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Investigating the coefficient of behavior of steel structures with a dual system of bending frame and knee brace

Number of pages: 154 File Format: word File Code: 31441
Year: 2016 University Degree: Master's degree Category: Civil Engineering
Tags/Keywords: Bending frame - Collapse of the structure - Earthquake - Incremental method - knee brace - Seismic design of the structure - Seismic improvement - Steel structure - structure - The behavior of steel structures
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  • Summary of Investigating the coefficient of behavior of steel structures with a dual system of bending frame and knee brace

    Dissertation for Master's Degree

    Civil Engineering - Structural Orientation

    Abstract:

    The main goal in seismic design of structures is to prevent the structure from collapsing during severe earthquakes, which is the basis of the theory that governs seismic behavior, the result of investigating the nonlinear behavior of the structure during an earthquake and the resistance due to the nonlinear performance of the structure during the earthquake and the resistance due to its nonlinear performance in Seismic design codes and regulations have introduced a number under the title of behavior coefficient to reduce the linear design force in order to guide the structure to non-linear performance. One of the seismic bearing systems that has been considered in terms of flexibility and economy is the knee brace system. In the knee brace system, at least one end of the diagonal brace is connected to the knee member that is obliquely placed between the beam and the column, instead of being connected to the place where the beam meets the column. The diagonal member provides the stiffness of the system, while the ductility under the effect of lateral loads is obtained through the bending flow of the knee member, and the knee member acts like a malleable fuse and prevents the buckling of the diagonal member. In order to obtain the coefficient of behavior of a problem that is studied for seismic improvement, the linear and non-linear behavior of the structure must be compared with each other. In this research, Young's method to obtain the coefficient of behavior of structures is introduced and fully described. After the initial design of the structure, the ductility of the structure is investigated by non-linear static analysis (increased load-pushover) and the time of the formation of the first plastic joint and the steps after that until the total destruction of the structure are determined. Using the non-linear analysis as well as the basic cut-displacement diagram, the parameters needed to calculate the Young's behavior factor such as ductility and additional strength and the allowable stress ratio factor as well as the amount of target displacement and so on. It can be calculated. The results obtained from this research to calculate the behavior coefficient show different values ??at different altitude levels. Also, the value of the coefficient of behavior in structures with inappropriate seismic performance at a height level can be lower than the average value obtained in other models.

    Keyword: coefficient of behavior - knee brace - ductility - seismic improvement - steel structure - additional load method

    Chapter 1

    Generalities of the research

    1-1- Introduction:

    Often, the structures are designed for severe earthquakes and accepting levels of damage, and control in terms of the elastic behavior of the structures in the range of moderate earthquakes, which are likely to occur annually, are not specified. It means that there is no estimate for the elastic behavior of structures in such a case. When severe earthquakes occur, the structure enters the non-linear range, and as a result, a non-linear design is needed for their design, but due to the complexity of the non-linear analysis, as well as the time-consuming and expensive nature of the non-linear programs compared to the linear analysis, the usual analysis and design methods are based on the linear analysis of the structure. One of the important and fundamental parameters in the seismic design of structures is the behavior coefficient. The value of this coefficient has been determined in some regulations from the results of tests and earthquakes are the best laboratory for investigating the behavior of structures. In order to consider the non-linear behavior of the structure with a linear analysis and determine the amount of energy loss due to hyster-zeiss behavior, damping, the effect of added resistance of the structure and the plasticity of the structure, a coefficient called the behavior modification coefficient or the behavior coefficient is used. In moderate earthquakes, they will suffer non-structural damage, and during strong and large earthquakes, they will have structural and non-structural damage, but their overall stability will be maintained.

    Considering the elastic performance of the structure against earthquakes, the sections of the design will be larger and this will make the design uneconomical. Therefore, by considering the non-linear behavior of the structure, it is possible to take advantage of the energy absorption properties of the structure and its plastic deformations and help to make the design economical. It is possible to take advantage of these characteristics of the non-linear behavior of the structure if the structure can tolerate the deformation of the dough. In other words, in the seismic design of the structure, it must be able to dissipate a major part of the input energy through inelastic deformations.In order to have a reasonable value for the non-elastic resistance of structures, the accuracy of the reduction in elastic resistance is essential.

