Report Back: HybriSem 2015

HybriSem 2015 logo final HybriSem 2015 was the final national seminar of the year and attracted a wide range of delegates from the built environment sector including engineers, contractors, concrete product manufacturers, material suppliers and more.

 
The event was held in Stellenbosch, Port Elizabeth and Kempton Park and was chaired by John Sheath, CEO and Director of the Concrete Society.
The seminar focussed on the latest developments and technology surrounding the use of hybrid concrete construction (HCC) methods, i.e. the combination of precast concrete and in-situ concrete on projects. In his opening remarks the Chairman posed a key question to the delegates, namely: “If the purpose of HCC is to provide improved value to a project and provide the industry will a multitude of benefits, why is it so under-utilised in South Africa?”
“I hope today that with the input from all our guest speakers, we will go some way towards answering that question, and what is more to the point - what can be done to change the mind-set of the industry to consider adopting its use more readily”, he said.
 

Watch the video overview here, courtesy of Concrete.TV:

 
 
Presentations:
 
Professor Jan Wium from Stellenbosch University presented findings from a survey recently carried out by the University into improvement in project delivery, in support of the National Development Plan and where hybrid concrete construction could improve this.
The survey revealed that currently consultants and contractors preferred in-situ concrete or precast concrete, in an equal percentage whilst the balance ‘depended on the situation’. Both professions chose precast for its time efficiency and final quality, but preferred in-situ for its cost.
He described the concerns of the professions relating to the design and construction of precast concrete, which covered design guidance, standardization and repetition, technical aspects, and late changes. The construction factors were identified through case study projects, including site visits and discussions with the project teams, at Grootegeluk and Shondoni coal bunkers; Cape Town dispatch plant for Value logistics; Bloemfontein Longridge reservoir, and the VWSA paint shop.
After an in-depth look at the various connections that are required in the use of hybrid concrete construction, he concluded by summarising the requirements that were needed to persuade the industry to utilise more of this unique method of construction.
 
Dr Vincent Teissier, visiting South Africa from the LafargeHolcim Center of Research in Lyon, France, described two innovative systems which maximised the potential of concrete by combining precast and in-situ concrete.
The first of these, which he described as a Pre-Wall System, featured a precast twin-wall panels, linked by steel connectors and filled with in-situ concrete.
No formwork was required, and a good quality finish due to precast manufacturing, structural load bearing capacity was achieved.
Principal applications include:
      • Residential buildings, offices, car parks, schools, military.
      • Industrial buildings, fire walls, technicals, etc.
      • Miscellaneous: fences, basins, silos, waste recycling plants, sound insulation walls.
The second system, presented by Dr Teissier’s, colleague Christophe Berger utilises a composite system associating precast & in-situ concrete + wood frames. The precast panel comprises a concrete wall plus a wooden frame provided to host insulation materials, linked together with elements of galvanised steel.
 
 
Key features were described as:
      • Increased speed of construction by maximising contribution from precast
      • Improved safety on site, no use of scaffolding
      • “Clean” job sites, with limited use of formwork
      • Various type of finish for external skins (colour, matrix, aesthetic concrete)
      • High thermal insulation and air tightness
Dr Teissier concluded by stating that Hybrid Concrete construction combines all the benefits of precasting with all the benefits of in-situ concreting. To date, cost savings up to 30% have been achieved by using this method of construction construction. Looking ahead, he sees greater potential being achieved by combining all of these elements with fully integrated design opportunities offered by the BIM (Building Information Model) technology.
 
Daniel Petrov, Technical Director of Echo Prestressed (Pty) Ltd, presented an overview of HCC using precast hollow core panels. Going back in time he described the Ronan Point disaster from 1968 which set back the use of precast concrete in construction.
But nearly 40 years later, saw a revival of the use of hybrid concrete construction as confidence in the system with its improved design and technology, provided the peace of mind that was necessary to re-introduce this system.
The advantages of using HCC with hollowcore units were described as follows:
      • SPEED - Repetition + Productivity
      • TIME - Reduction in Construction Time
      • BUILDABILITY - HC Integration with other Structural Elements
      • SAFETY - Improvement in Predictability
      • COST - Savings in Capital investment
 To achieve best practice in construction using hollowcore, Daniel cited:
      • Early involvement of specialist contractors
      • Using a lead frame contractor
      • Using best value philosophy
      • Holding planned workshops
      • Measuring performance
      • Trust
      • Close co-operation – with an emphasis on partnering
The presentation was brought to a close with a description of alternative applications of hybrid concrete using hollowcore, including a unique hollowcore gravity wall.
 
