IJHRB Preview 2012 1

About the CouncilThe Council on Tall Buildings and Urban Habitat, based at the Illinois Institute of

Technology in Chicago, is an international not-for-profit organization supported by

architecture, engineering, planning, development and construction professionals. Founded in 1969, the Council’s mission is to disseminate multi-disciplinary information

on tall buildings and sustainable urban environments, to maximize the international

interaction of professionals involved in creating the built environment, and to make

the latest knowledge available to professionals in a useful form.

The CTBUH disseminates its findings, and facilitates business exchange, through: the

publication of books, monographs, proceedings and reports; the organization of world congresses, international, regional and specialty conferences and workshops; the

maintaining of an extensive website and tall building databases of built, under

construction and proposed buildings; the distribution of a monthly international tall

building e-newsletter; the maintaining of an international resource center; the bestowing of annual awards for design and construction

excellence and individual lifetime achievement; the management of special task forces/working groups; the hosting of

technical forums; and the publication of the CTBUH Journal, a professional journal containing refereed papers written by

researchers, scholars and practicing professionals.

The Council is the arbiter of the criteria upon which tall building height is measured, and thus the title of "The World’s Tallest Building" determined. CTBUH is the world’s leading

body dedicated to the field of tall buildings and urban habitat and the recognized

international source for information in these fields.

CTBUH Journal

About the CouncilThe Council on Tall Buildings and Urban Habitat, based at

the Illinois Institute of Technology in Chicago, is an

international not-for-profit organization supported by

architecture, engineering, planning, development and

construction professionals. Founded in 1969, the

Council’s mission is to disseminate multi-disciplinary

information on tall buildings and sustainable urban

environments, to maximize the international interaction

of professionals involved in creating the built

environment, and to make the latest knowledge

available to professionals in a useful form.

The CTBUH disseminates its findings, and facilitates

business exchange, through: the publication of books,

monographs, proceedings and reports; the organization

of world congresses, international, regional and specialty

conferences and workshops; the maintaining of an

extensive website and tall building databases of built,

under construction and proposed buildings; the

distribution of a monthly international tall building

e-newsletter; the maintaining of an international resource

center; the bestowing of annual awards for design and

construction excellence and individual lifetime

achievement; the management of special task forces/

working groups; the hosting of technical forums; and the

publication of the CTBUH Journal, a professional journal

containing refereed papers written by researchers,

scholars and practicing professionals.

The Council is the arbiter of the criteria upon which tall

building height is measured, and thus the title of "The

World’s Tallest Building" determined. CTBUH is the world’s

leading body dedicated to the field of tall buildings and

urban habitat and the recognized international source for

information in these fields.

Council on Tall Buildings and Urban Habitat Issue Chief Editor: Sang Dae Kim

Volume 1 Number 1 March 2012

Amplitude Dependency of Damping in Buildings and Critical Tip Drift RatioYukio Tamura

Human-Induced Vibrations in BuildingsMichael J. Wesolowsky, Peter A. Irwin, Jon K. Galsworthy, and Andrew K. Bell

Strength Evaluation for Cap Plate on the Node Connection in Circular Steel Tube Digrid SystemSeong-Hui Lee, Jin-Ho Kim, and Sung-Mo Choi

Experimental and Analytical Investigation of Web-transferred Diagrid Node under Seismic ConditionInyong Jeong, Young K. Ju, and Sang Dae Kim

Validating the Structural Behavior and Response of Burj Khalifa: Synopsis of the Full Scale Structural Health Monitoring ProgramsAhmad Abdelrazaq

Parametric Analysis and Design Engine for Tall Building StructuresGoman Ho, Peng Liu, and Michael Liu

Anything Goes?Dennis Poon and Leonard Joseph

CTBU

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International Journal of High-Rise Buildings

ISSN 2234-7224

Volume 1 Number 1 March 2012

No. 1 2012

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CTBUH1.0319.indd 1 2012-04-13 오전 9:03:37

Volume 1, Number 1, March 2012

International Journal of

High-Rise Buildingswww.ctbuh.org

1 Amplitude Dependency of Damping in Buildings and Critical Tip Drift Ratio

Yukio Tamura

15 Human-Induced Vibrations in Buildings

Michael J. Wesolowsky, Peter A. Irwin, Jon K. Galsworthy, and Andrew K. Bell

21 Strength Evaluation for Cap Plate on the Node Connection in Circular Steel Tube Diagrid System

Seong-Hui Lee, Jin-Ho Kim, and Sung-Mo Choi

29 Experimental and analytical Investigation of Web-transferred Diagrid Node under Seismic Condition

Inyong JEONG, Young K. JU, and Sang-Dae KIM

37 Validating the Structural Behavior and Response of Burj Khalifa: Synopsis of the Full Scale Structural

Health Monitoring Programs

Ahmad Abdelrazaq

53 Parametric Analysis and Design Engine for Tall Building Structures

Goman Ho, Peng Liu, and Michael Liu

61 Anything Goes?

Dennis Poon and Leonard Joseph

Subscription information

■ Council on Tall Buildings and Urban Habitat

S. R. Crown Hall Illinois Institute of Technology 3360 South State Street Chicago, IL 60616

Phone : +1 (312) 567 3487

Fax : +1 (312) 567 3820

E-mail : [email protected]

■ Korean Council on Tall Buildings and Urban Habitat

#301 Ochang B/D, 208-2 Nonhyeon-dong, Gangnam-gu, Seoul, 135-010, Korea

Phone : +82 (2) 3290 4742

Fax : +82 (2) 921 2439

E-mail : [email protected]

Contents



Editor’s Note

The Council on Tall Buildings and Urban Habitat has developed into the world’s most influential and

renowned professional organization on tall buildings since its establishment in 1969. Today it leads the

industry by disseminating the latest information to professionals working on tall building design and

engineering, including the production of design guidelines, and volumes of books and technical papers

contributed by the world’s most experienced experts.

