Strength and Serviceability Checks

The composite beam module checks members for strength and serviceability conditions at both the construction (or pre-composite) stage and the final (or composite) stage. All checks are performed together in one Design Form. For this reason load combinations for each check must be created and put into a load class according to “Loading Composite Members” above.

The design method is automatically determined based on the design method specified in the load combinations.

Each check is performed on the whole member using the extreme values of internal force or deflection, rather than using values at each section along the member.

Each check returns a unity check (ratio of demand to capacity) value. The maximum unity check from all checks is called MaxUC and is available as a result which is visible on the member.

Construction Stage Strength Check

The construction stage strength investigates the capacity of the steel wide-flange cross-section (with no composite action) using the construction stage load combinations. It compares the flexural and shear capacity of the member, calculated according to AISC Specification Chapters F and G, respectively, to the maximum moment and shear forces.

If the plate ribs of the metal deck are perpendicular to the member (within 5 degrees), the member is considered to be continually braced.

The strength check does not support members that have a slender web.

The result returned for the construction stage strength check is the higher of two unity checks for bending and shear. Combined forces at each section are not considered in the check

Final Stage Strength Check

The final stage strength check investigates the capacity of the composite member using the final stage load combinations at the target degree of composite action.

The shear capacity of the composite member is taken available shear strength of the steel section alone as specified in Chapter G in accordance with Section I4.1(a) of the AISC Specification

The positive and negative flexural strength of the composite member are determined from the plastic stress distribution on the composite section for the limit state of yielding as specified in Section I4.2a and Section I4.2b of the AISC Steel Specification. If negative moment exists on the member requiring the negative flexural strength, the member is checked for compactness and a unity check value of 2.0 will be returned as well as a warning message if the member is non-compact. No non-compact members will be considered during the design selection process for members that have negative moment.

The result returned for the final stage strength check is the higher of two unity checks for bending and shear. Combined forces at each section are not considered in the check

Construction Serviceability Check

The construction serviceability check checks the deflection of the member due the self-weight of steel and concrete against the deflection limit set in the composite setup. The default construction deflection limit is 1/360. Camber is taken into consideration in the construction serviceability check. (For more information on how camber is designed when “Camber Definition” is set to “Design”, see Camber Design.)

Final Live Load Serviceability Check

The final live load serviceability check checks the deflection of the member due to the live loads present in the final stage against the deflection limit set in the composite setup. The default construction deflection limit is 1/360. Camber is not considered in the final live load serviceability check.

Final Total Load Serviceability Check

The final total load serviceability check checks the deflection of the member due to all loads present in the final stage against the deflection limit set in the composite setup. The default construction deflection limit is 1/240. Camber is taken into consideration in the construction serviceability check. (For more information on how camber is designed when “Camber Definition” is set to “Design”, see Camber Design.)

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