be ‘controlled’ and kept within permissible limits. Take another example, if a lintel above a
doorway deflects too much, it may cause warping of the door frame below it and,
consequently, the door itself may not open or close properly. Cracking is ugly and may or
may not be indicative of a structural problem. But it may, in itself, lead to problems. For
example, if cracking occurs on the outside face of a reinforced concrete wall then rain water
may penetrate and cause corrosion of the steel reinforcement within the concrete.
Responsibilities of a Structural Designer.
A structural designer should create a functional, economic and most importantly , safe
structure for the public to enjoy. The following are to be considered during structural
design of a building:
(a)
Proper foundation to be designed based on soil profile and SBC. Avoid eccentric or
floating column at the foundation level. If not possible, even extra cost is incurred ,
connect the eccentric footings to the nearest footing and make it combined with strap beam
arrangement.
(b)
Interact with architect and plan the structure layout from stability point of view. i.e
Plan a frame layout which is connected by beams and columns before dividing the floor
area for functional requirement. Proper connection of beam to column is very important
during seismic loading. Secondary beams can to be
planned to meet the other
requirements. Stability is very essential for any good structure to transfer the forces
smoothly to the ground.
(c)
As far as possible , floating columns are to be avoided. Floating column will not
allow smooth flow of force from beam to column and foundation . It produces heavy
moment during earthquake and cause damages to the building.
(d)
Concealed beams are adopted to support roof and connect to columns. Concealed
beam in a slab has no capacity to behave as regular beam. 125mm thick slab with 25mm
cover can have a maximum gap between top and bottom reinforcement of 55mm, which is
insufficient to provide beam action. However, it can minimize stress concentration and
useful under half brick wall. Therefore, it is recommended that concealed beam concept
should not be considered under full wall load or as a connecting member between two
columns.
(e)
Beam width should not be restricted only to wall width. Beam width should satisfy
code requirements, as per seismic code IS 13920, the width of a beam shall be 300mm
beam for a beam length more than 5m. Interact with architect and permit the beams to run
in side the rooms if required for better performance during seismic load.
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(f)
Structural engineer should advise the client to preserve the copy of structural details
and use it during any addition/ alternation to the building in future . Adding the extra floor Š
without knowing the structural strength is not advisable. Many buildings have failed due to
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over loading.
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Conclusion.
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There are many multistoried buildings have failed and collapsed in various cities. Owner £
and architect of a building should give equal importance to the safety and strength of the ÷
building and allow the structural engineer to design a structure to with stand all forces ˜
including seismic load.
fl;Lkhdg; nghwpahsh;
56
mf;Nlhgh; 2013