Seismic Design of Tunnels - Parsons Brinckerhoff

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Port and Harbor Facilities Neither standard seismic codes nor universally accepted seismic design criteria exist for waterfront facilities such as berthing (wharf) structures, retaining structures, and dikes. Recent advances in seismic design practice for other facilities, however, have prompted the development of several project specific seismic design criteria for waterfront facilities in high seismic areas (POLA, 1991; Wittkop, 1991; Torseth, 1984). The philosophy employed in the design, again, is based on two-level criteria: • Under an Operating Level Earthquake (OLE), a smaller earthquake, the structures should experience little to no damage and the deformations of wharf structures should remain within the elastic range. Generally, the OLE is defined to have a probability of exceedance of 50 percent in 50 years. • Under a Contingency Level Earthquake (CLE), a larger earthquake, the structures should respond in a manner that prevents collapse and major structural damage, albeit allowing some structural and nonstructural damage. Damage that does occur should be readily detectable and accessible for inspection and repair. Damage to foundation elements below ground level should be prevented (POLA, 1991). Generally, the CLE is to have a probability of exceedance of 10 percent in 50 years. The risk level defined for the CLE is similar to that of the design earthquake adopted in bridge and building design practice. Oil and Gas Pipeline Systems The seismic design guidelines recommended by ASCE (Nyman, et al, 1984) for oil and gas pipeline systems are in many ways similar to the principles used in the design for other important facilities. For important pipeline systems, the design should be based on two-level earthquake hazard: • The Probable Design Earthquake (PDE), the lower level, is generally associated with a return period of 50 to 100 years. • The Contingency Design Earthquake (CDE), the higher level, is represented by an event with a return period of about 200 to 500 years. The general performance requirements of the pipeline facilities under the two design events are also similar to those for other facilities. 18
2.4 Proposed Seismic Design Philosophy for Tunnel Structures Two-Level Design Criteria Based on the discussion presented above, it is apparent that current seismic design philosophy for many civil engineering facilities has advanced to a state that dual (twolevel) design criteria are required. Generally speaking, the higher design level is aimed at life safety while the lower level is intended for continued operation (i.e., an economical design goal based on risk considerations). The lower-level design may prove to be a good investment for the lifetime of the structures. The two-level design criteria approach is recommended to ensure that transportation tunnels constructed in moderate to high seismic areas represent functional adequacy and economy while reducing life-threatening failure. This design philosophy has been employed successfully in many of PB’s recent transportation tunnel projects (LA Metro, Taipei Metro, Seattle Metro, and Boston Central Artery/Third Harbor Tunnel). In these projects the two design events are termed as: • The Operating Design Earthquake (ODE), defined as the earthquake event that can reasonably be expected to occur during the design life of the facility (e.g., at least once). The ODE design goal is that the overall system shall continue operating during and after an ODE and experience little to no damage. • The Maximum Design Earthquake (MDE), defined as an event that has a small probability of exceedance during the facility life (e.g., 5 percent). The MDE design goal is that public safety shall be maintained during and after an MDE. Note, however, that the design criteria aimed at saving lives alone during a catastrophic earthquake are sometimes considered unacceptable. There are cases where more stringent criteria are called for under the maximum design earthquake, such as requiring rapid repairs with relatively low cost. A good example would be the existing San Francisco BART structures. As described in Chapter 1, BART warrants such stringent criteria because it has an incalculable value as possibly the only reliable direct public transportation system in the aftermath of a catastrophic earthquake. Therefore, the actual acceptable risk and the performance goals during and after an MDE depend on the nature and the importance of the facility, public safety and social concerns, and potential direct and indirect losses. 19
Page 1 and 2: 1991 William Barclay Parsons Fellow
Page 3 and 4: CONTENTS Foreword ix 1.0 Introducti
Page 5 and 6: Mononobe-Okabe Method 87 Wood Metho
Page 7 and 8: Figure Title Page 20 Typical Free-F
