BUILDING CONSTRUCTION

SEM 9
SIR JJ COLLEGE OF ARCHITECTURE
- 1701 RAJ ASHAR
- 1707 SIDDHARTH BHITALE

LONG SPAN BEAMS

DEFINITIONS OF LONG SPAN BEAMS
• BEAMS GRETER THAN 20 METER SPANS ARE KNOWN AS LONG SPAN BEAMS.
• THE USE OF LONG SPAN BEAMS RESULTS IN A RANGE OF BENEFITS, INCLUDING FLEXIBLE,
COLUMN-FREE INTERNAL SPACES, REDUCED FOUNDATION COSTS, AND REDUCED STEEL
ERECTION TIMES.
• MANY LONG SPAN SOLUTIONS ARE ALSO WELL ADAPTED TO FACILITATE THE INTEGRATION
OF SERVICES WITHOUT INCREASING THE OVERALL FLOOR DEPTH.
• THE DESIGN OF LONG SPAN STEEL AND (STEEL-CONCRETE) COMPOSITE BEAMS IS GENERALLY
CARRIED OUT IN ACCORDANCE WITH LOAD AND CONTEXT.
• MANY SOLUTIONS EXPLOIT THE BENEFITS OF COMPOSITE CONSTRUCTION, WHICH OFFERS
CONSIDERABLE STRENGTH AND STIFFNESS INCREASES OVER A BARE STEEL ALTERNATIVE.

TYPES OF LONG SPAN BEAMS

• PARALLEL BEAM APPROACH
• COMPOSITE BEAM WITH WEB OPENING
• CELLULAR COMPOSITE BEAM
• TAPERED GIRDER BEAM
• HAUNCHED COMPOSITE BEAM
PARALLEL BEAM APPROACH
• THE PARALLEL BEAM APPROACH IS EFFECTIVE FOR SPANS UP TO AROUN 20M.
• FLOOR GRIDS COMPRISE TWO LAYERS OF FULLY CONTINUOUS BEAMS RUNNING IN
ORTHOGONAL DIRECTIONS.
• SERVICES RUNNING IN EITHER DIRECTION CAN BE INTEGRATED WITHIN THESE TWO LAYERS,
SO THAT SERVICES PASSING IN ANY DIRECTION CAN BE ACCOMMODATED WITHIN THE
STRUCTURAL FLOOR DEPTH.
• A FURTHER BENEFIT IS THAT, BEING FULLY CONTINUOUS, THE DEPTH OF THE BEAMS
THEMSELVES IS REDUCED WITHOUT INCURRING THE EXPENSE AND COMPLEXITY OF RIGID,
FULL STRENGTH CONNECTIONS.

ADVANTAGES OF PARALLEL BEAM APPROACH

• IT RECUCES THE WEIGHT OF THE STEEL BEAMS BY MEANS OF CONTINUITY.
• IT REDUCES ERECTION COMPLEXITIES BY HAVING LESS NUMBER OF CONNECTIONS IN THE
ENTIRE FRAME.
• CAN BE USED IN RESIDENTIAL AND COMMERCIAL BUILDINGS WHERE LONG SPAN 15 TO BE
ACHIEVED.

DISADVANTAGES OF PARALLEL BEAM APPROACH

• AS COMPARED TO CONVENTIONAL APPROACH, TWO BEAMS ARE USED INSTEAD OF ONE
BEAM.
• DUE TO ORTHOGONAL CONNECTIONS IT IS NOT SUITABLE FOR COMPLEX DESIGN AND
ORGANIC DESIGN FORMS.
• NOT SUITABLE FOR SPAN MORE THAN 20 METER.
COMPOSITE BEAM WITH WEB OPENINGS
• COMPOSITE BEAMS WITH WEB OPENINGS HAVE BEEN SHOWN TO BE A COST-EFFECTIVE
SOLUTION FOR SPANS IN THE RANGE 20M TO 30M.
• WEB OPENINGS ARE TYPICALLY FORMED IN BEAMS TO ALLOW SERVICES TO PASS THROUGH
THE BEAM.
• THIS ENABLES THE STRUCTURAL AND SERVICE ZONES TO OCCUPY THE SAME SPACE, THEREBY
REDUCING THE EFFECTIVE OVERALL DEPTH OF FLOOR CONSTRUCTION FOR A GIVEN
SPANNING CAPABILITY.
• OPENINGS MAY ALSO BE FORMED FOR AESTHETIC REASONS, FOR INSTANCE WITH CAMBERED
BEAMS USED TO SUPPORT A ROOF.

