Ronald Hamburger, Senior Principal at Simpson Gumpertz & Heger, has been a practising structural engineer since 1974. Here he discusses his career and his work on The San Fransisco War Memorial Veterans Building – a project to restore a historic building in the city. The project is shortlisted in The Structural Awards 2016 “Structural Heritage” category.
Since I was a child I wanted to fly and design aircraft, and I went to a school that was a leader in that field. I soon learned that aircraft design included two principal endeavours – fluid dynamics and structural mechanics – and that I had more affinity for structural mechanics. I interned at Republic Aircraft, a one-time builder of military aircraft, but at this time aerospace firms were in great difficulty and I decided to apply my knowledge to buildings and other structures, for which there was a more steady market. I did become a private pilot, however, and still enjoy flight to this day!
Probably the proudest moment of my career so far was being inducted to the U.S. National Academy of Engineering in October 2015, recognising my work developing structural engineering requirements of building codes. Founded in the 1860s to give unbiased advice to President Lincoln during the Civil War, the Academy is a highly selective organization, and when I consider my fellow members I am in awe at having been selected.
As a relatively young city (owing its roots to the 1849 California Gold Rush) San Francisco doesn’t have as great a pool of heritage structures as a city like London. It was largely destroyed in the great 1906 earthquake and subsequent fire - barely 20 buildings survived and remain in use.
Reliable seismic design standards did not come into effect until the mid-1970s and many important improvements have occurred since then, leaving something like 70% of the city’s building inventory seismically deficient.
After the 1989 Loma Prieta earthquake, the City began restoring and upgrading vital government services and cultural resources, but ran out of money before they could complete the Veterans Building – so only recently has the necessary work been carried out. The Veterans Building and neighbouring Opera House (which I also helped upgrade) jointly served as the birthplace of the United Nations, hosting the initial treaty signing ceremonies – so they’re really significant structures that deserve our care and attention.
There were a number of challenges in bringing the Veterans Building up to scratch. When it was constructed engineers believed that if the first story were sufficiently flexible, it would protect the upper stories from the destructive shocks induced by earthquakes. We now know, however, that such “soft story” buildings are dangerous and can actually hasten the collapse of the first story - as indeed happened to many structures in the 1994 Northridge earthquake.
To create the soft story effect the original designers placed concrete shear walls
in upper stories, but used hollow clay tile in the first stories, hoping that a strong earthquake would shatter the clay tile but leave the building standing. Regardless, they did not place enough shear walls in the upper stories to protect the building, so we introduced new shear walls, largely placed around the central auditorium, to provide both lateral stability and also to act as acoustic protection for the auditorium.
These new ‘rocking walls’, are intended to provide stiffness, but also a means of benign energy dissipation, allowing the building to resist strong shaking without excessive damage. We confirmed the efficacy of this approach with nonlinear dynamic analysis and also greatly reduced foundation costs.
When renovating any historic building, the goal is to leave it looking essentially the same as you found it. By picking strategic locations for the walls we were largely able to accomplish this. Further, by using the rocking foundation approach, we were able to avoid costly foundation improvements that would have significantly increased project costs, possibly beyond the available funding.
I’m pleased to say we also improved the building’s popular function as a cultural facility, significantly enlarging the stage area, installing modern theatrical and acoustic systems and fitting air conditioning.
The Veterans Building project is therefore a major sustainability success, in that it preserves a major historic resource, improves an important cultural resource and protects the lives of the thousands of people who use the building on a daily basis - while maintaining most of the building intact.
It was highly satisfying that as structural engineers we served in the role of prime design consultant - usually the domain of the architect. It was very nice to be able to demonstrate that structural engineers know how to manage large, complex projects and bring them off smoothly.
It was a great relief when the project was completed, and we were able to reopen the house for its planned uses on time. Both the performing companies and public have been thrilled to have the beloved Veterans Building back on line, as a better and more amenable facility. I have always been excited about history and places where important events happened. Being able to help preserve such treasures is one of the most important aspects of my career.
Discover more about The Structural Awards.