What are the common fire protection measures for steel buildings?
Because of its own advantages, steel structure is widely used in modern buildings such as bridges, industrial plants and high-rise buildings. In the process of construction of a large number of projects, steel structure projects also reveal many quality common problems.
I. Some problems and solutions during the construction of steel structure projects
1、Production and production of components
The plate used in the portal steel frame is very thin, the thinnest available to 4 mm. Multi-thin plate material should be preferred to shear way and avoid flame cutting. Because cutting with flame will make the plate edge produce a large wave deformation. At present, most manufacturers of H-beam welding are using submerged arc automatic welding or semi-automatic welding. If the control is not good welding deformation should occur, so that the member bending or distortion.
2, column foot installation problems
(1) pre-buried parts (anchor bolts) problem phenomenon: overall or layout offset; elevation error; wire buckle did not take protective measures. Directly caused by the steel column base plate bolt holes are not aligned, resulting in insufficient length of the wire buckle.
Measures: Steel construction units work together with civil construction units to complete the work of pre-built parts, before the concrete is poured. Must review the relevant size and fixed firmly.
(2) Anchor bolt not vertical phenomenon: poor level of the footing of the frame column, anchor bolt not vertical, pre-buried anchor bolt level error after foundation construction is large. After the installation of the column is not in a straight line, east to west, so that the appearance of the house is very ugly, to the steel column installation error, the structure of the force is affected, does not meet the construction acceptance specification requirements.
Measures: Anchor bolt installation should adhere to the first base plate with the lower adjustment bolts leveling, and then fill with non-shrink mortar secondary grout, foreign this method of construction. So the anchor bolt construction, can be used out of the steel or angle steel and other fixed anchor bolts. Weld into a cage, perfect support, or take some other effective measures to avoid anchor bolts move one when pouring foundation concrete.
(3) Anchor bolt connection problem phenomenon: the anchor bolt at the foot of the column is not tightened, and the pad is not welded to the base plate; some of the anchor bolts that do not show 2 to 3 fillets.
Measures: Welded anchors and nuts should be taken; outside the chemical anchor bolts, fireproof coating and thermal insulation should be thickened to prevent the anchoring performance from being affected in case of fire; foundation settlement observation data should be supplemented.
3、Connection problems
(1)High strength bolt connection
1) Bolt equipment surface does not meet the requirements, resulting in bad installation of bolts, or the degree of bolt fastening does not meet the design requirements.
Cause analysis.
① The surface has impurities such as floating rust, oil and dirt, and the bolt hole biscuit has burrs, weld tumors, etc.
②Bolt installation surface is still defective despite the treatment.
Solution.
①The surface of the high-strength bolts have rust, oil and bolt hole biscuit problems, and should be cleaned up one by one. Before use, the bolts must be treated with rust prevention, so that the bolts for assembly shall not be used in the formal assembly. Bolts should be kept and issued by a person.
② processing assembly surface should take into account the construction and installation sequence to prevent repetition, and try to deal with before lifting.
2) The bolt fillet buckle damage, the screw can not be freely screwed into the nut, affecting the assembly of the bolt.
Cause analysis: The fillet buckle is seriously rusted.
Solution.
①Bolt should be selected before use, cleaned and rusted for pre-assembly.
②The bolt with damage to the fillet can not be used as a temporary bolt, and forcing into the screw hole is strictly prohibited.
③ Pre-matched bolt components should be stored in sets and should not be interchanged when in use.
(2) on-site welding phenomenon: quality assurance is difficult; the design requires full weld penetration of the first and second welding seam is not used ultrasonic flaw; the main beam and column of the floor is not welded; the arc plate is not used to weld.
Solution: Before welding the steel structure, check the certificate of conformity of the welding rod, select the welding containing strip according to the design requirements, use the welding rod according to the instructions and operating procedures, the surface of the weld shall not have cracks, weld tumor, one or two welds shall not have porosity, slag, arc pit cracks, one weld shall not have biting edge, not full welding and other defects, one or two welds according to the requirements of nondestructive testing, in the specified welds and parts to check The welders' steel marks. Unqualified welds shall not be handled without authorization, set out to modify the process before processing, the same part of the weld should not be reworked more than twice.
4, the deformation of the components
(1) The deformation of the member occurs during transportation, and the dead bend or slow bend occurs, causing the member to be unable to be installed.
Cause analysis.
1) Deformation due to welding when the member is made, generally showing slow bending.
2) When the member is to be transported, the support point is unreasonable, such as the upper and lower bedding is not vertical, etc. or the sinking of the stacking site, so that the member produces a dead bend or slow deformation.
3) Deformation due to collision in the transport of components, generally presenting dead bend.
Preventive measures.
1)When making members, adopt measures to reduce welding deformation.
2)In assembly welding, adopt measures such as reverse direction deformation, the assembly order should obey the welding order, use the assembly tire tool, and set enough brackets to prevent deformation.
3)In pending transportation and transport, pay attention to the reasonable configuration of pad points.
Solution.
1) member dead bend deformation, generally use mechanical correction method governance. That is, corrected with a jack or other tools or supplemented by oxyacetylene flame baking after correction.
2) structure occurs when the slow bending deformation, take oxyacetylene flame heating correction.
(2) The full-length distortion of the steel beam members after assembling exceeds the allowed value, resulting in poor installation quality of the steel beam.
Cause analysis.
1)The splicing process is unreasonable.
2) The size of the splicing node does not meet the design requirements.
Solution.
1) The assembled members should be set up on the assembling table, and the bottom surface of the members should be leveled to prevent warping when set for welding. The assembling table should be level at each pivot point, and the welding deformation should be prevented in the group welding. Especially the final assembly of the beam section or ladderway should be adjusted for deformation after the positioning welding, and pay attention to the node size to conform to the design, otherwise it is easy to cause distortion of the member.
(2) The members with poor rigidity of their own should be reinforced before turning over and welding, and the members should also be leveled after turning over, otherwise the members cannot be corrected after welding.
(3) member arching, the value of large dry or less than the design value. When the value of member arching is small, the beam will be deflected after installation; when the value of arching is large, the elevation of the extruded surface will easily exceed the standard.
5、Steel structure installation problems
(1) Steel column foot has gap pre-control measures before lifting steel column, should strictly control the foundation elevation, accurate measurement, and carefully level the foundation surface according to its measured value; such as the use of secondary grouting method, open pouring holes in the column foot base plate (also as exhaust holes), use steel mat plate to level the uneven bottom of the steel column, and pre-place the column foot support steel plate according to the design elevation, and then take secondary grouting.
(2) steel column displacement pre-control measures before pouring concrete foundation, the application of shaped chucks will be pre-buried bolts according to the design position stuck, to prevent displacement when pouring concrete; column low steel plate pre-set holes should be enlarged sample, determine the hole position before making pre-set holes.
(3) column vertical deviation is too large pre-control measures steel column should be lifted into position according to the calculated hanging point, and must use more than two points of lifting method, lifting should be temporarily fixed to prevent lifting deformation; column in place should be timely additional temporary support; vertical deviation, should be corrected before fixing.
II. Conclusion
Only in the process of construction management, strengthen the training and learning of technical personnel and workers on the specification standards and operation procedures, do a good job in the preparation before the start of construction, strengthen the quality control and supervision and inspection during the construction process, actively play the role of construction, supervision and other aspects, and do a good job in the process acceptance of each sub-project, in order to ensure the overall quality of the steel structure project.