Is the GCC over-designing its high-rise buildings?
Industry experts talk about the dangers of over-design within the GCC’s high-rise sector
Earlier this year, the Council on Tall Buildings and Urban Habitat (CTBUH) revealed that 106 buildings - 200m or taller - were completed in 2015 around the world. CTBUH’s 2015 Year in Review report said 13 ‘supertalls’ – buildings 300m or higher – were completed during the year, making it the highest annual total on record.
CTBUH’s list was dominated by Chinese cities, where 62 tall buildings were built in 2015. However, the Middle East’s presence is also marked on the list by cities like Dubai and Abu Dhabi.
The UAE follows China and Indonesia with the highest number of towers completed in 2015. Including towers in Dubai, Abu Dhabi, Manama, and Jeddah, the Middle East had nine completions last year, marking the first time since 2009 that the region had fewer than 10 entries of towers 200m or taller in a year, CTBUH said.
“As one might expect from the region’s most popular commerce and tourism destination, Dubai led the pack with four completions, while Abu Dhabi closed the year with three,” CTBUH’s report continued, adding that Dubai’s under-construction Marina 101 and The Address BLVD are expected to be amongst 2016’s top 10 tallest towers.
To say the Gulf has a soft spot for tall buildings would be an understatement. The region is home to both the tallest existing manmade structure in the world, the UAE’s Burj Khalifa, and the soon-to-be-tallest structure, Jeddah Tower.
Emaar’s recently launched tower at Dubai Creek Harbour, meanwhile, will cost $1bn (AED3.67bn). The building, which the developer says will be “a notch taller than Burj Khalifa”, will rival Kingdom Holding’s Jeddah Tower. CNN reported in 2014 that the latter will cost an estimated $1.23bn (SAR4.6bn) – and in the current economic climate of stagnant oil prices, that figure could climb.
But the obstacles faced by high-rise builders in the GCC extend beyond the financial, as Ahmed Osman, DeSimone Consulting Engineers’ managing principal, tells Construction Week. “GCC projects have the tendency to be more complicated – the structural engineering more challenging – than in other parts of the world, due to reasons both obvious and hidden,” he explains.
“Firstly, architects have more freedom to express their ideas and focus on striking designs. This is encouraged in order to win the hearts of owners and overcome their rivals, which consequently challenges the structural engineering design.
“[Hidden reasons include] strict rules and regulations relating to the number of car parks stipulated for every project, which leads to risky, deep excavations,” Osman continues.
“Engineers and contractors must design and build their structures carefully to avoid any catastrophic failures to their sites, and neighbouring sites as well. The harsh environment that attacks the structures – represented in chemicals found in soil; salty water attacking foundation elements; and high humidity and sand particles in the air – also have to be considered when designing the skins of tower projects.”
Varying soil structures represent a key consideration for GCC builders, especially for towers with deep foundations. Shad Khan, business development director at Keller Grundbau Middle East, tells Construction Week that soil composition may vary across different parts of a country. Experience, therefore, is a crucial element when designing deep foundations.
“For instance, the rock available in Fujairah is stronger than that in Dubai or Abu Dhabi,” explains Khan, noting that the practicalities of such differences can be difficult to absorb in a classroom environment.
“University studies and workshops are helpful, but the piling business needs a lot of knowledge. This comes from coordination between management staff, supervisory staff, and especially the engineers executing the job onsite, because they’re encountering the materials first hand,” he continues.
“Soil mechanics isn’t a specific [discipline] like, for instance, steel, where you know exactly where a bar will bend or when it will yield. Judgment and experience are [required] in foundations engineering.”
Rapidly crowding cities around the world have necessitated the evolution of vertical structures to accommodate growing population and spur economic growth. Record-breaking skyscraper heights also contribute to a city’s brand identity on the world map.
Dean McGrail, director of property and building at WSP | Parsons Brinckerhoff Middle East, contends that the contemporary aim of city development has evolved from meeting population demand to satisfying end-user preference for urbanised lifestyles. In McGrail’s opinion, the ‘demand-versus-space’ challenge explains why GCC developers are building higher and higher.
McGrail cites The Shard in London as an example of tall buildings generating brand value for their city: “The Shard created footfall in [its surrounding] area and restarted the local economy. Can you imagine Dubai without the Burj Khalifa?”
Clearly, the stakes are high when it comes to tower construction in the GCC. Developers’ high-profile ambitions must be matched by attention to structural safety and building practices.
