Development and Evaluation of a Shock Tunnel Facility for Conducting Full-scale Tests of Loading, Response, and Debris Characteristics of Structural Elements

This report describes the conversion of an existing large-cross-sectionalarea tunnel into a shock tube and the evaluation of the capabilities of this facility for blast loading and response studies of full-scale and large-scale structural elements. Also included are the results from a preliminary test series of full-scale wall panels conducted as part of the evaluation program and the design of a detailed test program to investigate the loading, response, and debris characteristics of wall panels. The basic tunnel, which is a section of a former coastal defense complex, is rectangular in cross section and 163 ft long. The first 63 ft of the tunnel, which is used as the compression chamber, has an 8by 8.5-ft cross section. The remaining portion of the tunnel, which expands in an 8-ft transition section to an 8.5by 12-ft cross section, 92 ft long, is used as the expansion chamber. The tunnel conversion included blocking off several doorways and other openings along the side of the tunnel, installation of a cylindrical steel liner in the compression chamber, and installation of an instrumentation system. Shock waves are generated in the expansion chamber of the tunnel by detonating strands of primacord which have been uniformly distributed throughout a section of the compression chamber. Evaluation tests conducted to date indicate that a wide range of air blast conditions can be generated depending on the explosive arrangement. Both peaked and flat-topped pulse shapes have been obtained, with total durations approaching 100 msec and flat-topped durations of about 40 msec. The upper overpressure operating limit is controlled at present by the strength of the expansion chamber and has been tentatively set at about 12 psi incident until further response information on the tunnel wal^s has been obtained. The preliminary wall panel test series, which included seven 8-in.-thick nonreinforced brick panels and three timber stud walls, confirmed the suitability of the shock tunnel for full-scale panel testing. The failure process was reproducible, and the failure times, even for brick paneJ«^ were much less than the loading durations.