Civil Engineering 2011

4 de Abril bridge in Catumbela
Armando Rito and Pedro Cabral
Catumbela

Further information

The 4 de Abril bridge in Catumbela, located on the Benguela – Lobito Highway, Republic of Angola, was designed by the engineers Armando Rito and Pedro Cabral and was recognized by Secil and the Order of Engineers with the Secil Civil Engineering Award in 2011.

The 4 de Abril bridge was designed by the engineers Armando Rito and Pedro Cabral and was built with 14,900m3 of concrete, 591,000 kg of pre-stressed steel and 1.7 million kg of passive steel. It is characterized both by the innovation of the techniques used and by the planning and execution of the works on the site. The bridge’s two U-shaped towers are notable for their transparency, due to the absence of cross-braces.

This engineering work is a contribution to local reconstruction that will benefit the community and promote unity between the two adjacent cities of Benguela and Lobito.

For the first time in the history of the Secil Civil Engineering Awards, the prize went to a pair of engineers. The award-winning engineer Armando Rito says that “this is indeed an important milestone in the history of the Secil Civil Engineering Awards because, for the first time, it has recognized a work in Africa, thus reflecting the internationalization of our Engineering, with particular emotional significance because it is located in a Portuguese-speaking country.” He adds that “I am very proud that this award is recognizing my work with the engineer Pedro Cabral, who made a huge contribution to the completion of the work, which is of undeniable value to the development of Benguela Province.

Armando Marques Rito

He graduated in Civil Engineering at the IST/UTL. He is a member of several national institutions and of the IABSE.

He was a Delegated Member of the CSOPT and Coordinating Lecturer of the ISEL bridges course, at the UCP.

He was the national expert on the CEN – Task-Group EC2, Part2 “Concrete Bridges” – Version 1, Task-Group Member 1.2: “Bridges” of thefib and the AIPCR Bridge Committee.

He has been invited to many international and national conferences. He has published about 70 articles on bridges and has had work published in national and international journals.

He has won medals from the AFPC- Association Française Pour la Construction (1997), the fip (1998), the ASCP (2009) and the GPBE (2010).

He was awarded the Engineering Prize for his Miguel Torga Bridge in Regua (1998) and the Vasco da Gama Bridge, as one of the designers (2000), in the “1st and 2nd Ibero-American Engineering and Architecture Biennials.”

He has built about 500 works, several of them of major dimensions – for example, the Arade cable-stayed bridges in Portimão and Catumbela in Angola, the Sado bridges in Alcacer-do-Sal and Arade on the A2, the Miguel Torga bridges over the Douro and the Corgo in Regua and the Sabrosa viaduct on the A24, the bridges over the Tamega on the A4 and over the Sabor on the IP4, the Loures viaduct on the A8, the Labriosque, Coura and Laceiras viaducts on the A3, the bridges and viaducts on the Mondego, Pranto and Lis access road on the A17, the Cacheu bridge in Guinea and the Kwanza bridge in Cabala, Angola, the Douro bridges at Sousa Uima and Covelo on the A41 – Douro Litoral and the Tua bridge in Douro Interior.

Pedro Castro Caldas Cabral

Pedro Castro Caldas Cabral was born in Lisbon in August, 1973 and graduated in Civil Engineering at the IST in October 1996. In 1996 he started work in the Armando Rito’s engineering company. In March 2007 he became a director and partner of the Company Armando Rito Engenharia, S.A.

Throughout his career he has participated in many bridge projects involving numerous types of structure and construction. The following are notable examples: in Portugal, the Corgo bridge, the viaduct at Vila Pouca de Aguiar, the Douro bridge and the Tua bridge; in Angola, the Catumbela bridge and the Kwanza bridge in Cabala; in Guinea-Bissau, the São Vicente bridge. His work has included general coordination of projects and technical assistance on works constructed by national and international companies.

Between 2004 and 2007 he was invited to run the course in Bridges and Special Structures in the Engineering Faculty of the UCP. Since 2008 he has been supervising newly graduated students in their training placements for admission to the Order of Engineers and has been working in partnership with the Faculty of Engineering of the Agostinho Neto University, Luanda, in the supervision of final year dissertations.

