Lec 2

Report
Prepared by: Eng. Haider Mohammed Jasim
- Box culvert is hydraulic structure consisting of two
horizontal and two vertical slabs built monolithically are
ideally suited for a road or railway bridge crossing with high
embankments crossing a stream with limited flow reinforced
concrete rigid frame box culverts with square or rectangular
openings are used.
-Four-sided culverts are typically referred to as box
culverts made of single or multiple cells for passage of
fluid, usually storm water for small discharge single
ceiled box culvert is used and for larger discharges
multi ceiled box culvert can be employed.
- Precast reinforced concrete (RC) box culverts are very
common and usually constructed as single or multicell
culverts.
SINGLE AND DOUBLE CELL OF BOX
CULVERT
When the box culvert loading to test purpose , the first crack occurred at mid-span of the top panel at
approximately 124.5 kN.
This cracking load was comparable with the theoretical cracking load of 112.5 kN, computed
based on elastic behavior. The following cracking occurred at the negative moment region at the
top of the wall panels. Two cracks occurred simultaneously on both walls at approximately
142.3 kN. Final cracks occurred at the negative moment region of the top slab panel at
approximately 155.7 kN, the maximum load attained during the test. the figures below show location
and sequence of cracking. Occurrence of each crack was accompanied by an increase in mid span
deflection caused by stiffness degradation.
APPLICATIONS
Short-span bridges (over highways, waterways,
railways, for golf courses, etc.)
 Conveyance of storm water, sewage or
industrial wastes (storm drains)
 Provide for emergency egress, as with this
tunnel

BOX CULVERT USED AS ATUNNEL AND SHORT SPAN
GENERAL INFORMATION
- box culverts are economical due to their rigidity and
monolithic action and separate foundations are not
required since the bottom slab resting directly on the soil
serves as raft slab.
-Three side culvert Placed on strip footing
and
used for short span bridges but the
size of this
type grater than the four side
box culvert
project
Designs are dependent on
specifications and applications and the shape of
this type is (U) shape and some time takes (arc)
shape.
-Pre cast box culvert more suitable from cast -in -place
-Box culvert installing is easy and more control .
Design and Analysis
Design Criteria
- AASHTO Standard Specifications for Highway Bridges and wastewater
applications
-AREMA Manual for Railway Engineering
-ACI 318, for tunnels and special design and ACI 350R, for wastewater applications
Analysis Methods
- Finite Element Analysis
- Moment Distribution
- AREMA Chapter 8, Part 16 formulas
- Beam Formulas
- Reinforced Concrete Analysis
Design Procedure
1-Determine the applied loads using the appropriate design criteria.
2- Investigate load cases which will give the maximum positive and negative
bending moments in the walls.
3-Determine the maximum shear and bending moments using the selected
analysis method.
4-Calculate the required wall thickness and reinforcing steel area to satisfy
the appropriate design criteria.
FINDING DIMENSION OF BOX CULVERT
From manning formula:Q=
A
when R= the hydraulic radius .
S= the slope of channel .
And friction losses and losses of inlet and out let
:.
+k (inlet) + k(out let)
Obtaining :
(General equation to calculate the dimensions of box culvert(
-In this formula the cross section is taken square immediately and get the initial
dimension and then can find correct needed according to requirements of the project
- Initial value of thickness of box culvert assume by dividing the clear widthover twelve
and then correct this
thickness=
according to deflection or shear effect
thickness
ANALYSIS AND DESIGN OF BOX CULVERT
-The design span length and wall height should be based on the
centerline-of-member to centerline-of-member dimensions
-The structural design of a reinforced concrete box culvert
comprises the detailed analysis of the rigid frame for moments ,
shear forces and thrusts due to various types of loading condition
-The box culvert is analyzed for moments , shear force and axial
force due to various loading condition by any of classical
methods such as moment distribution , slope deflection and
column analogy procedures
- The used method in design is the working stress method to avoid
any crack because the any small crack can cause to erosion in
steel bar and then failure.
outlined below:.
1- The weight of embankment and deck slab and the track
load are considered to be uniformly distributed load on the
top slab.
weight of fill+
weight of live load and
Impact load + weight of top
concrete slab.
Weight of top slab=
density of concrete × thickness
of box culvert.
weight of fill =density of fill × the height from edge of street to the edge of top slab (N).
weight of live and Impact load
2- The self weight of two side wall acting as
concentrated loads are assumed to produce
uniform soil reaction on the bottom slab.
) total concentrated load )
The weight of two wall
3-The earth pressure on the vertical side walls of the
box culvert is computed according to the columns
theory.
W1= (weight of fill + weight of
live and impact load )
× factor of lateral earth
pressure .
W2=W1+ weight of column soil (density ×length of wall )
4- When the culvert is full with water the pressure distribution on
side walls is assumed to be triangular with a maximum pressure
intensity in the base ,Water Pressure Culverts should be designed
assuming static water pressure on the inside of the walls.
Water pressure =density of water
×height of water
5-The soil reaction on the bottom slab is
assumed to be uniform.
Reaction of soil= weight of top slab +weight of
two walls
THE LOADS APPLIEED CRITERIA
The load applied depend on :.
- The depth and the slope of fill and the types of soil
such as (saturated or partial saturated ) and the
condition of soil (passive or active or rest condition )
The type of live load applied according to the type of
street (highway, sub Street ,etc…) and also
Surcharge loads from nearby impact loads
- The level of water inside the box culvert( full water
box culvert , partial, and empty ) and the type of flow
in side of box culvert (laminar or turbulent flow )
- Seepage under foundation if occur the uplift
pressure applied on the floor of box culvert but
commonly the value of this pressure is very small .
- Seismic loads where applicable.
DESIGN BOX CULVERT IN EMPTY CASE AT
DEPTH (4.1m) :-
From manning formula
the dimension
(3×5.33×0.4 m)
After we calculate the
applied load from the case
of load we draw the load
diagram .
COMPUTE MOMENT DIAGRAM ACCORDING TO MOMENT
DISTRIBUTION METHOD .
-The effect of shear stress and axial
stress can be negligible
To design consider one way slab and find
reinforcement
Ø10@ 13 cm c/c
Ø10@
13 cm
c/c
Ø32@ 11.5 cm
c/c
Ø10@ 13 cm c/c
Ø28@ 12.5 cm c/c
-Minimum reinforcement in
Ø10@ long direction for
13 cm temperature
c/c
Ø32@ 11.5 cm c/c
Ø32@ 11.5 cm c/c
SPECIAL CASE WHEN STREET
SLOPING:-
-DIFFERENT DISTRIBUTION LOA
THIS CASE AND THE RESULT
MOMENT LARGER VALUE FROM
NATURAL CASE .

similar documents