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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]

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]

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]

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]

Self-centering heavy timber frames rely on the self-centering beam-column timber connections to limit damage and provide the recentering capability. However, low compressive strength and stiffness perpendicular to the grain of the timber columns have long been a design challenge, which yields low initial post-tensioning forces and possibly a significant loss of post-tensioning forces over the building service life. To address this issue, this paper proposes a new design solution for the self-centering steel-timber hybrid beam-column connections, in which the timber column is replaced by a steel-timber composite column. Cyclic tests were conducted on four beam-column connection specimens with post-tensioning. During the gap-opening, the composite column provided a stiff foundation to the timber beam. The hysteretic curves of all four connections were in a flag shape. Compared with self-centering beam-column timber connections that had the same geometry and material properties, the proposed connection had a larger connection stiffness and an improved efficiency of dissipating energy. After the cyclic loading, the loss of post-tensioning force of the proposed connection was also lower than that of the counterpart timber connections. [ABSTRACT FROM AUTHOR]

This paper presents experimental testing on glulam beam–column moment-resisting connections using glued-in rods (GiRod) and compares the results with model predictions. Three connection geometries and varying numbers of rods and member size were tested and compared. This experiment will be helpful in grounding research by bringing in new experimental results and proposing an innovative experimentation method. Experimental results showed the high efficiency of glued-in rod connections to transfer loads and bending moment between spruce pine glulam timber members. The observed limit states of the connections were failed steel rods in ductile tensile yielding or wood splitting around the anchorage installed perpendicularly to the grain in the column. It was found that the tested connections behaved as a semirigid moment-resisting connection and exhibited a ductile failure mode when wood splitting was avoided by design. Comparison of experimental results with model predictions showed good agreement, with a deviation under 15% for the moment capacity of the connection. [ABSTRACT FROM AUTHOR]

In order to reduce the use of adhesives, the development of adhesive-free engineered wood products is one of the research focuses in timber structures. This paper studies the mechanical properties of cross-laminated timber beams connected by densified wood (DW) dowels. Four-point bending tests were performed to study the influence of the arrangement and number of DW dowels on the bending strength and effective bending stiffness of the dowelled cross-laminated timber (DCLT) beams with three layers. The modified planar shear test was adopted to determine the effective shear properties of the DCLT. Cross-laminated timber (CLT) beams were also tested as references. Although the bending and shear properties of the DCLT were lower than those of the CLT, the DCLT showed a significantly larger ductility. The gamma method is promising for determining the effective bending stiffness of the DCLT using the effective shear modulus obtained from the shear test. [ABSTRACT FROM AUTHOR]

The objective of this study was to monotonically test two 7.32×7.32-m (24×24-ft) cross-laminated timber (CLT) diaphragms designed using the provisions of ANSI/AWC 2021 (AWC. 2021. Special design provisions for wind and seismic. ANSI/AWC SDPWS-2021, Leesburg, VA: AWC). Each diaphragm used twelve 1.22×3.66-m (4×12-ft) CLT panels and plywood splines or glulam beams at panel shear connection locations. Diaphragms were tested in simple-span bending in general accordance with ASTM E455 (ASTM. 2017. Standard test method for static load testing of framed floor and roof diaphragm constructions for buildings. ASTM E455-2017. West Conshohocken, PA: ASTM), used 8d common [ 3.3×63.5-mm (0.131×2.5-in.)] nails for panel-to-panel spline connections used proprietary 7.9×200-mm (5/16×7-7/8-in.) screws for panel-to-beam connections. The calculated allowable seismic shear design capacity for both configurations, based on the panel shear connections, was 60.5 kN (13.6 kips) per reaction. The diaphragm tested with load applied parallel to the long dimension of the CLT panels failed due to spline nail withdrawal at 4.0 times the allowable seismic design capacity. The diaphragm tested in the orthogonal orientation did not fail at the safe working capacity of the steel test frame, which was 6.0 times the allowable seismic design capacity. Although this testing provided empirical verification that the SDPWS design provisions met the minimum strength target underlying the design requirements, it also identified opportunities for potential future research to reduce design conservatism. Experimental results from a series of diaphragm connection tests correlated to the connections used in the full-scale diaphragm testing are described in the Part 2 companion study (Line et al., forthcoming). [ABSTRACT FROM AUTHOR]

