International Concrete Abstracts Portal

Following the strong earthquake in Chile on March 3, 1985, an intensive study was conducted to ascertain why the large inventory of moderate rise buildings in the coastal city of Vina del Mar performed so well during the earthquake. The major findings were that the vast majority of the buildings in this coastal city had a high wall area to total floor area ratio and that the reinforcement detailing in the boundaries of these walls were considerably less than required by U. S. codes. Analytical studies indicated that the high percentage of walls led to significantly lower drifts under severe seismic shaking, thus lowering the ductility demands on the walls. At lower levels of ductility demand, experimental results have demonstrated that wall boundaries did not need special detailing of transverse reinforcement. The findings from the series of research studies following the Chilean earthquake have led to modified U. S. design procedures that relate the need for special detailing in wall boundary elements to expected strain levels along the compression edge of the wall. The expected strain levels are determined based on the aspect ratio of the wall and the percentage of wall area to floor area used in the building.

The development of concrete offshore structures is illustrated by briefly describing the background for their functions, the development of structural design, brief examples of concrete research and research results, industry research projects, and international standardization. Figures and main specifications of typical structures are shown.

Force-deformation relationship of high-strength reinforced concrete beam members observed in the laboratory test was idealized by a trilinear relation for use in a nonlinear earthquake response analysis. Methods to evaluate the relationship were examined and the reliability of the methods were discussed with respect to the observed relations. Calculated initial stiffness is shown to significantly underestimate the observed value; a large coefficient of variation was attributed to accidental and shrinkage cracking in the specimen prior to the test. A similar large coefficient of variation was observed in the evaluation of cracking moment. Yield and ultimate moments could be favorably estimated by the theory. An empirical formula was proposed to evaluate yield deformation. An importance of controlling the elastic modulus of concrete in construction is emphasized if a structure is expected to behave as designed during an earthquake.

Objective evaluation of structural damage in buildings which have been subjected to strong ground motions is an undertaking in which expert knowledge and the ability to process correlated but fuzzy information in a consistent way must be blended. Often, in the immediate aftermath of earthquakes, field data is collected by survey teams whose expertise is variable. The use of knowledge-based systems capable of reaching an unequivocal decision on the damage state of a given building on the basis of queries arranged in a consistent hierarchical order would remove human subjectivity. This paper describes the internal design of an expert system called EPEDA, which is used as a tool for making a numerical ranking of damage in reinforced concrete buildings. Damage to individual elements is quantified on the basis of severity, relative member importance, and number of affected elements. Factors contributory in nature to the damage are summed with this score, as are scores expressing the overall system vulnerability. The final score is expressed as a number ranging from zero to 100. An example case is worked out to illustrate how the system works.

Presents nondestructive and destructive dynamic field testing and structural identification studies on actual constructed facilities. The specimens discussed here include a 27-story reinforced concrete (RC) flat-slab building, an RC slab bridge, two 80-year-old steel truss bridges, and three RC slab on steel girder bridges of various ages. The seismic vulnerability of the mid-rise building was evaluated and the test bridges rated by code procedures as well as by field-calibrated comprehensive 3-D FE models developed by structural identification. Experimentally measured and analytically simulated modal flexibilities of the bridges were correlated with deflections obtained under proof-load-level truck-load tests. The rating factors obtained by filed- calibrated models exceeded the corresponding operating rating factors by two and a half to four times for all of the test bridges. These studies revealed our capabilities for evaluating vulnerability or reliability of different classes of facilities. The bridge rating efforts helped to identify and conceptualize a number of unresolved important issues that influence bridge rating and management. Serviceability aspects that emerged as critical were studied through the relative contributions of different mechanisms to bridge deflections.