Fire protection of historic buildings: A case study of Group-living Yard in Tianjin

Journal of Cultural Heritage 13 (2012) 389–396

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Original article

Fire protection of historic buildings: A case study of Group-living Yard in Tianjin Zhou Biao a , Zhou Xiao-meng a,∗ , Chao Ming-yong b a b

College of Environmental Science and Engineer, Nankai University, 300071 Tianjin, PR China Department of Chemistry and Chemical Engineering, Heze University, Heze City, 274015 Shandong, PR China

a r t i c l e

i n f o

Article history: Received 29 June 2011 Accepted 29 December 2011 Available online 21 February 2012 Keywords: Protection of historic buildings Group-living Yards Fire risk Yuan Residence Fire Dynamics Simulator (FDS)

a b s t r a c t Historic buildings are of great cultural, research and aesthetic value, and they can reveal past events and developments. Tianjin, an ancient city originated from Yuan dynasty, is famous for its Group-living Yards. Derived from settlements in foreign concession districts, these Yards exhibit different building styles and are now an integral part of Tianjin’s cultural heritage. However, many of these buildings disappeared due to the ravages of frequent fire disasters. To protect Group-living Yards and to alleviate fire losses, fire hazard survey was conducted. Then corresponding control and mitigation methods were proposed. Yuan Residence, one of the typical Group-living Yards, was employed as an example to demonstrate the availability of the methods proposed by using fire dynamics simulator. Finally, comprehensive suggestions and disaster mitigation methods were given for Group-living Yards in Tianjin, which gives guidance on developing policies and procedures for incorporating fire prevention and protection features into these buildings. © 2012 Elsevier Masson SAS. All rights reserved.

1. Introduction Located in northeastern part of the North China Plain since Yuan dynasty, Tianjin is nicknamed as World Architecture Museum because there are many buildings of different styles left from former foreign concession districts [1]. These buildings are of high appreciation value and provide concrete examples for cultural research. In Tianjin, many villas, office buildings, and barracks were built in the concession period, as time goes by, these extravagant buildings gradually evolved into Group-living Yards. Most of these buildings are of two or more storeys brick-wood structures with low fire resistance ratings. Thereby frequent fires bring about many casualties and pose significant challenges to government and local residents. Investigation shows that about 17,200 households still live in these buildings. Thus, eliminating or alleviating fire hazards while keeping the original styles of these buildings is an urgent issue. Fire safety control for historical buildings has been the subject of many researches in recent years. For instance, NFPA 914 gives requirements for fire protection, fire safety, and security in historic buildings [2]. NFPA 101 provides eight design fire scenarios specified for performance approaches in historic buildings [3]. The protection of museum and library collections is the subject of another document, NFPA 909, Code for the protection of cultural

∗ Corresponding author. Tel./Fax: +86 02 22 34 56 71 0. E-mail addresses: [email protected] (Z. Biao), [email protected] (Z. Xiao-meng), [email protected] (C. Ming-yong). 1296-2074/$ – see front matter © 2012 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.culher.2011.12.007

resources [4]. In addition, Bukowski et al. suggest that performance approaches are well suited to finding the balance between the need to protect often-irreplaceable buildings and their contents and the desire to preserve the significant historical or cultural aspects of the building [5]. Fire risk evaluation for historic building of the Potala Palace was investigated by Lei et al. using a kind of semiquantitative methods [6]. Hailong et al. studied the problem of fire spread in the Longxing Temple’s Great Mercy Storied-Pavilion in China [7]. Although some codes and researches for fire protection of historic buildings are available, discussions are still needed since these methods are not fit for Group-living Yards because of their unique characteristics in structures and fire situation. In this paper, our research is primarily on fire protection and disaster control for Group-living Yards in Tianjin. Firstly, potential fire hazards were generalized through analysis of fire cases occurred in these Group-living Yards, then corresponding fire mitigation and control measures were proposed and verified by computational fluid dynamic approaches. In the end, comprehensive methods for fire hazard mitigation and control were given with an aim to protect residents and these historical buildings. 2. Methodology Most traditional methods dealing with predictive problems require integrated observations which are difficult to make. In view of the difficulties, usually only a few observations are made within a short period of time to forecast future situations and to prepare for quick response [8]. In 1982, grey forecasting theory was proposed, which provided a non-traditional forecasting technique based on

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Fig. 1. Pillar-style Group-living Yards in Tianjin.

