As indicated in 2000 aisc code of standard practice

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As indicated in 2000 AISC Code of Standard Practice Section 6.4.4, for members less than 50-ft long, the cam- ber tolerance is minus zero/plus 1/2-in; an additional 1/8 in. per each additional 10 ft of length (or fraction thereof) is allowed for lengths in excess of 50 ft. An exception is also included: members received from the rolling mill with 75 percent of the specified camber require no further cambering. Furthermore it is specified that cam- ber be inspected in the fabricator's shop in an unstressed condition. What is the tolerance on sweep for curved girders ? Permissible variations in sweep for horizontally curved welded plate girders are specified in AWS D1.1-2000 Section 5.23.5. However, because the method of measurement for this sweep dimension is not defined, the tol- erance is sometimes misapplied. The permissible variation specified is the deviation of the theoretical mid-ordi- nate from a chord through the ends of a single fabricated girder section. If it is required to hold the ordinate of additional points along the beam within a certain tolerance, these require- ments should be specified in the contract documents. Note, however, that most girders have sufficient lateral flex- ibility to easily permit the attachment of diaphragms, cross-frames, lateral bracing, etc., without damaging the structural member or its attachment. What is the tolerance on twist of welded box members ? As stated in AWS D1.1-2000 Section, "…[the tolerance on] twist of box members … shall be individ- ually determined and mutually agreed upon by the contractor and the owner with proper regard for erection requirements." In the absence of a specified tolerance, an attempt is sometimes made to apply the provisions of ASTM A500 or ASTM A6/A6M. However, the provisions of these material specifications should not be applied to fabricated box members. In an unspliced member, the necessary tolerance on twist is generally a matter of serviceability or aesthetics. In a member that will be spliced, twist must be kept within limits that will allow safe and uncomplicated erection. Shop assembly of the entire member by the fabricator may be necessary to accomplish this. It is recommended that the fabricator and erector mutually agree on the means and methods necessary to achieve installation of an acceptable member in the completed structure (see the first question under "Other General Information"). Connection details for fabricated box members should accommodate twist in the completed member. In any case, the required twist tolerance should be specified in the contract documents. Note, however, because of high torsional strength and stiffness, correction of twist in a closed box or similar shape is nearly impossible and carries the potential for damage. If the actual twist of a fabricated member exceeds a specified tolerance, whether to attempt correction should be a case-by-case decision made by the SER.
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  • Fall '19
  • Structural steel

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