Hydrological study report

recommendations
The results of the hydrological study showed the possibility of re-establishing of
the bridge in the original position which is non perpendicular to the flood flow
channel. The study report also recommends the protection of the flood channel bed
in upstream and downstream the bridge for a distance of 20 m so that it
covers the flood channel bed and the foundation of the
bridge, as shown in Figure 10. The soil should be well
compacted before placing filter layer consist of 15 cm
sand followed by 15 cm gravel. The second layer of
protection consists of 50 cm typical thickness of hand
placed natural stone with mortar. As can be seen from
Figure 10, the west side level comply with the road level
Figure 10: Flood flow channel and bridge foundation protection.
Figure 9: X-Ray diffraction analysis for mortar samples from foundation and bridge.
(a) Mortar sample from foundation (b) Mortar sample
from bridge.
114 S. K. Elwan: Rehabilitation of Historic Railway Masonry Arch Bridge
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+(602.00)
0.90 6.06
3.22 1.50 0.40
3.00
4.72 1.34
2.06 2.06 2.06 2.06 2.06 2.06 2.06
1.12 0.55 0.55
2.96
0.15
0.32
Basalt stones 400mm. thick. Expansion Joint every 6 Arches (2472 mm.)
Continous RC Strip Footing
900mm. thick.
Hand Placed Stones with Mortar
20 meter behind and infront of bridge
Bored Piles rested on Dense Sand
with Diameter 500mm. & 600KN safe load
0.90 6.06
2.06 2.06 2.06 2.06 2.06 2.06 2.06
0.15
1.12 0.55 0.55
3.22
Bored Piles rested on Dense Sand
with Diameter 500mm. & 600KN safe load
Proposed Basalt stones flooring
50mm. thickness
Water Proof Membrane
with 80mm. screed for protection
Stabilized sand for Infill Layer
with specific density not more than 1.9 gm/cm3
Stainless Steel Dowels
Dia.=12mm.
every 400 mm. RC Shear Wall
300m. thick. at Expansion
Continous RC Strip Footing
900mm. thick.
Mortar Joints
According to Material report
Basalt stones
According to Material report
B B
C C
Section A-A
ELEVATION
0.32
0.32
Water Proof Membrane
with 80mm. screed for protection
Stabilized sand for Infill Layer
with specific density not more than 1.9 gm/cm3
Proposed Basalt stones flooring
50mm. thickness
Basalt stones
According to Material report
RC Shear Wall
Section B-B Section C-C
Continous RC Strip Footing
900mm. thick.
Stainless Steel Dowels
0.40 3.20 0.40
4.50
3.22
0.45
4.22 1.52
4.71 1.02
3.00
3.20 0.45 0.45 3.20 0.45
0.41
2.91
2.91
0.54
3.00
4.50
Figure 11: Proposed structural components
for the rehabilitated bridge.
S. K. Elwan: Rehabilitation of Historic Railway Masonry Arch Bridge 115
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Download Date | 5/31/16 12:57 AMwhile the east side account for the bed level of
the existing original part of the arch bridge which is in a good
condition and will be conserved as it is.
5 Conclusions
In this paper, guidelines have been presented for the
rehabilitation project of railway masonry arch bridge
located at Wadi Al-Aqeeq flood flow channel at AlMedina City. The historical
significance of the bridge
leads to the decision of reconstructing the bridge
which has collapsed during the flood of 1999. The new
usage of the bridge as a walkway bridge and the functional considerations for the
waterway openings result
in changing the original levels of the bridge and increasing the pier height.
Therefore, a 3-D finite element
model has been developed implementing the different
cases of loading to identify the level of stresses in structural elements. Also, a
complete soil investigation and
original material laboratory testing program have been
conducted to suggest the suitable foundation system
and the required material properties for all components
used in the rehabilitation project. A hydrological simulation was done to check the
non perpendicularity of the
bridge in its original position with respect to water
direction and the necking resulted from maintaining a
part of the bridge outside the flood flow to express the
geometrical properties of the original state of the bridge.
The adequacy of the waterway opening and any scour
potential has been considered. These complete intensive
structural studies have been integrated together to
establish the recommendations for the rehabilitation
project as follows:
1- The geometrical properties of the bridge have been
changed to fit the new usage as a waterway and
walkway.
2- Based on the finite element model, it was decided to
build the bridge with expansion joint every six
arches to eliminate the effect of temperature changes
to acceptable limits.
3- The results of the 3-D model also show the need to
implement reinforced concrete walls inside external
and internal piers due to high values of tensile stresses in the piers and to
ensure rigid joint with the RC
foundation avoiding movement of the bridge during
future expected high flood.
4- The foundation system is suggested to be raft strip
foundation with minimum thickness 800 mm rested
on a group of the drilled piles. The proposed foundation recommendation fit the
design requirements to
avoid soil scour under foundation level which was
the main cause of the bridge collapse.
5- The building material report recommends the use of
the original stone basalt resulting from the collapsed
bridge and to be completed with new stones having
the same properties. The report also recommends the
use of natural pozzolana together with ordinary
Portland cement as binding agents for the mortar.
It also recommends the use of superplasticizers to
increase workability and decrease water ratio to
avoid high porosity and increase density.
6- The hydrological study report also recommends the
protection of the flood channel bed in both upstream
and downstream the bridge for a distance of 20 m in
both directions to avoid any scour potential and
prevent undermining of the foundations.
Finally, on the basis of the previous concluding recommendations, the final
structural proposal for the bridge is
shown in Figure 11.
References
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century. Proceedings of the 4th International Masonry
Symposium, London, UK, 1995.
2. Melbourne C. Conservation of masonry arch bridges.
Proceedings of 9th I.B.Ma.C. International Brick-Block
Conference, Berlin, Germany, 1991.
3. Page J. Repair and strengthening of masonry arches.
Proceedings of IABSE Symposium on Structural Preservation of
the Architectural Heritage, Rome, Italy, 1993.
4. Broomhead SF, Choo BS. The British rail masonry arch bridge
assessment program. Proceedings of the 6th Canadian
Masonry Symposium, Saskatoon, Saskatchewan, Canada,
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5. Das PC. Examination of masonry arch assessment methods.
Proceedings of IABSE Symposium on Structural Preservation of
the Architectural Heritage, Rome, Italy, 1993.
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(3):204–13.
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249–79.
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Proceedings of the 6th Canadian Masonry Symposium,
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London: McGraw-Hill, 1991.
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