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Fourth day of Econf on IS 16700

 
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies. Thank Post    www.sefindia.org Forum Index -> E-conference on IS 16700 13th March to 18th March 2018
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sefi_admin
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PostPosted: Fri Mar 16, 2018 1:50 am    Post subject: Fourth day of Econf on IS 16700 Reply with quote

Dear All


Greetings! Welcome to the fourth day of the E-conference on "IS 16700- Criteria for Structural Safety of Tall Concrete Buildings". 


We hope you are having a good experience with  the Econference and are finding opportunities to participate in the discussion. There have been issues regarding delay in posting of mails and we regret the same. 


We will be discussing Sections 9 and 10 today. 


Section 9
Section 9 deals with Foundations. In this Code, separate factors of safety against  for unfactored (wind) loads and factored (earthquake) loads have been provided. Detailed and more rigorous specification for soil investigation including min number of boreholes and depth of boreholes have been provided. Min depth of foundation for different foundation types have been specified. 
A very important issue of soil modeling has been included. Use of soil-structure interaction, zoned spring constants is  required by this code. Foundation settlements have been specified. They have been relaxed, subject to a max. angular distortion ratio. 


Section 10 
For the first time in any structural code, there is a detailed discussion of non-structural elements. Most of the economic damage under  lateral load condition is not so much form structural damage as it is from the non-structural damage  or damage to “contents” of the building. 
This section introduced to the designer the Design strategy for Non-structural elements and provides design guidelines for the same. 


You can, needless to say, continue discussing earlier sections too.


Have a great day and  wishing you a very productive discussion on the relevant Section(s) of IS 16700!


Best regards,
Econference Moderators

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bsec
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PostPosted: Fri Mar 16, 2018 4:49 am    Post subject: Fourth day of Econf on IS 16700 Reply with quote

Dear All,

I have following observations / query in Clause 9 of the code :


a) Clause 9.2 should include bearing capacity as well, in addition to overturning and sliding.


b) Clause 9.3.1 (c) : It is not clarified whether the depth specified is from founding level or from ground level. The depth mentioned should be taken below the founding level (i,e. Raft bottom in case of raft foundation or pile bottom in case of pile foundation).


c) Clause 9.7.2 : Direction 'X' and 'Y' needs to be defined. Presumably these are horizontal axes in orthogonal direction. Further Seismic and Wind forces in vertical direction appears missing in this clause.


d) Clause 9.8.1 : Last sentence of this clause (i,e. "....angular distortion of raft not exceeding 1/500, and 50mm in rock") is not clear and requires clarification.


Best Wishes



Alok Bhowmick


On Fri, Mar 16, 2018 at 7:23 AM, sefi_admin <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear All


Greetings! Welcome to the fourth day of the E-conference on "IS 16700- Criteria for Structural Safety of Tall Concrete Buildings". 


We hope you are having a good experience with  the Econference and are finding opportunities to participate in the discussion. There have been issues regarding delay in posting of mails and we regret the same. 


We will be discussing Sections 9 and 10 today. 


Section 9
Section 9 deals with Foundations. In this Code, separate factors of safety against  for unfactored (wind) loads and factored (earthquake) loads have been provided. Detailed and more rigorous specification for soil investigation including min number of boreholes and depth of boreholes have been provided. Min depth of foundation for different foundation types have been specified. 
A very important issue of soil modeling has been included. Use of soil-structure interaction, zoned spring constants is  required by this code. Foundation settlements have been specified. They have been relaxed, subject to a max. angular distortion ratio. 


Section 10 
For the first time in any structural code, there is a detailed discussion of non-structural elements. Most of the economic damage under  lateral load condition is not so much form structural damage as it is from the non-structural damage  or damage to “contents†of the building. 
This section introduced to the designer the Design strategy for Non-structural elements and provides design guidelines for the same. 


You can, needless to say, continue discussing earlier sections too.


Have a great day and  wishing you a very productive discussion on the relevant Section(s) of IS 16700!


Best regards,
Econference Moderators
     



     



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bijoyav
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Joined: 13 Dec 2008
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PostPosted: Fri Mar 16, 2018 6:38 am    Post subject: Fourth day of Econf on IS 16700 Reply with quote

"NON STRUCTURAL ELEMENTS

10.1 DESIGN STRATEGY

NSEs shall be classified into three types depending on their
earthquake behavior, namely
1. Acceleration sensitive NSE
2. Deformation Sensitive NSE
3. Acceleration & Deformation sensitive NSE"

Now a days, it is a trend to have car lifts and bringing cars to
higher stories. Definitelythis will increase.

