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sir, i have several issues wid result of my model.......it iz giving me a large deflection in x direction, i have few limitations in introducing shear walls , i appled few shear walls bt still rezlts are nt in permissible limits, and secondly i am getting a large %age rft in bottom column , and thn getting ony 1 % after 2nd story,,,,i am confused whether there is sum issue wid model or sth else, i have checked manually base reactions, and it also comes quite higher in center columns...why, i dont knw....kindly help me out ? sir i tried to upload my model bt getting above error.... G-15 NEW.EDB

Assalam u alaikum rana sir as u said that design manually so I made a simple frame structure and did it manually then I model it in etabs and compare the results and I was happy that most of them matched but there is some problem that for shorter beams my results are different as this is a single span so I did not solve it using ACI moments coefficients. First I solved it using direct formuals and also did it using Moment Distribution mtd but results are changed I want to know how these values came for shorter beam? and how software calculated this. as mine are different. And what I did that I first solve the slab then transfer its dead load and live load separately on the supporting long and short beams by tributory area then using ACI coefficient I solved the longer beams and results got matched but did not find way to solve the shorter beams so solved it using direct formulas nd other methods but results were change. Then from beams I transferred the loading and moments to colums and sloved the col also. E.g for end columns where longer and shorter beams is meetng I took the greater moment which was negative moment of longer beam and used it. For axial load I transferred the loading and multiplied it with half span of the beam in conection with that column. image and file is attached. Same for elevation B. its value is also change. The attached image is the values for Moment 3-3. If I use wl^2/8 for this shorter beam then Mmax is 12.62 kip ft. my calculated factored load per unit length is 1.01 k/ft for this shorter beam whhich is Shown above so If I select Moment 2-2 values then for this end column it shows the moment to be 12.24 close to my value. But here it shows totally change values. Similarly for center short beam where tributory area is doulbe then this. Solving it by wl^2/8 gives close value for moment to be transferd on the center column. As the negative moments from longer beams will be canceled out. thanks in advance edb file + imagel.rar

Kindly inform me few things about Etabs!. how we can check eccentricity of our bldg after analysis in etab? What is the purpose of base shear's calculation during design of RC struct.? WHat are the parameters we have to check after completing our design in Etabs?

Respected Members, what is the main purpose of property modifiers in defining farme sections in etabs and how we can relate them to theoretical knowledge??

Aslamualikum: I want to ask that, in ETABs, when we define slab, I put slab thickness same in MEMBRANE & BENDING, is it right or wrong? and what is difference b/w shell,membrane,plate and thick plate? and how and when we use these ? read out help topic in ETABs. But i could not understand.. Can anybody explain me in bit simplest way.?

Is it fine to have time history analysis project at under grad level?one of my friends suggested to choose some high rise buildings in islamabad nd perform time history analysis and comparison ?is it fine?

