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Re: Steel connection design[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: Steel connection design
- From: Abolhassan Astaneh-Asl <astaneh(--nospam--at)ce.berkeley.edu>
- Date: Fri, 20 Feb 2009 11:36:18 -0800
Dear Mr. Cabalero: I would also add the following publications which have design oriented information on connections:
1. Handbook of Structural Steel Connection Design and Details, by Akbar R. Tamboli, published by McGraw Hill. This is a more recent book relative to Omer Blodgett's and the AISC books recommended in other responses, which by the way I second their recommendations.2. Guide to Design Criteria for Bolted and Riveted Joints, Second Edition, by G.L. Kulak, J.W. Fisher and J.H.A. Struik, published by the AISC and freely available for download at: http://www.boltcouncil.org/files/2ndEditionGuide.pdf. This is a must-have for anyone who does bolt or rivet design or evaluation.
As for strength of the splice (in steel and composite structures) and what it should be, it depends on the type of structure and the loads the splice has to resist. Traditionally, in buildings, and even in current practice, splices that carry only gravity load are designed to resist the applied design forces and not for the capacity of the spliced members. For loads that involve wind, the situation is not very clear to me. In most cases i have seen for cases that involve combined wind and gravity , the designers still use the applied forces established by the analysis to design splices. In some important cases, the splices for wind+ gravity cases are designed for the capacity of the members connected as well. We have to remember that this decision is left to discretion of the structural engineer. For cases involving seismic, again depending of the type of the structural system and level of ductility demand one can decide to design the splices for either applied design forces or for the capacity of the members. If If ductility demand is high , say the R-factor (Response Modification Factor) is higher than 3.0, then it might be prudent to design splices for the capacity of the members. certainly if the lateral force resisting system is "special" such as Special Moment Resisting Frame or Special Concentrically Braced Frame, then the splices of the lateral force resisting system system should be designed for to develop capacity of the members spliced. Even the splices of collectors and primary gravity load carrying members such as columns, in my opinion , should be designed for capacity of the members since the actual seismic forces developed in the entire structure will be different than the simplistic Static Equivalent forces we use in force-based design. In bridges, the situation is different and is more stringent than buildings. Until 1940's AASHTO specifications required that the splices be designed to develop member capacities ( allowable strength of splice be greater than the allowable strength of the members). Since then the requirement has been watered down and the current AASHTO Specifications (2007) requires that splices be designed to the larger of 75% of the capacity or (Capacity+applied forces)/2 . These requirements are regardless of the nature of applied loads. If I had a choice , I would design all splices that are on the non-redundant load path to develop capacity of the members since in these cases, the failure of a splice and lack of a parallel redundant load path can result in partial or full progressive collapse. That catastrophe of course would be a very high price to pay for not using couple of hundreds or even couple of thousands of extra bolts in the structure that may not cost more than a 0.1% of the total cost! I am more of a follower of the late John Alexander Low Waddell(1854-1938) , one the greatest bridge engineers and structural engineers of all times who in his famous "Des Pontibus" book in 1898 has said: "The strength of a structure is measured by the strength of its weakest part". I don't want to make the splices to be the weakest part of my structure and determine the strength of the entire structure. Do you? Hope this is of some help. A. Astaneh-Asl, Ph.D., P.E.Professor and Consultant on structural and Earthquake Engineering and Protection of Structures against Blast and Impact
(www.ce.berkeley.edu/~astaneh), (www.astaneh.net) ===================================== Dear ListPlease advise me with a good reference material discussing steel connection design or related to steel connection design(i.e. code, books, pdf, sites or lectures).
Furthermore, on splice connection design, what do thing is the best design approach(force based design method or member capacity based design method). Using member capacity design, it may require huge number of bolts and a thicker plates especially if the member that is spliced is a huge size wide flange member. Please advise which is the correct approach.
Thank you in advance.Regards, David Francis C. Caballero Structural Engineer License No. 0103970 Professional Regulation Commission Manila, Philippines email: engrfrancis05(--nospam--at)yahoo.com CP#: +63917-981-8588
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