Ports

Widely used for the construction of a variety of structures such as quay walls and breakwaters in harbours, bank reinforcements on rivers and canals, underpasses, as well as global hazard protection schemes, sheet piles have proven their performance in seismic areas in many countries around the globe.

Chile, the country that has suffered the strongest earthquakes in recorded history, provides an excellent example: Whereas its concrete-based ports have been severely damaged, the Port of Mejillones, constructed in 2003 using an HZ®/AZ® combined wall for the quay wall and AS 500 straight web sheet piles for the breakwater, has not suffered any damage throughout many heavy earthquakes with magnitudes of up to 7.7. This is the perfect example of the effectiveness of flexible sheet pile structures under extreme seismic conditions.

Nevertheless, a certain reluctance to use sheet piles in seismic areas remains common among some designers. This concern may come from their experience of conventional design methods which do not favour flexible walls in seismic areas. These design methods are usually comprised of pseudo-static calculations using the Mononobe-Okabe theory (1931).

Numerical studies and physical experiments (centrifuge testing) have shown that these conventional methods of design are overestimating the loads on retaining walls - especially in the case of flexible walls. Although EN 1998-5 allows for a reduction of the seismic action depending on the acceptable displacements (reduction factor “r”), this only applies to gravity walls and not to anchored walls such as sheet pile walls, despite their inherent ductility.

Today, powerful design tools using Finite Element Modelling (FEM) allow for dynamic calculations that can accurately predict the behaviour of the retaining walls undergoing different seismic loadings, including internal forces, deformations, increases in pore water pressures, and expected modes of failure.

Material cost savings thanks to dynamic design methods

A research project led by ArcelorMittal R&D and a study carried out by world-leading maritime consultant engineering company SENER demonstrated significant optimisation potential. In the study, a wide spectrum of cases was analysed (four water depths; four seismic accelerations; two soil conditions) that compared the conventional pseudo-static method based on EN 1998-5 using elasto-plastic subgrade reaction software and the fully dynamic advanced method using FEM software.

All of the cases studied showed substantial optimisation potential when using FEM design. The bending moments in pseudo-static design are 40% to 126% higher than those of FEM design. When considering the respective sheet pile sections, this could result in up to 50% of material cost savings using the advanced seismic design methods.

Hydrodynamic loads properly analysed contribute to additional material savings

Hydrodynamic loads are commonly considered pseudo-static and calculated according to EN 1998-5 using the Westergaard formula as a permanent load from the water during the entire duration of the earthquake. SENER used FEM and Computational Fluid Dynamics (CFD) to calculate the impact of hydrodynamic loads on a sheet pile wall during seismic action, considering soil-fluid interactions under dynamic analysis.

Using the traditional Westergaard formula in EN 1998-5 matches the hydrodynamic loads obtained by CFD at a certain point of time during the earthquake. However, as Westergaard considers these to be permanent loads during the entire earthquake, an overestimation of its effect is evident.

The FEM calculations carried out using Plaxis 2D compared the results obtained when using the traditional Westergaard load with those obtained when using a realistic time-dependent variable load (through a dynamic load or added masses). The results showed an increase of 24.5% in the bending moment (with respect to the effects from the purely seismic action) when using the traditional Westergaard load compared to 4% when using the instantaneous load. In this case study, considering a realistic hydrodynamic load translated into a material cost saving of 14% when considering the corresponding sheet pile sections.

Brochure - Seismic design of sheet piles: economic benefits of advanced design methods

To further enhance design and project efficiencies with sheet piling solutions in areas of high seismic risk, the brochure ‘Seismic design of sheet piles: economic benefits of advanced design methods’ presents innovative design methods for extreme dynamic loading conditions in ports and waterways and other infrastructure domains.

Feel free to contact ArcelorMittal Sheet Piling for more detailed information or for assistance with the dynamic design of sheet piles using FEM.

Text:
ArcelorMittal Sheet Piling
Constructalia

Images:
ArcelorMittal Sheet Piling
Puerto Angamos

Related link(s)

Seismic design of sheet piles: economic benefits of advanced design methods

The 2021 edition of ArcelorMittal Sheet Piling’s general catalogue ‘Steel foundation solutions’ is now available!

