Journals >> Abstract VOLUME 10. No. 2 (December 1997)
Multi-Storey Precast Concrete Framed Buildings : ( A.J. O'Leary)
Design and construction aspects of precast concrete moment resisting frames for the lateral load resistance of multi-storey buildings are described. The paper concentrates on the particular aspects of the framing system of a 13 storey building constructed in Wellington, New Zealand. The building is octagonal in plan with a perimeter lateral load resisting frame consisting of two storey high precast reinforced concrete elements. Each element includes a column plus two levels of beam stubs. In-situ concrete mid-span beam splices and grouted steel sleeve column rebar splices form the joints between individual units.
The paper briefly presents other similar precast systems used for multi-storey buildings. A review of laboratory testing recently completed will be given which confirms the good structural performance of the framing systems described.
North Harbour Stadium Roof : ( P. Tillson)
The paper covers the design structurally and architecturally of a large sports stadium. The structures is a large steel tubular space frame arch spanning the length of the playing field. Design aspects covered are the dynamic analysis and response of the frame for wind and other loadings. Mitigation of wind uplift loadings by venting, etc. The grandstand itself is precast concrete construction. The stadium facilities are multi-functional to allow the facilities housed within the grandstand to be hired out for conferences etc. between major events. This is essential to the survival of the stadium. The engineering of the roof for the eastern grandstand was not concerned just with efficient design; all the parties involved in the project realised that the stadium had to be visually unique to be successful. That meant aesthetic, innovative design in all disciplines was essential. The roof evolved with the grandstand and the overall planning. Auckland's weather is often inclement during the winter. Therefore maximum protection of spectators from the elements was a primary concern. The extension of the roof towards the field had to be maximized.
Embedment Length of Starter Bars Grouted into Reinforced Concrete Members: ( J. Restrepo and D. Wilkinson )
Cement-based grouted connections are widely used in the precast concrete and retrofitting building industries in New Zealand. The main difference in behaviour and capacity between reinforcing bars anchored in cast-in-place concrete and grouted starter bars is the potential bond failure that exists between the grout and the concrete. Current design methods for obtaining the embedment length of grouted starter bars in tension into reinforced concrete members are based on a nominal bond strength at the grout-concrete interface.
A series of tensile tests were performed to provide experimental verification to the recommended grout-concrete bond strength values and to investigate several variables that are believed to affect the grout/concrete bond strength. This paper discusses the findings of the experimental programme and proposes a method for evaluating the embedment length of grouted starter bars into reinforced concrete members.
Behaviour and Design of Multi-Storey Steel Framed Buildings for Fire Emergency Conditions: ( G. Charles Clifton )
This paper provides a brief, non-technical overview of the behaviour and design of multi-storey steel framed buildings for fire emergency conditions. It addresses the issues raised by Dr Buchanan and presents very brief details of current and proposed future research being undertaken to make the design of multi-storey steel framed buildings for fire emergency conditions more efficient and effective.
The paper commences by briefly addressing the requirements that the Building Control System (BCS) imposes on structural response in fire. This leads on to fitting fire into the limit state framework, taking into account any additional building owner and insurer requirements and discussing the differences between the structural effects of fully developed fire and severe earthquake. This is followed by the philosophy that HERA recommends should be adopted for multi-storey steel building response in fully developed fires, and on which all HERA fire engineering design recommendations are based.
The behaviour of multi-storey steel buildings in fully developed fires, as is being understood through full scale experimental tests and review of actual fire case histories, is then briefly covered. The paper goes on to address the adequacy of our current design and research tools for determining the response of steel framed buildings to fully developed fires. This is followed by a very short overview of current and proposed future research on this topic.
Ultimate Lateral Capacity of Piles Embedded in Soil : ( M.J. Pender )
Two well-known papers by Broms (1964a and b) set out a simple method for estimating the capacity of piles when loaded laterally. The papers deal with piles in sand and piles in saturated clay. They provide the long term capacity of piles in sand and the short term capacity of piles in clay. Short, long, and intermediate length piles are covered in both free head and fixed head configurations. The basis of these methods has survived more than 30 years since publication, the reason being that the method is based on simple ideas which have been found to give useful solutions to practical design tasks. Broms provided design charts for estimating pile capacity. These can be difficult to read and are not convenient for parametric studies. With these problems in mind a complete set of equations are presented from which the lateral capacity can be calculated.
The material given herein differs from the Broms papers in two minor respects. First, an additional soil profile is included, namely that for a normally consolidated clay which has a linear increase in shear strength with depth. The soil parameter which characterises this profile is the rate of increase of the undrained shear strength with depth. Second, for the saturated clay soil profile, Broms assumed that from the ground surface to a depth of 1.5 pile diameters there is no interaction between the pile shaft and clay, herein this depth is expressed as a variable, denoted by fo.
