Jump to content
  • Welcome to SEFP!


    Welcome to our community forums, full of great discussions about Structural Engineering. Please register to become a part of our thriving group or login if you are already registered.

Recommended Posts

Hi, can someone advice me about time history analysis, when we should use response spectrum and when to use a time history analysis

whether it depend on the building height? the building seismic design category or?

I'm very appreciete if someone willing to advice


Share this post

Link to post
Share on other sites

Dear Eko,

These are different analysis techniques, simplest is LSA (linear static analysis) which is normally used for simple/low rise building. When there are sophisticated structures having irregular masses or varying story heights or very high seismic area  advance analysis are required to get the more accurate and realistic results which may not be predicted with LSA like plastic hinges . Advance analysis like THA need time and expertise which might not be suitable for simple structures but for high rise and important structures THA may be used. If you need specifically for a project, share the details, i or any other senior may respond more precisely.


Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Our picks

    • *SEFP Consistent Design*<br style="color:#272a34">*Pile Design*<br style="color:#272a34">*Doc No: 10-00-CD-0005*<br style="color:#272a34">*Date: Nov 21, 2017*<br style="color:#272a34">

      This article is intended to cover design of piles using Ultimate Limit State (ULS) method. The use of ULS method is fairly new for geotechnical design (last decade). The method is being used in multiple countries now (Canada, Australia etc). The following items shall be discussed:


      Geotechnical Design of Piles (Compression Loads, Tension Loads and Lateral Loads)

      Structural Design of Piles (Covering both Concrete and Steel)

      Connection of Pile with the foundation (Covering both Concrete and Steel)

      Pile Group Settlement

      Things to consider


      1. Overview

      Piles provide a suitable load path to transfer super-structure loads to foundation where shallow foundation are not suitable - this can be due to a number of reasons like existing space constraints or suitable soil strata is not present immediately below structure. Other uses can be to meet design requirements like to have reduced settlement etc.

      This article shall cover the use of straight shaft cast-in-place concrete piles and straight shaft driven steel pipe piles. There are a number of additional piles types like belled concrete piles, precast concrete piles, screw / helical steel piles etc but the discussion to choose a suitable pile type is not in the intended scope of this article. The article is intended  to discuss design requirements for straight shaft piles only (both concrete and steel) . The aforementioned topic about pile selection is a very diverse subject and requires a separate discussion on its own.

      Click on the link to read the full article.
      • 9 replies
    • I am suppose to design a pile foundation for a machine weighing approximately 50 tons and with an operational loading of 100 tons. 
      I ll appreciate your help in terms of guidance & provision of notes...  
      Thank you..
      • 36 replies
    • Material behavior can be idealized as consisting of an 'elastic' domain and a 'plastic' domain. For almost 200 years, structural design has been
      based on an elastic theory which assumes that structures display a linear response throughout their loading history, ignoring the post-yielding
      stage of behavior. Current design practice for reinforced concrete structures is a curious blend of elastic analysis to compute forces and moments, plasticity theory to proportion cross-sections for the moment and axial, load, and empirical mumbo-jumbo to proportion members for shear.


      From the book "Design of Concrete Structures with Stress Fields" by A. Muttoni,  J. Schwartz and  B.Thurliman.

      • 0 replies
    • Dear Fellow Researchers, Academicians, and research students,


      NED University of Engineering & Technology in collaboration with Institution of Engineers Pakistan (IEP) is organizing 9th International Civil Engineering Conference (ICEC 2017) on December 22-23, 2017 at Karachi, Pakistan.

       The congress details are available at its website www.neduet.edu.pk/icec

       Also attached is congress flyer for information and dissemination among your peers.

       Abstracts submission deadline has been extended till October 31, 2017.

      Please click on the link to see the full description.
      • 0 replies
    • AoA all,

      Is it mandatory to do column concreting upto the soffit of the beam in a single pour ?

      What code says about the construction/cold joint location in column ?

      Majority of the contractors are pouring the column concrete upto the soffit of the beam (full height of the column), some contractors leave the column height about 9" to 12" below the beam level and then fill this 9" to 12" column height with the beams & slab concreting. On one site column concreting was stopped at the mid height and the remaining half was filled on the next day.



      • 5 replies
    • AOA 

      i am facing problems in shear wall design .what are the pier and spandral ?what will be the difference when we assign pier or spandral? without assigning these the shear wall design is incomplete .

      i am taking about etabsv16

      someone have document about shear wall design plz provide it 

      thank you

      • 10 replies
    • Salam Members,

      Congratulations to Engineers, PEC has become full signatory of Washington Accord, what are the benefits to Pakistani engineers for this agreement. 




      • 3 replies
    • Please clarify the following confusions one by one:-


      1. If we run P-delta analysis in ETABS, then should we ignore stiffness property modifiers for beams and columns? I have heard that if we perform P-delta analysis and apply stiffness modifiers at the same time then the moment magnification process is doubled...?


