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Experimental tests of cross-laminated timber (CLT)-concrete composite floor panels were conducted. The tests consisted of linear-elastic tests of square CLT-concrete composite panels with a novel shear connector to determine elastic orthotropic plate properties. After the linear-elastic tests, the panels were subjected to a patch load at the center of the panel and tested to failure. To investigate load transfer across longitudinal joints between adjacent panels, nonuniform bending tests were conducted. Results from the experimentally measured orthotropic plate properties showed that the shear connector increased the bending stiffness in the weak direction of the panel compared to prior test results using conventional shear connectors. The tests to failure exhibited larger differences in behavior between the strong and weak orientations of the specimens, with both showing substantial inelastic behavior prior to failure. Numerical finite element models of the patch-load test showed good agreement with experimental results. Analytical formulas using the obtained orthotropic plate properties did not agree with experimental results for the patch-load at linear scales, suggesting the simplified method is currently not suited for CLT-concrete two-way bending. Load-transfer tests found that the reinforced concrete topping is capable of transferring load across the longitudinal joint of two parallel panels to enable two-way bending of composite timber–concrete floors and that the addition of a plywood spline with closely spaced screws enables a higher degree of force transfer. [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]

Cross-laminated timber (CLT) is an engineered wood product offering several advantages for wood utilization in midrise and tall buildings. However, moisture intrusion poses significant risks since it can affect the durability of CLT structural members and their connections. There has been much research on connection performance to understand their seismic response. However, the impact of moisture on the performance of CLT connectors is less understood. Cyclic tests were conducted on a series of CLT shear wall-to-diaphragm L-bracket (angle bracket) connections after subjecting them to a wetting and redrying cycle. The study includes three exposure durations and four wood species (Douglas fir, Southern yellow pine, Norway spruce, and spruce-pine-fir) to investigate the effect of moisture exposure on the connection performance. The performance was characterized in terms of strength, stiffness, and energy dissipation. In addition, two existing engineering force-displacement models were fitted to the experimental data. Results indicate that the changes due to wetting and redrying cycling were not statistically significant for the load-carrying capacity and stiffness. In contrast, a statistically significant decrease in the total energy dissipation capacity was observed. [ABSTRACT FROM AUTHOR]

With the rapidly growing interest in using structural timber, a need exists to inspect and assess these structures using non-destructive testing (NDT). This review article summarizes NDT methods for wood inspection. After an overview of the most important NDT methods currently used, a detailed review of Ground Penetrating Radar (GPR) and Ultrasonic Testing (UST) is presented. These two techniques can be applied in situ and produce useful visual representations for quantitative assessments and damage detection. With its commercial availability and portability, GPR can help rapidly identify critical features such as moisture, voids, and metal connectors in wood structures. UST, which effectively detects deep cracks, delaminations, and variations in ultrasonic wave velocity related to moisture content, complements GPR's capabilities. The non-destructive nature of both techniques preserves the structural integrity of timber, enabling thorough assessments without compromising integrity and durability. Techniques such as the Synthetic Aperture Focusing Technique (SAFT) and Total Focusing Method (TFM) allow for reconstructing images that an inspector can readily interpret for quantitative assessment. The development of new sensors, instruments, and analysis techniques has continued to improve the application of GPR and UST on wood. However, due to the hon-homogeneous anisotropic properties of this complex material, challenges remain to quantify defects and characterize inclusions reliably and accurately. By integrating advanced imaging algorithms that consider the material's complex properties, combining measurements with simulations, and employing machine learning techniques, the implementation and application of GPR and UST imaging and damage detection for wood structures can be further advanced. [ABSTRACT FROM AUTHOR]

Connections in mass timber structural systems transfer lateral forces from mass timber elements such as shear walls to floor diaphragms. Cross-laminated timber (CLT) is a prominent engineered mass timber material used to manufacture walls and floor assemblies. Fire performance research of CLT walls and floors has been abundant in recent years in an effort to develop an understanding of the performance of structural members under fire. Some fire-protected structural elements, including connections, may not be directly exposed to flames in a fire event but will experience elevated temperatures. There is limited research on elevated temperature performance of CLT connections, and consequently a lack of understanding of their fire performance in CLT structures. To aid in bridging this knowledge gap, in this study a series of cyclic shear tests were conducted on a CLT wall-to-floor bracket connection assembly to characterize thermal degradation according to a matrix of 28 exposure duration–temperature combinations. Two different methods were employed to develop force-displacement backbone models from the experimental hysteresis data. Models from both methods indicate an overall degradation of the connection performance in terms of load carrying capacity, elastic stiffness, ductility, and energy dissipation with increasing exposure to elevated temperatures. [ABSTRACT FROM AUTHOR]

