Elevator shaft pressurization for smoke control in tall buildings: The Seattle approach

CONTAM simulations of both commercial and residential tall building models are conducted in order to study recently adopted Seattle code requirements for elevator shaft pressurization systems. In contrast to the International Building Code (IBC) requirements, the Seattle approach specifies across elevator door pressure minimums and maximums on only four “fire floors” (including one above, and two below, the fire floor). This is accomplished using a minimal pressurization of the entire elevator shaft in conjunction with venting of the four fire floors. The present study adresses the feasibility of calibrating such a system to meet the design objectives in tall buildings (system performance during an actual fire event is not considered). The two building models correspond to 37 story buildings with dual elevator and dual stairwell shafts extending the entire height of the building. Each model is calibrated to experimental data. Simulations are conducted for a variety of ambient temperatures and exterior building door positions. Coupled pressurization of the stairwells is also considered. The system requirements are found to be achievable for both elevator only and coupled elevator and stairwell pressurization systems. However, the observed pressure differences do change with changes in the ambient temperature as well as changes in the ground floor exterior door position. It is therefore recommended that such systems should be calibrated for pressure differences intermediate to the prescribed minimum and maximum values to compensate for changes to the system performance. Providing a relief vent to ambient on any recall floor may also be advisable.     

Experimental Investigation of the Effect of Fire Protection Lobby on Stair Pressurization System in a High-Rise Building

In this study, the stair pressurization system in a 40-storey high office building in Istanbul is investigated through field tests, in order to understand the effect of the presence of a non-pressurized vestibule (fire protection lobby, FPL) before entering the stair at each floor. The building without FPL is simulated by keeping only one of the two doors (of the stair and FPL) open at each floor. This method gave an opportunity to fix other parameters affecting the stair pressurization system and check solely the effect of FPL. Two different cases are taken into account, where the first one (all doors closed) analyses the condition that all stair doors are kept closed and the second one (critical doors are open) is conducted when the stairwell is opened to the floor on a given level (fire floor) and the stair termination door at the discharge floor is kept open. For both cases, the availability of the FPL is investigated by using the aforementioned arrangement. Under the conditions with approximately the same pressurized air flow rate at all doors closed condition, it is found that the availability of FPL increases the pressure difference between the stairwell and the corridor by a factor of approximately 2.2. This is also justified by using empirical formulations available in literature, where this ratio is calculated as 2.0. The results of this study showed that the FPL arrangement improves the effectiveness of pressurization system in a very high-rise building, despite some tolerable drawbacks.     

高层建筑加压送风系统试验研究

介绍了哈尔滨市一座高层建筑楼梯间及其前室、合用前室的加压送风系统的试验情况。分析了几种不同试验工况下，楼梯间与前室、合用前宣的正压值、门洞风速、加压送风量等问题，并对机械加压送风的若干问题作了探讨。试验结果表明，目前国内在加压送风系统设计、验收、防排烟产品质量方面存在不少问题，必须认真对待。《高规》中有关加压送风的某些条文有待进一步充实和完善。     

高层建筑加压送风系统影响因素的实验研究

通过现场实验研究，讨论风机设置于建筑上部的多点加压送风系统的设计，通过数值拟合的方法得出送风管道中的风速分布，风速与加压风机的流量、送风管道的截面积以厦管道的高度有关。在实际情况下，研究影响高层建筑加压送风系统的各种因素有着较为重要的意义。     

The effects of simulated fire pressure and outside wind on the internal pressure distribution in a five-storey model building

This paper presents some of the wind tunnel pressure measurements made on a five-storey model building (32 cells), with a vertical shaft and fixed leakage characteristics. Internal and external pressures measurements are presented for various wind angles and a simulated fire pressure in a room on floor 2 and floor 4. Comparison is made to assess the effect of fire on internal pressure distribution. Although the results are presented for all the wind angles investigated, a detailed discussion is confined only to a single wind angle. Implications of the combined effect of wind and fire on the shaft pressurization system design calculations must take these two factors into account.