This new edition introduces the new HZ 630M profile for HZ-M/AZ combined walls.

We also detailed the methodology used for running our life-cycle assessment to obtain our specific Environmental Product Declarations.

Download the new catalogue below or from our Document library.

Related link(s)

ArcelorMittal Sheet Piling: Steel Foundation Solutions

The HZ®-M Steel wall system, which is an HZ/AZ combined wall system, is one of the most preferred solutions for port structures and other deep excavations. A new section (HZ 630M), a 2020 catalogue, and updated software are now available.

New HZ 630M section of the HZ®-M steel wall system

The new HZ 630M section completes the existing range of the already large HZ®-M series. It was developed mainly for use in very hard driving conditions (installation in compact soils) and for structures with restrictions on the height of the system.

The flange thickness is 24.2 mm and the maximum height of an HZ 630M solution is only 672 mm (including connectors).

This new profile is available from now on and replaces the HZ 680M LT.

2020 HZ®-M Steel wall system catalogue available

The new catalogue has been extended to systems based on the latest HZ®-M king pile range combined with our enhanced AZ®-800 steel sheet pile generation as intermediaries. It provides new technical data needed for design according to Eurocode and includes a revised table for resistance to water pressure.

HZM™-AZ® Stresses software

An updated version of the HZM™-AZ® Stresses software is available.

Stress analysis for the HZM™ / AZ® combined wall system is based on the 'allowable stress design' method. It allows the user to easily select a solution based on bending moments and chosen safety factors on the steel stresses. The user can also prepare a basic material list for a straight retaining wall.

Additional features of the 2019 update include: calculating the wall properties of any combination with an AZ® infill sheet pile ranging from AZ® 12-770 to AZ® 28-700N and the new HZ 630M piles.

Text: ArcelorMittal Sheet Piling, Constructalia
Images: ArcelorMittal Sheet Piling

Related link(s)

HZM™-AZ® Stresses

HZ 630 M / HZ®-M Steel wall system

From port and terminal projects to giant cranes or retractable roofs (the latest trend in sport stadiums), ArcelorMittal crane rails are used in many applications and are present in every continent.

Working closely with customers

ArcelorMittal Europe – Long Products Rails & Special Sections is working closely with its customers to develop specific rails and new products according to their needs. Flexibility is another key factor in improving customer service. We can supply standard rail lengths from 6 to 36 metres, but other lengths are available upon request as well as finishing possibilities (cuts, special cuts, drilling, machining, bending, blasting-painting, etc.).

Incomparable knowledge, selection, and expertise

Crane rails are produced in several steel grade qualities and specifications according to customers’ requirements. Historical crane rails producer, ArcelorMittal Europe – Long Products Rails & Special Sections has built an incomparable knowledge and expertise of this product range. The company has also created with its customers numbers of rails as per all the MRS range used worldwide in major port projects and has established levels of quality control even stronger than the basic standards to secure our customers in their choice of a key product related to most often critical applications.

ArcelorMittal Europe – Long Products Rails & Special Sections has the largest products and grades portfolio, from the full range of DIN crane rails, MRS crane rails, CR crane rails, and many other specific rails, with hundreds of references in main ports worldwide.

Retractable roofs: a new trend in stadium construction

Retractable roofs are getting more and more popular in stadium construction, and ArcelorMittal crane rails are already present in some spectacular stadiums all around the world. Retractable roofs are designed to move panels that weigh hundreds of pounds in just minutes and they allow to control the stadium’s interior environment more effectively as they can be closed during inclement weather and opened on sunny days. After the roofs, retractable pitches might soon become the new trend.

From the world’s largest crane to the latest Ariane rocket

Another impressive application of crane rails is giant cranes. ArcelorMittal Europe – Long Products Rails & Special Sections has supplied crane rails for Sarens’ SGC-250, the largest crane in the world, capable of lifting 5000 tonnes, which is equal to 1408 elephants, 63 trains, or 20 planes.

