Designing Resistant Buildings For Natural Disasters

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In 18th and 19th centuries many of the British scientists laid the foundation engineering for the earthquakes. Due to the Industrial Revolution (1700-1900) England has powerfully subjective developments in a range of sciences not because of high seismicity. In Royal Society of London, Robert Hooke (1635-1703), known for his "Law of Elasticity", who gave his talks about the earthquakes and volcanoes, the first Scientist to become intent in the earthquake observable fact. The terms as "Epicentre" and "Focal Point" was also introduced by Robert Mallet. In 1848 he also published plans for the first Electromagnetic Seismograph, but the instrument was never built, later this Mallet theory was modified by Italian-born Luigi Palmieri (1867-1896) and built the first Automatic Seismograph and obtained the first Modern Earthquakes records.

In recent years the Natural disaster like Earthquakes has been considered as the major fact around the world, since the buildings are foremost issues that have been affected during the earthquake, can we predict the buildings from these disasters? Many Researches have been done for this issue that, which way the building can resists while occurring Earthquakes and Tsunamis. In San Francisco (1906), Missina, Italy was shaken by aggressive earthquake which ravaged that city and many others cities and towns, nearly 83,000 people died due to building collapse and damages that led to the first Earthquake Resistant Construction methods and therefore, the science of Earthquake Engineering. When coming to the prediction many people question is that can we predict the earthquake? William Hung Kan Lee (2000) states that an earthquake occurs suddenly, often with the demoralizing consequences, earthquake prediction are a matter of great interest among the civic and crisis officials. However, the term earthquake prediction is often used to three different things,

Highly Reliable to public

Short-term (within hours to weeks) prediction that will prompt some emergency measures for e.g. (Alert, evacuation, etc...)

Long-Term ( within Days to Months)

On the Basis of long term prediction of possible future strong earthquakes, i.e. their time, magnitude, location and probability, this may give some promise to assess value of selected parameters in the ground motion to be expected, this is referred to as the Seismic Hazard Assessment (SHA)

James R. Harris (1991) proposed the theories and practice for Earthquake Resistant Design Building, today's seismic provisions are specified how to calculate the unique earthquake induced lateral force. The main idea to construct a resistant building is that can resists the horizontal forces, which quotes to the central design of seismic building. Later on many cities have realised that their concrete and steel building were not seismically designed, where as that cannot resists the ground-shaking (Earthquakes).While designing a structure of a building, the structural engineer has more tasks and ensure whether it combines with the earthquake lateral force with other code-precise forces, such as wind or snow load, to attain the maximum feasible force. Based on the maximum combination the structure is designed for the earthquakes to resist the building. Although, calculating earthquake forces may be less than the wind or snow force.

Robert B. Olshansky, (2002) states that buildings which are tall don't have abnormal shapes have need of more wide-ranging design analysis. When a building has a complex shape the designer must make use of dynamic structural response analysis, a computer analysis that stimulates the buildings influential (side-to-side movement) during an earthquake. The model reflects the buildings performance, theoretically similar to a vibrating string.

Pankaj Agarwal, (1998) gives his statement as knowledge of the foundation soil is much essential to design an earthquake resistant building. There are some cases where the soil behave well under static loads will pose serious problem under the seismic loads. The problems relates to foundation soil can be classified mainly two groups

Influence of subsoil on the features of seismic movement, landslides and loss of soil resistance (liquefaction), these problems are not significantly affected by the structures and their foundations.

Problems caused by the loads transmitted to the soil by foundations and the settling of the foundations under static and seismic loads.

This problem commonly arises due to the loose unsaturated soils, which may be squashed as a result of earthquake. Earthquakes can harshly disrupt the foundation of buildings, consequently causing structural distress and the failure occurs and indemnity of buildings. This can sorted by designing proper foundation or by sensible site selection i.e. soil condition. So, as far as concern in this issue the Foundations for an earthquake resistant building plays a vital role and this gives that, how the building can be designed and which foundation will be appropriate for this current topic i.e. to resists the earthquake and prevent the buildings, losses of lives through building damages.

