KAFD Metro Station, Riyadh, Saudi Arabia

Analysis

Modern buildings demand modern technologies

25 April 2018 | By Andrew Watts

Andrew Watts, CEO of international building engineer Newtecnic, explains how technology has been developed and embraced in response to today’s complex structures and designs.

Because it is perceived as increasing risk, the construction industry is notoriously resistant to change through technology adoption. The idea of following tried and tested solutions is almost universal because “if it worked before it will work again”.

This attitude has restricted progress for an industry that produces waste of up to 50% on many projects. And negative environmental impacts, caused by easily correctable inefficiencies, persist as long as the building stands.

But the belief that new methods and technologies present increased risk is mistaken. In fact, the opposite is true because by using technology it is possible to reduce risk while creating more imaginatively conceived buildings at lower cost that use less energy, are more durable, look better and are interesting to inhabit. They also take less time to make and on completion appear effortless.

This seemingly implausible list of advantages has been proven across the world where, in partnerships with developers, architects and engineers, collaboration over data reveals absolute truths about buildings.

Much of this technology was developed to facilitate the highly complex structures of Zaha Hadid Architects and other designers who defy convention. Such audacious geometry comprising curves and sweeping planes cannot be built using traditional methods.

And by engineering these structures, new technology and practices have been devised that have revolutionised the construction of many buildings.

The use of engineering algorithms is similar to the use of tools in 14th century gothic cathedrals – callipers, plumb line and a set square, with which builders created magical effects.

Modern technology is simply an up-to-date tool. There is a continuum of ideas and tools in architecture even though many people treat history as a free toyshop rather than seeing themselves as adding to the wealth of past experience.

In practice, architects and developers use their local knowledge to imagine culturally appropriate buildings. The universal truth of mathematics is then applied to minutely examine myriad details because in buildings a lack of understanding of those details adds cost and complexity at every stage of construction and operation.

Waste not…

Traditionally rolled steel sections or reinforced concrete are used to support structures. They often dominate the building even though they are inevitably concealed behind panels. They make their presence felt at the design stage because the design must be worked around them.

This restricts designers to using straight lines when curves could deliver a better realisation of the original intention. In finished buildings, steel and concrete frames take up space, adding bulk, weight and as their name implies, inflexibility. This becomes problematic when other elements of the structure are more flexible.

At a technical level the junctions between components must be understood to ensure predictable building performance. The physical properties and capabilities of structural components is well documented but often building designers overspecify “to reduce risk”.

Technology and methods now exist to precisely simulate not just the performance of these components themselves, but also the interfaces between them and other components. This spells the end for considerable waste of materials, resources, and space design options when components are overspecified.

Arcs in curved buildings are inherently rigid. However, their flexibility can, when properly understood, bring many advantages to structures and the commercial ecosystem that produces them.

Arcs can be made from thin, light material that enhances structural integrity and sparks creativity from the endless possibilities that their profiles offer. That means completely new shapes can be developed and their behaviours precisely known before they have been physically made. The whole building can then be optimised to accord with any other functional parameters.

When design is freed from traditional industry practices, shapes and components can be based on the interpretation of physics and mathematics. And they can be “generatively” created.

Rather than being designed by a single person, geometry is created under the guidance of the engineering designer based purely on its function. In many cases the shapes have never been seen before, yet they are perfectly suited to the purpose.

Generative designs are often the starting point for human designers to adapt these shapes and to be inspired to develop new types of facade and detailing.

Design performance

Many landmark commercial and cultural buildings represent the aspirations and dreams of developers, architects, governments and owners. They want to build ideal structures with the confidence that projects will deliver in terms of design, performance and cost. They also want to fully understand risk. It is therefore crucial to find, explore and solve potential problems at the earliest stage.

This can be achieved when newly developed algorithms and methods are deployed. Based on sound engineering principles these methods examine the physics of components and junctions allowing a realistic examination of potential problems, their resolutions and outcomes.

