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MINISTRY OF EDUCATION AND TRAINING UNIVERSITY OF TRANSPORT AND COMMUNICATIONS TRINH THI HOA ANALYSIS OF THE EFFECT OF WATER TANKS ON THE DAMPING LEVEL OF HIGH-RISE BUILDINGS SUBJECTED TO EARTHQUAKES Field of study: Transport Construction engineering Code : 9580206 Major: Technical technology Construction of special works SUMMARY OF THE DOCTORAL THESIS HANOI - 2022 This research is completed at: UNIVERSITY OF TRANSPORT AND COMMUNICATIONS Supervisors: Assoc Prof.Dr NGUYEN THI TUYET TRINH Prof Dr NGUYEN TIEN CHUONG Reviewer 1: ……………………………………………… …………………………………………………………… Reviewer 2: ……………………………………………… ………………………………………………………… Reviewer 3: ……………………………………………… …………………………………………………………… This thesis will be defended before Doctoral- Level Evaluation Council at University of Transport and Communications at … hours……Day……Month……Year…… The thesis can be found at: - Vietnam National Library - Library of University of Transport and Communications PREFACE The urgency of the subject In addition to withstanding normal loads, one of the primary goals of the design of high-rise buildings is to withstand special loads such as high winds and earthquakes The International Building Code (IBC) - 03 or the European Standard Eurocode - Seismic Design for Structures, TCVN Standard 9386:2012 on earthquakes, TCVN 229:1999 on dynamic winds, and TCVN 2737:2020 on loads and impacts reflect the provisions for structures subjected to these special loads In the seismic design of high-rise buildings, the effect of an earthquake is an important issue due to the damage it causes to the building structure To satisfy both strength and strain limit states, the seismic design of high-rise buildings is a challenge for design engineers There are numerous seismic design options for high-rise structures at the moment, but the liquid damping (TLD) option is one of the most popular options because to its effectiveness and affordable price However, the complexity in optimizing the design parameters of the liquid storage tank, such as optimizing the size of the tank, the height of the water level in the tank, the number of tanks, the connection pillow between the tank and the structure building, the location of the tank above the building height, makes it difficult to standardize the design rules for the TLD liquid damping system With the above analysis, the thesis proposes the research content to analyze the influence of the water tank on the damping level of high-rise buildings when subjected to earthquakes, to study the optimal parameters of the water tank such as tank size, the height of the water level in the tank, the number of tanks and the connection pillow between the tank and the structure In particular, the study proposes a convenient method and computational model for the liquid damping system to properly reflect the working nature of the liquid wave in the reservoir, providing the best damping effect for the building when subjected to high-pressure earthquakes 2 Name and purpose of the study Thesis name : “ Analysis of the effect of water tanks on the damping level of high-rise buildings subjected to earthquakes ” Objectives of the study: Analysis of the effect of water tanks on the level of damping of high-rise buildings when subjected to earthquakes Building a computational model proposal for a liquid storage tank, including the tank and the liquid inside the tank According to the fluid mechanics model The proposed model accurately reflects the movement of liquid waves inside the tank Based on the proposed model, the thesis studies the effect of the liquid storage tank on the structure of the building subject to the effects of earthquakes - the influence of the connection between the tank and the building structure Apply the research results to analyze the damping effect of the water tank for a specific high-rise building subjected to earthquakes Object and scope of the study a) Research Object: The water tank is positioned on the high-rise building, and the tank is connected to the framework of the building b) Research scope: Research on rectangular, flat-bottomed water tanks placed on high-rise buildings subject to earthquakes Research Methods Theoretical analysis combined with numerical simulation method to study the effect of water tank on the level of damping for high-rise buildings subjected to earthquakes Besides, comparing and verifying some research results of the thesis with the experimental results of previous studies Scientific and practical significance of the study a) Scientific significance The thesis studies the influence of the water tank on the level of damping for high-rise buildings when subjected to earthquakes The thesis has built and proposed a computational model reflecting the real movement of the liquid inside the tank according to the fluid mechanics model The research results have suggested