konstruksi baja ii 97.ppt

KONSTRUKSI BAJA IIKONSTRUKSI BAJA II

FAKULTAS TEKNIKUNIVERSITAS ISLAM SULTAN AGUNG SEMARANG 2013

SYLABUSSYLABUSAnalisis dan disain batang tekan

prismatis, batang tekan dan lentur. Bahaya tekuk dan lipat batang tekan. Kolom komposit. Stabilitas balok lentur, stabilitas pelat

baja.Analisis dan disain struktur plat girder,

penggunaan pada : jembatan keretaPerencanaan kuda-kuda baja : bentuk

rangka, pembebanan, ikatan angin, gording batang tekan dan tarik, sistem sambungan.

Konsep dasar perencanaan baja plastis

INTRODUCTIONINTRODUCTION

PROFIL BAJAPROFIL BAJA

Zora Vrcelj, UNSW

The Benefit of Steel Material The Benefit of Steel Material as a Construction Materialas a Construction Material

EconomicDuctileHot rolled into standards shapesEasily fabricated by welding

Zora Vrcelj, UNSW

DUCTILITYDUCTILITYThe most important material characteristic of steel is its ductility.

Ductility allows very large strains to develop with increase in stress, prior to failure.

The advantages of ductility are: •It can give prior warning of future failure•It allows energy absorption in dynamic loading or in resisting brittle fracture•It allows for redistribution of actions, which is usually favorable

N.B At present, in achieving a ductile stress -strain curve it requires the yield stress fy to be less than 450 MPa. The yield stress is also called the Grade of the steel, i.e. Grade 350 steel has fy = 350 MPa Zora Vrcelj, UNSW

Stress-Strain Curve Stress-Strain Curve

Idealised stress-strain relationship for structural steel

The same stress-strain curve is assumed in compression,but we shall see that buckling of members and elements in compressionusually prevents high strains from being realisedZora Vrcelj, UNSW

Yielding under Biaxial Yielding under Biaxial StressesStresses

Zora Vrcelj, UNSW

Typical Steel Typical Steel Fabrication Fabrication

Hot rolling

Zora Vrcelj, UNSW

Steel Structural Sections

• Hot-Rolled Sections.

• Cold Formed Sections.

• Built-Up Sections.

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Steel Structure Sections Steel Structure Sections

• Hot-Rolled Sections.

W(a) Wide-flange Shape

S(b) American Standard

Beam

C(c) American Standard Channel

L(d) Angle

WT or ST(e) Structural

Tee (f) Pipe Section

(g) Structural Tubing

(h) Bars (i) Plates

a – Wide-flange : W 18 97

b – Standard (I) : S 12 35

c – Channel : C 9 20

d – Angles : L 6 4 ½

e – Structural Tee : WT, MT or ST e.g. ST 8 76

f & g – Hollow Structural Sections HSS : 9 or 8 8

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• Cold Formed Sections

(a) Channels (b) Zees (c) I-shaped double channels

(d) Angles (e) Hat sections

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• Built-Up Sections.

Built-up (W) shapes.

Built-up (C) Channels.

Built-up (L) Angles.

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• Tension Members.

(a) Round and rectangular bars, including eye bars and upset bars.

(b) Cables composed of many small wires.

(c) Single and double angles.

(d) Rolled W – and S – sections.

(e) Structural tee.

(f) Build-up box sections.

Perforatedplates

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• Compression Members.

(a) Rolled W-and S- sections.

(c) Structural tee.

(b) Double angles.

(e) Pipe section

(d) Structural tubing

(f) Built-up section12

(a) Rolled W-and other I-shaped sections.

(c) open web joist.(b) Build-up Sections.

(f) Built-up members

• Bending Members.

(d) Angle (e) Channel (g) Composite steel-Concrete

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Frames Frames Frames Frames

FRAMESFRAMESFRAMESFRAMES

FRAME IDEALISATIONFRAME IDEALISATIONFRAME IDEALISATIONFRAME IDEALISATION

Reduction of 3-D framework to plane frames

FLOOR BEAMS FLOOR BEAMS PROFILES PROFILES

Zora Vrcelj, UNSW

LOADSLOADS

LOADSLOADS

SUCCESSFULL SUCCESSFULL STRUCTURESTRUCTUREFunctional requirements – set by

clientSAFETY – consider for whole building

life including construction period (STRUCTURAL ENGINEERS)

Aesthetic satisfaction – set by architects

Economy – Capital cost is not just the structural component but financing and construction speed /maintenance costs can effect long term life cycle costing.

