BUILDING TALL

"Come, let us build ourselves a city, with a tower that reaches to the heavens, so that we may make a name for ourselves" (Tower of Babel, Genesis 11).

History of Building Tall in London

High-rise buildings had been built as early as 1951 with 1963 signifying the year when they started to be built extensively.
It's a common view that skyscrapers built in this period were poorly designed and scar the capital's landscape.
Projects such as the Gherkin and the Shard are justified based upon their exceptional design, others (Vauxhall Tower) are not.
There is not strategic, coordinated vision of what London wants it's skyline to be like.
Towers are being built in an ad-hoc fashion with no though to their impact on the city's character.
Millbank Tower in Pimlico contributes to this lack of vision and set a precedence for building high-rises along the Thames.
The Shell Centre in Southbank is London's first symbolic skyscraper as it was the first to exceed the 99m height of the Houses of Parliaments Victoria Tower which was the capital's unofficial height limit for over a century. This paved the way for the continuous scramble of the skies that's defined London's skyline every since.

Peculiarities of London

London has protected views (e.g. St. Paul's) which heavily influences the location & design of tall buildings in London.
It is argued that properly designed & sited tall buildings can be an asset to an urban landscape but some dominate & destroy the remote feeling of royal parks and/or compete with national monuments (e.g. New Zealand House, West End)

Legacies of Tall Buildings in London

Millbank Tower, Pimlico: Completed 1963 - Legacy: tall buildings on the river (e.g. The Shard, Nine Elms)
Shell Centre, Southbank: Opened 1963 - Legacy: skyscraper corporate HQs (e.g. Gherkin, Natwest Tower)
Centre Point, Soho: Office - Legacy: speculative commercial high-rise (e.g. One Canada Square, Pinnacle)
Balfron Tower, Bow: Residential - Legacy: residential tower blocks near arterial/elevated roads
Portland House, Victoria - Legacy: tall buildings at transport interchanges.
London Hilton, Mayfair: Completed 1963 - Legacy: sparked damaging trend of building tall on edge of Hyde Park.
New Zealand House, West End: Opened 1963 - Legacy - tall buildings in historic contexts.

Pinnacle Tower - London

The 7 floors of concrete core of London's £1 billion Pinnacle tower could be knocked down and re-built from scratch.
Proposal came following a review to make it more viable and cost efficient in the current market.
The 63 storey tower would be London's tallest tower if built but has laid dormant due to funding issues.

Designing Tall Buildings in London

The context of the building is important.
Tall buildings must be exceptionally designed and sensitively located with a planning mechanism that ensures this is delivered.

Factors Affecting Vulnerability to Progressive Collapse

The redundancy of the structure and available alternative load paths.
The retention of structural integrity in fire.
The strength, ductility and energy absorption capacity of the structure.

Impact of World Trade Centre on Future of Tall Building

September 11th, 2001 in New York.
Must be assumed the future events may be more severe and different extreme events than those that have occurred to date.
Limitation to damage from all eventualities has to be the aim.
Decisions must be made the owners, operators, designers and building managers based upon an understanding of all issues.
Coordination between design, building management and relationships with emergency services are required to maximise the protection of building occupants.

Methods to Prevent Progressive Collapse

Increase the capability of the structure to bridge over damaged parts by providing alternative load paths.
Use robust, ductile and energy absorbing structural elements.
Provide robust, resilient and durable passive and active fire protection.
Mitigate spread of smoke and design building to survive a complete 'burn out' of it's contents.
Provide robust and adequately sized escape routes with back-up power/lighting and prevent ingress of smoke.
Implement and trial evacuation strategies and emergency responses at regular intervals
For cladding/glazing, use laminated or toughened glass with fixings designed to resists potential explosion loading/impact/fire
Provide security against unauthorised entry and incident prevention measures such as barriers to protect the base of the building.
Use 3rd part inspection, testing and certification during design and construction to minimise quality risks.

