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Knowledge of building materials: some problems and solutions in the construction of steel structure.

position: Home >> News >> Industry news

Knowledge of building materials: some problems and solutions in the construction of steel structure.

Release date:2018-01-02 Author: Click:

   

[student's question] some problems and solutions in the construction of steel structure?

The steel structure is widely used in modern buildings such as Bridges, industrial buildings and high-rise buildings because of its advantages. In the process of large amount of engineering construction, the steel structure project also exposed a lot of quality problems. This paper mainly discusses the common problems and rectification measures in the main body acceptance and acceptance of steel structure in liaoning province in recent years.

A, steel knot

Some problems and solutions in construction process.

1. Production and production of components.

The panels used for the portal frame are very thin and the thinnest can be used up to 4 mm. The blanks should be cut in the preferred way to avoid flame cutting. Because cutting with flame can cause large wave deformation on the edge of the plate. At present, the welding of H section steel most of the manufacturers adopt submerged arc automatic welding or semi-automatic welding. If the control is not good to occur welding deformation, make the members bent or distorted.

2. Installation of column feet.

(1) problem of embedded parts (anchors) : whole or layout deviation; Error in elevation; The thread did not take protective measures. Directly cause the bolt hole of the steel column bottom plate is wrong, resulting in insufficient thread length.

Measures: the steel structure construction unit works together with the civil construction unit to complete the work of the embedded part, before the concrete is poured. Relevant dimensions must be checked and fixed firmly.

(2) the anchor is not perpendicular: the horizontal degree of the bottom plate of the frame column is poor, the anchor bolt is not vertical, and the horizontal error of the embedded anchor bolt is large after the foundation construction. The post installation is not on a straight line, and it is distorted, which makes the appearance of the house very ugly. The installation of the steel column causes errors, and the structural stress is affected, which does not meet the requirements of construction acceptance specifications.

Measures: the anchor bolt should be installed with the lower adjustment bolt of the bottom plate, and then the secondary grouting of the non-shrinkage mortar shall be filled in. When the anchor bolt is constructed, it can be used to anchor bolts such as steel bar or Angle steel. Weld into a cage, perfect support, or take other effective measures to avoid the casting of concrete when the anchor is moved.

(3) anchor connection problem: the anchor bolt is not tightened, and the pad is not welded with the bottom plate; Part of unexposed 2 ~ 3 screw anchors.

Measures: welding bolts and nuts should be adopted; In the case of chemical anchor bolt, it should be thickened with fire retardant coating and heat insulation to prevent the anchoring performance in case of fire. Basic settlement observation data should be supplemented.

3. Connection problem

(1) high strength bolt connection.

1) the bolt equipment surface does not meet the requirements, resulting in the improper installation of bolts, or the degree of bolt fastening does not meet the design requirements.

Reason analysis:

On the surface of the surface, there are rust, oil and other impurities, the bolt holes have burr, welding tumor and so on.

The mounting surface of the bolt is still defective.

Solution:

It 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 the formal assembly. Bolts shall be kept and distributed by special persons.

The assembly surface should be taken into consideration in the order of construction and installation to prevent repetition, and shall be handled before hoisting.

2) screw thread damage, screw can not freely screw into the nut, affecting the assembly of bolts.

Cause analysis: severe corrosion of silk buckles.

Solution:

Before use, the bolt should be selected and pre-arranged after cleaning and derusting.

The bolts that are damaged by the thread can not be used for temporary bolt.

The pre-selected bolt components shall be stored according to the set and shall not be exchanged when used.

(2) on-site weld phenomenon: the quality is not guaranteed; No ultrasonic flaw detection is used for the weld penetration of one or two welding seams. The main beam and column are not welded; No arc welding is used.

Solution: steel structure before welding, the welding of the inspection certificate, welding article contains the selection according to design requirements, according to the instructions and procedures require the use of electrode, the weld surface must not have crack, flash, a, level 2 weld can not have porosity, slag, crater crack, level of weld shall bite edge, under welding defects, such as a, level 2 weld nondestructive testing, in accordance with requirements in the weld and parts of the rules to check the welder's seal. The unqualified welds shall not be disposed of without authorization, and the modification process shall be determined before treatment, and the number of weld repairs in the same part shall not be more than twice.

