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This is a summary of the article’s author’s 10 years of experience in structural design, and represents personal opinions only. Feel free to exchange ideas and offer guidance. 1. Regarding the issue of the external corners of the slabs of box and raft foundations: (1) The area occupied by these external corners is extremely small compared to the total area of the foundation slab, so they were simply removed. It can be cut at a right angle or an oblique angle. (2). If the bottom slab rebar is arranged in two rows in both directions and remains unchanged in the cantilevered section, there is no need to add radial rebar at the internal corners; who has ever seen radial rebar used in independent foundations? Of course, it won’t hurt to add it. (3). If Party A and the boss aren’t too unbearable, the distribution rebar for the one-way slabs of the cantilever slabs can be changed to a diameter of 12. Don’t underestimate this change – it can save 30,000 to 200,000 yuan on a project without any problem. 2. Regarding the issue of cantilevered slabs for the base plates of box and raft foundations: 1) From a structural perspective, if cantilevered slabs can be used, it is possible to evenly distribute the rebar in the edge spans; especially when the rebar is arranged continuously across the entire base plate, this approach prevents an increase in the amount of rebar needed across the whole base plate, thus saving materials. (2) After installing the cantilever slab, the additional stress on the foundation base can be reduced; when the foundation is located on the edge of a natural soil layer or another type of artificial foundation, the use of a cantilever slab makes it possible to make use of the natural soil layer. If necessary, perimeter window wells with larger spans can be added. (3) It can reduce overall settlement; when the load is eccentric, installing cantilever slabs at specific locations can also adjust the difference in settlement and overall inclination. (4) The window well area can be considered as a wall built on a cantilevered beam; it is not advisable to have further long cantilevered beams. Although in calculations, this slab should not be treated as a cantilever slab. Of course, this rule is not absolute; when there are multiple basement levels, the window wells have relatively dense partition walls, and those partition walls can be connected to the interior walls, flexible consideration can be given. (5) When the groundwater level is high, extending the foundation slab helps to address the issue of buoyancy resistance. (6) From an architectural perspective, removing the overhangs facilitates the use of flexible waterproofing methods. When it is a multi-story building, the structure can also yield to the building. 3. Regarding the proportion of stirrups in beam reinforcement (about 10~20%): For example, in an 8-meter span beam with a cross-section of 400X600, the reinforcement consists of 6 bars of 25 mm diameter at the top, with 1/3 of them truncated, and 5 bars of 25 mm diameter at the bottom; the stirrups are arranged as 8@100/200(4), with increased density within a range of 1000 mm. Total amount of longitudinal bars: 3.85*9*8=281 kg; stirrups: 0.395*3.5*50=69. The ratio of stirrups to longitudinal bars is 1/4. If the ratio for double-leg stirrups is only 1/8, then the proportion of stirrups relative to longitudinal bars is smaller, so there is no need to be stingy when using stirrups. Not to mention the need to strongly cut and weakly bend. It already excludes the construction stirrups. 4. Regarding the calculated span of beams and slabs: The calculated spans mentioned in general manuals or textbooks, such as 1.1 times the net span, are applicable only to conventional structural design and are not suitable for widely used wide and flat beams. In simple terms, a beam-slab structure can be considered as having a rigid support on the center line of the beam; by eliminating the concept of a separate beam, the beam and the slab are treated together as a single member with a variable cross-section. In a flat-beam structure, when the beam height is only slightly greater than the slab thickness, the calculated length should be taken as the center of the beam. The bending moment at the beam center together with the beam thickness, as well as the bending moment at the beam edges together with the slab thickness, should be considered; reinforcement should be selected based on the larger of these values. (Borrowing the concept of the variable cross-section at the stepped independent foundation,) columns can also be considered as beams with extremely large cross-sections; therefore, when designing the reinforcement for such beams, the bending moment at the edge of the column should be taken into account. Peak shaving is normal; it’s a problem only if peak shaving isn’t done. 5. The lap length of the longitudinal bars is several times the diameter d of the bars; generally, d is taken as the smaller value of the bar diameters. This is on the premise that the strength of bars with larger diameters is not fully utilized. Otherwise, the larger value of the rebar diameter should be used. If the longitudinal reinforcement in the columns at the top of a frame structure is sometimes larger than that in the lower layers, a larger diameter for the reinforcement should be used; in some cases, the longitudinal reinforcement should even extend down one additional layer. In fact, putting two rebar bars together and tying them with wire doesn’t serve much purpose; it also weakens the bond between the rebar and the concrete. Therefore, wherever possible, mechanical connections or welding should be used for rebar. 