How To Maintain Reinforcement Continuity At Concrete Joints?

The concept and use of reinforcement continuity strip systems or ‘pull-out bar’ systems have been widespread in Asia & Europe over the last 30 years and is widely accepted means of providing reinforcement continuity across construction joints in concrete. The system utilizes the concept of overlapping reinforcement to provide a connection.

The Moment Bar Box system consists of specially selected, high yield reinforcing steel, housed in a galvanized steel casing with ribbed surface to provide an effective concrete bond. The end of the unit is sealed with a polystyrene block in order to prevent the ingress of concrete.

The Bar Box reinforcement continuity is manufactured using a reinforcing bar that meets the requirements of the local reinforcing bar standard.

Why Use Moment Bar Box?

The product design ensures fast and easy fixing by nailing to the formwork. Alternatively, it can be wired back to the main reinforcement cage. The concrete is then cast. After removing the formwork. The cover is removed and the bars are quickly straightened using the specifically designed rebend tool. The steel casing remains embedded in the wall and is filled with concrete when the next section is poured, the dimpled surface providing an efficient key.

When compared to traditional joint construction methods, the product offers a cost-saving by means of a less labour intensive installation process and simplification of formwork with the removal of the need to drill shuttering. This contributes to the acceleration of the construction process. As the bars remain enclosed within the casing until required, they are protected and the risk of injury from projecting bars is minimized. Easy to use, the system requires little onsite training in order to carry out the installation.

Most joints in concrete, on many different types of construction sites, have the potential to be formed using Moment Bar Box. It has been supplied to high rise commercial buildings, water treatment plants, hospitals, prisons, energy from waste facilities and many more types of construction sites.

Typical Joint Application

  • Floor slabs
  • Walls
  • Stairwells
  • Corbels
  • Diaphragm walls
  • Jumpforms
  • Brick support ledges

Maintain Robustness Of Your Concrete Joints
Let Us Drop You A Call For Consultation. For Free.


How to Install Moment Bar Box?

Step 1

A Moment Bar Box unit is installed by firstly nailing through the casing to the shutter face. The casing is annealed at points to make this operation easier.

Step 2

With the Bar Box unit securely in place, concrete can be poured and the entire unit will become part of the first pour of the concrete and structure.

Step 3

With the formwork struck, the Bar Box lid and end caps can now be removed and discarded. The lap bars contained inside the case will now be revealed for rebending.

Step 4

Check the stirrups are completely clean.

Step 5

With the Bar Box casing opened, the lap bars can be bent out using the correct tool according to our installation guidelines.


Related Articles You May Be Interested


Read More

Precast Lifting’s Dos & Don’ts For Safety & Productivity

2 of the most challenging aspects of constructing with precast concrete are the lifting/handling and connections. In this section, we will deal with the dos and don’ts of lifting, moving and handling of precast concrete elements with regard to safety, productivity and cost-effectiveness.

This article will not cover topics such as installation or troubleshooting as those topics are already covered quite comprehensively by the individual suppliers in their literature. Instead, we will focus on the bigger picture issues that are preventing the industry from moving forward.

Traditional Methods

Still to this day, reinforcement U Bars and Post Tension Wires are still used as lifting points for precast concrete elements, but those using these types of lifting points do not understand the dangers that they are exposing the workers to. Most lifting designs do not have any built-in redundancy, so a failed lifting point will most often result in an element crashing down to the ground. Even if there are no casualties, a dropped element is often then scrapped as the damage resulting in a dropped element is too much to repair them.

The cost of using a proprietary lifting anchor is approx. 0.5% of the cost of a typical element and therefore can be considered as very cheap insurance against losing a piece of precast concrete. Not to mentions all the likely liquidated damages that could be incurred as a result.

The reason why rebars and post-tension wire are not suitable as lifting points is simply due to the fact that they are not designed for it. Both steels are designed to work in tension and although rebars can be bent, the ductility of the steel is always reduced after the bar is bent due to yielding in the extreme fibres of the steel. So much so, that there are discrete limits on the size of the radius that you are allowed to bend them to. Generally between 4d to 6d depending on the code and the diameter of the bar. Attaching a crane hook to a U Bar will result in the partially yielded bar to be further bent around a radius that is even small than those allowed in the rebar codes. Therefore the risk of failure increases significantly using either rebar or post-tensioning wire.

This failure was reported via the Confidential Reporting of Structural Safety (CROSS) website https://www.structural-safety.org/

There are some proprietary lifting systems available in the market that seem to call this suitability in to question but to understand it fully, you need to cut through the wire and look at the cross-section. The wire products sold for lifting have a 7 strand configuration, but the central core strand is made of a fibre core and not a steel core in the case of a post-tension wire. This allows the wire to be much more flexible and bend around a smaller radius than its steel-cored cousin.

