Sensitivity Analysis of Soil Site Response Modelling in Seismic ... - ITC

More documents

Recommendations

Info

ased site-dependent amplification factors. For the classification scheme of the site, they have used SHAKE91 and checked the responses. And, observed that an increase in depth shifts the fundamental period, where amplification is most significant, toward higher values. Also added that, the significantly higher response at longer periods for deep soil deposits is an important expected result that should be accommodated in a seismic site response evaluation (Rodriguez-Marek and and Bray 1999). Overall, it can be concluded that one dimensional soil column analysis is a practical method and widely used in many studies and the applications have varieties in soil site effect analysis. Advanced methods Advanced methods refer to the different models that have been proposed to investigate several of the various aspects of site effects. These aspects usually involve complex phenomena. Various types of incident wave fields, such as near field (comparable or shorter than the wavelength concerned.), far field (It is used to refer a distance to a seismic source longer than the wavelength concerned), body waves, surface waves should be considered. The structure geometry may be 1D, 2D or 3D (Figure 2- 11). Or, the mechanical behaviour of materials may have a very wide range like, viscoelasticity (Viscoelastic materials are those for which the relationship between stress and strain depends on time), non-linear behaviour, water-saturated media and liquid domains. Figure 2-11 Subsurface geology could be referred as one-dimensional, two-dimensional or threedimensional (Smith 2001). Lacave et. al (2002) have distinguished these complex conditions into four. 1. Analytical methods 2. Ray methods 3. Boundary based techniques 4. Domain based techniques Above mentioned methods need heavy computational processes, on the other hand their flexibility and versatility have leaded the way to the understanding of the site effects. In one-dimensional response analysis the soil structure is essentially horizontal. However the conditions of other structures should also be taken into account. Sloping or irregular ground surfaces, the 32 Sensitivity Analysis Of Soil Site Response Modelling In Seismic Microzonation For Lalitpur, Nepal
presence of heavy structures or stiff, embedded structures or walls or tunnels all require twodimensional even three-dimensional analysis. For this kind of problem analysis, the common approach is to make the analysis using dynamic finite-elements (This method assumes that a continuum as an composition of discrete elements whose boundaries are defined by nodal points, and uses the response of the continuum can be described by the response of the nodal points; Figure 2-12) An example for a required three-dimensional analysis could be an earth dam in a narrow canyon, a site where the subsurface geology differs too much in 3D or a site where the soil response is influenced by response of other structures (Kramer 1996). Figure 2-12 Diagram showing the continuum and the nodal points (Kramer, 1996) Konno et. al. (1999) tested the analytical methods used for California using empirical modelling. They have used two dense 3D strong motion arrays and operated in California to directly measure the response of stiff quaternary soil to earthquake shaking. They have recommended that the site response measurements from these arrays along with detailed geotechnical and geophysical site investigations would provide important calibration and confirmation of site response modelling techniques used for seismic siting criteria development (Konno, Kato et al. 1999). Lacave et. al. (2002) have pointed out some of the concerns related to site effects evaluations. They have highlighted that the numerical models were a posterior computation, basically the analyser knew what to look and find. They have also found the compiling the sufficient input parameters, which depend on geotechnical and geophysical investigations to be expensive. Adding, “This issue may sometimes be overcome through parametric studies, but this is useful only when the results do not exhibit too much sensitivity (which is rarely the case)”. Here we can see that they have already proposed to overcome the situation by parametric studies such as this one. But they also argued the sensitiveness of the results. The result of this research might give some answers to this opinion. Empirical and semi-empirical methods Seismic waves of all types are progressively damped as they travel because