NCSEA (1)

NCSEA – Award

DHC is proud to have been awarded the National Council of Structural Engineers Associations 2015 Excellence in Structural Engineering Award, for work on the Ballard Drive Bridge, in Seattle, WA.

Click here to read published article on the project.

The Ballard Drive Bridge is one of the many historic bascule bridges located in the Pacific Northwest.  The application of engineering design was necessary to overcome the challenges associated with providing access platforms and containment for blasting and repainting the structure, while allowing the bridge to perform its normal operations. These operations not only include supporting vehicular traffic, but raising 250 to 500 times a month to allow for vessels to pass under. The complex loading of this process presented extreme design challenges beyond that of a traditional horizontal platform. Such items included intense wind loading on the underside of the platform, stabilization during raising, analysis of all bridge framing from irregular loading, and counterweight restrictions.

Creativity of Structural Design/Complexity of Criteria or Unique Problems:

The structural design utilized a flexible Safespan platform to minimize the increased dead weight on the bridge as opposed to typical scaffold or other rigid suspended platforms. This was extremely important, as every pound of platform meant additional counterweight was necessary to balance the loading due to the limited capacity of the bridge’s original motors.  Precisely calculating the counterweight was extremely important for the analysis of all bridge members because the increased counterweight wanted to overload the bridge similar to having two sumo wrestlers on a child’s seesaw. However, although this light system meant less demand on the existing bridge, the flexibility allowed it to act as a sail in the wind during lifting events. To prevent the exposed face of the Safespan platform from slamming into the underside of the bridge under high winds as well as sliding under its own weight, a series of rigid anti-uplift and horizontal bracing members were installed to hold the deck firmly in place while strategically transferring the load into the stronger framing members. Horizontal and vertical suspension cables were also installed to allow the platform to shift orientation and eliminate any sag or sway of the deck toward the water. The creativity of this structural design was not only necessary to overcome the complex challenges of the dynamic system, but also allowed the general contractor to use existing/typical material and installation techniques, resulting in an efficient project execution.

Innovative Application of Existing Materials and Techniques:

Typical Safespan platforms consist of longitudinal wire rope cables supporting metal corrugated decking, intermediate wire rope tie up cables, and various attachment assemblies that are compatible with different bridge members.  All components in this design utilized existing Safespan assemblies with the exception of the rigid anti-uplift bracing. However, these members were devised out of scaffold tube and clamps, which are cheap and readily available.  This device was used to choke around existing bridge members and push tight against the decking to stop unwanted movement at the tie up cable locations. To further stabilize the platform, typical tie up cables were horizontally installed, giving resistance to sliding under gravity while the bridge was lifting.  The distinct quality of this design was its ability to take advantage of existing equipment without the use of specialty-prefabricated pieces, which can be both costly and time consuming to produce. D.H. Charles Engineering used all the parts and pieces available to construct multiple phasing models and employed a solution that was both technically sound and realistic for the contractor to install.

Ingenuity of Design for Efficient Use of Material and Labor:

Safespan provided the equipment for this platform; however, Purcell Paintings and Coatings performed the installation.  Although the design process was extremely extensive due to the complexity of the dynamic bridge structure, it was safely erected using typical installation procedures for horizontal Safespan platforms. The only caveat was that counterweight had to be added to the existing structure at each installation phase. However, this is a small price to pay when looking at the overall scope and ease of accessing such a complicated structure without impeding its functionality.

Exceeding Client/Owner’s Needs or Expectations:

Careful consideration and evaluation of all the potential risks, as well as close collaboration between the contractor, engineers and city representatives, were critical to the completion of this venture. The final product functioned perfectly throughout the duration of the project.  The entire system proved safe and stable, requiring very little modification or maintenance as the job proceeded. Even with rain on 70% of the workdays, there were no breeches of the containment system, and the job finished on schedule and within budget.  Given that some said a Safespan platform could not be successfully installed and function properly on this bridge under the dynamic conditions, the incredible success of the design proved to exceed the expectations of not only the client, but also the entire industry.