2D Lifting

There are 2 very common ways of lifting 2-dimensional panels, namely, face lifting and edge lifting.

Face lifting is where a number of anchors are placed into the flat top of an element and the concrete is lifted in a flat position. This is commonly used for staircase landings, man-hole covers and floor units.

Edge lifting is where a number of anchors are placed along the thin edge of an element so that the concrete can be tilted up into a vertical position for storage and installation. This type is commonly used for shear walls, infill walls and façade panels.

The challenge with lifting and handling all precast components is the rigging required to attach the element to the crane but still allowing for the load to be equalised across all the anchors. Some real no-no’s for this would be if fixed-length chains or slings are used, or if you try and use a multiple of 3 anchors in any one lift, so 3, 6 and 9 anchors should only be used if absolutely necessary or with very advanced rigging to ensure the anchors are fully equalised.

Never Compromise On Safety!
Let Us Drop You A Call For Consultation. For Free.



3D Lifting

As we have moved towards PPVCs and PBUs the challenges associated with lifting have changed and in many ways become much more complex.

Often the element being lifted have a number of boundary conditions that we need to respect such as wall thickness, concrete weight and centre of gravity.

One of the biggest challenges associated with the lifting of these 3-dimensional elements is the weight of the element due to the availability and range of cranes available on site. There are a number of precasters exploring lightweight aggregates or the use of fibre reinforcement to reduce the weight of the elements, but many prefer to simply use thinner and thinner walls. The industry seems to be settling on a 90mm thickness for a PPVC wall, so back to back elements can provide a 200mm thick finished wall by backfilling the remaining 20mm with a cementitious grout.

The wall thickness will often mean that we need to use a lot more of a smaller capacity anchor rather than just a few larger capacity anchors. This, in turn, makes the equalisation of the loads even more challenging and most precasters prefer to use fabricated lifting frames to assist with the equalisation.

However, as most architects prefer to have a few different geometries in their buildings, it means that one standard lifting frame gets used for a variety of different geometries. Providing the frame is well designed, this can be a good way of minimalizing the capital outlay for a project, but excessive out of plane lifting should be avoided at all costs as this can result in the thin concrete wall spalling away and causing damage to the concrete or, worse still, a failure of the lifting point. Therefore the lifting frame should be designed to be as closely aligned to the wall geometry as possible.

Another challenge for 3-dimensional shapes that needs to be considered is the relative position of the anchors to the centre of gravity (COG). Providing the centroid of all the lifting points coincides with the COG when viewed in plan, then the element will be lifted flat with no tilting. However, as each PPVC might be slightly different, it is not practical to do this 100% of the time and some slight lifting or rotation is deemed to be acceptable.

One thing to be avoided wherever is that the centroid of lifting is lower than the COG. There are a number of exceptions to this, but in general, the element will be much more unstable than it would be if the centroid of lifting was above the COG.

Lifting In Thin Elements

The thin walls do create a challenge for lifting as you are required to place lifting anchors together with any required supplementary rebar (an additional bar near to, but not in direct contact with the lifting anchor) or complementary rebar (additional bar in direct contact with, or passing through the lifting anchor) into a very think section whilst respecting concrete cover and avoiding the mesh.

For Singapore, using supplementary rebars is not favoured by professional engineers, with most of them preferring to use anchors with complementary rebar, but the problem of placement still exists. According to SS EN 1992-1-1 the covered required to ensure bond transfer is just 1x bar diameter, so we only need a cover of 13 or 16mm depending on the capacity of the anchor being used. This makes it easier to fit inside the wall and transfer the lifting stresses into the concrete via bond transfer using the development lengths defined in SS EN 1992-1-1 Clause 8.4. One common trait that has been adopted by some professional engineers and needs to be stopped is the insistence on the complementary bars being the full height of the PPVC and returned under the slab at the base. This consumes an additional 7m+ of steel per lifting anchor which results in unnecessary and additional cost and additional embodied CO2 into the element which is bad for the bank balance and the environment. For a PPVC with 8 lifting points is results in about 90kgs of additional material with a cost of more than $70 per element that could be eliminated.

Health & Safety

The final, but the most important, piece of the puzzle is health and safety. At the moment, their elements are placed into position using a crane and then we need operators to climb up to the top of the element (3m+) just to disconnect the clutches and hooks. There are a number of remote release systems available on the market that contractors and precasters alike could consider and significantly improve the productivity and safety of precast operations on site.


