Knowledge of cable structure curtain wall?

The following is the relevant content about cable structure curtain wall knowledge brought to you by Zhongda Consulting for your reference.

Foreword

The cable-type point-supported glass curtain wall is composed of glass panels, connection systems and cable support systems. It is an emerging technology in the field of glass curtain walls in the mid-to-late 1990s. The point-supported glass curtain wall branch is an artistically beautiful curtain wall structure form. The cable-type glass curtain wall has the characteristics of large glass frameless, no large supporting steel structure, light and transparent, wide field of view, lightweight supporting structure, etc., which enhances the aesthetic feeling of integrating the interior and exterior of the building.

The working principle of cables

The cable-type glass curtain wall is a form of curtain wall in which the glass panels are fixed on the cable trusses with steel claws. It mainly consists of three parts: glass panels, cable trusses and anchoring structures. The cable truss is an important component that spans the curtain wall support span. The cable truss is suspended from the anchoring structure. It consists of high-tensile strength cables and connecting rods arranged according to certain rules. Cable trusses have the task of forming the curtain wall system, taking the loads borne by the curtain wall and transmitting them to the anchoring structure. Anchor structures refer to geotechnical engineering reinforcement and support structures such as anchor rods, anchor cables and soil nails based on anchoring technology. They bear the loads from the cable trusses and reliably transmit them to the foundation. At the same time, the anchor structures are also cable The main body on which the trusses are tensioned, the cable trusses must be strongly tightened to form a curtain wall system. In order to obtain a stable curtain wall system, considerable tensile force must be applied to tighten it. The larger the span, the greater the tensile force required. For this reason, an anchoring structure that can withstand considerable reaction force is required to maintain balance. The glass panels are fixed by steel claws installed on the cable trusses. After caulking, the curtain wall system is finally formed. Glass panels, cable trusses, and anchoring structures form the curtain wall system. The three are interdependent, restrict each other, and influence each other.

(China Economic and Trade Building Cable Curtain Wall)

The cable truss is a flexible tension structure. It has no stiffness before prestressing is applied. Its shape is also uncertain and must be applied Appropriate prestressing gives it a certain shape so that it can become a structure that can withstand external loads. Under given boundary conditions, the distribution and size of the applied prestressed system are related to the initial shape of the structure formed. How to most reasonably determine this initial shape and the corresponding self-balancing prestressed system is to determine the initial equilibrium state of the tension structure. This is a key issue in the design of tensioned structures such as cable trusses.

(Cable structure curtain walls can be seen everywhere in domestic airports)

It can be seen from the above analysis that the prestressing of the cable truss is its life, and the establishment of the prestressing of the cable truss is the cable truss. Measures necessary to obtain the necessary structural stiffness and dimensional stability. The value of prestress should be based on the principle that any steel cable of the cable truss will not relax under various possible load conditions and maintain a certain amount of tension reserve. In actual design, it needs to be combined with load calculation and trial calculation. , adjust to confirm.

In actual projects, the prestressing force of stay cables should be established using the following methods:

① Use reinforced concrete roof panels and other heavy roofs on single cables, and add roof panels on the roof panels. The load is lifted to build the slab joints, and then unloaded to establish prestress;

② Establish prestress by tensioning the stabilizing cables and load-bearing cables in the cable network;

③ In the double-layer cable system Prestress is established by tensioning the stabilizing cables or load-bearing cables, or adjusting the length of the stays between the load-bearing cables and the stabilizing cables;

④ In the transverse stiffening cable system, it is advisable to press down The supports at both ends of the transverse stiffening member force it into place, thereby establishing prestress on the longitudinal cables;

⑤ In a string-tensioned structure, it is advisable to establish prestress by means of tensioning cables, extending braces, etc. .

(Prestress detection)

What is prestress loss

Due to various reasons such as the tensioning process and material characteristics, the tensioning control of the cable The stress value continues to decrease in each process from the beginning of component production to installation and use. In fact, this loss of stress value is caused by the retraction deformation of the cable. It is very important to correctly understand and calculate the prestress loss. If the internal force of the cable is reduced to a certain level, it is likely to cause instability of the entire cable system, causing the entire cable system to be destroyed. Therefore, it is necessary to fully understand the various factors that cause prestress loss during the design and production process, so as to Develop a plan at the early stage of design to avoid potential safety hazards during construction.