In a fire situation it is possible that escapers may leave some of the shaft doors open or the fire room door may burn down. In such a case the pressurization system can become ineffective, causing escape routes to get smoke-logged. The effect of a combination of fire door openings was also investigated. The results for the following door opening combinations are presented and discussed:

1. (i) shaft door open alone;

2. (ii) fire room door open alone;

3. (iii) shaft and fire room doors open together.

It is shown quite clearly that these openings are significant for a range of wind angles.     

高层建筑防烟楼梯间和前室防烟设计的探讨

针对高层建筑防烟楼梯间和前室的不同组成，分析了影响其防烟设计的门的开启层数、数量，加压送风口的形式及加压部位正压值等诸多因素，提出了不同形式时加压送风风量的计算方法，在实际工程中可根据不同的情况使用。该方法与规范不同之处在于综合考虑了影响加压送风的各种因素，根据建立的数学模型对系统进行设计计算。     

采用变风量系统的消防楼梯间、前室及内走道的防排烟系统设计

防排烟规范对消防楼梯间、前室及内走道的防排烟有严格的规定。常规的正压送风系统采用电动风量调节阀或直接采用百叶送风。事实上,由于不可控的缝隙渗透和系统的变流量特性等,消防楼梯间及前室进行风量控制或正压控制是不易实现的。本文提出了采用变风量系统来实现正压送风的准确控制,该系统于1996年成功应用于新加坡的一个高层宾馆建筑并正常运作至今。面对现今规范对消防排烟系统要求的日益严格和变风量系统的普及,希望本案例能为同行提供参考。     

Characterization of Stack Effect in High-Rise Buildings Under Winter Conditions,Including the Impact of Stairwell Pressurization

To characterize the magnitude of stack effect within stairwells and elevator shafts, differential pressure measurements were taken in fifteen (15) high-rise buildings in four (4) different cities (Cleveland, Baltimore, Minneapolis, and Philadelphia) during the winter months of January–March, 2013. Test buildings ranged in height from 44 m to 150 m (143 ft–492 ft). Outside temperatures during testing ranged from ?12°C to 15°C (10°F–59°F). Based on the differential pressures measured, there was evidence of winter stack effect in all buildings tested. On the lower levels of all buildings, air was observed flowing from the building into the stairwells and elevator hoistways with pressure differential magnitudes ranging from ?2.7 Pa to ?24.9 Pa, ?12.0 Pa average (?0.011 in. w.g. to ?0.100 in. w.g., ?0.048 in. w.g. average). Similarly, in most buildings (excluding Buildings 6 and 7) air was observed flowing from the stair and elevator hoistways into the building on the upper levels with pressure differential magnitudes ranging from 0.5 Pa to 34.9 Pa, 11.2 Pa average (0.002 in. w.g. to 0.140 in. w.g., 0.045 in. w.g. average). Under winter conditions, the data suggests that large quantities of air can migrate, floor-to-floor, via unprotected elevator shafts. Data further suggests activation of the stairwell pressurization system can increase vertical air movement via unprotected elevator shafts. This behavior is expected to impact the movement of smoke floor-to-floor during a fire, as airflow is indicative of smoke migration. The exterior stack force on the building’s envelope (governed by the building’s height and temperature differential between the building interior and exterior) does not always translate proportionally to shaft-to-building differential pressures (i.e., “stack effect”), as each building is unique. Although a building’s height and outside temperature play important roles in determining vertical airflow movement within a building, height alone was not found to be a good predictor of vertical airflow (or smoke movement) within the building due to stack effect. Other variables, such as architectural layout, architectural leakage, wind effects, and ventilation systems should all be considered. Simplified algebraic calculations (i.e. hand calculations) do not treat the building as a complete system, and do not account for all variables involved. Therefore, simplified algebraic calculations may result in inaccurate shaft-to-building differential pressure predictions. Based on this analysis, unless conservative leakage values are used, the simplified algebraic calculations may underpredict the shaft-to-building differential pressures. Using simplified algebraic calculations may be suitable for preliminary approximations, however, for design purposes a more complex analysis is recommended. The more complex analysis should consider other variables that affect pressure differentials such as changes in architectural layout and envelope leakage from floor-to-floor, HVAC systems, and wind.     

