Southern Cross Tower: Steel Framed Building Design and Analysis

This report provides an in-depth analysis of the Southern Cross Tower, a high-rise steel-framed building located in Melbourne, Australia. The report covers various aspects of the building's structure, including an overview of the structure, design documentation, site visit documentation, and a detailed examination of the structural system. The structural system discussion includes foundation materials, building bearing strength, site classification, footing systems, steel beams for roofs and floor systems, steel columns, bracing members, secondary structures, design of truss chords, and composite materials. Furthermore, the report delves into the loading on the structure, including vertical loads, live loads, and wind loads, along with the corresponding strength calculations. The analysis incorporates both elastic-plastic and elastic structural processes and methods, providing a comprehensive understanding of the structural engineering principles applied in the construction of the Southern Cross Tower.

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SOUTHERN CROSS TOWER
A Research Paper on High Rise Steel Framed Building By
Student’s Name
Name of the Professor
Institutional Affiliation
City/State
Year/Month/Day

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EXECUTIVE SUMMERY
This research project analyses the high rise Southern Cross tower building where the steel frame
is used or where there is an important application of the structural steel networks. The southern
cross tower which is also referred to as 121 Exhibition Street is a 530 feet (one hundred and
sixty-one-metre skyscraper in Melbourne, Australia. the tower was constructed in the year 2004
and consisted of thirty-nine 39 levels of the accommodations offices. The building is about
seventy-five per cent possessed by the multiplex trust property. The analysis of the displacement
responses and the internal force with rare earthquakes have been carried out through the static
elastic-plastic pushover analysis, and the common earthquakes have been carried out by the use
of the method of static elastic time-history (Stern, 2014). This section also reviews the elastic-
plastic and elastic structural process and methods

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Table of Contents
EXECUTIVE SUMMERY.................................................................................................................................2
INTRODUCTION...........................................................................................................................................4
OVERVIEW OF THE STRUCTURE...................................................................................................................4
DESIGN DOCUMENTATION..........................................................................................................................5
SITE VISIT DOCUMENTATION......................................................................................................................6
STRUCTURAL SYSTEM..................................................................................................................................7
Foundation material building bearing strength and the site classification..............................................7
Footing system used................................................................................................................................8
Steel beams for roofs and floor system...................................................................................................9
Steel columns........................................................................................................................................11
Bracing members...................................................................................................................................12
Secondary structures.............................................................................................................................12
Design of truss chord.............................................................................................................................13
Composites materials............................................................................................................................14
LOADING ON THE STRUCTURE AND THE STRENGTH CALCULATION..........................................................15
Vertical Loads........................................................................................................................................15
Live loads...............................................................................................................................................17
Wind loads.............................................................................................................................................18
CONCLUSION.............................................................................................................................................19
BIBLIOGRAPHY...........................................................................................................................................20

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INTRODUCTION
The steel frame is a building system with the skeleton edge of the vertical pillars of steels and
horizontal beam built in the rectangular grid to maintain the floor, roofs and walls of the house
all devoted to the frame. The expansion of this type of technique made the building of the
skyscraper promising. Prefabricated steel structure has some of the obvious advantages that are
quick construction, environmental protection and production in the industry. Even though the
prefabricated structure has been used in many countries in the world. In various occasions, these
structures are for the high and low rise buildings. This research project analyses the high rise
Southern Cross tower building where the steel frame is used or where there is an important
application of the structural steel networks.
OVERVIEW OF THE STRUCTURE
The southern cross tower which is also referred to as 121 Exhibition Street is a 530 feet (one
hundred and sixty-one-metre skyscraper in Melbourne, Australia. the tower was constructed in
the year 2004 and consisted of thirty-nine 39 levels of the accommodations offices. The building
is about seventy-five per cent possessed by the multiplex trust property and twenty-five per cent
is possessed by the multiplex prime acumen fund. The current value of the building is the A $one
hundred and thirty million and its main tenants are the state of Victorian Government (Acton,
n.d.).
Construction of the basement part up to the ground floor level adopted in-situ slabs and the band
beam. This gave more duration to in the program for the chosen steel parts procurement,
fabrication and delivery of the structural steel. The designers having the demonstrable experience
with the construction of steel had a good learning forwards the medium from the inception. At

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times the prices of formworks increases and the climate of industries in the Melbourne favoured
the fabrication of site. The design exhibits the simplicity, typified by the regular grid, fifteen
meter clear spans on a sixteen by nine meters grid with the Gondek deck floor, allowing free
construction with the cycle of 8days per floor (Association, 2013).
The beam sizes were standardized using the 610UBs and 530.the slabs were normally one
hundred and twenty, thickened when important for the isolated weightier loadings. The
connection of the primary beams to the columns were the secondary beams and end bearings to
the core where the connection of web. The services were accommodated in the one-meter zone,
floor to floor height is four meters, applying the notches in some of the beams at the core
junction walls and some penetration of the web which were stiffened. The columns were
fabricated from the custom made four hundred and sixty section grades imported from Germany.
The enquiries from the design phase show that it was less expensive to import these sections,
there being more lead time. Splices were the full contract, situated one meter above the floor
with the three columns of storey lifts (Brannigan, 2012).
The engineering of fore was undertaken by Scott Lincoln adopted the spray of fire on the
columns up to the underside of primary beams for the passive protection. There were some of the
sprayings of fire of isolated beams trimmer. The system of curtain wall was fixed to the
structural steel by the welding using the sections of channels along the perimeter (Buckman,
2014).
DESIGN DOCUMENTATION
Before the growth of the Southern Cross, the government of Victoria was concerned since is the
main department were dispersed amongst more than fifteen offices through the Melbourne CBD.
It decided to combine monetarily and permit the bureaucracy access closer to the spring street,