Related Articles You May Be Interested


Read More

Never Make Safety Vulnerable For Any Reasons

An alarming change to common practices in coupler length are sweeping across India.

Couplers, or Mechanical Splices as are they are also called, are becoming a common method for connecting reinforcing bars together. However, from what we can tell, the way that couplers work is still greatly misunderstood by the vast majority of the Structural Engineering Industry. Therefore, the majority of Structural Engineers happily take the lead of the various standards organisations around the world who have written standards to empirically determine the performance of a system, but this has led to 2 key problems that jeopardizes the structural integrity of our concrete structures.

1. The samples are prepared by the supplier of the system and are usually prepared and installed perfectly. For obvious reasons, this perfect installation is not always possible on site due to manufacturing tolerances and site conditions.

2. The global standards and certification bodies that exist today, are mainly focussed on the initial proof of concept of a system rather than the on-going quality control. Even those bodies that have some element of on-going quality control do not simulate the on-site conditions.

In short, there is no “policing” of the quality control at site level.

For these reasons, most certified suppliers build in some additional robustness to allow for the issues that commonly occur on site, namely:

1. Imperfect thread lengths. There is a tolerance on the thread length that can easily result in the engagement of the 2 bars being 45% : 55% instead of the tested 50% : 50%.

2. Gaps between the rebars. In the case of prefabricated pile cages, it is impossible to have all the bars in exactly the same plane and as such a gap of up to 20mm between 2 bars could easily occur, again reducing the engagement of the thread.

As you can see, both of these will result in the same issue, that the engagement of the thread on the end of the rebar into the coupler will be compromised and a smaller engagement will occur. Thread length is defined to ensure that the amount of load transferred to each thread does not exceed the stripping capacity of that thread. If the stripping capacity is exceeded, then the failure mechanism will change to a stripping failure.

We therefore need to provide a sufficient safety factor against this that will also cover the typical onsite issues shown above.

In India, we have seen an alarming trend where people are marketing a “2D” coupler system where the length of the coupler has been reduced by about 20% to 2x bar diameter. It does pass all the necessary tests in the standard but does not perform well when you try to mimic the onsite problems listed above. We are sure it is only a matter of time before similar products appear in other countries as people strive for cost reduction, but we need to be aware that in this case, cost reduction is directly reducing the safety of the system.

Picture above showing shorter couplers 40mm failed tensile test.
Picture above showing Moment couplers 40mm passed tensile test.

We understand these issues and recently conducted some comparative tests and found that the 2D coupler strips with a bar gap of only 15mm, whereas the longer standard coupler that is marketed by certified suppliers continues to work properly well beyond this limit. This means that the total safety factor on the “2D” coupler is less than 20% even if the installation is performed perfectly.

Never Compromise On Safety!
Let Us Drop You A Call For Consultation. For Free.



Impact Of Coupler Strength With Reduced Embedment

  • Gaps between the bars of greater than 15mm fail with the shorter coupler, but still pass with the Moment coupler.
  • 40mm coupler with a reduced engagement of just 19% will result in a failure using the shorter coupler.
  • There is no factor of safety against failure of typical installation issues.

We should not be comfortable with this reduction in total structural safety and strongly urge structural engineers to investigate these topics more thoroughly and ensure the future robustness of our built environment for future generations.


Related Articles You May Be Interested


Read More

4 Ways To Connect Precast Concrete Wall To Foundation Effortlessly

When considering the best options for your building project, the benefits of going with a concrete wall panel system are many. By choosing a concrete wall panel system, these features may provide advantages that can be enjoyed by owners, architects, engineers and contractors on site. The benefits include:

  • Energy efficiency
  • Environmental reliability
  • Aesthetically attractive
  • Minimal preservation
  • Speediness of construction
  • Onsite Productivity

To enjoy the benefits, we must make sure the connection between the precast elements and of the precast walls to foundation is robust enough to ensure the safety and integrity of the structure. Here are 4 main ways to connect precast wall panels to foundation.

Corrugated Duct

Casting Corrugated Duct into the precast element is the traditional method to connect precast walls to foundation. Corrugated duct is used as a hole former for a variety of precast and cast-in-situ concrete works. The hot dipped galvanized metal duct is strong and durable for casting into precast walls and then to be connected with rebars from the foundation.

Although duct has been a commonly used method for precast connections, one of the major disadvantages of duct application is the huge amount of grout needed to fill up the duct in order to secure the connection between the precast wall and foundation.

Eventually, this traditional method will increase the cost and time of the overall construction.