the parameters of the liquid storage tank, the number of tanks, the location of the tank according to the height of the building, especially the proposed stiffness parameter of the link between the tank and the building through the ratio of the tank and the building Mass ratio and frequency ratio between the tank and the building to increase the damping efficiency of the building when subjected to earthquakes b) Practical significance The research results of the thesis can be used as a basis for the design of damping for the building structure through water tanks They were contributing to promoting the direction of research on solutions to apply water tanks to reduce shocks for building structures when subjected to earthquakes Thesis structure The thesis consists of an Introduction, chapters and a conclusion and recommendations Chapter 1: Overview of research and application of liquid storage tanks to damping for high-rise buildings subjected to earthquakes Chapter 2: Theoretical basis for analyzing the movement of liquid storage tanks on earthquake-resistant structures Chapter 3: Analysis of the effect of the water tank on the level of damping for the structure under the effect of earthquakes Chapter 4: Research on applying water tanks to damping for highrise buildings under the effect of earthquakes Conclusions and recommendations CHAPTER 1: OVERVIEW OF RESEARCH AND APPLICATION OF LIQUID STORAGE TANKS TO DAMPING FOR HIGH-RISE BUILDINGS SUBJECTED TO EARTHQUAKES 1.1 Impacts causing vibrations for high-rise buildings Impacts causing vibration for high-rise buildings include Vertical impact and horizontal impact Unlike ordinary buildings, the horizontal impact is an important factor for high-rise buildings In the design of lowrise buildings, the horizontal effects are generally less concerned than the vertical effects due to the effect of horizontal loads on small low-rise structures As the height of the building increases, the internal forces and displacements of the building due to horizontal impacts such as wind pressure and earthquake impacts, increase rapidly Creating a structural system to withstand these impacts is an essential issue in designing high- rise buildings Alternatively, proposing solutions to minimize the horizontal impacts caused is also essential Within the research scope of the thesis, consider the effects of earthquakes on the working of high-rise buildings From there, provide damping measures for high-rise buildings to reduce the impact of earthquakes 1.2 Measures to reduce vibrations for high-rise buildings under the effect of earthquakes Based on scientific and technical achievements of many different disciplines such as materials, energy, mechatronics, mechanics, cybernetics etc Quite a few anti-oscillation solutions have been researched and developed On the other hand, the oscillation process of the building is a process of accumulating, converting, and dissipating energy due to external influences as well as internal causes The problem is how to intervene in that energy conversion process to be able to control the vibration of the building within the allowable limit Since then, antivibration solutions for building structures have been born, along with devices operating with different mechanisms[17], [18] Damping according to the mechanism of action: Passive damper, Active damper; Semi-active damper [19] Damping according to vibration reduction solutions: Seismic solutions; damping solution [21],[22] 1.3 Water tanks on high-rise buildings and their damping effect Typically, water tanks on high-rise buildings are designed with the purpose of ensuring sufficient water supply for the daily life of the building; to supply water for fire prevention and to fight when a fire or explosion occurs in the building; using a water tank on the roof as a swimming pool for entertainment, entertainment and a part of adding value to the landscape of high-rise buildings From the current research results on the use of water tanks in the building as a liquid damping system (TLD), the content of the thesis proposes to study water tanks to dampthe structure of high-rise buildings under the influence of the water Use of earthquakes Tuned Liquid Damper concept The liquid damping system is a passive vibration control device – called TLD for short This equipment system can reduce dynamic effects such as earthquakes, wind storms or live loads by increasing the resistance characteristics of the structure The damping system can dissipate part of the energy released by the structure when subjected to dynamic loads The liquid damping system comprises liquid storage tanks with estimated length, width, and liquid depth to enhance the structure's equivalent resistance A water tank is an example of a liquid damping system, with the zero-viscosity liquid utilised in the tank being water [24], [25], [26] Types of liquid damping systems: