1. POST-TENSIONING CONSTRUCTION FOR SLAB / BEAM IN BUILDING, FACTORY
Post-tensioning system is applied to construct the slab with thinner concrete section and longer spans between supports in comparison with conventional reinforcement concrete. Post-tensioned (PT) slabs are typically flat slabs, band beam and slabs or ribbed slabs.
PT slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. This technique will help designers to enjoy clear open spaces for more architectural freedom, as well as to reduce total self-weight of structure and decrease the clear height from ceiling to floor of each level. Longer spans can be achieved due to pre-stress, which can be used to counteract deflections. Thanks to the above efficiencies, post-tensioned concrete technique is applied in a wide range of structures as high-rise buildings, factories, industrial infrastructure…
2. POST-TENSIONING TRANSFER BEAM/ TRANSFER SLAB IN BUILDING, FACTORY
In some cases of office buildings, hotels or hospitals..., it is sometimes needed to transfer at a certain level, some of the vertical loads to other alignments so as to obtain bigger spans at lower levels, which brings a much spacious for public buildings project. The transition from the smallest grid structures to larger column spacing is done by means of a transfer structure (with beams or slabs).
Post-tension solution is absolutely a very effective way to perform a transfer beam or transfer slab with smaller dimension and better deflection control compared to conventional reinforcement concrete beam or slab.
For post-tensioned transfer beam/ slab, the amount of normal reinforcement needed for flexion design is drastically reduced; the arrangement is simplified and any early age shrinkage cracking in concrete is effectively controlled.
3. POST-TENSIONING SLAB ON GRADE
Post-tensioned beam/ slab (foundations) on grade uses high-strength steel to actively reinforce residential foundations to minimize cracking and increase performance.
Post-tensioned industrial ground floors system allows thinner uniform crack-free elastic slab. It also offers an economic solution in regard to greater durability, higher loadings bearing and minimized maintenance or repair costs.
Structural Functions of Slabs-on-Ground are as below:
- Acts as a buffer between the soil below and the superstructure above to prevent unacceptable deformations in superstructure.
- Post-tensioned beam/ slab (foundations) on grade is designed to resist or span over moisture-induced deformations in the soil below, while still maintaining its top surface within permissible level tolerances.
4. POST-TENSIONED GROUND ANCHORS
Pre-stressed rock and soil anchors have become an important tool for the geotechnical engineers. Their safe and reliable use in both permanent and temporary applications is accepted throughout the world.
Soil Anchors, Rock Anchors are high pressure grouted anchors into soil ground with the anchor system installed before grouting work. The anchors transfer forces into the ground by means of a steel tendon and a well-defined grout body.
Those are the applications of soil anchors, rock anchors:
- Anchor the wall of excavation pit in basement construction.
- Anchor the supporting wall, beam.
- Stabilize the bank, dam in hydraulic construction.
- Stabilize and reinforce the structure with pier segment for bridge or high way.
- Stabilize the slope.
- Structure solution for deep foundation.
5. POST-TENSIONING CONSTRUCTION FOR SLAB / BEAM IN BRIDGE AND SETTLEMENT OF ROAD
Post-tensioning solution is ideally suited for pre-stressing long span girder at the site of construction, or bridge pier segment, without the need of costly factory type installations like pre tensioning beds. Post-tensioning technique is ideally suited for post-tensioning work. In this method a number of segments can be pre-stressed resulting in an integrated structure.
Post-tensioning system makes it possible to bring cost-effective solution in bridge construction, along with long spans, high intrinsic durability and enable to construct quickly, limit cracking, reduce structural depth and save maintenance cost.
6. POST-TENSIONING WALL OF SILO - TANK
Advantages of using post-tensioning system in tank construction:
- It provides the required resistance to the acting forces;
- It makes possible solutions more economic than those achievable with reinforced concrete or steel.
- It renders the concrete virtually free of cracks.
Namcong is committed to improve the standard of design and construction in the post-tensioning industry and we are a founding corporate member of the Post-Tensioning Institute.
The Post-Tensioning Institute of Australia (PTIA) was formed to represent the post-tensioning contracting industry in Australia, seeking to maintain a viable and competitive industry with high standards in design and construction of post-tensioning systems for the benefits of its members, employees, and clients.
The objectives of the PTI are:
- To ensure that the post-tensioning contracting industry is both viable and competitive
- To promote high standards in design, construction and materials for post-tensioning systems, consistent with world best practice, and verified by certification of its Corporate and Associate Members
- To develop industry work standards which establish appropriate skills of employees, personal development opportunities, a safe working environment, and environmental responsibility, and
- To achieve ongoing technical advances in materials and systems for post-tensioning.
It is many times required that modification has to be considered should any changes arise in building use or to the building codes. These modifications could involve cutting openings, such as those for stairs, elevators, and escalators, without generating any problem to existing structure.
NAMCONG has succeeded in researching and applying openings cutting solution and also been awarded the Intellectual Property Certificate for Neo Zip system, which is a valuable contribution to post-tensioned slab modification techniques.
Cutting holes and openings in post-tensioned slabs requires specific method conducted by our experienced personnel with specialized equipments. This process involves locating tendons, excavating concrete around tendons, detensioning and cutting the tendons, and re-anchoring them at the edge of the new opening.
This method is indeed essential for any projects that are deteriorated, expires its service life but requires upgrading or encounters any unexpected faults. This repair process involves in the repair and replacement of damaged tendons, which is preceded by a thorough investigation to the cause.
In various cases of changing loading, usage modification, incorrect construction practices, structure damage or even error in design process.
Post-tensioning system shall offer an optimal and economical solution for strengthening considered structure. A deep consideration shall be taken on every details such as tendons profiles, supports, anchorages, in order to implement strengthening in beam, floors or even removing columns.
External post-tensioning can be used for new structures as well as for existing structures needing strengthening. This technique has been used for various types of structures with reasonable compression characteristics.
Particularly, this technique shall be a priority solution to be considered in cases of substandard concrete, badly cracked concrete structure or any unexpected faults.
For this technique, the tendons are not installed inside the cross-section structure, the anchor system is installed externally. After completion of construction, the anchor and tendon are covered with epoxy painting or grouting for further protection.