Design and Analysis of Foundations for High-Rise Buildings

This report provides a detailed overview of the design of foundations for high-rise buildings. It begins with an introduction to the characteristics of high-rise structures and their increasing prevalence due to urbanization. The report then delves into the factors influencing foundation design, including design forces/loads (wind, seismic, and vertical), soil types, water table levels, ground contamination, and the presence of adjoining structures. Common foundation types, such as raft foundations, pile foundations, and piled raft foundations, are discussed. The report also explores design approaches, including ultimate limit state (ULS) and serviceability limit state (SLS) design, and outlines the foundation design process. It addresses design issues, challenges, and includes a case study to illustrate practical applications. The report emphasizes the importance of geotechnical investigations to determine soil properties and the use of methods like the substructure and direct analysis methods to evaluate soil-structure interaction. The document concludes by highlighting the crucial role of properly designed foundations in ensuring the structural integrity, stability, safety, and durability of high-rise buildings.

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DESIGN OF FOUNDATIONS OF HIGH-RISE BUILDINGS
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Table of Contents
1. Introduction.......................................................................................................................................3
2. Background........................................................................................................................................5
3. Factors influencing design of high-rise buildings foundations.......................................................6
3.1. Design forces/loads......................................................................................................................6
3.2. Soil types.....................................................................................................................................8
3.3. Level of water table...................................................................................................................12
3.4. Ground contamination...............................................................................................................12
3.5. Type of adjoining structures......................................................................................................13
4. Common types of foundations for high-rise buildings..................................................................13
4.1. Raft foundation..........................................................................................................................13
4.2. Pile foundations.........................................................................................................................14
4.3. Piled raft foundation..................................................................................................................17
5. Design approaches...........................................................................................................................20
5.1. Ultimate limit state (ULS) design approach...............................................................................20
5.2. Serviceability limit state (SLS) design approach.......................................................................21
6. Foundation design process..............................................................................................................22
7. Design issues.....................................................................................................................................26
8. Challenges in design of foundations of high-rise buildings...........................................................27
9. Case study........................................................................................................................................29
10. Conclusions..................................................................................................................................34
References................................................................................................................................................36

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1. Introduction
This report presents analysis of different aspects of design of foundations of high-rise buildings.
The key characteristics of high-rise buildings are: they have several numbers of storeys that
necessitate use of mechanical vertical transportation system (such as lifts or elevators for
occupants to reach their destination), their height have consequential effect on evacuation, and
their total height cannot be fully reached by available fire-fighting equipment. These buildings
are typically considered to have more than seven storeys or a height greater than 23 meters. The
high-rise buildings have become very common in many cities across the world due to rapid
urbanization, industrial development and urban population growth. Public and private developers
have preferred high-rise buildings because they maximize land use especially in urban areas.
These buildings are usually designed for multiple uses – office, mixed-use, residential and hotel
(Figure 1 below shows uses of 100 tallest buildings in the world) and therefore have to withstand
a wide range of lateral and vertical forces. The forces must be supported by strong foundations,
which distribute the forces to the ground. Therefore the stability and safety of high-rise buildings
largely depend on their foundations.

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Figure 1: Uses of 100 tallest buildings in the world (Kayvani, 2015)
Foundation is the lowest part of the building that transmits all loads of the building to the
ground (Poulos, 2017). The foundation connects the building with the ground and is in direct
contact with soil. The main functions of foundations of high-rise buildings include: ensuring
even distribution of the load, minimizing the load intensity, providing a level surface on which
the superstructure is constructed, providing lateral stability of the building, anchoring the
building against natural forces like earthquakes, protecting the building against undermining, and
protecting the building against ground moisture and soil movements (Ajdukiewicz, et al., 2017).
Design of foundations is very essential for any building (Nangan, et al., 2017), but it is more
critical for high-rise buildings because of the height of these buildings, the numerous forces
acting on them and their large number of occupants. These buildings are exposed to both
dynamic loads and static loads (Hallebrand & Jakobsson, 2016). The design of foundations of
high-rise buildings entails determining the most suitable type and size of foundation and its
materials. Therefore a properly designed foundation of a high-rise building improves the
structural integrity, stability, safety and durability of the building.
The main purpose of this report is to provide the suitable criteria for the design of
adequate foundations of high-rise buildings. The other sections of this report are: background,
factors influencing the design of foundations of high-rise buildings, common types of
foundations for high-rise buildings, design approaches, foundation design process, design issues,
challenges in the design of foundations of high-rise buildings, case study and conclusion.

