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TB-Lecture04-Design-Criteria

# TB-Lecture04-Design-Criteria - EGN-5439 Design of Tall...

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EGN EGN - 5439 Design of Tall Buildings 5439 Design of Tall Buildings Lecture 04 Design Criteria © L. Prieto-Portar, 2008

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Outline of the Design Criteria Outline of the Design Criteria The Basic Design Criteria Limit States Design Philosophy The Speed of Erection Loading Sequential Loading Strength and Stability Drift Limitations Stiffness Human Comfort Fire Creep, Shrinkage, and Temperature Foundation Settlement and Soil-Structure Interaction
(a) The building must not break in shear and (b) must not deflect excessively in shear. 1. The Basic Design Criteria for Tall Buildings. The pressure p = f (H 2 ); in other words, the pressure on a 100-story building is 16x the pressure on a 25-story building.

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The bending resistance of a building must provide, (a) that the building must not overturn, (b) the columns must not fail in tension or compression, and (c) the deflection due to bending (drift index) must not be excessive.
2. Limit States Design Philosophy. The aim of this approach is to ensure that all structures and their constituent components are designed to resist with reasonable safety the worst loads and deformations that are liable to occur during construction and service, and to have adequate durability during their lifetime. The entire structure, or any part of it, is considered as having “failed” when it reaches any one of various “limit states.” Two types of limit states must be considered: The ultimate limit states , corresponding to the loads to cause failure, endangering lives and causing serious financial losses, the probability of failure must be low. The serviceability limit states , which involve the criteria governing the service life of the building. Since the consequences are not catastrophic, a much higher probability of occurrence is permitted. A particular limit state may be reached as a result of an adverse combination of random conditions. Partial safety factors are employed for different conditions that reflect the probability of certain occurrences or circumstances of the structure and loading existing. The implicit objective of the design calculations is then to ensure that the probability of any particular limit state being reached is maintained below an acceptable value for the type of structure concerned.

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3. The Speed of Erection Process. The speed of erection is a vital factor in obtaining a return on the investment by minimizing the cost of interest payments on the large capital costs involved in such large-scale projects. Most tall buildings are constructed in congested city sites with difficult access, and with no storage areas. Careful planning and organization of the construction sequence become essential. The story-to-story uniformity of most multi-story buildings encourages construction through repetitive operations and prefabrication techniques.
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TB-Lecture04-Design-Criteria - EGN-5439 Design of Tall...

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