TALL BUILDING STRUCTURES TONGI UNIVERSITY Shanghai BOCOM Financial Towers The Bocom Financial Towers(Chinese:交银金融大厦)are two conjoined skyscrapers which reach 265 meters feet)in height the north tower and meters the south tower.They are located in Lujiazui Finance and Trade Zone,Pudong District of Shanghai,China and are split into the North and South Towers. Both towers were designed by ABB Architekten The north tower is the 64th tallest existing building in the world (the 8th in Shanghai)when measured up to the highest architectural point An atrium connects the two towers together and reaches a height of 163.4 meters. A swimming pool offering views over all of Shanghai is located on the 48th floor of the North Tower. Construction of the North Tower began in 1997 and was completed in 2002.It is 52 stories tall with four basement levels.The height to the top of spire is 265 metres and it has a roof height of 230 metres.At its widest point,the tower is15.8m s wide and metres. Construction of the South Tower was completed in1999 three years before the North Tower. It has 42 floor above ground and four below ground level.It has a ro height of 197.4 metres and the top floor is located 171.6 metres up.At its widest point,the tower is 15.8 metres wide and at its narrowest,it is 9.75 metres wide.It has a length of 31 metres. It was one of the three buildings part of the filming of Mission:Impossible Ill starring Tom Cruise.Ethan Hunt was shown sliding down the angled roof of the south tower. Rodrigo Martinez Arribas
TALL BUILDING STRUCTURES TONGI UNIVERSITY Rodrigo Martínez Arribas Shanghai BOCOM Financial Towers The Bocom Financial Towers (Chinese: 交银金融大厦) are two conjoined skyscrapers which reach 265 meters (869 feet) in height the north tower and 230 meters the south tower. They are located in Lujiazui Finance and Trade Zone, Pudong District of Shanghai, China and are split into the North and South Towers. Both towers were designed by ABB Architekten. The North tower is the 64th tallest existing building in the world (the 8th in Shanghai) when measured up to the highest architectural point. An atrium connects the two towers together and reaches a height of 163.4 meters. A swimming pool offering views over all of Shanghai is located on the 48th floor of the North Tower. Construction of the North Tower began in 1997 and was completed in 2002. It is 52 stories tall with four basement levels. The height to the top of spire is 265 metres and it has a roof height of 230 metres. At its widest point, the tower is 15.8 metres wide and at its narrowest it is 9.75 metres wide. It has a length of 31 metres. Construction of the South Tower was completed in 1999, three years before the North Tower. It has 42 floors above ground and four below ground level. It has a roof height of 197.4 metres and the top floor is located 171.6 metres up. At its widest point, the tower is 15.8 metres wide and at its narrowest, it is 9.75 metres wide. It has a length of 31 metres. It was one of the three buildings part of the filming of Mission: Impossible III starring Tom Cruise. Ethan Hunt was shown sliding down the angled roof of the south tower
TALL BUILDING STRUCTURES TONGI UNIVERSITY The Bocom Financial Towers is multi-tower high-rise building with frame tube system. The general characteristics of this kind of buildings are: .Can be used in tall buildings Inner tube.Outer frame. Large space,convenient to use .Flexible arrangement of building's elevation .Good natural lighting Commonly used in:hotel,office buildings The materials used are steel and glass Load-carrying features of frame-tube structures: Great lateral stiffness Elevator can be used as inner core tube to resist shear and bending Frame columns are arranged on the outer side to resist bending Displacement limitations of frame-tube structure: ·RCwall Maximum value of elastic story drift rotation<1/1000 Maximum value of elasto-plastic story drift rotation<1/120 SEISMIC MODEL TEST AND ANALYSIS OF MULTI-TOWER HIGH-RISE BUILDINGS.Wensheng LU And Xilin LU A scaled multi-tower high-rise building model of the BOCOM Financial Tower was tested in The multi-tower buildine is two odium o coniunction parts at diffe ent lev vels.It is well known that the podium and conjunction parts shall be designed very carefully to meet the internal force and the deformation between towers. From the point of structural properties,multi-tower high-rise buildings have the following characteristics, the height ex eeding the limitation o sen odes nd al the distribution of mass and lateral stiffness are sharply changed along the height; mega-member with huge space and large span; flexible weak connection between towers: new construction materials,methods and details. Rodrigo Martinez Arribas