The main outlet for the Council’s work is the CTBUH Journal, which has published for 12 years, including

practical articles on all aspects of tall building design and construction. It has received great response from

around the world and become a valuable resource for the industry.

Now the Council has decided to publish a new journal, the International Journal of High-Rise Buildings

(IJHRB), focusing on pure research content and investigations in tall building design. The IJHRB should

serve as essential compliment to the CTBUH Journal, adding to the Council’s already substantial body of

work. IJHRB will be published four times a year, with a different Chief Editor in charge of each issue.

Although the journal welcomes any papers on tall-building-related topics, we will concentrate on the

followings for the first two years:

- Architectural Planning & Design

- Construction Technology- Energy Savings

- MEP

- Structural Engineering

- Sustainability

I truly hope the IJHRB will energize the tall building industry. Many researchers will be able to present

their work and results through the journal and apply the contents to their everyday practice.

Professionals who wish to contribute their papers to the journal can find the necessary information in the

Overview and Paper Submission Guide at the back of this publication.

Sincerely,

Prof. Sang Dae Kim

Co-Chief Editor




March 2012, Vol 1, No 1, 1-13

Amplitude Dependency of Damping in Buildings and Critical Tip

Drift Ratio

Yukio Tamura†

School of Architecture and Wind Engineering, Tokyo Polytechnic University, Atsugi 243-0297, Japan

Abstract

The importance of appropriate use of damping evaluation techniques and points to note for accurate evaluation of damping

are first discussed. Then, the variation of damping ratio with amplitude is discussed, especially in the amplitude range relevant

to wind-resistant design of buildings, i.e. within the elastic limit. The general belief is that damping increases with amplitude,

but it is emphasized that there is no evidence of increasing damping ratio in the very high amplitude range within the elastic

limit of main frames, unless there is damage to secondary members or architectural finishings. The damping ratio rather

decreases with amplitude from a certain tip drift ratio defined as “critical tip drift ratio,” after all friction surfaces between

primary/structural and secondary/non-structural members have been mobilized.

Keywords: Damping, Wind-induced response, Amplitude dependency, Critical tip drift ratio, Damping evaluation technique

1. Introduction

In order to accurately evaluate the responses of build-

ings and structures under wind, earthquake or other exter-

nal excitations, their dynamic properties such as natural

frequencies, mode shapes and damping ratios should be

exactly known. Damping is the most important dynamic

but most uncertain parameter affecting the dynamic

responses of buildings and structures. This uncertainty

significantly reduces the reliability of structural design for

dynamic effects. For example, the C.O.V. of full-scale

data has been estimated at almost 70% (Havilland, 1976).

If the design value of damping ratio is set at 2% based on

the mean value of full-scale data, mean ± σ (standard

deviation) ranges from 0.6% to 3.4% (= 2% ± 1.4%). If

we evaluate wind-induced acceleration responses of a tall

building with almost 5.7 times difference between damp-

ing ratios (= 3.4/0.6), the acceleration responses show 2.4

times difference. Therefore, accurate evaluation of design

damping ratio is a pressing need for tall building design.

Another important suggestion on application of damping

devices can be derived from this fact. If we could assure

additional damping, say 4%, by applying a damping

device, the total damping ratio in the building would

range from 4.6% to 7.4%, i.e., the difference would be

only 1.6 times, and the difference between the resultant

acceleration responses would be only 1.3 times.

Unlike seismic excitations, wind excitations last for a

long period, e.g. a few hours, and induced building

responses are composed of a static component, a quasi-

static component, and a resonant component, as shown in

Fig. 1. If the response level exceeds the elastic limit, the

natural frequency shifts to a lower frequency due to

softening phenomena in the plastic region (Tamura et al.,

2001; Tamura, 2009). This natural frequency shift results

in an increase in the corresponding wind force spectrum,

and can potentially increase the resonant component. The

static component also shows some interesting behaviors

such as a sudden increase in the along-wind direction

(Tsujita et al., 1997; Tamura et al., 2001). There are vari-

ous uncertainties in the characteristics of wind-induced

responses of a building in the plastic region due to the

long-lasting excitation, static components, and softening

phenomena. Therefore, almost all wind loading codes/

standards, e.g. AIJ-RLB (2004) and ISO4354 (2009),

clearly require almost-elastic behavior even for extremely

strong wind conditions such as ultimate limit state design.

Thus, wind-induced responses of buildings are assumed

to be almost-elastic, and the gust loading factor and the

equivalent static wind loads in codes/standards are essen-

tially based on linear/elastic structural behavior (ISO

4354, 2009). In this paper, the dynamic behaviors of main

frames of buildings are also assumed to be in the elastic

region.

As there is no theoretical method for estimating

damping in buildings, it is estimated from full-scale data,

which shows significant dispersion for various reasons.

There are many potential causes of dispersion of full-

scale damping data as follows:

- Soil types

†Corresponding author : Yukio TamuraTel: +81 (0) 46 242 9547; Fax: +81 (0) 46 242 9547E-mail: [email protected]




March 2012, Vol 1, No 1, 15-19

Human-Induced Vibrations in Buildings

Michael J. Wesolowsky, Peter A. Irwin, Jon K. Galsworthy†, and Andrew K. Bell

Rowan Williams Davies & Irwin, Inc., Guelph, Ontario, Canada

Abstract

Occupant footfalls are often the most critical source of floor vibration on upper floors of buildings. Floor motions can degradethe performance of imaging equipment, disrupt sensitive research equipment, and cause discomfort for the occupants. It isessential that low-vibration environments be provided for functionality of sensitive spaces on floors above grade. This requiresa sufficiently stiff and massive floor structure that effectively resists the forces exerted from user traffic.

Over the past 25 years, generic vibration limits have been developed, which provide frequency dependent sensitivities forwide classes of equipment, and are used extensively in lab design for healthcare and research facilities. The same basis for thesecurves can be used to quantify acceptable limits of vibration for human comfort, depending on the intended occupancy of thespace. When available, manufacturer's vibration criteria for sensitive equipment are expressed in units of acceleration, velocityor displacement and can be specified as zero-to-peak, peak-to-peak, or root-mean-square (rms) with varying frequency rangesand resolutions.