While considering mass of cars, this create a lot of confusion. To me,
cars become acceleration sensitive if hand brakes are on along with
gear. If it is in neutral gear, what would be its condition? If hand
brakes only? In first gear with out hand brakes? How to model this?

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pradeep joshiaaa
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PostPosted: Fri Mar 16, 2018 6:38 am    Post subject: Fourth day of Econf on IS 16700 Reply with quote

Dear All,

1. Clause 9.3.1- This clause is more applicable to uniform soil strata. But when Non Uniform or Structures Sensitive to Settlements & Heavy load is considered requires extensive subsurface knowledge and closer spacing of Boreholes and no. of boreholes requirement can increase from min 3. This should have  been  highlighted that requirement of min 3 borehole is specifically for uniform soil strata.


 ASCE- Unless Bedrock is encountered first , Boring should be carried to such Depths that the Net increase in soil stress under the weight of the structure is less than 10% of the Average load of the structure, or less than 5% of the effective overburden stress in the soil at that Depth , whichever is the lesser Depth. This was the better criteria for Bore Hole Depth. 


But 9.31. (c) - 1,5 Times of estimated width of foundation in soil is mentioned. Code should avoid simplification based on Rule of Thumb.


2. Clause 9.6- When Expansion joint is preferably  removed in Seismic Zones building . How the Behaviour of Large NTA slab behaviour will act in case of Seismic excitations and how to incorporate the Temp variation, creep & shrinkage are others aspect that need clarity from Code writers.


3.Clause 9.7.1- Till date no concrete procedure has been highlighted by the code for finding the Modulus of sub grade reaction. Zoned springs also called pseudo coupled method is never provided by in the Geo technical Reports because Structural engineers don't share column loads initially at  time of Geo technical reports are prepared.  This is more a practical challenge and practice procedure missing . 


 Pseudo coupled Method produced computed moments are 18-25 % higher then those determined from the Wrinkler method . Which to Follow code must define. 


Soil Structure interaction is mentioned but for buildings height more than 150 m , but what happens when soil structure becomes significantly important in buildings with height less than 150 m. Procedure for carrying out the soil structure interactions and caution for adopting such a process is also not highlighted. Soil structure interaction should be jointly done with Structural consultant & Geo-technical consultant knowledge and approval, because by performing the analysis there will be decrease in the Base shear, Lateral forces but may increase the lateral displacement in association with P-delta. Soil Structures procedures for Foundation Deformations, Inertia SSI effects, Kinematic SSI effect should have been mentioned.


4. Clause 9.8.1 - According to Richards - Seismic Forces can  reduce SBC of Shallow Foundation & can cause Excessive Settlement. My main concern is that Preference is always given to Seismic Design & Analysis of Superstructure but Geo tech is always neglected by Code writers & practising Structural consultants.  I have not seen a Soil Report till Date that has ever mentioned the  Seismic Settlement.  The max vertical Settlement of 125 mm in raft is mentioned but with a rider of angular distortion. This is highly Debatable as High value of Settlement will be more attractive for angular distortion , which can induce significant amount of moments in superstructure for which it is never Designed. Best should have been if the parameters suggested by European Committee for Standardisation of Differential Settlement Parameters have been incorporated. 


Code has mentioned some very good technical  vocabulary but there description is missing .  Problem arise that in the end code becomes like Bhagwat Gita that every body has his own interpretation and the main intent of Safe & economical Analysis & Design gets Confused. I request that Handbook like SP printed earlier should again be brought in practise . Code should avoid the confusion and enlightened the Designer with right & good Approach towards Safe &  Stronger INDIA.


Regards


Pradeep Joshi




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On Fri, Mar 16, 2018 at 10:20 AM, bsec <forum@sefindia.org (forum@sefindia.org)> wrote:
[quote]            Dear All,

I have following observations / query in Clause 9 of the code :


a) Clause 9.2 should include bearing capacity as well, in addition to overturning and sliding.


b) Clause 9.3.1 (c) : It is not clarified whether the depth specified is from founding level or from ground level. The depth mentioned should be taken below the founding level (i,e. Raft bottom in case of raft foundation or pile bottom in case of pile foundation).


c) Clause 9.7.2 : Direction 'X' and 'Y' needs to be defined. Presumably these are horizontal axes in orthogonal direction. Further Seismic and Wind forces in vertical direction appears missing in this clause.


d) Clause 9.8.1 : Last sentence of this clause (i,e. "....angular distortion of raft not exceeding 1/500, and 50mm in rock") is not clear and requires clarification.


Best Wishes



Alok Bhowmick


On Fri, Mar 16, 2018 at 7:23 AM, sefi_admin forum@sefindia.org (forum@sefindia.org))> wrote:
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