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Long Term Deflection Due To Creep And Shrinkage
What Does Fundamental Period Of Vibration Of A Structure
Means
Long Term Deflection Due To Creep And Shrinkage
When Do You Use Uncracked Sections In The Analysis
What Is The Serviceability Limit State Of Design
serviceability limit statesthe structure should not become unfit
for use due to
excessive deflection, cracking or vibration
What Is The Ultimate Limit State Of Design
the whole structure or its elements should not collapse,overturn
or buckle when subjected to the design loads
Applicability Of International Code
Ubc code
Behavior Of Gravity Frame Under Ultimate Loading
Location Of Additional Extra Steel For Raft Foundation And Slab
Detail Require
hi it depends where you need the extra reinforcement for
if you need extra reinforcement for negative moment you provide
extra top bars for suspended slabs and bottom rebars for ground
bearing slabs
shear walls are designed against the worst case combinations of
axial force, shear and moment
shear walls are normally critical in flexure except for high
rise buildings where shear could also control the wall
thickness
coupling beams are rigid links connecting two planar shear
walls. a coupled shear walls are made possible by the rigid
connection of
the coupling beams to the shear walls
technically coupling beams are deeper than regular beams and
they are provided with diagonal reinforcement to control high
shear
stresses under seismic loadings
sway columns are when your frames are designed to carry lateral
loads
non-sway columns are only for gravity loads and there is an
independent lateral system
in aci code this is quantify by stability index Q
there are really no prescribed wind drift limits in any code
except a clause in british standards that states H/500 which is
the
internationally accepted limit for overall drift limi t for high
rise buildings
as for inter-storey drift it depends on serviceability issues
that you want to control but normally a drift index of H/300 or for
a
standard floor to floor height of 3.5meters a drift of 12mm will
be sufficient for facade/cladding works not to get damaged.
it depends but high rise buildings will have relatively long
period and seismic demands will be set to minimum as longer period
tends
to fall at the lower end of the spectra and lower forces.
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high rise building are commonly critical in wind serviceability
controlling inter-storey drifts and wind induced accelerations
capacity design?
capacity design as it is popularly known in seismic design was
actually conceptualized by george beca the founder of Beca Hol
lingCarter and Ferner BHCF engineering consultant in New Zealand.
but the concept is developed further by tom paulay in university
of
canterbury
some snippet of capacity design taken from the peer website:
The capacity design approach explicitly considers the problem of
determining the failure mechanism of members. The basic idea is
to force the member to fail in a ductile manner by making the
capacity of the member in other possible failure modes greater.
It
involves the simple application of plastic analysis on an
element-wise basis as shown below.
In the case of the beam shown at left, the preferred ductile
mode of failure is f lexure, while brittle shear failure is to be
avoided.
Therefore the shear corresponding to the plastic moment in the
beam is the design shear. The beam is then designed so that its
nominal shear strength is greater than this shear.
In order for capacity design to work, it is vital that
reasonable, probable capacities for a member be determined. Often,
beams have
significant overstrength in flexure which must be taken into
account in order to determine what the actual plastic moments might
be.
This procedure works well for designing the beams in a
strong-column/weak beam design and for joints, but doesn't work
nearly as
well for columns. Also, way the system behaves as a whole is not
considered.
Capacity design procedures are implemented in the New Zealand
code and in various parts of the concrete sections of the UBC.
They are also hidden in some parts of the UBC provisions.
SMRF or special moment resisting frames have special ductile
detailing requirements as per chapter 21 of aci code while OMRF
or
ordinary moment resisting frames don't have any ductility
detailing requirements and main body of the code is sufficient to
design
your frames
a building frame system is lateral stability system where the
frames are carrying gravity loads and all lateral loads are carried
by
shear walls
a bearing wall system is seismic lateral system is which seismic
actions and gravity loads are resisted by shear walls
a column sway is failure mechanism wherein the controlling
mechanism is the development of plastic hinging in columns
this mechanism is avoided in american codes and standards and
this is avoided in design by ensuring columns are 20% stronger
than the framing beams
a dual system is a structural resisting system where there are
two main lateral resisting system to carry seismic loads down
to
foundation
common dual systems are combination of shear wall and moment
resisting frames
beam sway is a mechanism in which plastic hinging occurs at the
beams and the plastic region in the beams are protected by
making sure the rotational capacities are not exceeded during
shaking by proper ductile detailing enabling the system to
supportgravity loads even during and after the most extreme ground
shaking
in the absence of a formal soil investigation report it is
always safe to assume a conservative soil type which is soil
profile type D.in
aci code.
if you have information on nearby site it is always safe to
assume one soil profile type below during the initial design.
hi most codes limit seismic drifts to 2 to 2.5% of storey height
depending on the period of structure
you can refer to IBC, ASCE code of practice for more details
