precast concrete closed spandrel arch bridge system as viable alternative to conventional beam...
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Precast Concrete Closed Spandrel Arch Bridge System As Viable
Alternative to Conventional Beam Bridge System
Chong Yong Ong1, a, Kok Keong Choong1,a, Geem Eng Tan2, b, Tai Boon Ong2,b 1School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal,
Seberang Perai Selatan, Pulau Pinang, MALAYSIA
2Rivo Precast Sdn Bhd, Lot 5127, Batu 6, Jalan Kenangan Off Jalan Meru, 41050 Klang, Selangor
Darul Ehsan, MALAYSIA
Keywords: precast closed spandrel arch bridge system, corrugated arch section, conventional beam bridge system, crown beam.
Abstract. A precast concrete closed spandrel arch bridge system developed for river crossing in
Malaysia is presented. The 7.1m clear rise and 20.1m clear span overfilled arch bridge was proposed.
Conventional beam bridge construction system has been ruled out due to the handling difficulty and
cost factors. A structurally efficient precast arch section with corrugated shape was conceptualized,
designed and developed. The economical viable solution adapted was a precast closed spandrel arch
bridge system consisting of two connecting half-leaf panels with insitu crown beam. This system has
been proven effective featuring simple precasting technique, handling process and practical jointing
system at the crown. Comparisons between Precast closed spandrel arch bridge system and
conventional beam bridge system is also highlighted.
Introduction
Bridges have been categorized as an important road structure which function as crossing over
rivers or valleys. For the past centuries, arch bridges was fully used as transport network system to
connect cities or countries. The most common arch bridge construction materials are stone, timber,
iron and steel. Due to the unbelievable durability and appealing aesthetic, many of these arch bridges
are still in service conditions.
The development of reinforced concrete since late of 18th
century by Francois Hennebique has
brought the innovation to current concrete structures [1]. One of the current trend is to prefabricate
components which is cost effective and short in construction period. Enchanted by the great features
of precasting techniques, it has been applied as a solution to bridge construction.
Conventional Beam Bridge System
Beam system has been extensively used in many countries covering from short to medium span
from 5m to 50m. For a simple supported beam under point load as shown in Figure 1(a), as the span
increases, the bending moment increases. This relationship can be illustrated in Figure 1(b). In cross
section design using stress block concept, bending moment is directly proportional to the lever arm
between resultant force of concrete in compression zone and steel in tension zone (Equation 1).
Hence, it may result in bigger, thicker and bulky cross section as span increases. Figure 2 shows the
different type of beam sections based on their respective span range. This system is basically suitable
for lower rise bridge requirement projects.
Applied Mechanics and Materials Vol. 802 (2015) pp 261-266 Submitted: 2015-04-29© (2015) Trans Tech Publications, Switzerland Revised: 2015-05-20doi:10.4028/www.scientific.net/AMM.802.261 Accepted: 2015-05-20
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TransTech Publications, www.ttp.net. (ID: 175.137.187.239-13/10/15,15:45:05)
(a) (b)
Figure 1: Structural Behaviour of Beam Bridge Under Point load: (a) Free Body Diagram, (b)
Bending Moment Diagram
M = Fst x z (1)
Where, M = Bending Moment
Fst = Resultant force of tensile steel
Z = lever arm between resutant force of concrete
in compression zone and steel in tensile zone
Figure 2: Precast Beam Types and Span Ranges [2]
Description of Project
A bridge system was proposed for a development project in Malaysia. The exhibited design was
conventional beam bridge system with an R.C. U-drain as to protect the elevated foundation. Figure 3
describes the bridge elevation section for the exhibited design.
Figure 3: Bridge Elevation Section for Exhibited Design
P
0.5P 0.5P
L Moment=0.25PL
262 Modern Civil Engineering in Trend of the Sustainable InfrastructureDevelopment
Beam M4 was selected in this exhibited design. The weight for one piece of 20m span Beam M4 is
18.52 tons (per metre width). In terms of handling, lifting and installation process, contractor may
face difficulty and inconvenience. Besides, 100 tonage of crane is needed for the handling, lifting and
installation purposes. Greater self weight of bridge panel may cause heavier foundation design which
is not preferred most of the time.
Hence, Precast Concrete Closed Spandrel Arch Bridge System was developed and proposed to
provide viable solution to the above problems.
