On stairwell and elevator shaft pressurization for smoke control in tall buildings

Elevator shaft and stairwell shaft-pressurization systems are studied as means of smoke migration prevention through the stack effect in tall buildings using the CONTAM simulation software. A thirty story building model is considered with exterior leakages calibrated to experimental data for both a residential and a commercial building. Stairwell pressurization is found to be completely feasible in the absence of elevator shaft pressurization. In contrast, coupled elevator shaft-pressurization systems are found to produce prohibitively large pressure differences across both the elevator and stairwell doors if (1) minimum pressure differences must be maintained at both open and closed elevator doors and (2) if the system must function properly when the ground floor exterior building doors are closed. Even in these cases situations arise in which smoke may enter the shaft and be actively distributed throughout the building by the fan system. These differences between stairwell and elevator shaft pressurization are directly attributable to the much larger leakage areas associated with elevator doors. Relatively large flow rates through the open elevator doors act to pressurize the ground floor of the building, indirectly causing large pressure differences across upper floor elevator doors. Furthermore, the results show that there is a strong coupling between the fan speed requirements of the stairwell and elevator shaft-pressurization systems. Fan requirements are also found to be sensitive to the ambient temperature. Effects of the fan location, louvers, vents, the building height, and the number of elevator cars and/or shafts are also addressed.     

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。     

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.     

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。     

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。     

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.     

A network-based smoke control program with consideration of energy transfer in ultra-high-rise buildings, CAU_ESCAP

Ultra-high-rise buildings allow for the efficient use of land, but they are vulnerable to disasters such as fires. Therefore, the development of network models for analyzing the characteristics of smoke movement in ultra-high-rise buildings is necessary for cost-effective design of smoke control systems and operation decisions. A new network-based smoke control program, CAU_ESCAP, is developed in this study, which is a program that can consider the energy transfer. CAU_ESCAP is validated with existing programs, ASCOS and COSMO, by analyzing the smoke movement. After that, fire in an ultra-high-rise building of 55 stories is applied with CAU_ESCAP for analyzing the smoke movement and the mass flow rate of the smoke control system due to the variation of heat release rate and door conditions of the fire floor. The pressure difference between the fire room and the protecting area does not vary in the closed-door case in the fire room, but vary significantly in the opened-door case. Therefore, the smoke from fire would be spread to other spaces if there is no instantaneous increase in the mass flow rate of pressurization when the door is opened by occupants for evacuation.     

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。     

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.     

高层建筑防烟楼梯间机械加压送风问题的探讨

本文分析了对高层建筑防烟楼梯间及其前室、消防电梯前室或二者合用前室进行机械加压送风的必要性，并在大量实际工程调研和资料分析的基础上，对不同的系统负担层数和送风部位给出了加压送风量；通过对不同计算公式的比较和对主要影响因素的分析，提出了加压送风量计算公式的选择，公式参数的确定及其他设计考虑要点。     

高层建筑电梯楼梯协同疏散的仿真实验研究

近年来高层建筑逐渐增多,但高层建筑普遍存在逃生线路长,火灾严重性大的问题。为了缩短高层建筑在消防疏散中的疏散时间,降低高层建筑火灾发生后的事故严重程度,利用疏散软件Pathfinder分析了高层建筑中使用电梯楼梯协同疏散的可行性。结果表明:高层建筑电梯可以作为协同疏散的辅助工具,增加一部电梯比单纯增加电梯最大运行速度要更加有效;设置每层电梯都使用总人数的固定比例进行疏散的时候,楼梯资源不易被充分利用;当设置n层及n层以上每层总人数的不同比例使用电梯进行向下疏散,存在最佳疏散楼层N11及最佳疏散比例20%,最后一个通过电梯疏散完毕与最后一个通过楼梯疏散完毕的人员仅相差2.7s,此方法可以为相关高层建筑火灾疏散策略的决策提供一定的参考依据。实验结果说明了电梯疏散的教育和培训很重要,在高层建筑中合理使用电梯进行疏散可以很大程度减少总疏散时长。     

