Ram B. Kulkarni

PAVEMENT MANAGEMENT SYSTEMS: PAST, PRESENT, AND FUTURE

The progress made over the past three decades in the key elements of pavement management systems was evaluated, and the significant improvements expected over the next 10 years were projected. Eight specific elements of a pavement management system were addressed: functions, data collection and management, pavement performance prediction, economic analysis, priority evaluation, optimization, institutional issues, and information technology. Among the significant improvements expected in pavement management systems in the next decade are improved linkage among, and better access to, databases; systematic updating of pavement performance prediction models by using data from ongoing pavement condition surveys; seamless integration of the multiple management systems of interest to a transportation organization; greater use of geographic information and Global Positioning Systems; increasing use of imaging and scanning and automatic interpretation technologies; and extensive use of formal optimization methods to make the best use of limited resources.

Statistical Analyses of Great Earthquake Recurrence along the Cascadia Subduction Zone

Goldfinger et al. (2012) interpreted a 10,000 year old sequence of deep sea turbidites at the Cascadia subduction zone (CSZ) as a record of clusters of plate-boundary great earthquakes separated by gaps of many hundreds of years. We performed statistical analyses on this inferred earthquake record to test the temporal clustering model and to calculate time-dependent recurrence intervals and probabil- ities. We used a Monte Carlo simulation to determine if the turbidite recurrence in- tervals follow an exponential distribution consistent with a Poisson (memoryless) process. The latter was rejected at a statistical significance level of 0.05. We performed a cluster analysis on 20 randomly simulated catalogs of 18 events (event T2 excluded), using ages with uncertainties from the turbidite dataset. Results indicate that 13 cata- logs exhibit statistically significant clustering behavior, yielding a probability of clus- tering of 13=20 or 0.65. Most (70%) of the 20 catalogs contain two or three closed clusters (a sequence that contains the same or nearly the same number of events) and the current cluster T1-T5 appears consistently in all catalogs. Analysis of the 13 cat- alogs that manifest clustering indicates that the probability that at least one more event will occur in the current cluster is 0.82. Given that the current cluster may not be closed yet, the probabilities of an M 9 earthquake during the next 50 and 100 years were estimated to be 0.17 and 0.25, respectively. We also analyzed the sensitivity of results to including event T2, whose status as a full-length rupture event is in doubt. The inclusion of T2 did not change the probability of clustering behavior in the CSZ turbidite data, but did significantly reduce the probability that the current cluster would extend to one more event. Based on the statistical analysis, time-independent and time-dependent recurrence intervals were calculated.

A risk analysis of an LNG terminal

The problem of evaluating the public risk associated with construction and operation of the proposed La Salle Terminal facility to import LNG and distribute to consumers is studied in detail. As spillage and ignition of LNG may cause severe public fatalities, it becomes necessary to determine the feasibility of such a project. The risk analysis shows that the risk levels to the public are less than those published in the literature as acceptable to society. The El Paso LNG Company and its subsidiaries plan to build and operate a marine terminal and LNG vaporization facility named La Salle Terminal, in Matagorda Bay, Texas. The La Salle Terminal will receive about 143 liquified natural gas (LNG) carriers per year from Algeria. From the carriers, LNG will be transferred to LNG storage tanks and from there it will be revaporized and distributed via high pressure intra-state pipelines. The paper aims at estimation and evaluation of the risk to the public from the operation of such a facility and to determine the feasibility of the project site. For this purpose, the model was divided into three components: 1. Development of accident scenarios and their associated probabilities; 2. Quantification of public risk; 3. Evaluation of public risk.

Considerations in probabilistic evaluation of seismic inputs

Abstract Two aspects pertinent to the probabilistic treatment of seismic inputs are covered in this discussion. The first aspect concerns the occurrence of great earthquakes taking into account spatial and temporal dependencies. A semi-Markov model is used for this purpose. This model takes into account the probability distribution of holding times between earthquakes, transition probabilities, and magnitude of the most recent great earthquake and the time since its occurrence. The use of this model is illustrated for an area in the circum-Pacific belt, and is shown to provide notable differences compared to the use of a Poissons model. Accordingly, the use of a semi-Markov model can significantly influence the selection of the magnitude of the OBE, because the OBE represents a risk function that is time-dependent. The longer the elapsed time since the last great earthquake, the larger is the magnitude of the earthquake having a reasonable probability of occuring in the next forty years. The second aspect is related to limiting values of ground motion parameters pertinent to very low probability of exceedance. Three possible approaches to modifying the tail of a probability distribution are proposed; these are: truncated, censored, or a constrained distribution. Without such modifications, the usual exposure risk analysis may suggest extremely high values of ground motion parameters which the site is not physically capable of transmitting.

Characterization of earthquake sources in the Gulf of Alaska

Abstract The characterization of earthquake sources in the Gulf of Alaska and the relative significance of earthquake sources for establishing seismic design inputs at a typical site for engineering purposes are discussed. Earthquake sources in the complex tectonic environment can be divided into two groups: (a) a subduction zone that underlies the entire region (maximum magnitude M = 8.5); and (b) individual thrust and strike‐slip faults associated with the plate motions (maximum magnitude M = 6 to 7.5). The sources of either group and individual earthquake events can be represented as planar surfaces for consistency with the physical process and a mathematically tractable computational scheme. Although the area is very active seismically, the degree of activity of individual sources varies significantly. Therefore, even for sources with the same maximum earthquakes, different magnitudes may apply for a selected design return period. The area is considered to be a “seismic gap.”; No great earthquakes hav...

Addressing Uncertainties in Environmental Site Audits

Real estate transactions may entail environmental liability for owners, operators, and financiers if hazardous substances are, or are suspected to be, present at the site, or were stored or processed in the past. Preliminary environmental site audits are generally conducted by owners/operators to get some understanding of potential environmental problems and liability before making acquisition decisions. In this paper, we describe a methodology to analyze uncertainties in estimating environmental liability from hazardous substances at multiple sites. The uncertainties arise because of the generally incomplete and not fully reliable information collected in preliminary site audits. The methodology uses an event tree model in which unknown states of nature (such as presence or absence of an environmental problem and the magnitude of the cleanup required, if any) are characterized by probabilities, and site investigation and cleanup costs are estimated for given states of nature. By analyzing the probabilities and costs associated with different branches of an event tree, the probability distribution of the total environmental liability at one or more sites can be derived. We illustrate the basic steps in the methodology based on recent experience in conducting preliminary site assessments to estimate liability at multiple facilities for property transactions.