Precast Concrete Closed Spandrel Arch Bridge System
In theory of structure, arch bridge possess lower bending moment than beam due to the arch shape
(Figure 4). As such, thinner section in arch bridge system required compared to beam bridge system
for the same span. This will result in reducing load on pile and optimize the foundation design as well.
(a) (b)
Figure 4: Structural Behaviour of Circular Arch under Point Load; (a) Free Body Diagram,
(b) Bending Moment Diagram
Precast concrete closed spandrel arch bridge system consists of precast arch element, spandrel
wall, foundation, wingwall and backfilling components (Figure 5).
Figure 5: Components of Precast Concrete Closed Spandrel Arch Bridge System
Several proprietary precast concrete arch bridge systems [3], [4], [5] have been developed to
replace conventional masonry arch construction, but their spans have been limited to range of 6m to
25.6m due to logistic and lifting limitations. Notably, the system comprises of a series of precast arch
segments enclosed with two end spandrel units. The empty enclosure above the arches is then
overfilled in compacted layers with suitable granular materials. The stability of the arch structure is
achieved through soil-concrete interactions with side fills providing the lateral supports to withstand
the service loads. The commercially available arch systems are generally assembled from single-leaf,
double-leaf or triple-leaf precast segments as shown in Figure 6 with their respective proprietary
jointing systems.
(a)
(b)
(c)
Figure 6: Precast arch segment types:
(a) Single leaf; (b) Double leaf; (c) Triple leaf
P
H1
V1
H2
V2 L
h
Moment = 0.25PL-Hh
Applied Mechanics and Materials Vol. 802 263
The arches can be in circular, elliptical or parabolic profile to suit the structural and functional
requirements of the specific project. Those systems are distinguishable from many design and
construction details but with one common feature – the simple rectangular reinforced concrete section
adopted for the precast segments. Understandably the rectangular section is easy for mould
fabrication. It also simplifies the precasting process. However the section becomes heavy and bulky
for longer span arch with the increased thickness. Subsequent costs of handling, transporting and
installation are also affected with the increased weight of the precast segments resulting in the
necessity of heavier machineries and equipment.
The idea of using ribbed section in ‘Tee’ or ‘inverted-Tee’ shape was explored initially but the
material savings were found to be not substantial in this context due to the reasons of self-weight.
Efficient structural shapes with high flexural stiffness and minimal self-weight are often exhibited in
natural forms like palm tree or banana branches. Inspired by nature, an alike folded plate section in
corrugated form was conceptualized and developed (Figure 7). With the proposed section, the
self-weight is minimized by approximately 40% of equivalent solid rectangular section. Unlike the
ribbed section, the main advantage of this corrugated shape is the equal sectional moduli for top and
bottom fiber to resist bending moment with minimum materials. Although moulding is complicated at
first glance, repetitions will offset all once standardization is done as demonstrated in this pilot
project. The general arrangement of this project is represented in Figure 8. Patent has been granted for
this new innovation of corrugated arch segment [6].
(a) (b)
Figure 7: Dimension Details: (a) Arch Profile, (b) Section A-A
(a) (b)
Figure 8: General Arrangement: (a) Elevation, (b) Bridge Deck Section
Design and Development
With the aim of achieving a complete solution for a bridge taking full advantage of precast
technology and limitation, the following aspects have been taken into account in the
conceptualization and development of the closed spandrel arch bridge system : functionality and
aesthetics, arch profile development and foundation design, constructability in precast way -
transportation and arch panel, connection, casting, de-moulding and stacking, site installation and
on-site joint, backfilling process.
The new closed spandrel bridge is designed to withstand the loading as specified in BS 5400: Part
1 & 2 (1978) [7], [8], BD 31/01 [9] and BD 37/01 [10] for a design period of 120 years. Primary live
loads considered for the design of the bridge are as follows: (a) HA-UDL + HA-KEL and (b) HB-45
unit guided at the centerline of the deck. The dead load of the precast arch panel is resisted initially
by a three-pinned arch system. Once the crown is connected, the ring of the precast arch panel acts as
264 Modern Civil Engineering in Trend of the Sustainable InfrastructureDevelopment
a two-pinned arch system to resist loads. They are modelled accordingly in design and analysis for all
possible loading stages. Figure 9 shows the results of envelope sagging bending moment (298kNm/m
width), hogging bending moment (282 kNm/m width), axial force (856kN/m width) and shear force
(194kN/m width) from the PLAXIS analysis.
