Some problems and solutions during the construction of steel structures

1. Production and production of components

The gantry steel frame is thin and can be as thin as 4 mm. Cutting of multiple sheets should be selected to avoid cutting with flame. Because cutting with flame will cause a large wave deformation of the board edge. At present, most manufacturers of H-beam welding use submerged arc welding or semi-automatic welding. If the control is not good, welding deformation should occur, and the component will be bent or twisted.

2, column foot installation problem

(1) Problems with embedded parts (anchor bolts): overall or layout deviation; incorrect elevation; no protective measures have been taken for wire fasteners. The bolt holes of the bottom plate of the steel column are directly misaligned, resulting in insufficient length of the thread fastener.

Measures: The steel structure construction unit cooperates with the civil construction unit to complete the work of embedded parts, before the concrete is poured. Relevant dimensions must be reviewed and firmly secured.

(2) Anchor bolts are not vertical: The horizontality of the foot of the frame column is poor, the anchor bolts are not vertical, and the horizontal error of the embedded anchor bolts after the foundation is large. The pillars are not in a straight line after installation, and they are crooked from east to west, which makes the appearance of the house difficult to see, which brings errors to the installation of the steel columns, the structure is affected by force, and does not meet the requirements of the construction acceptance code.

Measures: Anchor bolts should be installed by first leveling the bottom plate with the lower adjusting bolts and then filling them with non-shrinking mortar for secondary grouting. This method is used abroad. Therefore, anchor bolts can be used for fixing anchor bolts such as steel bars or angle steel. Welded into a cage, perfect support, or take some other measures to avoid moving the anchor bolt one bit when pouring the foundation concrete.

(3) Anchor bolt connection problem phenomenon: The column anchor bolt is not tightened, and the backing plate is not welded to the bottom plate; part of the anchor bolt is not exposed with 2 to 3 wire buckles.

Measures: Welding anchor rods and nuts should be adopted; outside the chemical anchor bolts, thicker fire-resistant coatings and heat insulation treatments should be used to prevent the anchoring performance from being affected in the event of a fire; additional observation data for foundation settlement should be added.

3. Connection problems

(1) High-strength bolt connection

1) The bolt equipment surface does not meet the requirements, which makes the bolts difficult to install, or the degree of bolt tightening does not meet the design requirements.

Cause Analysis:

① There are impurities such as floating rust and oil stain on the surface, and there are burrs and welding knobs on the bolt holes.

② Although the bolt mounting surface is still lacking after treatment.

Solution:

① The surface of high-strength bolts should be cleaned one by one if they have rust, oil stains, and bolt holes. Before use, it must be rust-proofed, so that the bolts used for assembly must not be used in the formal assembly. Bolts should be kept and distributed by a special person.

② When handling the assembly surface, consideration should be given to the order of construction and installation to prevent repetition, and try to handle it before lifting.

2) The bolt screw is damaged, and the screw cannot be screwed into the nut, which affects the assembly of the bolt.

Cause analysis: The wire buckle was severely rusted.

Solution:

① Bolts should be selected before use, and pre-configured after cleaning and rust removal.

② Bolts damaged by wire buckles cannot be used as temporary bolts, and it is strictly forbidden to force them into the screw holes.

③ The pre-selected bolt assemblies should be stored according to sleeves, and they should not be interchanged when in use.

(2) On-site welding seam phenomenon: It is difficult to guarantee the quality; the first and second grade welding seams which are designed to be fully welded are not used for inspection; the main beams and columns of the floor are not welded; arc welding plates are not used for welding.

Solution: Before welding the steel structure, check the qualification certificate of the electrode, select the welding rod according to the design requirements, use the electrode according to the instructions and operating procedures, and there should be no cracks or nodules on the surface of the weld. There must be no pores, slag inclusions, arc pit cracks, welds must not have undercuts, underfilled welds, etc., non-destructive testing of primary and secondary welds according to requirements, the welder's stamp should be checked at the specified welds and parts. Unqualified welds shall not be processed without authorization. After the modification process is determined, the welds shall not be repaired more than twice.

4.Deformation of components

(1) When the component is deformed during transportation, dead bends or slow bends occur, making the component unable to be installed.

Cause Analysis:

1) Deformation due to welding during the production of components generally shows a gentle bend.

2) When the component is ready for transportation, the support points are unreasonable. For example, if the upper and lower dunnages are not vertical, or the storage site is subsided, the component will be dead bent or slowly deformed.

3) Deformation due to collision during transportation of components, generally showing dead bends.

Precaution:

1) When manufacturing components, measures to reduce welding deformation are adopted.

2) During assembly and welding, measures such as deformation in the opposite direction are adopted. The assembly sequence should obey the welding sequence. Use assembly tires and set enough brackets to prevent deformation.

3) During transportation and transportation, pay attention to the reasonable allocation of pads.

Solution:

1) Dead bending of members, mechanical correction is generally adopted. Correction with jack or other tools or supplementation with oxyacetylene flame

2) When the structure is deformed slowly, oxyacetylene flame heating is adopted to correct it.

(2) The total length of the steel beam members after assembly is distorted beyond the allowable value, resulting in poor installation quality of the steel beam.

Cause Analysis:

1) The splicing process is unreasonable.

2) The dimensions of the assembled nodes do not meet the design requirements.

Solution:

1) Assembling components should be equipped with assembly tables. When welding is set, the bottom surface of the components should be leveled to prevent warping. The fulcrum of the assembly table should be level, and welding deformation should be prevented during group welding. Especially for the assembly of beam sections or stairways, it is necessary to adjust the deformation after tack welding, and pay attention to the size of the joints in accordance with the design, otherwise it is easy to cause component distortion.

2) Components with poor rigidity should be reinforced before turning over and welding, and leveling should also be performed after turning over, otherwise the components cannot be corrected after welding.

(3) The element is arched, and the value is large or smaller than the design value. When the arch value of the component is small, the beam is deflected after installation; when the arch value is large, the extrusion surface elevation is likely to exceed the standard.

Cause Analysis:

1) The dimensions of the components do not meet the design requirements.

2) During the erection process, the measured and calculated values are not used.