Failure Analysis Of Mishap At DMRC On 12 July
It was 12th July 2009 which proved to be the darkest day in the
history of DMRC. After achieving a milestone of providing a reliable and
easy mean of transportation to the capital of India, it is now facing
huge problems which are not only causing loss of human lives but also
causing immense damage to the most reputed infrastructure organization
of India. So far, this company has achieved every target ahead of
schedule under the excellent guidance of Mr. Sreedharan.
Let us try understanding what went wrong on that disastrous day
On 12th July, 2009, while lifting segments of the superstructure, an accident happened in the Badarpur – Secretariat section near P-67. The pier cap of pier P-67 got collapsed causing subsequent collapse of the
(i) Launching Girder
(ii) Span between P-66 and P-67 which had got erected and pre-stressed, already
(iii) Segments of the superstructure for the span between P-67 and P-68.
The incident left 6 people dead and many injured.
Site Investigation
After visiting the site, following observations were noticed
1. The pier cap of affected pier (P-67) has sheared from the connection point of the pier and pier
cap. It is a cantilever pier cap. It was informed by the contractor and DMRC representatives that the support system for viaductwas initially designed as portal pier till the casting of the pier was over. The shop owners put up resistance against casting of the other leg of the portal and it was subsequently decided by DMRC that this would be changed to a cantilever pier, similar to P-68 which is still standing at site.
2. It was noticed that the prop support of the cantilever has failed
from its connection to the pier.
3. The top reinforcement of the cantilever beam does not have any development length into pier
concrete. As learned from the sources, the top reinforcement of the cantilever beam had an “L”
bend of 500 mm only.
There is very nominal (or no trace) of shear reinforcement at the
juncture.
4. The launching girder has fallen below with the failure of pier cap. Also, the span between P-67
and P-68 has fallen inclined, supported by the ground at one end and pier cap (P-68) on the
other.
5. The boom of the crane, used for lifting the launching girder on 13
July, 2009, has failed in bending
and shows clear sign of overloading.
Analysis
i. The pier (P-67) was initially designed as a leg of a portal frame and subsequently changed to support cantilever pier cap.
ii. The same method was followed for P-68 and P-66.
iii. The alignment of track here is in curvature and gradually leaves the median of the road to align on one side of the road.
iv. The longitudinal reinforcement of the pier was protruding by around 1500 mm beyond top of pier.
v. The top reinforcement of pier cap was 36 mm in diameter and had a development length of 500 mm. only as an “L” from the top. There was insufficient bond length for the structure to behave like a cantilever beam.
vi. During launching operation of the launching girder itself, this pier cap developed crack and work was stopped for couple of months. During this period, the cantilever pier cap was grouted in crack areas and further strengthened by introducing prop or jacketing.
vii. However, the behavior of the structure changed due to introduction of this jacket and the cantilever pier cap remained no more cantilever.
viii. The segments of superstructure for the span between P-66 and P-67 was erected and launched and the prop beam / jacketing could sustain the load to that extend.
ix. During the launching of superstructure segments between P-67 and P-68, only 6 segments could be lifted and the whole system collapsed when seventh segment was hooked for lifting.
The sequence of failure is as follows:
a. The support of the prop / jacket got sheared from its connection due to inadequate section / welding.
b. The cantilever pier cap which was behaving as a simply supported beam due to introduction of prop / jacket started behaving like a cantilever beam suddenly after failure of the prop which it can not sustain ( It was inadequately designed). So, the so called “cantilever pier cap” collapsed.
c. The launching girder / span between P-67 & P-66 / the temporarily erected segments between P-67 and P-68, all got collapsed in one go.
Crane Failure
The launching girder was lifted by the cranes. However, it needed to be pushed little forward for
unloading it on the ground. So, all the cranes were asked to stretch there booms by some length.
During this operation, the 250 MT capacity crane on extreme left exceeded it’s capacity and the
boom failed and broke down. Since, there were unequal loading on the 250 MT crane by it’s side,
that also failed and broke down. The crane of 350 MT capacity didn’t broke but it toppled with it’s
base. The 400 MT crane remained intact.
Final overview
a. It is concluded that the failure of pier cap occurred due to inadequate prop / jacket. This was coupled with failure of cantilever pier cap due to inadequate development length of top reinforcement of the cantilever pier cap.
b. The failure of the crane was a case of operational inexperience for such synchronized crane operation. The crane -1 did not have the requisite capacity for the extended boom length and radius. Once crane – 1 failed, the crane – 2 was loaded almost half of the launching girder amounting to around 200 MT. For the extension of boom and radius, it did not have the requisite capacity so it failed, too. The crane -3 was loaded more than it’s capacity. However, in this case the crane got toppled instead of boom getting sheared. The crane -4 did not undergo the severe loading due to failure of other 3 cranes and most of the loads got grounded by that time.
