Behavior of Asphalts in the Production of Asphaltic Concrete, HR-107, 1965

Project 540-S of the Iowa Engineering Experiment Station (Project HR-107, Iowa Highway Research Board) was started in June, 1964. During the year ten 2-gallon samples of asphalt cement and ten 100-lb samples of asphaltic concrete were studied by the personnel of the Bituminous Research Laboratory, Iowa State University. The samples were from tanks and mixers of asphalt plants at various Iowa State Highway Commission paving jobs. The laboratory's research was in two phases: 1. To ascertain if properties of asphalt cement changed during mixing operations. 2. To determine whether one or more of the several tests of asphalt cements were enough to indicate behavior of the heated asphalt cements. If the reliability of one or more tests could be proved, the behavior of asphalts would be more simply and rapidly predicted.

Behavior of Carbonate Rocks as Concrete Aggregates, HR-15, 1962

The problem of determining the suitability of carbonate rocks as concrete aggregates is extremely complex and calls for more new data than has been available or obtainable from usual methods. Since 1955 the approach which has served as a primary basis for the project has been to gather as much new information as possible to apply to the problem. New information obtained by new and different techniques provides better understanding. This approach was decided on since, in all prior studies, a standard petrographic and petrologic approach correlated in many instances with standard engineering tests did not provide the answer in Iowa or elsewhere. One can theorize that concrete fails (excluding external causes such as traffic, foundation failure, etc.) because of stresses of internal origin. The stresses can be of a physical nature, such as frost action, or result from chemical activity such as the alkali aggregate reaction. If, as service records show, the aggregate is considered the cause of distress in concrete, it will without doubt be the manner in which an aggregate can create or contribute to stress of internal origin by physical or chemical means. Therefore the main emphasis was placed on studying physical and chemical properties of aggregates as well as the behavior of carbonate rocks in concrete environments. Although standard geologic and engineering methods were also utilized, the approach adopted required considerable effort in devising new techniques and methods. This report is intended to be a detailed summary of the research performed. Whenever possible, the work accomplished will be summarized and all pertinent data will be included. For further details, reference to the various theses and publications transmitted with this report or at previous times will be made wherever possible.

Modeling Merging Behavior at Lane Drops, InTrans Projects 13-466 and 06-277, 2015

In work-zone configurations where lane drops are present, merging of traffic at the taper presents an operational concern. In addition, as flow through the work zone is reduced, the relative traffic safety of the work zone is also reduced. Improving work-zone flow-through merge points depends on the behavior of individual drivers. By better understanding driver behavior, traffic control plans, work zone policies, and countermeasures can be better targeted to reinforce desirable lane closure merging behavior, leading to both improved safety and work-zone capacity. The researchers collected data for two work-zone scenarios that included lane drops with one scenario on the Interstate and the other on an urban arterial roadway. The researchers then modeled and calibrated these scenarios in VISSIM using real-world speeds, travel times, queue lengths, and merging behaviors (percentage of vehicles merging upstream and near the merge point). Once built and calibrated, the researchers modeled strategies for various countermeasures in the two work zones. The models were then used to test and evaluate how various merging strategies affect safety and operations at the merge areas in these two work zones.

Ultimate Load Behavior of Full-Scale Highway Truss Bridges: Phase II - Service Load and Supplementary Tests, Interim Report, HR-169, 1975

As a result of the construction of the Saylorville Dam and Reservoir on the Des Moines River, six highway bridges crossing the river were scheduled for removal. Two of these were incorporated into a comprehensive test program to study the behavior of old pin-connected high-truss single-lane bridges. The test program consisted of ultimate load tests, service load tests and a supplementary test program. The results reported in this report cover the service load tests on the two bridges as well as the supplementary tests, both static and fatigue, of eyebar members removed from the two bridges. The field test results of the service loading are compared with theoretical results of the truss analysis.

Problems of Bridge Supporting and Expansion Devices and an Experimental Comparison of the Dynamic Behavior of Rigid and Elastomeric Bearings, HR-105, 1965

The design of satisfactory supporting and expansion devices for highway bridges is a problem which has concerned bridge design engineers for many years. The problems associated with these devices have been emphasized by the large number of short span bridges required by the current expanded highway program of expressways and interstate highways. The initial objectives of this investigation were: (1) To review and make a field study of devices used for the support of bridge superstructures and for provision of floor expansion; (2) To analyze the forces or factors which influence the design and behavior of supporting devices and floor expansion systems; and (3) To ascertain the need for future research particularly on the problems of obtaining more economical and efficient supporting and expansion devices, and determining maximum allowable distance between such devices. The experimental portion was conducted to evaluate one of the possible simple and economical solutions to the problems observed in the initial portion. The investigation reported herein is divided into four major parts or phases as follows: (1) A review of literature; (2) A survey by questionnaire of design practice of a number of state highway departments and consulting firms; (3) Field observation of existing bridges; and, (4) An experimental comparison of the dynamic behavior of rigid and elastomeric bearings.

Ultimate Load Behavior of Full-Scale Highway Truss Bridges: Phase I - Ultimate Load Tests of the Hubby Bridge - Boone County, Interim Report, HR-169, 1975

As a result of the construction of the Saylorville Dam and Reservoir on the Des Moines River, six highway bridges crossing the river were scheduled for removal. One of these, an old pinconnected high-truss single-lane bridge, was selected for a testing program which included ultimate load tests. The purpose of the ultimate load tests, which are summarized in this report, was to relate design and rating procedures presently used in bridge design to the field behavior of this type of truss bridge. The ultimate load tests consisted of ultimate load testing of one span of the bridge, of two I-shaped floorbeams, and of two panels of the timber deck. The theoretical capacity of each of these components is compared with the results from the field tests.