Page 9 and 10: LIST OF TABLES Table Title Page 1 F
Page 11 and 12: FOREWORD For more than a century, P
Page 13: 1.0 INTRODUCTION 1
Page 16 and 17: 1.2 Scope of this Study The work pe
Page 18 and 19: Figure 1. Ground Response to Seismi
Page 20 and 21: Ground Failure Ground failure broad
Page 22 and 23: - Formation of plastic hinges at th
Page 24 and 25: • The effects of overburden depth
Page 27 and 28: 2.0 SEISMIC DESIGN PHILOSOPHY FOR T
Page 29: 2.3 Seismic Design Philosophies for
Page 33 and 34: expressed in terms of internal mome
Page 35: Comments on Loading Combinations fo
Page 39 and 40: 3.0 RUNNING LINE TUNNEL DESIGN 3.1
Page 41 and 42: Ovaling or Racking Deformations The
Page 43 and 44: 3.3 Free-Field Axial and Curvature
Page 45 and 46: Simplified Equations for Axial Stra
Page 47 and 48: 3.4 Design Conforming to Free-Field
Page 49 and 50: Applicability of the Free-Field Def
Page 51 and 52: Figure 6. Sectional Forces Due to C
Page 53 and 54: - In the JSCE (Japanese Society of
Page 55 and 56: Design Example 2: A Linear Tunnel i
Page 57 and 58: 5. Derive the ground displacement a
Page 59 and 60: 10. Calculate the allowable shear s
Page 61 and 62: It is believed that the only transp
Page 63: Based on Equations 3-7 and 3-8, the
Page 67 and 68: 4.0 OVALING EFFECT ON CIRCULAR TUNN
Page 69 and 70: Figure 7. Free-Field Shear Distorti
Page 71 and 72: Figure 8. Free-Field Shear Distorti
Page 73 and 74: R = radius of the tunnel lining t =
Page 75 and 76: Lining Properties Soil Properties R
Page 77 and 78: The expressions of these lining res
Page 79 and 80: Figure 11. Lining Response Coeffici
Page 81 and 82:
Thrust Response Coefficient, K 2 Fi
Page 83 and 84:
Thrust Response Coefficient, K 2 Fi
Page 85 and 86:
Figure 15. Normalized Lining Deflec
Page 87 and 88:
Figure 17. Finite Difference Mesh (
Page 89 and 90:
Table 2. Cases Analyzed by Finite D
Page 91 and 92:
maximum bending moment than the no-
Page 93 and 94:
Table 3. Influence of Interface Con
Page 95:
5.0 RACKING EFFECT ON RECTANGULAR T
Page 98 and 99:
Third, typically soil is backfilled
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thrust that is approximately 1.5 to
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San Francisco BART In his pioneerin
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general, flexibility can be achieve
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• 254 ft/sec for case I • 415 f
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locations of roof and invert are ap
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Figure 25. Structure Deformations v
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Factors Contributing to the Soil-St
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As Figures 28A and 28B show, earthq
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Figure 28A. West Coast Earthquake A
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Figure 29. Design Response Spectra
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Figure 31. Relative Stiffness Betwe
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developed for a one-barrel frame wi
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• For flexibility ratios less tha
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where g s = angular distortion of t
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Structure Deformation Free-Field De
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Because the Poisson’s Ratios of t
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Table 5. Cases Analyzed to Study th
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In comparison with the results show
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Structure Deformation Free-Field De
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• Pseudo-Concentrated Force Model
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deformations result. Section 2.4 in
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Figure 40. Moments at Invert-Wall C
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Figure 42. Moments at Invert-Wall C
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Table 7. Seismic Racking Design App
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136
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• The more frequently occurring e
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Use of this method will lead to a c
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142
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Duddeck, H. and Erdman, J., “Stru
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Tunnels, Report No. UMTA-MA-06-0100
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Seismic Design of Tunnels - Parsons Brinckerhoff

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