Question

Why the historic civil engineering works(facilities) could be remained?, while modern structures have only about 50 years of life

Answer 1

Hello there,

The tone of your question seems little unjust to our modern engineering. However, let us first built an understanding of this and get there later.

First of all, let us draw differences between these two eras -:

1.) Modern buildings are quite accurately designed to serve a specific period of time which in most cases is a short span of time. Older buildings however, were not designed in a formal sense and the ones that survived were way more costly in real terms than modern ones.

2.) OVERDESIGN VERSUS ACCURATE DESIGN -: While the ancient structures were overdesigned in order to attain longevity in life span they were designed far beyond measures of the safety factors like mammoth domes, giant columns and extra-wide beams, Whereas, our modern engineering works very precisely, accurately and specifically where we approximate design figures in three decimal places to immediate next digit and also we under design owing to the change that may occur with time. Also, with so much of enhancements in technology, we want to be safe otherwise whatever we build today may seem us like MODERN PYRAMID in the next 100 years or so.

3.) TOUGHER MATERIALS WHICH ARE WAY MORE EXPENSIVE --: Also, In ancient structures, you will see at places the entire structure is made of big chunks of stones and marbles which have a life span of centuries. Whereas in modern methods of construction we use polymers, concrete, steel, rebars as per our suitability.

4.) USAGE CONTINUITY -: Continuity of usage is the other factor which increases the life of a structure as it causes continuous maintenance to takes place.

5.) NOT ALL THAT'S GONE CAN BE SEEN-; Not all of what you see is old and standing, most of the old structures are long gone now. Only those ones that were desired to attain longevity are standing owing to the intelligence of engineers, the toughness of materials, uneconomic expenditure and will to attain longevity are standing.

6.) NOT, THAT WE CANNOT DESIGN STRUCTURES TO SERVE LONGER SPAN-: The catch is we don't want our structure to go beyond a specific period of time because with so much technological enhancement they will become redundant. There are engineering marvels which are designed to serve beyond 50 years if we don't put too much effort to destroy them like the skyscrapers entirely skeleton with steel sections or other noteworthy structures.

7.) FUTURE CALCULATIONS -: You can't argue the fact that we are seeing some most rapid population growth in terms of number, now think about designing any structure to meet the demand of the population of 100 years from now, that will be too expensive in monetary terms which will be called absurd today but earlier such slack were there over money and construction period, also the growth was not too rapid to accommodate those changes.

So I think I have given you a fair deal of idea to decide for yourself whether we can design buildings for larger designed life or not. Older buildings are fine and desirable from heritage point of view but today the need is sustainability.

Thank you. Hope you are helped. Please upvote if you liked the answer. Stay home and safe from coronavirus.