Another major application is the launching pad of the Ariane 6 rocket, for which crane rails have been supplied for the construction of the rail track.

Text: ArcelorMittal Europe Communications
Images: TaMaNKunG / Neil Mitchelll, Shutterstock; ArcelorMittal

Construction has begun on a new wharf at the British Antarctic Survey (BAS) Rothera Research Station, and Z sections from ArcelorMittal Europe – Long Products Sheet Piling are playing a leading role. The new wharf will be used to berth the RRS Sir David Attenborough. Commissioned by NERC and built by Cammel Laird for operation by BAS, this is one of the most advanced polar research vessels in the world. Construction of the wharf is being carried out on site and will take two years to complete.

The British Antarctic Survey

The British Antarctic Survey has a rich history of conducting scientific research at the earth’s southern pole. Since their first ship arrived in 1947, specialised vessels have allowed BAS to access remote areas that would not be possible otherwise.

The commissioning of the RRS Sir David Attenborough is part of the United Kingdom’s polar infrastructure investment programme. It is designed to keep Britain at the forefront of world-leading research in one of the most inhospitable regions on earth.

Research at the ends of the earth

Launched in 2018, the RRS Sir David Attenborough will commence sea trials in autumn 2019. The vessel will enable scientists to research oceans, ice, and the atmosphere. This floating, multidisciplinary research platform will give them access to state-of-the-art facilities including a scientific moon pool and containerised laboratories.

At almost 129 metres, the new vessel is much longer than its predecessors. This has necessitated the building of a new wharf at Rothera Research Station. BAM Nuttall, a leading construction and civil engineering company, is demolishing the existing wharf and constructing its larger replacement.

ArcelorMittal and BAM Nuttall worked closely on the design of the new wharf. The quay wall is made up of 200 sheet piles which are connected to a steel structure. Every pile has several holes for connections which are placed in different locations across the sheets, making each one unique. Fundamental to this close partnership is ArcelorMittal Sheet Piling’s ability to offer a complete solution comprising engineering design support, further fabrication and customisation, and bespoke logistics.

The AZ® piles selected for the quay wall have excellent strength-to-weight ratio. Weight was an issue as the sheet piles had to be shipped more than 11 000 kilometres to the site. Handling on site was also a consideration. AZ® piles are made from 100% recycled steel, helping to keep the total carbon footprint of the project down.

Prefabrication before shipping

ArcelorMittal and BAM Nuttall decided to pre-fabricate the sheet piles in the UK due to adverse weather conditions in the Antarctic. This meant that work normally done on site, such as welding and fitting of brackets, had to be carried out before the sheet piles were shipped.

The sheet piles arrived at Rothera in January 2019 after a month at sea. Demolition of the existing wharf also began in January and the first frames for the new wharf were installed in March. As work can only take place during the polar summer, the wharf is not expected to be fully operational until mid 2020.

When it is complete, the new wharf will allow polar research ships such as the RRS Sir David Attenborough to continue scientific investigation into deep-sea biology, seafloor geology, and climate change. Working in co-ordination with autonomous underwater vehicles (AUVs) and other equipment, the ship will enable scientists to capture, analyse, and share data that will give us a better understanding of our planet. It will also provide essential evidence to help policymakers determine what action we must take to protect the earth.

The RRS Sir David Attenborough in figures

Tonnage: 15 000 GT / 4475 DWT
Length: 128.9 m (423 feet)
Beam: 24 m (79 feet)
Draught: 7 m (23 feet)
Depth: 11 m (36 feet)
Range: 35 000 km (22 000 miles) at 13 knots
Endurance: 60 days
Crew: 28
Scientists: 60

Text: ArcelorMittal Europe Communication
Photos: © Robert Mcgillivray / Shutterstock.com, © Sergey Tarasenko / Shutterstock.com

ArcelorMittal Europe is constantly adding new BIM objects to our range of software. New BIM objects for sheet piling are now available on Constructalia.

For these new BIM objects and more, click here:

https://constructalia.arcelormittal.com/en/tools/bim