Seismic Protection of Fire Sprinklers in High Rise Buildings in UAE - Coursework Example

Just send a message if you need anything. Thanks! Seismic Protection of Fire Sprinklers in High Rise Buildings in UAE Table of Contents Contents Contents 2 1. Introduction The need for seismic protection of sprinkler systems is a controversial issue as building developers who want to avoid additional cost of bracing and hangers are obligated to determine and prove that the location of the building they will construct belong to a Zone 0 or with seismic acceleration equal or lower than 0.2g. UAE is generally considered as a region in Zone 0 despite the presence of faults near Dubai where tall buildings like Burj Khalifa is located. The following sections discuss the issues about the need for sprinkler system seismic protection, the concept behind this seismic protection requirement, and the applicability of such concept in UAE. 2. The Need for Seismic Protection of Sprinkler Systems Seismic events are common and it has the ability to cause damage due to excessive surface motion. According to Huggins (2005), earthquake commonly affects the construction features of a building including fire protection systems which the National Fire Protection Association in its NFPA 13 and NFPA 5000 under section 35.10 code of standards wants to protect (p.60). Seismic protection for sprinkler systems is generally not considered in Zone 0 or places where seismic activity according to NFPA 13 is zero. However, in areas with seismic activity of at least 0.10g some building codes such as IBC: 1603, 1.5 requires construction design to include seismic protection on water-filled pipe of sprinkler systems (Mitchell, 2003, p.15). According to Phan & Taylor (1996), earthquakes and other seismic activity often result to fires thus it is very important that sprinkler systems withstand seismic activities. Moreover, sprinkler systems often interact with other building elements such as suspended ceilings thus differential movement between suspended ceiling and the sprinkler system can cause damage particularly to pendant pipes and sprinkler heads. For instance, even without resulting fire, damaged pipes after an earthquake can cause water leak that will eventually damage building contents and finishes. Similarly, damaged sprinkler nozzles can result to reduced spray coverage and therefore compromised the effectiveness of the sprinkler system in case fire broke out after the earthquake. Lastly, since long straight runs of “unbraced pipe” tend to oscillate if shaken, it can cause damage to other pipes, ducts, wirings, and structural frame during an earthquake (p.8). According to the recommended design of fire sprinkler protection system, there should be pipe hangers and bracing system complying with NFPA 13 (Ghosh et al, 2011, p.160) that is actually intended to counter seismic force and relative displacement (Federal Emergency Management, 2003, p.126). The reason for this NFPA standard is the fact that early sprinkler systems were often affected by the ground and subsequent building movement during earthquakes. For instance, study of 1989 Loma Prieta earthquake in San Francisco and 1994 Northbridge earthquake in Los Angeles suggest that earlier sprinkler system did not survive these seismic forces because they lack structural support such as hangers and bracing (Cote, 2003, p.349). According to Morelli (1999), fire sprinkler systems were rendered unusable in past earthquakes because of inadequate lateral bracing, flexibility and clearance around the piping, and collision with other unbraced structural elements (p.3). 3. Seismic Protection for Fire Sprinkler System Concept Fire sprinkler system are generally placed in a certain building in order to control the fire minutes after it starts thus competent design, layout, and installation of such system is critical. Moreover, changes in occupancy, contents, storage arrangement, and other process including seismic movement can render the system ineffective (Jones, 2008, p.155). Fire sprinkler system is the first stage of fire-fighting and therefore should be protected from damage (Council on Tall Buildings and Urban Habitat, 1980, p.327). The criteria set by NFPA 5000 for the protection of sprinkler systems against seismic forces according to Huggins (2005) include eight items that must followed – mapped maximum spectral response acceleration, site class, design spectral response acceleration, seismic use group and occupancy category, seismic importance factor, seismic design category, seismic force resisting system, and analysis procedure (p.60). However, out of the eight items seismic force resisting system which is associated with seismic design category of the building is the most relevant to sprinkler protection. Here, NFPA 5000 clearly stated that there is no sprinkler protection required if there is very low (not more than 0.15g) mapped maximum earthquake spectral