Allen C. Estes

Minimum expected cost-oriented optimal maintenance planning for deteriorating structures: application to concrete bridge decks

Abstract Civil engineering structures are designed to serve the public and often must perform safely for decades. No matter how well they are designed, all civil engineering structures will deteriorate over time and lifetime maintenance expenses represent a substantial portion of the total lifetime cost of most structures. It is difficult to make a reliable prediction of this cost when the future is unknown and structural deterioration and behavior are assumed from a mathematical model or previous experience. An optimal maintenance program is the key to making appropriate decisions at the right time to minimize cost and maintain an appropriate level of safety. This study proposes a probabilistic framework for optimizing the timing and the type of maintenance over the expected useful life of a deteriorating structure. A decision tree analysis is used to develop an optimum lifetime maintenance plan which is updated as inspections occur and more data is available. An estimate which predicts cost and behavior over many years must be refined and reoptimized as new information becomes available. This methodology is illustrated using a half-cell potential test to evaluate a deteriorating concrete bridge deck. The study includes the expected life of the structure, the expected damage level of the structure, costs of inspection and specific repairs, interest rates, the capability of the test equipment to detect a flaw, and the management approach of the owner towards making repairs.

Lifetime Bridge Maintenance Strategies Based on System Reliability

This study proposes a methodology for a system reliability-based condition evaluation of existing highway bridges. The approach is illustrated for an existing steel bridge located in Colorado, USA....

Optimum Lifetime Planning of Bridge Inspection and Repair Programs

This study proposes a general methodology for determining the optimal lifetime planning of bridge inspection and repair programs based on minimizing the expected cost while maintaining an acceptable level of reliability. For individual bridges, this methodology determines the optimum inspection technique, and the numbers and timing of inspections and repairs. The methodology is demonstrated initially on a simple structure. Then, the method is applied to the optimal planning of inspection and repair programs for an existing bridge. The proposed approach to the problem of lifetime bridge maintenance is shown to be a viable method for optimizing inspection and repair investments during the expected remaining life of existing bridges. The results have important implications in the development of future reliability-based maintenance guidelines and criteria for the inspection and repair of bridges.

The Assessment of Teaching

The role of the teacher in the classroom carries tremendous responsibility. A group of students that can range from a half-dozen to several hundred depend on their professor to provide structure to a body of knowledge, to guide the learning process, to convey difficult subjects in a clear manner, to lead the classroom and out-of-class activities so that student time is used efficiently, and to provide a course of instruction in which the students can successfully complete the learning objectives. And somehow, the teacher is expected to establish some rapport with these students along the way. How does the teacher know when he or she is doing well? And how does someone who oversees a program know that the program’s faculty members are teaching at an appropriate standard? This Teaching Lessons Learned installment attempts to answer these questions, using tools and techniques currently in use at the U.S. Military Academy as illustrations.

The Nation's Architectural Engineering Programs: A Diverse Group

There are currently 17 ABET accredited Architectural Engineering programs in the United States. This paper presents curriculum data for these Architectural Engineering programs and discusses the challenges of finding common ground and conveying program needs to the rest of the academic community – especially when the programs are so small in number and so diverse in their structure and course offerings.

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

Project-Based Independent Study Capstone Course

This paper describes a unique project-based course used successful by the ABET-Accredited Civil Engineering Program at the United States Military Academy (USMA) to greatly enhance the academic program. The three general project classifications available within this senior course are service-based (i.e., USMA, the Army, local community, etc.), competition-based (i.e., steel bridge, concrete canoe, timber bridge, Big Beam), and research-based. The exceptional student work provided at little to no cost to the client has opened up a ground swell of service and research projects now constantly offered to the program coordinator by prospective clients. The authors believe these independent study projects are successful due to their students being prepared through open-ended design in nearly every course we offer and through some initial project-based learning in earlier courses. The mix of these open-ended projects usually ensures that each student can list a minimum of 3-5 project choices that meet their individual needs for a challenging, yet rewarding academic experience. Approximately 90-98 percent of the senior CE majors each year choose to work on one of these open-ended projects. With 45 to 60 CE majors graduating each year, it is easy to understand that one faculty member cannot advise the required 15-20 projects each spring. So many, if not all, of the CE program’s 17 faculty must buy-in to the project-based senior program from the onset. It will be shown through student assessment that this form of experience not only challenges, but also motivates the students like no other aspect of their academic experience. The students are providing a solution to a real world problem for a real client. The assessment will show that the students find project-based learning demanding, but enjoyable and worthwhile because it forces them to push the boundaries of their knowledge through initiative, self-study, perseverance, and creativity.

