26 Essentials of Steel Construction Costing

1. The overhaul load on the working platform should pay attention to the discounting of the main beam (0.85) and column (0.75);

2. The value of the strength of the steel structure, the correction of the strength, and for the axial tensile and axial compression members should be taken as the strength of the thicker member; pay particular attention to the correction of the butt weld without pad and the strength of the single angle of the single-sided connection; (in the lattice-type members in the calculation of the splicing bar and in the roof trusses in the calculation of the web using a single angle)

3. Calculation of deformation and stability and shear strength using gross sections; calculation of flexural, tensile and compressive strength using net sections;

4. Calculation of the amount of pre-arching: note the difference between improving the appearance and conditions of use and improving the appearance of conditions in two ways;

5. steel structure quote in the beam bending strength calculation, plastic section development coefficient should pay attention to the flange free outreach width and thickness of the ratio should be controlled within a certain range; H-beam representation (total height * total width of the flange * web thickness * thickness of the flange), section steel representation, the number of the height of the section;

6. the calculation point of the converted stress should be taken at the edge of the calculated height of the beam web; for localized compression calculation, if there is a reinforcing rib at the centralized load point, the local compressive stress may not be calculated. Therefore, the localized compressive stress at this point can be taken as 0;

7. Calculation of steel structure quote beams: strength, overall stability, local stability; (calculation of web, stiffening ribs (transverse, longitudinal, short direction, selection of web calculation points)) (internal force, generalized height-thickness ratio, critical stress)

8. combined beam web considering the calculation of strength after buckling, the beam according to the full cross-section of the effective determination of the cross-section resistance moment that is the maximum moment of inertia;

9. axial compressive strength calculation should pay attention to the calculation of high-strength bolts friction type connection (at the same time should pay attention to the impact of the net section); axial compressive stability calculation should pay attention to the single-axis symmetric cross-section should be used to convert the length of the slenderness ratio, as well as corresponding to the calculation of the height (the impact of the support settings);

Local stability (flange and web calculation), for the calculation of the local stability of the web plate does not match, by adding longitudinal stiffening ribs or take the effective web section (only consider the flange and web connection part of 20tw, that is, consider the strength of the web plate after buckling) for the calculation of the strength of the member and the overall stability, and the stability coefficient is still used for the full cross-section; at the same time pay attention to compression members and bending members of the stability factor is different from calculation of the stability coefficient for the pressure stability coefficient is mainly by the form of the cross-section and the slenderness ratio of the control (pay attention to the plate thickness of the section categories of the decision of the effect), the stability factor of the bending member should pay attention to the simplification of the calculation formula and the corresponding corrections.

10. lattice type members of the axial compression calculation, the calculation of the solid axis and solid web similar, and the imaginary axis shall be used to convert the length of the slenderness ratio; splicing, splicing plate calculation (axial compression, line stiffness and connecting weld calculation), pay attention to the limb of the length of the slenderness ratio of the calculation (limb calculation should pay attention to the splicing plate with the limb of the connection is a weld or the bolt of the influence of the length of the limb calculation) and the calculation of the component around the imaginary axis; and at the same time, pay attention to the splicing plate with a wire rigidity requirements, that is, on the same cross-section splicing board line rigidity to be greater than the limb line rigidity of 6 times;

11. with filler plate connected to the double angle steel or double channel steel members, can be calculated according to the solid web members, but filler plate distance should meet the requirements (compression 40i, two lateral support points between the filler plate between the number shall not be less than 2; tensile 80i; i for the limb of the radius of gyration);

12. Calculation of axial force of supporting members of axial compression members (location of supporting points, single column or multiple columns, number of supporting channels);

