Structural Steel

Bolting

Most field connections are made by bolting, either with high-strength bolts (ASTM A325 or A490) or with ordinary machine bolts (A307 bolts), depending on strength requirements.
Shop connections frequently are welded but may use these same types of bolts.
When high-strength bolts are used, the connections should satisfy the requirements of the ‘‘Specification for Structural Joints Using ASTM A325 or A490 Bolts,’’ approved by the Research Council on Structural Connections (RCSC) of the Engineering Foundation. Joints with high strength bolts are designed as bearing-type, fully-tightened, loose-to-slip or slipcritical connections (see Art. 5.3). Bearing-type connections have a higher allowable load or design strength. Slip-critical connections always must be fully tightened to specified minimum values. Bearing-type connections may be either ‘‘snug tight’’ or fully tightened depending on the type of connection and service conditions. AISC specifications for structural steel buildings require fully tensioned high-strength bolts (or welds) for certain connections (see Art. 6.14.2). The AASHTO specifications require slip-critical joints in bridges where slippage would be detrimental to the serviceability of the structure, including joints subjected to fatigue loading or significant stress reversal. In all other cases, connections may be made with ‘‘snug tight’’ high strength bolts or A307 bolts, as may be required to develop the necessary strength. For tightening requirements, see Art. 5.14.

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