Fig 1.7 Classification diagram of liquid damping device system [27] 1.4 Research situation and application of liquid damping system Research situation of liquid damping system Globally and in Vietnam, there are now three primary research directions pertaining to liquid damping (TLD).: Studying liquid wave oscillations in the reservoir and the interaction between the liquid wave and the tank wall; Soft tank study – the deformation of the tank wall has the opposite effect on the liquid inside the tank; Study on the damping effect of a multi-tank system (MTLD) Application situation of liquid damping system The tallest building in the United States uses a nearly 1300T TLCD system for damping; The 69-story building in Indonesia uses a TLD ~1150T liquid damping system for damping; Bai Chay Bridge in Vietnam uses TLD AND MTLD liquid damping system installed on abutment abutments to control the vibration of abutment abutments under the effect of horizontal loads 1.5 Conclusion Chapter Damping problems are focused on directions such as seismic isolation, energy dissipation, or dynamic balance The thesis researches and studies damping for earthquake-resistant structures in the direction of energy dissipation A liquid damper (TLD) is a type of damping device that operates on the energy dissipation mechanism Based on the results of earlier calculations for the liquid damping system, the following methods can be used to assess and compute the system.: - Equivalent conversion of liquid damping to a mass system (TMD) - Transform the water volume in the tank into solids that move separately from the tank and are attached to the tank using springs that have a set stiffness (as proposed by Houner) The value of the water pressure pressing on the tank wall and the bottom shear force will not be accurate when the liquid in the tank is converted to solidify through the masses because it will not accurately reflect the action of the liquid wave in the tank On the other hand, it can be hard or semi-hard when the tank is attached to the building's framework Considering the impact of the tank on the structure's level of damping, this issue has not yet been investigated and clarified One tank or numerous tanks can be mounted on the construction of the liquid tank system simultaneously The degree of shock absorption of the building under the influence of earthquakes is also significantly influenced by the number of storage tanks From the above analysis, the thesis aims to solve the following problems: (1) Build a computational model for a liquid tank including the tank and the liquid in the tank The proposed model reflects the nature of the movement of liquid waves inside the tank according to the model of fluid mechanics (2) Based on the proposed model, the thesis studies the damping effects of liquid tank parameters on the building structure in the case of single-tank system and multi-tank system (3) Studying the effect of the connection between the tank and the building structure (4) Apply the research results to analyze the damping effect of the water tank for a specific high-rise building structure subjected to earthquakes CHAPTER 2: THEORETICAL BASIS FOR ANALYZING THE MOVEMENT OF LIQUID STORAGE TANKS ON EARTHQUAKE-RESISTANT STRUCTURES 2.1 Working mechanism of TLD liquid damping system The primary function of the fluid damping system is to lessen the vibration of the structure, which is caused by the movement of the fluid in the reservoir and by the energy being lost as a result of wave vibrations and intrinsic viscous forces The damping capacity depends on the amplitude of the fluid motion and the breaking waveform [85] 2.2 Theoretical basis of analysis for one-tank system The exact theoretical basis for the problem of oscillations of moving fluid in a reservoir is challenging and complex Therefore, the theoretical basis can be divided into two main parts: - Theory of analysis of fluid vibrations with small amplitudes according to H Norman Abramson 1966 - Theory of approximation of fluid oscillations with large amplitude The scope of the thesis research will be limited to the theoretical part of liquid vibration analysis with small amplitude, linear analysis according to H.Norman Abramson 1966 applied to rectangular tanks.a) Specific oscillation characteristics of the liquid tank - Amplitude of vertical displacement of the water surface: m a x , y Amn cos m0 n 0 - a n x cos b b y (2.13) The frequency of oscillation of the liquid wave in the tank: fn 2 n2 n2 g h b b g (2.15b) n n h b b b) Container for liquid under the effect of conditioning load - Potential energy function (2.18) 2 4a n x (1) 2 2 (2 n 1) n n x0 cos t sin 2n 1 x cosh 2n 1 z a a h cosh 2n 1 a - Tank bottom shear (2.19) 8tanh 2n 1 r1 FH x0 f sin t 1 3 WF h fn n0 2n 1 r1 f 2.3 Multi-tank system analysis facility The Mutil Tuned Liquid Damper (MTLD) is a collection of multiple TLDs with