Steel structure engineering technology (version 20 16)?

Steel structure workshop mainly means that the main load-bearing components are made of steel. Including steel columns, steel beams, steel structure foundation, steel roof truss (of course, the span of the workshop is relatively large, and now it is basically steel roof truss) and steel roof. Note that the walls of steel structures can also be maintained by brick walls. Due to the increase of steel production in China, many steel structure workshops have been adopted, which can be divided into light and heavy steel structure workshops.

1, steel structure building is light in weight, high in strength and long in span.

2. The construction period of steel structure building is short, and the investment cost is correspondingly reduced.

3. The steel structure building has high fire resistance and strong corrosion resistance.

4. The steel structure building is easy to move, and recycling is pollution-free.

I. Inspection of steel structure workshop and steel structure members

1. The slenderness ratio of steel members can be determined according to the Code for Inspection of Steel Structure Engineering, and the slenderness ratio of steel members should be calculated according to the actual size.

2, the connection of steel structure support system, according to the provisions of the steel structure engineering specification for testing; The component size of the support system can be determined according to the provisions of the Code for Inspection of Steel Structure Engineering. It shall be verified or evaluated according to the design drawings or corresponding design specifications.

3. The width-to-thickness ratio of the cross section of steel structure members can be calculated according to the provisions of the Code for Inspection of Steel Structure Engineering, and should be evaluated according to the design drawings and relevant specifications.

Second, the steel structure painting

1. The quality of steel structure protective coating shall be inspected according to the current national product standards.

2. The derusting grade of steel surface can be determined by comparing the pictures specified in the current national standard "Rusting Grade and Derusting Grade of Steel Surface before Painting" GB8923.

3. The coating thickness of different types of coatings shall be tested by the following methods:

(1) The paint film thickness can be detected by a paint film thickness gauge, and the number of sampled components should not be less than the minimum capacity of Class A samples in Table 3.3. 13 of this standard, nor should it be less than 3 pieces; Each piece is measured at five positions, and the value of each position is the average of the dry paint film thickness of three measuring points 50mm apart.

(2) The coating thickness of thin fire-retardant coatings can be detected by a coating thickness tester, and the measuring method should comply with the provisions of CECS24 Technical Specification for the Application of Fire-retardant Coatings for Steel Structures.

(3) The coating thickness of thick fire retardant coatings shall be detected by measuring needle and steel ruler, and the measuring method shall comply with the provisions of Technical Specification for Application of Fire Retardant Coatings for Steel Structures CECS24. The thickness value and deviation value of coating shall be evaluated according to Code for Acceptance of Construction Quality of Steel Structure Engineering (GB50205). 6.7.4 The appearance quality of paint can be inspected and evaluated according to different materials and the Code for Acceptance of Construction Quality of Steel Structure Engineering (GB50205).

Three, steel structure steel grid

1, the detection of steel grid structure can be divided into node bearing capacity, weld, size and deviation, uneven members and deflection of steel grid structure.

2. The bearing capacity inspection of welded ball joints and bolted ball joints of steel grid structure should be carried out according to the requirements of JGJ78 "Standard for Quality Inspection and Evaluation of Grid Structure Engineering". For the existing grid structure with bolted ball joints, the joints can be taken out of the structure to test the ultimate bearing capacity of the joints. When the bolt ball joint is truncated, measures should be taken to ensure the structural safety.

3. Welds in steel grid structure can be detected by ultrasonic flaw detection, and the detection operation and evaluation should be carried out according to the requirements of Ultrasonic Flaw Detection and Quality Grading Method for Steel Grid Structure with Welded Ball Joints JG/T3034. 1 or Ultrasonic Flaw Detection and Quality Grading Method for Steel Grid Structure with Bolted Ball Joints JG/T3034.2.

4. The appearance quality of the weld of steel grid structure shall be inspected according to the requirements of Code for Acceptance of Construction Quality of Steel Structure Engineering (GB50205).

5. Deviation detection of welding balls, bolt balls, high-strength bolts and bars, detection methods and allowable deviation values shall be implemented according to the Standard for Quality Inspection and Evaluation of Grid Structure Engineering (JGJ78).

6. The wall thickness of steel tube members of steel grid can be detected by ultrasonic thickness gauge, and the decorative layer should be removed before detection.

7. The straightness of steel bar axis in steel grating can be detected by drawing method, and the straightness shall not exceed one thousandth of the length of steel bar.

8. The deflection of steel grid can be detected by laser rangefinder or level gauge, and there should be no less than 3 measuring points in each half span, and there should be 1 measuring point in the span, and the distance between the end measuring point and the end bearing should not be greater than1m..

Four, the real load test and dynamic test of steel structure performance

1. For large-scale complex steel structure systems, in-situ nondestructive real-load testing can be carried out to directly test the structural performance. The actual load inspection of structural performance can be carried out according to the provisions of Appendix H of this standard. The loading factor and judging principle can be determined according to the provisions in Appendix H.2, and can also be adjusted appropriately according to the specific situation.

