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Displacement-based design (DBD) methods were originally developed in the 1990s for concrete structures and later modified for light-frame wood buildings and mass timber buildings. DBD methods use displacement as the design criterion to minimize economic losses, control component damage, and enable rapid return to functionality for increased resilience. This paper introduces a performance-based design check procedure that uses the direct displacement-based design (DDD) method and numerical pushover analysis for the design of cross-laminated timber and light-frame shear (CLT-LiFS) buildings. Prestressing CLT panels with embedded posttensioning high-strength steel cables or external high-strength steel rods enable them to provide robust lateral load resistance and self-centering capacity. LiFS walls offer additional lateral load resistance and energy dissipation through the slip of nail connections. A six-story CLT-LiFS building was used as a design example meeting three performance levels (damage limitation, life safety, 15 and collapse prevention) based on ASCE/SEI 41-17 criteria. Each performance level corresponds to a set of three criteria: interstory drift limits, cable stress limits, and CLT compressive strain limits at the rocking interface. The design was checked using a series of nonlinear time history (NLTH) analyses with a suite of ground motion records. The results from the design check procedure and the statistical distributions of performance criteria from NLTH analysis confirmed that the six-story CLT-LiFS building met performance expectations. Additionally, a collapse fragility curve was developed to provide a comprehensive understanding of the building's behavior. [ABSTRACT FROM AUTHOR]

Prediction of pulp yield of Eucalyptus globulus wood samples based on partial least squares (PLS) regression can be optimized by utilizing specific near infrared (NIR) wavelengths. A critical feature of this approach is the weighting of constraint conditions. Equal weighting balances optimization in terms of calibration and prediction; however, there is a lack of knowledge regarding prediction performance of wood property models when different weight factors are used. In this study, pulp yield models were developed using two E. globulus data sets characterized by narrow (5%) and extreme (22.6%) yield ranges and represented by untreated and second derivative NIR spectra. The global optimization solver pySOT was used to optimize the performance of a PLS regression model in terms of wavelengths selected and number of latent variables. A linear function of R-squares for calibration ( R c 2 ) and prediction ( R p 2 ) sets was utilized as the objective function with the aim of maximizing α R c 2 + 1 - α R p 2 for all values of α between 0 (maximizing R p 2 without concern for R c 2 ) and 1 (only maximizing R c 2 ). Values of α ≤ 0.8 provided good predictive performance, whereas α ≥ 0.9 tended to overfit the calibration data indicating that models are robust for values of α from 0 to 0.8. Representative wavelengths for each data set were identified and assigned to corresponding wood components through a band assignment process. Strong agreement was observed for α ≤ 0.8 ; however, for α ≥ 0.9 , identified wavelengths generally occurred in regions unrelated to vibrations arising from specific wood components. [ABSTRACT FROM AUTHOR]

Near-infrared wavelengths selected by genetic algorithm were used to optimize partial least squares (PLS) regression models for loblolly pine (Pinus taeda L.) from the southeastern United States. Wood properties examined included density (D), microfibril angle, modulus of elasticity and tracheid coarseness (C), radial diameter (R), tangential diameter (T), and wall thickness (w)—measured by SilviScan. The optimization process was run for each property with Agenda 2020 samples utilized for PLS model development and the other sets used for prediction. The number of variables (i.e. wavelengths) varied from 10 to 100 with an optimum number identified by genetic algorithm. When compared to a full data set model (based on 700 wavelengths), calibration and prediction performance of optimized PLS regression models were superior for all properties. Importantly, representative wavelengths for each property were consistently related to recognized bond vibrations observed in specific wood components demonstrating that optimization targets wavelengths directly related to changes in wood chemistry within the examined loblolly pine samples. [ABSTRACT FROM AUTHOR]

Mass ply panel (MPP) is a new mass timber product that was recently introduced for structural applications in buildings. Although there have been several studies on characterizing the mechanical properties and structural performance of MPP, there is a lack of understanding regarding in-plane shear properties of the panels. More intensive studies should be done for MPP to provide a comprehensive understanding of its behavior. This paper presents an experimental study to characterize the effective in-plane shear modulus and shear strength of MPP in the major strength direction of the panel. Two experiments, including multiple span-length center-point bending tests and a novel large-scale shear test, were conducted. The test results were presented and compared with previous studies and the manufacturer's product report. The new test proposed for shear strength characterization has the potential to be an industry standard for mass timber panels. [ABSTRACT FROM AUTHOR]

