CIVL 311/CIVL 981

Autumn 2012 (Week 1)

CIVL 311: STRUCTURAL DESIGN 1 CIVL 981: SPECIAL TOPIC A
WEEK 1: INTRODUCTION TO REINFORCED CONCRETE

Dr. Neaz Sheikh Room 4 128 R 4.128 Email: msheikh@uow.edu.au

Consultation time: Friday 3.00 -5.00 pm

AGENDA FOR TODAY
 Topics covered weeks 1-6  Reinforced concrete (RC): an overview  Properties of Concrete and Reinforcement  Analysis and design of RC structures  RC Design based on AS3600-2009  Critical Load Combinations

Weeks 1-7
PART 1: DESIGN OF REINFORCED CONCRETE STRUCTURES  Week 1: Introduction to Reinforced Concrete (RC)  Week 2: Design of Beams- Serviceability  Week 3: Design of Beams- Ultimate Strength  Week 4: Design of Beams- Shear, Cracking, Detailing
(In Class Quiz on Topics covered From Week 1 to Week 3)

Week 5: Design of Slabs: One-Way slab  Week 6: Design of Columns and Walls  Week 7: MID-SESSION EXAM (Topics covered from weeks 1-6)

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

1

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Weeks 8-13
PART 1: DESIGN OF STEEL STRUCTURES  Week 8: Introduction to Structural Steel Design  Week 9: Bending Strength of Stable Beams  Week 10: Flexural-Torsional (Lateral) Buckling of Beams  Week 11: Strength of Webs (In Class Quiz) Week 12: Axially Loaded Members  Week 13: Connection Design

CIVL 311
CO-REQUISITE
ENGG 251: MECHANICS OF SOLIDS 5 ME H N S SOL DS
NOTE: PRE-REQUISITE OF ENGG 251 ENGG 152: ENGINEERING MECHANICS

Reference books
SJ Foster, AE Kilpatrick and RF Warner “Reinforced Concrete Basics: Analysis and design of reinforced concrete structures”, Pearson Australia 2010 ISBN ISBN9781442538450

Reference books
Yew-Chaye Loo and Sanaul Huq Chowdhury “Reinforced & Prestressed Concrete
Analysis and Design with emphasis on application of AS 3600-2009” Cambridge University Press ISBN 9780521141475

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

2

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Reference books
Warner, RF, Rangan, BV, Hall, AS and Faulkes, KA “Concrete Structures” Addison Wesley Longman. Melbourne 1998 (Library number 620 137/28) 620.137/28) Adequate alternative to Foster et al. (2010) but not as up to date – covers more topics than CIVL311. Useful for CIVL314.

Essential Reading
SAI-Global database in Library Print out the following pages
AS/NZS 1170.0: 2002 ( Pages 4-20) AS/NZS 1170.1: 2002 (P 1170 1 (Pages 5 12 19 21) 5-12; 19-21)

AS 3600-2009:
Section 2 [Pages 28-36], Section 3 [Pages 37-49], Section 4 [Pages 50-59] Section 6 [Pages 76-92], Section 8 [Pages 100-119], Section 9 [Pages 120133] and Section 10 [Pages 134-152]) (useful for CIVL 314 Structural Design 2)

Week 1 Essential Reading
Foster et al. (2010)
Chapter 1: Reinforced concrete- an overview Chapter 2: Methods of analysis and design

Reinforced concrete: an overview
Why Reinforced concrete?
Compressive Strength of concrete adequate (20-100 MPa) Tensile Strength is poor (2-10 MPa)
Wight and McGragor (2009) Fifth Ed.

Loo and Chowdhury (2010)
Part 1- Chapter 1: Introduction Part 1 Chapter 2: Design Properties of Materials 1-

AS/NZS 1170.0: 2002
Section 4: Combination of actions (pp. 15-17)

Plain concrete not suitable in structural members Small amount of steel reinforcement can improve performance Reinforced concrete: cheap and effective structural materials

AS 3600-2009
Section 2 (pp. 28-36) Section 3 (pp. 37-40;43-44) Section 4 (pp.50-52;57-58)

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

3

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Why Reinforced concrete?
Simple beam spanning few metres

RC: functions of concrete and reinforcement

Flexural Behaviour (deflection exaggerated)

Concrete carries compression Steel reinforcement carries tension

strain

stress

forces

Condition at a cracked section

Can be cast of any shape
RC-Aus (Version 2.0) Cement Concrete and Aggregate Australia

Massive structure
Warner et al (1998)

Reinforced Concrete Building Elements

Reinforced Concrete Building Elements

Wight and McGragor (2009) Fifth Ed.