different water levels that participate in the frequency control of the structure Fig 2.5 Frequency distribution in the MTLD system f f1 f0 N ; R f N f1 f0 i f i 1 f i f N f1 / N (2.22);(2.23) (2.24) 2.4 Theoretical basis for the analysis of the connection between the liquid tank and the structure Two types of interactions between the liquid tank and the structure: - Kinetic interaction - Inertial interaction 12 2.8 Verifying the method of HHTP for analyzing liquid storage tanks through the proposed model of Houner and Haroun Perform tank analysis with size a x b x hbể = x x (m); height of water level in the tank h = (m); Thickness of bottom plate da y 1( m ); tha nh 5( m ) ; Boundary conditions: Control of rotational and vertical displacements; Only consider the horizontal displacement of the tank, only consider the first type of vibration of the structure Centre note Fig 2.27 Model of liquid storage tank From the analysis results by the method of mathematical modeling on ANSYS APDL software and the results of analytical calculations according to the hypotheses, and the analytical formulas of H Norman Abramson and Housner and Haroun are summarized in Table 2.6 Table 2.6 Analysis results of liquid storage tank Research parameter Numerical results according to the analytical formula of H Norman Abramson applied to the reservoir model proposed by Housner and Haroun Numerical results of research according to tank model simulation on ANSYS APDL software Frequency f1 f1 = 0.364 (Hz) f1 = 0.315 (Hz) Bottom shear force F H E 97 E ( N ) FH 1.19 E N 2.9 Conclusion of chapter The content of Chapter has studied the working mechanism, theoretical basis, and typical models, along with liquid tank analysis methods The thesis proposes to use the finite element method in 13 combination with the proposed storage tankstorage tank model model to analyze the case studies of the liquid storage tank and the effect of the tank on the structure of the building Specifically, it is proposed to use ANSYS APDL software to simulate the number of liquid flows in the tank through the liquid elements integrated into the software This is a unique feature of ANSYS software compared to other software The reliability of the finite element method applied to this proposed model has been confirmed after comparing it with the experimental results of Luboya and the equivalent mass of Houner and Haroun model CHAPTER 3: ANALYSIS OF THE EFFECT OF THE WATER TANK ON THE LEVEL OF DAMPING FOR THE STRUCTURE UNDER THE EFFECT OF EARTHQUAKES 3.1 Analysis goal Analytical models Calculation method Effect of tank parameter Number of tanks Bonding effect between tank and structure tank size, water level height Effective function (HHQ) Analysis of the influence of TLD on the level of damping for the structure under the effect of earthquake Fig 3.1 Liquid tank analysis procedure 3.2 Analytical method Efficient function HHQ DTLD F TLD DN FN (3.1) 14 Analytical Models Fig 3.2 Simulation Simplified Model in ANSYS APDL Table 3.1 Finite elements model Finite Name in Structure Mesh size element Ansys Solid Acoustic elements for FLUID30 0.25m elements water Shell Structural element for SHELL181 0.25m elements walls and slab of tank Spring-dashpot element Spring Not COMBIN14 representing the element applicable building - Effects of earthquakes Fig 3.3 Seismic input motion of a recorded signal during El Centro earthquake[121] The frequency spectrum of El Centro is relatively wide, so it will cover the frequency values of the structure, making it easy to identify the 15 most unfavorable case when earthquakes affect the building structure - Calculation method In the study, the earthquake analysis method used is the method of direct integration of the ground motion equation - time history analysis Simultaneously, time-history dynamic analysis was performed with the full live analysis method in ANSYS APDL, combined with the built-in Newmark method 3.3 Analysis of the effect of the water tank according to the parameters (1) Effect of tank size and water level in the tank Case 1: The volume of the water tank is 1% of the volume of the structure Case 2: The volume of the water tank is 10%of the volume of the structure Table 3.3 Data analysis of water tank parameters Parameter Nomenclature Unit Parameter value b h m m 5; 10; 15; 20; 25 0.5; 1; 1.5; 2; 2.5 hb δthanh m m 3.0 0.5 δday m 1.0 Width of tank Water level in tank Tank height Concrete wall thickness Concrete thickness of tank bottom The normal frequency is determined according to the following formula: f slo sh 1 (3.9) f Displacement efficiency Ratio: DTLD/DNO (%) f stru ctu re 1 99.5% 99.0% 98.5% 98.0% 97.5% 97.0% 96.5% 96.0% 95.5% Normative frequency Fig 3.12 The graph of the relationship between the maximum relative displacement of the structure when placing the water tank and when not placing the water tank with the standard frequency (Mb+Mn = 