This case study investigates the engineering of point-fixed glass balustrades in Australia, focusing on design challenges and regulatory compliance. Point-fixed systems offer a sleek aesthetic but require careful consideration of factors such as wind loads, impact resistance, and the use of suitable glass and interlayer materials. The study highlights the importance of a performance-based approach to design, incorporating finite element analysis and rigorous testing to ensure the safety and durability of these innovative systems.
Introduction
Glass balustrades are defined as low or mid-height walls that serve as protective barrier to prevent people from falling between levels or restricting access. In contemporary architecture, there is a growing trend towards minimalist design, leading to an increased use of point-fixed glass balustrades. These glass barriers have been adopted in various applications, such as commercial buildings, residential houses and public spaces, offering an optimal balance of safety and aesthetic appeal.
Point-fixed glass balustrades are structural barriers protecting a difference in level greater than or equal to 1,000 mm where the glass panels serve as main structural element, connected to the supporting structure using point fasteners (fixings), which are mounted through drill holes in the glass. This type of barrier may or may not have a handrail as defined in AS 1288 [1]. In the context of this study, the discussions focus on the use of standoff fittings, which are common in Australia. Nevertheless, other point fix systems can be utilised, such as spider fittings. The required height of the glass barriers is influenced by the class of building, occupancy type and location, typically ranging from a minimum of 865 mm to 1,200 mm. The barrier height can also be increased for additional wind protection or privacy screens.
The design of point-fixed glass balustrades for the ultimate strength, stability and serviceability limit states must consider the most critical effects from design actions such as imposed live load from [1] [3], and wind load [4] separately, including design combinations [2] and other project-specific requirements.
Impact resistance, especially when subject to the risk of human impact (soft--body impact), is also a key requirement. The current set of imposed live loads outlined [1] [3] is typically applied as static impact load, and for non-standard barrier applications such as point-fixed glass balustrades, a dynamic analysis or impact tests are often required. However, impact testing of point-fixed glass balustrades is not always implemented on projects due to a variety of reasons such as use of previously tested systems, tight construction program, cost constraints and lack of knowledge and understanding of the requirements. This is compounded by the lack of definitive requirements on AS 1288 [1] concerning test method for determining the impact performance of point--fixed glass balustrade systems. Industry stakeholders have encountered significant challenges in achieving compliant installations due to the perceived lack of specific guidance within AS 1288 [1]. This has resulted in confusion and ongoing debate regarding acceptable product selection and installation practices within the construction sector.
For best practice approach, the impact testing provisions should be included in the project specifications with reference to ASTM E 2353 [6] or other applicable international standards [17] [18].
