UNIT-I
LIMIT STATE DESIGN & DESIGN OF CONNECTION
Introduction to Limit State Design
A Civil Engineering Designer has to ensure that the structures and facilities he designs are (i) fit
for their purpose (ii) safe and (iii) economical and durable. Thus saf

Where
l = centre to centre length of the supporting member
rvv = radius of gyration about the minor axis
b1, b2 = width of the two legs of the angle
t = thickness of the leg
= yield stress ratio (250/fy) 0.5
Table for Constants k1, k2 and k3
For double a

UNIT-III
DESIGN OF COMPRESSION MEMBER
Introduction
Column, top chords of trusses, diagonals and bracing members are all examples of
compression members. Columns are usually thought of as straight compression
members whose lengths are considerably greater

It can be seen that the effective length corresponds to the distance between the
points of inflection in the buckled mode. The effective column length can be defined as
the length of an equivalent pin-ended column having the same load-carrying capacity as

Table for Imperfection factor,
Steps in the design of axially loaded columns
The procedure for the design of an axially compressed column is as follows:
(i) Assume a suitable trial section and classify the section in accordance with the
classification .

Introduction
One of the frequently used structural members is a beam whose main function is
to transfer load principally by means of flexural or bending action. In a structural
framework, it forms the main horizontal member spanning between adjacent c

Design strength in bending (Flexure)
The behaviour of members subjected to bending demonstrated in Fig .1
Fig .1 Beam buckling behavior
This behavior can be classified under two parts:
Institute of Technology Madras
When the beam is adequately supported

Type2: Those which are laterally shift
Lateral-torsional buckling cannot occur, if the moment of inertia about the bending axis
is equal to or less than the moment of inertia out of plane. Thus, for
shapes bent about the minor axis and shapes with Iz = Iy

Low shear load is referred to the factored design shear force that does not exceed
0.6Vd, where Vd is the design shear strength of cross section as explained in 8.2.1.2 of
the code.
Fig.3 Interaction of high shear and bending moment
Design of Steel Struct

Laterally unsupported beams
Under increasing transverse loads, a beam should attain its full plastic moment capacity.
This type of behaviour in a laterally supported beam has been covered in Section 8.2.1.
Two important assumptions have been made therein

Effective length of compression flanges
The lateral restraints provided by the simply supported condition assumption in the
basic case, is the lowest and therefore the Mcr is also the lowest. It is possible, by other
restraint conditions, to obtain higher

The nominal shear yielding strength of webs is based on the Von Mises yield criterion,
which states that for an un-reinforced web of a beam, whose width to thickness ratio is
comparatively small (so that web-buckling failure is avoided), the shear strengt

Fig 7 A typical plate girder
The girder webs will normally be subjected to some combination of shear and bending
stresses. The most severe condition in terms of web buckling is normally the pure shear
case. It follows that it is those regions adjacent to

Fig 9 Postbuckling reserve strength of web
kv = 5.35 When the transverse stiffeners is provided at the support,
kv=4.0 +5.35(c/d)2 for c/d < 1.0 i.e., for webs with closely spaced transverse
stiffeners.
kv=5.35 +4(c/d)2 for c/d 1.0 for wide panels.
Fig 6.

Fig 6.14 Tension field action and the equivalent N-truss
6.3.5 Stiffened web panels
For tension field action to develop in the end panels, adequate anchorage should be
provided all around the end panel. The anchor force Hq required to anchor the tension
f

6.3.6.1 Compression flange buckling requirement
Generally, the thickness of flange plate is not varied along the span of plate
girders. For non-composite plate girder the width of flange plates is chosen to be about
0.3 times the depth of the section as a

Strength as governed by tearing of net section:
Since the number of bolts = 6,
= 396 * 420/1.25 + 1.0 * 768 *250 / 1.15
= 300123 N (or) 300.1 kN
Strength as governed by yielding of gross section:
= 1336 * 250 / 1.15 = 290435 N (or) 290.4 kN
Block shear st

Problem 2:
Analysis of single angle tension membersA single unequal angle 100 X 75 X 8 mm is
connected to a 12 mm thick gusset plate at the ends with 6 nos. 20 mm diameter bolts
to transfer tension. Determine the design tensile strength of the angle. (a)

(c) Classification based on force transfer mechanism by bolts : The bolted connections are
classified as bearing type (bolts bear against the holes to transfer the force) or friction type (force
transfer between the plates due to the clamping force genera

2. Bearing failure: If the connected plates are made of high strength steel then failure of bolt can
take place by bearing of the plates onthe bolts. If the plate material is weaker than the bolt
material, then failure will occur by bearing of the bolt on

HSFG bolts will come into bearing only after slip takes place. Therefore if slip is
critical (i.e. if slip cannot be allowed) then one has to calculate the slip resistance, which will
govern the design. However, if slip is not critical, and limit state me

Combined shear and tension failure
Bolt Subjected to Combined Shear and Tension A bolt required to resist both
design shear force (Vsd) and design tensile force (Tnd) at the same time shall satisfy
Where, V = applied shear; Vsd = design shear capacity; Te

Butt welds:
Full penetration butt welds are formed when the parts are connected together
within the thickness of the parent metal. For thin parts, it is possible to achieve full penetration of
the weld. For thicker parts, edge preparation may have to be d

Design of butt welds:
For butt welds the most critical form of loading is tension applied in the transverse direction. It
has been observed from tests conducted on tensile coupons containing a full penetration butt
weld normal to the applied load that the

Combined shear and moment in plane
Consider an eccentric connection carrying a load of P as shown in Fig. The
basic assumptions in the analysis are (1) deformations of plate elements are negligible,(2) the
total shear is assumed to be shared equally by al

Combined shear and moment out-of-plane
In the connection shown in Fig , the bolts are subjected to combined shear
and tension. The neutral axis may be assumed to be at a distance of one-sixth of the depth d
above the bottom flange of the beam so as to acc

Shear and torsion:
Considering the welded bracket shown in Fig. 3.31 (a), an assumption is made to the effect that
the parts being joined are completely rigid and hence all the deformations occur in the weld. As
seen from the figure, the weld is subjected

Design Example 1:
Design a Lap joint between plates 100? 8 so as to transmit a factored load of 100 kN using black
bolts of 12mm diameter and grade 4.6. The plates are made of steel of grade ST-42-S.
Solution:
1) Strength Calculations:
Nominal diameter of

UNIT II
DESIGN OF TENSION MEMBER, ANGLE STRUT &TRUSS
TENSION MEMBERS
Introduction
Tension members are linear members in which axial forces act so as to elongate
(stretch) the member. A rope, for example, is a tension member. Tension members carry
loads mo

Design strength due to yielding of gross section
Although steel tension members can sustain loads up to the ultimate load without
failure, the elongation of the members at this load would be nearly 10-15% of the
original length and the structure supported