Structural design review: a comprehensive summary of all key points!

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Structural design review: a comprehensive summary of all key points! 【Design Principles】○ Be able to construct the structural framework in accordance with the architectural design intent. ○ During construction, ensure that there are no conflicts with the building or its equipment; nothing should be missed or damaged. ○ Pay attention to the rationality of the structure itself; any issues should be resolved through consultation with the architects. ○ Fully express the design intent in a clear manner. ○ Ensure that the design parameters are consistent throughout the set of drawings. 【Design Steps】Design coordination – Computer-aided design – Template drawings – Reinforcement planning – Instructions and detailed drawings. Issues present: ○ Unreasonable scheduling leading to low efficiency; designers consume all the available time, leaving little or no time for review. ○Failing to follow the company’s standardized procedures, construction drawings were prepared without verifying the computer-generated data, resulting in rework. 【Design Coordination】○ Wall materials and exterior wall finishes: tiles, paint, or a combination of tiles and paint in certain areas. ○ How much the elevation of the floors in kitchens, bathrooms, entrances, and balconies should be reduced. ○ Height of balcony beams and location of balcony trim: top and bottom surfaces of balcony beams (affecting drawing accuracy). ○ Location of air conditioning units: on the top or bottom of beams. ○ Type of protruding window details. ○ Height of the outer structural beams. ○ Depth of the foundation (elevation of footings and foundation beams). ○ Slope of the roof: structural slope or architectural slope. ○ Elevation differences between floor surfaces must be accurately represented in the architectural drawings, especially when these differences are not located near doors. ○ Deviations and dimensions of walls, columns, and beams. ○ Whether beams are needed for stairs and their height. ○ Elevation of the elevator shaft, and whether there is a basement beneath it. ○ Elevation of the basement ceiling, location of fire lanes, and thickness of the soil covering it. ○ Beam width and slab thickness; whether local widening or thickening is required in coordination with the electrical engineering team. 【Electrical Engineering】(1) Basic principles and calculation parameters (general information) ○ Unit weight of concrete: 25 for frame structures, 26 for frame-shear wall and shear wall structures ； ○Ground roughness: Class C can be adopted in urban center areas ； Take Class B from the suburbs ； ○Basic structural period: T1. ○ Check whether the highest floor number in the wind load data matches the number of floors used in the calculations. ○ Determine the soil category of the site and verify that it does not conflict with the characteristic period: For the first seismic group, the characteristic period for Class 2 sites should be 0.35, while it should be 0.45 for Class 3 sites. ○Is the period reduction factor correct? ○ When the angle between the diagonal shear-resisting members is greater than 15°, has the corresponding additional seismic coefficient been entered? ○ When the direction of maximum seismic action is greater than 15°, has the angle of the horizontal forces in the overall data been adjusted to match this angle? ○ The floor numbers at which the 0.2Q0 adjustment applies in frame-shear wall structures. ○ Are the floor heights, concrete strength grades, steel bar strengths, and cover thicknesses correct? (These aspects are often overlooked on slabs, leading to rework; the floor heights for roof towers and pitched roofs should follow the same principles within a single project.) ○The seismic force amplification factor for roof small towers is generally taken as 1.0. Accidental eccentricity and bidirectional earthquakes should not be considered simultaneously; only one of them should be taken, otherwise the amount of reinforcement required will increase significantly. ○Simulation Construction 2 is applicable to cylindrical structures, and its calculations apply only to the foundation; ordinary frame-shear structures are calculated using Simulation Construction 1. ○Interlayer beams and staggered slabs cannot be used to create staggered floors. ○Special-shaped columns are calculated using biaxial bending. ○When the height difference between floors is less than the beam height, it should be entered as a single floor. ○The floor slabs surrounding larger openings do not meet the assumptions of rigid floors, and should be defined as elastic floors in numerical calculations. ○““Rigid slabs” are suitable for most civil buildings, and in the designs we typically create, we assume the use of rigid floor slabs ； ---- “Elastic plate 6”: accurate calculation of in-plane stiffness and out-of-plane stiffness ； Under this assumption, part of the floor load is transmitted to the vertical members through the out-of-plane stiffness of the floor slabs, which results in reduced reinforcement in the beams and an increased risk of failure. Therefore, the assumption of an elastic floor slab 6 is suitable for slab-column structures (beamless floor systems) ； ---- “Elastic plate 3”: infinite in-plane stiffness, with actual calculation of out-of-plane stiffness; suitable for thick plate transfer structures. ---- ““Elastic membrane”: true calculation of in-plane stiffness, zero out-of-plane stiffness ； It is suitable for structures with significantly reduced in-plane stiffness, such as framed floors, open industrial buildings, gymnasiums, structures with large openings in the floor slabs, floors with long planes, or structures with large recesses and weak connections between different plane sections. ○Multi-tower structures should be defined as such; when multiple stairwells protrude from the roof, those stairwells should also be defined as part of multi-tower structures. ○The roof slab of the basement is generally not considered as a fixed end; it is analyzed together with the superstructure. ○When calculating the reinforcement for rebar, the boundary conditions should be standardized: edge supports and areas with a height difference of >50 mm should be treated as simply supported structures, while shear walls should be considered as fixed-end structures ； When the cross-sectional dimensions of the beam with simply supported ends are large, the reinforcement should be appropriately increased ； ○When applying reductions for live loads, attention should be paid to their scope of application. The reduction coefficients specified by default are applicable to item 1(1) of clause 4.1.1 in the Load Code (GB50009); adjustments should be made for other types of buildings. Live load reductions are not considered for industrial buildings. ○In a frame-steel wall structure, when determining the seismic resistance rating of the frame portion based on the frame-steel wall structure type, the percentage of column overturning moment within the bottom reinforcement zone should be less than 50%. (2) Loads ○ Is the dead load on the slab appropriate for its thickness? ○ Are the live loads for special areas such as balconies, stairways, shops, elevator shafts, terraces, rooftop gardens, and storage rooms correct? ○ Is the direction of load transfer for the inclined sections of stairways correct? ○ Have the wall loads acting on the slab been taken into account? ○ When the roof has a slope designed for the building, the load associated with that sloping layer must be properly considered, and calculations should be performed based on the location of the slab spans. ○Be careful not to overlook the loads on elevator hooks, bases, and foundation pits. ○ Also, ensure that the loads on cantilevered canopies, air conditioning slabs, railings, and architectural decorative components are not omitted from the calculations ； ○For wall loads acting on the roof, care should be taken to calculate and input them based on the actual height of the building elevation (especially the loads on cantilever beams). ○The balcony cover on the roof is usually a sunken slab; in such cases, the standard value of the live load should be compared with the water accumulation load (water depth × 10/1.4), and the higher value should be used. ○Whether the loads on the walls above the beams have been overlooked, and whether the wall heights are correct, especially with regard to the roof parapets and frameworks. (3) Component dimensions ○ When using computer calculations, try to minimize the number of column cross-section types ； The number of column cross-section types per floor should be limited to 4–5 kinds. ○ For individual large columns (400X600), can their lengthwise dimensions be reduced? It is advisable to minimize the use of short columns, as they are costly and have poor load-bearing performance. ○Under normal circumstances, the beam height should not exceed 600 to avoid the formation of short columns. ○Have the beams with numerous ducts passing through them been appropriately widened and heightened? ； Have the plates with a large number of device conduit layers been appropriately thickened? ； ○Is the ratio of the beam cross-sectional dimensions to those of the column cross-sections appropriate (strong columns and weak beams)? ○ When there is a large column above a beam, the beam should be 50% wider than the column in order to accommodate the reinforcement bars. ○The height of the building’s perimeter beams should match the height of the building’s doors and windows. ○The linear stiffness of the foundation beam at the junction of the long sides of a single-pile cap or a two-pile cap made of