Structure Design of Sino Steel (Tianjin) International Plaza Xueyi Fu, Group Chief Engineer, China Construction Design International 1
1 Brief of Project 2
Location: Tianjin Xiangluowan Business District Building area: 395,181m 2 Tower T1: height 102.9m 24 stories Tower T2: height 358m 83 stories plan dimension of standard floor 53mx53m Main structure : R.C. core incorporated with an exterior hexagonal grid tube 3
Color rendering of Sino Steel International Plaza Whole Structural 3D Model 4
2 Foundation Design 5
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 foundation plan 6
Drill pour piles (C40) with pressure cement mortar Bearing capacities tested by static vertical loading on site T1 pile: D=1000mm (L=25m) 5000kN T2 pile: D=1200mm (L=54mm) 11000kN podium pile: D=800mm (L=22mm) 2450kN 7
3 Structural Framing of T2 8
Main structure of T2 : a R.C. core and an innovated exterior hexagonal grid net tube Typical floor structure of T2 : composite Main structure of T2 The typical composite floor structure of T2 9
Core of T2 Steel plates with section steel column and beams embedded in R.C. walls below Story 32 Above Story 32 R.C. walls with embedded steel columns at the corners and edges Thickness of external wall : 1150mm and 550mm from bottom to top Thickness of internal wall : 550mm Coupling beams depth Concrete grade Steel grade width : 700mm : same as the thickness of the wall : C60 : Q345B 10
Plan of Core (Red line-steel Plate) Detail of Steel Plate with Steel Beam & Column 11
Exterior Tube 1 ~ 4 story : CFRSP frame + diagonal bracings 5~42 story : innovated hexagonal grid net structure (CFRSP) 43~49 story : abnormal grids structure (RSP) 50~83 story : diagonal grid structure (RSP) 12
Exterior Tube Concrete-filled Rectangular Steel Pipe Bottom of Exterior Tube 13
Floor steel beam ends : Pin connection Thickness of RC slab : 100mm to 120mm 150mm for MEP floor 14
4 Key Techniques of T2 Structural Design 15
4.1 Exploration of the Characteristics of Hexagonal Grid Structure Rigid joint connection to ensure the structure overall stability (1) Effect Under Vertical Loading Relative large deflection under vertical loadings due to the contribution of bending moments and shear in inclined column weak structural stiffness in vertical direction Contra flexure point occurring in the column Main structural internal forces : bending moments and shear forces Deformation under Vertical Loading Moment under Vertical Loading 16
(2) Effect Under Horizontal Loading Good lateral stiffness : shear-bending feature Good ductility : horizontal beams could be designed to arrive yield firstly Moment under Horizontal Loading 17
(3) Solution 1. Pin connection of floor steel beam : accommodate the differential deformation between core and exterior tube 2. Not using the outriggers : reduce the moment upon the exterior tube under horizontal loading raise the efficiency and safety of the whole structure 18
4.2 Weakness of Hexagonal Grid Horizontal Beams Sections Proper weakness of horizontal beams section : beneficial for bending yield first under maximum earthquake like link beams in shear wall reduce cost 19
Typical Hexagonal Grid Structure and Loadings (kn m) 20
1. Adopting horizontal beams section = 30%~80% of the connected inclined column section 2. Beam section 30% of inclined column section : the stiffness of the integral structure dropped dramatically 3. Beam section 80% of inclined columns section : no improvement on the structural stiffness and working condition Vertical Deformation under vertical load Horizontal Deformation under Horizontal load 21
4.3 Adjustment of Inclined Angles of Slant Columns of Hexagonal Grid Structure Straightening up inclined columns without affecting the windows of building elevation reducing the angle α of inclined columns reducing the height of sections of columns reducing sectional area and inertia of column Straightening up inclined columns 22
The slant column section depth, area, inertia, geometrical length with the inclined angle variation 23
Calculation model of single slant column the section of column 1200 1200 100 100(mm) story height h=4.2m the point load applied on the top p=100mn Single slant column model Curve of vertical deformation of column top 24
Solution : Reducing the geometrical length of inclined columns Reducing the horizontal arm and ends bending moment Reducing vertical deformation Increasing the vertical stiffness of the structure Measure : Changing four corners slant columns the inclined angle from 30 degree to 19 degree 25
Behavior of slant columns under design gravity load of T2 Behavior of slant columns under design mild earthquake of T2 26
Effect 1. Combined design stress level same 2. Raising the structural efficiency 3. Reducing cost 27
4.4 Strong Joint-Weak Member Ductility Design Fact: the maximum bending moment at the corner of slant column under gravity and horizontal loads measure: changing the equal section to varied section for slant column strengthen the section in the joint zone (1/3 member length) weaken the section in the mid zone (1/3 member length) The section of slant column 28
