REINFORCED CONCRETE STRUCTURE I "Reinforced Concrete Code History" CIVIL ENGINEERING DEPARTMENT...

REINFORCED CONCRETE

STRUCTURE I

“Reinforced Concrete Code History”

Revised : 12-September-2013

1

CIVIL ENGINEERING DEPARTMENT

FACULTY OF CIVIL ENGINEERING AND PLANNING

INSTITUT TEKNOLOGI SEPULUH NOPEMBER

SURABAYA

Prepared By : LB3-ITS

Codes Development of RC

Philosophy design of RC were developed through out the 20th century, some

records of the development is shown below :

1. Working Stress Design (WSD) (1900-1999)

2. Ultimate Strength Design (USD) (1956-Now)

3. Unified Design Method (UDM) (2002-Now)

4. Strut and Tie Model (STM) For Shear (2002-Now)

2 Prepared By : LB3-ITS

P

0.8

0.7

0.65

Aksial Tarik Aksial Tekan Kecil

Kolom Bertulangan Spiral

Kolom Bersengkang

7.0'1.0

1.08.0

cAgf

Pu

65.0'1.0

15.08.0

cAgf

Pu

0.1f'cAg0

P

0.8

0.7

0.65

Compression Controlled Transition

Kolom Bertulangan Spiral

Kolom Bersengkang

t 6757.0

t 8348.0

t=0.002cdt=0.600

Tension Controlled

t=0.005cdt=0.375

Philosophy Design of RC

The development of codes in United States and in Indonesia will be shown in the

table below :

3 Prepared By : LB3-ITS.

Years American Concrete Institute

(ACI)

Indonesian Code’s

(PB & SNI)

1956

ACI 318-56

(WSD Based , USD was

introduced)

PB 55

(WSD Based – Deterministic)

1963

ACI 318-63

(WSD & USD Based)

Design of Bond, Shear, Diagonal

Tension, Combine Axial And

Flexure was based on USD

Still PB 55

1971

ACI 318-71

(USD Based, WSD was moved into

Alternate Design Method (ADM)).

PBI 71

(WSD Based)



table below :



(ACI)

Indonesian Code’s

(PB & SNI)

1977

ACI 318-77


Appendix A)

Still PBI 71

1989 ACI 318-89 PB’ 89

1991 ACI 318-92

SKSNI T15-1991

(USD Based, WSD moved in to

ADM)

Based On ACI 318-83

1995

ACI 318-95


Appendix A, UDM was introduced

in Appendix B)

Still SKSNI T15-1991



table below :

5 Prepared By : Bambang Piscesa, ST, MT.


(ACI)

Indonesian Code’s

(PB & SNI)

1999 ACI 318-99 Still SKSNI T15-1991

2002

ACI 318-02

(UDM Based, USD was moved

into Appendix C, WSD was

deleted, STM introduced in

Appendix A)

SNI 2847-2002

(USD Based, WSD moved into ADM)

Based On ACI 318-99

2005 ACI 318-05 Still SNI 2847-2002

2008

ACI 318-08

(UDM Based, USD was in

Appendix C, STM was in

Appendix A)

Still SNI 2847-2002

REINFORCED CONCRETE

STRUCTURE I

“Serviceability, Strength and Structural Safety”

Revised : 12-September-2013

6

CIVIL ENGINEERING DEPARTMENT

FACULTY OF CIVIL ENGINEERING AND PLANNING

INSTITUT TEKNOLOGI SEPULUH NOPEMBER

SURABAYA

Prepared By : LB3-ITS.

Serviceability, Strength and Structural Safety

To serve it’s purpose, structure must be safe against collapse and serviceable in

use. Three importance in structural design to ensure the structure serve it’s

purpose are :

1. Serviceability,

2. Strength,

3. Structural Safety

To ensure the serviceability of structure a few requirements needed :

1. Deflection be adequately small.

2. Cracks, if any, be kept in tolerable limits.

3. Vibration be minimized.


Serviceability, Strength and Structural Safety

To ensure the strength and structural safety of structure a few requirements

needed :

1. Strength of the structure is adequate for all loads that may foreseeable act on

it.