What it taught us?
a. Structural designs should be proof checked by experienced structural engineer.
b. Once failure observed, structure should be as far as practicable abandoned and new structure should be built up
c. More emphasis should be given on detailing of reinforcement to cater for connections and behavior of the structural components.
d. Any make-shift arrangement to save a failed structure should be avoided.
e. Reinforcement detailing in corbels, deep beams, cantilever structures should be checked as per the provisions of more than one type of Standards (both IS & BS should be followed).
f. Adequately experienced Engineer / Forman should be deployed for erection works.
This article has been written/submitted to us by a Civil Engineer and we are thankful to him/her for his so valuable inputs.
Let us try understanding what went wrong on that disastrous day
On 12th July, 2009, while lifting segments of the superstructure, an accident happened in the Badarpur – Secretariat section near P-67. The pier cap of pier P-67 got collapsed causing subsequent collapse of the
(i) Launching Girder
(ii) Span between P-66 and P-67 which had got erected and pre-stressed, already
(iii) Segments of the superstructure for the span between P-67 and P-68.
The incident left 6 people dead and many injured.
Site Investigation
After visiting the site, following observations were noticed
1. The pier cap of affected pier (P-67) has sheared from the connection point of the pier and pier
cap. It is a cantilever pier cap. It was informed by the contractor and DMRC representatives that the support system for viaductwas initially designed as portal pier till the casting of the pier was over. The shop owners put up resistance against casting of the other leg of the portal and it was subsequently decided by DMRC that this would be changed to a cantilever pier, similar to P-68 which is still standing at site.
3. The top reinforcement of the cantilever beam does not have any development length into pier
concrete. As learned from the sources, the top reinforcement of the cantilever beam had an “L”
bend of 500 mm only.
4. The launching girder has fallen below with the failure of pier cap. Also, the span between P-67
and P-68 has fallen inclined, supported by the ground at one end and pier cap (P-68) on the
other.
and shows clear sign of overloading.
i. The pier (P-67) was initially designed as a leg of a portal frame and subsequently changed to support cantilever pier cap.
ii. The same method was followed for P-68 and P-66.
iii. The alignment of track here is in curvature and gradually leaves the median of the road to align on one side of the road.
iv. The longitudinal reinforcement of the pier was protruding by around 1500 mm beyond top of pier.
v. The top reinforcement of pier cap was 36 mm in diameter and had a development length of 500 mm. only as an “L” from the top. There was insufficient bond length for the structure to behave like a cantilever beam.
vi. During launching operation of the launching girder itself, this pier cap developed crack and work was stopped for couple of months. During this period, the cantilever pier cap was grouted in crack areas and further strengthened by introducing prop or jacketing.
vii. However, the behavior of the structure changed due to introduction of this jacket and the cantilever pier cap remained no more cantilever.
viii. The segments of superstructure for the span between P-66 and P-67 was erected and launched and the prop beam / jacketing could sustain the load to that extend.
ix. During the launching of superstructure segments between P-67 and P-68, only 6 segments could be lifted and the whole system collapsed when seventh segment was hooked for lifting.
The sequence of failure is as follows:
a. The support of the prop / jacket got sheared from its connection due to inadequate section / welding.
b. The cantilever pier cap which was behaving as a simply supported beam due to introduction of prop / jacket started behaving like a cantilever beam suddenly after failure of the prop which it can not sustain ( It was inadequately designed). So, the so called “cantilever pier cap” collapsed.
c. The launching girder / span between P-67 & P-66 / the temporarily erected segments between P-67 and P-68, all got collapsed in one go.
Crane Failure
The launching girder was lifted by the cranes. However, it needed to be pushed little forward for
unloading it on the ground. So, all the cranes were asked to stretch there booms by some length.
During this operation, the 250 MT capacity crane on extreme left exceeded it’s capacity and the
boom failed and broke down. Since, there were unequal loading on the 250 MT crane by it’s side,
that also failed and broke down. The crane of 350 MT capacity didn’t broke but it toppled with it’s
base. The 400 MT crane remained intact.
Final overview
a. It is concluded that the failure of pier cap occurred due to inadequate prop / jacket. This was coupled with failure of cantilever pier cap due to inadequate development length of top reinforcement of the cantilever pier cap.
b. The failure of the crane was a case of operational inexperience for such synchronized crane operation. The crane -1 did not have the requisite capacity for the extended boom length and radius. Once crane – 1 failed, the crane – 2 was loaded almost half of the launching girder amounting to around 200 MT. For the extension of boom and radius, it did not have the requisite capacity so it failed, too. The crane -3 was loaded more than it’s capacity. However, in this case the crane got toppled instead of boom getting sheared. The crane -4 did not undergo the severe loading due to failure of other 3 cranes and most of the loads got grounded by that time.
