Weld Connections

Engr. Rolando A. Bitagun Jr.

• Welding is the process of joining materials (usually metals) by heating them to suitable temperatures such
that the materials coalesce into one material. There may or may not be pressure, and there may or may not
be filler material applied. Arc welding is the general term for the many processes that use electrical energy in
the form of an electric arc to generate heat necessary for welding.
• The weldability of a steel is a measure of the ease of producing a crack-free and sound structural joint. Some
of the readily available structural steels are more suited to welding than others. Welding procedures should
be based on a steel’s chemistry instead of the published maximum alloy content, since most mill runs are
usually below the maximum alloy limits set by its specifications
 Types of Welding

Shielded Metal Arc Welding (SMAW) – one of the oldest, simplest and perhaps most versatile type for
welding structural steel. It is the least expensive arc welding process. It is often referred to as the manual stick
electrode process. Heating is accomplished by means of an electric arc between a coated electrode and the
materials being joined.
 Types of Welding

Submerged Arc Welding (SAW) – a common arc welding process that involves the formation of an arc
between a continuously fed electrode and the workpiece. A blanket of powdered flux generates a protective gas
shield and a slag (and may also be used to add alloying elements to the weld pool) which protects the weld
zone.
 Types of Welding

Gas Metal Arc Welding (GMAW) – an arc welding process in which the source of heat is an arc formed
between consumable metal electrode and the work piece with an externally supplied gaseous shield of gas
either inert such as argon and /or helium. The process can be semi-automatic or automatic. A constant voltage,
direct current power source is most commonly used with GMAW, but constant current systems, as well as
alternating current, can be used.
Types of Welding

Flux Cored Arc Welding (FCAW) – a semi-automatic or automatic arc welding process. FCAW requires a
continuously-fed consumable tubular electrode containing a flux and a constant-voltage or, less commonly, a
constant-current welding power supply. An externally supplied shielding gas is sometimes used, but often the
flux itself is relied upon to generate the necessary protection from the atmosphere, producing both gaseous
protection and liquid slag protecting the weld. The process is widely used in construction because of its high
welding speed and portability.
 Types of Welding

• Electrogas Welding (EGW) – a continuous vertical position arc welding process developed in 1961, in which
an arc is struck between a consumable electrode and the workpiece. A shielding gas is sometimes used, but
pressure is not applied. In EGW, the heat of the welding arc causes the electrode and workpieces to melt and
flow into the cavity between the parts being welded. This molten metal solidifies from the bottom up, joining
the parts being welded together. The weld area is protected from atmospheric contamination by a separate
shielding gas, or by the gas produced by the disintegration of a flux-cored electrode wire.
 Types of Welding

• Electroslag Welding (ESW) – a highly productive, single pass welding process for thick (greater than 25
mm up to about 300 mm) materials in a vertical or close to vertical position. (ESW) is similar to electrogas
welding, but the main difference is the arc starts in a different location. An electric arc is initially struck by wire
that is fed into the desired weld location and then flux is added. Additional flux is added until the molten slag,
reaching the tip of the electrode, extinguishes the arc. The wire is then continuously fed through a
consumable guide tube (can oscillate if desired) into the surfaces of the metal workpieces and the filler metal
are then melted using the electrical resistance of the molten slag to cause coalescence.
Type of Joints

Butt Joint – used mainly to join the ends of flat

plates of the same or nearly the same thicknesses.
The principal advantage of this type of joint is to
eliminate the eccentricity developed in single lap
joints. When used in conjunction with full penetration
groove welds, butt joints minimize the size of a
connection and are usually more aesthetically
pleasing than built-up joints.

Lap Joint – is the most common type and has two

principal advantages. Ease of fitting, pieces being
joined do not require the preciseness in fabricating
as do the other types of joints. Pieces can be slightly
shifted to accommodate minor errors in fabrication or
to make adjustments in length. Ease of joining, the
edges of the pieces being joined do not need special
preparation and are usually, sheared or flame cut.
Lap joints utilize fillet welds and are therefore equally
well suited to shop or field welding.
Type of Joints

Tee Joint – is used to fabricate built-up sections

such as tees, I-shape, plate girders, bearing
stiffeners, hangers, brackets, etc. It permits sections
to be built-up of flat plates that can be joined by
either fillet or groove weld.

Corner Joint – are used principally to form built-up

rectangular box sections such as used for columns
and for beams required to resist high torsional
forces.

Edge Joint – are generally not structural but are

most frequently used to keep two or more plates in a
given plane or to maintain initial alignment.
Type of Weld

Groove Weld – a weld used to connect structural

members that are aligned in the same plane.

