Conceptual design of a building with columns and shear walls

1.The building shown, 20 × 35 m in plan, has columns on a 5 × 5 m grid and shear walls (with dimensions shown in m, 250 mm in thickness) in three alternative arrangements, (a), (b), (c), all with the same total cross-sectional area of the shear walls. Compare the three alternatives, taking into account the restraint of floor shrinkage, the lateral stiffness and the torsional one with respect to the vertical axis, the vertical reinforcement required for the same total flexural capacity at the base, the static eccentricity, the system’s redundancy, foundation systems, architectural constraints etc.

answer

residential at floor shrinkage observation full restraints at all corners corners are left freebut non uniform restrait

restraints along the edge

conclusion option a will have higher restraints to shrinkage. thus leads to cracks in the floor

option b is average option c wil not have effectively restrain the shrinkage. so possibily less cracks

the lateral stiffness observation comparatively lower lateral stiffness non uniform lateral stiffness in both xandy

in both x and y

conclusion option b will provie higher lateral stiffness for a pure sesmic .acceleration in xand y direction

torsion with respect to vertical axis

obserrvation corner walls provide more resistance edge walls provide good irregular wallsprovide with poor

twist resistance to twist resistance to twist

conclusion option a will best option with respect to torsion resistancewhere asoption c is the wrost condition

vertical reinforcement for similar base capacity

observation walls are subjected to normal flexural moment walls are subjected to walls are subjected to

and heavy twisting moment nominal twist moment heavy flexural moment

with twisting moment.

conclusion option c will require higherr verrtical reinforcement and option b will require the least

criteria

static eccentricity

observation structural symmentric structurally symmentric un symmentric

conclusion onlyoption cwill have static eccentrically and it is significant

system redundancy

observation uniform placement of lateral uniform palcement of lateral load concentrated lateral load

loadssupports in both the supports in both the axis supports in both the axis

conclusion option a and b are more redduntant than option c

foundation system

observation due to lshaped walls the geomentry walls are in the easy to fix walls are in line & concentrated

of foundation and its design will be the geomentry and design easy to fix the geomentry of

critical of foundation foundation but critical in design

conclusion option b and option c shall be incorporated with isolated footing/ and strip footing

option a is recommndated have pheriperal box foundation

archetectural constraints

observation walls obstruct only corners walls obstruct the faces of building vertical walls will not have passage

conclusion aarchetectural speakingoption a the perepered one option b is subjected to discussion option c is will not be accepted both archetectutally and commercially.

2.issues is the given framing

indirect lateral load transfer in x and y direction- the beams are connecting to another beamswhich is ineffective during lateral load transfer. in such condition,the primary beamsis prone to shear failure

issues of the given framing plan

eccentricity the longer the distance between centre of mass and centre of stiffness. the higher torsional movement

of the building as per the given plan eccentricity the building is subjected to higher torsional moment (torsional flexibility) in both x and y directions.

strong beam weeak column possibility- the size of column majority ass 25x 25cm. But all the beams have much deeper section 50cm inertia of beams is visually higher than column. if the column reinforcement is adequatly greater than that of beams. we are okay and since we do not have the reinforcement detail. that is doughtful

it is reccomded to have sight bigger sizes for column.

3.

observation in the given framing plan

floor plan the floor plan of building is not either uniform or syymentric so naturally any lateral load included in the floor will not have 100%inflence in same direction definatily a special lateral load resisting system for these torsinalmoments should be accomdated

random internal columns since the lateral columns are random they are uanble to transfer lateral loads effeciently

and cannot achievedesirable buildingresponse. so we have to assume and design those columns for only gravity loads

floor to floor variation in partion walls and in beams - partion walls will provide an important masscontol in a building and beams play key role in shear transferfrom floor to beam. all these elements are not in order. so heavy distortion and distribution of lateral loads will happen.

contd

1.suggestion on lateral load system and its foundation

2.heavy torsional forcesshould be controlled by respective lateral load system so corner shear walls are suggested.

3. the propotion of floor area is greater on the left side than that of the right side irregualar quadrilateral so corner shear walls on the left side should be heavier than the right.

4.corner shear walls prefferably by supported over a box foundation shear walls should be connecctedd by link beams to transfer from one to the other

5.the internal columns shall be supported by isolated footingsthose isolated footing can be connecctedd with shear walls through the beams

axis