Material models for soils

The choice of thematerial models for soils is limited in some finite element programs. The material models of the “linear elastic, ideal plastic” category can lead to incorrect predictions in the case of retaining wall structures – see, for example, (HÜGEL , 2005), (V ERMEER & W EHNERT, 2005) and recommendation E3-4 in (S CHANZ, 2006). The use of high-quality elastoplastic or hypoplastic material models is called for which can at least describe the main phenomena of the mechanical behaviour of soils:

  • stiffnesses not dependent on pressure,
  • different stiffnesses for unloading and reloading,
  • shear behaviour for drained and undrained conditions,
  • dilatancy behaviour.

For a detailed explanation of the main phenomena of the mechanical behaviour of soils, see, for example, (H ERLE &MAŠÍN, 2005) or (SCHANZ, 2006). High-quality material models may even be necessary during the feasibility studies for sheet piling structures.

Selected results from thefinite element

Selected results from thefinite element analyses can be summarised as follows:

  • Loading: In state 7 the finite element analysis indicates irreversible deformations due to the variable load q . According to DIN 1054:2005-01, the variable load should therefore be taken into account when checking the serviceability of the structure in the finite element model.
  • Earth pressure distribution: As expected, at the serviceability limit state the passive earth pressure is lower than that given by the calculations in example owing to the flexibility of the retaining wall. The active earth pressure is greater in thefinite element analysis . 20150715 86
  • Support at base of wall : The moment distributions calculated confirm that with an em-bedment depth of 4.8 m in the soil, the base of the sheet pile wall is partially fixed. 20150715 85
  • Deformations: As expected, the deformations of the sheet pile wall correspond to a flex-ible installation, the anchors yield. The large wall displacement causes corresponding settlement of the ground surface on the land side, a maximum inclination of approx. 1:80 occurs . During the construction phase, the deformations do not represent a problem for quay structures. When in service, the depression caused by the settlement can be compensated for by backfilling so that the area is traf ficable, e.g. for stacking containers. 20150715 87

Other possible issues for this boundary value problem might be the long-term behaviour of the quay structure due to other actions, the change in the water table over time and viscous processes in the stratum of clay with sea-silt. To do this, the finite element model described here would need to be adjusted with respect to the material model and the identification of parameters.

Sheet Piling Structures

The choice of thematerial models for soils is limited in some finite element programs. The material models of the “linear elastic, ideal plastic” category can lead to incorrect predictions in the case of retaining wall structures – see, for example, (HÜGEL , 2005), (V ERMEER & W EHNERT, 2005) and recommendation E3-4 in (S CHANZ, 2006). The use of high-quality elastoplastic or hypoplastic material models is called for which can at least describe the main phenomena of the mechanical behaviour of soils:

• stiffnesses not dependent on pressure,

• different stiffnesses for unloading and reloading,

• shear behaviour for drained and undrained conditions,

• dilatancy behaviour.

For a detailed explanation of the main phenomena of the mechanical behaviour of soils, see, for example, (H ERLE &MAŠÍN, 2005) or (SCHANZ, 2006). High-quality material models may even be necessary during the feasibility studies for sheet piling structures.

Dolphins

General

Dolphins are required in waterways and ports for various tasks: as berthing or mooring dol-phins. Their various functions require an analysis of different actions. Berthing dolphins must be designed for the impact of ships, mooring dolphins are subjected to the pull of mooring lines, wind loads and hydrodynamic pressures.

Dolphins can consist of single piles or groups of piles, the latter usually being met with in the form of lightweight timber piles in old structures. In the form of single piles, steel tubes or compound sections assembled from sheet piles, e.g. LARSSEN steel sheet piles, are to be recommended.