TALL BUILDING STRUCTURES TONGI UNIVERSITY Rodrigo Martínez Arribas The Bocom Financial Towers is multi-tower high-rise building with frame tube system. The general characteristics of this kind of buildings are: Can be used in tall buildings Inner tube. Outer frame. Large space, convenient to use Flexible arrangement of building’s elevation Good natural lighting. Commonly used in: hotel, office buildings The materials used are steel and glass. Load-carrying features of frame-tube structures: Great lateral stiffness Elevator can be used as inner core tube to resist shear and bending Frame columns are arranged on the outer side to resist bending Displacement limitations of frame-tube structure: RC wall Maximum value of elastic story drift rotation < 1/1000 Maximum value of elasto-plastic story drift rotation < 1/120 SEISMIC MODEL TEST AND ANALYSIS OF MULTI-TOWER HIGH-RISE BUILDINGS. Wensheng LU And Xilin LU A scaled multi-tower high-rise building model of the BOCOM Financial Tower was tested in 2000 on the shaking table which locates at the State Key Laboratory for Disaster Reduction in Civil Engineering of Tongji University, Shanghai, China. The multi-tower building is two or more towers connected with one large podium or conjunction parts at different levels. It is well known that the podium and conjunction parts shall be designed very carefully to meet the internal force and the deformation between towers. From the point of structural properties, multi-tower high-rise buildings have the following characteristics, • the height exceeding the limitation of present codes; • extremely irregular shape, including in plan and elevation; • the distribution of mass and lateral stiffness are sharply changed along the height; • mega-member with huge space and large span; • flexible weak connection between towers; • new construction materials, methods and details
TALL BUILDING STRUCTURES TONGI UNIVERSITY The traditional calculation models of multi-tower buildings is shown in the following figure: ak co Figure l.Typical twin-tower building 2）single tower eeresCeveotnutoverhehtiebuinsuhas 1)several towers on one large podium,e.g.five towers on one large podium; 2)towers with rigid connection at top; 3)towers with flexible connection between towers; 4)irregular shape of towers models Before.dur nd analysis of a s hand,it is very difficult to meet all the demands exactly.Hence,some main factors shall be determined strictly first. Physics Main Factors Shanghai Behavio BOCOM Financial Geometry Length 133 Property Elastic modules 12.96 Material Stress 16.92 Property Mas density Mass 6.96×10 Dynamic Penod 010 Property r Acceleration 2.64 Rodrigo Martinez Arribas
TALL BUILDING STRUCTURES TONGI UNIVERSITY Rodrigo Martínez Arribas The traditional calculation models of multi-tower buildings is shown in the following figure: Prototype Structures There are different styles of multi-tower high-rise buildings, such as, 1) several towers on one large podium, e.g. five towers on one large podium; 2) towers with rigid connection at top; 3) towers with flexible connection between towers; 4) irregular shape of towers. Similitude coefficients of models Before, during and after designing, constructing and analysis of a structural model for shaking table tests, the most important aspect is to satisfy the similitude relationship. On the other hand, it is very difficult to meet all the demands exactly. Hence, some main factors shall be determined strictly first
TALL BUILDING STRUCTURES TONGI UNIVERSITY considered.On the other hand.the capacity of the facilities of laboratory shall be taken into account. Micro-concrete and fine reinforcement is always used to build a model.These kinds of material and constructi on me nods have be dimension and reinforcement ratio is also determined by the similitude factor.Usually it spends 3 to 5 months to build one whole model The figure on the left shows the structural model of the Boco tested c which have r Elastic model can also be made of plastic and other materials.Those models shall keep elastic during test and the linear behavior will be measured by sensors. Shakine table tests For choosing suitable earthquake waves to input into the shaking table to excite the model,the soil type of construction site and the dynamic behavior of the be taker into account ing intens f each ea nquak waves vary from the step ep can dimensions such as strain displacement transducers and transducers are placed at critical and interesting places of the model. dtdrmulti- Th d thog e connection floor between towers are located at different levels. Rodrigo Martinez Arribas