Wight and McGragor (2009) Fifth Ed.

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

4

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Properties of Concrete and Reinforcement
Components of Concrete
Concrete = (cement + water)+ (sand + gravel) = (cement paste) + (aggregate)

Properties of concrete: compressive strength (

f c )

Properties of concrete: compressive strength ( f c )

Compressive Strength: standard cylinder test 150mm diameter by 300mm height Mean compressive strength, fcm Average strength of a set of cylinder tests g g y Sometimes referred to as the target strength

AS3600-2009 uses similar term fcmi for in-situ concrete mean strength (90% of the mean value of the cylinder strength)

Characteristic strength, f’c

Compressive strength at 28 days and which is attained by 95% of the tests.

Gain in compressive strength with time

Foster et al (2010) 2E

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

5

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Properties of concrete: tensile strength (

  f ct and f ct . f )

Standard Strength Grade of Concrete Characteristic strength, f’c (MPa), used for Grade (AS 3600-2009) eight standard grades of concrete are specified ( 20, 25, 32, 40, 50, 65, 80 and 100 MPa) 20,25 Plain concrete, ground slabs, footings 32,40 Slabs, beams and columns

Uniaxial tensile strength shall be determined from either flexural tensile strength or splitting tensile strength

In the absence of accurate data:

Uniaxial tensile strength

 f ct  0.36 f c
 f ct . f  0.6 f c
Foster et al (2010) 2E

50,65

Higher strength elements

100 lower floor columns in high rise buildings

Characteristic flexural tensile strength

Properties of concrete: stress-strain relationship

Properties of concrete: stress-strain relationship
cu = 0.003

cu = 0.003
From Warner, Foster and Kilpatrick 2007 p

Wight and MacGregor (2009)

Foster et al (2010) 2E

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

6

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Properties of concrete: Elastic Modulus

Properties of concrete: elastic modulus

 Determined experimentally  Secant of stress strain curve at 45% of peak stress  For design calculations AS3600 gives approx expressions  Depends of grade or strength of concrete

AS 3600-2009 For mean in situ strength, fcmi ≤ 40 MPa Ec = ()1.5 [0.043 √(fcmi)] MPa This covers most standard grades of concrete For mean in situ strength, fcmi > 40 MPa Ec = ()1.5 [0.024 √(fcmi) +0.12] MPa
These values have a range of ± 20%

For normal weight concrete density () can be taken as 2400 kg/m3
Foster et al (2010) 2E

Properties of standard grade concrete
Standard strength grade f’c (MPa) 20 25 32 40 50 65 80 100 Mean in situe com. Strength fcmi (MPa) 22 28 35 43 53 68 82 99 Mean insitue elastic modulus Ec (MPa) 24000 26700 30100 32800 34800 37400 39600 42200 Flexural tensile strength f’ct.f (MPa) 2.7 3.0 3.4 3.8 4.2 4.8 5.3 6.0 Uniaxial tensile strength f’ct (MPa) 1.6 1.8 2.0 2.3 2.5 2.9 3.2 3.6 Modular ratio (n= Es/Ec)

Properties of reinforcement  AS/NZS 4671: Steel Reinforcing Materials  AS3600-2009 provides information on structural use of reinforcement  Commercially available: reinforcing bars, hard-drawn wire, and welded wire fabric  Reinforcing bar: round and 12m lengths; bar diameters 10mm ~40mm; up to 16 diameters also available in coils; 50mm available by special order  Hard-drawn: manufactured in coils; cold-worked by rolling or drawing to increase strength; low ductility  Welded wire fabric: welding intersection of a series of longitudinal and cross bars. Used mainly in footings, slabs, etc.

