Following the terrorist onslaught on the New York World Trade Center in 2001, this paper seeks to look into the design features that would heighten the safety of tall edifices.
Design/methodology/approach - Using a questionnaire, informations have been collected via electronic mails and by station from designers and civil applied scientists ( AEs ) in Singapore. Structured interviews were conducted with public governments.
Findingss - The consequences show that AEs perceive tall edifices to be by and large safe in footings of structural design, fire safety characteristics and agencies of flight. The consequences besides show that AEs confirm the demand to better the safety of tall edifices further, are doing an attempt to turn to the heightened safety concern, will give full support to enterprises to turn to heightened safety concerns, will hold to carry on hazard appraisal during the design stage and will welcome a performance-based design codification. AEs do non hold that edifices should be designed to defy hydrocarbon fires or aircraft onslaughts. The study consequences further reveal that the four most effectual methods to better the safety of tall edifices are supplying issue marks with illuming at floor degrees, a separate design codification for super tall edifices, supplying fire safety and deliverance floors, and the decentalisation of fire systems.
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Originality/value - The importance of this paper is that it investigates the safety characteristics and steps that can cast some visible radiation on heightening the safety of tall edifices. The findings may be used by constructing governments to explicate future steps and codifications to better heighten the safety of tall edifices. Based on the findings, farther research on each executable method of bettering the safety of tall edifices may be undertaken.
The unprecedented devastation of the New York World Trade Center ( WTC ) by terrorists on September 11, 2001 ( 9/11 ) signified new menaces to tall icon edifices and has led to heightened concerns over the safety facets of tall edifices. Present safety characteristics in tall edifices might be unequal in get bying with such hazards, particularly when current edifice design and building have concentrated on the more normal types of accidents and catastrophes that can bechance constructions and their residents. There may be a demand to do edifices more robust and to guarantee better protection for a edifice 's residents.
After 9/11, some issues need to be addressed. For illustration, is it necessary to guarantee that edifices are capable of defying the sort of impact suffered by the WTC? In reevaluating the hazards to the built environment, should edifices be designed to defy aircraft onslaughts, or simply to guarantee that there is sufficient clip for the residents to evacuate before the edifice prostrations?
The aims of this survey are:
to look into how safe tall edifices are/should be ; and
to analyze the feasibleness of assorted methods to better the design of tall edifices to do them safer.
The positions of designers and civil applied scientists ( AEs ) and relevant edifice governments in Singapore were obtained through a questionnaire study and interviews. Singapore is a relevant state for this survey to be conducted because it is a little city state, where land is scarce, and tower block, high-density life is the norm. Singapore besides likely has one of the highest concentrations of tall edifices per hectare of land in the universe.
The importance of this paper is that it investigates the safety characteristics and steps that can cast some visible radiation on heightening the safety of tall edifices. The findings may be used by constructing governments to explicate future steps and codifications to better heighten the safety of tall edifices. Based on the findings, farther research on each executable method of bettering the safety of tall edifices may be undertaken.
Proposed methods to better safety of tall edifices
To measure the deductions of 9/11, the USA and the UK edifice governments and other related authorities bureaus have established groups and undertaking forces consisting edifice experts around the universe. These groups and undertaking forces seek to place life-safety issues and suggest new methods to better the public presentation of future tall edifices and guarantee sufficient emptying clip for edifice residents.
In planing edifices against menace, Mr Robert Prieto, of Parsons Brinckerhoff, Inc. , highlighted the three Rs of menace design: `` Design to defy the menace. Design to react to the menace. Design to retrieve from the menace '' ( Post, 2001a ) . From a literature reappraisal, some of the methods that have been suggested by applied scientists and practicians in an attempt to better the safety public presentation of tall edifices are summarized in Table I.
Column 2 of Table I shows that there are 23 possible ways to better the safety of tall edifices. These are categorized into five chief headers:
structural design ;
fire technology ;
agencies of flight ;
stuffs engineering ; and
codifications and ordinances.
How executable these methods will be is still unknown and remains to be determined. Therefore, this paper aims to happen out the suitableness of these methods by proving them in the field.
The survey comprised a sample study and structured interviews to garner the positions of AEs and edifice governments, severally. The intent of the study was to happen out AEs ' perceptual experiences of the safety of tall edifices in Singapore and the feasibleness of steps that could be adopted to better the safety degrees of tall edifices. The intent of the interviews was to analyze the edifice governments ' attempts in turn toing the safety of tall edifices after 9/11.
