Preliminary numerical study on the reduction of seismic pounding damage to buildings with expanded polystyrene blocks

Significance 

Earthquakes often result in extensive and fatal damage, especially in urban areas. It is well-known that buildings with different structures and heights exhibit different natural periods and shaking behaviors during earthquakes, depending on the seismic motion. During earthquakes, neighboring buildings with insufficient clearance between them have a high risk of colliding. Such collisions often result in impact force, whose characteristics differ from that of vibrations caused by seismic excitations. In most circumstances, even if the seismic resistance is guaranteed, such seismic pounding could cause severe damage to the structural and nonstructural components as well as the collapse of the building.

Installing shock-absorbing materials on the building walls is a promising strategy for reducing the damage to the buildings and mitigating disasters during seismic pounding. Among the available shock-absorbing materials, highly comprehensible materials like expanded polystyrene (EPS), which can be designed in different sizes and rigidities, have attracted considerable research attention lately. Nevertheless, despite the numerous applications of EPS materials in building and construction components, they are rarely utilized as shock absorbers attached to walls between neighboring buildings. This has been mainly attributed to the high costs of practical experiments required to verify its reduction effects on impact, which are yet to be verified.

To this note, Professor Daigoro Isobe and Mr. Tomohiro Shibuya from the University of Tsukuba conducted an elegant study on the damage reduction effects of EPS-based shock-absorbers installed between two neighboring buildings. A single case comprising two neighboring steel-framed buildings with different heights subjected to a single seismic wave was used for the preliminary simulation. Considering that EPS and metallic materials have significantly different nonlinear properties, a databased algorithm was devised and integrated into the numerical code to numerically reproduce the properties. Their work is currently published in the journal, Engineering Structures.

Briefly, the research team commenced their experimental work by independently exciting the buildings and comparing the damage results to that of the neighboring buildings. Next, EPS blocks were installed on the sidewall of one of the buildings, and their damage reduction effects were quantitively evaluated via finite element analysis based on the adaptively shifted integration-Gauss technique. Furthermore, appropriate parameter values like the block thickness and foaming variation were also evaluated.

The authors revealed that installing the EPS blocks resulted in a significant reduction in the ratio of the yielded members to all structural members as well as the acceleration peak at the collision time in both buildings. The effectiveness of the EPS blocks with any foaming thickness or ratio in reducing the damage during seismic pounding was comparable to that of shock absorbers installed between the buildings. Due to the limited shock-absorbing effect of the plateau region of the EPS material, it was recommendable to utilize the materials as an elastic damper to avoid potential permanent deformations and frequent repairs associated with reaching the plateau region.

EPS blocks with lower foaming ratios, which mostly function as elastic dampers, were considered appropriate for practical use. From the results, 33 was the most appropriate ratio. Additionally, thicker EPS blocks were considered inappropriate for practical use because they may induce unnecessary collisions between the buildings. Furthermore, it was worth noting that determining the possible maximum comprehensive stress for a given clearance between the buildings under seismic excitation was enough consideration for designing the sectional area of the EPS blocks.

In a nutshell, the Isobe and Shibuya study resulted in the numerical verification of the damage reduction effects of EPS blocks installed between two neighboring buildings subjected to seismic excitation. By reducing the response acceleration by about 90%, the EPS blocks reduced the damage to both structural components of the buildings and nonstructural ones within them, like furniture. In a statement to Advances in Engineering, Professor Daigoro Isobe stated that their findings would pave the way for advanced studies to verify the practical feasibility of EPS materials in reducing seismic pounding damage.

Preliminary numerical study on the reduction of seismic pounding damage to buildings with expanded polystyrene blocks - Advances in Engineering Preliminary numerical study on the reduction of seismic pounding damage to buildings with expanded polystyrene blocks - Advances in Engineering Preliminary numerical study on the reduction of seismic pounding damage to buildings with expanded polystyrene blocks - Advances in Engineering

About the author

Tomohiro Shibuya obtained his Master of Engineering from the Graduate School of Systems and Information Engineering, University of Tsukuba in 2021 under the supervision of Professor Daigoro Isobe. His research interests are structural analysis using the finite element method, which includes modelling of non-linear material properties and reduction of seismic pounding damage to neighboring buildings.

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About the author

Daigoro Isobe is a professor of Computational and Structural Engineering at the University of Tsukuba, Japan. He developed a finite element code based upon the ASI-Gauss technique, which was his doctor thesis work, and has conducted various structural collapse analyses since then. For example, the code had been applied to aircraft impact and progressive collapse analysis of the World Trade Center towers in 9.11 incidents, and had succeeded to show the main cause of the high-speed total collapse phenomena of the towers. These outcomes were scooped by the media and had influenced the structural design concept of high-rise buildings thereafter. Other investigations include the CTV collapse incident in 2011 New Zealand Earthquake and the collapse of the Nuevo Leon buildings in 1985 Mexican Earthquake, which was also broadcasted in the NHK TV program. He works as a Chief investigator of the Facility Simulation Working Group, E-Simulator Development Committee, E-Defense, NIED, and has succeeded to improve a simulation system using the ASI-Gauss code to analyze motion behaviors of non-structural components, such as ceilings, furniture, door frames, server cabinets, and so on. He has published over 400 journal papers, conference papers, book chapters, and books. He received the Ichimura Award upon these achievements in structural collapse analysis field, in 2014, in presence of Princess Akiko of Japan. He also received the Kawai Medal from JSCES (the Japan Society for Computational Engineering and Science) in 2015 and has approved as a fellow of the Japan Society of Mechanical Engineers (JSME) in 2021. He has been a director of JSCES since 2012, and is also a general council member of IACM since 2013. He contributed to the success of COMPSAFE 2014 (International Conference on Computational Engineering and Science for Safety and Environmental Problems) as a secretary general and had chaired the IWACOM-III (3rd International Workshops on Advances in Computational Mechanics) in October 2015, COMPSAFE 2020 in December 2020 and several other Workshops on Computational Mechanics held between two countries such as Korea-Japan and Germany-Japan. He is currently serving as the Technical Program Chair of the WCCM-APCOM 2022. He is also a chairman of the committee on Protection of Large-Scale Steel Structures, Ministry of Defense, Japan, and is a Guest Editor of two international journals of related fields. Now he serves as the President of JSCES.

Reference

Isobe, D., & Shibuya, T. (2022). Preliminary numerical study on the reduction of seismic pounding damage to buildings with expanded polystyrene blocksEngineering Structures, 252, 113723.

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