الفهرس Only 14 pages are availabe for public view
 |  | from | 241 |  |  |
| | | from | 241 | | |
Abstract
Conventional methods for the everyday practice of analysis have been believed to work well for many years. However practitioners have occasionally expressed doubt about those methods as well as the desire to have more accurate methods, should they be necessary.
To evaluate traditional methods used by Egyptian engineers, this research compares traditional methods in both static and dynamic analyses with the exact one that deals with the whole structure and real conditions that the structure subject to.
Two main systems were studied to measure their credibility to the practice: static and dynamic analyses for the whole structure as three dimensional analysis.
For static analysis evaluation, folded plates and cylindrical shells are analyzed to make a fruitful comparison between spatial and usual used traditional methods. Two models solved in textbooks were taken in consideration :
These models are folded plates and cylindrical shells solved accurately by spatial method with the same conditions of the solved traditional method model.
For folded plates as a first spatial structure, two main types where considered: triangular folded plates and trapezoidal folded plates to allow a detailed study and comparison.
Conventional method used in analysis of folded plate structures is based on assumptions stating that the connections between plates in transverse direction are assumed rigidly supported, but actually these connections suffer space displacements and deformations, which emphasizes the unreality of such assumption. Consequently, the actual induced internal forces will be different from those calculated by the conventional method, while a comprehensive 3-dimensional analysis using Finite element technique has been carried out for the structure as a whole to clarify the difference of the obtained straining actions compared with the conventional method. The comparison showed that for a certain folded plate configuration and number of vents, there is a great difference in the straining actions in both magnitude and direction depending on the location of the transverse cross section in the longitudinal direction. Furthermore, the forces and stresses in plates in the longitudinal direction showed a significant decrease compared with those obtained from conventional method due to the inclusion of the interaction effect of the different elements of the whole structure.
The following parameters are also taken into account to show the convergence or divergence between the two methods:
-The number of vents (one vent and four vents).
-The angle of inclination between plates.
The comprehensive study in this research clarified the great drawbacks in conventional used method, emphasizing the necessity for using the 3-diminsional analysis for the whole structure to get realistic results.
• Transverse bending moments not only have changed in magnitude but also in direction and sign by about 40% from traditional method.
• For stresses values of the traditional method, they can be reduced by about 40% to attain accurate results.
For cylindrical shells, as the second spatial selected structure, two main types where considered: cylindrical shell with vertical plates and cylindrical shell without vertical plates.
The following parameters are also taken into account to show the convergence or divergence between the two methods:
-The number of vents (one vent and four vents).
-The central angle of the arch of shell.