2. When the bearing capacity of a structure or member is in doubt, a prototype or full-scale model load test can be conducted. The test shall be entrusted to a professional organization with sufficient equipment capacity. Before the test, a detailed test plan should be made, including the test purpose, the selection or manufacture of test pieces, the arrangement of loading devices, measuring points and test instruments, the loading steps and the evaluation method of test results. The test plan can be made according to Appendix H and should be agreed by all parties concerned before the test.

3. For large and important new steel structure systems, it is advisable to carry out actual structural dynamic tests to determine the dynamic parameters such as natural vibration period of the structure. The structural dynamic test shall comply with the provisions in Appendix E of this standard.

4. The stress of steel bars can be detected by resistance strain gage or other effective methods according to the actual situation.

Verb (abbreviation of verb) Two major defects of steel structure workshop

Defects in steel structure engineering of modern construction industry in China. Steel structure has been adopted by many enterprises in the construction industry, but in order to optimize the structure, save resources and recycle, most construction enterprises have implemented new steel structures. This has also brought many defects and potential safety hazards to the steel structure workshop. In steel structure enterprises, most enterprises pay attention to the advantages of steel structure, but ignore the safety defects and hidden dangers.

Analysis of quality problems of steel structure engineering: The reasons why it is difficult to guarantee the quality of steel structure engineering are various and complicated, including problems caused by improper technology, problems caused by violation of process operation, problems caused by the technical level and sense of responsibility of builders, and quality problems caused by mistakes of decision makers.

(A) the problem of steel itself

When a company was processing the box column of a building 1200* 1200*60, during the welding process, it was suddenly found that the thick plate with 60mm web was torn, and the clear cracks visible to the naked eye divided the plate into two halves from the thickness direction. After nondestructive testing, it was found that the crack depth was about 3 mm At the same time, the cutting parts of several other plates of the same model and batch number were tested, and it was found that there was interlayer in the plates, and the rolling quality was not good. During the welding process, the material of the interlayer is pulled apart by the welding stress caused by welding. As a result, the thick plate is torn in the thickness direction. Cause analysis: Because of the particularity of the parts used, this part is used as a web in the component, and the vertical welding part is completely penetrated in the welding form, and the welding stress generated by welding is released outward due to delamination in the plate, thus tearing the plate along the thickness direction. According to the actual situation, the following measures can be taken to deal with it:

(1) A large number of interlayers in steel belong to the quality problems produced by steel mills during rolling, which have exceeded the requirements of national standards and specifications. You can ask the steel mill to send someone to verify and negotiate with them to return or exchange goods.

(2) If the number of interlayers is small, the opinions of the technical department and the owner can be solicited, and the information will be fed back to the steel mill to take remedial measures for the problems. According to the results of nondestructive testing, all the problematic parts can be gouged out by air gouging, exceeding their own depth, and then filled with welding materials with equal strength. After completion, surface treatment can be carried out, nondestructive testing can be carried out after the specified time, and the same component can be sampled for physical and chemical inspection, which meets the requirements of design specifications and can be used continuously;

(3) Under the witness of the supervisor, cut off the parts and replace them with qualified plates. Replaced parts are used for non-load-bearing and unimportant parts or as auxiliary materials. After completion, nondestructive testing shall be carried out after the specified time, and records shall be made.

(2) Problems in the construction process

Quality problems are easy to occur in the process of processing and manufacturing, and it is mainly special processes and important processes that are difficult to handle after processing. The proportion of quality problems in general processes is very small. In the above construction process, special processes include welding and painting, and important processes include blanking and assembly.

1. welding process. This process belongs to concealed engineering, and it is also one of the most prone to quality problems. According to the product quality report of a company in 2004, 80% of the quality problems in this process are due to welding quality, followed by 10% due to improper operation of the previous process and technical problems of operators, which is the main problem that directly affects the engineering quality. Therefore, such problems can only be detected and judged by professional testing companies using professional testing tools. Generally speaking, according to the types of defects in weld, it can be divided into slag inclusion, incomplete fusion, porosity and so on.

2. The painting process. This process is also a hidden process, which has less influence on the structure than on the building function. It is also a process prone to quality problems. The process quality problems mainly include: the paint film on the surface of the component falls off in a large area and locally, the paint film on the surface of the component falls off and sags, the thickness of the paint film is not enough, the thickness distribution of the paint film is uneven, and the color difference of the paint film is large.

3. Lofting and blanking process. This process belongs to the leading position before the parts are processed, and its quality directly affects the next process, and even leads to all the blanking parts being scrapped. This kind of situation is very common, so it is very important and necessary to strengthen the quality monitoring of the working procedure before blanking. The quality problems caused by this process mainly include: (1) the deformation of slender plate parts is more severe when cutting; Due to the uneven distribution of slag inclusion and components in cutting gas or plate, horse teeth, knots and cuts with excessive depth appear on the cutting surface; Parts cut or sawed by gas do not take into account the shrinkage and deformation of subsequent processes, resulting in excessive size of parts; Scrapping of batch parts due to errors in process documentation; The cutting size of blanking seriously exceeds the standard requirements.

