SUSTAINABILITY THROUGH INNOVATION IN DESIGN
AND CONSTRUCTION – CASE STUDY:
SECOND PENANG BRIDGE, MALAYSIA
1 Mohamed Taib, Dr. Ismail, Sulaiman, 2 Nazurah
(1,2 Jambatan Kedua Sdn Bhd)
ABSTRACT
Jambatan Kedua Ptd. Ltd. (JKSB), a wholly-owned company of the Malaysia Ministry of Finance, Incorporated (MoF Inc.) is the concessionaire for the Second Penang Bridge Project (PB2X). The bridge with estimated cost of RM4.5 billion is set to be the longest in South- East Asia with a total length of 16.9 km over water. The construction of the Second Penang Bridge commenced in November, 2008 and currently is at 88% progress and to be completed by September 2013. It faced various challenges in applying sustainability to both design, construction, operation and maintenance. The Second Penang Bridge is pioneering in Malaysia to be fully designed for seismic load for a 475year return period earthquake and a 2500 year return period earthquake with ‘no collapse’ criteria. This paper will further discuss on the project management, the fast-track concept and innovation in the implementation of a sustainable bridge design and construction.
INTRODUCTION
The Second Penang Bridge linking Batu Maung in Penang Island and Batu Kawan in Seberang Prai on the mainland when completed will improve trade efficiency and enhance logistics systems by providing better connectivity and accessibility to Penang International Airport. The bridge is aimed to alleviate the current overloaded traffic at the existing bridge and to meet the future traffic demand, apart from being one of the key elements in the development of Penang as logistics and transportation hub for the northern region of Malaysia under the Northern Corridor Economic Region (NCER) programme. Feasibility study on the
project started under the 8th Malaysia Plan and was completed in 2002. The preliminary Environmental Impact Assessment study was undertaken for the project and approved by the Department of Environment in 2007. Initial works including soil investigation, topographic survey, dredging works and test piles begin immediately by the previous concessionaire, UEM Group Bhd.
PROJECT DESCRIPTION
JKSB was appointed the concessionaire for PB2X in August 2008 for period of 45 years. It is responsible for the project management, design, construction, operation and maintenance. PB2X is divided into the following packages (Fig.2). Package 1 is the works for main navigation span, substructure and foundation and Package 2 is superstructure works of approach spans. Both packages are design and built contract with horizontal split responsibility. Package 3A is the interchange at Batu Maung, Package 3B is the land expressway at Batu Kawan, 3C is the trumpet interchange at North-South expressway and 3D the toll plazas and related works. Packages 3E, 3F and 3G are the toll collection system, traffic control and surveillance system and M & E works for Package 3A and 3C respectively.
SUSTAINABLE DEVELOPMENT
JKSB has undertaken the lifecycle management of PB2X where sustainable development and green echnology are key to building the future. Sustainable development is an enduring balanced approach to social progress, economic activity and environmental responsibility. The emphasis to a lowest lifecycle cost is to promote the concept of design for durability. Durability is influenced by the following factors [1]:
i. Design and detailing
ii. Specification of materials used in construction
iii. Quality of construction.
In our effort to conserve natural resources and protect the environment, high standards of environmental protection were incorporated into the project. Marine fauna were closely monitored to avoid changes to the sensitive marine environment.
Planning Stage
In the feasibility study, alternative alignments considered are the Northern Route, the Mid- Channel Route and Southern Route; with the Northern Route the highest IRR. However, the alignment of the Southern route was chosen as to promote socio-economic progress in the less developed south that would provide a balanced development ac ross Penang state.