The objective of this study was to conduct tests on diaphragm connection configurations that either matched or were similar to those used in the full-scale diaphragm tests described in the Part 1 companion study (Line et al. 2022). The goal was to quantify their lateral load-deformation performance as an isolated assembly to assist in further understanding the measured full-scale diaphragm behavior. Diaphragm connection configurations tested include the custom steel tension strap, panel-to-beam screw connections, and panel-to-panel nailed spline connections. Withdrawal strength, dowel bending yield strength, dowel bearing strength, and fastener dimensions, as well as the oven-dry specific gravities of the cross-laminated timber (CLT) and glulam materials used to fabricate the full-scale diaphragms were also quantified. The diaphragm connection lateral load test data for the proprietary screws and spline nails met or exceeded their target nominal capacities calculated in accordance with ANSI/AWC 2018 (AWC. 2018. National design specification for wood construction. ANSI/AWC NDS-2018, Leesburg, VA: AWC) for each connection configuration. Additionally, the overstrength was well aligned with the overstrength performance observed in the full-scale diaphragm tests. The dependence of full-scale diaphragm strength on the strength of its connections and the large overstrength in panel-to-beam screw connections quantified in this study highlight an opportunity to achieve more efficient designs with fewer screws. To do so would likely require the allowable lateral design strengths for screwed connections to be established empirically or by explicit consideration of various connection failure limit states. [ABSTRACT FROM AUTHOR]

Design models for timber structures with fire-resistance requirements usually take into account the loss in cross section due to charring and the temperature-dependent reduction in strength and stiffness of the residual cross section. Standards for glued timber elements like glued-laminated timber beams have assumed that structural adhesives do not influence the fire resistance, but further specifications of adequate adhesive requirements are missing. Investigations were therefore conducted to determine the influence of different adhesives on the load-carrying behavior of glued-laminated timber beams in fire. Large-scale fire-resistance tests in combination with extensive finite-element analyses showed that a modification of the zero-strength layer thickness of d0 = 7 mm currently used in a standard design code should be discussed for glued-laminated timber loaded in bending in a future release of this design code. An increase of the zero-strength layer d0 considering the finger-joint strength depending on the approved structural adhesive is not needed. [ABSTRACT FROM AUTHOR]

To study the lateral resistance of bolted glued-laminated (glulam) timber post and beam structures, two monotonic tests and eight cyclic tests were performed on full-scale, one-story, one-bay timber post and beam construction specimens. Four laterally strengthened structural systems were considered: a frame with an X-brace, a frame with a K-brace, a frame with a knee-brace, and a frame filled with light wood shear walls. Seismic performances were evaluated according to the experimental phenomena, hysteretic characteristics, stiffness degradation, strength degradation, and energy dissipation capacity. The results showed that the frame with an X-brace system and the frame with a K-brace system provided markedly better elastic stiffness but lower ductility. The frame with a knee-brace system showed increased elastic stiffness compared with the simple frame system and provided higher ductility compared with both the frame with the X-brace system and the frame with the K-brace system. Additionally, the frame filled with the light wood shear walls system performed well in terms of elastic stiffness and ductility. Finally, some suggestions were presented to improve the lateral resistance and ductility of each structural system. [ABSTRACT FROM AUTHOR]

Tests regarding the long-term behavior of posttensioned timber connections have been performed at the ETH in Zurich. The aim of these tests is to estimate the loss in tendon force that can be expected during the lifetime of a structure. Several posttensioned beam and beam-column timber specimens exposed to controlled and uncontrolled environmental conditions and loaded only with the axial prestressing force have been monitored for more than one year. The force in the tendon was measured together with the strains in the specimens and temperature and relative humidity in the testing environment. Creep tests performed on small glulam timber blocks loaded in compression have been started as well. The estimated creep coefficients parallel and perpendicular to the grain are used to calculate the losses with an analytical model for the larger posttensioned specimens. A prestressing loss in the range of 5-10%, depending on the geometrical properties and environmental conditions, has been found at the end of the one-year testing. Such a percentage is likely to increase up to 30% at the end of a 50-year service. Careful consideration has been given to identify the different variables affecting the losses of prestressing force in the long-term, including the environmental conditions. The tendon force losses were compared to the results obtained by a simple analytical model. A parametric study based on the model was performed in order to check whether the suggested ash reinforcement in the column is beneficial regarding tendon force losses in the long-term. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of an experimental study on the rotational behavior of bolted beam-to-column glulam connections reinforced using locally cross-laminated glulam members. Twenty-two full-scale connection specimens were tested through monotonic and reversed cyclic loading, from which the moment / rotational angle relationships were established. The results indicated that the cross-laminated technique leads to a more ductile failure mode with cross-aligned inner layers of laminas fractured, in contrast to the perpendicular-to-wood-grain tensile failure of unreinforced connections. The connection maximum moment was found to increase by 52% and 46% under monotonic and cyclic loading, respectively; moreover, the deformability ratio evaluated on the basis of the rotation angles corresponding to the yielding and maximum moments of the connections was increased by 94%. Locally cross-laminated connections were also found to dissipate more energy (25%) than unreinforced connections. A comparison of the cross-laminated technique with self-tapping screws indicated that the respective reinforcing effects were comparable with that of the screws being slightly higher. Because the locally cross-laminated technique is readily incorporated into the production of cross-laminated timber products, it may have broad applications in heavy timber-bolted connections. [ABSTRACT FROM AUTHOR]