Fig. 2. Group-living condition in Group-living Yards.

scarce and fuzzy information [9]. In this theory, future trends for a time span are described using approximate differential equations. The advantage of the theory is that it can be used with as few as four observations in a prediction process [10]. Thus, the limitations of traditional methods [11,12] are conveniently overcome. In this paper, grey forecasting theory is used to explain fire situations in these Group-living Yards. Fire Dynamics Simulator (FDS) is a computational fluid dynamics (CFD) model of fire-driven fluid flow which solves numerically a form of the Navier-Stokes equations appropriate for low-speed, thermally-driven flow with an emphasis on smoke and heat transport from fires. The formulation of equations and the numerical algorithm are illustrated in FDS Technical Reference [13]. Here FDS is used to show the availability of fire control and alleviation action.

of them are with a fire-resistance rating III, the rest 656 are with a fire-resistance rating IV. Take Hebei district as an example, more than 96% of the buildings there were built before 1947, whose stairs, windows, floors and roofs are all wood structure besides roofs are covered with linoleum. Wood used in these buildings dries up over the years and provides good conditions for combustion and flame spread (Figs. 3 and 4). Especially in winter, fire disasters can be caused easily when residents warm their tightly closed houses with stoves. Once these buildings are on fire, smoke inside the buildings can hardly escape. At the same time, with rapid heat accumulation, rising temperature can trigger flashover, and then lead to a three-dimensional combustion in a short time. For instance, a three-dimensional fire resulting in 13 death and three injuries occurred in Songjian Hutong on April 2, 1986.

3. Result and discussion 3.1. Fire statistics and cause analysis Statistical data from Tianjin Fire Research Institute shows that 204 Group-living Yards are located in Tianjin, which account for 38.6% of historic buildings of the city. Common features of these Group-living Yards revealed by our investigations are as follows: • • • • • •

brick-wood structure; long history; pillar-style (Fig. 1); group living (Fig. 2); narrow fire evacuation routes; close to city center;

3.1.2. Frequent electricity overload over aged wires and poor wire connections (20.66%) With the development of economy and the improvement in living standards, power consumption is greatly increased due to much more use of household electric appliances. Original configuration with aluminum wires may no longer meet the enlarged needs for electricity. However, corrective actions are often not properly made due to economic reasons, which results in frequent electrical overload. Furthermore, chaos wiring and poor wire connections (Fig. 5) can be seen in many places, making the situation even worse.

Fire data from 1998 to 2008, provided by Tianjin Fire Research Institute, are given in Table 1. Calculation with grey forecasting theory shows that the total number of fires in 2011 will be approximately 257, which indicates the seriousness of fire situation in these Group-living Yards and thus requires immediate improvements. As addressed above, major fire hazards are summarized as follows. 3.1.1. Large fire loads and low fire resistance rating (24.20%, percentage of fire accidents caused by this type of fire hazards, the same hereinafter) Most of these Group-living Yards are of brick-wood structures, in which wood plays a significant role in sustaining the whole structure. Among all the Group-living Yards, survey shows that 85

Fig. 3. Ageing wooden stairs.

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391

Table 1 Fire statistics from 1998 to 2008. Year

1998

1999

2000

2001

2002

2003

Total fire number Year Total fire number

261[14] 2004 345[20]

282[15] 2005 359[21]

329[16] 2006 371[22]

336[17] 2007 389[23]

340[18] 2008 391[24]

330[19]

3.1.3. Obstruction of emergency exit (33.80%) During an on-site survey, we found that some residents install kitchens and storage rooms using combustible materials in vacant areas along corridors. In some buildings, it is so crowded that even a walk through the corridors seems difficult. For example, the emergency exit in a building (26 households) at 117 Heping road was blocked by a temporary kitchen. The two-meter wide corridor of Table 2 The function and area of each room. Serial No.

