General Building Design and Construction Methods - Research Paper Example

? Analyze and review of general building design and construction methods, types of collapses and Impact of these collapses on the Building s. Analyze and review of general building design and construction methods, types of collapses and Impact of these collapses on the Building codes. The building codes and standard are developed to give engineers and designers a homogeneous line of action to every problem they face in the field. The basis of almost all the standards lies in, the need that is created when a field engineer faces a problem or failure is observed and later this is reported to design team. Which review the issues and causes associated to it and then suggest a change in the building design or a recommendation in alteration is building codes. The organization of this paper is done very similar to the steps taken in the production and improvement process of building codes and reviews of field problem, the paper will focus on the following steps, 1. Causes of collapses of buildings 2. General building design and Construction types 3. Progressive Collapse Analysis and Fire-Induced Progressive Collapse 4. Impact and modification of Fire-Induced collapse on Building Codes Causes of collapses of buildings In order to diagnose a problem and its solution we first need to understand that from where the problem starts and initiates and what its causes are. There is a wide range of causes which lead to the collapse of the buildings which include bad design in which the engineers and designer are responsible for erroneous theories, improper choice of materials or misunderstanding of their properties and etc. Then comes the faulty construction as the major cause of collapse, it may occur by weak supervision and corruption of by the contractor, use of inferior quality of steel and other material. Then another cause of failure of the structure is Foundation Failure in which there is liquefaction of soil or excessive settlement which was not forecasted in geotechnical investigation made before construction of the facility. Then unexpected failure modes is also one of the emerging reason of failures of structures, this is due to the fact that we are having a new type of structural system every day, which might be architecturally sound but it is very unstable as a structure and the lack of systems to analyze these systems are not yet developed, so there might be a failure by an unknown reason. Lastly but most important cause of failure is the Extraordinary or accidental Loadings, this has caused more catastrophes more than any other. These loading include the wind loads, exceptional earthquakes and impact of fire on structures. The codes have been really successful in developing standards and design procedures to cater to the problem such as earth quakes and hurricanes and broad research has been done in these areas, but lesser emphasis were been made on fire loading or fire induced collapse while the formulation of revised codes until the 9/11 event which caused a complete collapse of World Trade centre. Partly the reason for this was that the rare occurrence of fire in structures, even lesser forensic analysis of building and only a very few incidents were reported and recorded. The second major reason for this was that there were only a very few complete collapse of the structures due to fire. The Historical Survey of Multi-Story Building Collapses Due to Fire made by Hughes Associates, Inc , came to a conclusion that (Beitel, 2005) *1,only a data of 22 buildings(appendix 1) which had fire was available, and out of those only 6 buildings was higher than 21 stories. The World Trade Center case study made a clear to the world and especially the designer and engineers that fire poses more danger to multistory building and its inhabitants. Due to these facts there is a major change seen in the fire protection of buildings now and NFPA (National Fire Protection Association) has come up with new standards and codes for a better. General Building Design & Construction Types According to National Fire Protection Association, (NFPA 220, 2006) there are two basic types of construction: it either burns (combustible) or it does not (noncombustible). These types of construction can be further broken down into five categories. Type I is fire-resistive construction which majorly consists of materials such as precast concrete slabs, concrete columns and beams in this type the structural members are designed to resist fire for about 3 -4 hours and have sufficient fire resisting rating. Type II is Noncombustible, this type represents those building having steel beams and girders, they are susceptible to steel deformation and resulting collapse with less or no warning. Type III is the ordinary construction which consists of a mix of materials, including steel, wood and concrete, the older this type of building gets the more it is prone to fire. Type IV is the Heavy Timber in this type of structure almost all members and components are constructed from wood, these types have massive wooden structural members which requires a long burn time for failure. The connections, usually steel, are the weak points in this type of construction. Type V is Wood Frames, as the name suggests these are the common houses and other small structures made of wood as the basic material. It is important to note that buildings are built to meet certain codes. These codes are designed to give occupants time to escape during a fire. The appendix 2 contains a 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. Progressive Collapse Analysis and Fire-Induced Progressive Collapse When a primary structural element of a building fails, this causes the adjoining member to fail as well and the pattern of failure is propagated through out the structure, resulting in to complete collapse is termed as progressive collapse. A similar failure type is seen in case the building catches fire and as a result a collapse is seen. 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. Now these types of analysis are been employed in ASCE codes, International Building Codes, UBC and etc. At present the fire and building codes through out the world using performance-based systems. These 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 Materials and their response to fire – internal linings and finishes But the above attributes and services majorly consider the post fire situation and does not include the collapse analysis of the structure or failure of its key elements and that’s where the latest concept of fire induced progressive collapse comes into play. The new codes and standard embrace the collapse situation and then design it according, hence the failure is now consider before and incorporated into the construction of the facility. 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. In addition now structures are modeled and then tested against fire and structural response, fire resistance is seen and these steps are in addition to those test performed according to 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. These ASTM standards are used keeping in mind that they formulate considering empirical relationships. Because the heat that is stimulated in the furnace which is not similar to the real fire where the fuel is very different and exact conditions can not be created and these ASTM testing is done in 2-dimensional situation where as the real structure are in 3-Dimension and make a complex system. Impact and modification of Fire-Induced collapse on Building Codes As indicated in the discussion before as well that building codes which are for protection against fire have been drastically been modified to now not only cater with the problems created in the post-fire situation but now the codes gives guide lines to design even the structural members to within the fire induced loads and that the structure is stable against a progressive collapse. Although many associations and standardization authority have incorporated the fire induced loading situation which include the NFPA, ASCE, BS, UBC but after some research I have come to a conclusion that the most significant change and modification made with respect to fire protection is done in the International Building Code, which comes under the International Code Council and consequently have been used in the field. The council have done extensive research on the issue as its can be witnessed from the Chapter 7 of the IBC 2006, which solely deals with Fire Resistance Rated Construction. As we are aware of the fact that there are many things that existed in the previous versions of the codes which majorly include Shaft Enclosures, Fire Walls, Smoke Barriers, Opening Protectives, Ducts And Air Transfer Openings, Horizontal Assemblies and many other attributes. But the major modification regarding the structural design (IBC, 2006) included 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. All these attributes of the structure and its key elements were previously dictated and designed according to the conventional loads on the structure but the recent change in the approach clearly indicates that almost the whole structural design is done keeping in mind the safety from fire. Hence it can be concluded that the codes have change and modified their approach to the loading and modern day building engineers and designers are bound to make fire resistant structures for the safety of inhabitants and the structure as well. Works Cited 911Research. (2007, 12 07). WTC 1, 2 collapses. Retrieved 02 25, 2010, from 911Research: http://911research.wtc7.net/wtc/analysis/fires/index.html ASTM E119 - 10b, A. (2006). Standard Test Methods for Fire Tests of Building Construction and Materials. U.S: American Society for Testing And Materials. ASTM E84 - 10b. (2006). Standard Test Method for Surface Burning Characteristics of Building Materials. U.S: American Society for Testing And Materials. Beitel, J. J. (2005). Historical Survey of Multi-Story Building Collapses Due to Fire. Hughes Associates, Inc. David Scott, B. L. (2006). Fire Induced Progressive Collapse. New York: ARUP. IBC. (2006). INTERNATIONAL BUILDING CODES. US: INTERNATIONAL CODE COUNCIL, INC. NFPA 220, N. F. (2006). NFPA 220: Standard on Types of Building Construction. NFPA 5000. (2009). Building Construction and Safety Code. U.S: National Fire Protection Association. Appendix 1 Appendix 2 Read More