Background Theory

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United Arab Emirates University Collage of
Engineering Graduation Project Unit
Analysis and Design of Large-Span Steel Roofing
System
Final-Presentation
Bakheet Ahmad Al-Mansoori
200101695 Khalfan Ahmad Al-Mansoori
200101697 Saeed Nasser Al-Ahbabi
200101684 Saif Rashid Al-Mansoori
200101629
First Semester2006 - 2007
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Contents

• Introduction
• Background theory
• Structural systems
• Design calculation
• Cost calculation
• Results and discussion
• Conclusion and recommendations

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Introduction

• Al Jazira Mohammed Bin Zayed Stadium is a
  multi-use stadium in Al Jazira Club located in
  Abu Dhabi.
• The stadiums original capacity was 15,000 seats
  but it is currently going through an expansion
  stage which will increase the stadiums capacity
  to an all seated 40,000 ultra-modern air
  conditioned sporting arena.
• The expansion program includes two residential
  towers to be built beside the stadium and three
  phases the first two phases are carried out using
  reinforced concrete and pre-cast concrete
  structures whereas the third phase is designed
  using structural steel systems.

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Introduction

• This project focuses analysis and design of
  alternative structural systems to the future
  phase three of Al Jazira stadium.
• The actual structural system to be used in
  construction of phase three consists of an
  overhang steel roof truss supported by a framed
  column, which is in turn supported at the top of
  phase two.

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GP1 overview

• We design two alternative structural systems are
  proposed in the current project.
• First system, is a simple truss system which
  consists of overhang steel roof trusses supported
  by trussed columns.
• Second system is a modification of the former one
  by extending the height of the trussed column
  above the roof level to allow for installation of
  cables that are attached from the other end to
  the mid-points of the roof trusses.

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Graduation Project (II)

• calculating the structural loads acting on system
  (2), modeling and analysis of both system (1) and
  system (2) using SAP2000 software.
• Designing and detailing the analyzed systems
  according to the LRFD version of the AISC code.
• Developed Excel spreadsheets to facilitate the
  design of the high numbers of structural elements
  and connections included in the proposed systems.
  Structural details were presented using AutoCAD.

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Background Theory

• Steel
• Types of loads
• Load combination
• SAP 2000

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Steel

1. The aim of using steel is to reduce the dead
   weight.
2. Composed of Iron, Small amount of Carbon(lt2)
   and other chemical components (such as Manganese,
   Copper, Nickel, Silicon, and Aluminum)
3. The aim of the chemical components is to improve
   strength, toughness, hardness, ductility, and
   corrosion resistance.
4. Increasing the Carbon content leads to an
   increase in strength and hardness, but decreases
   ductility and toughness.
5. Strength and Ductility are the most important
   characteristics of structural steel.
6. Ductility is the ability of the member to
   undergo large deformations without fracture.
7. The economical production method began around
   the middle of the 19th century, by heating iron
   in contact with charcoal.
8. A more advanced process was introduced by Sir
   Henry Bessemer of England in 1855 (the Bessemer
   process).

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Steel

• Advantages of construction steel- High
  strength-to-weight ratio.- Ductility (large
  deformation before failure).- Flexibility in
  structural forms. - Long lifetime if properly
  maintained.- Recyclable material, environmental
  friendly.
• Disadvantage of construction steel- Buckling
  susceptibility.- Fireproofing cost, to prevent
  transmission of heat and the associated large
  reduction in strength. - High
  maintenance cost, e.g. paint coating.- Higher
  construction and maintenance cost in some parts
  of the world.

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Steel Specification

• The type of steel that was used in this project
  is (High strength Low-alloy) A572
• Grade 60, Fy 60 ksi , Fu 75 ksi.
• It gives a high resistance with acceptable cross
  section dimensions, especially for large span
  structures.
• Circular cross sections were used in this
  project.

