MK4 Post Tensioning System
MK4 has been developed based on complete Quality Assurance Programme conforming to ISO 9001:2000 and according to the requirements of the new European code ETAG-013 for Post Tensioning, including the design, production, supply and installation of all the required PT works, as anchorages, auxiliary equipment; pushing strands, stressing and injection. By this way, this complete quality system covers all Post Tensioning work performed by MK4 system.
MeKano4 is a specialized company that offers technical solutions for the construction of bridges and structures, by providing to the market a wide product and service range leading quality and services around the world.
The MK4 Post Tensioning System proposed, includes a gear range of anchorages, accessories and the necessary equipment to respond to the technical requirements for the construction of bridges and other structures. The design and calculation of all the components were performed according to the new European code ETAG-013, which verification is an obligation in all Post Tensioning structures built in the European Union.
As application, we are providing MK4 Post Tensioning system for any structure as bridges, buildings, tanks of liquefied gas LNG, silos, covertures, communication towers, nuclear power stations, suspended structures, etc.
MK4 POT Bearing
POT bearings are structural bearings which support vertical and horizontal loads and permit limited rotation around any horizontal axis and have therefore, an extremely wide range of applications.
They can be designed and manufactured for practically any load in a temperature range between -20ºC and 50ºC and have actually been tested for vertical loads up to 100.000 kN.
MK4 bearings are widely used in structural, marine and civil engineering applications, and particularly in bridges. Bearings are available in carbon steel as standard and in stainless steel for applications where corrosion is a potential problem.
MK4 bearings are designed to meet the requirements of the European Standard EN 1337-5 and have the qualification of the CE mark. Nevertheless, MK4 can also supply pot bearings complying with other standards, upon request.
MK4 POT bearings are available in three main types: type PF (Fixed), type PG or PT (longitudinally Guided sliding or
Transversally guided sliding), and type PM (Multidirectional or free sliding). All three types allow rotation. Fixed bearings provide restraint in all horizontal directions. Guided bearings allow movement in one horizontal direction and provide restraint in the other direction. Free sliding bearings allow movement in all horizontal directions. All three types utilize a confined elastomeric principle which enables the product to support high pressures. The inherent properties of the confined elastomeric material allow it to shift much like a viscous liquid upon rotation, offering minimal resistance.
As well as traditional bearings capable of accommodating loads, movements and rotations for standard structures,
MK4 is also well placed to provide customized solutions to suit specific requirements such as:
- Special bearings for Incremental Launching
- High rotation capacity
- Temporary restrictions of movement
- Temporary direction of movement
- High horizontal forces
- Anti seismic bearings
- Uplift bearings
- Shear Pins
- Special anchoring system
MK4 DMK Stay Cable System
The DMK Stay belongs to the latest parallel strand cable stay generation.
Stay is based on a bundle of self-protected prestressing strands that run inside a global polyethylene duct. Strands are anchored through the wedge system in the DMK anchor heads.
The following premises have been taken into consideration for the DMK Stay design:
- Stay behaviour according to the most relevant international recommendations
- Wide size range
- Easiness of installation
- Unitary stressing (strand by strand)
- Adjustable anchorages for full stay stressing or distressing
- Force checking or monitoring at any time.
- Replacement of the stay, as a whole or each strand individually
- Prepared for damper installation
- Adaptable for special solutions
Stay anchor heads have been tested according to the PTI Recommendations for Stay Cable Design, Testing and installation and have achieved the following successfully:
– Dynamic behavior: 2 million cycles, 200 N/mm2, upper load limit 45% GUTS
– Static efficiency: 95% of GUTS (Guarantied Ultimate Tensile Strength)
Basic stay is fully sealed to avoid the entrance of water inside and comprises at least 4 protective barriers to the steel of the strands at any point, this warrants the maximum durability of the tensile element against corrosion.
Standard sizes are composed of 7 to 127 strands with 0.6” diameter.
The strand to be used can either be 15.2 or 15.7 mm. nominal diameter.
The strand holes at the anchor heads and inner deviators are large enough to allow the self-protected strand and its envelope to go through. These characteristics allow the insertion “in situ” of the strands from the outer surface of one of the anchor heads, avoiding the need to pre-cut or pre-peel them before threading. This advantage reduces threading time and considerably makes the stay installation easier. It also permits the replacement of a stay strand by strand as stressed strands do not impede the access or movement of the one being replaced.
All DMK anchorages either adjustable or fixed types, allow unitary stressing with a monostrand jack. This gives freedom to decide where to place the adjustable end for global stay force checking or regulation and where to stress strand by strand.
