Dapeng Town Industrial Park, Tongshan District, Xuzhou City, Jiangsu Province, China
Bolt ball space frame construction is widely used in municipal buildings, industrial plants, large shopping malls and other modern buildings because of its own advantages. In the process of construction of a large number of projects, the bolted ball space frame construction project also reveals a lot of quality common problems. This paper mainly focuses on the common problems and corrective measures in the main acceptance and completion acceptance of bolt ball space frame construction in recent years.
The plates used in portal steel frame are very thin, the thinnest available to 4 mm. Preference should be given to the shearing method and avoid cutting with flame for multi-thin plate undercutting. 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.
(1) pre-buried parts (anchor bolts) problem phenomenon: overall or layout offset; elevation error; fillet buckle did not take protective measures. Directly cause the steel column base plate bolt holes are not aligned, resulting in insufficient length of the wire buckle.
Measures: The steel structure construction unit works together with the civil construction unit to complete the work of pre-built parts, before the concrete is poured. Must review the relevant size and fixed firmly.
(2) anchor bolts are not vertical phenomenon: frame column column footing level is poor, anchor bolts are not vertical, pre-buried anchor bolts after the construction of the foundation level error is large. Column installation is not in a straight line, east to west, so that the appearance of the house is very ugly, bring error to the steel column installation, 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 anchor bolt construction, can be used out of steel or angle steel and other fixed anchor bolts. Weld into a cage, perfect support, or take some other effective measures to avoid the anchor bolt moving one when pouring the foundation concrete.
(3) anchor bolt connection problem phenomenon: the anchor bolt at the foot of the column is not tightened, the pad is not welded to the base plate; some of the anchor bolts that do not show 2 to 3 silk buckles.
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 by fire; foundation settlement observation data should be measured.
(1) High strength bolt connection
The bolt equipment surface does not meet the requirements, resulting in bad installation of the bolt, or the degree of tightening of the bolt does not meet the design requirements.
Cause analysis:
① Surface impurities such as floating rust, oil and dirt, bolt hole biscuit burrs, weld tumors, etc.
② Bolt mounting surface is still defective even after treatment.
Solution:
① High strength bolt surface floating rust, oil, and bolt hole biscuit problem, should be cleaned up one by one. The bolts must be treated with rust prevention before use, so that the bolts for assembling shall not be used in the official assembling. 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.
The bolt fillet is damaged and the screw cannot be freely screwed into the nut, affecting the assembly of the bolt.
Cause Analysis: Severe rusting of the wire buckle.
Solution:
① Bolts should be selected before use, cleaned and rusted for pre-matching.
② The bolt with damage to the fillet cannot be used as a temporary bolt, and forcing into the screw hole is strictly prohibited.
③ The pre-matched bolt components should be stored in sets and should not be interchanged when in use.
(2) on-site welding phenomenon: quality is difficult to ensure; the design requires full weld penetration of the first and second welding seam did not use ultrasonic flaw detection; the main beam and column of the floor is not welded; not using the lead arc plate welding.
Solution: Before welding the steel structure, check the certificate of conformity of the welding rod, select the welding containing bar according to the design requirements, use the welding rod as required by 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 defects such as edge biting, not full welding, one or two welds according to the requirements of nondestructive testing, in the specified welds and parts to be checked 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.
(1) The member is deformed during transportation and dead or slow bending occurs, causing the member to be unable to be installed.
Cause analysis:
① The deformation produced by welding when the member is made, generally showing slow bending.
② member to be transported, the support point is not reasonable, such as the upper and lower bedding is not vertical, or stacking site subsidence, so that the members of the dead bend or slow deformation.
③ deformation due to collision in the transport of components, generally present dead bend.
Preventive measures:
① When the components are made, measures to reduce welding deformation are used.
② In assembly welding, use measures such as reverse direction deformation, the assembly order should obey the welding order, use the assembly tire tool, and set up enough brackets to prevent deformation.
③ In the pending transportation and transport, pay attention to the reasonable configuration of the pad point.
Solution:
① member dead bend deformation, the general use of mechanical correction method of 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 twist of the steel beam members after assembling exceeds the allowable 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 Assembled components should be set up assembled workbench, set welding to level the bottom surface of the components to prevent warping. 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 beam section or ladder way, to adjust the deformation after positioning welding, pay attention to the node size to meet the design, otherwise it is easy to cause distortion of the member.
② members with poor rigidity of their own, turn over before welding should be reinforced, members should also be leveled after turning over, otherwise the members can not be corrected after welding.
(3) Arching of members, 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.
Cause Analysis:
① The size of the components does not meet the design requirements.
② The erection process is not corrected according to the difference between the measured value and the calculated value.
③ The bridge with small span and small arching degree was ignored when assembling.
Solution:
① Strictly according to the bolt ball space frame member production allowed deviation for each step inspection.
② In the process of erection, the bars and the completion of assembly, as well as the end of construction of site joints, the upper arch degree measurement is carried out, and other adjustments are made in the construction.
③In the process of small assembling, the accumulated deviation should be strictly controlled, and attention should be paid to measures to eliminate the influence of welding shrinkage.
(1) steel column foot has a gap pre-control measures before lifting steel column, should strictly control the foundation elevation, accurate measurement, and according to its measured value of the foundation surface carefully leveling; such as the use of secondary grouting method, the foot of the column to open the pouring hole (also as a venting hole), the use of steel mat plate will be the bottom of the steel column uneven pad flat, and pre-placement of good column foot support plate according to the design elevation, and then take the 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) The 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.