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Types of load

• Dead load
• Live load
• Wind load
• Live roof load

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Load combination

• 1.4 D
• 1.2 D 1.6 L 0.5(Lr or S or R)
  
• 1.2 D 1.6 (Lr or S or R) (0.5L or 0.8W)
  
• 1.2 D 1.3W 0.5L 0.5(Lr or S or R)
  
• 1.2 D 1.0E 0.5L 0.2S
• 0.9 D (1.3W or 1.0E)
• Where
• D Dead load
• L Live load
• W Wind load
• E Earthquake load
• Lr Roof Live Load

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SAP 2000

• SAP2000 is a finite element-based software that
  represents the most sophisticated and
  user-friendly release of the SAP series of
  computer programs.
• Powerful graphical user interface unmatched in
  terms of ease-of-use and productivity.
• This program features powerful and completely
  integrated modules for design of both steel and
  reinforced concrete structures.
• The program provides an interactive environment
  in which the user can study the stress
  conditions, make appropriate changes, such as
  member size revisions, and update the design
  without re-analyzing the structure.

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Structural systems

• Structural system(1)
• it is consist of trusses only, and divided into
  three parts, column, shed and rakar as present in
  below figure

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• Structural system(2)
• it is consists of trusses and cable also have a
  same divination of system(1), However, it should
  be noted that the column height was increased to
  allow for the installation of the cable element
  connected to the middle of the overhang as shown
  in following figure.

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• Modeling, analysis and design procedure for both
  system
• The geometry of the proposed systems was
  generated in Auto Cad.
• the coordinates corresponding to each nodal
  point were identified.
• Such information along with joints are members
  numbers, tables of cross section dimensions,
  applied loads and load combinations are entered
  into the SAP2000 program.
• The cable properties should be take it from
  cables factory otherwise, is not available in
  SAP2000 program.

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Design calculations
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Tension members design
Design Requirements for tensions members-
Where Ø is the resistance reduction
factor- 0.90 for yielding failure. 0.75
for fracture failure. Pn is the nominal
strength of the tension member. Pu is the
factored tensile force.
Strength can be determined based on 3 potential
failure modes in our project- - Yielding of
the Gross Section. - Fracture of the Net
Section. - Stiffness for Tension Members.
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Tension members design
Strength can be determined based on 3 potential
failure modes in our project- - Yielding
of the Gross Section. - Fracture of the Net
Section. - Stiffness for Tension Members.
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Tension members design
Yielding of the Gross Section-
?t Pn 0.9 Fy Ag
Where Fy is the yield stress of steel
used, Ag is the gross area of the tension
member cross-section (Ag p (Dout
Din)2/4).
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Tension members design
Fracture of the Net Section -
ØPn 0.75 Fu Ae
Where Fu is the ultimate tensile stress of
steel. Ae is the effective net area at the
critical section.
Ae An U
Where An is the net area at the
critical section Ag (Dout Din)
tGusset Plate, U is a
reduction factor due to the shear lag effect when
not all the x - sectional area is directly
connected to the joint (U 1 for our project).
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Excel Spreadsheet For Design of Tension members
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Compression members design
Design Requirements-
Where Ø is the resistance reduction
factor 0.85. Pn is the nominal strength
of the tension member. Pu is the factored
tensile force.
Where Fcr critical buckling stress.
Ag gross area of the member .
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Compression members design
First of all we have to calculate the slenderness
coefficient-
Where ?c slenderness coefficient Fy
yield stress (ksi) E modulus of elasticity
(ksi) K effective buckling length
factor L laterally unbraced length of member
(in) r governing radius of gyration about the
axis of buckling (in)
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Compression members design
Compare to the value of 1.5, If is greater than
1.5 then the critical elastic buckling stress is
given by-
And if is less than 1.5 then the critical
inelastic buckling stress is given by-
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Compression members design
Local buckling can be avoided only if the
width-to-thickness ratio (b/t) of each element in
the cross section of the column does not exceed a
specific value called ?c.
The following figure summarizes the two cases of
elastic and inelastic overall buckling
Figure Elastic and inelastic buckling of
columns
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Excel Spreadsheet For Design of Tension members
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Zero members

• Members doesnt carry any load.
• check the stiffness.
• L/r lt 200Where
• - L the length of the member.- R the radius
  of the member.