Several approaches to prediction of floor vibrations are currently applied in practice. Each method is traceable to fundamentalstructural dynamics, differing only in the level of complexity assumed for the system response, and the required informationfor use as model inputs. Three commonly used models are described, as well as key features they possess that make themattractive to use for various applications.

A case study is presented of a tall building which has fitness areas on two of the upper floors. The analysis predicted thatthe motions experienced would be within the given criteria, but showed that if the floor had been more flexible, the potentialexists for a locked-in resonance response which could have been felt over large portions of the building.

Keywords: Human-induced vibrations, Sensitive equipment, Occupant comfort, Building performance, Vibration criteria

1. Introduction

The study of vibration in floors has become more of a

necessity in recent years due to the optimization of

materials in building design creating lighter structures,

combined with improvements in research and imaging

technology that demand a more stable operating environ-

ment. Research and healthcare facilities are a prime

example of spaces where a variety of uses and space

optimization places vibration sources closer to vibration

sensitive equipment and processes.

The primary source of vibration in most facilities is

human activity. As people walk, the impact from each

footfall induces floor motions that may easily transmit

to nearby spaces. Quantifying vibration from walking,

whether through measurement of existing spaces or

numerical predictions for guiding the design of a new

facility, is a complex task. This task is complicated in part

by the availability of a number of vibration measurement

and prediction methodologies, each associated with both

similar and unique assumptions. The difficulties in meas-

urement and prediction are further complicated by the

fact that the engineering community has not agreed to a

standard method for quantifying vibration and processing

methods for assessment of spaces of concern.

In this paper we discuss the impact of unwanted

vibrations both from a human perceptibility and sensitive

equipment standpoint. Generic and specific vibration

criteria that are commonly used in international practice

are presented. Several predictive models are discussed

that apply to both steel and concrete construction. Finally,

a case study involving aerobic activity will be presented,

showing the magnitude of vibration that can be induced

by human activity.

2. Impact of Unwanted Vibration

Floor vibration from footfalls and mechanical equip-

ment may be transmitted to the floor structure that

supports vibration sensitive healthcare/laboratory spaces.

Vibration affects sensitive instrumentation by causing

relative motion of its key internal components, or relative

motion between the instrument and the specimen or target

being studied. Figure 1 shows the impact of baseline

ambient vibration conditions on the image of an E. coli

bacterium taken with a Scanning Electron Microscope at

approximately 65,000X magnification.

†Corresponding author : Jon K. GalsworthyE-mail: [email protected]

16 Michael J. Wesolowsky et al. / International Journal of High-Rise Buildings

In healthcare/laboratory spaces housing vibration-

sensitive equipment, floor vibration can:

- Cause exceedances of manufacturer-specified vibra-

tion criteria for equipment within the space;

- Cause substantial “noise” or errors in measurement,

which interferes with the accuracy of measurement

results (e.g., imaging);

- Cause the reliability or performance of the equipment

to deteriorate; and/or,

- In extreme cases, cause damage or result in loss of

equipment calibration.

In addition to their effects on instrumentation, persist-

ent floor vibrations may also cause fatigue and dis-

comfort to building occupants, whether the usage of the

building is commercial or residential. High levels of floor

vibration can render a space unusable by its occupants,

and the impacts can be costly.

3. Vibration Criteria

Over the past 25 years, generic vibration limits have

been developed, which provide frequency dependent

sensitivities for wide classes of equipment, and are used

Figure 1. Coloured scanning electron microscope imagesof E. coli bacterium at approximately 65,000X magnifica-tion under two levels of ambient vibration. Figure 2. Vibration criteria curves.

Table 1. Generic vibration criteria for healthcare spaces (adapted from Amick et al., 2005)

Vibration criteria curveVelocity max level[1]

µm/s (µin/s)Description of Use

Workshop (ISO) 800 (32,000) Distinctly perceptible vibration. Appropriate to workshops and non-sensitive areas.

Office (ISO) 400 (16,000) Perceptible vibration. Appropriate to offices and non-sensitive areas.

Residential day (ISO) 200 (8,000)Barely perceptible vibration. Maximum recommended for general sleep areas.Usually adequate for computer equipment and microscopes with less than 40Xmagnification.

Residential night (ISO) 140 (5,600) Appropriate for most sleep areas such as hospital recovery rooms.

Op. Theatre (ISO) 100 (4,000)Threshold of perceptible vibration. Suitable in most instances for surgical suites,catheterization procedures and microscopes to 100X magnifications and for otherequipment of low sensitivity. Suitable for very sensitive sleep areas.

VC-A 50 (2,000)Adequate in most instances for optical microscopes to 400X, micro-balances, andoptical balances.

VC-B 25 (1,000)Micro-surgery, eye surgery and neurosurgery, CT, CAT, PET, fMRI, SPECT, DOT,EROS.

VC-C 12.5 (500)Appropriate for MRIs, NMRs, standard optical microscopes to 1000X magnifica-tion, and moderately sensitive electron microscopes to 1 µm detail size.

VC-D 6.25 (250)Suitable in most instances for demanding equipment, including may electronmicroscopes (SEMs and TEMs) at more than 30,000X magnification and up to 0.3micron geometries, and E-beam systems.

VC-E 3.12 (125)

A challenging criterion to achieve. Assumed to be adequate for the most demand-ing of sensitive systems including long path, laser-based, small target systems, sys-tems working at nanometer scales and other systems requiring extraordinarydynamic stability.

VC-F 1.56 (62.5)Appropriate for extremely quiet research spaces. Generally difficult to achieve inmost instances. Not recommended for use as a design criterion, only for evaluation.

