The strange fact that, we often tend to learn from a failure of structure more than the real success from a project. The actual cause of all such failures may be either due to human misjudgments or flawed materials and also can be due to acts of nature.
From each of such failures however, we must learn something positive so that we can try to improve our engineering practice for the next project.
There are many such examples that can be found where due to natural calamities lots of construction damages has occurred which had spotlighted the necessity for all forensic civil engineering experts to come out with certain new improvements.
Let us take a classic example of Tacoma Narrows bridge collapse during the year 1940, which is considered to be one of the spectacular mishaps that took place in history of America.
This Tacoma Narrows was the most flexible bridge that was built at that time which exceeded all the previous designs as regards to length, width and depth ratios. By exceeding all the previous parameters, the design engineers had taken an unprecedented risk.
Perhaps, they didn’t realize the implications of various dynamic forces that were involved. Only after the complete structure was twisted apart the design engineers understood the importance of aerodynamic forces involved in long and thin structures.
They had exceeded all the time-tested design rules without really realizing the impact of various primary and secondary forces that can make an impact.
In the recent times, all programmers of early computer programs too overlooked the secondary stress effect and also few other factors.
As an example, in Civic Center Coliseum at Hertford, Conn. where roof failure took place in 1978 and also another in Kansas City in 1979, at Kemper Arena, which alerted all designers that it will not be wise to blindly rely on computer analysis, as regards to long term effect on structures are concerned.
Another great experience was received by the design engineers when they learned that inadequacy of slab-to-column was the main reason of crash of the followings:
- Skyline Plaza Apartments in 1973 at Bailey’s Crossroads.
- L’Ambiance Plaza in 1987 at Bridgeport, Conn.
- Harbor Cay Condominiums in 1981 at Cocoa Beach, Fla.
Progressive failure played a major role in the twin tower of World Trade Center collapse during 2001 at New York too.
Specifically, both Habour Cay and Skyline structures were in fact made of construction of cast-in-place type while L’Ambiance was liftslab design.
The lift-slab problem generally occurred when steel-to-steel erection connectives was not sufficient. Nowadays, verifying punching shear for thin slabs and also stresses in connections among lift-slabs and columns can be a major design concern.
The results of changing details without involving designers resulted in failures of three different places on three different kinds of projects:
- Collapse of cooling tower formwork in West Virginia’s Willow Creek during 1978, that killed 51 workers.
- Walkways collapse in The Hyatt Regency Hotel during 1981, at Kansas City, Mo. Where 114 people died.
- Girder collapse in Walnut Street Bridge during 1985 at Denver.
All these mishaps given the designers a food for thought to decide what changes they should make in the construction process.