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Section 1915 Concrete-Filled Steel Columns
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Caps, base plates and connections shall be in accordance with ACI 318 and AISC 360 and shall be positively attached to the shell and anchored to the concrete core. Welding of brackets without mechanical anchorage shall be prohibited. Where the pipe is slotted to accommodate webs of brackets or other connections, the integrity of the shell shall be restored by welding to ensure hooping action of the composite section.
Steel reinforcement shall be in the form of rods, structural shapes or pipe embedded in the concrete core in accordance with ACI 318 and AISC 360 with sufficient clearance to ensure the composite action of the section, but not nearer than 1 inch (25 mm) to the exterior steel shell. Structural shapes used as reinforcement shall be milled to ensure bearing on cap and base plates.
Steel columns shall be of such size or so protected as to develop the required fire-resistance ratings specified in Table 601. Where an outer steel shell is used to enclose the fire protective covering, the shell shall not be included in the calculations for strength of the column section. The minimum diameter of steel columns shall be 4 inches (102 mm) except that in structures of Type V construction not exceeding three stories or 40 feet (12 192 mm) above grade plane, steel columns used in basements and as secondary steel members shall have a minimum diameter of 3 inches (76 mm).
Four minimum 1/2 in. (12.7 mm) diameter holes, top and bottom, shall be placed opposite each other, two at the top and two at the bottom of the column. The two bottom holes shall be rotated 90° relative to the two top holes.
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