response. Note that this is only applicable areas included in zone maps showing likely acceleration caused by gravity (Huggins, 2005, p.61; Mitchell, 2003, p.15-16). In other words, protection for fire sprinkler system in areas not in the zone maps should be determined by the building developed and proves that the force and displacement exceed 0.15g. It is therefore evident that the concept behind sprinkler system protection was based on the likelihood stronger seismic forces in some location and does not necessarily apply to all buildings. Similar concept is being applied in the United Arab Emirates as according to the 2008 seismic report of Ove Arup & Partners and Shell Global Solutions, seismic hazards in the region is no longer negligible. The report suggests that Dubai, which is classified as a city located in Zone 0, is dominated by small local and large earthquakes coming from the Zagros and Makran zones. There are two main faults identified in Dubai, the Western Coastal Fault along the coast of Abu Dhabi running through Dubai and Sharja to Al Khaimah. The second one, named Dibba Fault is located near the Oman Mountains which according to the report can cause significant ground motions and accelerations exceeding 0.25 m/s2. Moreover, the conservative estimate of seismic for Dubai is ranging from 0.075g to 0.20g (p.1). However, in its effort to come up with a reliable estimate of seismic hazard for UAE, Abu Dhabi’s Department of Municipal Affairs rejected the existence of these faults but accepted the concept of ground motion and spectral ordinate at periods of 0.2 s (Ss) as shown in Figure 3 below (Department of Municipal Affairs, 2011, p. 2-42). Figure 1- Map of UAE showing Zagros and Makran faults (Over Arup & Partners, 2008) Figure 2-The Western Coastal Fault and Dibba Fault (Over Arup & Partners, 2008) Figure 3- Ground motion and spectral coordinate at Dubai West Coast (Department of Municipal Affairs, 2011) Evidently, the concept on fire sprinkler system protection is more about the likely occurrence of excessive ground motion or seismic force that can affect the stability of buildings and its installed systems in a particular area. The above figure however shows that Dubai and other parts of UAE are indeed in Zone 0 which as mentioned earlier described by NFPA 13 and NFPA 5000 as a safe zone with no sprinkler system protection required. 4. Protecting Fire Sprinkler System in UAE’s High Rise Building from Seismic Activity Analysis of studies conducted about seismic activities in the United Arab Emirates suggests that UAE is classified as Zone 0 with generally no sprinkler system protection required. However, being historically untouched by strong seismic activity and scientifically classified as hazard free is not a guarantee that there will be no such incident in the future. The faults found in the region is enough evidence to assume that tall structures in the region must be designed and constructed with these possibilities in mind. For instance, in January 2011, residents of UAE experienced tremors from a 7.1 magnitude earthquake in Pakistan while Fujairah experienced 2.6 magnitude seismic activities in March (Thomas, 2011, p.1). In 2002, Fujairah and Abu Dhabi also experienced aftershocks of a 5.9 and 4.8 magnitude (respectively) earthquake coming from Iran’s southern coastline. Report from the GSHAP or Global Seismic Hazard Assessment Program suggest that UAE is in high-risk seismic region with 0 to 4.8 m/s2 seismic acceleration (Khaleej Times, 2011, p.1). These and other facts about seismic activity and earthquake faults surrounding UAE seems enough reason to be concern about the stability of tall structures in UAE particularly in Dubai where Burj Dubai or Burj Khalifa, the tallest building in the world is located. Background information about this building suggest that it is over 135 stories high and a structural efficient building as its steel spire that utilizes diagonal braced lateral system can withstand forces like wind, seismic activity, and structural fatigue (Baker et al, 2007, p.364). The question however is whether the fire sprinkler system installed in this building that is designed to withstand seismic activity and located in Zone 0 requires sprinkler system protection. According to Das (2011), seismic protection of non-structural components must be determined through calculation of seismic forces, design, layout, and bracing intended for such purpose (p.1). Evidently, with low seismic acceleration as 0.2g, the calculation will likely conclude in a no protection required clause. Consequently the design, layout, and bracing of the fire sprinkler system will be minimal and constructed in the assumption that no significant seismic event will ever occur. Analysis of the concept behind fire sprinkler system seismic protection discussed earlier shows that two main considerations are being considered. One is the importance of having a working fire sprinkler system