saw this news on property malaysia, which directed from:
http://bolehlandconstruction.blogspot.com/2009/06/ldp-puchong-jaya-interchange-major.html

http://4.bp.blogspot.com/_agTCuCLTwXE/Sj66dNezrNI/AAAAAAAAAA0/rXOb1H3sE2M/s1600/Drawing1-Model.jpg

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.

http://3.bp.blogspot.com/_afUZ_NAOL_4/Sl-rzi77HMI/AAAAAAAAAAM/Dzv0Q57TU6g/s1600/puchong-jaya2.jpg
Photo link from Litrak.com.my

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).

http://4.bp.blogspot.com/_agTCuCLTwXE/SkFd_EXU2eI/AAAAAAAAACE/CRrC4LrZOSE/s320/IMAG0055.jpg

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.

http://1.bp.blogspot.com/_agTCuCLTwXE/SkARX1djerI/AAAAAAAAAA8/ugnh6oYcaH0/s320/Drawing1-Model2.jpg

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.
http://2.bp.blogspot.com/_agTCuCLTwXE/Sj4mEzEqdLI/AAAAAAAAAAc/aQ187gPFRQA/s320/IMAG0022.jpg

12th span: You can see the crack width marked by the bridge repair company. One of them is 1.5mm
http://4.bp.blogspot.com/_agTCuCLTwXE/SkAVGNZtL1I/AAAAAAAAABE/QScXVpTHEuo/s320/IMAG0024.jpg

11th span: The crack lines in 11th span are spreading out from its mid span and they are not as widespreaded as the end (12th) span.
http://4.bp.blogspot.com/_agTCuCLTwXE/SkAVrvW_AMI/AAAAAAAAABM/4FaJZcfzZNA/s320/IMAG0026.jpg

11th span: The bridge on left hand side
http://3.bp.blogspot.com/_agTCuCLTwXE/SkAY7s3-PhI/AAAAAAAAABU/0gmbm7T7KCA/s320/IMAG0027.jpg

10th span: Crack width 2.1mm
http://1.bp.blogspot.com/_agTCuCLTwXE/SkAZUxErCZI/AAAAAAAAABc/Wk5u8HsX-p0/s320/IMAG0029.jpg

10th span: Except these funny marks that doesn't looks like structural crack, I couldn't see any crack line marking here. I also can not find any crack line by nake eye through 4m height distance. But, please help me to remember that this span does not crack on 21 June 09, this information could be useful one day in the future.
http://1.bp.blogspot.com/_agTCuCLTwXE/SkAaOu00O6I/AAAAAAAAABk/RYynPAR629o/s320/IMAG0033.jpg

5th to 9th span: Nothing special found
http://4.bp.blogspot.com/_agTCuCLTwXE/SkAbR6x28UI/AAAAAAAAABs/Z-LNKyGEm0w/s320/IMAG0034.jpg

4th span: Some more crack lines found and they are "still young" compared with others.
http://3.bp.blogspot.com/_agTCuCLTwXE/SkAbwxKF62I/AAAAAAAAAB0/OLEVGmcbaxQ/s320/IMAG0035.jpg

4th span: Crack width 1.25mm
http://4.bp.blogspot.com/_agTCuCLTwXE/SkAcuaG0dII/AAAAAAAAAB8/2tVnA8pcvQE/s320/IMAG0040.jpg

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.

What does it means?
The reinforcement steels are now exposed to corrosion. After sometime, when the reinforcements cross sections are largely rusted to the extend that the remains are incapacle to withstand the tension force anymore, they will yield, or just snap off.

Not serious enough?
Let's go further down. This may need some effort to understand.

Steel elongation limit: There's a requirement on the steel bar elongation limit. For high yield deformed bar (don't bother with this jargon, just treat it as steel bar), the first limit is 0.2% and the fatal limit is around 12%.

The 0.2% elongation indicates a point where the strain is permanent. For example:

-You pull a 1m long bar to 1.001m (the elongation is 1mm, the strain is 0.1%) then release, the bar shrink back to 1.000m. The strain is not permanent.

-You pull the same bar to 1.005 (elongation = 5mm, strain is 0.5% which is exceeding 0.2%) then release. The bar does not shrink anymore or just shrink a little, e.g. 1.004mm or 1.0045mm, which is permanent. Once you apply the same force to it again, it will go further.

If you keep pulling the 1m bar to 1.12m (12%), the necking will appear and prepare to listen to a big bang sound --- the steel snapped.

Where are we now?
We have gone through some critical requirements. So, what is the steel elongation of the bridge? Is it less than 0.2%, between 0.2% and 12% or has already exceeded 12%? Please allow me to do some pluck-from-the-sky since I can't count exactly how many crack is there:
-Assume the 12th span is 30m (believe me, the owner prefer me to assume it as long as possible for the following calculation)
-Assuming there's 300 cracks across the span, each of them are 0.5mm (compared with 1.5 shown in the figure, I've discounted alot)

Then, elongation of the bottom bars is now 300*0.5 = 150mm
Strain = 150/30000 = 0.005 or 0.5%, Oops, these bars are now on the way to the hell (>0.2%). Every overloaded truck passing on top of it will induce additional elongation to it, no return.

Let's see more photos:

The 1st span: before you proceed to the next photo, please guest the crack width...
http://4.bp.blogspot.com/_agTCuCLTwXE/SkK7DM1balI/AAAAAAAAACM/HnexQePMYUQ/s320/IMAG0051.jpg

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? ...

