Designing Resilience: NEESWood Capstone a Decade Later

In 2009, Simpson Strong-Tie participated in an unprecedented research event to highlight the importance of earthquake-resistant wood construction.

The event, the world’s largest earthquake test, was a collaborative Network for Earthquake Engineering Simulation project. It teamed academics, engineers, and industry researchers from around the world to subject a structure to what engineers refer to as the “maximum considered event” (MCE), a large, rare earthquake projected to occur, on average, approximately every 2500 years.

The test featured a full-scale, seven-story wood-framed condominium tower. The 40′ by 60′ tower included 23 one- and two-bedroom living units and two ground-level retail shops. It was built on the “E-Defense” (Earth-Defense) shake table in Miki City, Japan.

The tower, which weighed nearly 800,000 lb., was engineered with Simpson Strong-Tie solutions. The first floor was outfitted with steel special moment frames using Yield-Link® technology, and running along the height of the building above the steel frame were 63 Strong-Rod® anchor tiedown system (ATS) continuous rods securing the shearwalls. Throughout the building, our connectors secured the critical components of the seven-story structure.

The building was subjected to five tests — all modeled on the 1994 Northridge earthquake ground motions recorded at Canoga Park.

Phase 1: Seven-story structure

Test One: 60% of Northridge ground motion.

Test Two: 140% of Northridge ground motion.

After successful Phase 1 testing, the first-story steel SMFs were braced to remove their participation, effectively creating a six-story wood-only structure.

Phase 2: Six-story structure

Test Three: 60% of Northridge ground motion.

Test Four: 140% of Northridge ground motion.

Test Five: Intensity increased to 180% of Northridge ground motion (the MCE intensity).While there is not a direct correlation between MCE-level shaking and earthquake magnitude, shaking at that level could be thought of as the equivalent of perhaps a 7.5 magnitude event.

Colorado State University professor John Van De Lindt developed many of the performance-based building design procedures used on the NEESWood Capstone test. In a National Science Foundation webcast recorded shortly after the historic test, Van De Lindt said, “I think we had a very successful test. Basically, there was a 2,500-year earthquake we subjected the building to and it wound up [ . . . ]performing very, very well. We were expecting moderate damage, but it turned out that we had very, very light damage to the building. So in the end, after going in and inspecting, I think we proved exactly what we set out to prove.”

What Is Performance-Based Building Design?

Steve Pryor, Advanced Research manager at Simpson Strong-Tie, explained that the goal of this project was to “prove performance-based design can work to make wood structures behave reliably in an earthquake to whatever performance state is specified in the design.”

The basic concept of performance-based building design can be traced all the way back to ancient Babylonia. Hammurabi’s Code states, “a house should not collapse and kill people.”

Of course, the idea has evolved in the 38 centuries since someone chiseled King Hammurabi’s code into black basalt. The clearest definition came in 1982, in a paper by E.J. Gibson titled Working with the Performance Approach in Building. Gibson writes, “first and foremost, the performance approach is [. . . ] the practice of thinking and working in terms of ends rather than means. [ . . . ] It is concerned with what a building or building product is required to do, and not with prescribing how it is to be constructed.”

The NEESWood Capstone test was unique because it focused on wood. Historically, performance-based building design has been used primarily on steel and concrete projects. Van De Lindt explained, “This [design] has been developed for steel and concrete, and this is really the first time that there’s been any major development in this for wood structures. So, what I see is probably major developments over the next six months to two years in the design code. The [wood construction] industry within the US will be pushing to have buildings be five, six, even seven stories throughout the Pacific Northwest and all around the US as a result of this project.”

Pryor said, “It’s one thing to have a computer with high-powered processing project the results of a design, but until the rubber meets the road you don’t really know what’s going to happen. The project proved we can build a seven-story steel- and wood-framed structure, shake it hard, and have very little damage.”

Impact of the NEESWood Capstone Project

The NEESWood Capstone Project is still informing design innovation. On July 24, 2019, Simpson Strong-Tie is hosting a symposium in Honolulu called “The NEESWood Capstone Project a Decade Later: What Have We Learned and Where Are We Going?”

The event will bring together some of the key players from the NEESWood Capstone Project to discuss how the project has informed seismic design of wood buildings and explore the future of wood construction. Pryor is lead organizer of the event. He said “The old idea is that just avoiding collapse is good enough. We can do better than that. I would like for people to come away knowing there are better ways to design that go beyond building to the code minimum. We can implement design and construction that reduce damage, save lives, and increase resiliency.”

We still have seats available for this historic discussion. Register here.

Full agenda below:

When: Wednesday July 24, 2019

Where: East-West Center (Adjacent to University of Hawaii campus)

Hawaii International Conference Center at Jefferson Hall (Asia Room) 1777 East-West Road
Honolulu, HI 96848

Registration and Continental Breakfast
Introductions (Pryor)

Review of the NEESWood Capstone Design and Test Program (Prof. John van de Lindt)

• Overview of The NEESWood Project
• Industry Collaboration by Simpson Strong-Tie
• Performance-Based Seismic Design for Wood
• Lessons Learned about Mid-Rise Woodframe Buildings
• How high can (or should) we go?

Mass Timber in Japan (Hiroshi Isoda)

• Recent developments and testing in JapanBreak

NHERI Tall Building and Mass Timber (Shiling Pei)

• Mass Timber Opportunities and Existing Solutions (including connectors)
• New IBC Fire Provisions

Lunch – Guest Speaker: Ian Robertson

• NEES Tsunami Research and its Impact on US Tsunami Design Requirements

NEHRI Tall Building and Mass Timber Continued

• NHERI TallWood Two-Story Preliminary testing in 2017
• NHERI TallWood Test Planning for the 10-story PT Rocking Wall Building

Future of Design: Performance Based Design -> Resilience Based Design (John van de Lindt)

• From DDD approaches to Resilience-Based Design of Tall Wood Buildings

Break

Thinking Big: Changing Cities into Forests (Tachibana)

• Sumitomo Forestry’s plan for a 70 story wood structure, the W350 Tower.

Closing Panel: What’s next?

 

The post Designing Resilience: NEESWood Capstone a Decade Later appeared first on Simpson Strong-Tie Structural Engineering Blog –.

from Simpson Strong-Tie Structural Engineering Blog – http://seblog.strongtie.com/2019/07/designing-resilience-neeswood-capstone-a-decade-later/