6. The anchorage length of rebar is several times the diameter d of the rebar; this is a requirement under the premise that the strength of the rebar is fully utilized. When the strength of the rebar is not fully utilized, such as in the case of small protrusions on beams along the longitudinal rebar or at the ends of horizontal rebar in shear walls, the anchorage length can be reduced. For example, at the ends of the horizontal reinforcement in shear walls, only a straight hook of 10d is required. 7. The cost of columns is very low in frame structures, yet they play a decisive role in earthquake resistance. Experimental results show that, when spatial effects are taken into account, the longitudinal reinforcement in columns must be increased to about 2.5 times the calculated value in order to ensure that plastic hinges do not form in the columns. It is possible not to follow the calculated reinforcement requirements, by significantly increasing the longitudinal bars and simultaneously increasing the stirrups. 8. Seismic joints should be enlarged; statistics show that 40% of the seismic joints installed in accordance with regulatory requirements collided during earthquakes. Therefore, the spacing of seismic joints should be increased. 9. Anchoring? Overlapping? For example, at the center column joints, the longitudinal reinforcement beneath the frame beams is anchored into the column at a length equal to LAE; the lap length is 2*LAE minus the column width. If the diameter of the reinforcement is 25 mm, then LAE = 40D, and with a column width of 500 mm, 2*25*40 – 500 = 1500 mm. This lap length of 1500 mm is well above the value of 1.2*LAE, which is 1200 mm. And for columns with varying cross-sections, such as when the cross-sections of the upper and lower columns differ by 50, and the upper column is anchored into the lower column by 40D, should lapping be considered in this case for anchorage purposes? 10. Regarding rebound and re-compression: During the excavation of the foundation pit, the soil at the edge of the pit within the friction angle range is constrained and does not rebound; whereas the soil at the center of the pit rebounds. The rebound is primarily elastic in nature, and the rebounded material is removed manually. When the foundation is small and the bottom of the pit is under significant restraint, such as in the case of isolated foundations, the rebound effect can be ignored; when calculating settlement, the additional stress at the base should be taken into account. When the foundation pit is large, it is relatively less constrained; in the case of box foundations, settlement should be calculated based on the base pressure, with the portion constrained by the soil at the edges of the pit considered as a safety margin. This is one of the reasons why the calculated settlement is higher than the actual settlement. 11. The strip foundation under columns is generally considered to be calculable as a inverted floor slab when the stiffness is high and the axial force and span of the columns are not significantly different. In practice, most of it can be calculated based on the floor slab. That is, a modified inverted roof slab is used. First, calculate the continuous beam based on the average reaction forces. Then, balance the resulting support reactions with the axial forces of the columns; add the positive values of this difference to the 1/3 portion of the beam on each side of the column, and add the negative values to the 1/3 portion of the beam at the mid-span. Relatively speaking, the compressive stress in the 1/3 portion at the mid-span is lower. Multiple revisions may be required until the support reactions are in equilibrium with the column axial forces. 12. Additional reinforcement at the points where the main beam meets secondary beams: Stirrups should generally be added first. These additional stirrups can be considered as those that supplement the stirrups of the main beam where it is not possible to add stirrups within the cross-section of the secondary beam, or when there is a shortage of stirrups; they are added on both sides of the secondary beam, similar to the additional reinforcement used for openings in slabs. Additional reinforcement is generally required, but it is not absolute. The specifications state clearly that concentrated loads located below the beam or within the height range of the beam cross-section should be carried entirely by additional transverse reinforcement. In other words, concentrated forces located on the beam, such as columns on the beam, or beams added later to the beam, such as the bearing beam under a water tank, do not require additional reinforcement. Additional reinforcement should be added to the concentrated force at the bottom of the beam. However, the concentrated load within the height range of the beam section can be determined