This research investigated the mechanical characteristics of cross-laminated timber (CLT) connections fastened with structural wood screws, also known as self-tapping screws (STS). The CLT connection assemblies were toe-screwed (TS) at 45° and cyclically tested in tension and in-plane shear to evaluate the failure modes and applicability as seismic connections in CLT shear walls. The connection assemblies were representative of full-scale CLT shear walls connected to CLT floors as often seen in platform construction. Toe-screwed CLT connections exhibited screw fracture, head pull-through, and pinched hysteresis loops. Mechanical connection properties and backbone curves were extracted for comparison with design estimates. A head pull-through design method was developed, which predicted peak strength within 5% of test results. Connection parameters for ASCE/SEI 41 idealized-component curves were presented for use in performance-based design nonlinear-static pushover analysis. Combining the presented ASCE/SEI 41 parameters with the proposed design method and test results provides a simple and reasonably accurate nonlinear toe-screwed connection response curve. Partially threaded washer-headed screws were found to be superior to fully threaded screws in seismic applications due to their 15 times greater ultimate deformation capacity, substantially greater energy dissipation, similar peak strength, and similar elastic stiffness. However, the yield strength of partially threaded STS was found to be 48% of the yield strength of fully threaded STS. [ABSTRACT FROM AUTHOR]

Connections in mass timber structural systems are critical for transferring lateral forces from mass timber elements such as shear walls and diaphragms. Cross-laminated timber (CLT) is a prominent mass timber material used to manufacture these wall and floor assemblies. Although research exists that investigated the fire performance of CLT walls and floors, very little investigation has been devoted to the thermal performance of the connection systems themselves. This void in the data and knowledge surrounding CLT connections is an impediment for modeling the elevated temperature performance of CLT structures. Therefore, a series of shear tests were conducted on a CLT L-bracket connection assembly to characterize the thermal degradation of peak loads and initial stiffness as a function of exposure duration at a given temperature. A total of 116 specimens, including four control specimens, were tested according to a matrix of 28 exposure duration-temperature combinations. Two analytical models are developed to explain the thermal degradation—one assuming a mechanism based on first-order kinetics and the second using a statistical regression. The results of this work indicate that the degradation of peak load and initial stiffness with respect to exposure duration occurred at a linear rate and depended on temperature, according to the Arrhenius activation energy theory. This research is a step toward a holistic evaluation of elevated temperature modeling of CLT structures. [ABSTRACT FROM AUTHOR]

While the use of cross-laminated timber (CLT) panels for building construction has increased over the last several decades, current standards and existing literature provide limited information regarding the design of CLT diaphragms or the prediction of their deflections when subjected to wind and strong earthquake motions. This paper presents the design and assessment of a CLT diaphragm that was part of a full-scale two-story structure subjected to shake-table testing. An analytical model is proposed for diaphragm deflection accounting for in-plane shear and bending stiffness, as well as the stiffness of various connections. Moreover, a refined numerical modeling strategy is proposed in order to consider phenomena such as panel-to-panel gap closure. Results indicate that the analytical model yields conservative results both in terms of deflections and forces when compared to the numerical model that simulates similar sources of strength and stiffness. The analytical model is suitable for the design of symmetric diaphragms with regular shapes, whereas the numerical model can also be used to model asymmetric diaphragms with irregular shapes. [ABSTRACT FROM AUTHOR]

Mass timber construction has seen a growing interest in North America and worldwide. In the US, code provisions allow mass timber buildings to be up to 82 m tall, but with floor slabs requiring a noncombustible, usually cementitious, topping over mass timber panels (MTPs). Designing the MTP and concrete topping to act compositely can increase the strength and stiffness compared to noncomposite MTP floors. Several connections are available to create composite action between an MTP and a concrete topping, with self-tapping screws being the most widely considered practice. A new test fixture and testing method were developed to characterize connection properties and facilitate the selection of fasteners most suitable for developing composite action. Three conventional self-tapping screws were experimentally investigated at the single-fastener scale. The screws were subjected to withdrawal at 90° and 45° orientations to the interface plane between the MTP and concrete. Withdrawal from both the MTP substrate and concrete topping was investigated. Three MTP materials were tested: cross-laminated timber (CLT) consisting of two different wood species and a mass ply panel (MPP). Results demonstrated that the pullout failure of the screwhead from the concrete was the limiting failure mode. Comparisons were made between the experimental results and analytical models for screw withdrawal to assess the applicability of available models to the different MTPs. These models underestimated the capacity of the tested fasteners for all samples except for the fully threaded screws. [ABSTRACT FROM AUTHOR]

Synthesis of nano-crystalline hydroxyapatite (HAp) from fish scale ( Catla catla ) was carried out by calcining of raw fish scale between 200 °C and 1200 °C. The synthesized powders were characterized using thermogravimetry – differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The crystallinity, crystallite size, strain and cell parameters of fish scale derived calcined powders and chemically synthesized HAp (S-HAp) powders were estimated from XRD data. The average crystallite size of fish scale derived HAp powder increased with increasing calcination temperature. The fish scale derived HAp (FSH800) and S-HAp, calcined at 800 °C, showed crystallite size of 30 nm and 60 nm, respectively. ICP-AES analysis revealed that the fish scale derived HAp powder calcined at 1200 °C (FSH1200) contain significantly high amount of magnesium and strontium ions compared to S-HAp. After sintering at 1200 °C for 1 h, the relative density of FSH1200 was 20% higher than that of S-HAp due to better sinterability as a result of its small crystallite size and the presence of trace elements. In vitro cytotoxicity studies performed using human osteoblast-like cells (MG63) and mouse osteoblast cell line (MC3T3-E1) demonstrated that fish scale derived HAp (FSH1200) is non-toxic. [ABSTRACT FROM AUTHOR]