Literature Review

Many researches have been done for Earthquake resisting building and their causes factors have been carried out by many structural engineers (Prakash, 2002; Doboku Gakkai; 2000; Margaret., Majithia 2002; ) gives that the designs for earthquake force acting on the super-structure is strong-minded pretentious that the foundation is fixed; the structure is then designed to withstand that force. In charge to make that foundation stable during an earthquake, the ground adjoining is organized in such a way that it withstands the earthquake force transferred by the superstructure as well as the inertia force of the foundation itself. All the engineers made their study in resistant building elsewhere Atilla Ansal, et al. 2003 and Andrej S, Nowak, Theodore V, Galambos, et. al 2002, who worked particularly on the foundation of the earthquake resisting building and they stated that if the foundation of the structure is not designed accurately then the whole structure can be collapsed and damaged.

For example, William George Curtin, Norman Seward, et. al, 2001, who assured the reason for the failure of the foundation and whole structure of the building, that the function of a foundation is to transfer the load from the structure to the ground i.e. soil supporting it and it must do this safely, for if it doesn't then the foundation can cause the failure particularly in bearing and settlement, and that can led to the serious position to destruct the entire structure of the building. Gerry Shaw, 1999., Gary Parkinson, J. Golding 2000, examined that two reasons of foundation failure were as follows.

Bearing capacity. When the shear stress within the soil, due to the structures loading, exceeds the shear strength of the soil, catastrophic collapse of the following soil can occur. Before ultimate collapse of the soil occurs there can be large deformations within it which may lead to intolerable disparity movement or settlement of, and damage to the structure. In some of the cases nevertheless collapse an occur with little or in advance warning.

Settlement. Provided that the settlement is either acceptable that will not cause structural damage or excessive cracking when the earthquake occurs, will not damage services, or can be catered for in the structural design by three-pinned arches which can provide somewhere to stay settlement, of fixed frames. Problems will occur when the settlement is extensively too much or disparity. Settlement is the combination of two phenomena

Contraction of the soil

Consolidation of the soil

David J. Dowrik, 2002 subjected the foundation of the building to earthquake stresses, and major recommendation on structural design must be borne in mind

Foundation should preferably be designed as continuous(mat or raft) in order to avoid relative horizontal displacement

In case of isolated footing, they should be joined to each other by means of foundation beams or ties. These ties should be designed such that it will bear tension and compression forces.

It is recommended that parts of building foundations, which rest on soils of different types or are sunk to different depths, should be designed as separate units. Likewise in these cases there also must be structural liberty in the superstructure.

As mentioned in the above statement, the different foundation for the resistant building for earthquake will be discussed further and, since they have been considered as the main issue of this topic.

Therefore, the discussion and debates on foundation for earthquakes resistant, Reinforced Cement Concrete (RCC), Steel Structures and preventing for the people form the building damages during earthquakes has been following for a long period by the researches. Some of the researches conveyed that the enhanced design for resisting earthquake is the RCC structures where as David Anthony Fanella, et, al 2004 states that the floors and roofs constructed of reinforced concrete or concrete fill on metal deck are almost consistently rigid diaphragms (unless very large openings are made in such diaphragms). This type of concrete is that which resists the shear as long as it is reinforced. The reinforcement may be in the form of reinforcing bars laid out in both directions at the uniform spacing such that the load is distributed all over the corners of footing and can withstand the building when the earthquake occurs (Roger Paul Johnson, et, al. 1999). In many cases, a sufficient amount of longitudinal reinforcement may be present along the edges of concrete diaphragms, with or without the presence of beams, to resist the chord forces. If that is not this case, some extra chord reinforcement must be added.

Wai-Fah Chen, et, al 2001, E.M.Lui, et. al, 2000 stated that rather doing in the RCC the convenient and enhanced way to design resistant structure is Steel-Framed structure where the design is made in steel works and they may be classified as MEFs, braced frames, mixed construction(e.g., steel framed for vertical forces and reinforced concrete shear wall for the LFRS) based in their LFRSs. In concentric braced frames the lateral forces are resisted by the tensile and compressive. Whereas in the RCC framed structure the lateral forces acted along vertical forces so they have less compression and doesn't have the capacity to withstand and occurs some damages to buildings during the earthquakes.

Approach and Methods

Designing by Different Foundations

This research focuses on designing the foundation, RCC and Steel Structure design for earthquake resistant. There are different types of the foundations which have to be discussed for this research. Some of them are as follows.