4. Deformation of components.

(1) when the component deforms during transportation, it appears dead bending or slow bending, causing the component to be unable to install.

Reason analysis:

1) when the component is made, the deformation caused by welding is generally slow.

2) when the components are to be transported, the supporting points are not reasonable. If the upper and lower pads are not perpendicular, or the site is sunken, the components will be bent or slowly deformed.

3) deformation caused by collision in the transport of components is generally presented as dead bending.

Preventive measures:

1) when the components are made, the measures to reduce welding deformation are adopted.

2) in the assembly welding, the anti-direction deformation should be adopted, and the assembly sequence shall be in accordance with the welding sequence, using the assembly of the placenta, setting enough brackets to prevent deformation.

3) the reasonable configuration of cushion points should be paid attention to during transportation and transportation.

Solution:

1) the bending deformation of the components is generally governed by mechanical correction method. Use jacks or other tools to correct or excise the oxyacetylene flame for correction.

2) when the structure is slowly bent and deformed, the oxyacetylene flame is used to correct the heating.

(2) the full length distortion of the steel girder assembly is beyond the allowable value, resulting in poor installation quality of the steel girder.

Reason analysis:

1) the splicing process is not reasonable.

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

Solution:

1) assembling components shall be equipped with a assembling table, which shall be fixed to the bottom surface of the components to prevent warping. The assembly table should be at each fulcrum level to prevent welding deformation. In particular, the final assembly of beam section or stairway should be adjusted after positioning welding. Note that the size of the node should conform to the design, otherwise it is easy to cause distortion of the components.

2) if the component is less rigid, it should be strengthened before turning the body, and leveling should be made after the component is turned over. Otherwise, the component cannot be corrected after welding.

(3) the component arch, the numerical value is large or less than the design value. The building blocks of the members have a numerical hour, and the undergirder is mounted. When the arch value is large, it is easy to produce the overshoot.

Reason analysis:

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

2) during erection, no correction is made according to the difference between the measured value and the calculated value.

3) small span Bridges, small camber, neglected in assembly.

Solution:

1) each step inspection shall be conducted according to the allowable deviation of steel structural members.

2) in the process of erection, the bar parts are installed and the construction of the site joints is finished, and the arch degree is measured, and other adjustments are made in the construction.

3) in the small assembly process, the accumulated deviation should be strictly controlled, and measures should be taken to eliminate the impact of welding shrinkage.

5. Installation of steel structure.

(1) before the steel column is equipped with pre-control measures, the base elevation shall be strictly controlled, the measurement accuracy shall be measured, and the basic surface shall be carefully leveled according to the measured value. As the secondary grouting method is adopted, in the column foot motherboard watering holes (as vent), using steel plate at the bottom of the steel column unevenness flat, and in advance according to the design elevation place pedestal bearing steel plate, and then take the second grouting.

(2) before the steel column displacement precontrol measures are cast concrete foundation, the embedded bolt shall be stuck according to the design position to prevent the displacement when the concrete is poured; The reserved orifice of column low steel plate should be enlarged to confirm the hole position and then make the reserved hole.

(3) column vertical excessive deviation control counter measures of steel column should be according to the calculation of the hanging point hoisting in place, and more than two points of hoisting method must be used, should be temporary fixed when lifting, in case the lifting deformation; Temporary support should be added when the column is in place; The vertical deviation should be fixed before fixing.

Second, the conclusion

Only in the process of construction management, strengthen the technical personnel to the specification standards and operational procedures, workers training study, the real ready to before construction, strengthen the quality control in the process of construction, supervision and inspection, active play to the role of the construction, supervision and so on various aspects, do a good job in the process of the sectional works acceptance to guarantee the overall quality of the steel structure engineering.

All the above contents are arranged according to the problems encountered in the actual work of the students. For reference, please timely communicate and correct any questions.

Bridge steel structure


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