Seismic loss assessment of direct-DBD platform-type cross-laminated timber shear wall systems using FEMA P-58 methodology

Abstract

An efficient design method should provide practitioners with a means for sizing timber buildings to meet specific performance levels against estimated earthquake intensities. Displacement and energy design considerations in force-based design (FBD) procedures are not as precise as intended in complex systems, such as mid- to high-rise timber buildings. The main aim of this study is to tailor the direct displacement-based design (D-DBD) classical framework to platform-type cross-laminated timber (CLT) shear wall structural systems and validate their performance for low-rise to high-rise timber mixed-use buildings. A comparison with results obtained via the FBD analyses is also provided. To this end, timber buildings with heights of 4, 8 and 12 stories are designed via the D-DBD and FBD methods. The seismic performance of platform-type CLT wall buildings is assessed in terms of the repair cost, repair time and casualty rate using FEMA P-58 methodology. The seismic response of CLT shear walls shows that the FBD method may lead to an expensive overdesign, especially in high-rise platform-type CLT walls. Conversely, the D-DBD method develops structural systems which can sustain a comparable level of damage from low- to high-rise platform-type CLT walls. Although the seismic loss assessment of buildings shows slightly better performance for the FBD method than the D-DBD method, it is worth noting that the D-DBD method does not lead to an unsafe building. Consequently, the D-DBD method sounds like a proper alternative approach for designing the CLT shear walls to achieve target performance levels without requiring a premium upfront cost.

Keywords: Cross-laminated timber; Direct displacement-based design; FEMA P58; Force-based design; Fragility analysis; Seismic repair cost.

Fig. 1

Archetype buildings: a typical plan, b 3D view of 4-story building, c CLT shear wall, d angle bracket and e single-surface spline joint

Fig. 2

Design spectrum of Vancouver, BC: a acceleration spectra and b displacement spectra

Fig. 3

D-DBD method step-by-step flow chart

Fig. 4

Yield displacement and coupled-panel kinematic model of CLT wall: a yield displacement, b coupled-panel kinematic model, c free body diagram and d vertical loads between CLT segments

Fig. 5

Two-dimensional simulation of platform-type CLT walls in OpenSees: a structural model and b nonlinear finite element model

Fig. 6

Validation of simulation method with experimental results: a experimental model, b imposed horizontal top displacement and c hysteresis results

Fig. 7

a Response spectra of earthquake records and b seismic hazard curve of Vancouver, BC

Fig. 8

Population model of commercial office

Fig. 9

Design story shear force in the FBD and D-DBD methods: a 4-story building, b 8-story building and c 12-story building

Fig. 10

Total number of connections of CLT walls: a angle brackets and b vertical connections

Fig. 11

Peak inter-story drift ratio of CLT shear walls under design earthquake intensity: a 4-story CLT wall designed with FBD method, b 4-story CLT wall designed with D-DBD method, c 8-story CLT wall designed with FBD method, d 8-story CLT wall designed with D-DBD method, e 12-story CLT wall designed with FBD method and f 12-story CLT wall designed with D-DBD method

Fig. 12

Fragility curve of buildings: a 4-story CLT wall designed with FBD method, b 4-story CLT wall designed with D-DBD method, c 8-story CLT wall designed with FBD method, d 8-story CLT wall designed with D-DBD method, e 12-story CLT wall designed with FBD method and f 12-story CLT wall designed with D-DBD method

Fig. 13

Cumulative distribution function of repair cost: a 4-story CLT wall under 10% in 50 years, b 4-story CLT wall under 2% in 50 years, c 8-story CLT wall under 10% in 50 years, d 8-story CLT wall under 2% in 50 years, e 12-story CLT wall under 10% in 50 years and f 12-story CLT wall under 2% in 50 years

Fig. 14

Cumulative distribution function of repair time: a 4-story CLT wall under 10% in 50 years, b 4-story CLT wall under 2% in 50 years, c 8-story CLT wall under 10% in 50 years, d 8-story CLT wall under 2% in 50 years, e 12-story CLT wall under 10% in 50 years and f 12-story CLT wall under 2% in 50 years

Fig. 15

Cumulative distribution function of fatality: a 4-story CLT wall under 10% in 50 years, b 4-story CLT wall under 2% in 50 years, c 8-story CLT wall under 10% in 50 years, d 8-story CLT wall under 2% in 50 years, e 12-story CLT wall under 10% in 50 years and f 12-story CLT wall under 2% in 50 years

Fig. 16

Repair cost of structural and nonstructural components: a seismic hazard of 10% in 50 years and b seismic hazard of 2% in 50 years

Fig. 17

Time-based assessment of archetype buildings: a repair cost of 4-story building, b repair time of 4-story building, c fatality of 4-story building, d repair cost of 8-story building, e repair time of 8-story building, f fatality of 8-story building, g repair cost of 12-story building, h repair time of 12-story building and i fatality of 12-story building