General Building Design and Construction Methodologies - Research Paper Example

? Analysis of Building Design, Types of collapses and Impact of these collapses on the Building s. Analysis of Building Design, Types of collapses and Impact of these collapses on the Building codes. Whenever a collapse or failure is seen in the building or structure there is a risk of loss of human life and financial loss as well. There are many reasons or sources which can cause a collapse and it is of prime importance that the structure should be safe against any possible combination of loading, whether it’s the live, dead , wind, earthquake or fire, the building must resist it at all cost. This need highlighted the importance of having building codes and standards so that a uniform design approach and criteria should be followed by everyone. Hence no risk is to be taken. As we are aware of the fact that there are two phases of the establishment of the any facility or building, firstly it is the design of the structure and second is the construction or execution phase of the design. In the modern day the different building codes and standards restricts the builder and designer to make structures safe. It is also observed that when ever I collapse is seen these building codes and standards are reviewed for any mistakes and error and consequently they are changed and amended. If we scrutinize the building codes and standards we come to a conclusion that they are consider worst conditions in loading such as dead loading, live , wind and even earth quakes but fire loading was not seriously considered as a probable cause of collapse of the structure until collapse of the World Trade Center in New York terrorist attack. But now the latest codes consider the fire as an equally probable cause of collapse of structure. In this paper I would go about the problem in the similar manner as engineers and designers did when drafting the codes and standards against the fire and its impact loading, where I will focus on the following . 1. General building design and Construction methodologies 2. Causes Of Collapses Of Structures 3. Progressive Collapse Analysis 4. Fire-Induced Progressive Collapse 5. Impact of collapses on the Building codes and standards General building design and Construction methodologies As far as the fire protection is concerned the building design and type of construction the National Fire Protection Association, (NFPA 220, 2006) has classified into two types, and firstly there are those buildings where the construction material is combustible (wood, steel) and secondly noncombustible for instance concrete and bricks. On the other hand the Association has divided it into five sub categories according to the fire resisting rating and construction methodologies of the structure as a whole. Type I is fire-resistive construction this type of construction mainly consist of non combustible materials and have a fairly good fire resistance rating that is it can resists fire for about 3-4 hours and this category include materials such as precast concrete slabs, concrete columns and beams. Type II is Noncombustible type, it consists of building having steel beams and girders, which are low on fire resistance rating, and are prone to large deformation and resulting into ultimate failure. Type III is the ordinary construction which comprises of mixed construction material which used in combination of steel, wood and concrete. The older this type of construction gets the more will be the risk of fire and hence more chances will be there of a complete structural collapse. Then comes the Type IV which is Heavy Timber structures, as the name depicts that these building types consists of heavy wood and almost all the structural elements are of wood, which we all are well aware very much prone to fire but at the same time these type of structures burns for a longer time and hence no sudden collapse is seen and some time is given to the inhabitants to escape the facility. Lastly it is Type V which is Wood Frames these are those building types which have a wooden frame as main skeleton of the structure but there are other structural elements of other materials as well. The appendix 1 contains an extract of the NFPA 220: Standard on Types of Building Construction, Edition which gives the fire resistive rating of each type of building construction given and the rating of each structural component of the structure. Causes of Collapses of Structures There are many aspects of structures that can not be learned through theoretical knowledge but comes through the experience and some of the times these experiences are very bitter. Same goes for the failure or collapse of structure. In this case before going to any conclusion or solution we must closely examine the reason of the failure and then diagnose the problem. The process does not end here, but it just starts another one, which is the suggestion of the solution and then comes the prevention stage where engineers and designer conclude the problem and solution and in the end they make this part of the code and standard, restricting both the contractor and the designer not to repeat the same mistake. So this is how one failure and its analysis make a positive impact and hence prevents similar events to happen. There are many causes of collapse of structures which start at the stage of designing, where if a faulty design is made there are very probable chances of failure. Then another major reason for collapse is the wrong selection of material for a certain place and situation which was foreseen by neither the contactor nor the consultant/designer. Then the carelessness of contractor and some time corruption may affect the quality of construction of the structure to a considerable amount and later in the service life this may become a cause of failure. Then another emerging cause of failure these days is the because of the complex structures and diverse architectural outlooks which might look good when on drawing but are very complex and complicated as a structural system, and unexpected failure modes might occur resulting into collapse. Apart from the causes mentioned above there is another case where complete or partial collapse is seen, this is the case of accidental loading these loadings include the earthquakes, wind and recently added Fire loading. We have witnessed that there were many bindings as far as earthquakes, live and dead loading is concerned. But there are recent changes in code regarding two other loadings which include the massive wind loading keeping in view the Katrina and similar