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The following are some of the limitations or features not supported with curved members: Tapered section propertiesComposite decksPRIS ROUND sections Beta angleMember releases, global or tangentMember SpringsMember offsetsMember end springsPhysical membersMember Tension/compression Any span loads except "Uniform load throughout the length in global directions", such as: Member Loads - UMOM, CON, CMOM, LIN, TRAPArea Load, One Way, Floor LoadWind Load, Prestress, PoststressTemperature load, StrainFixed End LoadSnow LoadMoving load ImperfectionsGeometric stiffness, Pdelta, buckling, Pdelta KG with/without dynamicsMass for dynamics will not include the effect of the member cg being off the chord lineIntermediate section displacements, and hence the deflection diagramIntermediate section forces, and hence the bending moment and other forces diagram
Steel or concrete design at any location other than nodesMember selectionWeld design
*Limitations faced with curved beams in designing:
It is not advisable to perform steel design on curved members using STAAD. The reasons are : 1) The design codes are written for straight members, not curved ones. The rules in most standard design codes do not adequately address the peculiarities of curved members. LY and LZ for example in the KL/r checks are the straight line distances between the bracing points of a straight member. To use those rules on curved members without adjusting for the curvedness may not be correct. An out of plane load on a curved member causes major torsional moments, but most codes only discuss axial forces, bending and shear, not torsion. 2) STAAD can calculate the member forces only at the nodes of curved members. It cannot calculate them at intermediate span locations. Consequently, during steel design, these members will be designed for the forces at their ends only. Intermediate section points within the span cannot be designed. 3) STAAD can calculate the displacements at the nodes of curved members. It cannot calculate them at intermediate span locations. Consequently, deflection check cannot be performed for curved members.
Due to all these limitations, modeling the curved beams using a series of straight segments might be a better option.
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