Moment® Flat Slab System
Moment® Post Tensioning (MPT) System is designed and tested to meet stringent standards. The range of buildings and civil engineering applications includes:
• Commercial and residential high rise
• Retails shopping centers
• Load transfer structures
• Slabs on grade
• Silos and reservoirs
• Ground anchoring and earth retaining
Moment® Flat Slab System is normally adopted for bonded tendon. The strands are individually gripped in one triangle flat anchor head unit and transmit their pre-stressing forces by means of flat type anchor plate casting unit. The strands are stressed individually by means of a mono strand jack. The strands are contained in one flat duct (duct size: 20mm x 70mm) which is made of corrugated galvanized metal.
To ensure corrosion protection and to give adequate bond strength, the tendons are filled with suitable cement grout mix after complete stressing of the strands. Facilitating of concrete placing due to the absence of tendons in the webs, and ease for placing tendons.
Moment® Flat Slab System significantly reduce the amount of concrete and reinforcing steel required.
Moment® Post Tensioning Dead End Anchorage
Moment® Multi Strand Round System
Moment® Multi Strand Round System is a method of reinforcing and pre-stressing concrete, masonry and other structural elements. Today, it is used for a wide range of applications including office buildings, condominiums, hotels, parking structures, slab-on-ground foundations, ground anchors, storage tanks, stadiums, silos, and bridges.
The systems are normally adopted for bonded tendons. The tendons consist of a bundle of strands with a nominal diameter of 0.5″ (12.7 mm.) or 0.6″ (15.2 mm.). The number of strands per tendon can be from 4 strands up to 42 strands of diameter 0.5″ or 31 strands of diameter 0.6″. The strands in the tendons are contained in one round duct which is made of corrugated galvanized metal.
The strands are individually gripped in one anchor head unit and transmit their pre-stressing force by means of an anchor plate casting unit. For each anchor size, special spiral reinforcement is provided at the anchor plate casting to give adequate splitting reinforcement for bustling stresses developed at the anchorage zone. The strands in tendon are stressed simultaneously by means of a multi strand stressing jack from capacity 1,100 KN up to 5,000 KN. The strands can also be stressed individually by means of mono jack.
The Strands are formed with seven steel wires: one central wire around which the other six are wrapped. They are generally supplied already stabilized (low relaxation) and certified according to the regulations by an independent laboratory, in coils weighing kg 2500-3000.
Usually greased or waxed strands, incased in a HDPE sheath, commonly called unbounded, are used to manufacture the external tendons. Such Strands can be hot-dip galvanized too.
|Appearance||Nominal Dia (mm)||Tensile Strength (Mpa)||Relaxation (1000h)||Standards|
left or right lay
The Stressing Jack is placed over the strand and when tensioning starts they are automatically and simultaneously engaged in the pulling head of the jack. Once the required elongation and load are reached the lock-off device of the jack can be activated to house the wedges in the anchor head uniformly. The tensioning can be accomplished in more steps basing the elongation of the cable. A tensioned cable can be released using proper releasing device.
Stressing Jack will be removed after stressing and anchoring. In post-tensioning the prestressing force is applied directly to the concrete. In the case of pre-tensioning the anchor holds the strands until after the concrete has gained sufficient strength; the strands are then released, transferring the prestressing force to the concrete.
Cables are normally grouted after sealing their anchorages with the concrete or; if required, using the proper grouting caps. Before grouting the tendons, they should be flushed to ensure that no obstruction would impede the flow of the injected grout.
The sandless grout, injected using MPT grouting pump, is keep under pressure during its curing. The water-to-cement ratio is kept as low as possible. Usually the proportion of ingredients are: 36-38 liters of water, 100kg of cement and additive according to the instruction of the manufacturer. The mix produces 72-74 liters of grout.
Moment® Corrugated Duct
Moment® Corrugated Duct is used as a duct former for a variety of precast and cast-in-situ concrete work. The semi-rigid hot dipped galvanized metal duct is strong and durable for casting into concrete and is easily tied into position adjacent to reinforcing steel. It is available from 40mm to 120mm (OD measurements) and also customizable according to the length and diameter needed.
Corrugated Duct can be used for service penetrations, post tensioning ducts and precast connections.
The key benefits and features for Corrugated Ducts are as per below:
• Wide range of diameter available (ID 40mm to ID 120mm)
• Quantity as per the site requirement can be manufactured
• Easy benchmarking and thus production schedule
• Customer friendly – Bendable and can be cut as per customer requirement
• Ease of placement at site: Durable and tough
• Corrosion protection with hot dip zinc coating
Shapes of Moment® Corrugated Ducts are available in Circular, Rectangular and Oval.