Friday, December 28, 2007

My Comment on Collapse of Suspension Bridge over Bheri River

परीणाम : वजन नियन्त्रण सम्बन्धी प्रभावकरी कानुनी अभाब अनी लापर्वही

के भयो ?

December 25 - According to www.kantipuronline.com and www.mysansar.com, at least 15 persons died and tens of others went missing when a suspension bridge over the Bheri River at Shobhaghat near Mehalkuna bazaar, Surkhet district collapsed on Tuesday afternoon. Initially, 300-400 people were estimated to be missing. However, only 13 dead bodies were recovered by mid-night. Exact number of missing is still unknown. It has been reported that around 200 of those who fell into the river reportedly managed to swim to safety while a considerable number of others were rescued. Result of lack of regulation of weight over the suspension bridge and negligence of people

किन ?
Not only engineers and planners but everybody should know that engineering structures have its capacity to perform safely. In this terrible incidence, designer, regulator body, and people were failed to obey this simple principle of nature. Rural Nepalese people just think that iron structure never fails or at least steel/iron structures has an image of infinite strength which is not true in reality. On the other hand, there is lack of regulation of weight on suspension bridges in Nepal. I have personally never seen any detail specification on suspension bridge. In my opinion, regardless of specification and regulation, designer should post the live load limit of the bridge in terms of number of people in order to avoid premature bridge damage and structural collapse. This will be also a great humanitarian help to uneducated Nepalese people.
Just before writing this comment, my friend Hikmat BC, who is also from the same village told me that there were approximately 300-500 people on the bridge. In average, if we multiply 400 people times 55kg (average weight of people), it gives total weight of 22000 kg. This is far beyond the limit of ordinary suspension bridge. Despite the warning from security personnel, people stayed on the bridge enjoying the scenic view. I guess that defying security personnel’s order/request is a sign of bravery in recent day’s in Nepalese society. But the truth is whether we follow or not, natures always obey its law. As a consequence there was heavy loss of life. In this moment, I prey for the departed souls to rest in peace and bless their family members with the courage to overcome their sorrow.


के गर्न सकिन्छ ?
Finally as member of civil engineering society, I recommend the followings:

1. Bridge designer must provide the LIVE LOAD CAPACITY IN TERMS OF NUMBER OF PEOPLE and are posted on both sides of the bridge in plain Nepali language.
2. Try to increase factor of safety considering the worst case scenario.
3. Awareness education regarding the number of people can use the bridge at a time be provided to the people of surrounding areas.
4. During the special events such as MEELA-BAZZAR, local volunteers should be mobilized to control number of people over the bridge.

Desh Raj Limbu
www.drsonyok.web.scom


Thursday, December 27, 2007

GPR as a Highway Infrastructure Condition Diagnostic Tool

Ground Penetration Radar (GPR) is a powerful, reliable and high performance non destructive testing tool for solving various kinds of engineering problems related to geotechnical site investigation, construction, and maintenance of highways and bridges. It has been increasingly utilized for the management of highway infrastructures such as road pavements and bridges on a network level which requires condition assessment and deterioration modeling. GPR can determine the layer thickness and estimate moisture content of the in-situ soil underlying the pavement. It has a promising future because of its efficiency, quality, and non-destructiveness. GPR provides reliable and significant information to pavement condition evaluation that is very useful to predict the pavement’s structural capacity and performance. This will further help improve pavement maintenance and rehabilitation strategies, and in the long term, it provides rationalities in allocating funds. GPR in combination with other nondestructive evaluation methods such as Falling Wheel Deflectometer (FWD) or Rolling Wheel Deflectometer (RWD) can provide complete data for pavement layer thickness, deflection and elastic moduli for the mechanistic pavement performance prediction model. However, the application of GPR in highway engineering is limited because of our incomplete understanding of the dielectric properties of highway materials. 



Figure: Ground Pentration Radar (Sonyok and Zhang 2008)

Wednesday, December 26, 2007