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CHAMPLAIN TOWER COLLAPSE : Early Observations & Implications- Primary Geotechnical Failure

 
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pradeep joshiaaa
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PostPosted: Thu Jul 08, 2021 10:25 am    Post subject: CHAMPLAIN TOWER COLLAPSE : Early Observations & Implications- Primary Geotechnical Failure Reply with quote

My Initial Observations on Champlain Tower Collapse-

1. This is a Primarily a   Geotechnical  Technical Failure resulting in Brittle Structural Collapse with poor construction followed by Deviation in Structural Dwgs & Execution. The primary culprit is Geotech under design & understanding of concepts . Although Flat Slab & Non Ductile Detailing ( as it was not mandatory at that time 1980 ) , Closed Shear Links Missing , No Design of Progressive Collapse , Integrating Flat Slab Reinforcement Detailing missing, Loss of waterproofing system etc. Even with all these mentioned failures the Building was standing in Gravity Load . Differential Settlement of the Building caused redistribution of internal forces and due to overstress caused cracking in Floor Flat Slabs & some vertical members and exposure of reinforcement for corrosion is high near Sea side  that resulted into Loss of Gravity Load carrying Capacity of vertical members resulting into Progressive Collapse as several extra load was added in Terrace Lvl latter on.
2. Since this Building was Designed   in 1980 it  had a Similar Failure & Cracking Pattern as Seen in DOLPHIN TOWER constructed in 1971 in Florida sea side Area. This Champlain Building lacked Flat Slab  Seismic Design guidance as was constructed in the 80's and no one cared for retrofitting the same with time.  
3.Construction issues such as deviation in reinforcement shown in dwg and executed and spacing of hoops in vertical members, waterproofing & Seepage of water.
4.Main point of Settlement in corrosive action of soil with increased chemical content as near to sea this causes heaving of Foundation with formation of Gas pressure caused by Sulphate + Chloride +sea water . This resulted in Distortion in Foundation which resulted in Differential settlement in Years times. This cracking of Building was if checked would be going on min a decade old and showing distress gradually resulting into sudden Brittle failure when sudden extra water pressure was encountered unexpectedly from nearby area.
5. Sudden Change in Water LVL Fluctuation due to surrounding construction and formation of Sinkholes.
Conclusion - My Recommendation is that Geotechnical Experts should First check the Soil with basic Tests like CPT & SPT . This Failure is Collective work of GEOTECH +STRUCTURAL +CONSTRUCTION +COMPLIANCE failure . We cannot comment in isolation .

Million Dollar Question ???

1. Who will Pay for negligence ??? Engineers , Owner, Construction Team, Residents or Authorities
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vikram.jeet
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PostPosted: Thu Jul 08, 2021 2:11 pm    Post subject: Reply with quote

Structure 's Liability

Very difficult to say , once such failure happens .

Construction Agency  is in question for Defect Liability period only unless it is proved that  major deviations from drawings done resulted in failure. Culture of AS EXECUTED DRAWINGS  , generally do not exist .
Designers 's design / details are  in black & white , in records can be checked .

Geotechnical consultant report is in Black & white ,  but verifications is subjective.

RWA / Owner of Building , have to maintain / sublet maintenance of big towers , and maintenance team can be questioned.

Still difficult to say who is at fault.
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pradeep joshiaaa
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PostPosted: Thu Jul 08, 2021 2:45 pm    Post subject: Reply with quote

Solution of Problem is a Crystal Clear view of Problem. As in Such a Situation were many players are involved and economics played the major role over Safety , which is wrong First of all. The only Solution is " STRUCTURAL BUILDING RATING SYSTEM " i.e e.g.  Structural Rating of 5 means Building is Designed to Resist EQ with Low & Repairable Damage with only below 5 % cost of construction in case of Hazard to be anticipated  and at every 5 years Building Stability will be checked & reviewed plus Building is insurance with Life &  Building structure  .  Once Economics & Insurance comes into Role the common person or Home Buyer will himself Learn all the Nonsense of Design . Make People Aware more about the product i.e Structural Building that they want to live & pay EMI for half of there life is important then Doing Changes in Codes & regulation in Isolation .  Once there is Structural Rating System Compliance both common home buyer & owner will be aligned and Future Infrastructure Deficit in 2050 can be avoided or scaled down with min Risk Management.

Pradeep Joshi
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vikram.jeet
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PostPosted: Fri Jul 09, 2021 3:33 am    Post subject: Reply with quote

STRUCTURAL AUDITS FOR BUILDINGS /BRIDGES /OH TANKS

There is need to have periodic audit of structures in respect of structural strength. Those structures which are showing signs of distress  can be easily earmarked for corrective strengthening .  

Structural audit to be ensured by owner of tower , RWA of apartment building . For Bridges  and OHT , the responsibility lies with municipal authorities. But even for buildings , the monitoring to be done at municipal level, though responsibility for structural check to be with RWA/owner.

A 5 yearly condition audit can help . For Pvt buildings the corrective expenditures to be borne by owner/RWA who can collect such funds from residents / commercial tenants as per guidelines of municipal Authorities.  A culture needs to be developed in this respect. Residents/ owners /tenants must be apprised of such eventualities of expenditure for structural strengthening/ maintenance at time of booking/ allotments.

Idea is to save loss of lives  but residents must be convinced and prepared to pay for strengthening / retrofitts , if required.
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pvgraju
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PostPosted: Fri Jul 09, 2021 7:33 am    Post subject: CHAMPLAIN TOWER COLLAPSE : Early Observations & Implications- Primary Geotechnical Failure Reply with quote

Dear sir,

Main reason may be differential settlement only and lack of ductile detailing.

Coming to ductile detailing of slabs/flat slabs no specific details are available.

Literature says in case of flat slabs links shall be spaced at a closer distance. But what is the min/max spacing is not clear.

Regards,

P.V.Gavarraju.
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vikram.jeet
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PostPosted: Fri Jul 09, 2021 10:30 am    Post subject: Reply with quote

FLAT SLABS

Differential settlement
I  feel that flat slabs on soils susceptible to settlement , needs to be designed additionally for some minimum value of differential settlement . Though this provision will enhance supports moments due to differential settlement , but such happenings can be , to some extent , prevented / delayed to raise alarm.

Ductile detailing in flat slabs
Structure under severe EQ  resist much higher forces than designed ones thru ductility. Ductility provisions in flat slabs , being thin str member compared to rcc beams , seems near to impossible . Shear wall buildings shall thus incorporate shear walls to resist EQ.
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vikram.jeet
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PostPosted: Fri Jul 09, 2021 2:18 pm    Post subject: Reply with quote

Previous post:
Last line to be read as
FLAT SLAB BUILDINGS , thus incorporate shear walls to resist EQ.

Inconvenience regretted
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