Loads

The critical design loads for dolphins result from the impact of ships during berthing manoeu-vres or the pull on the mooring lines of ships. The latter effect is made up of ship movements due to currents, wind, waves or ice. Berthing dolphins are designed for the ship impact loading case with a force FS,k such that the berthing energy can be converted into deformation work in the dolphin. The energy absorption capacity Ak,exist of a dolphin is calculated from the ship impact force FS and the horizontal de flection f of the dolphin at the level of application of the force:

Ak,exist =1/2 · FS,k · f

The available energy absorption capacity Ak,exist of a dolphin should be selected such that it is greater than or equal to the required energy absorption capacity A. The required energy absorption capacity A describes the component of the kinetic energy of the ship that must be absorbed by the dolphin. This is calculated using the mass, length, speed, turning speed and displacement of the ship, the spacing of the dolphins and the clearance under the keel. An exact description of how to calculate the required energy absorption capacity can be found in EAU 2004 section 13.3.

Subjected to the critical impact action FS , the design value of the steel stresses may not exceedthe yield strength fy in the case of berthing dolphins. For mooring dolphins, the design value of the steel stresses due to line pull, wind loads and water pressure may be equal to the maximum steel stress fu.

Relevant Criteria About Choosing Pile Sections

The following criteria are generally relevant when choosing pile sections:

  1. Dimensions required according to DIN 1054:2005-01 for ultimate limit state (LS 1) and serviceability limit state (LS 2).
  2. Adequate moment of resistance for transport and installation of sheet pile wall Proper support is important during handling on the building site, e.g. attachment of crane slings, because otherwise inadmissible deformation of the sheet pile prior to driving can occur which is not the fault of the fabricator. Furthermore, driving by means of pressing, impact hammer and vibration places severe loads on the pile in some situations. These loads depend on:
    • the length of the pile,
    • the flexibility and position of the pile guides,
    • the method of driving plus the chosen driving parameters (mass and drop height of impact hammer), vibration parameters (amplitude of eccentric weights, frequency, static preload), pressing force in comparison to weight of section,
    • prior deformation of the sheet pile caused by transport,
    • the subsoil, especially type of soil, density in the case of non-plastic soils, consis-tency in the case of cohesive soils, natural obstacles such as rocks plus inclined, hard bearing strata, man-made obstacles such as existing works, and
    • deviations of the adjacent sections and piles (and their interlocks) already driven.

    Owing to the multitude of aforementioned influencing factors, the section is mainly spe-ci fied based on experience.

  3. Adequate material thicknesses taking account of intended service life and expected rate of corrosion. It should be remembered that the zone with the highest corrosion rate does not necessarily coin-cide with the point of maximum structural loading. If conditions are unfavourable or additional protection is required, active or passive corrosion protection measures can be specified instead of a heavier section.
  4. If applicable, planned multiple use of the sheet pile walls taking into account the afore-mentioned aspects

The choice of steel grade essentially depends on the desired steel properties, e.g. with respect to suitability for welding.

For driving and economic reasons, sheet piles are sometimes driven to different depths within the same wall according to R 41 of EAU 2004. A value of 1 m is customary for the so-called stagger dimension, and experience shows that a structural analysis of the longer sheet piles is then unnecessary.

Understanding The Tie Rod Hole Leak Problem

The conventional forming system of concrete walls utilizing tie rods.

The following description supports the understanding of the condition of leaking tie rod holes left from foundation forming systems that use 5/8 (15.88 millimeters) reinforcement rods. Tie rod holes are also commonly referred to as pinhole leaks, rod pocket leaks, and tie backer hole leaks in other regions of the United States. After constructing the foundation wall, these tie rods are removed with the wall forming system, leaving holes in the poured concrete wall. Some newer forming systems that use snap ties instead of tie rods to hold their forms together do not apply to this article.

Poured concrete foundation walls begin with the construction of forms in which to pour the cement. For many years, these forms called shuttering have been constructed from wood that is held together by steel rods called tie rods, tie backs, or tie reinforcement rods. These rods are situated approximately every eighteen inches (0.46 meters) and about five feet (1.52 meters) high from the basement floor across the entire basement. A second row is aligned vertically underneath and about one foot (0.30 meters) from the base of the floor. Basements higher than eight feet (2.44 meters) sometimes will have three rows aligned vertically.

How a tie rod hole is formed.