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2. Background
Construction of the first generation of high-rise buildings started in New York and Chicago in
the late 19th century. These cities experienced explosive growth and adequate land was not
available to meet the increasing demand for new buildings. As a result, builders had only one
option – to start building up (vertical buildings). The 12-storey Home Insurance Building that
was built by William Le Baron Jenney in 1884 is believed to be the first high-rise building of the
industrial era (Nicholson-Cole, 2016). Since then, high-rise buildings have become very common
in urban areas where rapid urban population growth and increased land prices have created a
high demand for commercial and residential buildings. As a result, high-rise buildings have
become more suitable and the commonest feature of architectural landscape in most urban areas
worldwide because they occupy less land area.
Some of the high-rise buildings in the world include: Burj Khalifa (828m), Shanghai
Tower (632m), Makkah Clock Tower (601m), Lotte World Tower (555m) and One World Trade
Center (541.3m). The 1,000m-tall Jeddah Tower that is under construction in Jeddah, Saudi
Arabia is expected to become the world’s tallest building once completed in 2020. Figure 2
below shows the height and timeline of high-rise buildings in the world. One common feature
among high-rise buildings is that they have strong foundations. New foundation designs is one of
the factors that have enabled architects to design very tall buildings. The high-rise buildings’
foundations support very heavy loads. Typically, low-rise buildings’ foundation systems are used
for high-rise building foundations but on an enlarged scale. The foundations of high-rise
buildings are usually wide and deep. For example, the foundation of Burj Khalifa features a 3.7m
thick raft and 194 1.5m-diameter and 45m long concrete piles.

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Figure 2: Height and timeline of high-rise buildings (Kayvani, 2015)
Therefore since the foundation is the one that carries the weight of the whole building, it is the
most important part of a high-rise building and must be designed properly.
3. Factors influencing design of high-rise buildings foundations
Below are some of the factors that influence the design of foundations of high-rise buildings:
3.1. Design forces/loads
Design forces or loads largely influence the design of foundations of high-rise buildings. The
design of high-rise buildings foundations is more complicated than that of mid-rise or low-rise
buildings because of the increase in height. Both lateral (horizontal) and vertical (downward)
forces are imposed on high-rise buildings. The most common lateral forces include: wind load,
earth and water pressure, and seismic load (Aly & Abburu, 2015). Wind load is a major concern
for high-rise buildings because wind load increases with an increase in height of the building
(Mittal, et al., 2014). Figure 3 below shows an increase in wind load with the increasing height
of a high-rise building. Seismic loads are imposed on the building during an earthquake. High-

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rise buildings are more vulnerable to earthquakes because of their excessive heights, low
structural damping, and use of lightweight materials for inner partition walls and the super
structure (Jayasinghe & Weerasuriya, 2014), hence their foundations should be designed by
considering seismic forces. Water/fluid pressure is proportional to liquid density and increases
linearly with depth. Earth/soil pressure is imposed on the substructure of the high-rise building,
including its foundation. Examples of vertical loads are: dead loads, live/imposed loads, snow
loads and other special loads (erection loads, impact, fatigue, foundation movement, vibration
and elastic axial shortening).
Figure 3: Wind load acting on a high-rise building (Daemei, et al., 2019)
The design forces are essential for the design of foundations of high-rise buildings
because they are all distributed to the ground via the foundation, as shown in Figure 4 below.
Engineers, architects and designers are using new design concepts, advanced designing methods
and tools, and new trends to reduce design loads (Sharma, et al., 2017), which also reduces the
size and cost of foundations of high-rise buildings. One such technique is use of spiral forming
and curved façade to reduce wind load, like it is the case for Shanghai Tower (Zhaoa, et al.,
2011). It is important to create 3D models of high-rise buildings during design stage so as to

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accurately predict design loads that will be supported by the foundation. This helps in
determining the most suitable type, size and construction materials of foundations of the high-
rise building.
Figure 4: Distribution of deign loads (Mishra, 2015)
Therefore appropriate methods should be used to estimate all types of loads acting on the
building from all directions, including live loads and dead loads (both the gravity loads and uplift
loads). Some of the factors that influence the quantity of design loads of the building are: type of
building structure, location of the building, material of construction, and number of floors. These
loads are the ones that act on the foundation hence should be considered as a key factor when
designing foundations of high-rise buildings.
3.2. Soil types
The type of soil can either break or make the foundation of a high-rise building. This is
because the interaction between the soil and the building affects the dynamic characteristics of
high-rise buildings (Li, et al., 2014). Some soils tend to deform when subjected to loadings and
with temperature variations. This deformation can cause settlement of the foundation thus
affecting the stability of the building. Loam, gravel, sand and rock are foundation-friendly soils