Corrugated Duct 1 Corrugated Duct 2 

Grout Coupler

Specifically for precast connections, Grout Coupler can be used for connecting precast walls, columns, beams either horizontally or vertically. The most popular connections used with Grout Coupler are:

  1. Precast concrete column to foundation connection
  2. Precast column to column connection
  3. Precast beam to column connection
  4. Precast wall to foundation connection
  5. Precast wall to wall connection

The rebars protruding from the foundation are simply inserted into the grout coupler, which has been casted in the precast wall. When pumped with Moment’s proprietary 100MPa grout, the grout coupler system is a bar break technology and is capable of carrying very high bar loads regardless of the rib profile on the reinforcing bar.

Although this is not the most popular application of grout coupler but the application of grout coupler for precast wall to foundation is still widely accepted in the market.

Grout Coupler 1 Grout Coupler 2Untitled design (1)

Precast Shoe

Mainly used for connecting precast column and foundation, Precast Shoe can also be used to connect precast wall panel to foundation. They are especially suitable for anchoring in flat structures such as the foundations or walls that have sufficiently large edge distance.

The advantage of this precast system with screw connection is the quick assembly. The connection is easy to adjust with a healthy tolerance and immediately loadable so that bracing is not required which results in less labour at site. However, they are not specifically designed for walls and therefore have a limitation on the wall thickness and thin walls cannot be connected using this type of product.

The system comprises of the precast shoe (cast into the precast wall) and the suitable anchor bolts (cast into the foundation) for the foundation base. Both elements are joined by load bearing nuts during assembly on site.

Wall Shoe 1 Untitled design (2) Untitled design (4)

The Most Cost Efficient Way To Connect Precast Wall To Foundation : Wall Shoe

Specifically designed for precast wall to foundation connection, the Wall Shoe system provides a bolted type connection, also described as ‘dry joint’ or ‘mechanical connection’. This product can be used for connecting precast wall or elements, either horizontally or vertically including thin wall application down to as little as just 100mm thick.

The system consists of Wall Shoe casted into a wall section and Anchor Bolt on the foundation. When they come together, there is a generous tolerance to ensure that the relative accuracies of in-situ and precast concrete can be easily accommodated. The assembly can then be simply secured using a locking plate and high strength nut.

Compared to the 3 methods above, wall shoe has the most cost efficient design as it requires the least grout to secure the connection on the foundation, which leads to enormous time gain.

Column Shoe 1 Wall Shoe 2 Untitled design (5)

Stop Compromising on Quality.
Let Us Drop You A Call For Consultation. For Free.


Related Articles You May Be Interested  


Read More

The Fastest Way to Connect Precast Wall to Foundation

Moment Wall Shoe system provides a bolted connection between precast concrete walls and foundations or two precast concrete walls.

The system consists of Wall Shoes and Anchor Bolts on the base. When they come together, the assembly is secured using a locking plate and high strength nut. Wall Shoes are cast into precast concrete walls, whereas Anchor Bolts are cast into foundations or other walls.

On site, the walls are erected on adjusted shim plates in the correct position and fixed to the Anchor Bolts with nuts and special washers as bolt connection. Precast concrete wall connections are finalized by grouting the recesses and joints underneath the wall.

Wall Shoe  Moment Wall Shoe

Example of Moment Wall Shoe application for precast wall

There are many benefits of using the Moment Wall Shoe System including high safety standards through connecting precast elements, shorter construction time and thus lower cost. In addition to these, below are the some of the key benefits:

1. Can be used for thin walls

This product can be used for wall thickness from 100mm. It will not risk the design of the wall while maintaining the safety and robustness of the building.

Moment Wall Shoe

2. Immediate load bearing

Moment Wall Shoe serves as a connecting elements inside bracing wall construction. Both the tensile force acting perpendicularly to the joint and the transverse forces in the longitudinal axis of the joint can be absorbed and transmitted. This solution offers the advantage of the fast, simple and safe connection of precast concrete elements by simply bolting them together.

Moment Wall Shoe

3. Minimal grout usage

After the wall have been installed and the nuts and washers are screw tightened, the connection is then ready for grouting. It should be grouted by following the instruction for grout mixing and it must be a non-shrinking type. The volume of the grout use for this system is lesser compared to the conventional method using corrugated duct and thus decreasing the overall cost and installation time.

Moment Wall Shoe

See How Easily You Can Connect Precast Wall To Foundation


1. The wall is installed on pre-levelled shim plates after being cast in the concrete.

Wall Shoe Installation 1

2. The nuts and washers are screwed into the foundation anchors and tightened.

Wall Shoe Installation 2

3. The connection is ready for grouting after placement and adjustment of the wall element to the foundation.

Wall Shoe Installation 3

4. The finalized connection after grouting has hardened.

Wall Shoe Installation 4
Wall Shoes are designed to withstand tension forces corresponding to the design values of resistances of Anchor Bolts. Both components are pre-designed so that the system have sufficient resistance against actions caused by external loads.