VC-G 0.78 (31.3)Appropriate for extremely quiet research spaces. Generally difficult to achieve inmost instances. Not recommended for use as a design sriterion, only for evaluation.

Notes: [1] As measured in one-third actave bands of frequency over the frequency range 8 to 80 Hz (ISO, VC-A and VC-B) or 1 to 80 Hz (VC-C through VC-G).




March 2012, Vol 1, No 1, 21-28

Strength Evaluation for Cap Plate on the Node Connection in

Circular Steel Tube Diagrid System

Seong-Hui Lee1, Jin-Ho Kim2, and Sung-Mo Choi3†

1Construction Technology Exam. Division, Korean Intellectual Property Office, Daejeon, Korea2Research Institute of Industrial Science & Technology, Incheon, Korea

3Department of Architectural Engineering, University of Seoul, Seoul, Korea

Abstract

Diagrid system has been in the spotlight for its superiority in terms of the resistance to lateral force when applied toskyscrapers. In diagrid system, most of columns can be eliminated because vertical loads (gravity loads) and horizontal loads(lateral loads) are delivered simultaneously thanks to the triangular shape of diagrid. However, lack of studies on connectionshape and node connection details makes it hard to employ the system to the buildings. In this study, the structural safety ofthe node connections in circular steel tube diagrid system which has been considered in the Cyclone Tower in Korea (Sevenstories below and fifty-one above the ground) was evaluated using the 4 full-scale specimens. The parameters are the extendedlength (20 mm, 40 mm & 60 mm), thickness (40 mm & 50 mm).

Keywords: Diagrid, Node, Connection, Stress concentration, Cap plate

1. Introduction

Skyscrapers today are irregular-shaped to be city

landmarks and function as vertical cities to enable the

efficient use of land. 3T (Twisted, Tilted & Tapered)

designs are being suggested for irregular buildings and

studies to develop new structural systems have been

actively made to satisfy slender shape ratio. In this

regard, new structural systems differentiated from tradi-

tional ones are being applied more often than before and

diagrid system is the one most frequently applied.

Diagrid system has been in the spotlight for its super-

iority in terms of the resistance to lateral force when

applied to skyscrapers. In diagrid system, most of columns

can be eliminated because vertical loads (gravity loads)

and horizontal loads (lateral loads) are delivered simul-

taneously thanks to the triangular shape of diagrid. The

behaviors (tensile/compressive) of the diagrid in axial

direction resist shear and thus minimize deformation.

And, it is more applicable to the buildings of irregular

shape than the traditional systems where the lateral

behaviors of columns resist shear and enables excellent

lateral resistance without additional reinforcement of

core. Because of these advantages, diagrid system has

been employed to the Swiss Re Building in London, the

Hearst Tower and the New World Trade Center in New

York, the Twin Tower in Guangzhou, the CCTV Building

in Beijing and Mode Institute in Japan. In Korea, the

diagrid system has been considered in projects for the

Cyclone Tower in Asan, Lotte Super Tower in Seoul and

Future-Ex in Daejeon. However, lack of studies on con-

nection shape and node connection details makes it hard

to employ the system to the buildings. Therefore, con-

nection details should be suggested and developed in

order to promote the application of the system and the

generalization of the connections with secured safety

should backup its application through structural perform-

ance evaluation and reliability verification for the con-

nection details which have been suggested so far.

In this study, the structural safety of the node connec-

tions in circular steel tube diagrid system which has been

considered in the Cyclone Tower in Korea (Seven stories

below and fifty-one above the ground) was evaluated

using the finite element analysis. And, 4 full-scale speci-

mens were fabricated for tests with the variables of

extended length (20 mm, 40 mm & 60 mm) and thickness

(40 mm & 50 mm) of cap plate to suggest economically-

efficient ways to mitigate stress concentration in columns.

1.1. Shape of diagrid connections

Because of the simultaneous resistance to gravity loads

and lateral loads which is inherent in diagrid system,

strong stress is generated in node connections in the

system. Securing reliability of connection details is signi-

ficantly important because of highly complicated stress

generation upon the application of lateral loads. Because

†Corresponding author : Sung-Mo ChoiTel: +82-2-2210-2396; Fax: +82-2-2248-0382E-mail: [email protected]

22 Seong-Hui Lee et al. / International Journal of High-Rise Buildings

diagrid members exist throughout the whole floors of a

building, the constructional efficiency of the connections

plays an importance role in shortening construction period.

Consequently, the node connections of diagrid system

should be decided in terms of construction efficiency and

the workability and constructability of the connections

should be considered from the planning stage in order to

maximize constructional efficiency.

In the diagrid connections of the Cyclone Tower in

Asan, Korea, node connections are formed at the inter-

section of columns as shown in Figure 2. A H-488 × 300 ×

11 × 18 beam made of 600 MPa steel (Fu: 600 MPa) was

set up horizontally at the center of the node connection.

A cap plate was set up at the bottom of a steel tube and

a stiffener plate was set up to support the cap plate.

2. Finite Element Analysis

Finite element analysis was conducted for the connec-

tions of the Cyclone Tower to evaluate their structural

performance.

2.1. Finite element analysis of cap plate

Increasing cap plate thickness and extending its length

have been suggested as the methods to mitigate stress

concentration in connections. So, the finite element analy-

sis was conducted for the two suggestions in this study.

2.2. Analysis model & method

Four objects with the variables of the extended length

Figure 1. Cyclone Tower in Asan, Korea.

Figure 2. Cyclone Tower, using diagrid system.




