Recent changes to building codes around the world have led to stricter design processes for exterior walls. Masonry cavity walls consist of exterior brick and internal concrete masonry wythes with insulation between them. Stricter requirements are leading to increased cavity width to allow more insulation and requiring designers to consider thermal bridging in ties that link layers together. Added insulation affects tie strength and stiffness which affects load capacity. The structural response of various connectors (z-tie, rectangular tie, plate connector, and a novel inclined connector) tested under tension, compression, and shear are compared. Tests were completed on 400 \(\times \) 400 mm wall sections that included interior and exterior wythes as well as connectors. Tests were completed using a cavity width of 175 mm which reflects trends seen in Canada and Scandinavia. Further context is provided by 3D thermal modelling that assesses tie effects on wall thermal resistance. Under tension, connectors failed by wythe anchorage; under compression, connectors failed by buckling. Despite similar failure modes, plate and inclined connectors had considerably larger capacities and ductility which may allow for walls to be constructed with fewer ties overall. Under shear, induced by slip between wythes caused by flexural or thermal deformation, inclined connectors were stronger than other connectors and had noticeable ductility. Plate and inclined connectors saw initial yielding followed by anchorage failure. Plate and inclined connectors decreased thermal efficiency by 10% compared to a wall without connectors.

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Mechanical Testing of Conventional and Novel Connectors in Masonry Cavity Walls

  • Douglas Tomlinson

摘要

Recent changes to building codes around the world have led to stricter design processes for exterior walls. Masonry cavity walls consist of exterior brick and internal concrete masonry wythes with insulation between them. Stricter requirements are leading to increased cavity width to allow more insulation and requiring designers to consider thermal bridging in ties that link layers together. Added insulation affects tie strength and stiffness which affects load capacity. The structural response of various connectors (z-tie, rectangular tie, plate connector, and a novel inclined connector) tested under tension, compression, and shear are compared. Tests were completed on 400 \(\times \) 400 mm wall sections that included interior and exterior wythes as well as connectors. Tests were completed using a cavity width of 175 mm which reflects trends seen in Canada and Scandinavia. Further context is provided by 3D thermal modelling that assesses tie effects on wall thermal resistance. Under tension, connectors failed by wythe anchorage; under compression, connectors failed by buckling. Despite similar failure modes, plate and inclined connectors had considerably larger capacities and ductility which may allow for walls to be constructed with fewer ties overall. Under shear, induced by slip between wythes caused by flexural or thermal deformation, inclined connectors were stronger than other connectors and had noticeable ductility. Plate and inclined connectors saw initial yielding followed by anchorage failure. Plate and inclined connectors decreased thermal efficiency by 10% compared to a wall without connectors.