A luxurious residential building in Metro Manila is being built with 700 tonnes of HISTAR® 460 sections produced by ArcelorMittal Europe – Long Products’ mill in Differdange. Called the Imperium, this building is not only earthquake resistant but will contain everything you could dream of: pool, fitness facility, recreation room, mini theater…
HISTAR®: Smaller, Faster, Lighter
Manila is located in one of the most severe seismic zones on the globe, and steel - especially HISTAR® steel - is an increasingly chosen answer for adding building stiffness and ductility while keeping column sizes reasonable. Where space optimisation and speed of construction are key, HISTAR® steel can allow for smaller and lighter pieces over conventional steel or concrete-only solutions.
The American structural engineering firm of Magnusson Klemencic Associates (MKA) from Seattle conceived the lateral-force resisting structure of the Imperium using a methodology called “Performance-Based Seismic Design” (PBSD). Don Davies, President of MKA, explains: “By using PBSD and nonlinear modeling techniques, we are able to better simulate the behavior of a structure under strong seismic ground motions or strong winds. This allows us to better predict how a building will perform and propose solutions that put materials where they are more efficient for their intended purpose.”
The lateral force-resisting system for the Imperium is a central concrete core with outrigger* bracing to perimeter columns for increased tower stiffness (Picture 2). HISTAR® steel rolled shapes are utilised in the composite outrigger columns and result in increased column strength and stiffness in both tension and compression. The use of embedded HISTAR® steel allowed the column sizes to be reduced by as much as 50% compared to the initially considered all-concrete columns for the project (Picture 3). This column size reduction increased the floor efficiency ratios and useable square footage of the units, offsetting other first costs and leading to true value-optimised design for the owner.
Another key factor for buildings located in highly seismic zones is ensuring strong column–weak beam behavior and the ability to dissipate energy absorbed from an earthquake in a ductile and predictable way. MKA engineers specified the use of Buckling Restrained Braces (BRB) as the outrigger bracing elements connecting the core to the perimeter outrigger columns. BRBs are like reliable giant fuses that are able to absorb a huge amount of energy during large earthquakes while protecting other structural elements in the tower. These BRBs engage through connection plates directly to the HISTAR® steel shapes within the perimeter columns, providing for a robust and efficient connection.
King of the Block
The Imperium is a 63-storey residential high-rise building designed by the global architecture firm CallisonRTKL. It features an architectural design with vertical lines and a circular form recognisable from afar. The Imperium is shifted forward with angled windows that ensure unobstructed views of the horizon and the nearby Capitol Commons Park. This appearance emphasises the building’s majestic positioning as "King" of the block, hence its Imperial name.
Expected to be completed by 2018, the Imperium will soon become a new landmark in Capital Commons, the new dream city in Metro Manila.
*Outrigger systems are structures designed to improve a building’s stability and strength by connecting the building core or spine to distant columns, much in the way an outrigger can prevent a canoe from overturning.
Image courtesy of CallisonRTKL, Design Consultant for the Project
Picture 2: in red, HISTAR® composite sections used as outriggers
Picture 3: reduction of the cross sections compared to a full concrete solution
©Courtesy of Magnusson Klemencic Associates
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