BEAMS & COLUMNS
BEAMS AND COLUMNS
Our Precast Beams & Columns provide a flexible solution to the structural component of your project. Precast Beams & Columns can be used for a number of applications from parking structures to the structural framework of commercial buildings. Precast beams & columns are perfect for below grade parking situations to help eliminate the need for a parking lot and reducing the size of the lot needed. Create an ideal framework for hanging Precast Structural and Architectural Wall Panels and setting Hollowcore Floor and Roof Plank with our Beams & Columns.
Advantages of Beams & Columns:
- Precast Prestressed Beams & Columns provide unlimited flexibility in design, shape and application.
- They are extremely durable compared to alternative building materials. Beams & Columns are produced indoors with high-strength concrete creating a quality, strong and durable product with no need for extra fireproofing.
- Beams & Columns work well with other precast components such as Wall Panels, Hollowcore and Double Tees to form a Total Precast application.
- Precast Prestressed Beams & Columns provide a clean, finished look for the structural component of the building.
Inventaa has a long range of standardized beams using both normal reinforcement and prestressed reinforcement. Our standard cross sections include IB-beams, RB-beams, LB-beams, ITB-beams and special flat beams FB-beams. In all types it is possible to provide exposed reinforcement for composite structure. We also produce standard rectangular columns, RC and circular columns, CC.
Only few companies in this region possess the necessary engineering skills, experience and resources to supply these products with the constant high level of quality and in a reliable and professional manner essential in all modern building structure.
Our experienced engineers in design as well as in sales and production combined with the use of “state of art” production technology ensures that these high standards are not compromised. Whether you select a product from our standard range or your project requires a different custom-made solution our experienced staff of engineers is always at your service to assist and advise you.
Using Precast beams and columns will save considerably on cost and time as time-consuming shuttering and scaffolding are avoided.
As production takes place under controlled conditions, the productions are of higher quality and more accurate compared to in-situ work.
Precast columns and beams are fast to install, and does not require any storage space on site, as the units are generally erected directly from the trailer into its final position.
Using prestressed beams will enable large spans, which opens up waste areas inside the building.
RB-beams have a rectangular cross section and are designated RB w/h, where w is the width and h the height of the beam. The beams are produced in standard width of 20, 24, 30 and 36 cm and heights varying from 40 to 90 cm in steps of 10 cm.
IB-beams have a predominantly an I-shaped cross section with rectangular section at the ends. They are designated IB w/h, where w is the width and h the height of the beam. The beams are produced in standard width of 30, 36 and 42 cm and heights varying from 70 to 160 cm in steps of 30 cm.
RB and IB-beams with alternative width and height can be produced within the limitations of size and weight. The weight of the beams is based on a concrete density of 25 kN/m3.
RB and IB-beams are usually used as roof and floor beams, supporting hollowcore slabs or TT-slabs, and are further used as bridge beams. Roof beams can also support steel purlins and sheeting creating a lightweight roof.
ITB-beams have a shape like an inverted T and are designated ITB h/t, where his the height of the beam and t is the thickness of the Hollowcore slab supported on the beam. The beams are produced in standard width of 48 cm and depth below the slabs varying from 15 to 50 cm. However special beams can also be designed.
LB-beams have a L-shaped cross section and are designated LB h/t, where h is the height of the beams and t is the thickness of the Hollowcore slab supported on the beam. The beams are produced in standard width of 36 cm and depth below the slabs varying from 15 to 50 cm in steps of 10 cm.
ITB and L-beams with alternative width and height can be produced within the limitations of size and weight. The weight of the beams is based on a concrete density of 25 kN/m3.
ITB and LB-beams are usually used as roof and floor beams supporting hollowcore slabs or TT-slab.
FB-beams are flat beams with nibs and are designated FB W , where W is the thickness of the slab supported on the beam. The beams are produced in standard width of 120 cm and depth below the slabs of 15 cm.
FB-beams with alternative width and height can be produced within the limitations of size and weight. The weight of the beams is based on a concrete density of 25 kN/ m3.
FB-beams are usually used as roof and floor beams supporting hollowcore slabs. The depth of 15 cm below the slabs makes them suitable for structures where minimum obstacles for services are required.
Columns are produced in steel or plywood moulds. Rectangular columns are cast horizontally, leaving the bottom and both sides fair-faced and the top surface smooth. Circular columns are cast vertically with fair-faced surface. The vertical casting limits the maximum height of circular columns to 8000mm. Rectangular columns only have limitations that are due to size and weight.
As a standard, all columns are delivered with dowel holes or projecting bars at the top of the columns, lifting holes or anchors are bracing inserts.
Other project specific cast-in parts in rectangular columns can be openings, welding plates, inserts and bolts. Cast-in parts are not allowed to project through the bottom and sides of the column. Cast-in parts in circular columns should be discussed with our design office.
Rectangular columns can be provided with corbels for support of structures like beams. They can be provided at the top and on both sides whereas corbels in the bottom of the mould side should be avoided. Corbels can only be provided at the top in circular columns.
Prestressed and normal reinforced beams and rectangular columns are produced in horizontal steel moulds, however only the base are made in full length and the side shuttering are moved down along the line for casting each individual beam. Circular columns are normally produced in vertical steel moulds.
Prior to casting, all cast in parts fixed in position and the mould is treated with a mould release agent. Hereafter reinforcement is kept in position and mould sides are fixed. All reinforcement will normally be prepared and prefabricated in our own workshop and placed in the mould using adequate spacers to ensure correct position and cover.