A questionnaire was designed for the study. The first subdivision of the questionnaire sought to find the profile and demographic inside informations of the respondents. In the 2nd subdivision, respondents were asked to rate the safety degree of tall edifices in Singapore ( V1 to V4 ) on a ten-point Likert graduated table, where 1 denotes `` really insecure '' , 5 denotes `` satisfactory '' and 10 denotes `` really safe '' . They were besides asked to rate the ability of these edifices to defy accidents and onslaughts ( V5 to V6 ) on a five-point Likert graduated table, where 1 denotes `` strongly disagree '' , 3 denotes `` neither agree nor disagree '' and 5 denotes `` strongly agree '' . The respondents ' positions on the heightened safety concern and the critical issues related to 9/11 ( V7 to V16 ) were besides obtained utilizing the same five-point Likert graduated table. The 3rd subdivision sought to find the feasibleness and pertinence of the methods uncovered from the literature reappraisal. Respondents were asked to bespeak whether they thought the proposed method should be adopted, non adopted, or were diffident. They were besides encouraged to notice and give grounds for their responses. The complete mail study bundle comprised a screen missive, the questionnaire and a stamped, self-addressed and envelope. Data for the study were collected via electronic mail, surface mail and telephone.
AEs were targeted for the study because the work that they do is straight relevant to constructing safety. Eighty and 160 questionnaires were sent to randomly selected AEs in the public and private sectors, severally. Public-sector AEs were identified through the Singapore Government 's published directory. Private-sector AEs were obtained from Internet Yellow Pages ( 2002a, B, degree Celsius ) .
Besides the study, structured interviews were conducted with authorities functionaries from the Building and Construction Authority ( BCA ) and the Fire Safety and Shelter Bureau ( FSSB ) . The intent of the interviews was to happen out their attempts in turn toing the safety of tall edifices. The BCA was selected because it is the chief regulator of Singapore 's building industry ( Building and Construction Authority, 2002a, B ) . The FSSB is the local authorization in fire safety and bomb shelter ordinances ( Singapore Civil Defence Force, 2002 ) . E-mails explicating the intent of the research were sent to the governments to bespeak permission to carry on the interviews. Agreements for the interview Sessionss were so made with interviewees who were involved in the reappraisal of edifice safety after 9/11.
Survey consequences and informations analysis
Thirty-four questionnaires were received, giving an overall response rate of 14 per centum. The public sector response rate ( 28 per centum ) was higher than the private sector response rate ( 8 per centum ) . The good response rate from public-sector respondents may be because the several Human Resource Departments agreed to administer the questionnaires. The low response rate from the private sector respondents may be because these AEs felt that their chief duty is to follow the design codifications, and it is up to the authorities to alter the codifications. To increase the response rate, phone calls were made to the AEs to bespeak their engagement. Unfortunately, some of the mark respondents were normally busy or administrative staff were loath to set the calls through.
The profile of the respondents is summarized in Table II. It can be seen that the bulk of the respondents held senior places in their organisations. The bulk of the respondents were applied scientists, and many of them were from the public-sector lodging authorization. Furthermore, the bulk of the respondents ( 79 per centum ) had worked in the building industry for more than five old ages. This would do their feedback more accurate and dependable. Almost all the respondents ( 88 per centum ) had been involved in the building of tall residential edifices. The public-sector respondents focused more on residential edifices, while the private-sector respondents were more involved in tall commercial edifices.
We now describe the profile of the interviewees. The interviewee from the BCA was a senior director who had a civil technology grade. Prior to fall ining the BCA, he had worked in the building industry for 25 old ages and was involved in the building of major substructure and edifice undertakings. The FSSB interviewee held a sheepskin in stuffs and measures in add-on to his civil technology grade. He had worked in the FSSB for more than 15 old ages and was involved in reexamining the Fire Code. The positions of these capable affair experts ( SMExperts ) were incorporated in the relevant treatment subdivisions.