13. solid web one-way bending and bending members of the overall stability calculation: the role of the moment in the plane of calculation (equivalent moment coefficient calculation, for single axis symmetric section members, but also for the flangeless side of the calculation); the role of the moment out of the plane of calculation; solid web bi-directional bending and bending members of the overall stability of the two-way bending and bending members of the overall stability of the two-way direction of both calculations should be carried out; lattice members and solid web similar (bending moments around the imaginary axis, in-plane) Overall stability calculation, its length to slenderness ratio should be used to convert the length to slenderness ratio for the stability coefficient, for out-of-plane stability, only need to limb members according to the axial force members to consider, and for bidirectional compression bending members, limb calculation according to the solid web unidirectional bending compression bending member of the overall stability considerations, pay attention to the calculation of the length as well as the limb axial force and bending moment of the value of the limb);

14. Calculation length of members: truss and frame structure (pay attention to the correction of swing column and the correction of the corresponding beam’s distal articulation), the difference between supported and unsupported, and the correction of beam’s calculation stiffness: higher axial pressure, distal node connection); for the support in the direction of the strong axis, i.e., the x-axis, it is the reduction of the calculation length in the direction of the weak axis, i.e., the direction of the y-axis. Note that for the strong (x-axis) and weak (y-axis) axes of the T-section of the double-legged steel combination on the roof frame, pay attention to the influence of the plane of the support setting on the calculation length. Usually the y direction is greater than the x direction, pay attention to the row of columns and frame columns for tension bending and compression bending calculations, should pay attention to the bending moment in the plane of action and the bending moment outside the plane of action corresponding to whether there is a support, and the corresponding impact of the presence or absence of side shift and calculation length, such as for the row of structures, often in the longitudinal direction of the setting of the support, it is in the longitudinal direction for the absence of side shift and transverse lateral side shift, the strength of the weak support frame of the calculation: pay attention to the support in the unit side inclination angle produces Horizontal force per unit of lateral inclination;

15. connection calculation, size limitations of the weld, the minimum bolt arrangement requirements; I-beam (T-beam) section butt weld bending calculation using commuted stress evaluation; fillet weld should pay attention to the positive weld (force perpendicular to the direction of the weld to improve the coefficient) and lateral weld (calculated length should not be greater than 60hf) calculation of the different, fillet weld length should not be less than 8hf and 40mm,; for the butt weld in the moment of Bending moment, the effective weld moment of inertia should be noted that the deduction of the weld length without the arc plate (each weld should be deducted 2t); for the moment of inertia and area of fillet welds, should be deducted from the end of the weld hf, weld corners do not need to be deducted (i.e., the weld length is calculated at the end if there is a weld at the corner of the weld, then there is no need to reduce the hf), and the weld width to take the effective width of the weld for the calculation of the area and the moment of inertia (he=0.7hf), and should be noted to participate in the calculation of the area and moment of inertia (he = 0.7hf ), at the same time should pay attention to the number of welded seams involved in the calculation, can not be missed; pay attention to the single fillet weld connection, the strength of the weld should be multiplied by 0.85 coefficient. Pay attention to the load transfer path of the stiffening rib (pay attention to the difference between the top tightening (bearing pressure calculation) and the use of welded seam (frontal fillet weld) transfer);

16. Calculation of bolt shear: ordinary bolts take the smaller value of shear bearing capacity (number of shear surfaces) and bearing capacity (minimum bearing thickness, according to the direction of force); high-strength bolts bearing pressure type pay attention to the location of the shear surface (bolster or threaded), ordinary bolts take the bolster diameter; high-strength bolts friction type is directly related to friction surfaces and pre-tension; calculation of the force of the bolt group, pay attention to the length of the connection of the axial Correction of the force of the bolt group, pay attention to the correction of the connection length on the axis (pay attention to the calculation of the connection length, only in the calculation of shear of the bolt group), as well as the correction of the increase in the number of bolts (such as filling the plate, one-sided connection, short angle connection and rivets riveted together with the total thickness), the calculation of the bolt tensile to take the effective cross-section at the threads; in the strength of the bolt connection, it is also necessary to calculate the strength of the connecting steel plate and the connecting plate (to take the connection of the steel plate and the connecting plate of the smallest net cross-section, and at the same time, pay attention to the folding line). (Take the minimum net section of connecting steel plate and connecting plate, and pay attention to the consideration of folding line, as well as the calculation of the minimum net section of angle steel, and expand the angle steel into a plane for calculation);