Green building practices have created an opportunity for the forest products industry to become a leader in the creation of in- novative building products derived from renewable materials. In other industries, sandwich composites have proven to be efficient structures by meeting structural demands of traditional panel products while consuming less material. A prototype molded-core sandwich panel made of span-rated oriented strand board (OSB) facings and a bidirectional molded wood-strand core was produced. Critical mechanical properties were evaluated to determine the feasibility of this product for use in building applications. The goals of this study were to generate details on structural performance of the product, validate the design, and provide suggestions for future product development. Results indicate that this molded-core panel performs particularly well in flexure while connection properties had the largest scope for improvement. Sufficient performance was observed to validate the design, warranting production and testing of panels sized for end-use. Future product development should explore different connection systems, perform detailed engineering analyses of the mechanical properties necessary for complete structural design, and characterize physical properties of the panel. [ABSTRACT FROM AUTHOR]

Limited research exists on the deformation compatibility behavior of mass timber beam-to-column connections. Therefore, to investigate this behavior, large-scale experimental monotonic testing was performed on five different glue-laminated (glulam) beam-to-column connections. The purpose of this research was to create a better fundamental understanding of the deformation compatibility behavior of mass timber beam-to-column connections. Three connections were custom-designed connections, and two were pre-engineered connections. Specimens included the presence of cross-laminated timber (CLT) decking on the beam, as well as combined lateral and gravity loading. Monotonic tests pushed specimens to a target story drift of 7.2% at a rate of 0.51 mm/s. The data were analyzed, and the yield force, yield displacement, initial stiffness, secant stiffness, and connection classification (categorized as either rigid, semirigid, or flexible) were calculated for each connection. Per the connection classification methodology used, all connections were classified as flexible (simple) connections. However, the pre-engineered connections use substantially more screws and plates thereby increasing the cost and effort of installation. The results demonstrate that in some cases simple custom connections can have a larger yield force and initial stiffness than pre-engineered connections, and due to the reduction in number of screws, there was less damage within the connection at the completion of the test. The forces required to push connections to 2% drift all exceeded the lateral force capacity of the connections; however, all connections maintained load-carrying capacity throughout testing. [ABSTRACT FROM AUTHOR]

New building code changes enable mass timber panels (MTP), including cross-laminated timber (CLT), to be used in moderate and tall buildings as a floor system, usually with a concrete topping. A floor system of CLT composite with a reinforced concrete topping slab can provide increased stiffness and strength, making the system more advantageous. Present connection methods used to produce composite action within timber-concrete composites (TCC) have limitations when considering constructability or performance. This study presents experimental results from four (4) shear connectors for CLT-concrete composite floor systems, including three developed for this study. The connectors included self-tapping screws (STS) at 45-degrees, a modified lag screw with an integral plate washer that bears on the CLT surface at installation, a steel angle anchored only at the end of the span, and an inverted-T steel section with stem perforations. Different tests were performed on the different connectors including individual fastener tests, push-off group tests, and full-scale one-way bending tests. The push-off group tests showed that the proposed washer-screw exhibited higher stiffness and strength than a conventional STS. The full-scale one-way bending testing showed that the STS specimen exhibited the lowest strength of the alternatives. The inverted-T section exhibited the highest stiffness, while the other three connections had similar stiffness to the STS. [ABSTRACT FROM AUTHOR]

The deformation compatibility behavior of glue-laminated (glulam) beam-to-column connections is not yet well understood. To investigate this behavior, 10 specimens representing five different glulam beam-to-column connections were tested under lateral cyclic loading. Three of the connections were custom-designed connections and two were pre-engineered connections. Specimens were large-scale glulam beam-to-column connections, and testing included combined gravity and lateral loading as well as the presence of a cross-laminated timber (CLT) deck. Connection characteristics such as yield force, initial stiffness, secant stiffness, and energy dissipation were calculated and compared across connections as well as observations made during testing. Results from the experimental testing indicated that pre-engineered connections demonstrated overall better performance than the custom connections. Pre-engineered connections had the largest remaining secant stiffness by the end of the loading protocol, greater energy dissipation, and larger average yield forces than the custom connections. Although all connections tested exceeded their lateral design capacities at drift levels less than 2% drift, all connections maintained load-carrying capacity throughout testing. [ABSTRACT FROM AUTHOR]

As oriented strand board (OSB) increases in use, improving the mechanical properties is of importance. Improved in-plane shear properties will allow for more efficient use as well as open up other opportunities in engineered wood products with high shear stresses. Based on classical laminated plate theory, composite laminates with laminate alignment patterns produce higher in-plane shear modulus and strength compared with typical alignment. Oriented strand board was manufactured 13.3-mm thick with and alignment patterns, and in-plane shear, bending, nail connection, and small-scale shear wall properties compared to commercial OSB. Results showed a 24% increase in shear modulus for the alignment when compared with the alignment using a method similar to a standard in-plane shear test. Results also show 10% reduction in bending modulus of elasticity in the parallel direction. Small-scale shear wall tests were insensitive to changes of in-plane shear properties. Lateral nail connection tests showed no reduction in connection yield load, implying that these panels can be used in similar applications without affecting connection properties. [ABSTRACT FROM AUTHOR]

