Civil Engineering material - Essay Example

To make a reliable and stable structure for living and working are one of the basic necessities every human feels greatly. Civil engineers are people which make this necessity to reality. Earth quakes are one of the greatest natural disaster humans face since the formation of planet. Causalities caused by the occurrence of earth quakes look very ugly on seeing them for the first time to naked eye. It is a blessing of nature that most of the quakes happen in the ocean. Many developed cities fall to this might force of nature; industries crashed down and also many of the civilizations vanished from the face of earth.

During the present century the building that is not demolished from earth quake was one of the greatest challenges faced by engineers and scientists all over the world. It is a known fact that the conventional ways of construction used by humans for centuries are helpless whenever earth quakes occur. Concepts like seismic analysis of land and earth quake resistant structures are known in great extent by the engineers. It is unfortunate to see that after all of these researches and principals developed as a result of it; engineers and building experts lack in correct designing and manufacturing of buildings.

In this paper; different techniques used by civil engineers to design an earth quake resistant building are discussed (Dhakal). . Demand is commonly expressed as intended load a building can handle. In designing of any building this demand of structure is also taken into account. This technique is called allowable stress design. Another parameter discussed greatly by the engineers and scientists all over the world during 20th century to present day is working stress. In this technique service or working loads of the buildings should not exceed the allowable load.

Linear analysis and elastic range are well defined to get an idea of working stress the structure is going to face in the future. Approximate strength of the structure is measured by dividing material strengths by appropriate material factors. This technique is called ultimate strength design. Ultimate strength design has advantage over working stress structure; as it uses separate factors to deal any uncertainty in capacity and demand during the design of the building. Variation in concrete strengths is much greater than steel based structures; so smaller factors are used for the designing of concrete designs as it is done while designing steel or iron based structures.

Third technique that is used by civil engineers is known as limit state design structure; this can be regarded as extension of ultimate strength design, only difference is that more parameters of designs are required to be fulfilled by engineers. Commonly two states are used by the engineers called service ability limit state (SLS) and Ultimate limit state (ULS). SLS is used by engineers to make sure that structure is proper functional and there is no discomfort caused by normal loading procedures related to building structure.

SLS criteria are satisfied by deflection, vibration and cracks are