Tag Archive for Tag: LRFD

Tag: LRFD Bases for ASD and LRFD

ASD is based on elastic theory. Design limits the maximum unit stress a member is permitted to bear under service loads to a level determined by a judgmental, but  experience-based, safety factor. Building codes establish allowable unit stresses, which are normally related to the minimum yield stress for each grade of steel. Plastic design is based on the ultimate strength of members.

View Article...

Tag: LRFD Member Design Example-LRFD

The design of a truss hanger by the AASHTO LRFD Specifications is presented subsequently. This is preceded by the following introduction to the LRFD member design provisions. LRFD Member Design Provisions Tension Members. The net area, An, of a member is the sum of the products of thickness and the smallest net width of each element. The width of each standard

View Article...

Tag: LRFD Nominal Resistance for LRFD

The nominal resistance of the various bridge components, such as flexural members, webs in shear, and fasteners (bolts or welds), is given by equations in the LRFD Specification. Each nominal resistance must be multiplied by a resistance factor, @ , which is a statistically based number that accounts for differences between calculated strength and actual strength. The @ factor, Table 11.10, provides

View Article...

Tag: LRFD Load Combinations and Effects

The following groups represent various combinations of service loads and forces to which a structure may be subjected. Every component of substructure and superstructure should be proportioned to resist all combinations of forces applicable to the type of bridge and its site. For working-stress design, allowable unit stresses depend on the loading group, as indicated in Table 11.6. These stresses, however, do not

View Article...

Tag: LRFD ASD versus LRFD

results in lighter or shallower members. For example, LRFD will typically result in material savings in the range of 10 to 15% when used for strength design of composite beams. In some cases, the material savings for certain components can be more than 30%. However, when the governing criterion is serviceability, such as deflection or vibration, ASD and LRFD will typically produce the same

View Article...