QUALITY ASSURED PRECAST KEEPS ABREAST OF CHANGING INDUSTRY
As evolution of our environment and the way in which we build things changes at a ferocious rate, PCNZ's ongoing journey of 10+years has demonstrated a strong commitment from PCNZ's members to research and develop improvements in precast product and quality. New solutions and ideas enhance the value to the industry of the PCNZ plant certification scheme - providing a safer more reliable built environment to building users.
But how did they do it ? Read through for an insight into PCNZ's latest industry initiatives and technology development case studies.
PCNZ are pleased to introduce our new President - Justin Bragg, one of two founders and Directors of Concretec NZ. Justin had 20 years of experience in engineering, manufacturing and management roles before cementing his future in the precast industry in 2005. Justin holds a Masters Degree in Civil Engineering from Auckland University and is an avid yachtsman and squash player.
PCNZ President's Commentary
The Precast NZ Plant Certification scheme provides customers with a level of confidence that products purchased from a PCNZ Certified Plant will be from an established operator with appropriate manufacturing facilities, testing systems, quality assurance programs, levels of expertise and experience which have been subject to independent third party audits. The number of precast plants meeting this level continues to increase and are listed on the PCNZ web site:
Precast NZ furthers wider construction interests by active involvement in New Zealand standards, including concrete design and conditions of contract. Shortly we expect to commence a review and update of the combined Master Builders / Specialist Trades conditions of subcontract SA-2009 to recognise the 2015 amendment to the Construction Contracts Act.
We also promote and support research projects covering design issues for incorporation into the concrete design standard as well as researching curing, to recognise the variables involved and the effects of accelerated heat curing as widely used in the precast industry.
We have made submissions and lobbied on relevant legislation including a recent update of the Construction Contracts Act which resulted in legislation providing a level of protection for retentions. We have also supported successful legal challenges on important matters of principle including the ability for receivers of failed companies to declare payments made to subcontractors void and claw back payments made by contractors prior to their receivership.
Our association with overseas bodies continues to provide benefits and the 2016 biennial meeting in Sydney in November was popular with a large number of members. Finally, we continue to actively promote the benefits of PCNZ, welcome new members and encourage associated companies to join.
We are active with Worksafe NZ on reviewing and updating the Approved Code of Practice, as well as developing our own specific industry guides. These will become more relevant with the new Health and Safety at Work Act 2015. Training will become very important.
Preast Lead Times
Small to medium precast projects achieved with very
short lead times in a busy market.
While the current construction market is very busy and lead times for precast are often quoted as several months, the reality is many projects run later than planned, which create “gaps” in pre-casters' forward work loads. Hence smaller projects can often be completed with quite short lead times, filling these gaps.
One recent example was an order placed 11th October 2016 for 16 off large 7.5 tonne - pre-cast foundation units for a CSP culvert in Karaka, South Auckland. Shop drawings were completed within one week of the order, and production commenced 19th October, with manufacturing completed in early November and all units installed on site by 15th November. Hence a lead time of just over one month from order to project completion. Similar examples are continuing through 2017 and we expect this will carry on..
NEW UNIVERSITY OF WAIKATO LAW & MANAGEMENT BUILDING
Construction of this 6000 square metre building, “Te Piringa”, designed by Opus Consultants, marks the 50th anniversary of the university.
The steel-structured building is being constructed on a hilly area of Hamilton and because of the deep clay subsoil on the site there was a necessity to reduce the overall deadload on the building . . . and this is where Litecrete comes in.
Litecrete lightweight precast concrete cladding panels, at 150 mm thick, are half the weight of standard precast, so that the architect can still achieve a solid concrete look AND take advantage of reduced deadload, smaller structural steel members and overall cost-savings.
The 5-storey office tower is clad with vertically-ribbed Litecrete panels which, along with vertical sunshade vanes, symbolise the tukutuku reed panels of a traditional meeting house. Litecrete was also used for internal wall areas to continue the emphasis on creating light, spacious, open areas for working and studying in, and for making the building as energy-efficient as possible.
CARLAW PARK - Student Accomodation Village
'Revitalisation of a forgotten Landmark'
Carlaw Park was once a significant destination for Auckland; in 1844 it was Auckland’s first flour mill, then In later years it became a Chinese market garden until 1921 when it was officially opened as the home of Auckland Rugby League. In 2002 the site was vacated and became an under-utilised and overgrown car park.
In 2012 Auckland University began the transformation of the site into a dynamic student accommodation village, This project brings a richness of activity back to the site and revitalizes a forgotten Auckland landmark.
