Chao Phraya Bridges, Bangkok, Thailand

The Kanchanaphisek Outer Ring Road (southern section), and in particular the Chao Phraya Bridge, has been a stop-and-start project since it was first conceived in 2001 and announced by Bangkok governor Samak. The 20km (12 mile) section of motorway will fulfil several functions by completing the connection around the city, and providing a road link to the new Bangkok International Airport at Nong Ngu Hao, Suvannabhum, which opened in 2006.

The idea for the industrial ring road system was originally put forward by His Majesty the King, in order to relieve the traffic congestion for the areas of Bangkok Port, Poochao Saming Phrai Road and Suksawat Road which are the main industrial areas.

To fulfil these expectations a futuristic bridge structure has been conceived for the Chao Phraya Bridge associated with this road. The bridge will have two steeple 'A' frame-like supports supporting a cable stayed structure in three sections.

The construction of the motorway section and the bridge started in 2004 and is due to be completed by 2007 in time for anticipated religious festival traffic. The road project, including the bridge, is estimated to cost over ¥25bn when fully complete. The finance will be provided by the Thai Government in collaboration with Chinese and Japanese investors. The industrial ring road project as of March 2007 is now 95% completed and will be opened by summer 2007.

The river crossing was actually planned as a dual tunnel system when the project was first conceived; however engineering problems with the geology beneath the river bed and cost issues ruled this out at an early stage.

KANCHANAPHISEK OUTER RING ROAD BRIDGE

The bridge for the Kanchanaphisek Outer Ring Road was designed by Parsons Brinckerhoff of New York who has had much experience in Thailand and with bridges of this type. Parsons Brinckerhoff are acting as designers and architects and offering engineering, project management, construction supervision and technical support services for the duration of the project.

The general contractor for the road and bridge project is CH Karnchang Public Company Ltd of Thailand (with a winning bid of 15.61bn Baht). This company fulfil the terms of the contract that the majority of labour and engineering expertise for this project should be from Thailand itself. Many insiders stated that CH. Karnchang won the contract since the government wants to make a settlement on compensation payments it owes to CH. Karnchang PCL over another project at a price lower than the current 6.255bn Baht awarded in a recent court case. The other three bidders for the bridge and expressway will function as subcontractors. These include Italian Thai Development PCL, VIjitphan Construction Co Ltd, Krungthon Engineer Co Ltd.

The bridge will be the longest cable stayed bridge in Thailand. It features two A-shaped towers located on the banks of the Chao Phraya River that combine traditional Thai design and contemporary architecture. As seen from the roadway, the towers are a stylised representation of the traditional Thai greeting where the hands are steepled together in front of the body as the individual bows and utters a greeting. The towers are a symbolic gesture of welcome to visitors of Bangkok.

The bridge is designed to carry four lanes of traffic in each direction. The structure will comprise a 500m (1,640ft) main span, with two side spans measuring 220.5m (723ft) each. The total length of the cable stayed span measures 941m (3,087ft). The total width of the cable stayed span, including the edge girders, is 36.7m (121ft). The superstructure consists of a pair of steel edge girders and floor beams spaced at 4m (13.1ft) intervals. Pre-cast concrete deck and cast-in-place strips are made composite to the steel frame. To eliminate tie-down devices completely, the design uses counterweight concrete to balance the bridge. The bridge provides a 50.5m (167ft) clearance to accommodate vessels entering and exiting Klong Toey Port, a major seaport located upstream from the bridge.

CHAO PHRAYA MEGA BRIDGE

The Mega Bridge (part of the industrial ring road project), as it has been called, will span a meander loop in the Chao Phraya River; thus it will have two major spans, but also in the middle there will be a complex circular intersection. This means that a motorist may cross the first bridge span and then branch off to the northern roads by using the intersection. The bridge was originally planned as far back as 1997; however it was held up for a major redesign (reducing the number of support pillars to two instead of one), and almost cancelled following the Thai economic crisis in 2001.

The bridge complex consists of two major spans, 702m long and 172m high and 582m long and 162m high respectively on concrete pylons. There are 3,500m of approach bridges, 500m of high-level road and 9.1km of graded road. The bridge(s) was completed in October 2006 and opened with a spectacular fireworks display.

The concept designer for the Mega Bridge was Yee Associates Architects and Designers. The project management for the engineering and construction were Norconsult International and the Thai companies MAA, Span and Team Consulting and Management International. There were a team of eight contractors working on the project, including the industrial ring road and the Mega Bridge. These included Italian Thai, Sumitomo, CH. Karnchang, Obayashi, Unique, Kajima, CMS Construction and Taisei Corporation.

The bridge and the immediate sections of highway cost in excess of 8.7bn Baht. This project was administered by the Public Works Department. The sections of the project were divided into three contracts which were worked on by two different contractor groups. Contracts 1 and 2 were for the Northern and Southern bridges and were by TNNS joint ventures (Taisei/NKK Corporation/Nishimatsu and Sino Thai Construction). Contract number 3 for the Western elevated interchange entrance and exits was done by KTU joint ventures (Tokyo Construction/Kajima and Unique Engineering).

The bridge is 51m high to allow clearance for shipping to pass beneath it to the container port at Klong Toey. The structure will be 4.2km long and will have seven lanes to link Pu Chao Saming Prai Road with Rama 3 Road. The intersection in the middle will have a 2.2km ramp to connect it with Sukaswat Road. The bridge itself will be supported by two large 'A' shaped cable supports similar to the style and type used in the construction of the Rama 3 Bridge completed in 2003. The two pillars will be supported by piles 70m deep and the structures will be designed to take three times the maximum load. The foundations took a 30hr continuous pour of concrete. The bridge straddles the Wongwein Yai area and connects the Industrial Ring Road project. The land areas beneath the bridge and intersection will be landscaped and redeveloped as leisure facilities.

BRIDGE CONSTRUCTION

For the Mega Bridge project the world’s largest Movable Scaffolding System (MSS) was commissioned. The movement of these huge steel structures safely and efficiently high overhead, plus steering and positioning; required the heaviest (1,20t) Formwork Traveller in South East Asia and some of the most heavy-duty hydraulics ever produced. Enerpac Hydraulics was chosen by the main contractor, Taisei, to design and supply the hydraulic systems to be integrated in the movable scaffolding system. The typical formwork arrangement required two custom-built 7.5kW low pressure hydraulic power units to actuate 24 pieces of 100t horizontal and 60 pieces vertical cylinders complete with clevis eye and mounting attachments to allow formwork pushing and pulling operations.

Click here for printable version