Once the forms are in place, the tie rods are fastened and support the shuttering which holds the weight and the form of the foundation wall. Once the cement is poured, these forms are left a few days for curing. When that step is accomplished, the tie rods are removed allowing the shuttering to be dismantled. When this step is completed, you are left with a poured concrete foundation. The walls now have holes where the tie rods were that are approximately 5/8 inches (15.88 millimeters) in diameter. In this type of conventional forming system, the tie rods ”(are not)” left in the wall. The only time supporting wall forming ties are left in the wall is when a contractor uses a wall forming system that utilizes (snap ties).

Why tie rods leak after construction.

After the wood forms are removed some contractors will apply hydraulic cement on the outside of the tie rod holes and spray a tar based coating. After a few years this coating will break down and water will begin to enter the holes. Over the years since pouring of foundations began, there have been varying attempts and methods to stop these leaks. Some work for a few years while others fail quickly. Repair contractors have applied a polyurethane caulk and cork method for a quick fix, but years later the leak returns. The leak returns because these methods do not utilize a sealing system that reacts or co-exists with water. Instead, they use methods or products to bond up the hole that will loosen later due to delamination of the product/surface area.

Revealing the tie rod hole from inside.

The inside of the wall is also coated with a trowel applied hydraulic cement to fill in the tie rod hole, then in some cases sprayed over with a white stucco type finish more commonly called structo-lite; a mixture of (Structo-lite and autoclaved Lime). Some builders will not apply this coating which makes it easier to see the location of the tie rod holes. In this case where the white coating is sprayed on, they are harder to see until they begin to leak. Removal of the trowel applied hydraulic cement reveals an open tie rod hole going all the way to the outside of the basement wall. A simple removal of the trowel applied hydraulic cement reveals a hole going through to the soil side where the exterior hydraulic cement has been applied in the same fashion.

Tie rod leaks can cause a lot of water damage in basements.

When tie rods holes begin to leak they can flood and destroy finished basements drywall and carpeting. Tie rod hole leaks have commonly been mistaken as drain tile failure. Due to the amount of water they can allow in it is understandable how this can happen. In some cases the leak is hard to detect since the water coming from the tie rod hole will dry on the wall leaving a puddle on the floor with no traceable evidence of where it came from originally. The photograph below shows a case of one tie rod hole leaking, washing in soil from outside making it easy to trace. The amount of water resulting from this condition is commonly mistaken for drain tile failure.

20150708a

Unsealed tie rod holes are entrance for termites, ants and other insects.

Most tie rod holes become an entrance for insects as they use the hole and old cork repair material for a nest as well as being a direct entrance from outside soil.

Repairing tie rod holes before finishing a basement.

If a home owner is planning to finish their basement and it has tie rod holes, they should consider repairing all of them before the installation of the final wall covering. Leaving the holes unsealed will eventually cause future problems behind the drywall or paneling. Below is a photograph showing extensive drywall removal to repair leaking tie rod holes left unsealed when the basement was finished without proper repair methodology for tie rod holes.

20150708c

(This article comes from trxplug.com editor released)

H-Beams vs. I-Beams

The differences between an H-beam and an I-beam are very slight. The two beams look very similar in construction and are often called the same thing — a W-beam or wide-flange beam. The beams are often used for different types of construction or different parts of the structure.

Flanges

Both the H-beam and I-beam have top and bottom flanges. The flanges on an H-beam are longer and stick out farther from the center web. The flanges on an I-beam are shorter and not as wide. The distance from the end of the flange to the center web is shorter on an I-beam than the same measurement on an H-beam flange.

Fabrication

Another difference between an H-beam and I-beam is the fabrication method used to make the beams. The I-beam is fabricated by milling or rolling the steel. The size of the I-beam is limited by the capacity of the milling equipment, which this is why I-beams have smaller flanges. H-beams are built up rather than milled, so they can be made any height and width.

Plates

Since I-beams are milled or rolled, the web and flanges have a bevel where the three pieces come together and look like one piece. H-beams have the top and bottom flanges attached to the center web by welding or riveting them together. You can actually see that the H-beam is made of three different metal plates.

Spans

H-beams are useful for longer spans than I-beams because the H-beam can be fabricated to any size. I-beams are good for spans of 33 feet to 100 feet because of the size limitation. H-beams can be used for spans up to 330 feet.

