Practical Applications of piled rafts

#### Calculation methods

In the analysis of piled raft, each pile is treated as two units - pile shaft and pile base - with a uniform settlement along the pile shaft and in the pile base. This assumption allows modeling of non-linear behavior based on the empirical relationship of the load-settlement curve according to DIN 4014 or EA-Piles.

As a combination of empirical and theoretical approaches, a new method has been developed for the nonlinear computation of piled rafts. It meets the requirements of the KPP Directive.

#### Multiple models for analyzing piled raft foundations

The behavior of the pile-soil system can be examined by considering linearly or nonlinearly analysis.
One distinguishes between the following nonlinear analyses of piled raft foundations by:

1. A hyperbolic function for the load-settlement curve of the pile
2. Using German Standard "DIN 4014" for the load-settlement curve of the pile
3. Using German recommendations "EA-Piles" for the load-settlement curve of the pile
4. A given load-settlement curve of the pile

Features
• User interface and help system are available in 3 languages: English, German and Arabic
• Analysis of an elastic or a rigid combined piled raft foundation
• Analysis of a rigid pile group or free-standing raft on a rigid pile group
• Numerical model of soil-structure interaction is under 9 calculation methods
• Design of the raft according to ACI, EC 2, DIN 1045 and ECP
• Generation of the FE mesh of the raft with different element types
• Automatic generation of the FE mesh of the raft
• Powerful mesh generator (for the generation of square, rectangular, circular and annular rafts)
• Beam elements for modeling stiff walls on the raft
• Translational and rotational springs on the raft can be added at nodes
• Elastic or fixed rotations and deflections can be taken into account
• Determining contact pressures, settlements, internal forces, subgrade reactions, reinforcement and pile loads
• Node coordinates and boundary nodes of the FE mesh can be imported from a table via MS Excel
• Arbitrary shape of slabs, holes are also possible
• Variable slab thickness and foundation depth in vertical and horizontal directions
• Consideration of the reduction coefficients α according to DIN 4019 Part 1
• Point loads, line loads, area loads and moments at any position independent of the finite element net
• Polygonal load with variable ordinates and line moment
• The soil is defined by a number of borings each boring has multi-layers with different soil material
• Variable thickness and discontinuous soil strata
• Consideration of the variation of the subsoil in the three directions according to three methods
• Drawing soil layers by different symbols and colors according to DIN 4023 for easy identification
• Consideration of groundwater and overburden pressure effects
• Color representation of the dimensions, slab plans and results on the screen or printer
• Presentation of the results as values in the plan, contour lines, circular diagrams
• Drawing results in isometric view
• Distribution of results in plan
• Drawing deformations as deformed mesh
• Principal moments as streaks
• Drawing sections of results from several calculation methods in one view
• Data and results of several projects can be displayed together
• Tabulation of data and final results on the screen or printer
• Results can be saved in an ASCII file
• The drawings can optionally be saved as a WMF file
• There are detailed explanations in the user manual with numerical examples
• Short help information can be requested at any interface location
• Import or export the data to MS Excel
• Export the results and diagrams to MS Excel
• Export the data and results to MS Word
• A group of data with results together in one presentation
• Copying drawings to the clipboard for use in word processors
Analysis of Piled raft of Torhaus in Frankfurt by ELPLA

Torhaus is the first building in Germany with a foundation designed as a piled raft. The building lies in Frankfurt city in Germany. It is 130 [m] high and rests on two separate piled rafts, where a street passes under the building. Measured instruments were installed inside the foundation to record piled raft settlement and stress. Many authors studied the foundation of the Torhaus and applied their analysis methods on piled raft. Some of them are Sommer et al. (1985), Sommer (1989) and Reul/ Randolph (2003).

Comparisons are carried out to evaluate the nonlinear analysis of piled elastic raft using composed coefficient technique. Here results of three-dimensional finite element analysis and field measurements are compared with those obtained by the present analysis. In the comparisons the present analysis is termed NPRH.

