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Built-Up Heavy Shapes No changes have been made to this section. Steel Castings and Forgings No changes have been made to this section. Anchor Rods and Threaded Rods No changes have been made to this section. The welding code, AWSD1. A user note is added to this section stating the information that is to be shown on the design drawings. Section B3. Required Strength The reference to the provisions in Appendix 1 for moment redistribution in continuous beams has been removed because this topic has been moved into this chapter.
Limit States Several additions have been made to this section for completeness of structural integrity requirements for connections. The limit states based on limiting deformations or yielding do not need to be considered for structural integrity requirements. Also, bolt bearing with short-slotted holes parallel to the direction of tension are to be assumed at the end of the slot.
Design for Stability No changes have been made to this section. Design of Connections Added to this section is the statement that self-limiting inelastic deformations are permitted. For beams, girders and trusses the supports shall be restrained against rotation unless analysis shows that restraint is not required.
Simple Connections The provisions for permitting inelastic rotation of a connection have been removed from this section. Moment Connections No changes have been made to this section. Moment Redistribution in Beams was Appendix 1, Section 1. Diaphragms and Collectors new section References to applicable sections for designing diaphragm and collector elements have been added in this new section.
Design for Serviceability was Section B3. Design for Ponding was Section B3. Design for Fatigue was Section B3. Design for Fire Conditions was Section B3. Design for Corrosion Effects was Section B3. Anchorage to Concrete new section This section includes references to Chapter I for design of steel and concrete acting compositely and Chapter J for design of column bases and anchor rods.
Several sub-sections have been moved here including, B4. The topics of quality control and quality assurance are now included in a new section. Classification of Sections for Local Buckling was section B4 The local buckling classifications for members have been separated for flexure and compression.
The classification for flexure remains the same while compression members are now classified as either slender or nonslender. The reference to Table B4.
New figures are included in the Examples column, which now include a larger number of applicable sections. The following table shows the changes that have been made to the element descriptions and the case numbering in this table.
Unstiffened Elements was Section B4. Stiffened Elements was Section B4. Section e has been added defining, b, the width of perforated cover plates. The following table shows the changes that have been made to the element descriptions and case numbering in this table. Gross Area was Section B3. Net Area was Section B3. A numbered list is now provided for effects that should be considered when analyzing the stability of a structure.
Added to this list includes stiffness reduction due to inelasticity and uncertainty in stiffness and strength. Removed from this list is member stiffness reduction due to residual stresses.
The list has been changed so component and connection deformations are now categorized under all other deformations that contribute to the displacement of the structure. Added to this section is the statement that any rational method that considers the effects listed in this section is permitted.
A user note is included in this section defining the term design, which is the combination of analysis to determine required strength and proportioning components to have adequate available strength. Direct Analysis Method of Design new section This section refers to sections C2 and C3 for the calculation of required and available strengths, respectfully, for this method of analysis. Alternative Methods of Design new section This section refers to Appendix 7 for the effective length and first-order analysis methods if justified by the provisions.
Several new sections have been added based on the requirements of this method. The content of this section have been moved from Appendix 7 in the Specification.
Also added is a statement that the approximate method of second-order analysis is permitted as an alternative to rigorous second-order analysis. Analysis will cover all gravity loads and applied loads that may influence the stability of the structure. Consideration of Initial Imperfections new section The effects of initial imperfections can be accounted for using either direct modeling or the use of notional loads covered previously in Appendix 7, Section 7.
A user note has been added stating that the imperfections considered are the locations of points of intersection of members caused by the out-of-plumbness of columns. Initial out-of-straightness of members is addressed in Chapter E for compression members and is not considered explicitly in analysis. Direct Modeling of Imperfections new Section The provisions in this section allow for the effects of initial imperfections to be accounted for directly by analysis. The pattern of initial displacement of points of intersection from their nominal locations shall be the maximum amount considered which causes the greatest destabilizing effect.
A user note has been added stating the initial displacements should be similar in configuration to displacements caused by loading and buckling with magnitudes based on permissible construction tolerances given in the AISC Code of Standard Practice. If gravity loads are supported primarily by vertical members and the ratio of maximum second-order drift to maximum first-order drift is less than or equal to 1. Added is a statement that notional loads are permissible for structures that support gravity loads primarily through nominally vertical members.
A user note has been added stating that using notional loads can create additional fictitious base shears and overturning moments. The correct horizontal reaction at the base is found using a force equal to but opposite in direction to the notional loads applied at the base.
Adjustments to Stiffness new section This section has been moved from Appendix 7, Section 7. The equations for the reduced flexural stiffness Eq. A and reduced axial stiffness Eq. A- , have been reformatted into a text description and moved into Section C2. A paragraph has been added for the stability analysis of a structure using materials other than structural steel. The bracing which defines the unbraced length will have stiffness sufficient to control member movement at braced points, which is covered in Appendix 6.
Sections D3. For open cross sections the minimum shear lag factor, U, has been changed from equal to or greater than 0. The alternate lesser value of U, based on the effect of eccentricity, has been removed. Table D3. Two new figures have been added for Case 2 examples, one is a single angle the other is a tee shape.
Case 8 is expanded to include double angles. Tensile Strength In Equation D the variable for effective edge distance, beff, has been changed to be. Dimensional Requirements No changes have been made to this section. Tensile Strength No changes have been made to this section.
This table is similar to the flexural member selection table, Table User Note F1. This section now references Appendix 7 in addition to Chapter C, for the determination of the effective length factor, K. The application of this section has changed from members with compact and noncompact sections to nonslender elements. The elastic buckling stress, Fe, now references Appendix 7 instead of Section C2.
The material in Section E5 c has been moved to Section E5 with the exception of the specific examples of different end conditions, requiring the use of Chapter H provisions, which has been removed. Compressive Strength This section is reorganized to improved clarity. The provision for end connection of built-up members shall be welded or by means of pretensioned bolts with Class A or B faying surfaces has been moved from Section E6.
The user note from section E6. This user note also states that the end connection should be designed to resist slip. Section E6. In Section E6. Dimensional Requirements Parts of this section have been reworded to improve clarity.
The use of the lateral- torsional buckling modification factor, Cb, in now limited to singly symmetric members in single curvature and all doubly symmetric members.
In Equation F the cross-section monosymmetry parameter, Rm, has been removed along with the upper limit as follows, Specification: The user note has been expanded to include the value of Cb for equal end moments of the same sign and also refers to the commentary for detailed analysis for singly symmetric members.
Yielding No changes have been made to this section.
Steel Code ANSI/AISC 360-05 and ANSI/AISC 360-10 (USA)
ANSI/AISC 360-05 - Specification for Structural Steel Buildings