Structure, Materials and Fire in Construction - Assignment Example

Your name) (Course instructor) (Course title) (Date of submission) Structure, Materials and Fire in Construction Concrete frame construction is widely used by Construction Industries across the world. Concrete is a mixture of sand, cement with water and it can be mould into different shapes .When Portland Cement was invented in 19th Century did concrete become popular in the Construction Industry. The European engineers are the one who pioneered current concrete designs together with different construction practices in 19th century and today, most engineering works are done by use of reinforced concrete, (Ozcebe et al, p.1). Futian Shangri-la Hotel for instance, is one of the tallest buildings in the city of Shenzhen located in the southern part of the Central Business District (CBD) and was build from concrete materials. The building was completed in 2008 and stands at 190.85m.The building is around 190m tall and has a small footprint of 40m by 40m.The concrete columns which are outside the building bend inward from level 27 of the building. Levels 12 and 26F are preserved for refugees as a fundamental requirement by the Chinese government in the Safety code. There are extra MEP levels which are located in the building and they stand above level 5 and level 36.With uncompromised platform of 20m by 20m on the upper floor the building is designed with the capacity to receive a chopper weighing 10ton on landing with quests. The building was constructed with lots of creativity and by use of outstanding technologies together with innovations and its design life is estimated at 50 years. (Dennis et al , p.2 & 3). Developing a building requires that appropriate materials are used. When designing foundation for instance, one must put into consideration the strength and functionality of the building. Futian Shangri-la Hotel ‘s foundation was build on pile diameters and lengths which provide adequate friction that helps to the building to resist heavy loads ( Dennis et al, p.2 & 3). (Alam, Nehdi and Youssef, p.565) explains that Super elastic Shape Memory Alloys (SMAs) are commonly used by engineers to reinforce bars when developing concrete frame structures and their seismic behavior is also being analyzed to check their suitability in building and construction. SMAs are unique building materials that have the ability to experience deformation and return to their normal shape when loaded or heated. It is important to protect occupants of any building from fire and also to provide room for evacuation incase of fire outbreak. It is this respect that concrete materials are highly recommended in building because of their resistance capacity to fire unlike other building materials. Concrete’s ability to resist fire in this case means that additional expensive protective finishes may not required when putting up a structure using concrete. ( Donn and Thomas, p. 4) argues that it is because of different properties inhibited by concrete that makes it competitive and preferred, especially in relation to its cost, performance and even its availability. For instance, in terms of cost, concrete materials are relatively stable in terms of price and this has helped contractors and clients to plan projects that would consume time with lots of certainty. Concrete materials are readily available unlike other structural materials which are imported and a case in point is in New Zealand where concrete products are produced. The materials used to make concrete are sourced from within thus making it more affordable. The rate of expansion in construction in Asia and other parts of Middle East is challenged by importation of building materials and this has created uncertainty .It is in this view that concrete materials are mostly preferred in building and construction. (Donn and Thomas, p.3-4) Durability is one of the advantages of concrete frames. Many concrete construction systems may be used in different ways to meet specific needs and at the same time secure least material advantage for desired value. Concrete when wet can be designed virtually in any form thus providing room for creativity among architects. Donn and Thomas are also of the view that when concrete is designed in accordance with established procedures, its walls and floors are capable of resisting vibration. However, the disadvantages of concrete frames may be explained as follows. Most unfortunately it is difficult to modify concrete once the construction has been made. All structures made using concrete are exposed to crack at some given point in time and also shrinking of the concrete makes it to crack especially when it dries up. It is because of such incidences that compromises the durability of the building. Concrete has been discredited because of low-thermal conductivity in a sense that when heated it can be seriously destroyed. Therefore, as much as concrete help to prevent the spread of fire its usefulness may not be realized in the process. Another disadvantage of concrete is that it corrodes with time when exposed to water especially when its submerged for a long time. This, therefore implies that the construction can collapse when weakened and cause damages. ( Clark, p.5-6) Recent findings according to (Larson, p.7) indicate that steel has been identified to be an alternative building material to wood and concrete. Steel frame construction is mainly used in areas prone to natural occurrences that are likely to destroy the structures. The introduction of new techniques for building like prefabricated steel panels and availability of related still frame materials have seen steel frame construction gain consideration in building and construction environment. Steel designs have improved within a considerably short time as notes (Larson, p.7) especially steel truss designs. The improvements are focused on the shape of parts of the structure which help to bring out the general look of the whole structure. According to ( Wei-Wen, and LaBoube, p .1) steel construction is classified into two families and they include construction using hot-rolled shapes and the other by use of plates. However, there is another type of steel construction which is grouped among cold-formed steel structures and it has sections created from steel plate and even flat bar by use of roll-forming machines. Generally in steel frame construction, framing depth in cold-formed structures varies from 2in to 12in and its material thickness varies from 1.22mm to 6.35mm but in other situations the depth may go up to 18in and the thickness may be 12.7mm. Given that the main purpose in this kind of framing is to hold load, strength and hardness are mainly considered in the design. (Larson, p.3). Material properties are significant in the performance of steel frame structures and therefore should be put into consideration when building .One of the properties of steel materials is the ability to be welded in a satisfactory manner with a lot of ease. This is determined by the type of chemicals composition used to make steel and it varies according to the type of steel materials and also welding used (Larson, p.37). Larson in his article, he emphasizes resistance to fatigue as an important material properties of steel frame. This is the ability of steel materials to withstand vibrations and repeated loads. Therefore, emphasis should be put on quality of steel material to be used in building and thus material properties should not be ignored when procuring such materials. Steel structures compared with other building materials such as concrete and timber have distinct qualities that make it preferred in construction according to (Larson, p.2).Firstly, steel is easy to prefabricate and can be produced in big masses and in situations where many steel materials are required to put up a structure it becomes easy. Steel frames are also easy to erect and install when building as compared to concrete and gives it an advantage over other materials. The lightness of steel materials cannot be compromised in construction unlike concrete materials and this is why it is able to resist strong winds that is known to bring down buildings. These advantages can result in reduction in the cost of construction . However, steel materials have a number of disadvantages and they include high maintenance cost. Steel materials are prone to corrosion when they are exposed to water and therefore must be painted after a period of time. It is important to note that steel materials loose strength whenever they are exposed to high temperatures because of fire and this makes it not suitable in construction. In some conditions steel loses its ductility and fracture at areas where concentration of stress is high. The situation is caused by extremely low temperatures which is uncontrollable natural occurrence. ( Clark p.5-6) It is therefore significant for contractors and even their clients to establish the right materials to use whenever they want to build structures of any kind. They should also analyze different material properties and even their costs so as to minimize the cost of construction. Most importantly, durability and safety of structures cannot be taken for granted and this depends especially on the type of materials used in building. Thus, concrete materials and steel materials are both recognized in building in a sense that both of them poses different strengths which make them qualify as building materials. Work cited Donn, M. & Thomas, G. (2010). Designing comfortable homes. Cement & Concrete Association of New Zealand, Wellington: New Zealand. http:// www.ccanz.org.nz/news-ccanz.aspx?id=65 A.J. Clark School of Engineering. Structural Steel Design and analysis. University of Maryland,Colege park (2002) p.5&6 Larson, Jay W. "Structural shape for use in frame construction." U.S. Patent No. 6,817,155. 16 Nov. 2004. Yu, Wei-Wen, and Roger A. LaBoube. Cold-formed steel design. Wiley, 2010. M. Shahria Alam, Moncef Nehdi* and Maged A. Youssef Smart Structures and Systems, Vol. 5, No. 5 (2009) 565-585 Department of Civil and Environmental Engineering, The University of Western Ontario London, Ontario, N6A 5B9, Canada Dennis C.K. Poon P.E., Ling-en Hsiao, Steve Zuo, Managing Principal, Thornton Tomasetti, Analysis and Design of a 47-story Reinforced Concrete Structure - Futian Shangri-La Hotel Tower Ozcebe, G., Ersoy, U., Tankut, T,, Akyuz, U., and Erduran, E., 2004. Rehabilitation of existing RC structures using CFRP fabrics. Proceedings of the 13th World Conference on Earthquake Engineering, Vancouver, Canada, Paper No. 1393. Effects of Fire on Steel Framed Buildings Steel frame can be defined as a building that is technically “skeleton framed” with the steel columns on for the vertical portion and the I-beams on the horizontal part. It is built in a rectangular framework to hold the floors, walls and the roofs in place by attaching them to the frame (The Steel Construction Institute, p. 1). The power of all engineering supplies decreases as their heat goes high and steel is not exempted. Steel is a powerful substance for building construction, agreed, its relative light mass and load –bearing capacities; it is a high-quality value for construction designers. Current high-rise and noncombustible structures could not be devoid of steel (Nacewicz, p.21). . One of the steel’s weak points is its performance in fire while not sheltered by fire resisting supplies. Exposed steel framing can go through great expansion once it is adequately heated and also losing nearly all of its load-carrying facility. This is described by a coefficient of thermal