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Reality check: In as much as we would like it to be, ETABS and other structural analysis and design software cannot cover EVERYTHING we have in mind. The Wind and the earthquake loads are applied perpendicular to the building axis. Non-sway Moment Magnification Factor (ns) is considered when the slenderness of a column predominantly depends on the gravity load effect. Computers & Structures Inc., 2003. If a column is slender, it will fail by buckling into the shape of a sine wave when the load reaches a particular value Pc, which is called the Euler buckling load or critical load that is given by the equation (2). Thesis, Department of Civil Engineering, Bangladesh University of Engineering and Technology. Main Menu @Badar (BAZ)@UmarMakhzumiKindly have a look. The 20' (6096 mm) column is very slender and requires a second order computer analysis. The columns original moments are then multiplied by the ns to get the moment required for the calculation of steel ratio. Reinforcement to be checked option is used when the designer inputs the number of rebars and the program will check if the inputted rebar is sufficient enough to carry such load. Click Here to join Eng-Tips and talk with other members! [Note: in v17.02 this warning message was sometimes erroneously given; this enhancement was a work-in-progress not intended to be visible in v17.02.]. From the above discussions and observations, it can be concluded that corner columns are most sensitive to become slender. The Initial P-Delta Analysis in ETAB-There are two ways to specify as follows 1 .Non-Iterative based on mass The load is computed automatically from the mass at each level as a story-by-story load upon the structure. It can be seen that the, is greater than 40.0 for three edge columns. The increase of dead and live load is directly influenced by this type of slenderness behavior. The. 3D view of sample ETABS model STEP 2: Declare the static load cases in x- and y-direction. What is the size of your aggregate; you could have a lot of shrinkage. So, if (klu/r)/(34-12M1/M2) is less than 1.0, then the column will not show any slenderness effect. Thanks SaeedHR. the displacement pattern suddenly increased hugely & then got normal . It can be seen that the kl/r is greater than 40.0 for three edge columns. The use of commercially available structural analysis and design software are increasing on a daily basis in design offices. Journal of Civil Engineering, The Institute of Engineers, Bangladesh (IEB), 25(2). According to Figure 2(a), the value of kl/r is greater or equals to 40 for six corner columns. delta ns factor in etabs - halosystemsinc.com As indicated intuitively by Figure 2, gravity loading will influence structural response under significant lateral displacement. It should be noted that ACI code (318-1999) is followed. EasyDeltaNS plugin for ETABS (FREE DOWNLOAD) engr.kristian 370 subscribers Subscribe 1K views 2 years ago EasyDeltaNS is a simple plugin for Etabs that easily extracts and locate columns with. For frames braced against side sway, k varies from 1/2 to 1, whereas for laterally unbraced frames, it varies from 1 to , depending on the degree of rotational restraint at both ends. Mix design is also attached. where Q is the stability index, is the total factored vertical load in the story, Vu is the total factored shear load in the story, lc is the height of the column measured center-to-center of the joints in the frame, and 0 is the first-order relative deflection between the top and the bottom of the story due to Vu. Scaling of Base Shear in ETABS Structural Calc an we release the edges of the beam so it wont transmit the shear and the moment to the column supporting the transfer beam ?? but there are 2 warehouse in the building at ground floor & 10th floor where the Live load of stacked materials are 450psf. Powered by Invision Community. On the other hand, when using Reinforcement to be Designed, the program will generate the area of rebar needed in that column for the designer to interpret into how many numbers of rebar required. Experimental and FE Analysis of Stiffness Steel I-Column with Slender Sections. Bangladesh National Building Code., 2006. Dobsin, R. A. Failure of Slender and Stocky Reinforced Concrete Column: Tests of Size Effect. ETABS uses a default value of 1 for effective length factors; you should revise the factor if you have stiffer beams. See section 10.10.6.5 and its commentary of ACI 318-08 which deals with minimum eccentricity of long columns. I don't know what the concrete object that has the cracking is. For P-delta effect its needed to divide columns to 3 sections at least. This method works best if you have a single rigid diaphragm at each . The Structural Importance Coefficient is taken as 1.00 for the earthquake analysis, and it is same as the wind load analysis. $0.00. The column that is longer or equal to 17.5' (5334 mm) is vulnerable due to the higher value of ns. The height of the basement column is 5' (128 mm). Inputs of optimization are transitional mass, rotational mass, length and width of structure and objects are period of first mode and (frequency of torsional mode/frequency of transitional mode). By using this site, you agree to our Terms of Use and Guidelines. Join your peers on the Internet's largest technical engineering professional community.It's easy to join and it's free. Thanks. For this study, the columns are checked for the 1.4DL+1.7LL load combination, since this load combination provides maximum gravity load on the structures. Just installed RAM SS 17.03 this morning and there still appear to be issues with this. Structural Concrete. https://www.sciencedirect.com/topics/engineering/plastic-shrinkage, Buy genuine ielts certificate online, we provide expert team to create great value for ielts. The