 

Create Effective Bolted Wall Connections Today.
Let Us Drop You A Call For A Consultation. For Free.


 

Related Articles You May Be Interested

 

Read More

The Secret Of Precast Wall To Wall Connection

Construction of precast walls are very rigid since the element are inherently stiff to begin with. Therefore, it is important to detail the connections in such a way to ensure robustness in the event of a natural disaster such as earthquake and absorb its energy to avoid complete collapse.

The Secret to Precast Wall Connection

There are a number of challenges when connecting precast walls, namely:

1. Connections are wet, so require temporary bracing.
2. Installation time can be lengthy, so crane time is not optimised.
3. Connecting of both vertical and horizontal rebar connections is practically impossible due to the stiffness of the rebars.

At Halfen Moment, we have a solution for all of these challenges, but here we would like to address the third one as it is arguably the most important fundamental.

So What is Moment Wire Loop Box?


Wire Loop Box are used for connecting precast wall to wall or to a column. After casting to the formwork, the precaster will just need to remove the tape and release the loop into the operating position. A vertical rebar (sometimes called a trimmer or cottering bar) is installed into the joint through the wire loops. Lastly, cementitious grout is poured or pumped into the joint.

The Secret to Precast Wall Connection

There are 3 types of Moment Wire Loop Box – Multi, Double and Single Loop Box.

The Secret to Precast Wall Connection

Wire loop boxes are installed to the formwork according to the spacing specified by the designer, before the panel is cast.

The Secret to Precast Wall Connection The Secret to Precast Wall Connection

A vertical rebar is installed into a joint through the wire loops of both precast panels before grouting.

Key Advantages


Fully compliant with EN1992-1-1 (Eurocode 2), Moment Wire Loop Box has been tested in accredited test labs to simulate performance in various application, transmitting forces from three directions (perpendicular, parallel and transverse load).

Below are the key advantages of wire loop box when compared with the traditional method of connecting precast walls:

  1. Flexible installation method for seamless connection between precast wall
  2. Reduces the total installation time by 50% with less labour
  3. Eliminates the clashes between U-bars from the traditional method
  4. Customizable length of steel box and wire loops
  5. Easy installation of wire loop box to the formwork with the option of magnet

The Secret to Precast Wall Connection

Multi wire loop box acts as a shear key and simplify the design of the formwork.

The Secret to Precast Wall Connection

Making precast wall connection easier and faster

Key Features


Consists of high-strength, galvanized steel casing and wire loops, wire loop boxes connect precast walls in an efficient and time saving method. Below are the key features of wire loop box:

Galvanized Steel Box
A robust sheet-steel box and wire loops contain the plastic latch and wire loops

Plastic Latch
Specially designed plastic latch to secure the wire loops in position for good anchorage embedment for in concrete
9.png The Secret to Precast Wall Connection

Flexible wire loops
Galvanized wire loops transmit force into the concrete and connect 2 walls to each other. Loops can be bent out and straightened with a hammer claw, screwdriver or a nail.

The Secret to Precast Wall Connection   The Secret to Precast Wall Connection

 

Wire Loop Box Makes Wall Connection Easier.
Let Us Drop You A Call For Consultation. For Free.


 

Related Articles You May Be Interested

Read More

Precast Connections You Must Know In 2020

Structural Connections For Precast Concrete Buildings

The precast joint connections on construction sites has always been a difficult challenge due to manufacturing tolerances and the need to transfer loads through the structure; even more so when you factor in a required resilience to a seismic events. Precast components are inherently stiff, so it is essential that the precast concrete connections are robust enough to allow the structure to absorb the energy of the earthquake, whilst providing enough robustness to avoid collapse.

There are a number of ways of doing this such as via:
• Grouted Coupler for precasts walls and columns to foundations connection
• Wire Loop Box for precast walls connection
• Precast Coupler for precast elements connection
• Dowel Systems for precast beam to column connection

Apply the latest technology of precast connections from Halfen Moment, available in Malaysia, Singapore, India & Philippines. Discover more now!

Moment® Grout Coupler

Grout coupler are traditionally used in the bottom of a column or wall as a means to connect on to starter bars protruding from the foundation. Although they might often be designed as a pin connection, the reality is that this will transfer moment from the foundation in to the wall or column and should therefore always be made of a ductile material that does not compromise the ductility of the steel reinforcement that it is coupling together. To that end, the coupler should always be of a “bar break” type where there is a considerable factor of safety between the bar failure and the coupler failure capacities.