ADVANTAGES OF COMPOSITE BEAM WITH WEB OPENING

• THE MAIN ADVANTAGE OF USING THIS TYPE OF BEAM IS TO EASE THE COMPLEXITY IN THE
SERVICES BY ALLOWING IT TO PASS THROUGH WEB OPENINGS.
• THE OVER ALL STRUCTURAL WEIGHT IS REDUCED TO SOME EXTENT BECAUSE OF OPENINGS
IN THE WEB OF THESE BEAMS.
• MAXIMUM SPAN OF 30 METERS CAN BE ACHIEVED USING THIS BEAM.

DISADVANTAGES OF COMPOSITE BEAM WITH WEB OPENING:

• ANY STRUCTURAL CURVATURE IS NOT POSSIBLE TO ACHIEVE IN THIS TYPE OF BEAMS BECAUSE
OF WEB OPENINGS
• LOAD BEARING CAPACITY IS LESS COMPARED TO OTHER LONG SPAN BEAMS.
• SHOWS DEFORMATION IN WEB OPENINGS, UNDER NON-UNIFORM LOADS
CELLULAR COMPOSITE BEAMS
• CELLULAR COMPOSITE BEAMS ARE SUITABLE FOR EFFECTIVE SPAN OF 15 TO 30 M.
• CELLULAR BEAMS ARE A FORM OF BEAM WITH MULTIPLE REGULAR WEB OPENINGS, FORMED
BY SPLITTING TWO ROLLED SECTIONS LONGITUDINALLY, TO FORM TWO TEE SECTIONS.
• THE TWO TEES, WHICH MAY NOT COME FROM THE SAME DONOR SECTION ARE THEN
WELDED TOGETHER TO FORM AN I-SECTION WITH WEB OPENINGS WHICH HAVE A
CHARACTERISTIC SHAPE (NORMALLY, BUT NOT NECESSARILY, CIRCULAR).

ADVANTAGES OF CELLULAR COMPOSITE BEAM:

• STRUCTURAL CURVATURE CAN BE PROVIDED BECAUSE OF DOUBLE T CONNECTIONS TO FORM
I SECTION IN THIS TYPE OF BEAM
• FLEXIBILITY IN PROVISION OF SERVICES THROUGH WEB OPENINGS
• LOW MAINTAINANCE COST

DISADVANTAGES OF CELLULAR COMPOSITE BEAM:

• THE FABRICATION COST IS HIGHER BECAUSE OF CUTTING AND WELDING OF THE SECTIONS IN
THIS TYPE OF BEAM.
• DUE TO THE PRESENCE OF THE HOLES IN THE WEB, THE STRUCTURAL BEHAVIOUR OF THESE
BEAMS WILL BE DIFFERENT FROM THAT OF THE PLAIN WEBBED BEAMS.
• CELLULAR COMPOSITE BEAMS ARE NOT APPROPRIATE FOR SHORT HEAVILY LOADED SPANS
 TAPERED GIRDER BEAMS
• TAPERED GIRDERS CAN BE A COST-EFFECTIVE SOLUTION IN THE SPAN RANGE 20 TO 25M.
• 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.
• THEY ARE ANOTHER SOLUTION THAT ALLOWS SERVICES TO BE ACCOMMODATED WITHIN THE
STRUCTURAL FLOOR ZONE

ADVANTAGES OF TAPERED GIRDER BEAM:

• IT IS ALSO POSSIBLE TO FORM WEB OPENINGS IN TAPERED GIRDERS IN REGIONS OF LOW
SHEAR, TOWARDS MID-SPAN WHICH CAN BE PROVED ESSENTIAL FOR SERVICES.
• COST EFFECTIVE UPTO SPAN OF 25 METER BECAUSE OF TAPERED SECTION.
• WEIGHT ECONOMY, WHICH IS TRANSLATED INTO LONGER OR TALLER STRUCTURES.