column section for the 25'x25' (7620 mm x 7620 mm) slab panel is increased compared to the 20'x20' (6096 mm x 6096 mm) slab panel to keep the steel ratio in the tolerable limit. However, if the value is lower than 1.0, then it is taken as 1.0 considering the safety factor. The vertical extension of the buildings is now essential for Bangladesh due to deficiency of land, cost of property, and to accommodate a vast number of growing human population in small areas. If not, the ACI Code 10.11.4 provides two quantitative criteria for determining if a story is treated as non-sway or a sway frame. Corner columns are more sensitive to becoming slender in comparison to the edge and the inner columns. Figure 2(c) shows the kl/r for the inner columns. If a little leakage is OK, then you might consider a perimeter drainage system around the tank and sump pit . This secondary moment reduces the axial load carrying capacity of a slender column (Nilson, Darwin, & Dolan, 2003). Total 18 load cases are considered in the models. The clear cover of the concrete column is taken as 1.5" (38 mm). The structural models are developed considering a commercial building located in a moderate earthquake influence zone and occupancy. From comparing Figures 5(a) and (b) it is seen that value of the s varies from 1.0 to 1.18. Another question, when do u have a transfer beam supporting a column carrying many floors, can we release the edges of the beam so it wont transmit the shear and the moment to the column supporting the transfer beam ?? Figure 3(a) represents the ratio of, There is no straightforward procedure for designing a sway column considering Sway Moment Magnification Factor (, According to the ACI code, for compression members in the non-, According to the ACI code, for the compression member in a sway frames, the effect of slenderness may be neglected when the, The objective of this study is to understand the effects of column design inputs on the slenderness of RC columns for beam-, 1. For this reason, it is concluded that the inner column is not slender susceptible compared to the corner and the edge column. Version 8.0. In Figure 5(a) only one column ns value is higher than 1.0, but the (klu/r)/(34-12M1/M2) value is less than 1.0 for that column. However, the warning that I am getting seemsto indicate that this provision is checked(albeit incorrectly). Frames that do not have adequate bracing against lateral loads show excessive sway, which jeopardizes the stability of columns. Pile length is 40 times of pile least dimension . if it is sway according to 10.13.4 the magnified delta s*Ms is the same as end moment Ms and if you go back to 10.13.3 Steps used to compute a Non-Sway Moment Magnification Factor (ns) are shown in the equations (3) to (6), (3) (4) (5) (6) If leakage is a serious problem then a waterproof membrane is nearly always prescribed. The concept of diagnosing whether the existence of any slender column effects is imperative and should be considered before the actual slenderness effect calculation procedure is performed (Ferguson, Breen, & Jirsa, 1987). The Structural Period is intended from Method A that is described in the BNBC. Mix design is also attached. https://www.sciencedirect.com/topics/engineering/plastic-shrinkage, Buy genuine ielts certificate online, we provide expert team to create great value for ielts. Effects of Slenderness in Reinforced Concrete Column Design, M. Engg. Therefore, the columns which are neglected due to a lower value (i.e., less than 1.0) of ns must be considered carefully for the sway moment effect even if the value is low. According to the ACI code approach, the 17.5' (5334 mm) column should be considered as a slender column, but ETABS does not consider it as a slender column as ns value is lower than 1.0. As suggested in the ACI Commentary 10.11.4, a compression member can be assumed braced if it is located in a story in which the bracing elements (i.e., shear walls) have a stiffness that is substantial enough to limit lateral deflection to the extent that the column strength is not substantially affected. where Ec is the elastic modulus of the column and Ig is the effective moment of inertia of the girder, which is equal to 0.35Igross, where Igross is the gross moment of inertia of the girder, Pu is the ultimate load of the column, and Cm is a factor which is a function of the column moments. Experimental Study on P-, Mustafa, S. A. P-Delta Check in Etabs - YouTube C m Factor ns Factor s Factor K Factor Effective Length Unitless Unitless . Figure 4(b) is illustrated for the ns against the kl/r for the edge columns of the three panels. From the preceding description of ns, it was concluded that slenderness effect in the inner column is as important as it is for other two locations. El factor cm y el coeficiente Delta_ns los calcula el programa, mientras que el factor de longitud efectiva K siempre lo asume igual a 1. For this study, the critical load combination that is used to calculate s is 0.9DL-1.43EQy since it had the largest sway effect on the frame. EasyDeltaNS plugin for ETABS (FREE DOWNLOAD) - YouTube In one of the methods, it has been mentioned that if the Stability Index is less than 0.05, then the frame is considered as braced. Berkeley, California, USA. Considering k value as 1.0 is conservative for ns analysis because k value ranges from 0.5 to 1.0 in a non-sway frame. Close this window and log in. In a RC frame, columns are rigidly attached to girders and adjacent columns. Department of Civil Engineering and Construction, Bradley University, USA. Also the ns is increased by about 59.0% for the same increment in column height (17.5' to 20.0') for the 20'x20' (6096 mm x 6096 mm) slab panel and ns is increased by about 72.0% for the 25'x25' (7620 mm x 7620 mm) slab panel.
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