Design Stage
Most of the bridge sections utilized IBS and prefabricated on land to reduce the amount of time spent at sea and the risks of damaging or polluting the marine environment. The segmental box girders (SBG) were optimally design for minimum weight and lesser embodied energy by adopting higher reinforcement ratios and less but higher strength concrete [2]. The use of hybrid pre-stressing encompassing both external and internal pre-stressing increases design economy.All concrete use of high performance concrete with RCPT < 800 coulombs in 56 days, concrete cover and crack width conforming to latest Eurocode requirement. Fly ash-based green cement are to be used for low temperature rises of the pile caps and piers to reduce risk of thermal cracking during concreting. The geotechnical design of the land expressway complies with 100% primary consolidation and a settlement requirement of 50mm in 20 years. Embankments are compacted to not less than 98% of the optimum dry density using the modified Proctor test. The ground improvement cheme carried out were prefabricated vertical drains and vibro stone columns with surcharge, and piled embankment. The bridge articulation use high density rubber bearings (HDRB) for seismic protection. HDRB use natural rubber, possess high damping properties and lower embodied energy. All design, detailing and specification are verified by the Independent Checking Engineer (ICE) prior to construction.
Construction Stage
Stringent quality control in accordance to project specifications is enforced to ensure minimal
maintenance. Internationally accepted best practice was adopted for the bridge construction
including equipment selection and working method statements. Every two months, periodic
site audit are done by the ICE.The dredging of the 270m wide construction channel involving 14 million cubic metres of the Great Kra Flats seabed. The sludge was disposed 40km away off Pulau Kendi by barges
installed with satellite tracking, trap door and draft sensor devices PB2X construction use repetitive steel formwork and machineries for casting of 291 nos. pile caps, piers, pylons and 8092 nos. of SBG.
A monthly environmental monitoring audit is done by and independent EIA consultant. Quarterly fisheries impact assessment for marine and fisheries resources including aquatic environment and aquaculture are also done.
FOUNDATION AND SUBSTRUCTURE DESIGN
For the marine portion, Soil Investigation (SI) works were carried out with 205 nos. of
boreholes drilled of which 50 percent were technical boreholes and 50 percent were common
geological boreholes
Bored piles of 2.0m diameter with average length of 120m were adopted for the Cable-Stayed
Bridge. It enables immediate in-situ evaluation of drilled soil layers to revise foundation
length due to changes in soil conditions. The bored piles have achieved a capacity of 25MN at
120m depth with 8m socketed in bedrock. Reversed Circulation Drilling (RCD) method was
adopted and the total time taken is 2 weeks to complete one point for each RCD. The integrity
of shaft concrete was checked using cross hole sonic login (CSL). The CSL worked with 2
pairs 60mm diameter access tube embedded in all bored piles. The platform constructed for the bored piling works which after the piling works are lowered down together with the Steel Fender to be reused as a pile cap soffit and side formwork for the Cable-Stayed Bridge pile caps. The 6m thick pile caps were cast in two layers using low heat cement and iced water pump into embedded cooling pipe system. For the approach spans of the marine bridge, the substructures adopt a variety of piling types which are the spun piles, steel tubular piles and bored piles. Spun piles of 1.0m diameter with prefabrication length of 65m with no joints were used over most of the entire approach spans substructure. The 1.6m diameter steel tubular piles with average driven length of 80m were used in deep water areas (adjacent to the Main Navigational Span). 1.5m bored of average length 85m were used at mudflats near to mainland due to difficulty in dredging. To minimize temporary works and in situ works, precast RC shells were used for the pile caps. The pile cap were designed to have two casting stages. The 1st layer is cast to act as a base for the installation of precast concrete shell and to act as permanent formwork for the 2nd layer pile cap construction. 518 nos. of low piers (maximum height 6m) were constructed in a single cast using one continuous set of prefabricated steel formwork from pier to crosshead. 60 nos. of high piers (>6m to 21.6m) were constructed using layers of
prefabricated steel formwork.
