LDP Puchong Jaya Interchange: Major crack line found
[postlink]http://lpdn28.blogspot.com/2009/07/ldp-puchong-jaya-interchange-major.html[/postlink]Posted By: KP
Structure: Lebuhraya Damansara-Puchong, Puchong Jaya interchange (Exit 1114)
Affected: Puchong residents (335,419 population)
Owner/ Management: Lingkaran Trans Kota Sdn Bhd
Design, supervision, construction and commission: Gamuda
Problem: Crack lines at bridge soffit
Corrective action: To Conduct Condition Assessment on Bridges Located along Lebuhraya Damansara-Puchong by Evenfit Consult.
Major crack lines found underneath the bridge!
I bet that not much people take this seriously (except the concessionaire) although thousands were using this bridge everyday either through the top or passing underneath it. The possible reason is that these defects do not causing anything fall down (yet).
The crack locations and widths are summarized in this figure. There are 2 rows of bridges running parallel throughout that supported by abutments at both ends , and 11 rows of piers in between.
For clarity, each space between supports (span) are labelled and colored. The U-turns and roads underneath the bridge are shown as well. From here, you can see how lucky was the owner that all defected parts are just nicely not above the road. That's why this issue were never brought up to newspaper.
Let's see some pictures taken on 21 June 09.
At 12th span, the whole stretch of soffit cracks. The crack lines have been filled by something by bridge repair company that makes them so obvious.
12th span: You can see the crack width marked by the bridge repair company. One of them is 1.5mm
Before showing you some even more suprising pictures, please allow me to share some information on how may a civil engineer look into the cracks.
The easiest way to assess the seriousness of this problem is to compare the crack width with the allowable one in the code of practice --- it is 0.3mm
So now you see:
0.3 vs 1.5 (12th span), 2.1 (10th span) ---- 5 to 7 times the allowable crack width.
The 1st span: DALANG!!!! It's 8.65mm!
Say there's 100 cracks with average width of 3mm, and the span is 30m, what is the strain now? (10%)
How about assuming 4mm crack width? (13.33%, fatal)
How about the span is 25m instead of 30m? ...
So, why this bridge is still standing?
Because, it is not solely rely on the reinforcement. Supposingly, this is a post-tensioned bridge. The tendons may still playing their role on sustaining the bridge from breaking down, but they are now unable to sustain the bridge from crack badly.
By assuming it as a post tensioned bridge, the following may be the reasons causing these crack:
1) Underdesign
2) Underprovided prestressing force
3) Inappropriate input of design parameters e.g. material properties, creep coefficient.
4) Out of tolerance in construction
5) Act of god (most of politicians like this one)
So now comes to the final question: is it safe?
It depends on who say it.
For me, I will try to avoid using it for this moment.
For the owner, it is subject to the appraisal report of the bridge repairing company.
For the bridge repair company... I can feel that they are now like a sardin between their paymaster and the public. I hope that they are able to convince me to use the bridge again.
For the politicians... I don't know. But I recalled the MRR2 series in my mind now.
Structure: Lebuhraya Damansara-Puchong, Puchong Jaya interchange (Exit 1114)
Affected: Puchong residents (335,419 population)
Owner/ Management: Lingkaran Trans Kota Sdn Bhd
Design, supervision, construction and commission: Gamuda
Problem: Crack lines at bridge soffit
Corrective action: To Conduct Condition Assessment on Bridges Located along Lebuhraya Damansara-Puchong by Evenfit Consult.
Major crack lines found underneath the bridge!
I bet that not much people take this seriously (except the concessionaire) although thousands were using this bridge everyday either through the top or passing underneath it. The possible reason is that these defects do not causing anything fall down (yet).
The crack locations and widths are summarized in this figure. There are 2 rows of bridges running parallel throughout that supported by abutments at both ends , and 11 rows of piers in between.
For clarity, each space between supports (span) are labelled and colored. The U-turns and roads underneath the bridge are shown as well. From here, you can see how lucky was the owner that all defected parts are just nicely not above the road. That's why this issue were never brought up to newspaper.
Let's see some pictures taken on 21 June 09.
At 12th span, the whole stretch of soffit cracks. The crack lines have been filled by something by bridge repair company that makes them so obvious.
12th span: You can see the crack width marked by the bridge repair company. One of them is 1.5mm
Before showing you some even more suprising pictures, please allow me to share some information on how may a civil engineer look into the cracks.
The easiest way to assess the seriousness of this problem is to compare the crack width with the allowable one in the code of practice --- it is 0.3mm
So now you see:
0.3 vs 1.5 (12th span), 2.1 (10th span) ---- 5 to 7 times the allowable crack width.
The 1st span: DALANG!!!! It's 8.65mm!
Say there's 100 cracks with average width of 3mm, and the span is 30m, what is the strain now? (10%)
How about assuming 4mm crack width? (13.33%, fatal)
How about the span is 25m instead of 30m? ...
So, why this bridge is still standing?
Because, it is not solely rely on the reinforcement. Supposingly, this is a post-tensioned bridge. The tendons may still playing their role on sustaining the bridge from breaking down, but they are now unable to sustain the bridge from crack badly.
By assuming it as a post tensioned bridge, the following may be the reasons causing these crack:
1) Underdesign
2) Underprovided prestressing force
3) Inappropriate input of design parameters e.g. material properties, creep coefficient.
4) Out of tolerance in construction
5) Act of god (most of politicians like this one)
So now comes to the final question: is it safe?
It depends on who say it.
For me, I will try to avoid using it for this moment.
For the owner, it is subject to the appraisal report of the bridge repairing company.
For the bridge repair company... I can feel that they are now like a sardin between their paymaster and the public. I hope that they are able to convince me to use the bridge again.
For the politicians... I don't know. But I recalled the MRR2 series in my mind now.
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