EXECUTIVE SUMMARY

A methodology is developed to estimate physical damage at the structural
component and global level and repair cost for instrumented reinforced concrete (r.c.) buildings shortly after the cessation of strong motion.

A methodology is also developed to estimate differential settlement between
foundations and the resulting physical damage at the global and structural
component level for instrumented r.c. buildings under operating loads.

For seismic conditions the developed methodology uses building-specific
knowledge of the facility’s structural system, input from the two three-dimensional accelerators in every floor and the building basement on time history of accelerations during the seismic event, non-linear dynamic analysis and a novel energy-based theory of seismic failure for r.c. structures to assess the locations and extent of structural damage so that the owners and occupants know immediately about the building safety. This assessment can be used to direct structural engineers to locations of physical damage, even if they are concealed behind architectural finishes. Moreover, this assessment has been used with construction cost-estimation principles to estimate repair cost which is invaluable for quickly arranging for financing.

Under operating conditions the most common reason for changes in the internal forces during the building life-span is differential settlement between foundations on cohesive soils subjected to consolidation or due to deep excavations in the vicinity of the building. It is not possible to measure the absolute value of settlements through strain sensors. However, it is possible to estimate the support reactions at the columns’ bottom cross-section on the foundations, at which locations the strain sensors are only placed in the instrumented r.c. building. The changes in values of the support reactions that will be estimated in sequential periodic measurements compared to the values measured in the initial condition of the building constitute the input for a finite element analysis.

 The sum of the measured axial forces on the columns equals the sum of the active vertical loads on the structure. The vertical loads that are applied on the members in the model are equal to the initial design loads multiplied by the ratio of the total active loads to the total initial design loads. Then the analysis is performed to derive stresses and moments that are compared to limit values in order to determine physical damage of structural members and the amount of differential settlement between foundations. The above analysis at the time of periodic measurements of strain will establish, timely, whether foundation movement is progressive and threatening to the building reducing dramatically the expense of remedial measures.