Computer software BRADS (Blast Resistant Anchor Design Software) was developed at the University of Ottawa for conducting two-degree-of-freedom (TDOF) analysis and window anchor design (Jacques, 2017, Jacques and Saatcioglu, 2017).
The algorithm underlying the software was developed to satisfy the requirements of CSA S852 , the new Canadian standard for Blast Resistant Window Anchor Systems. The tool can compute the required configuration of window retention anchors based on the major parameters known to influence anchorage capacity, including: substrate flexibility, glazing response, window aspect ratio, frame rigidity, the distribution of dynamic reactions, combined stresses, and anchor boundary conditions.
The window/substrate assembly in the software is subjected to total blast loads, including the loads applied on the substrate. Substrate geometry and material properties are specified. The user can select one of three pre-defined elastic substrates (concrete, masonry, or steel), or can specify a custom nonlinear mass-spring-damper element for the substrate. The dynamic properties of the window system, such as resistance, mass, and damping, are stored in a database within the software and are specified from a drop-down menu. The software includes dynamic properties for window systems commonly used in the blast-resistant construction industry. New windows can be added to the database to expand the functionality of the software by entering the properties of a specific window system. These properties may be obtained from protective window design software, hand calculation, finite element analysis, or from experimental tests. The blast loads used in anchorage design can consist of either: i) an impulsive pressure-time function with triangular idealization; ii) an exponential-decay pressure-time history defined using the TNT charge mass and stand-off distance; or, iii) as a series piecewise pressure-time history points entered by the user.
The software conducts TDOF analysis and computes maximum displacements for the substrate and the window. If the analysis predicts that the window achieves a stable equilibrium, indicating window failure has not occurred, the software calculates window edge support reactions distributed around the window perimeter. The automated analysis procedure will evaluate dynamic reactions generated during the pre-break and post-break phases, and consider the possibility of load reversal, when determining design anchorage forces during inbound and rebound response.
The number of anchors, diameter, strength, and geometry relative to the frame are input parameters. The software checks the capacity of each anchor and indicates whether it meets the requirement of capacity exceeding the applied load. The capacity check is done under combined stresses. A colour-coded graphical output consisting of the window and anchors is presented, with a green anchor indicating sufficient capacity, and red indicating a need for either increasing anchor size, reducing anchor spacing, or selecting an anchor with greater material capacity. This enables the designer to have full control over the design process.
The output consists of a printed design report that can be exported as an electronic file outlining the design data, analysis results in terms of substrate and window displacements, anchor shear, axial tension and bending moment values, as well as anchor capacities. The output is also available in a graphical format, displaying displacement time histories, resistance functions and the distribution of anchor forces with applied loads and capacities.
The necessary legal verbiage:
Although every effort has been made to ensure the accuracy of BRADS (the software product), the software product is provided by Eric Jacques “as is” and “with all faults.” Eric Jacques makes no representations or warranties of any kind concerning the safety, suitability, lack of viruses, inaccuracies, typographical errors, or other harmful components of this software product.
Eric Jacques assumes no responsibility or liability for the use of the software product, conveys no license or title under any patent, copyright, or mask work right to the product. Eric Jacques reserves the right to make changes in the software without notification. Eric Jacques also make no representation or warranty that such application will be suitable for the specified use without further testing or modification.
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