based on specific circumstances. When the cross-sections of the main and secondary beams are not significantly different and the load on the secondary beams is high, additional reinforcement should be added. When the main beam is very tall, the secondary beam has a small cross-section and the loads are low, such as when it is close to an additional hidden beam on the slab, the main beam may not require additional reinforcement. Also, when both the primary and secondary beam sections are very large, such as those formed due to process requirements, and the loads are relatively low, the primary beam may not require additional reinforcement. As a general principle, when the main beam cracks due to the secondary beam, if the concrete and stirrups in the section ranging from the top of the compressed zone of the secondary beam to the bottom of the main beam are capable of withstanding the shear forces generated by the secondary beam, no additional reinforcement is required for the main beam. For a concentrated force on the beam, the shear force generated is the same throughout the entire length of the beam; thus, the shear resistance requirement is satisfied, and it is naturally met at the location of the concentrated force. For primary and secondary deep beams as well as secondary beams, when the cross-sections and loads are small relative to those of the primary beams, this requirement can also be met. On the other hand, a few more rebar bars won’t make a difference. But sometimes, when you want to slack off on drawing, you can use this to argue with the boss. 13. Under normal circumstances, cantilever beams should have a constant cross-section, especially when the overhang length is short. Unlike cantilever slabs, the self-weight of cantilever beams accounts for only a small proportion of the total load, and creating a variable cross-section does not effectively reduce this self-weight. The stirrups of the variable-section cantilever beams are all different, which increases the difficulty of construction. The deflection of beams with variable cross-sections is also greater than that of beams with constant cross-sections. Of course, except for those with exposed main beams. Exposed large beams have a better visual effect when their cross-section is varied appropriately. 14. Cast-in-place slabs should generally be designed as two-way slabs. Firstly, double-sided panels have numerous support edges, providing good seismic stability; even if two sides collapse, there are still the other two sides. When a one-way slab collapses, one of its panels falls down. Second, the economics of double-sided panels. Mathematically, for example, in a two-way slab supported simply at all four corners, the mid-span bending moment coefficient for one direction is approximately 1/27, while for a one-way slab supported simply at both ends, this coefficient is 1/8. The ratio of these two values is 2*1/27 / 1/8, which is about 60%. Structurally, the thickness of double-directional slabs ranges from 1/40 to 50, while that of single-directional slabs ranges from 1/3 to 40. Double-directional slabs are thin; furthermore, even in the case of single-directional slabs, structural reinforcement must be provided on their non-load-bearing edges. 15. Beam pads: To reduce the additional bending moment exerted on brick walls due to the eccentricity of the support reactions, beam pads with internal notches can be used. 16. It is generally believed that when the diameter of the rib on the plate is 8 or more, it can prevent bending due to stepping on it during construction; however, based on field experience, only ribs with a diameter of 12 or more can ensure this. 17. For cast-in-place balcony balustrades, in terms of construction requirements, the slab thickness should be greater than 80 when using a single row of rebar, and greater than 120 when using two rows of rebar. Since the minimum length of the vibrator rod is 30, when arranging the rebar in a single row and the slab thickness is 60, with rebar diameters of 8+6 on both sides, only 23 remains on each side of the rebar, which is not sufficient for vibration. 18. When a room uses double-acting crossbeams, the slab should consider the overall bending moment. That is, for the small panels in the 4 corners separated by the cross-beams of the grid structure, the negative reinforcement should be considered to be cut according to the depth of the room’s bay, rather than merely based on the dimensions of that small panel. That is, the secondary beam is considered merely as a stiffening rib for the large slab. 19. When most of the rooms in a building are small with only one or two larger rooms, determining the thickness of the foundation slab based on the larger rooms would result in waste, while doing so based on the smaller rooms would make it difficult to arrange the rebar properly. When the load-bearing capacity meets the requirements, polyphenylene can be placed in the center of the larger rooms to reduce the load, and the thickness of the foundation slab can then be determined based on the smaller rooms. 20. The deflection at the end of the cantilever beam does not depend solely on its own deformation; the effect of failure within its supports is likely to be greater than the deformation of the beam itself.