Lecture 12- Concrete Formwork

Lecture 12- Concrete Formwork - C E M 6 2 C o n s t r u c t...

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Unformatted text preview: C E M 6 2 C o n s t r u c t i o n M e t h o d s CEM 602 Construction Methods Lecture 12 Concrete Formwork 1 L e c t u r e 1 2- C o n c r e t e F o r m w o r k C E M 6 2 C o n s t r u c t i o n M e t h o d s Formwork Materials L e c t u r e 1 2- C o n c r e t e F o r m w o r k 2 C E M 6 2 C o n s t r u c t i o n M e t h o d s Formwork Materials Lumber Dimension lumber is the most basic material (note actual sizes!). Softwoods are most commonly used. Southern Yellow Pine Douglas Fir Lumber is primarily used in a structural capacity with plywood used directly in contact with the concrete. 1 board foot = 144 nominal in3 Table 4-1B lists important structural L e c t u r e 1 2- C o n c r e t e F o r m w o r k 3 C E M 6 2 C o n s t r u c t i o n M e t h o d s Formwork Materials Lumber Stress-graded lumber is based upon a factor of safety of 2.5. For very short-term (impact) loadings, the working stress may be doubled. For loads less than seven days in duration and with less than ten reuses, a 25% increase in working stress (Table 4-2) may be used; however, this practice should be used very sparingly as labor, not lumber, is main cost factor. L e c t u r e 1 2- C o n c r e t e F o r m w o r k 4 C E M 6 2 C o n s t r u c t i o n M e t h o d s Formwork Materials Lumber L e c t u r e 1 2- C o n c r e t e F o r m w o r k 5 C E M 6 2 C o n s t r u c t i o n M e t h o d s L e c t u r e 1 2- C o n c r e t e F o r m w o r k 6 Formwork Materials Lumber C E M 6 2 C o n s t r u c t i o n M e t h o d s Formwork Materials Lumber Table 4-2A provides adjustments for moisture contents and temperatures. Repetitive gang form members 2 to 4 inches thick and up to 24 inches apart may enjoy a 15% increase in allowable bending stress; however, this increase should not be applied in addition to the limited reuse factor. Table 4-2B provides size and flat use factors for bending stress. Table 4-2C provides sizes of standard glued laminated timbers for reference L e c t u r e 1 2- C o n c r e t e F o r m w o r k 7 C E M 6 2 C o n s t r u c t i o n M e t h o d s L e c t u r e 1 2- C o n c r e t e F o r m w o r k 8 Formwork Materials Lumber C E M 6 2 C o n s t r u c t i o n M e t h o d s Formwork Materials Plywood Plywood is most common sheathing material although boards are occasionally used. Table 4-3 provides structural properties of plywood. Note the difference between plywood used the weak way and the strong way. (See fig. 4-6.) Formply has resin-impregnated fiber faces....
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This note was uploaded on 03/17/2012 for the course CEM 602 taught by Professor Amrkandile during the Spring '10 term at American University in Cairo.

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Lecture 12- Concrete Formwork - C E M 6 2 C o n s t r u c t...

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