Prestress loss is mainly caused by the following factors:

①Prestress loss caused by deformation of the tension end anchorage. When the steel stay cable is anchored, the gaps between the anchor and the component, between the anchor and the pad, between the pad and the component are squeezed, or due to the slippage of the steel bars, steel wires, and steel hinges in the anchor. , causing the tightened steel to loosen and shorten, thereby causing prestress loss;

② Friction at the turning point steering device between the cable truss and the connecting rod causes prestress loss;

( Tension test)

③Since the cables cannot be tensioned at the same time, during the tensioning process, the anchoring structure is tensioned by the latter cable truss, causing prestress losses in the front trusses;

(Cable net tension test)

④ Since the entire cable system is always in a shape-finding state, the cables will relax under long-term tension, thereby reducing the strength of the cable truss. Prestress;

⑤ Due to the deformation of the anchor point, the shortening of the cable truss span causes prestress loss.

(Curtain wall cable tension detector)

What are the classifications of prestressed cable curtain walls?

(1): Self-balancing point curtain wall system

This system is generally used in the renovation of old houses, because the original structure of old houses generally does not consider the additional force generated by prestressing, but The owner also admires the texture of stainless steel cables, so he recommended the self-balancing system. The central column of the self-balancing system is generally a steel pipe. Short stainless steel rigid struts are welded to the steel pipe. The shape is found through stainless steel cables or stainless steel tie rods. After prestressing is applied, a structural system with the same stress as an ordinary truss is formed. The self-balancing system truss is similar to Civil construction beams are articulated.

(2): Prestressed cable truss point curtain wall system

This system is generally used in new buildings, and the impact of prestress on the building has been taken into account in the structural design. The prestressed cable truss system uses short stainless steel rigid struts, stainless steel locks, stainless steel cables or stainless steel tie rods to find its shape. After applying prestress, a stress system is formed. The prestressed cable truss system is articulated with the civil construction beam through embedded parts and locks. connect.

(3): Prestressed single-cable point curtain wall system

With the soaring price of land and real estate, real estate in the city center is very valuable. The above curtain wall supports columns or trusses. It will also occupy a certain area. In order to meet the owner's needs for maximum utilization of space, the prestressed single-cable point curtain wall system came into being. This system is generally used in new buildings. The structural design must fully consider the impact of prestress on the building. Influence. The principle of this force-bearing system is a bit like a tennis racket. The system is formed by applying prestress to the nylon wire, so that it can resist the impact force of tennis balls. In this system, it resists wind load. In the prestressed single-cable point curtain wall system, the vertical cables generally bear the dead weight and wind load, and the other direction cables act as a balance. The prestressed cables are hingedly connected to the civil construction beams through embedded parts and locks.

Construction process

Measurement and setting out → Indoor scaffolding erection → Structural inspection → Embedded parts deviation processing → Cable rod installation → Point barge installation → Adjustment → Outdoor scaffolding installation → Glass installation → Adjustment →Clean and apply glue.

1. Measurement and setting out

1. The construction and installation of cable glass is mainly based on scaffolding, and the rods of cable glass are crisscrossed. If these factors are not considered during construction, It brings many problems, so measurement and setting out is the key to the entire process.

2. First, review based on the ±0.000 of the general contracting unit and the axis (see the measurement and setting out chapter for details). After the review is completed and the requirements are met, the cable rod plane is calibrated based on the relative position of the axis and the cable rod, and the cable rod line is bounced on the ground.

3. Use ink lines to flick the horizontal pull points onto the structural facade, as shown in the figure.

2. Erection of indoor scaffolding

1. Before erecting indoor scaffolding, a technical briefing should be conducted with the erection personnel to clarify the requirements for erection of the scaffolding and its relationship with the cable poles. The vertical pole should give way to the cable pole line bounced on the ground, as shown in the figure.

2. The small crossbar should avoid the pulling points at the elevation and affect the installation of the cable rods.

3. Structural inspection

1. After the positioning line of the support is elasticized, pull the vertical steel wire at the structure and the horizontal wire as the installation control line. Check the elevation dimensions of the structure, record the inspection dimensions, and provide feedback to the supervisor and owner.

2. After measuring and setting out the actual exact position of the curtain wall structure, the positions of all rods should be checked according to the steel structure support layout drawing. If the dimensions of the steel structure deviate and need to be reprocessed, the relevant personnel will be notified before the steel structure can be adjusted until the accuracy required for the curtain wall is achieved.

