Local Government Magazine
Technical Briefings

Precast Concrete Manholes: A Review

Stormwater manholes and access chambers are traditionally constructed using precast concrete components supplied by concrete pipe manufacturers. Many years of good performance has provided confidence in the adopted approach.

As a result manhole components have been accepted as fit for purpose and most TA specifications are related to hydraulic and operational requirements rather than the structural design.
Husham Issa Al-Saleem & Wayne Langdon, both from Humes Pipeline Systems, provided a review and upgrade of current practice in their paper presented at the recent 2016 Water New Zealand Stormwater Conference in Nelson. Issa – Precast Concrete Manholes – A review and Upgrade of Current Practice
They say the recent development of new performance design standards in New Zealand has increased serviceability life expectancy of main infrastructure components to 100 years.
Recent NZTA and TA specifications require a review of existing product designs to ensure compliance for “strength” and “durability”.
This paper presents the results of intensive research work conducted by the authors to achieve this goal. The main design parameters investigated were loading, load factors for the design of lids to suit various infrastructure construction conditions, lateral load on manhole walls, foundation stability and buoyancy.
Durability design is defined in the terms of the existing New Zealand Standards which define exposure conditions for which manhole components are designed to achieve 100 years’ life.
The paper also lists service conditions which allow designers to specify standard manhole components for safe bearing capacity, traffic loads and depth of installation.
The conditions cover existing design and construction practices allowing designers to select the correct product or carry out an alternative specific design.
Husham Issa Al-Saleem holds BSc, MSc (Civil Eng) qualifications from the University of Baghdad, Iraq, and is recognised in New Zealand with CPEng, IntPE, MIPENZ. Since 2009 he has been working as a senior civil engineer with Humes Pipeline Systems, where he is involved in research and development, management of technical projects, sales training and technical support.


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