Numerical simulation of fire-induced flow through a stairwell

Smoke movement and ambient airflow in a stairwell under fire scenarios are studied numerically using large eddy simulation. Numerical investigation is performed on a typical two-storey confined stairwell, with an open door on the top floor and a fire source on the ground floor. Results show the existence of fairly distinct layers of hot smoke and ambient air under different fire scenarios. It is found that heat release rate has a remarkable effect on distributions of smoke temperature, velocity and oxygen concentration. This paper indicates that detailed patterns of velocity, temperature and species concentration and their evolutions can be predicted by numerical simulation of a stairwell during a fire.     

建筑外围护结构整体气密性能检测关键技术

建筑外围护结构整体气密性能是低能耗建筑的一项重要技术指标,但是我国尚未建立相关的测试标准和测试方法。在国外建筑外围护结构整体气密性能检测标准的基础上,通过大量工程测试应用实践,结合我国建筑发展特点和科学技术水平,研究提出我国建筑外围护结构整体气密性能检测中关键问题的解决方法,提高相关测试方法和测试数据的科学性与真实性,为今后我国建筑外围护结构整体气密性检测标准的编制和测试方法的应用提供参考和借鉴。     

室外风对高层建筑竖井内烟气运动影响的数值模拟

采用火灾模拟专业软件FDS对不同火源位置、不同风向条件下火灾烟气的运动进行模拟,测定典型位置处温度、速度、CO及CO2体积分数变化情况。实验结果表明:在近地风场中,风向对竖井内烟气蔓延的影响大小顺序为迎风>背风>侧风,竖井开口位于迎风面时,外界风对竖井内烟气运动影响最大:火源位于中性面以上时,烟气通过竖井与前室的开口向竖井内蔓延,并向下运动;而火源位于中性面以下时,前室内烟气向外部运动,竖井内无烟气流入。     

建筑构件对渗风量及能耗的影响分析

从以下几个角度对建筑渗风及能耗的影响进行了计算分析 :建筑中各种类型窗、住宅建筑中阳台是否封闭、办公建筑中有无楼梯间门等在渗风方面的差别。计算分析表明 :建筑中窗的密闭性能对于渗风量影响很大 ,采用不同密闭性能的外窗 ,其渗风量可以相差几倍至几十倍 ;住宅建筑中封闭阳台有利于建筑节能 ;在办公建筑中加设楼梯间门都会起到投资少、节能效果显著的目的。     

前室机械防烟系统设计探讨

在建筑的防排烟系统中，前室的防烟对于保证人员的安全疏散和顺利的消防扑救相当重要。文章时前室防烟的理念做了阐述，明确前室机械加压送风系统在火灾时只应开启着火层的送风口、针对我国及上海市现行的建筑防排烟规范，文中通过实例时前室机械防烟系统不同的送风量计算方法进行了对比分析。     

The ASHRAE design manual for smoke control

For many years smoke has been recognized as a major killer in fire situations. In response to this problem, the concept of controlling smoke movement in building fires has developed. The American Society of Heating, Refrigeration, and Air-Conditioning Engineers and the U.S. Veterans Administration have sponsored a design manual for smoke control systems. This paper provides an overview of this manual with emphasis on the principles of smoke control, stairwell pressurization, zone smoke control, computer analysis, and acceptance testing.     

Smoke movement in elevator shafts during a high-rise structural fire

In high-rise fires, smoke is often the leading cause of fatalities. Therefore, in the event of a fire, the ability to predict the movement of smoke throughout a tall structure is of vital importance. Smoke moves depending on a number of interacting and complex factors including weather conditions, building construction, operation of HVAC equipment, as well as the location and intensity of the fire. Smoke often travels long distances from the fire floor, and in the particular case of a high-rise fire, smoke frequently moves to upper floors via open passages such as elevator shafts and stairwells.     

