Langtang reconstruction/ working document

Transcription

1 Langtang reconstruction/ working document We received the first project the Langtang committee prepared with the costs. We will use this project as a base of reflection and guideline for our proposal and analyze. To make this document, we also used a lot of documentation made by different NGO and international organizations on how to rebuild an earthquake resistant house in rural areas. This present document must be seen as a proposal to be used as a working tool for the Langtang Reconstruction project. This proposal and reflections are based on the request the Langtang people present to the government on June. Here is an extract of the Langtang Valley Rehabilitation Agenda written by the Comittee, concerning the house reconstruction: Reconstruction of Houses: The houses have to be reconstructed with respect to earthquake, weather condition, culture and tradition. The houses should be made according to the family members and should be environment friendly, good care should be given to sanitation and water system. We can divide the upper request of Langtang community in different main points : A : Earthquake resilient B : Confort C : Environnment friendly D : Acoording to the family members culture and traditions. First Plan send by the committee on the 12 of August A : Earthquake resistant houses: you can see in the annex langtang reconstruction working.odt 1/6

2 document a list of the most important rules to follow to build resistant houses. 1) Shape : First Plan : The proposed plan is in L shape and is non symmetric. A simple and symmetric building resist better on earthquakes. An asymmetry leads to torsion during earthquakes and is dangerous. Symmetry is also desirable in the placing and size of doors and windows. Conclusions: Simple rectangular shapes, behave better in an earthquake than shapes with many projections. If the L shape is desired then the L shape should be separated in several blocks. 2) Building materials and systeme : First plan : No much information is given. On the plan the house seems to be made of reinforces concrete frame with infill the wall seems quite thin and on the coding it's writhen stone walls 45 cm breadth. The infill wall panels in RC frame buildings do not act as shear walls - they act as diagonal struts. The gaps, due to a relative lack of bond between the masonry infill and the RC frame, drastically minimize the capability of infill walls from resisting the lateral langtang reconstruction working.odt 2/6

3 forces in a seismic event, as illustrated in Figure 3 a). Conclusions : Confined masonry building fig b) where the frame and the infill are acting together are much more efficient. Detailing of reinforcement in confined masonry is relatively simple. It is easier to perform an inspection of concrete construction in a confined masonry building compared to an RC frame building or a reinforced block masonry building. Due to a lower consumption of steel and cement, construction of a confined masonry building is expected to be more economical compared to an otherwise similar RC(reinforces concrete) frame building with infills (Seismic Design Guide for Low-Rise Confined Masonry Buildings ) A thick (at least 35cm) stone masonry walls can be used instead of reinforces concrete frames. In this case only horizontal beams need to be added to the stones (no vertical steal reinforcement) 3) Roof structure : Proposed Plan : The proposed roof is a reinforces concrete flat roof. The studies of past earthquakes show that the use of light roof is better. Reinforces concrete roof are heavy compared to timber or metal roofs, and that may be a disadvantage. However reinforced concrete roofs are stiff in their own plane which is a positive feature, while falling down a heavy roof is much more dangerous. They are called the concrete killer pancakes. It is difficult to lay stones around this bars in thik rubbel stones walls they are not expected to be effective in resisting seismic forces. langtang reconstruction working.odt 3/6

4 Conclusion : A heavy RC roof can be particularly dangerous it is also too expensive. A light timber or metal roof is to be preferred. It should be braced and attached to the walls. A two side roof on rectangular building is easier to build than L shape roof with slopes, there is no reentrant angle. B : Comfort 1) Weather conditions First Plan : No information about insulation is given. A cement plaster is not recommended for heat and damp (humidity) regulation. In the coding there is a 20mm tick plaster described and its price is 40% of the total price of the house which is far too expensive and no any comfort is provide Conclusions : A earth inside insulation and wooden facing as used in the traditional houses can be very good solution. These are also healthy and environmental friendly materials. A thick stone wall provides more thermal inertia and is much more comfortable in winter time. Thick stone walls should be place also according to the prevailing winds to protect the house. Openings should be made in the walls to the south to bring the warmth of the sun inside the building. Conclusions: It's more comfortable to have a sanitary inside especially in cold places like Kianjin Gumpa (3800m high village). A special attention has to be paid to the pipes and waste water canalizations. Attention is to be paid to the length, localization, inclination and protection from freezing. Think the waste treatment in a global scale (groups of houses). In addition a special attention should be paid on the fire smoke evacuation and the position of fire place and chimney tubes The actual place for rebuilding accorded is Kyanjin Gumpa for almost all the houses. There should be study about the local resource for water and energy supplies and the waste treatment to see if the place can support more than 100 houses to be rebuilt without creating a sanitary problem. How many of the existing houses and guest houses can be rebuild? 3) View and natural light: First Plan: The project seems to be wild open to all directions and well balanced Conclusions: To see the beautifull view on the mountains inside the houses is no doubt a comfort. To have as much as possible natural light is also a comfort and economy (less use of electricity). The openings should be made in according to the site, the view and the exposure to the sun and the wind without forgetting the structural stability of the house. 2) Sanitary conditions : First Plan : The sanitary are inside the houses. langtang reconstruction working.odt 4/6