(This article comes from eHow editor released)

Bearing capacity of open-ended pipe piles with restricted soil plug

The present study investigates the behaviour of plug on pile load capacity and effect of plug removal. The sand used as a foundation soil is poorly graded clean sand. It was prepared at different densities using a raining technique. To simulate the pile load test in the field, a new apparatus was manufactured. A driving–pressing system for pile installation was manufactured. The soil plug is removed by a device manufactured to remove the soil column entrapped inside the pipe piles during installation by driving and pressing devices. The present study focuses on the determination of effect of soil plug on the ultimate compression capacity of single open-ended steel pipe pile, and makes a comparison with closed-ended pipe pile. A new type of pipe piles is suggested; it is closed–open-ended pipe piles driven and pressed into sandy soil of different densities (medium and dense) in which axial compression load tests were performed on model piles. The pile end will be open to a predetermined depth in order to make pile penetration easy and closed at a distance in order to increase the pile base resistance. Twenty-four models of open-ended piles have been modified by closing the pile ends by a plate welded at a distance of 2D, 3D and 4D(where D is the diameter of the pile) from tip of the pile. These piles have been installed in sand by two types of installation, driving or pressing. It was concluded that the pile load carrying capacity in dense sand is several times greater than those in loose and medium sands, especially in the case of closed-ended or open-ended piles, since the pipe pile can produce external and internal skin friction in addition to end-bearing resistance that makes the total pile capacity close to that of closed-ended pile. On the other hand, the removal of soil plug decreases the pile load capacity. This decrease becomes apparent in dense sand. The decrease in load capacity is about 45%–63%, 55%–63% and 51%–79% in loose, medium and dense sands, respectively. Open-ended pipe piles behave as closed-ended, if the soil plug formed inside piles in a state of partial plug or full plug. The length of soil plug depends on the type of installation and relative density.

For the type of pile proposed in this study, open-ended piles are closed with a plate welded at a distance of 2D, 3D and 4D from the tip of the pile, and the open part of the pipe pile has a limited length, which was found to be 3D. This length revealed the maximum pile capacity due to the development of both interior and exterior skin friction in addition to end resistance. In addition, at this length, the soil column is pressed inside the pipe and hence the soil was densified leading to increase the skin resistance.

(This article comes from tandfonline.com editor released)

Wind versus oil: The pipe piles up in Lincoln County

As Lincoln County residents gathered in Canton Tuesday night to talk wind energy, the sun was setting nearby on miles of steel pipe piling up for a far more traditional sort of energy project.

The pipe sits less than a mile off the Worthing exit on Interstate 29, on land leased from Ron Albers by the owners of the Dakota Access pipeline.

Dakota Access would move North Dakota crude 1,134 miles, from the Bakken Oil patch to Patoka, Ill.

If it’s approved, of course. It hasn’t been.

The Public Utilities Commission has until Dec. 15, 2015 – one year from the date Dakota Access applied for a permit – to deny or grant the pipeline permission to lay 272 miles of the underground line in South Dakota. The evidentiary hearing on the matter will take place in September.

The oil would flow under northern Lincoln County, so plenty of landowners have a keen interest in the project.

Lincoln County resident Paul Zeeb called Tuesday, as I was driving to Canton for a wind farm hearing, to ask about the pipe pile. If miles of pipe sits ready to use on a farmer’s land near the pipeline route, he said, how can anyone have confidence that the PUC is truly weighing the matter?

“In all fairness, if we’re having hearings and we really have a say in it, why are they stockpiling pipe?” Zeeb asked.

It’s a question that’s come up in other contexts, as well. Landowners along the pipeline route have been paid easements already, with some taking deals before the pipeline was docketed on Dec. 15.

Albers told me Tuesday his land was leased Dec. 10, and pipe began to arrive in January.

Joey Mahmoud, an executive with Energy Transfer Partners, addressed the question of pre-permitting costs in January at a packed PUC public comment meeting.

