Aisc Design Guide 28
Selected bolt is also adequate. Check Horizontal Leg: Thus, tension strengths of the plate gross and net areas are adequate (per Chapter B, AISC Specification). Beam and Column Flange Net Areas Check Beam Flange:. Column Panel Zone Panel zone strength should be adequate, since the presence of a haunch bracket creates an enlarged panel zone (Section 7.1.8).
Continuity Plates Existing connection was not provided with continu- ity plates. Use AISC LRFD Part 10, 'Column Stiff- ening at FR and PR Moment Connections.' The local flange bending strength is: Thus, fracture of beam and column flange net area prevented (the web contribution is considered, Sec- tion 7.1.7). Column-Beam Moment Ratio (Section 4.3.3) Assume no weld fracture, and calculate like welded haunch.
Also, per Chapter K of the LRFD Specification, no continuity plates are required. 72 © 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher. Chapter 8 CONSIDERATIONS FOR PRACTICAL IMPLEMENTATION The selection of a particular connection modification scheme, the extent of work throughout the building lat- eral framing system, and its expected improvement to the seismic performance are critical decisions that are highly dependent upon the engineer's input on a rehabilitation project. The cost of the fabrication and erection work nec- essary to construct the structural details illustrated in this guide is usually only a small portion of the total cost of the rehabilitation work. Commonly, the costs associated with such related activities as the removal and restoration of collateral building finishes and services, tenant disrup- tion, and the exhaust of welding fumes (when required) are the dominant cost factors. These considerations can also be more important for practical implementation than those associated only with structural fabrication and erection for an individual connection. Several issues are discussed here which relate to the costs associated with modifying a WSMF.
Other factors, such as regional differences, seis- mic risk exposure, scheduling, and owner priorities, may impact the modification work. As noted in Chapter 1, the issue of whether or not to rehabilitate a building is not covered in this document. If the decision is made to modify an exiting WSMF build- ing, the question of whether to modify all, or only some, of the connections must also be addressed.
This aspect is not covered here either as it is viewed as a decision which must be answered on a case-by-case basis. Further information and guidance on these issues may be obtained from Interim Guidelines (FEMA 1995) and Advisory No. 1 (FEMA 1997). 8.1 Disruption or Relocation of Building Tenants The disruption to the normal activities in a building may be a significant consideration when selecting a modification strategy.
The following should be considered:. Will the building be occupied while the connection modifications are being made?. If the building is occupied, how much tenant disrup- tion can be tolerated? Must tenants be relocated or will only spaces near the modifications need to be vacated?. If access to the top beam flange is required, can the floors both above and below the work level be va- cated?.
Must work be done during periods of occupancy or could it be done during off-hours? 8.2 Removal and Restoration of Collateral Building Finishes Depending on the particular circumstances, the removal and restoration of collateral building finishes and services may be very costly.
In general, these costs would be simi- lar among the various modification strategies. However, the haunch and bolted bracket may pose interference problems which the RBS does not. Likewise, if access to the top flange of the beam is required, as in the case of the RBS and bolted bracket modifications, then additional costs would be likely. The following should be taken into consideration:. Is the ceiling or soffit finish around the connection re- movable or hard framed?.
Are there any partition walls occurring near the mod- ification which will be affected in order to gain access to the connection?. Do any sprinkler lateral lines pass within working dis- tance of the connection to be modified? If so, addi- tional requirements may be imposed in order to shut down the sprinklers so modifications can be made. If the connections to be modified are located on the exterior of the structure, does the exterior finish allow access to the connection without removal or, if the ex- terior finish must be removed, can it be replaced with- out being noticeably different?.
Removal and replacement of spray-on fireproofing must be considered. In older buildings, care must be taken to prevent the crumbling of the spray-on fire- proofing. The possible presence of asbestos also needs to be considered in older buildings. Do the mechanical ducts block access to the connec- tion?.
Is there historical value to the structure—must the ap- pearance be preserved? 8.3 Health and Safety of Workers and Tenants When buildings remain occupied during rehabilitation, the safety and comfort of the occupants need to be considered. In all instances, the safety of the workers is an important consideration. Listed below are a few of the relevant safety issues:. If the building tenants cannot be relocated and work must proceed during the night, will temporary modi- fications of the mechanical system have to be made in order to exhaust the fumes and bring in fresh air? 73 © 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher. If welding or cutting are required, is fire protection adequately addressed?. What protection to the building contents needs to be considered? 8.4 Other Issues There are a number of other issues which should also be considered in selecting modification strategy. Among them are: 74. Is the construction more suited to the use of bolted or welded repairs?.
Is noise a factor?. How will the new fittings be hoisted (by crane or ele- vator) and are there height or weight limitations?. How will the dismantled pieces be removed?. If partitions must be removed for access, are addi- tional security requirements necessary? © 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher. REFERENCES AISC (1997). Seismic Provisions for Structural Steel Buildings, American Institute of Steel Construction, Chicago, 1997. 'AISC Advisory Statement on Mechanical Properties Near the Fillet of Wide Flange Shapes and Interim Rec- ommendations; January 10, 1997,' Modern Steel Con- struction, Vol. 2, February 1997, p. 'AISC Initiates Research Into k Area Cracking,' Mod- ern Steel Construction, Vol.
9, September 1997, pp. LRFD Manual of Steel Construction, 2nd ed., Vol. I and II, AISC, Chicago, IL. Load and Resistance Factor Design Spec- ification for Structural Steel Buildings, December 1, 1993, American Institute of Steel Construction, Chicago. Guidelines for Cyclic Seismic Testing of Components of Steel Structures, Report No. ATC- 24, Applied Technology Council, Redwood City, Cali- fornia.
Structural Welding Code—Steel, AWS D1.1-94, American Welding Society, Miami, FL, 1996. Blodgett, O.W., Funderburk, R.S.
Aisc Design Guide 28 Download
And Miller, O.K. Fabricator's and Erectors' Guide to Welded Steel Con- struction, The James F. Lincoln Arc Welding Founda- tion, Cleveland, OH. Blodgett, O.W. 28.
Aisc Design Guide 28 Stability Design Of Steel Buildings
Scope: PURPOSE OF THIS DESIGN GUIDE With the 2005 AISC Specification for Structural Steel Buildings (AISC, 2005a), hereafter referred to as the AISC Specification, the state of the art was advanced to include three methods for stability design, including the introduction of a powerful new approach-the direct analysis method (DM). The DM is a practical alternative to the more traditional effective length method (ELM), which has been the basis of stability considerations in earlier editions of the AISC Specification, and continues to be permitted. In addition, the third method provided is a streamlined design procedure called the first-order analysis method (FOM), which is based upon the DM with a number of conservative simplifications. The primary purpose of this Design Guide is to discuss the application of each of the aforementioned three methods and to introduce the DM to practicing engineers.
The DM is permitted and referenced in Chapter C of the AISC Specification, and its procedural details are described in Appendix 7. As explained in Chapter C and in this Design Guide, the DM is required in cases where the second-order effects due to sidesway are significant.