Did any of you had chance to stand quietly looking down(?) the people, on the floor levels 01, 02 or 03 of Forum Mall, Bangalore at any point of time in your past life history? If so, this post may be a value addition to your further proceedings; if not, this is just a statutory warning.

The Forum Mall is one of the largest shopping malls (6,50,000 sq.ft.) in the country, constructed by the prestigious Prestige Group. Spreading over 5 centrally air-conditioned floors, the mall has round the clock security, efficient freight handling, 100% generator backup, managed indoor air quality and multi-level parking which can accommodate over 800 car parks simultaneously.

All the popular brands of clothing, electronics, entertainment, food and beverages viz Transit, KFC, Pizza Hut, Mac Donald's, Landmark, Westside, Soch, Isis, Mustard, Weekender, Provogue, Skullers, Benetton, Tommy Hilfiger, Archie's, Cafe Coffee Day, Apple, Witco and "last but not the least" - PVR Cinemas are camped at these mall (for lease) to broadband their USPs.

Now, here is something from the flavor of Newtonian Physics to taste which is a very basic stuff. The Mechanical Resonance is the tendency of a system to absorb more energy and oscillate at maximum amplitude at certain frequency, known as the resonant frequency. This may cause vibrations in improperly constructed structures (like bridges and buildings).

Many sources can kindle such vibrations - either external or internal. The external sources are Seismic activity, transportation-related sources such as trains, buses & trucks, heavy metal related works in industries, construction works going on in adjacent areas and even a very strong wind.

Internal sources like elevator & conveyance systems, fluid pumping equipments and even bulky uniform human activities such as aerobic exercises (that is why soldiers are trained not to march in lockstep across a bridge) can impart vibration into one part of a building, which can be felt elsewhere.

History already shouts the examples for ill-effects of bad construction. Remember the Basse-Chaîne Bridge incident in France. Also known as Angers Bridge, it was a suspension bridge over the Maine River. On April 16, 1850, when 478 French soldiers marched across in lockstep, the bridge collapsed, leading to the death of 226 of them (since they were marching together, they caused the bridge to vibrate).

Coming back to Forum from France. Anybody who stand in the walk ways of any floor (other than ground floor) holding the safety steel structures, can feel the abnormal amount of vibration impinged in their body (you cannot stand still beyond 2 minutes - the vibration will cause a mild head-ache).

The vibration is caused by the transfer of momentum from the movement of thousands of shoppers, walking simultaneously (hence in same frequency) inside the building structure, causing mechanical resonance. This scenario can be mapped to Angers Bridge incident without any hesitation but the difference is Forum didn't face any immediate impacts.

This problem can be resolved by installing large dampers (shock absorbers) in the building to absorb these vibrations, changing the natural frequency (fundamental tone) of the structure (this method was used in Millennium Bridge, London by 2000) or any of the available (proven or experimental) structural engineering methodologies. Otherwise...

On lighter side, my friend commented yellowish about this. "A lot of girls are crowded in the mall na, that's why its vibrating". But, if this issue is left unanswered, the only fantasy of thrill going to remain is "Who are all going to be inside the mall on the day of its final break-point : You, Me or Both?"


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