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whereas clay, silt and peat are bad options since they can cause development of cracks in the
foundation. Soils have different capacities to absorb water and generate earth pressure (through
expansion when temperature increases) that is imposed on the foundation. If the foundation is
not strong enough, the earth pressure can cause stresses that lift up the building. The soil also
provides the ground over which the foundation rests. If the soil or ground is non-uniform,
differential settlement can occur resulting to cracks and tipping of the building, as shown in
Figure 5 below. There are also different layers of soil. In most cases, weak soil layers are on top
while strong layers are at the bottom. The foundation of high-rise buildings must reach the strong
soil layer, as shown in Figure 6 below. This means that the foundation has to be deep enough to
pass through the weak layer until it reaches the strong layer where it safely transmits or
distributes the load to the soil/ground.
Figure 5: Settlement of the building (Mishra, 2015)

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Figure 6: Foundation driven to the strong soil (Amornfa, et al., 2012); (Understand Building
Construction, (n.d.))
When designing foundations of high-rise buildings, relevant geotechnical investigation
must be conducted so as to determine the conditions of the soil. The geotechnical investigation
entails safety analysis against overturning, sliding, buoyancy, base failure, settlements and
displacements (Katzenbach, et al., 2016). This will determine the bearing capacity of the soil,
which helps in selecting the most suitable type of foundation design, materials and construction
method. The geotechnical investigation should include in-situ soil testing, borehole drilling, and
multiple laboratory tests. All these helps to determine the stiffness and strength properties of the
soil. The soil frost line’s depth should also be determined from the geotechnical investigation so
that the soil can be improved so as to reduce the swelling effect. The properties of soil can then
be used to develop a geotechnical model of the site that is used to determine the appropriate
design parameters of the foundation. The geotechnical model should incorporate the soil-
structure interaction effect (Pitilakis & Clouteau, 2010); (Samali, et al., 2014). This interaction
has a significant effect on the performance of high-rise buildings foundations (Farghaly &
Ahmed, 2013). The soil-structure interaction effect can be evaluated using two categories of

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numerical approaches: substructure method and direct analysis method. In substructure method,
several springs are integrated to epitomize the foundation of the building and the adjacent soil, as
shown in Figure 7 below (Li, et al., 2014). In direct analysis method, a model is developed
combining the building, foundation and soil, and then examined as an integrated system, as
shown in Figure 8 below. This method can be used to examine the extensive response and
damage of the foundation, soil and superstructure when the building is subjected to earthquakes.
Figure 7: Substructure method (Li, et al., 2014)
Figure 8: Direct analysis method (Li, et al., 2014)

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The key geotechnical design parameters for high-rise building foundations are: ultimate
skin friction, end bearing resistance, lateral soil pressure, soil bearing capacity and stiffness.
These parameters should been comprehensively analyzed so as to determine the accurate soil-
structure interaction. Some of the methods that can be used for this analysis include: analytical
methods (p-y approach, Winkler method and elastic continuum method), numerical approach
(finite different approach, finite element approach and boundary element approach), and half-
space theory-based methods (direct method and indirect method) (Verma, et al., 2018).
3.3. Level of water table
A raised water table can cause the building to float thus tilting it or making it unstable,
reduce effective pressure that results to excessive settlement of the building, and create a wet
basement. On the other hand, a lowered water table has a tendency of increasing the effective
pressure thus causing extra settlements. When the water table is high, it means that the
foundation will be in a waterlogged area. This is not the best area to construct a foundation of a
high-rise building because the water will affect the construction process and when the foundation
is complete, water will start seeping into it. This weakens the foundation and can eventually
cause the building to collapse.
3.4. Ground contamination
It is also important to consider the contamination level of the ground when designing
foundations of high-rise buildings. This is because different types of contaminants present in the
ground have varied effects on the foundation. Generally, metal foundation members get affected
by corrosion when they are built in contaminated grounds, such as backwater areas, old sanitary
landfills and other old landfills for other pollutants or toxic wastes. Concrete foundations also get
affected by corrosion when located in grounds with sulfates. Samples of the soil should be taken