Search

The use of non-destructive testing (NDT) methods, such as the impulse response test and the parallel seismic test, for evaluating existing building foundations is discussed. NDT methods will become more important as more parts of the national infrastructure need replacement, renovation, or upgrading in the future.

Technological advances have made nondestructive testing (NDT) for concrete more reliable but civil engineers hesitate to use the method due to past problems. The development of digital electronics and computers can now eliminate these problems and facilitate data acquisition. Automated processing also eases the tedious task of arranging information into tables and graphs. Color graphics and digital signal processing improves data interpretation for more reliable analysis. These new technologies enhance NDT's functions in quality control and performance evaluation of concrete.

Structural distress in concrete swimming pools caused by settlement or consolidation of dissimilar bearing strata was documented in an ASCE technical note by Kovacs in 1992. A particular mechanism described in the note was of postconstruction fill collapse causing differential settlement. This creates strain in the pool shell, leading to cracking. Water leaking through the cracks can then cause further collapse of sensitive soils, and may eventually lead to failure of the pool foundation. The writer has experience of a similar situation, but in this case believes the cause to be water leakage prior to cracking of the pool. The pool was part of a large mountainside hotel complex, and the structural problems had potential for serious damage. The writer agrees with the points raised by Kovacs, and the subsequent discussion papers, but believes that this case history identifies other important factors that should also be considered, both in pool construction and remediation.