One example of this is the analysis of the relationship between concrete and steel building components. Because these behave differently under load and stress, and it is often at the junctions of these two materials that problems such as leaks in the facade or micro-cracking in the concrete can arise, mathematical methods have been devised to understand the real-life consequences of different design options.

Using algorithms removes guesswork from the construction of complex buildings. These risk-reducing solutions have a parallel with financial analysis models which find the “gaps” inside data to solve problems and create new solutions to problems that have not yet been fully defined.

In a building, the forces of compression, tension, shear and buckling must be understood and controlled. And it is by solving these interrelated energies that unexpectedly elegant solutions arise.

When these aspects of the building are explained to architects, developers, clients and city partners, creative possibilities expand and risks reduce because there will be “no surprises”.

Also, because these revelations are made available to all stakeholders, including building component manufactures, they more fully understand their role and the levels of risk that they are undertaking. This increases confidence throughout the supply chain by removing the uncertainly that so often leads to disputes between stakeholders.

It also has the advantage of showing regulators, planners and the public exactly how the building will perform far into the future.

Light and air

Around 40% of the world’s energy is consumed by buildings. It is therefore important to understand how to reduce consumption. This can be done by modelling climate in relation to the building and analysing the structure’s thermal conductivity, weather tightness and airflow. Glazing is also a significant factor in controlling the inside temperature.

By taking these considerations into account a balance can be achieved that reduces energy consumption and makes the building a better place to be. While it may be thought that more glass equals more light, it is possible to reduce the amount of glazing without affecting interior light levels to create interesting illumination, shadow and consequent cooling effects as a result.

In the hot climate construction projects that we work on, airflow and cooling are key priorities. In many cities, urban pollution levels mean that windows cannot be opened so the “standard solution” is often to install more air conditioning with all its inherent commissioning, maintenance and long-term operating costs.

However, buildings can and do successfully operate as their own supplementary cooling systems by allowing filtered air to naturally circulate throughout the interior.

This possibility stems from designing the building and its facade to maximise airflow. When algorithms automatically generate designs based on air flow the outcomes are genuinely unique and often very beautiful as well as being literally cool.

Constructive thinking

It might be imagined that this way of conceiving, designing, making and operating buildings is more expensive. It has been proven on many of our partnerships that the opposite is the case. A significant contributing factor to cost reduction is that quality assured and validated building components can be made in factories for onsite assembly.

It has been said that the worst place to make a building is on a building site because the human, financial and waste costs of this way of working, often in hazardous conditions, is high. Quality suffers and previously unseen problems are revealed during, or worse, after the construction phase.

Rethinking the construction process along industrial lines so that as much of the building as possible is fabricated under controlled conditions is the surest way to guarantee a successful outcome.

In this time of huge opportunity, it the responsibility of the construction industry to examine first principles and consider how today’s buildings, developers, designers and owners may be judged a century from now.


Case studies

KAFD Metro Station, Riyadh, Saudi Arabia

The design of the envelope of the KAFD Metro Station was driven by the need to provide a weathertight and thermally insulated envelope around a supporting structure.

The geometry of the envelope is not driven by a structural primitive that seeks to provide structural efficiency, but by the requirements to enclose the interior space with the minimum amount of internally air-conditioned volume.

Consequently, the zones for the depth of the facade and its supporting structure are required to be minimised to contribute to this concept.

The envelope system is driven by the need to minimise installation time through prefabrication while achieving a highly durable facade assembly.

In order to fix each cassette module to the supporting steel structure, the principles of “spider” fixing technology have been employed to ensure high levels of adjustment and flexibility, but avoiding the use of a casting, with its higher costs, by using two independent elements fixed to a single threaded bar.

This technology is derived directly from fixings for glazing panels which are supported on cables or lightweight steel structures. These “spider” fixings are used to accommodate high levels of movement of the supporting structures at serviceability without generating stress concentrations at the points of support.

The movement and adjustability is achieved by means of a ball joint located at the end of each spider leg which allows a limited degree of rotation.

