, beam cover thickness 40mm ； Class 3B environment, beam cover thickness 50mm ； Additionally, when the concrete strength grade is 25 or less, the thickness of the protective layer should be increased by 5 mm. The “Code for Design of Concrete Structures” GB50010 provides detailed explanations. You can also check page 56 of 16G101-1. 4. Why is the cover thickness for the longitudinal reinforcement in frame beams specified as 25 millimeters instead of 30 millimeters? Answer: Since frame columns bear compression forces while frame beams bear tension forces, too thin a cover layer will reduce the effective height of the beams and diminish the load-bearing capacity of their longitudinal reinforcement. 5. When the beam and column are flush on one side, which types of rebar need to be adjusted? Answer: The longitudinal bars in the beam that are located right next to the columns shift aside, and the beam stirrups also shift aside, resulting in a reduction of the horizontal dimension by one diameter of the column longitudinal bar. 6. On the main beams and secondary beams, what types of rebar are usually reserved for clearance? Answer: When not specified on the drawings, all the upper reinforcement bars of the main beam shall be shifted aside; the stirrups of the main beam shall also be shifted accordingly, reducing the height of the vertical edges by one diameter of the upper reinforcement bar of a secondary beam. 7. Is it reasonable to determine the stirrup size based on the outer dimension or the inner dimension? Why? Answer: It’s reasonable to use Ripi’s method, because if external reinforcement is used, the diameter of the rebar has to be considered as well, which is time-consuming and troublesome. 8. What is the minimum specified bending radius for stirrups? Answer: Not less than 2d. 9. What is the specified angle for the bend hooks of stirrups? Answer: 135 degrees. 10. What part does the hook length of stirrups refer to? Answer: The straight portion after bending. 11. What is the specified length of the hook for stirrups? Answer: 5d for non-seismic design ； The greater of 10 days and 75 millimeters for seismic or torsional resistance. 12. How are the dimensions of stirrups measured? Answer: Measure perpendicularly inside the two parallel sides. 13. How is the overlapping length of composite inner stirrups calculated? Answer: Subtract 2 times the thickness of the protective layer from the cross-sectional dimension, then subtract 2 times the radius of the longitudinal bars; divide by the number of longitudinal bar groups, multiply by the number of longitudinal bar groups in the inner stirrups, add 2 times the radius of the longitudinal bars, and finally add the shaping adjustment value. 14. In which direction are the hooks of beam stirrups usually oriented? Answer: Upward, mainly toward the side that is not under tension, toward the side containing the concrete slab. 15. Under what circumstances are the hooks of beam stirrups directed downward? Answer: When it is an upward-reversed beam, with the slab located below the beam. 16. Are the hooks of the column stirrups all at one corner? Answer: No, the 4 corners should be offset from each other. 17. What is the function of stirrups in beams? Answer: It serves to fix and restrain the longitudinal bars, as well as to bear a portion of the shear force. 18. What is the ordinary double spacing of stirrups? Answer: @100/20019, what is the typical spacing for stirrup reinforcement in millimeters? Answer: 100 millimeters. 20. What are the requirements for the stirrup reinforcement zone in primary seismic-resistant frame beams? Answer: 2 times the beam height. 21. What are the regulations regarding the stirrup reinforcement zones in seismic frame beams of grades 3 and 4? Answer: 1.5 times the beam height. 22. What consequences can arise if the bending radius of stirrups is too large? Answer: Reducing the effective height and width of components affects the quality of the building. But **there are no regulations, which is a pity. 23. In the pre-attached beam framework, how to reinforce it with stirrups? Answer: Stretch the stirrups into a spiral shape and insert them into the core of the framework to secure them; one stirrup is placed every approximately 2 meters. 24. Where are the upper corner reinforcement bars of a beam indicated using the flat method? Answer: At the centralized annotation location. 25. What is another name for the top angle bar of a beam? Answer: The continuous reinforcement or full-length reinforcement at the top of the beam. 26. Where can the continuous reinforcement bars in the upper part of the beam be connected? Answer: At the midpoint of one-third of the span of the beam. 27. What were the rebars at the supports of beams called before? Answer: Stirrup or negative moment stirrup. 