Award Winning Shoring Key to Success

In recognition for the successful collaboration and the innovative shoring design, this project was awarded the 2020 Scaffolding & Access Industry Association (SAIA) Shoring Project of the Year.

Originally built in 1962, Climate Pledge Arena (originally known as Key Arena) is located in the heart of the historic Queen Anne district of Seattle. To take advantage of its prime but densely populated location, the arena was built down into the ground, with a pavilion-like sloping roof that has become a staple of the Seattle skyline. As part of a $700 million remodel, the Seattle Center Arena would get entirely new facilities, meaning the entire interior structure of the arena would be demolished and rebuilt from the ground up. With the majority of the arena built underground, this meant the existing concrete retaining walls would no longer have the concrete floors to support them and would require soil anchors be installed for support. In order to install those new soil anchors, an 18,000 lb micro pile drilling machine had to be driven on the existing slabs. However, the drill rig was a load the slab was never designed to support.

Due to the rapid pace of construction, it was immediately clear that coordination and clear communication would be required for the project to succeed. DHC was met on site by scaffolding contractor Performance Contracting, Inc.,  as well as representatives of both the general contractor and the structural engineer (SEOR) for the structure. The site to be shored was walked extensively, with each party noting critical locations that either needed to be shored, to be left open for access, or obstructions that needed to be worked around. The area of highest concern was over the Event Level ramp. The SEOR made it clear the Main Concourse slab above the ramp need to be shored to support the drill rig. At the same time, the general contractor was adamant that the ramp had to stay open and unimpeded in order for construction to stay on schedule. With demolition well underway, the ramp saw a constant stream of dump trucks as material was moved out of the stadium. The scope was to design a shoring system that fully supported the upper slab while taking up no space on the floor below.

After exploring some initial options, it was eventually determined that the most feasible way to adequately support the Main Concourse slab while simultaneously leaving the ramp open would be to essentially build a “tunnel” in the shoring; the slab itself would be shored up using modular cuplok scaffolding, which would then be set onto large steel beams spanning the width of the access ramp. After confirming the type of drill rig that would be used, DHC performed a detailed moving load analysis of the drill rig to model the loading that would be applied to the shoring. This drastically reduced the load on any one shoring beam, allowing for the use of lighter, more easily erectable beams.

Due to the slab above the ramp dropping as the ramp descended, as well as the presence of concrete beams at awkward angles, the modular, flexible nature of cuplock scaffold was used to its fullest as the main support of the Main Concourse slab. To support the steel beams on either side of the ramp, RMD Kwikform Super Slims were used as vertical post shores. While originally designed for use in falsework and concrete wall pouring applications, the Super Slims had high axial capacity and DHC had experience in using them in shoring applications. By bracing them to each other, as well as anchoring them to concrete wall and ramp for stability, a stabile base for the shoring tunnel was created that took up less than a foot of width. Once fully installed, the tunnel shoring allowed for the tie back installation to successfully move forward without any hinderance to the demolition work.

Mark Palmatier, PE – Branch Manager – (425) 559-9775

Jasper Calcara, PE – President – (760) 436-9756

Chicago Office Opening


D.H. Charles Engineering, Inc. has a long-standing tradition of servicing clients in the State of Illinois since obtaining our IL SE license, and has developed close relationships with contractors, IDOT and CDOT OUC over the past twenty years working in the area.  Even though we’ve felt confident we could continue to meet the needs of our customers, as had been proven with the hundreds of projects completed, we knew a local presence would provide the extra level of support we wished to offer.  Therefore, after many years of looking for the right opportunity we are thrilled to announce the opening of our newest office in Chicago.

Andrew Schwarz, PE, SE, was born and raised in the Chicagoland area and continues to call the area home. He has over twenty years of experience in the structural and geotechnical engineering discipline, including starting out in the bridge design industry while also working in the building design industry.  For the last 10+ years, he has been working in the underground shoring and temporary works industry expanding his close relationships with contractors in the area.   Andy is excited to be joining the DHC team and looks forward to growing the Chicago and Midwest operations for the company while assisting the company nationwide.


The success of the Seattle, Portland and New York offices has proven that although our resources are now spread throughout the Country, we can effectively work as a team and can be depended upon to share our wealth of design experience and knowledge regardless of location.  Our customers have come to expect collaboration and support from all our team members in developing state of the art and cost-effective solutions for their construction engineering needs.


Andy and the entire DHC team look forward to servicing an expanded customer base and providing more on-site support to projects in the area.  Please contact any of our team members to discuss how we can be of assistance on your jobs or bids.

