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Building geometry concern
6

Building geometry concern

Building geometry concern

(OP)
Hi all,
please find the attached thread:
javascript:openindex(450,450,'http://www.tipmaster.com/includes/refinfo.cfm?w=45...)

Quote (BAretired)

There are no beams on gridlines D and E other than walls, acting as deep beams and shear walls combined.

Quote (BAretired)

The black object is hanging from the cantilevered wall above, which means that forms must be kept in place until the wall above cures.

So the black object is hanging from the cantilevered wall above, does this mean the cantilevered wall above (the dark green one) is acting as a hanger for the cantilever slab below (the cantilever slab at level +4.60) at the same time it acts as bearing wall supporting the cantilever slab resting on it (the cantilever slab at level +8.20)? If so, how it can be modeled in an FEA software?

RE: Building geometry concern

Section A-A shows the slab suspended from the cantilevered wall beam by means of hanger rods anchored in the concrete below the underside of slab. No need to model it in FEA software. The hanger rods are simply spaced as required to carry the slab reaction. There is no bending moment in the suspended part.

RE: Building geometry concern

(OP)

Quote:

Section A-A shows the slab suspended from the cantilevered wall beam by means of hanger rods anchored in the concrete below the underside of slab.
Thanks for your response.
This is my concern.

Can the cantilevered wall be a hanger (tension member) and a deep beam (compression member) at the same time?

RE: Building geometry concern

Why can't it do both?

Deep beams are and aren't compression members. And in this instance, it being a cantilevered deep beam, it would actually improve its ability to anchor the hanging reinforcing due to the compression in the zone right above the slab.

RE: Building geometry concern

Quote (hoshang)

Can the cantilevered wall be a hanger (tension member) and a deep beam (compression member) at the same time?

It can indeed, but the multi-colored wall beams in the picture above will be connected by vertical reinforcement, and must act as a shear wall, a bearing wall and a very deep cantilever, carrying the weight of five floor slabs and a roof in addition to lateral forces from wind and any seismic events which occur during the life of the structure.


RE: Building geometry concern

Quote (jayrod12)

You still have never actually told us why the 20% open area is a requirement. It doesn't make sense to many of us, and when we ask for clarification you just repeat yourself "20% open requirement". Why is that a requirement? What part of the code that you are designing around indicates that's a requirement? It seems extremely against most of our design codes to have just open air access between parking level and habitable space above. I do not believe the openings continue below Ground Floor. It would honestly be the first time I've ever seen it.

Hoshang indicated that the 20% open area is a municipal requirement but I do not know which municipality. It seems to me to be a very severe requirement, wasting large floor areas which could be more gainfully used. The intent is to get fresh air into the building instead of relying 100% on mechanical ventilation. I do not believe the ventilation openings continue below Ground Floor, but a substantial opening is required to move cars in and out of the Parking Floors. I would expect fire walls are required for the Car Lift.

Iraq does not have its own building code and I am not sure which code, if any, has been adopted.

RE: Building geometry concern

(OP)

Quote:

The black object is hanging from the cantilevered wall above, which means that forms must be kept in place until the wall above cures.

Quote:

the multi-colored wall beams in the picture above will be connected by vertical reinforcement, and must act as a shear wall, a bearing wall and a very deep cantilever, carrying the weight of five floor slabs and a roof in addition to lateral forces from wind and any seismic events which occur during the life of the structure.
My point is that:
Does that mean that forms (for slab at level +4.60) must be kept in place until the wall (between levels +4.60 and +8.20) only cures?
Or does that mean that forms (for slab at level +4.60) must be kept in place until all the walls above cures?

RE: Building geometry concern

@hoshang,

Forms must be kept in place until it is safe to remove them.

We cannot continue with this type of dialogue for the duration of the project. This is not a simple structural design and it is not the function of Eng-Tips to provide ongoing detailed advice about design of specific projects. The nature of your questions indicates to me that you are not capable of performing structural design in a reliable and competent manner. In the interests of safety of future tenants, you must retain a competent structural engineer to review what we have discussed to date, to work with the design team, and to see the project through to completion.