Mat or Raft Foundation

Shallow Foundation

Pile Foundation

1) Mat or Raft Foundation

"A Raft Foundation is continuous slab of concrete usually covering an area equal to or greater than the base of a building or structure to provide support for walls or lightly loaded columns and serve as a base for the ground floor". These foundations are rarely used for evenly loaded structures on soil with the poor bearing capacity and where variations in soil conditions necessitate a considerable spread of loads and this has a capacity where it can withstand when earthquake occurs. Since this foundation is not economic it is very costly but this the way to design the earthquake resisting building (Stephen Emmit, et, al, 2002)

Raft Foundation (J.A Hemsley 1997)

For example, Canary Wharf Office Tower, London, UK 263m high 50-storey steel framed office tower is the focal point of the canary wharf project, situated near Thames River in east London this was designed by using the raft foundation (J.A Hemsley et, al 1997).

2) Shallow Foundation

A Shallow or Deep Foundation (G.A. Leonards,, 1973) defines that shallow foundation as one in which the structural loads are transmitted to the soil at an elevation required for the function of the structure itself. Hsai-Yang Fang, et, al. 1998 states that the most economical is the shallow foundation where as the isolated spread footings area is less than 40% of the total area of the structure.

Example of Shallow Foundation in wood (T.A Newson., 2000)

On the other hand, it is general to consider that inclined loads only for force of superstructure in seismic load-capacity problem of shallow foundation. This seismic design of foundation is considered in the ground the inertia force acts opposite to earthquake direction and the failure occurs when the ground is shaken or vibration (T.A Newson et, al 2000).

3) Pile Foundation

A number of different ground improvement methods are suitable for use in the composite ground for the pile method. To simplify the model for testing the accurate area soil is the sandy soil where high improvement rate was adopted in the ground improvement method around the pile and cohesive soil was assumed to be the original ground.

Example of the Pile Foundation (B.C.Punmia 2002)

(Mahmoud E. Kamara, et. al.2005) A load path is necessary at pile caps to transfer tension forces from the reinforcing bars in the column or boundary member through the pile cap to the reinforcement of the pile or caisson. When the tension forces induced by earthquake effects are transferred between pile cap foundation and precast pile by reinforcing bars grouted or post-installed in the top of the pile.

For example, Burj Al Arab is one of the most luxurious hotel in Dubai was designed by Pile Foundations were stands at the height of 333m.

Opinions may differ on whether structures to withstand the disruptive forces of earth tremors and quakes should be designed as rigid or flexible or semi-flexible. Gregory J.Hancock et. al 2003 Reinforced concrete (RC) wall- Moment Resisting Frame (MRF) system is widely used in seismic regions. In this system, lateral force is resisted mainly by the walls, while MRF carries most of vertical load. To avoid the collapse during the earthquake, the members of the wall must be ductile enough to absorb and dissipate energy by post-elastic deformation then only the building can withstand itself. In evident this RCC structure is uneconomical to design a building to withstand the greatest disaster like earthquakes (Robert Park et,al. 1985. Thomas Pauly et., al 1988). The main advantage in the RCC design is that, when the frame joints are damaged it can be repaired with the epoxy injection and badly fractured concrete can be isolated and replaced. Frame members that have been pushed of the alignment during an earthquake should be jacked back into the proper position before repair. Damaged columns can also be strengthened with fibre-reinforced plastics wraps or other methods of exterior concrete confinement. These RCC frame building design must be followed by using the building codes or else they may lead to the collapse and damage to the buildings.

Yuhshi Fukumoto, George C. Lee, et. al.,2002 Structural steels for buildings are various kinds of advanced properties such as high strength, good weld-ability, heavy section, high ductility, high notch-toughness, heat resistance, stain- proof, high Young's modulus. etc... Several newly developed steels attaining such advanced properties had probability to be partially applied in actual buildings for the purpose of earthquake resistance, fire protection, weather proof, and so on. To assure the good behaviour of the steel structures, some of the requirements are

We predict that the results of this work will give a hand in agreeable the academic interest by strengthening the literature on foundation, RCC and Steel Structure and in sequence about the Seismic codes for the structures which resists the building during earthquake. The work done in this research would be awareness and helpful to design earthquake resists building research employees. This would agree to forecast and recreation of future environment of our odd loss of lives through the building damages and collapse.

Limitation for this work may possibly arise while using RCC design with structural elements prevented from significant yielding and retaining their strength and stiffness properties (Edmund Boot., 1995). However, Robert D. Way., 2002 identifies that differential movement between a structures contains a deep foundation that is supported by strata below the zone.

As for this design plan for earthquake resistant building will be obtained by the organization and the government for approval and soil test for the site plan will be produced to the certain government authorities before executing the project. All the safety measures will be produced by the organization to the staff working in the company.