Microclimate/Climate
- At the scale of The Petronas Twin Towers’ immediate environment, there is very little surrounding the buildings that directly affects their performative nature. In front of the towers lies Simfoni Lake, and although in most climates this water feature might help to cool the area surrounding the front lobby, this only exacerbates issues of heat and humidity commonly found in Kuala Lumpur. In terms of the surrounding topography, the coastal siting of the city of Kuala Lumpur also increases the humidity of the area all the while helping to temper any temperature swings the city might experience due to water’s ability to hold heat. A final microclimate concern involves the sparseness of building cover around the Petronas Towers. With fewer buildings near the skyscrapers, there is less incidental shading on the towers when the sun is out. This affected one of Cesar Pelli’s design decisions as he worked through creating the towers.
- The overall climate of Kuala Lumpur is hot and humid, with relatively little break from this throughout the year. One of the defining features of this area is the extremely high amount of rainfall experienced in the region throughout the year. This greatly decreases the amount of sunlight that reaches the building, but increases concerns for weathering and achieving a pleasant amount of indirect lighting in the interior of the structures.
Mechanical Systems
- Because of the incredibly humid climate, constant ventilation is of primary concern with these office towers. To alleviate the high cost of energy used when this sort of ventilation is required, the mechanical engineers incorporated energy recovery wheels into the scheme of the VAC systems. These wheels spin whenever air is supplied or exhausted and through coming in contact with this air would perform two functions: to dehumidify incoming air by 20% and to transfer heat from supplied air to exhaust air. This process saves the building nearly 50% of the energy it would have used to cool fresh air had it used a typical cooling tower.
Solar Profile
- As is typical of most office-towers in warmer climates, the goal in cladding this structure is to keep direct sunlight out while ensuring that all sunlight entering the building is filtered through low-e glass. To accompany the glazing choice, Cesar Pelli designed two ovoid rings that would encircle every floor at the top of the glazing. This would prevent solar rays of a high angle from entering the spaces below and visually demarcate every floor on the façade of the building.
Superstructure
- The main structure of the tower acts as a combination of typical steel space structures and one-way concrete construction.
- The tensile capacity of concrete is next to nothing, meaning that for all intents and purposes, no unreinforced concrete can be placed in tension (pulled apart) without failing. Because of this, concrete construction tends to feature monolithic design coupled with arched construction helps to ensure that none of the structure is in tension. The Petronas Towers make use of this in two ways: the sixteen columns that run along the perimeter of the star-shaped plans are connected via arched beams that cinch these columns together and provide lateral stability in the straighter parts of the structure; the central cores of the buildings are square and prototypically loaded reinforced concrete tubes. Those two systems are connected at floors 38 and 40 (near the skybridge) to add to the structural rigidity.
- Steel achieves its structural rigidity in a very different way: through the combination of multiple smaller parts and the amount of space between them. Steel works well in both tension and compression, so when an architect or engineer wishes to design a complex steel structure, they add space between members to ensure the moment is spread across a greater distance. The Petronas Towers use this structural system in the steel reinforcing inside the structural concrete, to support the floor decking on each level, to support the glass domes at the top of each tower and to support the skybridge that links the two towers together.
Domes
- At the top of each tower there is a large steel and glass dome supported in sixteen points by the structure that runs up the whole building.
- Just below the space created by these domes, the sixteen supporting columns connect in eight arches that in turn support eight reinforced concrete columns. These run through the domes space for the height of one floor and then become eight bundles of three steel tubes each. As these run the height of the spaces in the domed areas, they support six floors of shopping or office space and a ring of clerestory windows before splitting off and attaching to 24 space trusses that support the corrugated roofing and sky lighting. Rings of steel support these trusses where the webs meet the top chords at regular intervals and allow the exterior profile of the dome to jump and maintain the stepped character maintained in the higher portions of the tower. Finally, these trusses continue through the roof structure to form the shape of the pinnacle.