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providing it access to the treasury and parliament (Trabucco, 2010). A consortium of the private
bodies, comprising Babcock, multiplex and the Brown, recommended a skyscraper in the site of
the derelict and old south hotel. The main condition of the involvement of the government of
Victoria in the project was the mandate that the structure is a state of art, environmentally
maintainable growth (Buildings, 2015).
The major priority in the construction and design of the high-rise structures is to ensure their
inflexibility, steadiness and strength by taking into deliberations the effect of significant forces in
the wind overpowering the uneven shortening of vertical constructions from columns and walls
concrete reinforcement under the impact of the load. In Southern Cross Tower, the materials like
concrete and steel are majorly applied. The rigidity of the building skeleton assist in flexibility
and supporting the wind loads so as resist fluctuations is the seismic activities. In the facades of
the current skyscrapers, majorly polymers, aluminium, light curtain panels of darkened and
transparent glass, and steel profiles (Chung, 2013).
SITE VISIT DOCUMENTATION
We visited the site on 5th October 2018. The management received us and walked with us
around the site. Pomeroy pacific manages all the projects to ensure that the aims are delivered on
time, high quality and budget. They assign the calibre seniors to every project and give the
methodical and hand on the delivery approach which results in the reduced cost of the building,
quicker duration of the building, mitigated the project risks and successful completion of the
projects. We were showed the number of floors of the building, materials that were used to
construct the building. The field trip introduces us to the structural systems used in the Southern
Cross building and we were given the explanation how they support themselves as well as the
loads imposed on the building by the environment (Council, 2010).

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STRUCTURAL SYSTEM
Foundation material building bearing strength and the site classification
The total area covered by the Southern Cross tower is around 17,338m2. The storeys above the
earth surface are applied as the apartments for the workers of board maintainable building
machinery limited. The structural life of the design of the south cross tower is fifty years. All the
components of Southern Cross tower were invented in the factory and moved to the location of
its building for the quick assembly by the use of S eight point eight grade bolts of great strength
of which the ultimate strength of tensile is 800MPa and yielding strength is six hundred and forty
MPa. The ratio of ultimate tensile strength to yielding strength 8.0. Compared with the old
strengthened concrete assemblies, the assembled steel structures have the evident benefits, that is
, they are very light in mass, need short duration of building, need low intensity of labour and
can meet the demands of great urbanization and gives the environmental protection at the same
time (Deplazes, 2010).
The south cross tower uses the new type of the prefabricated structures of steel known as the
modular produced high steel frame structures with the slanting braces which might be applied for
the high rise building. The pillar is prepared of a square steel tube, the beam us a truss and the
brace is prepared of C shaped steel prepared near the truss pillar joint, and the floor is a
summarized steel sheet composite concretes slabs (Thurakit, 2014). The structure has the benefit
of a manufactured structure of steel and the use of this assembly could attain the requirements of
environmental protection and economic growth in Australia. This method can help to consume
the extra manufacture of steel but could also assist to resolve the conflict among the limited land
and the huge population upon which to build in Australia (Eisele, 2015).

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Figure 1: Foundation of Southern Cross tower (Eisele, 2015)
The bored piles of the retaining walls are the part of the foundation system they transfer the loads
in the addition to one hundred and twelve foundation piles into the ground. The pit building and
the first floors of the main Southern Cross tower were built in the top down technique to lower
the time of construction and the give the pit which observes stability and the serviceability of the
near structure. By applying this technique. It was possible to construct the floors basement and
the upper floors during the same period. Apart from the static role of the piles of the foundation
and part of the retaining wall are applied for the building. The piles were installed additional
with the heat exchanger tubes so that the piles function as the elements of exchanging heat to
create the closed system (Engineers, 2017).
The energy is transferred to the ground from the outside air and stored it until it is required. The
piles of energy can unload and load the seasonal storage. In the period of winter, the energy is
withdrawn hence cooling the ground arises. In the summer the ground that is cooled down can be
used for the cooling the Southern Cross tower through the ceilings (Establishment, 2010)
Footing system used

