New Construction - Strengthening
Here are some useful tips for new construction and strengthening of existing buildings.
Buildings should be designed by a competent engineer following the 1993 Bangladesh National Building Code. Earthquake resistant design involves the use of steel which is a ductile material. It is not economically possible to design a building to resist the extreme earthquake forces without some damage. The building code allows some damage at preferred locations but prevents building collapse and provides safety to life and property. Steel gives the building necessary properties to resist collapse if they are provided at the correct locations of the structure. Structural elements that provide the earthquake resistance include concrete or masonry shear walls, concrete frame, braced frame, rigid floor system and proper connections between them. Proper detailing of the steel reinforcements at critical locations of the building structure is of great significance. ACI (American Concrete Institute) code gives seismic design detailing requirements for reinforced concrete buildings. Other standard building codes such as IBC2000 may also be consulted.
Strengthening of non-engineered buildings can be done following the IAEE (International Association for Earthquake Engineering) manual on Guidelines for Earthquake Resistant Non-Engineered Construction.
Certain building types are likely to be more susceptible to serious damage or collapse and thus require structural assessment for earthquakes by a competent engineer. Such buildings if not properly designed may need special strengthening measures.
Some typical examples are given below:
- Old URM buildings with cracks in walls and roofs on timber beams.
- URM buildings on 5 walls.
- Multi-storied URM buildings with discontinuous lintel.
- Multi-storied RCF building with open parking space on ground floor. Soft-story action or weak column-strong beam action should be prevented.
- Multistoried buildings with large cantilever projections.
- Multi-storied buildings of irregular (unsymmetrical) shape or having setbacks.
- Buildings having mass eccentricity.
- Buildings with flat plates.
- Buildings having elevated water tanks or swimming pool on roof top.
- Adjacent multi-storied buildings with little gap, hence possibility of pounding.
- Slender high rise buildings.
- Buildings on soft soil (fill material).
- Buildings having elevated water tanks or swimming pool on roof top.
- Adjacent multi-storied buildings with little gap, hence possibility of pounding.
- Slender high rise buildings.
- Buildings on soft soil (fill material).
