China is a big country in the production and use of building curtain walls. In 2008, the total output value of the national curtain wall reached more than 20 billion yuan, and the total curtain wall area was about 80 million square meters, and it is increasing year by year. There are also thousands of curtain wall manufacturers in China, and there are more than 400 in Jiangsu alone. The production capacity of production enterprises is uneven, which leads to many hidden dangers in the quality of curtain wall engineering. The author participated in the selection of high-quality curtain wall projects for many years. According to the requirements of the selection rules, the problems found in the selection are summarized as follows.
First, there are problems
(1) Completion drawings
1. There are a few projects that do not provide a complete as-built drawing, mainly for some companies that entered the curtain wall industry for the first time, and their technical capabilities are poor.
2. The design description of some projects is too simple. The main material brands, materials and performance indicators used in the project are not explained. The detailed design description should include at least the following:
(1) The type of curtain wall included in the project;
(2) Design basis and standards;
(3) The main physical performance parameters of the curtain wall;
(4) Technical indicators of brand, specification, material and performance of main materials;
(5) Fire protection and lightning protection design requirements and measures;
(6) Processing, production, installation requirements, etc.
The general description of the as-built drawings is the general outline of construction acceptance, and many design management personnel of the project did not pay much attention to this.
3. There are many references to non-current standards in the general description, especially product standards, performance testing standards, and material standards. Many designers have a lack of attention to standard updates.
4. The physical performance of the curtain wall is not determined by calculation. In some projects, the concept of physical property grading of the curtain wall is vague. The wind pressure deformation performance grade, watertight performance grade, airtight performance grade and in-plane deformation performance grade of the curtain wall are not determined by calculation according to the provisions of Article 4.2 of JGJ102-2003. Some rely on experience, some apply in a fixed format, so that the physical performance level in the general description does not match the calculation, and some projects have not rated the physical properties of the curtain wall.
5. The design value of the rear anchor is not indicated in the design specification. Most of the designs for post-embedded parts are not marked and described in the design specification and the node diagram for the design pull-off values ​​of the post-chemical anchors and stone anchors, which may result in the inaccurate determination of chemical anchors during construction inspection. Design value.
6. Fire protection and lightning protection nodes are incomplete. Some projects do not have a separate node map for fire and lightning protection. They are simply labeled in the general large sample; the fire protection part pays attention to the separation of the horizontal floor and ignores the separation between the curtain wall and the wall; the metal and stone curtain wall or most of the window hole The engineering drawings do not have a fire separation node map.
7. Node graphs and component graphs are often missed. Some engineering node diagrams are less difficult to meet the construction requirements; some are indicated in the calculation book with double-span beam structure and are not reflected in the drawings; there is a bolt for the connection between the engineering column and the main structure, and the drawing has only 2 bolts. Drawings and design calculations are inconsistent; unit-type curtain walls generally lack unit cell hoisting design. Some engineering drawings missed the sectional view of the aluminum profile, the metal plate processing drawing, and the glass processing component drawing of the spot glass curtain wall.
8. The rib-supported point supports the glass curtain wall, and the glass rib does not use tempered laminated glass. The main channel access points support the glass curtain wall, and the glass ribs supported by the main channel are up to 8 meters without the use of tempered laminated glass. If the glass ribs are broken, the entire curtain wall will collapse.
9. The node design does not match the specification. In order to pay attention to the practical requirements of large span and high transparency, the individual point supports the glass curtain wall. There is no transverse tie rod between the steel pipe columns (bending and bending members) of more than ten meters long; some glass curtain wall closed profiles and upper and lower columns are connected to the length of the core column. It has not reached 250mm; both ends of the steel or steel pipe column are welded and cannot adapt to the displacement of the main structure.
10. Lack of dimensional dimensions related to design calculations. The completion drawings of some projects are the same as the schematic diagrams, and some important dimensions that affect the safety of the curtain wall structure are not marked or marked. In the absence of the blank injection width and thickness of the hidden frame glass curtain wall, the weld length of the adapter is missing.
11. The as-built drawings do not match the actual situation on site. There are more or less design or construction changes in the curtain wall project. Some projects do not reflect changes on the as-built drawings. If some projects use post-embedded chemical bolts, they are still embedded in the as-built drawings; The open back stone curtain wall construction adopts galvanized slab as waterproof structure, but the construction site uses aluminum-plastic composite panel as waterproof member; the open fan is connected with hook-type connection on the as-built drawing, but the site is hinged connection; there is an engineering site The added curtain wall is not reflected on the as-built drawings; some directly use the plan map or construction drawing to replace the as-built drawings, which shows to some extent the confusion of design management in these production enterprises.