PROJECT REPORTS
Queenstown Bay Reservoir : ( Dr. A.J. O'Leary, J.E. Mason, J.W.P. Hadley )
The Queenstown Bay Reservoir (QBR) project forms part of a major infrastructure upgrade being undertaken by the Queenstown Lakes District Council (QLDC) throughout the Wakatipu district in Central Otago, New Zealand.
Queenstown is a resort centre catering for both winter and summer outdoor tourist activities including snow skiing, white water rafting, hiking and climbing, etc. It is located in a glacial valley on a lake edge and is thus surrounded by steep hills. Much of the residential growth is on the sides of these hills.
The QBR project has been advanced by the QLDC on a competitively tendered design and construct basis. The successful tender was a joint submission from the main contractor, Naylor Love Limited, and the design engineers for the project, Kingston Morrison Limited.
All wall elements are precast off site. A maximum water depth of 8.5 metres was required to give the required water storage within the site restraints To keep the element weights down and allow for handling and cartage a system of whaler beams and cross ties was used to resist the hydro-static pressure.
The new reservoir replaces the existing two 450 m3 reservoirs on the site and will allow the QLDC to meet water supply and storage demands to the year 2020. The new reservoir will provide 8600 m3 of storage when both stages of the work are completed in December 1997. The existing reservoirs supply the central business district of Queenstown and the majority of the residential population for the town. Consequently it was a requirement of the contract that the water supply to the town be maintained at all times during construction of the new storage. The QBR is a water retaining structure of unconventional geometry that has undergone specific design and concept development to accommodate challenging site constraints and two-stage construction.
Rosebank Patiki Interchange Bridges : ( N. Sneop )
The $17M Rosebank Patiki Interchange located on Auckland's North West motorway is currently under construction for Transit New Zealand and will provide for traffic to enter and exit the motorway to and from the Avondale industrial area. To achieve this, three new road bridges and one cycleway / pedestrian bridge are to be provided, to either cross over the motorway or cross over areas of tidal estuary.
All road bridge structures consist of a cast-in-place concrete deck on post-tensioned and, or pre-tensioned precast concrete I girders, with concrete substructures supported on driven precast concrete piles.
ARTICLES FOR DISCUSSION
Recent Editorial Comment : ( P. Smith)
The article discusses how standards effect the profession. This is appropriate given the present environment in New Zealand with Standards New Zealand fighting for survival and government, in particular, obstinately refusing to recognise that Standards are as much for the public good as for the profession. The authour suspects that too much of the profession's output is in fact to minimum Standards and that by allowing the role of professional judgment to be removed, the role of the profession is reduced to a commodity.
In the past many engineers adopted design standards in excess of code minimums and building owners and the public in general have benefited from those decisions. Often the decision to design to greater than code minimums was driven by lack of confidence in the code, the likely seismic response of the building to any particular earthquake, or a hearty respect for earthquakes. Today's codes are so apparently sophisticated that they provide an unrealistic expectation of the state of the art.
Can Anyone Tell Me How?: ( E. Forrest )
By using a fictitious seismic event the author illustrates the anomaly between the Building Act's ten year limitation on legal proceedings and the requirement of a fifty year building life in the Building Code. The article raises the question of what use it is to have a fifty-year durability requirement when there is only legal redress for break down in the requirement for ten years. It also raises the question of how any damages can be recovered where the failure occurs beyond the ten year period and there is blatant negligence in the construction.
COMPUTER CORNER:
Member design to NZS 3404: 1997 ( G. Bird )
A description of the MemDes program for segment and member design to the new steel code. The program covers bending, axial, shear and combined action and also has a section for fire design of members giving the PSA for the fire loading and exposure.
A Review of Bridge Deck Behaviour by E.C. Hambly ( R. Collins)
A review of the book by E.C. Hambly describing computer structure modelling for bridge decks.
MATERIALS CORNER :
Greenweld Process for Engineered Timber : ( J. Parker)
The Greenweld* process is an advanced adhesive system for gluing wood at a wide range of moisture contents ( from kiln dry, 12% m.c. to more than 150% m.c. oven dry basis) and at a wider range of temperatures than conventional wood adhesive systems. The system has been installed in a number of finger-jointing plants in New Zealand USA and UK and is currently being extended to face and edge lamination uses, where the above features and the short clamping times required mean that gluing timber to increase value becomes more viable than with conventional cold cure or radio frequency cure systems.
