by 1、 Section form of steel structure members ★ 1.
Section form of tension members.
Section form of tension members is shown in Figure 9-1.
When the stress is small, hot-rolled section steel and cold-formed thin-walled section steel can be selected, As shown in Figure 9-1 (a).
When the stress is large, the solid web section composed of section steel or steel plate can be selected, as shown in Figure 9-1 (b).
When the member is long and the stress is large, the lattice section composed of section steel can be selected, as shown in figure 9-1 (c) As shown in.
★ 2.
The section form of the flexural member is called the flexural member only under the action of bending moment or the combined action of bending moment and shear force.
In practical engineering, the member mainly under bending and shear but with very small axial force is also often called the flexural member.
The flexural member in the structure mainly appears in the form of beam.
Generally, the flexural member and the generalized beam refer to the same object.
According to The bending deformation is different.
The member may be bent in one principal axis plane or in two principal axis planes.
The former is called unidirectional bending member (beam), and the latter is called bidirectional bending or oblique bending member (beam).
According to different support conditions, flexural members can be divided into simply supported beams, continuous beams, cantilever beams, etc.
according to different functions in the force transmission system of the structural system, flexural members can be divided into main beams, secondary beams, etc.
according to whether the section form and size change along the member axis, there are equal section flexural members and variable section flexural members.
In some cases, variable section beams can be used to connect sections Save steel; But it may also increase production costs.
According to different section composition, flexural members can be divided into solid web section and open web section.
The former can be divided into section steel section and welded composite section.
Flexural members made of section steel, I-beam (also known as I-beam) or wide flange I-beam (hereinafter referred to as H-beam) and channel steel with large section width height ratio (0.5 ~ 1.0) are usually used (as shown in the figure below) (a) ).
The material distribution of I-beam and H-beam on the section is more in line with the bending characteristics of members, and the use of steel is less, so it is widely used.
The flange of channel steel is small, and the section is uniaxial symmetrical, and the shear center is outside the web.
It is easy to twist when bending around the symmetry axis of the section.
Certain measures are often taken to make the external force pass through the shear center, or strengthen the restraint Conditions.
Cold formed thin-walled section steel (figure below) (b) ) it is also a section steel often used for flexural members.
The cold-formed thin-walled section steel processed and formed at room temperature has thin plate wall.
At present, the domestic production is mainly in the range of 1.5 ~ 3.0mm, so it is mostly used in occasions bearing small loads.
For example, roof purlins and wall beams in housing buildings.
Due to the limitation of rolling equipment, when the specification of section steel can not meet the requirements of flexural members When the requirements of bending members or considering the maximum saving of steel, Welded composite sections can be used (as shown in the figure below) (c) ).
The welded composite section is composed of several steel plates or steel plates connected with section steel.
Its section is relatively flexible.
In some cases, the distribution of materials can easily meet various needs of the project, so as to save steel.
I-shaped section composed of 3 steel plates, box section composed of 4 steel plates, and multi chamber box section composed of several box chambers.
In the project It is also widely used.
Open web section (figure below) (d) ) can reduce the dead weight of components.
It also facilitates the passage of pipelines in building structures, and sometimes plays a role in spatial rhythm change for exposed structural components.
In addition to steel components, composite beams composed of reinforced concrete and rolled or welded section steel are useful, which are used as concrete slabs of building floors, bridge decks, etc.
and also as components of beams And resisting bending moment.
★3、 The type and section form of compression bending members are subjected to pressure along the rod axis (axial force) and the bending moment around the centroid axis of the section are called compression bending members.
If there is only one bending moment around the centroid axis of the section, it is called unidirectional compression bending members; when there is bending moment around both centroid axes, it is called bidirectional compression bending members.
When the bending moment can be caused by eccentric axial force, this situation is called biased members.
Most steel columns in building frames are typical compression bending members; If the chord and web members in the steel truss are relatively thick and short, and there are strong rotational constraints at the ends, they are also compression bending members.
Figure 9-3 section form of compression bending member.
The section forms of compression bending members are distinguished according to their composition, There can be section steel (Fig.
9-3a, b), steel plate welding combined section (Fig.
9-3c, g) or section steel and section steel, section steel and steel plate combined section (Fig.
9-3d, e, F, h, I); according to geometric characteristics, there can be open section, closed section (Fig.
9-3g ~ J), biaxial symmetry and uniaxial symmetry section; in addition to solid web section (Fig.
9-3a ~ J), in order to improve the bending stiffness of the section, lattice section is often used (Fig.
9-3k ~ o).
II.
Connection mode of steel structural members.
The connection modes between steel structural members mainly include high-strength bolt connection, welding, etc.
★ 1.
The connection mode between columns is different due to different sections of columns.
For example, if the columns are H-shaped steel columns, high-strength bolt connection or mixed connection of high-strength bolt and welding can be used.
For example, there are many columns with box section Welding is adopted.
(Fig.
9-4).
★ 2.
The connection between the column and the beam is mostly H-shaped steel beam, and its connection with the column can be connected by high-strength bolts, welding and hybrid connection.
(Figure 9-5).
★ 3.
Beam to beam connection.
Beam to beam connection can be connected and welded by high-strength bolts.
III.
The biggest difference between steel structure engineering and concrete structure engineering is that most of its components are completed in the processing plant.
Therefore, the manufacturing quality of steel components, especially the dimensional accuracy, directly affects the on-site installation of steel structures.
Steel components are manufactured in the processing plant The process is as follows: preparation of component manufacturing instructions → correction of raw materials → setting out, marking and cutting → hole making and edge processing → assembly and welding → end processing and friction surface treatment → rust removal and coating → acceptance and shipment.
★ 1.
Prepare the component manufacturing instruction.
The manufacturing of steel components is a very important operation process in steel structure engineering.
Before manufacturing, prepare the component manufacturing construction instruction according to the design documents, construction drawings and manufacturing conditions.
Its main contents include: (1) standards and specifications based on construction; (2) technical requirements for finished products, including technical requirements for processes and various technical types of work; (3) processing and welding equipment and process equipment used; (4) qualification certificates of welders and inspectors (5) The manufacturer’s management and quality assurance system; (6) various inspection forms.
★ 2.
Correct the defects such as uneven surface, bending and wavy shape during rolling, transportation, loading and unloading and stacking.
Some of these defects need to be corrected before marking and blanking, and others need to be corrected after cutting.
During correction, pay attention to the following points: (1) Attention shall be paid to the corrected ambient temperature and heating temperature of carbon structural steel and low alloy structural steel.
When the ambient temperature of carbon structural steel is lower than – 16 ℃ and that of low alloy structural steel is lower than – L2 ℃, cold correction and cold bending shall not be carried out.
(2) During heating correction, the heating temperature shall be selected according to the steel properties, but shall not exceed 900 ℃.
Low alloy structural steel shall be cooled slowly after heating correction.
(3) The corrected steel surface shall be free of obvious concave damage, and the scratch depth shall not be greater than 0.5mm, and shall meet the requirements of current relevant national specifications for surface quality.
The allowable deviation of steel after correction shall meet the provisions of relevant steel structure specifications or other design data..
