Eşdeğer deprem yükü yöntemin tepe kuvveti açısından değerlendirilmesi
Eşdeğer deprem yükü yöntemin tepe kuvveti açısından değerlendirilmesi
Dosyalar
Tarih
1998
Yazarlar
Arıcıoğlu, Alper
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Özet
'Eşdeğer Deprem Yükü Yönteminin Tepe Kuvveti Açısından Değerlendirilmesi' isimli bu tezin kapsamında 'Yeni Türkiye Deprem Yönetmeliği' nin (Afet Bölgelerinde Yapılacak Yapılar Hakkındaki Yönetmelik) eşdeğer deprem yükü yöntemi bölümünde sözü edilen tepe kuvveti açısından incelenmiştir. Çalışmanın giriş bölümünden sonraki ikinci bölümünde 'Yeni Türkiye Deprem Yönetmeliği'nin genel ilke ve kuralları verilmiştir. Ayrıca bu bölümde 'Eşdeğer Deprem Yükü Yöntemi' ve bu yöntem ile hesabmın güvenilirliği için baz olarak alınacak olan 'Modlann Süperpozisyonu Yöntemi'nin yönetmelikte bahsedilen genel kuralları verilmiştir. Üçüncü bölümde ise bu inceleme için kullanılan 'Sayısal Deney Yöntemi' anlatılmış ve örnek olarak çözülecek yapıların özellikleri verilmiştir. Dördüncü bölümde ise seçilen örnek yapıların 'Eşdeğer Deprem Yükü Yöntemi' ve 'Modların Süperpozisyonu Yöntemi' ile çözümünden elde edilen sonuçlar verilmiş ve bu sonuçların ışığında tepe kuvvetinin hesabı için yeni bir öneri sunulmuştur. Bu öneri doğrultusunda, seçilen örnek yapılar tekrar hesaplanmış ve sonuçlar karşılaştırılmıştır.
Especially in major cities, the constructions of multi-story buildings become more popular. The increase on the usage of multi-story buildings caused problems on their analysis and design. The most important matter is the resistance and behaviour of the buildings under earthquake loads. Due to this reason, the new Turkish Seismic Code was published in September 1997 [3]. In this study that is submitted as M.Sc. Thesis, additional concentrated force, at the top level, in equivalent static earthquake load method are examined by applying a parametric test procedure on a number of structures. Typical multi-story structures are chosen and analyzed by using 'Equivalent Static Loads' which are computed according to the new 'Turkish Seismic Code, 1997'. The results are then compared with to those obtained by the method of 'Modal Superposition'. For each typical structure, the ratios of the design bending moments due to the two types of analysis are computed throughout the structure. These ratios, which are called the 'Computational Safety Factors (CSF)' [5] is used in the evaluation of various structure types. M CSF = ^2- (1) MD In this relationship, Ms represents design bending moments, obtained from Equivalent Static Load Method and Md represents design bending moments, obtained from Modal Superposition Method. Calculated CSF values, together with their mean values (CSFmea") and standard deviations (SD) are used in the comparison of methods. It can be said that if the CSFmean >1, the equivalent static earthquake load method is reliable for the considered system. A CSFmean <1 indicates that the equivalent static earthquake load method is not reliable enough. The CSFmean value for structural system which is weighted mean of CSF values at critical sections is calculated by the following equation: xix CSF_=|^ (2) And standard deviations (SD) of CSF values for overall beams and columns are calculated as given in the following equation: gD,=ZM.(«f-cg'-y (3) Calculated standard deviations give way to figure out the amount of deviation of the obtained safety factors at critical sections of the structure from the mean value. In order to comprehensively analyse various types of structure that are encountered with in everyday applications and classified in the codes, specific 'Typical Structures' are selected. These typical structures are;. Simple frames,. Frames with rigid columns,. Frames with constant rigidity columns,. Shear walls,. Shear walls with opening. Structures with shear walls and frames (Dual Systems) Each typical structure is arranged in 6, 8, 16 and 24 storeys. Earthquake design of each typical structure will be made for the soil profiles given in the code. Additional concentrated force at the top of structure is used by many countries seismic code. For example 'Uniform Building Code (1994)', 'National Building Code of Canada (1995)' and 'Turkish Seismic Code (1997)' use additional concentrated force at the top of structure. xx In Turkish seismic code, the additional concentrated force, at the top level is given by this empiric formula; AFN=0.07T,Vt (4) where; Ti is first natural period of structure and Vt is the total share force at the base. And the concentrated force, at the top level is not allowed to exceed 