Designing Mass Timber Construction to Mitigate the Potential for Disproportionate Collapse
November 19, 2025
2:00 PM to 4:00 PM Eastern Time
1:00 PM to 3:00 PM Central Time
11:00 AM to 1:00 PM Pacific Time
Patrick L. Hopple, P.E. and Eric Kjolsing, Ph.D, S.E., P.E.
Since the Ronan Point Apartments incident in 1968, there has been a push to inculcate design and detailing measures into mid and high rise buildings that would mitigate the potential for disproportionate collapse in the wake of an extreme loading event (e.g., explosion). At the present time, UFC 4-023-03 ``Design of Buildings to Resist Progressive Collapse`` is used by the Department of Defense, Department of State, and other entities to define design requirements aimed at reducing the potential for disproportionate collapse. Since 2016 (i.e., the year UFC 4-023-03 was last updated), there has been growth in the use of mass timber structural systems in buildings constructed in the United States. As such, an effort was recently completed that updated UFC 4-023-03 specifically for mass timber systems. This presentation describes the updated provisions to UFC 4-023-03. Furthermore, a design example that illustrates the primary strategies that can be utilized to mitigate the potential for disproportionate collapse of mass timber buildings is described in detail. K&C, LERA, and KPFF, who each have experience in designing mass timber structures for progressive collapse resistance, worked closely with the U.S. Army Corps of Engineers Protective Design Center to develop these UFC 4-023-03 updates.
Audience Learning Objectives
- To understand the extent of the disproportionate collapse mitigation testing performed on mass timber components to date.
- To understand potential collapse mechanisms for mass timber buildings.
- To learn strategies for safely designing and detailing mass timber buildings to mitigate the potential for disproportionate collapse.
Speaker Bio
Patrick L. Hopple, P.E. is a Partner at LERA Consulting Structural Engineers (LERA). With the firm since 2006, he specializes in the design of architecturally-exposed structural steel and architectural concrete structures, and has extensive experience in a variety of government, cultural, educational and healthcare facilities. Pat is a primary contributor to the firm’s Analysis and Modeling Standards Committee, and directs LERA`s Impact and Disproportionate Collapse Analysis, and Research and Development efforts. A leader in LERA`s federal practice, Pat was the Project Director for the design, investigation and seismic risk assessment of several US New Embassy Compound (NEC) and New Consulate Compound (NCC) projects in over 20 countries worldwide. He has lead research and development efforts for the application of mass timber and rammed aggregate earth in diplomatic facilities; alternate concrete technologies in diplomatic facilities; high-wind hazards and climate resiliency for diplomatic facilities and has co-authored a new concrete performance specification for the overseas federal projects.
Eric is a Principal Scientist at Karagozian & Case, Inc. (K&C). Eric began his career performing bridge design prior to returning to the University of California – San Diego to earn his PhD in Structural Engineering. His PhD research was in the fields of mechanical vibrations and energy harvesting. Following his PhD Eric has been heavily involved with the development of models to facilitate analyses of concrete, steel and wood structures subjected to time-varying loads. Representative work includes blast, impact, prestress loss, seismic and shock analyses of assets owned by power utilities and government agencies. Eric is a licensed Professional Engineer (Civil) and Structural Engineer in the state of California.
Patrick L. Hopple, P.E. is a Partner at LERA Consulting Structural Engineers (LERA). With the firm since 2006, he specializes in the design of architecturally-exposed structural steel and architectural concrete structures, and has extensive experience in a variety of government, cultural, educational and healthcare facilities. Pat is a primary contributor to the firm’s Analysis and Modeling Standards Committee, and directs LERA`s Impact and Disproportionate Collapse Analysis, and Research and Development efforts. A leader in LERA`s federal practice, Pat was the Project Director for the design, investigation and seismic risk assessment of several US New Embassy Compound (NEC) and New Consulate Compound (NCC) projects in over 20 countries worldwide. He has lead research and development efforts for the application of mass timber and rammed aggregate earth in diplomatic facilities; alternate concrete technologies in diplomatic facilities; high-wind hazards and climate resiliency for diplomatic facilities and has co-authored a new concrete performance specification for the overseas federal projects. Domestically, he has worked on a number of high-profile cultural, education and healthcare projects, some of them are the Lucas Museum of Narrative Art in Chicago and the National Museum of American Jewish History in Philadelphia. Several of his projects have gone on to win some of the industry`s highest honors, including the AIA DC Design Award in Architecture for the U.S. New Consulate Compound in Mexico; the ACEC NY Platinum Award for Engineering Excellence and the ENR Global Best Projects Award of Merit for the U.S. New Embassy Compound in Turkey; the AIA NY Best in Competition Award for the Vagelos Education Center; ENR Project of the Year, Southern California for the Broad Art Museum and more. Pat holds an Integrated Bachelor of Architectural Engineering/Master of Architectural Engineering from Penn State University, where he made Dean`s List and was the recipient of the Vincent L. Pass Scholarship.
Dr. Eric Kjolsing is a Principal Scientist at Karagozian & Case, Inc. (K&C). Eric began his career performing bridge design prior to returning to the University of California – San Diego to earn his PhD in Structural Engineering. His PhD research was in the fields of mechanical vibrations and energy harvesting. Following his PhD Eric has been heavily involved with the development of models to facilitate analyses of concrete, steel and wood structures subjected to time-varying loads. Representative work includes blast, impact, prestress loss, seismic and shock analyses of assets owned by power utilities and government agencies. Eric is a licensed Professional Engineer (Civil) and Structural Engineer in the state of California.