2. Strength of the structure must be predicted accurately.

3. The loads acting on the structure such as (Moment, Shear, Axial Forces)

must be known accurately.

4. Providing a carrying capacity just barely in excess of the known loads.


Uncertainty in Analysis and Design

These source of uncertainty, in which require a definite margin of safety as

follows :

1. Actual loads may differ from those assumed.

2. Actual loads may distributed in a manner different from those assumed.

3. Actual member dimension may differ from those specified.

4. The assumption and simplification inherent in any analysis and design may

different from those, in fact, act on the structure.

5. The actual structure behavior may differ from that assumed, owing to

imperfect knowledge.

6. Reinforcement may be not in its proper position.

7. Actual material strength may be different from that specified.


Variability of Loads (Q) and Strength (S)

Since the maximum load that will occur during a life of structure is uncertain. It

can be considered a random variable. A probability model for the maximum load

can be devised by means a probability density function for loads, as represented

by the frequency curve.

Strength of structure depends on the strength of material from which it is made.

For this purpose, minimum material strength are specified in standardized ways.

Actual material cannot be known precisely and therefore also constitute random

variable.


Variability of Safety Margin (M)

Structural Safety Margin (M) = S – Q > 0, this condition satisfied if strength is

larger that load acting on it. Since S and Q are random variables, the Safety

Margin (M) is also random variable. Failure of structure occur when M less than

O. So strength (S) must be larger than Load (Q). (S>Q)


Partial Safety Factor

Because the load acting on the structure is not only one type but also can be more

than two and since each type of load has different characteristic we need to

modified the equation where S > Q according to the load type.

• Example :

• (Dead +Life) --> Sn > Qd +Ql

• (Dead) --> Sn > Qd

• (Dead+Life+Wind) --> Sn > Qd + Ql + Qw

• (Dead+Life+Quake) --> Sn > Qd + Ql + Qq


nnn QS

Factored Load (U)

Increasing the load for design (Qd) from the average load (Q) known as factored

load for design. It is specified in codes (SNI 2847-2002) where :

• U=1.4D

• U=1.2D+1.6L

• U=1.2D+1.6L+0.5(A or R)

• U=1.2D+1.0L+1.6W+0.5(A or R)

• U=0.9D+1.6W

• U=1.2D+1.0L+1.0E

• U=0.9D+1.0E

• U=1.4(D+F)

• U=1.2(D+T)+1.6L+0.5(A or R)


Remarks :

D=Dead Load

L=Life Load

A=Roof Load

R=Rain Load

W=Wind Load

E=Earth Quake Load

T=Combination of Creep, Shrinkage and

Differential Settlement.

Strength Reduction Factor ()

Strength reduction factor () was defined to reduce the strength of the structure

because of the variability of material compound that made the structure. The value of

reduction factor determined in the codes (SNI 2847-2002).

1. Bending with or without tension, = 0.80

2. Compression member, spirally reinforced, = 0.70

3. Compression member, tied, = 0.65

4. Shear and Torsion = 0.75

5. Bearing on concrete = 0.65

6. Plain concrete, = 0.55

7. Compression member, low axial loads:

– Spiral = 0.8 – Pu/ fc’ Ag

– Tied = 0.8 – 1.5Pu/fc’ Ag


Design Method and Strength Requirement

Since there is strength and load, which the strength is reduced from its initial

value and the load is multiplied by the load factor the where initial design

equation :

• Design Strength (Sd) > Load Design (Qd) , Become :

• Reduced Design Strength ( Sd) > Factored Load (U)

• Generally above equation was written as below :

• Sn > 1.2 DL + 1.6 LL

• (Design equation for dead and life load where Sn = Nominal Strength or

Design Strength)


Safety Factor comparison

Safety factor determine the safety of structure against load applied on the

structure, the result of Ultimate Strength Design seems conservative compared

with Working Stress Method (ACI term : Alternate Stress Design (ASD)) usually

have safety factor 1.5 for upper structure’s.


121

LD

LDSF

Thank You

REINFORCED CONCRETE STRUCTURE I "Reinforced Concrete Code History" CIVIL ENGINEERING DEPARTMENT...

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