4. Installation of cable trusses

The construction and design of the cable-type point-connected glass curtain wall are closely related. The construction steps must be considered in advance during the design, especially the predetermined schedule must be specified in advance. The stress tensioning steps must be strictly followed during actual construction. If there is a slight change, it may cause a large change in internal force, which will seriously overload the supporting structure. Therefore, construction personnel must understand the intentions of designers, and designers must make thorough and detailed technical explanations and provide on-site guidance during key construction stages.

The installation process of cable trusses includes pre-tensioning of cable trusses, installation of anchor piers (connecting plates), construction of temporary support structures for construction, placement of cable trusses, prestressed tensioning, and overall position of the cable truss space. Inspection and adjustment, installation of stabilizing cables, installation of docking systems, etc.

1. Pretensioning of cable trusses

Prestressing must be applied to cable trusses during construction. Engineering experience shows that the prestress applied during construction will gradually diminish during subsequent use. Studies have shown that if the steel cables of the cable truss are pre-tensioned several times during construction, the prestress relaxation phenomenon in use can be solved. The specific method is to tension the steel cables of the cable truss by 60% to 80% of the prestress required by the design, and then relax the steel cables naturally for a period of time. If repeated several times, the pretensioning work of the cable truss can be completed.

2. Cable trusses in place

a. With the help of temporary supports, the cable trusses that have been pre-tensioned and prepared to the exact length can be put in place and then adjusted to the design requirements. initial position for preliminary fixation. This is the initial form of the cable truss. b. The installation entry and exit position, flatness, elevation, plane position, and verticality errors of the cable support structure are within the allowable range. Check that the pretension force at each position of each cable must reach the stress distribution value of the initial state required by the design.

(Stranded wire tension detection)

3. Prestressed tensioning

a. After the cable truss is in place, it can be carried out in the order given by the design Prestressed tension. When tensioning the prestress, use a wrench to adjust the tension on the anchor adjuster.

b. During the tensioning process, the position changes of the cable truss must be monitored at any time. If it is found that the final form of the cable truss may be significantly different from the design, appropriate adjustments must be made after obtaining the consent of the designer so that the cable-type point-connected glass curtain wall can reach the predetermined position of the design when completed.

c. In order to distribute the prestress evenly, tensioning needs to be performed at the same time. A better method is to apply all the prestressing force in three stages: 50% of the prestressing force is completed in the first stage, and 25% of the prestressing force is completed in the second and third stages.

4. When installing the stable cable, first place it in place, and then gradually and evenly adjust the tension of the tie rod to tighten the tie rod to meet the installation requirements.

5. The installation of the connecting system must be carried out after the cable truss has been calibrated and passed the supervisory acceptance. When installing, first install according to the connection claw position diagram and position the connection claw. Afterwards, it is necessary to review the positioning dimensions of each control unit and each piece of glass, and correct the positioning of the connecting claws based on the measurement results. The connecting claws connect the glass panel and the cable truss. The installation quality of the connecting claws is directly related to the installation quality of the glass.

5. Glass panel installation

The quality of glass installation is directly related to the appearance of the curtain wall after it is completed. Therefore, glass installation is also the most important step in the construction process of point-connected glass curtain walls. The scaffolding needs to be rechecked for stability and reliability. Before installing the glass, the steel cables should be adjusted again to achieve the grid size required by the design.

(1) Preparation before glass installation

1. Packaging, transportation and storage Before the glass is installed, it must be transported to the glass storage area for storage in preparation for installation. In view of the material characteristics of glass, the following points must be paid attention to during the packaging, transportation and storage of glass:

(1) For certain functional requirements, many curtain wall glasses have undergone special surface treatment. Non-corrosive packaging materials should be used to prevent damage to the panel surface.

(2) There should be eye-catching signs such as "Handle with Care" and "Up" on the packaging box.

(3) The packaging box should be strong enough to ensure that the product will not be damaged during transportation.

(4) The glass installed in the box should ensure that they will not collide with each other.

(5) Use a special vehicle to transport the glass to the installation location for installation. During the transportation process, the glass should be tied tightly with ropes to prevent the glass from falling and being damaged. During transportation, collisions should be avoided, handled with care, and rough loading and unloading strictly prohibited.

