www.sefindia.org

[vikram.jeet]

As per a report on TV Channel GNT :

TREE HOUSE IN RAJASTHAN
4 STOREY 40  SQ FT HOUSE IN BURARI DELHI ( 10×4 feet)
SLANT CLUB HOUSE BUILDING IN GAZIABAD , UP

All these building structures are shown and quite interesting .
May be available on net.

Tree house is built by a civil engineer , 4 storey with a tree trunk in center and branches out. Steel construction without disturbing the natural tree.

4 storey house is built by a mason size 10 × 4 feet , smallest in world . Mason constructed a bungalow for rich man who rewarded him with a vacant piece of plot of 40 sq ft.

TILTED CLUB HOUSE BUILDING is created by an Architect though inside columns str are straight but outside walls , false pillars are slant at about 25 degrees or so.

[vikram.jeet]

COLUMN BENDING MOMENTS (Gravity Loading) ,   - MANUAL DESIGN


In case analysis is not performed , Old version of IS 456 - 1957 & 1964 versions  provide following values for Column moments at a joint .

Single Bay Frames ( Portal frames)
Foot of upper column Mu = [ Ku / ( Ku + Kl + 0.5 Kb )]* M

Head of Lower column Ml = [ Kl / ( Ku + Kl + 0.5 Kb ) ] * M

Ku - - Stiffness of upper column
Kl - - Stiffness of Lower column
Kb -   Stiffness of beam
M - - Fixed end moment from beam being unbalanced moment in single bay frame

Multi bay frames
Exterior bay
Foot of upper column Mu = [ Ku / ( Ku + Kl + Kb ) ]* M'

Head of Lower column Ml = [ Kl / ( Ku + Kl + Kb ) ] * M'

Interior Bay :
Foot of upper column Mu = [ Ku / ( Ku + Kl + Kb1 + Kb2 ) ] * M '

Head of Lower column  Ml = [ Kl / ( Ku + Kl + Kb1 + Kb2 )] * M '

M' - -  Unbalanced moment at joint
Kb1 -  Stiffness of left beam
Kb2 - - Stiffness of right beam

Note :  Earlier frame analysis was performed manually using Kani method / Two cycle method  - time consuming and above formulas were very handy.

[vikram.jeet]

Two way slab coefficients

The earlier versions of IS 456 , 1964 provide two separate tables of coefficients One with provision of torsion reinforcement at corners , and Other one without provision of corner reinforcement of torsion. It was seen that  coefficients were 10 to 20 percent higher in case torsion corner reinforcement is not incorporated.

However later versions have deleted that table and only table giving coefficients with provision of corner torsion reinforcement is retained.

[vikram.jeet]

Hanging of Precast members

I think so long as members are symmetrical about Lifting  hook point/s , lifted member remains vertical . But if a L type precast demarcation boundary wall element ( 800mm base & 1800mm wall ht , length 1400 mm , wt about 1000 kg ,) is lifted from top of wall at centrally placed hook , the L shape precast member will tilt to the extent it's cg of mass falls in line with lifting point.

Design engineers engaged with precast design work can enlighten better on this aspect.

[vikram.jeet]

Foundations


Following be kept in view while designing /detailing

Foundation Level - It shall be as per soil report . There is existing GL which may not be ORIGINAL VIRGIN GL. There exists  top filled soil layer and soil report from experienced Geotech expert  generally  mention the extent of this top soil at various bore locations . Designer must add this loose filled top Zone in Foundation depth  while indicating in drgs because execution team will go by EGL.


Footings - Designer mostly take a clear cover to reinf bars as 50mm but at site 75 mm brick bats are kept as cover blocks over which bottom mesh reinf is found placed . 50mm cover blocks need to be insisted . Where execution is not strict ,it is better to adopt clear cover as 75mm during design stage.

[vikram.jeet]

Provision of Column Pedestals below Plinth Level  always Help

In Buildings ( without Basements) , Column pedestal provision is structurally advantageous manifold :

(I) It provides additional cover to Column reinforcements as needed by IS Code 456.

(ii) It reduces compressive stress in concrete due availability of larger xsec area . The bearing stress on footing top also reduces due to pedestal provision.

(iii) In case plinth beams are not proposed , it helps in reducing slenderness of columns . But Plinth beams are always advisable.

(iv) It reduces Punching shear stress ( Two way shear ) in footing .

(v) In case some foundation needs to be placed at a level lower than found level shown in drg due to firm strata availability  at certain location , the pedestal provision helps as it not only address slenderness problem , but larger X section can take additional moments .

Generally pedestals are not included in design and analysis of frames , but all above advantages  are taken as bonus to cater many unforseen situations  and Structural designers mostly propose them  as age old practice.

[spsvasan]

[quote="vikram.jeet"]Hanging of Precast members

I think so long as members are symmetrical about Lifting  hook point/s , lifted member remains vertical . But if a L type precast demarcation boundary wall element ( 800mm base & 1800mm wall ht , length 1400 mm , wt about 1000 kg ,) is lifted from top of wall at centrally placed hook , the L shape precast member will tilt to the extent it's cg of mass falls in line with lifting point.

Design engineers engaged with precast design work can enlighten better on this aspect.[/quote]


One observation - when unsymmetrical elements are lifted, the lifting point should be in alignment with the shear centre, rather than the centre of gravity.

In the case of symmetrical and anti-symmetrical section shear centre coincides with the cg. In unsymmetrical case, the shear centre is away from the cg

S.P.Srinivasan

[vikram.jeet]

Dear Er S P Shrinivasan,
Thanks for correction to my understanding . it could  be shear center. Still not sure.
Appreciate your in-depth viewpoint .

Best wishes and regards
Vikramjeet

[vikram.jeet]

Dear Er Srinivasan,
Just correct me if possible

Lifting of unsymmetrical precast members

For the L type precast wall element  , the shear center is at mid point junction of wall and base in the crossection. Lifting is also in alignment to shear center at top of wall  ( as discussed by you in yr post reg shear center ). Base and wall are monolithic .  I think while lifting , the L shape precast element will try to tilt to nullify unbalanced moment due to self wt of base cantilever transferred to wall . The tilting of member about hook point will create eccentricity about hook point to counterbalance the unbalanced base moment .

Further kindly  clarify about the lifting of C shape precast element lifting where shear center lies outside of the crossection.

[vikram.jeet]

Just to reiterate again :
Going by free body diagram of lifted L shape wall , I think , it is the cg which has to coincide at Line of lifting.