Andrew Schwarz, SE, PE – Branch Manager/Sr. Engineer – (872) 240-8033

Jasper Calcara, PE – President – (760) 436-9756

Luke Griffis, SE, PE – Vice President – (707) 537-8282


Temple Galaxia – Burning Man

10 Completed Exterior

Burning Man is an annual gathering held for one week every year in the harsh and unforgiving Black Rock Desert of Nevada where a community comes together to construct a temporary city filled with art installations and camps dedicated to radical self-expression and self-reliance. Participants are expected to be collaborative, inclusive, creative, and connective and in the end, leave no physical trace of the event out of respect for the environment. The centerpiece of last year’s event was the Temple Galaxia, a roughly 195’ diameter by 65’-tall spiral mountain-like structure constructed from numerous timber triangular trusses, making its construction very difficult and complicated.

02 Scaffold

Although the scaffold shoring ring at the heart of the temple Galaxia construction seems very straightforward at first glance, the hidden complexity of the design derives itself from the multi-directional loading conditions created by Galaxia’s sheer size, weight, irregular shape, and multiple phases of construction. With little room for error due to the limited construction window, a remote desert location, and the tight tolerances that would be required to ensure the final integrity of the structure, the project offered some unique challenges to overcome.

04 Scaffold & Full Crown (Low Res)

The scaffold would initially need to support the roughly 20-ton weight of the upper crown, which would also result in a top-heavy wind load. Then, as each of the (20) spiraling petals of the temple were constructed, an additional vertical, radial, and tangential load would be introduced to the scaffold system from the odd shape of the leaning trusses. Eventually the scaffold would need to support the worst-case scenario which would include the wind impact from the full profile of the Galaxia structure along with the imbalanced loading caused by the lean and twist of only half of the spiraling truss petals being in place. This resulted in a design requiring a spiraling bracing pattern to match the structure that it was supporting and extra shoring towers to prevent the individual petals from twisting during their installation.

11 Cradle Release

The second challenge would be developing an anchorage system capable of supporting such loads. Considering the “leave no trace” policy of the event, providing any concrete footings or deadmen was out of the question.  And given the remote desert location, using any heavy-duty anchorage that would require any specialized equipment would not be possible. Thus, we were limited to very low-capacity earth anchors creating the need for 88 bracing points around the perimeter of the scaffold supporting the spider web of ratchet straps required to tie down the scaffold structure.

09 Completed Interior

The next challenge would be to create an interface between the Galaxia structure and the scaffold that could adequately absorb and transfer the loading. This cradle structure would need to be custom built to fit Galaxia’s unique shape, rigid enough to maintain the proper elevation for the Galaxia build, and yet flexible enough to release the scaffold from underneath the temple once construction was completed. Initially, we considered supporting the Galaxia members directly from the metal scaffold framework, but after further consideration, using timbers would offer the flexibility we would need to handle potential field variances and meet the unique factors involved in Galaxia’s construction process.  Two continuous 6×12 timber rings were constructed over the top of the scaffold legs supporting crossing timber ledgers with reinforced notches cut specifically to align with Galaxia’s spiraling truss petals.

12 Completed Galaxia

After 22 days of construction, 12-hour workdays, and over 10,000 man-hours in the extreme temperatures of the desert playa, the temple Galaxia was successfully completed to the cheers of the volunteer construction crew. One of the most difficult parts of the process was removing the scaffold, which had shouldered the brunt of Galaxia’s weight amidst 30-40 mph dust storms and a complicated construction process. Workers speculated that the settlement of the Galaxia structure would be anywhere from 1 mm to complete and utter failure, but the whole timber cradle and scaffold ring worked out as planned. The temple became self-supporting after settling about 5” once the scaffold was removed, which was a pretty amazing result considering the complexity of the construction. Overall, the project was a huge success and ultimately a testament to all those who helped translate this true work of art into reality.

13 Galaxia Burn (Low Res)

All pictures courtesy of Bruce Schena

Written by Robin Ko

East Coast Office Opening


After successfully servicing clients on the East Coast for over 20 years, D.H. Charles Engineering, Inc. is excited to announce the opening of its newest office in New York City.  Although originally founded and headquartered on the West Coast, DHC has worked tirelessly to prove to its customers that regardless of location or time-zone, excellent service can be counted on day after day.  A culture of immediate response to all calls, and expert support by experienced engineers, has resulted in long and valued relationships with our national accounts.


Branch Manager and Sr. Design Engineer Chong Kim, P.E., has developed personal relationships with contractors throughout the greater NY, NJ and New England areas for over a decade.  His experience in design of complex excavation shoring systems, along with many other temporary works designs, made him an excellent fit for heading DHC’s expansion East.  He’s passionate about what he does, and brings innovative design ideas to his projects, with a positive and creative attitude.