12. The as-built drawings are confusing and the signing procedures are incomplete. Some engineering completion drawings have no drawing catalogues or catalogue contents that are too vague, and cannot accurately express information such as fireproof large samples, hidden frame curtain wall sashes, etc.; some of the as-built drawings are not in accordance with the facade → plane → section → large sample map → node map → The order of the component drawings is arranged in a sequence, so that the complete set of as-built drawings is very disorderly; some of the completed drawings of the project are not covered with the special seals of the construction unit or the signatures of the construction unit and the supervision unit, so that the as-built drawings cannot form valid legal documents.
(2) Design calculation problems
1. Some projects do not provide calculations. Some non-professional curtain wall manufacturers or initial reporting companies sometimes do not provide design calculations.
2. Missing part of the type curtain wall. Some projects do not provide design calculations for all curtain wall types of the project, only the main curtain wall types are calculated rather than comprehensive design calculations, such as the all-glass curtain wall of the hall, the connecting part of the cable-type curtain wall, the steel structure, the lighting roof, and the awning. Most of the missing.
Part of the wind load shape factor, while the negative wind pressure at the corner and the mouth is much larger than the large wind pressure. The performance requirements for the curtain wall structural material are much higher than the large surface requirements, and the corners are covered by the large design wind pressure. The design wind pressure of the mouth and the mouth will lead to the unsafe structure of the curtain wall; some projects do not distinguish the wind load shape factor of the large face and the corner of the corner, and all take the value of the maximum wind load shape factor of the corner of the wall. This is neither economical nor science.
4. The bending member is not calculated for stability. Due to the practical requirements of large-grid, large-span and high-through-hole, the supporting pillars are generally made of steel or steel pipe bending members, but most of the projects are not checked for stability according to the provisions of JGJ1m~2oo3.
5. Connector calculations are often missing. Due to the different calculation software used in some projects, the designer did not conduct a detailed inspection of the design calculation book, but only calculated the large items such as plate strength, beam column strength and deflection, and ignored other parts of the calculation, such as the lack of pre-embedded connections. Board calculation, connection bolt calculation, joint weld calculation, post chemical bolt calculation, connection angle calculation, etc. Due to the different structure and connection method of the curtain wall of each project, the calculation of the load and action of the curtain wall should be analyzed. Pay attention to the calculation details of each component and node. If it is calculated by the calculation software, it will cause some connectors to be missing or less. Count.
6. Some engineering curtain walls do not meet the static beam conditions and are still calculated according to the static beam.
7. Energy-saving design and thermal calculation projects. Since energy-saving design has been required since 2008, more than half of the inspection projects have no thermal calculations, and there is no common energy-saving design software that will not calculate the problem.
(3) Problems with materials and quality assurance information
1. Material and design requirements do not match. Some engineering design columns require aluminum profiles to be 6063T6 or 6063AT5, and purchases are 6063T5. The material properties vary greatly; there is an engineering steel keel standard that requires a wall thickness of 3.5mm and the actual feed is 2.5mm. The main material performance is lower than the design index, there will be serious safety hazards.
2. Two or more glues were used in the same project. There are two or more types of structural rubber or weathering resistant rubber certificates and quality guarantees for individual projects. Some engineering structural adhesives use one brand, while weather resistant rubber uses another brand. The use of two or more types of glue on the construction site can cause management confusion, and it is difficult to distinguish the responsibility when quality problems occur, and it is impossible to conduct a uniform compatibility test.
3. Physical performance testing of all types of curtain walls has not been carried out: Most of the curtain walls are mainly composed of composite curtain walls. For example, in the 32 projects examined by myself in 2008, there are 5 glass curtain walls (including a little branch and full glass), accounting for about 5 16%; 2 stone curtain walls, accounting for 6%; 14 glass curtain wall and stone curtain wall combination, accounting for 44%; 6 glass curtain wall and aluminum curtain wall combination, accounting for about 19%; glass curtain wall, aluminum curtain wall, stone 5 of the curtain wall combination, accounting for about 16%; combined curtain wall accounted for 80%. However, some projects only provide a physical performance inspection report for the curtain wall, which does not fully reflect the performance of other types of curtain walls in the project. There are five aluminum alloy glass curtain walls in the curtain wall project without "three-sex" test report, and there are 10 large-area stone materials. There is no “three-sex†test report on the curtain wall project. Most of the pollution detection of stone is not done; many projects do not test the compatibility of weather-resistant adhesives; some projects have no report on the compatibility test of structural adhesives. There are false reports.
