Pavement Texturing by Milling, HR-283, 1987

Experience has shown that milling machines with carbide tipped teeth have the capability of profiling most asphalt concrete (ac) and portland cement concrete (pcc) pavements. Most standard milling operations today leave a very coarse, generally objectionable surface texture. This research utilized a Cedarapids Wirtgen 1900C mill modified by adding additional teeth. There were 411 teeth at a 5 millimeter transverse spacing (standard spacing is 15 mm) on a 6 ft. 4 in. long drum. The mill was used to profile and texture the surface of one ac and two pcc pavements. One year after the milling operation there is still some noticeable change in tire noise but the general appearance is good. The milling operation with the additional teeth provides an acceptable surface texture with improved Friction Numbers when compared to a nonmilled surface.

Multiplan Spreadsheets for Highway and Hydraulic Engineering Computations in County Engineering Offices, HR-284, 1987

Multiplan spreadsheet solutions were developed for a set of hydraulic and highway engineering computations of common interest to county engineers. These include earthwork, vertical and horizontal curves, staking superelevated curves and sign inventories for highways. The hydraulic applications were ditch flow, runoff, culvert size and stage discharge.

Strengthening of Existing Continuous Composite Bridges, HR-287, 1987

Research was conducted to investigate the potential of strengthening continuous bridges by post-tensioning. The study included the following: a literature review, selection and rating of a prototype continuous composite bridge, tests of a one-third-scale continuous composite bridge model, finite element analysis of the bridge model, and tests of a full-scale composite beam mockup for a negative moment region. The study results indicated that the strengthening of continuous, composite bridges is feasible. The primary objective in applyig the post-tensioning should be to provide moments opposite to those produced by live and dead loads. Longitudinal distribution of that post-tensioning always must be considered if only exterior or only interior beams are post-tensioned. Testing and finite element analysis showed that post-tensioning of positive moment regions with straight tendons was more effective than post-tensioning negative moment regions with straight tendons. Changes in tension in tendons may be either beneficial or detrimental when live loads are applied to a strengthened bridge and thus must be carefully considered in design.

Special Surface Preparation Prior to Bituminous Overlays, HR-231, 1987

Research project HR-231, "Special Surface Preparation Prior to Bituminous Overlay", was initiated in 1982 to study the effectiveness of three different crack fillers in extending pavement life. In particular, this project was designed to determine if any of the fillers could substantially reduce the rate of subsurface deterioration and general deterioration of an asphalt pavement at crack locations. This project also sought to determine the effects of the various crack filling procedures on different thicknesses of bituminous overlays. The three fillers, a fly ash slurry, an emulsion, and a rubberized asphalt mixture, were used along with a control section with no crack filler material on a 2.5 mile section of Cerro Gordo Trunk Route S-25 south of the town of Thornton. This report discusses the construction and performance of each filler material and makes recommendations concerning future use of any of the materials used.

Effects of Deicing Salt Trace Compounds on Deterioration of Portland Cement Concrete, HR-271, 1987

A study was made of the detrimental effects of trace amounts of calcium sulfate (occurring naturally in halite deposits used for deicing) on portland cement concrete pavements. It was found that sulfate introduced as gypsum with sodium chloride in deicing brines can have detrimental effects on portland cement mortar. Concentrations of sulfate as low as 0.5% of the solute rendered the brine destructive. Conditions of brine application were critical to specimen durability. The mechanisms of deterioration were found to be due to pore filling resulting from compound formation and deposition. A field evaluation of deteriorating joints suggests that the sulfate phenomena demonstrated in the laboratory also operates in the field. A preliminary evaluation was made of remedies: limits on sulfates, fly ash admixtures, treatment of existing pavement, and salt treatments. This report gives details of the research objectives, experimental design, field testing, and possible solutions. Recommendations for further study are presented.

Pile Design and Tests for Integral Abutment Bridges, HR-273, 1987

Expansion joints increase both the initial cost and the maintenance cost of bridges. Integral abutment bridges provide an attractive design alternative because expansion joints are eliminated from the bridge itself. However, the piles in these bridges are subjected to horizontal movement as the bridge expands and contracts during temperature changes. The objective of this research was to develop a method of designing piles for these conditions. Separate field tests simulating a pile and a bridge girder were conducted for three loading cases: (1) vertical load only, (2) horizontal displacement of pile head only, and (3) combined horizontal displacement of pile head with subsequent vertical load. Both tests (1) and (3) reached the same ultimate vertical load, that is, the horizontal displacement had no effect on the vertical load capacity. Several model tests were conducted in sand with a scale factor of about 1:10. Experimental results from both the field and model tests were used to develop the vertical and horizontal load-displacement properties of the soil. These properties were input into the finite element computer program Integral Abutment Bridge Two-Dimensional (IAB2D), which was developed under a previous research contract. Experimental and analytical results compared well for the test cases. Two alternative design methods, both based upon the American Association of State Highway and Transportation Officials (AASHTO) Specification, were developed. Alternative One is quite conservative relative to IAB2D results and does not permit plastic redistribution of forces. Alternative Two is also conservative when compared to IAB2D, but plastic redistribution is permitted. To use Alternative Two, the pile cross section must have sufficient inelastic rotation capacity before local buckling occurs. A design example for a friction pile and an end-bearing pile illustrates both alternatives.

Improvement of Longitudinal Joints in Asphalt Pavement, HR-215, 1987

Research is reported which attempted to identify construction procedures that will provide an improved centerline joint on asphalt concrete pavements. Various construction procedures and their evaluation are described. Core densities were made and visual inspections were made 3 years after construction. Center cracking was measured at 4, 5, and 6 years. The only procedure to rank the same when comparing cracking and density (delete the 1:1 slope shoe on the edge) is described. This procedure had the highest average density and also the least cracking through 1985. This method provided the best performance for 4 years after construction and involved the removal of the 1:1 slope shoe from the paver when placing the surface course. This method had 9.0% cracked after 4 years and 100% cracked after 6 years of service.

Control Structures for Stabilizing Degrading Stream Channels Pottawattamie County, HR-236, 1987

Stream degradation due to steep stream gradients and large deposits of loess soil is a serious problem in western Iowa. One solution to this problem is to construct grade stabilization structures at critical points along the length of the stream. Iowa Highway Research Board project HR-236, "Pottawattamie County Evaluation of Control Structures for Stabilizing Degrading Stream Channels", was initiated in order to study the effectiveness of such structures in preventing stream degradation. This report describes the construction and 4-year performance of a gabion drop structure constructed along Keg Creek during the winter of 1982-83.

Evaluation des campagnes de prévention contre le SIDA en Suisse : rapport intermédiaire : juillet 1987

Principales constatations a) en termes de résultats (modification d'attitudes et de comportements), b) en termes de processus d'influences, c) à propos du test de dépistage du VIH. Recommandations.

Aproximación al análisis textual informatizado

Este articulo pretende acercar al lector conocedor del análisis textual clásico, como el análisis de contenido, a alguna de las técnicas mas recientes de análisis textual mediante programas informáticos. Para cada una de ellas se facilitan unas minimas bases teóricas, información sobre el tipo de material verbal adecuado para ser analizado, el tipo de cuantificación del texto utilizado por el programa, los indices calculados y finalmente la utilidad y aplicación de dichos indices. En todos los casos, y para facilitar la comprensión, se ofrecen datos sobre investigaciones en las que se ha aplicado dicha técnica. Se hace referencia a la lexicometria, la lexicometria cronológica, al análisis factorial de correspondencias de Benzecri (1974), al análisis de correspondencias de protocolos verbales, y al sistema.