Some problems and solutions in steel structure construction

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 a large number of engineering construction, steel structure engineering has also exposed many quality problems. This article mainly focuses on the common problems and rectification measures in the acceptance and completion acceptance of steel structure in Liaoning in recent years.

1. Some problems and solutions in the construction process of steel structure engineering

1. The production of components

The plates used for portal steel frames are very thin, as thin as 4 mm. The blanking of multi-thin plates should be cut in a way and avoid flame cutting. 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 automatic welding or semi-automatic welding. If the control is not good, welding deformation should occur, so that the component is bent or twisted.

2. Column foot installation problem

(1) Embedded parts (anchor) problem phenomenon: overall or layout shift; The elevation is wrong; The fastener is not protected. Directly cause the bolt hole of the steel column bottom plate to be out of position, resulting in insufficient wire buckle length.

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

(2) The phenomenon that the anchor is not vertical: the horizontality, the bottom plate of the frame column is poor, the anchor is not vertical, and the horizontal error of the embedded anchor after foundation construction is large. After installation, the column is not in a straight line, and it is crooked, making the appearance of the house ugly, bringing errors to the installation of steel columns, and the structural force is affected, which does not meet the requirements of the construction acceptance specifications.

Measures: The anchor installation should insist on leveling the bottom plate with the lower adjustment bolt first, and then fill it with secondary grout with non-shrinkage mortar, which is constructed by this method abroad. Therefore, when the anchor is constructed, the fixed anchor can be fixed by steel bars or angle steel. Weld into a cage, perfect the support, or take some other effective measures to avoid the anchor moving one bit when pouring the foundation concrete.

(3) Anchor connection problem phenomenon: the anchor bolt of the column foot is not tightened, and the pad is not welded with the bottom plate; Some anchors with 2~3 silk buckles are not exposed.

Measures: welding bolts and nuts should be taken; On the outside of the chemical anchor, the fireproof coating and heat insulation treatment should be thickened to prevent the anchoring performance from being affected by fire; Basic settlement observation data should be supplemented.

3. Connection problems

(1) High-strength bolt connection

1) The bolt equipment surface does not meet the requirements,

resulting in the bolt is not easy 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 on the surface, and there are burrs and welding tumors in the bolt holes.

(2) Although the bolt mounting surface is treated, there are still defects.

Workaround:

(1) The surface of high-strength bolts is rusty, oily and bolt holes should be cleaned up one by one. It must be treated with anti-rust before use, so that the bolts used for assembly shall not be used in formal assembly. Bolts should be kept and issued by a special person.

(2) The treatment of the assembly surface should take into account the construction and installation order, prevent repeated progress, and try to deal with it before hoisting.

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

Cause analysis: The wire buckle is severely rusted.

Workaround:

(1) Before use, the bolt should be selected, cleaned and rusted and preconditioned.

(2) The bolt damaged by the wire buckle cannot be used as a temporary bolt, and it is strictly forbidden to forcibly drive into the screw hole.

(3) The pre-selected bolt assembly should be stored according to the sleeve and shall not be interchangeable when used.

(2) On-site weld phenomenon: quality is difficult to guarantee; The design requires that the first and second stage welds with full penetration do not use ultrasonic flaw detection; The main beams and columns of the floor are not welded; No arc ignition plate welding was used.

Solution: Before welding the steel structure, check the certificate of the electrode, select the welding rod according to the design requirements, use the electrode according to the requirements of the instruction manual and operating procedures, the surface of the weld shall not have cracks, welding tumors, the first and second level welds shall not have

pores, slag inclusions, arc pit cracks, the primary weld shall not have undercut, not full welding and other defects, the first and second level welds shall be non-destructive testing as required, and the welder's steel seal shall be checked in the specified weld and part. Unqualified welds shall not be treated without authorization, and then processed after the modification process is determined, and the number of rework times of welds in the same part should not exceed twice.

4. Deformation of components

(1) The component is deformed during transportation, and there is a dead bend or slow bend, resulting in the inability to install the component.

Cause analysis:

1) The deformation caused by welding during the production of the component generally shows slow bending.

2) When the component is to be transported, the support point is unreasonable, such as the upper and lower skids are not vertical, etc., or the stacking site is subsided, so that the component is bent or slowly deformed.

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

Precautions:

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

2) In assembly welding, adopt measures such as reverse direction deformation, the assembly sequence should obey the welding order, use assembled tires, and set up enough brackets to prevent deformation.

3) During transportation and transportation, pay attention to the reasonable configuration of cushion points.

Workaround:

1) The component is dead bending and deformation, and is generally treated by mechanical correction method. That is, it is corrected with a jack or other tools or supplemented with oxyacetylene flame after roasting.

2) When the structure is slowly bent and deformed, oxyacetylene flame heating is adopted.

(2) The full length of the steel beam components is twisted beyond the allowable value after assembly, resulting in poor installation quality of the steel beam.

Cause analysis:

1) The splicing process is unreasonable.

2) The size of the assembly node does not meet the design requirements.

Workaround:

1) The assembly component should be set up with an assembly workbench, and the bottom surface of the component should be leveled to prevent warping when welding. The assembly table should be horizontal at each fulcrum, and welding deformation should be prevented in group welding. Especially for the post-assembly of beam sections or ladders, the deformation should be adjusted after positioning welding, and attention should be paid to the size of the node to conform to the design, otherwise it is easy to cause distortion of the components.

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

(3) The component arches, and the value is large or less than the design value. The arching value of the component is small, and the beam is flexed after installation; When the arching value is large, it is easy to produce the extruded surface elevation exceeding the standard.

Cause analysis:

1) The component size does not meet the design requirements.

2) During the erection process, it was not corrected according to the discrepancy between the measured value and the calculated value.

3) Bridges with small spans, small arching, neglected when assembling.

Workaround:

1) Strictly according to the allowable deviation of steel structure components to carry out each step inspection.

2) During the erection process, the members are installed and installed, and after the construction of the site joint, the upper arch measurement is carried out, and other adjustments are made during construction.

3) In the small assembly process, the cumulative deviation should be strictly controlled, and attention should be paid to measures to eliminate the influence of welding shrinkage.

5. Steel structure installation problem

(1) Before the steel column is hoisted, the foundation elevation should be strictly controlled, the measurement should be accurate, and the foundation surface should be carefully leveled according to its measured value; If the secondary grouting method is used, the watering hole (double as the exhaust hole) is opened in the bottom plate of the column foot, the steel pad plate is used to flatten the uneven place at the bottom of the steel column, and the column foot support steel plate is arranged in advance according to the design level, and then the secondary grout is taken.

(2) Before pouring the concrete foundation of the steel column displacement pre-control measures, the embedded bolts should be jammed according to the design position by applying the stereotype chuck to prevent displacement when pouring concrete; The reserved hole of the column low steel plate should be enlarged, and the reserved hole should be made after determining the hole position.

(3) The steel column of the pre-control measures with excessive vertical deviation of the column should be hoisted into place according to the calculated hanging point, and the lifting method of more than two points must be adopted, and the lifting should be temporarily fixed to prevent lifting deformation; After the column is in place, temporary support should be added in time; Vertical deviations should be corrected before fixation.

II. Conclusion

Only in the process of construction

management, strengthen the training and learning of technical personnel and workers on normative standards and operating procedures, effectively prepare before the start of construction, strengthen quality control and supervision and inspection in 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 steel structure engineering.

Do you understand the above introduction to the problems in the use of steel structure? Xirong steel structure specializes in the undertaking of Sichuan steel structure engineering, call to learn more!