Seismic Design Guidelines...design performed with reference to the JWWA-Guidelines and other standards in addition to this document. Design seismic ground motion settings should essentially

Seismic Design Guidelines

July 2013

Bureau of Waterworks

Tokyo Metropolitan Government

Contents

Chapter 1 General ............................................................................................................................................... 1

1. 1 Introduction .......................................................................................................................................... 1

1. 2 Range of Applications ........................................................................................................................... 1

Chapter 2 Fundamentals of Seismic Design ....................................................................................................... 2

2. 1 Procedure of Seismic Design ................................................................................................................ 2

2. 2 Setting Seismic Performance in Accordance with the Importance of the Water Supply Facility ......... 3

2. 3 Soil Survey ............................................................................................................................................ 3

2. 4 Design Seismic Ground Motion ............................................................................................................ 6

Chapter 3 Seismic Calculation Method of Distribution Reservoirs and Similar Structures .............................. 13

3. 1 General ............................................................................................................................................... 13

3. 2 Static Analysis ..................................................................................................................................... 15

3. 3 Dynamic Analysis ................................................................................................................................ 17

3. 4 Verification of Seismic Performance................................................................................................... 21

1

Chapter1 General

1．1 Introduction This document is a reference and source of information for seismic design decisions made by staff of the Bureau of Waterworks, Tokyo Metropolitan Government (hereinafter referred to as ‘the TMWB’) based on the Water Supply Facilities Earthquake Resistant Construction Method Guidelines and Explanation 2009 (hereinafter referred to as ‘the JWWA-Guidelines’). Moving forward, we would like to focus on high quality designs that are based on the performance designs targeted by the JWWA-Guidelines below:

(1) For design seismic ground motion, we want to extract ourselves from uniform horizontal

seismic coefficient or time-history waveforms, and determine the strictest seismic ground

motions for each individual structure; (2) We want to extract ourselves from static analysis and use dynamic analysis to perform designs that reflect

the actual conditions; (3) Appropriate analysis models and analysis conditions should be determined for each structure by the

responsible designers.

Seismic analysis in this document is purely a tool to assist designers make decisions during the design process. This is not to say that designers just need to follow this document and achieve the verification values enclosed, but that designers need to comprehend the limits of what can be expressed through seismic analysis, and use the seismic analysis to make a holistic judgement on the seismic capability of a facility. The TMWB will utilize this document for the foreseeable future and build experience with dynamic analysis and other factors of seismic design.

1．2 Range of Applications This document is mainly applicable for distribution reservoirs and similar structures of the TMWB. This document can also, however, be used as a reference for fundamental approaches to design seismic ground motion settings, applications of dynamic analysis and details of various kinds of analysis for structures other than distribution reservoirs and similar structures, such as ground-work tanks, shafts, covered conduits. However, structures other than distribution reservoirs and similar structures will have differing natural periods, facility distributions and seismic damage characteristics to distribution reservoirs and similar structures, so these factors should also be considered with design performed with reference to the JWWA-Guidelines and other standards in addition to this document. Design seismic ground motion settings should essentially be performed with consideration of the structure’s natural period, and analysis performed with reference to Seismic Impact, Seismic Calculation Method, and Verification of Seismic Performance in sections 3.3 and 3.4.4 to 3.4.6 of the JWWA-Guidelines.

2

Chapter2 Fundamentals of Seismic Design

2．1 Procedure of Seismic Design Water supply facilities are to be designed to achieve the seismic performance required dependent on the level of importance of the specific facility (seismic calculations are to verify that the respective facility achieves the required seismic performance). Seismic design of new facilities is to essentially adhere to the procedure identified in Fig. 2.1 below.

(1) Selection of construction site

…… Select site to construct facility.

(2)

Setting seismic performance in accordance with the importance of the water supply facility

……

Categorize water supply facilities by importance and determine the required level of seismic performance based on that importance. Refer to 2.2.

(3) Geotechnical investigation at construction site and soil survey of site

…… Perform as required based on the importance of the water supply facility and the soil and ground conditions of the selected site. Refer to 2.3.

(4) Selection of structural form and determination of facility specifications

…… Refer to the JWWA-Guidelines.

(5) Setting design seismic ground motion

…… Determine Level-1 and Level-2 design seismic ground motion. Refer to 2.4.

(6) Seismic calculation ……

Create a model of the structure and perform analysis using the appropriate seismic calculation method. Refer to 3.2 and 3.3 (distribution reservoirs and similar structures).

(7) Verification of seismic performance

…… Verify that the water supply facilities achieve the seismic performance specified in (2) above. Refer to 3.4 (distribution reservoirs and similar structures).

* Feedback is required for (5) to (7) based on investigation results.

Fig. 2.1: New Facility Seismic Design Flow For seismic diagnosis and design for seismic reinforcement of existing structures, perform (1) Survey of Facility Condition instead of (1) Selection of construction site above, and follow (7) Verification of Seismic Performance with (8) Reinforcement Design, and (9) Seismic Calculation and Verification of Seismic Performance Following Reinforcement.

3

2．2 Setting Seismic Performance in Accordance with the Importance of the Water Supply Facility The seismic performance required by facilities of different importance levels for the various levels of design seismic ground motion is shown in Table 2.4. In the level of importance at the TMWB, the distribution reservoirs and structures are classified as Rank A, and they shall be designed to secure seismic performance 1 against seismic ground motion of level-1, and seismic performance 2 against seismic ground motion of level-2.

Table 2.4: Seismic Performance of Distribution Reservoirs and Similar Structures by Importance

Design

Seismic

Ground

Motion

Seismic Performance

Seismic Performance 1 Seismic Performance 2 Seismic Performance 3

No loss of proper function due to earthquake.

No serious damage due to earthquake, limited repairs

required following earthquake, no significant

impact to function.

No serious damage due to earthquake. Repairs required following earthquake, but no significant impact to function.

Level-1 Seismic Ground Motion

Distribution reservoirs and similar structures of the

TMWB (Rank A)


Distribution reservoirs and similar structures of the

TMWB (Rank A)

2．3 Soil Survey

(1) Testing of Ground Dynamic Characteristics The following dynamic material values are required for ground response analysis (dynamic analysis). The various material values can be directly derived through testing and surveys.

i Poisson ratio ii Elastic wave velocity (longitudinal wave velocity Vp, transverse wave velocity Vs) or initial shear

modulus of rigidity (GO) iii Shear modulus of rigidity – strain relation (G / G0 - γ), attenuation constant – strain relation (h - γ)

(2) PS Logging (Elastic Wave Velocity Logging)

PS logging is a test procedure that enables the identification of detailed velocity distributions in the depth direction of boring locations. Deriving Vp and Vs from PS logging enables the indirect derivation of the ground Poisson ratio (ν), Young's modulus (E), and shear modulus of rigidity (G). Additionally, while it is preferable to measure surface ground natural period (TG) and ground shear wave velocity (Vs) from the elastic wave velocity logging or PS logging, these can also be predicted from the N value.

