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  1. Enrique2015

    Consider Upper Columns in Slab Design

    Traditional flat plate slab design (check any book) for example equivalent frame method , or ACI 318 Handbook. Always, accounts for columns above and below, the rotational stiffness of the node is different, which can affect punching shear checks. This makes sense, since usually form work are...
  2. Enrique2015

    etabs effective seismic weight

    Hello, So ETABS assumes that all elements tributary to the base have grounded mass (i.e not accounted for as seismic mass), so half of the weight of your walls and columns, and if you have any mats or slabs at ground floor, all that mass is neglected. Because of this seismic weight will always...
  3. Enrique2015

    Nodes in SAFE? Moment value at a particular point

    1)This seems to be detailing, i dont use it, but parameters could be wrong 2)You are looking at nodal stresses. Trying to figure out this from tables have not really practical application, and will be a hectic unnecessary task . Why dont you display stress contours, and locate maximum and...
  4. Enrique2015

    SAP2000 frame deflection issue

    One considers shear deformation (analysis) the other one doesn't, change shear stiffness on the beam to something high and see if results match. Also for some of the design post processors such as composite beam, CSI uses Moment area method to calculate deflections, not results from analysis...
  5. Enrique2015

    Dual Resisting Frame Analysis and Design in Etabs

    This depends of what type of dual system material etc. It can be done in one model, in a nut shell: 1) Run the model for 100% of seismic force and design your walls/braces 2)Run the model for 25% of your seismic (i.e a SF of 0.25 on your load case) loads and assign a small stiffness modifier to...
  6. Enrique2015

    Structural Steel Design Software - Opinions?

    Old timers use SAP2000 because was one of the first FEA programs and the first one form CSI. If you are going to be doing mostly buildings, use ETABS, SAFE and CSIxRevit. You should also consider price to own, perpetual license vs subscription etc. ETABS has various levels, so is not one size...
  7. Enrique2015

    Extent of software validation

    Any respectable software should include multiple verification examples for analysis and design capabilities, against book examples, theory, journals, design manuals ,etc. If they don't have dot use it! www.structuralapps.com www.Tilmanllc.com
  8. Enrique2015

    To couple or not to couple?

    You will only have to design the beam as a "seismic" coupled beam if you want to use this beam as part of your lateral system, otherwise you will size and design the beam as gravity only. Of course if you end up with a 50" deep beam (exaggerating) you will need to include it since even with...
  9. Enrique2015

    User Defined Wind Loads & Diaphragms

    Well some of these have been mentioned above 1) This should not be done with semi rigid diaphragm as is completely unrealistic assumption, the load will be lumped at the closest node in the floor, a lumped concentrated load only makes sense with rigid diaphragms, for a semi rigid, you should...
  10. Enrique2015

    Etabs dynamic analysis (more understanding)

    Well Not sure if it is "correct" but depending of irregularities definitely could be expected, equivalent static analysis and dynamic Response spectrum analysis can not be scaled with one factor for all dynamic quantities, for RSA each demand is combined using modal load combination rules, so...
  11. Enrique2015

    No EC8 in ETABS???

    EC 8 is considered in ETABS when perforating special seismic analysis for certain ductile elements. refer to below:
  12. Enrique2015

    Property Modifiers

    Modifiers will affect stiffness, hence everything in the model will be affected, by some degree. In most cases Modifiers in ETABS are used to try to somehow capture the effect of cracking in concrete structures. In SAFE you can do an explicit nonlinear cracking analysis so you don't need...
  13. Enrique2015

    Basement wall in etabs

    The frame idea is completely unrealistic, if you are assuming that below grade level all lateral forces will be transferred to surrounding soil foundation , then you can use lateral restraints at base. In many case or when you are designing in big cities , the city code does not allow to use...
  14. Enrique2015

    Structural Modeling in ETABS 9.7.4

    A wall in ETABS is simply a vertical shell, you can simply divide the wall in horizontal strips and assign an incremental surface load to each strip. This is an approximation and slightly conservative but OK for all practical purposes. New versions of ETABS offer distributed area loads so this...
  15. Enrique2015

    ETABS Pier Output

    When designing a composite piers (i.e C shape or L-shape, etc) the program internally divides the wall in legs , and torsion is decomposed into shear for ondividaiul legs (i.e Shear flow)The problem I find with EATBS, is that it has so many parameters and variables for preferences and overwrites...
  16. Enrique2015

    can long load bearing concrete shear wall be designed not to take lateral forces?

    This process is not uncommon, multiple consulting companies that I am familiar with in the NYC area use this approach, they prefer to do load take down for gravity loads and use a "lateral only" model for lateral loads. Also, please notice that the fact that you are using membrane elements...
  17. Enrique2015

    Earthquake Forces on Pile Foundations

    This question could have two parts, since it depends what are you designing, I am going to assume that you already have all your geotechnical data, and you are designing the number of piles, capacities, and pile cap , in other words foundation design. It's common in the industry and specified by...

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