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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 3 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.

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.

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.

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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 Leviat, 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 Loop Box?

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

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

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

Key Advantages

Below are the key advantages of 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 loop box to the formwork with the option of magnet

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

Making precast wall connection easier and faster

Key Features

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
 

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.

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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 Leviat, available in Malaysia, Singapore, India & the Philippines. Discover more now!

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.

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.

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.

 

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.

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.

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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

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.

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.

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.

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.

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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 terms 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 below).

*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 JT 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, providing defined ductile behaviour and performing like a continuous reinforcing bar.

Fig 1: MOMENT JT connections perform beyond the yield point of the bar whereas Lap Splices are only defined in the elastic area. This indicates that the MOMENT JT connection which works as a continuous bar provides additional strength and safety all around independent of the quality of the surrounding concrete.

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.

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 JT 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 JT 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 JT 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.

MOMENT JT connection offers many advantages to the designer and builder to help improve the 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 JT connections, the proven mechanical splice method, provides you with the ability to design and build concrete structures to withstand the test of time.

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With the advent of Industrialized Building System (IBS), there is one aspect of the supply chain that has remained unregulated and subject to risk of poor quality solutions creeping in to the market place that might be structurally unsound. This largely comes from the fact that the metallurgy of these connections is critical to their suitability, so the selection of the right steel is vital to ensure their performance.

Metallurgy plays a crucial role in enabling sustainability

When construction methods changed to IBS, there was a sudden influx of new technologies to assist in the connections of the precast element; but there is a natural lag before product codes can catch up and provide the same level of total robustness as traditional construction methods.

IBS approach has been widely adopted, as it reduces construction time frames compared with conventional methods.

While the scope of BS8110 did not cover all of these new connections, at least there were some minimum requirements for the mechanical splicing of reinforcing bars.

Thankfully, the CIDB in Malaysia realised that there was a gap and has identified CREAM* as a certification body who can provide the same service locally to provide confidence to the users, purchasers and specifiers of constructional steels and to ensure its safety and reliability, government, private and/or non-profit bodies. However, for other more advanced technologies, where no standards exist today, this type of certification is not possible as CREAM needs a standard to audit against.

For these the engineering community needs to better understand the metallurgy and ensure that the products are fit for purpose. But at least for mechanical splices, the publication of ISO 15835:2018 means that CREAM certification is now possible.

*The Construction Research Institute of Malaysia (CREAM) is a research and development (R & D) institution for the construction industry in Malaysia. Committed to ensure that R & D programs meet the needs and requirements of the national construction industry by implementing quality management systems that meet MS ISO 9001.

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The East Coast Rail Link (ECRL) (Malay: Laluan Rel Pantai Timur) is a planned standard gauge double-track railway link infrastructure project. The construction began in August 2017 was suspended from July 2018 to April 2019. The project was continue with revised construction cost and southern alignment of the rail link.

ECRL will be connecting 6 different states starting from Selangor going to Wilayah Persekutuan Putrajaya, Negeri Sembilan, Pahang, Terengganu and stops at Kelantan. This project effectively connects the West Malaysia & East Malaysia with efficient time & cost management for customers.

There will be a total of 14 passengers only stations, 1 freight only station and 5 combined passengers & freight stations. MRL aims to ensure customers’ comfort towards the whole journey.

This project that costs RM44 billion cuts the travelling time of West-East Malaysia to 4-hour with total of 640km versus average of 7-hour drive for 474km. Now we can avoid long ride during festive seasons and opt for cheaper options than flying on plane or helicopter.

Any railway project will not be completed without interchange stations – and ECRL will not missed the opportunity for increase accessibility for their potential users. Currently, the project aims to have 3 interchange stations with Keretapi Tanah Melayu Berhad (KTMB), Express Rail Link (ERL) presently connects KL Sentral and KLIA and Mass Rapid Transit (MRT) that connects Sg. Buloh to/from Kajang.

There will be 2 service provided by ECRL namely Passenger Train that can speeds up to 160km/h and Freight Train that speeds up to 80km/h. This development too will include with double tracking for simultaneous ride to and fro at any point of the track.

The development of the ECRL will encourage economic growth along the corridor, many business opportunities will rise with this project. Upon announcement of this project, there are 1,321 submissions from Construction Industry Development Board (CIDB), break down to – 859 submissions or 65% are of G7 category of CIDB-rated companies, 134 submissions from Grade G5, 132 submissions from Grade G4 and 104 submissions and 92 submissions from Grade G3 and Grade G6 respectively. The project also encourages bumiputera participation that consists of 994 bumiputera engineering and construction companies representing 75.25% of the overall registration.

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