Content uploaded by Andrew Whittaker
Author content
All content in this area was uploaded by Andrew Whittaker on Dec 28, 2014
Content may be subject to copyright.
Collapse of the Cypress Street Viaduct as a result of the Loma Prieta earthquake
... The seismic vulnerability of pre-1970s reinforced concrete (RC) buildings and bridges with poor reinforcement detailing (e.g., the presence of lap splices in the plastic hinge region and poor confinement of concrete) has been highlighted by real-life events, laboratory testing, and analytical studies (Nims et al. 1989;Lew 1990;Lynn et al. 1996;Jennings 1997;Moehle et al. 2002;Sezen and Moehle 2006;Opabola and Elwood 2021a, b). Over the last few decades, various retrofit techniques (e.g., external jacketing, adding shear walls, and protective seismic device installation) have been developed to improve the structural performance of older-type RC structures (Pincheira 1993;Martinez-Rueda and Elnashai 1995;Priestley et al. 1996;Seible et al. 1997). ...
Current seismic evaluation and retrofit guidelines and standards, such as the ASCE standard ASCE/SEI 41-23, Seismic evaluation and retrofit of existing buildings (ASCE 41), provide recommendations for nonlinear modeling parameters and acceptance criteria for as-built reinforced concrete (RC) structural components but do not address nonlinear modeling parameters and acceptance criteria for retrofitted RC structural components. This research addresses this gap by proposing ASCE 41-type nonlinear modeling parameters and acceptance criteria specifically for RC columns retrofitted with fiber-reinforced polymer (FRP) jackets. Using an experimental database of 70 FRP-jacketed RC columns with continuous or spliced longitudinal reinforcement, we propose formulations for predicting the nonlinear modeling parameters at lateral (a nl) and axial failure (b nl), and residual strength ratio c nl. Additionally, the study demonstrates that the elastic response of FRP-jac-keted columns can be predicted using existing effective stiffness and yield rotation models for as-built flexure-governed RC columns. Furthermore , this study recommends multipliers to a nl and b nl to develop acceptance criteria aligned with the Immediate Occupancy, Life Safety, and Collapse Prevention performance objectives. The proposed nonlinear modeling parameters and acceptance criteria are recommended for adoption by seismic evaluation and retrofit guidelines.
... The earthquakes in California (e.g., The 1971San Fernando Earthquake, 1989Loma Prieta Earthquake, and 1994 Northridge earthquake) highlighted the structural vulnerabilities associated with pre-1970 RC bridges (Nims et al. 1989;Lee 1990;Lew 1990;Jennings 1997;Seible and Priestley 1999). In particular, most bridge columns constructed before 1970 are susceptible to shear or splice failure in the plastic hinge region. ...
A significant proportion of existing bridges in high seismic regions were constructed prior to the 1970s. As a result of poor reinforcement detailing, pre-1970s bridge columns are susceptible to lap-splice or shear failure in the plastic region. Given the high economic impact of retrofitting all pre-1970s reinforced concrete (RC) bridges, it is essential to identify the most vulnerable bridges for retrofit prioritisation. Analytical fragility functions are useful for quantifying the seismic vulnerability of existing bridge stock. However, the accuracy of these fragility functions relies on the adequacy of the adopted modelling approach. This paper presents a hinge-type modelling approach for capturing the seismic response of as-built splice-deficient and retrofitted RC bridge columns. Fragility analysis is carried out for typical seat and diaphragm abutment two-span bridges using the proposed hinge-type modelling approach. The results showed that the vulnerability of the bridges depends on the column failure mode and the limit state under consideration. Also, the common notion that the column is the most vulnerable component may not necessarily be true. The study underscored that retrofitting columns without retrofitting other components may not effectively mitigate the damage and associated risk.
... On 19 August 2016, a suspension railway bridge in Tolten-Chile collapsed due to train-induced vibrations [56]. On [61,62]. The collapse of these two bridges killed forty-one persons. ...
This review presents an up-to-date account of research in multi-hazard assessment and vibration control of engineering structures. A general discussion of the importance of multi-hazard consideration in structural engineering, as well as recent advances in this area, is presented as a background. In terms of performance assessment and vibration control, various hazards are considered with an emphasis on seismic and wind loads. Although multi-hazard problems in civil engineering structures are generally discussed to some extent, the emphasis is placed on buildings, bridges, and wind turbine towers. The scientific literature in this area is vast with rapidly growing innovations. The literature is, therefore, classified by the structure type, and then, subsequently, by the hazard. Main contributions and conclusions from the reported studies are presented in summarized tables intended to provide readers with a quick reference and convenient navigation to related publications for further research. Finally, a summary of the literature review is provided with some insights on knowledge gaps and research needs.
