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How to find roof stability of old building?
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udit_hiray
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PostPosted: Sun Oct 28, 2018 7:30 am    Post subject: How to find roof stability of old building? Reply with quote

Dear sir,
You can use ferroscanner by hilti to create a 2D image of the slab reinforcement.
https://www.hilti.in/measuring-systems/detection-systems/r41791
Regards,
Udit
On 28-Oct-2018 12:31 PM, "pramodkulkarni" <forum@sefindia.org (forum@sefindia.org)> wrote:[quote]            Firstly you can find the rebar dia & spacing with the help of NDT .Secondly you need not to check deflection as slab thickness is mostly governed by span to depth ratio & not by loading.
Thirdly solar panels are very light weight & in Railway we are directly laying it on AC sheet of platform covering .


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On 23-Oct-2018, at 11:27 AM, Ravikumar forum@sefindia.org (forum@sefindia.org))> wrote:


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kishore patil
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PostPosted: Sun Oct 28, 2018 2:30 pm    Post subject: How to find roof stability of old building? Reply with quote

Load of panel and supprting structures are very less compared to live load for which terrace is designed.(Generally 5Kn/sqmt) after fixing panel live load is sharply reduced that is for maintenance only. and need not to check.Even if to find out geometrical properties or bar details bar locater and with other instrumentation yo can find approx dia and spacing of bars
and last simply find out the weight of panel and supporting structure and you can check deflection with incremental loading.





On Sun, Oct 28, 2018 at 12:37 PM Abhishek Sharma <forum@sefindia.org (forum@sefindia.org)> wrote:

[quote]            Dear sir just check the column reinforcement and concrete, in short if you know the load carrying capacity of columns you can erect a steel structure to carry your additional load which transfer the load directly to the columns. So you don't need to calculate deflection neither of beams nor slabs

On Sat 27 Oct, 2018, 3:04 PM RAJEEVAN, forum@sefindia.org (forum@sefindia.org))> wrote:

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kansari
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PostPosted: Sun Oct 28, 2018 6:30 pm    Post subject: How to find roof stability of old building? Reply with quote

you can always assume minimum reinforcement must have been provided. With that consideration, calculate the deflection.

On Sat 27 Oct, 2018, 2:12 PM sktrisal, <forum@sefindia.org (forum@sefindia.org)> wrote:

[quote]            Find the load carrying capacity by an actual load test.Solar panel do not have much dead load but you have to secure them against wind load so the geographical location is important.the wind load effect in my view is most important.i have seen these panels being dragged and twisted by wind load
Sktrisal


On Fri, 26 Oct 2018, 15:38 Ravikumar, forum@sefindia.org (forum@sefindia.org))> wrote:

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Rudra Nevatia
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PostPosted: Mon Oct 29, 2018 3:30 am    Post subject: How to find roof stability of old building? Reply with quote

Careful Kishore ! It is not gravity loads but overturning and uplift due to wind that causes distress. Elevated solar mounts on rooftop aggravate this problem.

Regards
Rudra Nevatia


On Mon, Oct 29, 2018, 7:53 AM kishore patil <forum@sefindia.org (forum@sefindia.org)> wrote:

Quote:
Load of panel and supprting structures are very less compared to live load for which terrace is designed.(Generally 5Kn/sqmt) after fixing panel live load is sharply reduced that is for maintenance only. and need not to check.Even if to find out geometrical properties or bar details bar locater and with other instrumentation yo can find approx dia and spacing of bars
and last simply find out the weight of panel and supporting structure and you can check deflection with incremental loading.





On Sun, Oct 28, 2018 at 12:37 PM Abhishek Sharma <forum@sefindia.org (forum@sefindia.org) (forum@sefindia.org (forum@sefindia.org))> wrote:

Quote:
Dear sir just check the column reinforcement and concrete, in short if you know the load carrying capacity of columns you can erect a steel structure to carry your additional load which transfer the load directly to the columns. So you don't need to calculate deflection neither of beams nor slabs

On Sat 27 Oct, 2018, 3:04 PM RAJEEVAN, forum@sefindia.org (forum@sefindia.org) (forum@sefindia.org (forum@sefindia.org)))> wrote:

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sangeeta_wij
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PostPosted: Mon Oct 29, 2018 5:30 am    Post subject: How to find roof stability of old building? Reply with quote

Dear Ravi Kumar
It’s possible these days to determine steel reinforcement dia and spacing using a Ferro Scanner; if you don’t wish to use anything so elaborate, simply remove cover in a small portion and find out the dia and spacing. Although Solar Panel Loads may not be more than the permitted Live Load of 150 Kg/m2 on flat terraces, but the installation and it’s connection with the roof, will be governed more by Wind Loads and you will need to satisfy the safety / stability against wind(you will actually need to check if it’s giving you tension in supporting columns).
If it’s a Govt Project, be prepared to create a 3D model and use this opportunity to check if the building violates other safety provisions as well, as the seismic codes have substantially changed in the last year or more.