    The regulation [1] UBC97 by analyzing structures based on their adequacy, considers the effects of non-linear response of the building, additional resistances and ductility of different elements. According to the above criteria, the main attention against earthquakes is focused on lateral safety, that is, preventing the destruction of the structure under the effect of the strongest earthquake that is possible during the useful life of the structure. So a structure that is designed based on such a philosophy (seismic design) enters the non-linear range under the strong forces of an earthquake. As a result, the design of structures for linear behavior under vibrations caused by large earthquakes is basically not economical. Therefore, structures are designed for a shear force much smaller than the yield shear force. Reduction in elastic resistance of structures should be done carefully. The manner and amount of this reduction in resistance can be very effective in performing the desired behavior in the structure, therefore, identifying the parameters involved in this field and estimating their relative importance in providing the correct amount of elastic resistance reduction in the design of structures is a very important and necessary category. is Therefore, there will always be an expectation of non-linear behavior for the structure, i.e. the behavior of the structure in deformation beyond the elastic limit caused by forces beyond the elastic limit. Also, the experience of the effect of earthquakes on structures shows that structures behave non-linearly during an earthquake and therefore waste a significant amount of incoming energy in the form of damping and residual. Therefore, the structure can be designed for an earthquake force much lower than the required force in the linear mode.

    The behavior coefficient used in the NEHRP, UBC regulations [2] is a constant coefficient that expresses the effect of ductility and extra strength of any structural system. In the interpretation section of the regulation, it considers it necessary to apply design engineering judgment in its use. Here, the question arises, what is the basis of engineering judgment based on, and on what principles should the designer consider the value of this coefficient. In this case, there is no mention in the regulations, and this shows the complexity of this coefficient. Therefore, obtaining this coefficient for any different structural system is a time-consuming and complex matter for design engineers.

    Certainly, only in a non-linear analysis, it is possible to determine the location of the joints of the paste by considering the paste behavior of the structures and investigating issues such as strength and ductility. In order to consider factors such as the ductility of different structural systems and uncertain degrees, the additional resistance in the structures as well as the ability to absorb and consume energy in the building, various regulations reduce the calculated forces according to the type of structural system and with the help of a coefficient called the behavior coefficient. In this system, at least one end of the diagonal brace is connected to the knee member that is obliquely placed between the beam and the column, instead of being connected to the place where the beam meets the column. The diagonal member provides the stiffness of the system, while the ductility under the effect of severe lateral loads is obtained through the flow of the knee member, and the knee member acts as a malleable and replaceable member and prevents the buckling of the diagonal member. The base shear force on structures during earthquakes was estimated as a fraction of the structure's weight. At that time, for the seismic design of the building, a percentage of the weight of the building was applied to the building as a horizontal load equivalent to the earthquake load, and the building was designed for it, and the total design shear force was obtained as V=CW.

    For the first time in 1933, in Los Angeles, a regulation was approved that set the basic shear factor of 0.1 for special structures and the value of 0.08 It was intended for normal structures.

  • Contents & References of Investigating the coefficient of behavior of steel structures with a dual system of bending frame and knee brace

    List:

    Chapter One: Research overview. 1

    1-1- Introduction.. 1

    1-2- History-Behavior coefficient. 3

    1-3- History- knee bandage. 4

    1-4- Seismic plan .. 6

    1-5- Behavior coefficient .. 8

    1-6- Necessity of research. 8

    1-7- The upcoming process. 10

    2- The second chapter: a review of the subject literature. 11

    2-1- Introduction.. 11

    2-2- Structure behavior against earthquake. 11

    2-2-1- Effects of various types of deterioration and buckling in the structure. 12