28. How long is a row of rebars at the end supports of a beam required to extend into the net span? Answer: One-third of the net span. 29. How long are the two rows of bars at the end supports of a beam required to extend into the net span? Answer: One-quarter of the net span. 30. How is the length of a row of rebars at the middle support of a beam calculated? Answer: Take one-third of the larger net span on each side multiplied by 2, and add the width of the middle support. 31. How is the length of the two rows of bars at the middle support of the beam calculated? Answer: Take one-fourth of the larger net span on each side multiplied by 2, and add the width of the middle support. 32. What does Lae mean? What is it usually called? Answer: The seismic anchorage length is commonly referred to as the straight anchorage length. 33. What does Lle mean? How many ties should be used within the overlapping range? Answer: The lap length should be secured with no fewer than 3 ties. 34. What is the relationship between the anchorage length and the lap length? Answer: Multiplying by the correction factor is a linked relationship. 35. What are the types of correction coefficients? Answer: 1.2 ； 1.4 ； 1.6 There are three in total. 36. What does the 50% reinforcement lap area percentage mean? Answer: Half overlapped and half not overlapped. 37. For a 25% area percentage, how many of the 8 rebars are allowed to be connected in the same section? Answer: 2. 38. Where are longitudinal bars at the bottom of a beam allowed to be connected? Answer: At one-quarter of the way down from the beam, near the support. 39. Under what circumstances is 0.4Lae used? Answer: When the direct anchor is insufficient. 40. What is the name of the 0.4Lae+15d right-angle hook in the catalog? Answer: It’s called a bent anchor. 41. What methods can be used to ensure accurate calculation of the beam length? Answer: After calculating, conduct thorough verification, careful checking, and repeated reviews until everything is accurate. 42. When calculating the rebar for a beam, what should be calculated first? What comes second? What comes next? Answer: First, calculate the length of the beam; next, calculate the width of the supports; and then, calculate the net span of each span of the beam. 43. For the top edge nodes of beams, is it acceptable if the longitudinal reinforcement in beams and columns does not have hooks? Answer: Absolutely not. 44. What are the various construction methods for the top edge nodes of beams? Answer: 1. 65% of the longitudinal bars at the column edges shall be anchored into the beam by 1.5Lae ； 2. The rebars on the beam are anchored into the column by 1.7Lae. 45. When the heights of the left and right spans of a beam are different, under what conditions can the longitudinal reinforcement of the beam be bent to pass through? Answer: Bending is possible when the ratio of the support width to the difference in beam height is less than one-sixth. 46. When the cross-sections of the upper and lower columns are different, under what conditions can the longitudinal reinforcement of the columns be bent to pass through? Answer: Bending is possible when the ratio of the beam height to the difference in cross-sectional widths of the columns is less than one-sixth. 47. What should be done when the cross-section of a beam changes and the longitudinal bars cannot be bent to pass through? Answer: A curved anchor on one side, and a straight anchor on the other. 48. What should be done when the cross-section of a column changes and the longitudinal reinforcement cannot be bent to pass through? Answer: The rebar in the lower column is bent and anchored 200 mm into the edge of the upper column, while the rebar in the upper column is anchored straight into the beam for a length equal to 1.5 times Lae. 49. What are coordinates used for? How to express it? Answer: It is used to indicate direction and positioning, represented by three arrows: right, up, and forward. 50. On the coordinate axes, which direction does X represent? Which direction does Y represent? Which direction does Z represent? Answer: X represents the direction from left to right ； Y represents the direction from bottom to top ； Z represents the direction of vertical entry into the layout. 51. In the flat method, what does the symbol in front of the multiplication sign represent for a beam cross-section? What does it mean after the multiplication sign? Answer: The value before the multiplication sign represents the beam width, while the value after the multiplication sign represents the beam height. 52. In the flat method, what does the value before the multiplication sign represent for a column cross-section? What does it mean after the multiplication sign? Answer: From the perspective of the page, the value before the multiplication sign represents the value in the X direction of the column, while the value after the multiplication sign represents the value in the Y direction of the column. 