Olafur Haraldsson

Seismic Resistance of Socket Connection between Footing and Precast Column

A new concept has been developed for connecting spread footings and precast columns in bridges. The socket connection is constructed by precasting the column, erecting it, and casting the reinforced concrete footing around it. This system saves construction time on site because, in little more than the time needed to construct the footing, both the column and footing can be constructed. Site erection is facilitated by the fact that the field tolerances are essentially unlimited. The longitudinal column bars are straight and are terminated with mechanical anchors. This arrangement improves constructability, because no bars cross the interface between the column and footing, and it provides better transfer of forces in the connection region than is possible with conventional bent-out longitudinal bars. The surface of the column is roughened to improve adhesion to the surrounding cast-in-place concrete. Axial-load tests demonstrated that the connection can resist column axial loads far above those expected in practice. Cyclic, lateral-load tests demonstrated that the seismic performance of the connection is at least as good as, if not better than, that of a comparable cast-in-place system. The recent deployment of the new system in a highway overpass provided both field experience and initial estimates of the potential time savings.

Measures of the Seismic Vulnerability of Reinforced Concrete Buildings in Haiti

Following the 12 January 2010 Haiti earthquake, teams of students and faculty members from the United States and Haiti surveyed 170 reinforced concrete (RC) buildings in Port-au-Prince and Léogâne. This paper summarizes the survey results and compares them with results from a similar survey done after the 1999 earthquakes near Düzce, Turkey. The survey results demonstrate that the frequency of damage in RC buildings was higher in Haiti than in Turkey. This increased level of damage is consistent with practical screening criteria based on cross-sectional areas of building columns and walls. Based on these criteria, 90% of the structures surveyed in Haiti would have been classified as seismically vulnerable before the earthquake. Damage was more frequent in structures with captive columns. A two-tiered screening process is suggested to rapidly assess the vulnerability of scores of poorly built low-rise RC buildings in future earthquakes.

Bridge Column Maximum Drift Estimation via Computer Vision

AbstractThis paper considers the viability of applying computer vision techniques for estimating the peak experienced seismic displacement of damaged bridge columns, for use in postdisaster triage assessment. The primary objective of the associated study was to determine if there is a statistically robust relationship between peak seismic displacement and damage observations extracted from two-dimensional (2D) images captured after an event. To this end, correlations were developed using images and experimental test data from lateral-load tests performed on a series of reinforced concrete bridge columns. Computer vision algorithms based on a combination of image segmentation, feature extraction, and nonlinear regression analysis were used to estimate peak drift. The results presented in this paper indicate strong correlations between parameterized crack patterns and experienced structural displacement, regardless of the position of the camera. Key findings include the necessity of using nonlinear machine ...