    2-2-2- hysteresis cycle curve. 15

    2-2-3- The principles and philosophy of seismic design. 17

    2-3- The concept of behavior coefficient. 19

    2-3-1- parameters affecting behavior coefficient. 21

    2-3-1-1- Malleability. 23

    2-3-1-2- additional resistance coefficient (additional resistance). 27

    2-3-1-3- Indeterminate coefficient. 31

    2-3-1-4- damping coefficient. 32

    2-4- An overview of the conducted research. 33

    2-4-1- Newmark and Hall. 33

    2-4-2- Lai and Biggs. 35

    2-4-3- Riddle and Newmark. 35

    2-4-4- Al-Qadamsi and Mahrez. 36

    2-4-5- Riddle, Hidalko and Cruz. 37

    2-4-6- Arayez and Hidalgo. 37

    2-4-7- Nassar and Krawinkler. 38

    2-4-8- Vidik, Fajfar and Fischinger. 40

    2-4-9- Miranda and Bertrava. 41

    2-4-10- An overview of the research done on the knee brace system. 43

    2-5- Methods of calculating the coefficient of behavior. 44

    2-5-1- American methods. 44

    2-5-1-1-Yong's plasticity coefficient method. 45

    2-5-1-1-1- The formula of the structure's ductility coefficient. 47

    2-5-1-1-2- The formula of force reduction factor due to plasticity. 47

    2-5-1-1-3- formula of additional resistance factor. 47

    2-5-1-1-4- The formula of the allowable stress coefficient (Y). 48

    2-5-2- formulation of behavior coefficient. 48

    3- Principles and basics of seismic design. 51

    3-1- Introduction .. 51

    3-2- Non-linear static analysis and Pushover analysis. 52

    3-2-1- Lateral load distribution in non-linear static analysis. 53

    3-2-1-1- General power distribution. 54

    3-2-1-2- distribution according to modes. 55

    3-2-1-3- Uniform distribution. 57

    3-2-2- FEMA-356 method for wear analysis. 58

    3-3-1- Force response-change of location of the structure. 58

    3-3-2- Laboratory assessment of force-displacement relationships. 62

    3-4- Design based on performance levels of structural components. 63

    3-4-1-Performance level 1 for structural components-non-stop usability. 64

    3-4-2- Performance level 3 for life safety structural components. 64

    3-4-3- performance level 5 for structural components - collapse threshold. 65

    3-5- Investigating the seismic and non-linear behavior of the knee brace. 67

    3-6- An overview of the passive knee brace system. 69

    3-7- Section and length of the yielding knee element. 70

    3-8- Basics of knee brace frame design. 72

    3-9- V-M interaction of knee elements. 74

    3-10- requirements of elbow elements. 76

    4- Chapter 4: Modeling, design and calculation of required parameters of behavior coefficient. 78

    4-1- Introduction.. 78

    4-2- Introducing the modeling method and the investigated models. 78

    4-2-1- How to model and calculate the length of the elbow element. 79

    4-2-2- Naming the models. 80

    4-3- Equivalent static analysis and design of dual bending frame and knee brace system. 82

    4-3-1- Calculation of earthquake coefficient. 83

    4-3-1-1- Calculation of earthquake coefficient for 5-story structures: 83

    4-3-1-2- Calculation of earthquake coefficient for 9-story structures. 84

    4-3-1-3- Calculation of earthquake coefficient for 13-story models. 84

    4-4- Non-linear analysis considerations. 85

    4-5- Determining and controlling the behavior coefficient of the dual bending frame and knee bracing system. 86

    4-5-1- The process of calculating the coefficient of behavior of the structure for the 5S-DB-M model. 86

    4-5-2- The process of calculating the structural behavior factor for the 5S-DB-T model. 91

    4-5-3- The process of calculating the behavior factor of the structure for the 5S-DB-B model. 93

    4-5-4- The process of calculating the behavior factor of the structure for the 5S-XB-M model. 95

    4-5-5- The process of calculating the behavior factor of the structure for the 5S-XB-T model. 97

    4-5-6- The process of calculating the behavior factor of the structure for the 5S-XB-B model. 99

    4-5-7- The process of calculating the behavior factor of the structure for the 9S-DB-M model. 101

    4-5-8- The process of calculating the behavior factor of the structure for the model101

    4-5-8- The process of calculating the behavior factor of the structure for the 9S-DB-T model. 103

    4-5-9- The process of calculating the behavior factor of the structure for the 9S-DB-B model. 105

    4-5-10- The process of calculating the behavior factor of the structure for the 9S-XB-M model. 107

