8 Case study 8: Shanghai Tower piled raft
8.1 General
The Shanghai Tower is a mega tall skyscraper in Lujiazui, Pudong, Shanghai, Figure 81. It is considered the secondtallest building in the world after Burj Khalifa. The height of the tower is 632 meters. It consists of a 124storey tower, a 7storey podium and a 5storey basement.
The tower has a 5storey basement, and its foundation depth is 31.4 [m]. The thickness of the raft under the tower is 6 [m] and the area of the raft is 8945 [m^{2}]. The raft of Shanghai tower is supported by 955 bored piles with a diameter 1.0 [m]. The spacing between the piles is 3 [m] and the piles are distributed in different foundation arrangements where the entire raft area is divided into four sub areas A, B, C and D as shown in Figure 82. The length of the pile in area A is 56 [m], while the length of the pile in other zones is 52 [m].
Extensive studies with different calculation methods were carried out by Sun etc. al. (2011), Xiao etc. Al. (2011), Tang and Zhao (2014), (2014), Su etc. al. (2013), (2014) and Zhao, X. and Liu, S. (2017).
8.2 Analysis of the piled raft
Using the available data and results of the Shanghai piled raft, which have been discussed in detail in the references, the nonlinear analysis of piled raft in ELPLA according to El Gendy et al. (2006) and El Gendy (2007) is evaluated and verified using the loadsettlement relation of piles from the pile load test given by Xiao etc. Al. (2011).
For simplicity, the piled raft is considered double symmetric and only a quarter of the foundation system is analyzed. The foundation system is analyzed as an elastic raft supported on unequal rigid piles.
8.3 FENet
The raft is divided into triangular elements with a maximum length of 1.5 [m] as shown in Figure 83. Piles are divided into five elements with 14 [m] length.
8.4 Loads
According to Tang and Zhao (2014), the tower foundation carries a total dead and live loads of 6710 [MN] and 963 [MN], respectively. The total vertical load used in calculating the settlement is 7672 [MN]. The column and wall sections and loads are listed in Table 81The system of loading acting on the piled raft is shown in Figure 84.
Table 81 Section and load of columns and walls

Section 
Average load [MN] 
Distributed load [MPa] 
Horizontal super columns 
5.3×3.7[m] 
4×450.16 
22.96 
Vertical super columns 
3.7×5.3[m] 
4×461.75 
23.55 
Diagonal columns 
5.5×2.4[m] 
4×231.22 
17.52 
Core walls 
t_{flange} = 1.2[m], t_{web} = 0.9[m] 
3099.87 
16.50 
Total load 

7672.387 

8.5 Pile and raft material
The concrete grade of the raft and piles is C50. The following values were used as pile and raft material:
Modulus of elasticity E_{p} = 33234 [MN/m^{2}]
Poisson's ratio v_{p} = 0.167 []
Unit weight γ_{b} = 23.60 [kN/m^{3}]
8.6 Load settlement curve
Figure 85 shows the loadsettlement relation resulted from the pile load test given by Xiao etc. Al. (2011).
8.7 Soil properties
The site for the Shanghai Tower is in the new Pudong development district of Shanghai. The groundwater level is about 0.5~1.5 [m] below ground level. The foundation depth of the tower is 31.4 [m] below ground level.
Geotechnical investigation indicates that the ground conditions comprise horizontally stratified subsurface profile which is complex and highly variable. The subsoil below the ground level is composed of clay, silty clay and sand, underlain by a completely decomposed granite. According to the soil type and physical properties, the subsoil is divided into nine layers and fourteen sublayers. The top layer is the bearing layer for shallow foundation while the fifth, seventh and ninth layers are the endbearing layers for piles.
The soil profile and geotechnical parameters are summarized in Table 82. The subsoil layer under the raft up to 105 [m] deep are indicated in the boring log shown in Figure 86.
Table 82 Summary of geotechnical profile and parameters
Strata 
Substrata 
Subsurface Material 
Level at top of stratum z [m] 
Modulus of compressibility
E_{s} [MPa] 
Bulk Density
γ_{Bulk} [kN/m^{3}] 
1 

Fill 
4.5 
0 

2 

Plastic to softplastic silty clay 
2.7 
3.97 
18.4 
3 

Flow plastic muddy silty clay interspersed with sandy silt 
1.5 
3.84 
17.7 
4 

Flow plastic muddy clay 
3.0 
2.27 
16.7 
5 
1a 
Soft plastic clay 
11.5 
3.56 
17.6 
1b 
Soft plastic to plastic silty clay 
15.5 
5.29 
18.4 

6 

Hard plastic clay 
20.0 
6.96 
19.8 
7 
1 
Medium dense to dense silty sand with sandy silt 
24.0 
11.45 
18.7 
2 
Dense silty sand 
30.8 
75 
19.2 

3 
Dense silty sand with sandy silt and clay 
59.1 
60 
19.1 

8 

absent 



9 
1 
Dense sandy silt 
63.4 
70 
19.1 
21 
Dense silty sand with coarse and gravelly sand and clay 
71.7 
80 
20.2 

2t 
Hard plastic to plastic silty clay with clayed silt 
82.7 
35 
20.0 

22 
Dense silty sand with fine sand and sandy silt 
84.0 
85 
19.3 

3 
Dense fine sand 
96.0 
90 
19.7 

3t 
Hard plastic to plastic silty clay with clayed silt 
100.5 
35 
19.1 
8.8 Results
Figure 87 to Figure 811 show the settlement and pile reactions for the piled raft analyzed using the "Given loadsettlement curve from pile load test" method.
8.9 Measurements and other results
8.9.1 Measured settlement
The construction of Shanghai started 29 November 2008 and finished on 6 September 2014. According to Su etc. al. (2014), the settlement of the core and mega columns reached 60 and 45 [mm], respectively; on 30 April 2013 under nearly 75% of the building load. As expected, these values are less than the computed values because it doesn’t consider the long term settlement due to the consolidation of the clay layers. The soil below the tower will continue to consolidate until reaching the final settlement therefore calculation methods need to take consolidation effect into account.
8.9.2 Calculated final settlement
Several analyses were used to assess the response of the foundation for the Shanghai Tower. According to Sun etc. al. (2011), the computed values of maximum settlement ranges between 101 and 143 [mm].
A comparison between the computed settlement obtained by ELPLA and that obtained by other methods is presented in Table 83.
Table 83 Comparison between ELPLA results and those of other methods
Method 
S_{max.} [mm] 
S_{min.} [mm] 
S_{Diff}_{.} [mm] 
ELPLA 
129 
64 
65 
Xiao etc. al. (2011)  Computed 
143 
44 
99 
Xiao etc. al. (2011)  Predicted 
112 
68 
44 
Tang and Zhao (2014)  Hybrid Method 
107 
90 
17 
Tang and Zhao (2014)  Empirical Formula 
121 
 
 
Tang and Zhao (2014)  Predicted Method 
>120 
 
 
Sun etc. al. (2011)  Computed 
101 
37 
64 
8.10 Conclusion
This case study shows that ELPLA is a practical tool for analyzing large piled raft problems in significantly lowered computational time.
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