Journals >> Abstract VOLUME 12. No. 2 (September 1999)
LETTERS TO THE EDITOR
University Education of Civil Engineers: (Professor R. Park)
Education; Where is it Going: (Dr.P. Lipscombe)
Twist in and Experiences with Buildings: (Professor T. Paulay)
Shrinkage of Auckland North Shore Clays: (G. Farquhar)
TECHNICAL PAPERS
Comparative Analyses of the Response of Single Storey Torsionally Unrestrained Ductile Systems: (P. Dusicka and B.J. Davidson)
The response of a structural system to earthquake induced ground motion can result in various levels of torsional behaviour. Modern design codes attempt to provide criteria to reduce the additional damage and possible failure resulting from this additional demand on the lateral load resisting system. Recently, proposals for a new mechanism based design (MBD) strategy for the torsional effect in ductile buildings were suggested by Paulay. This numerical study compares the strength requirements and the ultimate ductility demands of single storey torsionally unrestrained systems which were designed using the proposed MBD method and the current code approaches. The proposed design strategy appears promising with its rational approach, although several issues need to be addressed. A significant strength increase resulted using the new MBD approach as compared to the established code based methods. With the proposed method, an overall conservatism was observed in the response of systems with low values of rotational mass moment of inertia. Sensitivity to stiffness eccentricity and rotational mass moment of inertia were also studied. These characteristics are not currently incorporated in the proposed MBD procedure.
Design of Prestressed Concrete Masony Walls: (P. Laursen and J. Ingham)
This article presents techniques for the design of prestressed concrete masonry (PCM) walls. Proposed design equations for determining creep and shrinkage, flexural behaviour and shear strength are presented. These are verified by experimental results. The article primariy focuses on in-plane response corresponding with the research currently being conducted at the University of Auckland.
Half Hinges in Reinforced Concrete Beams: (R. Fenwick and S. Despande)
Half hinges, which are commonly found in bridges at expansion joints located in a span, and in the beams at the corners of many multi-storey buildings, present the designer with a number of problems. These regions are often congested and difficulties can arise in developing a practical and efficient reinforcement arrangement.
The results of a series of tests are described. These illustrate the way in which half hinge joints work, and they show the relative efficiency of different reinforcing arrangements. On the basis of these and other tests, which have been reported in the literature, recommendations are made for the design and detailing of half hinges.
Field and Laboratory Testing of Volcanically Derived Soils: (M.J. Pender, V.M. Meyer, T.J. Larkin, L.D. Wesley and G.C. Duske)
This is a brief report on part of recent field and laboratory testing on the properties of volcanic ash soils.
At three sites CPT and vane shear strength profiles were obtained, as well as insitu measurements of the shear wave velocity, and the recovery of 100mm diameter samples for laboratory measurement of soil properties. One of the sites was in Tauranga, another in Hamilton, and the third at Ramarama (40 km. South of Auckland). A brief summary of the findings is given. More detailed results are in papers, copies of which are available from the authors.
What Every Engineer Should Know About Welding Procedures: (W. Scholtz and D.K. Miller)
Welding Procedure Specifications (WSPs) are developed by the fabricator responsible for the welding to be performed. The Engineer may be required to review the WSPs for comment and approval. This responsibility as it relates to welded construction typically falls on the structural engineer, whose formal training may have included little exposure to welding engineering principles. While all the issues cannot be addressed in one paper, the goals of this article are to identify some of the key items that must be considered, and to provide the technical principles that should be applied when welding procedures are being evaluated.
ARTICLES FOR DISCUSSION
Period of Vibration of Buildings: (R. Park)
A discussion on how much cracking, and in what situations, should be allowed for in calculating the moment of inertia of concrete members subject to aseismic design, and hence the period of vibration.
What Stiffness? (T. Paulay)
Further discussion on the stiffness and strength of members used in aseismic design, with comments on Esli Forrest’s article in Vol.12, No.1, plus a warning against excessive deflections.
Theory and Reality: (C.R. O'Grady)
A letter commenting on the gaps over the years between code requirements and the performance of actual buildings, especially in earthquakes. Additional observations are made about what moment of inertia of members should be used in aseismic design, the merits of shear walls, and the fundamental effects of architectural decisions on the form of a building, and hence its aseismic design.
Shrinkage of Auckland North Shore Clays:
Letters from Malcolm Stappelton, Stephen Crawford and J. Grant Murray commenting on the paper of this title in Vol 12, No.1, from the point of view of geotechnical specialists.
PROJECT REPORTS
The Otira Viaduct: (N. Snoep)
The Otira viaduct is a 442m long two lane concrete box girder road bridge built to bypass an actively eroding mountainside which is threatening to cut State Highway 73, which is one of three crossings of the Southern Alps, linking the East and West sides of the South Island. The viaduct is the longest span reinforced concrete bridge in New Zealand.
MATERIALS CORNER
Design for Chloride Durability of Reinforced Concrete Structures in Exposure Classifications C and B2 of NZS 3101: 1995: (L. Gaerty)
The Building Act 1991 and the subsequent NZ Building Code required greatly increased provision for ensuring durability. Consideration is given to the assessment of the diffusion of chloride ions into plain concrete and also that with supplementary cementitious additives.
COMPUTER CORNER
Analysis of Reinforced Concrete Columns: (R. Fenwick and K. Al-Sayegh)
A user friendly, visual and interactive program has been written for the analysis and design of reinforced columns of virtually any cross section, for uni-axial and bi-axial bending. Interaction diagrams can be developed.
Are We Becoming Over Computerised: (E.J. Forrest)
This article advises that preliminary designs should be made with hand methods or Mini programs before Mega programs are run, to guard against gross errors which may occur through incomplete understanding or data inputting of the larger applications.
Understanding of Basic Structural Behaviour: (G. Bird)
Some simple structures with simple restraint and loading conditions are offered as a challenge to readers to check their understanding of basic structural behaviour.
STANDARDS NEW ZEALAND REPORT
Standards for Structural Engineers: (I. Brewer)
A review of current progress on revisions to the Loadings, Masonry Structures not Requiring Specific Design, Glazing, NZ3604 in Digital Format, and Concrete Reinforcing.
Timber Framed Buildings; NZS 3604
A description of the background to, and of, the new Standard out in May 1999.
Changes to Galvanising Standards: (W.L. Mandeno)
Two well known standards for galvanising have been withdrawn, and they have now been replaced by new standards.
NOTES FROM THE REGIONS
News of Meetings and Visits from the Auckland (S. Tucker), Wellington (C. Ashby), and Christchurch (L. Cotter).