53. In a structure diagram, what is the difference between a cut-off line and a truncation line? Answer: The cutoff line is a short, thick diagonal stroke drawn at the intersection of the two vertical lines ； A break line is a straight line that is broken in the middle and connected by three consecutive zigzag lines. 54. On a structural diagram, what is the difference between leader lines and dimension lines? Answer: There are often textual instructions near the leader line or an arrow at one end; the dimension line must contain the dimension value, and there must be extension lines touching both ends of it. 55. In a structural diagram, what is the difference between the center line and the axis? Answer: The center line is a dotted line, while the axis is a thin solid line; different line types serve different purposes. 56. What is the difference between axis numbers and detail reference numbers on a structural diagram? Answer: The shaft number is a set of digits or letters inside a circle. The detail index number is a digit or letter separated by a line within a circle, or a digit or letter enclosed in double circles. 57. Why is scale used in drawing? Answer: The ratio indicates the comparison between the drawn object and the actual object. 58. On architectural drawings, what do the numbers following the scale symbol represent? Answer: The scaling factor of the object being drawn. 59. Why are elevations used in drawing? Answer: It facilitates indicating the height positions of various parts. 60. What do the numbers with a minus sign in the marked values mean? Answer: Below the surface of this layer or below the value of plus or minus 0. 61. What are the 3 specified values for seismic frame columns in standard floors in the non-connection zone? Answer: 1. Greater than 1/6 of the column net height ； 2. Greater than 500mm ； 3. Greater than the long side dimension of the column cross-section. 62. In the non-connection zone of seismic frame columns, there is a portion of three-halves hn – where does this refer to? Answer: Including the basement, it is the first floor from the bottom. 63. Where does the calculation of the lower longitudinal reinforcement in a frame beam begin? Where to start again? Where else should it start from? Answer: Start by subtracting the protective layer from the outside of the column, then subtract the horizontal clear distance from the inner surface of the column’s longitudinal reinforcement, and also start from the inner surface of the hooks on the beam’s reinforcement. 64. Where does the calculation for the longitudinal reinforcement at the bottom of a frame column begin? Where to start again? Where else should the measurement start from? Answer: It starts from subtracting the foundation protection layer from the cushion layer, then from the upper surface of the reinforcement mesh on the foundation slab, and also from the upper surface of the stirrups beneath the foundation slab beams. 65. What is the vertical spacing of rebar, and what is the horizontal clear spacing of rebar? What are their values? Answer: The distance between the upper and lower rows of rebar in a beam is called the row spacing, while the minimum distance between the outer edges of the rebar is called the clear distance. The spacing shall be not less than the diameter of the reinforcement plus the clear distance; the horizontal clear distance between the longitudinal reinforcements at the top of the beam shall be not less than 30 mm and 1.5d ； The horizontal clear distance between the longitudinal bars at the bottom of the beam shall be not less than 25 mm and 1d. 66. Why is the bending radius of the longitudinal bars in the new regulations much larger than before? Answer: Experiments have shown that an excessively small bending radius can cause hidden fractures within the rebar, affecting the structural strength of the components and shortening the service life of the building. 67. When bending steel bars into right angles, where on the bending machine should the bending point be positioned to achieve an accurate bend? Answer: It is located at the edge of the central stake, on the side opposite to the direction of the rebar hook. 68. What specific tasks should be carried out on steel bars before shaping? Answer: 1. Straighten bent materials ； 2. Verify the number of roots ； 3. Check the cutting dimensions ； 4. Perform a test bend ； 5. Determine the storage area for semi-finished products ； 6. Prepare the labels ； 7. Prepare the bundling wire ； 8. Prepare the transport vehicle. 69. Why is there an elongation rate after steel bars are bent? Answer: The calculation is based on the bend angle, and an actual arc is formed. 