Transmission loss characteristics of an annular cavity with arbitrary port locations using Green's function method.
The prediction of transmission loss characteristics of a short chamber requires the study of both longitudinal as well as transverse modes. This prompts the development of a three-dimensional (3D) transfer matrix, which can address the wave propagation in all three directions. Accordingly, an analytical methodology for transmission loss characteristics of an annular cavity using Green's function method is presented in this paper. The 3D wave equation is used to derive the mode shape functions for the cavity. The average pressure on the inlet and outlet ports is predicted using the Green's function derived from the mode shapes. Three different port location configurations of the annular cavity are considered for establishing the analytical methodology, viz., face-inlet-face-outlet (FIFO), side-inlet-side-outlet (SISO), and face-inlet-side-outlet (FISO). Numerical model results are used to corroborate the analytical results. The effects of geometrical parameters on the transmission loss are studied.
ACOUSTIC ATTENUATION PERFORMANCE OF CIRCULAR EXPANSION CHAMBERS WITH EXTENDED INLET/OUTLET
Abstract The acoustic attenuation performance of circular expansion chambers with extended inlet/outlet is investigated. Three approaches are employed to determine the transmission loss: (1) a two-dimensional, axisymmetric analytical solution for the concentric configuration; (2) a three-dimensional computational solution based on the substructure boundary element–transfer impedance matrix technique; and (3) experiments on an extended impedance tube set-up with expansion chambers fabricated with fixed inlet, outlet, and chamber diameters, and varying lengths for the extended ducts and the chamber, and varying offset locations of the inlet and outlet. The transmission loss results from all three approaches are shown to agree well for the concentric configurations. The computational approach is also applied to determine the acoustic attenuation performance of asymmetric expansion chambers with extended inlet/outlet, which also compares well with the experiments. The effect of geometry (lengths of the extended ducts and expansion chamber, and the offset angles of the asymmetric configuration) on the multidimensional wave propagation and acoustic attenuation performance is discussed in detail.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.