Prior to the inception of combined wall systems, sheet piles were commonly used for earth retention and support of excavation projects. During this time, the largest domestic sheet pile section had a section modulus of about 60 in³/ft. If design stresses exceeded that, engineers had to get creative by adding steel cover plating to the top and bottom flanges of the sheet pile. The additional steel would boost the section properties. This cover plating fabrication was a solution for the time when heavy civil/marine applications like deep excavations and port berthing structures needed something more than sheet pile could offer. It was effective, but not the most efficient solution. The plating material and fabrication were costly with poor engineering economics. Today, there are at least two hot rolled sheet pile series with wider, lighter and stronger sections that approach moduli of 100 in³/ft. Today, cover plated applications are rare and usually a last resort when efficient heavier sections are not available.
The right combination
Higher modulus wall solutions were explored early on by pile manufacturers. Dating back to the early 1900s, mill engineers envisioned multiple concepts, but as with most innovations, barriers to market such as manufacturing costs, application demand and expected return on investment dead-ended most patents before they received serious market consideration.
The real breakthrough in high modulus wall design came when pile producers combined steel sheet pile sections with large beam shapes, (King Pile Combi-Wall) resulting in system properties and weight efficiencies like no other prior concept. The marriage of two conventional hot rolled sections made the combi-wall concept more attractive with minimal financial risk to develop.
Unlike wide flange (WF) beams, H-King pile beams are designed to be geo-structurally supported by soil, so the buckling and slenderness ratios that govern unsupported column design can be stretched, allowing for wider and lighter dimensions compared to wide flange shapes.
Although there are two domestic mills that make hot rolled sheets, none produce an H-King pile. Suppliers can offer an alternate with domestic sheets and WF beams, but there are engineering and material cost limitations. There is only one North American beam producer that makes the heavier, deeper WF sections. Even still, the flange widths are narrow and the connector weld locations create second moment properties. The result is poor unit weights with lower properties. Lastly, the weld-on connectors are not domestically produced. For these reasons, 100 percent domestic beam systems are not as viable.
Combi-wall breakdown
Traditional high modulus combined walls are made up of three components: 1) king pile the primary load member, either beam or pipe; 2) sheet piles the intermediate spanning elements that reduce panel weight, but contribute little structurally; 3) interlocking bars the weld-on connectors that structurally join the two piles. The system width is measured in panels from the centerline of one king pile, across the sheet piles to the centerline of the other. Like sheet pile, combi-wall properties are specified in the same units: section modulus (in³/ft), moment of inertia (in⁴/ft) and bending moment (kip-ft/ft). When a designer or contractor is considering pipe or beam combi-wall options, wider, lighter and stronger are the key measurable variables, but there are other commercial, structural and installation factors that impact overall cost and feasibility.
Pipe Z and H-King Z: pros and cons
The shape of the primary load member (beam or pipe) has pros and cons. Pipe can get wide and deep, so the inertial properties are good, but the cross-sectional area is spread throughout the diameter, so the section modulus is not proportionate and often lower than what the analysis requires. More steel is needed, so the wall thickness must increase. Striking a balance between the pipe diameter (30-inch to 84-inch) and wall thickness (0.375-inch to one inch) to meet both property requirements can be an iterative process. The pipe Z panel widths (7.5-feet to 12-feet) require fewer panels to install compared to H-King single and double beam configurations (5.75-feet to 8.33-feet), but the pipe unit weight is typically much higher and site restrictions often limit the section depth. A larger OD pipe will have more concrete and rebar for the splash apron, cap and moment connection. They may also have backfilling requirements inside the pile. Pipe is readily available with ample domestic and foreign production. Hot rolled Z sheets also have foreign and domestic options and the weld on pile connectors are well sourced. If the material is available, 12-week lead times are possible. H-King beams are specifically designed for high modulus wall loading to maximize structural properties and weight efficiency. They achieve very high modulus numbers with single and double pile layouts with 33-inch to 48-inch beams. Since no domestic mills produce a true H-King high modulus system, lead times typically range from 16 to 20 weeks. All these factors should be considered when evaluating the most economical solution.
Piling market
Since 2016, the market has one H-King combi-wall producer. ArcelorMittal (Luxembourg) has been the gold standard in high modulus walls for decades. Their current HZM system was an evolution from the original HZ predecessor. Beam modifications and mill upgrades in the mid-2000s, combined with 700mm and 770mm AZ sheet piles resulted in better strength to weight efficiencies, further distancing their competitive advantage. Salzgitter Mannesmann's Peiner system (Germany) was a formidable competitor until the line was discontinued in 2016. Since then, HZM has been the sole sourced king beam combi-wall system in the world.