Datas were entered into the Statistical Package for Social Sciences ( SPSS ) package for analysis. Average evaluations for all the variables were calculated ( Table III, column 3 ) . A one-sample t-test of the mean was carried out to look into whether the population would hold with the variables surveyed. For variables V1 to V4, the void hypothesis ( H 0 ) that tall edifices are regarded as insecure and the alternate hypothesis ( H 1 ) that tall edifices are regarded as safe are set out as: H 0. I?a‰¤5. H 1. I? & gt ; 5. I? is the population mean, and is taken as 5 on a ten-point evaluation graduated table.
For variables V5 to V16, the void hypothesis that respondents disagree with the variable and the alternate hypothesis that respondents agree with the variable are set out as: H 0. I?a‰¤3. H 1. I? & gt ; 3. The degree of significance ( I± ) was set at 0.05. If the deliberate p-value is greater than or equal to 0.05, H 0 is non rejected and the consequence is non important. If the p-value is less than 0.05, H 0 is rejected and the consequence is important beyond the 5 per centum degree. The consequences are shown in Table III ( columns 4 and 5 ) .
An independent samples t-test was carried out to find whether the public and private sector respondents shared the same positions on the variables surveyed or otherwise. The degree of significance ( I± ) was besides set at 0.05. The nothing and alternate hypotheses are: H 0. I? public=I? private. H 1. I? publica‰ I? private. When H 0 is non rejected, it is concluded that there is no difference in the average evaluations by both sectors. The rejection of H 0 agencies that both sectors of the building industry have differing positions with regard to the variable being tested. Levene 's Test was used to look into for equality of discrepancies between the two groups of respondents ( Gray and Kinnear, 1997 ) . It was found that there was no important difference, and hence a pooled estimation of the population discrepancy was used. The consequences of the t-test of the difference between agencies are given in Table III ( columns 6-9 ) . The consequences show that there is no important difference between the positions of public and private sector respondents except for point V16. In point V16, both public and private sector professionals disagreed that tall edifices should be designed to defy aeroplane onslaughts, but private sector professionals disagreed to a greater extent.
In the 3rd subdivision of the questionnaire, the respondents indicated whether a suggested step should be implemented ( agree ) , non implemented ( disagree ) or they are diffident about its pertinence in bettering the safety of tall edifices. The consequences are shown in Table I ( columns 4-7 ) . The four most popular methods are:
supply issue marks with illuming at floor degrees ;
supply a separate design codification for ace high-rise edifices ;
supply fire safety and deliverance floors ; and
supply a decentralized fire system.
These consequences are now discussed.
How safe tall edifices are/should be
The one-sample t-test consequences ( Table III ) show that in general, the respondents are of the sentiment that tall edifices in Singapore are safe ( V1 ) . They besides have more than equal structural design ( V2 ) , fire safety ( V3 ) and means of flight ( V4 ) . Among the four safety appraisal of tall edifices, the average safety evaluation for structural design is highest at 7.88. Respondents felt that this facet of the edifice is the most earnestly considered in guaranting the safety of edifices. In add-on, tall edifices will be able to defy normal accidents ( V5 ) , but will fall in upon an aircraft onslaught ( V6 ) .
The above consequences may be biased towards the sentiments and perceptual experiences of the respondents. This is because the population surveyed is likely to react that edifices are safe because they are involved in the design procedure, and stating that a edifice is insecure brings into inquiry their design patterns. In add-on, a big per centum of public functionaries responded to this study. These public functionaries can non be seen to hold no assurance in the safety of tall edifices when they have a responsibility of attention to normal citizens.
Of the 10 steps proposed ( V7-V16 ) , six ( V7, V9, V10, V11, V13, V14 ) are significantly of import ( p & lt ; 0.05 ) . Respondents felt that there is a important demand to better the safety of tall edifices ( V7 ) . Consistent with this response, the respondents disagreed that tall edifices do non necessitate extra safety steps ( V12 ) . This shows that there is room for betterment and supports the demand to heighten edifice safety.
Respondents felt that they have the expertness to better the safety of tall edifices ( V9 ) . The findings are promoting. It shows that AEs have the proficient capableness to do tall edifices even safer. The respondents besides agreed that they have made an attempt to turn to the heightened safety concern ( V10 ) . In add-on, they will give fullest support to the building industry to turn to the safety of edifices ( V11 ) . However, this issue is non their chief concern ( V8 ) , possibly because the tall edifices are already structurally safe ( V2 ) .
