design and analysis of rc beam
TRANSCRIPT
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Design of Concrete Structures-1
CE-2105
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Presentation of design and analysis of RC beam(as per ACI code)
Dr.Md. Rezaul Karim Associate Professor
Department of Civil Engineering (CE)Dhaka University of Engineering & Technology
Advisor
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Our Group Member’s
Kazi Abu Monjur Std Id: 121042Md. Rabiul Islam Std Id: 121044Md. Irafanul Kabir Std Id: 121045Md. Shorab Hossain Pavel Std Id. 121058Mohammad Anis Std Id. 121050
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Contents of Presentation
Objectives Singly Beam Design & Analysis Doubly Beam Design & Analysis T-Beam Design & Analysis
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Objectives
• Gain the concept about USD method
• Gain the analysis concept of Singly, Doubly and T-
Beam
• Gain the Design procedure of Singly, Doubly and T-
Beam
• “In what sitution what Types of beam we should
consider
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As a Civil Engineer
What should I have to
consider ???For Structures
Design?
Design
Strength
Serviceability
Durability
Implacability
Economy
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Design
Parameter
ß1=0.85-0.05(f’c-4000)/1000 and 0.65 ≤ß1
≤0.85
Strength factor Φ should be adjust by ACI code provision
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Singly Reinforced Beam
Analysis Over Reinforced as Doubly
Analysis of Singly Reinforced Beam
ρ < ρ max
Analysis Under Reinforced as Singly
Mn=Asfy(d-a/2)
a=Asfy/.85f’cb
Mn=ΦMnAdjust Φ by ϵt or c/dt
Assume bGenerally b=d/2
No
Yes
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Design Calculating the factored loadsMu=It’s depends on beam support Wu=1.2DL+1.6LL
Adjust Φ by ϵt or c/dt Mu=Φ ρfybd2(1-0.59ρfy/f’c)
Determineb and d
As= ρ
Design complete
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For Economy Design should be revised
As=Mu/ Φfy(d-a/2)Assume
a Check a
Alternate solution use lower ρ
as ρ=0.6 ρmax or ρ=0.75 ρmax etc
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When a beam design as a Doubly reinforced beam ?
Doubly reinforced Beam
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Step :1 Checking the Beam (Singly nor Doubly)
ρ> ρ max
ρ
N×As
ρmax= .85 βḟc/fy×
0.003
This condition is satisfy thus the beam is doubly reinforced beam
Step :2
Check the Limits on reinforced
ratioIf ρ>cy Compression bar yield
But ρ<cy Compression steel below yield stress
cy= .85 βḟc/fy××
𝐴 ś𝑏𝑑
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Step : 3
Determination the moment
capacity
ρ>cy
Where
n s y s s s s2
aM A f A f d A f d d
OR ρ<cy
n s y s s s s2
aM A f A f d A f d d
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Design step of Doubly reinforced
beam Step
1: Load Calculation
This condition is satisfy compression steel’s will be needed i.e doubly reinforced beam
Wu=1.2 DL+1.6LL
Mu= Its defends on beam supports characteristics Step 2
: Check the Capacity of the Section
Mn>MuWu=1.2 DL+1.6LLΦMn=Asfy(d-a/
2)
ρ max × bd ρmax= .85 βḟc/fy×b=width of beam d= Effective depth
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Step
3: Determine the area of steel
Excess Moment M1=Mu-Mmax
A= =ἑsEs
u =2.5 “ (assume)
If then Compression reinforced yield stress ,so using lower compression stress
As=A+As(max)
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Checking Design
Design of beam is OK
must be adjust
= 0.65+(t-0.002)
=u
Now Mu=asfy(d-) >Design Moment
Hence Ok
If (As-A)<As
Wrong
True
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T- BeamWhen and why A T-section consider as a T-beam or a
rectangular Beam ??
hf<a consider as T-Beam hf>a consider as Rectangular-Beam
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• b≤
• b ≤
•
where L= Span of beam
𝐶𝑙𝑒𝑎𝑟 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒𝑜𝑓 𝑏𝑒𝑎𝑚2
8hf
•
• b ≤
•
where L= Span of beam
𝐶𝑙𝑒𝑎𝑟 𝑆𝑝𝑒𝑎𝑐𝑖𝑛𝑔𝑜𝑓 𝑏𝑒𝑎𝑚2
b-bw 6hf
•
b 4bw
b 2hf
For Symmetrical
For having a Slab on side
For Isolated
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Analysis of T- Beam
Check is it symmetric or
Isolated or hanging one slab??
hf>a???
No
Yes
Analysis consider as rectangular beam
Analysis consider as T- beam
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Mn1=Asf fy(d-hf/2)
Asw=As-AsfAsf=.85f’c/fy(b-bw)hf
Mn2=Aswfy(d-a/2)
Mn=Mn1+Mn2
Mu=MnAdjust
by t or c/dt
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Design of T- Beam
Established the hf generally slab
thickness
Determine b according to ACI
code
Choose bw & d
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Calculate a trial As but not exceed hf
For check the a trial As
Check or c/d
Ensure that ρw≥ ρw min
hf<a No
Yes
Ok
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Thanks to All
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Any Query ??