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Cross-laminated timber (CLT) has gained considerable interest in recent years as a low-carbon alternative to steel and concrete in construction. While CLT structures are designed to withstand extreme events, such as strong earthquake shaking, without collapsing, the aspect of postevent repairability is not explicitly addressed in current US design codes. This study thoroughly investigated the repairability of a previously tested 6.1×6.1 m (20×20 ft) cantilever CLT diaphragm that was damaged from reversed cyclic loading. Inspection and assessment of each of the components and connections indicated that the damage was localized to the connections (glulam-to-CLT screws and CLT-to-CLT surface splines), and the damaged diaphragm was deemed repairable. The repair strategy was intended to restore the capacity of the postrepaired diaphragm to the design strength of the initial undamaged diaphragm by replacing the damaged fasteners and surface splines with new connections. The repaired diaphragm was subsequently retested. The test results showed that the repaired diaphragm displayed slightly higher peak strength and comparable deformation capacity when compared to the initial diaphragm. This research underscores the potential viability of repairing damaged CLT diaphragms for performance restoration. However, further testing that encompasses other diaphragm configurations and varied fastener types may be needed to develop more comprehensive and effective repair strategies. [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]

This paper presents a new two-dimensional shear-wall and diaphragm model developed as part of a Network for Earthquake Engineering Simulation (NEES) Project entitled NEES-Soft: Seismic Risk Reduction for Soft-Story Woodframe Buildings. A large portion of the older multistory buildings in the California region were constructed with a deficiency that makes them vulnerable to collapse in the first story during earthquakes. This deficiency is referred to as soft-story. The new model presented in this paper was developed using a corotational formulation, which makes it suitable for modeling the side-sway collapse of wood shear walls under large displacement as well as estimating the in-plane stiffness of floor diaphragms. To achieve high computational efficiency, a nodal condensation technique is used to eliminate the degrees of freedom (DOFs) associated with the nail connections from the global DOFs of the model. To verify the validity of the new model, the model was coded into a computer program and was used to analyze selected shear walls and diaphragms tested by various institutions and research programs. Good agreement was observed between the test and model-predicted backbone and cyclic curves for shear walls with various gravity loads and different anchorage conditions. The model is highly flexible and has been shown to be able to model older shear wall construction with horizontal sheathing boards and diagonal bracings. [ABSTRACT FROM AUTHOR]