Civil Engineering/Tie beams in isolated footings
I would to ask that in isloated footing what is the criterai of seclecting the size and reinforcemnet of tie beam.
and how the tie beam should connect with the footing with different thickness i mean that weather the top should be keep same or the bottom.
If you browsed my past Q & A, using appropriate keywords you will find the answers, such as:
Subject: Plinth/Tie beam
Date Asked: 2013-11-15 20:01:51
Date Answered: today
Sir. what is the importance of plinth beam , and what is the minimum storey number that plinth beam can be considered. thank you
A tie beam is only necessary if the ground conditions are poor so that individual pad foundations could have differential settlement, or if there is a wall that needs support between the pad foundations. There is no direct relation between numbers of storeys and the need for a tie beam- it depends more on ground conditions.
QUESTION: From my experience, beams joining footings or pile caps are strap beams. So they are also called plinth beams? And tie beams usually join neck columns. Please can you elaborate?
Strap beam is another name for tie beam. It depends on what you wish to achieve- if it is purely to support walls, then these beams can span between columns near the ground level. If you want them to stabilise bases, then they should be located either with their bottom surfaces or top surfaces in line with the tops of the bases, with rebar to connect both together as a fixed connection.
You just answered the following question:
Name: Abdul waheed
Subject: doubts regarding plinth beams
Question: Mr. Arshad khan Asslamalaikum
I am constructing a house in India and construction is going on I am giving some details below and my question is at the end of this page.
When we did excavation for foundation we found v. hard soil or some place rocks
Footings are below 3’ to 4’ inside ground.
Column sizes are 15’’x9’’ and distance in between columns are 13’ (maximum)
Built up area 1500sq.ft. and we got cellar + ground + Ist floor + 2nd floor.
Cellar height is 9’ and all other floor heights are 10’-6’’ including beam and the beam height is 12’’ and slab thickness is 4 ½’’.
And cellar floor is just for parking purpose no rooms no other walls in this floor.
The engineer from whome I took the design told me that plinth beam is not required in your case.
We are already on second floor level structural work Is going on it was necessary In to use plinth beam at ground level considering all above detail or it is good That we avoid plinth beams that engineer given me assurance of more than 100 Percent but still always feel uneasy that we did not used plinth beams so I would like to clear these things with you.
Second question is what is the basic function or usage of the plinth beam in small residential houses.
Hope to get answer from you thanks
Answer: Hi Abdul,
In principle plinth (or tie) beams between pads are only required if:
1. You expect differential settlement or rotation of individual pads (such as in poor ground conditions or big differences in applied pressures between adjacent pads.
2. You need the beams to support walls or floating ground floor slabs.
3. The foundations are at different levels- such as a building built on the side of a hill.
So, in your case, based on what you say, it appears that there is no need for them.
And many others too...........!!
If the bases bottoms are at the same level, place soffit of beam there. If the tops are at the same level, place the top of beams at that level.