RE: Building geometry concern

Depends how you want to design the wall between 4.6 and 8.2. If it were me, I'd design it for the dead load applied by each of the subsequent pours above, a staged analysis to ensure the deflection stays within tolerance.

However, you could leave the formwork in place for all the pours. It would need to be designed accordingly, and I assume by the last couple wall pours it won't be doing anything as the wall stiffness will far exceed the formwork stiffness.

RE: Building geometry concern

(OP)
Hi all,
Sorry for not been clear.

Quote (hoshang)

My point is that:
Does that mean that forms (for slab at level +4.60) must be kept in place until the wall (between levels +4.60 and +8.20) only cures?
Or does that mean that forms (for slab at level +4.60) must be kept in place until all the walls above cures?

Quote (BAretired)

Forms must be kept in place until it is safe to remove them.
My intent is regarding this:
If forms (for slab at level +4.60) must be kept in place until the wall (between levels +4.60 and +8.20) only cures, then your SECTION A-A applies (vertical bars stop there), meaning this section A-A will be repeated at each floor. So, my thought is that the hanger force will go to the back span wall at each floor.

If forms (for slab at level +4.60) must be kept in place until all the walls above cures, then vertical bars must extend to the roof, and my thought is that the hanger force will go to the back span wall at the roof.
Is my thought reasonable?

RE: Building geometry concern

Quote (hoshang and BA)

If forms (for slab at level +4.60) must be kept in place until all the walls above cures, that seems extremely unlikely, but speed of construction is a factor to be considered then vertical bars must extend to the roof, and my thought is that the hanger force will go to the back span wall at the roof.
Is my thought reasonable? No, but the precise distribution of forces, moments and stress in the finished wall will never be known, particularly when wind or seismic forces occur. Some conservatism in design is warranted.

1. It is time to put aside the walls on Grids D and E and give some thought to the rest of the building. This is not the time to worry about stripping forms.
2. Do you have any information about soil conditions at the site? If so, what kind of foundations are you anticipating?
3. Have you considered downsizing the building due to inadequate parking?
4. With a Show Hall at Ground Floor, do you really need one at First Floor? If not, can you reduce the height of building by one story? That would be a significant cost reduction.
5. Do you have a detail for the Car Lift?
6. Lots more to come.



RE: Building geometry concern

(OP)

Quote (BAretired)

1. It is time to put aside the walls on Grids D and E and give some thought to the rest of the building. This is not the time to worry about stripping forms.
I don't worry about stripping forms.
Does the cantilever slab @ level +8.20 will be bearing on the wall in your section A-A?

RE: Building geometry concern

Cantilever slab is a misnomer. It is not a cantilever slab; it is a continuous one way slab supported by cantilevered beams. And yes, the Second Floor slab bears down on the green wall beam between First and Second Floor.

RE: Building geometry concern

(OP)

Quote (BAretired)

yes, the Second Floor slab bears down on the green wall beam between First and Second Floor.
You mean like this:

The load path would be such this:

The hanger force from the first floor and the bearing force from the second floor will induce an in-plane moment in the back span. Am I correct?

RE: Building geometry concern

Quote (hoshang)

Quote (BAretired)
yes, the Second Floor slab bears down on the green wall beam between First and Second Floor.

You mean like this:

Yes, except you have the top and bottom steel in the 2nd Floor slab reversed.
EDIT: Also, it may be prudent to extend hanger bars into the next tier, so that the double slab load could be shared by more beams.

Quote (hoshang)


The hanger force from the first floor and the bearing force from the second floor will induce an in-plane moment in the back span. Am I correct?

The First Floor hanger force and the Second Floor bearing force will induce a moment in both the cantilever and back span. Delete the term "in-plane".

RE: Building geometry concern

(OP)

Quote (BAretired)

EDIT: Also, it may be prudent to extend hanger bars into the next tier, so that the double slab load could be shared by more beams.
Can you elaborate more on this?

Quote (BAretired)

The First Floor hanger force and the Second Floor bearing force will induce a moment in both the cantilever and back span. Delete the term "in-plane".
If I understand it correctly, The First Floor hanger force and the Second Floor bearing force will induce an (out-of-plane) moment in both the cantilever and back span. Am I right?

