Rebound loading

There are other options for upgrading existing CMU masonry walls. One option would be to add steel members between the frame to reduce the vertical spans of the wail. Steel members should normally be tied to the existing wall. If they are not, then rebound load should be evaluated. 

Headed studs are normally used to secure a roof slab to a structural steel framing system for rebound loads in new designs. This option may not available for upgrading existing structures. It may be necessary to provide through bolts to the structural frame with a backing plate on the top side of the stab. 

Filler loading Volume, parts Mooney viscosity Optimum cure (at 141°C), min Modulus (at 300%), MPa Tensde strength, MPa Elongation, % Hardness, Shore A NBS abrasion (ASTMD1630) Rebound, %... 

Rebound Response to the dynamic blast load, will cause the window to rebound with a negative (outward) deflection. The outward pane displacement and the stresses produced by the negative deflection must be safely resisted by the window while positive pressures act on the window. Otherwise, the window which safely resists stresses... 

Boundar y conditions need to be assessed based on the type of connections to be used for the member supports. The engineer must keep in mind that support details must provide sufficient strength, ductility and stability to enable the member to develop full collapse mechanism. Support capability to resist reaction forces for both the loading and rebound phases of the response must be considered when assessing boundary conditions. 

Connections for precast panels can be a problem for blast loaded buildings. Typical connections for walls rely on direct bearing for support of the panel for positive loads, and weld plates for negative loads such as wind suction. Rebound of stiff panels due to blast toad can be very high, and the connections typically used in conventional design may be inadequate to resist this load. Substantial and expensive changes arc often required to develop the full capacity of precast panels. 

The peak rebound reaction is -2.33 kips (-10.36 kN) at t - 0.05 sec. Use the dynamic reaction for the roof in-plane loads analysis. 

Note that the rebound peak is conservative because it occurs after the load dissipates and after several cycles of response without reductions due to damping. 

Note that the peak rebound reaction occurs after a number of cycles, and after the blast load disappears. 

The analysis of the existing masonry wail revealed that the wall only provides a small percentage of the required resistance for the specified blast. Due to the symmetry of the wall and the reinforcement (for the upgrade system), the analysis for the rebound blast loads was not required. 

Bar joists have adequate lateral support to prevent the top chords of the joists from laterally buckling under the loads published in the manufacturer s load tables. For required resistance higher than the load tables or for plastic behavior of the joists, additional lateral bracing may be required. Evaluations should be based on as-built dimensions and field inspections at the elements and welds. If rebound resistance is required, additional uplift bridging may be required. 

The PAT process has been unable to stabilize organic materials such as rubber crumbs or wood chips because these substances have a memory effect and rebound to their original size after compression. The process requires low moisture content in the waste stream because waste loading is sensitive to moisture content. For hazardous and mixed wastes, influent particle size must be less than 0.25 inches in order to achieve proper brick formation and adequate stabilization. 

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