0.2Vt; AFN<0.2Vt (5) The empirical formula, practical by the seismic code, includes the natural period of structure. It causes some problems to obtain the solution. In this study two empirical formulas are proposed for additional concentrated force, at the top level; AFN=0.015HNVt/R (6) AFN=0.035HTVt/R (7) where; Vt is total share force at the base, Hn is the total height of the building and R is structural behaviour coefficient. CSF values obtained for 6 story simple frame are given in Fig. la, Fig. lb and for 24 story simple frame are given in Fig. 2a, Fig 2b, respectively. xxi 0,5 1,5 CSF 2 Figure la 6 Story Simple Frame CSF Values For Beam Figure lb 6 Story Simple Frame CSF Values For Column xxii 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6H 5 4 3 2 1 = Ft=0.07TV = Ft=0.015HV/R ?Ft^.OSSIFO.SV/E f 0,5 1,5 CSF 2 Figure 2a 24 Story Simple Frame CSF Values For Beam 0,5 1,5 CSF 2 Figure 2b 24 Story Simple Frame CSF Values For Column xxui Figures show that the solutions for AFn=0 has CSF<1 values at the top storeys, this result shows that it is necessary to use the additional concentrated force at the top of structure in equivalent static earthquake load method. The solution of multi-story buildings for AFN=0.07TiVt has CSF>2 value so the additional concentrated force at the top of structure must be decrease. The tables, given below, show the CSF values at top story columns for each analysis of selected typical structure. Table 1 CSF Values For Top Story Columns In Simple Frames (Soil Profile Z2) Table 2 CSF Values For Top Story Columns In Frames With Rigid Columns (Soil Profile Z2) Table 3 CSF Values For Top Story Columns In Frames With Constant Rigidity Columns (Soil Profile Z2) XXIV Table 5 CSF Values For Top Story Columns In Shear Walls With Opening (Soil Profile Z2) In these tables, first rows show the results of analysis for AFn=0, second rows show the results of analysis for the formula given by 'Turkish Seismic Code', third and fourth rows show the result of analysis for the formulas proposed in this thesis for additional concentrated force at the top level. These results show that CSF values obtained from proposed empirical formulas are less than obtained from empirical formulas given by 'Turkish Seismic Code'. But from the third rows of tables, it can be seen that in some typical structures CSF values less than 1. In the analysis for the additional concentrated force given by the proposed empirical formula, these problems don't appear. These results are written in bold. It is not needed to use the restriction (AFN ^ 0.2Vt) given by 'Turkish Seismic Code' with this empirical formula. As a result, the additional concentrated force, at the top level, in equivalent static earthquake load method must be used without restriction of total height of building and using the following proposed empirical formula is more realistic.
Especially in major cities, the constructions of multi-story buildings become more popular. The increase on the usage of multi-story buildings caused problems on their analysis and design. The most important matter is the resistance and behaviour of the buildings under earthquake loads. Due to this reason, the new Turkish Seismic Code was published in September 1997 [3]. In this study that is submitted as M.Sc. Thesis, additional concentrated force, at the top level, in equivalent static earthquake load method are examined by applying a parametric test procedure on a number of structures. Typical multi-story structures are chosen and analyzed by using 'Equivalent Static Loads' which are computed according to the new 'Turkish Seismic Code, 1997'. The results are then compared with to those obtained by the method of 'Modal Superposition'. For each typical structure, the ratios of the design bending moments due to the two types of analysis are computed throughout the structure. These ratios, which are called the 'Computational Safety Factors (CSF)' [5] is used in the evaluation of various structure types. M CSF = ^2- (1) MD In this relationship, Ms represents design bending moments, obtained from Equivalent Static Load Method and Md represents design bending moments, obtained from Modal Superposition Method. Calculated CSF values, together with their mean values (CSFmea") and standard deviations (SD) are used in the comparison of methods. It can be said that if the CSFmean >1, the equivalent static earthquake load method is reliable for the considered system. A CSFmean <1 indicates that the equivalent static earthquake load method is not reliable enough. The CSFmean value for structural system which is weighted mean of CSF values at critical sections is calculated by the following equation: xix CSF_=|^ (2) And standard deviations (SD) of CSF values for overall beams and columns are calculated as given in the following equation: gD,=ZM.