COMPLEX GLOBAL PROJECTS - KARACHAGANAK EXPANSION PROJECT

What is the Project?

The Karachaganak Field Expansion Project (KEP), Kazakhstan.
One of the largest gas condensate fields in the world.
Increase gas re-injection to aid maintaining reservoir pressure
Extend oil production, maximise liquids recovery & optimise future liquids take-off.

Execution Strategy

KEP will be a multi-stage development to reduce execution risk & create a feasible and manageable work programme.
With discrete independent projects and specific scopes and objectives for each stage.

Key Challenges of the Project

Location, climate & complexity of the systems.

Risks of Mega Projects

Megaprojects are complex and fragile.
Clear project definition at early stages of project is required.
Technical & organisational complexity required.
Must have right resources and an experience project team.
Focus on lowest cost rather than value.
Cost and schedule targets are a key success factor which the industry's performance in is declining.
Lack of experienced staff and skilled labour.
Industry is stretched with increased number of mega-projects.
Long equipment and material lead in times.
Stakeholder attention.

CONCRETE INNOVATIONS

Bendable Concrete

Formally known as Engineered Cementitous Composites (ECC)
Developed in 2000 by Michigan University.
It's tensile ductility reduces cracking & fracture problems.
300 times more deformable in direct tension than conventional concrete.
Tensile strain capacity of 3-5% compared with 0.1% of conventional concrete.
Can self-heal upon cracking.
Can be used with common construction equipment.
Under shear tension failure mode it's loading capacity is increased by 50% and it's ultimate deformation by 200%.
Under shear compression failure mode it's load capacity increases by 50% and it's ultimate deformation remains the same.

Case Study - Mitaka Dam, Japan

Severely damaged 60 year old structure.
Evidence of cracking, spalling & water leakage.
Successfully repaired in 2003 using a 20mm layer of ECC sprayed onto surface.

Concrete Canvas

Won material of the year 2009.
Once the cloth shelter is erected, the hardening process is started by adding water.
Originally designed for shelters, the British Army now use it to create fortified positions.

Pervious Concrete

High porosity concrete created by a high void content.
Allows water from rain to pass through.
Reduces run-off and allows groundwater recharge, often used in parking areas, residential streets & walkways.

Self-Compacting Concrete (SCC)

Developed in late 1980s in Japan and increasingly used in EU.
Does not require vibration for placing & compaction as it is able to flow & compact under it's own weight whilst achieving the same engineering properties as traditional vibrated concrete.
Suitable for many applications: precast elements, basements, cladding, column encasement, top-down construc

Advantages of SCC

Noise eliminated
Healthier and safer working environment
Reduced demand for skilled labour
Faster placing time
Improved surface finish
Reduction in making good costs

Disadvantages of SCC

More expensive - approximately £10-23/m3
More cement & special mix required.
Requires different handling & more tests on site.
Improved formwork quality & increased pressures.

Economic Applications for SCC

Precast elements
Exposed walls and columns
Watertight basements
Wall cladding
Dense reinforcement
Column encasement (e.g. Albion Wharf)
Top-down construction

Other Concrete Innovations

Termodeck - Precast cement slabs with holes through the centre to promote passive ventilation.
Holocore Slabs - Can integrate services in the slabs (e.g. HVAC services)
Pre-assembled concrete block walls.
Lightweight slabs (cobiax biaxial flat slabs - 35% weight reduction)
Insulated concrete formwork
Nudura - Claimed to be 6-7 times faster than traditional concrete wall construction.
Insulated Concrete Formwork (ICF) - Formwork is built using large, hollow polystyrene blocks which are filled with concrete & reinforcing bar as the project progresses, with the polystyrene remaining in place as an insulating layer to a completed structure.
Extensia - Reduced thickness industrial concrete floors (225mm thick to 175mm) without the need for joints & 20% carbon saving.

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Undergraduate Advanced Construction (Summary Notes) Notiz am Summary , erstellt von d.moran-10 am 03/06/2014.