Environmental Impacts of Multi-Storey Buildings Using Different ...

- 20 -The boards are usually about 90x20mm size, in panels which may be from five layers thick upto ten layers thick (100-200mm panel thickness). The panels can be used for all the walls andfloors of large buildings. Room sizes are small because all the walls are structural walls andfloor spans are limited.3.4.4.5 Post-tensioned Timber Frames and WallsA new form of multi-storey timber construction being developed in New Zealand, based onrecent developments in reinforced concrete construction for seismic areas, uses post-tensionedtimber frames and walls. For further information see Section 4.4, Multi-storey TimberBuilding Research.3.4.5 Height Limits for Multi-Storey ConstructionHeight limits considering the gravity load resisting structure are as follows (see the TimberDesign Guide, Buchanan, A., 2008):• The upper limit for light timber framing for gravity structures is in the order of 5 to 8storeys, depending on the configuration of the building.• The upper limit for LVL post and beam gravity systems could be in the order of 15 to25 storeys, depending on the configuration of the building.• The economically competitive span limit of timber floor construction utilisingengineered wood products is likely to be around 8 or 9 metres. Typically, spans ofaround 6 metres are generally the maximum used in practice with engineered woodproducts and other systems available at present.Height limits considering the lateral load resisting structure are as follows:• The upper limit for plywood shear walls is in the order of 5 to 8 storeys, depending onthe configuration of the building.• The upper limit for solid LVL shear walls is untested and is the subject of research atpresent, however they would be expected to exceed the capacity of plywood shearwalls by a considerable margin.• The upper limit for timber moment resisting frames is likely to be in the order of 5 to10 storeys, depending on the configuration of the building.• The upper limit for plywood floor diaphragms will be driven by the capacity of nailedconnections from the plywood to the framing. The loads imposed by seismic flooraccelerations are likely to exceed nail capacities at about 15 to 25 storeys, dependingon building configuration. Site glued connections would allow the possibility of higherbuildings however the issue of glue durability and the suitability for site applicationmay render a structural site glued option impractical.• The upper limit for using gypsum plasterboard bracing systems is likely to be around 4storeys, depending on the configuration of the building.Hybrid structures are possible with a combination of timber gravity load resisting structureand steel and/or concrete lateral load resisting structure. With this combination of materials,a predominantly timber building could be designed and constructed which would be limited inheight only by the capacity of the timber gravity load resisting system and the floordiaphragm system, i.e. 15 to 25 storeys.