Muneeb Badar

Dear Mr. Waqas, Your study about Non Linear Analysis is quite impressive. I just want to add some more details. There are three types of design. 1- Service Level Earthquake (SLE) 2- Design Basis Earthquake (DBE) 3- Maximum Considered Earthquake (MCE) SLE is at service level. Which means that in EQ there should be no problem for non structural members. DBE: In code based design, we use DBE level earthquake. This earthquake is frwquent earthquake with return period of 475 years( I think). During this code uses actualy 100% forces and reduce these forces by reduction factor R. Means we design our structures for reduced forces as explained before. Actually in this case code allows the structure to yield at certain locations for certainm members. But code do not specify these locations and members as R is the overall division factor. So during an earthquake it is not necessary that the members will yield which we assumed to be yield. For example if beam at any location yielded then it will not transfer forces to the column. But we are not sure that column will yield first or beam will yield first. Code tried to take this by incorporating the stiffness modifiers but still it is not 100% reliable. So thats why nobody can gurrantee the building to perform 100% in earthquake when designed by Code. MCE: This is the third and extreme level of earthquake.Return period is 2475 (I think). This can only be incorporated by using Non Linear Time History Analysis. In this we can check the reinforcement designed on DBE level for capicity check by considering the actual yielding and energy disspation. We can set a limit for structure for example Life Safety, Immediate occupancy or collapse prevention. We allow the memebrs to yield upto acertain level and beyond that level we ll not allow the structure to yield. We can actually see that which member is yielding and the after yeidling what is the force and design for that force. The difference is that in code based design we aare not sure how much energy is dissipated in the structure. Code just provide 2 or 3 types or R factors depending upon the building type. So ist ios not 100 % accurate. Secondly code reduces the forces for all modes of structure but actually it can not happen. We can not reduce all modes because we can only reduce the modes which are yielding. So thats why 21.1.1 says that integrity should be maintained. But code do not give any gide line how to maintain that integrity. By using that R factor??? how can we do that????? So code just wrote that thing. Actually that integrity can only be assured by using the Non Linear Time Histoiry Analysis and stops the stucture to deform beyond which we do not require to deform. Sorry if I write something out of topic. Thanks Muneeb

Dear Hasan, As Mr. Muhammad Imran described, peak ground acceleration is the effect which anything observes during earthquake. While the spectral acceleration is the effect of ground movement on a single degree of freedom structure. Spectral acceleration is used to prepare the Response Spectrum Curve as this curve is between spectral acceleration and time period. While peak ground acceleration is used to develope ground motion curve which is between time and peak ground acceleration. Response spectrum curve can also be used to develope ground motion. Thanks