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ACI 435.8R
Observed Deflections of Reinforced Concrete Slab Systems, and Causes of Large Deflections
Organization:
ACI - American Concrete Institute
Year: 1997
Abstract: Synopsis: This report is in two distinct parts
Part I is a summary of published studies on slab deflections (3 from Australia, 1 from Scotland, 1 from Sweden, 2 from U.S.). The summary focuses on construction practices and materials quality. Comparison of deflections calculated by various methods with actual long-term deflections is made in some cases.
Part II summarizes several construction problems and material deficiencies which can contribute to large long-term deflections. Focusing on large construction loads, the authors show that construction loads may be considerably higher than design loads and that high construction loads cause high initial deflections because concrete has a lower modulus of elasticity when loaded at an early age. Furthermore, concrete creeps more when it is loaded at an early age, thereby causing additional high long-term deflections, even when construction loads are sustained only for a few days.
The authors then suggest a method of form removal and reshoring that has proved successful in the New York City area in preventing large slab deflections. Essentially, no more than an 8-foot slab span is left unsupported until a slab is mature.
A reader interested only in the Committee's findings and recommendations may proceed straight to Part II of the report.
Part I is a summary of published studies on slab deflections (3 from Australia, 1 from Scotland, 1 from Sweden, 2 from U.S.). The summary focuses on construction practices and materials quality. Comparison of deflections calculated by various methods with actual long-term deflections is made in some cases.
Part II summarizes several construction problems and material deficiencies which can contribute to large long-term deflections. Focusing on large construction loads, the authors show that construction loads may be considerably higher than design loads and that high construction loads cause high initial deflections because concrete has a lower modulus of elasticity when loaded at an early age. Furthermore, concrete creeps more when it is loaded at an early age, thereby causing additional high long-term deflections, even when construction loads are sustained only for a few days.
The authors then suggest a method of form removal and reshoring that has proved successful in the New York City area in preventing large slab deflections. Essentially, no more than an 8-foot slab span is left unsupported until a slab is mature.
A reader interested only in the Committee's findings and recommendations may proceed straight to Part II of the report.
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| contributor author | ACI - American Concrete Institute | |
| date accessioned | 2017-09-04T16:26:43Z | |
| date available | 2017-09-04T16:26:43Z | |
| date copyright | 01/01/1985 (R 1997) | |
| date issued | 1997 | |
| identifier other | UBFMPAAAAAAAAAAA.pdf | |
| identifier uri | http://yse.yabesh.ir/std/handle/yse/89960 | |
| description abstract | Synopsis: This report is in two distinct parts Part I is a summary of published studies on slab deflections (3 from Australia, 1 from Scotland, 1 from Sweden, 2 from U.S.). The summary focuses on construction practices and materials quality. Comparison of deflections calculated by various methods with actual long-term deflections is made in some cases. Part II summarizes several construction problems and material deficiencies which can contribute to large long-term deflections. Focusing on large construction loads, the authors show that construction loads may be considerably higher than design loads and that high construction loads cause high initial deflections because concrete has a lower modulus of elasticity when loaded at an early age. Furthermore, concrete creeps more when it is loaded at an early age, thereby causing additional high long-term deflections, even when construction loads are sustained only for a few days. The authors then suggest a method of form removal and reshoring that has proved successful in the New York City area in preventing large slab deflections. Essentially, no more than an 8-foot slab span is left unsupported until a slab is mature. A reader interested only in the Committee's findings and recommendations may proceed straight to Part II of the report. | |
| language | English | |
| title | ACI 435.8R | num |
| title | Observed Deflections of Reinforced Concrete Slab Systems, and Causes of Large Deflections | en |
| type | standard | |
| page | 47 | |
| status | Active | |
| tree | ACI - American Concrete Institute:;1997 | |
| contenttype | fulltext |