Buildings are evolving in height, construction materials, use, and compartmental composition at staggering pace. The tall buildings of today are a completely different entity to that of a decade ago with the propensity for change even greater in the immediate future. The advancements in structural engineering have arisen to make possible the increase in height, size and complexity. Forensic analyses of tall building fires have indicated that the needs of modern tall buildings are beyond the scope of applicability of current fire safety codes and engineering practices. The ever increasing heights combined with the limited number of vertical escape routes results in these two components becoming coupled. The considerable time that occupants spend within the stairwells means that for any fire strategy to be successful stairwells must remain smoke and heat free and the entire building structurally sound. Without adequate protection the number and width of stairwells is irrelevant, as smoke-logged stairwells are unusable and the Fire Safety Strategy is therefore void. Reported failure rates for stairwell smoke control systems are extremely high, this implies that safe stairwell tenability levels are currently not guaranteed, thus the cornerstone of contemporary tall building fire safety design may not be valid. This research project investigates current smoke control methods used for the protection of stairs in tall buildings through the review of literature and theory for the methodologies. In understanding the design assumption and actual stresses smoke control systems are subjected to, a novel concept for smoke control will be presented, investigated and developed. It is intended that this work will become a proof of concept, or otherwise for the novel smoke control system. Several conceptual smoke control systems were developed around the following principles; localised solution to minimise under or over pressurisation of the stairwell, performance be independent of fire size, perform under extreme environmental conditions and be effective when protecting a fully open door. Three concepts were investigated using CFD modelling, these being: - Concept 1- vertical perimeter vents to the opening resulting in converging flow field - Concept 2 - concept 1 with the additional horizontal vent - Concept 3 – concept 2 with baffle chamber The preliminary modelling predicted that Concept 3 would provide the most robust solution. The provision of baffles provided stability to the vent flow which contained an area of high pressure within the baffle chamber, relatively to areas adjacent to the baffle chamber, this encouraged smoke flow away from the chamber. It appeared that the effectiveness of the system was a function of baffle flow and pressure load caused by wind and fire characteristics, the larger the pressure load across the door the greater the vent velocity required to limit or prevent smoke flow through the opening. Full-scale experiments were undertaken to prove in principle that the proposed baffle smoke control system can limit the passage of smoke through an opening under generated pressure loads. The experiments did demonstrate in principle the baffle smoke control system could be effective in limiting smoke flow through an open door under the pressure loads tested.

Recently, plenty of large/public buildings have been completed in Taiwan. For bright indoor environment and comfortable feelings, these buildings often utilized lots of large spaces such as atria. However, it is difficult to maintain tenable conditions within atria and large spaces in case of fire. Therefore, the alert of smoke detectors and the efficiency of smoke control systems are both very important when a fire occurred and people needed to evacuate. In large space buildings, the smoke exhaust fan and smoke storage are major design concepts of the passive smoke management systems in order to maintain tenable conditions in means of egress. In this research, the operation strategies of passive smoke management and fire detection systems in large space buildings will be systematically analyzed. The full-scale hot smoke test can be performed to evaluate the temperature distribution of smoke layer and the smoke descending rate at ABRI large space fire lab in Tainan. In the other hand, the beam detectors can not only detect smoke layer by fire more earlier but show excellent smoke rejection if they can be effectually connected with passive smoke control systems. It is anticipated that through the execution of this research project, the concept developed in this study can be applied to improve the passive smoke management performance of large space buildings in Taiwan.

In recent year, there were many fire accidents in MRT and subway station,due to faolure in smoke control system and emergency operation strategies. The goal of this project is to use two sofeware¡XFDS and Star-CD to simulate the fire in MRT station and predict the height of smoke layer and its descending rate .The comparison of the two indicated sucessful result can be obtained with deviations within engineering tolerance..

This thesis promotes the responsible use of CFD technology through the development of the simulation based design strategy applicable to the design of the tire engineered smoke control ventilation systems. The correct representations of the problem of interest and measures that may be adopted to ensure the accuracy of the simulated solution are two key aspects of this promotion. The development process presents the application of the proposed procedure through three industrial challenges that have subsequently been approved by the relevant fire authorities. The challenges consist of the design of fire engineered systems for residential high rise buildings and covered car parks which in turn demonstrate the robustness of the proposed procedure. The proposed procedure consists of four key stages namely: Qualitative Design Review (QDR); Quantitative Analysis (QA); Assessment; and Fire Services' comments. QDR identifies the ventilation strategy, the potential tire scenario and the appropriate assessment approach applicable to the problem of interest. QA uses the chosen tire analytical approach to evaluate parameters identified in the QDR. The assessment stage is where outputs from the analysis are assessed based on the assessment criteria defined in the QDR. Fire Services' comments are there to account for any additional requirements the fire officer responsible might had have as he/she has the final say on whether the fire engineered system is approved for installation. A review of the current legislative literature i.e. building code, prescriptive and performance based codes is presented. Furthermore, the criteria applicable for the assessment of simulation based design solution are also discussed. The concept of smoke control is discussed in detail which includes an overview of the mechanism of smoke movement and the provisions available to limit smoke spread. A survey of the current Computational Fluid Dynamics (CFD) software packages suitable for the assessment of smoke movement is also included.

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

Avstängda kärnkraftverk berövar många människor av elektricitet och det skulle ha en negativ inverkan både på företagets framtoning och mänskliga aktiviteter. På grund av detta behöver tillgängligheten av utrustningen i alla byggnaderna som kärnkraftverken består ses till. HVAC-system (Heating, Ventilation and Air Conditioning) spelar en viktig roll när det gäller tillgänglighet av utrustning eftersom dessa system ser till pålitligheten är på topp genom att anpassade omgivningsförhållanden till utrustningen. Att designa ventilationssystemet rätt är därför mycket viktigt och måste göras noggrant. Denna rapport introducerar metodologin för att designa och optimera ett ventilationssystem för en av byggnaderna i ett kärnkraftverk. Utöver detta utvecklas och beskrivs en metodologi för att designa ett rökkontrollssystem för en byggnad som ingår i kärnkraftverket. Dessa metodologier har implementerats för en byggnad i en demineraliseringsstation, Hinkley Point C project. / During nuclear power plants shutdown many people could be deprived of electricity and it would have a negative impact both on the company’s image and on people activities. As a consequence, availability of equipments in the different buildings which compose the power plant needs to be assured. HVAC system (Heating, Ventilation and Air Conditioning) plays an important role on the reliability of these equipments as it makes sure that ambient conditions in the buildings fit the operating temperature range of the equipments. Consequently sizing a ventilation system is really important and it needs to be carried out seriously. This paper introduces the methodology to size and optimize a ventilation system for nuclear power plants’ building. This paper also develops the methodology used to size a smoke control system in a nuclear related building. Direct application of this methodology has been realised for a specific building which is the demineralization station of Hinkley Point C project.