排水系統是建築物中不可或缺的重要服務設施，相較於建築空調設備、機電動力設備等專業領域，建築給排水設備領域之研究發展顯得相對缺乏，且不良的設計非常容易產生排水通氣性能的缺失，同時將造成建築物在設備器具使用上之健康衛生環境問題。因此，為了掌握實際建築物於非穩定排水負荷下之管內空氣壓力變動情形，本研究建置了攜帶式排水壓力管路量測儀器設備及現場量測機制，其檢測方式屬於非破壞性檢測方式，未來可擴大應用於實際建築物案例之現場量測。實驗前，透過人為控制排水及長時觀測方式，進行量測儀器基本性能測試，並且運用快速傅立葉轉換(Fast Fourier Transform)理論之頻譜分析方法，探討排水管內空氣壓力變動與存水彎水位變動關聯。
後續則透過實驗數據及空氣壓力變動理論，進一步分析實際辦公大樓於非穩定排水負荷下之管內空氣壓力變動情形，包含變動頻率、最大壓力值與平均峰壓值，以及個別標準差，並且透過空氣壓力變動係數值修正，以及運用數學模式預測其峰壓值，超越峰壓值及空氣壓力變動係數之機率，則透過瞬間壓力密度之機率密率函數加以說明。因此，本研究建置之攜帶式排水管路壓力量測設備及現場量測機制，未來可擴大應用於實際建築案物進行長時觀測，將有助於確實掌握排水系統管內空氣壓力變動情形。

A drainage system is one of the most essential facilities in building services engineering. Unfortunately relevant technology used today to analyze it was developed decades ago. This research investigated the case of existing building drainage systems in Taiwan, including our previous studies. Firstly, the purpose of this paper is the development of a non-destructive testing method of air pressure fluctuation in a stacked building drainage system using field observation and experimental study of stack fluid mechanisms. A portable testing device is developed to execute field testing in existing drainage systems to determine air pressure fluctuation in the stacks of buildings. Meanwhile, the Fast Fourier Transform Process is adopted in this paper to analyze the power spectrum of air pressure fluctuation in a drainage stack and to verify the previous theoretical study. Validation obtained from case-studies can be used to confirm the practicality of this portable and non-destructive testing method. As a result, the proposed testing method can be applied to the diagnosis of existing building drainage systems and improve the design of a drainage system in an existing housing complex.
The study examines air pressure variations along a discharging stack with unsteady discharging flow rates, including the fluctuation frequency, the maximum and average pressures with their respective standard deviations at a drainage stack of an in-use office building. With a modified constant, the maximum air pressure at the drainage stack could be described by the probability density function of the measured data using earlier proposed mathematical expressions for steady discharging flow rates. The average prediction and the maximum under-prediction of the absolute peak pressure were determined with the margin of errors taken within certain confidence levels. Finally, the results would be useful for understanding the air pressure in drainage stacks and help increase the potential of installing a real-time monitoring system in a high-rise drainage stack.

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