Cable stayed Bridge Static Analysis
Cable stayed Bridge Static Analysis
(OP)
I would like to do static analysis of long span cable stayed Bridges. I heard StaadPro or Sap2000 software is good for Bridge Analysis. Could you please help me to find a way of downloading any of those softwares for free.
Thanks.
Thanks.






RE: Cable stayed Bridge Static Analysis
http://www.csiberkeley.com/
RE: Cable stayed Bridge Static Analysis
RE: Cable stayed Bridge Static Analysis
Zambo
RE: Cable stayed Bridge Static Analysis
The normal liner/elastic analysis assumes the equilibrium condition at the "unloaded" geometry whereas the true equilibrium should be in the deflected shape of the structure.
RE: Cable stayed Bridge Static Analysis
this wway any simple FE program will do the problem, and being linear, any program should give reasonable results, depending on your model !
good luck
RE: Cable stayed Bridge Static Analysis
Doesn't this over simplify the analysis. Due to the sag of the cables they are more akin to springs than axial rods.
Zambo
RE: Cable stayed Bridge Static Analysis
To refine a linear-elastic solution there are at least two ways to model the cable. My earlier remark of solving the equilrium at the "loaded" shape is a common iterative method. One can actually sum the deflections (linear portions of dx, dy & dz) with the original geometry to obtain a new shape for the next analysis which yields the a new set of revised deflection. By doing it iteratively, always with the new deflection added to the original "unloaded" geometry a solution will converge, indicating an equilirium position has been reached.
There is nothing wrong with the traditional linear-elastic theory. The extra accuracy to go deeper is just seldom required for the normal engineering applications
The other method is to use the stability functions to modify the stiffness. If a member is subjected to an increasing axial load it can eventually buckle or have zero bending siffness. The stability function automatically reduce the member's bending stiffness to zero when the Euler buckling load is approached.
The same stability functions are equally applicable to member subjected to tension, as in the case of a cable where the tension increases the bending stiffness. The stability functions are introduced to the stiffness terms of a structural member as indiviual multipliers.
(There is a third method which takes the deflection into account by "adding" a correction term to the element's stiffness matrix. It produces comparable results)
Either method will yield the similar result. With the stability function one performs the analysis at least twice. The first one is to obtain the tension/compression for modifying the stiffness in the members for the next analysis. In general 3 to 4 iterations should yield a good convergence.
I admit that there is some over-simplification but the methods are based on the fundamental laws of physics - equilibrium and the elastic theory.
I have investigated large deflection theory (nonlinear geometry in elastic material range) in my undergraduate project back in 1976. I computerised three different methods (as described above) and conducted tests on both tension and compression members in the laboratory to verify my results. For tension member I hung the load on a "V" shape structure comprised of just spring elements. On loading the "V" could drop several times more than a practical structure would be able to tolerate. The theoretical predictions and laboratory results were in excellent agreement with each other.
As far as I am aware the equilibrium that can be significantly influenced by its deflected shape is a rubber tyre (ot tire). Most civil and building structures cannot be made too flexible and that is equally true for a cable stayed bridge.
RE: Cable stayed Bridge Static Analysis
thank you for your informative post. I am currently working for a contractor on a medium (some may say short!) span cable stay bridge, main span 185m. We are responsible for the construction engineering which entails carrying out the construction stage analysis of the bridge. Currently we are having an alignment problem on the bridge which we are resolving by the use of shims (the bridge is segmental) and additional stay forces(an increase in the number of strands in the stays is required). The structure is sensitive during construction of the cantilevers to both weight of permanent & temporary works and to temperature. It is my opinion that the designer should study the construction stages as well as the in service design analysis. For this I would still recommend a specialist software package, several of which have been mentioned earlier in the thread.
Zambo
Zambo