- One interesting feature of these spaces is the termination of the cores that run along the height of the building. These end to allow the space to open up and support the highest six floors of the elevator.
Skybridge
- The main structural feature of the skybridge is its ability to move independently of the two towers. With the bridge so high in the elevation of the structures, there would have been no way to accommodate for the massive amount of sway the towers face when loaded laterally by heavy winds. If the skybridge were made as a rigid piece of the towers, it would have either been ripped out from between the buildings or would have buckled.
- The solution is elegant both from an engineering standpoint and as an architectural design feature. Starting from the base of the bridge’s support, two upside-down v-shaped arches spring to the bottom of the bridge, attached at the bottom to a single spherical bearing ball on each side. These springing points serve a dual purpose: they allow the arches to push/pull/twist depending on the sway of the towers and take the vertical load of the skybridge back into the structure of the main towers.
- The next important piece to the skybridge is the hinge that connects the two arches to the actual structure of the bridge. This serves a different purpose than the hinges down below: it allows the bridge to move up, down, or to twist with the changing angle of the supporting arches. So when the towers are closer together, the bridge is allowed to rise, and when they’re further apart, the bridge can sink lower. If the bridges happen to move in opposing parallel directions, this hinge can slide angularly to handle this movement, keeping the center of the hinge directly centered under the bridge at all times.
- The structure of the actual bridge is very simple in comparison. Keeping in mind the need for glass to have room to move with the ever-changing position of the bridge, expansion joints were used along the length of the steel structure. That structure itself consists of a steel frame that rests on top of two girders attached to the hinge at the center of the bridge.
- The ends of the bridge are, of course, not rigidly connected to the towers either. The whole piece can slide in and out of the nearby structures without buckling or ripping apart.
- From a functional standpoint, there is more to the building of the bridge than simply attracting tourists or creating an interesting design. The two-story tunnel provides an escape-route halfway through the building in the case of a fire and can help to stabilize the sway to which each tower is exposed.
Foundation
- As originally planned the two towers would have faced major problems resting on the limestone bedrock 60-150 meters below the surface in Kuala Lampur. Because of the steep angle of the bedrock and the incredible weight the towers would exert on this particular type of limestone (1,140 kilopascals each), Cesar Pelli and Thornton Thomasetti decided instead to move the buildings 60 meters to the south and to install friction piles 40-105 meters into the ground.
- These piles differ greatly from those typically used in the construction of skyscrapers. The average tall building will develop support by resting on hard bedrock below the soil, transferring loads vertically downward onto that rock. With friction piles, the upward force of friction acting on the sides of the piles helps to transfer the building’s loads into the nearby soil. In the case of the Petronas Towers specifically, one-hundred and four 2.16m2 concrete piles use the high resistance of Kuala Lampur’s soil to stay on top of the soil.
- Those piles directly support a 4.5 meter thick raft lying 21 meters below the line of the soil which adds to the bearing capacity of the foundation system.
- The type of concrete used in this system is of grade M80, which means the concrete can support up to 80 Newtons per square millimeter after it has been left to cure for 28 days. Some considerations when making this type of concrete involve maintaining a low water-to-cement ratio and the addition of specific types of admixtures (like fly ash or slag) that help to increase bearing capacity. Because this low water-cement ratio is necessary for keeping the piles from becoming too brittle, the workability of this kind of cement is incredibly low. Pouring the piles had to take place for 52 consecutive hours to ensure that layers of disconnected cement would not form. If new concrete were poured over dry concrete, it would have been nearly impossible to maintain a strong connection between the layers, placing high stress on the steel rebar reinforcing the pile.
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- Address
- Kuala Lumpur, Federal Territory of Kuala Lumpur
- Height - Top (m)
- 452
- Height - Architectural (m)
- 452
- Height - Roof (m)
- 379
- Height - Top Floor (m)
- 375
- Height - Observation Floor (m)
- 170
- Floors (above ground)
- 88
- Floors (below ground)
- 5
- Construction start
- 1,992
- Construction end
- 1,998
- Elevators
- 39