(6) It should be stored on a special glass storage rack in the glass storage area, and a dedicated person should be arranged to manage it.

2． Structural size verification

Glass installation is a very precise work. Excessive structural size deviation will cause difficulties in glass installation. Before installing glass, it is necessary to check whether the verticality of the steel structure and the elevation of the claw joints meet the drawing requirements.

3. Clean up construction waste

During cable truss construction, it is inevitable to leave a lot of construction waste in the toe steel channel. Before glass installation, steel brushes and cloths should be used to clean the soil, dust, debris, etc. at the bottom of the steel channel.

(2) Glass installation

You need to pay attention to the following points during the glass installation process:

1. Check the glass specifications and dimensions when unpacking. Glass with chipped edges, cracks, obvious scratches, etc. is not allowed to be installed.

2. The dust on the glass and suction cup must be cleaned to ensure that the suction cup has sufficient suction power. The number of suction cups is determined based on the weight of the glass. It is strictly prohibited to use suction cups with insufficient adsorption force.

3. Install neoprene rubber pads into the bottom steel channel (two for each piece of glass, corresponding to 1/4 of the width of the glass from the edge).

4. When lifting glass, the glass should be sent to the installation position at a constant speed. When the glass is in place, the personnel on the scaffolding should grab the suction cups as soon as possible to control and stabilize the glass to avoid collisions and accidents.

5. After the glass is stabilized, personnel should pay attention to protecting the glass. When there is a groove in the upper part, let the upper part enter the groove first; when there is a groove in the lower part, slowly put the glass into the groove, and then use a foam filling rod to fix the glass to prevent the glass from swinging in the groove and causing accidental breakage.

6. The installation hole of the glass in the middle part has been locked in advance, and fasteners are used to fix the glass on the claw joint during installation.

7. After the glass is installed, the size of the upper and lower, left and right, and front and rear gaps of the glass should be adjusted, the frustum fasteners should be tightened, and then the glass should be fixed.

8. After all adjustments are completed, the flatness of the overall facade should be checked. Only after it is confirmed to be correct can glue be applied.

9. The following work needs to be done before gluing:

(1) Use "xylene" to clean the parts of the glass and steel channel that need to be glued.

(2) Use foam rods to plug the gap between the glass and the steel channel. Pay attention to the straightness and leave a clear height of 6mm for the glue thickness.

(3) Protective tape should be pasted on all parts that need to be glued. Note that the tape is parallel to the glue seam.

10. When gluing glass, first cut the corresponding bevel for the glass glue opening according to the size of the glue seam. The glue should be applied evenly. The order of operations is generally: vertical glue seam, from top to bottom. .

11. After the glue is filled, check whether there are bubbles in the glue joint. If there are any, they should be dealt with in time to eliminate the bubbles.

12. After the surface is modified, quickly remove the adhesive tape stuck on the glass.

13. After the glue has solidified, clean the inside and outside glass and make protective signs.

Quality Control

Due to the secondary adjustment and positioning of the cable, it is necessary to conduct a comprehensive construction quality inspection before gluing the glass, such as: three-dimensional correction of the glass panel, The reliability of bolted connections of various types of anchors, especially those with structures or steel columns participating in tie rod support structures, observe whether they are deformed and make necessary records.

Quality control points:

1. For the embedded parts and anchors that have been measured and corrected, the height difference is <2mm, the plane position difference is <3mm, and the axial difference is <1mm (based on 3 ﹒ 6m altimeter) is appropriate.

2. For the second cable adjustment and positioning, the key points of quality control are:

① Make the glass surface meet the basic requirements of the horizontal, vertical and plane three-dimensional requirements of the curtain wall at the same time , to ensure the correct tension and consistency of the cable;

②The effectiveness of the lock head after locking.

3. Qualification of materials. In glass curtain walls, as structural materials, it is particularly necessary to strengthen inspections.

Re-examination of strength should be carried out when necessary. These structural materials include steel supporting structural parts, such as steel columns, anchors, bolts, stainless steel cables, connectors, etc.

When inspecting and re-inspecting, conduct visual inspection one by one at the same time; when connecting threads, special attention must be paid to the matching tolerance of the threads, which is often easily overlooked.

4. When installing the glass and the joint, sealant must be injected and the threads must be tightened to prevent rainwater from leaking from the holes. And check the tightness of the barge joints.

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