Cause of Damage and Failures in Silo Structures

Silos are special structures subjected to many different unconventional loading conditions, which result in unusual failure modes. Failure of a silo can be devastating as it can result in loss of the container, contamination of the material it contains, loss of material, cleanup, replacement costs, environmental damage, and possible injury or loss of life. Silo damage and failures that occurred in different regions of the world are presented in the paper using illustrative photos. Also provided are a review and discussion of the common or spectacular silo failures due to explosion and bursting, asymmetrical loads created during filling or discharging, large and nonuniform soil pressure, corrosion of metal silos, deterioration of concrete silos due to silage acids, internal structural collapse, and thermal ratcheting. Silo damage and failures from several earthquakes are also presented.     

Analysis of Life-Cycle Maintenance Strategies for Concrete Bridge Decks

This paper presents the development of a project-level decision support tool for ranking maintenance scenarios for concrete bridge decks deteriorated as a result of chloride-induced corrosion. The approach is based on a mechanistic deterioration model and a probabilistic life-cycle cost analysis. The analysis includes agency and user costs of alternative maintenance scenarios and considers uncertainties in the agency cost and the corrosion rate in the deterioration model. The tool presented in this paper can be used to find the optimal condition index of a given bridge deck that minimizes life-cycle cost. Based on the results obtained on three existing bridge decks, it is shown that the total life-cycle cost (user cost plus agency cost) is a nonlinear function of the maximum tolerable condition of the deck, Sm, and that for a practical range of Sm, the relationship between total life-cycle cost and Sm is convex.     

Seismic Performance Assessment of Simply Supported and Continuous Multispan Concrete Girder Highway Bridges

Seismic evaluations of typical concrete girder bridges are conducted for both a multispan simply supported and a multispan continuous girder bridge common to the Central and Southeastern United States. These evaluations are performed for an approximate hazard level of 2% in 50?years by performing nonlinear time history analyses on three-dimensional analytical models. The results show significant vulnerabilities in the reinforced concrete columns, the abutments, and also in unseating of the girders. In general, the longitudinal loading of the bridges results in larger demands than the transverse loading. However, the simply supported bridge sustains bearing deformations in the transverse direction which are on the same order as their longitudinal response. These results suggest that both longitudinal and transverse loading are significant and should be considered when performing seismic hazard analyses of these bridges.     

Reliability-Based Life-Cycle Management of Highway Bridges

The objective of bridge management is to allocate and use the limited resources to balance lifetime reliability and life-cycle cost in an optimal manner. As the 20th century has drawn to a close, it is appropriate to reflect on the birth and growth of bridge management systems, to examine where they are today, and to predict their future. In this paper, it is attempted to shed some light on the past, present, and future of life-cycle management of highway bridges. It is shown that current bridge management systems have limitations and that these limitations can be overcome by using a reliability-based approach. It is concluded that additional research is required to develop better life-cycle models and tools to quantify the risks, costs, and benefits associated with highway bridges as well as their interrelationships in highway networks.     

Impact of Commercial Vehicle Weight Change on Highway Bridge Infrastructure

Heavy trucks represent a major load to highway bridges in the transportation infrastructure system. These loads are directly related to the truck weight limits of the jurisdiction, and largely determine the standard loads for bridge design and evaluation. Thus, truck weight limit is one of the major factors affecting bridge deterioration and expenditure for maintenance, repair, and/or replacement. Truck weight in this paper not only refers to the truck gross weight but also to the axle weights and spacings that affect load effects. This paper presents the concepts of a new methodology for estimating cost effects of truck weight limit changes on bridges in a transportation infrastructure network. The methodology can serve as a tool for studying impacts of such changes. The resulting knowledge is needed when examining new truck weight limits, several of which have been and are still being debated at both the state and federal levels in the United States. The development of this estimation method has considered maximizing the use of available data (such as the bridge inventory) at the state infrastructure system level. In application examples completed (but not reported herein), the costs for relatively inadequate strength of existing bridges and for increased design requirement for new bridges were found dominant in the total impact cost.     

Ontology for Relating Risk and Vulnerability to Cost Overrun in International Projects

Risk management is about identifying risks, assessing their impacts, and developing mitigation strategies to ensure project success. The difference between the expected and actual project outcomes is usually attributed to risk events and how they are managed throughout the project. Although there are several reference frameworks that explain how risks can be managed in construction projects, a major bottleneck is the lack of a common vocabulary for risk-related concepts. Poor definition of risk and patterns of risk propagation in a project decrease the reliability of risk models that are constructed to simulate project outcomes under different risk occurrence scenarios. This study aims to extend previous studies in risk management by presenting an ontology for relating risk-related concepts to cost overrun. The major idea is that cost overrun depends on causal relations between various risk sources (namely, risk paths) and sources of vulnerability that interfere with these paths. Ontology is used to develop a database system that represents risk event histories of international construction projects and to construct a model for estimation of cost overrun. It will form the basis of a multiagent system that can be used to simulate the negotiation process among project participants about sharing of costs considering the risk allocation clauses in the contract, sources of vulnerability, and causal relations between risk events and their impacts. The ontology is constructed by interaction with Turkish contractors working in international markets and extensive literature review on risk-related concepts. The validation test results provide evidence that the ontology is fairly effective to help Turkish contractors to assess cost overrun by considering sources of vulnerability and risk in international construction projects.     