of the inelastic properties (stiffness etc) of the Rocks and soils (Bolt 2001). The amplitude of seismic waves changes for two main reasons; first, the wave front usually spreads out as it travels away from the source and, because the energy in it has to be shared over a greater area, the amplitude decreases. Second, it happens when some of the wave energy is absorbed (Musset and Khan 2000). Many empirical attenuation laws have been derived on the basis of available strong ground motion recordings. They all relate to the magnitude, distance and ground motion parameter; they also might consider the site parameter in a simple manner such as Rock or non-Rock. The reason for this is detailed information on strong ground motion recording sites are generally missing. But a very important development in this area has been in Japan. They have installed 1000 sites with 20 m deep boreholes for obtaining P and S waves after the destructive earthquake Kobe. The network is called K-Net. (K-Net 2002) Sensitivity Analysis Of Soil Site Response Modelling In Seismic Microzonation For Lalitpur, Nepal 33
Page 1 and 2: Sensitivity Analysis of Soil Site R
Page 3 and 4: Disclaimer This document describes
Page 5 and 6: Abstract For a proper design of ear
Page 7 and 8: 6.4. Sensitivity for Unit Weight ..
Page 9 and 10: Figure 3-7 The display of results f
Page 11 and 12: List of Tables Table 1-1 Investigat
Page 13 and 14: 1. Introduction 1.1. Scope of the s
Page 15 and 16: Figure 1-2 The seismic hazard map o
Page 17 and 18: 1.3. Research Objectives Sensitivit
Page 19 and 20: Methodology A) Literature Review B)
Page 21 and 22: • Array method using ambient vibr
Page 23 and 24: Shear wave velocity Just like the o
Page 25 and 26: • Hard copy maps of the engineeri
Page 27 and 28: 6. Chapter six the assessment of th
Page 29 and 30: place where the ground responses we
Page 31 and 32: Figure 2-2 A probabilistic seismic
Page 33 and 34: Figure 2-4 The deterministic seismi
Page 35 and 36: create stronger shaking and make lo
Page 37 and 38: agreed on the method’s functional
Page 39 and 40: n = - e trans / e longitudinal Stra
Page 41 and 42: Several other studies have looked t
Page 43: the two approaches are not going to
Page 47 and 48: other parameters are kept constant.
Page 49 and 50: Sensitivity Analysis Of Soil Site R
Page 51 and 52: In addition to the above-mentioned
Page 53 and 54: As mentioned by Ordonez (2002), the
Page 55 and 56: In the first option the dynamic soi
Page 57 and 58: The third option lets you to choose
Page 59: SHAKE 2000 METHODOLOGY MAIN MENU Cr
Page 62 and 63: Lalitpur is on the south of Kathman
Page 64 and 65: solidated sediments of the valley c
Page 66 and 67: 4.3. Seismicity Nepal is within the
Page 68 and 69: Figure 4-6 Map showing, seismic dat
Page 70 and 71: m. The numbers of blows are counted
Page 72 and 73: Figure 5-1 Map showing borehole loc
Page 74 and 75: For the other input parameter, stro
Page 76 and 77: and the third one is from real reco
Page 78 and 79: Scenario 1 Scenario 2 Scenario 3 PG
Page 80 and 81: 7). Though the magnitude is great a
Page 82 and 83: B 23 - Analysis No. 1 - Profile No.
Page 84 and 85: used is Los Angeles, Magnitude: 6.2
Page 86 and 87: Soil Profile No. 1 - Analysis No. 1
Page 88 and 89: The soil profile is divided into fo
Page 90 and 91: the input data, all spatial calcula
Page 92 and 93: Table 5-10 The relations between th
Page 94 and 95:
Methodology 2 Input and Output Rela
Page 96 and 97:
Figure 5-16 The natural frequency m
Page 98 and 99:
tween the inputs and outputs of the
Page 100 and 101:
R 2 = 1- SSE SST SSE= ∑ (Yi-Ỳi
Page 102 and 103:
6.3. Sensitivity to Input Motions T
Page 104 and 105:
When the response spectra are consi
Page 106 and 107:
Unit Weight (Kcf) 0,35 0,3 0,25 PGA
Page 108 and 109:
PGA Values for Differing Depth Valu
Page 110 and 111:
In order to give some range of valu
Page 112 and 113:
Avouac, personal communication) and
Page 114 and 115:
Based on the results of the sensiti
Page 116 and 117:
• Using similar earthquake signal
Page 118 and 119:
• IRIS, I. R. I. f. S. (2003). Se
Page 120 and 121:
108 Sensitivity Analysis Of Soil Si
Page 122 and 123:
Los Angeles Simulated strong ground
Page 124 and 125:
Appendix B: Soil Profile Informatio
Page 126 and 127:
medium to coarse Sand 2 5 16.4 18 1
Page 128 and 129:
Clay 1 1 3.3 16 102 0.10 300 984 60
Page 130 and 131:
6188 118 Sensitivity Analysis Of So
Page 132 and 133:
26 0.29 1.15 1.85 1.31 0.93 27 0.2
show all

Sensitivity Analysis of Soil Site Response Modelling in Seismic ... - ITC

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?