How about....
http://4.bp.blogspot.com/_agTCuCLTwXE/SkK7YCb7gbI/AAAAAAAAACU/6x_IzSVAA98/s320/IMAG0054.jpg

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)

Some other defects:

The 1st span: The exposed bottom reinforcement to be patched
http://3.bp.blogspot.com/_agTCuCLTwXE/SkK8LY11mII/AAAAAAAAACk/60TA7jCJZWI/s320/IMAG0049.jpg

The 1st span: Some more exposed bottom reinforcement to be patched
http://2.bp.blogspot.com/_agTCuCLTwXE/SkK8Dzu6TnI/AAAAAAAAACc/wc4kGP11fyI/s320/IMAG0052.jpg

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.

^^ apparently the answers is in today's star metro central

http://thestar.com.my/metro/story.asp?file=/2009/7/23/central/4371503&sec=central

just in case anyone else still carry the same worry as me, who are using that bridge everyday, here's a case study to read on:


Shrinkage cracking at interior supports of continuous pre-cast pre-stressed concrete girder bridges

This study deals with the control of cracking at interior supports of continuous pre-cast pre-stressed concrete (PCS) girder bridges. Since PCS-girder bridges are constructed by placing in-situ concrete decks on the PCS-girders at time intervals, the differences in material properties and age at loading between the deck and girder lead to time-dependent material behaviors. In addition, the continuous deck by providing a negative moment connection at interior supports, also causes the transverse cracking of the concrete deck at interior supports. In that way, cracking at interior supports is predicted with the analytical model introduced in the companion paper. Based on the ACI model, the ultimate shrinkage strain is expressed as a function of concrete slump and the relative humidity while the other remaining factors such as unit weight of cement and air content are assumed, in accordance with the typical values in mixed concrete. Finally, field recommendations in terms of concrete slump and relative humidity are suggested to minimize early transverse cracking of concrete decks at interior supports.

Author Keywords: Continuous pre-cast pre-stressed concrete bridges; Field recommendation creep; Shrinkage; Continuity of spans


direct link:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2G-456W64P-5&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=916f9457d7793b696b504372044e008d

Litrak: Interchange is safe
Thursday July 23, 2009 By THO XIN YI
Source: http://thestar.com.my/metro/story.asp?file=/2009/7/23/central/4371503&sec=central

http://thestar.com.my/archives/2009/7/23/central/m_01ldpflyover.jpg

LITRAK, the concessionaire of the Damansara-Puchong Expressway (LDP), has assured roadusers that the highway’s Puchong Jaya Interchange is safe for the public to use.

Many roadusers are alarmed by the cracks that have appeared at the base of the bridge.

They found out about the situation from a widely-circulated e-mail titled LDP Puchong Jaya Interchange: Major Crack Line Found, which was obtained from an anonymous blog.

The blogger claimed that the cracks range from 1.25mm to 8.65mm in width while the permissible range is only 0.3mm.

http://thestar.com.my/archives/2009/7/23/central/m_04dass.jpg

Dass: No new cracks were found during our
fortnightly inspection after the cracks were sealed.

The blogger warned of the possibility of the steel being exposed to corrosion and eventually giving way when it could no longer withstand the force of the tension.

“Now comes the final question: Is it safe?” the blogger wrote.

The e-mail caught the attention of Public Works Department (JKR) director-general Datuk Seri Prof Judin Abdul Karim, who visited the site together with his officers and Malaysian Highway Authority (LLM) deputy director-general Mohd Shuhaimi Hassan.

Also present were Litrak chief executive officer Sazally Saidi, engineering department senior manager Francisco Anthony Dass and communications head Bhavani Krishna Iyer.

Litrak assured roadusers that the cracks were not a threat to safety.

It also said the blogger had made conclusions without any in-depth knowledge and history of the cracks.

http://thestar.com.my/archives/2009/7/23/central/m_04flyover.jpg

Visible: The cracks at the base of the interchange

“We discovered the cracks during an annual inspection programme conducted last year and started repair works in March this year. The photos taken by the blogger were after the cracks were sealed in May.

“The blogger assumed the width of the cracks based on some markings on the bottom slab when the figures actually represent the length of the cracks in metres,” Sazally said.

Dass said the cracks were most probably due to shrinkage, and that these were only hairline cracks.

“As they were too fine, we had to groove the cracks, seal and inject epoxy inside.

“As advised by our consultant, we have been monitoring the areas repaired regularly to check whether the problem is solved or if new cracks have appeared. That is why we have not painted it till now,” he said.

Dass added that there were no new cracks found during their fortnightly inspection, with the last one held on July 14.

Bhavani said Litrak had no idea who was behind the anonymous blog.

“Many roadusers have e-mailed us to voice their concerns and we have explained the actual situation.

“In fact, we do not mind having a one-to-one session with the blogger as we have nothing to hide,” she said.

scary mannn

LDP bridge is safe, says board
Saturday July 25, 2009
> http://thestar.com.my/news/story.asp?file=/2009/7/25/nation/4391335&sec=nation

PETALING JAYA: The Puchong Jaya Intersection-Damansara Puchong Expressway bridge is safe, said the Malaysian Highway Board.

The bridge undergoes annual checks by consultant specialists appointed by expressway concessionaire Litrak, the board said in a press statement yesterday.

From the studies carried out, the cracks were not critical and had not affected the structural integrity of the bridge structure, it added.

The consultants involved in repairs had cemented the cracks using the epoxy injection method.

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