To optimize building design and safety, Flex-Joist™ tension-controlled open web steel joists are engineered to exceed standard steel joist design for strength, reliability and ductility. This alternative design approach gives building owners and specifiers the option of consistently higher steel joist performance at an affordable cost.
Increased strength, higher reliability index, and improved ductility provide an enhanced timeframe for emergency management in the case of an overload situation. The Flex-Joist™ system can be coupled with a third party overload sensoring system to further enhance building safety.
Standard SJI joists are designed based on procedures derived from the American Institute of Steel Construction (AISC) design specifications. AISC states that their design specifications result in an average member reliability index of β = 2.6, where β is the ratio of the standard deviation to the mean. Flex-Joist™ has been demonstrated to have a system reliability index of β = 3.4, or 31% higher than the industry standard.
By selectively increasing the size of the weakest components without decreasing the size of the strongest components, the strength of a Flex-Joist™ is substantially increased at an affordable cost.
The Flex-Joist™ design is based on limit states control, so it has a much higher probability of achieving a ductile tensile yielding limit state that is characterized by slow collapse, with large inelastic deformations and inelastic reserve capacity. This very ductile behavior gives sensory warning of impending collapse, allowing more time for evacuation and response.
A Flex-Joist™ project is ideally suited for the optional, post-erection installation of electronic sensors by a third party provider. In the event of an overload, the bottom chord and end webs of a Flex-Joist™ will be highly stressed prior to collapse. Sensors and alarms installed along these components by the third party provider can establish an early warning system for possible overload removal, roof shoring, and evacuation of personnel.
Disclaimer: No joist will withstand sudden and catastrophic impact forces that exceed system capability. Flex-Joist™ design offers probability of high ductility and time delay under static gravity overload conditions.