RE: Building geometry concern

1. The lowest beam carries a double load, 1st and 2nd floor slab. The EOR may decide to extend the hangers into the tier above as a means of sharing that load with other beams.

2. No, you are not, as is evident from your question. The terms "in-plane" and "out-of-plane" are confusing and unnecessary. The direction of moment induced in the deep beam from gravity loads is evident without further description.

EDIT: I checked on the internet to find the meaning of "in-plane moment". According to one video, you were correct the first time. However, from my perspective, I still advise that you drop the term "in-plane" because it is confusing and unnecessary. It is not commonly used for a beam with gravity load acting on it.

RE: Building geometry concern

(OP)
Hi BAretired,
My mistake. I thought you were considering walls acting as hangers and bearing. So, your intent is using deep beams acting as hangers and bearing. If so, may I consider this approach:

RE: Building geometry concern

Hi hoshang,

  • Yes, that would work just fine. It saves a little concrete too, but forming the orange and blue cantilevers may be more trouble than it's worth. As EOR, it's your choice.
  • If the municipality requires enough parking for four residential floors plus two sales floors, some downsizing may be necessary. At present, parking accommodates only 10 cars, five on each floor below grade. We could eliminate the 1st Floor Show Hall and one level of residential space. That may not appeal to your client, but it may be a necessity.

RE: Building geometry concern

(OP)
Hi BAretired,
thanks for your response. Another question as in the image below (written as red text):

RE: Building geometry concern

hoshang, why the hell don't you answer my other question regarding downsizing? I am getting fed up with answering your questions about a building which will likely never be built.

RE: Building geometry concern

(OP)

Quote (BAretired)

hoshang, why the hell don't you answer my other question regarding downsizing?
This is the architect's task, not mine. He may downsize or add another basement floor.

Quote (BAretired)

I am getting fed up with answering your questions about a building which will likely never be built.
No, the building will be built. It's a time-consuming municipality agreement here.
Another question as in the image below (written as red text):

RE: Building geometry concern

Quote (hoshang)

This is the architect's task, not mine. He may downsize or add another basement floor.
Thank you. I thought you were the prime consultant. We will have to wait for his or her decision.

I consider the two short parts as wall, but after the building is completed, all parts will be tied together with reinforcement, so they will all act as wall. The long sections should be designed as deep beams, with adequate reinforcing into the back span, but the distinction between wall and beam loses significance when the work is completed to the top.

RE: Building geometry concern

"No, the building will be built. It's a time-consuming municipality agreement here."

We've pointed out "fatal" flaws in the design ("flaw" = failure to meet a requirement, as much as they've been explained to us).

The only way this building is getting built is if either ...
1) they change the requirements, give the building an exemption, or a different interpretation; or
2) they change the design (to satisfy the requirements, and also waste nearly all the time you've spent on it).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Building geometry concern

(OP)

Quote (BAretired)

I consider the two short parts as wall,

Quote (BAretired)

The long sections should be designed as deep beams, with adequate reinforcing into the back span,
So, I need to consider two stages of analysis:
1- before the building is completed to the top

Here, the the long sections (deep beams) are bearing on the short parts (walls). Here, I'd assume the deep beams as beams on elastic support, am I missing something?
2- after the building is completed to the top

RE: Building geometry concern

I don't believe you are missing anything.

RE: Building geometry concern

Apologies, but why do this ?
why have alternate short walls, which AISI forces each overhang to work in isolation ?
Why not have all the walls overhang and they'd work together, no?
What's happening on the different floorplans (to create alternating walls) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Building geometry concern

(OP)
Hi BAretired,
what's the difference between the two stages regarding load path?
Sorry for being late.
Other concerns:
How one can figure the support for the main stair knowing that it's recommended previously a wall on grid D and E?

RE: Building geometry concern

Just when I thought this thread might finally die, it comes limping back to life. On the positive side, if BA keeps going even I (a lowly site civil) might be able to design a building by the end of this!

