Post Tensioning

POST TENSIONING

Post-tensioning, or PT, has become increasingly popular over the past few years, as the technology has been perfected with better materials and construction methods has made this system a preferred one. PT works are predominantly used in most projects that are currently in progress in Bahrain.

ARMCON established its Post tension division in 2016 and provide structural solution for civil engineering projects. Post tensioning of the concrete structure is cost and time effective for almost all medium to large span structure. Economy in the project can be achieved by considering correct structural framing. Our in-house engineering team often works with consultant and client to match up the requirement.

ARMCON post tension unit provides customer single window solution from conceptual design of structure to execution. All the structural design checked by a Bahrain registered structural engineer, matching the required standards.

Pre-stressing steel in housed in sheathing duct, allow moving of strand as tension force applied to strand after gaining sufficient strength of concrete. Strand elongate as it istensioned and locked into the place by using anchoring component, that keep mechanical connection between strand and anchorage device and keep the force in to the strand throughout life span. Elongation result should be checked and verified by the engineer before cutting excess strand. Cementitious grout is poured in to the duct after filling hole with cement and sand mortar. This is called Bonded Post tension.

MATERIAL

STRAND

A typical strand used in Post tension having tension strength of 1860 N/mm², in comparison typical non Pre - stressed rebar having 460 N/mm². Strand is manufactured from 7 individual cold - drawn wires, outer wires helically wound around one center wire (king wire) as per code, Strand coatings do not affect the anchorage’s capacity or efficiency. For improved corrosion protection we offer systems using galvanized iron ducts.

SHEATHING

The materia l for the duct shall be high density polyethylene with more than 2% carbon black to provide resistance to ultraviolet degradation. The thickness of the wall shall be 2.3±0.3mm as manufactured. The duct shall be corrugated on both sides. The duct shall tran smit full tendon strength from the tendon to the surrounding concrete over a length. The duct shall be sufficient strong to retain shape and to resist damage during construction.

ANCHORAGES

The pre stressing force is transferred to the concrete at the anchorage. Anchorage where the stressing take places are called active anchorage, and the other are called passive anchorage. Sometimes stressing is made from both ends of a tendon to reduce friction losses. The anchorage shall be safe and secure against b oth dynamic and static loads as well as impact.