International Concrete Abstracts Portal

An experimental program was carried out to investigate the behavior of concrete filled steel plate walls. Seven wall-panel specimens were tested under repetitive in-plane pure shear loading. Each specimen was made by connecting a pair of surface steel plates with partitioning webs and tie bars, and filling the boxes so-formed with concrete. The parameters investigated were the thickness of the surface steel plate, the number of partitioning webs and the presence or absence of headed stud bolts. Results describing a restoration force characteristic of a large loop area are presented. Rigidity after the onset of cracking approximates the cumulative value of truss rigidity (rigidity of resistance mechanism consisting of longitudinal and transverse tension chord members of steel plates and compression diagonals of concrete) and in-plane shearing rigidity of surface steel plates. The skeleton curve for the shear stress vs. shear strain relationship could be theoretically idealized into a quadri-linear curve with three control points.

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.

Presents a review of (1) previous experimental studies on the earthquake response of square reinforced concrete columns and a discussion of their applicability to bridge columns in areas of moderate and high seismic risk; (2) confinement steel design for rectangular columns based on different codes and methods and an example column to compare these codes; and (3) two concrete confinement models in relationship to their application in estimating a range of displacement ductility for square columns, rectangular columns, and pier walls. The results of part (1) showed that previous tests on square columns are mostly under relatively large axial stresses which represent the state of building columns and that the data are generally aimed at areas of high seismic risk. Part (2) showed a considerable variation among different codes and methods in terms of the amount of lateral reinforcement and the parameters considered in design. The results of part (3) indicated that measured displacement ductilities were generally within a range calculated using the two confinement models selected in this study.