Damage Accumulation in Wood Structural Members Under Stochastic Live Loads

Damage accumulation in wood structural members was assessed using realistic stochastic modeling of live load. The model indicates that practically all damage occurs when the live load intensity is equal or nearly equal to the nominal live load, Ln, a quantity required by codes for design. Currently, basic allowable stresses for wood are calculated assuming a period of 10 years spent at the nominal live load. The model indicates that the time the live load is at or above the nominal is not 10 years but about 40 days in a reference period of 50 years, strongly suggesting that the 10-year period generally assumed for setting allowable stresses is much too long

Fence Designs for Deer Control: A Review and the Results of Recent Research in Southeastern New York

Research on fences for deer control over the last 45 years has involved either the nonelectric or electric designs. The conventional nonelectric fence has been a vertical 8-to 10-foot woven-wire type which has proven effective in several states over the past 30 years. Some installations have included a 2-to 3-foot overhang of barbed or smooth wire at the top. All versions of this fence have been deemed excessively expensive by many consumers, although a recent New York study reported the 8-foot fence in new, high-density fruit orchards to be a very cost-effective control option

ASSESSING DEER DAMAGE IN YOUNG FRUIT ORCHARDS

Evaluations of systematic damage assessments of 5, 10 and 20 percent of all apple trees in 12 orchards were compared. The 10% assessment technique was selected as the most accurate and efficient in estimating summer and fall damage. Analysis of several parameters of tree vigor found significant differences between browsed and unbrowsed trees for tree basal diameter and central leader diameter over 2 successive years. These subtle yet important differences in tree development were felt to severely limit the possibilities of relating browsing to growth and. later, yields. Methods and considerations for making control decisions on a per acre basis are discussed

Assessment of Aging of Nuclear Power Plant Civil Structures

ABSTRACT Research is being conducted by ORNL for the USNRC to address aging of civil structures in light-water reactor plants. The importance and operating experience of nuclear power plant (NPP) civil structures is reviewed. Factors that can lead to age-related degradation of reinforced concrete structures and containment metallic pressure boundaries (i.e., steel containments and liners of reinforced concrete containments) are identified and their manifestations described. Background information and data for improving and developing methods to assess the effects of age-related degradation on structural performance are provided. Techniques for detection of degradation are reviewed and research related to development of methods for inspection of inaccessible regions of the containment pressure boundary presented. Application of structural reliability analysis methods to develop condition assessment tools and guidelines is described

Underground railroads: citizen entitlements and unauthorized mobility in the antebellum period and today

In recent years, some scholars and prominent political figures have advocated the deepening of North American integration on roughly the European Union model, including the creation of new political institutions and the free movement of workers across borders. The construction of such a North American Union, if it included even a very thin trans-state citizenship regime, could represent the most significant expansion of individual entitlements in the region since citizenship was extended to former slaves in the United States. With such a possibility as its starting point, this article explores some striking parallels between the mass, legally prohibited movement across boundaries by fugitive slaves in the pre-Civil War period, and that by current unauthorized migrants to the United States. Both were, or are, met on their journeys by historically parallel groups of would-be helpers and hinderers. Their unauthorized movements in both periods serve as important signals of incomplete entitlements or institutional protections. Most crucially, moral arguments for extending fuller entitlements to both groups are shown here to be less distinct than may be prima facie evident, reinforcing the case for expanding and deepening the regional membership regime

Electron-beam Calibration of Aerogel Tiles for the HELIX RICH Detector

The HELIX cosmic-ray detector is a balloon-borne instrument designed to measure the flux of light isotopes in the energy range from 0.2 GeV/n to beyond 3 GeV/n. It will rely on a ring-imaging Cherenkov (RICH) detector for particle identification at energies greater than 1 GeV/n and will use aerogel tiles with refractive index near 1.15 as the radiator. To achieve the performance goals of the experiment it is necessary to know the refractive index and its position dependence over the lateral extent of the tiles to a precision of O(10$^{-4}). In this paper we describe the apparatus and methods developed to calibrate the HELIX tiles in an electron beam, in order to meet this requirement.Comment: 27 pages and 16 figures. Accepted for publication in Nuclear Instruments and Methods

Vulnerability assessment and feasibility analysis of seismic strengthening of school buildings

The majority of structures in seismic-prone areas worldwide are structures that have been designed either without seismic design considerations, or using codes of practice that are seriously inadequate in the light of current seismic design principles. In Cyprus, after a series of earthquakes that occurred between 1995 and 1999, it was decided to carry out an unprecedented internationally seismic retrofitting of all school buildings, taking into account the sensitivity of the society towards these structures. In this paper representative school buildings are analysed in both their pristine condition and after applying retrofitting schemes typical of those implemented in the aforementioned large-scale strengthening programme. Non-linear analysis is conducted on calibrated analytical models of the selected buildings and fragility curves are derived for typical reinforced concrete and unreinforced masonry structures. These curves are then used to carry out a feasibility study, including both benefit-cost and life-cycle analysis, and evaluate the effectiveness of the strengthening programme

Probability based design of punching shear resistance of column to slab connections

The paper analyzes the dependence of punching shear strength reliability index β, calculated according to EN 1992-1-1:2004 (2004) and STR 2.05.05:2005 (2005) in reinforced concrete floor slab-to-column joint on the values of random factors. The paper deals with theoretical research of the influence of independent random variables, such us the value of the characteristic compressive strength fck of concrete, the area As of the longitudinal reinforcement, effective cross-section depth d and the ratio of the self-weight and the effective load on the value of the reliability index β. The paper presents experimental results of reinforced concrete slabs with different longitudinal reinforcement ratio ρ subjected to a concentrated load. I t was determined that when the effective load makes around 50% of the construction self-weight load, i.e. Gk /Qk = 2 and when minimal variation coefficient estimates are taken (for concrete strength δfc = 0.1, for effective depth δd = 0,1 and for the area of longitudinal reinforcement cross-section δAs = 0.05 or δAs = 0.075 and when Gk = Qk i.e. Gk /Qk = 1 where δfc = 0.1, δd = 0.1 and δAs = 0.05) the reliability index β of the analyzed slabs calculated according to EN 1992-1-1:2004 (2004) as well as β calculated according to STR 2.05.05:2005 (2005), is bigger than EN 1990:2002 (2002) recommendation for the minimum value of reliability index – 3.8 for RC2 construction reliability class ultimate. In other cases the reliability index β is close to 3.8 or much smaller than 3.8

Composite slab numerical strength test method under partial connection approach

The present uneconomic strength determination approach for profiled composite slab (PCS) constitutes a serious challenge that contributed significantly to design conservatism. This study seeks to address this challenge by developing and a subsequent experimental validation of a numerical strength determination function for PCS through implementing a rational-based approach. Hence, a procedural algorithm lead to the development of PCS determination function using longitudinal shear estimation method by considering section slenderness and deck characteristics. The strength test performance between the developed scheme and the experiment-based test results indicates high similarity, demonstrating the viability of the proposed strength determination methodology developed