Analysis of Piled raft of Messeturm in Frankfurt by ELPLA

Messeturm was the tallest high-rise building in Europe until 1997. ‎The building lies in Frankfurt city in Germany. It is 256 [m] high and standing on a piled raft foundation.

Using instruments installed inside this foundation, an extensive measuring program was established to monitor the behavior of the building. Because these instruments record raft settlements, raft contact pressures and loads on pile heads and along pile shafts, the building was a good chance for many authors to verify their analysis methods for piled raft.

A series of comparisons are carried out to evaluate the nonlinear analysis of piled raft using DIN 4014 [5] for load‑settlement relation. In which, results of other analytical solutions and measurements are compared with those obtained by the present analysis. In the comparisons the present analysis is termed NPRD.

Analysis of Piled raft of Westend 1 in Frankfurt by ELPLA

Westend 1 is 208 [m] high skyscraper and standing on a piled raft. The tower lies in Frankfurt city, Germany. It was completed in 1993. The tower was the third tallest skyscraper in Frankfurt and also in Germany until 1993.

The building has a basement with three underground floors and 51 stories with an average estimated applied pressure of 412 [kN/m2]. The foundation area is about 2900 [m2] founded on Frankfurt clay at a depth of 14·5 [m] under the ground surface. Raft thickness varies from 4·65 [m] at the middle to 3 [m] at the edge. A total of 40 bored piles, 30 [m] length by 1.3 [m] diameter. Piles are arranged in 2 rings under the heavy columns of the superstructure. The subsoil consists of gravels and sands up to 8 [m] below the ground surface underlay by layers of Frankfurt clay extended to more than 100 [m] below the ground surface. The groundwater level lies at 4.75 [m] under the ground surface.

Analysis of Piled raft of Skyper in Frankfurt by ELPLA

Skyper is 154 [m] high-rise building supported on a piled raft foundation. The tower was one of the tallest three skyscrapers in Frankfurt, Germany when it was completed in 2004. Using the available data and results of the Skyper piled raft,  the nonlinear analyses of piled raft in ELPLA are evaluated and verified using the following load-settlement relations of piles, El Gendy et al. (2006) and El Gendy (2007):

1- Hyperbolic function.
2- German standard DIN 4014.
3- German recommendations EA-Piles (lower values).
4- German recommendations EA-Piles (upper values).

The foundation system is analyzed as rigid or elastic piled rafts. In which, the raft is considered as either rigid or elastic plate supported on rigid piles. A series of comparisons are carried out to evaluate the nonlinear analyses of piled raft for load-settlement relations of piles. In which, results of other analytical solutions and measurements are compared with those obtained by ELPLA.

Analysis of Piled raft of Burj Khalifa in Dubai by ELPLA

Using the available data and results of the Burj Khalifa piled raft, which have been discussed in detail in the previous references, the nonlinear analyses of piled raft in ELPLA are evaluated and verified using the following load-settlement relations of piles, El Gendy et al. (2006) and El Gendy (2007):

1- Hyperbolic Function for Load-Settlement Curve.

The foundation system is analyzed as an elastic piled raft in which the raft is considered as an elastic plate supported on equal rigid piles.

A series of comparisons are carried out to evaluate the nonlinear analyses of piled raft for load-settlement relations of piles. In which, results of other analytical solutions and measurements are compared with those obtained by ELPLA.

Analysis of Piled raft Shanghai Tower in Shanghai by ELPLA

The Shanghai Tower is a mega tall skyscraper in Lujiazui, Pudong, Shanghai, It is considered the second-tallest building in the world after Burj Khalifa. The height of the tower is 632 meters. It consists of a 124-storey tower, a 7-storey podium and a 5-storey basement.

The tower has a 5-storey 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 [m2]. 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 . The length of the pile in area A is 56 [m], while the length of the pile in other zones is 52 [m].

GEOTEC Software is providing universities and consulting companies with the right tools for the last 25+ years. We also assist our clients in various geostructural projects. From basic to advanced problems, GEOTEC Software can provide you with the right technical assistant.