Prestressed cable construction technology and structural determination of cable
 
(Shenzhen as the Instrument Factory, Shenzhen 518133)
 
Summary: prestressed cable structure is a lightweight, high-strength modern structure, but it is also the construction of more complicated, more stringent requirements. This article from the special nature of cable force measurement and cable force of research and development for the start of the construction of such a structure made of a set of recommendations and effective approach for peer reference.
Key words: prestressed cable structure of cable force
 
INTRODUCTION
Prestressed cable structure is a lightweight, high-strength, efficient and modern high-tech content structure, it is point supported glass walls, glass roof and lighting tensioned membrane covered Peng, such as the external light for the construction of the supporting structure of an ideal system. Its shape lightweight, flexible arrangement, the force is reasonable; it Qiaomiaodiqiang the mechanical structure of the United States and the United States and the art of body building organically together, with a strong flavor of the times, won the domestic and international architects and loved by the masses. Accompanied by a point supported glass walls, glass roof and lighting tensioned membrane covered Peng, such as building development, prestressed cable structure also has been rapid development. But the design and construction of such structures is very difficult, especially in the construction of the structure of a form of control is difficult. During the construction of prestressed cable installation can be imposed on prestressed forming. Structure has yet to bear load when it is necessary to ensure that the structure of the geometric shape with the design requirements, but also to claim the value of prestressed also meet design requirements, it is certainly difficult. According to point supported glass curtain wall and lighting in the top structure of the cable engineering practice, the current structure of prestressed cable in the construction of two errors. One is the only attention to the structural geometry of the initial control, barely prestressed cable will be installed, the cable will form factor of the basic adjustment in place, even if completed its mission without the effective control of the cable, to the left of the project quality Hidden dangers. Another misunderstanding is the cable structure and its neglect of the special nature of Rafah, prestressed cable and reinforced concrete structures in the same Tendon view, the reinforced concrete structure and method of Rafah, anchoring methods, working conditions, etc. Conditions corresponding to the various pre-widening losses to the cable structure copy the design, construction, the result was too complex to design and construction staff confused and difficult to operate, prestressed cable structure hindered the promotion of technology. From the basic structure of prestressed cable principle of另辟蹊径from steel-La Suosuo determination of the research and development proceed, combined with cable-tensioned in structure and characteristics of Tension has repeatedly raised gradually in place of prestressed construction technology, Prestressed cable so that the structure of control has become very convenient, easy-to-use, easy to supervision, and more convenient to use units of the management and maintenance, prestressed cable structure is conducive to the promotion of technology.
 
First, prestressed cable structure construction technology analysis and recommendations
Practice shows that, as long as all aspects of construction error in the design and control of all the relevant norms of the requirements, then the basic cable structures Dimension is easy to control. Morphology control of the difficulty lies in how to coordinate the construction process of the inevitable errors and cable-stronghold in the process of pre-tensioning the elastic deformation and mutual influence. Prestressed how the regulation and control, fine-tune the shape of the structure, this fine-tuning the process is very complex, complicated interaction, being out of moving body. Before the first to the construction of various factors on the impact of cable forces are clearly calculated after the hands of both difficult to achieve nor necessary. Construction technology and engineering practice tests showed that the structure of the cable Tension control should be to shape the main control, stress control, supplemented by, because of the shape is not in place under the impact of the construction process, too, and cable force as long as the error in the structure of control Safety within the scope of it. However, this degree of security control in the design within the scope of the permit, construction personnel must be aware of, and design staff closely cooperate with the security in the design of control within the scope of the permit, within the pre-tension cable can neither too high nor too Small. Further analysis showed that the structure of the cable prestressed cable is exposed, visible tangible, the simplest approach is to push and pull the hand, we can feel the tension in the cable size, it is only quantitative difficult. If the development of a measuring instrument can be directly measured in the pre-tension cable, but also very easy to use, then the Rally of the control cable can be solved, pre-widening variety of the so-called "loss" is also not There, the design and construction, it need not consider what "Tension control stress" and "effective prestressed" complex concept, all with cable force detector test to claim the Rally, are honest, effective cable Rally. It should also be noted that the structure of the cable prestressed cable head-anchor of the general set up the regulation of cable-bolts, as shown in Figure 1.

Tightening bolts used to be on the length of cable and prestressed to regulate, not only can regulate the construction stage, the stage can also use regulation. Cable-bolts of the regulation is generally 30 ~ 40 mm, may need to zoom in or out can still appropriate, therefore, do not have control of prestressed for what Anchorage loss, loss of friction, cable-fulcrum elastic deformation losses, different cable - Rafah when the mutual impact of the loss, and so difficult to calculate and difficult to quantitative losses. Tension has repeatedly proposed to use, and gradually the construction process in place. Tension adjustment is completed with cable force detector test to the claim that the actual establishment of an effective cable force. Also should be noted that in the pre-tension cable is generally in control of Rally broken the 15 percent, the biggest under Fenghe Rally, the general also control the cable breaking rally of 35 percent, but the biggest rally of the time is short, so Cable stress relaxation of the problem may also do not have to consider. Practice shows that the use of the cable-guide cable structure of the shape of fine-tuning, after three to four times repeatedly can meet the requirements of the shape and design of prestressed control values. However, taking into account the cable structure itself and mutual influence of the complexity of the structure of the Netherlands after its connection point, thread, clamping points, and so there will be some relaxation, the main structure there will be some relaxation deformation, and the cable structures are generally dependent In the main structure, the main structure to bear the load deformation will also affect the internal forces in a cable adjustment, prestressed cable structure built six months to one year after the cable force should conduct a comprehensive inspection and adjustments to ensure that the structure of the cable Work is necessary. The proposed works in the use of the owners in the course of a certain time every cable force should also make the necessary checks and maintenance, the new structure to take cautious approach is necessary. Only through constant practice and concluded that this new structure of the construction process will gradually mature.
 
Second, the claim determination and the principle of The Development
Research and analysis show that: the determination of the cable-intervention and non-intervention of the two. The so-called intervention-force measurement refers to the cable or cross-End, the cable will be disconnected after a series connection Rally sensors, cable force will be directly read out, this is one of the most accurate and intuitive method of measurement, in Figure 2a, 2b shown.

By the formula we can see that detect the vibration of the cable cycle T cable can be calculated within the Rally H, a relatively simple principle, but the shock will signal into a signal, the computer processing before export value of the claim. This process needs the equipment, the workers have great difficulty, not for high-altitude operations. Another cable side of the boundary conditions on the cable shock cycles have an impact on the cable force measurement also affect the accuracy. Another measure of the claim is based on the principle of horizontal displacement δ cable and the cable Rally H, P and horizontal of the length of cable between the function and its mechanics as shown in Figure 3. Cable H Rally greater lateral force under the P δ smaller displacement.