A team of faculty and cadets from West Point studied the performance of SIPs subjected to blast loads to develop novel strengthening techniques
Shock tube testing was used to assess the blast performance of a proprietary metal mesh drapery known as “GuardianCoil”. The system was used to stop projectiles from fragmentation of unreinforced masonry (URM) walls and glazed windows and was installed on the unloaded/interior side of these non-structural elements. Each test sample was subjected to a single, destructive pressure-impulse combination generating high velocity projectiles. The GuardianCoil contained the entirety of the unreinforced masonry block walls and prevented potentially life threatening projectiles from penetrating the test area. It also contained the entirety of the large glass fragments within the first meter of the drapery. The pieces of mortar or glass that penetrated the test area were limited to the weave size, and did not pose a life safety hazard.
This study evaluated bond behavior of lap-spliced reinforced concrete beams subjected to high strain rates. Eleven companion pairs of beams, each consisting of two nominally identical specimens, were designed, built and tested. One beam from each companion pair was tested under static loads generating an average strain rate of 10-5 s-1 , while the other was subjected to high strain rates in the range of 1.0 s-1 generated using a shock tube. Average peak dynamic beam resistance increased by 30% relative to the reference static conditions due to high strain rate effects. Part of this increase was attributed to improvements in the load carrying capacity of the lap splices, which on average experienced a dynamic increase factor (DIF) applied to bond strength of 1.28. Regardless of strain rate, it was found that the bond strength of splices with and without transverse reinforcement increased in proportion to the ratios of the minimum cover depth and the splice length to bar diameter, respectively.
A new line of blast-resistant steel doors for the minimum anti-terrorism market was developed and validated for the manufacturer through combined experimental and analytical research. Full-scale shock tube blast testing was used to determine the response of the doors relative to ASTM F2927 door and glazing classifications. A number of parameters affecting door response were considered, including door aspect ratio, construction methodology, door-frame construction, as well as anchor size and quantity. The experimental portion of the study was complemented by an analytical investigation to develop door design tools. Finite element analysis was employed to generate door resistance curves. This was followed by single-degree-of-freedom dynamic analyses to predict the various levels of protection for the blast scenarios studied.
Historic sash windows protected by “SecureTM” security blinds were tested under simulated blast loading using a shock tube in order to establish the blast performance of the blinds. The security blinds were placed near the inside face of the windows and consisted of vertical blades and an optional horizontal locking bar. The specimens were tested with different orientations of the blades from fully-closed to fully-open. Reflected pressures on windows ranged between approximately 12 kPa and 70 kPa, with almost constant duration (varying between 13 ms and 16 ms). The shades were effective in reducing the debris generated by blast pressures, however, a failure mode was observed at shade opening greater than 45 degrees whereby wood debris from the frame wedged between the blades and prevented them from closing. No damage or permanent deformation of the shades was observed.
High strain-rate loading on the flexural response of typical light-frame wood construction was investigated. Stud grade spruce-pine-fir (S-P-F) lumber specimens were tested within a range of low and high strain-rates between 6×10-6 1/s to 0.4 1/s using a servohydraulic actuator and a shock tube.
As-built and glass-fiber-reinforced polymer (GFRP)-retrofitted reinforced concrete columns were subjected to simulated blast loading using a shock tube. Retrofitting involved various configurations of longitudinal and transverse GFRP layers to enhance flexural and shear capacity. Retrofitting significantly increased the strength and stiffness of reinforced concrete flexural members and greatly improved blast response. Furthermore, the addition of transverse GFRP wraps led to enhancements in the debonding strain and behavior of longitudinal GFRP, as well as an increase in post-peak ductility of concrete.
The Canadian Safety and Security Program (CSSP) funded the University of Ottawa to develop blast-resistant window retention anchors to improve Canada’s preparedness and prevention capabilities against blast threats. The project included a significant experimental component consisting of shock tube blast testing of full size windows anchored to different substrates (concrete, steel block masonry and stone masonry). The objectives of the tests were to collect much-needed experimental data on anchor performance, develop new design tools and procedures, and develop a new national design standard on blast-resistant window retention anchors, CSA S852. The experimental data obtained from blast testing of windows was used to validate analysis procedures developed for the purpose of blast-resistant window anchorage design and assessment.
Externally-bonded carbon fiber reinforced polymer (CFRP) retrofits were studied for enhancing the blast resistance of reinforced concrete slabs and walls. Companion sets of reinforced concrete wall and slab specimens were subjected to a total of sixty simulated explosions using a shock tube. Externally bonded FRP retrofits were an effective retrofit technique to improve the blast resistance of reinforced concrete structures, provided that debonding of the composite from the concrete substrate is prevented. The test results also indicated that FRP retrofitted reinforced concrete structures may survive initial inbound displacements, only to fail by moment reversals during the negative displacement phase.