Creating ETABS Default.edb file Creating Default.edb file for ETABS When you start ETABS and click on New Model…, it asks to choose edb file, either default or custom. In this tutorial you will be able to create a default.edb file. The advantage for this option is, you can immediately start working on building the model instead of first defining the material and section properties. The choose.edb option is for selecting an ETABS file which is not default but you want to use parameters of the model used in other project. So, in this tutorial you are going to make a default edb file containing all the information, units and options in which you want to work and don’t want to waste your time every time you start a new model. We will work in SI units in this tutorial. 1-Start ETABS 3-Select kN-m from lower right corner units drop box. 4-Start a new model and when asked for edb file, Choose No, because at this time you are creating your first edb default file. 5-Select “Grid Only” option and press ok. No we will work menu by menu. So first one is file menu. FILE menu i-Print Setup Select your default printer and paper size. DEFINE menu Select your units to be N-mm i-Material Properties Select add new materials and define different concrete strengths you use commonly. For example Conc. 21: 21N/mm² compressive strength and 420N/mm² steel strength with 4700√f’c as modulus of Elasticity. Conc. 25, Conc. 30, Conc. 35, Conc. 40 etc. ii-Frame Sections Select the first section in the list then scroll to the bottom and while holding the Ctrl button select the last section in the list, then click on delete button. All frame sections except the last one will not be deleted. You can add new sections and once you have defined your section, you will be able to delete also this last undesired section. Add all the sections, you want to be in your project, for example rectangular, circular etc. Define as many sections as you can. Sometimes, you want to optimize your sections and want to increase say a beam’s depth by 50mm and check if it is passing or not. So first define the smallest section and then define all other sections with depth increment of 50mm (or 3 inches) keeping the width same. Once you have reached the limit for the depth of the members, say 1000mm then start defining the sections with width increment. This step is most time consuming, but as you do it, I bet it will be much time saving for your next models. If a beam say 250x300 is failing, you will not need to define another section say 250x400, rather you will just select it from the pre-defined sections and change the section to see if its passing or not and so on. You MUST concentrate hard on this step and on cover values and material of sections, because once you define the sections, it will be hard to catch the error in cover or depth or width values. For an example you can have your sections like this:- B-250x300 B-300x300 C-300x300 B-250x350 B-300x350 C-400X400 B-250x400 B-300x400 C-500X500 Note: Cover to rebar center is distance b/w edge of beam to centroid of reinforcement. I recommend you to use two layers of the main bars you use commonly for top and bottom reinforcement and #3 bars or (T10) bars for stirrups and 40mm cover. Remember when you use two layers, the distance b/w bars (vertically) should be larger of 25mm(1”) or main bar dia. For example for moderate height and size of buildings. You can 2 layers T-16 main T-10 stirrups so cover = depth – 40cover – 10stirrups – 16 (1layer of T016)-(25/2mm) for half of dist b/w bars. = depth – 80. iii-Wall/Slab/Deck Sections Define all your slab sections here. For example 2way150 (two way slab 150thick) 1way125(one way slab 125 thick) etc. Please select material for each section carefully. Membrane and bending thickness is same mostly. But if you have pre-cast slab with 75mm topping, your bending thickness will be 75mm and your membrane thickness will total thickness (slab+topping). If you have flat slab, select shell option, otherwise membrane option. For one way slab use special one way slab distribution option. SHELL: Transfers load to horizontal boundary elements (beams in two way slab with beams). MEMBRANE: Transfers load to boundary nodes (columns in flat slab). Slab load is distributed by 45 degree tributary area method. iv-Static Load Cases Define all your static load cases. To be simple, define Dead, Live, EQ and wind loads. Put dead load multiplier 1 in one of any dead load case. No need to put separate Self wt load case. Usually dead load cases are DL, WALLS,Finishes. For simplicity and for small projects, you can use only 1 case as DL (including all finishes, walls, self wt) etc and one LL. For earthquake loads, you must define four cases EQX1- X direction + Y Eccent. EQX2- X direction – Y Eccent. EQY1-Y direction + X Eccent. EQY2-Y direction – X Eccent. Eccentricity ratio should be 0.05(5%). These four directions are necessary for irregular buildings. If you have perfectly regular and symmetric building, you can use only one X and one Y direction. v-Special Seismic Load Data Select do not use special seismic load data and press ok. vi-Mass Source Select “From loads” option because we will not generally put additional masses inside our model and self weight is also being calculated with DL (self wt. multiplier is 1). So everything will calculated based on your given loads. Use 100%DL(all dead load not just self wt.) + 25%LL (see UBC-97 code). For light buildings you can use 100%DL + 15%LL. ANALYZE menu i-Set analysis options Unselect dynamic and P-Delta option, if you do not want to use these options. (UBC Equivalent Static Process, used in moderate size buildings.) If you run your model with dynamic option selected, you will not be able to see static seismic calculations in summary file, even if you remove dynamic option and run the model again. This is a bug in ETABS. So if you are sure that you will use STATIC process, remember to check dynamic option is unselected before running your model. OPTIONS menu i-Preferences>Concrete Frame Design Select your code. For ACI, ACI-02 is best. Select seismic design category. If you want to convert UBC Seismic zone to seismic category, refer to ACI table R1.1.9.1 in Chapter 1. Do not change pattern load factor. Utilization factor limit is the additional ETABS factor of safety. It’s not recommended to change this factor also. ii-Preferences>Reinforcement Bar Sizes Change to your needs and delete unnecessary bar data. iii-Preferences>Live Load Reduction Select your parameters. Usually no live load reduction is selected. And that’s it. You are done. You have successfully configured everything you needed for your next models. Now it’s the time to save it in proper location. Click Save As… in file menu and select the installation folder of ETABS, if there is already default.edb file, overwrite it, otherwise save as “Default.edb”. Now every time you start a new model and when asked to choose edb, just select the Default.edb button and you will find all the settings there.