Fillet Welds – a weld most widely used due to ease

of fabrication, adaptability and overall economy. They
require less precision in the fitting up because of the
overlapping of pieces, whereas other weld types
requires careful alignment with specific gap or what
you call as root opening.

Slot Weld and Plug Weld – a weld used to transmit

shear in a lap joint when the size of the connection
limits the length available for fillet and other edge
welds. Slot and plug welds are also useful in
preventing overlapping parts from buckling.
Location of Elements for Welding Symbol

Groove Weld – a weld used to connect structural

members that are aligned in the same plane.

Fillet Welds – a weld most widely used due to ease

of fabrication, adaptability and overall economy. They
require less precision in the fitting up because of the
overlapping of pieces, whereas other weld types
requires careful alignment with specific gap or what
you call as root opening.

Slot Weld and Plug Weld – a weld used to transmit

shear in a lap joint when the size of the connection
limits the length available for fillet and other edge
welds. Slot and plug welds are also useful in
preventing overlapping parts from buckling.
 Bolts in Combination with Welds

Bolts shall not be considered as sharing the load in combination with welds, except that shear
connections with any grade of bolts permitted by Section 501.3.3 installed in standard holes or short
slot transverse to the direction of the load are permitted to be considered to share the load with
longitudinally loaded fillet welds. In such connections. The available strength of the bolts, shall not
be taken as greater than 50% of the available strength of bearing type bolts in the connection.

In making welded alterations to structures, existing rivets and high-strength bolts tightened to the
requirements for slip-critical connections are permitted to be utilized for carrying loads present at the
time of alteration and the welding need only provide the additional required strength.
 Design and Analysis of Fillet Welds

Longitudinal Weld – force is parallel to the weld length.

Transverse Weld – force is perpendicular to the weld length

 Design and Analysis of Fillet Welds

The design strength, ØRn, and the allowable strength, Rn/Ω, of welds shall be the lower value of the
base material and the weld material strength determined according to the limit states of tensile
rupture, shear rupture or yielding as follows
∅ = 0.75 Ω = 2.0

For the base metal

𝑅𝑛 = 𝐹𝐵𝑀 𝐴𝐵𝑀

For the weld metal

𝑅𝑛 = 𝐹𝑤 𝐴𝑤

𝐹𝐵𝑀 − 𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑎𝑠𝑒 𝑚𝑒𝑡𝑎𝑙 𝑝𝑒𝑟 𝑢𝑛𝑖𝑡 𝑎𝑟𝑒𝑎

𝐹𝑤 − 𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑤𝑒𝑙𝑑 𝑚𝑒𝑡𝑎𝑙 𝑝𝑒𝑟 𝑢𝑛𝑖𝑡 𝑎𝑟𝑒𝑎
𝐴𝐵𝑀 − 𝑐𝑟𝑜𝑠𝑠 − 𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑎𝑠𝑒 𝑚𝑒𝑡𝑎𝑙
𝐴𝑤 − 𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑤𝑒𝑙𝑑
 Longitudinal and Transverse Fillet Weld

For fillet weld groups concentrically loaded and consisting of elements that are oriented both
longitudinal and transversely to the direction of applied load, the combined strength, Rn, of the fillet
weld group shall be determined as the greater of

𝑅𝑛 = 𝑅𝑤𝑙 + 𝑅𝑤𝑡

or
𝑅𝑛 = 0.85𝑅𝑤𝑙 + 1.5𝑅𝑤𝑡

𝑅𝑤𝑙 − 𝑡ℎ𝑒 𝑡𝑜𝑡𝑎𝑙 𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑜𝑛𝑔𝑖𝑡𝑢𝑑𝑖𝑛𝑎𝑙𝑙𝑦 𝑙𝑜𝑎𝑑𝑒𝑑 𝑓𝑖𝑙𝑙𝑒𝑡 𝑤𝑒𝑙𝑑𝑠

𝑅𝑤𝑡 − 𝑡ℎ𝑒 𝑡𝑜𝑡𝑎𝑙 𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡𝑟𝑎𝑛𝑠𝑣𝑒𝑟𝑠𝑒𝑙𝑦 𝑙𝑜𝑎𝑑𝑒𝑑 𝑓𝑖𝑙𝑙𝑒𝑡 𝑤𝑒𝑙𝑑𝑠
 Size of Fillet Welds (NSCP 2015)

Maximum size of fillet welds of connected parts shall be:

