Shear - Tensile Compression Stresses Slip

Ted 126 Spring 2007

Shear

• Shear strength in mechanical engineering and structural engineering is a term used to describe the strength against the type of structural failure where a component fails by shearing when it splits into two parts that slide past each other. • The shear strength of a component is most important for beams but also relevant for e.g. plates. • In a reinforced concrete beam, the main purpose of stirrups is to increase the shear strength.

Shear

• Riveted and bolted joints may also be mainly subjected to shear stress.

• Cantilevers, beams, consoles and column heads are subject to composite loading, consisting of shear, tensile and compressive stress.

Tensile stress

• Tensile stress (or tension) is the stress state leading to expansion; that is, the length of a material or compression member tends to increase in the tensile direction. • Tensile stress is the opposite of compressive stress.

• Structural members in direct tension are ropes, soil anchors and nails, bolts, etc. • Beams subjected to bending moments may include tensile stress as well as compressive stress and/or shear stress.

Tensile Strength

• The tensile strength of a material is the maximum amount of tensile stress that it can be subjected to before failure. • The definition of failure can vary according to material type and design methodology.

Compressive stress

• … applies to materials resulting in their compaction (decrease of volume). • When a material is subjected to compressive stress then this material is under compression. • Usually compressive stress applied to bars, columns, etc. leads to shortening.

Slip

• A slip joint is a mechanical construction allowing extension and compression in a linear structure.

• A slip-critical joint, from structural engineering, is a joint which relies on friction (rather than shear or tensile strength) to hold two things in place.

Slip

• The most common slip-critical joint is where a girder meets a larger beam. • Typically an angle plate joins the two. • One beam is welded to the angle plate, the other has holes which are generally oversized or slotted.

• The bolt through this plate doesn't actually take the load as a shear joint or a bearing joint, – it simply creates normal force and therefore

friction between the two steel faces.