
BEAMS
DESIGN EXAMPLE
The following consideration has been made:
A single span roof structure. Hollowcore slabs spanning 17m supported on prestressed beams spanning 10m.
Loads:
Chippings 
g = 1.00 kN/m2 
Insulation & roofing 
g = 0.25 kN/m2 
Screed 
g = 1.50 kN/m2 
HCS 400mm 
g = 4.95 kN/m2 
Live Load 
g = 0.75 kN/m2 
Total characteristic load Pk
Pk = ½ x 17 (1.00+0.25+1.50+4.95+0.75) = 71.83 kN/m
Total ultimate design load Pd
Pd = ½ x 17 (1.4(1.0+0.25+1.50+4.95)+1.6 x 0.75) = 101.83 kN/m
Required beam size
From the load and deformation tables the following beams have sufficient capacity to sustain the load.
RB 36/90: quls = 150.7 kN/m > Pd
quls = 81.7 kN/m > Pk
RB 36/100: quls = 158.0 kN/m > Pd
quls = 93.5 kN/m > Pk
Assuming the load on the beams has little or no eccentricity a IB 36/100beam would be the most economical as the self weight is only 75% of a RB 36/90beam. In case of eccentric load resulting in significant torsion on the beam as RB 36/90 would be a better choice.
Shear reinforcement shall be designed for the specific loads.
Deformation
The following deformations can be found using a IB 36/100beam:
 Short term chamber:
Csh = 8.8 mm
 Short term deflection for live load, Qk:
ash = ½ x 17 x 0.75 x 1.4/10 = 0.9mm
 Short term deflection for dead load:
ash = ½ x 17 (1.00+0.25+1.50+4.95) x 1.4/10 = 9.2mm
 Resulting short term deflection for dead load:
a1= 8.8+9.2 = 0.4mm
Conclusion:
Elastic settlement for full live load is 0.9mm < span/130.
Combined short term deflection for dead load and camber is: 0.4mm < span/250.
Concentrated loads:
In case the beams are supporting concentrated loads the overall moment and shear capacity shall be checked.
Service and ultimate moment capacity, Msls and Muls can be derived from the load tables whereas the shear capacity shall be calculated in each individual case.


Columns
Design specifications
Columns are designed according to BS 8110. The capacity of columns depends on the cross section, reinforcement, material properties, column length and combination of applied axial force and moment. Reference is made to BS 8110, part 3 where design charts for rectangular columns are shown.
As an alternative, rectangular columns can be prestressed. Prestressing is advantageous for slender columns subjected to relative high moments compared to axial load. We can advise on the use of prestressing.
Connections:
Connections between column and column or column and beam are usually a pinned dowel connection where only axial and horizontal forces can be transferred. Transfer of moments requires special design considerations. Connection between column and foundation can either be a pinned dowel connection or a fixed. Forming a pocket in the foundation where the column is inserted and grouted easiest does fixation. For moderate loads a Precast foundation is a preffered solution.
Cross Section
RCcolumns have a rectangular cross section and are designated RC w/h, where W is the width and h the height of the column. The columns are produced in standard cross sections as per table below. CCcolumns have a circular cross section and are designated CC d, where d is the diameter. The columns are produced in standard cross section as per table below.
RC  Column
h/mm
w/mm 
200 
240 
300 
360 
420 
480 
600 
700 
200 








240 








300 








360 








420 








480 








600 








700 








CCColumn
h/mm 
200 
240 
300 
360 
420 
480 
600 
700 
SPECIFICATIONS AND TOLERANCES
GENERAL MIX SPECIFICATIONS
Strength:
Min. characteristic cube strength fcu = 40 N/mm2 for normal reinforced beams and columns. For prestressed beams fcu = 60N/mm2.
Cement:
OPC complying with requirements in BS 12 and ASTM C 150, type 1.
Microsilica:
Densified or undensified Microsilica grade 920 or 940.
Water:
Clean water with total dissolved solid contents not exceeding 700 p.p.m.
Admixture:
Water reducing admixtures complying with ASTM C 494.
Coarse Aggregates:
Crushed aggregates complying with BS 882.
Fine Aggregates:
All fine aggregates are sand complying with BS 882.
Reinforcement:
All reinforcement steel complying with BS 4449.
Prestressing Strands:
All prestressing strands complying with either BS 5896, ASTM A416 or EN 138/79.
BEAM DIMENSIONS AND TOLERANCE
Dimensions Tolerances
Length, L + 12mm or L/1000*
Height, h + 8mm
Width, w + 8mm
Side camber, a +8mm or L/500*
Camber, Csh +50%
Position of cutouts +10mm
Position of inserts etc. +10mm
*whichever is the larger.
COLUMN DIMENSIONS AND TOLERANCES
Dimensions Tolerances
Length, L + 12mm or L/1000*
Cross section, w,h,d + 10mm
Curvature, a + 5mm or L/750
Corbel position. Lc + 10mm
Position of cutouts +10mm
Position of inserts etc. +10mm 