1. Along edges of material less than 6mm thick, not greater than the thickness of material
2. Along edges of material 6mm more in thickness, not greater than the thickness of material minus 2mm,
unless the weld is especially designated on the drawings to be built out to obtain full throat thickness
Available Strength of Welded Joints (AISC 360-10)
Shear Lag Factor (NSCP 2015)
Strength of Elements in Tension

The design strength ∅𝑃𝑛 and the allowable strength 𝑃𝑛ൗΩ of affected and connecting elements
loaded in tension shall be the lower value obtained according to the limit states of tensile yielding
and tensile rupture.
1. For tensile yielding of connecting elements:

𝑃𝑛 = 𝐹𝑦 𝐴𝑔
∅ = 0.90 𝐿𝑅𝐹𝐷 𝛺 = 1.67 (𝐴𝑆𝐷)

2. For tensile rupture of connecting elements:

𝑃𝑛 = 𝐹𝑢 𝐴𝑒
∅ = 0.75 𝐿𝑅𝐹𝐷 𝛺 = 2.0 (𝐴𝑆𝐷)
Strength of Elements in Tension

The design strength ∅𝑃𝑛 and the allowable strength 𝑃𝑛ൗΩ of affected and connecting elements
loaded in tension shall be the lower value obtained according to the limit states of tensile yielding
and tensile rupture.
3. For block shear failure:
Shear Yielding – Tension Rupture (0.6FyAgv < 0.6FuAnv)

𝑃𝑛 = 0.6𝐹𝑦 𝐴𝑔𝑣 + 𝐹𝑢 𝑈𝑏𝑠 𝐴𝑛𝑡

Shear Fracture – Tension Rupture (0.6FyAgv < 0.6FuAnv)

𝑃𝑛 = 0.6𝐹𝑢 𝐴𝑛𝑣 + 𝐹𝑢 𝑈𝑏𝑠 𝐴𝑛𝑡

∅ = 0.75 𝐿𝑅𝐹𝐷 𝛺 = 2.0 (𝐴𝑆𝐷)

Example No. 1

Determine the design strength for the bearing type connection done on 2-A36 Steel Plates 15mm
thick using A325 M20 bolts on standard hole sizes. Consider that the threads are not in line with
the shear plane and assume that deformations at bolt holes are considered in the design.
Example

Solve for the design strength of the E60 weld used to connect two A36 plates, 12mm thick each,
as shown.

A36
𝐹𝑦 = 248𝑀𝑃𝑎
𝐹𝑢 = 400𝑀𝑃𝑎

E60
𝐹𝐸60 = 𝐹𝑢 = 60𝑘𝑠𝑖 6.9 = 414𝑀𝑃𝑎
Example
Strength of Elements in Tension
Yielding in Gross: Block Shear Failiure:
𝑃𝑛 = 248𝑀𝑃𝑎 250𝑚𝑚 12𝑚𝑚 = 744𝑘𝑁 0.6𝐹𝑦 𝐴𝑔𝑣 = 0.6 248 150 12 (2) = 535.68𝑘𝑁
𝑃𝑢 = 0.9 744𝑘𝑁 = 669.6𝑘𝑁
0.6𝐹𝑢 𝐴𝑛𝑣 = 0.6 400 150 12 (2) = 864𝑘𝑁
Fracture in Net:
400 1.0 250 12
𝑃𝑛 = 400𝑀𝑃𝑎 250𝑚𝑚 12𝑚𝑚 = 1200𝑘𝑁 𝑃𝑛 = 535.68𝑘𝑁 +
𝑃𝑢 = 0.75 1200𝑘𝑁 = 900𝑘𝑁 1000

𝑃𝑛 = 1735.68𝑘𝑁

𝑃𝑢 = 0.75 1735.68𝑘𝑁 = 1301.76𝑘𝑁

Example

Shear Strength of Weld

𝐹𝑛𝑤 = 0.6𝐹𝐸60 = 0.6 414 = 248.4MPa

𝑅𝑤𝑙 = 248.4𝑀𝑃𝑎 (150𝑚𝑚)(12𝑚𝑚)(0.707)(2) = 632.23𝑘𝑁

𝑅𝑤𝑡 = 248.4𝑀𝑃𝑎 250𝑚𝑚 12𝑚𝑚 0.707 = 526.86𝑘𝑁

𝑅𝑛 = 𝑅𝑤𝑙 + 𝑅𝑤𝑡 = 1159.09𝑘𝑁

𝑅𝑛 = 0.85𝑅𝑤𝑙 + 1.5𝑅𝑤𝑡 = 1327.69𝑘𝑁 (𝑔𝑜𝑣𝑒𝑟𝑛𝑠)