HOW TO DO AREAMESH.pdf

3/11/13www.sefindia.org :: View topic - etab model checking www.sefindia.org STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI] Search Like Subscriptions Digest Preferences Profile FAQ 28k Send Memberlist Usergroups Register Security Tips Donate Log in Search Log in to check your private messages etab model checking Goto page 1, 2 Next www.sefindia.org Forum Index -> SEFI General Discussion View previous topic :: View next topic Author fazal_mahmud_siddique SEFI Me m be r Poste d: W e d O ct 24, 2012 10:58 pm Message Post subje ct: e tab m ode l che ck ing Respected SEFIAN, I am a fresher of ETABs. I am grateful to those experience sefian who has taken part their posting in numerous point. Lots have requested to get a example .EDB file for learning and gaining confidence.smilarly, I am suffering from some of same doubt. So, I have uploaded one .EDB and .$et file (both for static and response spectrum)for a G+5 RCC building having a lift and stair case and sloping roof. The building is taken identical for simplicity . It has a slopping roof at top floor in the rear end panel . I modeled it and analyzed both for static analysis and dynamic analysis (response spectrum). Both analysis file are same except static seismic load and response spectrum case. Esteemed sefian are requested to go through it and clear the point of my doubt. Joine d: 14 Jun 2011 Posts: 5 MODELING ASPECT: (i)stair case ( Waist slab is provided 150 mm thick , assigned as “WAIST” of thickness ½ x 150=75 mm as shell, remaining 75 mm is provided as dead load UDL)along with floor finish of 1.00KN/m2 i.e 0.075x25+1=2.875 kn/m2 because I want to consider the stiffness of waist slab for half thickness. (ii) Lift as wall of 200mm thick. Assigned as shell. (iii) Slopping roof portion. (same style as stair case slab) assigned as shell (iv) shear wall (Assignment of “Pier” and “spandrel”) (v) all other Hz floor slab assigned as “ membrane” of thickness 125 mm. ANALYSIS ASPECT: Meshing option: (i) stair case ( Meshing procedure) (ii) Lift shear wall (Meshing procedure) ( If my process is incorrect please brief so that can follow) (i) Slopping roof portion. (Meshing procedure) Doubt: 1. Meshing Area: I am meshing the area element as below Selected the Shell/AREA /Wall element to be meshed. Then gone to Assign >Shell/Area > Area object mesh option > Floor Meshing option: Checked Auto mesh object into structural element (under this head) Checked Mesh at Beam and other meshing line Checked Mesh at wall and ramp edge(if wall and ramp is there in the model,if not unchecked) Checked Mesh at visible grid Checked Further Sub divided oot mesh with max size of say 0.5 m (for finer meshing) Checked Ramp and Wall Meshing (if Ramp ,stair waist,Wall is in the Model)for sloping roof Checkd Sub divide into say 5 vertical and 8 horizontal (the ramp/waist was not meshed until it was done) www.sefindia.org/forum/viewtopic.php?t=13023 1/10 50 KN/m2 for roof slab (0.0. 2.3/11/13 www.1. (1. different viewed differently. “Txm” and “Tym” ( for in filled brick wall) www.2 *0. if it is to be performed how it can be done . all the response quantities (Member forces.more over it takes lot of time to extrude.and for above 3. where Ta is as per clause 7.75 KN/m2 on super roof or 1.sefindia.2 Reduced Live Load +. displacements. (1.30 or 0.2 DL + 1. Can user defined as per code” (in filled brick wall) 0.1. but what will be the real solution.2 DL + 1.00 .FL T 5 4 3 2 1 Base Reduction in % 10 20 30 40 50 50 50 Pattern Live Load: Pattern live load is not intended as it not done as per IS 456-2000.2 DL + 0.09H/√X for” EQX” And Tys= 0.org/forum/viewtopic.25 0r 0. Can we do this for live load reduction Going to Option Reduce live load/user defined and putting the table as below No. Also note down the Time period for “Modal analysis” for 1st Mode and 2nd Mode Ie.6 where Vb’ is less than VB. the design base shear (Vb’) shall be compared with a base shear (VB) calculated by using a fundamental period Ta. So the pattern live load factor is kept “0” Load combination: Given manually specially for Seismic loading i. I went through SEFI general discussion. story forces.e. story shears and base reactions) shall be multiplied by VB / Vb’ Can we do like this: First we run analysis by static seismic load by giving user defined time period (Fundamental period Txs= 0.09H/√Y for “EQY” and note down the storey shear for the EQX and EQY load cases.