Sunday, October 11, 2026 8:00 AM - 10:00 AM, 210-211
Empirical equations for impact assessments are numerous and not always consistent in the resulting performance estimates. In addition, high-fidelity analysis results (e.g, Finite Element Analysis) can predict notably different penetration estimates than the available empirical equations, especially for unique and deformable impactors. Due to the renewed interest in nuclear energy, specifically the design of new small modular reactors, now is a good time to review the current state of designing for impact. This session will provide a forum to discuss currently available equations, observed inconsistencies, case studies, and new research in the field of impact loading. Representatives and engineers supporting the design development for small modular reactors will be solicited (specifically) to participate in this session and, ideally, participate in a ‘lessons learned’ round table.
Learning Objectives:
(1) Discuss the environment in which impact assessments are an important consideration;
(2) Report on the history and breadth of the available design equations;
(3) Explain current design practices for impact assessment;
(4) Review at least one recent case study highlighting approaches to overcome potential pitfalls.
This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.
Recent Tornado Missile Impact Analyses by Fluor
Presented By: Tarek Kewaisy
Affiliation: FLUOR, Mission Solutions
Description: The design of concrete structures to withstand the damaging effects of missile impacts poses computational challenges to the design engineer and requires proper understanding of the complex physical phenomena involved in an impact event. Structural design of nuclear facilities typically involves consideration of various potential impact conditions that may be caused by operational accidents or natural hazards (e.g. tornadoes and earthquakes).
In a recent project, Fluor was tasked with designing various concrete structures within a nuclear facility to withstand different classes of tornado-generated missile impacts (i.e., steel ball, steel pipe, and automobile) using applicable guidance from NRC RG 1.76, Chapter 3 of NUREG-0800, Chapter 6 of ASCE MOP 58, Appendix F of ACI 349-13, BC-TOP-9A, and Kennedy’s review paper. The steel pipe impacts were found to cause the most critical loading conditions for local damage and global structural responses of all concrete components.
Fluor engineers considered different, engineering-oriented, analytical approaches with varying levels of complexity to compute pipe impact loading effects including time history (TH), single degree of freedom (SDOF), and equivalent static (ES) analyses. During the analytical process, multiple computational challenges were identified and practical limits of implementing various approaches were determined.
The discussion will address important aspects and recommendations for 1- defining the design-basis impact forcing function, 2- estimating conservative ES impact loads, 3- using finite elements (FE) for dynamic impact analyses, 4- Implementing the SDOF approach in the design of concrete components for impact, and 5- improving impact-resistance of concrete through design/detailing.
Recent Tornado Missile and Aircraft Impact Analyses by SGH
Presented By: Derrick Watkins
Affiliation: SGH
Description: SGH has performed a variety of impact analyses recently, including both tornado missile and aircraft impact for various new nuclear facilities. This presentation will identify some of the challenges encountered during the analyses and how they were resolved.
Recent Tornado Missile and Aircraft Impact Analyses at S&L
Presented By: Gunup Kwon
Affiliation: Sargent & Lundy
Description: During standard plant design of a small modular reactor, the structure required to be designed for aircraft impact. A full finite element model was developed for the reactor building including the surrounding soil for aircraft impact analysis. The energy absorption from the soil response and its effect on concrete damage was quite noteworthy. Challenges were also encountered for establishing gravity by using dynamic relaxation before full dynamic analysis. We will discuss these two topics about the aircraft impact model.
Recent Tornado Missile and Aircraft Impact Analyses at Rizzo
Presented By: Malik Corum
Affiliation: RIZZO International
Description: The design of nuclear facilities often requires a variety of impact analyses, including both tornado missile and aircraft impacts. During the design phase of a reinforced concrete pedestal supporting an exhaust stack, the structure was required to meet tornado-driven missile criteria consistent with NRC Regulatory Guide 1.76. Local and global design evaluations presented several challenges, including limitations in applying empirical impact equations outside their original test basis, variability in methodologies for generating equivalent static impact forces from transient missile loading and the limitations of the simplified static approach in capturing the dynamic and inelastic nature of the impact response. The presentation will discuss these challenges in detail and provide insights on how they were resolved.