A check of PA effects is not necessary for permanent di-agonal bracing used as part of the temporary bracing scheme.. The column itself is adequate by inspection for the verti-cal compon
Trang 1Revision and Errata List, March 1, 2003
AISC Design Guide 10: Erection Bracing of Low-Rise Structural Steel Buildings
The following editorial corrections have been made in the First Printing, 1997 To facilitate the incorporation of these corrections, this booklet has been constructed using copies
of the revised pages, with corrections noted The user may find it convenient in some cases to hand-write a correction;
in others, a cut-and-paste approach may be more efficient
Trang 2Force in diagonal = 4.9 kips (47.2/40) = 5.8 kips
This force is less than the bracing force of 38 kips for
which the permanent bracing is designed
One bolt in each angle is adequate to resist the
tempo-rary bracing force in the diagonal The permanent
brac-ing connections are adequate by inspection
The roof strut itself is a W24X55 spanning 40 feet The
strut force is 4.8 kips Per Tables 4.1 and 4.2, it can be
seen that this member is adequate to carry the strut force
A check of PA effects is not necessary for permanent
di-agonal bracing used as part of the temporary bracing
scheme
Lastly, the column on the compression side of the
diago-nally braced bay must be checked
The column itself is adequate by inspection for the
verti-cal component of the temporary bracing force This
ver-tical component is 5.8 (25/47.2) = 3.1 kips which is far
less than the column axial capacity
4.5 Beam to Column Connections
In the typical erection process, the beam to column
connections are erected using only the minimum
num-ber of bolts required by OSHA regulations This is done
to expedite the process of "raising" the steel in order to
minimize the use of cranes Final bolting is not done
un-til the structure is plumbed
In addition to the connection design strength using
the minimum fasteners, additional design strength can
be obtained by installing more fasteners up to the full de-sign strength This additional dede-sign strength can be in-corporated in the temporary bracing scheme Because
of the complexity of integrating final connections in the temporary supports this topic is not developed in this guide, however the principles are fully developed in current literature such as LRFD Manual of Steel Construction, Volume II (14) and [ASD] Manual of Steel Construction, "Volume II – Connections" (13)
4.6 Diaphragms
Roof or floor deck can be used during the erection process to transfer loads horizontally to vertical bracing locations The ability of the deck system to transfer loads is dependent on the number and type of attach-ments made to the supporting structure and the type and frequency of the deck sidelap connections Because of the number of variables that can occur with deck dia-phragms in practice, no general guidelines are presented here The designer of the temporary bracing system is simply cautioned not to use a partially completed dia-phragm system for load transfer until a complete analy-sis is made relative to the partially completed dia-phragm strength and stiffness Evaluation of diadia-phragm strength can be performed using the methods presented
in the Steel Deck Institute's "Diaphragm Design Manu-al" (8)
5 RESISTANCE TO DESIGN LOADS — TEMPORARY SUPPORTS
The purpose of the temporary support system is to adequately transfer loads to the ground from their source in the frame Temporary support systems trans-fer lateral loads (erection forces and wind loads) to the ground The principal mechanism used to do this is tem-porary diagonal bracing, such as cables or struts, the use
of the permanent bracing or a combination thereof Temporary diagonal struts which carry both tension and compression or just compression are rarely used Cable braces are often used In cases when the building is framed with multiple bays in each direction, dia-phragms are used in the completed construction to trans-fer lateral loads to rigid frames or braced bays Before the diaphragm is installed temporary supports are re-quired in the frame lines between the frames with per-manent bracing
The use of cables to provide temporary lateral brac-ing in a frame line requires that the followbrac-ing conditions
be met:
1 Functional strut elements (beams, joists, girders) to transfer the lateral load to the cable braced bay
2 Functional transfer of the lateral load into the brac-ing tension cable and compression column pair
3 Functional resistance of the anchorage of the cable and the column to their respective bases and to the ground
27
Calculating:
The area of the frame (Af) is computed as follows:
First frame
Thus the total frame area is:
The net area of joists is computed as:
Thus,
F at the level of the roof strut is:
Rev.