Sichuan steel structure engineering design and construction experience summary!

With the vigorous construction of steel structure

engineering, the requirements for steel structure construction are becoming more and more stringent, and the quality of its construction is related to the final quality of the project. The following sorted out the relevant points of Sichuan steel structure engineering, let's take a look together.

About 80% of the cost of steel structure engineering is directly affected by the price of steel, so the type of structure should be reasonably selected and the amount of steel used should be accurately calculated.

When selecting the structure, the characteristics of different structural forms must be fully considered, and the structure with a smaller span and better economy should be selected as much as possible, and if there is a large suspension load, the grid structure can be selected; When the roof span is large, the suspension cable can be selected. For general steel structure engineering, the use of frame support system has good economy. When designing the structural system, a simple and regular plan and façade layout should be selected under the premise of meeting the building function, and the layout scheme design needs to be calculated many times to optimize the final effect.

First, the key points of steel structure design

1. Key points of structural layout

(1) The mechanical model is clear. Limit the range of influence of large or moving loads as much as possible so that they are transmitted to the foundation in the most direct line. The distribution of anti-lateral supports between columns should be uniform. Its center of shape should be as close as possible to the line of action of lateral forces (wind shock). Otherwise, the torsion of the structure should be considered. The anti-side of the structure should have multiple lines of defense, such as a supporting frame structure, and the column should be able to withstand at least 1/4 of the total horizontal force alone. (2) The layout of the floor plane secondary beam of the frame structure can sometimes adjust its load transfer direction to meet different requirements. Usually in order to reduce the cross-section, the secondary beam is arranged in a short direction, but this will increase the section of the main beam, reduce the net height of the floor, and the top side column will sometimes be difficult to support.

2. Estimate the cross-section

(1) The steel beam can choose channel steel, rolled or welded H-beam cross-section, etc. According to the load and support situation, the cross-sectional height is usually selected between 1/50~1/20 of the span. When the flange width is determined according to the l/b limit of the lateral support between the beams, it can avoid the complex calculation of the overall stability of the steel beam, and this method is popular. After determining the cross-sectional height and flange width, the plate thickness can be estimated according to the locally stable structural provisions in the specification. (2) The column section is estimated according to the length and slenderness ratio. Usually 50< &lambda;&lt; 150, simple selection value around 100. According to the different axial compression, two-way bending or one-way bending, steel pipe or H-beam section can be selected. (3) Corresponding to different structures, the structural requirements for cross-sections in the specification are very different. (4) There is no fixed requirement for the selection of component cross-sectional form, and structural engineers should reasonably choose a safe, economical and beautiful cross-section according to the force of the component.

3. Material selection

The most commonly used material selection is Q235 and Q345. Usually the main structure uses a single steel grade for easy project management. From an economic point of view, it is also possible to choose a combination cross-section of steel with different strengths. When the intensity plays a control role, Q345 can be selected; For stable control, Q235 should be used.

4. Node design

(1) Welding. The weld shall not be arbitrarily enlarged in the welding design. The center of gravity of the weld should be as close as possible to the center of gravity of the connected component. Other details can be found in the regulations on weld construction. (2) Connection plate. The connecting plate can be simply taken as the thickness of the beam web plus 4mm, and then the net section shear resistance is calculated. (3) Beam web. The beam web should be measured for the net cross-sectional shear resistance of the web at the bolt hole. The pressure-bearing high-strength bolt connection also needs to verify the local pressure of the hole wall.

Second, Sichuan steel structure construction points

1. Quality control of embedded bolts

(1) When constructing foundation embedded bolts, first be familiar with the drawings, understand the intention of the drawings, and make an installation template.

(2) The embedded bolt is positioned on the main reinforcement and formwork of the column with the installation formwork and steel bar to ensure that the embedded bolt is not displaced by civil pouring concrete construction.

(3) The spacing, height and height between the control bolts can be controlled within the allowable error range; Protect the bolt buckle from damage during concrete pouring.

(4) After the completion of the civil works, use the theodolite and level to review the elevation and axis of the anchor bolts, and make a record, and hand over the next process for acceptance.

2. Quality control of component production

The construction of steel structure engineering usually goes through two stages: factory production and on-site installation. The general production process of steel structure is divided into: lofting→ blanking→ panel→ cutting→ assembly→ submerged arc welding→ drilling→ assembly→ corrective molding→ riveting spare parts cutting→ production and assembly→ welding and welding inspection→ anti-rust treatment, painting, numbering → component acceptance and delivery.

In the production of steel structure,

according to the steel structure production process, grasp the key processes for quality control, such as controlling the processing of key parts, the process and measures of the main components, the processing equipment used, the process equipment, etc.

3. Quality control of welding engineering

(1) Before welding the steel structure, the certificate of conformity of the welding rod should be inspected, and the welder must hold the certificate of work according to the requirements of the manual.

(2) There shall be no cracks and welds on the surface of the weld, no pores, slag inclusions, arc pit cracks in the first and second level welds, no undercut and other defects in the primary weld, no undermining and other defects in the first and second level welds,

non-destructive testing of the first and second level welds as required, and the welder's steel seal should be checked in the specified welds and parts.

(3) Unqualified welds shall not be treated without authorization, and the modification process shall be determined and then processed, and the number of weld rework in the same part should not exceed 2 times.

