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Rapid Load Test code published by BSI

 

The BSI (British Standards Institution) has recently published the code for RLT in the UK (BS EN ISO 22477-10:2016). This code describes  Geotechnical investigation and testing; Testing of geotechnical structures; Testing of piles: Rapid Load Testing (RLT).

 

The StatRapid is fully compatible with this code and can be used to determine the static bearing capacity and load settlement behaviour of foundation piles.
 

The code can be purchased in the web shop of the BSI.

http://shop.bsigroup.com/en/ProductDetail/?pid=000000000030292492

 

For more information on StatRapid or Rapid Load Testing you can always contact Allnamics.

 

Do you want to read more about RLT on our website? Click here to search for RLT.

 

Best Wishes for 2017!

kerstkaart-2016

Research project DOT500 – Vibratory Driving Prediction and Analysis

 

On May 6th 2016 a monopile foundation has been vibratory driven into the ground for a full-scale test of a newly developed wind turbine.

 

Allnamics performed vibratory driving predictions in order to quantify the required vibro hammer (CV320). During actual installation Allnamics performed so-called VDA monitoring. The Vibratory Driving Analysis results in records of strain and acceleration in the pile. This offers the possibility to verify assumptions made for the prediction and consequently effectively close the double loop of the learning system.

 

The time-lapse presented below offers an impression of the monopile installation.

 

 
 
If you want more info about VDP or VDA?  Contact us!
 
More info about the CV320 or Cape Holland ?
 
More info about the DOT500 ?

 
 

StatRapid testing at Yara Sluiskil

 

On the 4th of July 2016 Allnamics checked the capacity and stiffness of 4 production piles (Fundex-type), commissioned by contractor Ballast Nedam Industriebouw BV.

 

The piles are part of the tank foundation for the UREA Granulation 8 Project on the production yard of Yara in Sluiskil, the Netherlands. Rapid Load Testing system StatRapid has been deployed, with which, following CUR guideline 230, the load-displacement behaviour of the piles has been determined.

 

The proof load testing was a contractual requirement and the (positive) results are regarded as representative for the entire tank foundation. Consequently the foundation slab has been cast with high confidence in the foundation design.

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Dynamic Pile Testing for Amstel Towers Hotel in Amsterdam

 

In April 2016 Allnamics has performed PDA-monitoring and DLT-testing for our client Voorbij Funderingstechniek BV, for the Amstel Towers Hotel near Amstel station in Amsterdam. The tests were done on 51 m long precast concrete piles, driven in sections, with a mechanical joint.

 

PDA monitoring (Pile Driving Analysis) was done during full installation cycles of selected production piles. Main goal of the test was to check the tensile stresses during driving, in particular at the location of the mechanical joint.

 

DLT-monitoring (Dynamic Load Testing) was done during restrike (approx. 10 blows) on piles that had been installed a couple of days earlier. Main goals of this test were to check the strength of pile shaft and joint and the static bearing capacity  of the pile.

 

Both tests were performed with the in-house developed Allnamics PDR-system, fitted with combined strain and acceleration sensors, which were mounted near the pile head. The PDR reads and stores the monitoring data real time and transmits them with a wireless connection (by WiFi) to the field computer of the monitoring engineer. The wireless connection offers great advantages during upending and positioning of the pile and makes it possible for the monitoring engineer to do his monitoring job on a good location, at a safe distance from the pile and without traditional worries about the long cable getting stuck or damaged during handling or piling.

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Photo 1 : Monitoring with WiFi connection, at a safe distance from the pile

The tests showed that the tension stresses during driving were acceptable and that the available static bearing capacity is sufficient for the design loads of the piles.

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Photo 2 : no trouble with long cables during upending of the pile

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Photo 3 : pile and monitoring equipment at end of PDA

New Axilog Vibration Monitoring Systems

 

On July 21, 2016 Allnamics received two axilogII systems from Leiderdorp Instruments BV. These state of the art vibration monitors will be deployed on those Allnamics projects where the vibration levels have to be recorded in accordance with BS, SBR or DIN guidelines and where online real time monitoring has to be performed.

 

AxilogII Systemen overdracht

Photo 1 : AxilogII systems received by Allnamics.

A big advantage of the axilogII vibration monitors is that tracking can be done from anywhere, whether from your or the client’s office, or even at home. Also, the axilogII can be programmed with multiple alarm levels, which allows  an early  warning in the event the actual thresholds are approached. In case of long-term monitoring it is also possible to automatically generate reports.

Photo 1 : The brand new AxilogII systems.

Photo 2 : The brand new AxilogII systems.

For more information about performing vibration measurements or if you want to take a vibration monitoring course you can of course contact us.
 
For more information about the axilogII vibration monitoring system we like to refer to the website of Leiderdorp Instruments http://axilog-uk.leiderdorpinstruments.nl/.