prestressed pipe piles should be greater than the linear stiffness of the frame columns on that cap. ○Whether the axial compression ratio of the seismic wall meets the requirements. (4) Output results ○ The calculation sheet should be complete; special attention should be paid to: ① The overturning moment ratio of the frame columns in frame-shear wall structures ； ②Frame structure: Check results for weak stories under extreme earthquake loads ； ③Data on deflection and crack checks for large-span structural members ； ④Axial compression ratio of seismic walls. ○Do the calculation results meet the requirements of the specifications? ； Layer stiffness ratio, stiffness-to-weight ratio, period ratio, shear-to-weight ratio, axial compression ratio, displacement ratio, elastic displacement, elastoplastic displacement of the weak layers in frame structures, etc. ○Check for any information regarding excess limits, and determine whether the reinforcement ratio is economically reasonable. ○Are there any anomalies in the calculation results? (5) Manual supplements ○ Single pile capacity calculation sheet, cap calculation sheet. ○There should be a pile layout calculation process for multi-pile caps. ○For pile foundations requiring settlement calculations, whether the calculated settlement amount meets the requirements. ○When there is a weak underlying layer at the pile tip, a check on that underlying layer should be conducted. ○There should be a calculation sheet for the reinforcement of ground beams. For ground beams connected to the short direction of single-pile or two-pile caps, the effect of the moment at the base of the columns must be considered. ○When uplift is possible, verify whether the uplift resistance check of the underground structure and the crack width check of the uplift-resistant piles meet the requirements (take the self-weight partial coefficient as 0.9). ○When determining the bearing capacity of a single pile through pile testing, the value of its bearing capacity should be reduced by the lateral friction force resulting from the extended portion of the pile used in the testing ； When there is a liquefiable soil layer, the reduction in lateral friction resistance of the liquefiable layer must also be taken into account ； When there is a large amount of backfill soil, the effect of negative side friction force caused by soil settlement around the pile must be considered. ○When the thickness of the shear wall does not meet the minimum thickness requirement specified in the codes, a stability check should be conducted. ○Are the materials of the embedded parts and lifting rings, as well as their calculation and design, reasonable and safe? 【Graphics】○ Are there any abnormal text and annotations? (The text is marked with a ?, the size is inconsistent, the text is either too large or too small, the annotations do not match the actual length or are not whole numbers, and the symbols and values related to rebar are clearly incorrect.) ） ； ○Any extra text, dimension lines, and unnecessary axes can be removed; irrelevant axes as well as axis numbers should all be deleted ； ○Check whether the lines such as axes and beam lines are correct, whether the line widths are appropriate, and that the rebar lines should be thick ； ○Are the texts overlapping or covered? ； ○Are there any leaks, excess filling, or incorrect filling in the walls, columns, post-cast strips, etc.? ； Are the same filling patterns used for different types? ； ○Is the drawing scale abnormal, and is the indicated scale correct? ； ○Check whether the figure title, figure number, project name, drawing issuance date, and drawing list in the legend are correct. ○Is the textual description clear? 【Plan template】 ① Axes: ○ Are the axis numbers and dimensions correct, and do they correspond to those in the architectural drawings? ○ Is the total dimension equal to the sum of the individual dimensions? ○ Is the accuracy of the angles sufficient? For diagonally oriented axis networks, use the ends of the longer axes as reference points, rather than starting points or angles, to determine the axes. ○ Are there any axes that have not been positioned, or any unnecessary axis numbers? ○ For arc-shaped axes, is the radius indicated, and is the center of the circle clearly defined? ② Contours and elevations: ○ Does the structural contour match that of the building? ○ Are the elevations of various parts of the structural plan indicated, and do they correspond to the corresponding positions in the building? Pay attention to areas such as the building’s overfill layer, bathrooms on each floor, outdoor terraces, roof gardens, stair locations, elevator shafts, water traps in pools, and public kitchens where elevation adjustments are necessary. ○ Are the locations where the elevation changes occur, as well as the rebars used for this purpose, shown as solid