Papers by Author: Zachery I. Smith

Abstract: Based on Federal Aviation Authority (FAA) requirements, project specific blast loads are determined for the design of a new airport traffic control tower. These blast loads must be resisted by exterior wall panels on the control tower, protecting building occupants from intentional explosives attack scenarios. Such blast resistant walls are typically constructed of thick reinforced concrete panels or composite steel plate and rolled sections, as conventional building cladding systems have relatively low blast resistance. While these more robust design approaches are valid, the additional cladding mass they represent will significantly increase the base shear and overturning demand in seismic zones. This paper investigates the use of a light structural system comprised of a steel stud wall assembly partially embedded in a thin layer of concrete to obtain composite action. Fiber reinforced polymer (FRP) composites are also included to increase the blast resistance and aid in keeping the panel weight to a minimum. Two full-scale composite steel stud walls are designed, constructed, and tested dynamically in the BakerRisk shock tube. The stud walls consist of back-to-back 150 mm deep, 14 gauge (1.8 mm thick), cold-formed steel studs spaced at 610 mm on center. Both specimens have a 50 mm thick normal weight concrete layer, reinforced with welded wire mesh that is welded to the stud compression flanges to achieve composite action. Two layers of Tyfo® SEH-51A fiber reinforced composites are used on the tension flange of the steel studs. A single layer of Tyfo® SEH-51A composites is used on the tension face of the concrete layer between the studs for one of the specimens. Web stiffeners are used at the bearing support to prevent premature web crippling shear failure of the specimens. The stud walls are analyzed using single-degree-of-freedom (SDOF) models. A non-linear moment-curvature relationship, accounting for actual material constitutive properties, is used for determining the resistance function of the walls. Blast pressure and impulse data from the shock tube tests is used to compare analytical predictions to the measured displacement-time response. Analytical predictions of panel response for both tests are within ten percent of the observed response based on displacement.

Abstract: Suspension and cable-stayed bridge cables are currently vulnerable to multiple scenarios that can jeopardize the integrity of the bridge. These can include accidental truck fires and more recently, terrorist attacks. The inherent nature of suspension and cable-stay bridges leaves little redundancy to their structural loads paths. For this reason they are more susceptible to terrorist attacks than possibly any other structure. This paper looks at a composite cable shield composed of various materials each tailored to protect against unique threats. Several test specimens were manufactured by Fyfe Co. LLC and proof tested by the U.S. Army Corps of Engineers. Multiple threat scenarios were simulated by plastic explosives, extreme heat differentials, and various cutting mechanisms. The distinctive prefabricated connections provide for fast installation and a very robust design to prevent cable shield separation under extreme loads. Through the use of several advanced composite materials the cable shields provide a widespread umbrella of protection for potential threats.