The direct and indirect costs of cardiovascular disease in South Africa in 1991

BACKGROUND: In South Africa, cardiovascular disease (CVD) is the leading cause of death among all population groups, other than blacks, among whom it ranks third. CVD therefore has a severe impact on the South African economy. OBJECTIVES: To ascertain the availability and quality of South African data on the cost of CVD and to estimate the impact of CVD on the South African economy during 1991. METHODS: The direct health care costs and the indirect costs related to loss of productivity were estimated. Where no direct or complete detailed South African data were available, projections were made based on reasonable assumptions of data and models developed in other countries; these were applied to the limited available South African data. The major disease outcomes considered for this cost estimation were: expenditure on ischaemic heart disease, cerebrovascular disease (stroke), venous thrombosis and embolism, and peripheral vascular diseases and related conditions. These diseases are responsible for the majority of fatal cases of CVD reported in South Africa. RESULTS: The estimated total cost of CVD in South Africa in 1991 was between R4.135 billion and R5.035 billion. This does not include the cost of rehabilitation and follow-up of CVD patients since the necessary data were not available to estimate it. About three-quarters of the direct health care costs were carried by the private sector. The direct health care costs were estimated to be approximately 42% of the total cost. The rest reflects the indirect cost of earnings foregone as a result of premature morbidity and mortality. CONCLUSION: To determine accurately the total economic burden of CVD on the South African economy, additional data will have to be collected. The estimated economic burden of CVD in South Africa clearly highlights the need for a broad-based population strategy, part of an overall national effort to prevent, diagnose and cost-effectively treat CVD.     

The economic cost of obesity: the French situation

OBJECTIVE: To estimate the economic burden of obesity in France. DESIGN: A prevalence-based approach identifying the costs incurred during a given year (1992) by obese subjects. MEASUREMENTS: Direct costs (personal health care, hospital care, physician services, drugs) and indirect costs (lost output as a result of cessation or reduction of productivity caused by morbidity and mortality); economic benefits due to the reduced incidence of hip fractures. RESULTS: The direct costs of obesity (BMI > or = 27) were 11.89 billion French Francs (FF), which corresponded to about 2% of the expenses of the French care system. Hypertension represented 33% of the total amount and cancer 2.5% of the direct cost of obesity. Indirect costs represented FF 0.6 billion. These are conservative estimates as far as all obesity-related diseases and all health care and indirect costs were not included due to missing information. CONCLUSION: These results were remarkably similar to previous reports on the economic costs of obesity in other western countries (USA, Sweden, Netherlands, Australia) which concluded that the cost of obesity amounted to around 2% to 5% of the total cost of health care in industrialized societies.     

Thermal analysis of twin-channel induction furnaces

Twin-channel induction furnaces (TCIFs) are used extensively in many processing industries due, mainly, to their relatively low operating costs. However, thermal stresses in the refractory lining caused by high temperatures during the loading cycle can cause erosion of the lining and premature inductor failure. Prevention of premature failure by close monitoring of the thermal regime of the inductor is very important to operators and relatively simple and reliable tools need to be developed to this end. The present work is an attempt to develop such a tool using thermal modeling software and unidirectional axial channel flow estimation from analysis based on the first law of thermodynamics. This avoids the complications and uncertainties associated with the coupled multiple field analysis approach. The results of the analysis show plausible agreement with the reported flow data and a comprehensive set of scenarios can be devised on the basis of the developed approach to simulate start-up, transient operation, and steady-state operation of TCIFs.     

Costs of asthma according to the degree of severity

An increase in asthma-related morbidity and mortality has been reported recently, resulting in a substantial increase in the economic impact of this condition. Little information is available relating to the costs of asthma depending on the degree of severity of the disease. Total, direct and indirect costs generated by asthma patients who sought medical care for asthma control over a one-year period in a northern area of Spain were determined. Data were obtained from the patients themselves and severity of illness was classified into mild, moderate and severe according to the International Consensus Report on Diagnosis and Treatment of Asthma, 1992. The average total annual asthma-derived cost was estimated at US$2,879 per patient, with averages of US$1,336 in mildly asthmatic patients, US$2,407 in moderate asthma and US$6,393 in severe asthma. At all levels of severity, indirect costs were twice as high as direct costs, and at the same degree of severity, direct costs due to medication and hospitalization were higher among females than males. A minority of severe asthmatics incurred some 41% of the total costs. The cost of asthma was surprisingly high and varied substantially depending on the degree of severity of the disease. Further knowledge of the costs of asthma across various levels of severity will contribute to a better characterization of optimal intervention strategies for asthma care.     

