Building Failures (1)

8/19/2019 Building Failures (1)

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STRUTTING , SHORINGAND UNDERPINNING


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UNDERPINNING

Underpinning is the installation of temporary

or permanent spport to an e!istingfondation to pro"ide either additionaldepth or an in#rease in $earing #apa#ity%


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There are several existing

conditions which may lead to theneed for underpinning

&onstr#tion of a ne' pro(e#t 'ith a

deeper fondation ad(a#ent to an e!isting

$ilding

Settlement of an e!isting str#tre &hange in se of a str#tre

Addition of a $asement $elo' an e!istingstr#tre


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Process !f Underpinning

Underpinning is a##omplished $y e!tendingthe fondation in depth or in $readth so iteither rests on a more spporti"e soilstratm or distri$tes its load a#ross agreater area% Use of mi#ropiles and (etgroting are #ommon methods innderpinning% An alternati"e to nderpinningis the strengthening of the soil $y theintrod#tion of a grot% All of thesepro#esses are generally e!pensi"e andela$orate%


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Types of Underpinning

)ass &on#rete Underpinning

*eam and $ase nderpinning

)ini+piled nderpinning


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"ass #oncreteUnderpinning

Also no'n as -traditional nderpinning,

-This nderpinning method strengthensan e!isting str#tre-s fondation $ydigging $oxes $y hand nderneath andse%uentially pouring concrete in astrategi# order%

The .nal reslt is $asi#ally a fondation$ilt nderneath the e!isting fondation%

This nderpinning method is generallyapplied 'hen the e!isting fondation is ata shallow depth, ho'e"er, the methodstill 'ors "ery 'ell e"en at .fty feet

deep% The method has not #hanged sin#e its

in#eption 'ith its se of tilitarian toolss#h as sho"els and post hole diggers%

Hea"y ma#hinery is not #alled for in thismethod de to the tight nature of the$oxes $eing dg%


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&eam and $ase underpinning

The $eam and $ase method of nderpinning is a more te#hni#allyad"an#ed adaptation%

A reinforced concrete $eam is #onstr#ted $elo', a$o"e or inrepla#ement of the e!isting footing%

The $eam then transfers the load of the $ilding to mass concrete$ases, 'hi#h are #onstr#ted at designed strategi# lo#ations% *asesi/es and depths are dependent pon the pre"ailing grond#onditions%

*eam design is dependent pon the #on.gration of the $ilding andthe applied loads

"ini'piled underpinning

)ini+piles ha"e the greatest "ale 'here grond #onditions are "ery

"aria$le, 'here a##ess is restri#ti"e% )ini+piled nderpinning is generally sed 'hen the loads from thefondations need to $e transferred to sta$le soils at #onsidera$le

depths+ sally in e!#ess of 0%1 metres%

)ini+piles may either $e agred or dri"en steel #ased, and are

normally$et'een 201mm and 311mm in diameter%


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)ethods of nderpinning

Pit method

Pile method

&hemi#al method Other method


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Pit method


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Pit method


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Pile method


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#hemical method

In this method the foundation soil is consolidated by employing chemicals.

Perforated pipes are driven in an inclined direction beneath the foundation .

The slopes are provided such that the entire area under the existing footing

comes under the area used to be strengthened.

After the pipes are installed, solution of sodium silicate in water is injected

through the pipes. This is a two-injection method. The pipes are withdrawn

and at the time of withdrawal of pipes, calcium or magnesium chloride is

injected through pipes.

hemical reaction ta!es place between these two chemicals and the soil isstrengthened by consolidation. This method is suitable for granular soils


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(TRUT

A strut is a str#tral #omponent designed to resistlongitdinal #ompression% Strts pro"ide ot'ards+fa#ing spportin their length'ise dire#tion, 'hi#h #an $e sed to eep t'o other#omponents separate, performing the opposite fn#tion of a tie%

They are #ommonly sed in ar#hite#tre and engineering% In piping, strts restrain mo"ement of a #omponent in one

dire#tion 'hile allo'ing mo"ement or #ontra#tion in anotherdire#tion%

Strt #hannel made from steel, alminm, or .$re+reinfor#edplasti# is sed hea"ily in the $ilding indstry and is often sed in

the spport of #a$le trays and other forms of #a$le management,and pipes spport systems%

Strt is a #ommon name in tim$er framing for a spport or $ra#eof s#antlings lighter than a post%


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(TRUTTING )ND (*!RING

(horing

It is the means of providing support to get stability of a structure temporarily under

certain circumstances during construction, repair or alteration.

Such circumstance arises when

". The stability of a structure is endangered due to removal of a defective portion of

the structure.

#. The stability of a structure is endangered due to une$ual settlement during

construction itself or in long run.

%. ertain alterations are to be done in present structure itself. &g' remodeling of

walls, changing position of windows,etc.

(. Alterations are carried out in adjacent building for remodeling, strengthening of

foundation, etc.


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Installation of shoring

5or shoring tim$er or steel t$es may $e sed% Sometimes $oth are sed in #om$ination% If tim$er is sed its srfa#e shold $e#oated 'ith a preser"ati"e so as to prote#t against 'et rot%

The shoring shold $e designed $ased on the load it has to sstainand dration of load%

Shoring may $e gi"en internally or e!ternally depending on the#ase and in #ertain #ases they may $e pro"ided on either side ofthe 'all to prod#e additional sta$ility%

Shoring shold $e installed only after getting the permission ifne#essary, of the lo#al athorities%

There is no time limit to 'hi#h the shoring has to $e ept, it mayrange from 'ees to years depending on the #ase%


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Types of shoring

)a!ing or inclined shores

*lying or hori+ontal shores

ead or vertical shores


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Ra+ing or inclined shores


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,lying or hori-ontal shoring


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Dead or vertical shoring


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Dead or vertical shoring


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Building Failures (1)

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