RC Lecture 3

RC Lecture 3 - TOPIC 4: LOAD COMBINATIONS AND DESIGN...

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CIVL2007 Theory and Design of Structures II RC Component (30 March 2007) page 66 TOPIC 4: LOAD COMBINATIONS AND DESIGN ENVELOPES - LECTURE NOTES - General In order for RC structural elements such as beams, slabs and columns to be designed, appropriate levels of bending moment, shear force, and axial force need to be determined. All likely (and sometimes unlikely) forms of loading need to be considered in design as, after-all, it is the responsibility of the structural engineer to account for all possible types of loading on a structure. The most common forms of load are known as dead load (permanent and generally gravity loads), live load (moving or imposed load of a non-permanent duration) and wind load. Millau Viaduct, France (http://en.structurae.de/structures/data/index.cfm?ID=s0000351)
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CIVL2007 Theory and Design of Structures II RC Component (30 March 2007) page 67 Load Combinations Characteristic Values of Loads Characteristic values of loads should be used in design. The most commonly considered loads are dead load (G k ), imposed load (Q k ) (otherwise known as live load), and wind load (W k ). The dead and live loads are vertical while the wind load may be horizontal or vertical (the direction of wind load depends on the orientation of the structural elements, e.g. walls are subjected to horizontal windward or leeward pressures while roofs are subjected to vertical suction pressures). Another type of vertical load to consider is due to snow, while other horizontal loads to consider are due to earthquake, soil or water pressure. Snow loads are obviously not an issue in Hong Kong however such loads may be dominant in certain countries (e.g. Canada). For the determination of common levels of load in Hong Kong, reference should be made to the following two documents: The Hong Kong Code of Practice for Dead and Imposed Loads for Buildings Hong Kong Code of Practice on Wind Effects Partial Safety Factors for Loads The load used in design, otherwise known as the design load, is obtained by multiplying the characteristic load by a partial safety factor γ f , namely: γ f G k , γ f Q k or γ f W k . The partial safety factor γ f is introduced to take into account unforeseen increases in load or stress redistribution, inaccurate assessment of load effects, variation in dimensional accuracy, and the importance of the particular limit state under consideration.
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This note was uploaded on 10/24/2009 for the course BENG Civl2007 taught by Professor A.smith during the Spring '09 term at HKU.

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RC Lecture 3 - TOPIC 4: LOAD COMBINATIONS AND DESIGN...

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