Function

Area (m2 )

1–1

Inhabitation

68.07

1–2

Inhabitation

–

1–3

Public passageway (with sundries)

51

1–4

Inhabitation

32.5

1–5

Inhabitation

40.2

1–6

Communal kitchen

44.5

1–7

Inhabitation

30.22

1–8

Inhabitation

17.43

1–9

Inhabitation

18.93

1–10

Inhabitation

22.86

1–11

Inhabitation

23.16

1–12

Inhabitation

24.26

2–1

Inhabitation

68.07

2–3

Corridor

36.17

2–4

Communal kitchen

51

2–5

Inhabitation

15

2–6

Inhabitation

29

2–7

Communal kitchen and corridor

–

2–9

Inhabitation

17.43

[5pt] 2–10

Inhabitation

15

2–11

Inhabitation

21.2

2–12

Inhabitation

18.93

2–13

Inhabitation

22.86

2–14

Inhabitation

23.16

2–15

Inhabitation

24.26

3–1

Inhabitation

41

3–2

Inhabitation

31.8

3–3

Inhabitation

34.5

3–4

Inhabitation

19.4

3–5

Inhabitation

18

3–6

Communal kitchen and corridor

–

3–7

Inhabitation

28

3–8

Inhabitation

16.25

3–9

Inhabitation

17.03

2–8

Balcony

30.22

Fig. 4. Wooden stairs.

Taikang building (70 households) at Heping District was occupied by temporary kitchens, leaving only a very narrow way of about 0.4 m. Furthermore, there kept many flammable materials such as broken paper boxes, woody brackets, etc. Under such circumstances, evacuation becomes very difficult in case of a fire. 3.1.4. Shortage of water sources and fire fighting devices (4.13%) Safety inspection results show that most households are not equipped with fire hydrants, and some of them are even far from municipal water. Although some households are equipped with fire

Fig. 5. Chaos wiring and poor wire connections.

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hydrants, most of them can not work properly due to insufficient water pressure. 3.1.5. Lack of general fire safety knowledge and self-rescue abilities (8.71%) Some residents lack general fire safety knowledge. They connect wires randomly, replace fuse wires with copper wires, and do not know how to protect themselves in case of a fire. For example, a man was burned to death in a fire at 16 Taiwan Road in 2005. He took no action except for crying. 3.1.6. High population density but with no fire separation (8.50%) Survey shows that approximately 80.3% of the Group-living Yards are inhabited with 10 or more households, and a majority of these Group-living Yards are interconnected with each other with no fire separation. For example, Taikang building, a three-storey building located in Heping district, inhabited with about 70 households and more than 280 residents. Another building located at 5 Yantai Road is a four-storey staff dormitory renovated from an old warehouse, each floor of which was divided into more than 30 rooms by gypsum wallboards. 3.2. Fire features of Group-living Yards In northern China, most residents rely on stoves to warm their homes, which can cause flashovers easily. Once a flashover occurs, it is extremely dangerous for people who are in the building. A building is just like a hearth filled with firewood, when a Groupliving Yard catches on fire, a flashover can easily occur. A number of studies on flashover have been done by other researchers. For example, Peacock et al. reviewed the experimental studies of real-scale fires that quantify the onset of flashover in terms of measurable physical properties [25]. However, there is disagreement over the definition of flashover ever since it was observed, and accurate flashover prediction remains rather difficult. In studies by Thomas [26], Babrauskas et al. [27] and many others, a concept that flashover was defined as the occurrence of criticality in a thermal balance sense was applied to room fires. In other studies, Hagglund et al. [28] reported that flashover was experimentally observed when gas temperature 10 mm below the ceiling reached 600 ◦ C; Results of tests conducted by Budnick and Klein in the master bedroom of a single-width mobile home showed that no flashover was observed when roof temperature reached 300 to 375 ◦ C, and flashover occurred when roof temperature reached 634 to 734 ◦ C [29]. Parker and Lee suggested a heat flux of 20 kW/m2 to ceiling would result in roof ignition [30]. As addressed above, it is suggested that not only temperature but also heat flux play an important role in flashover occurrence. Thus, in addition to temperature, heat flux to exposed items within a fire room has also been a criterion for flashover. To summarize, ceiling gas temperature higher than 600 ◦ C or heat flux to ceiling greater than 20 kW/m2 can be predictive of flashover in a fire room. Several approaches have been taken to estimate the onset of flashover within a room. These methods are typically based on simplified mass and energy balances on a single-compartment fire. For instance, Babrauskas developed a simple combustion model to estimate the minimum heat release rate to produce flashover [31]:



Q˙ = 750A

h

where Q˙ is the estimated rate of heat release in kW, A is the door area in m2 and h is the door height in m.

Fig. 6. A photo of Yuan Residence.

McCaffrey et al. [32] performed a regression analysis to provide a correlation for calculating upper layer gas temperature: 2/3 −1/3 Q˙ hk AT T = 480( √ √ ) (√ √ ) gCp 0 T0 A h gCp 0 T0 A h

where T is the temperature rise in regard to ambient in ◦ C, hk is the effective heat transfer coefficient of ceilings in kW·m–2 ·K–1 , AT is the effective heat transfer of door area, g is gravitational constant 9.8 m·s–2 , Cp is specific heat of gas in kJ·kg–1 ·K–1 , 0 is ambient gas density in kg·m–3 (approximately 1.2), T0 is ambient temperature A means to calculate the effective approximately 22 ◦ C or 295 K. kc/t was presented in literature heat transfer coefficient, hk = [32], where k is thermal conductivity of wall material, t is a representative time of exposure. In all, exposure time t will be another significant parameter in forecasting flashover. Analysis of above mentioned equations and fire protection action for historical heritage indicates that Q, hk and t all play a significant role in flashover occurrence. Thereby, our emphasis is primary on these parameters. Removing combustible materials inside buildings may lower Q largely. Thermal conductivity hk may be lessened by using fire retardant paint on insider wall or ceiling. And fire extinguishing system could shorten combustion time. In order to demonstrate the action rule, a case study was done in following parts. 3.3. A case study 3.3.1. Yuan Residence introduction Yuan Residence was set up for Yuan Shikai (1859–1916), a military leader and politician in late Imperial China, and the first President of the Republic of China [33]. Built in 1918, it is the only existing residence in Tianjin that is of German-style. It covers an area of 1836 m2 with three stories above ground and one storey below. Nowadays, special protection is given to the building due to its historic importance and unique building style (Figs. 6 and 7). The layouts of the first, second and third floor of the building are given in Figs. 8–10 respectively. 3.3.2. Analysis of flashover risk in Yuan Residence Fire load refers to the quantity of combustible or the quantity of heat generated by combustion in a given area. Distribution of combustible materials in a building can be shown by fire load density. The greater the fire load within a building, the greater the risk is. Usually, fire load can be divided into three categories:

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Fig. 7. Yuan Residence-certified historical and stylistic architecture.

• fixed fire load. Such as combustible/flammable materials used in building construction and interior decoration; • movable fire load. Such as furniture and clothes for everyday life; • temporary fire load. Such as temporary combustibles. For residential buildings, fixed fire load and moveable fire load should be considered. The function and area of each room of Yuan Residence and the heat release value of each houseware/material in the rooms are presented in Table 2 and Table 3 respectively [34]. Fire load can be calculated with the following formula: q=

 Mv hc

Fig. 9. Layout of the second-floor.

Fire growth factor should consider fuel load density (˛f ) and the influence of walls and ceilings (˛m ), which can be obtained by the following formula: ˛ = ˛f + ˛m Where ˛f = 2.6 × 10−6 q5/3 and ˛m is given in Table 4. With the ˛ value obtained above, heat release rate Qf can be calculated by the following formula: Qf = ˛t 2

At

Where Mv is the mass of each combustible in kg, hc is the effective heat release value for per unit of each material in MJ/kg, At is floor area in m2 .