Moment® Wire Loop Box

Wire loop boxes are prefabricated components with a constant rebate geometry and 1 or 2 high strength (c. 1600-1800MPa) wire loops. Loops from adjacent elements then overlap during installation of the panels and are secured using a reinforcing bar and a high early strength grout to complete the connection.

They are usually used to connect 2 adjacent precast panels together, where the interlocking rebar and wire loops provides robustness in the event of an Earthquake to ensure that grout degradation would not result in complete collapse.

Loop Box Used on Site

Moment® Connection Loop

Connection Loop is a single-wire loop used to connect 2 precast boxes for the prefabricated prefinished volumetric construction (PPVC).

In order to connect 2 precast elements, both precast elements has to be cast with the Moment® Connection Loop at the wall. A rebar will then be inserted through the intersection of 2 loops. After placing the rebar, the gap between the precast elements will need to be grouted using a 40Mpa or 70MPa non shrink grout depending on the application. Material strength of the Moment® Connection Loop is 1770N/mm  and complies to EN12385-4:2002+A1.

Moment Connection Loop PPVC

HEK Precast Coupler

The HEK Precast coupler is an innovative and versatile solution for fast and easy connection of precast concrete elements.

Cast-in DEMU Fixing anchors i.e. T-FIXX®, bolt or bar anchors transfer the tension and shear force into the precast element.

The main advantage of the system is the fast and efficient positioning of precast elements. The connection can be subjected to load immediately after installation. This results in a substantial improvement in construction time.

 HALFEN HEK Precast couplerHEK Precast Coupler Application with DEMU Fixing Anchor

Invisible Connections

Shear dowel systems are always a challenge as they generally require very tight tolerances to ensure effective load transfer, so systems without grout and oversized holes are almost impossible. Traditionally, precast slabs such as stair landings used to be supported by a steel angle bolted to the wall. Installation was slow, required high degrees of accuracy, tied up the crane with costly hook- time and could only be used on straight walls.

But by keeping the grouting to a minimum, one such technology – Invisible Connections – has revolutionized the use of precast all throughout Northern Europe; it is a patented system, with its origins in Norway, to connect precast concrete without use of corbels or steel angles, and is used extensively throughout Europe due to the independently tested and certified European Technical Approval (ETA [4]) that provides engineers with peace of mind about the capacities.

The product range of Invisible Connections consists mainly of TSS Telescopic Stair Connectors & BSF Telescopic Beam Connectors.

85  BSF Telescopic Beam Connectors

Another topic relating to Invisible Connections will be covered as a future topic in our Academy site.

 

There are many good technologies available, but a dependence on local testing and local reference projects will hinder and slow down their introduction. An increased readiness to accept the certification schemes for prequalification that exist overseas such as ETA[4] and ICC certification where appropriate, will mean that the technologies can help keep pace with the requirements of the precast industry.

 

Stop Compromising on Quality.
Let Us Drop You A Call For Consultation. For Free.


 

Related Articles You May Be Interested

 

Read More

Your Only Rebar Coupler For Precast Connections

Ideal Coupler For Precast Connections

The connection between precast concrete is a safety critical component in today’s structural precast construction. The success of this construction method goes beyond the structural performance of precast beams and columns; it also includes the performance of the precast connection. For the connection, the performance is not only limited to the structural robustness, but also embodies simplicity and productivity during the erection process. The connection types employed will not only affect the construction cost and speed but also have an impact on the sections that can be used via the ability for forces and moments to be redistributed throughout the finished structure.

Moment Grout Coupler, consists of a one piece design, is a rebar coupler designed for precast connections. Compliant with ISO 15835, each grout coupler combines the benefits of the Moment JT threaded system and will achieve barbreak when used together with Moment’s proprietary 100MPa grout.*

Specifically for precast connections, Grout Coupler can be used for connecting precast walls, columns, beams either horizontally or vertically. The most popular connections used with Grout Coupler are:

  1. Precast concrete column to foundation connection
  2. Precast column to column connection
  3. Precast beam to column connection

1. Precast Concrete Column To Foundation Connection

For this type of connection, the high tensile steel starter bars are left protruding from the foundation. After that, a precast column with vertical sleeves at the end is placed over the starter bars. The sleeves are the filled in with grout to provide a connection. This connection has the ability to provide moment resistance at the connection between column end to footing. Additional technologies such as precast shoes can then be used to eliminate the need for propping.