(3) Determine Survey Items to Match Analysis Conditions

Select survey items and methodology for the soil survey based on the type of structure and the ground characteristics. When surveys and indoor testing are determined by Japanese Industrial Standards (JIS) and The Japanese Geotechnical Society (JGS) standards, the surveys and tests are to be performed according to those defined standards.

4

Table 2.5: Comparison of Survey Items and Soil Tests

No Survey Item Symbol Unit Test Method (Standard)

Where Used in Design Analysis

Static Dynamic

1

On

-Locatio

n Testin

g

N Value N – Standard Penetration

Test (JIS A 1219)

Used for overall structure calculations

○ ○

2 Layer Thickness – m Ditto ○ ○

3 Groundwater Level – m Liquefaction judgment,

buoyancy ○ ○

4 Deformation Coefficient E0 kN/ m2

Hole Horizontal Load Test

(LLT) (JGS 1421) Earth spring constant ○ ○

5 Shear Wave Velocity Vp Vs

m/s PS logging

Ground natural period TG Poisson ratio ν

Young's modulus E0 Shear modulus of rigidity G

○ ○

6 Surface Layer Ground

Predominant Period and Amplification Ratio

Tp Ap

sec –

Microtremor measurement

Ground natural period TG △ △

7 Permeability Coefficient k – Site permeability test Drainage planning,

effective stress analysis, etc.

△ △

8 Ground Density in Direction of Depth

ρ – Density logging Ground dynamic analysis △ ○

9

Ind

oo

r Soil Testin

g

Weight per Unit Volume γt

γs kN/ m3

Soil Particle Density Test

(JIS A 1202)

Soil load and bearing capability calculations

○ ○

10 Moisture Content ω Soil Moisture Content

Test (JIS A 1203)

Void ratio (e), Degree of saturation (Sr)

○ ○

11 Wet Density ρt Soil Wet Density Test

(JIS A 1224)

Bearing capability, subsidence, soil pressure, slope stability calculation

○ ○

12 Average particle size D50 % Soil Particle Size Test

(JIS A 1204) Liquefaction judgment ○ ○

13 Fine Fraction Content

Ratio Fc %

Fine Fraction Content Ratio Test

(JIS A 1223) Ditto ○ ○

14 Cohesion

(Cohesive Soils) C

kN/m2 Soil Triaxial

Compression Test (UU) (JGS 0521)

Bearing capability, soil pressure, slope stability

calculation ○ ○

15 Angle of Internal Friction

(Sandy Soils) φ ° Ditto ○ ○

16 Plasticity Index Ip – Soil Liquid Limit and

Plastic Limit Test (JIS A 1205)

Liquefaction judgment, soil category

○ ○

17 Compression Index

(Cohesive Soils) Cc –

Soil Consolidation Test (JIS A 1217)

Consolidation settlement (e-logp graph)

△* △

18 Volume Compressive

Coefficient (Cohesive Soils)

mv – Ditto △* △

19 Shear Modulus Of

Rigidity/Initial Shear Modulus Of Rigidity

G/G0 – Repeated Load Triaxial

Test (JGS A 0542)

Repeated Load Hollow Cylinder Torsion Test

(JGS A 0543)

Dynamic deformation characteristics, seismic

response analysis △* ○

20 Attenuation Constant h – Ditto △* ○

21 Liquefaction Strength

Ratio R –

Repeated Load Undrained Triaxial Test

(JGS 0541)

Liquefaction judgment, liquefaction strength

characteristics evaluation, effective stress judgment

△ ○

Legend: ○: Often used; △: Sometime used; *: Nos. 17 - 20 used for 1-dimensional ground response analysis.

5

(4) Determining the Engineering Bedrock

The engineering bedrock is the bedrock used for seismic design when creating a model of the ground, and is a critical part of seismic design. The engineering bedrock spreads uniformly across the applicable site, and is assumed to be the upper surface of a ground layer with a much higher constant (remains linear) shear wave velocity than the upper ground layers. The engineering bedrock must be determined from a wider overall perspective, with ground information from surrounding sites utilized in addition to data for the applicable site. The engineering bedrock is the upper surface of a contiguous layer with an N value of 50 or above, and generally with a shear wave velocity of Vs ≧ 300m/s or higher. However, the engineering bedrock can be appropriately determined when there are detailed ground survey results available, and consideration must be given to individual site ground characteristics in the judgment. The engineering bedrock for seismic damage estimation in the Tokyo Regional Disaster Prevention Plan is set at Vs ≧ 500m/s or above, so when using Method 2 for Level-2 seismic ground motion (refer to 2.4), there may be the need to make assumptions concerning ground structure from ground survey depth to the engineering bedrock. This is because confirming the bearing layer (ground layer with targeted N value of 50 or higher, and where Vs is around 300m/s or higher) is the main purpose of standard ground surveys as part of the design process, and ground surveys down to where Vs ≧ 500m/s are rarely performed.

(5) Calculating Ground Natural Period There are two types of ground natural period; the natural period TG during normal periods (minimal strain), and the natural period TG’ during earthquakes (large strain). The former can be actually measured through PS logging and microtremor measurement. The latter can either be calculated using the convergent rigidity from the 1-dimensional ground response analysis results (refer to 2.4.4 (6)), or derived from earthquake observation records. When these are not possible, the ground natural period during normal times TG can be calculated from the N value, with shear wave velocity VS derived from Table 2.11. The ground natural period during an earthquake (TG’) is most important, however, to evaluate the ground’s behavior during an earthquake, so the fundamental approach is to calculate the ground natural period during an earthquake (TG’) when dynamic analysis is performed.

Suiteki-kun One Point Lesson Shear Wave Velocity and the Engineering Bedrock

Fig. 2.14: Shear Wave Velocity and the Engineering Bedrock

Engineering Bedrock Waveform

Earthquake Source Fault

Hypocenter

Ground Surface

Wave Propagation

Amplification

Ground Surface Waveform

Vs = 100 - 300 m/s

VS generally smaller in shallow layers.

VS increases with N-value.

Engineering bedrock used by the TMWB Vs = 300m/s or higher

Ground bedrock VS = 3000m/s ~ 6000m/s or higher

Engineering bedrock used for Tokyo metropolitan damage estimation VS = 500m/s or higher

6

2．4 Design Seismic Ground Motion

(1) Method of Determining Level-1 Seismic Ground Motion There are two methods of determining level-1 seismic ground motion in the JWWA-Guidelines; the conventional method of determining level-1 seismic ground motion (the method in the 1997 JWWA-Guidelines), and the economy verification is also examined. The fundamental stance of the TMWB is to utilize the conventional method for determining level-1 seismic ground motion for the seismic design of the TMWB’s water supply facilities.

(2) Flowchart for Determining Level-1 Seismic Ground Motion

The flowchart for determining level-1 seismic ground motion (static analysis) is shown in Fig. 2.21 below.