Excellence in Precast
Modulated into three ‘blocks’ the Carlaw Park Student Village is manufactured using architectural precast concrete. Monarc Creative Precast 'Tabasco' colour concrete was selected for its local resource abundance and natural pigmentation providing an earthen undertone. Colours were accentuated with post erection concrete stains. Dynamic window depth was created through custom precast mouldings providing continuity of appearance and depth.
Designed with Sustainability
Carlaw Park celebrates sustainability excellence and was awarded the 2015 Concrete 3 Sustainability award for Excellence in Commerical Concrete Construction.
North / East orientations follow natural land form and capture the sun’s natural light and energy
Precast concrete thermal mass helps to minimize heating requirements.
Constructed using sustainable and recyclable materials that are durable and low maintenance
Precast provided speed of construction, thermal and acoustic insulation and high fire ratings
Ryman Health Care, Petone. Base Isolated Precast Structure,
Several buildings are currently under construction at the Ryman Health Care Petone site, one of these is the Village Centre.
The precast building comprises five suspended levels with below ground basements.
The site is located close to a fault line and the structure is relatively heavy consisting of precast walls, ribs and timber infill suspended floors, custom 1200 x 600 shell beams, brick veneer and a heavy roof. In addition, the Engineers Mitchel Vranjes were challenged with a very high water table and liquefiable soils which required remediation and also the requirement to increase seismic loads by a further 30% due to an Importance Level of 3 (high occupation level).
Traditional elastic design using these parameters resulted in a relatively high seismic coefficient, well in excess of unity.
From previous building designs for Ryman throughout NZ, Mitchel Vranjes anticipated extreme design difficulty and very high uplift loads.
They also recognized that the traditional use of transfer beams supporting shear walls at basement level, would not be possible unless architectural configuration was changed significantly. In summary, MV elected to design a base isolated structure on large pre-stressed precast beams.
The proposed base isolated structure for this site was considered ideal as this type of solution is particularly suited to a heavy squat type building of low period.The base isolated building will experience a, “period shift”, resulting in lower seismic lateral loads.
The structure has been modelled in ETABS by Opus and the isolators are sized based on the Maximum Credible Earthquake (MCE) event.
The cantilevered columns supporting the isolators, the floor diaphragm immediately above the isolators and the basement raft foundation are all designed for the MCE event; this event also captures the maximum expected drift of the isolator, estimated as 700mm for this building.
Another issue with this site is the potential for liquefaction and the subsequent differential settlements that may be introduced post-earthquake and a very high water table.
The water table is approximately 2.5 metres above the sub-grade level of the basement foundation level. This equates to 25kPa up-thrust on the underside of the slab.
The MV design rationale was that a 1 metre reinforced concrete slab will effectively counteract this uplift under the action of its self-weight. Whilst a thinner slab may be possible we would then have to rely on the flexural strength of the slab to span between columns. This would result in residual stresses within the slab with a reduction in capacity under a seismic event.
A “zero stress” slab was considered to be the most appropriate; this has been constructed at 1 metre depth (25kPa) - balanced! The other consideration for the slab is that it must be adequate for the cantilever moment from the columns; a 1 metre depth slab works well for this loading case and also for punching shear.
Remediation to a depth of 4 metres below slab was also undertaken by the installation of stone columns; these occupy approximately 14% of the overall plan area and comprise 600mm diameter columns at 1.5 metre centres.
Two types of isolators were adopted for this building
Lead Rubber Bearing (LRB) - 1000 diameter
Sliders (Stainless Steel and Teflon)
The sliders were chosen as the internal support columns can be reduced in size due to a reduced moment demand.
This reduction in column size was required for vehicles turning within the carpark area.
The sliders are a Teflon type bearing attached to the column.Immediately above this bearing a large stainless steel plate is attached to the underside of the floor diaphragm pre-stressed shell beams.
The moment in the bearing is distributed half into the column and half into the upper diaphragm. The diaphragm has to be very rigid, thus the use of a two way beam grid system that takes the loads. The beam system comprises precast custom made 1200 x 600 shell beams.
The base moment in the column is distributed into the raft slab.
The seismic mass is approximately 160,000 kN.y. This was not an option.
Associate Member Companies
0800 Ducting Limited
Argon Construction Limited
Austin Carr (2008) Limited
Golden Bay Cement
HJ Asmuss & Co Limited
Holcim (New Zealand) Limited
Humes Pipeline Systems
Hynds Pipe Systems Limited
Machinery Movers Limited
RC Macdonald Limited
Reid Construction Systems
Roadex Logistics Limited
Sika (NZ) Limited
Supacrete Concrete Limited
Thorpe Reinforcing Limited
Professional Associate Members
Clark Precast Limited
Gregory Draughting Limited
Kevin A Badcock
Mike Herlihy Consulting Limited