#

RE: Building geometry concern

Quote (hoshang)

what's the difference between the two stages regarding load path?
I don't understand your question. Are there just two stages? It seems to me that the stress in the wall changes with each new floor added to the cantilevers. Depending on the sequence of form removal, it is possible to determine with some confidence, the most critical combination throughout the construction period. If in doubt, make it stout.

Quote (hoshang)

Other concerns:
How one can figure the support for the main stair knowing that it's recommended previously a wall on grid D and E?

Walls on Grids D and E are likely not the only supports for the main stair. Requirements for fire separation between floors may require a wall on Grid 2. The rectangle between stair flights is part of the 20% "open area", so it could have a bearing wall all around the opening. We have not talked about the material enclosing each of the "open areas".

Until you know the story height of each floor, the stair shape will change. Story heights shown today will change as design progresses, so stair support must wait until later. It is possible that stairs will be precast and moved into position by crane. None of this has been discussed to date.

It is time to address the floor and roof framing plans. The large span between Grid B and C will require careful consideration.



RE: Building geometry concern

(OP)

Quote (BAretired)

I don't understand your question. Are there just two stages? It seems to me that the stress in the wall changes with each new floor added to the cantilevers. Depending on the sequence of form removal, it is possible to determine with some confidence, the most critical combination throughout the construction period. If in doubt, make it stout.
I meant the stages mentioned in my post on 27 Apr 24 06:52.
1- before the building is completed to the top
Here, the the long sections (deep beams) are bearing on the short parts (walls). Here, I'd assume the deep beams as beams on elastic support,
I suppose the load path here would be such that:
Level +4.60 cantilever slab formwork is kept in place. The long section (deep beam) above 4.60 level is erected. Gravity loads from cantilever slab (bottom of deep beams) will be transferred to deep beams (long sections) in addition to deep beam's self-wight (if Level +4.60 cantilever slab formwork is removed after the deep beam gets the required strength). Run analysis. After level +8.20 floor is poured, the cantilever slab in this floor is supported by the deep beam between levels +4.60 and +8.20 and run analysis. My point: if one keeps Level +4.60 cantilever slab formwork after level +8.20 floor is poured and got required strength, one needs to perform analysis once rather than twice. and so on.
2- after the building is completed to the top
Here what will be different than stage 1?

Quote (BAretired)

Walls on Grids D and E are likely not the only supports for the main stair. Requirements for fire separation between floors may require a wall on Grid 2. The rectangle between stair flights is part of the 20% "open area", so it could have a bearing wall all around the opening. We have not talked about the material enclosing each of the "open areas".
The blue one can't be added since it would obstruct the corridor pathway.

RE: Building geometry concern

I don't know much about buildings, but if those red walls are the "only" structural thing holding that building up, well, that looks kinda "minimal".

The little orange squares are foundations, yes? These are just columns in the car park levels, and structural walls in the above ground floors ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Building geometry concern

  1. I think you have the idea.
  2. Wasn't talking about the blue one. I was talking about the rectangle with a cross half way between D and E. I interpret that to be part of the "20% open area". If so, it needs a wall around it. That wall could be a stair support if you wish. It would have to extend down to foundation level, which it does not do at this time. In any case, that is for you to sort out as EOR.

Quote (rb1957)

The little orange squares are foundations, yes?
The little orange rectangles, where shown, are columns. Foundations have not been shown yet. They will likely be either footings or piles.

RE: Building geometry concern

I was trying to find the minimum turning radius for a parking structure. If the plan view below is considered minimal, we don't have enough room to do a 180 degree turn from the Car-lift to the drive aisle, even after moving the two cars currently blocking the drive aisle to Grid A.

There needs to be some serious discussion with the Architect about parking. Adding another story below ground doesn't cut it.



RE: Building geometry concern

(OP)

Quote (BAretired)

Wasn't talking about the blue one. I was talking about the rectangle with a cross half way between D and E. I interpret that to be part of the "20% open area". If so, it needs a wall around it. That wall could be a stair support if you wish. It would have to extend down to foundation level, which it does not do at this time. In any case, that is for you to sort out as EOR.
If the wall between D and E could be a stair support, how should it be poured (knowing there exists two landings with five steps between them)? Or one should pour it once and extend dowels into the landings?