In the present paper, we assume Qf reaches maximum value when a fire reaches flashover. Qf can be got by formula: Qf = 7.8Aroom + 378(Avent



Hvent )

where Aroom is total area excluding vent area in m2 , Avent is vent area in m2 , Hvent is height of vent in m. With regard to Yuan Residence, the Time to Reach Flashover (TRF) is estimated by the above-mentioned calculation method, details are illustrated in Table 5.

Fig. 8. Layout of the first-floor.

Fig. 10. Layout of the third-floor.

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Table 3 Heat release values for different housewares/materials. Name of housewares/materials

Heat release value per unit 1200 (MJ/piece)

Large cupboard

Name of housewares/materials

Heat release value per unit

Fridge

28.1 (MJ/piece) 31.1 (MJ/piece)

Bookcase

540 (MJ/piece)

Washing machine

Small furniture

250 (MJ/piece)

Cotton

18.89 (MJ/kg)

Square table

420 (MJ/piece)

Wood

17–20 (MJ/kg)

Extended table

600 (MJ/piece)

Wool

Armchair

330 (MJ/piece)

Paper

Sofa

840 (MJ/piece)

Cotton

Padded chair

70 (MJ/piece)

Unpadded chair

Nylon

250 (MJ/piece)

Clothes

Kneehole desk

2200 (MJ/piece)

PVC

Desk

1200 (MJ/piece)

20.7–26.6 (MJ/kg) 16–20 (MJ/kg) 16.5–20.4 (MJ/kg) 31.6 (MJ/kg) 17–21 (MJ/kg) 17.95 (MJ/kg)

Chinese liquor

17–21 (MJ/kg)

Desk with metal finish

840 (MJ/piece)

Tea

17–19 (MJ/kg)

Single-drawer desk (empty)

330 (MJ/piece)

Cigarettes

15–16 (MJ/kg)

Wardrobe (empty)

500 (MJ/piece)

Coffee

16–18 (MJ/kg)

Computer

150 (MJ/piece)

Peanuts

23–25 (MJ/kg)

2

Wooden floor

Cooking oil

38–42 (MJ/kg)

Carpet

83.69 (MJ/m ) 50 (MJ/piece)

Sugar

15–17 (MJ/kg)

Curtain

10 (MJ/m2 )

Pasta

10–15 (MJ/kg)

Television

31.9 (MJ/piece)

Meat

Flour

17.6 (MJ/kg)

Butter

3.3.3. Fire hazard mitigation in Yuan Residence The model of Yuan Residence is given in Fig. 11. FDS are used to demonstrate these measures. The primary concern of this research is TRF, because to some extent, the longer the TRF, the lower the risk to exposed residents. In this paper, TRF is defined as either the time when the heat flux to the ceiling exceeds 20 kW/m2 or the temperature of the ceiling gas layer reaches 600 ◦ C, whichever lower is determined as TRF. Fig. 12 shows that the use of fire retardant paint on wall or ceiling and the removal of combustibles from inside the building can increase the TRF and thus can reduce the risk of fire disasters. Table 4 The ˛m values of decoration materials with different flammable ranking. Flammable ranking for decoration materials

˛m (kW/s2 )

A B1 B2 B3

0.0035 0.014 0.056 0.35

Table 5 Calculated results for Yuan Residence. Area

Fire load density/(MJ/m2 )

Fire growth coefficient/(kW/s2 )

Critical heat release rate/(kW)

TRF/(s)

1–8 1–10 2–11 2–13 2–5 3–5 3–6 3–8 3–9

379 4 262 430 6.25 336 7.2 172 388.6

0.1076 0.056 0.0839 0.0797 0.056 0.0982 0.056 0.0488 0.1098

1289.3 No flashover 1708.8 3060.4 No flashover 1315.0 No flashover 1573.8 4204.9

110 143 196 116 180 196

39.8 (MJ/kg) 30–33 (MJ/kg)