March 2012, Vol 1, No 1, 29-36

Experimental and Analytical Investigation of Web-transferred

Diagrid Node under Seismic Condition

Inyong Jeong, Young K. Ju†, and Sang-Dae Kim

School of Civil, Environmental, and Architectural Engineering, Korea University, Seoul, Korea

Abstract

The diagrid structural system is considered to be not only the best structural system for constructing free form structures, butalso a very effective system in resisting lateral load. As a newly investigated structural system, its complicated node has notyet been completely investigated and minimal experimentation of manufacturing and constructing the system have beenconducted. Therefore, the constructing cost of the diagrid structural system is still comparatively high. In this paper, the cyclicperformance of a diagrid node with an H-section brace will be discussed. Design details that consider productivity wereproposed and their structural performances were assessed through experimental and analytical investigation

Keywords: Diagrid, Node, Web-transferred, Test, Analysis

1. Introduction

The development of structural technology makes it

possible to construct higher buildings. Attempts to defy

gravity have been performed in many ways, such as

developing high strength materials or new structural

systems. However, aesthetic variety has been limited to

only low-rise buildings or to the use of several methods

such as set-backs or a change of exterior materials.

Recently, however, aesthetic diversities in tall buildings

have been attracting people’s attention, and many

attempts at aesthetic diversity are being made, resulting in

the current trend of 3T (Twisted, Tilted and Tapered).

Among these attempts, the diagrid structural system is

gaining acceptance as the most appropriate structural

system for free form tall buildings. The most distinctive

characteristic of the diagrid system is that it has no

vertical columns and consists of triangular modules,

braces and beams, resisting external forces. This charac-

teristic provides free form buildings with many possi-

bilities. Also, these triangular modules act as trusses

resisting external forces with their axial behavior and

very high structural efficiency. The Heast Tower in New

York saved 20% steel material using the diagrid system

(Rahimian, 2006).

Despite these merits, study of the diagrid system is at

an initial stage. Several theoretical studies such as seismic

performance factors (Kim, 2009; Kim, 2009), optimal

angles (Moon, 2007) and progressive collapse (Kim,

2008) are in progress. Construction cost is relatively high

due to the lack of production and construction experience.

To overcome this lack of experience, a series of tests

were conducted and supported by the Korea Institute of

Construction and Transportation Technology Evaluation

and Planning. With this support, a material test, monotonic

tensile/compressive test, mock-up test, cyclic test, and

frame test were conducted and are illustrated in Figure 1.

Among these tests, the cyclic test will be discussed in this

paper, including further research about the test. The

seismic performance of diagrid nodes with H-section

braces was assessed through experimental and analytical

studies. The analysis was conducted using the same con-

dition as that of the cyclic test and the results were well

matched with the test results. Therefore, the generalized

behavior of the diagrid node was derived by expanded

parameter analysis.

†Corresponding author : Young K. JUTel: +82-2-3290-3327; Fax: +82-2-928-7656E-mail: [email protected] Figure 1. A series of Diagrid experiments.

30 Inyong JEONG et al. / International Journal of High-Rise Buildings

2. Experimental Study

2.1. Test specimen

Figure 2 illustrates the test specimen. The X-shape node

at which the H-section braces are intersected has a con-

tinuous flange and transferred web. Through the trans-

ferring zone, the axial stress of the web flows to the side

stiffener.

The parameters of the web-transferred node are the

overlapped length between the side stiffener and web, and

the welding method of the major parts. The stress trans-

ferring efficiency of the transferring zone depends on the

overlapped length; therefore, the structural performances

of the node according to the overlapped length were deter-

mined. For tall buildings, very thick plates, and conse-

quently a considerable amount of welding, are used to

manufacture the diagrid nodes. If partial penetration

welding, which reduces the amount of welding required,

can be applied in manufacturing the nodes, the total

welding amount would be decreased significantly. There-

fore, the partial penetrating welding method is introduced

as a parameter.

Five specimens are illustrated in Figure 3, and the para-

meters are tabulated in Table 1. The MA-00, MA-01 and

MA-02 specimens have the same form, with an over-

lapped length of 70 mm, while their welding methods

differ. The MA-03 and MA-04 specimens have an over-

lapped length of 105 mm and 42 mm, respectively.

2.2. Test setup

To describe a structure that is applied by lateral forces,

tensile force is applied to one brace and compressive

force is applied to the other brace. The angle between the

two braces is 24 degrees, and is scaled to 1/5. Yield

strength and displacement are calculated with the area of

brace section in Eq. (1) and Eq. (2).

(1)

(2)

Forces are applied twice at one cycle and the magni-

tude is increased as axial deformation of the brace

reaches 2 mm, 4 mm, 8 mm and 12 mm, which is one,

two, four and six times of yield displacement, respect-

ively (Figure 4). The tests are completed when the speci-

mens are fractured or the applied load is decreased to

80% of maximum strength.

Figure 5 shows the test setup. Two actuators were

installed at each brace to apply tensile and compressive

loads to each brace simultaneously. For the convenience

of the test setup, the lower actuator was installed horizon-

Pu

Fy

Ag

× 357MPa 6 720mm2

,× 2 400kN,≈= =

δy

PyL/EA

2 400kN, 103

× 1 200mm,×

210 000MPa, 6 720mm2

,×

------------------------------------------------------------- 2mm≈= =

Figure 2. 3D image of specimen.

Figure 3. Details of parameters.

Table 1. List of specimens

Specimens MA-00 MA-01 MA-02 MA-03 MA-04

Web-Flange welding FP(a) PP(b) PP PP PP

Flange-Flange welding FP FP PP PP FP

Side stiffener welding FP FP FP PP FP

Overlapped length L(c) L L 1.5L 0.6L

(a) FP: Full Penetration welding, (b) PP: Partial Penetration weld-ing, (c) L = 70 mm.




March 2012, Vol 1, No 1, 37-51

Validating the Structural Behavior and Response of Burj Khalifa:

Synopsis of the Full Scale Structural Health Monitoring Programs

Ahmad Abdelrazaq†

Headg, Highrise & Complex Building, Samsung C&T, Seoul, Korea

Abstract

New generation of tall and complex buildings systems are now introduced that are reflective of the latest development inmaterials, design, sustainability, construction, and IT technologies. While the complexity in design is being overcome by theavailability and advances in structural analysis tools and readily advanced software, the design of these buildings are still relianton minimum code requirements that yet to be validated in full scale. The involvement of the author in the design andconstruction planning of Burj Khalifa since its inception until its completion prompted the author to conceptually develop anextensive survey and real-time structural health monitoring program to validate all the fundamental assumptions mad for thedesign and construction planning of the tower.