Fig. 2.21: Flowchart for Determining Level-1 Seismic Ground Motion (Static Analysis)

Conditions of relevant structures

Ground surface standard horizontal seismic coefficient Kh01

Type I Ground: 0.16

Type II Ground: 0.20 (Refer to Table 2.10 for ground types.)

Type III Ground: 0.24

Modification factor for zone CZ Tokyo: Cz=1.0

Above ground / underground

Structure design horizontal seismic coefficient Kh1

Kh1=Cz・Kh01

Engineering bedrock standard horizontal seismic coefficient

K'h01

Depth of structure center of gravity: Z

K'h01=0.15

Surface layer ground thickness: H


Kh1= Cz (Kh01－Z/H(Kh01－K'h01))

START

END

Above ground structures

Underground structures

Soil and ground conditions (ground type)

7

(3) Deriving Seismic Coefficient for Distribution Reservoirs and Similar Structures (Common for Level-1 and Level-2 Seismic Ground Motion) i Omission of Distribution Reservoirs and Similar Structure Natural Period Calculation

Distribution reservoirs and similar structures, in general, have high horizontal shear rigidity, and a relatively small natural period. Additionally, they are positioned close to the ground surface and so the ground surface acceleration is used as the design seismic coefficient (note from p.125 of the JWWA-Guidelines/Overall).

ii Categorization of Aboveground Structure and Underground Structure When the majority of the structure is underground (when around 2/3s of the structure is underground), use the design seismic coefficient at the center of gravity of the structure derived by linear interpolation of the seismic coefficient between the ground surface and the engineering bedrock (note from p.125 of the JWWA-Guidelines/Overall).

iii Structures Located Below the Engineering Bedrock

When the center of gravity of the structure is located below the engineering bedrock, use the standard horizontal seismic coefficient at the engineering bedrock for the design horizontal seismic coefficient.

iv Categorization of When to Use Seismic Coefficient Method or Seismic Deformation Method

The JWWA-Guidelines do not clarify when to apply the differing analytical methods in static analysis (p.59 of the JWWA-Guidelines/Overall). The analytical method should be selected with consideration for the ground conditions and structural characteristics of the relevant structure. The seismic coefficient method should be used when the inertial force will be the dominant factor, and the seismic deformation method should be used when the impact of ground deformation during an earthquake will be the dominant factor. When the relative impacts of the differing methods are not clear, use the seismic deformation method for structures that are more than around 10 m deep. Refer to 3.2.3 (1) for details of the categorization of the different analytical methods. This does not mean that the seismic deformation method is used for all underground structures, but that for those structures that are determined to be underground structures, the seismic deformation method should be used when it is determined that the impact of ground deformation during an earthquake will be the dominant factor.

(4) Method of Determining Level-2 Seismic Ground Motion

There are four methods in Table 2.9 for determining level-2 seismic ground motion in the JWWA-Guidelines. The TMWB determines level-2 seismic ground motion as shown below, categorized by dynamic analysis and static analysis. i Dynamic Analysis: Use Both Method 2 and Method 3, and Utilize a Minimum of Three Waveforms ii Static Analysis: Use the Greater Design Seismic Coefficient of Methods 2 and 4

Table 2.9: Method of Determining Level-2 Seismic Ground Motion (JWWA-Guidelines’ Stipulation)

Determination Method

Method 1 Evaluate seismic ground motion with an assumed hypocenter fault, and use the seismic ground motion at the respective location.

Method 2 Use the seismic ground motion from the relevant Regional Disaster Prevention Plan, etc.

Method 3 Use records of strong earthquakes with seismic coefficients of 6-upper to 7 for sites that have similar ground conditions (ground type).

Method 4 Design seismic coefficients and design response spectrum based on observations from the Southern Hyogo Prefecture Earthquake.

(5) Flowchart for Determining Level-2 Seismic Ground Motion (Static Analysis)

8

Fig. 2.25: Flowchart for Determining Level-2 Seismic Ground Motion (Static Analysis)

1-dimension ground response analysis

Soil and ground conditions (ground Type, etc.)

Determine ground surface standard horizontal seismic

coefficient Kh02

Structure characteristic coefficient CS

Above ground or underground


Kh2=Cs・Kh02

Depth of structure center of gravity Z

Method 4

Surface layer ground thickness H


Kh2= Cs (Kh02-Z/H (Kh02 - K'h02))

）

START

END

Above ground structures Underground structures

Engineering bedrock time history acceleration waveform for method 2 i. Northern Tokyo Bay earthquake ii. Tama Region Epicentral

Earthquake iii. Tachikawa Fault Earthquake

Ground surface standard horizontal seismic coefficient for method 4 Kh02

Type I ground: 0.70 Type II ground: 0.80 Type III ground: 0.60

* Use only for areas where an earthquake intensity of 6-upper or greater is predicted for the Tachikawa Fault Earthquake.

(Refer to (2) for details.)

Use the greater of the max. value from method 2 and the design horizontal seismic coefficient from method 4.

Ground surface standard horizontal seismic coefficient for method 2

Kh02=αmax／980 (αmax: Max. surface acceleration)

Method 2

①

②

⑤

⑩

⑪

⑩

⑫

③

④

⑥

⑨

Structure characteristic coefficient Cs Modification factor for zone CZ

Applied seismic ground motion

Method 2 Determine from the max. acceleration α'max

at the bedrock of the applied wave.

K'h02=α’max/980

Method 4

K'h02＝0.50

⑧

⑭

⑦

⑬

Use seismic ground motion determined at ⑥.

9

(6) Flowchart for Determining Level-2 Seismic Ground Motion (Dynamic Analysis) Follow the flowchart in Fig. 2.28 for dynamic analysis of level-2 seismic ground motion. Select a minimum of three waveforms to use as input seismic ground motion for the dynamic analysis.

Fig. 2.28: Flowchart for Determining Level-2 Seismic Ground Motion (Dynamic Analysis)

Selecting input seismic ground motion (method 2)

① Method 2 waveform Predominant waveform around ground natural period during earthquake (1st waveform)

Evaluation and study of soil

and ground conditions

START

END

1-dimension ground response analysis

Engineering bedrock time history

acceleration wave for method 2 (A)

Engineering bedrock time history acceleration

wave for method 3 (B: Epicentral type)

A-①: Northern Tokyo Bay Earthquake

(ward area *1)

A-②: Tama Region Epicentral

Earthquake (Tama region *2)

A-③: Tachikawa Fault Earthquake *3

B-①: Kobe Marine Observatory Bridge NS

B-②: JR Takatori Station NS

B-③: Higashi-Kobe Ohashi Bridge

N78E (GL-35m)

B-④: Port Island NS (GL-83m)

B-⑤: 2004 K-NET Tokamachi NS

B-⑥: 2007 Kariwa Village NS

Derive the ground surface velocity response spectrum for each waveform.

