Post-Tensioned Bridges & Infrastructure
Bridge decks, viaducts, and civil engineering structures in prestressed concrete for optimized spans.
Post-tensioning in civil engineering structures
Post-tensioning was born in the field of bridges and remains the reference technology for concrete civil engineering structures. Since the first prestressed bridges designed by Eugene Freyssinet in the 1930s, the technique has continually evolved to enable ever-greater spans, faster construction, and more durable structures.
A post-tensioned bridge deck uses high-capacity prestressing cables (T15S or T15 Super strands, grouped in units of 12, 19, 27, or 37 strands) housed in metal or HDPE ducts. After stressing and anchoring, the ducts are grouted with cement grout to protect the cables against corrosion and ensure bond between the steel and the concrete.
Construction methods
Cast-in-place on falsework is suited to bridges of medium span (20-50 m) in accessible areas. The deck is cast in place on temporary shoring, then stressed.
Balanced cantilever construction enables spans of 50 to 200 metres without ground-level shoring. The deck is cast in symmetrical segments from each pier, with each new segment prestressed against the previous one. This method is particularly suited to crossings over deep valleys, rivers, and traffic routes that cannot be interrupted during works.
Precast segmental construction combines the advantages of precasting (controlled quality, speed) with those of post-tensioning (long spans). Segments are manufactured in a factory, transported to site, and assembled by post-tensioning. This method allows a long-span bridge to be built in weeks rather than months.
Advantages of post-tensioning for bridges
Post-tensioning reduces the number of piers needed by increasing the span of each bay. Fewer piers means fewer deep foundations — often the most expensive element of a bridge project. For a 200-metre crossing, a post-tensioned bridge with 3 spans (60+80+60 m) replaces a reinforced concrete bridge with 8-10 spans, cutting foundation costs by a factor of three.
Durability is enhanced by the permanent compression state of the concrete and by the protection of the cables (cement grouting or greased sheaths). A well-maintained post-tensioned bridge has a service life of 100 years or more, compared with 50-75 years for a reinforced concrete structure exposed to freeze-thaw cycles and reinforcement corrosion.
In the African context, post-tensioning offers a major logistical advantage: prestressing cables, which are light and compact, are easily transported to remote sites, while the quantities of concrete and passive reinforcement are reduced. For isolated construction sites where material supply is a challenge, this resource optimization is decisive.
Typical applications
BEPCO works on road bridges (national roads and motorways), pedestrian bridges, motorway interchange overpasses, urban viaducts, and port infrastructure (quay walls, jetties). Our team masters on-site stressing techniques, elongation monitoring, and duct grouting in accordance with international standards.
Key Benefits
50-200 m spans
Balanced cantilever or segmental construction for the most ambitious crossings.
Fewer piers
50-70% reduction in deep foundations — the most significant saving.
100+ year service life
Compressed concrete and protected cables for exceptional durability.
Construction without falsework
Cantilever and segmental methods allow building over water or live traffic.
Frequently Asked Questions
What is the maximum span of a post-tensioned bridge?
Post-tensioned concrete bridges routinely achieve spans of 50 to 200 metres using balanced cantilever construction. The world record for a prestressed concrete bridge is 301 metres (Shibanpo Bridge, China). In Africa, spans of 80-120 metres are commonly built for river and valley crossings.
Is post-tensioning used for bridges in Africa?
Yes, the majority of modern bridges in Africa use post-tensioning. BEPCO has been involved in the construction of bridges and civil engineering structures in several West African countries. Post-tensioning is particularly suited to the African context because it reduces the quantities of materials to be transported to often remote sites.
How does post-tensioning reduce the number of piers?
By increasing the span of each bay. A conventional reinforced concrete bridge spans 15-25 m per bay, requiring numerous closely spaced piers. With post-tensioning, each bay can reach 50-100 m, dividing the number of piers by 3 to 5. Since pier foundations often account for 40-60% of the total cost of a bridge, this reduction generates substantial savings.
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