The Burj Khalifa Project is the tallest structure ever built by man; the tower is 828 meters tall and comprises of 162 floorsabove grade and 3 basement levels. Early integration of aerodynamic shaping and wind engineering played a major role in thearchitectural massing and design of this multi-use tower, where mitigating and taming the dynamic wind effects was one ofthe most important design criteria established at the onset of the project design. Understanding the structural and foundationsystem behaviors of the tower are the key fundamental drivers for the development and execution of a state-of-the-art surveyand structural health monitoring (SHM) programs. Therefore, the focus of this paper is to discuss the execution of the surveyand real-time structural health monitoring programs to confirm the structural behavioral response of the tower duringconstruction stage and during its service life; the monitoring programs included 1) monitoring the tower’s foundation system,2) monitoring the foundation settlement, 3) measuring the strains of the tower vertical elements, 4) measuring the wall andcolumn vertical shortening due to elastic, shrinkage and creep effects, 5) measuring the lateral displacement of the tower underits own gravity loads (including asymmetrical effects) resulting from immediate elastic and long term creep effects, 6)measuring the building lateral movements and dynamic characteristic in real time during construction, 7) measuring thebuilding displacements, accelerations, dynamic characteristics, and structural behavior in real time under building permanentconditions, 8) and monitoring the Pinnacle dynamic behavior and fatigue characteristics. This extensive SHM program hasresulted in extensive insight into the structural response of the tower, allowed control the construction process, allowed for theevaluation of the structural response in effective and immediate manner and it allowed for immediate correlation between themeasured and the predicted behavior.

The survey and SHM programs developed for Burj Khalifa will with no doubt pioneer the use of new survey techniques andthe execution of new SHM program concepts as part of the fundamental design of building structures. Moreover, this surveyand SHM programs will be benchmarked as a model for the development of future generation of SHM programs for all criticaland essential facilities, however, but with much improved devices and technologies, which are now being considered by theauthor for another tall and complex building development, that is presently under construction.

Keywords: Realtime-structural health monitoring program, Construction sequence analysis, Survey monitoring programs,cloumn shortening, Gravity load management, wind seismic engineering management, Foundation settlement

1. Introduction

The Burj Khalifa Project is the tallest structure ever

built by man, Figure 1, that rises 828 meters into Dubai

skyline tall and it consists of 162 floors above grade and

3 basement levels. While integrating wind engineering

principles and aerodynamic shaping into the architectural

design concept was an important consideration in miti-

gating and taming the dynamic wind effects, managing

the gravity load flow to the building extremities was

equally significant in overcoming the overturning mo-

ment due to extreme lateral loads. Most of the tower

overturning resistance is managed mostly by the tower’s

own gravity loads. In addition, all the vertical members

are proportioned to resist gravity loads on equal stress

basis to overcome the differential column shortening

issues that are generally difficult to manage in supertall

buildings.

The structure of Burj Khalifa was designed to behave

like a giant column with cross sectional shape that is a

†Corresponding author : Ahmad Abdelrazaq Tel: +82-2-2145-5190, Fax: +82-2-2145-6631 E-mail: [email protected]

38 Ahmad Abdelrazaq / International Journal of High-Rise Buildings

reflection of the building massing and profile. The story

of structural system selection and the structural system

optimization is a novel one and cannot be covered here in

details, however, this paper will provide 1) a brief on the

key issues that led to the structural system selection and

the key issues considered in integrating structural design

concepts and construction planning into the architectural

design concept, 2) a detailed understanding of the overall

structural and foundation system behaviors of the tower

that are considered critical to the development of the

survey and structural health monitoring (SHM) programs

for the tower; 3) and a detailed description of the compre-

hensive real-time SHM and survey programs developed

for Burj Khalifa.

The development of the survey and SHM program for

Burj Khalifa, at the time of the system installation, is

probably one of the most comprehensive survey and real-

time SHM programs in the history of supertall buildings

that will track the structural behaviors and responses of

the tower during construction and during its lifetime and

it included:

- Monitoring the reinforced concrete bored piles and

their load dissipation into the soil.

- Survey and monitoring of the tower foundation settle-

ment, corewalls and column vertical shortening, and

the lateral displacements of the tower resulting from

its asymmetrical geometric shape and structural

system asymmetry.

- Monitoring of the tower vertical element strains and

stresses due to gravity load effects.

- Installation of a Temporary Real Time Monitoring

Program to monitor the building displacement and

dynamic response under lateral loads (wind and

seismic) during construction.

- Installation of Permanent Real Time Monitoring

Program to monitor the building displacement and

dynamic response under lateral loads (wind and

seismic in particular). The intent of this monitoring

program is to confirm the actual dynamic character-

istics and response of the building, including its

natural mode of vibration, estimate of damping,

measuring the building displacement and accel-

eration, immediate diagnose of the change in build-

ing structural behavior, identify potential of fatigue at

structural elements that are considered fatigue sen-

sitive and that could be subjected to severe and

sustained wind induced vibration at different wind

speeds and profiles, and most importantly in pro-

viding real-time feedback on the performance of the

building structure and immediate assistance in their

day-to-day operations, etc.

- Providing sufficient data to predict the fatigue

behavior of the pinnacle under low/moderate/severe

wind and seismic excitations.

- Tracking the wind speed profile along the building

height in an urban, but semi open field setting con-

sidering the scale of the project relative to its

surroundings.

- Correlating the building measured responses with the

predicted behavior of the tower.

These extensive survey and SHM programs have, since

their inception, resulted already in an extensive feedback

and insight into the actual in-situ material properties, the

towers structural behavior and response under wind and

seismic excitations, and continuous change in the building

characteristics during construction. In addition and most

importantly, the SHM program will provide the building

owner ongoing and continuous feedback on the perform-

Figure 1. Photo of the Completed Burj Khalifa.