lines? Are there any intersections between solid and dashed lines? ○ Are the roofs and basements designed with proper slope gradients? If the building has its own slope gradient, has the load associated with that slope been taken into account? ○ Are the connections between beams and slabs in adjacent areas correct, and are the joints properly marked? ○Are there any omissions regarding the holes made in the slabs for buildings and equipment? ③ Column and wall locations: Have the lower-level walls and columns been indicated using thick dashed lines? Are there any walls or columns depicted where they shouldn’t be? Are there any columns shown on top of beams? ○ Do the walls and columns align with the building design? Could their positions and dimensions affect the building’s functionality? ○ Have all holes made in concrete walls for buildings and equipment been accounted for? ○ Ensure that the top elevations of walls and columns meet the required building elevation standards, as well as the requirements for beam-slab connections. ④ Beams: ○ Are all perimeter beams of the building at the same height? Pay attention to their relationship with the surrounding walls. ○ Carefully check each beam’s location, number, dimensions, number of spans, and whether its top elevation corresponds correctly to the slab elevation. ○ Is there anything unusual about the height or width of the beams? If the height of a cantilever beam is less than 1/6 of its span, and generally the height of a beam is less than 1/15 of its span, excessive beam dimensions can affect the installation of doors, windows, or stairwells in a building. ○Is there sorghum beam placed on top of a shorter beam? ○ Are the positions of the beams incorrect, such as spanning across a living room? Has the arrangement of beams affected the aesthetic appearance of the building? ○ Priority order for beam alignment: halls, main rooms, guest rooms, stairways, kitchens and bathrooms, storage rooms, etc. ⑤Building elevators: ○ Are there numbers assigned to them? ○ Is the elevation of the elevator shaft properly indicated? Is the machine room covered, and are hooks installed on its top? ○ Have the stair columns been marked and positioned correctly? ○ Is the starting point of the stairs indicated? ⑥ Openings and shafts: ○ Are the air vents, utility shafts, and flue ducts properly included? ○ Are the openings properly positioned and sized, with appropriate reinforcement at their edges (beams are required if the edge length is more than 12 times the thickness of the slab)? ○ Are the sump pits, drainage channels, and roof drains included? Do their positions and sizes match those specified in the building design? ⑦ Details and structural columns: ○ Are the exterior balconies, parapets, structural columns required for the facade, walls, and canopies properly connected to the main structure (with the main structure serving as a support), and is their projection on the floor plan correct? ○Are its location and dimensions complete? ○ Are the detailed drawings shown on the plan, and do they correspond to the corresponding numbers? Do the elevations and location axes match those on the plan? ⑧ Pay attention to the cutting direction and the reference numbers in the detail drawings. Is the index position correct? Whether the corresponding sample exists. ⑨Post-cast strips: Is the spacing between post-cast strips greater than 55 meters? Are they properly positioned? Do they pass through important structures such as frame beams and areas subjected to high stress? Is the layout of the basement consistent with the positioning of the post-cast joints in the side walls? ⑩ Instructions for the formwork drawings: ○ Are the basic floor elevations specified, as well as the concrete strength grade and water resistance rating? ○ Is there any indication regarding the thickness of special floors? [Reinforcement diagram for floors] ○ What is the maximum allowable thickness for floor-type staircases under normal conditions? (If exceeded, it is advisable to consider them as beam-type staircases.) ○ When there are large openings in the roof layer or when the floor height is high, it is advisable to move the reinforcement layer down by one level. ○The length to which the negative reinforcement of large overhanging slabs extends inward should be ≥1.5 times the overhanging length. ○ The concrete strength grade for roof slabs is generally C25, the slab thickness is usually 100, and the reinforcement used in slabs not specified otherwise is generally 8@180. ○Check for any omissions regarding the slab’s elevation and thickness. ○ When using PMCAD to generate the reinforcement drawings for slabs, it is recommended to use its “slab reinforcement calculation diagram” to verify the results, especially when grade II steel is used. ○ When arranging the reinforcement in a slab, it is advisable to use the