RE: Building geometry concern

Hoshang, you are the EOR,not I. You figure it out. If you can't, retain someone who can.

RE: Building geometry concern

(OP)

Quote (BAretired)

I think you have the idea.
I think you didn't answer my question on 3 May 24 12:33:

Quote (hoshang)

Here what will be different than stage 1?

RE: Building geometry concern

Nothing of any importance. What do you think will be different than Stage 1?

RE: Building geometry concern

(OP)

Quote (BAretired)

Nothing of any importance. What do you think will be different than Stage 1?
You mentioned this difference here:

Quote (BAretired)

I consider the two short parts as wall, but after the building is completed, all parts will be tied together with reinforcement, so they will all act as wall. The long sections should be designed as deep beams, with adequate reinforcing into the back span, but the distinction between wall and beam loses significance when the work is completed to the top.
So I'm looking for the difference.

RE: Building geometry concern

There is no difference. Stop making simple things complicated.

If I understand you correctly, you are saying Stage 1 is during construction and Stage 2 is after construction. I did not call them stage 1 and 2; you did.

Obviously, during the course of construction vertical wall reinforcement will be placed tying the wall sections together so that after construction, they will be adequately connected. That is true of any concrete wall with cold joints between subsequent pours.

You should be getting in touch with the architect and other consultants to make sure we are all on the same wavelength about parking, car-lift, open areas and story height.

Parking is completely up in the air and has been from the beginning. It appears that the architect is happy with cars overhanging drive lanes or parked in the middle of them. I am not and doubt that the authorities will be. It now appears that the turning radius for accessing the car-lift does not meet minimal requirements.

The Main Stair has more risers than the Secondary Stair. That needs to be changed.

Has the architect indicated what measures are required to ensure fire separation between floors at the car-lift location? What about the "open floor" locations?

Three meters is much more than required if flat plates are to be used on residential levels. I suspect it is also too much for the parking levels, although it is hard to say until we see the structural drawings for floor framing.

I question The need for a Show Hall on First Floor level. I suggest downsizing by removing the upper Show Hall and one level of residential space.

How are you proposing to frame the 2.85m cantilevers between Grid A and D?

These issues should be updated on the preliminary Architectural and non-existent Structural drawings, so that everyone is aware of the latest decisions without rummaging through reams of text. Perhaps the architect should be party to this thread.

RE: Building geometry concern

(OP)
Hi BAretired,
your help is highly appreciated.
Another concern.
Suppose one uses piles to support excavation. Can one use these piles as vertical force resisting members in the places of the columns since these columns should be located on property lines? If not, i.e., if one uses piles for excavation support only and uses columns on property lines for vertical loads, doesn't these piles reduce available bearing area for mat foundation?

RE: Building geometry concern

Quote (hoshang)

Another concern.
Suppose one uses piles to support excavation.

That is a major concern, and has to be carefully assessed as neighboring basements, if they exist at all, will not likely be as deep as yours. A geotechnical firm must be retained to determine soil properties as well as foundation types recommended.

Quote (hoshang)

Can one use these piles as vertical force resisting members in the places of the columns since these columns should be located on property lines? If not, i.e., if one uses piles for excavation support only and uses columns on property lines for vertical loads, doesn't these piles reduce available bearing area for mat foundation?

On the east and west sides, existing buildings extend to the property lines. It will be difficult to get equipment close enough to property lines to install piles. This issue is best discussed with piling contractors in the area. I do not have the answer to your question.

RE: Building geometry concern

5
man, this is a slow moving train wreck !

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Building geometry concern

(OP)
Hi BAretired,
Just for discussion, suppose existing buildings don't extend to the property line and one uses piles to support excavation. Can one use these piles as vertical force resisting members in the places of the columns since these columns should be located on property lines? If not, i.e., if one uses piles for excavation support only and uses columns on property lines for vertical loads, doesn't these piles reduce available bearing area for mat foundation?

RE: Building geometry concern

The site plan is shown below.

Buildings to the east and west extend to property line.
On the south border, two houses are believed to be set back from the property line.
The north border is skewed parallel to Main Street.