(according to categories of Live Load) Seismic (STATIC): Programme time period is used. In one pdf tutorial by CSi (old one) it was suggested that Select area object to be meshed then go to Edit then check the option Mesh Quads/Triangles into say 5 by say 8 Area Or by using check intersect at visible grid check point object in edge Check Intersect with selected line object ****Which one we should follow (1)step or (2) step In the second procedure shell (slab panel) was defragmented and become difficult to modify or select the slab panel .0 *LL1) .2 Seismic X or Y)= i. 0.php?t=13023 2/10 .50*LL3) I am not confirmed whether auto load combination does it or not.etab model checking 2. zoom etc. Live load reduction: live load reduction is kept off as I am not confident about it.e.2 Seismic X or Y)depending upon the categories of LL whether it is 0.00Kn/m2 (0. (1.e. 0.00KN or 3. Seismic (DYNAMIC): Response spectrum analysis gives much less result without enhancing it by proper scale factor: Scaling of dynamic base shear As per clause number 7. is the following procedure is correct.1.00/m2 (0.8.50 +.2 of IS 1893(Part 1) :2002 If we generate earthquake loads by response spectrum method.sefindia.60 +.org :: View topic . which one is preferable sir.09H/ √B can be used though all beams are not loaded by brick wall.2 Seismic X or Y) i.25*LL2). 2012 3:40 pm Post subje ct: R e : e tab m ode l che ck ing Ge ne ral Sponsor Dear Er Fazal.50 KN/m2 ……….zip 454.981=1. …… 0 --(1893.09H/√X or 0.75 KN/m2 and roof floor for (Live load >3. ( rather than Txs and Tys as it scales more than 2 times) Then we run analysis for response spectrum and noted the storey shear for it. www.00 Kn/m2) Remarks DEAD DEAD Wall(SIDL) AREA (SIDL) LIVE1 LIVE2 1.50 KN/m2) ………… -----.…… 0 --(1893- Response spectrum Functions for IS 1893-2002 Response spectrum Cases as U1= (spec1 ) = 0.sefindia. ----0 0 0 (for floor ( For roof (For 1 ( SUPER IMPOSED DEAD) ( SUPER IMPOSED DEAD) ( > 0.0 and super roof) LIVE3 (>3.php?t=13023 3/10 .981=1.0.981 (I*g/2R).506 in this model Please comment on the fundamental time period sir: (i) Tx= 0.075 *H0. Damping. If it is less than the static case then we enhabnce the scale (0.981 respectively. Machine slab of lift) EQX (in case of static analysis) ---2002) applied for (X +y eccent) EQY (in case of static analysis) ---2002) applied for (Y + X eccent) Note: TIME PERIOD : Programme Calculated.75.… REDUCIBLE LIVE REDUCIBLE LIVE REDUCIBLE LIVE QUAKE QUAKE (= 0.org/forum/viewtopic.561x.…… stair.sefindia.and direction for U1 and U2 ( generally it is observed that the Higher Time period is found in first mode along short direction of the building) Static Load Cases : (static analysis) Load DEAD SELF) Area Wall LIVE1 slab) LIVE2 Type Self wt multiplier -------DEAD auto lateral load -----……….1.981 and VBy ( response spec) / Vby (static case) *0.3/11/13 www.1.0/m2 for super roof live load 0.1.75 or First mode time period for modal analysis.zip Description: Filename: Filesize: rahul model.981) by VBx ( response spec) / Vbx (static case) *0.05 Mass Source (i) From Load option selected Multiplier 1 1 1 0.50 % for floor Live load of 2.0 -----.2 KB Download Downloaded: 236 Time(s) Back to top Jeet_mbm Poste d: Fri O ct 26.535x.etab model checking Can we take average time period Tx= ½(Txs +Txm ) and Ty= ½(Tys +Tym ) which will be used for “static analysis for base shear.00 % 0.75.25 % 0.981 (scale factor) CQC – Modal combination and SRSS –Directional combination. I have got U1 .org :: View topic .531 and U2-1.00 KN/m2) . as scale factor) and U2 (spec2)= 0. ………. And final analysis is done.50KN/m2 LIVE3 And Checked both option (i) Include lateral mass oly (ii)Lump lateral mass at storey levels rahul model. I observed when the floor horizontal slab are modeled assigning it as “ Membrane “ of Joine d: 14 Jun 2011 Posts: 5 www. In other word by your first method (through Assign menu) you are meshing a main object keeping your main object as intact. Regarding two methods of meshing.php?t=13023 4/10 . I would like to thank and my heartfelt gratitude to my respected Sir and reputed Sefian Mr. As per ETAB manual we should name a same Pier label to whole vertical wall along the Joine d: 26 Jan 2010 Posts: 31 Location: De lhi NC R height.sefindia. 4. To consider particular structure. For Time period of structure it would be advisable to follow user defined time period depending upon type of structure (With infill or without infill).Floors 1 2 3 4 5 6 7 5. advisable to make your own load combination.sefindia. 6. having very less infill walls. Hope you have found some suitable explanation for your doubts. In case of building with infill you will find that first mode time period is too high as compared to codel “Infill brick” formula. Instead of using different labels for each wall at storey level. Please explain you view is detail why you model waist slab as 75 mm shell instead of 150 mm as you already model that in actual inclined plane. Rahul Leslie who gave me the real boost up and valuable clarification and advice and trips regarding my quarries sparing his valuable time. It definitely encouraged and help me a lot towards learning of “etabs” Sir. Sir. The reason behind in your model you have not modeled infill walls and soil medium (flexibility) etc. 1. I am really happy and grateful for your kind valuable view and advice regarding my doubt in ETABS and pay my respect for checking the etab sample model.3/11/13 www. That will give you better understand at post analysis stage. Please explain you view is detail why you model waist slab as 75 mm shell instead of 150 mm as you already model that in actual inclined plane. 