Two Alternative System Reliability Approaches to the Serviceability Condition Assessment of Spillway Gate Systems on Dams
The U.S. Army Corps of Engineers is one of the Nation’s largest managers of infrastructure. It is responsible for maintaining and operating the Nation’s navigable waterways and is the primary agency for maintaining federal flood control dams. This includes a vast amount of infrastructure that includes roughly 270 navigation dams, 350 reservoir dams, and 238 lock chambers (Bullock and Foltz 1995). The navigable inland waterways carry roughly 17% of the Nation’s intercity cargo – an important economic role (USACE 2004). Over half of the locks and dams are over 50 years old. The entire inventory is deteriorating over time and requires billions of dollars to upgrade, maintain, and repair. The Corps of Engineers requires that a strength-based reliability analysis be completed to justify major rehabilitation projects. Reliability methods are preferred for cost-benefits analyses and for quantifying risk. More often, however, it is the general serviceability of a structure that dictates the requirements for maintenance and repair. The Corps of Engineers has developed a Condition Index (CI) rating system for a variety of structures that assesses the general serviceability condition of a structure based on periodic visual inspections. A Condition Index (CI) is a rating between 0 and 100 that describes the condition of a structure at a point in time. The CI is based on a series of observations by an inspector. At the component level, the inspector classifies what he or she sees into the predefined descriptive category that best matches the observation. Some CIs also include measurements. More often, the condition scores are based on descriptive word pictures that are often vague and difficult to quantify. Chouinard et.al. (2003) developed a deterministic CI rating system for spillway gate systems on dams. The gate system contained 122 separate inspectable components, each with its own condition rating table. The structure was decomposed into a seven-level structural hierarchy of systems, sub-systems, and components. The highest levels are shown in Figure 1. Estes et.al. (2005) developed a reliability-based approach that assigns probabilistic CI ratings for groups of components, systems, and projects. The approach accounts for the considerable uncertainty associated with the CI process which includes: • Uncertainty in the ability of different inspectors to reliably choose the correct condition state and to a greater degree, the appropriate score within a condition state 17 ANALYSIS AND COMPUTATION SPECIALTY CONFERENCE th
REMR Management Systems - Navigation and Reservoir Structures, Condition Rating Procedures for Concrete in Gravity Dams, Retaining Walls, and Spillways.
Abstract : The purpose of this report is to describe a proposed system for determining a condition index (Cl) that numerically rates the condition of the concrete in a gravity dam monolith, retaining wall, or spillway on a scale of 1 to 100 by evaluating each concrete distress objectively. The rating system described herein allows the CI to be determined by the use of a visual investigation with limited equipment. The rating is related primarily to structural integrity and secondarily to serviceability. The CI procedure was developed by assigning deduct values to defects which include the following distress categories: alignment, cracking (checking, D-cracking, pattern, horizontal, vertical and transverse, vertical and horizontal, diagonal, random, and longitudinal floor), deposits, leakage, steel deterioration (corrosion stains, reinforcing, prestressing, and armor), and volume loss (abrasion, honeycomb, pop-outs, scaling, spalling, and disintegration). The deduct values are, in part, subtracted from 100 to establish the CI. Primary deduct values were determined with the intent of obtaining a CI of 40 when deterioration of a concrete monolith caused the safety of that monolith to become questionable. Nominal deduct values were assigned for defects in serviceability. The CI should be determined on at least one of each type of monolith and the more distressed monoliths. At least 20 percent of the monoliths should be rated. (MM)
Implementation of Tourism Satellite Account: Assessing the Contribution of Tourism to the Croatian Economy
Compiling the indicators of tourism consumption and the output of tourism industries, Tourism Satellite Account (TSA) provides a framework for internationally harmonized measurements of direct macroeconomic contribution of tourism. Ivandic and Marusic provide a detailed methodological approach for the transfer of TSA theoretical concepts to the assessment of tourism economic contribution on the case of the Croatia. Giving that the TSA compilation is still characterized by a surprisingly wide range of ‘styles’ used, the chapter contributes to a better understanding of the issues related to measurement of direct tourism impacts. It also gives a set of baseline criteria for resource allocation within tourism policy and the further evaluation of its effectiveness.