01
Section Analysis
Spans, loads and anchorage layout are assessed against post-tensioning requirements.
Post-Tensioning
Solutions
OUR PROCESS
Post-tensioning process
02
Quotation
Tendons, ducts and stressing equipment are specified in the post-tensioning package.
03
Prestress Design
Prestressing force and losses are calculated in the post-tensioning design.
04
Detailing
Duct, anchorage and grouting details are drawn up.
05
Preparation
OHS measures, the stressing area and equipment are mobilised to site.
06
Stressing
Post-tensioning tendons are stressed under control, with every stage recorded.
07
Handover
The stressing report and anchorage protection are handed over to the operator.
EXECUTION
Post-tensioning with
controlled prestress
01Silo Solutions
Analysis
The need for post-tensioning in a bridge, silo or wall section is established using a load model.
02Silo Solutions
Engineering
Tendon geometry, anchorages and grouting are resolved on a single post-tensioning drawing.
03Silo Solutions
Post-Tensioning Works
Stressing is carried out in stages, with every step recorded. A tension report is issued at handover.
ABOUT THE SERVICE
Post-tensioning for
controlled spans and stiffness
Post-tensioning is an engineering method in which high-strength steel tendons in selected zones of a reinforced-concrete structure are stressed after the concrete has been cast, introducing a controlled compressive force into the structure. It can be used to achieve long spans, control tensile stresses in reinforced-concrete members and make more efficient use of cross-sections in certain structures.
The system can be used in a wide variety of structures, from bridges and slabs to water tanks and large reinforced-concrete silos. However, the tendon layout and stressing forces must always be determined by the structural design of each individual structure.
In silo projects, post-tensioning may be incorporated specifically to control hoop tension in large-diameter reinforced-concrete structures. The horizontal pressure exerted on the silo walls by the stored material makes the circumferential load-bearing system particularly important.
Rayf Teknik's slipform experience on tall reinforced-concrete structures helps establish the correct construction sequence on post-tensioned silo projects. As the silo shell is raised by slipform, the post-tensioning ducts, anchorage zones and other embedded items must be prepared in accordance with the design elevations.
Slipforming and post-tensioning are not the same process. The first is a method of constructing the reinforced-concrete structure; the second is a stressing technique used within the structural load-bearing system. The two can, however, be used together on the same silo project, which is why the site teams must work from shared construction drawings rather than independently of each other.
Once the concrete has reached the required strength, the tendons are stressed to the design values. Recording the stressing forces and inspecting the anchorage zones are key stages of the process. In bonded systems, the tendon ducts are also grouted as required by the design.
On post-tensioned silo projects, installing the tendon system details correctly as the slipform rises reduces the need for later modifications to the hardened concrete. All details relating to the stressing system must therefore be communicated to the site team before concreting.
Drawing on its experience in reinforced-concrete silos, slipforming and industrial structures, Rayf Teknik focuses on ensuring that, on projects incorporating post-tensioning, the construction method progresses in harmony with the other structural components. The aim is not merely to carry out the stressing operation, but to ensure that the structural behaviour envisaged in the design of the reinforced-concrete structure is achieved on site through correct construction details.
TECHNICAL SPECIFICATIONS
Post-tensioning technical specifications
Post-tensioning tendons, anchorages and stressing records are planned to suit the cross-section. Typical values are finalised through the site survey and structural analysis.
#
Specification
Value
01
Scope
Post-Tensioning Solutions
02
Category
Steel & Erection
03
Site
Tall structures and reinforced-concrete sections
04
Execution
Project-specific
05
OHS
In line with the site programme
06
Handover
With survey records and documentation
TECHNICAL ADVANTAGES
Why post-tensioning?
Post-tensioning increases spans, controls cracking and can allow slimmer sections. The benefits are assessed point by point.
RAYF
Prestressing
Post-tensioning tendons place the section in compression, improving span capability and crack control.
01
Prestressing
Post-tensioning tendons place the section in compression, improving span capability and crack control.