2. With Regards Jitendra Sharma Back to top fazal_mahmud_siddique SEFI Me m be r Poste d: Mon O ct 29. While in other method (Through Edit Menu) you are dividing the main object into smaller size objects. In general if your structure is regular and uniform then you will find approximately same time period as by codel “bare frame” formula and first mode time period. 3. Sir. In live load reduction—ETAB do that correctly. 8. I would like to discuss some of my observation as below 1. But it would be (order of floors )as following No. From my side it would be conservative to use “With infill” time period in such case. being a fresher of ETABs.org/forum/viewtopic. as infill structure or bare frame is again design engineer’s decision.etab model checking I appreciate you for your effort to model such building efficiently. I am forwarding herewith my views and request to comment and elaboration as below. I would say both these method are conceptually different but ultimately result is same. Make a correction in your user defined table Reduction in % 10 20 30 40 50 50 50 Which Pattern live load you are talking about ? In general cases ETAB do load combinations rightly as per IS code method. I will never forget his useful help to me.org :: View topic . 2012 10:56 pm Post subje ct: ETAB Mode l che ck ing Respected Sir. At the same time . 7. three quarters of the full design live load is on the adjacent panels only. It was my ignorance.L.Floors 1 2 3 4 5 6 7 Thank you very much Sir. Instead of using different labels for each wall at storey level. Sir.sefindia.5. Cl 3-1. Make a correction in your user defined table Reduction in % 10 20 30 40 50 50 50 (order of floors )as following No. Thank you very much Sir for your kind clarification regarding the two ways of meshing procedure. If I assign full thickness of sloping slab/waist slab it will give much lesser result. lesser reinforcement. But .4 In no case shall design moments be taken to be less than those occurring with full design live load on all panels. 4. I observed when the floor horizontal slab are modeled assigning it as “ Membrane “ of reqd. 2. To be in the conservative side I used “membrane” in case of Horizontal floor slab. When I assigned slab as “shell” it shows much lesser BM.). I did it experimentally. So I thought that at least the rigidity of half of actual thickness provided may be considered to get the desirable Moment .sefindia. I have cleared myself that Etabs does the live load reduction in Column (axial Force only) in Indian Code also.5. I am not also confirmed whether sloping roof/waist slab is transferring its load to the beam properly or not while meshing it in my way. a) b) maximum positive moment near mid span of a panel may be assumed to occur when and maximum negative moment in the slab at a support may be assumed to occur when three quarters of the full design live load is on the panel and on alternate panels. high reinforcement.3 when the Live Load (L. While in other method (Through Edit Menu) you are dividing the main object into smaller size objects. Please give your view and correct me Sir. thickness. I am grateful to you for your kind advice and making correction in this regard. I would say both these method are conceptually different but ultimately result is same. It was found that full load transferred to the beams which gives higher result for BM. Which Pattern live load you are talking about ? Sir. As I know sloping roof or slab cannot be assigned as “membrane” but as “Shell”.2.SF in the related beam . Regarding two methods of meshing. Larger moments will occur when some spans are loaded Figure below is showing a continuous beam with Loading Pattern www.org/forum/viewtopic.) exceeds 3/4 Dead Load (D. Sir. again 2 as floor/slab which support two numbers slabs above or 3rd.2. Perhaps this was because slabs pertaining rigidity. But I am not all confirmed whether my procedure is correct or incorrect . As per ETAB manual we should name a same Pier label to whole vertical wall along the height.SF and Reinforcement .e floor immediate beneath the roof slab or 2nd slab from Top for which reduction factor is taken 10%. 