بررسي و ارزيابي سامانه‌هاي پايش ارتعاش خطوط راه‌آهن در ابنيه تاريخي و پيشنهاد سامانه مناسب براي ابنيه تاريخي ايران - مطالعه موردي بناهاي تاريخي محور چهارباغ اصفهان

eva‎luation and Assessment of Vibration Monitoring Systems for Railway Lines in Historical Structures and Proposing an Appropriate System for Historical Buildings in Iran - A Case Study of Historical Buildings Along Chaharbagh Avenue, Isfahan

مهندسي راه آهن و برنامه ريزي حمل و نقل

With the rapid expansion of metro lines, one of the key concerns for organizations dedicated to the preservation of historical buildings is protecting these structures from the impacts of metro line construction. To address this issue, Structural Health Monitoring (SHM) has gained recognition as a practical approach worldwide. A review of the literature reveals that, so far, no system has been developed that continuously monitors the vibrations affecting historical buildings and provides a history of vibration data. This thesis addresses this challenge. After eva‎luating possible configurations for various measurement systems, a vibration monitoring system was developed to monitor the condition of historical structures. The developed system was then implemented in a case study involving the historical section of Metro Line 1 in Isfahan. The results of vibration monitoring indicate that the current vibration levels affecting the historical buildings along Chaharbagh Avenue in Isfahan are within the permissible range (less than 72 dB). However, in the long term, these vibrations may exceed the permissible limits due to potential fatigue. Therefore, it is necessary to monitor the structural behavior over time using the systemʹs results. The system’s outputs can be accessed on the website with the domain imvms.ir. The vibration data collected over one year was analyzed, and factors such as changes in groundwater levels, train speed variations, and comparisons of different monitoring methods were eva‎luated. A comparison of direct and indirect monitoring methods shows that the difference between the two is approximately 0/005 mm/s, which equates to around 25%. The study of groundwater level effects indicates that an 8-meter change in the water table results in a change in Peak Particle Velocity (PPV) of about 0.005 mm/s (approximately 20%). Furthermore, in medium-density soil, the maximum change in PPV due to a 9-meter change in the water table was about 0/004 mm/s (approximately 16%). The study of train speed effects shows that increasing the speed from 15 km/h to 65 km/h causes the vibrations affecting historical buildings (Siosepol Bridge and Chaharbagh School) to increase by 9 dB. A review of vibration history reveals that the vibrations affecting the historical structures (Siosepol Bridge and Chaharbagh School) increased by an average of 8 dB in May compared to April. This increase may be due to several factors, including the deterioration of the metro fleet, increased train headways, and a rise in metro passenger numbers compared to April. Additionally, studies show that on the first and last days of the week, when passenger volume is higher, vibrations increase by 2 dB compared to other days. Finally, a comparison of vibration levels alongside and on the slab track between the second half of 2023 and the first half of 2024 shows that vibrations alongside the slab track in the first half of 2024 increased by an average of 5 dB compared to the second half of 2023. Likewise, vibrations on the slab track in the first half of 2024 increased by an average of 4/5 dB compared to the second half of 2023. One possible cause of this increase in vibrations could be the deterioration of the wheels in the rail fleet.

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