Selecting input seismic ground motion (method 3 epicentral type)

① Long period predominant Response speed period of around 0.8 - 2.0 sec.

② Short period predominant Response speed period of around 0.1 - 0.3 sec.

③ Predominant waveform around the ground natural period during earthquake Response speed around the ground natural period during earthquake

Calculate ground natural period TG from VS convergence value.

⑦

Sites on ground susceptible to liquefaction, soft ground, structures that would be influenced by sloshing (PC tanks), and areas that are expected to experience a seismic intensity of 6-upper or higher from the Genroku Kanto Earthquake will fall into the subduction-zone earthquake category.

Engineering bedrock time history

acceleration wave for method 3

(C: Subduction-zone type)

C-① 2003 K-NET Chokubetsu EW

C-② 2011 K-NET Hitachi NS

Selecting input seismic ground motion (method 3 subduction-zone type)

① Method 3 (subduction-zone type) waveform

Select waveform (minimum 1 waveform) with a predominant response velocity for the period band being evaluated (ground predominant period, storage water predominant period, structure predominant period, etc.).

When method 2 waveform broadly encompasses any or all of waveforms ①, ② or ③ from method 3, 2 waveforms are sufficient for method 3 epicentral-type.

*1. Tokyo ward area excluding Toshima ward, Kita ward, Itabashi ward and Nerima ward.

*2. Tama area, Toshima ward, Kita ward, Itabashi ward and Nerima ward are relevant areas.

*3. Use only for areas where an seismic intensity of 6-upper or greater is predicted for the Tachikawa Fault Earthquake.

10

(7) Level-2 Seismic Ground Motion – Method 2 (Regional Disaster Prevention Plan)

For level-2 seismic ground motion, select multiple seismic ground motion waveforms from Table 2.14 which show the seismic damage estimation, perform a 1-dimensional ground response analysis on those waveforms and select the one that has the greatest impact. Waveforms can be used directly for dynamic analysis. For static analysis, derive the ground surface standard horizontal seismic coefficient from the largest maximum surface acceleration value. For 1-dimensional ground response analysis, the basic approach is to use FDEL, DYNEQ or other analysis codes that can appropriately evaluate acceleration levels when shear strain is high.

Table 2.14: Input Seismic Ground Motion Waveforms (Select More than 1) for Method 2 1-Dimensional Ground Response Analysis

Earthquake Assumption Engineering Bedrock Surface

Maximum Acceleration Note

Northern Tokyo Bay

Earthquake* 697 gal

Tokyo ward area (exclude Toshima ward, Kita ward, Itabashi ward

and Nerima ward.)

Tama Region Epicentral Earthquake* 739 gal

Toshima ward, Kita ward, Itabashi ward, Nerima ward and Tama area.

Tachikawa Fault Earthquake

－ Use for areas with 6-upper earthquake.

*: Waveform with the maximum acceleration from all meshes (wave from with time history acceleration of Vs ≧ 500m/s at engineering bedrock surface.)

The hypocenters have not been determined for the Northern Tokyo Bay Earthquake, or the Tama Region Epicentral Earthquake, so similar earthquakes may have a hypocenter directly under any area of the metropolitan region. As a result of this, we must consider the worst case scenario for water supply facilities when using these as the design seismic ground motion, and use the waveform for the mesh directly above the hypocenter (consider that the hypocenter may be epicentral to water supply facilities). The locations of the hypocenters have been determined for the Tachikawa Fault earthquake and the Genroku Kanto earthquake, with those locations having specific characteristics. For this reason, use the waveform in the mesh at the location of the water supply facilities when using these earthquakes for design seismic ground motion (do not move the hypocenter, consider the damping of the seismic wave over distance from the hypocenter).

Northern Tokyo Bay Earthquake Tama Region Epicentral Earthquake

Fig. 2.16: Overview of Definitions when Using Predicted Earthquakes for Design Seismic Ground Motion

Tachikawa Fault Earthquake Genroku Kanto Earthquake

Fig. 2.29: Seismic Coefficient Distributions for Assumed Earthquakes

★ Hypocenter

Engineering Bedrock Surface

★ Hypocenter

Engineering Bedrock Surface Directly Above

Hypocenter

Facility Location Facility Location

11

(8) Waveforms to Use for Method 3 (Epicentral) For method 3 (epicentral) earthquakes, use the measured waveform data from the Hyogo Prefecture Nanbu Earthquake, Niigata Prefecture Chuetsu Earthquake or the Niigata Prefecture Chuetsu Offshore Earthquake shown in Table 2.18 and perform 1-dimensional ground response analysis. Select the following waveform based on those results. i Method 3-1: Short period predominant Choose 0 or 1 waveform.

Waveform where ground surface response velocity spectrum is predominantly 0.1 - 0.3 sec. ii Method 3-2: Long period predominant Choose 0 or 1 waveform.

Waveform where ground surface response velocity spectrum is predominantly 0.8 - 2 sec. iii Method 3-3: Ground natural period predominant Choose 0 or 1 waveform.

Waveform where ground surface response velocity spectrum is predominantly around TG’: the ground natural period during an earthquake.

There is no need to select the waveform in method 3 with the applicable period characteristics when the waveform from method 2 (predicted earthquakes in Regional Disaster Prevention Plan) is of a size that encompasses any of the waveforms from i. to iii. above. For this reason, there will be two to three waveforms selected in method 3 (epicentral earthquake)

Table 2.18: Input Seismic Ground Motion Waveforms for Method 3 (Epicentral Earthquake)

Earthquake Name Waveform Name Seismic Ground Motion

Characteristics Max. Accel.

Seismic Intensity

Measurement Location

B－①

1995 Southern Hyogo Prefecture Earthquake

Kobe Marine Observatory Bridge NS

Strong earthquake observation on solid ground

818 gal 6-Upper Ground surface

B－② JR Takatori Station NS Strong earthquake observation near seismic intensity 7 area.


B－③ Higashi-Kobe Ohashi Bridge N78E

Strong earthquake observation on soft ground

443 gal 6-Upper GL-35m

B－④ Port Island NS Strong earthquake observation on soft ground

679 gal 6-Upper GL-83m

B－⑤ 2004 Mid Niigata Prefecture Chuetsu Earthquake

K-NET Tokamachi NS Epicentral observation of predominantly short-period epicentral strong earthquake

1,716 gal 6-Upper Ground surface

B－⑥ 2007 Niigata-ken Chuetsu-oki Earthquake

Kariwa Village NS (Japan Meteorological Agency)

Epicentral observation of predominantly long-period strong earthquake


(9) Waveforms to Use for Method 3 (Subduction-Zone Type) Select a method 3 (subduction-zone type) waveform when any of the below are applicable: i Construction site has high risk of liquefaction, or on soft ground; ii Structure will be influenced by sloshing (PC tank); iii Facility is predicted to experience 6-Upper seismic intensity from Genroku Kanto Earthquake (refer to

Fig. 2.29). There is no need to select a subduction-zone type waveform when none of the above are applicable. For method 3 (subduction-zone) type, perform 1-dimensional ground response analysis on the observed waveforms for either of the earthquakes shown in Table 2.19; the 2003 Tokachi-Oki Earthquake and the 2011 Tohoku Region Pacific Coast Earthquake; and select the waveforms (1 or more) that have the same predominant period band response velocity as the object being evaluated (ground predominant period, storage water predominant period, structure predominant period, etc.).