3. In other word by your first method (through Assign menu) you are meshing a main object keeping your main object as intact.etab model checking Sir.php?t=13023 5/10 . In live load reduction—ETAB do that correctly.org :: View topic . Hence. 4.L. Shear force. As per IS 456:2000 clause 31. slab from Top for which Reduction factor is taken 20%) and so on upto reduction factor 50% Please give an understanding and your valuable comments Sir.3/11/13 www. my doubt is whether No of stories upported as in the Table automatically understand 1 as (floor/slab which support 1 number slab above i. Accordingly. That means slab is not pertaining any rigidity to the frame. When a structure is uniformly loaded with Live Load relief will be provided for moments due to redistribution of moments amongst all the spans. Accordingly. com Etab model checking. I have not find any option of applying pressure of Linearly varying in Etabs Sir.org/forum/viewtopic. 6.Siddique Ji www. In case of building with infill you will find that first mode time period is too high as compared to codel “Infill brick” formula.php?t=13023 6/10 . That will give you better understand at post analysis stage. but conservatively. In general if your structure is regular and uniform then you will find approximately same time period as by codel “bare frame” formula and first mode time period. Whether pattern live load factor to be put as “0. I want to know. having very less infill walls.docx Description: Filename: Filesize: Etab model checking.M. does ETABS carryout analysis for Pattern Loads as per the instruction of the IS 456:2000 clause mentioned above . Thank you very much Sir.etab model checking So.sefindia. 5.sefindia.docx 20. How Earth pressure in case of Basement is applied in Etabs Sir. as infill structure or bare frame is again design engineer’s decision.M. 7. With Regards F. From my side it would be conservative to use “With infill” time period in such case. I will be highly grateful to you and obliged.3/11/13 www.org :: View topic . But it would be advisable to make your own load combination. To consider particular structure.Siddique Guwahati. Assam fazalarju@gmail. Thank you very much Sir.72 KB Download Downloaded: 152 Time(s) Back to top Jeet_mbm Poste d: Thu Nov 01. performed in the program automatically. The reason behind in your model you have not modeled infill walls and soil medium (flexibility) etc. F. In general cases ETAB do load combinations rightly as per IS code method. "The pattern loading is approximately. For Time period of structure it would be advisable to follow user defined time period depending upon type of structure (With infill or without infill).75” or “0” in etabs I have gone through the 'Concrete Frame Design Manual' that comes with ETABS and found a lines which I am not able to interpret. Please elaborate briefly so that I can follow Sir. 2012 10:37 am Post subje ct: R e : ETAB Mode l che ck ing Ge ne ral Sponsor Dear Er. I want to know one more thing Sir. Thank you very much Sir. plz find attached file www. With Regards Jitendra Sharma Retaining wall with Earthpressure EP.PLEASE POINT OUT. 2) No live load reduction is considered. As you know live load reduction is only done in vertical members. Give me some time. Don’t go with other consideration in attached model. I would say that your observation for shell and membrane is absolutely right. I am waiting for your kind reply regarding Pattern live load in Etab Moreover .org/forum/viewtopic. Live load reduction. Modeling of particular slab as shell or membrane shall be finalized at DBR stage itself. But I would say first go with full thickness of waist slab and check the behavior.Siddique Back to top Manoharbs_eq Ge ne ral Sponsor Poste d: Mon Nov 05. Thanks to SEFI. its only for your reference for Earth pressure EP).sefindia. Following are my observations 1) Building 1st mode is in torsion plz add some stiffness.zip Description: Filename: Filesize: Retaining wall with Earthpressure EP.org :: View topic .I request kindly to have a look particularly in the Lift portion ie shear wall. (Please see the attached model. Regarding ETAB.15 KB Download Downloaded: 181 Time(s) Back to top fazal_mahmud_siddique SEFI Me m be r Poste d: Sun Nov 04. I doubt something missing in the modelling and design particularly in the shear wall in my earlier model. which give much support reaction. 