rebar at the bottom of the slab as a reference point for dividing the slab into sections, with the negative rebar arranged from left to right and from top to bottom along the beams ； On consecutive slab spans, the same support negative reinforcement needs to be drawn only once; there is no need to draw it for each slab ； ○Elevation representation: Within a continuous area, if the elevations of all slabs are the same, only one elevation value needs to be specified; differential lines are used to distinguish between different elevations, rather than indicating each slab individually. ○ Check whether the slab thickness values are correct (in accordance with the company’s standard procedures). Pay attention to the slab thickness of the ground floor in high-rise buildings, as well as the thickness of slabs in transfer floors, and ensure that weak areas are reinforced. (The weak areas refer to sections where the floor slab is narrow and there are large openings.) ○ The rebar at the openings and at locations with changes in elevation must be disconnected. ○Whether the reinforcement bars in the stressed area meet the minimum reinforcement ratio requirement of max(0.2%, 0.45 ft/fy); whether there is sufficient reinforcement for the cantilevered slab; and whether the anchorage length is adequate. ○Are the reinforcement symbols at the corners of large slabs missing? Are the reinforcing bars at the exposed corners indicated with ○? Are the temperature-related reinforcement bars for roofs and terraces omitted? (Recommendation: Provide detailed drawings in the general specifications and address these details in the individual plans; this will help avoid omissions.) ○ Slabs with a short span greater than 4500 should come with calculations for checking cracks and deflection. ○ Is the value of the load applied to the slabs reasonable and consistent? ○ Are the symbols used to represent the bottom reinforcement bars correct? ○ The reinforcement at the edge supports that connect to overhangs and canopies should not be determined merely based on structural requirements; it should be coordinated with the reinforcement in the overhanging sections. ○ When the slab thickness is large, the diameter of the stress-reinforcing bars may be too small, which does not meet the structural requirements ； ○Indicate whether there are any contradictions with the floor plan. [Beam reinforcement diagram] ○ The number of merged layers should not be too few nor too many (communicate with the project supervisor and reviewers before drawing). ○ The selection of longitudinal reinforcement bars in the beam cross-section should be reasonable; the longitudinal reinforcement bars across the entire beam should be coordinated with each other, and it should not happen that beams with larger spans, larger cross-sectional dimensions, or greater reinforcement at the supports have relatively smaller longitudinal reinforcement bars. ○When the calculated values differ significantly (by more than 20%), such beams should not be grouped as a single beam. For beams where one end is connected to a shear wall and the other end to a frame column, it should be determined based on the span-to-depth ratio (whether it is less than 5) whether they should be constructed as coupling beams (LL). ○The results obtained from computer calculations are generally not enlarged; however, for spans of 6 meters or more as well as cantilever beams, an appropriate enlargement can be applied. ○Check whether the beam markings are complete and whether there are any missing reinforcement elements. Pay attention to the bottom reinforcement of cantilever beams and short-span beams, as well as the reinforcement at the supports of continuous beams. ○ Check whether there is any conflict between the reinforcement running along the entire length of the beam and that at the supports. ○ Verify whether the reinforcement can be properly arranged within the available space. ○ Ensure that the reinforcement ratio does not exceed 2.5% or is lower than the maximum allowable value (0.2%, 0.45 ft/fy). ○ When the reinforcement ratio exceeds 2.0%, check whether the diameter of the minimum stirrups has been increased by one size level. ○ When there is a significant difference in reinforcement on either side of the same support, separate reinforcement arrangements should be used, especially when the reinforcement ratio exceeds 2.0%. ○ For non-frame beams, use stirrups with enhanced reinforcement at the beam ends; for frame beams, no such enhancement is required. ○ Verify that the number of stirrup limbs is appropriate – generally, 2 limbs are used for lengths less than 350, 4 limbs for 350–600, and 6 limbs for 650–800, etc. ○ Ensure that the anchorage length of the beam reinforcement at the supports is sufficient, particularly the horizontal anchorage length. ○ Check that the area of the bottom reinforcement