1%M) 16 Ratio: DTLD/DNo(%) 100.0% 95.0% 90.0% 85.0% 80.0% 75.0% 70.0% 65.0% 60.0% Normative frequency Fig 13 The graph of the relationship between the maximum relative displacement of the structure when placing the tank and when not placing the water tank with the standard frequency (Mb+Mn = 10%M) -Hiệu theo lực 101% Ratio: FTLD/FNO (%) 101% 100% 100% 99% 99% 98% 98% 97% 0.5 1.5 2.5 3.5 Normative frequency Ratio: FTLD/FNO(%) Fig 3.16 The graph of the relationship between the ratio of the maximum structural bottom shear force when placing the water tank and when the water tank is not installed with the standard frequency (Mb+Mn = 1%M) 105% 100% 95% 90% 85% 80% 75% 70% 65% 60% Normative frequency Fig 3.17 The graph of the relationship between the ratio of the maximum structural bottom shear force when placing the water tank and when the water tank is not installed with the standard frequency (Mb+Mn = 10%M) 17 Table 3.11 Summary table of analysis results for water tank parameter Computational analysis case Mass ratio: (Mb+Mn)/M = 1% Mass ratio: (Mb+Mn)/M = 10% Analysis results for displacement DTLD/DNO = (96% 98.9%); corresponds to a frequency ratio of 1, then the ratio: DTLD/DNO = 96.5% DTLD/DNO = (71% 98.6%); corresponds to a frequency ratio of 1, then the ratio: DTLD/DNO = 78% Analysis results for force FTLD/FNO = (97% - 101%); corresponds to a frequency ratio of 1, then the ratio: FTLD/FNO = 98% FTLD/FNO = (73% - 98%); corresponds to a frequency ratio of 1, then the ratio: FTLD/FNO = 80% relative displacement (m) (2) Effect of number of tanks on damping degree - Displacement 0.5 0.4 0.3 0.2 0.1 -0.1 -0.2 -0.3 -0.4 -0.5 Khi bể Nokhông waterđặt tank chứa One Khi đặtbig bểwater chứa tank 15*15*3m Khi đặtsmall bể chứa Six 7.5*7.5*0.8m water tanks 10 20 30 40 Time(s) Fig 3.23 Graph the relationship between the relative displacement of the structure over time Force 4000000 Structural bottom shear force (N) 3000000 Six small water Khi đặt bể nhỏ tanks 2000000 1000000 Khi khơng có bể No water tank -1000000 0.00 5.00 10.00 15.00 20.00 -2000000 25.00 30.00 35.00 Khi big đặtwater bể lớn One tank -3000000 -4000000 Time (s) Fig 3.24 Graph of relationship between structural bottom shear force over time 18 The division from large tank into small tanks makes the damping effect of the tank better for the structure under the effect of earthquakes 3.4 Influence of the joint bearing between the water tank and the structure on the level of damping Table of hardness values Kb of the bearing between the tank and the structure, corresponding to research cases Table 3.15 Kb hardness parameter value for the cases research Cases Rigidity of spring bond between tank and structure – Kbi (N/m) Hardness ratio of cases Kbi / Kb3 Liquid tank frequency (Hz) TH1 1.76E+05 0.25 0.063 TH2 3.52E+05 0.5 0.089 TH3 7.03E+05 0.126 TH4 1.41E+06 0.178 TH5 7.03E+06 10 0.398 TH6 7.03E+07 100 1.260 TH7 7.03E+08 1000 3.984 * Calculation results * Displacement 94% Ratio :DTLD /DNO (%) 92% TH1 90% 88% 86% TH5 TH2 TH6 TH7 84% 82% TH4 80% 78% TH3 76% 0.100 1.000 10.000 100.000 Normative frequency Fig 3.31 Graph of the relationship between the relative displacement of the structure and the reference frequency 19 Force 96% TH1 Ratio: FTLD /FNO (%) 94% TH6 92% TH7 90% 88% TH5 TH2 86% 84% TH4 82% 80% TH3 78% 0.100 1.000 10.000 100.000 Normative frequency Fig 3.34 Graph of relationship between the ratio of the maximum structural bottom shear force with the standard frequency Evaluation according to the stiffness of the connection between the tank and the structure for seven corresponding research cases, presented in summary as shown in Table 3.16 Table 3.16 Summary table of case studies on the connection between the water tank and the structure under the effect of earthquakes Cases Rigidity of spring Analysis Hardness ratio bond between tank results for of cases Kbi / and structure – Kbi displacement – Kb3 (N/m) DTLD/DNO(%) Analysis results for force – FTLD/FNO(%) TH1 1.76E+05 0.25 93% 94% TH2 3.52E+05 0.5 86% 87% TH3 7.03E+05 78% 80% TH4 1.41E+06 82% 84% TH5 7.03E+06 10 87% 89% TH6 7.03E+07 100 89% 91% TH7 7.03E+08 1000 89% 91% The effect of the water tank on the structure under the effect of earthquakes is most effective when the stiffness of the connecting bearing 20 is Kb3, corresponding to the case where the frequency is and the mass ratio between the tank and the structure is 10 %(TH3), then the damping efficiency of the water tank is 22% for displacement and 20% for force 3.5 Conclusion Chapter Chapter proposed a practical function of displacement and force of the structure to evaluate the damping level of the water tank Simultaneously, building analytical models for water tanks and structures according to the method of approximation The thesis uses the ground acceleration spectrum in the El Centro earthquake (USA) to study the structure, applying the time-history analysis method