When the German Hoesch sheet pile mill closed in 2016, a large void was left in the North American piling market. As the exclusive partner of Hoesch, JD Fields & Company, Inc. (JDF) grew their Larssen "Z" line to 100,000 annual tons in the U.S., Canada, Mexico and the Caribbean. With only two domestic mills producing a limited range of light to heavy sections, news of Anshan Zizhu coming on line with a new mill had North American distributors scrambling to China in hopes of replacing the lost tonnage. After careful consideration, Zizhu recognized the market success Hoesch experienced with JD Fields, and selected them as their exclusive North American piling partner. The mill leaned on JDF's experienced sales and engineering leadership for domestic market and technical input with the new "ZZ" (Double Z Series). Agreeing to maintain the grade 60 standard JDF had established in North America, the "ZZ" launch was a successful collaboration resulting in the smoothest product release of a full range of light to super heavy "Z" sections with outstanding quality.
High modulus math: JDF + ZZ = HZZ
King beam and pipe combi-wall systems all share a common thread in their build and functionality: welded interlock connectors. These components add 2045 plf to each beam depending on the configuration and require costly fabrication. Now imagine the time and money to be saved if all of that could be estimated. That is exactly what JDF and Anshan Zizhu set out to do when they developed the new HZZ system.
On the coat tails of a successful sheet pile launch, both partners were intrigued with the possibility of developing a high modulus wall solution to compliment the Double Z series. Not interested in just another "me too" king beam system, JDF challenged the mill to produce a beam that did not require a welded interlock connection. Anshan's technical team was progressive in embracing this out-of-the-box concept. After multiple design iterations, a breakthrough came in the shape of a unique hot rolled flange with a drop down nose and Larssen interlocks on the edges of the section. The HZZ Direct Connect Flange Technology™ was born.
The nose shape serves three structural purposes: 1) It pushes the web-flange connection away from the x-y plane, addressing any concerns of having the weld on the shear axis; 2) Gives the beam strength to resist transverse stresses in the same manner as hot rolled beams or the flange-web transitions in a hot rolled sheet pile; and 3) Provides an excellent surface area for automated full penetration welds.
Features and benefits
From a commercial perspective, removing two, four or six connectors reduces up to 40 lb/ft per beam, eliminates fabrication and decreases lead-time. Regarding drivability, high modulus wall beam lengths can reach 100 feet with driving depths of 50 feet or more. H-King beam systems have good driving characteristics, but if there is a weak link, it's the connector. In comparison, the HZZ beam-sheet interlock connection is an integral part of the system, not a component add-on. The single beam configuration does not command a bottom interlock connection; further material savings are realized by using hot rolled plate.
In a double pile scenario, the direct connect flanges are needed on top and bottom to interlock the beams, but the system allows for variable flange thicknesses. By selecting the heavier, thicker HZF 35T for corrosion durability on the top waterside and applying the lighter HZF 25 on the less corrosive soil side, the system offers custom weight efficiencies without compromising design integrity. These product innovations set HZZ's engineered beam technology apart from any other.
Paradigm shift
Combined walls are marketed and specified through product look up tables in catalogs. Take the HZM system for example, it is comprised of 11 beam sizes varying in weight and height, with two, four or six connectors, and four typical stock sheet pile sections. These components are offered in a variety of single and double beam configurations resulting in over 100 different wall solutions.
The HZZ Direct Connect system is not limited to a finite number of beams or connectors. The hot rolled flange design and fabrication process allows for unlimited combinations of section height, web thickness and flanges for single and double beam layouts. This is the first and only high modulus combined wall system that can design and build a custom wall solution based on specific application requirements. This is a reversal in the catalog specification that will challenge the conventional marketing process.
JD Fields immediately recognized that the HZZ system customization feature would be restricted within the pages of a printed manual. They had to envision a marketing medium that would showcase the dynamic versatility. The solution will be revealed in interactive design software in Q1 2019. The online platform is currently under construction, but JDF is already quoting and taking orders. The HZZ Wall Builder™ tool is going to be the most comprehensive technical graphic interface and marketing platform with cradle to grave input modules and comparison tools. From geostructural analysis, durability and cost engineering, to custom generated CAD files and data tables, this platform will revolutionize high modulus wall applications.