(a) (b) (c)
Figure 9: PLAXIS Envelope Results: (a) Bending Moment, (b) Axial Force and (c) Shear Force
Construction Method
Arch panels were prefabricated and cured for at least 28 days at factory. At the same time, the
keyway of the footing for the sitting of arch panels was levelled and checked for the critical
dimensions. Once it was done, installation works for arch panels started. First, the arch panel was
lifed from the ground and was pitched into horizontal position as shown in Figure 12(a) and 12(b).
Then, arch panels were hoisted from both sides and were self-propped at the mid span as shown in
Figure 12(c) and 12(d). The installation work was done in two days. Once after finishing the
installation, keyway was grout and crown beam would be cast later to connect both panels to form
rigid support at the mid span. The completed views of precast closed spandrel arch bridge system are
represented in Figure 13 and Figure 14.
(a) (b) (c) (d)
Figure 12: Installation Sequence: (a) Lifting from ground, (b) Pitching into position,
(b) Hoisting from both ends, (d) Self-prop at mid span
Figure 13: Installed Arch Panels Figure 14: Completed arch and spandrel
Material Comparisons
It is also important to compare the overall materials used for each system. From Table 1, it is
clearly shown that the total concrete used by beam bridge system is about 1.5 times than arch bridge
system which is 617 m3 and 394 m
3, rescpectively. However, for arch bridge system,a total of 1814m
3
backfill is used. It is not a critical issue which soil backfill materials can be easily found nearby the
Applied Mechanics and Materials Vol. 802 265
project site. In short, reducing usage of concrete materials for arch bridge system is able to bring the
sustainable solution to bridge construction.
Table 1: Overall Materials Comparison (Concrete Volume) For Conventional Beam Bridge
System and Precast Closed Spandrel Arch Bridge System
Bridge Structures Conventional Beam
Bridge System
Precast Closed Spandrel
Arch Bridge System
Foundation : Piles
Pile Cap
Strip Footing
84 pcs
93 m3
-
-
-
216 m3
Abutment 141 m3 -
Transition Slab 32 m3 -
Bridge Components : Panel
Concrete Deck
Soil Backfill
R.C Spandrel Wall
230 m3
(30 sets)
121 m3
-
-
142 m3
(20 sets)
-
1814 m3
36 m3
Concluding Remarks
Precast closed spandrel arch bridge system with corrugated section as viable alternative to
conventional beam bridge system has been described. A structurally efficient corrugated arch bridge
system offers higher stiffness, better aesthetic value and material save compared to beam bridge
system. With the development of precast concrete closed spandrel arch bridge system, it is able to
further explore in new applications such as military bunkers, utility vaults or aircraf shelters . Thus, it
is anticipated that this precast concrete arch bridge system will offer better solution to sustainable
bridge construction in the near future.
References
[1] D.G. Mcbeth, F. Hennebique and L.G. Mouchel, Francois Hennebique ( 1842-1921 ), Reinforced
Concrete Pioneer, Proceeding of the ICE – Civil Engineering, Volume 126, Issue 2, 1998, pp.
86-95
[2] G.E. Tan, T.B. Ong, C.Y. Ong and K.K Choong, Development and Standardisation of New
Precast Concrete Open Spandrel Arch Bridge System, 37th
International Association for Bridge
and Structural Engineering (IABSE) Symposium Madrid, 2014, Vol 102, pp. 799 - 806
[3] Product Brochure: Matiere Arch by ACPi Persys Engineering
[4] Product Brochure: Hume Bebo Arch 2002
[5] Product Brochure: Techspan Precast Concrete Arch System, The Reinforced Earth Company
[6] Malaysian Patent MY-142912-A. 2008. Corrugated Arch Elements for Culvert, Bridge, Crossing
or Shelter and a Construction Thereof.
[7] British Standards Institute. BS5400-1:1978: Steel, concrete and composite bridges. General
statement. London
[8] British Standards Institute. BS5400-2:1978: Steel, concrete and composite bridges. Specification
for loads. London
[9] Highways Agency (UK). BD31/01, Departmental Standards. The Design of Buried Concrete Box
and Portal Frame Structure. Department of Transport, Highway and Traffic, November 2001
[10] Highways Agency (UK). BD37/01, Departmental Standards. Loads for Highway Bridges,
Design Manual for Roads and Bridges. Department of Transport, Highway and Traffic, 2001
266 Modern Civil Engineering in Trend of the Sustainable InfrastructureDevelopment