Design of Concrete Structures-1

CE-2105

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

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

Contents of Presentation

Objectives Singly Beam Design & Analysis Doubly Beam Design & Analysis T-Beam Design & Analysis

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

As a Civil Engineer

What should I have to

consider ???For Structures

Design?

Design Strength

Serviceability

Durability

Implacability

Economy

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

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

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

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

When a beam design as a Doubly reinforced beam ?

Doubly reinforced Beam

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

 

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

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

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)

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

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

• 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

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

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

Design of T- Beam

Established the hf generally slab

thickness

Determine b according to ACI

code

Choose bw & d

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

Thanks to All

Any Query ??