Table 2.19: Input Seismic Ground Motion Waveforms for Method 3 (Subduction-Zone Type)

Earthquake Name

Waveform Name

Seismic Ground Motion Characteristics

Max. Acceleration

Seismic Intensity

Measurement Location

C－① 2003 Tokachi-Oki Earthquake

K-NET Chokubetsu

EW

Records of strong subduction-zone earthquake where long-periods were predominant.


C－② 2011 Tohoku Region Pacific Coast Earthquake

K-NET Hitachi NS

Records of strong subduction-zone earthquake where short-periods were predominant.

1,598 gal 6-Upper Ground surface

12

Table 2.33: Examples of Input Seismic ground motion Waveforms for Method 3 (Epicentral)

i Short period predominant

ii Long period predominant

iii Near ground natural period most predominant

JR Takatori Station NS is most predominant.

K-NET Tokamachi NS is most predominant.

Port Island NS is most predominant.

Waveforms to Use for Input Seismic Ground Motion

i. Short period:

K-NET Tokamachi NS

ii. Long period: JR Takatori Station NS

iii. Near ground natural period: Port Island NS

Takatori St. NS K-NET Tokamachi NS Port Island NS

Period (s)

Vel

oci

ty R

esp

on

se S

pe

ctru

m

(cm

/s)

Vel

oci

ty R

esp

on

se S

pe

ctru

m

(cm

/s)

Period (s)

Vel

oci

ty R

esp

on

se S

pe

ctru

m

(cm

/s)

Period (s)

K-NET Tokamachi NS Port Island NS Takatori St. NS

K-NET Tokamachi NS Port Island NS Takatori St. NS

13

Chapter3 Seismic Calculation Method of Distribution Reservoirs and Similar Structures

3．1 General

(1) Selecting Seismic Calculation Method

As shown in Table 3.1, static analysis, of which the TMWB has many design examples, is fundamentally used for seismic calculation methods for distribution reservoirs and similar structures. But for specific facilities, dynamic analysis can be used concomitantly. For new designs or reinforcement design (large scale facilities), cross-section design is performed using static analysis, and the cross-section is verified using dynamic analysis. Modify design cross-sections and repeat design calculations when the required seismic performance is not achieved in the dynamic analysis. However, static analysis is used in the seismic diagnosis to determine if seismic reinforcement design is required.

Table 3.1: Seismic Calculation Method of Distribution Reservoirs and Similar Structures

* Large scale facilities: Applicable to purification plants (capacity greater than 100,000 m3 per day) and water

stations (effective capacity greater than 5,000 m3 per day). In addition to the structures

above, verify distribution reservoirs and similar structures that have a capacity of 5,000 m

3 or above using dynamic analysis.

(2) Seismic Design Flowchart for Distribution Reservoirs and Similar Structures of the TMWB

The seismic design flowchart for the distribution reservoirs and similar structures of the TMWB is shown in Fig. 3.1. At the TMWB, dynamic analysis is performed for seismic ground motion of new designs or large-scale reinforcement design, and then the seismic ground motion that is the most severe for the applicable structure is used by looking at the ground response analysis of the various design seismic ground motions. The basic process is for the design cross section to be determined by static analysis, and for that to be verified via dynamic analysis. If the design cross section achieves unsatisfactory dynamic analysis results, the design cross section is redefined through static analysis. The dynamic analysis model is modified based on the new design cross section and the dynamic analysis verification repeated. This is to confirm that the new design cross section is satisfactory. The TMWB essentially uses 2D FEM for the dynamic analysis, and the FEM model must be modified if the design cross section is changed. There is a lot of time and effort involved in these cases, so care is taken to ensure that the design cross section will not need to be changed in dynamic analysis. One example of this is the use of nonlinear static analysis (pushover analysis). Pushover analysis is still a form of static analysis, but it directly verifies the nonlinear properties of the structure, in many cases achieving responses similar to dynamic analysis. In this way, re-verification through pushover analysis of the design cross section determined through linear static analysis can minimize modifications of the cross section at the dynamic analysis stage.

Design Seismic Ground Motion

(Target Seismic Performance) New Structure

Existing Structure

Seismic Diagnosis Seismic

Reinforcement Design

Seismic Reinforcement

Design (Large Scale Facilities

*)


(Seismic Performance 1)

Static analysis (linear)





(Seismic Performance 2)


Dynamic analysis (non-linear)




Dynamic analysis (non-linear)

14

Fig. 3.1: Seismic Design Flow

Collect documentation, survey site,

soil survey, etc.

Setting design seismic ground motion

Level 1: Conventional method

Level 2:

Dynamic analysis: methods 2 & 3

Static analysis: methods 2 & 4

Perform ground response analysis

Input waveform (methods 2 & 3)

Seismic design from static analysis (L2)

All cross sections

Use greater value from method 2 and 4

for L2 horizontal seismic coefficient

For above ground distribution reservoirs

and similar structures

Ground surface acceleration ÷ 980

= Std. horizontal seismic coefficient*

Dynamic analysis verification (L2)

Analyze design cross section determined

through static analysis

Min. 3 waveforms from method 2 and

method 3 for input seismic ground

motion.

2-3 representative cross sections are

used.

Determine design cross section

Large scale facility

Applicable.

Reinforcement design from static analysis

Seismic ground motion levels 1 & 2

N/A

Dynamic analysis verification (L2)

Analyze design cross section determined

through static analysis

Min. 3 waveforms from method 2 and

method 3 for input seismic ground

motion.

Determine reinforcement cross section

END

START

Existing

Seismic diagnosis from static analysis

Seismic ground motion levels 1 & 2

New

Verify seismic performance

OK

NG

Ou

tsou

rce executio

n d

esign

Ou

tsou

rce Seismic D

iagno

sis

O

utso

urce Seism

ic Re

info

rcem

ent

Outsource soil survey

Seismic design from static analysis (L1)

All cross sections

For above ground distribution reservoirs

and similar structures:

Ground surface acceleration ÷ 980

= Std. horizontal seismic coefficient*

Verify

OK

NG

New/Existing


Level 1: Conventional method

Level 2:

Static analysis: methods 2 & 4

Verify


Level-2 seismic ground motion

Dynamic analysis: methods 2 & 3

Perform ground response analysis

Input waveform (methods 2 & 3)

OK

NG

*: As per p. 125 of Overall section of the JWWA-Guidelines, no requirement to natural period of distribution

reservoirs and similar structures.