4. The physical performance test report of the curtain wall does not match the project site. In the report of the physical performance test of the curtain wall, some reports do not reflect the actual situation on the spot. The test was carried out according to the span of the most unfavorable position selected by the design calculation, the plate size, the wind load design value and the profile type; the test of the open fan was not included in the curtain wall test with the open fan.
5, the detection of the rear anchor is not standardized. Due to design changes, old tamping and pre-embedded parts, most curtain wall projects have problems with buried tongues. Chemical bolts must be tested for pull-out resistance at the construction site. Some projects use a variety of chemical bolts to do only one type of pull-out test report; some projects use a large number of chemical bolts, but only a set of three pieces of chemical bolts test, far less than the number of inspections required by JGJ145; some projects The pull-out detection value of chemical bolts does not reach twice the design value, which leads to safety hazards in the project.
6. There is a large deviation in the re-inspection of major materials. The main curtain wall materials that need to be re-examined are aluminum profiles, steel plates, aluminum plates, stone materials, and main force bolts. The following major problems were found during the inspection:
(1) Substitute the material re-inspection report with the material certificate provided by the supplier that does not indicate the project name and is inconsistent with the construction time;
(2) Re-inspection report for steel or aluminum profiles for main components;
(3) Some stone curtain walls do not provide a report on the bending strength of stone;
(4) The weld joint between the anchor rib and the flat plate of the embedded part of the flat plate is not tested for mechanical properties;
(5) Imported materials cannot provide customs inspection reports.
7. The glue injection record does not meet the specifications. The quality of glue injection of structural adhesives is closely related to the safety of curtain walls. Some projects have the following shortcomings in injection molding:
(1) In the engineering of the existing structural rubber fork with weathering adhesive, the compatibility test of the structural adhesive and the weathering adhesive is not carried out before the formal injection;
(2) The width or thickness of the structural adhesive injection is smaller than the drawing and calculation book size;
(3) The compatibility test and the adhesion performance test report require primer to be applied during injection, and the original record of primer should not be provided during inspection;
(4) The glass plate was not subjected to the physical peeling test before installation;
(5) The injection molding and curing curing process were not effectively controlled. The temperature and humidity in the plate injection recording were not within the scope of the specification. The complete curing time of the one-component and two-component structural adhesives did not reach 14 days and 21 days, respectively. Installed on the upper wall, causing deformation and reduced adhesion.
8. The epoxy dry adhesive does not use epoxy adhesive properly. "Technical Specifications for Metal and Stone Curtain Walls" (JGJ133-2001) stipulates that the bonding between stone curtain wall hangings and stone should be bonded by two-component epoxy adhesive, but a considerable part of the project still uses marble adhesive. The marble adhesive is not deoiled, which is easy to cause stone pollution. Under low temperature conditions, the bonding strength is weaker than that of epoxy adhesive dry glue, and the marble adhesive is afraid of humidity, high temperature resistance, easy weathering and insufficient shearing force. The displacement generated under the influence of temperature difference and vibration is large, and the stone is easy to crack.
9. The point support curtain wall using the tension cable system did not see the cable tension record. The tension cable rod is the bearing component of the point support curtain wall, and the cable rod tensioning record records the wind pressure resistance and safe use of the curtain wall.
10. There is no water spray test record or water spray test record parameters are incomplete. Most of the projects did not have the water spray test record or the water spray test record parameters were incomplete; some did not carry out the water spray test according to the water spray device specified in the specification.
11. There is no record of lightning protection. The steel structure project does not provide weld inspection report, and some engineering site concealed engineering records are incomplete, and the installation quality record is incomplete.
(4) Engineering quality
1. Appearance problems. There are mainly stone curtain wall glue joints caused by improper use of rubber varieties, the color of the stone is caused by improper selection, red rust, mildew; a few engineering glass curtain wall panels are not seamed during installation, the glue seam is misplaced after the glue; metal curtain wall Drums or depressions appear on the wall.
2. The problem of the glass window opening window hardware falling off. The problem of falling off the hardware of the glass curtain wall opening window is more common. Some of them do not have the positioning wind bracing, so that the opening angle is too large, some sliding brackets are rusted, and some handles loose or even fall off.
3. Leakage. Some projects have leaks due to improper handling at the top, and some of the exposed frame walls have no drainage design or designed drainage that does not leak as designed.
4. The glue cracks and foams. Some engineering silicone weatherproof sealants have hardening cracks and blistering in many places, which affects the normal use function of the sealant. The main reason for cracking and foaming of sealant is as follows:
(1) Producing inferior sealant produced from low-quality raw materials;
(2) The use of expired sealant products;
(3) The proportion of the thickness and width of the sealant is seriously wrong. If it is too thick or too thin, it will cause cracking or foaming of the glue joint;
(4) The injection molding operation is discontinuous, and repeated injection of glue may cause uneven surface and foaming;
(5) If the temperature difference of the construction environment is too large, it will easily lead to cracking of the sealant joint.