SERVICE GALLERY
Post-tensioning project gallery
01 / 12
Post-tensioning solutions by Rayf Teknik
OTHER SERVICES
Services offered alongside post-tensioning
View Details ↗
Bridge & Viaduct Piers
Bridge piers and viaducts
PierBridge
SlipformMethod
ViaductApplication
Geometry, verticality and load-bearing capacity are critical for bridge and viaduct piers and pylons. Tall wall-section pier shafts are raised using controlled formwork methods.
View Details ↗
Reinforced-Concrete Silos and Storage Structures
Konya Çimento / Topkapı Şişe Cam
10,000 tSilo
SlipformMethod
KonyaSite
Reinforced-concrete silos are designed to store large volumes of bulk materials. Product loads, the discharge system and process connections define the geometry of the shell.
View Details ↗
Silo Slipform Systems
Ilgın / Konya — cement plant
BİKİLTAŞClient
SlipformScope
KonyaSite
Silo slipforming allows tall reinforced-concrete silos to be built in one continuous pour. Concreting, reinforcement fixing and hydraulic lifting advance together in a single coordinated production cycle.
View Details ↗
Structural Steel
Seza Yapı — Seydişehir road construction site
Seza YapıClient
HangarFabrication & erection
SeydişehirSite
Structural steel delivers high load-bearing capacity for platforms, galleries and production buildings. It is also used to support equipment lines connected to reinforced-concrete structures.
POST-TENSIONING SUPPORT
Get support from
Rayf Teknik for your
post-tensioning projects.
We prepare site surveys and quotations for post-tensioning work on bridges, viaducts and silos.
Information & FAQ
Frequently asked questions about post-tensioning
Where post-tensioning is used, how stressing is recorded and how anchorages are protected.
What is post-tensioning?
Post-tensioning is a prestressing method in which steel strands or tendons are stressed once the concrete has gained sufficient strength, placing the section in compression. The member is cast with ducts or sheaths left in place; the tendons are then stressed and anchored. This compression increases span capability, limits crack widths and improves deflection control. It can be used in bridges, silos, water tanks and tall walls. Stressing stages are recorded, and grouting and protection form part of the handover.
Prestress losses arise from friction, wedge seating and shortening of the concrete. If the calculation ignores these losses, crack control will not be achieved. On site, whenever the measured elongation deviates from the calculated value, the stressing stage is reviewed.
Which structures use post-tensioning?
Typical applications include bridge and viaduct piers, deck elements, silo walls, water tanks and long-span industrial slabs. The common requirement is to limit cracking and deflection under service loads. For each structure, tendon geometry, anchorage pockets and stressing sequence are calculated separately. Limited site space and crane access influence the choice of method. During the site survey, the cross-section, spans and adjacent works are assessed together.
The tendon profile in a deck and a vertical tendon in a pier are not the same detail. Using the wrong template means missing an anchorage pocket, so the geometry of each member is drawn separately.
Can post-tensioning be combined with slipforming?
Yes – and on most tall silo or wall projects the two are planned together. If post-tensioning ducts, anchorage zones and embedded pipes are not placed at the correct elevations as the slipform rises, concrete will have to be broken out later. For this reason, the stressing calculations and the slipform programme are developed on the same drawings. Tension is applied once the concrete strength is sufficient for stressing. At handover, both verticality and stressing records are provided.
The slipform does not wait for stressing; stressing waits for concrete strength. The two schedules are therefore linked. Premature stressing can cause the anchorage to crush the concrete.
What records are provided at post-tensioning handover?
Stage-by-stage stressing values, anchorage type, grouting status and protection details are entered in the handover file. Measured elongations are compared with calculated values, and any deviation is explained. The maintenance note covers protection of the anchorage pockets and the elevations for any future intervention. Open items are closed out during the site walkdown. From these records, the operator can track the prestressing history of the structure.
If an anchorage pocket is left unsealed, corrosion will eat away at the prestress. Protection – whether paint or mortar – is a handover item, and operators must never use the pocket as a storage recess.