Steel Lecture 2

Steel Lecture 2 - TOPIC 4 FLEXURAL MEMBERS LECTURE NOTES...

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CIVL2007 Theory and Design of Structures II Steel Component (4 May 2007) page 35 TOPIC 4: FLEXURAL MEMBERS - LECTURE NOTES - Unless otherwise noted, all clauses cited in this lecture have been taken from the Hong Kong Code of Practice for the Structural use of Steel (2005) {otherwise known as HK Steel Code (2005)}. General Flexural members can be divided into 2 categories for their analysis, namely restrained beams and unrestrained beams: Restrained beams Restrained beams refer to beams provided with full lateral restraint to their top (compressive) flanges and with full torsional restraint at their ends. In such a case, lateral-torsional buckling (LTB) should not occur before the plastic moment capacity is reached. Full lateral restraint can be assumed when the compression flange of a beam is connected positively to a floor or to similar structural elements capable of providing a lateral restraining force. This lateral restraining force shall be 2.5% of the maximum force in the compression flange of the member, or more simply 2.5% of the squash load of the compression flange. This lateral force should be provided uniformly along the flange with the self weight and imposed loading from the floor forming the dominant mode of loading on the member. Unrestrained Beams When the condition for full lateral restraint given above cannot be satisfied, the resistance of beams to lateral-torsional buckling should be checked.
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CIVL2007 Theory and Design of Structures II Steel Component (4 May 2007) page 36 Shear Strength of Members (8.2.1) For loads parallel to the webs and d/t < 70 ε for hot-rolled sections or d/t < 62 ε for welded sections, the shear capacity V c given below should not be less than the design shear force V as follows, V 3 A p V v y c = where: A v = shear area, and given by: For rolled I, H and channel sections: tD For welded I, H and channel sections: td For rolled and welded RHS: 2td For rolled and welded T-sections: t(D – T) For CHS: 0.6A For solid rectangular sections: 0.9A For others: 0.9A o , where A o = area of the rectilinear element of the section which has the largest dimension in the direction parallel to the load. For d/t larger than the above limits, shear buckling resistance needs to be checked. This is however outside the scope of this course. Definition of the remaining notation can be found in Figure 3.3. (Figure 7.1, HK Steel Code 2005) Note: CHS = circular hollow section, SHS = square hollow section
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CIVL2007 Theory and Design of Structures II Steel Component (4 May 2007) page 37 Moment Capacity of Fully Restrained Beam (8.2.2) The moment capacity of a beam M c should not be less than the design bending moment M. The moment capacity is dependent on the level of the shear, namely a Low Shear Condition and High Shear Condition . Low Shear Condition
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Steel Lecture 2 - TOPIC 4 FLEXURAL MEMBERS LECTURE NOTES...

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