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The process of construction of a fully prefabricated structure can be categorized into the
foundation, first-floor beam, floor and wall, roofing, and finishing. In the foundation stage. The
approaches involve the pouring of the foundation and hammering the concrete piles. This
approach cannot apply the prefabricated foundations due to the changes in the soil and site
leading to the process slowing. With the increase of the height of the Southern Cross building
increases the loads, the raft foundation was not good to transfer the loads well to the ground
hence the pile foundation was applied often. The major role of the pile foundation was to transfer
the loads with the piles to the lower ground level which is able of sustaining the load with
enough safety factor (Finnerty, 2013).
Figure2: How loads of the Southern Cross tower are being transferred to the earth (Goldsmith,
2015)
Steel beams for roofs and floor system
The next process is the roofing process where it is carried out by roofing structures from
prefabricated steel which need installation onsite. The prefabricated steel installation is a dry

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process and only require to be joined by bolts hence there will be no time wastage as in the case
of the concrete roof structure process. The last process of construction of the prefabricated
buildings is the finishing which can take about 3 months after the construction process has taken
about 5 months for the residential structures. The process includes the doors and windows
installation which are also prefabricated units. Modular contractors manufacture structures at the
off-site location or in a factory. They may also work as projects contractors, finishing the
structure, site work, installation, and delivery coordination, or modular contractor whose
responsibilities are to installation, delivery, and construction of specifically the modules and the
general contractor whose is responsible for the whole project (Gong, 2010).
The modular manufactured steel frame structures with the diagonal braces are comprised of the 2
types of modules; the major floor and the pillar with the diagonal braces. The constituents inside
the similar modules are soldered in the factory and the bolts of great strength are applied to join
the module on the site. The major module of the floor comprises the column trusses, bases and
the concrete composite –steel sheet slabs. A truss is composed of the C shaped steel, angle steel,
arm braces, steel plates joined by the welding. Conferring to the action of every truss concerning
resistance of lateral loads, the trusses are grouped into secondary classes and girders. The arm
braces are welded vertically to the truss chords and are applied to join the upper and lower
diagonal braces (Habitat, 2011).
The floor system in the Southern Cross tower needs huge floor span to make superior space
elasticity for the accommodation of a better diversity of the floor span (Tatum, 2009). It is
important to decrease the weight of the floor so as to decrease the column size and the
foundations and hence allow the use of larger space. Floors are needed to resist the vertical loads
and they are normally supported by the secondary beam. The spacing of the supporting beams

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must be well-matched with the resistance of the floor slabs. The floor system was made buildable
by the prefabricated or the precast elements of the steel and strengthened concrete in many
combinations. The system of floor beams must have enough stiffness to avoid large deflection
which could lead to the damage of the slab finishers and plaster (Hemsley, 2010).
Steel columns
The pillar base is made of the tube of square steel, plates and flanges. The bases of the column
cannot join to the transverse and longitudinal trusses and labs making the major module of the
floor but also join to the major floor unit with the lower and upper module on location to make
the entire structure. The major purpose of the diagonal braces is to minimize the operative
column dimension and concurrently to lengthen the joints and increase the joint region. Such a
structural scheme is known as a frame structure with strengthened joints which are considered
for security purposes (Hicks, 2015).
In the design of the steel columns, there are some of the things that were taken into
consideration. no part of the steel column was less than a quarter thick, no ,materials in the
column body and applied as the stay plate was of less thickness than 1/32 of its unsupported
width, measured between the rivets centre transversely, or 1/6 of the length between rivulet
centre in the stress direction (Taranath, 2016). The tie plates had more than 4 rivets and are to be
spaced so the length ratio to the least gyration radius of the joined parts did not exceed forty
(Huang, 2014).
Steel is a common metal of construction that was used in the building of the Southern Cross
tower because it has better performance in the withstanding of the tensile and compressive
forces. Steel bars were used to strengthen the concrete and to add the extra performance and the
extra layer of resisting fire was put onto the steel surface. The eight steel poles transmit the

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structural loads and enable the formation of the floor area that is column free. It maximizes the
flexibility to adopt the different arrangements spatially (Huberman, 2011).
Bracing members
The pillar with the oblique braces comprises of the diagonal braces, column, and the trapezoid
plates known as the difficulty ribs. One end of the diagonal brace is joined via welding to the
pillar, where the additional end is joined to the arm brace and truss by the bolts to work together
with the frame. The rib of the pillar toughness can reinforce a pillar and be applied to join the
diagonal brace to the column. The diagonal braces have the lateral strong lateral stiffness
resistance which could make the construction capable to repel lateral load from the earthquakes
and wind. Since the surrounding area is very small the windows sizes and the door openings on
the walls are not interfered with (J, 2013).
The bracing system provides the lateral stability to the whole Southern Cross tower. It may be in
arrangement of the triangulated frames, shear cores or walls, and the inflexible articulated
frames. In the steel structures, it is very common to have the vertical truss that is triangulated to
deliver the bracing. For the stiff structure, the sheer core and walls are mostly used. The
efficiency of the Southern Cross tower to resist the lateral forces is dependents on the site and the
kinds of bracing systems used (Joseph, 2017).
Secondary structures
The purlins and girts are components of the second frame of the metal building. The girt is the
horizontal structural associate in the framed wall that gives the lateral support to the wall panel to
fight the wind loads. The purlins perform the similar service for the roof panel. The purlins and
girts are also referred to as the sheeting rails. These secondary frame members are applied in the
Southern Cross tower. Another secondary member, the strut is also known as the eave girt or the