8.3 7.5 6.6 6.1 5.7 5.3 5.0 4.7 Es= 200 GPa

Poisson’s ratio  = 0.2 (AS 3600-2009 Section 3.1.5) Coefficient of thermal expansion 10x10-6/°C ± 20% (AS 3600-2009 Section 3.1.6)

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

7

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Properties of reinforcement

Properties of reinforcement

Types of reinforcing steel (AS 3600-2009; Table 3.2.1)
Type Designation Ductility Yield stress Class (MPa) N L N L N 250 500 500 500 500 Uniform strain 0.050 0.015 0.050 0.015 0.050 Usage

Plain bar Deformed bar Deformed bar Welded wire mesh Welded wire mesh

R250N D500L D500N D500L D500N

Fitments, stirrups, ties Fitments Reinforcement for beam, column, slab) Slabs Slabs tension reinforcement

Stress-strain curves for reinforcement

Properties of reinforcement AS/NZS 4671: 2001
Property 250N 500L 500N 300E 500E

Properties of reinforcement Details of normal ductility reinforcement
Designation and diameter (mm) N10 N12 N16 N20 N24 N28 N32 N36 N40 Nominal area (mm2) 80 110 200 310 450 620 800 1020 1260 Calculated area (mm2) 79 113 201 314 452 616 804 1018 1257 Calculated mass (kg/m) 0.617 0.888 0 888 1.58 2.47 3.55 4.83 6.31 7.99 9.86

Yield stress (MPA) Rek,l Rek,u Ratio Rm/Re

≥250 ≥1.08 ≥5.0

≥500 ≤750 ≥1.03 ≥1.5

≥500 ≤650 ≥1.08 ≥5

≥300 ≤380 ≥1.15 ≤1.50 ≥15.0

≥500 ≤600 ≥1.15 ≤1.40 ≥10.0

Uniform elongation Agt(%)

Rek.L= lower characteristic value of the yield stress; Rek.U= upper characteristic value of the yield stress; Rm= Maximum tensile strength; Agt= percentage of elongation at maximum force

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

8

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Properties of reinforcement Design areas of various numbers of reinforcing bars
No of bars 1 2 3 4 5 6 7 8 9 10 Area (mm2) N10 80 160 240 320 400 480 560 640 720 800 N12 110 220 330 440 550 660 770 880 990 1100 N16 200 400 600 800 1000 1200 1400 1600 1800 2000 N20 310 620 930 1240 1550 1860 2170 2480 2790 3100 N24 450 900 1350 1800 2250 2700 3150 3600 4050 4500 N28 620 1240 1860 2480 3100 3720 4340 4960 5580 6200 N32 800 1600 2400 3200 4000 4800 5600 6400 7200 8000 N36 1020 2040 3060 4080 5100 6120 7140 8160 9180 10200

TUTORIAL QUESTION 1
Compute the second moment of area about x’ axis (centroidal axis).

y

Engineering Mechanics Statics (11 Ed.) by R.C. Hibbeeler

Locate the centroid Procedure to compute centroid of a composite body Composite Parts: Using a sketch, divide the body or object into a finite number of composite parts that have simpler shapes Moment Arms Establish the coordinate axes on the sketch and determine the coordinates of the center of gravity or centroid of each part y y

y

 A~ y A

y

Summations Determine the coordinates of the center of gravity by applying the center of gravity equations

x

 ~W x W

y

 ~W y W

z

 ~W z W
Engineering Mechanics Statics (11 Ed.) by R.C. Hibbeeler

Engineering Mechanics Statics (11 Ed.) by R.C. Hibbeeler

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

9

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Procedure to calculate second moment of area of a composite area Composite Parts Using a sketch, divide the area into its composite parts and indicate the perpendicular distance from the centroid of each part to the reference axis Parallel Axis Theorem If the centroidal axis for each part does not coincide with the reference axis, the parallel axis theorem should be used to determine the moment of area of the part about the reference axis I  I  Ad 2 Summation The second moment of area of the entire area about the reference axis is determined by summing the results of its composite parts about this axis
Engineering Mechanics Statics (11 Ed.) by R.C. Hibbeeler Engineering Mechanics Statics (11 Ed.) by R.C. Hibbeeler

I  I1  I 2

y

y

Analysis and Design of RC structures

The Design Process
(i) Concept Design: Critical load actions are identified Promising alternative structural concepts are identified Few concepts are shortlisted that fits with the constraints (ii) Preliminary Design: Alternative concepts are compared with great details considering cost, structural efficiency an functionality. Simplified d Si lifi d and approximate analysis and d i calculations are carried i t l i d design l l ti i d out to determine approximate member sizes The best concept is chosen (iii) Detailed Design: Preliminary design is checked using accurate calculations; modifications are made, if necessary. Serviceability checks are made components with connections are designs (detailed) Drawings and specifications are prepared

