Etabs isolated column footing

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Does anyone practice the design philosophy that ensures the formation of plastic hinges at the bottom of the column, near the foundation, for isolated footing? BAZSir when you mentioned isolated foundations only, is there any specific item other than what Rana has described that you would were thinking. I don't have any idea about this topic other than that isolated foundations can rotate but don't know how that would be related to this discussions.

Taylor and R. And that "if" depends on the soil-structure interaction and the strength of the soil. If the above scenario is not feasible then you may proportion the footing to allow the rocking behavior so that energy may be dissipated provided footing rotation is in permissible limits, which will depend on the soil-rotation relationship. In that case, the foundation should be detailed for attaining necessary ductility levels.

These things are not discussed in the ACI code. I have not read these things in RCC books as well. Kudos BAZ. I found another thread on the forum where isolated foundation rotation was discussed. Yes, we can go a step ahead to non-linear design and soil structure interaction but usually thats not done. Please correct me if wrong, I think that all is done in weaker soils and high seismic zones, so I personally have not experienced this kind of analysis.

That is why I posted it. We assume that hinge will form if longitudinal reinforcement of vertical members can develop 1. The proportioning of foundation for the design seismic forces is not enough. The analysis is not limited to high seismic zones and it is also not limited to weaker soils.

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There is also another point in this discussion. The assumption of a fixed based for isolated foundations is not valid because these foundations are susceptible to rotation. If the foundation rotates then it is a pinned end and the only forces there would be shear and axial. The usual practice is to assume hinge for isolated foundations unless they are massive, and fixed for raft in analysis.

You need to be a member in order to leave a comment. Sign up for a new account in our community. It's easy! Already have an account? Sign in here. Fatima Khalid posted a topic in General DiscussionDecember 3, Palash Engr posted a topic in Concrete DesignJuly 26, Fatima Khalid posted a topic in Foundation DesignJuly 23, By MuhammadUsman Started 12 hours ago.

By Aye Min Khaing Started 16 hours ago. By hali Started Friday at AM. By Muhammad Munaf Started April 22, Foundation is one of the essential parts of the structure. Foundation is defined as that part of the structure that transfers the load from the structure constructed on it as well as its weight over a large area of soil in such a way that the amount does not exceed the ultimate bearing capacity of the soil and the settlement of the whole structure remains within a tolerable limit.

Foundation is the part of a structure on which the building stands.

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The solid ground on which the foundation rests is called the foundation bed. As we know that there are different types of soil, and the bearing capacity of the soil is different for each type of soil. So depending on the soil profile, size, and load of the structure, engineers chose different kinds of foundation.

The terms Shallow Foundation and Deep Foundation refer to the depth of the soil at which the foundation is placed. The main aspects of different types of foundation, along with their images, are given below.

As economic feasibility is one of the main factors in foundation type selection, it is also discussed briefly with each type of foundation. To know other factors that affect the range of foundation read: Factors Considered for Selection of Foundation. This is the most widely recognized and most straightforward type of foundation, as this is the most economical type of foundation. They are typically utilized for shallow establishments to convey and spread concentrated burdens caused, for instance, by pillars or columns.

They are generally used for ordinary buildings Generally up to five stories. Isolated footing type foundation comprises footing directly at the base of the segment.

Design of Isolated Footing using ETABS

This kind of foundation is free footings. Generally, every section has its footing. The footings might be rectangular, square, or roundabout. Isolated footings can comprise both reinforced or non-reinforced material. For the non-reinforced footing, however, the stature of the footing has to be more prominent to give the vital spreading of the load.

They should possibly be utilized when it is sure beyond a shadow of a doubt that no differing settlements will happen under the whole structure.

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Spread footings are inadmissible for the orientation of large loads. It is given to lessen the twisting minutes and shearing powers in their primary areas. The size of the footing can be roughly calculated by dividing the total load at the column base by the allowable bearing capacity of the soil. Wall footing is also known as continuous footing. This type of footing is used to distribute loads of structural or non- structural load-bearing walls to the ground in such a way that the load-bearing limit of the soil isn't outperformed.

Wall foundation runs along the direction of the wall. The width of the wall foundation is generally times the width of the wall.

The wall footing is a continuous slab strip along the length of the wall. Stone, brick, reinforced concrete, etc. The combined footing is very similar to the isolated footing. When the columns of the structure are closely placed, or the bearing capacity of the soil is low and their footing overlap each other, combined footing is provided.

The foundations which are made common to more than one column are called combined footings.Welcome to our community forums, full of great discussions about Structural Engineering.

etabs isolated column footing

Please register to become a part of our thriving group or login if you are already registered. For strip footing analysis in etabs, can we assign elastic beam Strip as shell element or not?? You need to be a member in order to leave a comment.

Sign up for a new account in our community. It's easy! Already have an account? Sign in here. Fatima Khalid posted a topic in General DiscussionDecember 3, Palash Engr posted a topic in Concrete DesignJuly 26, Fatima Khalid posted a topic in Foundation DesignJuly 23, By MuhammadUsman Started 12 hours ago.

By Aye Min Khaing Started 16 hours ago. By hali Started Friday at AM. By Muhammad Munaf Started April 22, By Ali Shan Started March By using this site, you agree to our Terms of Use and Guidelines. Software Issues Search In. Register or Sign In. Recommended Posts. Report post. Posted March 27, Share this post Link to post Share on other sites.

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etabs isolated column footing

Sign In Now. Go To Topic Listing. WHY DO WE CARE During an extreme seismic event, the code-based structure is expected to maintain its load-carrying capacity for gravity loads even after the structure deforms into inelastic range so that it does not pose any life safety hazard.Welcome to our community forums, full of great discussions about Structural Engineering.