in case a fire occurs during or after the earthquake. Second, is the possibility of being under seismic stress and damaged when a particular building is located in areas other than Zone 0. Evidently, the central focus is retaining a working fire suppression system which in essence is often necessary regardless of seismic activity. According to Hover (1993), there is some inherent logic in ensuring seismic safety of buildings as aside from protection of owner’s investment; such initiative can lead to better performance of the building and reasonable life safety of occupants during an earthquake (p.22). This is probably the same logic that led to the seismic structural design of Burj Khalifa despite being located in Zone 0. Note that there are a number of conflicting belief about seismic activity in UAE but as discusses earlier, they all arrived in one conclusion - the fastest seismic acceleration in the region is 0.2g. However, since fire sprinkler system is being regarded as the first stage of fire fighting, it is more advantageous to keep them intact and working regardless of seismic activity particularly in tall buildings where fire fighting is historically difficult. Moreover, evacuating or rescuing people from the 110th floor are much more demanding compared to smaller buildings. The need to protect sprinkler system against seismic forces particularly in UAE must not completely focus on the maximum value of seismic acceleration in the region as there are indication that seismic activity can go beyond scientific calculations and historical values. It is important to note that most of the study reviewed in previous section, except Abu Dhabi Department of Municipal Affairs, considers the faults and impact of seismic activities in Iran, Iraq, and other surrounding countries that may in the future significantly affect UAE. The need for seismic protection therefore must also focus on the role of sprinkler systems in fire suppression and protection of human lives. More importantly, the additional cost of installing an earthquake proof fire protection system is so small compared to its benefits. 5. Conclusion The need to protect fire sprinkler system against seismic forces is a controversial issue as the concept for seismic protection is based on the idea that only buildings located in areas with seismic acceleration faster than 0.2g are qualified. In UAE, similar concept is being applied despite unexpected and increasing intensity of tremors felt recently in some parts of UAE. Seismic protection of sprinkler system must not be regarded as case to case process as earthquakes, a historically destructive and unpredictable natural phenomenon, can affect even regions that are scientifically categorized as Zone 0. It should be compulsory particularly in high-rise building where fire suppression can do much more regardless of seismic events. 6. References Baker W, Korista D, & Novak L, (2007), The Structural Design of Tall and Special Buildings, Wiley Interscience, pp.361-375 Burj Khalifa, (2012), Structural elements- elevators, spire, and more, EEMAR, available online at http://www.burjkhalifa.ae/the-tower/structure.aspx#fire Cote A, (2003), Operation of Fire Protection Systems, National Fire Protection Association, Jones & Bartlett, UK Council on Tall Buildings and Urban Habitat, (1980), Tall Building Criteria and Loading, ASCE Publications, US Das M, (2011), Seismic Protection for Fire Sprinkler Systems in Canada, AON Fire Protection Engineering, Canada Department of Municipal Affairs, (2011), West Coast Fault – Real or Factitious Earthquake Threat to United Arab Emirates, DMA, Abu Dhabi Federal Emergency Management Agency, (2003), NEHRP Recommended Provisions for Seismic Regulations for New Buildings and other Structures, FEMA, US Gosh S, Dowty S, & Dasgupta P, (2010), Significant Changes to the Seismic Load Provisions of ASCE 7-10: An Illustrated Guide, ASCE Publications, US Huggins R, (2005), Sprinkler Shake-up, AFSA, US, pp.1-5 Jones M, (2008), Fire Protection Systems, Cengage Learning, US Khaleej Times, (2012), Earthquakes in the UAE- Some facts, Khaleej Times Online, available online at http://www.khaleejtimes.com/DisplayArticle08.asp?xfile= /data/openspace/2011/January/openspace_January21.xml§ion=openspace Mitchell J, (2003), Earthquake Protection for Fire Sprinkler Systems: You now have to prove its not required, Sprinkler Age, US Morelli U, (1999), Handbook for the Seismic Evaluation of Buildings, DIANE Publishing, US Ove Arup & Partners, (2006), Seismic Report: Dubai LNG Seismic Hazard Desk Study, ARUP, UK Phan L. & Taylor A, (1996), State of the Art Report on Seismic Design Requirements for Nonstructural Building Components, DIANE Publishing, US Thomas J, (2011), Earthquake risk map to help build safer building in Abu Dhabi, The National, available online at http://www.thenational.ae/news/uae-news/earthquake-risk-map-to-help-build-safer-buildings-in-abu-dhabi Read More

