Page 43 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

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FABRICATION AND ERECTION*

FABRICATION AND ERECTION 2.5

must be shown on contract documents. The AISC “Specification for Structural Steel Buildings”
requires alternate core toughness defined in ASTM A6, “Supplementary Requirement S30,” when
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the pieces have flanges more than 2 in thick (1 / 2 in for seismic) and are connected with complete-
joint-penetration (CJP) welds fusing through the thickness of the flange. Also, frame members
exposed to low temperature and subject to large live loads may demand an enhanced level of toughness
(see ASTM A6, “Supplemental Requirement S5”).
Clearances and Interferences. In addition to dimensioning pieces to fit, pieces must be designed
and detailed with consideration of a path for assembly in the field and with access for fasteners and
tools necessary to make connections. Welds and bolt holes should be visible. Bolts require a clear
length equal to the length of the bolt on one side of the connection for entry, and room for the wrench
on one side. When tension control bolts are used, room for bolt entry and the wrench have to be on
opposite sides of the connection. Access for welds should be provided so that the welder can aim the
electrode normal to the surface of the completed weld. Steel erection is very labor intensive, and a
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clear path permitting the placement of pieces with a simple movement and at least / 2 in clearance is
essential to efficient work. Tucking ends of pieces between flanges and reversing direction to final
placement is time consuming. When stiffeners or other details block entry of a connection, the con-
nection should be extended beyond the interfering detail so the mating piece can be erected without
performing dangerous maneuvers in the air.
Shop Drawing Approval. When shop drawings have been completed and checked, they are sub-
mitted to the engineer for review or approval. Responsibility for specific information on shop draw-
ings is the subject of ongoing controversy. In general, the engineer reviews the shop drawings to see
that the drafter has interpreted the design requirements properly.

2.3 FABRICATION PRACTICES AND PROCESSES:
MATERIAL PREPARATION

Steel fabrication shops are most commonly organized into departments such as receiving, detail
material, main material cut and preparation, assembly fit and fasten, and shipping. Many shops
also have paint departments. Material is received by trucks or by rail, off-loaded, compared to
order requirements, and stored by project or by size and grade. Material is received from the mill
or warehouse as individual pieces or in bundles. The pieces or bundles are identified with the size
specification grade and heat number. Identity of the material in storage is maintained by segre-
gating the material by grade, keeping the material in identified bundles or stacks, or marking the
material. When the material is cut to be processed into a specific piece in the structure, it is
marked with a piece mark and may be further labeled with the specification and grade. Any mate-
rial left after cutting is marked with the grade and returned to the receiving yard. Material han-
dling is a major consideration in the structural shop, and organized storage is key to reducing
handling.
Detail material consists of the usually small parts that the shop attaches to main pieces to
become shipping pieces. To keep the flow of work in the shop consistent, the detail material is pre-
pared just before the main material, so it is ready for assembly when the large pieces are ready for
assembly. Where it is feasible, fabricators create standard pieces such as standard clip angles to
enhance repetition and permit work to be performed in reasonable groups. Angle shapes are usually
processed in machines that automatically feed, punch holes or slots in both legs, and shear the angle
in a single operation. Methods for processing plate vary with the size and shape of the final piece
and the equipment in the shop. When large numbers of plates of the same narrow width are to be
made, the fabricator buys bar to avoid extra cutting. Plates can be sawn but are most often sheared
or thermal cut.
Thermal cutting offers the ability to create plate of any useful shape, including reentrant cor-
ners. It also offers the ability to bevel the edges as for groove welds and cut holes. Thermal cutting

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