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Cross-laminated timber (CLT) buildings are constructed by connecting CLT panels with dowel-type fasteners and mechanical anchors, which govern the lateral behavior of these structures. Although these connections are mostly distributed along the perimeter of the CLT panels, creating highly redundant structures, previous research on the lateral behavior of CLT structures has mainly focused on the behavior of the connections placed at the base of the CLT shear walls, such as hold downs and angle brackets, while limited attention has been paid to the connections between perpendicular walls and their effect on the lateral response of CLT shear walls. This paper presents a comprehensive experimental study aimed at investigating the effects of the interaction between perpendicular walls on the lateral response of CLT shear walls. CLT shear walls with three different aspect ratios were analyzed by means of monotonic and cyclic tests, both in single wall configuration and connected to perpendicular walls. The experimental findings demonstrate that the structural interaction due to the perpendicular walls significantly affects the lateral response of a CLT shear wall, resulting in increased lateral stiffness, lateral capacity, and deformation capacity. In addition, the study presents two analytical models for the prediction of the lateral stiffness and the lateral capacity of CLT shear walls connected to perpendicular walls. The analytical models were validated based on the experimental results, showing reasonable agreement. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results of a study investigating the behavior of bolted glued-laminated (glulam) timber brace connections with slotted-in steel plates under monotonic and cyclic loading. A total of 12 brace specimens with one or two slotted-in steel plates and two different bolt sizes were studied with the aim to determine the ductility of the connections and brace assemblies. The use of self-tapping screws as perpendicular-to-grain reinforcement to prevent splitting and enhance brace ductility was also investigated. The results of the study showed that both connections in a brace can experience significant plastic deformations if the connections exhibit a postyield hardening response. In braces with connections that exhibited postyield softening, plastic deformations were limited to one of the brace connections, resulting in lower brace ductility ratios. The use of self-tapping screws was found to be effective at preventing splitting and increasing the connection yield and ultimate strengths, while also increasing the brace ductility when compared with an identical connection without reinforcement tested under cyclic loading. [ABSTRACT FROM AUTHOR]

Significant advancements have been made in the area of composite structures. Aligned with an innovative design, the motivation behind this research is, first, to make efficient use of timber as an environmentally friendly material and, second, to employ steel alongside timber effectively to prevent buckling of the steel. This research aims to bridge this knowledge gap by exploring the integration of steel, carbon fiber–reinforced polymer (CFRP), and timber. The objective is to create innovative composite column structures that leverage the unique properties of each material to enhance structural performance and efficiency. The authors conducted tests on a set of 24 columns under compression conditions. The results of the structural tests demonstrated significant compression capacities relative to their mass, highlighting the significant advantages of material synergy within these elements. The study thoroughly quantifies these benefits, shedding light on the potentially transformative impact of these innovative composite columns in the field of structural engineering. A significant finding was the influence of the timber section's geometry on preventing column buckling. Furthermore, the positioning of steel within the sandwich columns played a vital role, with steel elements having a greater area with timber exhibiting enhanced structural performance and reduced likelihood of debonding. This paper introduces a new parameter, the inelastic transition area denoted as INT±70% peak , which characterizes the smoothness or abruptness of the transition once the inelastic region begins and the graph descends. This parameter bears significance in risk analysis for structures susceptible to progressive failure. All specimens displaying substantial energy absorption featured larger timber sections, highlighting the pivotal role of timber in absorbing higher levels of energy during structural loading. The findings contribute to the growing body of knowledge on composite materials and their applications in modern construction. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally and numerically the buckling behavior of three-layered cross-laminated timber (CLT) panels under in-plane axial compression. The main aim is to assess the panels' ultimate limit load and their typical failure mechanisms. A total of 14 specimens were tested. Seven of them were homogeneous (HO series), entirely made of beech, whereas the others were hybrid (HB series), made of beech (outer layers) and Corsican pine (inner layer). The tests gave evidence of a rather stable column buckling capacity for CLT panels, with evidence of major failure mode due to bending. In some cases, rolling shear and delamination were highlighted as additional failure mechanisms. Finally, further assessment of experimental evidence is provided by extended analytical calculations (based on existing formulations, including the Eurocode 5 approach) and even finite-element (FE) numerical analyses for the examined three-layer CLT compositions. Comparative results are discussed in terms of structural performance, capacity, and weakness of analytical models for CLT solutions. [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]