The immediate reaction from many when modular concrete construction is described, is a perception of dull grey boxes. The next presenter set out to dispel this perception. Charles van Eck of Tilt Up Systems presented the tilt up method of construction which, after many years of trying to persuade owners and designers to capitalise of the benefits of the system, is now growing at a steady pace in South Africa.
 
In describing tilt-up to delegates, Charles stated that a high quality finish is obtained; rapid construction is achieved due to pre-manufacture of the panels, and a hardwearing/durable and cost -effective end product is obtained.
A comprehensive look at some of the iconic projects that have embraced tilt up were shown.
In summary, Tilt Up addresses weaknesses in traditional construction methods; delivers high quality within tight time and monetary constraints; is gaining acceptance across South Africa and is destined to become the construction method of choice for low rise projects.
 
In his second presentation, Daniel Petrov gave an overview of the different connections required when constructing with HCC. These are Frame (column to column, foundation to column, column to beam and floor to beam), Wall and Balcony connections, as well as joint reinforcers.
Some type of connection is needed between each produced precast unit. Demands for connection types vary among different precast products, local building conditions and restrictions, and loads on the structure. Generally every country has its own system for precast connections.
Typically, precast connections can be done with an industrially-produced connection part, wet connection, bolt, or weld connection. In precast connection design the key variables are strength, volume changes, ductility, durability including fire and corrosion, simplicity in production, installation and maintenance, temporary loading conditions, economy and appearance.
There are several pre-tested connections for hollow-core slab floors. Hollow-core slabs are normally installed on neoprene strips that can also be used as part of the final connection. Neoprene strips ensure a uniform bearing of floors.
Connections at longitudinal joints are used between the edges of the hollow-core floor unit and beams or walls running parallel with the floor. Their main function is to transfer horizontal shear on the precast units.
Examples of each connector were shown and the special features that they exhibited.
 
Werner Jerling, MD of Stefanutti Stocks Civils, brought a different perspective to the seminar with a contractor’s view of hybrid concrete construction (Mike Stevenson, Contracts Director presented in Port Elizabeth).
Delegates were shown local examples of projects using HCC in bridge and infrastructure barriers, marine structures, mining construction, bulk storage, sports facilities and industrial and high-rise buildings.
Werner stressed the importance of a high level of designer and contractor interaction when designing for HCC structures. Teamwork was paramount he said. In addition, alternative bidding processes must be considered, which could include the contractor engaged in to do pre-construction engineering, design and construct programmes, and some form of collaboration or partnering.
When designing for HCC, Werner emphasised that the following factors must be taken into account:
    • Mould design limitations
    • Casting and curing of elements
    • Lifting and placement
    • Safety during construction (access etc.)
    • Stitching execution
He continued with a comprehensive look and the pros and cons of HCC from a contractor’s point of view, followed by casting yard, moulds, transportation and erection considerations.
Looking to the future Werner shared some of his ideas of possible applications in the future:
        • 3D Development of complex shapes to be manufactured.
        • 3D Mould manufacture (As blanks or as disposable moulds)
        • 3D Printed inserts and components
        • Elements with a variety of concretes and materials in. In particular to achieve high performance only where the elements need it
        • Clever methods to reduce weight
        • Use of high tech adhesives and composites in hybrid construction
        • Integration of fireproofing in hybrid elements
        • Integration of instrumentation for intelligent structures or elements
 
The final speaker for the day was Krzysztof Szymczak, MD of Logiman. The presentation focused on the design and construction of concrete coal surge bunkers at Sasol’s Shondoni Colliery. Two bunkers were constructed one of 15,000 tons capacity and the other of 4,000 tons capacity.
 
Krzysztof explained to delegates that the reasons why the hybrid concrete method had been chosen for these structures were safety (fewer people, reduced in-situ work and reduced time on Site); quality (superior quality product in factory environment at ground level and superior surface finish); time (faster erection time – structure is pre-made); and cost (reduced quantities – lighter construction).
A comprehensive description was then made on the project including design parameters, construction and risks.
This presentation was a fitting end to the seminar, as it portrayed the very best in hybrid concrete construction, and was recognised as such, through the project receiving two technical commendations in the Concrete Society’s 2015 Fulton Awards.
 
The seminar was formally closed by the chairman, who took the opportunity to thank the CMA for their support and input into organising the event, in association with the Society.
Thanks were also expressed to Lafarge South Africa as the main sponsor for the national seminar, and to the many others sponsors at the various venues around the country, namely:
PPC, BASF, Chryso-abe, The Concrete Institute, SIKA, Samson Technologies, Corestruc and Sanika Waterproofing.

 

 

HybriSem 2015 - Photo Gallery
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