Hardened Facades Effects on Structural Systems
Analytical Study and Test of Blast-Resistant Facades Effects on Structural Braced Frames
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To ensure the safety of U.S diplomatic personnel overseas, the U.S Department of State (DoS) has developed facade retrofits capable of resisting high blast loads. Historically, these hardened facades have been primarily used in reinforced concrete frame structures that are perceived to perform better against high lateral forces generated by these facades. As the DoS builds and renovates existing steel-framed buildings, it is vital to understand the effects of hardened facades on steel structures to avoid potential collapse situations that would pose a threat to the building occupants.
An analytical study evaluated the global lateral response of steel frames representative of typical diplomatic facilities using hardened and conventional facades against high blast loads. Conventionally-designed steel frame buildings when used in conjunction with blast-resistant facades could be susceptible to failure due to the high blast reactions transferred to the Lateral-Force-Resisting-System (LFRS). However, when used with conventional facades, the rapid failure of the facade significantly reduces the loads on the LFRS. A test program was initiated to validate the findings from the study. Two tests have been planned using a full-scale, conventionally designed three-story steel braced frame. Test 1, in which a conventional curtainwall was installed on the steel frame structure has been conducted and the results validated the initial findings that conventional facades do not generate significant lateral loads in the LFRS. Test 2 which is in progress, will use a hardened facade and is expected to be performed in the fall of 2018. A review of the research program findings along with a brief discussion of new tools and methods to reduce blast reactions transferred to the LFRS are presented.
The U.S. State Department owns buildings and leases space in buildings for diplomatic purposes worldwide. Many of these buildings were not built considering any blast-resistant requirements, are not on an
Beginning in late 2010, an analytical study (McKay et. al., 2011) evaluated the global lateral response of different types steel frames representative of typical diplomatic facilities using hardened and conventional
First, an analytical study (McKay et. al., 2011) was performed to that included an extensive literature review and simple analytical modeling of a variety of typical steel building types. The
In order to be consistent in the evaluation of the different LRFS and to be able to relate their performance to existing consensus documents, PEC used the Structural Performance Levels
Test 1 Data
Drift Displacement Response: Nine (9) displacement gauges consisting of string potentiometers and scratch gauges were used to measure the lateral (drift) displacement vs. time of the structure (as shown in
Discussion of Results from Analytical Study and Test 1
Effects of Blast-Resistant (Hardened) vs. Conventional (Non-Hardened) Façade Systems – In the analytical study, all three and six-story buildings, shown in Table 2, were analyzed dynamically for reactions transferred from
Conclusion and Future Work
An analytical study, performed using conventional structural analysis methods and tools, evaluated the lateral response of typical steel LFRS against the effects of blast loads using conventional and blast-hardened façade
We would like to acknowledge State Department’s Bureau of Diplomatic Security Research and Development branch, and The Energetic Materials Research and Testing Center (EMRTC) for their contributions to this effort.
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