Mass plywood panel (MPP) is a veneer-based engineered wood product that recently was introduced in the mass-timber construction industry. Preliminary studies show that MPPs can be a preferred construction material for shear walls, floor diaphragms, and roof assemblies. However, no design guide exists regarding the use of MPPs as structural elements. This is compounded by a lack of engineering properties and parameters needed beyond the generic values provided in the product report. To assess the engineering properties and provide a benchmark dataset, a comprehensive experimental testing program characterized the performance of MPPs in flexure, in-plane shear (parallel to major strength direction), compression, and tension. Additionally, the characteristic values of MPPs were derived based on the test results to provide an initial indication of design values of MPPs. The test results presented in this study provide a fundamental basis for the development of a design guide for MPPs. [ABSTRACT FROM AUTHOR]

The main objective of this work is to characterize the stress–strain relationship of cross-laminated timber (CLT) wall panels when loaded in compression and how different confinement mechanisms provide compression reinforcement for the CLT panels. CLT crushing tests were performed to define the behavior of CLT under compression up to the failure point, defined here as the strain at which the gross stress falls by 20% from the peak value. Testing included monotonic uniform compression experiments of five-ply CLT with specimens that were 0.457 m wide by 1.52 m long. The motion of the specimens perpendicular to loading direction was restrained at midlength to prevent buckling. Twelve specimens were tested, including six bare CLT specimens and six reinforced specimens of CLT—three with self-tapping screws while the other three with self-tapping screws and an additional U-shape steel plate at the bottom of the specimens. Various damage points were observed during the tests, including (1) point at the onset of damage (through visual observation and instrumental observation) (2) point of initiation of strength degradation, (3) point at which buckling occurs, (4) point at which 25.4 mm delamination was observed, and (5) failure point. Three axial compression stress–strain models were adopted, calibrated, and compared. Results indicate that a stress–strain model combining linear and cubic functions for the elastic and softening responses, respectively, captures well the CLT inelastic behavior under compression. [ABSTRACT FROM AUTHOR]

An optimization problem was developed by using a genetic algorithm to select wavelengths for establishing multivariate calibration models based on partial least squares (PLS) regression. Two near infrared (NIR) data sets represented by untreated and second derivative spectra were used to predict Eucalyptus globulus pulp yield. The optimization process was run with the number of variables (i.e., wavelengths) varied from 10 to 100 to determine the optimum wavelengths and number of latent variables for PLS regression model. A linear function of R-squares for calibration and prediction sets was utilized as the objective function of the optimization problem. The optimum wavelengths selected by genetic algorithm helped to considerably improve the performance of the PLS regression model, not only for the calibration sets but also for the prediction sets. The optimum number of latent variables varied over a wide range, from the maximum allowed (20) to a lower limit of six. Representative wavelengths for each data set were also statistically determined and assigned to corresponding wood components through a band assignment process, which showed strong agreement. [ABSTRACT FROM AUTHOR]

In nonlinear structural analysis, shear walls within whole-system models are often modeled using a spring model with a single degree of freedom where the lateral stiffness of the shear wall is modeled as a nonlinear spring. The stiffness of the spring is often described by the hysteretic relationship between the lateral restoring force and shear wall lateral deformation. In this study, a new shear element is introduced, which couples the lateral and vertical stiffness of the shear wall. This new shear element is able to better describe the behavior of shear walls in mid-rise and tall buildings. An illustrative example is presented to help explain the application of the new shear element in finite element modeling. In the examples, the new shear element is used to calculate displacement and internal forces for cold-formed steel frames. The results show that without including vertical wall stiffness, the lateral displacement is significantly underestimated. The difference increases with the height of the building and for a ten-story frame the new model demonstrates an increased lateral displacement at roof level of 64.1% when compared with current typical shear element model (lateral stiffness only). [ABSTRACT FROM AUTHOR]