DISADVANTAGES OF TAPERED GIRDER BEAM

• THE LACK OF DESIGN CODE CRITERIA AND HIGH CONSTRUCTION COSTS, HAS KEPT THEIR USE
IN A DORMANT STAGE.
• IN THE LINEAR ELASTIC RANGE THE CLASSICAL BENDING STRESS FORMULA IS SUFFICIENTLY
ACCURATE FOR MODERATE TAPER (LESS THAN 20-DEGREE TAPER), BUT THE EFFECT OF TAPER
ON SHEAR STRESS IS QUITE SIGNIFICANT.
HAUNCHED COMPOSITE BEAMS
• IN HAUNCHED COMPOSITE BEAMS, SPANS IN EXCESS OCAN READILY BE ACHIEVED DUE THE
USE OF HAUNCH.
• HAUNCHES MAY BE ADDED AT THE ENDS OF A COMPOSITE BEAM TO PROVIDE MOMENT
CONTINUITY.
• THE STIFFNESS AND STRENGTH OF THE CONNECTIONS MEAN THAT THE REST OF THE SPAN
CAN BE SHALLOWER (THE BENDING MOMENT DIAGRAM IS 'LIFTED' AND THE EFFECTIVE
STIFFNESS OF THE BEAM SUBSTANTIALLY INCREASED), AND SERVICES PASSED UNDER IT.
• IN BUILDINGS WHERE SERVICES ARE LIKELY TO NEED FREQUENT REPLACEMENT (FOR
EXAMPLE IN HOSPITALS), HANGING THE SERVICES UNDER THE BEAMS RATHER THAN PASSING
THEM THROUGH HOLES IN THE WEBS, OR THROUGH A TRUSS, CAN BE ADVANTAGEOUS.

ADVANTAGES OF HAUNCHED COMPOSITE BEAM

• LONGEST SPAN UPTO 30 METERS CAN BE ACHIEVED EFFICIENTLTY IN THIS TYPE OF BEAM.
• CREATED A SERVICE BAY IN THE AREA BENEATH THE SLAB AND EQUAL TO THE DEPTH OF
HAUNCH.
• BY THE USE OF GUSSET PLATE, MULTIPLE BEAM CONNECTION IN DIFFERENT DIRECTIONS IS
POSSIBLE IN THIS TYPE OF BEAM.

DISADVANTAGES OF HAUNCHED COMPOSITE BEAM

• MATERIAL OVERWORK AND SPECIALIST WORKFORCE NEEDED FOR THE STEEL CONSTRUCTION
IN THIS TYPE OF BEAM.
• LIKELY LOSS OF DUCTILITY IN THE OVERALL SYSTEM.
• LACK OF AESTHETICS AND NON-UNIFORM CLEAR HEIGHT IF USED IN RESIDENTIAL
CONSTRUCTION.
COMPOUND GIRDER
WHEN THE LOADS ARE HEAVY FLANGE AREA IS INCREASED BY ADDITION OF PLATES WHICH ARE
RIVETED / BOLTED TO THE TOP AND BOTTOM FLANGES FORMING A COMPOUND GIRDER

• They are used either when heavy loads need to be carried or when long span may be required.
• Connecting to members to form a combined member
• For heavier loads and for spans 50 to 120 ft use plate girders or trussed built up girders of
smaller sections

NON-STANDARD STEEL SECTIONS

PLATE GIRDERS
• A plate girder is a steel beam that is widely used in bridge construction.
• Depending on the design requirements and as per the nature of the structure; metal
thicknesses for web, flanges, stiffness, etc are determined.
• A plate girder is used when we need deeper sections having higher stiffness to carry heavy
loads.

