Rotations in a shear-beam model of a seven-story building caused by nonlinear waves during earthquake excitation

Abstract

SUMMARYWe model a seven-story, reinforced-concrete building in Van Nuys, CA, which was damaged during the 1994 Northridge earthquake. We use a one-dimensional, layered, shear-beam model with bi-linear material properties, and we examine how the rotations (local strains and drifts) in this model depend upon the distribution of the stiffness along the building height, the nonlinear properties of the reinforced concrete, and the nature of strong motion. We show how, following the powerful waves propagating up and down the building, point rotations take place that differ from the corresponding average drift angles. These point rotations are larger near the rigid floor slabs (near the top and bottom ends of the columns, shear walls, and nonstructural members found at all floors) and propagate as slow waves up and down the building. These slow rotational waves occur only while the material is experiencing large nonlinear deformations, and their amplitudes grow with ductility. We note that recording these rotational waves in real time may provide a powerful new vehicle for health monitoring of full-scale structures excited by large transient forces when their structural members enter large nonlinear deformations.

Amplification of linear strain in a layer excited by a shear-wave earthquake pulse

“…Because one of the principal design criteria is governed by the allowed maximum drift (average rotation of structural members between adjacent floors), and because the possible damage can be related directly to the exceeding of certain drift amplitudes [3,26,29] and to the wave motion in buildings in general [6], it is seen that the results we present in this paper for a layer of soil will apply also to the approximate, one-dimensional representation of the building response.…”

Energy dissipation by nonlinear soil strains during soil–structure interaction excited by SH pulse

“…This building was studied extensively using different models and representations [11,13,20], and the body of those results can be used to complement future comparisons and interpretations of its response.…”

“…The classical earthquake engineering approach correlates damage of structures with the largest relative response of the equivalent single-degree-offreedom system, in a formulation that is typically based only on the largest relative peak of response [55]. While this approach can be refined to involve many largest peaks of the relative response [16,17] in the near field of strong ground shaking, it appears that the damage is more governed by the strong pulses that emanate from the broken asperities on the moving fault, and hence by the power of these pulses and the energy those pulses carry [37,[11][12][13]. Therefore, we select for our studies the excitation in terms of simple pulses, to simulate the actions of strong ground motion near faults.…”

The laboratory investigation of the innovative sensor for torsional effects in engineering structures’ monitoring

“…However, again far from the hardware complexity of this approach, it is also vulnerable to building's deformations. Additionally, during earthquakes, where all is in moving, there is a problem with proper a choice of an external reference frame for such mea− surement [18]. For the above reason, one of the most prom− ised techniques seems to be sensors based on the Sagnac effect [19] which allows to detect rotation rate in civil engi− neering constructions without any reference point.…”