Respondents agreed that there is a demand for hazard appraisals to be conducted on tall edifices during the design stage ( V13 ) . These hazard appraisals will help edifice interior decorators in placing the likely menaces faced by edifices ( Broughton, 2002 ; Linn, 2002 ) . Buildings are so designed to turn to the menaces to heighten their safety public presentation.
Respondents besides agreed that a performance-based codification might supply better safety counsel than the normative codification for tall edifices ( V14 ) . The SMExperts revealed that the governments have already recognized the demand for a performance-based codification because it offers more flexibleness to interior decorators. For alone edifices such as airdromes and large-sized indoor bowls, interior decorators may non be able to use the conventional normative codifications straight.
The findings show that respondents are opposed to planing edifices to defy hydrocarbon fires ( V15 ) and aircraft onslaughts ( V16 ) . This may be because it will be excessively expensive to construct such constructions, when the menace is improbable and unpredictable. SMExperts confirmed that edifices are designed based on possible burden events and believable jeopardies. Aircraft onslaught is non a sufficiently believable jeopardy to be considered in the design of edifices, and therefore edifice codifications do non necessitate that such events be considered for edifices in Singapore. The deduction is that edifices may non defy such utmost impact, particularly in the presence of the resulting fires because these constructions have non been designed for such menaces.
SMExperts emphasized that it is more executable to concentrate on other signifiers of menaces such as truck and handheld bombs, which are physically transported by human existences. Resources should be directed towards air power and other security steps instead than to beef uping edifices against aircraft impact.
Fire in edifices is a believable jeopardy which has been addressed in most edifice design. Harmonizing to the SMExperts, if edifices are improbable to see any menace posed by jet fuel, edifices need non be designed to defy hydrocarbon fires.
How to plan safer tall edifices
A ranking of the feasibleness of the proposed methods, based on the per centum of respondents who agreed with the method, is shown in Table I ( column 7 ) . For the intent of this survey, a proposed method is considered executable to do tall edifices safer when more than 50 per centum of the respondents agreed with it. Twelve methods are found to be executable and are discussed in the undermentioned subdivisions.
Four possible methods to better the safety of tall edifices through structural design were proposed. One of these was found to be acceptable by more than 50 per centum of the respondents ( see Table I ) . The bulk of the respondents agreed with hardening of stairwells ( point 1.3 ) against blast impact. Strong stairwells are of import because flight stairwaies are the chief agencies by which edifice residents evacuate from edifices in an exigency. Existing codifications normally permit the usage of dryboards and masonry for stairwell enclosures, and these are susceptible and more prone to damage. This will do flight stairwaies to be blocked by fallen stuffs from stairwell walls. Reinforced concrete walls will hold higher opportunities of lasting a blast onslaught. It is recommended that codifications be changed to indurate stairwells.
The bulk of the respondents did non hold with supplying prostration floors ( point 1.1 ) , which would be provided between, say every 10 floors, to transport the weight of the dust of the floors that prostration above it, and act as a arrest to progressive prostration ( Lane and Clark, 2001 ) . Some respondents felt that prostration floors impose significant structural demands ; for illustration, closely separated columns of larger sizes may be necessary.
The bulk of the respondents did non hold with the proviso of a sacrificial facade ( item 1.2 ) . In this system, there is an exterior wall, a perpendicular air pocket behind it and another structural wall indoors. The exterior wall is designed to absorb blast impact and contain harm, and act as a first line of defense mechanism for the edifice 's structural unity ( Nadel, 2002 ) . Some respondents felt that this system may give architectural the look of edifices and blockade the positions of the residents. Furthermore, the facade may necessitate to be spaced far apart from the internal wall for effectivity, and this would take up valuable infinite.
Respondents besides did non hold that heavy tonss should non be allowed on roofs ( point 1.4 ) . In the WTC towers, heavy tonss were placed on the roofs to stabilise the edifices ' wind-induced sway, but these could be a conducive factor to the prostration ( Building, 2001b ) . Some respondents felt that it is the norm to use rooftop infinite to house works and equipment such as lift motor suites and H2O armored combat vehicles, and interior decorators may confront the job of re-siting edifice services if rooftop infinite is non utilised. Furthermore, for practical grounds, some M & A ; E systems rely on gravitative force per unit area to work.
