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SEM-9, ROLL NO. 27,
Long Span Beam
Types of long span beams:
Parallel beam
Composite beam with web opening.
Tapered girders
Stub girder
Haunched composite beam
Composite trusses
Parallel beam approach
 In the parallel beam approach (PBA), secondary or 'rib' beams pass over primary or
'spine' beams to form a grillage of members. The primary beams are placed in pairs
so that they pass either side of the columns and are attached by large steel-brackets
which transfer the shear forces into the column. Secondary beams are designed to
span the greater distance because they can develop composite action with the slab.
 The PBA system enables continuity of the beams to be achieved without the high
cost of moment-resisting connections. Beam lengths are only limited by handling
and transportation requirements. This improves efficiency for long-span
applications and can save erection time and costs as the piece count is significantly
lower than for conventional construction. Economic comparisons have shown that
the PBA system can be advantageous for certain floor layouts for highly serviced
buildings. Whilst it may appear that the PBA system would lead to deeper floor
construction, their depth remains shallow because of the continuity of the beams,
and the overall depths are comparable with the other forms of construction noted
 A parallel beam of radiation passing through free space can be quantified by
quoting the number of particles passing through a unit area. See flux, fluence, and
energy flux in this article's glossary.
Composite beam with web opening
 Composite beams are constructed from more than one material to increase stiffness
or strength or to reduce cost. Common composite-type beams include I-beams where
the web is plywood and the flanges are solid wood members (sometimes referred to
as "engineered I-beams").
 Composite beams are stronger than the sum of their constituent parts and exhibit a
favorable combination of the strength characteristics of both materials. This means a
steel and concrete composite beam will posses both the compressive strength of
concrete and the tensile strength of steel.
 Composite beams have higher stiffness, thus it has less deflection that steel beams.
Composite beams can cover for large space without the need of any intermediate
columns. Composite construction is faster because of using rolled steel and prefabricated components than cast-in-situ concrete.
Tapered girders
 Tapered beams are extensively used for structural applications due to their high
stiffness-to-mass ratio. They provide many advantages over prismatic beams such as
better shear carrying capacity, higher lateral stability, and weight savings.
 Tapered girders can be a cost effective solution in the span range 10 m to 20 m. They
are another solution that allows services to be accommodated within the structural
floor zone. The depth of the girder increases towards mid-span, where applied
moments are greatest, and thereby facilitating hanging services under the shallower
regions near the beam supports. It is also possible to form web openings in tapered
girders in regions of low shear, towards mid-span. These provide more options for
service integration.
 The tapering of the web depth can be implemented to avoid the use of excessive
material quantities. Due to the web slenderness, the girder panel usually suffers
instability due to the presence of normal and/or shear stresses.
Stub girders
 A stub-girder floor system is a composite system constructed from a continuous steel
beam and a reinforced concrete slab separated by a series of short, typically wide,
flange sections called stubs. The finite element method has been used in the analysis
of this composite system where it is capable to represent the constituent parts, adopt
adequate elements and use appropriate solution techniques.
 As the behaviour of stub-girders presents significant nonlinear effects, it is
fundamental that the interaction of all different components should be properly
modelled as well as the interface behaviour. The present work focuses on the
modelling of stub-girders with full and partial shear connection in two and three
 The proposed model contains all the main structural parameters and their associated
nonlinearities (concrete slab, steel beam, stubs, and shear connectors). In this model,
the shear connectors are modelled as springs to consider the geometry of studs in
addition to the nonlinearity due to the interaction between the shear connector and
the concrete slab.
 Tests and numerical results available in the literature are used to validate the models.
Based on the proposed finite element model, an extensive parametric study of stubgirders is performed, considering the material properties, relative dimensions and
shear connector characteristics, where valuable recommendations and conclusions
are achieved.
Haunched composite beams
 Haunched composite beams in which steel beams are designed to act in conjunction
with concrete slab of definite width could result in shallow beams, provide a long
unobstructed space for services and increase in speed of construction.
 Haunched beams are designed by forming a rigid moment connection between the
beams and columns. The depth of the haunch is selected primarily to provide an
economic method of transferring moment into the column. The length of the haunch
is selected to reduce the depth of the beam to a practical minimum
 The apex haunch joint is commonly used for roof beams. It consists of two beams
spliced with bolted end plates, and optional haunches attached at the top and/or
bottom. The haunches are created from beams or plates
 The haunch is the area between the top of a bridge girder and the bottom of the
concrete deck. Haunch geometry can be influenced by a variety of factors. A primary
function of the haunch is to maintain a uniform deck thickness. Haunches are often
needed to account for camber and cross-slope.
Composite trusses
 A composite truss consists of a steel truss fabricated from rolled sections, such as HSS,
angles and WT, and a concrete slab atop the steel truss. Composite action between
steel and concrete is achieved through the addition of headed shear stud connectors.
 The Composite Roof Truss is made of two materials such as timber and steel or
wrought iron. Due to Combination of two materials this truss known as the composite
roof trusses. In this roof, the tension members are made from steel and compression
member are made from timber.
 Truss is basically a triangle or arch shapes frame used a majority in roof cover it.The
Composite Roof truss is defined as a truss whose compressive members are of timber
and whose tension members are steel.
 The Composite Roof Truss is made of two materials such as timber and steel or
wrought iron. Due to Combination of two materials this truss known as the composite
roof trusses.
Advantages of a steel roof structure
 It is easy and quick to erect – compared to timber framing, its installation is less labourintensive and does not require a large number of workers.
 It has high strength.
 It is a relatively cheap solution.
 Properties of steel – it does not require drying out or maintenance.
 Steel roof trusses can be lighter than wooden rafter framing.
 Moisture resistance (however, it must be properly prepared beforehand) – this
prevents the appearance of mould or fungi.
 It has high resistance to adverse weather conditions.
 Unlike wooden rafter framing, the one made of steel will definitely not be inhabited
by insects, pests or parasites.
 At the production stage, steel elements are covered with special additional protective
and anti-corrosive coatings.
Disadvantages of the steel roof structure
 Corrosion proofing must be carried out.
 Although the steel roof structure is effectively protected against corrosion, if this
protective coating is scratched, it will become susceptible to corrosion.
 Although it does not require regular maintenance, regular inspections are required.
 Due to its low weight, heavy roofing, such as ceramic and especially cement tiles,
cannot be laid on it.
 Steel trusses cost more than their wooden counterparts.
 For large or complicated roofs, steel trusses may prove to be an uneconomical
 As the individual finished elements are large, transporting them to the construction
site can be challenging.
Types of material in beams
Timber, laminated timber
Concrete beam
(precast or in-situ)
steel beam (cut on site/
Case study Liège-Guillemin’s railway station
Liège-Guillemin’s railway station is the main station of the city of Liège, the third largest city
in Belgium. It is one of the most important hubs in the country and is one of the 4 Belgian
stations on the high-speed rail network.
Address: 4000 Liège, Belgium
Architect: Santiago Calatrava
Opened: 1 May 1842
Code: XHN
Owner: National Railway Company of Belgium
Platforms in use: 5
Tracks: 10
Serves: Liège