Similarly, damaged sprinkler nozzles can result to reduced spray coverage and therefore compromised the effectiveness of the sprinkler system in case fire broke out after the earthquake. Lastly, since long straight runs of “unbraced pipe” tend to oscillate if shaken, it can cause damage to other pipes, ducts, wirings, and structural frame during an earthquake (p.8). According to the recommended design of fire sprinkler protection system, there should be pipe hangers and bracing system complying with NFPA 13 (Ghosh et al, 2011, p.160) that is actually intended to counter seismic force and relative displacement (Federal Emergency Management, 2003, p.126). The reason for this NFPA standard is the fact that early sprinkler systems were often affected by the ground and subsequent building movement during earthquakes.

For instance, study of 1989 Loma Prieta earthquake in San Francisco and 1994 Northbridge earthquake in Los Angeles suggest that earlier sprinkler system did not survive these seismic forces because they lack structural support such as hangers and bracing (Cote, 2003, p.349). According to Morelli (1999), fire sprinkler systems were rendered unusable in past earthquakes because of inadequate lateral bracing, flexibility and clearance around the piping, and collision with other unbraced structural elements (p.3). 3.

Seismic Protection for Fire Sprinkler System Concept Fire sprinkler system are generally placed in a certain building in order to control the fire minutes after it starts thus competent design, layout, and installation of such system is critical. Moreover, changes in occupancy, contents, storage arrangement, and other process including seismic movement can render the system ineffective (Jones, 2008, p.155). Fire sprinkler system is the first stage of fire-fighting and therefore should be protected from damage (Council on Tall Buildings and Urban Habitat, 1980, p.327). The criteria set by NFPA 5000 for the protection of sprinkler systems against seismic forces according to Huggins (2005) include eight items that must followed – mapped maximum spectral response acceleration, site class, design spectral response acceleration, seismic use group and occupancy category, seismic importance factor, seismic design category, seismic force resisting system, and analysis procedure (p.60). However, out of the eight items seismic force resisting system which is associated with seismic design category of the building is the most relevant to sprinkler protection.

Here, NFPA 5000 clearly stated that there is no sprinkler protection required if there is very low (not more than 0.15g) mapped maximum earthquake spectral response. Note that this is only applicable areas included in zone maps showing likely acceleration caused by gravity (Huggins, 2005, p.61; Mitchell, 2003, p.15-16). In other words, protection for fire sprinkler system in areas not in the zone maps should be determined by the building developed and proves that the force and displacement exceed 0.15g. It is therefore evident that the concept behind sprinkler system protection was based on the likelihood stronger seismic forces in some location and does not necessarily apply to all buildings.

Similar concept is being applied in the United Arab Emirates as according to the 2008 seismic report of Ove Arup & Partners and Shell Global Solutions, seismic hazards in the region is no longer negligible. The report suggests that Dubai, which is classified as a city located in Zone 0, is dominated by small local and large earthquakes coming from the Zagros and Makran zones. There are two main faults identified in Dubai, the Western Coastal Fault along the coast of Abu Dhabi running through Dubai and Sharja to Al Khaimah.

The second one, named Dibba Fault is located near the Oman Mountains which according to the report can cause significant ground motions and accelerations exceeding 0.25 m/s2. Moreover, the conservative estimate of seismic for Dubai is ranging from 0.075g to 0.20g (p.1).

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