Suitability of the Structure for its Environment:

The nature of the project not only required complete containment of blasting operations for environmental purposes, but also demanded a fully functional bridge. Given both of these items were achieved, it is evident the design had an extremely low impact on the bridge and the surrounding environment. The structure came and went, leaving the bridge in better shape than before and with no signs of its existence.  This is the ideal result of a structure perfectly designed to fit its environment.

 

 

 

 

 

 

 

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SSPC – George Campbell Award

DHC is proud to have been awarded the Society of Protective Coating’s (SSPC) George Campbell Award, for work on the Fremont Bridge, in Seattle, WA.  This honor is bestowed as recognition of outstanding achievement in the completion of a difficult or complex industrial or commercial coatings project.

In an attempt to paint a clear picture, imagine yourself working on the underside of a car in the median of a busy street.  In addition, assume you are constantly interrupted by someone jacking the back end ten feet off the ground.  To further complicate your task, suppose you are not resting comfortably on the ground, but suspended from the underside of the car itself.  Lastly, and most importantly, let’s envision that the car is not your own, but in fact is a historic 1965 Shelby GT350 in mint condition.  If you are able to put yourself in this scene, you may start to grasp the level of pressure put on the team approaching the Fremont Bridge project.

The respected and experienced firm of Purcell Painting & Coatings was awarded the contract to access, enclose and paint the bridge while protecting the local environment and ensuring roadway and boat traffic would not be impacted.  The Fremont Bridge is a double-leaf bascule bridge spanning the Fremont Cut and connecting the Seattle neighborhoods of Fremont and Queen Anne.  It was opened to the public in 1917, and added to the National Register of Historic Places in 1982.  According to WSDOT, due to low clearance, the bridge opens on average 35 times a day to allow for boat traffic.

After much planning and coordination, led by Sr. Engineer Josh Rubero, P.E. and President Jasper Calcara, P.E., D.H. Charles Engineering, Inc. developed and designed a lightweight Safespan suspended platform system which was capable of supporting workers and debris when the bridge was in use, while also remaining stable and secure when the bridge was raised throughout the day.  Raising the platform presented extreme challenges to the design team, as the suspended deck and bridge structure would be exposed to complex loading conditions not normally experienced by a traditional horizontal platform.  Intense wind loading on the underside of the platform, stabilization during raising, and very sensitive counterweight restrictions were only a few of the issues addressed throughout the design process.

With intimate involvement of WSDOT, the project was ultimately completed safely, on schedule, and to everyone’s extreme satisfaction.  Due to the historic significance of the Bridge, the vibrant, colorful and heavily populated neighborhoods it services (Fremont bills itself as the Center of the Known Universe), and the complex and unique challenges presented, DHC is proud to have been part of such a successful project.

-Josh Rubero, P.E.

salinas river bridge project

SIAC – A Historic Challenge

As our nation’s buildings and bridges continue to age and deteriorate, contractors are regularly challenged with completing retrofit, painting, abatement and other upgrades, without overloading or damaging the existing structures.  With more and more federal, state, and local entities rewriting their specifications to put the structure evaluation and certification responsibility on the contractor, it has resulted in a new set of challenges for an industry not familiar with this complex issue.

Serious risk to worker and structure safety can result from the substantial loads imparted by temporary work platforms and scaffold systems, as well as the extreme wind forces that can develop when an improper containment program has been implemented.  Coordination between the engineer designing the temporary access/containment systems, engineer certifying the existing structure, specialty subcontractors, general contractor, and the owner’s reviewing representatives, can be a drawn out process fraught with complications.  Therefore, a clear understanding of the actual structure condition and its potential vulnerabilities is critical in project planning and execution.

