- Reconstruction demands serious study of the factors that led to collapse of buildings during the quake
Jun 20, 2015-
The April 25 quake followed by its 7.3 magnitude aftershock on May 12 has damaged or destroyed over 500,000 private buildings—residential, commercial—and national heritages. As many as 40,000 residential buildings in and around Kathmandu have been seriously affected. Some of these buildings can still be used while others should be completely demolished. On visiting numerous houses to provide free consultation I noticed fear in the eyes of all the houseowners. After each such rapid visual assessment, residents would immediately ask for a quick solution to rebuild their damaged houses. Such hurry for a quick fix, however, could prove to be fatal depending upon the nature of damages developed at various locations of the structure.
Haste makes waste
A detailed study of the structure of buildings in the Valley is a must for the implementation of strengthening techniques. Still, as we expect aftershocks to continue for a while, we cannot ignore the fact that the reconstructed structures are more vulnerable when the casting is fresh. We have suffered enough due to the low quality of construction, why suffer more by hurrying reconstruction? Further, reconstruction does not imply merely plastering the exposed, reinforced or concrete, structures. How can a building whose structure has already been damaged badly with-stand another shock by merely being polished outside?
Another conclusion that can be drawn by observing the damaged buildings is that the haphazard use of cement is not enough to make them hazard-resistant. Many reinforced concrete structures have also been seriously damaged due to various reasons. They include the nature of soil beneath the foundation, less detailing of the structures, disarrangement of the grid in allocating columns, beam-column joint detailing, overlap length misinterpretation (lap splice), poor workmanship and inappropriate spacing of shear reinforcement among others. Such buildings cannot withstand sudden jerks during earthquakes though they could perform well during normal times. Buildings that will be constructed in the future should, therefore, not repeat these shortcomings during construction.
The load-bearing wall structures, life -span of the structures, construction materials and techniques used, use of excessive uncooked bricks and unstable ground beneath are some other major reasons for the failure of structures. The load-bearing structures where wood has been used wisely have performed very well and survived the devastating quake. Nonetheless, more research is needed with regards to the wise use of wood to strengthen buildings with a traditional Nepali facade.
Topmost priority should be given to reconstruct culturally sound towns and villages. With regards to national heritages that have been destroyed, the artefacts should reflect the orginal work.
In the long-run, Nepal needs a national policy to guide reconstruction of partially or fully damaged structures. Quite a few of them have enormous cultural and national value. So while reconstructing them, great care must be taken to restore them back to their old form. At the same time, new technologies must be adopted in its reconstruction so that such national monuments are able to withstand other probable natural disasters in the future. Their identity and quality should never compromised. New buildings should reflect the ancient glories they signify and uphold our national values.
Plan for posterity
The need of the hour is to conduct a detailed study regarding why some structures fell while others withstood the quake despite similar horizontal motion impact. Likewise, using debris to create a new, modern, green concrete could be another aspect of the study. Many researches have already shown positive results with regards to the use of fallen concrete, fibers, tyres and other materials which are yet to be experimented in Nepal. They could be a good source of raw material for new construction. Wise use of those materials could be a good approach to constructing strong buildings that are also resilient in times of natural disasters.
Neupane is a structural engineer
Published: 21-06-2015 08:20