1Grout Coupler

2. Precast Column To Column Connection

Similar to the above application, this enables the launching of one column section on top of another one whilst providing full moment continuity across the joint. This is specifically important on projects with large column sections as the height of the element is often limited to less than 1 storey because of crane capacity limits.

IMG_2553

3. Precast Beam To Column Connection

You can use grout couplers to overcome one of the biggest challenges in precast concrete construction; a moment resisting frame. In this application, you provide clearance holes through the precast column and use a grouted coupler to provide full continuity through the precast column.

Picture1

To broaden the field of application, two product types are available: Full Grout Coupler and Half Grout Coupler. The rebars used with a Full Grout Coupler require no bar end preparation, such as threading, and are simply inserted to meet at the nominal centre point of the coupler.

For more information on Moment Grout Coupler, please contact our offices where we can showcase you the actual Grout Coupler as well as our latest innovative precast accessories.

*Lower grout grades might be possible, but it depends on the rib profile of the individual rebar supplier.

Connect Precast Elements The Easy Way.
Let Us Drop You A Call For Consultation. For Free.


 

Related Articles You May Be Interested

Read More

How To Connect ‘Mistakenly Shortened Rebars’ At Site?

There are 2 common methods to connect reinforcement bars.

The traditional way of connecting rebar is by overlapping 2 rebars, with typical lap lengths of between 30 and 50 times the diameter of the rebar in accordance with EN1992-1-1.

The modern way of connecting rebars is by using a mechanical splice system; a mechanical connection between two pieces of rebar that enable the bars to behave in a manner similar to continuous length of rebar. Most mechanical splices join rebar end-to-end along with the rebar threads, providing many of the advantages of a continuous piece of rebar, which is more reliable. Read more: Mechanical Splices VS Lap Splicing

MBC- The Ideal Coupler for Remedial & Repair Works


If the rebar lap length was shortened by mistake, we will not be able to connect both rebars if:
1) The lap length is less than that specified for a particular application.
2)  There is no way we can thread on either side of the rebars at site/ the rebars are being planted vertically

Like any other engineering problem, this situation may have other solutions like welding, drilling in additional rebar, depending on the site conditions, codes, materials used and the structure that is going to rest on this foundation.

However, the best way to connect this is the Moment Bolt Coupler (MBC), a bolted coupler which does not require any rebar preparation, designed for the connection of two rebars which haven’t been previously threaded.

Each MBC coupler features a serrated hollow body which will grip the rebar. A number of bolts along one side will press the bar against the serrations and lock both bar ends and complete the connection.

Bolts Designed to Shear Off at a Specified Torque


MBC coupler is a cost effective method of joining reinforcing bars, particularly when the fixed bar is already in place and there is insufficient space for a hydraulic swaging press. Below are the benefits of MBC coupler.

• No threading required. Installation can be done by using a wrench.
• Bar ends are supported within the coupler by reversed teeth on the internal wall, and as the lock shear bolts are tightened, the conical ends embed themselves into the bar and press the bar on to the teeth.
• Excellent for remedial & repair works where one bar is already fixed in concrete.
• Capacity load higher than 108% characteristic yield strength of grade 500 reinforcing bar.
MBC Bolted Rebar Coupler
Nut runner is strongly recommended to tighten the bolts for higher precision and faster installation.

 

The Simplest Way To Join Short Rebars.
Let Us Drop You A Call For A Consultation. For Free.


 

Related Articles You May Be Interested

The Bolted Coupler Which Does Not Require Rebar Preparation

Read More

[First in Malaysia] CREAM Certified MOMENT Mechanical Splicing System

Halfen Moment is proud to announce that we are the first company in Malaysia to receive quality certification in accordance to ISO 15835 standard by Construction Research Institute of Malaysia (CREAM), an independent and transparent certification body in Malaysia under CIDB which delivers certificates of conformity to companies that manufacture or fix on-site concrete reinforcing steel or their accessories. 

View our CREAM Certificate

TODAY, the demand for efficient splicing systems have become increasingly important due to increased construction complexities, design requirements, escalating costs and limitations of traditional lap splicing methods. This has driven the need for alternatives that provide both structural robustness and cost effectiveness.

Why So Many Construction Structures Collapsed- How Safe Are We?

With all these catastrophes all around the world, Malaysia has been exposed to the stark reality that we can no longer be considered immune to such tragedies of tragic proportions in term of lives lost, property destruction and even economic collapse.

The government and regulatory bodies have therefore taken serious steps in reviewing current building regulations and codes, to enable structural engineers and constructors to take immediate and necessary precautions to ensure the safety of their design as they are liable if anything happened to the buildings. (refer provisions under CIDB act)


*MS 2500 (Profile) Enforced 1 December 2016 Consultation with industry and testing body on 5 January 2017: Testing requirements for design requirements are not clearly stated. The meeting agreed to adopt AS4600 and EN9590 Part 5 in addition to MS2500. CIDB has submitted the MS2500 revise application to DSM on January 6, 2017.