Owners, engineers and contractors working in the marine piling and deep foundation industry have a lot to be excited about. Look for this game-changing platform in Q1 2019. Fields' technical team currently offers no cost engineering seminars and lunch and learns on the HZZ system and its Wall Builder design software.Evolution of Steel Piling & High Modulus Walls for Post Panamax Marine Structures
October 30, 2018
Prior to the inception of combined wall systems, sheet piles were commonly used for earth retention and support of excavation projects. During this time, the largest domestic sheet pile section had a section modulus of about 60 in³/ft. If design stresses exceeded that, engineers had to get creative by adding steel cover plating to the top and bottom flanges of the sheet pile. The additional steel would boost the section properties. This cover plating fabrication was a solution for the time when heavy civil/marine applications like deep excavations and port berthing structures needed something more than sheet pile could offer. It was effective, but not the most efficient solution. The plating material and fabrication were costly with poor engineering economics. Today, there are at least two hot rolled sheet pile series with wider, lighter and stronger sections that approach moduli of 100 in³/ft. Today, cover plated applications are rare and usually a last resort when efficient heavier sections are not available.
The right combination
Higher modulus wall solutions were explored early on by pile manufacturers. Dating back to the early 1900s, mill engineers envisioned multiple concepts, but as with most innovations, barriers to market such as manufacturing costs, application demand and expected return on investment dead-ended most patents before they received serious market consideration.
The real breakthrough in high modulus wall design came when pile producers combined steel sheet pile sections with large beam shapes, (King Pile Combi-Wall) resulting in system properties and weight efficiencies like no other prior concept. The marriage of two conventional hot rolled sections made the combi-wall concept more attractive with minimal financial risk to develop.
Unlike wide flange (WF) beams, H-King pile beams are designed to be geo-structurally supported by soil, so the buckling and slenderness ratios that govern unsupported column design can be stretched, allowing for wider and lighter dimensions compared to wide flange shapes.
Although there are two domestic mills that make hot rolled sheets, none produce an H-King pile. Suppliers can offer an alternate with domestic sheets and WF beams, but there are engineering and material cost limitations. There is only one North American beam producer that makes the heavier, deeper WF sections. Even still, the flange widths are narrow and the connector weld locations create second moment properties. The result is poor unit weights with lower properties. Lastly, the weld-on connectors are not domestically produced. For these reasons, 100 percent domestic beam systems are not as viable.
Combi-wall breakdown
Traditional high modulus combined walls are made up of three components: 1) king pile the primary load member, either beam or pipe; 2) sheet piles the intermediate spanning elements that reduce panel weight, but contribute little structurally; 3) interlocking bars the weld-on connectors that structurally join the two piles. The system width is measured in panels from the centerline of one king pile, across the sheet piles to the centerline of the other. Like sheet pile, combi-wall properties are specified in the same units: section modulus (in³/ft), moment of inertia (in⁴/ft) and bending moment (kip-ft/ft). When a designer or contractor is considering pipe or beam combi-wall options, wider, lighter and stronger are the key measurable variables, but there are other commercial, structural and installation factors that impact overall cost and feasibility.
Pipe Z and H-King Z: pros and cons
The shape of the primary load member (beam or pipe) has pros and cons. Pipe can get wide and deep, so the inertial properties are good, but the cross-sectional area is spread throughout the diameter, so the section modulus is not proportionate and often lower than what the analysis requires. More steel is needed, so the wall thickness must increase. Striking a balance between the pipe diameter (30-inch to 84-inch) and wall thickness (0.375-inch to one inch) to meet both property requirements can be an iterative process. The pipe Z panel widths (7.5-feet to 12-feet) require fewer panels to install compared to H-King single and double beam configurations (5.75-feet to 8.33-feet), but the pipe unit weight is typically much higher and site restrictions often limit the section depth. A larger OD pipe will have more concrete and rebar for the splash apron, cap and moment connection. They may also have backfilling requirements inside the pile. Pipe is readily available with ample domestic and foreign production. Hot rolled Z sheets also have foreign and domestic options and the weld on pile connectors are well sourced. If the material is available, 12-week lead times are possible. H-King beams are specifically designed for high modulus wall loading to maximize structural properties and weight efficiency. They achieve very high modulus numbers with single and double pile layouts with 33-inch to 48-inch beams. Since no domestic mills produce a true H-King high modulus system, lead times typically range from 16 to 20 weeks. All these factors should be considered when evaluating the most economical solution.
Piling market
Since 2016, the market has one H-King combi-wall producer. ArcelorMittal (Luxembourg) has been the gold standard in high modulus walls for decades. Their current HZM system was an evolution from the original HZ predecessor. Beam modifications and mill upgrades in the mid-2000s, combined with 700mm and 770mm AZ sheet piles resulted in better strength to weight efficiencies, further distancing their competitive advantage. Salzgitter Mannesmann's Peiner system (Germany) was a formidable competitor until the line was discontinued in 2016. Since then, HZM has been the sole sourced king beam combi-wall system in the world.