Four possible methods to better the safety of tall edifices through fire technology were proposed. Three of these were found to be acceptable by more than 50 per centum of the respondents ( see Table I ) .
Astaneh-Asl 's ( 2002 ) probe of the WTC prostration revealed that the firefighting systems were centralized at the stairway nucleus. This bunching together of the services meant that when that location was hit, the whole firefighting system may hold failed. He hence recommended that sprinkler pipes, moisture and dry risers should be decentralized, and placed at different locations of the edifice. Respondents agreed with the method ( item 2.3 ) , but some cautioned that this would take to increase in cost.
A sum of 61 per centum of the respondents agreed that supplying burden detectors ( point 2.4 ) is executable, and may increase the safety of tall edifices. Load detectors can be used to understand and supervise edifice behaviour. Prompt action could be taken and exigency forces alerted one time information is fed to the monitoring system. Furthermore, burden detectors, if decently developed, are utile tools in supplying warning signals to determine whether edifices are safe for entry during an exigency event. This would supply better protection to firemans and exigency forces, as they are able to measure the hazard of partial or entire prostration of a edifice under menace.
A sum of 53 per centum of the respondents agreed that supplying a separate firemans ' stairway is executable ( item 2.1 ) . In the WTC incident, firemans running up the stairwells rushed headfirst into office workers who were hotfooting down on the same steps ( Post et al. , 2001 ) . Respondents who objected to a separate firemans ' stairway argued that the current fire codification already has a dedicated lift for usage by firemans. The infinite required for a firemans ' stairway might be indefensible as this reduces salable infinite and may imply excess building and care costs. One respondent questioned how edifice residents could be prevented from utilizing this stairway during an exigency.
Respondents did non hold to planing redundancy in fire systems ( item 2.2 ) . This may be because excess standpipes for firefighting, separate fire pump suites, excess sprinkler systems, excess fire dismay systems, and double fire bid Centres will necessarily take to be addition. Some respondents weighed the pertinence of this method against cost effectivity, long-run care, cost and clip of installing and other options.
Meanss of flight
Nine possible methods to better the safety of tall edifices through agencies of flight were proposed. Six of these were accepted by more than 50 per centum of the respondents ( see Table I ) .
A sum of 63 per centum of the respondents agreed that wider stairwaies might be necessary for tall edifices ( item 3.3 ) because these could suit more people to rush up emptying. Unfortunately, wider stairwaies would increase cost and cut down gross due to reduced salable floor infinite. There is besides debate sing cut downing the standard breadths of stairwaies because there is rarely a demand to evacuate the whole edifice at one clip, as normally merely occupants on stray floors in the affected country demand to be evacuated ( Post and Angelo, 2001 ) .
Supplying issue marks with illuming at floor degree ( item 3.4 ) received the most support from the respondents. Well-marked and lit marks are cardinal constructing design characteristics that facilitated the emptying of many edifice residents at the WTC Towers ( Federal Emergency Management Agency/American Society of Civil Engineers, 2002 ) . Such a safety characteristic would hold the extra advantage of assisting residents in following flight paths if they have to creep on the floor. However, certain issues need to be addressed, such as the care of issue marks near floor degree, which are capable to more wear and tear and hooliganism.
The construct of fire safety and deliverance floors is appealing to the respondents ( point 3.5 ) . Fireproof refuge countries can harbor people in the center of an emptying and service as deliverance points ( Post, 2001a ) . These countries should non incorporate furniture, and are designed to be wholly fireproof. Some respondents commented that proprietors may non hold to supply these countries as they can non bring forth gross but alternatively incur care costs.
A sum of 58 per centum of the respondents agreed to the proviso of extra stairwaies in tall edifices ( item 3.6 ) . Similarly, some respondents are concerned about infinite and cost. Some suggested that the figure of stairwaies be increased merely at lower floors to provide to the big Numberss of falling residents from upper floors. This could forestall congestion and easiness emptying, peculiarly in exigency instances affecting mass emptying of residents. This suggestion is a good via media between cost and safety.
Fifty-six per centum of the respondents perceived sky Bridgess to be executable in edifices ( item 3.8 ) . Besides being an alternate flight path, sky Bridgess could function as normal entree between edifices. Twenty-six per centum of the respondents did non favor sky Bridgess in position of the possibility that the construction of the sky Bridgess might be affected when a edifice was under menace. Besides, sky Bridgess could be a agency to let the spread of fire to the other edifice. A sky p that is overloaded with escapees may fall in, doing more human deaths. Some respondents, peculiarly designers, were concerned about the aesthetics of edifices.