The Design Process
(i) Concept Design (ii) Preliminary Design (iii) Detailed Design

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

10

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Design Phase i. Analysis of the structure ii. Design of Structure iii. Design of Sections iv. Checking
RC-Aus (Version 2.0) Cement Concrete and Aggregate Australia

(to calculate a set of internal bending moment, forces and deflections at critical locations for the most adverse condition of the load cases)

Methods of Analysis of Structures
Linear Elastic Analysis [Section [Section
6.2-6.4 AS 3600-2009; page 79]

(behaviour of the structure as a whole to ensure stability, robustness, and satisfactory interactions between th constituent parts of th structure. b t the tit t t f the t t (to determine appropriate section sizes and concrete properties , reinforcement requirements, shear force and axial load resulting from analysis) (ensuring that design satisfies serviceability requirements)

Non-Linear Analysis of Framed Structures
6.6-6.9 AS 3600-2009; Page 82]

Finite Element Method of Analysis

V. Detailing of Members

Brief Review: Analysis of Structures
The primary objective of structural analysis is to obtain, for each load combination, a set of internal forces and moments throughout the structure that are in equilibrium with the design loads for the required load combination 1. Analysing the complete 3D structure ( can be very lengthy process but for some structure unavoidable) 2. Dividing the 3D structures into 2D frames (much simpler analysis, and very often due to repetition, only a few frames will need to be analysed) 3. Dividing 2D frames into sub frames (used extensively because repetition of sub-frames is likely and it further simplifies the analysis to the extent that a manual analysis can be performed, if necessary)
RC-Aus (Version 2.0) Cement Concrete and Aggregate Australia RC-Aus (Version 2.0) Cement Concrete and Aggregate Australia

2D Frame

Full Sub Frame: End of the columns remote from the beams are generally assumed to be fixed, unless assumptions of pinned end (e.g. at the footing)

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

11

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Loading Arrangement
Partial sub-frame: In all cases where only the immediate joining span is considered, the stiffness of beam is halved to reflect the increased flexibility that will exist in the full frame MAXIMUM SPAN MOMENT 1. MIN 2. MAX (2) Single l m Si l column ( only applicable l li bl when beam are analysed as a continuous beam) 1. 2. 3. 4. MAX MIN (1) MIN MAX (2) MAX MIN (1)
RC-Aus (Version 2.0) Cement Concrete and Aggregate Australia

MIN MAX (2)

Stiffness halved

MAXIMUM SUPPORT MOMENT MIN MAX MIN MAX (4) MAX MIN MAX MAX (3) MIN MAX MAX MIN (2) MAX MAX MIN MAX MAX MIN MAX MIN

A continuous beam ( more conservative approach to determine bending moments in beams)
RC-Aus (Version 2.0) Cement Concrete and Aggregate Australia

To produce a maximum moment at a support, the adjacent span must carry the maximum load and the next span must alternate with minimum and maximum load This produces (n-1) load cases where n is the number of spans With two loads to produce maximum span moment, this gives total of (n+1) load cases

(1)

What is the maximum and Minimum Load?
Ultimate Limit State Design

Design Requirements Rd≥Ed
Rd= Design Capacity (Strength) of the cross-section Ed= Design action effect

Maximum 1.2 G +1.5 Q 1.35 G Minimum ?????

Rd≥ Ru
Rd= Design Capacity (Strength) of the cross-section Ru= Nominal capacity of the cross-section

= Strength (or capacity) reduction factor

RC-Aus (Version 2.0) Cement Concrete and Aggregate Australia

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

12

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Tutorial Question 2: Values of  for strength design using elastic analysis
Stress resultants Pure bending (for ductile members) Pure axial compression Pure axial tension Shear Torsion Bearing Bending, shear and compression in plain concrete Values of  0.8 0.6 0.8 0.7 0.7 0.6 0.6

Load Combination: Beam-Cantilever System weight of RC= 25 kN/m3 Dead Load= self weight+ 2 kPa (additional Load) Imposed load = 3kN/m