Balloon-type mass timber shear walls are one of the most efficient structural systems to resist lateral loads induced by earthquakes or high winds. They are a viable solution for high-rise buildings because they have several key advantages, such as reducing connections and avoiding accumulating compression perpendicular to grain in the floors. This system, however, is not included in current Canadian building code and has no design guidelines in the Canadian timber standard, so it is out of reach of most designers. A multiyear research project has been initiated to quantify the system performance and develop the necessary technical information to codify balloon-type mass timber shear walls. In this paper, the limits for the building height of balloon mass timber shear walls were investigated theoretically. A mechanics-based analytical model was developed to analyze the building height limits governed mainly by the mass timber panels. The influence of loading types (seismic versus wind loads), lateral load levels, panel deformation contribution, seismic force modification factors, and vertical joints between panels on the building heights was investigated using the developed model. The results of this study will give a valuable insight into the seismic performance of balloon type cross-laminated timber (CLT) shear walls. [ABSTRACT FROM AUTHOR]

The building industry requires the development of a ductile lateral force resisting system made of mass timber to help mass timber to continue to grow in popularity as the primary structural building material. The OpenSees framework was used to develop a numerical model of a single-story timber frame with a timber buckling-restrained brace, which was validated by the results of a previously completed series of quasistatic cyclic timber buckling-restrained brace (TBRB) component and subassembly tests. The experimental validation included a model developed for the hysteretic behavior of the TBRB and the rotational capacity of beam–column joints made with mass ply lam (MPL) panels, two slotted-in steel plates, and a number of steel dowels. The single-story model TBRB braced frame was then expanded to a numerical model of an eight-story mass timber buckling-restrained braced frame. The TBRB frame was analyzed with static pushover, quasistatic cyclic loads, and earthquake simulations. During the simulation of eleven design-level earthquake ground motions, the building experienced a peak interstory drift at of 2.54% at the first-floor level and a peak floor acceleration of 1.7g at the roof. The numerical model developed in this research of a timber buckling-restrained braced frame with TBRBs is novel and could be used to design timber buckling-restrained braced frames as a ductile lateral force resisting solution for mass timber buildings in seismic regions. [ABSTRACT FROM AUTHOR]

This study proposed a novel type of self-centering (SC) timber beam–column connection utilizing shape memory alloy (SMA) bars and investigated its cyclic behavior through experimental and numerical studies. In this SC connection, anchor bars consisting of SMA bars, steel bars, and couplers were utilized to connect the beam and column and achieve SC and energy dissipation capabilities. The configuration of the SC timber beam–column connection and material properties of the SMA bars were first introduced. The cyclic behavior of the SC timber beam–column connection was systematically investigated through experimental and numerical studies. A series of cyclic loading tests were conducted on the SC timber beam–column connection to evaluate its stiffness, SC, and energy dissipation capabilities, and the effect of multiearthquake loading. A detailed finite element model of the timber connection was also built and validated using the experimental results. Results indicated that the timber connection could exhibit a desirable flag-shaped hysteretic behavior, indicating favorable SC and moderate energy dissipation capabilities. The connection remained functional without any repair work after experiencing two consecutive cyclic loads up to 4% drift ratios, demonstrating its potential to withstand multiple seismic events. [ABSTRACT FROM AUTHOR]

The building industry requires the development of a ductile lateral force–resisting system made of mass timber to allow mass timber to continue to grow in popularity as the primary structural building material. A timber frame with mass ply lam (MPL) beams and columns with a timber buckling-restrained brace (TBRB) was subjected to a quasi-static cyclic loading protocol defined according to the qualification procedure of conventional buckling-restrained braces (BRBs). Two of the TBRBs in this study included a carbon fiber–reinforced polymer (CFRP) wrap to help confine the two ends of the mass ply panel (MPP) casing and improve the performance of the brace. The experiments showed that the TBRB without any CFRP wrap met the requirements for qualification of conventional BRBs, and the mass timber braced frame was able to reach a drift ratio of 3.0%. The TBRB with CFRP wraps met the requirements for qualification of conventional BRBs; the confinement provided by the CFRP wraps postponed failure of the TBRB by enabling the steel core to reach a maximum strain of 3.1% in both tension and compression and the mass timber braced frame to reach a maximum drift ratio of 4.5%. [ABSTRACT FROM AUTHOR]

A viscoelastic damper (VED) reinforcement option focusing on recovering the seismic performance of earthquake-damaged historic timber structures on a slope, as regulated by a direct displacement-based design procedure, was proposed in an attempt to extend the service life of culture buildings while ensuring deformation control of the weak area. A timber frame with an unequal height of column feet (UF) was designed, and a timber frame with an equal height of column feet (EF) served as the control group. The two full-scale timber frames consist of two-story units, a roof, and four spans. A series of cyclic loading tests were conducted on Models EF and UF to investigate the seismic performance of timber frames before and after reinforcement. It was found that the pulling out of the tenon and the sliding of column feet was significant at the upper embedding end. The upper embedding story is the weak area of the timber structure on a slope. The damage patterns of the two damped frames were not significantly different from those of the corresponding bare frames, and the ductility coefficients of all tested frames were greater than 10. The test results also revealed that the designed VED restored the seismic performance of the UF to the undamaged level while effectively controlling the deformation of its weak area. In addition, the effect of uniformly arranged dampers on the seismic performance of timber frame UF was also investigated. [ABSTRACT FROM AUTHOR]

