Differential settlement of soil in two connected buildings of different mass
Differential settlement of soil in two connected buildings of different mass
(OP)
Hi,
I have two buildings of different mass that are connected together by foundation beams (at foundation level) and by beams (at storey level)
Its a reinforced concrete frame of only one storey. I know these are not big structures but do you think there would be any issue with differential settlement due to the difference in mass between the two buildings? Do you think its ok to connect them together as shown in the pictures?



I have two buildings of different mass that are connected together by foundation beams (at foundation level) and by beams (at storey level)
Its a reinforced concrete frame of only one storey. I know these are not big structures but do you think there would be any issue with differential settlement due to the difference in mass between the two buildings? Do you think its ok to connect them together as shown in the pictures?








RE: Differential settlement of soil in two connected buildings of different mass
I should be thinking in terms of kN/m2 and not the mass of the building as a whole right?
Therefore since both buildings have only one storey their load in kN/m2 is about the same therefore there shouldnt be a problem for differential settlement,
However if one of the buildings had 2 storeys then in that case there could be a problem with differential settlement.
RE: Differential settlement of soil in two connected buildings of different mass
Yes you are correct. It doesnt matter about mass. Only matters about what the increase in contact pressure that the soil "feels". The difference between one storey and two storey residential construction isnt that much and i woudlnt be worried about differential settlement between the two portions.
I would be more concerned with the ground conditions and if they are consistent across the site.
Have you any borehole info?
PS-it looks a very modern house design, are all the wall openings going to be glass?
RE: Differential settlement of soil in two connected buildings of different mass
I am a civil engineer and this is actually my first project, i have done the architectural design using a BIM software and now i am doing the structural design in order to produce construction drawings and reinforcement detailing.
Actually no i do not have any borehole info, thats another concern i have, here at my country they do not usually carry out site investigations through bore hole data when the project is only residential of 2 storeys. i dont really know why they do not carry out site investigations, the only thing they might do is to use a digger to dig a maximum of 2 meter hole to check the soil. But even this rarely happens, I think it could be the fact that the geology in my country is pretty well known.
However they do build a good base from good grade gravel of about 35cm thick for the foundation to sit on. They also build very strong foundations on all residential projects, They use 45-50cm thick raft foundation with foundations beams embedded within the raft foundation connecting all columns together....You cant possible get a stronger foundation design than this other than also adding piles underneath the foundation slab.
However I very well know that site investigation is the most important part of a project and could save a lot of money if done properly and will allow for issue to be discovered early in the design phase.
RE: Differential settlement of soil in two connected buildings of different mass
Do you know anything of what soils you can expect? Clays sands etc, groundwater in the area. Is it a flat site?
I should clarify, I did not mean a machine borehole, I meant a small MM hand auger borehole. However this may not be common practice for your area. As you have said, some money spent on geotech could save a lot of head aches down the line. What if you build over a peat layer or a layer of man made fill? The house will start settling pretty fast and the house owner will come looking for someones head.
If you have an experienced engineer that knows the geology and has experience in local soils then you may get away will him/her supervising the excavation of footings during construction. I would even recommend doing a trial pit off as there is still the unknown. Side note - remember to backfill the trail pit properly.
i would try gather as much information as you can, geology maps, do a walk over of the site/area. Have a look for any construction sites close to your site. You might be able see an excavation etc.
At the end of the day, i would be asking for two trial pits to 3m depth with some pocker penetrometers on the side walls. If the house owner says no then at least you have it as back up down the line (if you get it in email form).
Good luck.
RE: Differential settlement of soil in two connected buildings of different mass
If the ground is bad, well, then there's something to worry about! Nothing that can't be addressed in design; however.
f-d
ípapß gordo ainÆt no madre flaca!
RE: Differential settlement of soil in two connected buildings of different mass
On the contrary, BIM modelling saved me a lot of time when we had to change something on the design, basically once you have a 3D model of the
building and once you setup your drawing preferences all drawings (sections, plans, elevations, isometric) are automatically created, and the
best thing is that when you change something on the 3d model it's automatically reflected on all drawings. That is what i like most with BIM
software. However this is mostly for Architects
Also it helps me a lot with visualisation and understanding of the building, it also helps a lot with communicating ideas, but yes this is just a
residential project however once you learn how to use the software you become really fast pretty quickly. And of course I can also use the architectural
model to model the frame of the building to be used for structural analysis.
Regarding the site investigation, I will certainly ask for a trial pit of 3m deep, and i will certainly gather all the information i can,
I still have a lot of studying to do on the site investigation, and i will certainly come back with more questions, i just hope you are here to help.
Can you suggest a good accurate pocket penetrometer? I found this one from a simple google search but seems very cheap, what do you think?
https://www.globalgilson.com/pocket-penetrometer
RE: Differential settlement of soil in two connected buildings of different mass
a) assume everything settles uniformly and ignore any moment or shear at the beam connections
b) assume it does not settle uniformly and design so that moment and shear at the connections is handled by the beams
c) don't connect the two buildings and allow them to settle independantly
method c is probably the more common approach. the grade beams and story beams going across the ends of the patio / breezeway would typically be designed as a fence and not connected to either structure
RE: Differential settlement of soil in two connected buildings of different mass