FE modeling of concrete beams and columns reinforced with FRP composites

Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure. In the present work, numerical analysis of square and circle short columns, and reinforced concrete (RC) beams reinforced withfiber reinforced polymer composites are carried out. This work is divided into two parts. In thefirst part, numerical study of axial behavior of square and circular concrete columns reinforced with Glass Fiber Reinforced Polymer (GFRP) and Basalt Fiber Reinforced Polymer (BFRP)bars and spiral, and Carbon Fiber Reinforced Polymer (CFRP) wraps is conducted. The results of the first part showed that the axial capacity of the circular RC columns rein-forced with GFRP increases with the increase of the longitudinal reinforcement ratio. In addition, the results of the numerical analysis showed good correlation with the experimental ones. An interaction diagram for BFRP RC columns is also developed with considering various eccentricities. The results of numerical modeling of RC columns strengthened with CFRP wraps revealed that the number and the spacing between the CFRP wraps provide different levels of ductility enhancement to the column. For the cases considered in this study, column with two middle closely spaced CFRP wraps demonstrated the best performance. In the second part of this research,flexural behavior of RC beams reinforced with BFRP, GFRP and CFRP bars is investigated along with validation of the numerical model with the experimental tests. The results resembled the experimental observations that indicate significant effect of the FRP bar diameter and type ont he flexural capacity of the RC beams. It was also shown that Increasing the number of bars while keeping the same reinforcement ratio enhanced the stiffness of the RC beam.     

Commitment decisions with partial information updating

In this paper, we extend the results of Ferguson M. Naval Research Logistics 8 . on an end‐product manufacturer's choice of when to commit to an order quantity from its parts supplier. During the supplier's lead‐time, information arrives about end‐product demand. This information reduces some of the forecast uncertainty. While the supplier must choose its production quantity of parts based on the original forecast, the manufacturer can wait to place its order from the supplier after observing the information update. We find that a manufacturer is sometimes better off with a contract requiring an early commitment to its order quantity, before the supplier commits resources. On the other hand, the supplier sometimes prefers a delayed commitment. The preferences depend upon the amount of demand uncertainty resolved by the information as well as which member of the supply chain sets the exchange price. We also show conditions where demand information updating is detrimental to both the manufacturer and the supplier. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005     

A squared-euclidean distance location-allocation problem

This article is concerned with the analysis of a squared-Euclidean distance location-allocation problem with balanced transportation constraints, where the costs are directly proportional to distances and the amount shipped. The problem is shown to be equivalent to maximizing a convex quadratic function subject to transportation constraints. A branch-and-bound algorithm is developed that utilizes a specialized, tight, linear programming representation to compute strong upper bounds via a Lagrangian relaxation scheme. These bounds are shown to substantially dominate several other upper bounds that are derived using standard techniques as problem size increases. The special structure of the transportation constraints is used to derive a partitioning scheme, and this structure is further exploited to devise suitable logical tests that tighten the bounds implied by the branching restrictions on the transportation flows. The transportation structure is also used to generate additional cut-set inequalities based on a cycle prevention method which preserves a forest graph for any partial solution. Results of the computational experiments, and a discussion on possible extensions, are also presented.     

Evaluation of an integrated supplier-buyer quality-control system

In this article, a quality-control design framework that employs information for the supplier-buyer system is modeled. Significant operational savings may be obtained by using the integrated plans developed under this framework. This is especially true when the cost of a defective is high, and the variable sampling and rework costs are low. Analysis of the interaction of defective, rework, and variable sampling costs reveals that the savings are the result of a shift of control effort from the process-control to the lot-acceptance stage, which is the consequence of tradeoffs involving both stages. The managerial impact of adopting integrated plans is discussed.     

The reporting time problem: Integration of intelligence with verification

This article is a theoretic study of the following problem in verification: Mobile units under control of an agent, whom we call the HIDER, travel on a known transportation network and must at the conclusion of their itinerary report locations at fixed time intervals to a monitoring authority, whom we call the SEEKER. The purpose of this reporting requirement is to verify that illegal units do not infiltrate the network from sources under the control of the HIDER. We assume that the SEEKER has an independent intelligence-gathering capability which gives sightings of both legal and illegal units. The purpose of this article is to quantify the advantage of frequent over infrequent reporting. © 1992 John Wiley & Sons, Inc.     

Waiting times for M/G/1 queues with service-time or delay-dependent server vacations

This article shows how to determine the stationary distribution of the virtual wait in M/G/1 queues with either one-at-a-time or exhaustive server vacations, depending on either service times or accrued workload. For the first type of dependence, each vacation time is a function of the immediately preceding service time or of whether the server finds the system empty after returning from vacation. In this way, it is possible to model situations such as long service times followed by short vacations, and vice versa. For the second type of dependence, the vacation time assigned to an arrival to follow its service is a function of the level of virtual wait reached. By this device, we can model situations in which vacations may be shortened whenever virtual delays have gotten excessive. The method of analysis employs level-crossing theory, and examples are given for various cases of service and vacation-time distributions. A closing discussion relates the new model class to standard M/G/1 queues where the service time is a sum of variables having complex dependencies. © 1992 John Wiley & Sons, Inc.     

‘The People are Revolting’: An Anatomy of Authoritarian Counterinsurgency

Rather than win hearts and minds, authoritarian counterinsurgency is said to rely heavily on coercion. It has a reputation for effectiveness, if also for its amorality. Still, the research into authoritarian counterinsurgency is surprisingly lacking. By distilling common features from key cases, this article concludes that this approach goes beyond the indiscriminate violence that typically captures the imagination. Like their democratic counterparts but differently, authoritarian regimes also engage in mobilisation, create narratives, and turn military advantage into political gain. The analysis explains how these tasks are undertaken and, by contradistinction, sheds light on more liberal approaches as well.     

Utility assessment procedures for polynomial-exponential functions

This article develops a methodology for testing constant exchange risk properties and identifying an appropriate form for a decision maker's utility function. These risk properties characterize six different utility functions which are sums of products of polynomials and exponential functions. Such functional forms are commonly used in decision analysis applications. The practical advantage of this methodology is that these constant exchange risk properties eliminate the usual arbitrariness in the selection of a parametric utility function and often reduce the data requirements for subsequent estimation. The procedure is straightforward to apply. The decision maker need only provide certainty equivalents for two-outcome gambles and determine the more-preferred gamble in paired comparisons. The technical details of the procedure can be handled by interactive computer software.     

A simulation study of the efficiency of empirical Bayes' estimators of multiple correlated probability vectors

Empirical Bayes' methods had been used by Brier, Zacks, and Marlow [1] for estimating performance characteristic vectors of success probabilities. The problem is that of estimating k-dimensional success probabilities of dependent binomial random variables, which are highly correlated. The present study reinforces the results of the previous one by showing, via simulations, that the relative efficiency of the empirical Bayes estimators, compared to the Stein-type and to the maximum-likelihood ones, is very high. This holds even if the success proportions are based on a small number of trials. We study the case of equicorrelation structure with positive correlations.