TYPES:

RIVERTED PLATE GIRDER

It is a combination of flanges, web, and other necessary stiffness. There are connected by a
mechanical method, revert, and plates are not welded together.

• Generally, 90% of the shear is carried by the web.

• Connection of the web and the flange is stabilized by the angel sections reverted to the
flange. Reverts need to be designed for the horizontal shear.
• The reverts that make the connection between the web and flange angles need to be
designed for horizontal shear and vertical loads that applied to the flange when they
transfer to the web.
• Angle sections are used as web stiffness in revert girders.

WELDED PLATE GIRDERS

Welded plate girders are most widely used in construction due to the ease of production and it is a
much more efficient type of girder.

• These sections are mainly used in bridge construction.

• The plate girder bridge is very stiff and it can retain very high loads while resisting the lateral
movements.
• This action can be observed in the railway bridges. Further, they are used to develop the box
type girders.
STUB GIRDER
• The bottom chord is typically formed from a shallow open section (UC), on which sit short
lengths (stubs) of deeper I sections (UB).
• The top chord, at least in the final state, is formed by the composite slab, and therein lies
one of the disadvantages of this option - until composite action with the cured concrete is
achieved the beams may need temporary support/restraint.
• Composite interaction is achieved by welding shear studs to the top of the UB stubs.
• The number of elements/surfaces associated with a stub girder may increase the cost of fire
protection compared with simpler solutions.
• A big advantage of this option is that spans in excess of 20 m can be economically achieved.
• Services and/or secondary beams can pass through the gaps between the beam stubs,
reducing overall construction depth.
COMPOSITE TRUSSES
• Composite trusses, which use the concrete slab as the upper chord in the final state, can
achieve spans in excess of 20 m.
• The main disadvantages are that during the construction phase the truss may be rather
flexible (laterally), and that in the final state the costs of fire protection can be high given the
large number of surfaces to protect.
• Clearly one of the prices to pay for the spanning ability is that fabrication cost is higher than
for a plain beam.
• Services can be passed through the gaps between the truss' members to reduce overall floor
depth
CASE STUDIES
CASE STUDY 1:

IKEA, COMMERCIAL CENTRE, CYPRUS

PROJECT TYPE: COMMERCIAL & WAREHOUSE

AREA: 22000 SQ. M.

TIME FOR ERECTION12 MONTHS (JULY 2006 TO JUNE 2007)

COST: 4 720 000 EUROS

TYPE OF BEAM USED: CELLULAR COMPOSITE BEAMS

SPAN OF CELLULAR BEAMS: 16 TO 24 METERS

SPAN OF SECONDARY BEAM: 4 TO 16 METERS

DEPTH OF CELLULAR BEAMS: 750 X 137 MM CELLULAR COMPOSITE BEAMS

DEPT OF SECONDARY BEAMS: 250 X 137 MM BOX SECTIONS

CASE STUDY 2:

ENOVOS CAR PARK, LUXEMBURG

PROJECT TYPE: CAR PARKING

AREA: 5760 SQ. M

TIME FOR ERECTION: 2 YEARS (2013-2015)

HEIGHT: 2.2 M. CLEAR HT. (FROM LOWER END OF BEAM)

TYPE OF BEAM USED: CELLULAR BEAMS WITH SINOSOIDAL OPENINGS

SPAN OF CELLULAR BEAMS: 15.75 METERS

SPAN OF SECONDARY BEAMS: 5 METERS

DEPTH OF CELLULAR BEAMS: 750 MM TO 575 MM CELLULAR BEAMS

DEPTH OF SECONDARY BEAMS: 220 MM TO 250 MM T SECTIONS

REFERENCE

REKHA MA’AM PRESENTATION

https://www.scribd.com/document/476673498/2-Long-Span-Beams-Salahuddin