浅析高层建筑消防电梯设计的问题探讨

消防电梯是消防人员在火灾或者紧急事故发生时进行救援所使用的重要通道,这个通道对于保障建筑中居民的人身与财产安全具有重大的意义。因此,高层建筑中消防电梯的设计必须与安全消防的具体要求相符合。本文就消防电梯设计中容易出现的问题提出了阐述,并对高层建筑消防电梯设计的安全性能设计的改进提出了建议。     

前室加压送风系统形式的数值模拟分析

针对《高规》中,对于前室或合用前室加压送风口开启控制方式没有明确规定这一问题,采用CFD模拟方法,结合加压送风机特性曲线,对设置常开型风口和常闭型风口的系统进行模拟分析;为将CFD技术应用到检测正压送风系统的合理性方面,提供了模型基础。     

Overview of the Structural Design of World Trade Center 1, 2, and 7 Buildings

This paper summarizes the primary structural systems that comprised World Trade Center (WTC) 1, 2, and 7, which were destroyed in the terrorist attacks of September 11, 2001. There were four major structural subsystems in the towers: the exterior walls, the core, the floor system, and the hat truss. The major structural systems within WTC 7 were the foundation, exterior moment frames, floor system, interior columns, and column transfer trusses and girders. At the time of design and construction, the WTC towers were innovative in many ways, and resulted in a tremendous increase of open-plan commercial office space in downtown Manhattan. As the first of four papers, this paper summarizes the structural and passive fire protection features of each building, and focuses on the structural systems which played a critical role in the outcome of the attacks of September 11, 2001. Three companion papers address the effects of aircraft impact damage on the WTC towers and debris damage on WTC 7, the effects of fire on the three buildings, and how these events contributed to building collapse by describing the contribution of key structural systems to the overall building behavior and collapse, such as the floor systems and hat trusses in WTC 1 and WTC 2 and the floor connections around Column 79 in WTC 7.     

高层建筑电梯口防护探讨

结合高层建筑施工现场实际情况,以具体工程为例,分析了高层建筑电梯口的施工特点,根据JGJ 80-91建筑施工高处作业安全技术规范,分别介绍了电梯口防护门和电梯井内安全网的作法及安全管理措施,以指导实践。     

冬季寒冷地区超高层建筑防烟楼梯间热压效应研究

采用现场实测与数值模拟方法,研究热压作用对超高层建筑楼梯间压差分布的影响.通过对楼梯间与前室压差分布进行实测,指出由于避难层对楼梯间的分隔作用,使得压差在不同分区内,呈现错位增长的分布规律.用Fluent模拟对实验研究进行补充,通过拟合模拟数据,对原有热压计算公式进行修正,提出适用于有一处避难层的超高层建筑的热压差计算...     

住宅建筑防火层数确定的若干问题

本文通过"住建规"、"建规"、"高规"对住宅建筑层数折算不同规定的分析,仔细探讨了底层与顶部跃层扣减以及"临界层"的问题。希望通过对问题的探讨,扩展大家的视野以及解决疑难问题的思路。     

Erster und zweiter Rettungsweg in Wohngebäuden

First and second escape ways in residential buildings The existence of two redundant escape ways is a fundamental concept to ensure a safe egress of occupants in the event of fire. Fire safety requirements for means of egress are defined by the state specific building codes in Germany. This publication focuses on a further clarification of existing requirements and amongst others explains why some means of egress, such as permanent installed ladders are not suitable for this purpose. However, in contrast to this fire service equipment can also provide the second escape way in particularly for residential buildings. Different means are used depending on the applied strategy and infrastructure of the fire service. A summary of reported fire incidents of the Berlin fire service in the years 2012 and 2013 shows that smoke filled stairwells were also used to evacuate trapped occupants. In order to protect these occupants from smoke intoxication, escape hoods or positive pressure ventilation fans, to allow for a smoke free stairwell, have been used.