Zora Vrcelj, UNSW

Working Stress Design (Allowable Stress Design),widely known as (ASD) – used for over 100 years.

Limited States Design (Load & Resistance Factor Design),also known as (LRFD) – first introduced in 1986.

A limit state means “A set of conditions at which astructure ceases to fulfill its intended function”.

Two types of limit states exist, these are:- Safety (Strength).- Serviceability (Deformation).

A)

B)

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DESIGN APPROACHDESIGN APPROACHBased on on limit state design– Serviceability limit state,

concerned with , ‘function’:• Deflection (avoiding excessive cracking or

bending)• Vibration- Strength limit states, Ultimate

limit state concerned with ‘collapse’:• Yielding• Buckling• Overturning

Zora Vrcelj, UNSW

Assume load effects on structures = Q Assume Resistance to these loads = R

Establishing frequency distribution for (Q) & (R):

Thus always Rm > Qm, and the ratio of R/Q defines the “Factor of Safety”, such:

= Factor of Safety (F.S.).RQ

Frequency distribution of load Q and resistance R.

Fre

quen

cy

Resistance R, Load Q

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Allowable Stress Design (ASD): suppose R is the reduction in resistance. suppose Q is the increase in loading.

67.1

85.0

4.1

15.01

4.01

1

1..

11

RR

QQ

Q

RSF

Q

QQ

R

RR

QQRR

Load & Resistance Factor Design (LRFD)

1.4 D = 0.90 R (First load case) 1.56 D = R LRFD F.S. = R/D = 1.56 LRFD, compared to: F.S. = R/Q = 1.67 ASD

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Limit State Design Limit State Design

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ASTM (A33) Steel with Fy = 33 ksi up to 1960.Today steel offer wide choice of yield from 25 ksi upto 100 ksi,among other different characteristics. The majority of constructionsteels are grouped under the following main groups:

A) Carbon SteelsCarbon Steels:low carbon [C < (0.15%)]mild carbon [0.15% < C< 0.3%] such as A-36, A-53.medium carbon [0.3% C < 0.6%] A-500, A-529.high carbon [0.6% < C < 1.7%] A-570

B) High-Strength Low-Alloy SteelsHigh-Strength Low-Alloy Steels:Having Fy 40 ksi to 70 ksi, may include chromium,

copper, manganese, nickel in addition to carbon.e.g. A-242, A-441 and A-572.

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C) Alloy SteelsAlloy Steels:These alloy steels which are quenched and tamperedto obtain Fy > 80 ksi. They do not have a well definedyield point, and are specified a yield point by the “offsetmethod”, examples are A-709, A-852and A-913.

Typical stress-strainRelationsfor various steels:

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A) Carbon Steel Bolts (A-307):

These are common non-structural fasteners with

minimum tensile strength (Fu) of 60 ksi.

B) High Strength Bolts (A-325):

These are structural fasteners (bolts) with low carbon,

their ultimate tensile strength could reach 105 ksi.

C) Quenched and Tempered Bolts (A-449):

These are similar to A-307 in strength but can be

produced to large diameters exceeding 1.5 inch,

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D) Heat Treated Structural Steel Bolts (A-490):

These are in carbon content (upto 0.5%)

and has other alloys. They are quenched and

re-heated (tempered) to 900oF.

The minimum yield strength (Fy) for these bolts

ranges from 115 ksi upto 130 ksi.

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REVIEW ON REVIEW ON COMPRESSION COMPRESSION MEMBERSMEMBERS

BCN 3431 Steel Design

Compression MembersCompression MembersStructural elements that are

subjected only to axial compressive forces (columns, truss members, or bracing systems, etc)

Smaller compression members are sometimes referred to as struts.

BCN 3431 Steel Design

Type of FailureType of FailureA long, slender column becomes

unstable when its axial compressive load reaches a value called the critical buckling load.