The Certification Challenges:

  • Many structures in the United States well over 100 years old, and complete or legible as-built drawings are not commonly available.
  • Engineers and/or contractors are forced to perform extensive field surveys to determine framing sizes, and must estimate material properties.
  • Current load demands coupled with excessive deterioration has already pushed many of these structures to their limit.
  • Many engineers with experience in analysis or design of these structures have no experience in the temporary access and containment design industry.
  • Many engineers in the temporary access and scaffold industries do not have experience or willingness to evaluate and certify the permanent structures.
  • Older buildings and bridges were regularly constructed with framing built-up out of many small plates, channels, and lattice assemblies; riveted together to form large sections. In comparison to the large solid steel beams and columns used in today’s construction, these historic shapes are much more time consuming to evaluate.

In a world of razor thin margins, it is critical that bidders request and evaluate the structure design loads, as-built documentation, levels of deterioration, or reserve capacities, prior to presenting their proposal.  State and federal agencies are getting better at outlining these resources and requirements in the bid documents, however, inconsistencies are still commonplace, and can results in tens of thousands of dollars in unexpected design fees, when overlooked.

The Document Impact:

  1. When the reserve load rating of the bridge or building is provided in the project specifications, the costs involved in the structure certification is typically minimal.
  2. When complete as-built plans and stress sheets are provided, costs can be kept under control, as a complete structural analysis is not always necessary.
  3. When complete and detailed as-built plans are available, but no stress sheets are provided, the design costs can be significant as a full structural analysis is often necessary.
  4. When no plans are available, the fees to collect complete structure dimensions and details, and ultimately prepare a full structural analysis, can be extremely high.

The following case studies demonstrate many of the challenges discussed so far in this article, and although each experienced different challenges, the common themes exhibited were the following:

  • All projects were all completed successfully.
  • DHC was involved in both the temporary access/support system design and structure evaluation.
  • All parties were proactive in their coordination and planning.

Myrtle Street Water TankCase Study – Myrtle Street Water Tank – Enclosure of existing bridges, towers and tanks with netting or shrink-wrap, can often result in these structures being exposed to higher wind forces than they were originally designed to sustain.  Therefore, a wind monitoring program and enclosure removal plan is regularly developed to ensure that a critical load limit is never exceeded.  For the massive steel water tank located in Seattle, WA, the as-built plans were examined, and a complete 3D computer model of the structure was developed in order to determine at what wind speeds the system could remain enclosed.  The time and expense to remove and reinstall enclosure or access systems can be extreme, and therefore a careful evaluation of various wind speeds vs. structure and access solutions is important on many jobs.

golden gate bridge Ft. Pint Arch projectCase Study – Golden Gate Bridge Ft. Point Arch – In order to complete the retrofit of this historic structure, a complex scaffold, suspended platform, cable frame, and containment system was erected over the Civil War Fort Below.  Approval from the bridge authority was contingent on the contractor proving that no existing framing would be overloaded at any time.  Although, surprisingly detailed plans and stress sheets were available, a complete structural analysis of each and every framing member was performed, with many pushed to the design limit.  It was careful planning, coordination between all trades, and a professional submittal package, that proved critical in gaining approval for installation.

Wakefield BuildingCase Study – Wakefield Building – When this 1920’s 5 story reinforced concrete structure was rocked by the 1989 Loma Prieta earthquake, much of its damage remained hidden for many years.  It wasn’t until significant retrofit work had begun in the basement, that it was discovered that various primary structural support columns were completely shattered.  Designing an emergency shoring system capable of supporting all the floors above while columns were cut and replaced at the basement level, required an extensive assessment of the existing structure and careful evaluation of various shoring options.  In lieu of a costly custom fabricated steel support system, a dense matrix of relatively light system scaffold was erected.  This system was installed on all floor levels, effectively collected the weight of the building and diverted it away from the damaged columns, and allowed the contractor make the cuts and repairs, while using a very cost-effective and locally available resource.

salinas river bridge projectCase Study – Salinas River Bridge – The California Department of Transportation has traditionally required that painting and abatement platforms be designed for a live load of 45 psf, with an additional concentrated load of 1,000 lb.  Using historic inspection reports and performing a supplemental structural analysis, it was determined the existing highway bridge could not support the proposed 45 psf required by the state.  Therefore, close coordination with contractor and DOT was necessary in order to develop detailed construction procedures and load monitoring program to ensure loading stayed within the bridge’s reserve capacity.  In this specific case, the DOT allowed for a load rating of less than that outlined in the specifications, however, this variance has not been consistently approved on all bridges.