TALL BUILDING STRUCTURES TONGI UNIVERSITY Rodrigo Martínez Arribas Design and construction of model As stated previously, the focus of shaking table test is on the dynamic behavior and earthquake resistance capacity of the structures. Hence the main similitude factors must be strictly obeyed during design, while the dimension, reinforcement, mass and stiffness are also considered. On the other hand, the capacity of the facilities of laboratory shall be taken into account. Micro-concrete and fine reinforcement is always used to build a model. These kinds of material and construction methods have been maturely used in Tongji University, which are used to build nearly 50 models during last decades. The main structural members are entirely reproduced similarly, and the dimension and reinforcement ratio is also determined by the similitude factor. Usually it spends 3 to 5 months to build one whole model. The figure on the left shows the structural model of the BOCOM Financial Tower which have been tested on the shaking table. Elastic model can also be made of plastic and other materials. Those models shall keep elastic during test and the linear behavior will be measured by sensors. Shaking Table tests For choosing suitable earthquake waves to input into the shaking table to excite the model, the soil type of construction site and the dynamic behavior of the prototype structure shall be taken into account. During test, the exciting intensities of each earthquake waves vary from the frequently occurred earthquake to the seldom occurred earthquake step by step, and the exciting inputs can be one dimension or three dimensions. Sensors such as strain gauges, displacement transducers and acceleration transducers are placed at critical and interesting places of the model. It is found that the responses of multi-tower buildings have very complex behavior during earthquake action. The dynamic properties and the damage area are different if the position and the stiffness of the connection floor between towers are located at different levels
TALL BUILDING STRUCTURES TONGI UNIVERSITY ANALYSIS The conjunction floors The coniunction floors at higher levels can significantly reduce ton drift of the tower However the higher order vibration modes affect the seismic response,and the internal force in the conjunction floor and the local members are relatively higher.For example,the torsion of each and the interaction betw en towers caus rge stress ir on or an e nt an and th cracking always is at those areas Even more the dynamic properties of structures change a lot after cracking,e.g.,the frequencies can decrease 30~50%.If the podium floors between twin-tower cracks,each tower will have individual dynamic response except collision between each other. Shanghai BOCOM Financial Tower The stiffness of foundation The shaking table test and the traditional seismic analysis of high-rise building always neglect the effect of foundation.Unfortunately,the nature frequencies of most multi-tower buildings nt f equency of site soll,es buildings with irregular shape, Modes BOCOM 1 2.732Hz 2 1.931H 3 0.659Hz uakes ac order analysis both pr ve that soft soil site may increase the damage intensity of multi-rise building CONCLUSIONS FOR MULTI-TOWER HIGH-RISE BUILDINGS Considering the above-mentioned aspects,the following conclusions can be drawn. 1)The dyn stiffness change sharply at different level hence the higher order vibration modes are dominant.Secondly,the members near those areas are easily destroyed under earthquake action. Rodrigo Martinez Arribas
TALL BUILDING STRUCTURES TONGI UNIVERSITY Rodrigo Martínez Arribas ANALYSIS The conjunction floors The conjunction floors at higher levels can significantly reduce top drift of the tower. However the higher order vibration modes affect the seismic response, and the internal force in the conjunction floor and the local members are relatively higher. For example, the torsion of each tower and the interaction between towers cause large stress in the conjunction floor and the joint area. The same condition is to the large podium under highrise towers. Tests and theoretic analysis show that cracking always is at those areas. Even more, the dynamic properties of structures change a lot after cracking, e.g., the frequencies can decrease 30~50%. If the podium floors between twin-tower cracks, each tower will have individual dynamic response except collision between each other. The stiffness of foundation The shaking table test and the traditional seismic analysis of high-rise building always neglect the effect of foundation. Unfortunately, the nature frequencies of most multi-tower buildings meet with the dominant frequency of site soil, especially those buildings with irregular shape, which have complex vibration modes, as shown in the next table. When earthquakes act to multi-tower buildings, the higher order modes such as torsion modes and interaction modes between towers take great affection on the seismic behavior. Tests and analysis both prove that soft soil site may increase the damage intensity of multi-rise buildings. CONCLUSIONS FOR MULTI-TOWER HIGH-RISE BUILDINGS Considering the above-mentioned aspects, the following conclusions can be drawn. 1) The dynamic behavior of multi-towers high-rise buildings is usually different from traditional high-rise buildings. First of all, the distribution of floor mass and the lateral stiffness change sharply at different level hence the higher order vibration modes are dominant. Secondly, the members near those areas are easily destroyed under earthquake action