New NY Bridge – Photo By: New York State Thruway Authority

The success of the recently opened Seattle office has proven that although DHC resources are now spread throughout the Country, they can effectively work as a team and be depended upon to share their wealth of design experience and knowledge regardless of location. Their customers have come to expect collaboration and support from all team members in developing state of the art and cost-effective solutions.

DHC looks forward to servicing an expanded customer base and providing more on-site support to projects in the area.  Please contact any of our team members  to discuss how we can be of assistance on your jobs or bids.

Chong Kim, PE – Branch Manager/Sr. Engineer – (914) 292-4337

Jasper Calcara, PE – President – (760) 436-9756

Luke Griffis, SE, PE – General Manager – (707) 537-8282


DHC Expands to Seattle Area

After much planning and the steady encouragement of many of our customers, DHC is proud to announce the opening of an office in the greater Seattle area.  With main branches in Santa Rosa & San Diego, and satellite offices in Oakland & Sacramento, the Seattle location becomes the 5th for DHC.

This new office is being managed by John Meissner, PE, who is a native of the Pacific Northwest and is excited about the opportunity to meet with many customers personally in coming months.

Even without local branches, DHC has maintained a tradition of effectively servicing contractors throughout the US and Canada, and has developed long-lasting relationships with many of them.  Nonetheless, we look forward to the opportunity to meet many new and existing customers in person, and plan to host various training programs and introductory meetings in the coming months and years.

If you would like to learn more about DHC, or to meet in person, please do not hesitate to contact John Meissner, President Jasper Calcara, or General Manager Luke Griffis.

Partial List of Engineering Services Provided:

  • Excavation Shoring/Safety
  • Tunneling and Boring
  • Scaffold Structures
  • Bridge Jacking and Support
  • Suspended Platforms
  • Crane and Rigging
  • False/Formwork
  • Structural Shoring
  • Re-shore
  • Fall Protection
  • Rebar Cage Stabilization
  • Containment Design





Industry Leader – Guest Lecturer – UCSD

D.H. Charles Engineering, Inc. (DHC) was invited to be a guest lecturer for roughly 120 graduating seniors of the University of California San Diego (UCSD) Structural Engineering department.  With an established passion for educating the construction industry in engineering challenges and safety, DHC was more than happy to accept the invitation, and had the perfect candidate to send to the classroom.


Chong Kim, P.E., a senior engineer and alumni of the same program at UCSD, has worked on thousands of construction engineering designs throughout the US and Canada in his career at DHC.  He took that experience on a wide variety of projects, and developed a presentation titled Temporary Structures and Construction Engineering Industry, to present to students taking the SE140 course.

2015-05-07 10.03.39

SE140: Structures and Materials Laboratory, introduces students to real world challenges and applications of structure design, including: Problem formulation, concept design, configuration design, project management, team working, ethics, and human factors.  –UCSD Course Curriculum

The variety of situations and challenges faced on a construction site can be overwhelming, with many codes and design approaches never discussed at the University.  Therefore, the presentation narrowed the field of construction engineering and focused in on the following key areas:

  • Excavation Shoring
  • Construction Slopes
  • and Slope Stability Analysis
  • Tunneling and Boring
  • Scaffold Structures
  • Bridge Jacking and Support
  • Suspended Platforms
  • Crane and Rigging
  • False/Formwork
  • Structural Shoring
  • Re-shore
  • Fall Protection
  • Rebar Cage Stabilization

Most students do not have the real-world experiences that come with time and that are hard to find in text books, so it was important to illustrate each subject area with as much photographs, colorful anecdotes, and challenges that were faced on particular projects.

excavation shorint

It was important to Chong that he connected with the students on a personal level, as he could clearly recall sitting in their position all those years ago.  He focused on the challenges and fears all young professional faces when starting their first jobs, as well as how to evolve as the their careers take them in different directions.  But most importantly, he wanted to exemplify how important it is to continue to take on challenges and overcome their professional and personal fears.  Presenting in front of peers was a first for Chong, and something he was very proud of accomplishing.

There were many insightful questions from students throughout the presentation, showing that they were truly interested in and engrossed with the subject matter.  The open discussions covered many aspects of construction engineering, codes, loads, workplace environment, as well as general challenges facing engineers in today’s world.


Evoking passion for what we do as engineers is the most important thing an educator can do, and based on the enthusiasm and response of the students, we are hopeful we were able to accomplish this.  We want to extend a special thank you to Professor Lelli Van Den Einde, Ph.D. for bringing us into her classroom and organizing the guest lecturer opportunity, and wish the best of luck to the class of 2016!


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.