If the pipeline project fails to get permitted, Mahmoud said, the easement money won’t come back to the company. The costs are sunk, just like the costs for pipe, environmental impact studies, surveying, engineering and public relations.

The work’s ongoing. Just a few days ago, Dakota Access filed some slight changes to the pipeline route, some of which were based on input from the January meetings in Sioux Falls and around the state. The pipeline path was moved further away from the Sioux Falls landfill, for example.

The contrast is stark between Dakota Access – backed by the Fortune 100 company Energy Transfer Partners – and the plan of the local investor-driven Dakota Power Community Wind. Zeeb’s question, given the context and the timing, really puts that into perspective.

Essentially, the crude oil pipeline is a big enough investment and a sure enough deal that the company can spend millions on easements and pipe before even getting a permit.

The company’s fact sheet says it will offer $47 million in easements to South Dakota landowners. If it fails to get a permit, that money’s gone.

The pipeline is fighting a well-organized opposition in hopes of gaining a permit for a permanent pipeline, but it’s doing so with the confidence of a proven product with a guaranteed market and a bankroll to match. It’s also clear that the company’s experience and strength in lobbying and permitting far outstrips the experience of the groups opposed to the project, as well.

So that’s the pipeline. Let’s talk about the wind project.

Dakota Power Community Wind is making deals with landowners that don’t pay much until the wind turbines are placed.

Right now, they’re looking at permits to build five test towers that would determine how much wind capacity there is, a process that could take three to five years. Only then, if the investors are convinced and willing to pay, would turbines be built.

Test tower landowners get a one-time, $1,000 payment. The 100-odd landowners who’ve signed up for options will get $100 a year until the turbines are built. If the turbines are built, they get 4 percent of the gross revenue.

If Dakota Wind had more money, it might spend more, but it doesn’t. Dakota Wind’s project developer Rob Johnson says the wind farm’s raised about $2.5 million so far. That’s barely enough for a single turbine.

The wind farm is fighting a well-organized opposition in hopes of gaining temporary permits, doing so to prove the value of a product (turbines) it’s barely raised enough money to build even one of. The project and its backers have worked on wind projects in South Dakota, but they’re essentially locals facing off against locals.

If the pipeline is built, of course, no one will see it. If the wind turbines are built, they would be a blight or a beauty, depending on your perspective.

For the next few months, at least, the pipeline’s the visible one.

(This article comes from Argus Leader editor released)

Development of Steel Sheet Piling

Metal sheet piling was a natural advancement in the evolution of this product as we entered the “Iron Age” in the mid-1800’s. Cast iron was used to make some crude sections, but these were not successful due to lack of ductility. Toward the end of the century, Bessemer steel was developed and mills began hot-rolling I-beams, channels and angles, among other structural shapes. Freistadt-type piling appeared about 1890, fabricated from a rolled channel section as shown in Figure 1. Z-bars riveted to the web provided a groove into which the flange of a channel could slide, thus forming a crude but innovative interlock. A “Universal” type sheet piling introduced in Great Britain about 1895 utilized hot-rolled I-beams and special clips to join the flanges of the I-beams together. The efficiency of this wall was low because the I-beams were aligned in the weak structural direction.

Don C. Warrington
Figure 1: Freistadt Sheet Piling

LARSSEN SHAPES

Inventors were striving to develop a sheet piling that would contain interlocks rolled into the beam during the manufacturing process, rather than attached afterwards by riveting. Gregson (USA) patented a bulb and jaw interlock in 1899, however this still resulted in production of a flat section with relatively small section modulus. Trygve Larssen obtained a German patent in 1904 for a deep, hot rolled section that greatly increased the strength and efficiency of steel walls and represented a major advancement. Larssen’s piling wall assumed a “wave shape” when assembled and all subsequent developments for efficient sheet pile walls are based on this concept. Larssen’s section still contained a partially fabricated interlock and it was not until 1914, that a rivetless Larssen interlock appeared in Germany.