Foster et al (2010) 2E

Draw Bending Moment Diagram wa B L1 RA wc

A

C RC

L2

Consider unit weight of RC= 25 kN/m3 Hence, self weight=[500x300+150x(4000-300)]x25x10-6= 17.6 kN/m Additional load= 2x4= 8 kN/m for services Total Dead Load= 17.6+8=25.6 kN/m Imposed load= 3x4= 12 kN/m
Foster et al (2010) 2E

R A 

 MC  0

+Ve

- R A L1  wa  L1 

L1 L  wc  L 2  2  0 2 2  wa L1 wc L2  2   RA     2 L1   2

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

13

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Draw Bending Moment Diagram wa B L1 RA
R A   MC  0
+Ve

Possible Combinations
NOTES MB was calculated at mid-span

wc

A

C RC

L2

The actual Mmax occurs at 3.464m from A One should calculate the actual Mmax by finding the point of zero shear.

Case 1: Load combination 1.35G

- R A L1  wa  L1 

L1 L  wc  L 2  2  0 2 2  wa L1 wc L2  2 RA    2  2L   1  

M B  RA 

L1 L2  wa  1 2 8 2 L L2  wa  1  wc  2 8 4
L 2
2 2

1.35G MB= 199 kN-m
M B  wa 
2 L1 L2  wc  2 8 4

1.35 G MC= -156 kN-m
M C   wc  L2 2 2

M C   wc 

Load on the cantilever produces negative moment in the main span, which opposes the positive moment caused by the load on the main span. This needs careful consideration

Case 2: Load combinations 1.2G+ 1.5Q
1.5 Q 1.2G
L2 L2 M B  wa  1  wc  2 8 4

Case 3: Alternate Load Combination
1.5 Q 1.2G
M C   wc  L2 2 2

In the calculation, it is assumed that load must be the same on the beam span and on the cantilever, which needs further consideration Load on cantilever produces negative bending moment which opposes positive moment in the beam span Reduction f design dead load in the R d ti of d i d d l d i th cantilever portion til ti may increase the beam mid-span moment. Hence for Cantilever Portion assume minimum load

For iti l F critical MB

1.5 Q 1.2G MB= 321 kN-m 1.2G

For critical MC

1.5 Q 1.2G

1.5 Q 1.2G MC= -219 kN-m

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

14

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Case 3: Alternate Load Combination
For critical MB 1.5 Q=18 kN/m 1.2G=30.75 kN/m MB= 344 kN-m For critical MC 1.5 Q 1.2G 1.5 Q
1.2G 0.8 G=20.5 kN/m

Little different from the book

Notes on this calculation

MB was calculated at mid-span The actual Mmax occurs at 3.464m from A One should calculate the actual Mmax by finding the point of zero shear. The permanent load included self weight plus a long term 2 kN/m² load.

MC= -219 kN-m

Simplified Analysis: AS 3600- 2009
Simplified method for RC continuous beams and one-way slabs

Conditions: [AS 3600-2009 Distribution of load to supports

Section 6.10.2.1]

a) Ratio of adjacent span lengths should not be more than 1.2 ) f my b) Loads uniformly distributed c) Imposed action (live load) should not be more than twice the permanent action (dead load) d) Members of uniform cross-section e) Reinforcement arrangements according to AS 3600-2009. f) Bending moments at supports caused only by the actions of loads applied to beams or slabs
Foster et al (2010) 2E

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

15

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Simplified Analysis: AS 3600- 2009
Negative design moment at the critical section ( at the face of the support) [Section 6.10.2.2]

Simplified Analysis: AS 3600- 2009
Positive design moment [Section 6.10.2.3]

a) At the first interior support: (i) Two spans only for Ductility Class N For ductility class L (ii) M More th n t than two sp ns spans b) At other interior supports

FdLn2/9 FdLn2/8 FdLn2/10 FdLn2/11

a) In an end span b) In interior span of ductility class N for ductility class L

FdLn2/11 FdLn2/16 FdLn2/14

c) At interior faces of exterior supports (i) For beams where support is a column (ii) For beams and slabs where support is a beam

FdLn2/16 FdLn2/24

Fd= Uniformly distributed design load per unit length

Fd= Uniformly distributed design load per unit length

Simplified Analysis: AS 3600- 2009
Transverse Shear Force [Section 6.10.2.4]

