Some Problems in Construction of Steel Structure and Their Solutions

- Dec 13, 2017 -

Due to its own advantages, steel structures are widely used in modern buildings such as bridges, industrial plants and high-rise buildings. In a large number of project construction process, steel structure project also exposed a lot of quality common problems. In this paper, we mainly talk about the common problems in acceptance and final acceptance of steel structures in Liaoning Province and the corrective measures in recent years.
First, part of the steel structure construction process and solutions
1, component production problems
The gantries used for the gantry are very thin, and the thinnest is 4 mm. Multi-sheet cutting should be the preferred shear mode to avoid flame cutting. Because the use of flame cutting plate edge will have a great wave deformation. The current H-beam welding most manufacturers are using submerged arc welding or semi-automatic welding. If the control is not good welding deformation occurs, so that the components are bent or twisted.
2, column foot installation problem
(1) embedded parts (anchor) Problem phenomenon: the overall or layout offset; elevation error; threading did not take protective measures. Directly caused by the steel plate floor bolt hole is not aligned, resulting in lack of threaded length.
Measures: The steel structure construction unit, together with the civil construction unit, will complete the work of embedding the pieces before pouring the concrete. Must review the relevant size and fixed firmly.
(2) The phenomenon that the anchor bolt is not vertical: the horizontal difference of the foot column of the frame column and the anchor bolt is not vertical, and the horizontal error of the embedded anchor bolt after foundation construction is large. Column is not installed in a straight line, staggering east, so that the appearance of housing is not easy to see, to the installation of steel columns bring error, the structure affected by force, does not meet the construction acceptance requirements.
Measures: Anchor bolt installation should be the first to adjust the bottom of the bottom leveling bolt leveling, and then fill the secondary grouting mortar non-shrinkage, foreign law construction. Therefore, anchor bolt construction, can be used steel or angle anchor bolts and other fixed. Welded into a cage, improve the support, or take some other effective measures to avoid pouring anchor concrete anchor when the shift.
(3) the phenomenon of anchor bolt connection: column foot bolt is not tightened, the plate is not welded with the floor; some did not reveal 2 to 3 threaded buckle anchor.
Measures: Welding anchor rod and nut should be taken; outside of chemical anchor bolt, thickening fire-retardant coating and heat-insulating treatment should be thickened to prevent the anchorage performance from being affected by fire; supplementary observation data of foundation subsidence should be made up.
3, the connection problem
(1) high-strength bolt connection
1) Bolt equipment surface does not meet the requirements, causing the bolt is not good to install, or the degree of bolt does not meet the design requirements.
Cause Analysis:
① floating rust on the surface, oil and other impurities, bolt holes Bi burr, welding tumor.
② Although the bolt installation surface is still defective.
Solution:
① high-strength bolt surface rust, oil and bolt holes, should be cleaned one by one. Before use must be rust-proof treatment, so that the bolts used in assembly shall not be used in the official assembly. Bolts should be kept and distributed by hand.
② processing assembly surface should take into account the construction and installation order to prevent duplication, and try to handle before lifting.
2) Screw thread damage, the screw can not be screwed into the nut, affecting the assembly of the bolt.
Analysis: Serious serious rust wire.
Solution:
① bolts should be used before the selection, after cleaning rust pre-prepared.
② threaded threaded bolts can not do temporary use of bolts, forbidden into the screw hole.
③ pre-optional bolt assemblies should be stored in sets, shall not be used interchangeably.
(2) The phenomenon of on-site weld: the quality is difficult to guarantee; design requirements full penetration of the first and second welds did not use ultrasonic testing; floor girders and columns are not welded; not using arc plate welding.
Solution: Before the welding of steel structure, check the welding certificate, according to the design requirements of the selection of welding strip, according to the instructions and procedures require the use of electrodes, the surface of the weld shall not be cracked, welding tumor, one or two welds There shall be no holes, slag inclusions, crater cracks, a weld may not undercut, under welding and other defects, the first and second welds nondestructive testing as required, the provisions of the welds and parts to check the welder's seal . Unqualified weld shall not be handled without permission, set out to modify the process after treatment, the same part of the weld repair times should not be more than twice.
4, the deformation of components
(1) Deformation of components in transit, appear dead or bent, resulting in the component can not be installed.
Cause Analysis:
1) The components produced due to the deformation of the welding, the general slow rendering.
2) If the component is going to be transported, the supporting point is unreasonable. For example, the upper and lower padding are not vertical, or the sinking occurs on the stacking site, causing the components to die or bend slowly.
3) Deformation due to collisions during transportation of components, generally showing dead curves.
Precaution:
1) When the components are made, the measures to reduce the welding deformation are adopted.
2) Assembly welding, the use of deformation and other measures in the reverse direction, the assembly sequence should be subject to the welding sequence, the use of assembly of the tire, set up enough brackets to prevent deformation.
3) To be shipped and transported, pay attention to the reasonable allocation of pad.
Solution:
1) Structural dead bending deformation, the general use of mechanical correction method. That is, with jack or other tools to correct or supplemented with oxyacetylene flame roasted after correction.
2) When the structure is bent and deformed, take oxyacetylene flame to heat and correct.
(2) The total length of the steel beam after assembling distortion exceeds the allowable value, resulting in the poor quality of the steel beam installation.
Cause Analysis:
1) stitching process is unreasonable.
2) Assembly node size does not meet the design requirements.
Solution:
1) assembly components to be assembled assembly workbench, as the welding components to be leveling the bottom to prevent warping. Assembly table should be the level of the fulcrum, welding to prevent welding deformation. In particular, the final assembly of beam sections or stairways should be adjusted after positioning welding deformation, pay attention to node size to meet the design, otherwise easily lead to component distortion.
2) The parts with poor rigidity are to be reinforced before turning over, and the leveling should be performed after turning over the components, otherwise the components can not be corrected after welding.
(3) Arch components, the value of dry or less than the design value. Component arching numerical hours, the installation of the beam under the flexible; arching numerical, easy to produce extrusion surface elevation exceeded.
Cause Analysis:
1) Component size does not meet the design requirements.
2) erection process, not based on the measured value and the discrepancy of the calculated value of the amendment.
3) A bridge with a small span, with a smaller camber, neglected when assembled.
Solution:
1) strictly in accordance with the production of steel structure components to allow deviation test step.
2) In the erection process, the rod is installed and completed, and the construction site joints are completed, the crown camber measurement, and other adjustments in the construction.
3) In the small assembly process, the cumulative deviation should be strictly controlled, pay attention to take measures to eliminate the impact of welding shrinkage.
5, steel installation problems
(1) pre-steel column foot gap pre-control measures Before lifting the steel column, the base elevation should be strictly controlled, accurate measurement, and according to the measured value of the underlying surface carefully leveled; such as the use of secondary grouting method, Hole (also serves as a vent), the use of steel pad flat bottom uneven steel column, and pre-designed height of the column foot bearing steel plate, and then take the second grouting.
(2) Pre-control measures of steel column displacement Before pouring concrete foundation, the fixing bolts shall be used to fix the embedded bolts according to the designed position so as to prevent the displacement when concrete is poured. The reserved holes of low steel plate should be enlarged to determine the positions of the holes Make reserved hole again.
(3) The column vertical deviation is too large Pre-control measures should be hoisting steel columns in accordance with the calculation of the lifting position, and must be used more than two lifting methods, lifting should be temporarily fixed to prevent lifting deformation; column in place Temporary support should be added in time; for vertical deviations, it should be amended before fixing.

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