Figure 3
Figure 2: Historical Sheet Pile Sections

In the United States, Lackawanna Steel Co. (later acquired by Bethlehem Steel Corp.) was a flat sheet piling shape and several arched types with rolled, integral interlocks as early as 1910.Carnegie Steel Co. (U.S. Steel Corp.) offered three flat sections with rolled-on interlocks and one fabricated section. By 1929, Carnegie’s catalogue illustrated four deep-arch, two shallow-arch and two straight sections. Some of these and other historical sections of sheet piling are showing Figure 2.

Z-TYPE SHAPES

Z-shaped piles followed the Larssen concept for a wave-shaped profile but with the added advantage that the interlocks are formed on the outer elements of the section. The extra metalis put to best use, since it is well out from the neutral axis of the wall. Larssen interlocks are located on the neutral axis. Surprisingly, Z-shaped piles were produced in Europe as early as 1911. The Ransome profile looked very much like some of today’s lightweight Z-shapes. The deeper Lamp Z-pile introduced about 1913, resembles a modern ball and socket Z-type pile.

In Europe, Z-type shapes fell from favour when the Larssen U-types were developed. Two Z-shapes were introduced in the United States in the 1930’s and became quite popular. PZ-38 and PZ-32 offered wider and deeper sections than any of the arch shaped shapes then available. Z-shaped piles obtained some impetus in the U.S. from the long-standing controversy regarding the actual moment-resisting properties of U and Arch shaped sections.

Figure 4
Figure 3: Typical Hot-Rolled Steel Sheet Piling

Z-shaped piles interlock on the wall extremities and provide a solid web connecting the two flanges. When the PZ-27 section was introduced in the 1940’s, its section modulus of 30.2 in3/ft was almost three times that published for the arch section with the identical weight per square foot of wall. This section subsequently became the all-time most popular sheet piling section in history. Z-type shapes are now produced with section modulii ranging from 8.6 to about 85 in3/foot of wall.

The Z-type piling is predominantly used in retaining and floodwall applications where bending strength governs the design and no deflection (swing) between sheets is required. Most producers do not guarantee any swing although some can generally be attained or area can be built by providing some bent pieces in the run. Turns in the wall alignment can be made with standard bent or fabricated corners. Typical configurations are shown in Figure 3.

Z-piles are not used in applications when interlock strength is required such as filled cells. These sheets would tend to stretch and flatten in these cases. No minimum interlock strength is offered for this reason. When interlock tension is the primary consideration for design, an arched or straight web piling should be used.

STRAIGHT WEB SECTIONS

Flat profile sections were originally produced only because of mill rolling limitations. Competition and customer demand prompted the expansion into structurally efficient sheet piling. It was discovered that these flat profiles had strength in tension that was advantageous for building circular, filled structures from sheet piling. About 1908 a large cellular cofferdam was built on the Black Rock River in Buffalo N.Y. in order to de-water the site for a new lock. This conceptwas progressively expanded to include circular and diaphragm-shaped cells for piers and breakwaters that might have formerly been built of timber cribs or masonry.

The use of large diameter, cellular cofferdams was given a special impetus in the 1930’s when the Tennessee Valley Authority began a series of hydro dams and navigation locks on that river system in the south-eastern United States. Not only did TVA engineers develop new design methods for designing these large structures, they developed better ways of installing and maintaining them.

Flat sheets have little strength to resist bending, but do have very strong interlocks to resist “hoop” stress. These piles are used almost exclusively for building large, filled cellular structures. Flat sheets must provide some ability to “swing” between sheets so that a circle can be closed. Most manufacturers will guarantee a minimum swing of 8 to 10 degrees between adjacent sheets for standard lengths of piling. For overly long pieces, these warranties must generally be negotiated.

Available interlock strengths must be known in advance in order to design a structure that will be safe against bursting. Most manufacturers will guarantee a “minimum” interlock strength based on tension tests conducted on a number of representative production samples. It has been determined from experience that interlock dimensional tolerances that fall within certain limitations will provide tension values characteristic of the entire production run. Flat sheet piling is available only as a hot rolled product, since the cold-finishing process does not provide an interlock with sufficient strength in tension. Interlock strengths have been gradually increased due to the demand to build larger cells for deeper cofferdams.

