ATTEN: Manager Liu
ADD: Longhua Development Zone, Jing County, Hengshui City, Hebei Province
Above all, I mentioned zero state. If you pay attention to it, you will find that later I mentioned "analysing zero state". This is because I think two zero states may be mentioned in the process of cable structure analysis, design and construction. And these two zero states are not a concept at all. So, I want to discuss this problem with you in depth. As mentioned above, before knot shape finding analysis, an initial geometric model for shape finding analysis will be established, which may be called analytical zero state. This zero-state model is only a simple topological relationship. On the basis of it, the initial conditions of the cable are given. The equilibrium prestressing state can be obtained by using the non-linear finite element method. This zero state is the starting state of software analysis, it has no practical engineering significance, but I use it to get a means of equilibrium state and then there is a zero state in the construction process. Here we may call it construction zero state. After the design is completed, the construction unit simply connects the crepe members according to the geometric and topological relationship provided by the design institute. At this time, although most of the crepe members are connected, the prestress of the cables is not fully realized, because the tension has not yet begun.
When the tension is completed, the prestress of the cable reaches the design value, and the prestress state is obtained. It can be seen that the following pass (1) analysis zero state calculation prestressing state (2) construction zero state tension prestressing state analysis zero state and construction zero state are ultimately obtained prestressing state, but they are two completely different concepts. The analysis of zero state has been discussed in the previous blog article, but not in detail. Here we talk about how the zero state of construction came into being. After the design institute has completed its design, the information given to the construction unit includes: the topological relationship, the specific value of prestressing force. These data are usually the result of the equilibrium state of prestressing force. That is to say, cable length and prestress are the data of tension state. According to these data, the construction unit will calculate the length of the cable in loose ground state, that is, the length of the cutting material. Then, the length of the cut material is transported to the construction site for construction. According to the topological relationship provided by the design institute, it is very difficult to calculate the zero state of construction by software, unless it is a relatively simple knot system.
Because it is very likely that the stayed cables are in a state of extreme relaxation before tensioning, just like a rope piled on the ground, which can not be calculated by finite element method. However, there is a theory of four-mechanism displacement theory, which is said to be able to accurately calculate the zero state of the construction of truss knots. I remember that Qian Danjun, a teacher of Ranji University, used this theory to calculate the construction tension process of Century Lotus Stadium in Foshan. Interested friends can find money teachers to discuss. Therefore, the analysis of zero state is only a treatment method, which has no practical engineering significance; while the construction zero state is the structural state before the construction tension, which has practical engineering significance.