hurricane and then come the fire loading keeping in view the 9/11 event into consideration. At the moment my main areas of focus would be Fire induced collapse and their reasons for failure.Although there are very few complete collapse of structure due to fire loading but their possibility can not be eliminated at all. I have research on the collapses due to fire and have some to a conclusion that they are a few but very crucial. The Historical Survey of Multi-Story Building Collapses Due to Fire made by Hughes Associates, Inc , came to a conclusion that (Beitel, 2005),only a data of 22 buildings(appendix 2) which had fire was available, and out of those only 6 buildings was higher than 21 stories. These survey in addition to the 9/11 report has made it clear to every one especially the engineers that fire induced collapses are potentially equivalent to any other. Progressive Collapse Analysis Progressive collapse is seen when one key member of the structure fails and this results into failure of the adjacent member and similar trend is the transferred to the entire structure consequently there is a complete collapse. Normally this is the worst condition which a structure can face and hence the designer and engineers should idealize this case to design the facility. So when we are considering fire loading the progressive collapse is a possibility engineers have to consider. So in order to design a building to resist the collapse by a fire the modern day Building codes have employed Progressive Collapse analysis of non-linear behavior of structures in fire. There is a lot of work been done in this field and the progressive analysis is considered in almost every new building code and standard such as UBC, ASCE, ACI codes and ASTM as well but after some research I have come to a conclusion that the most work done in binding the contractor and the designer to incorporate the fire induced failure analysis is the International Building Code, IBC which I will discuss in detail in next section. Fire-Induced Progressive Collapse At present the fire and building codes through out the world using performance-based systems to analyze the fire induced progressive collapse and these systems cater to almost the recent development in the progressive collapse analysis of fire in a structure. David scott along with other fellow researcher at the ARUP consultants which are one of the biggest consultants of UK have concluded in their paper that performance-based systems include aspects like ( (David Scott, 2006) Calculation of fire size Means of detection and suppression Smoke management Fire initiation and development Means of escape Fire fighting facilities and response Control of fire spread both within the building and to adjacent buildings Compartmentation Real performance of structures in fire Emergency light and power In addition to the above considerations fire induced progressive collapse is also considered now a part of the design and the collapse in case of fire is now stimulated before the construction on theoretical basis as well as on models during the design procedure. In addition according to the improved approach of designer now they consider aspects such as structural materials, loading pattern, ability to redistribute load, ductility of elements and joints into design as a part of fire protection measures. These analysis and simulations are also assisted by some standards as well the prominent and widely used among them is ASTM E-119, Standard test method for fire tests of building construction and material and ASTM E-84, Standard test method for surface burning characteristics of building materials, with a restriction that these system can not stimulate the same fire as that which takes place in an actual environment whose fire fuels are very different and have different temperature variations but still they give us a good empirical relation to work on. Impact of collapses on the Building codes and standards There are many bodies and association that are working and researching to safeguard the human life and making the structure safer by the imposition of different codes and standards, some of them have a localized jurisdiction and others have global. Prominent among these are NFPA, ASCE, BS, ASTM, UBC , Euro codes and IBC. But after some research I have come to a conclusion that the most effective and widely used one is International building Codes and its global acceptance and authority has made it my choice of discussion. Another reason of this selection is that the code not only considers the post fire situation and its remedies but also provide the restriction on each structural member so that it can have a better fire resistance rating. The Chapter 7 of the IBC 2006 solely deals with Fire Resistance Rated Construction. There are many aspects that were present in the previous versions as well which include Shaft Enclosures, Fire Walls, Smoke Barriers, Opening Protectives, Ducts And Air Transfer Openings, Horizontal Assemblies. But the new code provide bindings which were never consider before these include Fire-resistant joint systems, fire-resistance rating of Structural members, minimum slab thickness, minimum dimension of concrete columns, minimum cover for prestressed concrete beams, minimum cover for main reinforcing bars of reinforced concrete beams, cover thickness for prestressed concrete floor or roof slabs, minimum equivalent thickness (inches) of bearing or nonbearing concrete masonry walls. These aspects were never restricted by the fire rating of the structure but were done so by considering the loading on the system which was just some combination of live loads, earthquake and dead loads. But this major change is seen and done by IBC to cater to the possible fire induced collapse. References ASTM E119 - 10b, A. Standard Test Methods for Fire Tests of Building Construction and Materials. U.S: American Society for Testing And Materials, 2006. ASTM E84 - 10b. Standard Test Method for Surface Burning Characteristics of Building Materials. U.S: American Society for Testing And Materials, 2006. David Scott, B. L. (2006). Fire Induced Progressive Collapse. New York: ARUP NFPA 220, N. F. (2006). NFPA 220: Standard on Types of Building Construction. IBC. INTERNATIONAL BUILDING CODES. US: INTERNATIONAL CODE COUNCIL, INC., 2006. Beitel, J. J. (2005). Historical Survey of Multi-Story Building Collapses Due to Fire. Hughes Associates, Inc 911Research. (2007, 12 07). WTC 1, 2 collapses. Retrieved 02 25, 2010, from 911Research: http://911research.wtc7.net/wtc/analysis/fires/index.htm Appendix 1 Appendix 2 Read More