March 2012, Vol 1, No 1, 53-59

Parametric Analysis and Design Engine for Tall Building Structures

Goman Ho1†, Peng Liu2, and Michael Liu2

1Arup, 5/F, Festival Walk, 80 Tat Chee Avenue, Kowloon Tong, Hong Kong SAR, China2Arup, 3008, 30/F, Jing Guang Centre, Hu Jia Lou, Chaoyang Dirtrict, Beijing 100020, China

Abstract

With the rise in CPU power and the generalization and popularity of computers, engineering practice also changed from handcalculations to 3D computer models, from elastic linear analysis to 3D nonlinear static analysis and 3D nonlinear transientdynamic analysis. Thanks to holistic design approach and current trends in freeform and contemporary architecture, BIMconcept is no longer a dream but also a reality. BIM is not just providing a media for better co-ordination but also to shortenthe round-the-clock time in updating models to match with other professional disciplines. With the parametric modeling tools,structural information is also linked with BIM system and quickly produces analysis and design results from checking tofabrication. This paper presents a new framework which not just linked the BIM system by means of parametric mean but alsocreate and produce connection FE model and fabrication drawings etc. This framework will facilitate structural engineers toproduce well co-ordinate, optimized and safe structures.

Keywords: BIM, Parametric modeling, Structural analysis, Finite element

1. Introduction and Background

It is interesting to know that the A5 CPU used in a

hand phone (such as iPhone 4S) or tablet is more power-

ful than a Cray 2 computer which cost US$17m[1] in

1985. Following the first Z1 computer in 1935, the size of

computer is reducing but increase in speed. In 1965,

Gordon Moore presented his Moore’s Law that the

components in integrated circuit doubles every ten years.

In early 80’s, the availability of minicomputers allowed

software applications shifted from military or aerospace

industry to domestic use. One of the well known is the

release of Unigraphics system by McDonnell Douglas.

Unigraphics converted the Automated Drafting and Ma-

chining (ADAM) coding into current named as Computer

Aided Design (CAD), Computer Aided Manufacturing

(CAM) and Computer Aided Engineering (CAE) appli-

cations. Although Unigraphics was already in 3D, the

cost of minicomputer was still too expensive for some

small firms which were common in buildings industry by

that time.

Following the very early Personnel Computer (Apple I)

assembled by two youngsters in mid-80’s, the cost of

computers became more affordable by building industry

practices. The work for draftsman changed from hand

drawings to 2D CAD drawings and in 90’s in 3D draw-

ings. With 3D environment, the true communication lan-

guage of Architecture, Engineering and Construction

(AEC) industry is no longer “drawings” as emphasized

by Carl Culmann by 1860’s. It is because the structures

are getting more complicated and hardly be defined by

means of 2D drawings. The definition of drawings now-

adays may mean - “3D objects”.

At the same time, structural engineers also changed

their practice from hand calculations to now very complex

3D nonlinear transient dynamic analysis. Without com-

puters and software, a lot of ideas will still be on a piece

of paper. For examples, the geometry of Watercube for

Beijing Olympics was created by scripts and then analy-

zed by computer. The National Stadium geometry was

first created by CATIA; box sections were “intruded”

following the centerline and twisted to ensure the external

envelope which follows the “Bow” shape.

Although there were drawings for both Watercube and

National Stadium projects, the 3D computer model were

still the key for communication between various parties

from designer to fabricators and erectors.

2. BIM

With the popularity of 3D modeling techniques, the

industry is moving forward to Building Information

Modeling (BIM) in early 20’s. According to Ghang Lee[2],

“BIM is the “process” of generating and managing build-

ing information in an interoperable and reusable way. A

BIM system is a system or a set of systems that “enables”

users to integrate and reuse building information and

domain knowledge through the lifecycle of a building”.

In the early stage of BIM, structural engineers use BIM

to produce the global model of the building structures and

†Corresponding author : Tel: +852-2268-3154; Fax: +852-2268-3945E-mail: [email protected]

54 Goman Ho et al. / International Journal of High-Rise Buildings

BIM is only a tool to produce computer models. Figure 3

show an architectural image of a building project, the

Revit 3D and GSA (structural analysis) model. Through

BIM tools, engineers can extract the floor plan and

produce the floor plan in seconds as Figure 4.

3. Parametric Modeling

Because of the trends in free form surface, contem-

porary architecture requirement and buildings getting

taller, the automation of generating the global structural

Figure 1. Photo of National Stadium and WaterCube for 2008 Beijing Olympics (©Marcel Lam Photography).

Figure 2. CATIA Model showing the twisting and bending of box elements in National Stadium.

Figure 3. Architect Image (With courtesy of Studio PeiZhu) Vs Revit Model Vs GSA Structural Model.




March 2012, Vol 1, No 1, 61-72

Anything Goes?

Dennis Poon† and Leonard Joseph

Thornton Tomasetti, Inc.

Abstract

When Cole Porter wrote the song “Anything Goes” in 1934, he did not include skyscraper examples. The recently completedChrysler and Empire State buildings followed decades of tall building development in a logical and predictable line. Today,dramatic improvements in materials and methods of analysis, design and fabrication have given architects and engineersfreedom to imagine, and contractors to build, towers in configurations never seen before. If writing now, Porter would surelyhave mentioned such designs to demonstrate anything goes. Or does it? This article explores the possibilities and challengesof tall building structural design through current and proposed projects. Examples include engineering buildings with outwardforms that appear structurally unfavorable and taking advantage of load reduction through shaping opportunities.

Keywords: High-rise buildings, Anything goes?

1. Introduction

‘Pushing the envelope’ and ‘Thinking outside the box’

are widely used expressions. While ‘envelope’ originally

referred to aircraft performance limits, and ‘box’ to the

boundaries of a nine-dot puzzle, these days both phrases

could easily relate to building design and construction.