      2. ETABS considers selenderness of a column by applying moment magnification factors. If we run P-delta analysis also, does it mean that the selenderness of column is being over-estimated? I mean once the moments are magnified in P-delta analysis process and again through moment magnification process?


      Please help me understand the software myth and clarify above confusions.
      • 1 reply
    • Assalam o alaikum.
      According to ACI 12.5.2,
      development length for fc' = 3000, fy=60000, for normal weight concrete and epoxy less reinforcement, The required development length comes out to be
      for #3 = 8.2 inch
      for #4 = 10.95 inch
      for #6 = 16.42 inch
      for #8 = 21.9 inch
      And if in my case, ACI 12.5.3 is not fulfilled, it means now i have to provide ldh as mentioned above. ldh is STRAIGHT EMBEDMENT LENGTH + RADIUS OF BEND + ONE BAR DIAMETER as shown in figure attached. Now my question is, if in my case, main reinforcement of beam is of #6 and #4, minimum column size required will be 18 inch and 12 inch respectively. Lets say by any means, i can not select #4, #3 bars and size of column where bars are to be terminated is 12 inch, how to fullfil this development length???
      • 11 replies
    • Dear all,

      I am trying to design shearwalls through ETABS with temperature load applied over shell. At various location, spandral section fails in Shear due to temperature and piers (sometime in shear, mostly in flexure).  (See Attached Image)

      Certainly all the problem in Shearwalls are due to temperature. I don't want to increase cross section of spandral or pier at some location just due to temperature load case as it will appears non-uniform with rest of the wall. 

      I have seen stiffness modifier affect distribution of forces and also rigid/semi rigid daiphragm assumption. 


      Can anybody guide how to properly design the shear wall with temperature load applied in ETABS or share any similar experience. Thanks in Advance.    
      • 15 replies
  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Uzma
      How can I transfer response spectrum loads from etabs to safe
    • By Eko Juwanto
      Hi, can someone advice me about time history analysis, when we should use response spectrum and when to use a time history analysis whether it depend on the building height? the building seismic design category or?
      I'm very appreciete if someone willing to advice
    • By Rana
      First of all my apologies, if my question seems stupid because of my unfamiliarity with the topic.
      When defining response spectrum load case in ETABS, we have three directions; u1, u2 and u3.
      Lets assume the excitation angle = 0 and building principle direction is u1
      So I will apply response spectrum function (per IBC 2006) in u1 direction by a scale factor.
      My question is why we don't apply u2 and u3 in the SAME LOAD CASE.
      My understanding is, according to WILSON in his book on STATIC & DYNAMIC ANALYSIS, CHAPTER 15. The response is calculated for each direction separately. Then this response is combined by different methods (CQC, SRSS etc) which is called MODEL COMBINATION.
      In CQC method response in 2 directions is assumed to be a portion of 1 direction means S2=a.S1
      Where a = 0 to 1.0, recommended value is 0.50 to 0.85
      I know in EQ building has only one principle direction. Although EQ can hit from any direction but there is always one major direction. or you can say major acceleration in 1 direction. Lets say u1.
      As in CQC method the response in other direction will be some portion of response in major direction. I also know that If we have equal spectra CQC is reduced to SRSS method which is independent from the excitation angle theta.
      My confusion is we will do MODAL COMBINATION (cqc or srss) only when we want to combine u1, u2 and u3 at the same time. But if we are applying only u1 in one response spectrum load case, then we DONT have to do modal combination. It is the same thing as in CQC S2=a. S1. Now in this case a=0. so S2=0. All we have is only response in u1 direction.
      Then in my building models what i do? include u1 and u2 both in one load case or in separate load cases?
    • By Alaa Masoud Abd EL-Rahman
      First , I am Very Happy to Participate in Forum Such As This Forum , I need to Make Engineering Discussion With These Questions
      1.       Why We Make Scale Factor Between Static And Dynamic Seismic Analysis ?
      2.       After Scale Factor We Design By Load Combinations Included Dynamic Cases Only
                Or Static Load Only Or Dynamic And Static ?
      3.       What is Diaphragm And What is Importance of Diaphragm In Seismic And Wind?
      4.       When We Define Diaphragm? And We Define As Rigid Or Semi Rigid And What is the Different Between Them?
      5.       Different Between Displacement And Drift Due to Seismic ?
      6.       Displacement Due to Seismic Results From Etabs We Multiply it X 0.70 X R ,Why And What About Drift ?
      7.       We Make 3 Cases For Each Case ( X AND Y ) in Static Analysis What About Dynamic Same Or Not
                Static Analysis
                Ex With + Eccentricity
                Ex With – Eccentricity
                Ey With + Eccentricity
                Ey With – Eccentricity
      8.       Why We Don't Combine Seismic And Wind in Load Combinations?
      9.       In Dynamic Analysis , Forces Cause Mode Shapes Or Mode Shapes Cause Forces?
      10.   Difference Between Response Spectrum ( Dynamic ) And Time History , Which Best?
      11.   What is the Effect of Seismic in Slabs And Beams?
      12.   Design Of Slabs And Beams By Load Combination Included Seismic Right Or Wrong?
      13.   After Finishing 3D Model , What are the Checks For Seismic?
      14.   Slab On Grade , I Put In Etabs Or Not ?
      15.   How Building Make Damping For Seismic ,What is Factors Damping Depend on?
      16.   Different Between Point Drift – Story Drift – Diaphragm Drift ?
    • By saleem khan
      Hello everyone, I hope all of you will be fine. In etabs when we apply Response Spectrum loading on a multistoried building with 2 basement floors. At what floor level this loading will be applied as in equivalent static seismic analysis, we can apply EQX & EQY on any floor we like as this option is available in etabs but the problem is with response spectrum and time history analysis. please if someone knows and have the experince, share it i shall be very thankful.  
    • By m_naeem_b
      I want to learn about the reponse spectrum function in ETABs,? what is this? How it applies? and why? also some other options in "define tab" in ETABs near with reponse spectrum function?
    • By waqar saleem
      i need some literature related to response fSpectrum Analysis, if anybody having plz share and if anybody have done this type of final year project plz guide!!! thanx
    • By Yasir Gul
      from where to specify in etabs 2015 whether our time history function is using velocity displacement or acceleration data file
    • By Ahmed Waqar
      Dear All
      If we doing response spectrum analysis as per UBC. do we need to lower our base shear because in UBC it is stated that direct result from spectrum shall be used to design for eerthquakes. If we do so then where is R value.
    • By Hasan Tariq
      Dear all ,
      Can any one tell me the difference between 
      Spectral Acceleration  / g
      Spectral Acceleration / PGA
      Are they mean same in the response spectrum .
      can any one explain e 
  • Recent Discussions

