Critical Analysis of Construction Materials: Case Study of Leadenhall Building and Sydney Opera House

Introduction

The two buildings I have chosen for this assignment are the Leadenhall Building in London and the Sydney Opera House. Both buildings are iconic in their own right but have very different designs and structures. In this assignment, I will look at the construction materials used for each building in turn.

Leadenhall Building, London

Construction of The Leadenhall Building began in Autumn 2011 using some of the most advanced technologies available at the time. (Anon., n.d.)

The Leadenhall building is located in London. Nicknamed the Cheese grater because of its iconic slanted design, it stands at 802ft high and its purpose is an office tower. It was designed by Rogers Stirk Harbour and Partners. Other structures in the area include the Nat West Tower and 30 St Mary’s Axe (The Gherkin)

During the 1960s the site housed an office block that stood at 12 stories tall. This was then demolished to house the new building in 2007/2008.

Located in the heart of the city, it houses many different companies including banks and insurance companies. Its location is easily accessible to public transport. (underground stations, Bank, Liverpool St, Moorgate and Aldgate)

Design and Structure

The Leadenhall building is a steel structure. When designing the building, there were specific requirements to protect views of London landmarks. Because of this, the designers developed an idea to angle the building at 10 degrees to ensure these views were not lost.

The building features a seven-storey landscaped open Galleria space of nearly half an acre at its base, providing lawns, seating, trees, retail units and exhibition spaces for public. The main reception of the building is accessed by escalators from the Galleria space.

Most of the structural and architectural components, with solid concrete floors, were manufactured off site and then delivered and assembled on site, which accounts for around 85% of the total construction cost. (Anon., n.d.)

The columns and beams of the outside tube frame are connected by nodes and all the linkages of the external frame are connected with the use of pre-stressed bolts made of steel rods with up to 76mm diameter. The construction of the building was 50% complete in November 2012. The topping out of the building happened in June 2013. (Anon., 2020)

The building features a sustainable design with office areas protected from solar radiation with the use of solar reactive venetian blinds fitted in the cavity of the double layer glass facade on the east, south and west sides of the building.

Water usage is minimised through low-flow water fixtures and fittings. The building also uses energy and water metering system for efficient management of water and energy consumption.

The building construction produced virtually zero waste since most of the components were designed and manufactured offsite. (Anon., 2020)

[image: The construction of the 50-storey building was started in 2011. Image courtesy of The Leadenhall Development Company Ltd.] [image: The 802ft-high Leadenhall Building features a tapering form. Image courtesy of The Leadenhall Development Company Ltd.]

As can be seen from the above extract, the Leadenhall Building produced its own unique design challenges. The main challenge in constructing the building was the very small floorplan, this was solved by the manufacture of the main steel structure being done away from the construction site and transported to the site. Each delivery of steel was made at low congestion times and unloaded and erected to a very tight time scale due to the lack of storage facilities on site. (Anon., 2020)

The Sydney Opera House

Sydney Opera House, located in the bay of Sydney Harbour, is a performing arts centre which since it opened in 1973 is now seen as masterpiece of modern architecture and a symbol of Australia.

It was designed by Danish architect Jørn Utzon, following an international architectural competition in 1957. His entry was said to have been excluded by the technical judging panel, but later reinstated on the recommendation of one of the judges, architect Eero Saarinen who would not endorse any other design.

Despite early controversy, the long-term success and appreciation of the building has led to it inspiring many architectural designs that incorporate complex geometries using computer-aided design techniques.

In 2007, it was inscribed in the World Heritage List by UNESCO who said ‘…It represents multiple strands of creativity, both in architectural form and structural design… it is one of the indisputable masterpieces of human creativity, not only in the 20th century but in the history of humankind.’

Work on the Sydney Opera House started in 1959. It was built on Bennelong Point adjacent to Jon Bradfield’s Sydney Harbour Bridge where it would be visible from all sides. In 1966 during an interview for Danish television, Utzon said ‘…it was an ideal project for an architect… first because there was a beautiful site with a good view, and second there was no detailed programme’.

At the centre of Utzon’s individual design was a set of joining vaulted shells that became one of the most challenging engineering projects ever attempted. Each of the shells is made of pre-cast concrete rib segments rising to a ridge beam, held together by 350 km of tensioned steel cable. Geometrically, each half of each shell is a segment of a sphere; however, the ‘sails’ were originally designed as parabolas, for which an engineering solution could not be found.

Although described as reinforced-concrete shells, they are in fact a series of concrete ribs that support a total of 2,194 precast-concrete roof panels which are in turn clad with over 1 million tiles. The tile surface is highly detailed and uses two types of tile – one glossy white, one matte cream – with clearly expressed joints.

The design of the shells involved one of the earliest uses of computer analysis to understand the complex forces they would be subject to, and it took some years to find the solution – that all the shells would be created as sections from a sphere, supported on arched ribs. This solution avoided the need for expensive formwork construction by allowing the use of precast units which could be tiled at ground level. Large parts of the site were used throughout construction as ‘factories’ for these precast components.

