View TO BUILD Online

ECSA banner 19 july 16 take off july 2017
ArcelorMittal
KZN Constructio take off 9 Feb 2018
Centurion Systems  take off Dec 2018
Bloembuild take off 27 July 2018

Bridges at Hopetown

Online since 29.10.2017 • Filed under Professions - Engineering • From Issue 22 page(s) 54
Bridges at Hopetown

Upington-based contractors Botes & Kennedy Manyano were appointed to undertake the widening of the 312 metre bridge on the N12 carriageway over the Orange River at Hopetown in the Northern Cape.

 

The R88-million South African National Roads Agency SOC Ltd (SANRAL) project began in mid-2016 and is on track for completion by the end of February next year. It also includes a smaller bridge being widened a short distance to the north.

 

The main bridge is a twelve span, simply supported structure constructed with precast pre-stressed I-beams. It comprises 11 concrete piers, each measuring 12 metres in height, between a north and a south abutment. The road widening project requires new piers to be built alongside the existing ones and to similar dimensions.

 

The 12 spans for the new part of the bridge are created by 60 concrete I-beams, each measuring 26 metres long, with straight horizontal alignment and flat vertical alignment. The beams rest on elastomeric bearings on top of the piers. To complete the contract, the contractor will build a new road, laying down new sub base layers and a Cape Seal.

 

The concrete mixes for the project included designs for 15 MPa, 30 MPa, 40 MPa and 50 MPa, according to Brendan Croney, technical consultant at AfriSam’s Centre of Product Excellence (CPE). The company’s CPE is based in Roodepoort which has SANAS accredited laboratories.

 

Mammoth amount of materials

The substantial project will consume 4,000m3 of concrete and 500 tonnes of reinforcing steel, with about 28,000 bags of AfriSam High Strength Cement (CEM II A-M (L) 52.5N) delivered from the Ulco factory near Barkley West. A range of concrete mixes for the project was designed by the contractor to ensure optimal durability and certain workability requirements. These meet the client’s specification for performance-based concrete and include standard concretes and the ‘W’ concretes that meet durability indices for oxygen permeability, sorptivity and chloride conductivity.

 

Almost 9,700m2 of formwork was used in the construction of the 11 new piers, nine of which had been completed by August 2017.

 

The new abutments on the north and south banks of the river needed considerable earthworks to be done, according to Botes & Kennedy Manyano site agent, Jeann van Tonder. At each abutment, 13 piles were drilled to an average depth of about 10 metres and socketed into bedrock.

 

‘Before work could begin on the new piers, a causeway had to be constructed out into the river so that mass concrete bases could be poured, onto which a 1,7 metre deep concrete base could be constructed for each new pier,’ says van Tonder.

 

The piers were then cast in three lifts of 3,6 metres each and a final 1,5 metre lift. Concrete was poured from the causeway utilising a crane and concrete buckets.

 

AfriSam

W www.afrisam.com

Botes & Kennedy Manyano

W www.botes-kennedy.co.za

Issue 22

Issue 22

November 2017

This article was featured on page 54 of
To Build Magazine Issue 22.

Share this

Water world Africa take off 29 March 2018
China prefab house fair take off 18 May 2018
 Affiliated Members AAAMSA - The Association of Architectural Aluminium Manufacturers of South Africa | Tel: 011 805 5002 Institute for Landscape Architecture in South Africa KSA - Kitchen Specialist Association | Tel: 0827878806 SAIA