The geometry was rationalised through a set of early stage iterative studies that introduced a slight double curvature in the perforated parts of the envelope which were subjected to larger deflections.

This allowed a significant reduction in the size of the steel of the primary shell structure for these areas, without visibly changing the architectural intent. These studies were made possible as a result of applying the results of a preliminary finite element (FE) analysis of the building to the structural model of typical areas of facade.

The project required the use of a set of current technologies to achieve the weather tightness of the building and coordinate economically with the supporting steel structure, avoiding the need to generate a project-specific technology.

The use of well-understood components enabled a higher level of optimisation of the assembly in order to meet the durability requirements for the facades.


Grand Théâtre de Rabat, Morocco

As part of the programme of cultural development in Morocco, and inspired by the Bouregreg River, the dramatic sculptural form of the Grand Théâtre de Rabat in Morocco incorporates an 1,800 seat theatre, a 7,000-seat amphitheatre and a smaller experimental performance space.

Clever use of GRC panels meant the fluid design envisaged by architect Zaha Hadid was successfully interpreted, resulting in the addition of a cultural venue of the highest standards for the city of Rabat in Morocco.

The main envelope system for the Grand Théâtre project is based on an opaque glass-fibre-reinforced concrete (GRC) rainscreen cladding, fixed to the primary structure, which is a mix of reinforced concrete and steel.

The main driving parameter for the design of the GRC system was the required 60-year lifespan of the envelope system. This required the use of monolithic GRC panels, up to 4m x 2m in size, which did not require the conventional steel backing frame to be cast-in underneath the panel.

Computational fluid dynamics (CFD) analysis for cladding pressures was undertaken and subsequently validated by an early stage wind tunnel test. This analysis allowed the use of realistic values for wind loads, which drive the stress and deflection analysis of the panels while taking into full account the effects of the geometry of the building.

Structural calculations for each component were undertaken for each project-specific configuration by using finite element modelling and scripting to automate the structural analysis process for all panels.

The design of the adjustable steel fixing bracket was conceived so that only one fixing type was used across the whole project, which would minimise cost.

Physical tests were designed to validate a single design for the connection between GRC panels and steel fixings, which could be used safely across the entire project.


K. Çamlica TV Tower, (KCTV Tower) Istanbul

The high-rise nature of the KCTV building (approximately 300m) is at the core of the design and analysis for the envelope system enclosing the primary concrete structure, whose principle purpose is to support the antenna TV mast.

In addition, the tower has ten accessible floors, including a restaurant space on its upper part. The use of these floors requires deflection limits to be controlled to ensure comfort and serviceability for the building occupants.

The highly modelled form of the building together with its significant height determines an essential part of the behaviour of both structure and envelope, the design of which is driven by the effects of wind.

The project’s location at the top of a hill makes it subject to high wind speeds. The complex geometry of the tower requires detailed understanding of wind effects which include the dynamic excitation of the tower.

The envelope uses an innovative unitised system that integrates thin glass fibre reinforced concrete (GRC) rainscreen panels, stiffened by a steel frame which is fixed directly to a steel framed insulated backing wall.

The key parameters informing the design of the envelope system are speed of installation, which determined the use of fully unitised panels with integrated exterior cladding, and accommodation of movement, which is provided using unitised joints which are designed to sustain the required amount of movement.

From the computational fluid dynamics CFD study, preliminary structural loads were established by averaging cladding pressures across representative areas of the building and applying the corresponding pressure distributions as load cases in the structural finite element model.

Due to the height of the building, a wind tunnel test was undertaken during the early stages to establish peak cladding pressures. This allowed the design to develop accurate sizes of facade components from the first stage studies, providing the data to optimise the envelope build-up and obtain an accurate understanding of the impact of the facade loads on the structural behaviour of the concrete structure.

Wind tunnel testing provided a tool for calibrating the CFD studies, which were aimed at exploring the dynamic response of the tower under wind effects due to its irregular geometry, to calibrate the stiffness of the primary structure.

For further information: http://www.newtecnic.com/