SESOC

Journals Abstracts

These are short abstracts of the material printed in our journal which is published twice annually. The Journal covers items of interest to structural engineers, including but not limited to: technical papers, project reports, materials information, code reviews.

Journal: Vol 15 No. 2 2002

 

Title
Minimum Specifications for Concrete Durability Vol 15 No 2 2002
Author/s

J R Mackechnie
Abstract

Modern Portland cements are well ground and careful& selected materials that give good early strength development and comisfentpeif2ormance. New Zealand is blessed with high performing cements in terms of strength and good quality aggregates for concrete production. This has lead to a very competitive ready mix industry where cement contents are kept to the minimum. The quality of some of these concrete mixes was investigated using compressive strength and permeability testing. Results from the study indicate that a minimum threshold level of cement is required in concrete to provide a closed microstructure needed for durability. Given the high strength performance of New Zealand cement, the use of low structural grades with high w/c ratios need to be reviewed due to their relatively open microstructure.
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Title
Experimental Testing and Numerical Modelling of Two-Way Concrete Slabs under Fire Conditions Vol 15 No 2 2002
Author/s

Linus Lim, Andrew Buchanan, Peter Moss
Abstract

This paper describes the tests and computer modelling of two-way concrete slabs exposed to fire. The fire tests were conducted to investigate the influence of tensile membrane action in concrete slabs at elevated temperatures. Six slabs were tested comprising three reinforced concrete plain flat slabs and three composite steel-concrete slabs. The slabs measured 3.3 m by 4.3 m and had thicknesses ranging from 90 mm to I30 mm. The slabs were simply& supported at all four edges on a 3 m x 4 mj5mace and were horizontally unrestrained. The slabs were subjected to a live Load of 3.0kPa and heated with the 1SOstandard fire. All the slabs performed very well as they supported the full design loads for three hours in the IS0 fire withgout collapse, despite suffering significant deflections and loss of flexural strength. The fire tests illustrates the significant effect of tensile membrane action in the slabs. Finite element analyses of the slabs with the S4FIRprogram showed good agreement with the test results.
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Title
A Calculation Method for Plastic Analysis Vol 15 No 2 2002
Author/s

Esli Forrest
Abstract

Our traditional approach to moment-force analysis is based on pre-yield elastic concepts. It centres on a concept of increasing load with linear elastic stress response from zero to yield point. In earthquake design however, we are forced to think beyond the yield point. This applies to both steel and concrete. With timber, failure occurs without a very long curvature increase beyond the yield point and so a single linear approach is acceptable. With steel and reinforced concrete however, a bilinear or events-linear system of analysis for bending moment and displacement is necessary. Due to the yield plateau that occurs in structural grade steels, with I sections, the whole section for practical purposes develops plasticity. The stress and strength increase after yield, due to strain hardening, is generally not considered in design. However, in reality it is important as it allows the plastic (hinge) zone to spread, and hence sustain high rotations before a failure strain is reached.
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Title
The Seismic Performance of Flooring Systems Executive Summary Vol 15 No 2 2002
Author/s

Technical Advisory Group of Precast Flooring Systems
Abstract

This report has been prepared by the Technical Adv3ory Group on precast flooring Systems. The group has been formed to disseminate the results of recent research to the industry and provide info into the direction for future testing. The fundamental messages the group wishes to take to the industry are • The preferred seating arrangement for hollowcore units supported on concrete beams is shown below/ It is considered that using this seating detail will ensure improved seismic performance above that of the commonly used detail of providing plastic cut-offs in the cores to prevent infiltration of the topping concrete. The proposed detail has no cost penalty over the existing practice. • Hollowcore units& should not be positioned parallel and immediately adjacent to beams. They should be located a distance away (500-800 mm) and linked to the beams by the concrete topping only • Exterior column should be tied back into the structure either by transverse beam, or by ductile reinforcement in the floor slab. The reinforcement shall be capable of resisting a force equal to 5% of the gravity axial load in the column.
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Title
Design of Multi-Story Buildings for Satisfactory In-Service Response to Wind Induced Vibrations Vol 15 No 2 2002
Author/s

Thomas Mahoney, G Chares Clifton
Abstract

Steel framed multi-storey buildings are generally lighter in weight than reinforced concrete framed multi-storey buildings. The principal reason for this lies in the self weight of the flooring systems used in each instance. The lighter weight of steel framed buildings makes them potentially more susceptible to unacceptable levels of acceleration generated by wind-induced vibration under serviceability limit state conditions.
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Title
Some Considerations In Design Of Reinforced Concrete Interior Beam-Column Joints Of Moment Resisting Frames Vol 15 No 2 2002
Author/s

Prof Robert Park
Abstract

During the past forty years a great deal of research on the behaviour of beam-column joints of reinforced concrete moment resisting frames subjected to seismic loading has been conducted in structural testing laboratories all over the world. Based on the results of these tests design recommendations have been developed and incorporated in the seismic design codes of the different countries. It is of concern that the recommended approaches for the design of reinforced concrete beam-column joints in New Zealand', the USZ, Japan3 and Europe4 vary significantly mainly due to different interpretations of test data, different models of behaviour, and different performance criteria.
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Title
Articles for Discussion_To every Action there is ??? Vol 15 No 2 2002
Author/s

Esli Forrest
Abstract

We have got what we wanted - a completely deregulated construction industry. Everyone can compete with everyone in every aspect. Nothing is sacrosanct. Design, supervision, new ideas, standards of performance, professional ethics, and the fees that are charged to execute them, all are subject to the driving force of the dollar. The only yard-stick is that the minimum requirements in performance of a totally non prescriptive building code are met. It will, we are told, encourage innovation.
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Title
Project Corner_Nam Cheong Station Hong Kong Vol 15 No 2 2002
Author/s

Philip Young, Robert Cook, Rohit Patel
Abstract

The construction of buildings below ground can present a number of high risk problems. The designer is faced with the inexact science of soils, all too often coupled with an inadequate site investigation. The integration of geotechnical engineering with civil and structural engineering, and of permanent with temporary works, combined with varying sensitivities and constraints of adjacent development and the tight construction programme, present both challenges and opportunities. The premium placed on land values, particularly in a thriving city such as Hong Kong, means that the easy sites have all been used up and that there is pressure to build down as well as up. Nam Cheong Station on the West Rail Project, was a project that involves both above and below ground structures, with very challenging site constraints. Knowledge of practical methods and sequence of construction is of vital importance to the success of such a construction project. This article describes the key design issues that had to be dealt with and the approach that was taken by the Alternative Design Team led by Robert Benaim & Associates, working with Contractor Balfour Beatty Zen Pacific Joint Venture (BBZP JV).
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Title
Some Considerations on Education and the Health of Structural Engineering in NZ Vol 15 No 2 2002
Author/s

Dr Richard Fenwick
Abstract

Of the 40 years that have passed since I graduated, one third has been spent as a practising structural engineer and the remainder as an academic. This career history in itself, highlights one of the major changes that has occurred in engineering education. When I started at Auckland University in 1975 practical experience was highly valued and the majority of academic staff employed at that time had a similar level of practical experience. However, over the years the emphasis has changed.
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