 

Recorder function of PDR used for offshore PDA-test

 

In september 2015, Allnamics was asked to monitor stresses in the flange and on the inside of a monopile for an offshore windfarm, during installation of the pile with an impact hammer. Special challenge was that all the instrumentation had to be mounted on the inside of the pile, with limited space AFoto01available for placing sensors and equipment. On top of that, drilling and welding were not allowed and the test had to be completed within 3 weeks after the first enquiry. The recorder mode of the Allnamics PDR, ingenuity and improvisation made it possible!! AFoto02

 

The instrumentation consisted of 2 acceleration sensors placed vertically, 2 horizontal strain gauges on the flange and 4 vertical strain gauges on the inside of the pile wall; this setup also incorporated a “normal” PDA (Pile Driving Analysis) setup. 2 PDR-systems were used for data acquisition of these 8 channels, with the acceleration sensors used for triggering.

 

Challenges

Main challenge for this project was that the instrumentation had to be installed on the inside of the pile, because of the hammer sleeve. Obviously this would make it impossible to establish a wireless connection to a computer on the vessel. But a cabled connection was also not possible, because the pile did not contain a cable outlet hole or snorkel hole near the pile head and below the hammer sleeve.Measuring on the inside of a pile without any communication from the outside was solved by using the Allnamics-PDR in recorder mode. All monitoring data were saved and stored in the PDR-systems during pile installation and transferred to a computer after they were retrieved from the pile.

 

Figure 1 : Configuration D: PDR operating in recorder mode

Figure 1 : Configuration D: PDR operating in recorder mode

 

The required battery life time of the PDR needed to be approximately 12 hours. The installation cycle was expected to be around 3000 blows By using an external battery the monitoring time could be extended to 12 hours. The standard memory is already able to record 10.000 blows.

 

Positioning of sensors

Next challenge was the restrictions imposed by the space that was needed for the grippers of the upending tool and an airtight platform that had to be mounted inside the pile, before removal of the equipment. This required mounting of the instrumentation above the platform, less than 1 m below the pilehead. All in all very little space for positioning the sensors and recorders was left.

 

Photo 1 : The gripping tool just before pile upending

Photo 1 : The gripping tool just before pile upending

 

 

Photo 2 : airtight platform in mobilization port

Photo 2 : airtight platform in mobilization port

 

Photo 3 Finding space to place sensors and monitoring equipment (pile in horizontal position)

Photo 3 Finding space to place sensors and monitoring equipment (pile in horizontal position)

 

Mounting of sensors

The next challenge was the way to mount the acceleration sensors and the PDR-systems without drilling holes in the pile or welding on the pile. For the strain gauges (and their tension relief) this was solved by glueing them on the pile. For the acceleration sensors this was solved by adapting their housing, so they could be bolted to the earthing stubs that were already inside the pile.

 

hoto 4 : Earthing stub used for mounting the acceleration sensor and the strain gauge glued directly on the pile

Photo 4 : Earthing stub used for mounting the acceleration sensor and the strain gauge glued directly on the pile

 

For suspension of the PDR-systems this was solved by placing wooden stub between the flange and the platform ring. The stubs were kept in position by using the bolt holes in the flange and the stiffener plates of the platform mounting ring. Each PDR was suspended between 2 stubs, with elastic bands.

 

Photo 5 : One of the 2 PDR’s mounted between 2 wooden stubs (pile in horizontal position)

Photo 5 : One of the 2 PDR’s mounted between 2 wooden stubs (pile in horizontal position)

 

Execution of the project

Next challenge was to prepare and monitor the project within 3 weeks from the first enquiry. The mounting of the sensors had to be done outdoors, in the mobilization port prior to pile installation on site. Conditions were quite hostile that day, cold and very windy!

 

 

 

Photo 6 Installing the sensors from a cherry picker: 2 acceleration gauges & 6 strain gauges

Photo 6 Installing the sensors from a cherry picker: 2 acceleration gauges & 6 strain gauges

 

But al sensor mounting and glueing went smooth and successful. After all these challenges were solved, there was one more left: Allnamics had no monitoring specialist available in the planned time frame for the offshore testing campaign….  Luckily our German partner company Fichtner could provide us with one of their specialists to do the job offshore!  The PDR’s were successfully retrieved and had recorded all blows, giving the client valuable information of the pile during driving without disturbing the production process.

 

Photo 7 : The piles on deck of the installation vessel

Photo 7 : The piles on deck of the installation vessel

 

Photo 8 : Bringing the pile in position

Photo 8 : Bringing the pile in position

 

Photo 9 : Hammering down the pile down

Photo 9 : Hammering the pile down

 

Photo 10 : Exciting moment: just after lifting the hammer

Photo 10 : Exciting moment: just after lifting the hammer

 

Photo 11 : The equipment after pile installation and installation of the airtight platform.

Photo 11 : The equipment after pile installation and installation of the airtight platform.

 

In case you are interested in more information on Pile Driving Analysis or the PDR, please feel free to contact us.

