Andreas Heiduschke

Heavy Laminated Timber Frames with Rigid Three-Dimensional Beam-to-Column Connections

AbstractThis article presents the seismic performance of a timber frame with three-dimensional (3D) rigid connections. The connections were made with self-tapping screws and hardwood blocks were used to support the beams. The frame was designed to resist high seismic excitations with the goal of controlling the drift. The moment-rotation characteristics of the connections were measured in the laboratory by applying static cyclic loads. The frame made of laminated wood beams and columns, and cross-laminated lumber deck, was subjected to seismic, white noise, snapback, and sinusoidal sweep excitations. The synthetic seismic excitation was designed to contain a considerable amount of energy close to the frame’s first natural frequency. The structure showed no significant damage up to a peak ground acceleration of 1.25g. Failure of the frame occurred due to shearing of the columns with a peak ground acceleration of 1.5g. The designed structure fulfilled with current serviceability limits up to 0.8g.

Fiber-Reinforced Plastic-Confined Wood Profiles Under Axial Compression

The objective of this research was to provide engineered wood products based on formed wood profiles for structural applications. The formed profiles can be optionally reinforced with technical fibers and/or textiles laminated onto the outer wood surface. The purpose of such composite confinement is to strengthen the wood profile in circumferential direction and to protect wood against environmentally induced damage. The presented research work deals with the analysis and testing of wooden tubes reinforced with fiber-reinforced plastic (FRP) composites. Axial compression tests were conducted to analyze the load-carrying behavior of timber columns with circular hollow cross sections. Static tests showed that the tubes were capable of sustaining high buckling loads as long as brittle failure modes could be prevented. Brittle failure was observed for unreinforced columns, whose longitudinal splitting was due to the expansion of the tubes in circumferential direction, resulting in tension perpendicular to the grain failure. The tests of reinforced tubes demonstrated that load-carrying capacity and ductility can be significantly enhanced by the composite confinement. Standard design equations were applied to estimate the load-carrying capacity of the composite tubes. The results obtained from experiments were used to verify the analysis.

Performance and Drift Levels of Tall Timber Frame Buildings under Seismic and Wind Loads

This paper discusses the potential for use of multi-story timber frames when subjected to earthquake and wind loadings. With the advent of new technologies and materials, such as laminating and composite-fibre reinforcement, the performance of tall spatial timber frames can be significantly enhanced. Two issues are of concern when designing tall timber frames: flexibility that translates into relatively large drifts and non-linearity that represents uncertainty in estimating fundamental periods. This article focuses on the potentials and limitations in designing tall timber frames from serviceability and safety points of view.

The Use of High-Strength Composites in the Reinforcement of Timber

The use of high-strength composites in the reinforcement of structural timber has been documented to enhance the strength and stiffness of wood structural members. Global reinforcement is applied over the entire surface of the reinforced member. Local reinforcement is a targeted strengthening of highly-stressed zones susceptible to failure. Both types of reinforcement enhance the capacity of the reinforced members and mitigate brittle failure modes. This paper presents an overview of the application of fiber-based composites in the reinforcement of beams, columns and connections of timber structures and discusses the state-of-the-art technologies in reinforcement. The applications are illustrated on the reinforcement of beams, arches, frames and beam-to-column connections.

High-Performance Composite-Reinforced Earthquake Resistant Buildings with Self-Aligning Capabilities

This paper describes the experimental procedures and presents preliminary results of the international project entitled “High- Performance Composite-Reinforced Earthquake Resistant Buildings with Self-Aligning Capabilities”. The goal of the project was to increase our understanding of the seismic performance of woodlaminated frames with locally reinforced members. Two sets of experiments were performed. First, a full-scale one-story frame with relatively rigid connections was tested on a shaking table, Kasal et al. (J Perform Constr Fac, 2013). To achieve a stiff connection, hardwood blocks and self-tapping screws 120–250 mm long were used to facilitate the connection between beams and columns. Next, a scaled three-story frame was tested. Highly stressed regions of beams and columns of the second frame were reinforced with glass fiber (GF) sheets to mitigate potential brittle failure in anticipated weak zones. Frictional connections between beams and columns permitted a control of the magnitude of dissipated energy in the system. The connections were expected to behave stiffly under small excitations, dissipate energy through friction during moderate seismic excitation, and degrade at higher seismic loads. While the friction can be relatively well predicted, the degradation of the connection cannot, due to the uncertainty in properties of wood.