15

3．2 Static Analysis (1) Static Analysis Procedures

Constructing Analysis Model Determine analysis model (linear/nonlinear; 2D/3D) Create analysis model (structure model/ground model) Load calculation

Fig. 3.7: Design Flow for Static Analysis

*1: Calculation of natural period not required for distribution reservoirs and similar structures.

Yes

No No

3.4

START

Determining water supply facility importance Determining target seismic performance Calculating ground natural period Judging ground type Selecting structure type Selecting foundation type Determining facility specifications

Select analysis method

Initiation stress ≦ allowable stress

Seismic coefficient method Seismic deformation method

Calculating structure natural period *1

Determining horizontal seismic coefficient

L1: Conventional method

L2: Greater of method 2 or 4

Method 2: Acceleration response spectrum defined in

Regional Disaster Prevention Plan

Method 4: Acceleration response spectrum from

JWWA-Guidelines

Determining design displacement amplitude

L1: Uh method

L2: Greater of method 2 or 4

Method 2: Ground response analysis

Method 4: JWWA-Guidelines: Uh method

Surface layer ground natural period used for the Uh

method is to be determined using calculation method from

3.2.4 (vii) Ground Displacement Amplitude.

Seismic Coefficient Method

Normal loading:

Fixed load, full load, earth pressure, water pressure, buoyancy

Load during earthquake: Inertia force, hydrodynamic pressure, earth pressure

Seismic Deformation Method

Normal loading:

Fixed load, full load, earth pressure, water pressure, buoyancy

Load during earthquake: Inertia force, hydrodynamic pressure, ground displacement, peripheral shear force

Setting design seismic coefficient Setting design seismic coefficient

Structure calculations (structure, foundation piles) (Normal, Level-1 seismic ground motion)

Verify sectional force (Normal, Level-1 seismic ground motion) Calculate initiation stress (bending, shear, axial)

Structure calculations (structure, foundation piles) (Level-2 seismic ground motion)

Verify Sectional Force (Level-2 seismic ground motion) Calculate response value for verification Sd, Limit value for verification Rd

γi: Sd/Rd ≦ 1.0 (γi: Structure coefficient)

END

Ch

ange to

material sectio

n an

d stru

cture

Ch

ange to

material sectio

n an

d stru

cture

Laying depth Generally down to less than 10 m.

Laying depth Generally down to depth greater than 10 m.

Yes

No No

2.4 2.4

3.2

3.2

3.4

16

(2) Acquiring Load During Earthquake (Example)

GL

GL

慣性力の作用方向

▽

▽

③

柱柱隔壁

②

①

①⑦ ①

⑧①

⑧④⑤

③

④ ⑤

⑦⑦ ⑦

常時荷重図

地震時荷重図

⑤

⑥

①

②

① ① ① ① ①

①

④④ ④

Fig. 3.22: Examples of Obtaining Earthquake Loading (Seismic Coefficient Method)

Normal Load

Load During Earthquake

Direction of Action of Inertial Force

Pillar Pillar Barrier Wall

Earth Pressure: Use of modified Mononobe-Okabe formula Hydrodynamic Pressure: Use of Westergaard's formula Soil Spring / Pile Spring: Use of formula from section IV on substructure work in Specifications for Highway

Bridges (Japan Road Association, March 2012) Buoyancy: Calculate buoyancy during earthquake categorizing non-liquefied and liquefied layers (Sewage

Facility Seismic Design Examples of Calculations for Processing Plants and Pump Plants (Ver. 2); Japan Sewage Works Association, 2002)

17

3．3 Dynamic Analysis

(1) Dynamic Analysis Procedures

解析計画

設計条件の設定

動的解析手法の選定

解析モデルの構築

池状構造物の動的解析· 常時応答値の算定· 地震時応答値の算定

照査用応答値Sdの算定

照査用限界値Rdの算定

γiSd／Rd≦1.0γi：構造物係数

解析の目的，対象，範囲，評価する地震の影響，照査項目

構造物・基礎・地盤・液体の条件決定等

END

部材／構造の変更

YES

NO

静的解析による耐震計算

地盤応答の分析（1次元地盤モデルの動的解析）

（地盤応答の比較）

計算法，次元，モデル

構造・地盤のモデル化，入力地震動・境界条件の設定等

解析結果の妥当性評価

３.３

３.３

３.３

３.３

３.３

３.３

３.２

設計地震動

２.４

３.４

START

Fig. 3.1: Design Flow for Dynamic Analysis

(2) Selection of Differing Analysis Model System As part of the dynamic analysis of distribution reservoirs and similar structures, it is important to appropriately evaluate the effects of the dynamic interaction between the structures and the ground during an earthquake, as there is significant contact between the structures and the ground over a wide area. Table 3.1 shows the methods to express the dynamic interaction in the ground and structure analysis models system, and the standards used for the dynamic analysis of the TMWB’s distribution reservoirs and similar structures. The model system essentially consists of the independent structure model expressed using a spring model of the boundary of the structure and the ground, and the combined ground-structure model expressed through an FEM model of the earthquake behavior of the entire surface ground layer (shallower than the engineering bedrock).

be evalua 整Ɽ瘠牥晩捩瑡潩瑩浥

敲瑡潭敤獬映牯猠牴捵畴

敲愠摮朠潲湵㭤搠瑥牥業

敮椠灮瑵猠楥浳捩洠瑯潩

氠浩瑩挠湯楤楴湯ⱳ攠

coefficient Analysis aims, objects, range, impact of earthquakes to

Analysis Plan

Setting design conditions

Analysis aims, objects, range, impact of earthquakes to be evaluated, verification items

Static analysis earthquake

calculations

Design earthquake

seismic ground motion

Selecting dynamic analysis method

Constructing analysis

model

Dynamic analysis of distribution reservoirs and similar structures Calculate normal response value Calculate response value during

earthquake

Change

material/structure

(Compare ground response) Evaluate validity of analysis

results

Calculate verification response value Sd

Calculate verification limit value Rd

Determine structure, foundation, ground, liquid conditions, etc

Calculation methods, dimensions, models

Create models for structure and ground; determine input seismic ground motion, limit conditions, etc. Ground response analysis

(1-dimensional ground

model dynamic analysis)

ϒiSd/Rd ≦ 1.0 ϒi: Structure coefficient

18

Table 3.11: Types of Models for Distribution Reservoirs and Similar Structures and the TMWB Standards

Analysis Models

TMWB Standards Structure Models

Ground Models

Nonlinear Ground

Properties General Image

Combined Ground- Structure

Model

Facilities in Su

rface Gro

un

d Layer

Facilities Where

Liquefaction is Not a Concern

Beam model or

FEM model

FEM Model

Use total stress model

地震動

全応力モデル

工学的基盤面

Facilities Where

Liquefaction as a Concern

Use effective stress model

地震動

全応力モデル

工学的基盤面

有効応力モデル

全応力モデル

液状化

Independent Structure

Model

Facility in Solid Ground

Spring model

Use total stress model

地震動

工学的基盤面

The fundamental approach of the TMWB is to use the combined ground-structure model. For distribution reservoirs and similar structures that will not be impacted by the surface layer ground, for example, those structures that are on engineering bedrock-like solid ground, an independent structure model is used as there will be limited influence from dynamic interaction between the ground and the structure, and displacement of the structure will essentially not be an issue.