Joint test by CABR (scale 1:5) The sketch of test loading 29
Effect:1. the end of mid zone yield firstly 2. the material utilized efficiently VON-MISES stress contour of slant column (N/mm 2 ) 30
4.5 Effective Stiffness of Steel Beam Studs in Hexagonal Exterior Tube The horizontal floor ring beams in hexagonal exterior tube tension and compression alternately. Resulting in tensile and compressive stresses in connected floor slab Stress contour of typical floor slab 31
Studs as shear connection between floor slabs and exterior tube steel ring beams FEA model for studs connection Because the deformation of studs and surrounding concrete the shear rigidity of the studs limited Adopting spring simulating stud Floor slab tensile stress under gravity load design combination decreased from 5MPa to 2.3Mpa 32
4.6 Adoption of Special Construction Measures The corner inclined columns larger moment larger axial force under horizontal loading The section of corner inclined columns larger As a result part of middle zone gravity loads move to the corner zone the section of corner inclined columns larger the absorbed gravity loads larger This vicious circle makes corner inclined columns design very difficult and complicated Axial force of lower structure under structural self-weight 33
Releasing beams connection in construction Cutting the transfer route The middle zone structure take their structural self-weight by themselves After completion of the main structure Construction Measure 1 these beams connected Beam moment of lower structure under structural self-weight 34
Construction Measure 2 The part of self-weight of middle zone of super 30 stories diagonal net structure moves to the corner of lower hexagonal grid tube Not jointing the 8 slant columns at each corner on top of the transitional zone in construction the self-weight of upper diagonal net structure go to lower middle zone of hexagonal grid tube directly After completion of the main structure the 8 slant columns at each corner connected before adopting construction measure 2 after adopting construction measure 2 Axial force of transition zone under structural self-weight 35
Detail of Construction Measure 1 Base on the simulation of construction sequence Differential deformations of post joint beam ends under structural self-weight The horizontal differential deformation could be neglected The vertical differential deformation Δ increased with the story arising At floor 49(H=209.7m) Δ =59mm At floor 42(H=194.1m) top of hexagonal structure Δ =52mm 36
Deformation during construction Detail of post jointing steel beams 37
1. M20 bolt hole Φ36mm for releasing beams 2. Clearance of 20mm between releasing beam ends and outbound short beams 3. Story height pre-adjustment : adding 1~2mm at 1-49 story height in middle zone structure during construction 4. After completion of the main structure the post joint steel beams welded to the outbound short beam to form integral structure 38
Detail of Construction Measure 2 Differential deformations of post joint slant columns ends under structural self-weight The horizontal differential deformations small neglected The vertical differential deformations about 67mm 39
1.Take the gap between sleeve and column 20mm 2.Take the clearance 40mm between slant columns and outbound short tube from main structure 3. Story height pre-adjustment: adding 2mm at transition zone top story height 4.After completion of the main structure, the 8 post joint slant columns at each corner connected Detail of the Post Jointing Inclined Column 40
Post Cast Floor Strips 41
Result of the Special Construction Measures Under action of structural self-weight the member forces of the slant columns at 4 corners reduced by 37% the member forces of the slant columns at middle zone increased by 22% Under combined action of gravity, wind and earthquake the member forces of the slant columns at 4 corners reduced by 10% the member forces of the slant columns at middle zone increased by 5% 42
Check of Structural Safety during Construction The simulation analysis of overall process of construction include adopting special measures The bearing capacity and stability of the integral structure OK under structural self-weight and 10 years period wind load action 43
5 Structural Performance of T2 44
Main Modes of T2 Maximum story drift ratio Ratio of base shear to total gravity under mild earthquake spectrum of china code 45
X direction Y direction Shear of core and exterior tube under mild earthquake spectrum of China Code X direction Y direction Overturn moments of core and exterior tube under mild earthquake spectrum of China Code 46
Structural performance of T2 under the combined earthquake action 47
6 Conclusions 48
Sino Steel (Tianjin) International Plaza has the first worldwide application of hexagonal structure as its exterior tube of this super high rise building. Elastic and plastic dynamic analysis shows that this project can achieve good seismic performance. Three invention patents had been applied in China Patent Bureau. 49
THANKS 50