Seismic risk management for water pipeline networks - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 627

5. If the bending angle is more than the critical angle, a new DCIP is

selected to obtain a greater critical bending angle θ cr than the calcu-

lated one.

6. If the bending angle is less than the critical angle, then calculate the

relative ground displacement

Δ u G in Equation (23.9).

7. Estimate the seismic displacement u of a single DCIP joint given in

Equations (23.6), (23.7), (23.8) and (23.11).
If the seismic displacement is less than the critical joint displace-
ment

Δ

joint , the seismic design of the unrestrained joint pipeline is
completed.
8. If the seismic displacement is greater than the critical joint displace-
ment, a new DCIP is selected to obtain a greater critical displacement
than the calculated one.
9. In case the pipe joint is restrained, non-linear structural analysis is
requested to obtain the seismic stress

Δ

σ ′

2 L at the joint.

10. If the seismic stress is greater than the critical stress σ cr , a new DCIP

is selected to obtain a greater critical stress than the calculated one. If
the seismic stress is less than the critical stress, the seismic design of
the restrained joint pipeline is completed.

Note that the JWWA method is not based on observed seismic damage data
of restrained and segmented joint pipes. Thus, it cannot be used as a seismic
safety-assessment procedure for restrained and segmented joint pipes in
Japan. To solve this diffi culty, a newly developed seismic assessment proce-
dure is proposed for restrained and segmented joint pipes, which is detailed
in the following subsection.

Seismic performance analysis of the new segmented joint

From the past earthquakes in Japan, because there are no extensive damage
data for restrained and segmented pipes, seismic performance analysis
needs to rely on an engineering mechanics-based theoretical approach.
Owing to the superior seismic performance of the new segmented joint,
water pipeline engineers often adopt this type of joint when the retrofi tting
action is planned. In this subsection, the ultimate strength of the new-type
joint of DCIP is investigated by the theoretical approach to obtain the
seismic capacity of this joint for the Level 2 ground motion (MCE) in Japan.
The axial force S that is necessary to pull out from the joint can be cal-
culated from the shear stress, which is sinusoidally distributed along the
pipe axis. If the shear stress τ G (i.e. shear stress acting between the pipe

surface and the surrounding ground) due to ground strain

ε G is less than

the critical shear stress τ cr , as shown in Fig. 23.6, slippage is initiated at the

pipe surface, and the maximum pull-out force is calculated from the shear