Order of Design: A typical Frame Building (i) Slab ( which transmits floor load to the supporting members) End Span

(i) At the face of interior support (ii) At mid-span (iii) At the face of the end support
Interior Span

1.15FdLn/2 FdLn/7 FdLn/2

(ii) Beams (transmits loads to columns, wall, etc) (iii) Column/Walls ( transmits loads to the footings) (iv) Footings (transmits loads to ground creating bearing pressure on the soil)
RC-Aus (Version 2.0) Cement Concrete and Aggregate Australia

(i) At the face of supports (ii) At mid-span

FdLn/2 FdLn/8

Fd= Uniformly distributed design load per unit length

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

16

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Structural Design Requirements: Limit States

RC Design Based on AS 3600 and AS/NZS 1170 Design Loads and Actions
AS/NZS 1170 Provides quantitative data for loads Dead load expressed as a table of unit weights Live loads considered uniformly distributed over floor area Note: Design loads in AS/NZS 1170 are highly idealized It gives reasonable upper limit of load effect Also, small enough to allow for economic design

Serviceability
(associated with poor performance of the structure, which even though not life threatening, must be avoided)

Strength
(associated with collapse or other forms of structural damage likely to endanger life)

Durability
(associated with corrosion of embedded reinforcement: concrete cover; fire resistance)

Robustness
(no progressive collapse)

Load Combinations
Strength Design Dead load acting alone Dead load + live load Dead load + long-term live load Dead load + live Load + wind Dead load + wind action reversal Dear load + earthquake + live load
Section 4.2; AS /NZS 1170.0: 2002

Load Combinations
Serviceability Design Dead load + live load Dead load + short-term live load Dead load + live Load + wind G + lQ G + sQ G + sQ + Ws

1.35 G 1.2 G + 1.5 Q 1.2 G + 1.5 1Q 1.2 G + cQ + Wu 0.9 G + Wu G+ Eu+cQ

s is a factor applied to live load that acts for short period of time s= 0.7~1.0

l is a factor applied to live load that acts for long period of time (l=0.4~0.6 with a maximum 1.0 for machinery installed for long period of time) c is a combination factor (c=0.4~0.6 with a maximum of 1.2 for machinery installed for long period of time)

Stability Design
Forces tending to move the structure compared with forces tending to maintain stability (Refer AS/NZS 1170 [Section 4.2] for load combinations)

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

17

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

AS 3600-2009 Table 2.3.2

Design Requirements Serviceability Design

Values of  for strength design using elastic analysis
Stress resultants Pure bending (for ductile members) Pure axial compression Pure axial tension Shear Torsion Bearing Bending, shear and compression in plain concrete Values of  0.8 0.6 0.8 0.7 0.7 0.6 0.6
Type of member All members Members supporting masonry partitions Members supporting other brittle finishes Members subjected to vehicular or pedestrian traffic

Calculated Deflection < maximum allowable deflection
Limits for calculated vertical deflection of beams and slabs
Deflection to be considered Deflection limitation (/Lef) for spans 1/250 1/500 where provision is made to minimize the effect of movement, otherwise 1/1000 Manufacturer’s specification but not more than 1/500 1/800 Deflection limitation (/Lef) for cantilever 1/125 1/250 where provision is made to minimize the effect of movement, otherwise 1/1000 Manufacturer’s specification but not more than 1/250 1/400

The total deflection The deflection which occur after the addition or attachment of the partitions The deflection that occur after the addition or attachment of the finish The imposed action (live load or dynamic impact) deflection

AS 3600-2009 Table 4.10.3.2

Design for durability

AS 3600-2009 Table 4.3
Surface and exposure environment

Exposure Classifications
Exposure classification A1 A1 A2 U U

Durability in AS 3600 consist of a range of deemed to comply requirements concerning deterioration-related matters (e.g. size of concrete cover and the quantity of concrete)
Required cover for standard formwork and compaction
Exposure classification Required cover*, mm Characteristics strength (f’c) 20 MPa 20 (50) 25 MPa 20 30 (60) 32 MPa 20 25 40 (65) 40 MPa 20 20 30 45 (70) ≥50 MPa 20 20 25 35 50 65