Laminated bamboo lumber (LBL) is regarded as an alternative framing material for the construction industry. However, there is limited knowledge of its behavior in connection with commonly used sheathing material, such as oriented strand board (OSB). This study characterized the lateral load carrying capacity of LBL-OSB connections and studied the applicability of the yield models presented in the national design specifications to LBL connections. Two different connection geometries, edge and plate, which were representative of those present in a wall, were analyzed. The strength of the connections was characterized using monotonic testing. After the destructive testing, portions of the framing and sheathing materials from the samples were further evaluated for dowel bearing strength. Experimental results indicate that the LBL-OSB connections have similar lateral load carrying capacity as conventional Douglas fir-OSB connections. No statistical significance was observed in the strength differences of edge and plate connection geometries. The results further indicated that existing yield models used for design of nailed connections can predict the capacity and the mode of yielding for edge connection geometry between OSB sheathing and LBL framing members of grade and dimensions considered in this study, provided that the dowel bearing capacity of the materials is known. [ABSTRACT FROM AUTHOR]

An attempt has been made to correlate shape memory behavior and the micromechanical characteristics of the martensite crystals in the polycrystalline microstructure of thermally and thermomechanically processed nearly equi-atomic Ni-Ti shape memory alloy. The nanoindentation measurements have shown that suitable schedule of thermo mechanical treatment improves the hardness of the martensite phase. The recovery index parameter (η) obtained from the load-depth profile illustrates the recovery of the indentation strain of the martensite phase. [ABSTRACT FROM AUTHOR]

This study investigated the effect of exposure to elevated temperature on the yield strength of single-shear nail connections when subjected to lateral loading. Solid sawn lumber and laminated veneer lumber were used as framing members and two different thicknesses of both oriented strand board and plywood were used as the sheathing members. The connection geometries evaluated were typical of those encountered in lateral force resisting systems such as shear walls or roof diaphragms. The connection geometries were (1) edge connection-nail positioned 19 mm from the panel edge, loaded parallel to the grain of the main member, and (2) plate connection-nail positioned 19 mm from the panel end, loaded perpendicular to grain of the main member. Data collected from monotonic tests on 480 nail connections, after exposure to elevated temperatures, were analyzed for yield strength. In addition, 210 dowel bearing strengths were evaluated for the same treatments. The results indicated that exposure to elevated temperature caused significant degradation in lateral yield strength after exposure. The highest degradation occurred when exposed to 200°C for 2 h. For example, for plywood (11.2 mm) and solid lumber connections, the decrease in yield strength after exposure to 200°C for 2 h was 26% for edge connections and 56% for plate connections. The results further indicated that, given thermal degradation of the dowel bearing capacity of a material, the existing yield models stipulated in National Design Specifications (NDS) can predict yield load values for nailed connections for a given sheathing and framing member combination under those thermal degradation conditions. Additionally, the yield models predicted a predominant yield mode (IIIs), consisting of a single plastic hinge being formed just beneath the surface of the thicker member. These predictions were consistent with observed yield modes. [ABSTRACT FROM AUTHOR]

The overall goal of this study is to gain an insight into the load sharing aspect between oriented strand board (OSB) and gypsum wall board (GWB) in shear wall assembly during racking load. Sixteen standard 2,440×2,440 mm walls were tested monotonically, in total, out of which 11 (Type A) were sheathed on both sides (OSB on one side and GWB on the other), while five walls were tested without GWB (Type B). Digital image correlation (DIC) was used for data acquisition and analysis which is a full-field, noncontact technique for measurement of displacements and strains. The system returns full-field three-dimensional displacement and strain data measured over the visible specimen surfaces. Overall, these tests suggest that initially during loading of a wall the load is shared between OSB and GWB. However, the proportion of load sharing is not known. As GWB fails first at about 60% of ultimate load capacity of the wall, the load shifts to the OSB panel which resists it until the failure of the wall. The tests also revealed that the load path in wall Types A and B is different and so is the failure pattern. Strains were locally concentrated around the fasteners, while the strains in the field of the panel were below the detection limit of DIC system. [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]

• Cross-laminated timber rocking walls dissipate energy through connection damage. • Slip-friction connections were originally developed for steel structures. • The SFC system was designed as a hold-down in a self-centering CLT rocking wall. • Quasi-static, cyclic tests with SFC connections showed elastic-plastic behavior. • Passive damping was close to typical idealized friction hysteresis models. Cross-laminated timber (CLT) rocking walls limit internal building forces and dissipate seismic energy mostly through severe connection damage and related wood crushing. While collapse-prevention and life-safety performance can be achieved, the connections and CLT walls are permanently damaged and may be unreliable for resisting aftershocks. Slip-friction connections (SFCs), also known as slotted-bolted connections, are highly resilient passive dampers originally developed for steel structures. As part of a thorough research program to apply SFCs to CLT rocking walls, connection tests were conducted to better understand a novel application of multiple modern timber technologies. The research objectives were to design and test a slip-friction connection connected to cross-laminated timber with inclined self-tapping screws (STS) to determine the stiffness and passive damping properties of the assembly. The SFC system was designed for use as a slip-friction hold-down in a self-centering CLT rocking wall system. A series of quasi-static, cyclic axial tests with slip-friction connections was shown to impart ductile and elastic–plastic characteristics to an otherwise non-ductile CLT connection. Because the timber connection forces were limited below the STS yield strength by the slip-friction connectors, no wood damage was observed during SFC sliding. Compared to other sources, passive damping was found to be excellent and close to typical idealized friction hysteresis models. The slip-friction connections are a unique design using an efficient CLT to SFC connection, with no slack, that performs consistently after consecutive tests. Additionally, cursory equivalent-viscous-damping ratios were extracted for the elastic range of the STS to steel connection for small amplitude excitations below the slip force threshold. [ABSTRACT FROM AUTHOR]