70. In the new regulations, what are the bending elongation rates for rebar at 45 degrees and 90 degrees respectively? Answer: 1d and 2d respectively. 71. Is the elongation rate related to the formation of longitudinal bars? How exactly is it done? Answer: Yes, when marking lines before molding, the extension length of each section is removed. 72. How many types of connections are there for steel bars? Answer: Overlap ； Welding ； Mechanical connection. 73. Under the new circumstances of the current era, what is the best connection method for rebar? Answer: Threaded connection is the best. 74. What does non-contact connection of steel bars mean? Answer: A specified distance is left between the two overlapping rebar bars. 75. Why is non-contact connection of steel bars being promoted these days? Answer: To ensure the bond between concrete and steel reinforcement. 76. What are the requirements for stirrups in beam-column joints? Answer: Encrypted layout. 77. In column reinforcement, how else can the inner stirrups be arranged? Answer: Replace with 2 tension straps. 78. What meanings does the “+” sign represent in the beam notation system? Answer: 1) The height to which the component is lifted ； 2) Indicates the reinforcement bars in the beam core. 79. What meanings does the “-” minus sign represent in the beam notation system? Answer: It only indicates the height by which the component is reduced. 80. In the beam notation, what various meanings are represented by the parentheses ( )? Answer: 1) The component changes height ； 2) Number of beam spans ； 3) Number of stirrup limbs. 81. What does the “/” slant dash mean in beam notation? Answer: Rebar is arranged in rows. 82、“ ； ”What does a semicolon mean in flat method beams? Answer: The longitudinal bars are divided into top and bottom ones. 83. In the flat method, what are the different ways to indicate the total score? Answer: 2 types, centralized annotation and in-situ annotation. 84. Which takes precedence, centralized annotation or in-situ annotation? Answer: In-situ labeling values take precedence. 85. Are the top corner reinforcement bars of the beam not included in the in-situ markings? Answer: It is already included in the in-situ labeling. 86. Why does the content of the concentrated annotation appear again at the in-situ annotation location? Answer: Local structural changes occur, such as changes in the cross-sectional height and width, elevation, or reinforcement; design errors may also be present. 87. What are the approximately 6 main categories of content related to flat method shear walls? Answer: 1) Wall beam ； 2) Wall columns ； 3) Horizontal distribution bars of the wall ； 4). Vertical distribution reinforcement of the wall ； 5) Diagonally intersecting rebar and hidden supports ； 6) Opening reinforcement. 88. What are the types of wall beams? Answer: There are hidden beams ； Diagonal beams and edge beams. 89. What are the types of wall columns? Answer: There are hidden columns ； corner post ； wing wall column ； end post ； Counterweight column. 90. What are the horizontal rebar bars inside a wall called? Answer: They are called horizontal distribution bars for the wall. 91. What are the rebar bars placed inside a wall called? Answer: It is called the vertical distribution reinforcement of the wall. 92. What symbol is used to represent the wall in a shear wall? Answer: Q. 93. In which direction are the hooks of the horizontal reinforcement bars in the wall oriented? Answer: Facing inward toward the wall. 94. In walls and wall columns, what should be the length of the upper hooks on the vertical rebar? Answer: Anchor length minus plate thickness plus cover thickness. 95. What are the different methods for placing the horizontal distribution bars in shear walls at corners? Answer: 1) Turn directly on the outside ； 2) Bend a hook on the inner side of the column corner reinforcement, with a hook length of 0.8Lae. 96. In a shear wall of uniform width, what is the difference in the horizontal length of the stirrups between the wall beams and the wall columns? Answer: 2 times the diameter of the column longitudinal reinforcement. 97. For the diagonal cross-reinforcing members in shear walls, which line is used as the anchorage point? Answer: The line connecting the edges of the upper and lower openings. 98. In shear wall diagonal cross-reinforcements, where is the zone of increased stirrup density? Answer: At the intersection of the hidden braces along the line connecting the upper and lower openings. 99. When does a opening in a shear wall need to be flanked by hidden beams and columns, depending on its size? Answer: 800mm. 100. At what size of openings in shear walls are reinforcement bars required at the edges of the openings? Answer: When it is greater than 300 mm and less than 800 mm.