The opera house is supported on 580 concrete piers sunk up to 25 metres below sea level. The two main halls are positioned side by side, with glass curtain walls revealing the foyer spaces. The Monumental Steps, nearly 100 m wide, lead up to the two halls.

The enterprise and construction process was high profile and not without controversy. The administration, eager for work to begin for fear that public opinion might turn against the development, pushed for the construction to start before many structural issues had been fully resolved. This forced Utzon to adopt a radical approach to the building construction, integrating it with the design process in a joint and state-of-the-art way.

One fundamental problem was that the concrete podium columns were not strong enough to support the structure according to the final designs, and so had to be rebuilt. The roof shells went through several iterations before an acceptably economical solution was found. The ‘sails’ were built using cranes that had to be specially made and shipped from France.

The original air-conditioning solution best demonstrates the commitment to aesthetic integrity and sustainability. By operating Sydney Harbour’s plentiful water as the heat exchange medium, it enabled the iconic silhouette to remain uncluttered – a ground-breaking creativity on a world scale and the largest sea water heat pump system of its kind at the time. Further initiatives such as chilled beams also provided the original basics to build on in terms of low energy methods.

Concrete Versus Steel

Costs

Structural Steel: A large majority of all steel manufactured today comes from recycled materials; A992 steel. This recycling usage makes the material much cheaper when compared to other materials. Although the price of steel can fluctuate, it typically remains a less expensive option compared to reinforced concrete.

Concrete: A large cost benefit to concrete is the fact that its price remains relatively consistent. On the other hand, concrete also requires ongoing maintenance and repairs, meaning added costs throughout its lifetime. Supply-and-demand may also impact the availability of concrete. Even though it can be poured and worked with directly onsite, the process to completion can be lengthy and could accrue higher labour costs.

Strength

Structural Steel: Structural steel is extremely strong, stiff, tough, and ductile; making it one of the leading materials used in commercial and industrial building construction.

Concrete: Concrete is a composite material consisting of cement, sand, gravel and water. It has a relatively high compressive strength but lacks tensile strength. Concrete must be reinforced with steel rebar to increase a structure’s tensile capacity, ductility and elasticity.

Fire Resistance

Structural Steel: Steel is inherently a non-combustible material. However, when heated to extreme temperatures, it’s strength can be significantly compromised. Therefore, the IBC requires steel to be covered in additional fire-resistant materials to improve safety.

Concrete: The composition of concrete makes it naturally fire resistant and in line with all International Building Codes (IBC). When concrete is used for building construction, many of the other components used in construction are not fire resistant. Professionals should adhere to all safety codes when in the building process to prevent complications within the overall structure.

Sustainability

Structural Steel: Structural steel is nearly 100% recyclable as well as 90% of all Structural Steel used today is created from recycled steel. Due to its long lifespan, steel can be used as well as adapted multiple times with little to no compromise to its structural integrity. When manufactured, fabricated and treated properly, structural steel will have a minimal impact on the environment.

Concrete: The elements within concrete are natural to our environment, reducing the harm to our world. Concrete may be crushed and used in future mixtures. This type of recycling can reduce a presence of concrete in landfills.

Versatility

Structural Steel: Steel is a flexible material that can be fabricated into a wide array of designs for endless applications. The strength-to-weight ratio of steel is much higher when compared to other affordable building materials. Steel also offers many different aesthetic options that different materials, such as concrete, cannot compete with.

Concrete: Although concrete can be precast into many different shapes, it does face some limitations when it comes to floor-to-floor construction heights and long, open spans.

Corrosion

Structural Steel: Steel may corrode when it encounters water. If left without proper care, it could affect the safety and security of a structure. Professionals should care for the steel with such processes such as water-resistant seals and paint care. Fire-resistant features may be included when water-resisting seals are applied.

Concrete: With proper construction and care, reinforced concrete is water resistant and will not corrode. However, it’s important to note that the steel reinforcement inside should never be exposed. If exposed, the steel becomes compromised and can easily corrode, compromising the strength of the structure.

Concrete and the Environment

In general, it is not the ingredients, so much as the processes we use to make concrete that proves to be environmentally unfriendly.

• Quarrying for the sand and other aggregate materials like limestone or granite can destroy and pollute an area.
• To make cement takes a lot of energy and water to produce.
• There’s a lot of waste in the mixing process. The concrete hardens quickly and if there’s not enough time to lay it down before it hardens, builders just throw it away.
• Concrete is known for its high carbon emissions into the atmosphere, which contributes to greenhouse gases. This occurs in the process of making cement when the clay burns at high temperatures and the limestone burns to create the high temperatures.

Bibliography

1. Anon., 2020. Design Build Network. [Online] Available at: https://www.designbuild-network.com/projects/the-leadenhall-building-london-uk/ [Accessed 8 January 2020].
2. Brakefield, K., n.d. swantonweld. [Online] Available at: https://blog.swantonweld.com/steel-vs.-concrete-which-comes-out-on-top [Accessed January 2020].