17. bolt group eccentric tensile calculation, ordinary bolt group first according to the small eccentric tensile (assuming that the center and the axis in the center of the bolt group, and the bottom row of bolts by tension rather than pressure) calculations, if not satisfied, then according to the large eccentric tensile calculations (assuming that the center and the axis in the outermost row of bolts in the center line, i.e., with the force of the equilibrium of the force to solve the force of the bolts), the high-strength bolts according to the small eccentric tensile calculations, and purely bending components according to the calculation of the large eccentric tensile members; note that the beam-column connection, the support of the role of the support can be used to bear beams to transfer over the shear force;

18. steel – concrete combination structure, in the strength, cracking, deformation calculations, do not take into account the role of sorghum bracket; for the calculation of the negative moment zone, attention should be paid to the combination of the beam plastic neutralization axis of the solution; shear connectors should be noted in the calculation of the correction of the connectors bearing capacity;

19. the combination of beam deflection calculation, should pay attention to the standard combination and quasi-permanent combination of converted cross-section moment of inertia of the solution (do not take into account the contribution of the compression steel plate), as well as the stiffness of the discount; combination of the calculation of the plate, the compression steel plate concrete in the determination of the effective height in the calculation of flexural capacity, the compressive strength of the concrete and the compression steel strength of compression steel plate steel should be multiplied by a factor of 0.8 discount, and the requirements of the self-resonance frequency shall not be less than 15Hz;

20. mixed structure (damping coefficient under the action of multiple earthquakes can be taken as 0.04), section steel and concrete column axial compression ratio calculation should take into account the strength of concrete and steel sections, note the difference with reinforced concrete structures, axial compression ratio can be used to solve for the area of the steel section;

21. fatigue calculation of steel structure, for reciprocating dynamic loads need to carry out this calculation, using the allowable stress amplitude method, the stress is calculated according to the elastic condition; when calculating, attention should be paid to the location of the calculation point (weld (16 items of category 8), other are the main metal), the way of force, construction mode, etc.; the load adopts the standard value, and do not need to consider the power coefficient; in fatigue checking, can not be ignored in the basic combination of Fatigue calculation is mainly for the power part (i.e., gravity load can not be considered), combined I-beam flange and web weld calculation see specification 7.3.1;

22. plastic design: material requirements, structural requirements, allowable length ratio, member load calculation (plastic moment of inertia, that is, the plastic center and axis above and below the part of the center and the axis of the area of the moment, for the I-beam cross-section contains the flange and the web), for compression bending members, including in-plane stability, out-of-plane stability (need to be based on the lateral support points and bending moments of the segmental calculation, the length of the ratio according to the lateral support point of the segments to determine the calculation) calculations, and for the bending member is only the calculation of the in-plane; the spacing of the out-of-plane lateral support points that is, for the calculation of the calculation of segmental calculation of the length of the segment;

23. steel pipe structural calculations: structural requirements (the ratio of outer diameter and wall thickness), weld length calculation (divided into round tube and round tube, rectangular tube and rectangular tube, rectangular tube and round tube in three forms), the calculation of the bearing capacity of the rod: should take into account the node tube cross-section shape (divided into round tube and round tube, rectangular tube and rectangular tube, rectangular tube and round tube in three forms), the form of the node (X, T or Y, TT, K, KK), the state of the branch pipe force (compression, tensile);

24. for compression bending members, should be calculated in the plane of action of bending moment, bending moment effect out of the plane of stability, for a single axis symmetrical section, calculated in the plane of action of bending moment stability, for the flange pressure, but also should be calculated on the other side of the web endpoints;

25. for the checking of nodal plates, attention should be paid to the calculation of the effective width of the plate (Code of Design for Steel Structures, 7.5.2);

26. Partially welded butt welds are calculated as fillet welds. The effective width of the weld shall be determined according to the bevel form of the weld (V one-sided bilateral, K, J, U), and the shear strength shall be multiplied by 0.9 when the weld cross-section at the fusion line is equal to, or close to, the shortest distance, s, at the fusion line.