combined with Newmark's time integration method to analyze 50 cases of tank parameters and 02 cases of an other number of tanks, along with 07 cases of change in stiffness of the connection between the tank and the structure The results of the study are summarized as follows: - The damping effect of the water tank on the structure is best when the reference frequency value is between 0.8 and 1.5 - The larger the mass ratio between the water tank and the structure, the better the damping effect of the tank to the structure However, the damping effect is only effective when the mass ratio between the water tank and the structure is between 1% and 10%, and if the ratio exceeds 10%, it will not bring more effective damping - Along with a value of the oscillation frequency of the tank and the volume of the tank, the system of many small tanks (large tanks divided into many compartments) always has a better damping effect than the system of one large tank (the tanks not have many compartments) Specifically, when placing a large tank, the largest top displacement of the structure is reduced by 22%, and the maximum bottom shear force of the structure is reduced by 20% When placing six equivalent small tanks, the maximum peak displacement is reduced by 25.9%, the maximum bottom shear force of the structure is reduced by 54.2% - The stiffness of the joint bearing (Kb) with the mass ratio of the water tank and the structure from 1% to 10%, respectively, and the reference frequency equal to 1, the damping effect of the water tank to the structure is the best Specifically, corresponding to the standard frequency of 1, the mass ratio between the water tank and the structure is 10%, there will be Kb=7.03E+05(N/m), then the maximum peak displacement of the structure will decrease 22%, the maximum bottom shear force of the structure is reduced by 20% 21 CHAPTER 4: RESEARCH ON APPLYING WATER TANKS TO DAMPING FOR HIGH-RISE BUILDINGS UNDER THE EFFECT OF EARTHQUAKES 4.1 Selection of high-rise building structure The building selected for research, when applying a water tank to reduce shocks under the effect of earthquakes, has the following dimensions: The width of site B = 22 (m); the length of the premises L = 58.8 (m) and the height of the building h = 108 (m) (30 floors) 4.2 Building a model to analyze the influence of water tanks on highrise buildings Recommend model a) Analytical assumptions with the equivalent model for the structure - The axial displacement under the effect of vertical loads is negligible - Very small rotation angle displacement is ignored - The assumption that the vertical displacement is very small can be ignored - Only consider horizontal displacement, ox axis (direction with small bending stiffness) - The volume is concentrated mainly on the floors The column volume is divided equally between the two floors related to the column b) Proposing the equivalent model for the high-rise building structure system Model structure in Etabs b) equivalent volume model Fig 4.2 Equivalent transformation model of the structure 22 Define model parameters +) Model parameters of the building structure +) Parameters of water tank 4.3 Study on the effects of water tanks on high-rise buildings when subjected to earthquakes a) Earthquake data (using data from the El Centro earthquake) b) The front-end of the water headers - Efficiency of displacement and force when the tank is placed compared to when the water tank is not installed Floor Absolute displacement efficiency when placing tanks on the 30th floor compared to no tanks Absolute displacement efficiency when placing tanks on the 15th floor, tanks on the 30th floor, compared with no tanks Absolute displacement efficiency of floors (%) Fig 4.15 Graph of the absolute displacement efficiency of the floors Relative displacement efficiency Floor when placing tanks at 30th floor compared to no tanks Relative displacement efficiency when placing tanks on the 15th floor, tanks on the 30th floor, compared with no tanks Relative displacement efficiency between floors (%) Fig 4.16 Graph of relative displacement efficiency between floors 23 Floor Cutting force efficiency when placing tanks on 30 floors Cutting force efficiency when placing tanks on 15, tanks on 30 floors Effective cutting force at floors (%) Fig 4.17 Efficiency graph Shear force at floors 4.4 Conclusion Chapter The content of Chapter studied the application of water tanks to damping for high-rise buildings subjected to earthquakes The parameters of the water tank and the parameters of the connection between the tank and the structure are determined based on the research results in Chapter Conduct a study on the behavior of the building when changing the location of the water tank according to the heightof the buildings under the effect of the El Centro earthquake Specifically, the research results are as follows: Placing the entire