  • Latest Forum and Club Posts

    • I have a query , that in Flat slabs , as we have only supports in shape of columns,  where we may give overlaps of bottom mesh and top mesh ?  may it be showed through drawing please ?
    • Dear experienced fellows  After completing the model in Etabs, what's the next step for foundation design. What i have learnt is that: 1- Do we have to import the Edb file into SAFE? I didn't get this point of modelling foundation in Etabs coz i have learnt that foundation is modelled in SAFE only 2- we have to get the forces value i.e Factored axial loads and bi axial moments from reactions in ETABS and design foundation in SAFE accordingly? Thnx in anticipation
    • Dear sir. After completing the model in Etabs, what's the next step for foundation design. What i have learnt is that: 1- Do we have to import the Edb file into SAFE? I didn't get this point of modelling foundation in Etabs coz i have learnt that foundation is modelled in SAFE only 2- we have to get the forces value i.e Factored axial loads and bi axial moments from reactions in ETABS and design foundation in SAFE accordingly? Thnx in anticipation
    • There are three spring values we normally use in 3D structural analysis... kx, ky, and kz (being kz as vertical, and horizontal springs particularly against lateral loads) vertical springs are calculated as discussed above or as per geotechnical report... horizontal springs are calculated as half of vertical spring value Kx = Kz/2 Ky = Kz/2 I don't have any backup literature (for now)... one can dig the internet or consult a geotechnical engineer/company (this is mostly their expertise),... though I designed few structures some 20 years ago in SAP 90 (few structures in FJFC bin Qasim, Rousch power plant, Bestway cement Hattar) and till-to-date they are still standing and operating perfectly please post here... if anyone find some reference to that
    • Please see the following:   Thanks.  
    • For residential construction, basement walls act as propped cantilevers because of ground floor slab. You can model your wall as a propped cantilever and design for those forces. Also, check these topics out: The last post on the above linked thread has a solved example too. and this: Thanks.  
    • The only reference I know in this regard is ACI Detailing Manual. However, as a matter of doing structural design, you can bent bars up if you can show by analysis that the reinforcement configuration using bent bars would satisfy moment demand in the beam.  Thanks.
    • Hinges at both levels only can lead to the loss of gravity-load-carrying capacity.
    • I am designing a retaining wall (cantilever) for a basement. I have applied only 2 ft additional depth as surcharge load other than the earth pressure load. The height of the wall is 10 ft. My stability checks are satisfying for foundation width of 6.83 ft (2 ft heel, 9'' stem, 4 ft toe), which i think is very high. What can i do to reduce the dimension of my wall footing?
    • Thanks for your reply. Can u please help me in providing reference from codes for its detailing, as I have to use in one of my projects. Thanks.  

Important Information

By using this site, you agree to our Terms of Use and Guidelines.