Seventy per centum of the respondents agreed that rooftop helipads could increase the safety of tall edifices ( item 3.9 ) because residents trapped in the upper floors of tall edifices can be rescued. However, there is a bound to the figure of residents that can be rescued utilizing choppers. This construct may besides be impractical because the human inclination is to fall instead than go up to upper floors during exigency events. Furthermore, deliverance by choppers requires particular deliverance squads and accomplishments, which might non be readily available.
The bulk of the respondents did non hold that fireproof lifts ( point 3.1 ) would heighten the safety of tall edifices. The chief concerns are the supply of electricity to power lifts, the demand to protect against power failure during fire, and agencies of flight if lifts fail. Some respondents pointed out that big crowds waiting at lift anterooms may do pandemonium during emptying. However, some respondents suggested that lifts are utile to evacuate the disableds, the aged and kids.
Mr Jeremy Hodge, of Building Research Establishment Ltd, believed that another reply to get awaying to safety is the installing of flight chutes, which would non take up much room but would enable people to skid to the bottom really rapidly ( Lane, 2001a ) . In this survey, half the respondents felt that flight chutes were executable ( item 3.2 ) . Respondents suggested that the stuff used for the flight chutes must be fire-retardant and lasting, particularly if the system is deployed out in the unfastened. Escape chutes functioning single floors might be more efficient, and the issue points of the chutes must be decently controlled. Of the respondents that did non hold to this method, some felt that this flight means is non suited for the aged and kids. Skiding down from great highs entails high kinetic energy, and people may be injured when residents collide into one another during the sliding procedure.
The bulk of the respondents besides did non hold with inward emptying ( item 3.7 ) . The chief ground for the expostulation is that residents might be trapped in the edifice. Furthermore, the human inclination would be to fly an onslaught site and people would be unwilling to wait inside a damaged edifice to be saved ( Post, 2001a ) . This expostulation by Singapore respondents is surprising because Singapore already has in topographic point an inward emptying system, in the signifier of bomb shelters being built in each high-rise flat.
Behaviour of stuffs under utmost temperature
Three possible methods to better the safety of tall edifices through improved stuffs engineering were proposed. None of them were considered executable by the bulk of the respondents ( see Table I ) .
Blast-resistant glazing may cut down casualties originating from winging glass in the event of a blast ( Madine et al. , 2001 ) but less than 50 per centum of the respondents agreed with utilizing it to better the safety of tall edifices ( item 4.1 ) . Some respondents questioned the extent of protection, particularly in the event of an aircraft or bomb onslaught.
One school of idea is to beef up window systems by cramping their corners, so that glass is more hard to interrupt ( Madine et al. , 2001 ) . However, the respondents in the present survey did non hold with this ( item 4.2 ) . One respondent warned of the possibility of over design with immense connexion inside informations, when the beef uping consequence may be limited.
Madine et Al. ( 2001 ) suggested adhering the glass into window frames for greater strength as the blast burden could be transferred to the construction of the edifice. Again, respondents were non agreeable to this ( item 4.3 ) . Some respondents considered blast-resistant glazing more effectual than adhering the glazing into window frames to control blast impact, as the strength of glass panel itself is more important. There might be troubles in building and assembly of such Windowss, in position of factors such as thermic consequence and enlargement articulations.
Codes and ordinances
Three possible methods to better the safety of tall edifices through amendments of codifications and ordinances were proposed. Two of these were accepted by more than 50 per centum of the respondents ( see Table I ) .
Respondents did non hold to the infliction of a height bound on edifices ( item 5.2 ) . This is consistent with old surveies ( Angelo, 2001 ; Forgey, 2001 ; Galloway, 2001 ) . In land-scarce metropoliss, holding rigorous height bounds does non let the optimum usage of land. A height bound imposed on a edifice may forestall developers from maximising returns on investing.
