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Short & long term deflections
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SHORT- AND LONG-TERM DEFLECTIONSAsevident fromthenames, short-termdeflectionreferstotheimmediatedeflection after casting and application of partial or full service loads, while thelong-term deflection occurs over a long period of time largely due to shrinkage andcreep of the materials. The following factors influence the short-term deflection ofstructures: (a)magnitude and distribution of live loads,(b)span and type of end supports,(c)cross-sectional area of the members,(d) amount of steel reinforcement and the stress developed in the reinforcement,(e)characteristic strengths of concrete and steel, and(f)Amount and etent of cracking.Thelong-termdeflectionis almost twotothreetimes of theshort-termdeflection. The following are the ma!or factors influencing the long-term deflectionof the structures. (a)humidity and temperature ranges during curing,(b)age of concrete at the time of loading, and (c) type andsi"e of aggregates, water-cement ratio, amount of compressionreinforcement, si"e of members etc., which influence the creep and shrinkage ofconcrete.