Life-Cycle Cost of All-Composite Suspension Bridge

This paper reports on the design of two highway suspension bridges made of conventional steel and advanced all-composite carbon fiber reinforced polymer (CFRP), and analyzed their life-cycle costs. The writers assumed that the pultrusion molding method would mainly be used for all composite highway bridges, because of its relatively high quality control performance and mass-production capability. First, the writers obtained the steel and composite highway bridge design in the same dimensional specification. Second, they acquired the future cost of the CFRP pultrusion product through hearing research from a fiber reinforced polymer manufacturer. Third, they calculated the initial costs of the steel bridge and CFRP bridge based on the design specification and the future cost of CFRP. Fourth, they compared the life-cycle cost of the steel and CFRP bridges under several conditions of discount rate, repair cost, and cycle. Finally, they found the critical condition where the CFRP bridge becomes more life-cycle cost-effective than the conventional steel bridge, if they could have expected the drastic cost reduction of the CFRP product.     

工程项目管理中的成本管理

工程项目成本管理是为保障项目实际发生的成本不超过项目预算而开展的项目资源计划、项目成本估算、项目预算编制和项目预算控制等方面的管理活动。是保证施工企业正常经营的重要的基础管理工作。     

Probabilistic Strength Estimates and Reliability of Damaged Parallel Wire Cables

Cable reliability analysis involves the combined evaluation of cable capacity and cable load in a probabilistic manner. Assessment of cable capacity is only possible through visual inspections of the wires, field sampling, laboratory analysis of the degraded wire populations, and analytical techniques. In addition to a brief presentation of cable mechanics and deterministic models that approximate cable strength, this paper discusses inspection methodologies and statistical methods of estimation of the sizes of the degraded wire populations, and wire properties, leading to cable capacities. These capacities are described by probability distributions. The paper also discusses fundamentals of reliability analysis as they apply to bridge cables. Load criteria of present standard specifications (such as AASHTO or other international codes) are not applicable to long-span suspension bridges. The paper discusses criteria of bridge loading and reliability indices for bridge cables. More work is needed in the evaluation of loading for long-span bridges.     

Computer Model for Life-Cycle Cost Analysis of Roadway Pavements

This paper describes the development of a computer model that performs life-cycle cost analysis (LCCA) of roadway pavements, analyzing the cost of both the agency and the user. Agency costs are a function of the type of rehabilitation, restoration, resurfacing, or reconstruction (i.e., 4R) treatment applicable to each pavement type, given its surface distress and structural condition. The cost of each treatment is calculated from the unit prices specified for the activities involved and the roadway geometry. User costs include vehicle operating and nonvehicle operating costs, which are a function of pavement roughness, as well as user delay costs, which are a function of lane closure practice. User benefits are calculated as savings in user costs due to reduction in pavement roughness from its current state to that of a new pavement. At the roadway network level, sections are flagged for analysis in decreasing benefit-cost order, whereby the cost of the most capital-intensive 4R treatment is considered. Sections flagged at the network level are carried forward to the project level analysis. The project level analysis allocates the available budget among the sections selected to maximize user benefits over the analysis period. The software package implementing this methodology, called pavement investment decisions (PID) is generic; that is, it allows customizing through a series of input screens to fit the pavement management database and practices of any state Department of Transportation (DOT).     

Probability-Based Bridge Network Performance Evaluation

This paper presents a comprehensive mathematical model for evaluating the overall performance of a bridge network based on probability analyses of network connectivity, user satisfaction, and structural reliability of the critical bridges in the network. A bridge network consists of all nodes of interest in a geographical region. These nodes of interest are connected to each other through multiple paths. The network performance evaluation in terms of connectivity is formulated by using an event tree technique. The network performance measure of user satisfaction deals with traffic demand and capacity of each link in the network. Moreover, the shortest paths in terms of total traffic costs are identified by network optimization algorithms for each pair of the origin and destination nodes of interest under the specified traffic demands. Using this information, the minimum-weight spanning tree (MST) that consists of the identified shortest paths is constructed. The bridges associated with MST are defined as the critical bridges in the network. The network performance in terms of structural reliability of the critical bridges can be computed from system reliabilities of the critical bridges by using a series-parallel system model. Finally, by combining the above three criteria, a single numerical measure is proposed to evaluate the overall performance of the bridge network. This novel approach is illustrated on a group of fourteen existing bridges with different reliability profiles located in Colorado. This study provides the basis of a network-level bridge management system where lifetime reliability and life-cycle costs are the key considerations for optimal bridge maintenance strategies.     

