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On May 18, 2021, the SEG Plaza building experienced a sense of vibration
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Shenzhen started the emergency response at the first time
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The municipal emergency Bureau and Futian District government organized the property management party to evacuate the personnel in the building in an orderly manner, implement closed management of the building, and carry out necessary traffic control in the surrounding areas
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The vibration and vibration of SEG Plaza building are published in official channels such as “Shenzhen release” every day At the same time, the Municipal Bureau of housing and urban rural development organized academicians, experts and authoritative technical teams to demonstrate and analyze the causes of structural safety and vibration of the building
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How is the progress of event handling, whether the building structure is safe, whether the causes of vibration are found out, and how merchants are resettled..
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Recently, the heads and experts of relevant units were interviewed by the media and answered reporters’ questions on issues of public concern
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Is the building safe? Authoritative experts believe that the building structure is safe and can continue to be used
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The person in charge of the Municipal Bureau of housing and urban rural development responded that the Bureau organized various forces to do a good job in technical disposal in accordance with the principle of “science, accuracy, seriousness and stability”
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First, an expert group composed of five academicians and survey and design masters of the Chinese Academy of engineering, including Yue Qingrui, Zhou Fulin, Nie Jianguo, Chen Zhengqing and Chen Xiangsheng, was established to be responsible for the overall technical control
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The professional fields include engineering diagnosis and treatment, vibration control, composite structure, wind engineering and geotechnical engineering
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Second, Shenzhen Urban Public Safety Technology Research Institute, as the leading unit of the general technology, organized MCC Construction Research Institute and Shenzhen housing safety and construction project quality inspection and appraisal center to carry out “back-to-back” inspection, monitoring and appraisal
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China Academy of Building Sciences and Guangdong Academy of Building Sciences respectively provided advice on relevant schemes and technical achievements, Tsinghua University 16 scientific research teams including Guangzhou University, Harbin Institute of Technology (Shenzhen), Hunan University, Tongji University and Shenzhen University provided technical support and carried out professional demonstration and analysis
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Third, the original design unit, the third-party authority and the expert team shall conduct triple audit and check on the results of safety demonstration and cause analysis
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Response of the expert group: first, Huayi design company, the original design unit, carried out structural safety review and calculation of the building according to the original design specifications and current design specifications, which was reviewed and approved by Guangdong overrun Committee; Second, MCC Construction Research Institute and Shenzhen housing safety and construction engineering quality inspection and appraisal center have systematically tested the structural dynamic performance of the building, and adopted technologies including laser Doppler vibration measurement, ultrasonic phased array test and audio acceleration test to analyze the structural structure, structural damage, material performance, joint working performance of composite structure, joint connection The setting of shear wall and core tube are comprehensively tested and analyzed, and the checking analysis and evaluation are carried out independently according to the test data, according to the original design code and the current design code, and the structural safety appraisal opinions are issued; Third, the Chinese Academy of Building Sciences issued a passing demonstration opinion on the design review and testing and appraisal
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Since May 18, the third-party authoritative testing organization has carried out real-time and continuous monitoring on the vibration, inclination, settlement and other indicators of SEG Plaza Building: the maximum acceleration is 0.067m/s2, which is less than the relevant provisions of the national technical code for concrete structures of high rise buildings – jgj3-2010 on the peak wind-induced vibration acceleration limit of 0.25m/s2; The inclination rate is between 0.00% ~ 0.05%, which is less than the allowable value of 0.2%; The daily settlement variation is -0.45mm ~ 0.42mm, and the cumulative settlement is -0.62mm ~ 0.42mm
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The settlement of the building is stable
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Opinion of the expert group: through the above a large number of detection, monitoring, testing, analysis and demonstration, and through multi-party review and appraisal, the main structure of SEG Plaza building is safe and can continue to be used within the design load range and under normal use
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Why does the building vibrate? The wind-induced vortex induced resonance of the mast is the direct cause
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Through technical investigation, environmental and equipment operation investigation and test, the expert group excluded the influencing factors such as subway operation, surrounding engineering construction or blasting, air conditioning unit operation and so on
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Through the key analysis of wind-induced vibration and structural cumulative damage, the expert group believes that the coupling of wind-induced vortex induced resonance of mast and the change of dynamic characteristics of building and mast causes the sensible vibration of SEG square building
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1
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Wind induced vortex induced resonance of mast is the main external cause of induced vibration of building
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First, carry out special dynamic performance test and Analysis on the mast
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Doppler laser vibration measurement and vibration video image recognition are adopted
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The results show that 21 asymmetric wind-induced vortex induced resonances with a frequency of 2.12hz occurred on the mast from May 18 to 20
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The second is to carry out continuous dynamic performance monitoring and analysis of the building
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From the basement of the building to the top mast, the acceleration and other real-time monitoring are carried out, the vibration shape, frequency, damping ratio and other dynamic parameters are measured, and the main vibration modes under various vibration conditions of the first 20 orders are obtained
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The results show that the induced vibration of the building from May 18 to 20 is a high-order bending torsion combined mode, and the vibration frequency is the same as that of the mast is 2.12hz
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Third, the excitation test verifies that the vibration of the mast can drive the vibration of the building
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A total of 26 working conditions and 63 groups of excitation tests at different positions, directions and frequencies were carried out for the mast and the building
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The results show that the fourth-order asymmetric vibration of the mast can drive the high-order flexural torsional combined vibration of the building at the frequency of 2.12hz
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In conclusion, under the specific wind field conditions of steady state and lasting for a certain time, the tower mast produces the fourth-order reverse potential asymmetric vortex induced resonance with a frequency of 2.12hz, which excites the high-order bending and torsion combined mode with the same frequency of 2.12hz, and then causes the sensible vibration of the main structure of the building
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2
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The change of the dynamic characteristics of the building and mast is the main internal cause of the induced vibration of the building more than 20 years later
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After the building has been used for more than 20 years, the cumulative damage of profiled steel plate composite floor and mast connection points on some floors has changed the structural frequency, damping ratio and other dynamic characteristics
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The mast and the main structure of the building have a common vibration frequency of 2.12hz, forming the necessary condition for resonance
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The above local cumulative damage only affects the dynamic characteristics of the structure and does not affect the safety of the main structure
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How to solve the problem of building induced vibration? The expert group believes that the removal of the mast can effectively solve the problem of induced vibration of the building, and the original lightning protection and navigation mark functions of the mast can be re arranged on the roof after the mast is removed
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The person in charge of the Municipal Bureau of housing and urban rural development responded that the mast demolition construction scheme organized and formulated by the Bureau has gone through three checks: first, the original design unit reviewed the impact of demolition construction on the safety of the main structure; Second, the demolition scheme is further improved according to the advisory opinions provided by Guangdong Academy of Building Sciences on the construction scheme; Third, the demolition scheme has been demonstrated by an expert group composed of experts recommended by the Ministry of housing and urban rural development, the Provincial Department of housing and urban rural development and well-known experts in Shenzhen
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The demolition project will be implemented at an appropriate time in the near future, and the damage repair project will be carried out simultaneously, with an effective construction period of about 32 days
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If affected by extreme weather such as rainstorm, typhoon and high temperature, the construction operation will be stopped in time and the construction period will be postponed
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In order to ensure the safety of people’s lives and property, strict protective measures will be taken to close the SEG Plaza building and some surrounding roads during the demolition.
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