On the north and south sides, steel sheet piling will be needed to prevent collapse of soil beyond the site borders.

On the east and west borders, sheet piling, if used, would have to be placed tight against the existing buildings, which would be damaged by vibration from the pile driver. Moving sheet piling away from existing buildings or using secant piles may be possible, but that would reduce the footprint of the proposed parking levels, which is not an option.

There appears to be no easy solution to the problem. Others may wish to comment.

RE: Building geometry concern

Quote (hoshang)

Just for discussion, suppose existing buildings don't extend to the property line and one uses piles to support excavation. Can one use these piles as vertical force resisting members in the places of the columns since these columns should be located on property lines? If not, i.e., if one uses piles for excavation support only and uses columns on property lines for vertical loads, doesn't these piles reduce available bearing area for mat foundation?

If the existing buildings do not extend to property line, the East and West border could be supported using sheet piling, same as the North and South borders. Sheet piling would extend from Ground Floor down to Elev. -7.2 (or -10.8 if the Architect adds one parking floor).

The mat foundation would extend to the sheet piling. The foundation wall would bear at the edge of the mat and would need offset piles to carry the load from above.



RE: Building geometry concern

(OP)

Quote (BAretired)

On the east and west borders, sheet piling, if used, would have to be placed tight against the existing buildings, which would be damaged by vibration from the pile driver. Moving sheet piling away from existing buildings or using secant piles may be possible, but that would reduce the footprint of the proposed parking levels, which is not an option.
Using secant piles, can one use these secant piles as vertical force resisting members in the places of the columns since these columns should be located on property lines? If not, i.e., if one uses secant piles for excavation support only and uses columns on property lines for vertical loads, doesn't these secant piles reduce available bearing area for mat foundation?
Here, where I live, I found this is done frequently. Please find the images:

RE: Building geometry concern

Quote (hoshang and BA)

Using secant piles, can one use these secant piles as vertical force resisting members in the places of the columns since these columns should be located on property lines?

Okay, I see what you are suggesting. Yes, I believe that could be done, but you would have to leave clearance between the existing building and the secant piles to avoid damaging the building.

If not, i.e., if one uses secant piles for excavation support only and uses columns on property lines for vertical loads, doesn't these secant piles reduce available bearing area for mat foundation?

Well yes, they would reduce bearing area, but if each column load is being carried by piles, why would you need a mat foundation at all?

Here, where I live, I found this is done frequently. Please find the images:

That is interesting. Thanks for the photos. I have never used secant piles on a project. I see no reason why the secant piles could not be used for vertical loads as well as lateral support for the neighbor's soil provided they are drilled deep enough to develop enough skin friction.

RE: Building geometry concern

(OP)

Quote (BAretired)

I see no reason why the secant piles could not be used for vertical loads as well as lateral support for the neighbor's soil provided they are drilled deep enough to develop enough skin friction.
If so, how (two) basement floor slabs and beams are supported on secant piles since secant piles are already poured up to ground level before (two) basement floor slabs are poured? Would one use shear friction concept for this?

RE: Building geometry concern

Of course not! The bottom floor is slab on grade, so does not need structural support. The upper parking level floor could rely on the pile at each column location (a temporary gap in the secant pile wall) to carry a floor beam. The secant piles carry their own weight plus the Ground Floor slab. Detailing to accommodate the upper parking level floor may require a little thought. That is why you get paid the big bucks!



RE: Building geometry concern

(OP)

Quote (BAretired)

The bottom floor is slab on grade, so does not need structural support. The upper parking level floor could rely on the pile at each column location (a temporary gap in the secant pile wall) to carry a floor beam. The secant piles carry their own weight plus the Ground Floor slab. Detailing to accommodate the upper parking level floor may require a little thought. That is why you get paid the big bucks!
Can you elaborate more on this:
The upper parking level floor could rely on the pile at each column location (a temporary gap in the secant pile wall) to carry a floor beam.
Also, what about the floor slab indicated in the image below:

RE: Building geometry concern

Quote (hoshang)

Using secant piles, can one use these secant piles as vertical force resisting members in the places of the columns since these columns should be located on property lines?