But this need for caution frequently leads to over-design; a significant challenge for consulting engineers. DeSimone’s team, which has worked on projects such as Abu Dhabi’s Regent Emirates Pearl Hotel and Al Maryah Tower, is all too familiar with this phenomenon, which Osman describes as “unfortunate”. He continues: “We still see that tower projects in the Middle East are over-designed; not only by local consultants, but also big names in the industry.
“Some projects have excessive amounts of reinforcements – in some instances, more than double what is needed. We also notice that large amounts of concrete, large column dimensions, drop beams, and so on, are used,” Osman continues.
“Designers tend to rely too much on structural engineering software models and do not perform checks and balances to verify the output of such models. The parameter settings in such models also need to be reviewed and accurately [measured].”
Whilst offering suggestions to mitigate such design errors, Osman echoes Khan’s views on the role of experienced engineers whilst constructing towers: “In good structural engineering firms, seasoned engineers with vast experience in tower projects will guide the design from the beginning. They will use engineering modelling only as a tool, not as guide for their designs.”
Over-design is not restricted to structural designs alone. Burak Kizilhan, deputy general manager and board member at AE Arma-Elektropanç, tells Construction Week that the practice is common within the mechanical, electrical, and plumbing (MEP) contracting sector as well. AE Arma-Elektropanç has previously worked on tower projects in Europe and the wider Middle East, and is currently working on Abu Dhabi’s Bab Al Qasr Hotel and Serviced Apartments project, which the contractor will hand over in 2016.
Kizilhan says the creation and implementation of home-grown green building codes has reduced instances of over-design in the UAE. “This used to happen between 2006 and 2009, but Dubai Municipality implemented green building regulations,” he notes.
For MEP works, an upper limit of 10% factor of safety (FOS) for sensible loads, and 5% FOS for latent loads, is now allowed by Dubai Municipality’s regulations, Kizilhan continues. Firms must stick to the basics of sound MEP contracting to create effective heating, ventilating, and air-conditioning (HVAC) systems for towers.
“Some of these considerations include the selection of air- and water-cooled systems, or district cooling chilled water lines, based on power availability and cooling loads, and developer and local authority limits for electric power and treated sewage effluent (TSE) water availability,” Kizilhan adds.
“Contractors must also check electrical load optimisation is possible through options such solar heaters, LED lights, orientation of building fenestration, green roofs, external wall insulation, and so on.”
A key element of designing MEP systems for towers is to ensure smooth waterflow across the structure, and water providers in the GCC’s construction industry, such as Xylem, are working diligently to enhance the upward mobility of water in supertalls. Xylem’s Middle East portfolio includes Dubai’s Burj Khalifa and Turkey’s Courtyard by Marriott. Speaking to Construction Week, Vincent Chirouze, regional director for Xylem in the Middle East and Africa, says the evolution of water systems must be given more significance as a part of towers’ MEP systems.
“Construction companies tend to emphasise the importance of windows and insulation, [whereas] they should focus on the entire system. It is important to evaluate the right system, looking at what is bringing heat or energy into or out of the building, and design everything in parallel.”
Chirouze also points out the oft-repeated error of over-designed systems: “We see products that are often sized larger than necessary to compensate for maximum load. For example, a hotel may experience high water consumption in the mornings when most guests shower. However, a larger pump may not be needed and can put excessive stress on the system, which ultimately increases costs and can be highly inefficient.”
DeSimone’s Osman says construction teams must persevere and collaborate in order to maximise the efficiency of regional tower projects. “The engineer must have construction knowledge and reflect this knowledge in the structural engineering designs.
“It is about construction and not just design, as the ultimate goal is to create a building. Unfortunately we find many [examples] in the Middle East where this is not the case, and the consultant and the contractor are challenging each other,” he concludes.
Elevating the Emirates
Toshiba Elevator Middle East’s MD, Mohamed Iqbal, tells Construction Week he is confident that GCC tower construction will continue on its upward trajectory. What’s more, he is keen to contribute to this growth.
“Our portfolio allows us to work on integrated building management systems designed to enhance the total energy efficiency of the whole building,” he explains.
Toshiba Elevator’s busiest regional market is the UAE, where it is involved with tower projects such as Damac Towers by Paramount in Dubai and Marina Square in Abu Dhabi.
In the UAE capital, the company has worked on the City of Lights development as well. The project comprises 94 high-speed elevators, 24 of which boast top speeds of 6m per second.
Abu Dhabi’s Addax Port Office Tower, meanwhile, boasts two Toshiba Elevator systems, with 10 cars for both low and high zones.
The company is also involved with Dubai Marina’s 86-storey Damac Heights project, which features 12 elevators with top speeds of 5m per second. The elevators are divided into three zones, with the service elevator serving all 91 floors of the structure.