Study of the fire performance of hybrid steel-timber connections with full-scale tests and finite element modelling

Connection design is critical in timber buildings since the connections tend to have lower strength than the structural members themselves and they tend to fail in a brittle manner. The effect of connection geometry on the fire performance of a hybrid steel-timber shear connection is investigated by full-scale testing. These tests were conducted by exposing the test specimens to the standard time-temperature curve defined by CAN/ULC-S101 (CAN/ULC-S101, 2007)

Seismic response of six-story steel frame building with self-centering energy-dissipative (SCED) braces combined with linear viscous dampers

The self-centering energy-dissipative (SCED) brace is an innovative cross-bracing system that eliminates residual building deformations after seismic events and prevents the progressive drifting that other inelastic systems are prone to experience under long-duration ground motions. Previous studies of SCED braces have focused on the use of friction dampers as the primary energy-dissipating element within the brace. This study uses a six-story prototype building model to determine whether the addition of viscous dampers to the SCED-braced frame can efficiently reduce the accelerations while providing similar or better drift and base shear response. Two main design cases were studied: one with viscous damping only and one where viscous damping was combined with the friction damping within the SCED brace. The viscous damping constant at each story was calculated by determining the equivalent damping necessary to match the energy dissipation provided by a SCED brace with full friction damping at a design drift and modal frequency. The resulting hysteretic behavior of the structure was then modeled using the nonlinear structural analysis package OpenSees to determine the dynamic response of the structures. The best dynamic response was achieved by using 50% of the full SCED brace friction damping combined with viscous damping equivalent to the remaining 50% of the friction damping evaluated at the first modal frequency. This design resulted in a modest 15% increase in base shear while achieving significant performance improvements, decreasing accelerations by 30% and drifts by 20%

Adaptation of advanced high R-factor bracing systems into heavy timber frames

Timber provides attractive earthquake performance characteristics for regions of high seismic risk, particularly its high strength-to-weight ratio; however, current timber structural systems are associated with relatively low design force reduction factors due to their low inherent ductility when compared to high-performance concrete and steel systems. This experimental study investigates the adaptation of an advanced structural bracing system for heavy timber frames to improve the seismic performance of hybrid timber-steel buildings. This may justify the use of high force reduction factors (R-factors) to reduce seismic design forces and will provide energy dissipation to improve seismic performance. The study focuses on the design and quasi-static cyclic testing of a friction damping device within a timber frame to dissipate seismic energy and increase seismic performance. The bracing system is incorporated into the timber frame using select steel elements at the beam-column connections and glued-in rods to fasten the steel and timber elements together. The test frame demonstrated excellent cyclic performance, high ductility and did not experience any damage in timber connections, supporting the use of this type of connection detail in heavy timber structures

Development of a heavy timber moment-resisting frame with ductile steel links

To improve the seismic performance of mid-rise heavy timber moment-resisting frames, a hybrid timbersteel moment-resisting connection was developed that incorporates specially detailed replaceable steel yielding link elements fastened to timber beams and columns using self-tapping screws (STS). Performance of the connection was verified using four 2/3 scale experimental tests. The connection reached a moment of 142 kN?m at the column face while reaching a storey drift angle of 0.05 rad. Two specimens utilizing a dogbone detail in the steel link avoided fracture of the link, while two specimens absent of the dogbone detail underwent brittle failure at 0.05 rad drift. All four test specimens met the acceptance criteria in the AISC 341-10 provisions for steel moment frames. The STS connections exhibited high strength and stiffness, and all timber members and self-tapping screw connections remained elastic. The results of the experimental program indicated that this hybrid connection is capable of achieving a ductility factor similar to that of a steel-only moment-resisting connection. This research suggests that the use of high ductility factors in the design of timber systems that use the proposed hybrid connection would be appropriate, thus lowering seismic design base shears and increasing structure economy

Self-centering energy-dissipative (SCED) Brace: Overview of recent developments and potential applications for tall buildings

The self-centering, energy-dissipative (SCED) brace is an innovative cross-bracing system that eliminates residual building deformations after an earthquake while simultaneously dissipating energy to reduce drifts. Several recent studies are summarized which have confirmed and extended the capabilities of SCE

Nailed connection behavior in light-frame wood shear walls with an intermediate layer of insulation

The shear strength and stiffness of light-frame wood shear walls is highly dependent on the behavior of their individual nailed connections. Eighty-four nailed connection specimens were tested under shear loading to determine the effect of including rigid insulation as an intermediate material between the sheathing and framing elements in a light-frame wood shear wall. Each specimen contained common 10d or 16d nails, 15.9 mm oriented strandboard sheathing, spruce-pine-fir lumber, and rigid insulation in varied thicknesses between 0 and 38.1 mm. From the load-deformation results, maximum load, yield load, and stiffness were assessed using curve-fitting and yield-point determination methods. The results indicate that, as the insulation thickness increases, the connection strength and stiffness both exhibit a steep reduction. In addition, nonlinear two-dimensional (2D) finite-element models of the same nailed connections were developed. These models showed good correlation with experimental data and served to confirm that the decline in strength and stiffness observed in the tests is due to the introduction of the insulation