The answer is yes...secant piles can be used for resisting vertical loads in addition to supporting the neighbor's soil.

Quote (hoshang)

What about this floor slab? (P1 floor shown)

Well, what about it? Look at your own photos. Does that answer your question? Can you come up with a framing plan which supports that floor slab? Draw the framing plan for that floor. If you find that it cannot be done, forget about using secant piles.

RE: Building geometry concern

(OP)

Quote (BAretired)

The answer is yes...secant piles can be used for resisting vertical loads in addition to supporting the neighbor's soil.
If secant piles can be used for resisting vertical loads in addition to supporting the neighbor's soil, what about the floor slab indicated in the image below:

Can secant piles support this floor slab? If so, how do you recommend?

RE: Building geometry concern

I have never used secant piles. You should talk to a piling contractor.



Quote (hoshang)

Just for discussion, suppose existing buildings don't extend to the property line
Well, do they or don't they? Don't keep us in suspense. If the gap is large enough, I think it would be more economical to use sheet piles rather than secant or tangent piles.

RE: Building geometry concern

This appears to be the proposed building site in Erbil, Iraq.


The building on the left (east) extends all the way to the property line (see below). Using secant piles would reduce the usable floor area in levels P1 and P2 of the proposed building. Driving sheet piling close to the property line would damage the existing building.



RE: Building geometry concern

(OP)

Quote (BAretired)

So how do they do this?
What do you mean? I can't figure the query.

Quote (BAretired)

Can Floor P1 bear here?
How can Floor P1 bear on the back side of the image? On the piles?

Quote (BAretired)

What is this material?
Does it retain the soil?
This is the basement wall of the existing building.
I used a reduced axial stiffness at the bottom of the columns that are on the property line since these columns bear on small areas of the mat foundation. Am I right? Or should I consider flexural stiffness reduction of these columns?

RE: Building geometry concern

at least you have a full size model of the basement floors ... you can try parking in it. The image, with the cars parked on the vacant lot, already tells you a lot.

at least the road the building fronts onto isn't a main street, so backing out may not be as hazardous as first thought.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Building geometry concern

The architect's parking plan (20% opacity) was overlaid on the Google photo (see below). The white cars in the Google photo appear slightly larger than those in the parking plan, but the overlay gives a rough idea of the relationship of proposed to existing.

  • The car in the Car Lift cannot make a 180 degree turn in the space available, assuming a minimum outer turning radius of 7.77m, even if the cars between Grid 1 and 2 are moved to Grid A.
  • Above Ground Floor, Stair #2 extends east to Grid A. Below Ground Floor, Stair #2 must move to make room for the two cars adjacent to it.


  • RE: Building geometry concern

    Quote (hoshang, BA)

    This is the basement wall of the existing building. Okay, but in your case, there is no basement wall. The secant piles, if used, would be cantilevers 7.2m high.

    I used a reduced axial stiffness at the bottom of the columns that are on the property line since these columns bear on small areas of the mat foundation. The columns do not extend below Ground Floor and so far as I know, there will not be a mat foundation. Am I right? No! Or should I consider flexural stiffness reduction of these columns? That question makes absolutely no sense.

    We don't know how deep the existing footing is and we don't know how much load it is carrying from the two story building. That affects the lateral pressure on the piles. We know nothing about the type of soil the secant piles are intended to retain. If a soil report exists, I have not seen it.

    I do not believe that either sheet piling or secant piles are feasible on the east property line.

    I am not sure where the south property line should be. I may have assumed it too far north on the overlay.

    The parking arrangement is inadequate for the occupancy, even if it functioned perfectly, which it will not. The site is simply too small for the proposed structure.

    RE: Building geometry concern

    how about leasing some of those parking spots on the opposite side of the road ?

    "Hoffen wir mal, dass alles gut geht !"
    General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

    RE: Building geometry concern

    "appears to be the proposed building site in Erbil, Iraq."

    dee-amn!! how on earth did you sleuth that info ??