Digital modeling, designing, detailing and fabrication tools

developed in recent years have made unusual shapes and

complex geometries practical to construct, if not neces-

sarily the most economical solutions. Current and planned

cutting-edge buildings are indeed pushing building enve-

lopes to new shapes, and those shapes are often far from

boxy. As composer Cole Porter named his song, “Any-

thing Goes.”

In the world of tall towers, does anything goes still

apply? On one hand, big buildings have big budgets and

the potential for economies of scale: research and testing

for determining performance of a cutting-edge technology

may be too great a cost for a small project, and small

production runs may result in high unit costs, but the

reverse is true for a mega project. For a large building, it

can make sense to create and dedicate a factory to manu-

facture a custom design, where the performance payoff is

great enough. On the other hand, size and scale pose their

own challenges, including the need to consider four non-

negotiable conditions: gravity load, wind behavior, earth-

quake response and geometric limitations. One or more

conditions can govern building structural design, based

on the direction of the overall building concept. Rather

than ‘anything goes,’ a better, if less catchy phrase might

be ‘any goal by taking the right direction.’ Key decisions

make the difference between theoretically possible but

unaffordable concept sketches and practical, affordable

completed buildings. Identifying key decisions early and

finalizing them as a collaborative process within the owner-

ship/design/construction team is essential, as will be shown

through case histories of contemporary projects.

Let’s start with gravity, a constant and ubiquitous effect

that cannot be ignored. What if we actually push the

(building) envelope over, literally, by building on a slant?

Gravity creates a tower overturning moment with zero

story shear force. The 26-story, 374-ft (114 m) mirror-

image Puerta de Europa towers in Madrid, Spain designed

by Philip Johnson/John Burgee and engineer Leslie E.

Robertson Associates and completed in 1996, lean toward

each other by 15 degrees from vertical. The concept is

visually simple: the side elevation of each tower is a

parallelogram with the outer edge of the roof almost over

the inner edge at the ground. See Figure 1. In theory a

building of uniform density could simply balance its

weight on that inner corner. In practice balancing a

building on a fulcrum leaves no reserve against additional

moments from wind or earthquakes. Directing load to

such a balance point would also be difficult, as floors in

tall narrow buildings typically span from perimeter

columns to a central core, which is needed anyway for

vertical circulation and services (elevators and stairs,

water, power and telecom risers). Even for a core located

near the inside bottom corner to fit vertically within the

parallelogram shape, gravity loads will not conveniently

flow to the inside corner. In theory a core could resist the

overturning moment, but it would be impractically costly

†Corresponding author: Dennis PoonTel: +1-917-661-7800, Fax:+1-917-661-7801E-mail: [email protected]

62 Dennis Poon and Leonard Joseph / International Journal of High-Rise buildings

for a gravity overturning moment many times greater

than the wind overturning moment. Connecting the outer

sloping face to the core where they meet at the roof uses

geometry to advantage, creating a tall, stiff triangle against

overturning. Triangulation, however, is only a partial

solution to the challenge due to load reversal and strain

effects.

The outer sloping face columns could cycle between

tension and compression from minor lateral loads, com-

plicating determination of effective stiffness and splice

designs. Construction-phase strains are also complicated:

overturning effects deform the entire building as upper

levels are built, potentially pulling lower floors out of

alignment, but the triangulation achieved at the top could

lock in misalignments whether intentional or not. Long-

term strains in central core concrete will occur from

shrinkage as its relative humidity approaches that of

conditioned air in the building, and from creep under

sustained load such as dead load, a continued increase in

strain over time that gradually slows years after con-

struction. Where compressive stress varies due to flexure,

creep will exaggerate core curvature and upper floor

displacements.

The engineer’s solution to all these concerns was post-

tensioning, running high strength tendons along the outer

sloping face from a 15,400 ton (14,000 tonne) counter-

weight below grade to jacking points at the roof level.

Tensioning the tendons compresses the outer face columns,

keeping joints in contact for maximum stiffness. As the

outer face columns shorten from induced compressive

strain, the horizontal component of that movement draws

the roof level and core top sideways, creating a righting

moment that offsets base overturning and minimizes

stress differences across the core and resulting deforma-

tions from differences in creep. While not supertall build-

ings, the Puerta de Europa towers illustrate the complex

and subtle ways that arbitrary forms can affect building

strength and behavior, the value of strategic decisions to

provide effective solutions to such challenges and the cost

premiums associated with unusual designs.

Another visually dramatic building design with both

gravity and seismic challenges is the CCTV Headquarters

building in Beijing, China. The design by Rem Koolhass

of the firm Office of Metropolitan Architecture (OMA)

was engineered by Arup. Two towers sloping six degrees

are joined at the base by a building extension forming an

L in plan. The towers are also joined at the upper floors

by an opposite L in plan as separate cantilevers meet at

a right angle to form a bent torsional tube. See Figures

2(a) and 2(b).

At 49 stories and 768 ft (234 m) in height the building

is not a supertall tower, but presents numerous design

challenges. Its large cantilevers mean that balancing gra-

vity loads about a tower edge is not remotely possible.

Gravity overturning must be resisted by the structure. The

designers chose to develop maximum stiffness by bracing

Figure 1. Puerta de Europa Elevation. Credit: Royal Production, Philip John /Alan Ritchie Architects.

Introduction to Paper Submission

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Journal: Jeary, A. P. (1986) "Damping in buildings - a mechanism and a predictor." Journal of

Earthquake Engineering and Structural Dynamics, 14, pp. 733~750.

Book: Bendat, J. and Piersol, A. (1986) Random data analysis and measurement procedures.

John Wiley & Son, New York, USA.

Proceedings: Tamura, Y. (2003) "Design issues for tall buildings from accelerations to damping

-Tribute to Hatsuo Ishizaki and Vinod Modi-." Proc. the 11th International Conference on

Wind Engineering, INV.W2, Lubbock, Texas, USA, June, pp. 81~114.

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