Most flat sheet piling has been used to construct temporary cellular cofferdams. After the initial use, the sheets are pulled and used in other portions of the project or perhaps sold for another project elsewhere. Other flat sheets are used in permanent structures such as breakwaters, earth containment sites, piers and other applications.

COLD FINISHED PILING

Since the early 1970’s another method of producing steel sheet piling has greatly expanded the availability and the selection of sections. This new method uses hot-rolled sheets in coil form, fed through a series of cold-rolling stands to form “Z” or “arch” shapes complete with a simple, hook-type interlock. This involves a relatively inexpensive capital expenditure compared to the hot-rolled product and has attracted a number of new producers.These steel pilings are shallow-depth sections, cold formed to a constant thick-ness of less than 0.25 inch and manufactured in accordance with ASTM A 857. Yield strength is dependent on the gauge thickness and varies between 25 and 36 kips per square inch (ksi). These sections have low-section moduli and very low moments of inertia in comparison to heavy-gauge Z-sections. Specialized coatings such as hot dip galvanized, zinc plated, and aluminized steel are available for improved corrosion resistance. Light-gauge piling should be considered for temporary or minor structures. Light-gauge piling can be considered for permanent construction when accompanied by a detailed corrosion investigation. Field tests should minimally include pH and resistivity measurements.

Figure 5
Figure 4: Typical Cold-Rolled Sheet Piling Sections

See Figure 4 for typical light-gauge sections.

HIGH MODULUS SECTIONS

There is a limited but regular demand for sheet piling with strength properties that exceed those available from standard products. These may be required for deep excavations, poor soil conditions, deeper dredge lines and other special conditions.

SHEET PILING NOMENCLATURE & IDENTIFICATION

U.S. producers of sheet piling standardized the identification of sheet piling sections so they could be specified without reference to a particular manufacturers product. The identification included a “P” (piling”) “Z” (type or shape) and “27” the weight, or PZ-27. Arch and flat shapes were similarly described. Non-U.S. and cold-finishing producers have their own “in house” identification systems. There is now no universal nomenclature system. It is common practice recently to specify the bending moment to be satisfied which then allows the contractor considerable flexibility in his selection of a section and a supplier. This bending moment specification should not be used blindly, however, as many sheet pile designs (especially those using vinyl or pultruded fibreglass sheeting) are principally governed by deflection.

ORDERING SHEET PILING

Like other steel products, steel sheet piling may be ordered by reference to a standard specification. In the United States this standard is published by the American Society of Testing Materials (ASTM) 1916 Race Street, Philadelphia, PA 19103-1187. The basic ASTM Specification A-328 and others listed may be obtained by writing to the Society or visiting their website//www.astm.org.

This specification covers the steel making process, the chemistry requirements, the minimum yield and ultimate strength. Delivery is referenced in ASTM Specification A-6. The ASTM Specification does not cover interlock tolerances, straightness, interlock strength, nor does it cover rental or second hand material. These are between buyer and seller.

Other Specifications include:

  • Canadian Specification CSA 44 W, CAST 44W/70
  • British Specification BS4360 – Various Grades
  • European Specification: ST SP 37; ST SP 45; ST SP 5.

STEEL SHEET PILING TODAY

While the annual consumption of sheet piling in this country rarely exceeds 250,000 U.S. tons, the number of producers and the availability of sections has increased dramatically in the last ten years. In 1960 there were two U.S. producers, each offering nine sheet piling sections. Today there are at least 14 U.S. and non-U.S. producers offering over 200 sections in this country. Competitive factors have generated development of new, wider, more-efficient sections. Large Z-shapes are now available for deep construction with section modulus of almost twice that previously available. A wall system has been developed using large H-sections combined with light Z-shapes that greatly increases the section modulus. Light weight “gauge” material is produced on the cold forming mills for economical shallow bulkheading and trench work.

Higher strength steels up to 60 ksi yield point have also been effectively used in sheet piling design. These grades offer the opportunity to save weight or to extend bending or interlock strengths beyond those of conventional grades. For those applications that require it, corrosion resistant steel can also be specified as well.

(This article comes from pilebuckinternational.com editor released)