(3) Selection of Calculation Methods

The methods available to calculate dynamic response values (dynamic analysis methods) are the time history response analysis method and the spectrum method. For time history response analysis, there is direct integration, response analysis in frequency domain, and mode analysis. Direct integration is the main type of time history response analysis used for dynamic analysis of the TMWB’s distribution reservoirs and similar structures, as nonlinear response needs to be derived to verify seismic performance 2 for level-2 seismic ground motion, and because the aim is to evaluate accumulated time-history displacement.

(4) Constructing Analysis Model

An outline for constructing an example of a combined ground-structure model for dynamic analysis of the TMWB’s distribution reservoirs and similar structures is shown in Fig. 3.35. For dynamic analysis of distribution reservoirs and similar structures, the behavioral characteristics of the structure and the ground during an earthquake need to be fully comprehended and the following items verified. It is important to construct a suitable model for each facility to be verified. Refer to the main document for the details of each item.

Main Items for Constructing Analysis Models

Determining input seismic ground motion Creating structure model Creating model of water in the structure Determining damping conditions Modelling of other details

Modelling of the ground Modelling of ground-structure interface Determining boundary conditions Determining drainage conditions

Total Stress Model

Engineering bedrock

Liquefaction

Total stress model

Effective stress model

Total stress model

Engineering bedrock

Seismic ground motion


Seismic ground motion Engineering bedrock

19

Fig. 3.35: Samples for Constructing Analysis Model (Combined Ground-Structure Model)

For

Co

mb

ined

Gro

un

d-S

tru

ctu

re M

od

el

Bas

e vi

sco

us

bo

un

dar

y

Bea

m e

lem

ents

Jo

ints

(Sp

rin

g el

em

ents

)

Liquefied layer Non-liquefied layer

B [

Effe

ctiv

e st

ress

mo

del

]

Ac

[To

tal s

tres

s m

od

el]

Dc1

[To

tal s

tres

s m

od

el]

As

[Eff

ecti

ve s

tres

s m

od

el]

Asg

[Ef

fect

ive

stre

ss m

od

el]

Dsg

[To

tal s

tres

s m

od

el]

Dc2

[To

tal s

tres

s m

od

el]

Engi

nee

rin

g b

edro

ck

H

ori

zon

tal r

olle

r b

oun

dar

y, v

isco

us

bo

un

dar

y, s

imila

r fr

ee b

ou

nd

arie

s, e

tc.

E

nsu

re s

uff

icie

nt

late

ral a

rea.

[Fo

r ex

amp

le, f

ive

tim

es t

he

vert

ical

dis

tan

ce.]

Bo

un

dar

y C

on

dit

ion

s (L

ater

al)

3-D

imen

sio

nal

C

on

sid

erat

ion

s

Bra

ce s

ub

stit

uti

on

me

tho

d

Wal

l ele

me

nt

sub

stit

uti

on

m

eth

od

Fi

nit

e e

lem

en

t m

eth

od

Rig

id

zon

es

Mo

del

ling

of

EXP.

J

No

nlin

ear

sp

rin

gs

Tran

smis

sio

n o

f co

mp

ress

ive

forc

e o

nly

Be

am e

lem

en

ts

Rig

id b

eam

No

de

s

Mat

eri

al

thic

kne

ss

S

pri

ng

elem

ents

(T

ran

smis

sio

n o

f co

mp

ress

ive

forc

e o

nly

)

Inp

ut

Seis

mic

Gro

un

d M

oti

on

T

ime

his

tory

acc

eler

atio

n w

avef

orm

Ap

ply

2E

wav

e to

en

gin

eeri

ng

bed

rock

Fo

r th

e gr

oun

d s

urf

ace,

per

form

inve

rse

amp

lific

atio

n a

nal

ysis

on

1-d

imen

sio

nal

gro

un

d

mo

del

to

ret

urn

to

bas

e gr

ou

nd

surf

ace

wav

efor

m.

Acceleration (gal)

Tim

e (

sec)

Dam

pin

g

H

yste

reti

c d

amp

ing

of

tota

l sys

tem

: aut

om

atic

ally

co

nsi

der

ed d

ue

to n

on

linea

r hy

ster

etic

ch

arac

teri

stic

s.

T

ota

l sys

tem

vis

cou

s d

amp

ing:

con

sid

ered

in R

eyle

igh

dam

pin

g

S

ub

terr

anea

n ra

dia

tio

n d

amp

ing:

co

nsi

der

ed in

vis

cou

s b

ou

nd

ary

Bo

un

dar

y C

on

dit

ion

s (B

ase

)

V

isco

us

bo

un

dar

y

Gro

un

d M

od

els

N

on

-liq

uefi

ed la

yer:

to

tal s

tres

s m

od

el

L

iqu

efie

d la

yer:

eff

ecti

ve s

tres

s m

od

el

N

on

linea

r m

od

el [

Tota

l str

ess

mo

del

]

H-D

Mo

del

, R-O

Mo

del

No

nlin

ear

mo

del

[Ef

fect

ive

stre

ss m

od

el]

S

and

elas

topl

asti

c m

od

el (

Oka

mo

del

, etc

.)

D

ynam

ic d

efor

mat

ion

char

acte

rist

ics

S

trai

n d

epen

den

t re

lati

on

ship

of

shea

r m

od

ulu

s

of

rigi

dity

G a

nd

dam

pin

g co

nst

ant

h

Shea

r st

ress

Sk

elet

on

cu

rve

Shea

r st

rain

γ

Hys

tere

tic

curv

e

Mo

del

ling

of

Gro

un

d-S

tru

ctu

re

Inte

rfac

e

Use

joi

nt

elem

ents

to

exp

ress

det

ach

men

t o

r sl

idin

g,

etc.

, in

th

e gr

ou

nd

-str

uct

ure

co

nta

ct

surf

ace.