(«f-cg'-y (3) Calculated standard deviations give way to figure out the amount of deviation of the obtained safety factors at critical sections of the structure from the mean value. In order to comprehensively analyse various types of structure that are encountered with in everyday applications and classified in the codes, specific 'Typical Structures' are selected. These typical structures are;. Simple frames,. Frames with rigid columns,. Frames with constant rigidity columns,. Shear walls,. Shear walls with opening. Structures with shear walls and frames (Dual Systems) Each typical structure is arranged in 6, 8, 16 and 24 storeys. Earthquake design of each typical structure will be made for the soil profiles given in the code. Additional concentrated force at the top of structure is used by many countries seismic code. For example 'Uniform Building Code (1994)', 'National Building Code of Canada (1995)' and 'Turkish Seismic Code (1997)' use additional concentrated force at the top of structure. xx In Turkish seismic code, the additional concentrated force, at the top level is given by this empiric formula; AFN=0.07T,Vt (4) where; Ti is first natural period of structure and Vt is the total share force at the base. And the concentrated force, at the top level is not allowed to exceed 0.2Vt; AFN<0.2Vt (5) The empirical formula, practical by the seismic code, includes the natural period of structure. It causes some problems to obtain the solution. In this study two empirical formulas are proposed for additional concentrated force, at the top level; AFN=0.015HNVt/R (6) AFN=0.035HTVt/R (7) where; Vt is total share force at the base, Hn is the total height of the building and R is structural behaviour coefficient. CSF values obtained for 6 story simple frame are given in Fig. la, Fig. lb and for 24 story simple frame are given in Fig. 2a, Fig 2b, respectively. xxi 0,5 1,5 CSF 2 Figure la 6 Story Simple Frame CSF Values For Beam Figure lb 6 Story Simple Frame CSF Values For Column xxii 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6H 5 4 3 2 1 = Ft=0.07TV = Ft=0.015HV/R ?Ft^.OSSIFO.SV/E f 0,5 1,5 CSF 2 Figure 2a 24 Story Simple Frame CSF Values For Beam 0,5 1,5 CSF 2 Figure 2b 24 Story Simple Frame CSF Values For Column xxui Figures show that the solutions for AFn=0 has CSF<1 values at the top storeys, this result shows that it is necessary to use the additional concentrated force at the top of structure in equivalent static earthquake load method. The solution of multi-story buildings for AFN=0.07TiVt has CSF>2 value so the additional concentrated force at the top of structure must be decrease. The tables, given below, show the CSF values at top story columns for each analysis of selected typical structure. Table 1 CSF Values For Top Story Columns In Simple Frames (Soil Profile Z2) Table 2 CSF Values For Top Story Columns In Frames With Rigid Columns (Soil Profile Z2) Table 3 CSF Values For Top Story Columns In Frames With Constant Rigidity Columns (Soil Profile Z2) XXIV Table 5 CSF Values For Top Story Columns In Shear Walls With Opening (Soil Profile Z2) In these tables, first rows show the results of analysis for AFn=0, second rows show the results of analysis for the formula given by 'Turkish Seismic Code', third and fourth rows show the result of analysis for the formulas proposed in this thesis for additional concentrated force at the top level. These results show that CSF values obtained from proposed empirical formulas are less than obtained from empirical formulas given by 'Turkish Seismic Code'. But from the third rows of tables, it can be seen that in some typical structures CSF values less than 1. In the analysis for the additional concentrated force given by the proposed empirical formula, these problems don't appear. These results are written in bold. It is not needed to use the restriction (AFN ^ 0.2Vt) given by 'Turkish Seismic Code' with this empirical formula. As a result, the additional concentrated force, at the top level, in equivalent static earthquake load method must be used without restriction of total height of building and using the following proposed empirical formula is more realistic.
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Sosyal Bilimler Enstitüsü, 1998
Anahtar kelimeler
Deprem,
Deprem yükü,
Yönetmelikler,
Earthquakes,
Earthquake load,
Regulations