4. Connection engineering quality control

(1) When lashing lap, the number of stirrups for each column should be calculated according to the spacing required by the drawing, and the stirrups should be put on the lap bars extending from the lower layer first, and then the column should be reinforced.

(2) Within the lap length, the fasteners of the steel bar should be no less than 3, and the fastener should be inwarded into the column so that the stirrups can move upward.

(3) When the foundation floor adopts double-layer steel reinforcement mesh, steel bar feet or concrete support feet should be set under the upper steel mesh to ensure the correct position of the steel bars.

(4) If the main bar of the column is lapped with light round steel bars, the corner hook should be 45° with the template, and the hook of the middle steel bar should be at an angle of 90° to the template.

(5) When the cast-in-situ column is connected with the ribs used for foundation connection, its stirrups should be one diameter smaller than the column ribs to facilitate connection. At the same time, the position of the ribs must be fixed firmly to avoid the deviation of the column axis.

5. Quality control of component installation

(1) Before the installation of the steel structure, the quality of the components should be inspected, and the permanent deformation and defects of the components should be dealt with when they exceed the allowable value.

(2) When installing steel columns, check whether the cushion iron under the column bottom plate is solid and flat, and prevent the anchor bolts under the column bottom plate from being unstable.

(3) Whether the control column is vertical and whether there is displacement, in the installation project, temporary support measures should be taken before the structure has formed a stable system.

(4) When the steel structure is installed to form a space fixed unit and is accepted and qualified, the construction unit is required to timely pour the space of the column floor and the top surface of the foundation with expanded concrete.

(5) Check the verticality and overall plane bending of the main structure of the steel structure.

6. Fastener connection quality control

(1) Pay attention to the processing quality of the friction surface of high-strength bolts and the protection before installation to prevent pollution and rust. Before installation, the anti-slip coefficient test of the friction surface of the high-strength bolt is carried out, the factory certificate and batch number of the high-strength bolt are checked, and the axial force test is regularly drawn for the high-strength bolt of different batch numbers.

(2) The installation of high-strength bolts requires free penetration, and it is not allowed to knock and ream. Therefore, a certain tire frame mold should be prepared during the production of steel structure to control its deformation, and practical fixing measures should be taken to ensure its dimensional stability when the component is transported. (3) During the installation of steel structure, the contact surface of the plate stack should be flat, the contact surface must be greater than 75%, and the edge gap should not be greater than 0.8mm. Strictly control and inspect the installation process of high-strength bolts, including operation sequence, installation method, fastening sequence, initial screwing and final screwing, and the torque wrench for tightening bolts should be calibrated. After the final screwing is completed, it should be checked one by one, and the under-screwing and over-screwing should be repaired or replaced.

7. Rust removal and painting engineering

(1) The construction personnel should adopt different rust removal methods according to the requirements of the drawings and the rust removal level.

(2) The quality control of the painting project should be so that before the steel structure is painted, the surface of the painted component shall not have foreign matter such as welding slag, oil, water and burrs, and the number of brushing passes and thickness should meet the design requirements.

(3) There must be a certificate of conformity for the coating materials, and the fireproof paint coating project must be constructed by the construction unit approved by the fire department.

Third, Sichuan steel structure project attention points

1. If there is a gutter, the tie rod cannot be designed to fit the top of the column, otherwise it may cause the downpipe to be installed.

2. The arrangement of the bolt position of the flower basket on the horizontal support should be reasonable, not too far from the main beam, should consider the convenience of installation, and also consider the layout position of the corner brace.

3. Do not unilaterally consider factors such as "pulled edge, pressed edge" on the pull hole of the purlin, and punch holes with unequal margins, because it is easy to install backwards during installation, and the result is unfavorable.

4. The position of high-strength bolts should be reasonable, consider the construction space of the torsion breaker and torque wrench, not

during installation, because the space is too small, the torsion breaker and torque wrench cannot be in place, etc., resulting in high-strength bolts plum head can not be screwed or high-strength bolts can not be tightened.

5. If possible, try to adopt a symmetrical bolt arrangement method up and down.

6. If the steel structure has a maintenance brick wall, it must be docked with the construction unit and the civil construction unit in advance.

7. The connection between the wind-resistant column and the steel beam should be connected

by spring plate as much as possible, because the lower deflection of the beam of the middle span is relatively large after installation, and if the beam of the gable wall is connected with the wind-resistant column by bolts, it will cause the roof to be uneven.

8. The roof purlin layout drawing and the detailed drawing of the steel beam should be carefully checked.

9. The gusset plate

has no stiffeners, and some designers have not designed it, resulting in deformation of the gusset plate during subsequent welding.

10. When the beam and column are made into the tie rod connection plate, the hole is not properly extended, and in some places because the connecting plate on the tie rod is too long, the space is too small, and the tie rod is too long to put in.

11. Try to use countersunk screws when installing purlins with strip windows.

12. The upper strip window of the doorway is too close to the upper frame of the doorway, and there is no place for the awning.

13. The pull bar between the adjacent purlins above and below the window frame is not properly arranged, and the end of the pull bar conflicts with the window frame.

14. Anti-condensation paint should be applied under the gutter, or polyurethane insulation layer should be sprayed, and other thermal insulation treatments can also be done.

The above is some experience in Sichuan steel structure engineering design and construction summarized by Xirong Steel Structure for everyone, I hope it will be helpful to you!