Stru

ctu

re, F

ou

nd

atio

n P

ile M

od

els

B

eam

(M

φ)

elem

ents

[ A

pp

ropr

iate

no

nlin

ear

eval

uat

ion

]

No

nlin

ear

mo

del

Ske

leto

n cu

rve:

tri

-lin

ear

mo

del

(A

pp

rop

riat

ely

eval

uat

e sp

lits

and

crac

ks,

yie

ld, a

nd

pro

of s

tres

s)

H

yste

reti

c cu

rve:

mo

difi

ed T

aked

a m

odel

,

tri

-lin

ear

mo

del

(M

asin

g ru

le)

C

on

tain

ed w

ater

: ad

ded

mas

s m

ode

l

20

(5) Determining Input Seismic Ground Motion i Types of Seismic Ground Motion

Define design seismic ground motion and input seismic ground motion to be used for dynamic analysis of distribution reservoirs and similar structures as shown in i. and ii. below. A design seismic ground motion will be determined from advance investigation, and from this, an input seismic ground motion that can be directly input to the analysis model needs to be determined to perform dynamic analysis of the distribution reservoirs and similar structures. A time history acceleration waveform is to be used for the input seismic ground motion. (i) Design Seismic Ground Motion

This is determined in section 2.4 of these guidelines. This is the seismic ground motion that is determined prior to constructing the analysis models used for seismic calculations of the distribution reservoirs and similar structures. This is the seismic ground motion waveform that has not been aligned with the analysis models and code that will be used for distribution reservoirs and similar structure seismic calculations.

(ii) Input Seismic Ground Motion This has been aligned with the analysis models and code for the distribution reservoirs and similar structures, and is a seismic ground motion that can be directly input into the models (time history acceleration waveform). This may be a conversion of a design seismic ground motion as required. For example, in cases where the design seismic ground motion is the E + F waveform at the engineering bedrock, the input seismic ground motion can be determined by converting this into a 2E wave, for example, that does not accept impact of surface layer ground (does not include reflective wave), for the analysis model.

ii Methods to Input Seismic Ground Motion

As shown in Fig. 3.37, dynamic analysis of distribution reservoirs and similar structures is done upwards of the engineering bedrock, with the input seismic ground motion applied to the engineering bedrock, in the 1-dimension ground FEM model and the 2-dimension combined ground-structure model. When analysis is performed on the independent structure model, the time history acceleration waveform at the ground surface is applied to the various elements and nodes of the structure.

地震動工学的基盤面

液状化

地震動地震動

Fig. 3.37: Methods to Input Seismic Ground Motion

Incident wave (E) and Reflective wave (F)

The seismic wave is the sum of the incident wave (E) from the hypocenter, and the reflective wave (F) from the surface layer ground. The reflective wave from the surface layer ground is not present at the ground outcrop, so the reflective wave and the incident wave are the same, resulting in a seismic wave of 2E.

Fig. 3.38: Incident Wave (E) and Reflective Wave (F) Source: Page 35, Introduction to Civil Structure Seismic Design (Japan Society of Civil Engineers, 2002)

(

基盤

)(

表層地盤

)

E + F

2E0

E0F0 E0

入射波E

反射波F

露頭2E

E F E)

地震波

Liquefaction

Engineering Bedrock

Outcrop 2E

Incident Wave

E

Reflective Wave

F

Gro

un

d

Surface layer gro

un

d

Seismic Wave




21

3．4 Verification of Seismic Performance

(1) General

The seismic performance of the TMWB’s facilities is determined by the design seismic ground motion and the importance categorization of the facility (refer to 2.2). The critical state for various seismic performances are outlined below. i The critical state of seismic performance 1 shall appropriately be decided within a range in which the

mechanical characteristics of the respective components of the water supply facility do not exceed the elastic region as a result of an earthquake.

ii The critical state of seismic performance 2 shall appropriately be decided within a range in which the components of the water supply system do not give a serious impact to the facility and can easily recover even though plastic deformation of the component of the water supply facility has occurred.

iii The critical state of seismic performance 3 shall appropriately be decided within a range in which the components of the water supply system do not give a serious impact to the facility and can recover even though plastic deformation of the component of the water supply facility has occurred.

Verification of seismic performance shall be conducted by verifying that the state of the respective components which show a change due to design seismic ground motion does not exceed the determined critical state of the respective components. The relationship between seismic performance and critical state, damage state and limit value for verification are shown in Table 3.14 and Fig. 3.53. The limit value for verification shall be determined corresponding to the determined seismic performance and the relevant seismic ground motion.

Table 3.14: Seismic Performance and Critical State, Damage State and Limit Value for Verification

Seismic Performance Seismic Performance 1 Seismic Performance 2 Seismic Performance 3

Critical State *1 Critical State 1

(less than yield resistance)

Critical State 2 (less than maximum load bearing

capacity)

Critical State 3 (less than final displacement and

shear capacity)

Damage State

No damage or no water leak even though a crack is generated. No need to repair.

Slight crack and water leak occur but recovery can be quickly made after earthquake.

Crack width expands and water leaks but entire facility does not collapse. Can be repaired.


Rank A – –


– Rank A –

Limit Value for

Verification*2

Static Analysis

Stress ≦ Allowable stress

Sectional force (bending) ≦ Max yield bending resistance

Sectional force (shear) ≦ Shear capacity

–

Dynamic Analysis

–

Curvature ≦ Curvature at maximum load bearing capacity

Sectional force (shear) ≦ Shear capacity

–

*1： Critical State ･･･ Critical state is evaluated by verifying that the state of damage of each of the materials of the structure

is within the critical state for each material.

*2： Limit Value for Verification

･･･ In addition to the limit values shown in the table, allowable crack width and allowable water leak volume, amongst others, can be used to directly verify watertightness. Additionally, level of deformation to assure water stopping performance of waterstops and other similar structures are options for expansion joint verification. Limit values for verification for each material do not need to be consistent across the entire structure, with different limit values identified for each material to correspond to the seismic performance of the structure as a whole.

22

Fig. 3.53: Relationship between Seismic Performance and Critical State and Damage State

(2) Judging Failure Mode Material failure modes are essentially bending failure or shear failure. It is important that shear failure mode is avoided, even when there is damage as a result of an earthquake, to prevent brittle failures and also to endure the proper toughness of the materials. The JWWA-Guidelines do not specify about failure mode judgment, but the TMWB judges failure mode as per Table 3.16 for new designs, seismic diagnosis, and for reinforcement design.

Table 3.16: Judging Failure Mode

Category Judgment Location Judging Failure Mode

New Design Linear End of member

Judge failure mode and confirm that it is bending failure.

Nonlinear Location where plastic hinge occurs

As above

Existing Seismic Diagnosis

Linear End of member

As above

Seismic Reinforcement Design

Linear End of member

Judge failure mode. Make overall judgment on failure mode reinforcement based on importance of facility, structural characteristics, constraints of construction, economics, etc., and determine whether reinforcement is required, and the necessary timing.

Nonlinear Location where plastic hinge occurs

As above

Bend Crack Point C

Yield Point Y

Max. Load Bearing Point M

End Point N

Seismic

Performance 2

Seismic

Performance 1

Damage

Level 1

Cri

tica

l Sta

te 1

Cri

tica

l Sta

te 2

Cri

tica

l Sta

te 3

Damage

Level 2 Damage Level 3 Damage Level 4

Bending Moment

Curvature

Mc

My

Mm

φc φy φm

Material Curve M-φ

φn

Seismic

Performance 3

Documents

Seismic Design Guidelines...design performed with reference to the JWWA-Guidelines and other standards in addition to this document. Design seismic ground motion settings should essentially