Design of Isolated Footing using ETABS

Please register to become a part of our thriving group or login if you are already registered. They used to put same bars in top and bottom of footing. What can be the reason? In part of footing where there is positive pressure, the footing is in complete contact with soil and tension is in bottom side of footing.

But in part of footing where there is negative pressure the footing is no more in contact with ground. Either it is designed as it is and reduced contact area is used for calculations or it is made to become in contact with ground by help of over burden loads. In either case, the bending of footing is in such a way which causes tension of footing at top of foundation demanding top reinforcement in footing.

Mostly top reinforcement is less than bottom reinforcement but for simplicity, if it is not affecting economy much same reinforcement can also be used for top and bottom. Code says we can provide temperature based minimum steel either in one layer at center or at any face or we can divide total steel in two layers i. According to Zahid Ahmad Siddique Professor at UET Lahore in his book concrete structures mentions it is better to provide temperature steel in two layers if thickness of footing increases 18 inch.

I am not prefer to provide temperature reinforcement in foundation. Because foundation are under the soil and there is very minimal temperature variation isnide the soil.

But what about shrinkage specially when they are not yet backfilled. And what about the uplift issues? Sure for upliftit requires, yes the foundation which is not backfilled for longer period shrinkage can be provided. You need to be a member in order to leave a comment. Sign up for a new account in our community. It's easy! Already have an account? Sign in here. Fatima Khalid posted a topic in General DiscussionDecember 3, Palash Engr posted a topic in Concrete DesignJuly 26, Fatima Khalid posted a topic in Foundation DesignJuly 23, By MuhammadUsman Started 12 hours ago.

By Aye Min Khaing Started 16 hours ago. By hali Started Friday at AM. By Muhammad Munaf Started April 22, By Ali Shan Started March By using this site, you agree to our Terms of Use and Guidelines. Foundation Design Search In. Register or Sign In.

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Recommended Posts. Report post. Posted August 2, Share this post Link to post Share on other sites. When the foundation is in tension b. To counter shrinkage cracks Regards.

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Uplift will reverse moment diagram. Top reinforcement is needed in isolated footing majorly for two reasons.Log In. I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it. Thank you for helping keep Eng-Tips Forums free from inappropriate posts. The Eng-Tips staff will check this out and take appropriate action. Click Here to join Eng-Tips and talk with other members!

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Students Click Here. Related Projects. In structural analysis on CASAD software, there are two types of working systems, we keep column end node either fixed or pinned with the footing. If you are required to fix the column at the base to transfer the lateral load down to the foundation or to stiffen your structure, then you can design the footing to resist that moment, however if it is not required and you can get away with pinned bases, then you can design the footing for a pinned base with no moment on it theoretically this works however in practicality there is no such thing as a truly fixed or truly pinned connection.

This is entirely dependent on what you have decided for your structure. Obviously, if you are fixing the base, the base plate and footing will be larger than if you were just pinning the base so it will be more expensive in that department.

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As for safeness, if you follow the loads and design everything appropriately both options are equally safe in my opinion. If a beam is connected to it. The way I understand it. Am I correct?

etabs isolated column footing

There are a few ways of looking at this assuming I understand the question. I am assuming we are looking at a simple three member frame 2 columns and a beam.

There are a few options you have to restrain the frame laterally. The first would be to fix the rotation of the beam at the ends thus designing a moment connection of the beam to the column. The base will still be pinned at the foundation.Excel Sheets. July 28, A combined footing is also provided when the property line is so close to one column that a spread footing would be eccentrically loaded when kept entirely within the property line. Unknown July 29, at AM. Newer Post Older Post Home.

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Please register to become a part of our thriving group or login if you are already registered. If I provide pin support then sway of my building is 1. Some one in this forum replied to a thread I am unable to find the same thread that if soil is stiff then we can provide fix support other wise pin support for loose soil.

But I think it is upto our will then whether we provide fixed or hinged, sizes of our footings will become accordingly. In my case, building is in Quetta with BC 0. Suggest me please. Since we normally don't consider soil structure interaction in structural analysis, therefore I am quite certain that the statement quoted by you about choice of pin or fixed based on soil type is flawed.

Anyhow, for concrete columns unless special detailing is done at coulmn joints, they would always transfer moment that should be accounted in the design. Using fixed based would likely result in conservative design for structural members than using pinned base. The real response would stand somewhere inbetween a pin and fixed base.

As Umar said t he real response would stand somewhere in between a pin and fixed base, similarly extent of column fixity at base depends upon the rotational flexibility of foundation that depends on foundation stiffness and soil stiffness both.

In general it can be said that for rigid raft foundations,foundation supported on stiff piles or basement walls this rotational stiffness is high and one can confidently assume fixity of column at base. But in conditions of individual footing pads on deformable soil,foundation could have considerable rotational flexibility and consequently assumption of fixed column base could show a considerable variance with respect to distribution of column moments on bottom storey i.

Therefore, It is recommended to model the rotational stiffness of foundation rather than assuming fixity at base in cases of individual column pads on deformable soil to represent quite realistic partial fixity available at column base. This methodology can be seen in "Seismic design of reinforced concrete and masonary building by M.

Footing & Mat Foundation Modeling on Etabs

N Priestley" page Assuming that you are referring to the book by 'T. Paulay and M. Priestley, copyright by John Wiley and Sons', can you indicate exact reference to the chapter and article or example numberin which this methodology has been explained? I have myself tried to locate the content on your referred page in the above book, but was unable to find it.

I reviewed the book and found out that the footings are best modelled assuming a rotational spring with a stiffness of K f where:. Can you please help me in calculating the value of I f with an example? I don't know how to calculate it. You need to be a member in order to leave a comment.


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