TALL BUILDING STRUCTURES TONGI UNIVERSITY 2)The door-shaped building structure has bad earthquake resistant ability.Because aw conjunction block is on thetop of the building,and the dynamic of ncreas odium is sienificant which will cause the damaee .building near the transfer flo tower works separately if cracks appear after higher intensity earthquake. 4)The flexible connections between towers can significantly reduce the drift of multi- tower high-rise buildings,and they will be destroyed and act as energy dissipation members du 5)For irregular shape multi-tower buildings,such as Shanghai Reception Center with shape the and constructed. Furthermore,suggestions on design,construction and maintenance of multi-tower buildings are put forward 1)It is very opriate conceptions and detailed eartha e resistant measures s according to the 2)Simplify the force route of lateral action and vertical weight.It is necessary to avoid applying different axis system to the podium and towers individually. 3)The stiffness and mass from the bottom to the top of the whole building shall distribute near one straight line,and the stiffness ratio of the superstructure to the adjusted within 0.5 2.0 nea n and the po dium roof must be strength ened,e.g.the pe ed Th of the shear-walls. columns and beams at the critical zone must be designed carefully 5)It is essential to analyze earthquake resistance of the whole structure during and after serious earthquake,and to analyze the dynamic behavior of the separated towers with partial podiums after the podium roof and floors are severely damaged,and to evaluate the 6)The seismic tion sha ing ta st is of importance fo th eanakeaety nd figurative pr hof those kinds of complex structures 7)It is essential and helpful for both architects and engineers to keep well cooperation between each other to solve the problem among beauty scene,function and safety. 8)Site tests and sensors embedded in the prototype structures will be helpful to mprove the analysis methods and the knowledge in this field. Rodrigo Martinez Arribas
TALL BUILDING STRUCTURES TONGI UNIVERSITY Rodrigo Martínez Arribas 2) The door-shaped building structure has bad earthquake resistant ability. Because the rigid and heavy conjunction block is on the top of the building, and the dynamic response of the towers under earthquake action will increase. 3) The couple action between transfer floors of multi-tower building with large podium is significant, which will cause the damages near the transfer floors, and each tower works separately if cracks appear after higher intensity earthquake. 4) The flexible connections between towers can significantly reduce the drift of multitower high-rise buildings, and they will be destroyed and act as energy dissipation members during a moderate earthquake. 5) For irregular shape multi-tower buildings, such as Shanghai Reception Center with U-shape, the responses are very complex. Not only the couple actions between towers but also the internal forces in the narrow shape slab are affective to the safety of the building. 6) Multi-tower building may be severely damaged when it is subjected to strong earthquakes. However the building will keep in safety if it is appropriately designed and constructed. Furthermore, suggestions on design, construction and maintenance of multi-tower buildings are put forward: 1) It is very important to design and construct multi-tower buildings according to the appropriate conceptions and detailed earthquake resistant measures. 2) Simplify the force route of lateral action and vertical weight. It is necessary to avoid applying different axis system to the podium and towers individually. 3) The stiffness and mass from the bottom to the top of the whole building shall distribute near one straight line, and the stiffness ratio of the superstructure to the podium shall be adjusted within 0.5~2.0. 4) Members near tower bottom and the podium roof must be strengthened, e.g. the reinforcement ratio shall be increased and the performance of concrete beams, slabs, columns and shear walls shall be enhanced. The ductility property of the shear-walls, columns and beams at the critical zone must be designed carefully. 5) It is essential to analyze earthquake resistance of the whole structure during and after serious earthquake, and to analyze the dynamic behavior of the separated towers with partial podiums after the podium roof and floors are severely damaged, and to evaluate their earthquake resistance. 6) The seismic simulation shaking table test is of importance for the earthquake safety research on multi-tower high-rise buildings. Shaking table test is proved to be a relative effective, economic and figuratively measure for the seismic research of those kinds of complex structures. 7) It is essential and helpful for both architects and engineers to keep well cooperation between each other to solve the problem among beauty scene, function and safety. 8) Site tests and sensors embedded in the prototype structures will be helpful to improve the analysis methods and the knowledge in this field
TALL BUILDING STRUCTURES TONGI UNIVERSITY Rodrigo Martinez Arribas
TALL BUILDING STRUCTURES TONGI UNIVERSITY Rodrigo Martínez Arribas