Over the past decade, cross-laminated timber (CLT) panels have gained popularity worldwide. To achieve larger spans and to increase the resistance to diaphragm seismic and wind forces to be transferred through CLT floor or roof systems, CLT-concrete composite (CCC) floors have been developed as an alternative. While significant testing has been performed under gravity loading, limited experimental data exist on the in-plane performance of CCC systems. This study presents results from an experimental program designed to characterize the in-plane shear behavior of CCC diaphragm connections using different CLT to concrete screw connector orientations in a test setup that simulates the expected seismic load path in diaphragms for platform-type construction. Tested variables include concrete slab thickness, composite screw angle, and single spline connection systems consisting of nails or screws. Experimental results and observed damage progression from cyclic testing are presented and discussed. Results indicate that CCC systems achieved increased stiffness and strength values when compared to bare-CLT systems, but slab thickness did not influence the strength and stiffness of the system for the load paths simulated. Additionally, CCC floor systems with 45° composite screw connectors displayed increased strength but overall similar stiffness values when compared to the CCC systems with 90° composite screws. The results provide useful engineering parameters, such as elastic stiffness, peak load, displacement capacity, and ductility ratios that can be used in the development of codified design parameters or in performance-based designs. [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]

A full-scale 2-story mass timber building was tested on the University of California San Diego Natural Hazards Engineering Research Infrastructure (UCSD-NHERI) uniaxial shake table during the period from June 2017 to September 2017. The main objective of the experimental program was to test the performance of mass timber building designs with different seismic lateral force–resisting systems. The focus of this study is on a building configuration designed using self-centering post-tensioned cross-laminated timber (CLT) rocking walls with U-shaped steel flexural plate energy dissipators. The shake-table tests were designed to subject the building to a series of earthquake ground motions of increasing intensity, ranging from a service-level earthquake to 1.20 times the maximum considered earthquake intensity. Between each ground motion, low-amplitude white-noise excitations were applied to the building, which responded as a quasilinear system. In this paper, two output-only operational modal analysis methods are used to estimate the modal parameters (frequency, damping, and mode shapes) based on acceleration data collected during the white-noise shake-table tests. The correlations of observed damage and repairs performed during the experimental program with changes in estimated modal features are reported. The modal parameters estimated from the testing program are also compared with a linear finite-element model that is used to validate the modal identification results and study the performance of the two system identification methods for CLT rocking structures. [ABSTRACT FROM AUTHOR]

This paper presents the behavior of floor diaphragms of a shake-table experiment of a full-scale 2-story mass-timber building structure. The structure consists of glued-laminated timber beams and columns, and floors and walls were designed and built making use of cross-laminated timber panels. Two different floor systems were designed, where the roof consists of a topped cross-laminated timber (CLT)-concrete composite system, and the floor level consists of untopped CLT panels connected with plywood single-surface splines. The CLT floor systems were designed to remain essentially elastic over the whole series of shake-table tests, which included testing of three lateral force–resisting systems tested at three different seismic intensity levels (service level, design basis, and maximum considered earthquake) for a total of 34 shake-table earthquake tests. Results from the testing indicate that CLT diaphragms designed to remain essentially elastic based on basic principles of structural mechanics and existing test data can achieve desired seismic performance objectives. In addition, sources of overstrength in certain elements of the diaphragm need to be explicitly considered for a holistic diaphragm design. [ABSTRACT FROM AUTHOR]

Timber–concrete composite (TCC) floors exposed to fire experience charring and thermal degradation of timber, leading to a reduction in load-carrying capacity. Finite element (FE) modeling supplements data from experimental fire testing and allows for fast and economical investigation of additional design parameters. This research presents fire test results of three large-scale TCC floor specimens and development of an FE modeling methodology for TCC floors in a fire. TCC floors constructed with nail-laminated timber, cross-laminated timber, or mass ply panel, with truss plates or angled screws as shear connectors, are loaded with a uniformly distributed service-level live load and exposed to the ASTM E119-20 standard fire curve. A 2D FE modeling methodology is presented and benchmarked against the test data. The methodology integrates sequentially coupled thermal-structural analyses, which make use of temperature-dependent thermal and mechanical properties of timber and concrete. The deflection and failure times of the FE models are benchmarked against test data. Connector forces from FE models show that shear connectors remain elastic throughout the fire exposure. FE results indicate that the load-carrying capacity is dependent on tensile stress redistribution to the uncharred timber section. The FE modeling methodology effectively calculates the mechanical and fire behavior of TCC floors and highlights limits of the applicability of analytical design methods. [ABSTRACT FROM AUTHOR]

