IEK INTERNATIONAL CONFERENCE

Theme: The Role of Engineering Practitioners in the Implementation of the Constitution

Title: An Assessment of the Adaptability of Empirical & Mechanistic Design

Procedures for PCPs in Kenya

P. O. JangayaMoi University

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Introduction DelftTU

• Generally, CC roads are associated with

high initial construction costs, and low cycle

costs compared to AC roads.

• Types of CC? “cheapest”.

• As at “1st ¼ of 2010”, cement concrete roads

constituted approximately 0.002 % of

Kenya’s road network – Mbagathi Way, NRB

Introduction

• CC design procedures: Empirical,

mechanistic & mechanistic-empirical.

– Empirical: based on long term experience with

concrete roads -> adequate experimental data.

– Mechanistic: based on mathematical models of

material behaviour and determination of

stresses within the structure -> ‘new’ countries.

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Introduction DelftTU

• Practice

– Empirical: e.g. Germany (described by RStO

01 (2001) & revised after every 10 years),

Austria and Belgium.

– Mechanistic: e. g. the Netherlands, South

Africa, and Canada.

. Major works done at Mbagathi Way, BUT

not first one.

Mbagathi Way in brief DelftTU

• Approx. 3 km long, built in 2006 – 2007

• Design done based on

S.A. design procedure

• 210 mm thick DJPC

pavement done by

Kabuito Contractors Ltd

What next after REHAB? DelftTU

• Monitoring program?

• Development of own design code?– Evident in draft from Ministry of Roads in

2009– In this document, -- a lot of borrowing from

what is already available from other countries especially from South Africa.

– Why the heavy borrowing?– Any progress on this draft?

My contribution

• 2010 IEK Conference

• Why the literature survey?

– Clauses from the draft.

– to make objective & informed decision(s) for

adoption/adaption.

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German design procedure

Alternative designs of CPs for German expressways for heaviest traffic loadings and a frost-proof pavement structure of 900 mm: (1) concrete pavement on cement-bound base (2) concrete pavement on geotechnical fabric and cement-bound base (3) thick concrete pavement on crushed aggregate base

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Dutch design procedure DelftTU

Traffic loadings: Axle loads, Directional factor, Design traffic lane,

Substructure: Modulus of substructure reaction

Concrete:

Strength Parameters, Elastic modulus

Traffic load stresses:

Load transfer at joints,

Westergaard equation

Temperature gradient stresses: Eisenmann/Dutch method

Concrete slab thickness: Miner fatigue analysis

Climate: Temperature gradients

Adaptability to Kenya

• Parameters considered, include:

– traffic loadings;– temperature gradients (climate); – concrete grades; – Characterization of substructure;

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Conclusion

• Kenya, just starting to appreciate use of

CC, needs:

– design procedure which allows the use of a

country’s nationally determined parameters

for inclusion in its models

– procedure should also be one that does not

require a lot of field data (experience)

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Conclusion

• Dutch “better” addresses:

– overloaded trucks,

– temperature variations – what’s required,

– concrete grades

• German “better” addresses:

– characterization of the substructure

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Issues

• Do we need monitoring program for Mb. W

• Any challenges with Mbagathi Way

• Progresses with the design codes.

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Appreciation & Acknowledgement

IEK Conference organising committee

VLIR-UOS MU-K CSE project

Moi University

Session & programme chair

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END!!

Thanks

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