Short- and Long-Term Effects of Element Costs and Failure Costs in Pontis

Experts familiar with bridge maintenance in Idaho estimated unit costs for Pontis bridge elements. These costs were compared to those provided by the California and Oregon departments of transportation. Some of the differences are due to regional variations in repair and rehabilitation costs, some reflect decisions to avoid certain actions by assigning them prohibitively high costs, and others reflect modeling decisions regarding the cost of leaving an element in its current condition. For a 5-year scenario, the projected needs using the Oregon element costs were from 1.6 to 6 times higher than those based on Idaho or California element costs. Likewise the projected benefits using Oregon element costs ranged from 2.2 to 40 times higher than the benefits projected using Idaho and California element costs. A 25-year scenario indicates that Pontis’ cost-optimal priorities allowed the Network Health Index to decrease, even when a more-than-ample budget was provided.     

Fault Tree Analysis of Schoharie Creek Bridge Collapse

The United States has witnessed several bridge collapses that have resulted in human fatalities. One such failure was the Schoharie Creek Bridge (1987), which motivated the improvement of bridge management policies and procedures. This paper offers a detailed review of the events that resulted in this bridge failure through the use of fault tree analysis. A fault tree is a graphical depiction of the various failure paths that lead to an undesirable outcome. The tree presented considers a host of catastrophic events ranging from vessel collision to fire. Fault trees also provide quantitative assessment and comparison of different failure mechanisms. The results of this analysis present scour as the source of the collapse of this bridge, which was in reality the root cause. Knowledge of the vulnerabilities particular to a bridge aids in the management of similar bridge types, allowing focus upon critical aspects. Recognition of historical bridge failures offers awareness to current bridge engineers and managers that aids in the decision making that promotes public safety and structure preservation. Lessons learned will help avoid similar catastrophic failures in the future.     

Negotiating the indirect cost of research: A review of the process.

Notes that a considerable portion of the cost of federally sponsored research is used in the reimbursement of the indirect costs of the research. The percentage of indirect costs has been increasing over the last decade. This increase has led both investigators and federal agencies to seek procedures that would reduce the share of the research budget devoted to indirect costs. Under the assumption that any attempt to achieve this goal will be enhanced by an understanding of the process, the present authors review the procedures used as the indirect costs are negotiated between representatives of the federal government and a university. Attention is drawn to those stages of the process at which investigators can assess their university's indirect cost policy. It is concluded that the evaluation should focus on the total cost bill presented by the university rather than on the so-called indirect cost rate that is used to distribute the indirect cost recovery within the university. Factors that may account for the large variability across universities in the indirect cost rate are reviewed. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Occupational injury and illness in the United States. Estimates of costs, morbidity, and mortality

OBJECTIVE: To estimate the annual incidence, the mortality and the direct and indirect costs associated with occupational injuries and illnesses in the United States in 1992. DESIGN: Aggregation and analysis of national and large regional data sets collected by the Bureau of Labor Statistics, the National Council on Compensation Insurance, the National Center for Health Statistics, the Health Care Financing Administration, and other governmental bureaus and private firms. METHODS: To assess incidence of and mortality from occupational injuries and illnesses, we reviewed data from national surveys and applied an attributable risk proportion method. To assess costs, we used the human capital method that decomposes costs into direct categories such as medical and insurance administration expenses as well as indirect categories such as lost earnings, lost home production, and lost fringe benefits. Some cost estimates were drawn from the literature while others were generated within this study. Total costs were calculated by multiplying average costs by the number of injuries and illnesses in each diagnostic category. RESULTS: Approximately 6500 job-related deaths from injury, 13.2 million nonfatal injuries, 60,300 deaths from disease, and 862,200 illnesses are estimated to occur annually in the civilian American workforce. The total direct ($65 billion) plus indirect ($106 billion) costs were estimated to be $171 billion. Injuries cost $145 billion and illnesses $26 billion. These estimates are likely to be low, because they ignore costs associated with pain and suffering as well as those of within-home care provided by family members, and because the numbers of occupational injuries and illnesses are likely to be undercounted. CONCLUSIONS: The costs of occupational injuries and illnesses are high, in sharp contrast to the limited public attention and societal resources devoted to their prevention and amelioration. Occupational injuries and illnesses are an insufficiently appreciated contributor to the total burden of health care costs in the United States.