Looking Forward:

With proactive planning, a clear understanding of project documents, and the involvement of experienced professionals, even projects with the most sensitive of structures can be repaired/painted successfully and under budget.  It is my hope that through education, clear specifications, and an expanded industry awareness, contractors will not be hit with unexpected delays and design costs on such a regular basis.

D. H. Charles Engineering, Inc. has been in the shoring, scaffold, and temporary structure’s design industry for over 20 years, and has developed complex and simple solutions for buildings and bridges throughout the United States and Canada. Our ability to evaluate and certify the existing structure while simultaneously developing and designing a wide array of access, containment, and shoring systems, has given our customers the confidence to pursue these jobs without reservation.

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Engineering Solutions – Enclosed Scaffold on High Profile Bridges

Enclosed scaffold systems on bridges can expose some of the most complex erection and engineering challenges to face the scaffold industry today.  Extreme heights, elaborate bridge profiles, severe wind speeds and other complications regularly drive scaffold contractors and engineers to develop state-of-the-art solutions.  The following three high-profile bridge projects may have faced similar design obstacles, but ultimately they each implemented unique and individually successful solutions.

Dames Point Bridge – FL

Dames Point Bridge, FL Project

Abhe & Svoboda, Inc. (ASI) was faced with the daunting task of providing full access and enclosure of all stay cables on the Dames Point Bridge in northern Florida.  With scaffold heights pushing 300 feet, D.H. Charles Engineering, Inc. (DHC) worked closely with ASI and bridge engineers to develop an enclosure and wind speed removal scheme which would allow for completion of painting operations, while ensuring that scaffold and bridge components would not be overloaded.  After completion of preliminary engineering, the system was eventually designed and certified to withstand 40 mph wind speeds when enclosed with shrink wrap, and 131 mph wind speeds with the enclosure material removed.

The primary challenge was proving that the 7-foot wide scaffold, being secured to only the bridge suspension cables, could reach the tremendous heights without overstressing scaffold elements or exceeding the capacity of bridge stay cables.  Stresses in the scaffold members were directly related to how much the framework would actually move horizontally under wind load.  On most projects the scaffold is tied uniformly to rigid support elements so that the entire scaffold exhibits minimal deflection between unyielding tie points.  In this case, the supports themselves, the stay cables, varied in length up to 700 feet and each point on each cable was able to move a different distance under the same load.  Due to this complication and the non-uniform geometry of the bridge, a simplified linear design approach was ruled out.  Ultimately, a complete 3D model of the entire scaffold system was developed, accounting for the different rigidity of each and every cable stay tie point.  Vertical diagonal bracing and anchorage to the bridge were then strategically placed, in order to finalize the design and confirm adequacy of the overall system.

The work was completed successfully, but not before the entire system and engineering was put to the test by Mother Nature.  Original weather reports had Tropical Storm Fay projected to completely miss the project site.  However, a last minute shift in direction brought the storm to the scaffold before ASI could completely remove the enclosure material as directed by the design plans.  Scaffold workers rushed to make large X-cuts throughout the shrink wrap in order to increase wind flow through the enclosure and reduce impact on the scaffold.  Although the enclosure material completely disintegrated due wind speeds in excess of 80 mph, there was essentially no damage to the scaffold itself, and the project was completed on schedule.

San Francisco-Oakland Bay Bridge – CA

San Francisco-Oakland Bay Bridge Renovation – CA

As construction wraps up on the high profile east span replacement, it not as widely known that the west suspension span of the Bay Bridge underwent a significant seismic retrofit not too long ago.  To complete a portion of this work, the roughly 460 foot tall main towers were enclosed with an access scaffold and containment system over their entire height, in two phases.  Unlike the Dames Point Bridge, this system was designed for maximum anticipated wind speeds, with no plans to remove the enclosure material.  Although dealing with very high leg loads and other design issues proved difficult, it was the containment and geometry of the bridge tower legs that resulted in most of the complications during the design phase.

