AISC-Design-Guide-1-Errata-2003.pdf
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1、Revision and Errata List, March 1, 2003 AISC Design Guide 1: Column Base Plates The following editorial corrections have been made in the Second Printing, September 1991. To facilitate the incorporation of these corrections, this booklet has been constructed using copies of the revised pages, with c
2、orrections 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. Example 15 (ASD Procedure): Design a base plate for an axial load of 60 kips and a moment of 480 in.-kips. Bending is about the strong axis and the c
3、olumn depth is 8 in. The ratio of the concrete to plate area is four, for the plate and the anchor bolts is 36 ksi, and is 3 ksi. (See Fig. 14) 1. 2. Assume 14 x 14 in. plate. The effective eccentricity is e = 480/60 = 8 in., which is greater than half the plate width. Thus an anchor bolt is require
4、d. It is assumed at 1.5 in. from the plate edge. =5.1 in. This is reasonable when compared to N which is 12.5 in. This is reasonable for the bar sizes available. 5. The critical section is at (14 - 0.95 x 8)/2 = 3.2 in. The moment, for a 1 in. strip, determined from the bearing stress distribution i
5、n Fig. 14, is: Fig. 14. Design Example with Large Eccentricity The moment based on the critical section on the anchor bolt side is determined as follows. The full plate width is not always available. It is assumed that the critical plate width is based on the load spreading out at 45 degrees, shown
6、in Fig. 15. This width is then equal to twice the distance from the bolt to the critical section for each bolt, provided that the critical section does not intersect with the edge of the plate. The moment for a 1 in. strip, is then: The moment from the bearing stress distribution governs, and the re
7、quired plate thickness is then: Fig. 15. Critical Plate Width for Anchor Bolt (Tension Side) 22 Use a 14 x 1 in. x 1 ft 2 in. plate LRFD Procedure: 1. Determine the factored load and factored moment. 2. Determine the allowable bearing stress: 3. Assume a plate size, N x B. 4. Use the factored loads
8、to determine the length of bearing A, equal to the smallest positive value from the equation for A. If this value is reasonable, go to the next step. If it is close to the value of N, the solution is not practical since this implies that bearing extends to the vicinity of the anchor bolt. If this we
9、re so, the anchor bolt could not develop its full tensile capacity. It is then necessary to return to step 3 and pick another, larger plate. Rev. 3/1/03 Rev. 3/1/03 kips 7.48 3.74 5. Determine the resultant anchor bolt force T from the above equation. If it is reasonable go to the next step. Otherwi
10、se return to step 3. (The design of the anchor bolt is covered in the following section.) 6. Determine the plate thickness from the following: the critical plate width is based on the load spreading out at 45 degrees, shown in Fig. 15. This width is then equal to twice the distance from the bolt to
11、the critical section for each bolt, provided that the critical section does not intersect with the edge of the plate. The moment for a 1 in. strip, is then: Example 16 (LRFD Procedure): Design a base plate for axial dead and live loads of 21 and 39 kips, respec- tively, and dead and live load moment
12、s of 171 and 309 in.-kips, respectively. Bending is about the strong axis and the column depth is 8 in. The ratio of the concrete to plate area is 4.0. Fy for the plate and the anchor bolts is 36 ksi, and is 3 ksi. The moment from the bearing stress distribution governs, and the required plate thick
13、ness is then: 3. Assume 14 x 14 in. plate. The effective eccentricity is e = 700/88 = 7.95 in., which is greater than half the plate width. Thus an anchor bolt is required. It is assumed at 1.5 in. from the plate edge. Design Aid for Plates with Large Eccentricities: Maitra (1978,1978a) has develope
14、d a graphical solution for the case with anchor bolts that eliminates the need to solve for A and T using the previous equations. It can be applied to either ASD or LRFD design. The procedure follows: ASD Procedure: 4. From the graph in Fig. 16, determine the value of and then calculate A. If the va
15、lue of A is reasonable, go to the next step. Otherwise, return to step 2 and try a new plate size. 5. From the graph, determine the value of Then get the anchor bolt force from the following: The moment based on the critical section on the anchor bolt side is determined as follows. The full plate wi
16、dth is not always available. It is assumed that 23 This is reasonable for the bar sizes available. 6. The critical section is at (14 - 0.95 x 8)/2 = 3.2 in. The moment, for a 1 in. strip, determined from the bearing stress distribution in Fig. 14 with 3.06 for 2.1 ksi, 1.14 for .78 ksi and 21.2 kips
17、 for T is: 1. Determine the maximum allowable bearing stress: 2. Assume a plate size, N x B 3. Calculate This is reasonable when compared to N which is 12.5 in. and then: 6. Determine the thickness as before. Example 17 (ASD Procedure): Use the Maitras graphi- cal solution to solve the previous ASD
18、problem, with an P = 60 kips, M = 480 in.-kips, the column depth d= 8 in., Fy = 36 ksi, and = 3 ksi. 1. Fp = 2.1 ksi. 2. Assume a 14 x 14 in. plate. 3. = 480 + (60 x 5.5) = 810 in.-kips Rev. 3/1/03 Rev. 3/1/03 Rev. 3/1/03 in-kips 10.6 5.3 1.24 in. APPENDIX B - SOME PRACTICAL ASPECTS OF COLUMN BASE S
19、ELECTION DAVID T. RICKER David T. Richer is Vice President, Engineering, The Berlin Steel Construction Company, Inc., Berlin, Connecticut. The following three methods can be used effectively to prepare a landing site for the erection of a column: 1. Leveling plates (see Fig. 1). 2. Leveling nuts (se
20、e Fig. 2). 3. Preset base plates (see Figs. 3 and 4) LEVELING PLATES For small- to medium-sized base plates, say up to 22 in., the use of leveling plates is probably the most effective method to prepare for column erection. The leveling plates are usually in. thick and are sheared to the same size a
21、s the base plates. Sometimes the leveling plates are made about 1 in. larger in each direction than the base plate, but this is not necessary. It is not necessary to remove the edge burr left by the shear. Shearing may cause the plate to curl and if so the plate should be flattened to within standar
22、d plate flatness tolerances. The holes in the leveling plates are usually made in. larger than the anchor bolt diameter, but this is not a firm figure and may vary among fabricators. Leveling plates are sent to the field in advance of the main column and grouted in place, usually by the general cont
23、ractor or foundation subcontractor. Since this work is done in advance it permits time for an accuracy check. Once set, plates are relatively tamper proof. If a leveling plate is found to be Fig. 1 Column Base with leveling plates 43 out of level or at the wrong elevation, it is easily removed, the
24、grout broken up and cleaned away, and the leveling process repeated correctly. When a column is first “stood-up“ and the hook let go, there is a short period of time when it must stand alone before being tied in with beams or guy cables. During this interval the column may be subject to wind loads;
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