1. Surface of members in contact with the ground (a) Members protected by a damp-proof membrane (b) Residential footings in non-aggressive soils (c) Other members in non-aggressive soils (d) Members in aggressive soils: (e) Salt rich soils and soils in areas affected by salinity 2. Surface members in interior environments (a) Fully enclosed within a building except for a brief period of weather exposure during construction ( residential/non-residential) (b) In industrial buildings, the member being subjected to repeated wetting and drying 3. Surface members in above-ground exterior environments in areas that are: (a) inland areas (>50 Km from coastline) (i) Non-industrial and arid climate zone (ii) Non-industrial and temperate climate zone (iii) Non-industrial and tropical climate zone (iv) Industrial and any climate zone (b) Near-coastal ( 1 km-50 km from coastline) and any climate zone (c) Coastal and any climate zone 4. Surface members in water (a) In freshwater (b) In soft or running water 5. Surface of maritime structure in sea water (a) Permanently submerged (b) In pray zone (c) In tidal/splash zone 6. Surface members in other environment

A1/A2 B1

A1 A2 B1 B2 C1 C2

A1 A2 B1 B1 B1 B2 B1 U B2 C1 C2 U

Note: Bracketed figures are the appropriate covers when the concession given related to the strength grade permitted for a particular exposure classification is applied. • Cover should not be less than the greater of the maximum nominal aggregate size and bar diameter. •Covers may need to be increased to improve fire resistance

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

18

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Reinforcement spacing
No minimum spacing is specified by the standard, it only states that “the minimum clear distance between parallel bars including bundled bars shall be such that the concrete can be properly placed and compacted. For crack control, recommended that the centre-to-centre spacing of bars shall not be greater than 300 mm near tension face of the beam. For general guidance on reinforcement spacing.
Bars between which clear spacing is measured Horizontal bars in beams Horizontal bars in slabs, walls and footings Vertical bars Bars in ribs of hollow block or concrete-joist slab construction Helical reinforcement Direction in which spacing is measured Horizontally Vertically Horizontally Vertically Horizontally Horizontally Minimum clear spacing ( or pitch) shall be greater value of-

Design Life of Structures
Standards Structure/Structural components Design Life (year)

AS 3600-2009 AS 3735-2001 AS 2159-1995 AS 4997-2005

General concrete structure Liquid retaining structures Piling, including concrete Maritime structures

50 ± 20%* 40-60 40-60 Temporary works ≤5 Small craft 25 Normal commercial 50 Special/residential 100 100

25 mm 25 mm 50 mm 25mm 40 mm 15 mm

1db 1db 3db 1db 1.5 db 1db

1.5 a 1.5 a 1.5 a 1.5a

As 5100-2004

Concrete element for bridges

* More stringent requirements would be appropriate for structures with design life in excess of 50 years (e.g., monumental structures) ,while some relaxation of the requirements may be acceptable for structures with a design life less than 50 years (e.g., temporary structures)

Pitch or helix

40 mm

3db (pitch)

1.5 a (pitch)

a = the maximum aggregate size db= diameter of the largest bar; twice the diameter of the larger bar in the bundle; diameter of the bar forming the helix Loo and Chowdhury (2010)

Tutorial Question 3- Tutorial hand-in

Tutorial Question 4
Calculate the critical moments for the floor system consisting of a slab supported on a number of parallel beams with cantilever extensions. [Dead load consists of self weight plus an additional 1 kPa over the floor area. Self weight of RC= 25 kN/m3; Live load 3 kPa]
Apply the same assumptions ti as applied in Example Problem wb wc

400

Cross-section of a beam cantilever system

L2= 10 m RC Hibbeler (2010) Side view

L3= 3.5 m

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

19

CIVL 311/CIVL 981

Autumn 2012 (Week 1)

Tutorial Question 5
Calculate the critical moments for the floor system consisting of a slab supported on a number of parallel beams with cantilever extensions. [Dead load consists of self weight plus an additional 1 kPa over the floor area. Self weight of RC= 25 kN/m3; Live load 3 kPa]
Apply the same assumptions ti as applied in Example Problem wc Cross-section of a beam cantilever system wc wb

5m

15 m Side view

5m

Dr. Neaz Sheikh University of Wollongong Lecture Notes Based on Foster et al. (2010)

20