The diamond shaped voids between the tower bracing resulted in horizontal and vertical gaps of up to 60 feet between available tie points.  The independent scaffold walkways did not prove adequate to allow the scaffold to free span these gaps.  Therefore, plan bracing and horizontal ties were used so that the entire scaffold cross section shown below could be analyzed as a giant truss with each walkway acting as either the tension or compression chord, depending on wind direction.

Using the geometry of the tower legs to our advantage, we were able to brace the scaffold chords tight to the tower steel in multiple directions, and transmit the high loads over long spans with a light and very efficient framework of scaffold.  Preliminary analysis showed that extreme axial loads would develop in horizontal tubes of the compression chord, and overload many of the members.  However, the flexibility of modular scaffold allowed for multiple options to resolve this problem.  One solution included placing truss ledgers at locations of maximum load to increase strength of the individual framing, while another was to simply install ledgers at every cup along the height of the scaffold to spread the load to multiple tubes.  Use of systems scaffold also allowed for the cross section of the entire scaffold tower to be easily tapered as the tower reduced in size over its height.  This scaffold was ultimately erected at multiple locations throughout the scope of the project, and performed exceptionally well.

Golden Gate Bridge – San Francisco, CA

When performing a state of the art retrofit on one of the most beloved bridges in the world, contractors were forced to extreme measures to perform their work without impacting the integrity of the structure.  At the south approach of the Golden Gate Bridge, a roughly 300 foot arch gracefully bows over the civil war fort below.  This popular tourist destination was built in the 1850’s, and was to remain open to the public during the extensive work above.  Suspended platforms, complex scaffold and extensive containment systems were widely used to allow for work throughout the arch.  The most complicated of the many systems designed for Shimmick Obayshi, included a 200 foot tall cuplok scaffold system, partially supported by a suspended aluminum space frame platform, and completely enclosed with shrink wrap.

The bridge district required that every structural element of the existing arch be checked for the loads to be imposed upon it from the scaffold system, in conjunction with original bridge design loading.  Therefore, DHC had to demonstrate that elements originally exposed to wind pressures across their 2 foot width could now support wind from a 36 foot wide sail.  Normally, a very dense scaffold system, or possibly an external bracing scheme would be implemented to help relive the structure from the increased loads.  However, due to restrictions from the fort below, and limited access in general, a very minimal framework of scaffold would be allowed.  Therefore, an intricate hybrid system of cables, scaffold and suspended platforms was ultimately developed to satisfy the bridge’s enclosure needs

Numerous 7 foot by 10 foot systems scaffold towers were erected around the main arch columns, which free spanned up to 70 feet vertically and were spaced as far apart as 42 feet 6 inches on center.  This scaffold was either directly supported from the ground, or set on an independently suspended work platform.  These individual scaffold bays were then tied together with a matrix of cables, which acted as the supporting skeleton of the shrink wrap.  These cables were installed with very specific sags between the support points at each scaffold tower, in order to control the high tension loads that would develop, and attempt to pull the opposing scaffold together.

Golden Gate Bridge - San Francisco, CA scaffolding plans

The cabling proved to be the backbone of the entire scheme, allowing for a light and efficient overall system while providing the vast enclosure required for the work site.  Although the cabling was efficient from an installation point of view, it proved to be challenging on the engineering, as the cables developed extreme tension loads which were passed to the highly taxed bridge elements.  Eventually, by simultaneously manipulating the cable sizes, spacing, sag, scaffold assembly and wind speeds a system was chosen which met everyone’s needs and gained approval from the bridge district.

With the overwhelming magnitude of the project, elaborate site restrictions and endless field changes, it was truly impressive that a scaffold implementing so many complex support, bracing and reinforcing schemes could work in harmony to meet the demands of this world class bridge.