For extremely stocky members, failure maybe by compressive yielding rather than buckling.

COMPRESSION MEMBERS COMPRESSION MEMBERS COMPRESSION MEMBERS COMPRESSION MEMBERS

Column: elastic bucking load effective length factor

First order (linear, no P- effects)

Second order (nonlinear, P-effects)Analysis Method:

BCN 3431 Steel Design

COMPRESSIVE STRENGTHCOMPRESSIVE STRENGTH

Pu ≤ c Pn

Pu ≤ c Ag Fcr

Pu = sum of factored loadsPn = nominal compressive strengthFcr = critical buckling stressc = resistance factor for

compression members = 0.85

Local bucklingLocal buckling

LOCAL BUCKLINGLOCAL BUCKLING

BCN 3431 Steel Design

Local StabilityLocal StabilityIf the elements of the cross

section are so thin that local buckling occurs, the strength corresponding to any buckling mode cannot be developed.

BCN 3431 Steel Design

Local Stability Local Stability If the shape has any slender element

(b/t or h/tw greater than the specified limits of AISC B5), the compressive design strength must be reduced.

In most cases, however, a rolled shape that satisfies the AISC width-thickness requirements can be found, and this procedure will not be necessary.

BCN 3431 Steel Design

Wide Flange Shape                    

PT. GUNUNG GARUDA                    

TypeType

DesignationH X B t1 t2 r

Cross Section

Weight

Moment of Inertia

Section Modulus

Ix Iy Zx Zy

    (mm) (mm) (mm) (mm) (cm2) (kg/m) (cm4) (cm4) (cm3) (cm3)

GG-WFS-01 100 x 100 100 x 100 6 8 10 21.9 17.2 383 134 76.5 26.7

GG-WFS-02 125 x 125 125 x 125 6.5 9 10 30.31 23.8 847 293 136 47

GG-WFS-03 150 x 75 150 x 75 5 7 8 17.85 14 666 49.5 88.8 13.2

GG-WFS-04 150 x 100 148 x 100 6 9 11 26.84 21.1 1020 151 138 30.1

GG-WFS-05 150 x 150 150 x 150 7 10 11 40.14 31.5 1640 563 219 75.1

GG-WFS-06 175 x 175 175 x 175 7.5 11 12 51.21 40.2 2880 984 330 112

GG-WFS-07 200 x 100 198 x 99 4.5 7 11 23.18 18.2 1580 114 160 23

GG-WFS-08 200 x 100 200 x 100 5.5 8 11 27.16 21.3 1840 134 184 26.8

GG-WFS-09 200 x 200 200 x 200 8 12 13 63.53 49.9 4720 1600 472 160

GG-WFS-10 250 x 125 248 x 124 5 8 12 32.68 25.7 3540 255 285 41.1

GG-WFS-11 250 x 125 250 x 125 6 9 12 37.66 29.6 4050 294 324 47

GG-WFS-12 250 x 250 250 x 250 9 14 16 92.18 72.4 10800 3650 867 292

GG-WFS-13 300 x 150 298 x 149 5.5 8 13 40.8 32 6320 442 424 59.3

GG-WFS-14 300 x 150 300 x 150 6.5 9 13 46.78 36.7 7210 508 481 67.7

GG-WFS-15 300 x 300 300 x 300 10 15 18 119.8 94 20400 6750 1360 450

GG-WFS-16 350 x 175 346 x 174 6 9 14 52.68 41.4 11100 792 641 91

GG-WFS-17 350 x 175 350 x 175 7 11 14 63.14 49.6 13600 984 775 112

GG-WFS-18 350 x 350 350 x 350 12 19 20 173.9 137 40300 13600 2300 776

GG-WFS-19 400 x 200 396 x 199 7 11 16 72.16 56.6 20000 1450 1010 145

GG-WFS-20 400 x 200 400 x 200 8 13 16 84.1 66 23700 1740 1190 174

GG-WFS-21 400 x 400 400 x 400 13 21 22 218.7 172 66600 22400 3330 1120

GG-WFS-22 450 x 200 450 x 200 9 14 18 96.8 76 33500 1870 1490 187

GG-WFS-23 500 x 200 500 x 200 10 16 20 114.2 89.6 47800 2140 1910 214

GG-WFS-24 600 x 200 600 x 200 11 17 22 134.4 106 77600 2280 2590 228

GG-WFS-25 600 x 300 588 x 300 12 20 28 192.5 15111800

09020 4020 601

GG-WFS-26 700 x 300 700 x 300 13 24 28 235.5 18520100

010800 5760 722

GG-WFS-27 800 x 300 800 x 300 14 26 28 267.4 21029200

011700 7290 782

Notes:                      

