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Cross-laminated timber (CLT) has gained considerable interest in recent years as a low-carbon alternative to steel and concrete in construction. While CLT structures are designed to withstand extreme events, such as strong earthquake shaking, without collapsing, the aspect of postevent repairability is not explicitly addressed in current US design codes. This study thoroughly investigated the repairability of a previously tested 6.1×6.1 m (20×20 ft) cantilever CLT diaphragm that was damaged from reversed cyclic loading. Inspection and assessment of each of the components and connections indicated that the damage was localized to the connections (glulam-to-CLT screws and CLT-to-CLT surface splines), and the damaged diaphragm was deemed repairable. The repair strategy was intended to restore the capacity of the postrepaired diaphragm to the design strength of the initial undamaged diaphragm by replacing the damaged fasteners and surface splines with new connections. The repaired diaphragm was subsequently retested. The test results showed that the repaired diaphragm displayed slightly higher peak strength and comparable deformation capacity when compared to the initial diaphragm. This research underscores the potential viability of repairing damaged CLT diaphragms for performance restoration. However, further testing that encompasses other diaphragm configurations and varied fastener types may be needed to develop more comprehensive and effective repair strategies. [ABSTRACT FROM AUTHOR]

The gust factor commonly is used in wind engineering community to convert mean wind speeds into gusty winds, which exhibit significant variability in real observations of typhoon winds. This study proposes a probabilistic gust factor model that accounts for uncertainties of wind speed statistics. The statistical characteristics of wind speed from nine typhoons, including the mean, standard deviation, skewness, kurtosis, power spectral density (PSD) parameter, peak factor, and gust factor, were examined. The effects of nonstationary characteristics in terms of time-varying mean wind speed and non-Gaussian attributes of fluctuating winds on the gust factor are discussed. These wind speed statistics were incorporated into a non-Gaussian moment-based translation model to perform the Monte Carlo simulation of peak factor and gust factor. The simulation results for different gust durations were juxtaposed with observations to substantiate the accuracy of the probabilistic model. Subsequently, a standardization framework for estimating site-specific probabilistic gust factor curves was developed. This approach was applied to determine the gust typhoon wind speed hazard curve at a real bridge site with flat open terrain. The present model enables the consideration of gust factor dispersion to achieve a probabilistic gust wind hazard curve and facilitate the development of performance-based wind engineering. [ABSTRACT FROM AUTHOR]

This paper reports on a study to extend a recently proposed direct displacement design (DDD) procedure for midrise engineered wood-frame structures and develop a set of factors for use in the procedure to meet specified performance levels with certain target probabilities. Representative index multistory building configurations were selected from the archetype buildings developed for the FEMA ATC-63. Seismic hazard levels and performance requirements recommended by ASCE 41-06 and modified for use in the National Science Foundation sponsored NEESWood project were used. The archetype buildings, originally designed using current force-based design procedures, were redesigned using the simplified DDD procedure (also described herein) with a range of nonexceedance (NE) probability adjustment factors ([C.sub.NE]). Specifically, the design interstory shear forces and the sheathing nail spacings were determined for each structure designed using [C.sub.NE]. Nonlinear time-history analysis was performed for each archetype structure under the 2%/50 year seismic hazard level and peak interstory drift distributions were developed. The NE probability at the 4% drift limit was then plotted against building height and design charts were developed for each different value of [C.sub.NE]. Given the building height and desired NE probability, engineers/designers can select the appropriate minimum value of [C.sub.NE] using these charts. Additional analyses could be performed to consider other hazard levels and performance requirements. Using design charts of this type, engineers/designers are able to specify a target drift limit as well as a target NE probability when using the simplified DDD procedure. Thus, a true performance-based procedure for the seismic design of midrise wood-frame structures is described. DOI: 10.1061/(ASCE)ST.1943-541X.0000188 CE Database subject headings: Displacement; Seismic design; Shear wall; Frames; Wood structures. Author keywords: Direct displacement design; Performance-based design; Seismic design; Wood shear wall; Wood-frame structures.

This paper presents a simplified direct displacement design (DDD) procedure which was used to design the shear walls for a six-story woodframe structure. The building was tested in the final phase of a Network for Earthquake Engineering Simulation (NEES) project. Specifically, NEESWood Capstone Building was designed to meet four performance expectations: damage limitation, life safety, far-field collapse prevention (CP), and near-fault CE The performance expectations are defined in terms of combinations of interstory drift limits and prescribed seismic hazard levels associated with predefined nonexceedance probabilities. To verify that design requirements were met, a series of nonlinear time-history analyses (NLTHAs) was performed using suits of both far-field and near-fault ground motion records. The distributions of interstory drifts obtained from the NLTHA confirm that the Capstone Building designed using DDD meets all four target performance expectations, thereby validating the DDD procedure. Additionally, collapse analysis in accordance with the recently proposed Applied Technology Council project 63 (ATC-63) methodology was performed. The results of incremental dynamic analyses confirmed that the Capstone Building designed using the DDD procedure has adequate capacity margin against collapse, as dictated by the ATC-63 methodology. DOI: 10.1061/(ASCE)ST.1943-541X.0000181 CE Database subject headings: Displacement; Wood structures; Structural design; Shear walls; Earthquake engineering; Seismic effects. Author keywords: Displacement-based design; Wood structures; Shear walls; Earthquake engineering; Seismic hazard; Structural engineering; Performance-based design.

Site-built wood-frame (light-frame) construction is the most common form of construction for residential structures in the United States. Such structures have suffered significant damage in recent earthquakes, and wood-frame construction practices in the western United States (WUS) have improved considerably in the last 2 decades. On the other hand, little is understood about the expected performance of wood-frame structures located in the central and eastern United States (CEUS), where the seismicity is moderate compared to the WUS and construction practices seldom provide earthquake resistance. This paper examines the seismic performance of typical one- and two-story wood-frame structures in the CEUS. Six structures with two foundation types were considered, for which conditional limit state probabilities (fragilities) were evaluated considering three possible failure mechanisms: excessive interstory drift, wall uplift, and sill plate splitting. This examination shows that seismic damage to wood-frame structures in the CEUS under earthquakes of moderate intensity is unlikely to lead to loss of life, but may result in significant financial losses. An evaluation of two possible retrofit strategies illustrates how the expected seismic performance of the CEUS structures can be improved by adding more anchor bolts and perimeter sheathing nails to the shear walls. CE Database subject headings: Earthquake engineering; Structural reliability; Rehabilitation; Shear walls; Wood structures; Frames; Building, residential; Seismic effects.

The majority of single-family dwellings in the United States are light-frame wood construction. Residential construction practices have evolved gradually over the years, most light-frame wood structures have not been structurally engineered, and many residential buildings suffered significant damage in recent hurricane and earthquake disasters. As a result, new concepts and methodologies are evolving to better predict and evaluate the performance of wood frame structures exposed to natural hazards and to support improved residential building practices. This paper examines the behavior of typical light-frame wood structural systems in the central and eastern United States under earthquake hazards. Nonlinear structural analysis tools and stochastic methods are used to model the uncertainties in ground motion intensity and structural response. Fragility curves defining damage state probabilities as a function of ground motion intensity are developed for typical lateral force-resisting shear wall systems subjected to increasing levels of ground motion. A comparison of these fragilities with those embedded in HAZUS provides additional perspective on damage potential for residential construction in regions of low-to-moderate seismicity. DOI: 10.1061/(ASCE)0733-9445(2008)134:8(1353) CE Database subject headings: Standards and codes; Deformation; Earthquakes; Reliability; Shear walls; Structural engineering; Wood structures.