2012 10:49 pm Post subje ct: e tab m ode l che ck ing Sir. Hope I m able to address some of your issues.zip 51. We all are on same journey of learning. Joine d: 14 Jun 2011 Posts: 5 with regards F. I think this clears your doubt ! Pattern load . For example if we model particular slab as shell then one should ensure that proper load get transfer to respective beams by help of proper meshing. To apply this you have to mesh the retaining wall in vertical plane so that u can apply idealized pressure in that respective small shell element.M. We can request RAHUL JI for his understanding regarding this. Right now I have very limited understanding for patter load in ETAB. In ETAB if we say storey 2 column beams the columns which supports the storey 2 slab ( column between storey1 slab and storey2 slab).3/11/13 www. 2012 4:01 pm Post subje ct: Dear sir. Otherwise your approximation is also looks ok. For inclined shell members I have to check the behavior. It is matter of idealization (approx) in analysis. Earthpressure.sefindia.etab model checking Thank you very much for your kind words. In such journey role of good team is very important and we all should be thankful to SEFI Admin and SEFI Senior members to lead such dynamic team. which designer should agree/understand Joine d: 26 Jan 2010 Posts: 31 Location: De lhi NC R beforehand because these approximations affect overall chemistry between different structural members. I will reply on this in detail.php?t=13023 7/10 . I animated the modal under different mode.e2k text file because i have lower version of Etabs. can we provide Shear wall across that direction.M.sefindia. in analysis out put plz check the co-ordinates by then we can judge the direction where the stiffness to be added. Mode its movement (to and fro) seems somewhat straight way in the Y axis direction. 2012 10:19 am Post subje ct: sir another note it is preferable to have 3rd mode as torsion as far as possible.rar 80. www. but 1st mode shall not be. Does it reflect the occurrence of torsion in the building. torsion. But I am ignorant how to detect limiting torsion. Joine d: 17 O ct 2011 Posts: 37 Please send me . To give stiffness to the building in the direction of torsion takes place. 2012 9:52 pm Post subje ct: SEFI R e gulars Dear sir.e. I observed the torsional effect in the 1st. however it is advisable to reduce the eccentricity between center of mass and rigidity.sefindia.Siddique Guwahati Assam Back to top pujan73 Poste d: Tue Nov 06. (ii)Centre of Mass and centre of rigidity have also shown a considerable differences. In Y direction in case of my model or we can introduce other thing to give stiffness. With regards F. Rgds Manohar Back to top Manoharbs_eq Ge ne ral Sponsor Poste d: W e d Nov 07. But in 2nd.org :: View topic . 2012 10:18 am Post subje ct: Dear sir. Please give your valuable views in this regards.$et or .etab model checking rahul model.3/11/13 Joine d: 17 Jul 2012 Posts: 225 www. Is it the sole way to find out the torsional effect. please do check the dynamic mass participation ratio both x and y direction. Back to top Manoharbs_eq Ge ne ral Sponsor Poste d: W e d Nov 07.rar Description: Filename: Filesize: rahul model.org/forum/viewtopic. (i)Whether it can be found out as numerical output from show table. one small tip usually torsion can be controlled by adding shear walls at Joine d: 17 Jul 2012 Posts: 225 the outer boundary. First thing is it necessary to perform dynamic analysis? only then the modal analysis or ritz analysis is effective. Thank you very much for uploading the model showing correction for Live load reduction.44 KB Download Downloaded: 139 Time(s) Back to top fazal_mahmud_siddique SEFI Me m be r Poste d: Tue Nov 06. It seems not to move straight way (to and fro) in X axis direction but with some rotational movement.php?t=13023 8/10 . mode by Joine d: 14 Jun 2011 Posts: 5 eye estimation. 2012 9:37 pm Post subje ct: Etab Mode l che ck ing Dear Sir. Thanks. Your observation have taught me a new finding i. sefindia.709 people like Structural Engineering Forum of India.3/11/13 www. 2 Next SEFI General Discussion You cannot post ne w topics You cannot re ply to topics You cannot e dit your posts You cannot de le te your posts You cannot vote in polls You cannot attach file s You can download file s in in in in in in in this this this this this this this Go forum forum forum forum forum forum forum Translate topic Go © 2003.org Forum Index -> SEFI General Discussion Page 1 of 2 Jum p to: Translation: Goto page 1.etab model checking Joine d: 17 Jul 2012 Posts: 225 Back to top Display posts from pre vious: All Posts Oldest First Go All tim e s are GMT + 5.php?t=13023 9/10 .5 Hours www.org :: View topic .sefindia.org/forum/viewtopic. www.sefindia. 28. Indian Domain Registration Structural Engineering Forum of India Like Structural Engineering Forum of India shared Sanjeev Kumar's photo. 2008 SEFINDIA. etab model checking F acebook social plugin tsunami earthquake USA TODAY .Authorities say light Alaska earthquake felt in Anchorage.org :: View topic .sefindia.3/11/13 www.sefindia.php?t=13023 10/10 .Tsunami debris causing controversy in Haw aii Fox New s .org/forum/viewtopic. tow ns to the northw est powered by powered by www.