increase, normally represented by the sign“a”and varies by the chemical composition of the steel. It is a gauge of the change in measurement lengthwise of a substance in reaction to a change in its hotness. Thus, any structure built on steel materials enlarges as temperatures rise and contract by falling temperatures. The slither speed of steel is responsive to higher temperatures and turns to be significant for gentle steel over 840F (450 C). Thermal increase can effect in steel beams pushing sustaining columns or walls away of alignment, mounting the danger of structural collapse (United States Fire Administration, p. 1). An observation by United States Fire Administration ( p. 1), affirms that fire in steel structures tremendously spreads through melted expansion joints. In this case, if automatic sprinklers are not available to protect further spread of fire, excessive heating leads to collapse of the building. Additionally, at some instances, the high temperatures cause unattractive properties such as elongation and bending of the steal framed buildings (Nacewicz, p.21). In addition, the phenomenon of catenary action in composite beams is evident. This results from thermal expansion in the structure due to extreme temperatures. This is greatly especially because steel frames have a definite degree of end restraint. Though negligible at standard temperatures, the end restraints are significant at high temperatures due to restraint to thermal expansion. In turn, this causes massive internal force and moment within the building (The Steel Construction Institute, P. 1). A study by The Steel Construction Institute (p. 1), suggests that local buckling is a major effect of fire on steel framed buildings. In fact, the unprotected steel frames are deformed and shortened. This may result to permanent deformation of the building. The shortening mainly comes about as a result of restrained thermal expansion (Usmani et al, p. 7). Nacewicz et al (p.21), asserts that, during a fire incident, steel absorbs a major quantity of thermal energy. After this disclosure to fire, it returns to steady form after cooling to ambient heat. Through this series of heating and cooling, individual steel members might turn out to be a little curved or spoiled, normally without disturbing the firmness of the entire structure. Significant figures of steel members could be salvaged following a post fire assess of a fire affected construction. If the element is straight after disclosure to fire, the steel is suitable as lots of steel members can be left untouched for the rest of their service time (The Steel Construction Institute, p. 1). Steel members that contain minor distortions can be made dimensionally reusable by easy straightening methods, and the member could be placed to persistent use with complete expectation of performance by its particular mechanical properties. Nonetheless, the members that have turned out to be unusable due to extreme twist may just be scrapped. In this regard, it is uncomplicated to retrofit steel constructions after fire. According to Usmani et al (p. 10), twist of steel at high temperature is described by presumptuous that the change in damage consists of thermal strain, slink damage and mechanical or strain related damage. Structural actions of steel structures while subjected to fire depend upon a numeral of valuables such as matter degradation at high temperature and limit firmness of the construction around the fire. High temperature and gradients across a structural element are the driving force behind large deflections and axial forces. Buildings exposed to fire interact, thus influencing the structural behavior. Steel has a narrow power, signifying that, at a convinced hotness the effectiveness of the element will decrease to none (Gewain et al, p.3). On the other hand, researches in the building and construction industry have observed that when steel framed buildings are subjected to temperatures above 800° Celsius, they lose ninety percent of their strength. However, despite the high heating steal framed structures do not fragment into piles of rubble. Indeed, if the building tends to collapse due to extreme temperatures, the effect tends to remain localized in the area that experienced the high temperatures. Additionally, only the low carbon steel is used in buildings. Thus, the building bends rather than shatters (Usmani et al, p. 10). This means that if a building is compromised by extreme heats, it can cause a bend only on that region leading to toppling or sagging a part of the structure. In this regard, further structural destruction on steel framed building by fire ought to be prevented. Encasing the column or beams with plasterboard or concrete or spraying the beams to insulate them from heat of fire. This is vital due to the fact that steel softens at extreme temperatures (The Steel Construction Institute, p. 1). Indeed, is very essential to note the behavior of steel on high temperatures and methods obtainable to guard it against harm done by fire ( Gewain et al, p. 3). Works Cited Gewain, Richard., Nestor, Iwankiw & Farid Alfawakhiri. "Facts for Steel Building." Fire (2003): 3. Nacewicz, Rebecca. Investigation of Fire Impact on Structural Steel Through Case Studies. Worcester: Worcester Polytechnic Institute, 2006. The Steel Construction Institute. Design Recommendations For Composite Steel Framed Buildings in Fire. Berkshire, UK: The Steel Construction Institute, 2003. United States Fire Administration. Building Construction: Fire Effects on Steel Structures.( 2012).http://www.usfa.fema.gov/downloads/pdf/coffee-break/cb_fp_2012_50.pdf.( 23 01 2013). Usmani, Asif., Zhang, Jian., Jiang, Jian., Jiang, Yaqiang., & May, Ian. "Using Opensees For Structures In Fire." Journal of Structural Fire Engineering (2010): 1-17. Read More