Best Regards
Sangeeta Wij
President,WISE India
Managing Partner
SD Engineering Consultants LLP
Vice President(North),Indian Association of Structural Engineers,
Fellow and Chartered Engineer, Institution of Engineers
H333 New Rajinder Nagar(Lower Ground Floor),
New Delhi-110060
Ph:9811776210;01145128530


From: kedar_kavathekar [mailto:forum@sefindia.org]
Sent: 27 October 2018 14:12
To: general@sefindia.org
Subject: [SEFI] Re: How to find roof stability of old building?



I think you can find deflection slab/s by Load Test Method. We have used this method to find out actual deflection in slabs by sampling method. We also don't have RCC details for the building.


On Fri, 26 Oct 2018 at 15:38, Ravikumar forum@sefindia.org (forum@sefindia.org))> wrote:
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Nandy
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PostPosted: Mon Oct 29, 2018 6:30 am    Post subject: How to find roof stability of old building? Reply with quote

Dear sir/madam, This isS. Priyankafrom India,Tamil Nadu, Chennai. I have completed B.E.Civil Engg from Anna university.I have got 5 yrs experience in design field. If any part time civil engineers work is there, kindly let me know the details.



Thanks & Regards,

S. Priyanka.
















On Mon, Oct 29, 2018 at 11:06 AM sangeeta_wij <forum@sefindia.org (forum@sefindia.org)> wrote:

Quote:
           Dear Ravi Kumar
It’s possible these days to determine steel reinforcement dia and spacing using a Ferro Scanner; if you don’t wish to use anything so elaborate, simply remove cover in a small portion and find out the dia and spacing. Although Solar Panel Loads may not be more than the permitted Live Load of 150 Kg/m2 on flat terraces, but the installation and it’s connection with the roof, will be governed more by Wind Loads and you will need to satisfy the safety / stability against wind(you will actually need to check if it’s giving you tension in supporting columns).
If it’s a Govt Project, be prepared to create a 3D model and use this opportunity to check if the building violates other safety provisions as well, as the seismic codes have substantially changed in the last year or more.




Best Regards
Sangeeta Wij
President,WISE India
Managing Partner
SD Engineering Consultants LLP
Vice President(North),Indian Association of Structural Engineers,
Fellow and Chartered Engineer, Institution of Engineers
H333 New Rajinder Nagar(Lower Ground Floor),
New Delhi-110060
Ph:9811776210;01145128530


From: kedar_kavathekar [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: 27 October 2018 14:12
To: general@sefindia.org (general@sefindia.org)
Subject: [SEFI] Re: How to find roof stability of old building?



I think you can find deflection slab/s by Load Test Method. We have used this method to find out actual deflection in slabs by sampling method. We also don't have RCC details for the building.


On Fri, 26 Oct 2018 at 15:38, Ravikumar forum@sefindia.org (forum@sefindia.org) (forum@sefindia.org (forum@sefindia.org)))> wrote:
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nmatia
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PostPosted: Mon Oct 29, 2018 9:12 am    Post subject: Re: How to find roof stability of old building? Reply with quote

without making the things too complicated what you can do is :

1. do the visual inspection of the building and find out if there is any crack in the existing structure. if not then
2. calculate the load intensity of the solar panels load/area occupied . if thatintensity is less then the live load then total load is not a problem for you in this case
3. if total load is ok with you then find out the slab moment for concentatred load you can use reyonds handbook for that now caalculate the total moment due to  dl of slab + moment due to concentrated load and comapre it with moment resisting capacity of the slab calculate the moment resitence of the slab first by using min rf in the slab . if it is ok then your slab is safe .
4. if slab is not workable due to min rf then open the slab by removing cover of slab from bottom and find out the dia and spacing of existing rf and calculate the moment carrying capacity using that rf .
5. even then it is not workable then provide a steel beam/ or concrete beam ( depending upon the condition)  on top of slab to support the solar panels .
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Arun Kelkar
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PostPosted: Mon Oct 29, 2018 10:30 am    Post subject: How to find roof stability of old building? Reply with quote

