Improving the performance of concrete using 3D fibres

This paper examines whether 3D fibre reinforcement can improve the toughness and flexural strength of concrete, when compared to equal dosage of straight steel fibres. This work was carried out to determine structural qualities that may lead to potential enhanced performance when concrete is subjected to a bomb blast and in addition the same structural qualities may act as a safety measure in earthquake situations. The majority of injuries caused from bomb attacks are a result of fragmented building components energised by the blast wave, therefore it is vital to reduce fragmentation of concrete. It is known that fibre reinforcement can reduce fragmentation of concrete by increasing energy absorption. A three point beam test was conducted on two batches of beams reinforced with straight steel and 3D fibres respectively, so that flexural strength and post crack toughness could be calculated and compared. A paired comparison test was carried out between the straight steel fibres and the 3D fibres. 3D and straight steel fibres were also embedded in cubes, so that pull out testing could be conducted and compared for the two fibre types. 3D fibre reinforced samples proved to have a higher flexural strength and post crack toughness than straight steel samples. 3D fibres also had a much higher pull out value. After testing, 3D fibres continued to span the rupture plane after initial crack formation during 3 point bend testing, which held together the concrete matrix. These findings suggest 3D fibre reinforced concrete would perform better as a blast protection material when compared to straight steel fibre reinforced concrete, as the results show 3D fibres produce tougher concrete that hold together fragments after loading

Corporate Pension Policy and the Value of PBGC Insurance

This paper derives the value of PBGC pension insurance under two scenarios of interest. The first allows for voluntary plan termination, which appears to be legal under current statutes. In the second scenario, termination is prohibited unless the firm is bankrupt. Optimal pension funding strategy under each scenario is examined. Finally,empirical estimates of PBGC liabilities are calculated. These show that a small number of funds account for a large fraction of total prospective PBGC liabilities, that those total liabilities greatly exceed current PBGC reserves for plan terminations, and that PBGC liabilities could be substantially reduced by the prohibition of voluntary termination.

An Equilibrium Theory of Excess Volatility and Mean Reversion in Stock Market Prices

Apparent mean reversion and excess volatility in stock market prices can be reconciled with the Efficient Market Hypothesis by specifying investor preferences that give rise to the demand for portfolio insurance. Therefore, several supposed macro anomalies can be shown to be consistent with a rational market in a simple and parsimonious model of the economy. Unlike other models that have derived equilibrium mean reversion in prices, the model in this paper does not require that the production side of the economy exhibit mean reversion. It also predicts that mean reversion and excess volatility will differ substantially across subperiods.

Riding the Yield Curve: Reprise

We investigate the efficacy of riding the yield curve. This strategy dictates holding longer-term treasury bills when the yield curve is upwardsloping. We find that the strategy is surprisingly effective. it stochastically dominates buying and holding shorter-term bills for large subperiods, and nearly dominates for the entire sample period, 1949-1988. Our empirical results suggest that abnormal profit opportunities are available from selectively increasing the maturity of a short-term portfolio.

Valuation and Optimal Exercise of the Wild Card Option in the Treasury Bond Futures Market

The Chicago Board of Trade Treasury Bond Futures Contract allows the short position several delivery options as to when and with which bond the contract will be settled. The timing option allows the short position to choose any business day in the delivery month to make delivery. In addition, the contract settlement price is locked in at 2:00 p.m. when the futures market closes, despite the facts that the short position need not declare an intent to settle the contract until 8:00 p.m. and that trading in Treasury bonds car, occur all day in dealer markets. If bond prices change significantly between 2:00 and 8:00 p.m., the short has the option of settling the contract at a favorable 2:00 p.m. price. This phenomenon, which recurs on every trading day of the delivery month, creates a sequence of 6-hour put options for the short position which has been dubbed the "wild card option." This paper presents avaluation model for the wild card option and computes estimates of the value of that option, as well as rules for its optimal exercise.

National history through local: Social evils and the origin of municipal services in Cincinnati

National history through local: Social evils and the origin of municipal services in Cincinnat

Physicians Open a Can of Worms: American Nationality and Hookworm in the United States, 1893-1909

Physicians Open a Can of Worms: American Nationality and Hookworm in the United States, 1893-190