Referee StatRapid deployed for foundation new building Shipping- and Transport College

 

On March 21st 2016 a ‘Rapid Load Test’ has been performed according to CUR guideline 230 on a Terr-Econ pile in the Waalhaven, Rotterdam.

 

Immediate cause was the hypothesis, based on SIT results, of a crack being present just below the rebar. StatRapid par excellence is ideal to verify in such cases whether a crack will close when the pile is being loaded. If so, the pile is perfectly fit to be loaded in compression and can therefor be included in the foundation. The test results in a cyclic Load-Displacement diagram (analogues to a Static Load Test), from which the pile stiffness under work load can be extracted.

 

Foto 1 : Overview of the project location.

Foto 1 : Overview of the project location.

For more information on the StatRapid or Rapid Load Tests you can contact us.

 

 

8MN RLT near Jaarbeurs exhibition centre in Utrecht (NL)

 

In March 2016 Allnamics has performed a 800-ton Rapid Load Test (RLT) on a busy square between Utrecht Central Railwaystation and Jaarbeurs exhibition centre. The test has been performed with the 4/8 MN StatRapid device.

 

The test has been executed together with Brem Funderingsexpertise. With the 4/8 MN StatRapid device, produced by Cape Holland and developed together with Allnamics, loads up to 800 ton (8 MN) were generated, using a drop mass of 40 ton.

 

Photo 1 : 4/8 MN StatRapid device on site at Jaarbeursplein in Utrecht.

Photo 1 : 4/8 MN StatRapid device on site at Jaarbeursplein in Utrecht.

 

The most important test results are available on site (graphical and numerical) on the screen of the field computer direct after each load cycle. That enabled local construction authorities and the main contractor to evaluate the first test results already on site. The printed report was available on the next day.

 

Photo 2 : The StatRapid ready for testing.

Photo 2 : The StatRapid ready for testing.

 

Photo 3 : First evaluation of test results direct after a load cycle.

Photo 3 : First evaluation of test results direct after a load cycle.

 

Compared to traditional static load testing (SLT) StatRapid has the advantage that the required reaction mass can be reduced from 800 ton to 40 ton, the required footprint for testing can be reduced tot approx. 4x4 m² and the total time needed for mobilization, testing and demobilization can be reduced to 1 working day. At the same time the accuracy of RLT results is equal to SLT results for piles in sand, with the results elaborated with the unloading point method, according to the Dutch guide line CUR 230. The same method has been adopted by the Eurocode for Rapid Load Testing, which will be published later in 2016.

 

Compared to dynamic load testing (DLT) StatRapid has the advantage that the accuracy and reliability of the results are much better. Main reasons for that is the fact that load and displacement are measured directly with loadcells and an optical displacement system (instead of derived from strain and acceleration with DLT) and the fact that elaboration of the unloading point method for RLT is user-independent, whereas the elaboration of DLT requires many assumptions and is therefore user-dependent.

 

Compared to Statnamic (another way of doing RLT) StatRapid has the advantage that it does not use combustion fuel and igniters. Storage, transport and use of those are subject to strict regulations, making the test method more expensive and more complex. Next to that, with the StatRapid it is very easy to apply multiple load cycles.

 
For more information on StatRapid or Rapid Load Testing you can always contact Allnamics.
 

VDA monitoring at research project in Middenbeemster (NL)

 

In March 2016 Allnamics has participated in a research project on the relation between vibro driving of sheet piles and the vibrations in an adjacent building. Allnamics’ contribution was monitoring strains and accelerations in the sheetpile during driving and extraction. The monitoring was done with the wireless Allnamics PDR-system and the in-house developed VDA (Vibratory Driving Analysis) Software.

 

From the measured strains and accelerations the VDA software derives relevant data like frequencies, forces, penetration speeds, stresses and displacement amplitudes. After installation the data can be presented and reported as a function of penetration depth or as single time traces.

 

Photo 1 upending sheet pile with monitoring equipment

Photo 1 : Upending sheet pile with monitoring equipment.

 

Photo 2: PDR with combined strain and acceleration sensors

Photo 2 : PDR with combined strain and acceleration sensors.

 

Photo 3 : Vibro driving of sheet pile right next tot he building.

Photo 3 : Vibro driving of sheet pile right next to the building.

 

The acceleration sensors used for VDA are 10 times more sensitive than the standard sensors that are used for PDA (Pile Driving Analysis) during impact driving. Because the sensors are equipped with our USID (Universal Sensor IDentification), the PDR can automatically detect the sensors, retrieve the sensor data and calibration factors and apply them during monitoring. So there is no need for manually entering sensor data and calibration factors, which often causes (human) errors when preparing the equipment.

 

Other companies involved in the research project are Fides Expertise, TNO, Leiderdorp Instruments and Hektec . The piling rig and test building were provided by piling contractor Gebr. Van 't Hek BV

 

For more information on VDA monitoring or the research project you can contact us.