Year in and year out, our nation’s most historic and important bridges require extensive repair, maintenance, and retrofit work.  The scaffold industry has played a vital role in allowing this work to be completed efficiently and safely while being exposed to some of the most hazardous conditions in the construction world today.  Pushing the engineering and erection envelope has allowed scaffold contractors to stay at the forefront of this industry, has exhibited in some of the most impressive projects over recent years, and leaves us excited to see what the future brings.

Ballard Drive Bridge Engineering Project

SAIA – Balancing Needs – A Bascule Bridge Story

Published in the September 2012 issue of SAIA

By Jasper Calcara, PE

If you can imagine the risks of two sumo wrestlers jumping on a child’s seesaw, you can start to visualize the challenges facing engineers on the Ballard Drive Bridge painting project.

The Ballard Drive Bridge is just one of many historic bridges scattered throughout the Pacific Northwest, which has maintained regular service for nearly 100 years.  Due to their age, continuous use, and exposure to the elements, these bridges require regular inspection, maintenance, and repainting.  Performance of this work can often result in difficult challenges for specialty bridge and painting contractors to provide efficient, safe, and contained access.

Ballard Drive Bridge Engineering ProjectThe 218’ span double-leaf bascule bridge was one of four bascule bridges built in Seattle between 1917 and 1925, and acts as a critical artery for local roadway and boat traffic.

It was added to the National Register of Historic Places in 1982, and uses a system of finely tuned counterweights and machinery to raise the bridge to near vertical.

Purcell Painting & Coatings, was contracted to blast and paint the entire structure, and contain all the lead paint debris, without restricting operations of the bridge. Raising the bridge anywhere from 250 to 500 times a month prohibited dismantling and reinstalling the access system each time, and therefore the platform would have to rise with the bridge.

Raising the platform presented extreme challenges to the design team, as the suspended deck and bridge structure would be exposed to complex loading conditions not normally experienced by a traditional horizontal platform.  Intense wind loading on the underside of the platform, stabilization during raising, analysis of all bridge framing, as well as very sensitive counterweight restrictions were only a few of the issues to be resolved.

After working with multiple engineering groups who were unable to devise a suitable solution, Purcell decided to proceed with the system proposed by D.H. Charles Engineering.  President Jasper Calcara, PE and suspended platform design engineer Josh Rubero, PE outlined a Safespan suspended platform and staged containment program, which would allow for full erection, stabilization, and containment within all bridge limitations.  The key to the design was the use of extremely light decking, as every pound of platform added to the bridge had to be carefully counterbalanced within strict limitations.

The platform loading and added counterbalance proved to be the sumo wrestlers on the seesaw, wanting to overload the bridge if too much weight was added to each side of the pivot point.  It was such a critical issue that a city engineer was on site throughout the duration of the project, carefully monitoring the addition and removal of over 900 pieces of 50 lb. counterweights strategically placed in accordance with the design plans. With the loading limits satisfied, the stability of the platform and strength analysis of the bridge framing had to be resolved.

Ballard Drive Bridge Engineering ProjectThe Safespan platform consists of corrugated steel decking, longitudinal support cables and vertical suspension devices, which result in a very flexible overall system.  Although the deck is very light, it lacks the critical rigidity that a typical scaffold or suspended platform system provides.  Unfortunately, it was the weight of more rigid systems that made them impossible to utilize, and engineers were faced with the task of stabilizing a system that would turn into a nearly 4,500 square foot flexible wind sail.

When the platform rotated to near vertical, engineers were concerned with high winds hitting the exposed face of the decking and slamming it into the underside of the bridge, while gravity attempted to shift the deck out of position.  Therefore, a series of rigid anti-uplift and horizontal bracing members were installed to hold the deck firmly in place, while intentionally passing the load to the stronger framing points of the bridge substructure.  Lastly, an array of vertical to horizontal suspension cables were devised to allow the platform to shift orientation, and eliminate any sag or sway of the deck toward the water.