... (3) We believe that the approximate coincidence between the collapsed sections of the Cypress Street viaduct and the local distribution of Bay mud is only that--a coincidence. Certainly, the southern (uncollapsed) portion was driven to the point of failure (Nims et al., 1989), if not actual collapse, understandably insofar as it must have experienced much the same ground motion as the northern portion which did collapse. While small differences in ground motion can lead to large differences in structural performance at the point of collapse, and, while ground motion amplitudes at 2ST are indeed slightly smaller than at OHW and EMV at frequencies less than 2 Hz (Figures 3a, 4a, and 7), we do not believe these small differences could have been confidently predicted in advance. ...
The basis of this study is the acceleration, velocity, and displacement waveforms of the Loma Prieta earthquake (18 October 1989; M = 7.0) at two rock sites in San Francisco, a rock site on Yerba Buena Island, an artificial-fill site on Treasure Island, and three sites in Oakland underlain by thick sections of poorly consolidated Pleistocene sediments. All seven records clearly show shear-wave first motion opposite to that expected for the main-shock radiation pattern and peak amplitudes greater than expected for sites at these distances (95 ± 3 km) from an earthquake of this magnitude. While the association between these ground motion records and related damage patterns in nearby areas has been easily and eagerly accepted by seismological and engineering observers of them, we have had some difficulty in making such relationships quantitative. -from Authors
... The details of the Cypress structure collapse and various collapse scenarios have been documented in several publications (e.g., Nims et al., 1989;Governor's Board of Inquiry, 1990;Miranda and Bertero, 1991). In the explanation of the collapse, the following two questions deserve particular attention: Was the seismic demand large enough to explain transverse collapse of several individual bents or was collapse caused by failure in the weakest bent and subsequent cascading? ...
Focuses on an engineering evaluation of the ground motions recorded during the Loma Prieta earthquake. Several records are used to illustrate the large seismic demands generated by soft soil ground motions. Strength capacities of modern code-designed structures are compared to the strength demands in order to assess the damage potential of the Loma Prieta ground motions. The Cypress structure is used as an example to illustrate the application of simple demand/capacity concepts for an evaluation of structural performance. -from Authors
The structural health monitoring (SHM) of buildings, infrastructures, and civil engineering & industrial equipment is in full expansion. One of the key drivers behind the ever-increasing need for SHM is that a major part of the infrastructures has been built during the last century with life-limited materials and processes.
p>Earthquakes can cause considerable fatalities, injuries and financial loss. The forces of nature cannot be blamed, as the problem lies with the structures in seismic regions that may not have been designed or constructed to a sufficient degree to resist earthquake actions or they may have design flaws. This Structural Engineering Document (SED) concerns reinforced concrete and masonry buildings together with geotechnical aspects and presents in a concise and practical way the state of the art of current understanding of building failures due to earthquakes. It classifies the different types of seismic failure, explains the reasons for each failure, describes good practices to avoid such failures and also describes seismic retrofitting/upgrading procedures for pre-earthquake strengthening and post-earthquake repair and/or strengthening techniques for deficient buildings. Carefully selected photographs and diagrams illustrate the different failure types. This document could be considered as quite unique, as this is the first time such material concerning characteristic seismic failures of buildings has been presented together in one single document. It is intended to be a valuable educational reference textbook aimed at all levels of experience of engineers. It provides background information, ideas, guidance and reassurance to engineers in earthquake regions faced with the task of building a safer future for the public and to protect lives.
</iframe
Collapse analysis is becoming increasingly significant as the performance-based design is being gradually adopted in the seismic design of bridges. The traditional dynamic finite element method (FEM) becomes inadequate for the collapse analysis of RC bridge, a dynamic finite element method based on explicit time integration (ETI) is introduced in this study. The element with one Gauss integration point is adopted to shorten the CPU time, and contact and impact of broken reinforced concrete are taken into consideration in the method. Cypress viaduct collapsed in the Loma Prieta Earthquake in 1989 is analyzed by using a FEM code LS-DYNA. The simulation results indicate that the proposed method can predicts qualitatively collapse process of RC bridges well.
ResearchGate has not been able to resolve any references for this publication.