1. According JIS 1993                    2. Tensile Strength : 400 - 510 N/mm2                    

TypeType

DesignationH X B t1 t2 r

Cross Section

Weight

Moment of Inertia

Section Modulus

Ix Iy Zx Zy

    (mm) (mm) (mm) (mm) (cm2) (kg/m) (cm4) (cm4) (cm3) (cm3)

SK SNI 07 – 0329 - 2005SK SNI 07 – 0329 - 2005SK SNI 07 – 0329 - 2005SK SNI 07 – 0329 - 2005

Lateral bucklingLateral buckling

BCN 3431 Steel Design

Critical Buckling StressCritical Buckling StressFor λc > 1.5 Fcr = (0.877 / λc

2) Fy

For λc < 1.5 Fcr = (0.658 λc2) Fy

λc = (KL / rπ) √ Fy / E

λc = slenderness parameterKL/r = slenderness ratioKL = effective lengthr = radius of gyration

BCN 3431 Steel Design

Critical Buckling Stress Critical Buckling Stress These equations are based on

experimental and theoretical studies that account for the effect of residual stresses and initial out-of-straightness of L/1500.

Maximum suggested slenderness ratio is 200.

BCN 3431 Steel Design

LATERAL BUCKLINGLATERAL BUCKLING

DIFFERENCES ON DIFFERENCES ON CODES CODES

FB = Flexural Buckling

BCN 3431 Steel Design

Effective LengthEffective LengthIf a compression member is

supported differently with respect to each of its principal axes, the effective length will be different for the two directions, and the larger slenderness ratio should be used for the determination of Fcr.

Effective length factor Effective length factor – isolated – isolated columncolumnEffective length factor Effective length factor – isolated – isolated columncolumn

Some standard cases are given below (Trahair & Bradford, 1998):

L is the column length; ke is the EFFECTIVE LENGTH FACTOR

For column design or checking we generally use

the effective length Le

LkL ee

SLENDERNESS RATIOSLENDERNESS RATIO

NE

L l

NE

l

l

L

NE

lL

NE

lL

NE

l

L

2

2

L

EINE

2

24

L

EINE

2

22

L

EINE

2

24

L

EINE

2

2

4L

EINE

Ll 2/Ll Ll 7.0 2/Ll Ll 2

Theoretical ke

1.0 0.5 0.7 0.5 2.0

AS4100 ke

1.0 0.5 0.85 0.7 2.2

Effective length factor Effective length factor – – isolated columnisolated columnEffective length factor Effective length factor – – isolated columnisolated column

SK SNI

BCN 3431 Steel Design

•REFERENCES :• Brockenbrough, RL., Johnson, C., 1981, Steel

Design Manual, USS Corporation• Bresler. B, Lin.T.Y., Scaizi,JB., Design of Steel

Structure, 2nd ed, John Wiley& Son, Inc. New York, 1968

• Yayasan Lembaga Penyelidikan Masalah Bangunan, Peraturan Perencanaan Bangunan Baja Indonesia ( PPBBI ), 1984

• Salmon, Charles G., & Johnson, John E., Wira,M,S,C.E, Struktur Baja, Disain dan Perilaku, Erlangga, Jakarta, 1991

• Bowles, Josep. E & Silaban Ph.D, Pantur, Disain Baja Konstruksi ( Structural Steel Design ), Erlangga Jakarta, 1985

• Amon, Rene & Knobloch, Bruce, Mazunder, Atanu, Perencanaan Konstruksi Baja untuk Insinyur dan Arsitek I, II, Pradnya Paramita, Jakarta, 1988

• Gunawan,dkk, Konstruksi baja I dan II, Delta Teknik, Jakarta