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Zero members
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Welded connections design

• Use SMAW process, and E 80 electrodes.
• Fexx 80 Ksi
• t(G.PL) 0.5 in
• Fy 60 Ksi
• Fu 75 Ksi

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Welded connections design

• ? Strength of Longitudinal weld
• Weld fractureFRn/in 0.75 (
  0.6Fexx)(0.707Sw)
• Shear rapture of the member FRn/in 0.75
  (0.6Fu) t member
• Shear rapture of gusset plateFRn/in
  0.75(0.6Fu) t (G.PL)

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Welded connections design
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Bolted connection design

• In the construction site either welding or
  bolting could be used however, bolting is more
  recommended for quality control, ease and safety
  reasons.

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Bolted connection design
There is two typical types of high strength bolts
are commonly used, A325 and A490.
Fv (ksi) Bolt type
48 A325N
60 A325X
60 A490N
75 A490X
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Bolted connection design

• High strength bolts can be used to form two main
  types of connections, Shear failuer in Bolts and
  Bearing Failure at Bolt Holes depending on the
  load transfer mechanism of each connection type.
• In Shear failuer in Bolts
• ?Rn Pu
• ?Rn 0.75 Fv Agv Nb Ns

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Bearing Failure at Bolt Holes At the external
bolts- Since Le 2 in gt 1.5d t smaller
of 1 - t 0.5 in (gusset plate)
2 - t (2 3/8)
in (splice plate) ØPn/bolts 0.75(2.4)(d)(t)Fu
At the internal bolts- Since S 3d
so, ØPn/bolts 0.75(2.4)(d)(t)Fu
The factored bearing resistance of the
connection ØPn (number of external bolts
ØPn/bolts for the external) (number of
internal bolts ØPn/bolts for the internal)

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Beam design

• The design of beam which stand on trusses joint
  of system and carried the concrete slab.
• The all beams are a same in the design for both
  systems.

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• The beam is rotated by 31dgree around the globule
  axis.
• It is effected by previews types of load.
• The beam should be design to resist the moment
  and shear.
• The moment which govern the design should be the
  maximum moment of moment due by different types
  of load combination.

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• The beam should be design to resist the moment
  and shear.
• The moment which govern the design should be the
  maximum moment of moment due by different types
  of load combination.
• Find
• Max. Mx
• Max. My

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• Beam section selecting
• Assume LbL22.08ft
• steel type used is Fy50 ksi
• Cb1.14
• From LRFD manual-beam sections charts
• We find the beam section according Max.Mu and
  beam length.

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• Then find corresponding design moment

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• Design moment in y direction
• Moment check

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• Shear check

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Base connection
The design for connection between the trusses
system and concrete slab Base Plate
Dimensions-   a 2 Øb b Le Lmin Dout 2a
2b

Where- Dout outer diameter of member. Øb
diameter of bolt.
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Base connection
- Check bearing stress on the concrete slab below
the base plate-
- For determine the base plate thickness-
Where- t base plate thickness Rz
compression force. Fy area of bolt.
diameter of bolt.
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Base connection
Anchor bolts- - The bolt is subjected to
tension and shear - For shear-
Where- V shear force. Ab area of
bolt. n number of bolt.
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Base connection
Anchor bolts- - The bolt is subjected to
tension and shear - For tension-
Where- Tu tension force. Ab area of
bolt. n number of bolt.
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systems cost

• Systems weight calculation
• 1-calculated the volume for each member.
• V(Dout Din )Lmember
• 2-calculated the weight for each
  member. W VSpecific weight of steel

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• Cost Calculated
• the cost of steel 6500Dhs/ton
• the total cost total weight(ton)cost / ton
• system(1) cost 6.30371 ton6500Dhs/ton
  40.974 Dhs
• system(2) cost 6.41431 ton 6500 Dhs
  41.693 Dhs.

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Results and Discussion

• System 1 is better than system 2 because its
  economically.
• The trusses must be welded in the factory.
• The transportation process must be under the
  observation of the Consultant to
  avoid any damages to the parts.

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conclusion Recommendation

• Analysis and preliminary design proposed systems
  by used SAP2000
• Tension and compression members manually design.
• Welded and bolted connection design.
• Zero members design.
• Beam design.
• Base connection design.
• Cost calculation for both system.
• At the end of GP2 we recommend our collage to
  give the student different courses of structural
  soft war .