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In 2017, a moisture monitoring study was initiated on an eight-story, mass timber building located in Portland, Oregon. A detailed description of the monitoring program and initial monitoring results from the first year of the program were published previously. It was discovered that by the end of Year 1, some of the mass timber components had not dried below 19% moisture content (MC). This technical note is a follow-up to the original paper to examine how the building changed over its first 3 years after construction. All of the locations monitored over 3 years have reached stable moisture contents between 10% and 15%, which are acceptable for building functionality and performance. The main conclusion from this study is that mass timber buildings can naturally recover from construction wetting provided that such buildings are properly enclosed and further moisture intrusion is prevented. [ABSTRACT FROM AUTHOR]

The understanding of, and ability to predict, the seismic behavior of woodframe structures has improved immensely in the last 10 years. Two notable projects occurred in succession, the Consortium of Universities for Research in Earthquake Engineering (CUREE) and California Institute of Technology (Caltech) CUREE-Caltech Woodframe Project, and the Network for Earthquake Engineering Simulation (NEES) NEESWood Project, which provided greater understanding, improved analytical modeling, and advances in force- and performance-based seismic design (PBSD) of woodframe buildings, respectively. The NEESWood project focused on the development of a PBSD philosophy (and procedures) for midrise woodframe buildings and included full-scale system-level validation. To date, the complete design procedure has not been systematically explained, which serves as the impetus for this paper. While the method was shown to be quite viable, some challenges remain, including identifying a format that would facilitate widespread adoption and use by engineers. Thus, this paper examines the progress, current state, and challenges for PBSD of midrise woodframe buildings. [ABSTRACT FROM AUTHOR]

Light-frame wood (woodframe) buildings have been tested at full-scale sparingly around the world, primarily due to the cost associated with such testing and a general lack of facilities large enough to test at system level. The data from the tests that have been performed are used to help develop nonlinear time history analysis models that can predict the behavior of woodframe buildings during strong ground shaking. It is difficult to test buildings to the point of collapse because such tests can damage costly test equipment, i.e., the shake table. This paper presents the results of a dynamic collapse test on a light-frame wood garage wall and the results of a numerical model to simulate the wall behavior all the way to the collapse point. The tested wall was heavily damaged as a result of subjecting it to a ground motion recorded during the 1995 Kobe earthquake. Then, 85% of a near-fault ground motion recording from the Northridge earthquake was used, which immediately collapsed the test specimen. A specialized wood shear wall analysis program, formulated using a corotational formulation and large deformation theory, was utilized to model the garage wall. The numerical model provided a good prediction (predicted the peak wall displacements to within 15% of the measured values), but as a direct result of the observed failure mechanism of the wall, it was determined that additional contact elements were needed in the model. Failure was observed at the sill plate of the garage wall returns and also in the sheathing due to a moment failure where the header connected to the wall returns. Finally, it was observed that variability in the stiffness of the hold-down connections has a significant influence on the uplift predictions. [ABSTRACT FROM AUTHOR]

In July 2009, a full-scale midrise light-frame wood apartment building was subjected to a series of earthquakes at the world's largest shake table in Miki, Japan. This article focuses on the test results of that full-scale six-story light-frame wood building. The objectives of the testing program were to (1) demonstrate that the performance-based seismic design procedure developed as part of the NEESWood project worked on the full-scale building, i.e., validate the design philosophy to the extent one test can and (2) gain a better understanding of how midrise light-frame wood buildings respond, in general, to a major earthquake while providing a landmark data set to the seismic engineering research community. The building consisted of 1,350 m2(14,000 ft2) of living space and had 23 apartment units; approximately one-half one-bedroom units and one-half two-bedroom units. The building was subjected to three earthquakes ranging from seismic intensities corresponding to the 72-year event to the 2,500-year event for Los Angeles. In this paper, the construction of the NEESWood Capstone Building is explained and the resulting seismic response in terms of base shears, selected wall drifts, global interstory drifts, accelerations, hold-down forces, and roof drifts are presented. Detailed damage inspection was performed following each test and those results are summarized also. The building performed excellently with little damage even following the 2,500-year earthquake. The global drift at roof level was approximately 0.25 m and maximum interstory drifts were approximately 2% for the floor average with individual wall drifts reaching just over 3% in one corner of the building at the fifth story. [ABSTRACT FROM AUTHOR]

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 CP. 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. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) is a type of mass timber panel used in floor, wall, and roof assemblies. An important consideration in design and construction of timber buildings is moisture durability. This study characterized the hygrothermal performance of CLT panels with laboratory measurements at multiple scales, field measurements, and modeling. The CLT panels consisted of five layers, four with spruce-pine-fir lumber and one with Douglas-fir lumber. Laboratory characterization involved measurements on small specimens that included material from only one or two layers and large specimens that included all five layers of the CLT panel. Water absorption was measured with panel specimens partially immersed in water, and a new method was developed where panels were exposed to ponded water on the top surface. This configuration gave a higher rate of water uptake than the partial immersion test. The rate of drying was much slower when the wetted surface was covered with an impermeable membrane. Measured hygrothermal properties were implemented in a one-dimensional transient hygrothermal model. Simulation of water uptake indicated that vapor diffusion had a significant contribution in parallel with liquid transport. A simple approximation for liquid transport coefficients, with identical coefficients for suction and redistribution, was adequate for simulating panel-scale wetting and drying. Finally, hygrothermal simulation of a CLT roof assembly that had been monitored in a companion field study showed agreement in most cases within the sensor uncertainty. Although the hygrothermal properties are particular to the wood species and CLT panels investigated here, the modeling approach is broadly applicable. • Moisture and thermal properties of cross-laminated timber (CLT) were measured. • New method was developed for measuring water absorption on top of CLT panel. • Vapor diffusion contributed to water uptake in parallel with liquid transport. • 1-D transient hygrothermal model was validated with laboratory experiments. • Simulation of a CLT roof assembly compared well with field measurements. [ABSTRACT FROM AUTHOR]

The use of mass timber structural products (such as glulam and cross-laminated timber) in commercial buildings is increasing in prevalence around the world. Whereas moisture management during the construction process is important for all building types, it is especially important for buildings with wood structural members. The exposure of mass timber products to the environment during construction can result in wetting of the wood, and mass timber products may take longer to dry than lightweight wood-frame construction. To better understand the moisture conditions to which mass timber framing systems are subjected, a monitoring study was initiated on an 8-story, mass timber framed building located in Portland, Oregon. The study used wireless sensors to continuously monitor moisture content in the wood components over the transportation, construction, and operation of the building for a 1-year period. This study witnessed record levels of rainfall during construction, representing very adverse conditions for mass timber projects. However, the data showed consistent drying of all mass timber products after the completion of the building, with glulam and light framed wood products drying at a faster rate than cross-laminated timber. The method to install the instrumentation was also examined carefully for potential bias, which provided valuable lessons to future on-site moisture monitoring projects. [ABSTRACT FROM AUTHOR]