The bulk of the respondents agreed that codifications may necessitate to be revised to supply for longer flight clip ( item 5.1 ) . Some respondents said that when stipulating the flight clip several factors have to be considered, such as flight waies and obstructors, occupant features ( aged, kid, handicapped, etc. ) and the location of the last individual to get away from the edifice, whether this individual is on the highest floor or at the remotest location in the edifice. It was suggested that the flight clip, if implemented, should bind in with the fire structural demands of edifices.
Seventy-nine per centum of the respondents agreed that a really tall edifice should hold a separate design codification ( item 5.3 ) . The chief ground is its possible as a mark for terrorists and a long emptying clip ( Post et al. , 2001 ) . Having a separate design codification may be a good via media between safety and cost, since the codification allows a high appraisal attack to constructing design.
The SMExpert from the FSSB said that his organisation has programs to revise the Fire Code every five old ages. Code demands will be refined and amended to take likely terrorist menaces into consideration. Any lacks in edifice demands that may allow terrorist Acts of the Apostless will be identified, and betterments made. The FSSB will besides implement a codification of behavior for firemans in measuring the fortunes for them to come in a edifice under menace. In the USA, security-related codifications and criterions are besides being reviewed ( Ichniowski, 2001 ; Lane, 2001b ; Maas, 2001 ; Pearson, 2001b ) .
In the wake of 9/11, the issue of safety in tall edifices was brought into greater focal point. In measuring the safety of tall edifices originating from the 9/11 incident, this survey sought the positions of AEs and edifice governments in the building industry in Singapore.
While the respondents in this survey in general perceived tall edifices in Singapore to be safe, there may be sample prejudice because the respondents were involved in the design of edifices and many are public functionaries. Notwithstanding this, with rigorous authorities ordinances, all edifice designs reference functionality, lastingness and fit-for-purpose affairs. The governments interviewed attributed the good safety records of edifices to strict conformity with edifice codifications and an efficient firefighting squad. Notwithstanding this, AEs felt that it is of import to farther better edifice safety ( V7 ) . This survey besides found that edifices in Singapore can defy normal edifice accidents, but are likely to fall in upon aircraft onslaught.
This paper found that AEs ( see Table III ) :
have the necessary expertness to better edifice safety ( V9 ) ;
are doing an attempt to turn to heightened safety concerns ( V10 ) ;
will give full support to enterprises to turn to heightened safety concerns ( V11 ) ;
agree to carry on hazard appraisal during the design stage ( V13 ) ; and
will welcome a performance-based design codification ( V14 ) .
These findings indicate that the attack to constructing design may hold to alter after 9/11. While bing designs are equal, respondents besides felt that extra safety steps are necessary ( V12 ) . However, there is no demand to overreact to the point of guaranting that all edifices can defy hydrocarbon fires ( V15 ) and aircraft onslaughts ( V16 ) .
The paper contributes to knowledge by bring outing that the four most effectual methods to better the safety of tall edifices are supplying:
issue marks with illuming at floor degrees ;
a separate design codification for super tall edifices ;
fire safety and deliverance floors ; and
decentalisation of fire systems.
Eight other steps were besides found to be executable ( see Table I ) . A height bound on edifices and limitation of burdens on roof are the most unwanted steps.
Future surveies on bettering the design of tall edifices may do usage of these findings. It is recommended that farther surveies into the strength decrease of stuffs subjected to intense fires should be carried out. This is because constructions may be able to defy the impact of aircraft onslaught, but may finally neglect after a decrease in their stuff belongingss with lifting temperature.
While many of the methods proposed may be able to better the safety of edifices, increased cost is a critical concern ( Leftly and Lane, 2001 ) . Before the alterations materialize in the codifications, it is necessary to find whether the building industry is able to absorb the new steps and whether AEC professionals and clients are convinced of the demand to beef up edifices further. Safety steps proposed must be practical without doing edifice proprietors bear unneeded costs. Besides seeking to do edifices stronger by supplying redundancy or more back-up beds, it is recommended that the relevant parties explore and detect new agencies to contend fire.
Finally, it is of import to look at edifice safety as a whole system alternatively of supplying bit-by-bit back-up beds or increasing the border of safety. Ultimately, each edifice may hold a alone solution depending on factors such as cost, infinite, proficient, economical and political issues. A balance between realistic costs and highly improbable events should be maintained.
Table IPossible methods to better the safety of tall edifices
Table IIProfile of respondents
Table IIIResults of study and statistical trials
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