Patent Application
20250146274
Cross laminated timber (CLT) panels are typically pre-manufactured away from the construction site and installed on site with fasteners. CLT panels can be used to build shear walls to provide lateral stability under wind and earthquake loadings. As CLT panels are relatively strong in their strength and stiffness, they do not bend, distort or deform much under lateral loadings. As a result, a traditional CLT panel shear wall typically develops a rocking mechanism under lateral loadings. The rocking mechanism commonly relies on angle brackets or other connections at the lower corners of the CLT panel in order to hold the panel down to other structural members. The potential failure of the angle brackets or other connections would cause the CLT panel to rock, or even overturn in extreme situations, which would cause the CLT panel shear wall to collapse in a disastrous mode. This potential failure mode exists in all walls built with other rigid panels, including precast concrete panels, which currently limits their use to low-rise buildings only. For mid-rise and high-rise buildings, walls built with rigid panels including CLT and precast concrete panels demand new configurations with safe mechanisms under lateral loadings.
The present invention provides a wall system consisting of a frame, a suspended-infilled cross-laminated timber (CLT) panel, steel angles and fasteners, arranged in such a way that the wall system develops a shear mechanism under lateral loadings. The design minimizes the unfavorable rocking mechanism of the rigid panels used in traditional construction and thus reduces the damage to the building that might exhibit during an earthquake or a hurricane. It permits buildings to be built with rigid panels such as CLT in mid-rise and high-rise buildings to greater heights than the current practice.
The present invention has two columns spaced apart horizontally and two beams spaced apart vertically. The two columns and two beams form four sides of a planar frame in the vertical plane. The two columns and the two beams are made of either solid sawn lumber, engineered lumber, steel or precast concrete. The two columns and the two beams have the same or similar width across the plane of the planar frame. Each member of the two columns and the two beams has one steel angle connected on the inside face toward the centre of the planar frame. The each member of the columns and the beams is configured to connect to one leg of the steel angle with either screws, bolts, welds or cast-in-concrete studs, depending on the material of the columns and the beams. The other leg of the steel angle is configured to connect to the flat side of the infilled panel with at least one fastener. The CLT panel is infilled inside the planar frame. The infilled CLT panel does not contact directly with any of the four inside faces of the planar frame. The infilled panel connects to the each member of the planar frame through the steel angles and associated fasteners. Thus, a gap between the inside face of the planar frame and the edge side of the infilled CLT panel is formed in order to allow the infilled panel to rotate and translate inside the planar frame, and to allow for the member thickness of the steel angles and related fasteners. Overall, the infilled CLT panel is suspended inside the planar frame through the steel angles and their associated fasteners.
The location of the aforementioned steel angles can be positioned such that the finished surface of the steel angles and the fasteners is flush against the flat side of the infilled rigid panel.
The aforementioned steel angle may be replaced by a steel plate, either flat or bended to suit the finished surfaces of the planar frame and the infilled panel. The steel plate is connected to the outside of the each member of the columns and beams with either screws, bolts, welds or cast-in-concrete studs, depending on the materials of these members.
The foregoing summary and the following detailed description should be read in conjunction with the appended drawings. These drawings show different embodiments of the present invention. It should be understood, however, that the teachings are not limited to the embodiments shown.
A wall system consisting of a planar frame, an infilled CLT panel, steel members and fasteners, is provided. The infilled CLT panel is suspended inside the frame with fasteners. The gap between the infilled CLT panel and the frame allows the CLT panel to rotate and translate when the frame deforms into a parallelogram shape under lateral loadings. The fasteners connected through steel members between the frame and the CLT panel bend and deform under the loadings. The bending and deformation of the fasteners dissipate energy during the racking behavior of the frame. Therefore, the wall system exhibits a ductile behavior under lateral loadings. The wall system provides a safe structural solution under wind and earthquake loadings.
The at least one fastener 110 passes through the steel angle 120 and into the infilled CLT panel 130. The at least one fastener 110 may be any dowel-type connector, such as lag screws and self-tapping screws. When the wall system sustains lateral loadings, the at least one fastener 110 bends and deforms relative to the CLT panel 130, which allows the panel 130 to rotate and translate relative to the planar frame members. All of the fasteners 110 work together to be designated as the yielding elements for energy dissipation required for lateral load resistance design. The at least one fastener 310 between the steel angle 120 and each of the planar frame members can be screws, bolts and other connections suitable for the material and the cross-section shape of the columns 140 and the beams 150. The at least one fastener 310 may be designed to be elastic for lateral load resistance design, which does not yield when the wall system sustains lateral loadings. Therefore, the wall system may be designed with yielding to the fasteners 110 and localized bearing to the wood on the infilled CLT panel 130 surrounding the fasteners 110 during major earthquake or wind events. Controlled damages are expected for the yielded fasteners 110 and the CLT panel with locally crushed holes surrounding the fasteners 110 under design events. The extent of the damages can be visibly inspected after these events. The damaged wall system can be repaired by either drilling new holes on the steel angles 120 for new fasteners 110 or by removing all damaged components including the fasteners 110 and the CLT panel 130 and replacing them with new ones, depending on the extent of the damages and the intention of the structural engineer.
A different arrangement of a wall structure alternative to
The wall structures may be used in new construction or existing building restoration for mass timber construction in order to improve their earthquake or wind resistance. In each embodiment, the wall structure develops a ductile shear mechanism under lateral loadings, which is safer than the unfavorable rocking mechanism used in traditional construction for the CLT panels. The wall system permits buildings to be built safely with CLT or other rigid panels in mid-rise and high-rise buildings to greater heights than the current practice.
Various changes may be made to the embodiments shown herein without departing from the scope of the present invention which is limited only by the following claims.