Context: There is scarcity of data on thyroid function abnormality in COVID-19 patients in world literature. Aims: The objective of this study was to assess thyroid function tests in hospitalized patients of COVID-19. Settings and Design: Sixty (60) patients with COVID-19 detected by RT-PCR admitted in General Medicine isolation ward and COVID block of a tertiary care teaching hospital were selected by semi-purposive sampling. Materials and Methods: These patients were assessed for thyroid function tests, including total T3, free T3, total T4, free T4, TSH and anti-TPO antibody along with other baseline investigations. Patients with pre-existing thyroid–related ailments, those on levothyroxine or anti-thyroid drugs or other drugs known to interfere with the results were excluded. Results: There were 43.3% patients in mild, 26.7% in moderate, and 30% in severe category, according to local COVID-19 severity classification protocol. 35% patients had one or more abnormality in the thyroid function, low TSH being the most common (18.33%). 9.1% patients had characteristic pattern of thyroiditis. In most of the others thyroid function did not match any typical pattern. There was no significant difference in any of the parameters of the thyroid function test between mild, moderate, and severe groups. Conclusion: Thyroid function may be abnormal in all categories of patients during COVID-19 infection, even in absence of pre-existing thyroid ailments. Although low TSH is the commonest abnormality and typical pattern of thyroiditis can be seen in a subsection of patients, in majority of the patients, thyroid function abnormality does not follow any characteristic pattern and likely represents a combination of thyroiditis and sick euthyroid syndrome in different points of its spectrum. [ABSTRACT FROM AUTHOR]

Background: Humans are accidental hosts in the zoonotic disease Scrub typhus. The disease though widespread in our county, it remains grossly underdiagnosed because of its non-septic clinical manifestations and lack of access to specific laboratory facilities. Aims and Objectives: The objective of present study is to evaluate the clinical presentations of Scrub Typhus among the study group. Furthermore, to assess the various laboratory findings in Scrub Typhus cases among the study group is the other objective of this study. Materials and Methods: The present study is an Institution-based, observational, and cross-sectional study conducted for 18 months with the admitted patients having 14-70 years of age. Data collected regarding patients' demographic profile, symptoms, clinical findings, laboratory, and radiological findings. Data had been summarized as mean and standard deviation for numerical variables and count and percentages for categorical variables. Results: In our study, we found that most of the patients were 14-20 years old and female population was higher. It was found that 34.3% of patients had Eschar, 42.9% of patients had Rash, and 91.4% of patients had Pallor, 8.6% of patients had Ascites, 25.7% had Edema, 8.6% of patients had Jaundice, 11.4% had shock, and 57.1% had pneumonia/pneumonitis. The present study showed that 65.7% of patients had drug response (Doxycycline). Conclusion: Knowledge of geographical distribution, evidence of exposure to vector, clinical features such as fever, rash, eschar, headache, and myalgia along with high index of suspicion are crucial factors for early diagnosis and that helps in timely treatment of the cases. [ABSTRACT FROM AUTHOR]

This paper presents a new alternative energy dissipation solution to be used with cross-laminated timber (CLT) self-centering walls. CLT is a relatively new building product in North America and could potentially be used for high-rise construction. The development of high-performance seismic design solutions is necessary to encourage innovative structures and the design of these structures to new heights. The objective of this paper is to propose a wall-to-floor connection system that is easy to install and replace (structural fuse) after the occurrence of a large damaging event. The proposed energy dissipators are fabricated following concepts used in developing steel buckling restrained steel braces (BRB), having a milled portion, which is designed to yield and is enclosed within a grouted steel pipe. The connection system is investigated experimentally through a test sequence of displacement-controlled cycles based on a modified version of the test method developed by the American Concrete Institute (ACI) to facilitate development of special precast systems (ACI T1.1-01 Acceptance Criteria for Moment Frames Based on Structural Testing). Digital Image Correlation (DIC) was used to analyze strain behavior of the milled portion, as well as track movement of the panels during quasi-static uniaxial and cyclic testing. The results show the yield behavior and energy dissipation properties of the connection system. Damage was focused primarily in the energy dissipators, with negligible deformation and damage to the CLT panels and connections. [ABSTRACT FROM AUTHOR]

Introduction: Measles is affecting millions of people in the developing countries particularly in India with significant morbidity and responsible for thousands of death in spite of having a safe, effective, and cheap vaccine. Pulmonary complications account for 90% measles-related death. The objectives of this study were to describe age distribution, clinical features, complications, and clinical outcomes of measles cases in a referral infectious disease hospital of West Bengal. Methods: We conducted a retrospective descriptive study including 584 patients and collected information from record section on demographics, clinical features, complications, and clinical outcomes using data abstraction form. Results: The mean age of 584 measles cases was 3.7 years (±1.2 years). The most common complication was pneumonia (149 cases) followed by diarrhea and encephalopathy. Very severe pneumonia occurred in 34 cases requiring intensive care out of which 13 patients died. The average duration of stay in the hospital was 5.7 days (±3.2 days). Surprisingly, 45 cases admitted to this hospital were <9 months of age with subsequent death in 5 cases. Conclusion: Substantial number of measles cases was seen in zero to <9 months of age group and fatality due to complication was more among them. [ABSTRACT FROM AUTHOR]