Experimental Study of Elevator Loading and Unloading Time During Evacuation in High-Rise Buildings

To date, there are various types of elevators, such as evacuation elevators, that are being utilized during high-rise building evacuations in several countries, in accordance with their respective building codes. In order to enhance the effectiveness of elevator evacuation, evacuees’ behaviors should be better understood, in this way taking human behavior into consideration will allow for elevators to be better utilized. However, there are few studies on this topic since nearly no elevator evacuation events or experiments have been previously recorded. In this paper, 64 experiments were carried out to study how evacuees behave and what factors influence their behaviors during evacuation. Several key data, such as elevator loading and unloading time, time to open and close elevator doors were collected. We found that loading time (6.0 s) is much shorter than the time to open and close the doors (15.4 s). According to our findings, the number of evacuees influences evacuees’ behaviors when using elevators, but smoke does not. Furthermore, the shapes of queuing, such as arch and line, will influence the duration of time for evacuees going through elevator doors. The evacuees in the arch shape (5.3 s) pass faster than those in the line shape (6.4 s). Several interesting phenomena were observed in our experiments, such as push, hesitation, re-entering the elevator, stair-preference, and social bonding. Finally, several suggestions, such as the width of doors and the design of elevator lobbies, are proposed to building designers on the issues mentioned above. The basic data of our experiments can be used to calibrate and validate elevator evacuation simulations.     

高层建筑加压送风设计若干问题的探讨

分析了讨论了门的开启层数与数量，加压送风防烟系统的正压度，加压送风口的型式等问题，提出了它们的确定方案及加压送风量的计算步骤与方法。     

A Comparative Study on the Influence of Ventilation on Weather- and Fire-Induced Stack Effect in the Elevator Shafts of a High-Rise Building

This work assessed the impact of ventilation on both weather- and fire-induced stack effect in an 18-story high-rise office building. Elevator shafts are considered the main route of vertical air movement. Pressure distribution induced by cold weather within the elevator shafts was calculated theoretically. Computational fluid dynamics simulations of fire in the same high-rise building under different ventilation conditions were carried out with a fire dynamics simulator. It was found that ventilation exerted a more complex impact on fire than the weather-induced stack effect. For the weather-induced stack effect, the ventilation condition of the building only affected the height of the neutral pressure plane; in fire situations, it did not only affect the height of the neutral pressure plane in a similar manner to the weather-induced stack effect, but also influenced temperature and pressure distributions in the elevator shafts. The smoke movement and the distributions of temperature and pressure in elevator shafts are also learned. The smoke movement in high rises experienced four typical stages after ignition. The ventilation condition of the fire floor influences gas flow into elevator shafts, while that of the upper floors impacts the smoke rise speed in vertical shafts. When the stack effect finally reaches steady state, the gas temperature in the shaft decreases exponentially with height. Based on this assumption, a theoretical model was presented to characterize the fire-induced stack effect in typical high rises. Results showed that the model successfully predicts the pressure distribution in high-rise buildings.     

对防烟楼梯间及其合用前室分别加压送风防烟方案的流体网络分析

应用流体网络分析法,对现行高层建筑防火规范第8章第8.3.2条表8.3.2-2中的风量控制数据进行了校验性计算,揭示了分别加压送风的流动特性。计算结果表明,向防烟楼梯间加压是徒劳的,因为加压送风会直接从防烟楼梯间的疏散外门流失。     

高层建筑电梯活塞效应对电锑井及其前室烟气运动影响的数值模拟

通过对电梯运动产生的活塞效应的理论进行相关分析,采用CFD工具FDS5.4.1建立高层建筑典型的竖向疏散通道物理模型,选择大涡模拟方法进行数值模拟,研究电梯在不同运行过程中竖向疏散通道中的烟气运动规律,分析前室与建筑空间的压力差及烟气运动路径、速度的变化。模拟结果显示:电梯活塞效应会使电梯井及其前室的压力发生变化,电梯运动使得前室与建筑空间之间的压力差呈现先升后降的趋势;电梯向下运动一定程度上可以减缓烟气的扩散,而电梯向上运动会加速烟气通过前室向其它楼层地扩散。