3.4. Suggestions In view of the fire situation in the Group-living Yards, comprehensive control and mitigation measures, which consist of active control actions and passive actions, should be considered. 3.4.1. Active control actions 3.4.1.1. Establish fire risk evaluation system with respect to Groupliving Yards. Fire risk evaluation system plays an important role in prevention and mitigation of fire hazard, therefore, the system should be established. Firstly, a detailed investigation of the Group-living Yards should be conducted, including identification of fire hazards, estimation of potential losses, disasters and consequences. For example, an estimation of consequences caused by obstruction of emergency exits, fire roads and so on should be made. Then an objective evaluation of the current situation of the Groupliving Yards should be carried out, including a detailed research of the structure of buildings, the distribution of combustibles, the structure and number of habitants, the value and distribution of heritages, causes of fire, fire-fighting facilities, fire safety management and so on. At last, fire risks of different regions should be evaluated using a risk rating method, regions at higher risk should be addressed with higher priority. 3.4.1.2. Strengthen fire fighting abilities of firefighters. Fire emergency preparedness plan should be completed. Training and drills should be conducted regularly to strengthen the abilities of firefighters, so that when a real fire happens, firefighters are well prepared and their skills are sharp. 3.4.1.3. Strengthen fire protection equipment for extinguishing initial fire. Because of the special structures of these Group-living Yards, and also because past fire disasters usually occurred at night when residents were sleeping, detection of fires at the

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395

The time to reach flashover /s

Fig. 11. Fire Dynamics Simulator (FDS) model of Yuan Residence.

200

Calculated results FDS calculation results Using only fire retardant paint on insidewall(by FDS) Using only fire retardant paint on ceiling(by FDS) Both using fire retardant paint on insidewall and fire retardant paint in ceiling(by FDS) Removing five wooden desks(by FDS) Removing five wooden beds (by FDS)

160

120

80

1-8

2-11

2-13

3-15

Area

3-8

3-9

Fig. 12. Time to Reach Flashover (TRF) compared in different situations.

incipient stage becomes critical in preventing disasters. Fire detection and alarm system itself can not stop fire progress, but it can help alert people so that evacuation and fire fighting could be more effectively organized. For initial fire warning in these Group-living Yards, single fire detection method is not enough, automatic fire alarm system should be used to increase the detection rate.

3.4.2. Passive actions – increase fire safety awareness and strengthen fire safety management Local governments at all levels should conscientiously perform their fire safety duties in accordance with Fire Control Law of the People’s Republic of China and Tianjin Fire regulations. Fire control laws/regulations and fire safety knowledge should reach the public through various ways. Fire department in the city should familiarize residents with fire preventative measures and self-rescue techniques. Furthermore, specific education on fire characters can help residents better understand fire hazards in their daily life. Taking preventative measures, learning fire-fighting skills, and keeping calm in case of a fire can help save themselves and others. In order to prevent fire disasters caused by stove fires, residents should pay special attention to the following: • never stack combustibles around a stove; • never introduce oils or flammable liquids into a fire; • always make sure there are no embers before disposal of stove ashes; • routine checks on gas stove and gas pipes should be carried out.

4. Conclusion Suggestions are given as to how to provide fire protection to Group-living Yards in Tianjin. It is hoped that this research can give some useful support to fire protection and heritage conservation. Main conclusions are as follows:

• fire situation in Group-living Yards in Tianjin is severe, control and mitigation actions should be taken urgently to improve the fire safety situation of these historic buildings; • investigations over past fire disasters of Group-living Yards in Tianjin reveal the following main fire risks: ◦ large fire loads and low fire resistance rating, ◦ frequent electricity overload over aged wires and poor wire connections, ◦ obstruction of emergency exit, ◦ shortage of water sources and fire fighting devices, ◦ lack of general fire safety knowledge and self-rescue abilities, ◦ high population density but with no fire separation; • Yuan Residence is studied by fire hazard identification, fire danger and hazard analysis. Fire safety protection proposals were given in pursuance of flashover theory, and validated by FDS. Removing combustible materials from inside the buildings, using fire extinguishing system or fire retardant paint could increase TRF and alleviate fire loss; • in the end, comprehensive suggestion including active and passive control measures were proposed, which hopefully would

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