is at least 0.5 times that of the top reinforcement (for grade 1 frames) or 0.3 times (for grade 2 and 3 frames). ○ All beam reinforcements must be verified against the calculation documents, with special attention paid to frame-supported beams, cantilever beams, and long-span beams. ○ When using concentrated notation, check whether the reinforcement in the long-span and cantilever sections is sufficient. ○ The reinforcement at different elevation levels must not be connected; ensure that there are detailed drawings showing this. ○ Verify that the suspension bars and stirrups are sufficient. ○ Check whether torsional reinforcement is provided and whether it is adequate; for beams with overhangs (especially those with long overhang lengths), torque effects need to be considered, and additional reinforcement should be added. Independent beams with overhangs also require verification regarding their torsional reinforcement. ○To determine whether the reinforcement of roof beams with large spans meets the requirement that the crack width on the beam surface be less than 0.2: a simple approach is to use a flexure moment modulation factor of 1.0 at the beam ends, and a coefficient to increase the designed flexure moment of 1.2 or 1.3; after recalculation, the reinforcement should be determined based on these new results. 【Wall and Column Chart】○ Check each column and hidden column to see if they are numbered, whether the numbers are repeated or missing, and whether any details are repeated or omitted. ○Check one by one whether the columns and walls are properly positioned, especially the length of the walls. ○Are there any omissions or redundancies in the wall and column drawings? Do they conform to the architectural plan and structural plan? ○Is the detail fully indicated (for main bars or stirrups), and does the number of main bars match that shown in the detail? ○Is the top elevation of wall columns that need to be supported at a specific location indicated? ○ Do the dimensions correspond to the plan? ○ The reinforcement details for all wall columns must be checked against the calculation sheets. ○ Is there any missing reinforcement? Do the longitudinal and stirrup reinforcements meet the requirements specified in the codes? ○For columns with a large cross-sectional height, are the stirrups at the top and bottom of these columns reinforced throughout their entire height? ○ For columns with a width greater than 200, is the spacing between the longitudinal reinforcement bars at the column ends less than 200? ○ Is the distribution of reinforcement bars in the walls appropriate (i.e., does it meet the minimum reinforcement requirement)? ○ Is the spacing between the tension bars in the walls a multiple of the spacing between the distribution bars? ○ Are the horizontal and vertical reinforcement bars in the bottom reinforcement layer and in frame-supported walls strengthened? ○Note whether the volumetric stirrup ratio for short columns (columns with a shear-span ratio of no more than 2) is sufficient (rsv/1.2%), and whether stirrups are provided at full height: ---- Frame columns intersecting with half-landing beams of stairs are generally short columns. ---- Frame columns within elevator shafts should be considered short columns, as they are connected to the shaft’s ring beams. ---- Frame columns intersecting with beams located beneath ground-floor storefront signboards are typically short columns. ---- Frame columns situated at the starting point of pitched roofs are usually short columns. ○ For frame columns adjacent to windows, when the ratio of clear height to cross-sectional height is no more than 4, stirrups must be provided at full height (the volumetric stirrup ratio may be less than 1.2%). ○Restrained edge members: When the axial compression ratio is 0.3, the minimum stirrup ratio and minimum reinforcement ratio specified in the codes must be satisfied ； Axial compression ratio 1/200 ○ The reinforcement calculation for ladder slabs is generally carried out by checking against ql2/10 for long-span ladder slabs. ○For cantilevered stairs and spiral stairs, it is necessary to check the calculation documents. ○ Pay attention to the relationship between the elevation of the landing platforms and that of the floors, as well as to whether the floor level represents an extension of the floor slab’s rebar. ○ Ensure that the minimum reinforcement ratio for the bending members in the stair treads, landing slabs, and detailed drawings meets the requirements, especially when the concrete thickness on the floors is large. ○ Check that no reinforcement is omitted in the landing slabs; when the span is large, reinforcement should be determined based on calculations. ○When the stair beam is connected to the frame column, it shall be designed as a frame beam, with attention paid to the spacing S of the stirrups