Lecture (Lum) 4.17.12 Concrete Culverts & Pipelines Designx

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29 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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Presentation by:




Howard Lum, P.E., S.E.

Design Criteria

AASHTO Design Standards

Concrete Box Culvert Design

Steel Pipe Design

Cut
-
and
-
cover Construction

Tunneling Methods

Loads:

California Building Code

Caltrans/AASHTO LRFD Standards

Concrete Box Culverts:

ACI 318 & AASHTO LRFD

Steel Pipes:

AWWA M11


Steel Pipe Design Guide

Concrete Pipes:

AWWA M9


Concrete Pressure Pipe

HS
-
20 (20
-
ton)
semi
-
truck

Axle Load (LL) =
32 kips

Wheel Load =
32k/2 = 16 kips

Max Impact =
30% of LL

Live Load diminishes
uniformly below grade

AASHTO equation:

LL1 = 4 kips / Z
1
2
(in ksf)

LL2 = 16 kips / Z
1
2
(in ksf)

ACI 318


LRFD

U = 1.2 (D + F + T) + 1.6 (L + H)

where D: Dead; F: Fluid/Water; T: Temperature;


L: Live; H: Soil/Ground Water

F

F


Determine Mu (moment), Vu (shear) and Pu
(axial) based on factored loads


Assume concrete section, As (reinforcement), f’c
(concrete compressive strength) & Fy (60 ksi)


Check Flexure:


Mn = 0.9 (As*Fy)*(d
-

a/2) > Mu


Check Shear:


Vn = 0.9 (Vc + Vs) > Vu


Check Axial Compression:


Pn = 0.7 Pn > Pu

Tire contact area (rectangle):

length in the direction of traffic = 10 inches

width of tire = 20 inches


Direction of Traffic

10”

20”

Internal Pressure
(Hoop Stress)

Min. pipe thickness


t = p*D/(2S)

p: internal pressure
(psi)

D: outside diameter

S: allowable stress
(20,000 psi)

External Loads

Wc (dead load) =

DH



Check

axial stress

and deflection

Deflection governs

as mortar lining is

rigid

with low

tolerance

Allow
. Deflection


= 2% of pipe D


Open excavation and temporary support prior to
pipeline installation

Advantages:

Conventional excavation equipment

Lower cost of construction

Exposed ground conditions

Disadvantages:

Access and Right
-
of
-
way issues

Disturbance to neighborhood

Traffic control

Environmental issues

25 feet

68 feet

18 feet

1.
Drill and Blast Tunneling

2.
Micro
-
tunneling

3.
Tunnel Boring Machine (TBM)

4.
New Austrian Tunneling Method (NATM) or
Sequential Excavation Method (SEM)




Micro Tunneling
TBM

Diameter ranges from 18” to
108” (9 ft)

Length
-

less than 1,500 feet

Straight drives between
shafts

Limitations:

Boulders and rocks

Very soft ground

Mixed face conditions

Construction debris or fill

Shaft construction

First TBM invented in 1846 for
Fréjus Rail
Tunnel

between France and Italy through

the Alps

Adaptable to various ground conditions

Hard Rock vs. Soft Ground TBM

Soft Ground TBM:

Earth Pressure Balance (EBP)


up to 7 bars
pressure

Slurry Shield (SS)


high pressure


Arrowhead Tunnel TBM’s