Conceptual design of a building with columns and shear walls
Question 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.
ANS-
When structure are having symmetry
in plan then our structure are more
stable in any situation .
-so structure is more restrained it
will be more shrikage , expanding
and comes cracks are more .
-so in plan 1 comes more cracks and
deflection chances will we high wrt. to
structure 2and 3
but structure c , having diffrent shapes wall
so plan c is torsionally weak
because of in plan c , center of mass of total
plan wrt. eccentricity of these plan will be
changed .
-so we can say that if in structure
walls having diffrent sizes there
there eccentricity will be changed
so earthquake comes near to
pheriphery of plan and due to
diffrent vibrations comes near the
base portion so plan will be comes
into rotation condition
-
-redaundancy plan a and b , more
with res[pect to plan c
because there will be an eccentricity is more
in plan c in left side 10 m wall ,
which cannot carry structural load
-lateral stiffness plan c , is more
wrt. plan a and b
because off eccentricity in plan c
wall provided 10m size left side
will comes and more and increase distance
between center of mass plan and eccentricity
of whole structure so rotation will
comes .and structure are not able to carry
equal load either both direction equally
so much more damaged held in plan .
Question 2:
Discuss the suitability for earthquake resistance of the moment resisting
framing plan of a three-storey building depicted here (cross-sectional dimensions in cm),
the eccentricity of the centre of mass (as centroid of floor plan) to the centre of stiffness
(from the moments of inertia of the columns) are shown. Suggest an alternative. Also,
is there torsional flexibility? Are the two fundamental translational modes of vibration
larger than the fundamental torsional mode of vibration. Discuss qualitatively.
ans.
there is 2 way eccentricity in frame
along x and y direction
-also with stiffness eccentricity -
x direction larger when compared to
y direction .
-there is 2 continious frame in structure
that B1 AND B2 in the x direction
and B9,B10,B11,B12 In y direction
-all other beams are broken
in midway in frame .
-
-there will be torsional flexibitlity
in this structure .
-to avoid torsional restrains
is better to make rooms dimesions
even in x and y direction .
-to provided columns in junction
of 2 walls if it is fesiable better
-and to provided shear walls
in appropriate location
-fundamental translation mode of vibration
is larger than fundamental torsional mode
of vibration
Question 3:
A multi-storey building with basement,
with a quadrilateral (non symmetrical floor plan)
plan as, has interior columns in an irregular
(not in a grid) pattern in plan that serves
architectural and functional considerations. Partition walls and interior beams supporting the slab have different layout in different stories. However, there is no constraint to the type, location and size of the lateral force resisting components and sub-systems on the perimeter. Proposals are to be made and justified for the choice of the lateral-load-resisting system and its foundation.
ANS .-
In above plan there is totaly
unsymmetry because of columns
are not provided properly
grid pattern .so structure
are unsuitable to design
to any zone ,
-if we reduced weight of this structure
and provided flat slab in wooden structure
-and also not provided beam
connected to columns because of
we are not eaisily able to make ,
proper beam columns connection
and proper detailig/reinforcement
we are not eaisily provided
according to code
so provided flat slab
is more appropriate than
a regular beam column
connection .