Historically, the seismic design of topsides structures like marine loading arms and hose towers has been done inconsistently and to a wide array of design codes and requirements. The root of this problem has been a forced reference to conventional building codes like the UBC or ASCE 7, which are poorly suited for marine structures and particularly to these kinds of installations.
ASCE 61-14 has taken the first steps towards creating appropriate standards for seismic design of topsides structures. However, more needs to be done, and designers have learned valuable lessons about shortcomings that remain in the first edition of the new standard.
This paper will discuss the lessons learned from recent design projects for both marine loading arms and hose towers at marine oil terminals in California. The paper will discuss the difficulties encountered in a project currently under construction, which will be the first new loading arms installed at a California marine oil terminal since the inception of MOTEMS nearly 10 years ago.
The authors are participating on a task committee for ASCE 61-19 to address the shortcomings in current methodologies and will present specific recommendations for changes to the seismic design codes for ASCE 61-19.