    4-5-11- The process of calculating the behavior factor of the structure for the 9S-XB-T model. 109

    4-5-12- The process of calculating the behavior factor of the structure for the 9S-XB-B model. 111

    4-5-13- The process of calculating the behavior factor of the structure for the 5S-XB-M model. 113

    4-5-14- The process of calculating the behavior factor of the structure for the 13S-DB-T model. 115

    4-5-15- The process of calculating the behavior factor of the structure for the 13S-DB-B model. 117

    4-5-16- The process of calculating the behavior factor of the structure for the 13S-XB-M model. 119

    4-5-17- The process of calculating the behavior factor of the structure for the 5S-XB-M model. 121

    4-5-18- The process of calculating the behavior factor of the structure for the 5S-XB-M model. 123

    5- Collection and conclusion. 126

    5-1- Introduction. 126

    5-2- Calculated behavior coefficient. 126

    5-3- Presentation of comprehensive behavior coefficient. 127

    5-4- Presenting the appropriate behavior coefficient based on the appropriate performance of the model. 127

    5-5- Summary of results. 128

    5-6- Suggestions. 130

    * List of sources and sources. 131

    Appendixes. 134

    Abstract. 140

     

    Source:

    [1] uajg, C.M., “Establishing R(or Rw) and Cd factor for building seismic provisions”, J. of struct. Engrg., ASCE, vol.117,NO.l,pp.19-28m1991.

    [2] Wakabayashi, M., “Designing of Earthquake – Resistant Buildings”, MC Graw-Hill, 1986

    [3] Miranda, E., V. V. Bertrro, “Evaluation of strength reduction for earthquake – Resistant design” Earthquake spectra, Vol. 2, Vol. pp357-379-01994

    [4] Riddell. R, P. Hidalgo and E. cruz, "Response modification factor for earthquake resistant design of short period structures" [5] Nassar. A. A, J. D. Ostras and H. Krawinkler.” Seismic design based on strength and ductility demands". Proc. Tenth world conference on earthquake engineering. Vol. 10. pp. 5861-5866.1992

    [6] uang, C. M., and Bertero. V. V, "Implications of Recorded Earthquake Ground Motions on Seismic Design of Building Structures" Report N. UCB/EERC-88/13.

    Earthquake Engineering research center, University of California Berkeley, November 1998.

    [9] Cosenza, E., and Monfredi, G." seismic design based on low cycle fatigue criteria", Earthquake engineering and structural dynamics, vol. 21, pp. 837-848, 1992

    [10] Powell, G. H., and all ahabadi, Ro, seismic damage prediction by deterministic methods: concepts and procedures", Earthquake engineering and structural dynamics, vol 16. pp. 719-734,1998

    [11] uang, C. M. (1992), "seismic force reduction and displacement amplification factor" proceedings", of the 10th world conference on earthquake engineering Balkema, Rotterdam, 5875-5880

    [12] Lee. D.G., song. J. k and yun. C.B., "Estimation of system - Level ductility demands for multi story structures", J. of engineering structures, vol 19, no 12, pp. 1025-1033, 1997

    [13] Housner, G.W. "limit design of structures to resist earthquake", proc. First world conf. on earthquake engineering, pp 5-1 to 5-13, Berkeley, California, 1959

    [14] Bertero, V.V, "State - of - the report on: design criteria" world conf. on earthquake engineering. , paper No 2005, 1996.

    [15] Rojhan, C., "An Investigation of structural response modification factors" proceedings of 9th world conference on earthquake engineering, Tokyo-Kyoto, Japan, PP.1087-1092, 1988

    [16] Aristizabal-ochoa JD. Disposable knee bracing: Improvement in seismic design of steel from" Journal of structural engineering, ASCE 1988; 112(7): 1544-52

    [17] Balendra. T, sam M.T, liaw . C.Y, "Diagonal bracing with ductile knee anchor for a seismic steel frame" Earthquake engineering and structural dynamics 1990; 19: 847-58.

    [18] Mina Naeemi and majid bozorg "Seismic performance of knee braced frame" world academy of science, engineering and technology - vol3

Investigating the coefficient of behavior of steel structures with a dual system of bending frame and knee brace
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