What it taught us?
a. Structural designs should be proof checked by experienced structural engineer.
b. Once failure observed, structure should be as far as practicable abandoned and new structure should be built up
c. More emphasis should be given on detailing of reinforcement to cater for connections and behavior of the structural components.
d. Any make-shift arrangement to save a failed structure should be avoided.
e. Reinforcement detailing in corbels, deep beams, cantilever structures should be checked as per the provisions of more than one type of Standards (both IS & BS should be followed).
f. Adequately experienced Engineer / Forman should be deployed for erection works.
This article has been written/submitted to us by a Civil Engineer and we are thankful to him/her for his so valuable inputs.
Filed under Civil
Engineering Disasters | 9
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Tacoma Narrows Bridge Collapse
It was an unfortunate morning of 7th
November 1940 when winds having speed of 42 miles per hour suddenly
twisted the Tacoma Narrows Bridge and lead to its collapse. This
accident though didn’t look any lives but it surely made the civil
engineers to think new ways to combat bridge collapses.
Some of the important statistics of this
bridge are -
It is located in Tacoma, Washington, USA and was completed in 1940. This was a suspension type of bridge with length of 7,392 feet and was built at the cost of $6.4million.It had the longest span of 2800 feet.
It is located in Tacoma, Washington, USA and was completed in 1940. This was a suspension type of bridge with length of 7,392 feet and was built at the cost of $6.4million.It had the longest span of 2800 feet.
The bridge was designed by engineer
Moisseiff who had strengthened it with a solid steel girder beneath the
roadway.But the problems started soon it was opened to traffic.Under
strong winds, it swayed much beyond the permissible limits and thus sent
rippling waves along the deck. It took just 4 months before this bridge
collapsed after its completion.
On investigating it was found that the
solid steel girders provided to strengthen the bridge were actually
blocking the wind which caused the bridge to twist.Due to this a
swirling motion developed which ultimately lead to the collapse. After
knowing the reason for collapse a new bridge was constructed which had a
truss so that it can allow the passage of wind
This bridge also got the name “Galloping
Gertie” due to its unusual twisting and rolling behavior.
See this video to see how this “Galloping Gertie”
used to sway.Civil Engineering Disasters – Collapse Of Bridges
September 11, 1916. Quebec Bridge (Canada)
This is not the first destruction of the bridge. The first time tragedy occurred in 1907.
About first collapse of the bridge
The bridge was nearing completion, when the local engineering began noticing increasing distortions of key structural members already in place. After four years of construction, the south arm and part of the central section of the bridge collapsed into the St. Lawrence River in just 15 seconds. Of the 86 workers on the bridge that day near quitting time, 75 were killed and the rest were injured.
About second collapse of the bridge After a Royal Commission of Inquiry into the collapse, construction started on a second bridge, but September 11, 1916, when the central span was being raised into position, it fell into the river, killing 13 workers.
This is not the first destruction of the bridge. The first time tragedy occurred in 1907.
About first collapse of the bridge
The bridge was nearing completion, when the local engineering began noticing increasing distortions of key structural members already in place. After four years of construction, the south arm and part of the central section of the bridge collapsed into the St. Lawrence River in just 15 seconds. Of the 86 workers on the bridge that day near quitting time, 75 were killed and the rest were injured.
About second collapse of the bridge After a Royal Commission of Inquiry into the collapse, construction started on a second bridge, but September 11, 1916, when the central span was being raised into position, it fell into the river, killing 13 workers.
December 15, 1967. Silver Bridge (USA)
On December 15, 1967, the Silver Bridge collapsed while it was choked with rush hour traffic, resulting in the deaths of 46 people. Investigation of the wreckage pointed to the cause of the collapse being the failure of a single eye-bar in a suspension chain, due to a small defect only 0.1 inches (2.54 mm) deep. It was also noted that the bridge was carrying much heavier loads than it was originally designed for and was poorly maintained.The new bridge that replaced the Silver Bridge was named the Silver Memorial Bridge.
March 17, 1945. Ludendorff Bridge (Remagen,
Germany)
28 U.S. army engineers were killed while working to strengthen the bridge, and 93 others were wounded.
28 U.S. army engineers were killed while working to strengthen the bridge, and 93 others were wounded.
May 9, 1980. Sunshine Skyway Bridge (Florida,
USA)
The Sunshine Skyway Bridge was collapsed on May 9, 1980, when the freighter SS Summit Venture collided with a pier (support column) during a storm , sending over 1200 feet of the bridge plummeting into Tampa Bay. The collision caused six automobiles and a bus to fall 150 feet, killing 35 people.
