Cost effective mitigation strategy development for flood prone buildings -Preliminary Building Schema

Within Australian communities there is a wide range of building types. These vary in many attributes that include floor area, number of storeys, age, architectural style, fit out quality, construction material types and the level of maintenance. For mitigation research it is necessary to take this variety of building types and spatial distribution and discretise it into building classes or categories of similar, if not identical, vulnerability. This 'pigeon holing' strategy makes research on impact, risk and mitigation more tractable in that vulnerabilities can be assigned to each class with the reduced variability within the class captured in the uncertainty of the model. Available exposure information can also be mapped to the schema along with building types that can benefit from retrofit interventions. This report presents the preliminary building schema proposed for the Cost Effective Mitigation Strategy Development for Flood Prone Buildings BNHCRC project. The report discusses the utility of a building schema and which building attributes are important for distinguishing between houses of differing vulnerabilities in the Australian building stock. The proposed schema divides each building into foundations, bottom floor, upper floors (if any) and roof to describe its vulnerability. Through this arrangement it is made possible to assess vulnerability of structures with different construction material used in different floors and also to assess vulnerability of tall structures where only bottom floors are supposed to be inundated. The schema classifies each floor system based on the following attributes: - Construction period - Fit-out quality - Storey height - Bottom floor system - Internal wall material - External wall material Allowing for combinations that are invalid in an Australian context, the draft schema defines 60 discrete vulnerability classes based on the above mentioned attributes. Furthermore, the schema proposed 6 roof types based on material and pitch of the roof. This proposed schema is the initial categorisation of residential structures as to vulnerability class for this project. It is expected to change and be refined as the project is taken forward and the specific building types for retrofit research are identified. The concept of 'nestability' may be subsequently used where mitigation research focuses on several building types that fall within a single broader category and become sub-classes. The draft schema has been developed in recognition of the current and projected ability to define national building exposure and of the parallel BNHCRC mitigation projects examining vulnerability to earthquake and severe wind. While vulnerability schema are hazard specific, alignment has been sought with the schemas for other hazards where possible.