The development of cross-laminated timber (CLT) technology has opened up new opportunities for low-density hardwood species, which have traditionally not been rated as construction-grade materials for structural engineering applications. Several characteristics of CLT, namely thermal performance, seismic behavior, and speed of construction, have raised interest among designers. The CLT technology has recently been used for residential and nonresidential multistory buildings and it has been identified as one of the ways of achieving tall timber building construction. As CLT gains acceptance in the industry, low-density wood species, not specified in current ANSI standards, need to be investigated for potentially successful use in CLT panels. This paper presents a study that demonstrates the viability of a Forest Stewardship Council (FSC) certified sustainable plantation grown low-density species, hybrid poplar (marketed as Pacific Albus), for use in performance-rated CLT panels by following the ANSI/APA PRG-320-2012: Standard for performance-rated cross-laminated timber shear and bending test guidelines to determine the structural viability of the CLT panels. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented based on the topic of diagnosis of sexually transmitted diseases syndrome-wise in a subdivision level hospital of rural West Bengal, India.

Wood guardrail posts are among the most common wood materials currently used in highway construction. Preservative treated hem-fir is an important species for guardrail applications in the western United States. The service life of treated timber post guardrail systems has been estimated to be between 10 and 20 years. However, there is surprisingly little information on performance of timber guardrails. One aspect of the estimate of service life is wood durability. This study assessed the flexural properties, level of decay, and residual preservative levels in chromated copper arsenate preservative treated hem-fir guardrail posts removed from a project near Bellingham, Washington. Increment cores were removed from each post to assess preservative treatment and fungal colonization. The posts were tested for flexure properties in a three-point bending test. Posts that met the American Wood Protection Association standards for preservative penetration tended to have lower levels of internal decay after 20 years in service, and all but six posts retained sufficient flexural properties to meet AASHTO standards. [ABSTRACT FROM AUTHOR]

Background: Microbiological confirmation of pulmonary tuberculosis (TB) is of paramount importance in the era of immunocompromised host and emergence of multi-drug resistance. Objectives: To assess the value of sputum induction (SI) with hypertonic saline nebulization as a diagnostic tool in patients with suspected pulmonary TB who have no/inadequate sputum or have a sputum smear negative for acid fast bacillus (AFB). Materials and Methods: One hundred patients with clinical and radiological evidence of pulmonary TB with no/inadequate sputum or smear negative with spontaneous sputum were studied. Sputum was induced with 20 mL of 3% hypertonic saline solution delivered through ultrasonic nebulizer. The specimens were subjected to Ziehl Neelsen staining and were examined under oil immersion lens for the presence of AFB. The specimens were also subjected to mycobacterial culture in BACTEC 460 TB system. Results: Ninety five patients could produce adequate sputum after SI. Sputum from thirty two patients were found to be positive both in smear and culture while sputum from another three patients were smear negative, but culture positive. Conclusion: SI is a safe, cheap and non-invasive procedure and provides significant yield in the diagnosis of pulmonary TB; thus, increasing the case detection rate of smear positive pulmonary TB. [ABSTRACT FROM AUTHOR]

Timber-concrete composite (TCC) floors are becoming more commonly used in mass timber construction due to their increased stiffness and strength relative to nonconcrete composite timber floors. Current building codes do not recognize the contribution of the composite action of TCC floors to their combined strength and fire performance. Extensive structural testing is required for structural engineers to design fire protection in timber buildings that use TCC floors using either alternate means and methods or structural fire engineering. This paper presents two experimental studies conducted to examine (1) properties of shear connection systems used in TCC floors through ambient temperature direct shear tests, and (2) the behavior of TCC floors through large-scale fire tests performed at the National Research Council (NRC) in Canada. The main objective of this research is to collect data on the fundamental behavior of TCC floors in a fire. The results indicate that TCC floors have improved fire performance when compared with mass timber floors. In addition, the research quantifies the force-slip behavior of the shear connectors used and benchmarks the flexural behavior of TCC floors at ambient and elevated temperatures to existing analytical models. [ABSTRACT FROM AUTHOR]

• Cross-laminated timber requires connection development for seismic resiliency. • Slip-friction connections tested in CLT shear walls with static, cyclic loadings. • Idealized hysteretic models accurately represent CLT rocking walls. • Repeatable performance and structural protection beyond allowable loads. • CLT walls were observed to consistently return to center. Construction of tall-wood buildings is increasing in North America. Cross-laminated timber (CLT) is one of the dominant structural mass-timber products and is a high strength, lightweight, value-added, wood-composite panel suited for shear walls. The advent of tall-wood buildings necessitates further connection development for increased seismic resiliency to meet life-safety and performance-based design objectives. A novel slip-friction connection (SFC) was tested on six 1.52 m by 3.04 m CLT walls subject to static and pseudo-static cyclic loading. The SFC used Belleville springs and brass shims to provide stable slip forces and equivalent-viscous damping ratios between 0.28 and 0.63. Half of the wall tests included a short post-tensioned restoring rod with Belleville washers. Inclined self-tapping screws (STS) were used to connect the SFCs to the CLT walls, and the SFCs were designed to reliably dissipate energy while protecting the rocking walls from damage. The wall's response followed the idealized parallelogram, or flag shaped, hysteretic models observed in other slip friction systems. Results indicate repeatable performance and structural protection at least 2.5 times STS design loads. Self-centering and partially-centering wall conditions were tested by changing the SFC slip forces, while maintaining an initial 23 kN restoring force. Based on these experiments designers will be able to apply SFCs to CLT rocking walls. [ABSTRACT FROM AUTHOR]

