Fasteners, Load and Stress

1. Fasteners, Load and Stress

2. Loads Load is an engineering term for the forces that are exerted on a structure. Loads are considered either static or dynamic: Static loads (constant) Dead loads (weight of the structure) Live loads (weight of occupants, furnishings, snow load Dynamic loads (Sudden and vary in direction and intensity)wind loads, seismic loads.

3. Forces Forces are determined by their magnitude, direction, and point of application.

4. Classes of forces Forces are determined by their magnitude, direction, and point of application.

5. Force nomenclature Tension is a force to stretch a beam in one direction. Compression is a force that presses on a beam in one direction. Shear is the tendency of loads to deform or fracture a member by sliding one section against another. Turning moment is a force that produces motion around a point or an axis. Forces may either be uniform (uniform loading) or concentrated. Non concurrent forces create turning moments. Non concurrent forces may create deformation, or raking in timbers when the beam itself is presented with compressive and tension forces. Deflection is a common form of surface failure.

6. Joints Joints are the connections made between different parts of a structure. Most joints lock two building parts tightly together. However, in some structures in which a high degree of expansion is unavoidable, expansion joints are constructed.

7. Classes of joints Joints are the connections made between different parts of a structure. Most joints lock two building parts tightly together. However, in some structures in which a high degree of expansion is unavoidable, expansion joints are constructed. In wood frame construction three common classes of joints are seen: lap joints, mortise and tenon joints, and dovetail joints. 1. Lap joints are just that, two timbers lapping each other. a. This joint requires a fastener, just as a nail or wooden peg to hold the parts together. The joint is only as strong as the fastener. A scarf joint is a lap joint joining two timbers at 180 degrees. Used principally in compression. 2. Mortise and Tenon joints are created by passing the prepared end (tenon) of one timber into a prepared slot (mortise) of another. Most mortise and tenon joints are then pinned with a fastener. Used principally in tension. 3. Dovetail joints are locking joints that do not require a fastener. As the name implies the tenon end swells to the end and thus resists tension pressures by tightening the joint as pressure is applied.

8. Fasteners Fasteners in wood frame construction are nails. They may be wooden pins called trenails, or iron nails. Nails are rated by their size but called penny, 8d, 12d, 60d. 1. Wooden trenails are carved pegs that are set into a mortise and tenon joint pulling the joint tight.

9. Hand wrought

10. Cut nails. Made from sheets of iron in rolling mills. 1790s-1820s cut from common sides, hand head 1810s-1820s cut from opposite sides, hand head 1815-1830s cut from common sides, machine heads 1820s-1830s cut from opposite sides, machine heads.