When the German Hoesch sheet pile mill closed in 2016, a large void was left in the North American piling market. As the exclusive partner of Hoesch, JD Fields & Company, Inc. (JDF) grew their Larssen "Z" line to 100,000 annual tons in the U.S., Canada, Mexico and the Caribbean. With only two domestic mills producing a limited range of light to heavy sections, news of Anshan Zizhu coming on line with a new mill had North American distributors scrambling to China in hopes of replacing the lost tonnage. After careful consideration, Zizhu recognized the market success Hoesch experienced with JD Fields, and selected them as their exclusive North American piling partner. The mill leaned on JDF's experienced sales and engineering leadership for domestic market and technical input with the new "ZZ" (Double Z Series). Agreeing to maintain the grade 60 standard JDF had established in North America, the "ZZ" launch was a successful collaboration resulting in the smoothest product release of a full range of light to super heavy "Z" sections with outstanding quality.
High modulus math: JDF + ZZ = HZZ
King beam and pipe combi-wall systems all share a common thread in their build and functionality: welded interlock connectors. These components add 2045 plf to each beam depending on the configuration and require costly fabrication. Now imagine the time and money to be saved if all of that could be estimated. That is exactly what JDF and Anshan Zizhu set out to do when they developed the new HZZ system.
On the coat tails of a successful sheet pile launch, both partners were intrigued with the possibility of developing a high modulus wall solution to compliment the Double Z series. Not interested in just another "me too" king beam system, JDF challenged the mill to produce a beam that did not require a welded interlock connection. Anshan's technical team was progressive in embracing this out-of-the-box concept. After multiple design iterations, a breakthrough came in the shape of a unique hot rolled flange with a drop down nose and Larssen interlocks on the edges of the section. The HZZ Direct Connect Flange Technology™ was born.
The nose shape serves three structural purposes: 1) It pushes the web-flange connection away from the x-y plane, addressing any concerns of having the weld on the shear axis; 2) Gives the beam strength to resist transverse stresses in the same manner as hot rolled beams or the flange-web transitions in a hot rolled sheet pile; and 3) Provides an excellent surface area for automated full penetration welds.
Features and benefits
From a commercial perspective, removing two, four or six connectors reduces up to 40 lb/ft per beam, eliminates fabrication and decreases lead-time. Regarding drivability, high modulus wall beam lengths can reach 100 feet with driving depths of 50 feet or more. H-King beam systems have good driving characteristics, but if there is a weak link, it's the connector. In comparison, the HZZ beam-sheet interlock connection is an integral part of the system, not a component add-on. The single beam configuration does not command a bottom interlock connection; further material savings are realized by using hot rolled plate.
In a double pile scenario, the direct connect flanges are needed on top and bottom to interlock the beams, but the system allows for variable flange thicknesses. By selecting the heavier, thicker HZF 35T for corrosion durability on the top waterside and applying the lighter HZF 25 on the less corrosive soil side, the system offers custom weight efficiencies without compromising design integrity. These product innovations set HZZ's engineered beam technology apart from any other.
Paradigm shift
Combined walls are marketed and specified through product look up tables in catalogs. Take the HZM system for example, it is comprised of 11 beam sizes varying in weight and height, with two, four or six connectors, and four typical stock sheet pile sections. These components are offered in a variety of single and double beam configurations resulting in over 100 different wall solutions.
The HZZ Direct Connect system is not limited to a finite number of beams or connectors. The hot rolled flange design and fabrication process allows for unlimited combinations of section height, web thickness and flanges for single and double beam layouts. This is the first and only high modulus combined wall system that can design and build a custom wall solution based on specific application requirements. This is a reversal in the catalog specification that will challenge the conventional marketing process.
JD Fields immediately recognized that the HZZ system customization feature would be restricted within the pages of a printed manual. They had to envision a marketing medium that would showcase the dynamic versatility. The solution will be revealed in interactive design software in Q1 2019. The online platform is currently under construction, but JDF is already quoting and taking orders. The HZZ Wall Builder™ tool is going to be the most comprehensive technical graphic interface and marketing platform with cradle to grave input modules and comparison tools. From geostructural analysis, durability and cost engineering, to custom generated CAD files and data tables, this platform will revolutionize high modulus wall applications.
Owners, engineers and contractors working in the marine piling and deep foundation industry have a lot to be excited about. Look for this game-changing platform in Q1 2019. Fields' technical team currently offers no cost engineering seminars and lunch and learns on the HZZ system and its Wall Builder design software.
