The Vision

This research project focuses on developing seismically resilient tall Cross Laminated Timber (CLT) systems at 8~20 story height range that can be cost competitive to be built in seismic regions of the U.S. The researchers, collaborating with industry partners and stakeholders, propose a vision to enable construction of the first CLT building in the U.S. over 10-story by the year 2020 (CLT2020).
In order to accomplish this vision, a roadmap for enabling building of tall CLT structures in the U.S. was summarized based on Tall CLT Building Workshop held in January 2014 in Seattle WA, as shown below.

The research team also proposed following tiered performance expectations for tall CLT buildings under seismic loading (see Table 1). The researchers are currently working on developing resilient structural systems suitable for tall CLT construction. Please follow the development of the project by visiting the website or contacting the project PIs.

Table 1: Proposed tiered performance expectations for tall CLT buildings

Seismic Hazard Levels  (POE1)

System performance

Structural components

Non-structural components

Estimated Repair Time4

Tier 1: Code Minimum (Optimizing current system and detailing, force-based design)

Service Level Earthquake

(50% in 30 yrs.)

Immediate Occupancy:

Minor non-structural damage

Remain Elastic

Minor damage, repairable

1~7 days

Design Basis Earthquake

(10% in 50 yrs.)

Life safety:

Extensive structural damage allowed but not affecting stability

Lateral system exhibit inelastic behavior, extensive repair can be done but costly

Moderate damage, repairable

1-6 months

Maximum Considered Earthquake

(2% in 50 yrs.)

Collapse prevention:

Severe damage, Probability of Collapse <10%

Large residual deformation, ductility fully developed, not repairable

Major damage, not repairable

> 6 months

Near Fault Ground Motions2

N/A

N/A

N/A

N/A

Tier 2: Code Plus (Innovative detailing or advanced protection systems, PBSD)

Service Level Earthquake

(50% in 30 yrs.)

Immediate Occupancy

Elastic

Minor damage, repairable

1~7 days

Design Basis Earthquake

(10% in 50 yrs.)

Limited/Planned Damage

Lateral system exhibit inelastic behavior, repair needed at planned locations

Moderate damage, repairable

1~2 months

Maximum Considered Earthquake

(2% in 50 yrs.)

Life safety:

Extensive structural damage allowed but not affecting stability

Lateral system exhibit inelastic behavior, repair may be costly

Moderate damage, repairable

2~6 months

Near Fault Ground Motions

Collapse prevention:

Severe damage, Probability of Collapse <10%

Large residual deformation, ductility fully developed, not repairable

Major damage, not repairable

> 6 months

Tier 3: Resilience (Resilient structural systems implemented, PBSD)

Service Level Earthquake

(50% in 30 yrs.)

Continuous Operation

Elastic/Resilient system operational

No damage

0~30 min

Design Basis Earthquake

(10% in 50 yrs.)

Immediate Occupancy

Resilient system operational

Minor contents damage

1~7 days

Maximum Considered Earthquake

(2% in 50 yrs.)

Planned Damage3

Resilient system repair needed at planned locations

Moderate damage

1~2 months

Near Fault Ground Motions

Limited Damage

Probability of Collapse negligible

Damage extended to unplanned locations, repair may be costly

Moderate damage

2~6 months

1. Probability of exceedance. 2. Near fault ground motions are characterized by strong velocity and displacement pulses at relatively long period which is very likely to induce collapse. This effect is not explicitly considered in current seismic design standard. 3. It is expected that the resilient systems will have “fuse”-like components that are designed to behave nonlinearly during strong earthquakes and easy to replace in post-earthquake inspections. 4. Repair time associated with the damage to structural and non-structural system assumes all resources needed to conduct the repair (e.g. financing, labor, material, etc.) are readily available. Thus the actual down time for the building functionality may be much longer than listed in the table due to other factors influencing the restoration efforts following an earthquake.

Project Description Link at NSF