5. A piece of glass spans two fire zones. In some projects, there are two fire-proof partitions of the same curtain wall glass across the building. There is a project that not only has one glass spanning two fire compartments, but also fire-proof galvanized iron sheet directly on the glass, there is no gap between them, which is obviously contrary to JGJ102- 2003 specification requirements; when the glass curtain wall is fireproofed with fireproof glass, it is not placed at the glue joint of the glass curtain wall glass and sealed with fireproof sealant.
6. The tempered glass bursts. When some curtain walls are put into use, the tempered glass bursts. There are several reasons for the bursting of tempered glass:
(1) The glass is not edging or the quality of the edging is not high, resulting in glass edge cracking caused by stress concentration at the edge of the glass;
(2) The temperature difference between the inside and outside of the glass or the center and the edge is large, and glass cracking may also occur;
(3) The tempered glass is broken by the excessive stress caused by the secondary detonation treatment;
(4) The internal nickel sulfide in the tempered glass increases in volume when the temperature changes significantly, resulting in local stress concentration, resulting in self-explosion of the tempered glass;
(5) The installation method is incorrect, causing the glass to cause crushing stress and causing cracking of the glass.
7. Turn on the aging of the fan seal strip. In some projects, the fan seal strips are not overlapped or the strips are aging and hardened, and the strips are shortened to make the gaps too large to affect the airtight performance. When the sealing strip loses its function, it will cause water to seep in rainy days, and howling in the windy weather.
8. The bottom end of the hidden frame or semi-hidden frame curtain wall is not provided with a bracket. Some engineering hidden frame or semi-hidden frame curtain wall glass has no toe at the lower end. Silicone structural sealants have low ability to withstand permanent loads and have significant deformation, so metal supports should be provided for long-term stress. The JGJ102-2003 specification stipulates that the hidden frame or semi-hidden frame curtain wall glass shall be provided with two stainless steel or aluminum alloy retaining strips with a thickness of not less than 2 mm and a length of not less than 100 mm at the bottom end of the glass. Some of the works are not designed and constructed according to the specifications.
9. The stone plate is loose or cracked. Most of the damage of the stone curtain wall is cracked along the bottom of the groove at the slot. The centerline of the slot does not coincide with the center line of the thickness of the slot. The inward or outward offset of the slot reduces the strength of the stone, under the influence of temperature difference or vibration. Causes stone damage.
10. The expansion joint is not handled properly. The expansion joints of several engineering columns, the gap between the beam and the column are not glued and the gap is too large. Some rubbers are glued but the glue is incompatible with the rubber pad to cause discoloration.
11. The beam is turned over. Glass curtain wall engineering beam rollover phenomenon is more common, the main reason is the pursuit of transparency, the glass plate is getting bigger and bigger, now all are hollow glass, the weight is concentrated on the outside of the beam, the beam and the column are generally connected with two bolts according to the conventional, resulting in The side of the beam is turned over.
Second, preventive measures
The existence of the above problems is not conducive to the healthy development of the curtain wall, and even constitutes a safety hazard. In order to prevent such problems from occurring, the following recommendations are made:
1. Enhance quality awareness and improve quality management. The curtain wall project is a very demanding and meticulous work. The curtain wall project involves safety and the quality of the century is the first. It is necessary to establish a complete enterprise curtain wall engineering quality assurance system, including organizational personnel or departmental responsibilities, implementation of the whole process of the project and inspection rules, quality work rewards and punishments regulations, etc., so that the creation of quality engineering activities becomes the conscious action of all employees of the enterprise. Improve the quality management level of the company in an all-round way.
2. Emphasis on design review and selection of designers. The curtain wall engineering design is the leader. Without good design, there will be no good projects. Good design works need to be guaranteed by the following conditions:
(1) Excellent engineering must have excellent designers as the main design;
(2) Designers must be familiar with standards and specifications, design documents must meet the requirements of industry norms, and there must be no obvious deviation from the norms;
(3) The review procedures of the design documents meet the requirements, and the proofreading and auditing personnel cannot take the form. The design documents should be thoroughly inspected and reviewed and the review opinions issued. After being modified, the design documents can be signed. The approving personnel should also be familiar with the standard specifications, check the main requirements of the engineering design, and do a good job at all levels.