SEISMIC DESIGN CONSIDERATION
Second Penang Bridge area is located within the stable Sunda tectonic plate with low seismic
activity level. However, this low seismic region is situated about 300-600 km from Sumatran
faults which have produced earthquakes with ground motions that are felt in buildings in
Georgetown, Kuala Lumpur and Singapore. In line with the current design requirement, the Second Penang Bridge is pioneering in Malaysia to be fully designed for seismic load for a 475year return period earthquake and a 2500 year return period earthquake with ‘no collapse’ criteria. The seismic design was based
on Design Response Spectrum from a Seismic Hazard Assessment Study conducted for the
project. The seismic design criteria are as per Table 1. However, during the design review
process, the ICE had highlighted that the spun piles at the approach marine bridge by Package
1 Contractor could only safely cater for the 475 year earthquake and found to be overstressed
under the 2500 year earthquake event and the piles would experience section failure due to
brittleness. Hence, a resolution between JKSB, ICE and Package 1 designer was reached by changing the
bridge articulation via introducing seismic bearing as construction was already at an advanced
stage [3]. Package 2 Contractor was instructed to adopt High Damping Rubber Bearings (HDRB) to replace the conventional mechanical pot bearings (see Fig. 3). HDRB has the ability to withstand large displacement in bilateral and rotational direction, durable with minimal maintenance as well as utilizing natural rubber available locally. The design was carried out by Tun Abdul Razak Research Centre (TARRC) at Brickendonbury, United Kingdom, a laboratory of the Malaysian Rubber Board (MRB).
MARINE BRIDGE DESIGN
The superstructure of approach spans adopts SBG of 14.08m width, 4.0m length and 3.20m
depth. Short line casting was selected because it does not require extensive casting facilities,
special heavy lifting equipment and storage. Segments typically weighed between 69 – 100
tonnes. Early strength of 15 MPa after 10 hours is required for internal, side and cantilever
formwork to be stripped. Typically on average 15 SBG are cast every day using 22 nos. of
moulds. The segments are launched to the sea via barges and erected on a span-by-span using
overhead self launching girder. 40 nos. complete spans of 14 segments are easily able to be
completed within one month period. All segments are epoxy glued together to prevent leakage
of water into the SBG.
The cable stayed bridge utilizes post tensioned concrete beam-and-slab decks. The concrete
cross girders are cast in-situ with a 250mm deck slab. At the pylon the deck is built-in into the
legs to provide fixed support. The semi fan layout stay cables system is designed based on
parallel strand system with associated anchorages and deviation saddles of low relaxing high
strength steel strands of diameter 15.7mm are arranged symmetrically in 2 planes of 18nos. of
cables. The typical spacing of the cables at the edge beam and pylon is 6m and 2.525m
respectively. The cables are symmetrically tensioned and anchored both at the edge beams
and at the pylons. The bridge also considers the rupture of any two adjacent stay cables with a
combination of 10% live load at ultimate limit state. Corrosion protection is provided for the
main tension elements by using at least 3 complete nested barriers. The strands are galvanized
and individually sheath inside a grease filled HDPE duct and additionally surrounded by
external HDPE duct. The erection cycle for each deck segment is typically 12 days.
GREEN BUILDING TECHNOLOGY
The design of the Toll Plaza and Administrative Building Complex was based on
requirements of 80% of IBS, 80 (Gold) for PLUS Toll Plaza and 88 (Platinum) for PB2X Toll
Plaza. The details of additional works to achieve target score of platinum are:
i. To reduce air conditioned area and maximize air conditioner set efficiency (to BEI
less than 100).
ii. To reduce day lighting to less than 50% floor area
iii. To reduce internal noise level with additional insulation (to less than dB 40)
iv. Rain water harvesting for 30% reduction in potable water consumption
v. Water efficient with no potable water for landscape
vi. Installation of metering and leak detection (FMS)
vii. To recover condensate water from air conditioners.
CONCLUSION
The implementation of this fast-track project particularly on its construction techniques are to
be exemplary and reference to other upcoming bridge constructions of its kind. The
execution of design & build concept for the major portion of the project is anticipated to
produce impressive results and lead to many innovations as well as promoting a cost-effective
bridge engineering and maintenance practice in Malaysia. JKSB is committed to complete
the Second Penang Bridge with the highest quality, timely delivery, within the budgeted cost
and to contribute towards sustainable development.