• Twenty in-plane shear tests on CLT surface spline connections were performed. • Splines were constructed using nails and three different screw spacings. • Nail spline connections were more ductile than the screw connections. • An engineering performance model for the CLT splines is presented. Cross-laminated timber (CLT) panels have been used as structural diaphragm elements that form the primary lateral force-resisting system in mass-timber buildings. To better understand the overall performance of CLT diaphragms, an experimental program including monotonic and cyclic in-plane shear panel-to-panel spline connections tests was conducted. The spline connections were constructed using nails and screws with different spacings. Experimental results from the testing program allow for characterization of the performance of the connection systems in terms of elastic stiffness, strength, and ductility. Based on the results of this specific testing program, nailed spline connections displayed similar performance in terms of stiffness and strength and were more 58.7% more ductile than the screw connections, which is partly explained by the larger overstrength factors observed for the screw connections. A simplified performance model is presented to aid designers in determining the elastic, inelastic, and post-peak force parameters of the various spline connections tested. [ABSTRACT FROM AUTHOR]

Abstract A Zr based alloy has been developed with a β phase (BCC) dominated microstructure by adding Nb and Mo as alloying elements. Effect of Nb has been highlighted throughout the study due to its effectiveness on volume fraction of β-Zr and Mo 2 Zr as well as on transformation temperature. It has been found that increment of Nb concentration enhances the β-phase volume fraction through the reduction of α→β transformation temperature. Detail TEM analyses elucidates the above explanation. Graphical abstract Image 1 Highlights • Zr based alloy has been synthesized by high energy ball milling and annealing. • Influence of Nb on formation of β-Zr and Mo 2 Zr phases in Zr-(0–15)Nb-5Mo alloys. • Increasing Nb in the alloy has decrease the α→β transformation temperature. [ABSTRACT FROM AUTHOR]

Aims: The aim of the present study is to substantiate and compare the quality and extent of nerve block by using intrathecal bupivacaine or extradural bupivacaine alone and in combined spinal-epidural (CSE) technique using smaller dose of intrathecal bupivacaine and extradural injection of a smaller dose of bupivacaine or normal saline. Setting and Design: A prospective study design was set up with 60 adult patients scheduled for vaginal and lower abdominal operation under CSE technique and single spinal or epidural technique. Materials and Methods: 60 patients undergoing infra-umbilical surgery were divided into three groups (Group). Group A1 (control) 10 patients received 3 ml of intrathecal heavy bupivacaine. A2-10 patients received 16 ml isobaric bupivacaine extradurally Group B (n = 20) patients received 2 ml intrathecal heavy bupivacaine and 10 ml normal saline extradurally. Group C patients (n = 20) received 2 ml heavy bupivacaine intrathecally and 10 ml isobaric bupivacaine extradurally. A total duration of this study was 18 months. Duration of motor block, sensory block, analgesia, onset of sensory block and cephaloid extent of sensory block and side-effects noted among patients. Visual analog scale in the post-operative period was recorded. Statistical Analysis: The results were analyzed statistically by applying analysis of variable, odds ratio and Chi-square test. Results: Patients were comparable regarding the onset time and height and duration of sensory block with a significant difference, though there was no difference in duration of motor block and analgesia. The side-effects in the control group are higher than the other two groups. Conclusion: Quality of nerve block in combined technique using bupivacaine both intrathecally and extradurally is better and associated with lower side-effect compared with intrathecal heavy bupivacaine or extradural isobaric bupivacaine alone. [ABSTRACT FROM AUTHOR]

Residential energy use is a significant contributor to greenhouse gas emissions and climate change. Reducing energy efficiency in conventional wood-framed houses are thermal bridges: direct paths that allow heat to flow through the studs instead of the insulation. One suggestion for reducing thermal bridging is the staggered stud (SS) wall. SS walls use bottom and top plates with studs alternating between sides of the wall. This allows sheathing to be applied to both sides while eliminating thermal bridges. A literature review has revealed a lack of laboratory test data for SS walls used as shear walls, raising concerns about their safety. The objective of this study was to evaluate the seismic performance of typical SS walls and compare their behavior to similar conventional walls. Monotonic and cyclic laboratory tests were conducted with and without gypsum wallboard. The staggered stud specimens performed similarly to conventional walls. Some minor differences were identified, but the data raised no immediate concerns about the use of SS walls as an energy efficient option in areas of seismic hazard. [ABSTRACT FROM AUTHOR]