Struktur Baja

Dimana saja struktur baja dipakai ?

Shanghai Sports Stadium

has a gross area of 170,000 m² (plan area 61,700 m²)

More than 4,000 tonnes of hollow sections and1,000 tonnes of steel plate were supplied to build the Shanghai Sports Stadium

Bird Nest Stadium

Sejarah Bangunan Baja Iron Bridge, England, 1779

Firth of Forth Bridge, Scotland, 1881

Eifel Tower, France , 1882

Empire State Building, USA, 1931

Akashi Kaikyo Bridge, Japan , 1998

Proses Pembuatan Baja

Definisi Baja

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2 and 2.04% by weight, depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten (wikipedia.org)

Jenis-jenis baja dikenal • Carbon steel, also called plain carbon steel, is steel where the

main alloying constituent is carbon; the other elements present are in quantities too small to affect the properties. The only other elements allowed in carbon steel are: manganese (1.65% max), silicon (0.60% max), and copper (0.60% max).

• Stainless steel is defined as a steel alloy with a minimum of 11.5% chromium content by mass. Stainless steel differs from carbon steel by amount of chromium present. Carbon steel rusts when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by forming more iron oxide. Stainless steels have sufficient amount of chromium present so that a passive film of chromium oxide forms which prevents further corrosion.

• HSLA steel (high strength low alloy steel) is a type of steel alloy that provides many benefits over regular steel alloys. In general, HSLA alloys are much stronger and tougher than ordinary plain-carbon steels. They are used in cars, trucks, cranes, bridges, and other structures that are designed to handle large amounts of stress, often at very low temperatures.

Tujuan Kuliah Baja 1

Mahasiswa dapat merencanakan kekuatan penampang elemen struktur baja terhadap gaya aksial, lentur, geser dan kombinasinya.

Isi Kuliah Baja 1

Kuliah ini mempelajari perencanaan elemen-elemen struktur baja, yaitu batang tarik, batang tekan, balok, dan balok kolom dengan menggunakan metoda load and resistance factor design (LRFD)

Beban pada Struktur (Loads)

Secara garis besar dibagi :1. Dead Load permanent loads (gravity loads)

– the weight of structure self weight– nonstructural component floor covering, partition, and

suspended ceilings

2. Live Load not permanent loadStatic Load and dynamic loads

3. Wind Load4. Earthquake Loads

Building Codes, Design Specification

• Tata Cara Perencanaan Struktur baja untuk Bangunan Gedung (SNI 03-1729-2000)

• American Institute of Steel Construction (AISC, 1999)

Steel Characteristics

LL

Tensile Test

APf

The stress and strain can be computed as follows:

Where: f = axial tensile stressA = cross sectional area= axial strainL = length of specimen L = change in length

Ductility can be measured by the elongation, defined as:

100xLLL

eo

of

Where: e = elongation (%)Lf = length of the specimen at fracture

L0 = original length

Indealization of stress – strain curveFy = yield stress

Fu = the ultimate tensile strength

The ratio of stress to strain within the elastic range, denoted E and called Young’s modulus or modulus of elasticity (modulus elastisitas)

fE

E baja = 200000 MPa High Strength Steel

0.002

Standard Cross Sectional -Shapes

• Hot-rolled shapes

• Build up section

• Cold formed section

Concept in Structural Steel Design

Design Philosophies 1. Allowable Stress Design

required strength <= allowable strengh

- safety factor - Elastic design or working stress design- Service loads

2. Plastic Design - based on consideration of failure conditions.- Collapse mechanism, plastic hinge- Failure loads

3. Load and Resistance Factor Design (LRFD) - based on consideration of failure conditions- Load factors and factored strength

Factored load factored strength (loads x load factors) resistance x

resistance factor

ASD LRFD

Kombinasi beban DD + LD + (Lr or S or R)D + 0.75L + 0.75(Lr or S or R)D ± (0.6W or 0.7E)D + 0.75L + 0.75(0.6W) + 0.75(Lr or S or R)D + 0.75L±0.75(0.7E) + 0.75S0.6D±(0.6W or 0.7E)

Kombinasi beban 1.4D1.2D + 1.6L + 0.5(Lr or S or R)1.2D + 1.6(Lr or S or R) + (0.5L or 0.5W)1.2D +1.0W + 0.5L + 0.5(Lr or S or R)1.2D±1.0E + 0.5L + 0.2S0.9D ± (1.0W or 1.0E)

Load and Resistance Factors

nii RQ Where

Qi = a load effect ( a farce or a moment)

I = a load factor

Rn = the nominal resistance, or strength of the component under consideration

= resistance factor