5 C : Environment friendly First Plan : The first plan use a lot of cement. A large use of cement. Approximate cost of cement bag in Ktm is 670 Rs. Approximate cost of transport by porter from road to Kyanjin Gumpa is 3500 Rs (more then 5 times the price of material). There should be added the price of transport from Ktm to Shyabru Besi. Conclusions : 3 good reasons to use less cement as possible: Cement and reinforced concrete are not environmental friendly materials. Because of the price of transportation, it increase a lot the price of the house. It is difficult to have easy control on the quality of material. There is a possibility to have an important deterioration during the transport and storage due to humidity which can make the cement weaker and unusable Favor the use of local materials like stones and wood. Use local knowledge to enable the local people to build their own houses. Provide a technical support that can be easily assimilated and learned by the local peoples. D : According to the family members, culture and traditions First Plan : The plan don t seems to have a lot to do with the traditional house style. A single plan cannot be appropriate for all types of families (according to the number of members and age) Conclusions : Developed different types of house according to the size of the families. Think the project in a modular way. Give the possibility of future extension and new building constructions? Favor the use of local materials like stones and wood. The traditional house is a two storey houses made of stone walls and wood. Work on this model to improve the local techniques. The question of timber is quite complex : Need to know what is the possibility to reuse the timber from the existing houses, the broken trees by the avalanches or to cut more woods in the National Park. See with the government what is possible and what will be the price. See what wood can be used for the structural purpose, which one can be used for inside facing, for doors windows and furniture and which one can be used for roof coverage. An NGO called SEBEN wants to install a saw machine in Langtang. It can be an interesting and challenging project; the problem is they cannot use the broken wood because of the stones inside. Before the earthquake the price of cutting wood in the national Park was quite expensive. We need more information and studies, to know if it is interesting to use wood and on what purpose. The use of wood seems to be important in the traditional style of houses. The wood can be very interesting to be used as horizontal beams in the walls, for the roof and floor structures, or for roof coverage. langtang reconstruction working.odt 5/6

6 According to the upper analyze and reflections here are some proposals for house design and building techniques. These are only proposal to be used for a more reflection on Langtang Reconstruction with the participation of all Langtang community, different NGO, government and local institutions: -Use of as much as possible local resources, materials and labor is the main answer to how to rebuild. This will reduce the cost because of the difficulty of transport. Especially if most of the houses are to be rebuild in Kyanjin Gumpa. The local houses and materials available are stones and timber. Need further discussions with National Park and NGO to know how much it will cost to use timber for the constructions. Need more studies to know what quality of timber can be provide. Wood can be used for : Flooring if a two storey house is constructed. Roof structure. Horizontal beams in stone masonery Complete or partial structure of the walls of the second floor if this kind of solution is accepted by the engineers. Timber frame with sub frames and infilling. Roof covering Doors and windows It depend on the availability of wood, quality, project for installing saw machine, possibility of cutting wood in National Park and price to be payer for cutting wood. The windows should be made on the traditional style. -Thick stone masonry with horizontal beams seems to be a good solution for one or two storey houses. The beams can be made of : - reinforced concrete - timber - gabion bands (see annex for more details). The gabion solution proposed by Randolph Landenbach is particularly interesting because of its simplicity and low cost. The chosen solution will decides the kind of stone masonry, the kind of mortar to be used and so the price. Stone masonry needs a lot of unskilled labor. It is much easier to supervise and control the quality. The techniques are easy to understand and to implement. This will create work for local people if they what to do the constructions and so the money will go more for the local economy. langtang reconstruction working.odt 6/6