water tank on top of the building will provide a better damping effect than arranging the tank along the building height Specifically, when placing 06 water tanks on top of the building, the absolute displacement at the top of the building decreased by 10%, the relative displacement between the 14th and 15th floors was reduced by 6.8%, the maximum shear force between the 22nd and 23rd floors decreased by 25 % When placing 03 tanks on the top of the building and 03 tanks on the 15th floor, the absolute displacement at the top of the building is only reduced by 7%, the relative displacement between the 14th and 15th floors 24 is only reduced by 4.2% (this deflection easily causes breakage) local damage of the structure), the shear force between the 22nd and 23rd floors is only reduced by 20% compared to when the tank is not placed CONCLUSIONS AND RECOMMENDATIONS CONCLUSIONS The thesis has analyzed the theoretical basis, proposed to use the numerical simulation model of the calculated liquid flow and the method of chemical analysis through ANSYS APDL software to analyze and calculate for the liquid storage tank Use the displacement and force efficiency functions of the structure to evaluate the damping level of the fluid reservoir Applying the time-history analysis method to study 50 cases of tank parameters, 07 cases of joint stiffness between the tank and the building and the cases of changing the tank location according to the building height, The research results obtained are as follows: The damping effect of the water tank on the structure is best when the ratio of the natural vibration frequency between the water tank and the structure is from 0.8 to 1.5; The greater the mass ratio between the water tank and the structure, the better the damping effect of the water tank on the structure However, the damping effect only comes into play when that mass ratio is from 1% to 10%; The system of many small water tanks or one large water tanks with many compartments will achieve better damping effect than the system of one large water tank without compartments; When the stiffness of the joint bearing between the water tank and the structure is determined corresponding to the mass ratio between the water tank and the structure from 1% to 10% and the ratio of the natural vibration frequency between the water tank and the structure equal to 1, then the damping effect of the water tank on the structure will be the best; When considering the first mode vibration of the building, the plan to arrange the entire water tanks on the top of the building will have a 25 better damping effect than to arrange the water tanks along the height of the building RECOMMENDATIONS AND DIRECTIONS FOR FURTHER RESEARCH (1) Look at tank systems with a variety of tank layers (2) Research to adjust the number of tanks at different structure floors, corresponding to different types of specific vibrations (3) To control the oscillations of liquid waves in the tank in favor of the structure, look for tanks with various tank material structures or investigate various types of liquids (4) Study the nonlinearity of waves, as well as the nonlinearity of structures for structures with distinct properties (5) Create a research team to carry out large-scale tests and obtain reliable data to confirm the findings of a more general nature LIST OF SCIENTIFIC WORKS DISCLOSED Trinh Thi Hoa, Nguyen Thi Tuyet Trinh (2020), “An overview of calcultaing methods for fluid damping (TLD)”, Transport Magazine No 3-2020 Trinh Thi Hoa, Nguyen Thi Tuyet Trinh, Nguyen Tien Chuong, Nguyen Thuong Anh (2020), “Application of Ansys software to analyze the interaction in the water tank under the effect of the harmonic load with the impact of water waves in the tank taken in to account”, Transport Magazine No 8-2020 Trinh Thi Hoa, Nguyen Thi Tuyet Trinh (2021), “Optimized design of tuned liquid damper for mitigating seismic induced vibration in case of high-rise building”, Conference Proceedings CIGOS (Scopus), No 102021 Trinh Thi Hoa, Nguyen Thi Tuyet Trinh, (2022), “Studying the in fluence of bearing stiffness between liquid storage tanks and high – rise building structures subject to earthquake effects”, Transport Magazine No 1-2022 ... Displacement 0.5 0.4 0.3 0.2 0.1 -0.1 -0.2 -0.3 -0.4 -0.5 Khi bể Nokhông waterđặt tank chứa One Khi đặtbig bểwater chứa tank 15*15*3m Khi đặtsmall bể chứa Six 7.5*7.5*0.8m water tanks 10 20 30 40 Time(s)... 3000000 Six small water Khi đặt bể nhỏ tanks 2000000 1000000 Khi khơng có bể No water tank -1000000 0.00 5.00 10.00 15.00 20.00 -2000000 25.00 30.00 35.00 Khi big đặtwater bể lớn One tank -3000000 -4000000... damping system in two cases mass ratio between water tank and structure µ=1% +) Tỷ lệ khối lượng bể kết cấu 2% (a) Acceleration spectrum of the building top and the (b) The peak acceleration spectrum
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