The Sunshine Skyway Bridge was collapsed on May 9, 1980, when the freighter SS Summit Venture collided with a pier (support column) during a storm , sending over 1200 feet of the bridge plummeting into Tampa Bay. The collision caused six automobiles and a bus to fall 150 feet, killing 35 people.
June 28, 1983. Mianus River Bridge
(Connecticut, USA)
Three people were killed when their vehicles fell with the bridge into the Mianus River 70 feet below, and three were seriously injured. Collapse due to failure of the Pin and Hanger assembly supporting the span.
Three people were killed when their vehicles fell with the bridge into the Mianus River 70 feet below, and three were seriously injured. Collapse due to failure of the Pin and Hanger assembly supporting the span.
October 21, 1994. Seongsu Bridge (Seoul, South Korea)
On October 21, 1994, Seongsu Bridge connecting Seongsu-dong and Apgujeong-dong of Gangnam-gu, Seoul, collapsed. The slab (48 m) between the fifth and the sixth leg of the Bridge collapsed so 32 people died and 17 people were injured. One of its concrete slabs fell due to a failure of the suspension structure. This structural failure was caused by joints of trusses (steel structures) supporting the bridge slab were not welded to the full; the welding thickness, which should be over 10mm, was only 8mm; and further, connecting pins for steel bolts were poor.
January 4, 1999. Rainbow bridge (China)
In January 4, 1999, a pedestrian Rainbow bridge across the Qi River in the Sichuan province collapsed three years after it was built. The collapse of the Rainbow bridge led to 40 deaths and 14 injuries. Parts of the bridge were rusty, concrete used in its construction was too weak and there were serious welding problems.
In January 4, 1999, a pedestrian Rainbow bridge across the Qi River in the Sichuan province collapsed three years after it was built. The collapse of the Rainbow bridge led to 40 deaths and 14 injuries. Parts of the bridge were rusty, concrete used in its construction was too weak and there were serious welding problems.
March 4 , 2001. Hintze Ribeiro Bridge
(Castelo de Paiva, Portugal)
On March 4, 2001, the Hintze Ribeiro Bridge, made of steel and concrete, collapsed in Entre-os-Rios, Castelo de Paiva, Portugal, killing to 70 people, including those in a bus and three cars that were attempting to get to the other side of the river.
On March 4, 2001, the Hintze Ribeiro Bridge, made of steel and concrete, collapsed in Entre-os-Rios, Castelo de Paiva, Portugal, killing to 70 people, including those in a bus and three cars that were attempting to get to the other side of the river.
August 28, 2003. Bridge Daman (Daman, India)
At least 25 people, including 23 children, die when a bridge in the western coastal area of Daman collapsed into a muddy river, throwing a school bus, 10 vehicles and pedestrians into the swirling waters due to heavy rains.
At least 25 people, including 23 children, die when a bridge in the western coastal area of Daman collapsed into a muddy river, throwing a school bus, 10 vehicles and pedestrians into the swirling waters due to heavy rains.
November 7, 2005. (Almunecar, Spain)
Five Portuguese and one Spanish national died near Almunecar on Spain’s, after a 20-ton section of motorway viaduct fell from 80 meters onto workers below.
Five Portuguese and one Spanish national died near Almunecar on Spain’s, after a 20-ton section of motorway viaduct fell from 80 meters onto workers below.
December 2, 2006. (Bihar, India)
Thirty-three people are killed when a 150-year-old bridge, being dismantled, crashed on the train near the Bhagalpur railway station in the state of Bihar.
August 1, 2007. Minneapolis I-35W bridge
(Minneapolis, USA)
On August 1, 2007, during the evening rush hour, the main spans of the bridge collapsed, falling into the river and onto its banks. Thirteen people died and approximately one hundred more were injured. The 1,907-foot bridge fell into the Mississippi River. Currently under investigation.
On August 1, 2007, during the evening rush hour, the main spans of the bridge collapsed, falling into the river and onto its banks. Thirteen people died and approximately one hundred more were injured. The 1,907-foot bridge fell into the Mississippi River. Currently under investigation.
August 13, 2007. Tuo River bridge (Hunan,
China)
The 140-foot-high bridge spanning the Tuo River in the central Hunan city of Fenghuang collapsed as workers removed scaffolding from its facade. Investigation underway.
The 140-foot-high bridge spanning the Tuo River in the central Hunan city of Fenghuang collapsed as workers removed scaffolding from its facade. Investigation underway.
