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| NOTE.--The working unit-stresses given in the table are intended for railroad bridges and trestles. For highway bridges and trestles the unit-stresses may be increased |
| twenty-five (25) per cent. For buildings and similar structures, in which the timber is protected from the weather and practically free from impact, the unit-stresses may be |
| increased fifty (50) per cent. To compute the deflection of a beam under long-continued loading instead of that when the load is first applied, only fifty (50) per cent of the |
| corresponding modulus of elasticity given in the table is to be employed. |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| | BENDING | SHEARING | COMPRESSION | |
| |---------------------------------+-----------------------------------------+-------------------------------------------------------------------------| Ratio |
| | Extreme | Modulus of | Parallel to | Longitudinal | Perpendicular | Parallel to | For | Formulae for | of |
| | fibre | elasticity | the grain | shear in | to the grain | the grain | columns | working stress in | length |
| KIND OF | stress | | | beams | | | under 15 | long columns over | of |
| TIMBER |--------------------+------------+--------------------+--------------------+--------------------+--------------------| diameters | 15 diameters | stringer |
| | Average | Working | | Average | Working | Elastic | Working | Elastic | Working | Average | Working | working | | to |
| | ultimate | stress | Average | ultimate | stress | limit | stress | limit | stress | ultimate | stress | stress | | depth |
|-----------------+----