EXPLAINER| Gujarat tragedy: What is a suspension bridge? What led to Morbi bridge collapse?

By PTI

NEW DELHI: What is a suspension bridge? How does it switch the load to the bottom? Those have been questions on the minds of many on Monday, a day after a century-old suspension bridge in Gujarat’s Morbi over the Machchhu river collapsed, leaving 134 folks lifeless.

Just earlier than the bridge collapsed, CCTV footage confirmed, some males have been attempting to rock the suspension bridge from one facet to a different.

Saptadip Sarkar, a structural engineer working with Delhi-based Engineers India Limited solutions these questions.

“The deck of the suspension bridge, which bears the weight of the people walking on it in addition to its own weight, is held in place by the means of vertical suspenders which are made from ductile material and subjected to tension,” he mentioned.

“These suspenders are then connected to the main cable which is also ductile and subjected to tension. The main cable, which spans between the points connected by the bridge and is intermediately supported by vertical main column piers, has two functions. The first is to support the vertical suspenders and the second is to maintain the verticality of the piers,” he mentioned.

Overall, the burden of the deck, together with the site visitors of individuals, is transferred to the bottom via the vertical piers, that are in compression, defined Sarkar.

So, at what factors is such a sort of bridge probably the most weak? Quite a couple of, it seems.

“To begin with, the main cable, suspenders and the points at which the suspenders connect to the bridge deck are all vulnerable to failure,” Sarkar mentioned.

“In fact, the main cable requires the most attention in terms of regular checks and maintenance over the service period of the bridge. The reason for this being the fatigue load that it is continuously subjected to during its service,” he mentioned.

Fatigue load refers to constantly subjecting a fabric to some pressure till it develops a crack.

Referring to the suspension bridge in Morbi, Sarkar mentioned its cables are of a extremely ductile materials and will have stayed in place for much longer, regardless of the form of deflection being intentionally created by the folks seen within the video (CCTV footage).

“Also, the bridge that failed was recently renovated, so fatigue failure can be safely ruled out as a possible cause,” noticed Sarkar.

So then what was it that gave approach? The connection factors the place the vertical suspenders meet the deck of the bridge are subsequent in line to warrant consideration, the structural engineer mentioned.

“It is through these points that the loads of the deck and people are together transferred to the suspenders. The suspenders, in turn, transfer the loads to the main cable,” he elaborated.

“As I understand it, the dynamic loading created by the synchronous and deliberate movements of the people on the bridge created excessive deflection from the point of view of the joint of the suspender to the bridge deck,” he added.

On the transmission of forces to the bottom, Sarkar additional mentioned that the primary cables are in slope and so the stress within the cable on the pier junction has a horizontal and a vertical part.

“While the horizontal component of this force is catered to by the cables anchored at the two ends through tension, the vertical component creates a compression in the pier,” he mentioned.

“Failure occurs when the structural integrity at any of these points described is compromised,” he concluded.

NEW DELHI: What is a suspension bridge? How does it switch the load to the bottom? Those have been questions on the minds of many on Monday, a day after a century-old suspension bridge in Gujarat’s Morbi over the Machchhu river collapsed, leaving 134 folks lifeless.

Just earlier than the bridge collapsed, CCTV footage confirmed, some males have been attempting to rock the suspension bridge from one facet to a different.

Saptadip Sarkar, a structural engineer working with Delhi-based Engineers India Limited solutions these questions.

“The deck of the suspension bridge, which bears the weight of the people walking on it in addition to its own weight, is held in place by the means of vertical suspenders which are made from ductile material and subjected to tension,” he mentioned.

“These suspenders are then connected to the main cable which is also ductile and subjected to tension. The main cable, which spans between the points connected by the bridge and is intermediately supported by vertical main column piers, has two functions. The first is to support the vertical suspenders and the second is to maintain the verticality of the piers,” he mentioned.

Overall, the burden of the deck, together with the site visitors of individuals, is transferred to the bottom via the vertical piers, that are in compression, defined Sarkar.

So, at what factors is such a sort of bridge probably the most weak? Quite a couple of, it seems.

“To begin with, the main cable, suspenders and the points at which the suspenders connect to the bridge deck are all vulnerable to failure,” Sarkar mentioned.

“In fact, the main cable requires the most attention in terms of regular checks and maintenance over the service period of the bridge. The reason for this being the fatigue load that it is continuously subjected to during its service,” he mentioned.

Fatigue load refers to constantly subjecting a fabric to some pressure till it develops a crack.

Referring to the suspension bridge in Morbi, Sarkar mentioned its cables are of a extremely ductile materials and will have stayed in place for much longer, regardless of the form of deflection being intentionally created by the folks seen within the video (CCTV footage).

“Also, the bridge that failed was recently renovated, so fatigue failure can be safely ruled out as a possible cause,” noticed Sarkar.

So then what was it that gave approach? The connection factors the place the vertical suspenders meet the deck of the bridge are subsequent in line to warrant consideration, the structural engineer mentioned.

“It is through these points that the loads of the deck and people are together transferred to the suspenders. The suspenders, in turn, transfer the loads to the main cable,” he elaborated.

“As I understand it, the dynamic loading created by the synchronous and deliberate movements of the people on the bridge created excessive deflection from the point of view of the joint of the suspender to the bridge deck,” he added.

On the transmission of forces to the bottom, Sarkar additional mentioned that the primary cables are in slope and so the stress within the cable on the pier junction has a horizontal and a vertical part.

“While the horizontal component of this force is catered to by the cables anchored at the two ends through tension, the vertical component creates a compression in the pier,” he mentioned.

“Failure occurs when the structural integrity at any of these points described is compromised,” he concluded.