He is a senior member of the Order of Engineers and belongs to a number of professional associations. He has attended several postgraduate courses in the area of bridges and participated as a speaker at various conferences and seminars on structures in Portugal and abroad. He has published and presented more than 30 articles on bridge design and construction.

Introduction

The Highway between Benguela and Lobito crosses the river Catumbela around 7 km from its source and about the same distance from the town of Catumbela. There were major difficulties to overcome to adhere to the layout in crossing the river and its embankments in the location defined in the Highway (Via Rapida) design, which was already under construction when the bridge project began.

These difficulties were due to topographical constraints, the deployment of existing structures and roads that forced the use of tight curvatures, the very limited extension of the development of the crossing and the need to use a very low ground level to prevent significant landfills, but allowing local resetting beneath the construction. Moreover, the normally strong river spates and the very short time required to build the bridge suggested avoiding laying foundations in the minor bed.

The construction project was in an urban development area, especially on the right bank of the river and the construction of a significant numbers of houses was, therefore, already processed and settled on the banks of the river in such a way as to ensure that spates did not flood the river bank areas of the town, while an avenue was built along the north bank.

The solution to be adopted therefore needed to resolve, flexibly and cheaply, a range of local constraints.

After studying several alternatives, the solution adopted for the new bridge over the river Catumbela was a design in which the bridge is a cable-stayed section with a central span of 160 m above the minor bed, thus ensuring the lowest possible ground level and that no pillars would be needed in the river and a shorter duration of work and the maintenance of local links between the two sides of the Highway and between the Highway and both banks of the river. The approach adopted also managed to achieve a substantial reduction in the costs and duration of the construction work and impact of the problems arising from the foundation implementation difficulties.

In urban areas, where local constraints suggest the use of large spans or emblematic works, cable-stayed bridges are generally the most suitable choice.

Aesthetically it is a very accomplished solution because of its clear visibility and the instinctive understanding of its structural system and the balance of the forces involved. The slender road section and towers and the fine web created by the cable stay system provide well designed structures of this type with an unsurpassed lightness.

The Catumbela bridge has a solid 450 m long concrete deck. The cable-stayed part is entirely suspended, without any supporting points apart from those on the transition pillars where the access viaducts provide structural continuity to the bridge.

The deck, which is very slender at only 1.60 m high, is visually identical in the bridge and viaduct areas. It is developed in a soft suspended vertical curve of moderate height held by white cable stays.

The use of high towers, while allowing some reduction in the amount of steel in the cable stays, makes bridges look ‘stiff’ and we therefore believe that the slight increase in the cost of the steel cables stays for towers of moderate height is fully justified . The result is a more balanced, lighter and more beautiful structure.

All shapes underwent detailed aesthetic assessment. The towers were modelled and detailed so as to provide the structure with an aesthetic enhancement and simultaneously give it a resistant appearance. The use of saddles allows for efficient treatment of the anchoring lines and the towers themselves.

The Main Contractor was the Angola Roads Institute (INEA) of the Ministry of Public Works of the Republic of Angola (MinOP) and its construction was managed by the Mota-Engil / Soares da Costa consortium. The cement used was from the Secil Lobito Plant in the vicinity of the work.

Location: Benguela / Lobito Highway, Benguela province, Republic of Angola

Main Contractor: MINOP – Ministry of Public Works of the Republic of Angola and INEA – Angola Roads Institute

Design: Armando Rito Engenharia, S.A.: Armando António Marques Rito, Pedro Castro Caldas Cabral

Construction: Mota-Engil / Soares da Costa Consortium

Main materials quantities:

Concrete:

Foundations: 2 800 m3

Towers and pillars: 3 150 m3

Deck: 8 950 m3

Pre-stressed steel:

Bar: 148 500 kg

Cord: 250 000 kg

Cable: 192 500 kg

Passive steel: 1 700 000 kg

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