In cases were beams are prestressed, all beams with similar strand patterns are prepared for casting in the same line. All reinforcement will normally be prepared and prefabricated in our own workshop and placed in the mould using adequate spacers to ensure correct position and concrete cover.
The specially manufactured casting equipment is employed to pour concrete into the moulds. To ensure the highest quality possible, all concrete is mixed in our own mixer plants. From the batching plants the concrete is transported directly to the mould. All casting of the individual beam or column takes place in one continuous operation.
When the beams are prestressed, side moulds will be removed and fixed to the adjacent beam position (if any) and it will be casted in the same way until all beams on the same line are casted.
The concrete mix is evened out using a combination of both mould and and hand-held vibrators when casting both beams and columns.
When casting both beams and columns vibration will be by a combination of mould vibrators and hand-held vibrators.
After casting, all exposed surfaces will be covered with a tarpaulin to avoid vaporization.
Prestressed strands will be cut only after the concrete on the last casted beam has attained the prescribed strength of 40 N/mm2 which enable it to take the prestressing force.
With normal reinforced beams and columns the items will be demoulded 16-24 hours after casting and lifted to the stockyard for further curing. In the stockyard, the item will again be covered with tarpaulin or Hessian and kept in a humid environment for another 5 days.
Beams sides and soffit have a smooth fair faced surface off mould finish. The corbel of inverted T-beams and L-beams will have some minor blow-holes in the surface due to the casting method.
The beam top is usually fair faced, however, in cases where exposed reinforcement is needed, such as for composite structures, the surface will be made rough for better bondage to the top concrete.
Beam top is fair-faced, however in case exposed reinforcement, for composite structures, surface will be rough for better bond to the top concrete.
Quality control is performed according to Inventaa standard quality procedures in the well-equipped laboratories. The testing equipment is calibrated and maintained at fixed intervals to ensure the test results are at par.
The material used in production of concrete undergoes inspection and testing as per company inspection procedures. Comprehensive strength of concrete is determined by standard test cubes from the green concrete.
All moulds are individually checked before casting. The final product is checked and inspected to ensure it meets the required finish and is free from any snags.
All elements are cured as per British Standards and company procedures. During the curing period, the elements are regularly watered and kept covered with polythene sheets to retain the moisture around panel.
A full schedule of company standard quality control procedures can be requested from the Quality Department.
As a special service, we can offer a full Quality Control Report for the individual project consisting of casting dates, cube test and other quality checks for the particular project. This service should be agreed with our sales department.
TRANSPORTATION AND INSTALLATION
Both columns and beams are normally transported on flat-bed trailers and lifted directly from the trailer into position.
Columns are placed in the foundation and aligned using jacks. When using pocket foundations, temporary support can be removed after final alignment and grouting.
When proper curing of grouting is obtained the columns are ready to receive Precast beams.
Beams can either be placed directly on the column or on shims depending on tolerances and surface quality of the column. In some cases a dowel bar is projected from the column into the beam and a slotted hole is then provided in the beam.
The following consideration has been made:
A single span roof structure. Hollowcore slabs spanning 17m supported on prestressed beams spanning 10m.
|g = 1.00 kN/m2
|Insulation & roofing
|g = 0.25 kN/m2
|g = 1.50 kN/m2
|g = 4.95 kN/m2
|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 36/100-beam would be the most economical as the self-weight is only 75% of a RB 36/90-beam. 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.
The following deformations can be found using a IB 36/100-beam:
– 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
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.
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 are designed according to Quality Standards. The capacity of columns depends on the cross section, reinforcement, material properties, column length and combination of applied axial force and moment.
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 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.
RC-columns 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. CC-columns 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
SPECIFICATIONS AND TOLERANCES
GENERAL MIX SPECIFICATIONS
Min. characteristic cube strength fcu = 40 N/mm2 for normal reinforced beams and columns. For prestressed beams fcu = 60N/mm2.
OPC complying with requirements
Densified or undensified Microsilica grade 920 or 940.
Clean water with total dissolved solid contents not exceeding 700 p.p.m.
Water reducing admixtures complying with Standards.
Crushed aggregates complying with Standards.
All fine aggregates are sand complying with Standards.
All reinforcement steel complying with Standards.
All prestressing strands complying with Standards.
BEAM DIMENSIONS AND TOLERANCE
Length, L + 12mm or L/1000*
Height, h + 8mm
Width, w + 8mm
Side camber, a +8mm or L/500*
Camber, Csh +50%
Position of cut-outs +10mm
Position of inserts etc. +10mm
*whichever is the larger.
COLUMN DIMENSIONS AND 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 cut-outs +10mm
Position of inserts etc. +10mm
The capacity of the beams is based on Standards and is shown for simply supported beams in both curve and table format. The capacities are shown for maximum reinforcement and specified as Muls, Msls, quls and qsls. Where maximum reinforcement isn’t necessary we will specify a lower degree of reinforcement.
Muls is the ultimate moment capacity and quls is the ultimate load in kN/m that can be applied to the beam in excess of the self weight. Muls and quls may never be exceeded.
Msls is the service moment capacity and qsls is the service load in kN/m that can be applied to the beam in excess of self weight. Msls and qsls are based on stress limitations for class 2 members as per Standards. Our design office can verify the capacities at serviceability limit state for class 1 and class 3 members.
The capacity of class 1 and lass 2 members are usually controlled by the concrete tension and compression limitations for service load conditions, while class 3 members are usually controlled by ultimate limit state conditions.
The shear capacity shall be checked in each individual case.
The beams meet the requirements of 1.5 hours fire resistance as a standard, however this can be increased if required on individual projects.