Although the structural evaluation of the bridge and platform design were extremely extensive, the final product functioned perfectly throughout the duration of the project.  The entire system proved safe and stable, requiring very little modification or maintenance as the job proceeded. Even with rain on 70% of the workdays, there were no breeches of the containment system, and the job finished on schedule and within budget.

The careful consideration and evaluation of all the potential risks, as well as close collaboration between the contractor, engineers and city representatives, were critical to the completion of this project. With another innovative solution executed with precision, the industry is that much more prepared for the next challenge to be presented.

Hydraulic Bracing Project

MD Brace System Aids Cast-in-Place Job Off Lake Michigan

By: Tommy Marciniak – SPECIAL TO CEG

Completing a cast-in-place project that measures 46 ft. (14 m) wide by 39 ft. (11.9 m) long by 35 ft. (10.7 m) deep near the shores of Lake Michigan is a challenging project in and of itself. Now add in the challenge of being in the middle of an active British Petroleum (BP) refinery, and you have the unique situation that Superior Construction Company Inc., of Gary, Ind., found themselves.

“When the project started, in February of 2012, my original plan was to use a slide rail shoring system,” said Paul Armstrong, superintendent of Superior Construction.

With its modular, flexible design the slide rail shoring system can comply with a wide variety of shapes and sizes. Installed from the top down and removed from the bottom up, minimizing excavation size, soil disturbances, restoration time and cost. Installation is done with low vibration, providing soil support for excavations, adjacent structures and existing utilities.

“I went to the internet and started searching for slide rail shoring systems,” said Armstrong, “that brought me to GME’s Web site. After a couple of conversations, they sent two representatives over to review the project in person.” One of those people was Dennis Parker, product manager of GME.

“After meeting with Paul, we had a good idea of what he wanted and how he wanted to proceed with this project,” said Parker.

Originally, the project was designed to be three smaller pits, meant to be used for sulfur retention.

As the project progressed, the three small pits morphed into one large pit, located in the middle of the active refinery. With the change of location and the change to one large pit, some site demolition was needed, requiring the vibration alarms to be removed. “With the partial site demolition that needed to occur and the vibration alarms removed, everybody involved in the project turned to sheeting,” said Parker. “That opened the door for GME and Sunbelt Rentals Pump & Power Services, to quote our new MD Bracing system.”

“We [Superior Construction] already had trench boxes on site from Sunbelt,” added Armstrong. “They were already an approved vendor through BP; it just made the whole process a little easier.”

The GME MD Brace System is the only large sheeting and bracing system 100 percent designed and built in the United States. The system consists of enclosed hydraulic rams and static extensions, which can be stacked and staged on top of each other during initial installation to help speed up installation time. Engineered to use a variety of sheet piles, the MD Brace is a cost saving system when compared to traditional weld and cut systems. It is designed for use on linear applications, bridge footings, pump stations, soil remediation’s, tank installations and a myriad of other large projects.

“Sheeting and bracing seemed like it was a great deal that saved the client time and money by doing one large pit instead of three smaller ones,” said Robert Morrow of Jacobs Engineering, the general contractor of the BP project.

“With the MD Bracing System now able to be used, we contacted DH Charles Engineering Inc., to have them perform the site specific engineering for the project,” said Parker.

“First look at the job, (a year prior to actually breaking ground), this project appeared to be a very good candidate for the use of hydraulic bracing,” said Jasper Calcara, president of DH Charles Engineering, Inc. “With the phasing of bracing installation and removal, along with the other aspects of the design, hydraulic bracing was the leading candidate.” Phasing refers to installing the entire system to full depth, then, as the project progresses, removing part of the shoring, while maintaining a safe and secure working area.

With stamped and approved plans in place, using 50 ft. (15 m) long SZ-21 sheeting with four sets of the MD Brace rings, the requirement changed.

“After multiple revisions, over the course of a year, it was finally decided that the design would be based on groundwater level at 17 feet below grade,” said Calcara. “This project combined almost every difficult issue that can impact a shoring pit; depth, building surcharges, deflection concerns, very strict clearance requirements retention of groundwater and poor soils.”