    "Hoffen wir mal, dass alles gut geht !"
    General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

    RE: Building geometry concern

    Quote (rb1957)

    how about leasing some of those parking spots on the opposite side of the road ?

    I like the idea, but would the authorities allow it? Many cities require sufficient parking to serve the occupancy within the same building.

    Quote (rb1957)

    "appears to be the proposed building site in Erbil, Iraq."

    dee-amn!! how on earth did you sleuth that info ??

    I looked on the architect's title block, then searched near the Gulan Tower in Erbil with Google Earth.

    RE: Building geometry concern

    (OP)

    Quote (hoshang)

    I used a reduced axial stiffness at the bottom of the columns that are on the property line since these columns bear on small areas of the mat foundation.
    Please find the attached image:

    I meant using reduced axial stiffness for the green labeled columns since these columns are on the property line and they bear on small area of the mat foundation.

    Quote (BAretired)

    The columns do not extend below Ground Floor and so far as I know, there will not be a mat foundation.
    Please find the attached image:

    RE: Building geometry concern

    Quote (hoshang)

    I used a reduced axial stiffness at the bottom of the columns that are on the property line since these columns bear on small areas of the mat foundation.

  • We are definitely not on the same wavelength.
  • The axial stiffness of the columns is not affected by what they bear on.
  • Secant piles should form a continuous foundation wall on Gridline A.
  • Columns on Gridline A start at Ground Floor and bear on a wall of secant piles.
  • Leaving gaps for columns could allow soil to slough into the excavation.
  • The type of soil is unknown, so we need a soil report.
  • A mat foundation makes no sense at all. It cannot extend under the secant piles because they must be placed first in order to retain the soil.


  • The following was printed in light green text on the image:

    Quote (hoshang)

    Column on property line bearing on small area of mat foundation.

  • This is not the concept shown on the architectural drawings.
  • Columns should bear on a wall, in this case a wall composed of secant piles continuous along Gridline A.
  • The proposed concept puts a large stress on the soil and a large shear and bending moment on the small nib projecting out of the mat. It is simply the wrong concept; do not use a mat.


  • RE: Building geometry concern

    In addition to having insufficient parking stalls, the car in the Car-lift cannot make a 180o turn in the space available. The black semicircle shown below is the minimum space required to make the turn. Good luck with that!

    The site is too small to accommodate the proposed building, even if it is downsized by one or two floors.

    RE: Building geometry concern

    (OP)

    Quote (BAretired)

    The axial stiffness of the columns is not affected by what they bear on.
    I know that The axial stiffness of the columns is not affected by what they bear on since k=AE/L.
    My intention is when one needs to find the bearing area for a single column footing,
    he uses this:
    A=p/q
    where p is axial load and
    and q is the allowable bearing pressure
    So I thought if I could reduce the axial stiffness of the columns, then it would attract smaller axial load and would need a smaller bearing area Since there would be a small area available for the columns on the property line.

    RE: Building geometry concern

    Quote (hoshang)

    So I thought if I could reduce the axial stiffness of the columns, then it would attract smaller axial load and would need a smaller bearing area Since there would be a small area available for the columns on the property line.



    I can't believe I'm still following these threads but I just can't look away.

    RE: Building geometry concern

    Quote (dold)

    I can't believe I'm still following these threads but I just can't look away.

    I think I have finally learned how to look away.

    RE: Building geometry concern

    "So I thought if I could reduce the axial stiffness of the columns, then it would attract smaller axial load and would need a smaller bearing area Since there would be a small area available for the columns on the property line."

    I think what you are saying (in a very clumsy way, but I think we have to remember your native language is almost certainly not English) is ...
    If I make all the columns the same area, then they are equally stiff, and react the same load;
    but if the columns have different areas, if the ones in the sides are 1/2 the area used previously (which would reduce the load they can support) then I'd have to increase the area (and the load reacted) for the other columns in order that I maintain the same overall load capacity.

    Now I don't know buildings this doesn't sound unreasonable (maintaining the total load capacity), but I'd've thought this is probably backwards ... you want the outer supports to be more effective (I'm picturing bending moments applied from seismic loads ??).

    "Hoffen wir mal, dass alles gut geht !"
    General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

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