3. Implement standard specifications and accurately calculate the first. Good engineering must be a safety project. Safety comes from the accurate calculation of the design stage and the correct implementation of the design documents during the construction phase. To accurately calculate, you need to pay attention to the following issues:
(1) The curtain wall designer should carefully analyze the force state of the curtain wall components and correctly and reasonably select the calculation parameters;
(2) Strictly adopt the current national and industrial standards for calculation. Since 2008, the standards, inspection standards and materials and other related standards and specifications for building curtain wall products have been revised and updated. The design documents should be updated according to the current standards. The mandatory provisions in the specification must be executed without compromise;
(3) Correctly select the calculation software, carefully review the calculation process, and do not lack items or items.
4. Emphasis on data collection and implementation of special personnel. The engineering data is a true portrayal of the project. Through the engineering materials, you can understand the ins and outs of the project and distinguish the pros and cons of the project. The problems or accidents can be traced through the engineering data. Many companies often do not pay attention to the collection and collation of materials, so that Chuangyou's work is at a loss. The data of excellent engineering also represents the image of the company. The more data is accumulated, the more it can prove the performance and ability of the company, which will add to the development of the company. To do a good job in the data compilation of the curtain wall project, we must start from the following aspects:
(1) It is necessary to make special regulations and strictly enforce the requirements for data collation and filing of curtain wall projects;
(2) It is necessary to arrange full-time information staff who have received special training and have the information of the staff member to be responsible for the organization and archiving of the materials;
(3) The quality inspection department and the person in charge of the project shall regularly check the arrangement of the materials during the implementation of the project and find out the problems in time;
(4) The project management personnel should have a thorough understanding of the requirements related to the curtain wall project and retain various materials according to relevant requirements.
5. Strengthen construction management to ensure project quality. Due to the complex construction environment of the building curtain wall project, the personnel allocation, construction technology and construction operation are different. In order to grasp the on-site construction quality management work, it is recommended to focus on the following aspects:
(1) Scientific planning, carefully set up the construction project department
Before the construction of Chuangyou Project, scientific planning should be carried out according to the scale, type, cycle and technical content of the project, the construction organization design should be prepared, the personnel of the project department and the construction and installation team should be determined, and the obligations and mutual cooperation obligations should be clearly defined. Organize construction.
(2) Control procurement and control material quality
The quality of raw and auxiliary materials is directly related to the quality of the overall construction project. According to the design and contract requirements, the list of raw and auxiliary materials should be listed. For the special materials and materials that have important requirements on structural safety, strict procurement control procedures should be established, the source of materials should be controlled, and the goods should be purchased in strict accordance with the engineering contract requirements and material inspection specifications. And inspection work. In terms of material control, the construction project department should communicate with the designers frequently to avoid the occurrence of 6063T6 profiles for a certain engineering design and 6063T5 profiles for engineering procurement.
(3) Emphasis on prior control and improvement of pre-control measures
To ensure the quality of on-site installation, we must do "pre-control, prevention-based", and do three basics, that is, the engineering department will pay the project to the project department, and the project department will pay the end of the installation team leader, and the team leader will pay the installation workers. During the installation process, the project manager and the project quality inspector shall carry out the control and inspection according to the requirements of the corresponding technical regulations, and make a good record of the process control. During the installation process, the inspection of the “three customsâ€, ie the first inspection and the concealed project inspection, shall be strictly implemented. Submitted with the finished product. The first part of the installation process must be inspected by the operator's self-inspection and quality inspector. The inspection can only be carried out in batches. The quality inspector also needs to conduct random inspections on each process and find out the problems in time to correct them.
(4) Strengthen testing and supervision to ensure intrinsic quality
Strengthening the engineering inspection and supervision mechanism can ensure the inherent quality of the excellence project. Key projects in the project should be controlled, such as: anti-extraction test of curtain wall engineering, structural adhesive compatibility test, air tightness, water tightness, wind pressure resistance, plane displacement, thermal performance and other standard specifications. It is necessary to implement key supervision, carry out production after passing the test before the construction, and contact the design department in time to correct and prevent the problems found in the test to ensure that it meets the engineering design requirements. Secondly, the Enterprise Engineering Department should follow up and supervise the responsible personnel of the Chuangyou Project Arrangement to correct the possible misconduct of the construction project department and ensure the construction quality.
Third, the conclusion
The curtain wall is a symbol of urban modernization. Under the pleated walls, there is no dirt inside. People must feel the majestic beauty of the curtain wall, and the fork must feel safe and ancestors. We hope that the design, production and production level of curtain wall enterprises can reach domestic and international level, and it is expected that all curtain wall projects will become high-quality projects.
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