4. Assembly process. This process plays an important role in the processing quality of parts, and its quality is greatly affected by the previous process, so it is very important to strengthen process monitoring before assembly. The quality problems caused by this process mainly include: the position of assembled parts is wrong, such as 3450mm to 4350mm；; Wrong use of parts, 2# parts should have been assembled, but 3# parts were assembled; Parts are incorrectly assembled in the correct position, for example, the hole 45mm on the board was originally outward, but 45mm was actually installed inward; The assembly clearance of assembly parts exceeds the requirements of specifications and technical documents, and the clearance of 3mm is now 7 mm; Some parts are not corrected during assembly, and the deformation after assembly cannot be eliminated; In order to save trouble, the operator cuts without authorization, resulting in the position and size of the hole on the part exceeding the standard; There is no surface treatment in the welding area; Assembly error caused by wrong drawing size.

Six, nine advantages of steel structure workshop

1. Earthquake resistance: The roofs of low-rise villas are mostly sloping roofs, so the roof structure is basically a triangular roof truss system composed of cold-formed steel members. After light steel members are sealed with structural plates and gypsum boards, a very strong "plate-rib structure system" is formed, which has stronger earthquake resistance and horizontal load resistance, and is suitable for areas with earthquake intensity above 8 degrees.

2. Wind resistance: I-steel structure buildings are light in weight, high in strength, good in overall stiffness and strong in deformation capacity. The weight of the building is only one-fifth of that of the brick-concrete structure, which can resist the hurricane of 70 meters per second and effectively protect life and property.

3. Durability: The residential structure of light steel structure is all composed of cold-formed thin-walled steel members, and the steel skeleton is made of ultra-anticorrosive high-strength cold-rolled galvanized sheet, which effectively avoids the corrosion of steel plates during construction and use, and prolongs the service life of light steel members. The structural life can reach 100 years.

4. Heat preservation: the main heat preservation material used is glass fiber cotton, which has good heat preservation effect. The insulation board used for the external wall can effectively avoid the "cold bridge" phenomenon of the wall and achieve better insulation effect. The thermal resistance of R 15 thermal insulation cotton with a thickness of about 100mm can be equivalent to that of a brick wall with a thickness of1m.

5. Sound insulation: Sound insulation effect is an important index to evaluate a house. The windows installed in the light steel system are all made of insulating glass, which has good sound insulation effect, and the sound insulation is more than 40 decibels; The sound insulation effect of the wall composed of light steel keel and thermal insulation gypsum board can reach 60 decibels.

6. Health: Dry construction can reduce the environmental pollution caused by wastes, the building steel structure materials can be recycled 100%, and most other supporting materials can be recycled, which is in line with the current environmental awareness; All materials are green building materials, which meet the requirements of ecological environment and are beneficial to health.

7. Comfort: the light steel wall adopts high-efficiency energy-saving system, which has breathing function and can adjust indoor air humidity; The roof has ventilation function, which can form a flowing air chamber above the house to ensure the ventilation and heat dissipation requirements inside the roof.

8, fast: all dry operation construction, not affected by environmental seasons. A building of about 300 square meters needs only five workers for 30 working days to complete the whole process from foundation to decoration.

9. Environmental protection: the material can be recycled 100%, which is truly green and pollution-free.

10, energy-saving: all walls are made of high-efficiency and energy-saving materials, with good thermal insulation and sound insulation effects, which can reach 50% energy-saving standards.

Seven, steel structure engineering quality problems.

(1) Complexity: The complexity of quality problems in the construction of steel structure projects is mainly manifested in many factors that cause quality problems, and the reasons for quality problems are also very complicated. Even the quality problems of the same nature sometimes have different reasons, so the analysis, judgment and treatment of quality problems increase complexity. For example, welding cracks may appear in the weld metal or under the thermal influence of the parent metal, and may appear on the weld surface or inside the weld; The crack direction can be parallel to the weld bead or perpendicular to the weld bead, and the crack can be cold crack or hot crack. There are also reasons for improper selection of welding materials and improper preheating or post-heating of welding.

(II) Severity: The severity of construction quality problems of steel structure engineering projects is as follows: generally, it affects the smooth progress of construction, resulting in delays in construction period and increased costs. Seriously, buildings collapse, causing personal injuries and property losses, resulting in adverse social impacts.

(3) Variability: The quality problems of steel structure construction will continue to develop and change with the external changes and the extension of time, and quality defects will gradually emerge. For example, due to the stress change in the weld of steel members, the weld without cracks is cracked; Due to the action of hydrogen in the weld after welding, delayed cracks will occur. For another example, if the members are overloaded for a long time, the steel members will bend and deform under the arch, resulting in hidden dangers.

(4) Frequent occurrence: As the modern buildings in China are mainly concrete structures, the managers and technicians engaged in building construction are relatively unfamiliar with the fabrication and construction technology of steel structures, while the concrete constructors who are mainly migrant workers do not understand the scientific construction methods of steel structures, resulting in frequent accidents in the construction process.

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