News & Publications

Failure of Arecibo Radio Telescope
A dramatic end of an iconic structure, the 305 meter radio telescope in Puerto Rico, December 1, 2020.
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When tensile structures fail they fail catastrophically -- there's no reserve capacity in a parted cable like there is in a bent beam.  These kinds of structures, like cable-stayed bridges, are susceptible to degradation due to corrosion of the cables.  Bridge designers are now including dehumidifying features in the cables to forestall corrosion.  Arecibo's cables might not have been protected that way because the state of the art of such designs had not advanced as far when it was designed.  So the failure could be seen as one of "deferred maintenance" or perhaps as a condition in the original design that prevented thorough inspection of critical connections.  The original support was with 4 cables, and one had already failed, leaving 3 to support the weight of the receiver structure.  When one of those 3 failed, the remaining 2 were insufficient to support the weight plus the impact load of the failure of the 3rd cable (the "dynamic" load the speaker on the video talked about, related to load redistribution), which suggests to me the "safety factor" of the cable assembly under service loads may have been between 2 and 3.  If that's so, it seems low to me.  Another interesting lesson to learn from this failure is the interrelated nature of the various failures -- the failure of the receiver support cable causing the failure of the catwalk support cables, the failure of the cables causing the collapse of towers, the collapse of the towers causing failure of the roadways.

I sure hope the telescope is rebuilt there!

From Temblor.net:
Magnitude 4.5 Pleasant Hill earthquake felt throughout the S.F. Bay area and into the Central Valley
https://temblor.net/earthquake-insights/magnitude-4-5-pleasant-hill-earthquake-felt-throughout-the-s-f-bay-area-and-into-the-central-valley-10015/

ASCE GGB October 2019 Dinner Program: Standard of Care in Engineering Practice
Joshua B. Kardon presented a talk on the standard of care at the Golden Gate Branch of the American Society of Civil Engineers on October 24, 2019  (http://branches.asce.org/golden-gate/).  The presentation helped civil engineers understand what the “standard of care” is, what it is not, who determines it and how, so they can manage their own risk of professional negligence.  Case studies were presented to illustrate basic concepts of the standarof care. 

From Temblor.net/earthquake-insights/ridgecrest-earthquake-shut-down-cross-fault-aftershocks-9249/   Ridgecrest fault rupture, with a main rupture and distributed faulting over 20 m (70 ft). Photo by USGS. To see a series of fault rupture images, see Stewart et al. (Jonathan P. Stewart, Editor (2019), Preliminary Report on Engineering and Geological Effects of the July 2019 Ridgecrest Earthquake Sequence, Report GEER-064, issued July 19, 2019, 69 p., http://geerassociation.org/administrator/components/com_geer_reports/geerfiles/GEER_Ridgecrest_report_ver1.pdf).

August 30, 2019

SEAOC Convention Presentation

​​​​​​​Joshua B. Kardon presented a juried paper titled "The Standard of Care: The Boundary Between Negligence and Non-negligence" at the Annual Convention of the Structural Engineers Association of California at Squaw Creek, California August 28-30, 2019.

September 5, 2019

IABSE 2019 Congress

Joshua B. Kardon presented a juried paper titled, "Professional Liability Risks of Engineering Systems and Designing for Durability" at the International Association for Bridge and Structural Engineers 2019 Congress in New York City, September 4-6, 2019,

February 4, 2011

Working with Architects: Bring the Engineer in Early – A Structural Engineer’s Perspective

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(This piece I wrote appeared in the AIA East Bay (Oakland, CA) Newsletter of September, 2006.)

Architects know that structural engineering is only a portion of the work necessary for a successful project. By the terms of their licenses, California Architects have to know how to do the structural engineering of a project, and they can take responsibility for the structural engineering for any building except hospitals. However, because most building projects are complex, even (or especially) the small residential remodel projects, architects and owners turn to structural engineers to provide their professional services. Ideally, the involvement of a structural engineer results in more economical construction and better structural performance of a building. This is most likely to occur when the structural engineer is involved in the design process from the very beginning.

There are many pressures on a house design, each has to be balanced to provide desired utility, functionality, reliability, quality, and beauty. Architectural considerations affecting space, circulation, light and air have to accommodate structural engineering considerations affecting strength, stiffness, durability and economy. In most situations, optimization of one of the variables results in a necessary sub-optimization of another. A common example is the architectural need for a window that conflicts with the structural engineering need for a shear wall. In another example, the architectural design intent may be ideally achieved on an upper story floor plan without regard to the floor plan of the story below, resulting in discontinuities in the lateral and vertical load paths. The best solution takes all the competing pressures on the design and comes as close as possible to meeting all the diverse and competing demands.

Inclusion of the structural engineer early in the design development stage of a project can result in an initial layout of walls and openings that provides a rational and direct load path while at the same time fulfilling the architectural needs. A rational and direct load path translates directly into less expensive construction and better structural performance in an extreme environmental event.

When a project proceeds through architectural programming and design development without the input of a structural engineer, architectural decisions are made that may not take into account the structural consequences of those decisions. Then, when a structural engineer is brought into the project later for production of construction documents, the structural design may have to impart adequate structural performance by “working around” the architectural design solutions already in place. The structural elements required in such cases, like steel moment frames, complicated collector assemblies, and heavy beams to accommodate overturning loads, add to the construction cost.

Additionally, when an engineer has to rely on many such elements to provide an adequate structural system, the accusation of “over-engineering” is heard. This complaint is usually brought up by the Contractor who provided an initial construction cost estimate based on the early designs that did not benefit from the input of a structural engineer. When the construction documents are complete, incorporating all the “work arounds” that result from late structural engineering input, and the actual cost of construction is higher than the initial estimate, the design team is then blamed for the difference.

Early involvement of the structural engineer results in better project outcomes for the owner and for the architect.