Without going deeper into the theoretical measurement of slab deflection I would suggest the following 2 safer methods:-
1. Provide 2 MS ( ISMB 200 or 250, suitably designed ) supporting beams at 1/3 span touching the slab bottom, supported and anchored on the slab supporting RCC beams. This will strengthen the slab for the additional load. Provide Epoxy paint to MS beams on Erection.
2. Remove the existing B.B.coba WP from the top of the slab carefully and replace theWP treatment by light wt. Polymer coatings overlaid by light wt. concrete screed.
I think now you need not worry further about Solar Panelloads on the terrace.


On Mon, Oct 29, 2018 at 11:06 AM sangeeta_wij <forum@sefindia.org (forum@sefindia.org)> wrote:

Quote:
           Dear Ravi Kumar
It’s possible these days to determine steel reinforcement dia and spacing using a Ferro Scanner; if you don’t wish to use anything so elaborate, simply remove cover in a small portion and find out the dia and spacing. Although Solar Panel Loads may not be more than the permitted Live Load of 150 Kg/m2 on flat terraces, but the installation and it’s connection with the roof, will be governed more by Wind Loads and you will need to satisfy the safety / stability against wind(you will actually need to check if it’s giving you tension in supporting columns).
If it’s a Govt Project, be prepared to create a 3D model and use this opportunity to check if the building violates other safety provisions as well, as the seismic codes have substantially changed in the last year or more.




Best Regards
Sangeeta Wij
President,WISE India
Managing Partner
SD Engineering Consultants LLP
Vice President(North),Indian Association of Structural Engineers,
Fellow and Chartered Engineer, Institution of Engineers
H333 New Rajinder Nagar(Lower Ground Floor),
New Delhi-110060
Ph:9811776210;01145128530


From: kedar_kavathekar [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: 27 October 2018 14:12
To: general@sefindia.org (general@sefindia.org)
Subject: [SEFI] Re: How to find roof stability of old building?



I think you can find deflection slab/s by Load Test Method. We have used this method to find out actual deflection in slabs by sampling method. We also don't have RCC details for the building.


On Fri, 26 Oct 2018 at 15:38, Ravikumar forum@sefindia.org (forum@sefindia.org) (forum@sefindia.org (forum@sefindia.org)))> wrote:
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shenoy
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PostPosted: Wed Nov 07, 2018 8:07 am    Post subject: Reply with quote

Hi Ravi Kumar,

I have been involved in certifying the Existing roof tops to accommodate Solar panels, as many organizations are into this due to various initiatives by the Governments.

There are To Steps to the solution of your problem.
1. Find out the Structural Demand of the Roof due to change in Loading (Type, Magnitude, Occurrence, Direction)- Demand
2. Check Whether the existing Roof can meet the demand- Capacity  
3. If the Capacity is more than the demand, The Roof is safe. Otherwise not.

While majority of the posts above have concentrated on the Step 2. I would like to deal with Step 1

Type of Load.

I shall Start with the Wind load. Because the Other types would depend on  this.
The Solar panel is generally inclined 12 Degrees to 20 Degrees , depends of which part of the Globe you are. The wind load acts on a structure always, perpendicular to the surface, Towards it or away from it. There are Coefficients known as External Pr Coefft and Int Pr Coefft, which depend on wind directions ,angle and degree of permeability of building.
These are
algebraically added , and act as
multiplying factors to the Design wind Pressure.

The Design wind pressure is obtained be as per IS 875 Part 3.
The based on the application of the wind load, for the most critical load combination, you need to calculate the support reaction. Most of the cases you would require holding down ballasts to keep the Solar Panel from flying/ dislocation. The are not small in size !

So It is not the weight of the panel which is the new addition, as most of the above posts indicate! The weight of hold down ballasts is much more than that, unless you choose to use anchors to fix the panels to the existing roof which most of the organizations do not allow...

Hence It is a wrong notion that the weight of the panel is much than the Imposed load on the roof, hence safe ! The Nature, type, magnitude and the directions are different. Do not go by only DL Magnitude  compared to Imposed load magnitude !

Now the Actual Dead Load and Imposed Load.
------


Rest in the next Post.... I need to attend a meeting now....Sorry....


I could not resist posting this since Ravikumar should not go ahead with certifying the buildings without proper analysis....


Dr. Premanand Shenoy
Roy & Shenoy
Mangalore.
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