“Going from full depth dewatering to having water at a depth of 17 feet was a huge change in the project for us,” said Parker. “We had to change everything on the project; the sheets changed to 50 feet long SZ-27 sheets with a sealant on them. The number of MD Brace rings stayed the same, but two additional cut and weld rings was required at the bottom of the system, one of which was a sacrificial ring.”

“From an engineering standpoint, I cannot say enough about DH Charles,” said Armstrong, “when the project conditions changed or a problem arose, we had an answer on how to proceed the next day without any project time lost.”

With the final shoring design submitted and approved, the project was able to break ground, under tight time constraints. “All material was on site when it was promised. GME did a great job with its manufacturing time line to make that happen for us,” said Morrow.

The success of this project relied on constant communication between all parties.

“Dennis and myself were proactive as a team, which allowed us to stay ahead of the project, which allowed us to have an overall smooth project (from an engineering stand point)”, added Calcara.

“From GME’s stand point, we wanted to give Superior Construction the closest thing we could to a turnkey operation,” said Parker.

“That meant, not only did GME source the sheets needed for the system, we had an installation consultant out on site to instruct them on installation and removal of the system just as we do with our slide rail shoring system.”

“Being there for the first full week of installation and consulting with them on the removal of the system, proved to be a great learning experience,” added Benjamin Sybesma, assistant slide rail manager of GME and the installation consultant on site.

“There proved to be many obstacles throughout this job, but through hard work and persistent communication, GME and Superior Construction were able to work through it and produce an excellent and safe shoring project.”

“Having the GME installation consultant on site was a big thing,” said Armstrong. “Having that built in was a key for the overall safety of the site and the people around the site.”

Access to the site was another minor obstacle that had to be overcome. Since the project was taking place inside an active refinery, space was limited. The excavating was done by John Deere 350 and an 85 D mini. All other equipment needed for the site had to be lifted over a 70 ft. (21 m) tall by 30 ft. (9 m) wide wall by a crane.

With the project commencing under tight time constraints, one thing stood out about the system: the flexibility of the MD Brace system. This was the first time that Superior Construction had used a system like the MD Brace, so there was a small learning curve. However, by using the MD Brace system, Superior Construction was able to gain some advantages over using a traditional beam and cut process with sheet pile. “With the MD Brace, we didn’t have to worry about welding or the exposure involved with trying to place beams,” added Armstrong. “That allowed us to save a lot of labor time.”

“Being a hydraulic system, [the MD Brace] provided an extra level of protection to the adjacent structures by actively pushing against the sheets, and minimizing potential movement,” said Calcara.

The MD Brace has the adjustability to work with rectangular and non-rectangular excavations to be safely shored.

“The flexibility of the system allowed us to work with what the sheets gave us. That same flexibility, and overall ease of the system, enabled us to save time during the installing and even more so during the removal of the system” said Armstrong. “Overall, once the project got underway, I had no issues with the system that weren’t quickly solved. I would push to use the MD Brace again on a similar project, especially one with similar time constraints.”

Jacobs Engineering provides full-service engineering, design, construction and construction management services. For more information, visit www.jacobs.com

Sunbelt Rentals is one of the largest equipment rental companies in the United States. The company serves a wide variety of customers from commercial contractors to specialized service industries. For more information, visit www.sunbeltrentals.com

DH Charles Engineering Inc. is a civil/structural engineering firm specializing in providing construction-engineering services to contractors throughout the United States and Canada. For more information, visit charlesengineering.com

Superior Construction Co. Inc., located in Gary, Ind., is a general contractor with ties in the highway, industrial, concrete material and wastewater treatment industries. For more information, visit www.superior-constructions.com

GME is a producer of trench shoring and shielding equipment. The products it offers range from a single hydraulic shore system, trench shields, slide rail systems and hydraulic bracing systems. As an industry pioneer since the 1960’s, it holds patents on many trench shield features and continues to lead the industry in the areas of product development, innovation and effectiveness. For more information, visit www.gme-shields.com.