Condition Evaluation for Reliability Assessment of Existing Structures

Risk analysis is a necessary component of project planning and maintenance. Among other facets, risk analysis includes evaluation of loads (demands) and responses (capacities), or the reliability of a structure. Reliability assessment is based on a logical format for analyzing the probability of unsatisfactory performance using probabilistic estimates of loadings and responses. This paper discusses specific aspects of structural reliability assessment related to the current condition of constructed structures. The most accurate application of reliability relies on historical performance data for identical structures under like conditions. Rarely is such data readily available, however. Differences in environment, construction quality, design, loadings, maintenance, etc. can have substantial impact on the performance of a structure. This impact can be initially estimated, but divergences from initial estimates during the life of the structure are more difficult to determine and quantify. Condition assessment information can be used as an informative tool and more formally to create a performance-correlated database. This database can be used for adjusting the reliability assessments as a structures condition deviates from the predictions made for a structure of the current age and loading history.

Participation of Women in Architectural Engineering: What Causes it?

Under-representation of women in engineering is of concern as the decreasing supply of qualified engineers continues to plague the nation’s advancement. Understanding what factors influence choices of engineering disciplines has the potential for altering education to accommodate a more diverse student body that can be successful in engineering. There are seventeen accredited architectural engineering programs in the nation and they are very different. They vary greatly in terms of the emphasis of curriculum, the length of the degree, the degree of inclusion of architecture studios, and whether they are collocated in a department of civil engineering. Despite these differences, architectural engineering programs graduate on average 30% women which is far higher that the percentages of women in other engineering programs. This paper compares the percentage of women in architectural engineering programs to those in civil, mechanical and electrical engineering programs nationwide and attempts to explain the difference. A survey of women in the Cal Poly architectural engineering department was administered to discover why these women personally chose AE as a major, why they persist in the major, and why they think women are so largely represented in the major. The results represent a competitive advantage that architectural engineering programs have and are of great interest to the Architectural Engineering Institute.

Interdisciplinary Design Experience for the Masses

The Architectural Engineering Department (ARCE) at California Polytechnic State University (Cal Poly) is one of the few ABET accredited engineering programs in the United States that exists outside a college of engineering. Housed in the College of Architecture and Environmental Design (CAED), ARCE resides with the departments of Architecture (ARCH), Construction Management (CM), Landscape Architecture (LA), and City and Regional Planning (CRP). The college has a 60 year tradition of interdisciplinary collaboration at the lower division levels. In order to enhance the collaboration of disciplines at the upper division levels, the college has recently committed to providing an upper division interdisciplinary experience for every student in the form of an interdisciplinary team oriented, project based five unit studio laboratory. The challenges in creating and executing such an upper division interdisciplinary course are immense and fall into three major areas: institutional, logistical and pedagogical. Institutional issues include support from the university and multiple department heads. Logistical issues range from finding open time within the multiple departments to offer the course to the seemingly mundane tasks of ensuring all students are in the correct location at the correct time. Pedagogically, the course needs a unified and integrated approach that must be agreed to and implemented by a team of professors. Traditionally professors work as individuals and team teaching of this magnitude is a paradigm shift that requires a significant time and mental commitment. This paper addresses these three challenge areas: institutional, logistical and pedagogical. It discusses the specific issues, both good and bad, associated with this course and how they were addressed.