MOMENT JoinTec ‘Barbreak’ Connection

MOMENT JoinTec ‘Barbreak’ mechanical connections conform fully with applicable codes including BS 8110 Pt 1:1997 Clause 3.12.8.16.2 Bar in Tension and ISO 15835. MOMENT JoinTec ‘Barbreak’ Mechanical Connections actually provide defined ductile behaviour and performs like continuous reinforcing bars Fig 1. MOMENT JoinTec ‘Barbreak’ Mechanical Connection performs in excess of the ultimate strength point of the bars.


Fig 1: MOMENT JoinTec ‘Barbreak’ mechanical connections perform beyond the yield point of the bar whereas Lap Splices are only defined in the elastic area. This indicates that the MOMENT ‘Barbreak’ connection which work as a continuous bars provides additional strength and safety all round independent of the quality of the surrounding concrete.

Design Codes and Specifications

In reinforced concrete design, the Structural Engineer is faced with the task of determining where and how reinforcing bars must be spliced in a structure. This must be done to ensure that the national regulations are adhered to and also to make sure that the structure will not suffer a progressive collapse if overloaded.

Due to the minimum connection strength required, it is generally assumed in design that the occurrence of a mechanical connection of two reinforcing bars does not result in a reduction of the anticipated structural strength nor the longitudinal ductility of the reinforcing steel. This would maintain the properties which the reinforced concrete member would have had with a continuous unspliced bar. That is, it is assumed that the use of a mechanical connection does not introduce a structural weakness that could jeopardize the overall structural performance.

Design requirements of the applicable codes as in BS 8110 and EN 1992-1 generally assume a minimum connection strength, but are silent on the details about test methods and conformity assessment. ISO 15835, which is used as the basis for CREAM’s assessment covers all aspects of coupler production and assessment including:

  1. To assess the serviceability, a test is made on a representative gauge length assembly comprising reinforcement of the size, grade and profile to be used and a coupler of the precise type to be used, the permanent elongation after loading to 0.6fy should not exceed 0.10mm,
  2. It also covers tests for couplers to be used for mechanical splices in reinforced concrete structures under predominantly static loads and additional requirements for couplers to be used in structures subjected to high cycle elastic fatigue loading and/or to low cycle elastic-plastic reverse loading to represent seismic activities.

MOMENT JoinTec ‘Barbreak’ Mechanical Connection and Seismic Design

In a structure undergoing inelastic deformations during an earthquake the tensile stresses in reinforcements may approach the tensile strength of the reinforcements. The requirements for MOMENT JoinTec ‘Barbreak’ mechanical splices are intended to avoid a splice failure when the reinforcement is subjected to expected stress levels in the plastic regions. In addition to that, in plastic hinge regions, the first part to fail is the concrete where excessive spalling occurs. Once the concrete spalls, the lap splice behaviour is severely compromised, whereas the mechanical splice behaviour remains intact.


Lap Splices (2011 – Turkey) – Concrete spalling results in lower or zero capacity as the concrete that is critical in the load transfer has disappeared.


Mechanical Splices (2017 – Mexico City) – Concrete spalling has no effect on capacity as the mechanical connection is still present.

In seismic consideration:

  1. MOMENT JoinTec ‘Barbreak’ connections promote full strength capabilities and offer in tension more than the specified ultimate strength of the reinforcing bars ensuring that rupture will only occur in the reinforcing bar before failure in the mechanical connection.
  2. MOMENT JoinTec ‘Barbreak’ connections are manufactured to the exact standards to withstand a breaking strength of more than 700MPa  thereby promoting adequate strength and ductility so that failure initiates in the concrete rather than the steel reinforcements in the event potential inelastic straining may occur during seismic excitation.

Conclusion

MOMENT JoinTec ‘Barbreak’ connection offer many advantages to the designer and builder to help improve design and reduce construction time and cost while providing versatility and can help to solve many construction problems today.

As Malaysia progresses in nation building, federal governance, regulations and codes for construction regarding seismic frame construction become more stringent, MOMENT JoinTec ‘Barbreak’ connections, the proven mechanical splice method, provides you with the ability to design and build concrete structures to withstand the test of time.

cream rebar coupler

 

 

Locally Approved Couplers For Quality Connections.
Let Us Drop You A Call For Consultation. For Free.


 

Related Products You May Be Interested

 

Read More