Sharon L. Wood

Performance of reinforced concrete buildings during the 1985 chile earthquake : implications for the design of structural walls

The 1985 Chile earthquake provided a rare opportunity to study the seismic response of buildings with reinforced concrete walls. More than 230 moderate-rise reinforced concrete buildings were located in the coastal city of Vin~a del Mar at the time of the earthquake. The majority of these buildings relied on structural walls to resist vertical and lateral loads. However, the walls did not have the reinforcement details required in current U.S. codes to ensure ductile response. A survey of damage following the earthquake indicated that most of these buildings sustained no structural damage. Analyses of the buildings indicated that the structural walls provided sufficient stiffness to limit the displacement response and the earthquake damage. The Vin~a del Mar building inventory is used to evaluate current building code provisions in the U.S. for structural walls. The excellent performance of the Chilean buildings during the 1985 earthquake suggests that requirements for boundary elements in walls may be relaxed if sufficient wall area is provided.

Influence of Viscoelastic Dampers on the Seismic Response of a Lightly Reinforced Concrete Flat Slab Structure

A 1/3-scale model of a section of a three-story lightly reinforced concrete flat slab structure was constructed. Researchers installed a viscoelastic damper (VED) seismic rehabilitation system on the model and subjected it to seismic simulations on a shaking table. Successive simulations were conducted with increasing base accelerations until the horizontal displacement limit of the shaking table was reached. The dampers were then removed, and the simulations were repeated until structural failure occurred. This paper summarizes the responses of the model. Brief comparisons of the responses of the model with and without VEDs installed are made. The VEDs improved energy dissipation characteristics and serviceability of the structure by reducing interstory displacements. Earthquake simulation responses indicated that the damper configuration that was employed in the experimental investigation permitted rotations of the VEDs, which lowered their energy dissipation efficiency. An alternate arrangement for the VEDs is proposed to alleviate this problem.

Sensitivity of Seismic Assessment of a Double‐Deck, Reinforced Concrete Bridge

Engineers are assessing the seismic vulnerability of thousands of reinforced concrete bridges located throughout the United States. Many of the bridge evaluation procedures are new, and the engineering effort necessary to implement them varies. Consequently, the assessment methodology varies among the responsible agencies, and in some cases, from one bridge to the next. This paper documents the sensitivity of an evaluation of a double-deck, reinforced concrete bridge to the manner in which the assessment was conducted. Large differences arose from the selection of linear versus nonlinear models. The computed splice vulnerabilities and concrete contribution to shear capacity varied also. In contrast, the assessment results were relatively insensitive to the way in which the investigators estimated the flexural ductility capacities, the transverse reinforcements contribution to shear resistance, and the joint vulnerability. Even if the variations among the evaluation procedures are reduced, the results of the evaluations will still be sensitive to the selection of the ground motion and foundation stiffness.

Measured Response of Roof Diaphragms and Wall Panels in Tilt‐Up Systems Subjected to Cyclic Loading

An experimental program was developed to study the strength and deformation capacity of tilt-up structures with plywood roof diaphragms. Two models of tilt-up systems were constructed and tested in the laboratory. The structures were representative of one-story warehouse construction in the western U.S. The overall dimensions of the two test specimens were the same; however, the number and distribution of reinforced concrete wall panels were varied. Each specimen was subjected to a series of lateral load reversals. Two aspects of the measured response of the test specimens are discussed in this paper: the in-plane displacements of the plywood roof diaphragm and the transverse response of the perimeter wall panels. The wall panels experienced nearly rigid-body rotation during the entire testing series, and the observed nonlinear response of the test specimens may be attributed to the inherent flexibility of the plywood diaphragm.