Found this while browsing, I don't use design option from etabs so it's for those that use it. If in the same ETABS model a load combination is defined in two methods:
Load combination U1= 1.2DEAD+1.6LL , where DEAD is defined as a combination of SW+WALL+SDL
Load combination U2= 1.2SW+1.2WALL+1.2SDL+1.6LL (Loads are individually added)
Then the design results of a column in both the cases are different. Column capacity ratio exceeds the limit under load combination U2.
Design Using load combination U1 Design Using load combination U2
The difference can be attributed to the fact that U1 is a combination of a combination.
The minor axis bending moment is zero. So the minimum eccentricity moment is considered for both the load combos U1 and U2. In both cases the minimum eccentricity moment is 35.952 kN-m (M2,min). Then for the second order effect this moment is amplified by the Delta_ns factor. For the case of U1, this factor is 1.585. This leads to a design moment of 35.952 kN-m X 1.585 = 56.965 kN-m. For the case of U2, this factor is 3.145. This leads to a design moment of 35.952 kN-m X 4.145 = 113.070 kN-m.
Now the question arises, why the Delta_ns factor is different for cases U1 and U2 even though both have apparently the same original loading. U1 is a combo of combo. It has 1.2DEAD+1.6LL in it, where DEAD = Combo(SW+WALL+SDL). The DEAD consists of some permanent dead load and some superimposed dead load. On the other hand, U2=1.2(SW+WALL+SDL) + 1.6LL. The total moment diagrams and axial force diagram for U1 are the same as those for U2. However, for case U1 program cannot distinguish between the permanent dead load and superimposed load correctly. This causes the beta_d factors to be different for the two cases resulting in different EI and Pe values. Eventually the Delta_ns factors are different.
It is recommended to avoid using a combination of combinations for the purpose of design. While a combination of combinations is not a problem for enveloping analysis results, it is not appropriate for design. This is because some of the design parameters are invariably dependent on the type of loading and this information is lost when combos are used within a combination.
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Posted by: hessi - 09-21-2011, 07:04 AM - Forum: Archive
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Hi dudes!
I can't access to ACI papers. I really appreciate if you would prepare this papar for me.
1.Title: Slump Loss and Rheology of Superplasticized Mortar and Concrete With Different Polysaccharide Syrups
Author(s): G. Mantegazza and E. Alberti
Publication: Special Publication
Volume: 148
Pages: 105-120
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I find many of the threads here are very valuable.
Many of them includes many posts with long answers.
I think that considering a possibility of convenient printing option will be very helpful.
What I had in mind is a page with all posts in black and white and plain text or something similar.
Posted by: David90 - 09-21-2011, 05:09 AM - Forum: Archive
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Title: FEMA 276 "Applications of the NEHRP Guidelines for the Seismic Rehabilitation of Buildings"
Author & Publisher : FEMA
Language: English
Year: 1999
Plasticity of Metals: Experiments, Models, Computation
Author: E. Steck, R. Ritter, U. Peil, A. Ziegenbein | Size: 7.49 MB | Format:PDF | Publisher: Wiley-VCH | Year: 2001 | pages: 380 | ISBN: 3527277285
This is the final report, drawing its conclusions and results from many individual papers and co–workers at the Institute for Structural Analysis of the Technical University of Braunschweig.
It shows the correlation between energetic and mechanical quantities of face–centred cubic metals, cold worked and softened to different states.
Constitutive models for the plastic of metals are developed and the application of these models is presented.
The improvements achieved by this contribution cover the material functions, the shape of yield surfaces, and the consideration of distributed experimental data within the numerical analysis
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The book provides an elementary tutorial presentation on computational fluid dynamics (CFD), emphasizing the fundamentals and surveying a variety of solution techniques whose applications range from low speed incompressible flow to hypersonic flow. It is aimed at persons who have little or no experience in this field, both recent graduates as well as professional engineers, and will provide an insight to the philosophy and power of CFD, an understanding of the mathematical nature of the fluid dynamics equations, and a familiarity with various solution techniques. For the third edition the text has been revised and updated.
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The study of fluid dynamics is a central theme in modern applied mathematics. It is used to model a vast range of physical phenomena and plays a vital role in science and engineering. This textbook provides a clear introduction to both the theory and application of fluid dynamics that is suitable for all undergraduates coming to the subject for the first time. Students need only a basic knowledge of vector calculus, complex analysis, and simple methods of solving differential equations. Numerous exercises (with hints and answers) illustrate the main ideas and serve to organize the reader's understanding. The wide range of topics discussed include inviscid and viscous flows, waves in fluids, boundary layer flow, and instability in flows, along with historical information and many references to important experiments. This is a comprehensive and absorbing introduction to the mathematical study of fluid behavior.
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The importance of an integrated approach in urban design is becoming increasingly apparent. This book explains how to overcome related challenges in environmental design of urban buildings and offers guidance on the use of new materials and techniques and the integration of new philosophies. Supported by the EC's SAVE 13 programme, Environmental Design of Urban Buildings includes contributions from experts at the National and Kapodistrian University of Athens, Greece, the Hellenic Open University, Greece, Cambridge Architectural Research, UK and REHVA/University of Ljubljana, Slovenia. A free CD-ROM containing multi-media software tools and climatic data accompanies the book.
CONTENTS Environmental Urban Design
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