Glued-in rods are proficient and high-performance connectors, finding application in the construction of new timber edifices as well as retrofitting of pre-existing timber structures. Given the prevalence of high-rise timber constructions facilitated by the advent of cross-laminated timber (CLT), there exists an opportunity for the incorporation of glued-in rods in the connectivity solutions for these load-bearing structural elements. This study examines the empirical behavior of CLT connections employing multiple glued-in rods. To achieve this objective, comprehensive experiments were conducted, involving full-scale tests on specimens subjected to both monotonic and cyclic loading conditions. The investigation included variations in the embedment lengths of the rods (250 and 350 mm) as well as their orientations with respect to the wood grain (parallel, perpendicular, and interposed amid layers). The monotonic test results showed that glued-in rods embedded on the edge of the CLT could provide high-capacity connections. The angle at which the rod was oriented relative to the wood grain had an impact on both the failure mode and the shape of the force-displacement curve in the connections. To calculate the pull-out strength of the glued-in rods anchored in CLT, a design equation is proposed based on the shear strength of the bondline. Additionally, a comparative investigation was performed to study the effect of the reinforcement by screws on the connections strength under monotonic loading in tension and in compression. Moreover, it was observed that glued-in rod connections keep their elastic properties until failure under cyclic loading. The results obtained from this research exemplified that this specific connection type could present a reliable and sturdy option for use in CLT construction projects. [ABSTRACT FROM AUTHOR]

One of the obstacles to the recent trend toward taller timber buildings is the limited load-carrying capacity of softwood columns. With the aim of promoting the structural use of European beechwood (Fagus sylvatica L.) in high-performance applications, the buckling behavior of beech glued-laminated timber (GLT) columns reinforced with glued-in steel bars was investigated experimentally and numerically. Axial compression experiments were carried out on full-scale stocky and slender columns, and a finite-element model was developed and validated against the experimental data. The influence of geometric and material parameters on the load-carrying capacity of the steel-reinforced beech GLT columns was studied in parametric analyses. The experimental and numerical data demonstrate the high potential of this new structural product for high-strength columns in demanding residential, office, and industrial applications. The load-carrying capacity mainly depends on the cross section size, the column slenderness, the position and diameter of the reinforcement bars, and the initial deformed shape of the column. An eccentric layout with steel bars in the corners of the cross section is very effective in increasing the load-carrying capacity. Four corner steel bars of 20 mm diameter, 50 mm edge distance, and grade ST900/1100 were found to increase the load-carrying capacity of a 200-mm-wide square GL48h column by almost 40% across the slenderness ratios relevant to structural applications. The glued-in steel reinforcement is also expected to be able to provide an alternative load path for structural robustness, by enabling the columns to carry tensile forces. A design method for corner-reinforced beech GLT columns under axial compression was developed based on the empirical and numerical data. [ABSTRACT FROM AUTHOR]

Diaphragms transfer the forces exerted by lateral loads to vertical elements through an in-plane shear action. Cross-laminated timber (CLT) has garnered considerable interest as a diaphragm material, particularly for midrise nonresidential construction. This article discusses the findings of tests performed on two full-scale 6.1 m (20 ft)×6.1 m (20 ft) cantilever CLT diaphragms composed of three-ply CLT panels. The diaphragms were subjected to in-plane shear loads with a cyclic loading protocol. Two different layouts of CLT panels were considered for this study (simple span and two-span continuous panels). The displacement, force, or strain responses of various components of the diaphragms were measured and analyzed. The peak capacity of the diaphragms was governed by the fasteners used and exceeded the LRFD capacity by a factor close to two. Test results showed the primary energy dissipation mechanism for the diaphragms was via the slip of diaphragm components parallel and perpendicular to the direction of load and rotation of CLT panels, nearly all of which could be attributed to fastener deformations. Observation of strain data revealed deep-beam-like behavior of the diaphragms where the resistance to coupled tensile and compressive forces was primarily contributed by the outer portion of the edge panels, with little to no contribution from the inside panels. In the compression zone, a near-uniform compressive strain pattern was observed at the top and bottom ply, aligned along the major axis of the CLT panels. In the tension zone, the tensile strain was observed only in the top ply aligned along the major axis (where tension straps were installed), and compressive strain was observed in the bottom ply. The results of the strain data were used to suggest a design procedure for the tension and compression chords. [ABSTRACT FROM AUTHOR]