Stochastic Dynamic Northern Corn Rootworm Population Model, January 2000

A complete life cycle model for northern corn rootworm, Diabrotica barberi Smith and Lawrence, is developed using a published single-season model of adult population dynamics and data from field experiments. Temperature-dependent development and age-dependent advancement determine adult population dynamics and oviposition, while a simple stochastic hatch and density-dependent larval survival model determine adult emergence. Dispersal is not modeled. To evaluate the long-run performance of the model, stochastically generated daily air and soil temperatures are used for 100-year simulations for a variety of corn planting and flowering dates in Ithaca, NY, and Brookings, SD. Once the model is corrected for a bias in oviposition, model predictions for both locations are consistent with anecdotal field data. Extinctions still occur, but these may be consistent with northern corn rootworm metapopulation dynamics.

Demonstration of Load Rating Capabilities through Physical Load Testing: Sioux County Bridge Case Study, RB32-013, 2013

The objective of this work, Pilot Project - Demonstration of Capabilities and Benefits of Bridge Load Rating through Physical Testing, was to demonstrate the capabilities for load testing and rating bridges in Iowa, study the economic benefit of performing such testing, and perform outreach to local, state, and national engineers on the topic of bridge load testing and rating. This report documents one of three bridges inspected, load tested, and load rated as part of the project, the Sioux County Bridge (FHWA #308730), including testing procedures and performance of the bridge under static loading along with the calculated load rating from the field-calibrated analytical model. Two parallel reports document the testing and load rating of the Ida County Bridge (FHWA #186070) and the Johnson County Bridge (FHWA #205750). A tech brief provides overall information about the project.

Demonstration of Load Rating Capabilities through Physical Load Testing: Ida County Bridge Case Study, RB32-013, 2013

The objective of this work, Pilot Project - Demonstration of Capabilities and Benefits of Bridge Load Rating through Physical Testing, was to demonstrate the capabilities for load testing and rating bridges in Iowa, study the economic benefit of performing such testing, and perform outreach to local, state, and national engineers on the topic of bridge load testing and rating. This report documents one of three bridges inspected, load tested, and load rated as part of the project, the Ida County Bridge (FHWA #186070), including testing procedures and performance of the bridge under static loading along with the calculated load rating from the field-calibrated analytical model. Two parallel reports document the testing and load rating of the Sioux County Bridge (FHWA #308730) and the Johnson County Bridge (FHWA #205750). A tech brief provides overall information about the project.

Demonstration of Load Rating Capabilities through Physical Load Testing: Johnson County Bridge Case Study, RB32-013, 2013

The objective of this work, Pilot Project - Demonstration of Capabilities and Benefits of Bridge Load Rating through Physical Testing, was to demonstrate the capabilities for load testing and rating bridges in Iowa, study the economic benefit of performing such testing, and perform outreach to local, state, and national engineers on the topic of bridge load testing and rating. This report documents one of three bridges inspected, load tested, and load rated as part of the project, the Johnson County Bridge (FHWA #205750), including testing procedures and performance of the bridge under static loading along with the calculated load rating from the field-calibrated analytical model. Two parallel reports document the testing and load rating of the Sioux County Bridge (FHWA #308730) and the Ida County Bridge (FHWA #186070). A tech brief provides overall information about the project.

Pilot Project - Demonstration of Load Rating Capabilities through Physical Load Testing: Tech Transfer Summary, RB32-013, 2013

This project demonstrated the capabilities for load testing bridges in Iowa, developed and presented a webinar to local and state engineers, and produced a spreadsheet and benefit evaluation matrix that others can use to preliminarily assess where bridge testing may be economically feasible given truck traffic and detour lengths.

Demonstration of Load Rating Capabilities through Physical Load Testing (4 vol), RB32-013, 2013

The objective of this work, Pilot Project - Demonstration of Capabilities and Benefits of Bridge Load Rating through Physical Testing, was to demonstrate the capabilities for load testing and rating bridges in Iowa, study the economic benefit of performing such testing, and perform outreach to local, state, and national engineers on the topic of bridge load testing and rating. The three final reports document one each of three bridges inspected, load tested, and load rated as part of the project. The bridges include the Sioux County Bridge (FHWA #308730), the Ida County Bridge (FHWA #186070), and the Johnson County Bridge (FHWA #205750). Actions included testing procedures and performance of the bridge under static loading along with the calculated load rating from the field-calibrated analytical model. A Tech Transfer Summary provides overall information about the project.

Integration of Bridge Damage Detection Concepts and Components (3 volumes), TR-636, 2013

This work is divided into three volumes: Volume I: Strain-Based Damage Detection; Volume II: Acceleration-Based Damage Detection; Volume III: Wireless Bridge Monitoring Hardware. Volume I: In this work, a previously-developed structural health monitoring (SHM) system was advanced toward a ready-for-implementation system. Improvements were made with respect to automated data reduction/analysis, data acquisition hardware, sensor types, and communication network architecture. The statistical damage-detection tool, control-chart-based damage-detection methodologies, were further investigated and advanced. For the validation of the damage-detection approaches, strain data were obtained from a sacrificial specimen attached to the previously-utilized US 30 Bridge over the South Skunk River (in Ames, Iowa), which had simulated damage,. To provide for an enhanced ability to detect changes in the behavior of the structural system, various control chart rules were evaluated. False indications and true indications were studied to compare the damage detection ability in regard to each methodology and each control chart rule. An autonomous software program called Bridge Engineering Center Assessment Software (BECAS) was developed to control all aspects of the damage detection processes. BECAS requires no user intervention after initial configuration and training. Volume II: In this work, a previously developed structural health monitoring (SHM) system was advanced toward a ready-for-implementation system. Improvements were made with respect to automated data reduction/analysis, data acquisition hardware, sensor types, and communication network architecture. The objective of this part of the project was to validate/integrate a vibration-based damage-detection algorithm with the strain-based methodology formulated by the Iowa State University Bridge Engineering Center. This report volume (Volume II) presents the use of vibration-based damage-detection approaches as local methods to quantify damage at critical areas in structures. Acceleration data were collected and analyzed to evaluate the relationships between sensors and with changes in environmental conditions. A sacrificial specimen was investigated to verify the damage-detection capabilities and this volume presents a transmissibility concept and damage-detection algorithm that show potential to sense local changes in the dynamic stiffness between points across a joint of a real structure. The validation and integration of the vibration-based and strain-based damage-detection methodologies will add significant value to Iowa’s current and future bridge maintenance, planning, and management Volume III: In this work, a previously developed structural health monitoring (SHM) system was advanced toward a ready-for-implementation system. Improvements were made with respect to automated data reduction/analysis, data acquisition hardware, sensor types, and communication network architecture. This report volume (Volume III) summarizes the energy harvesting techniques and prototype development for a bridge monitoring system that uses wireless sensors. The wireless sensor nodes are used to collect strain measurements at critical locations on a bridge. The bridge monitoring hardware system consists of a base station and multiple self-powered wireless sensor nodes. The base station is responsible for the synchronization of data sampling on all nodes and data aggregation. Each wireless sensor node include a sensing element, a processing and wireless communication module, and an energy harvesting module. The hardware prototype for a wireless bridge monitoring system was developed and tested on the US 30 Bridge over the South Skunk River in Ames, Iowa. The functions and performance of the developed system, including strain data, energy harvesting capacity, and wireless transmission quality, were studied and are covered in this volume.

Dynamic Deflections to Determine Roadway Support Ratings, HR-245, 1983

The Benkelman Beam structural test of flexible pavements was replaced in 1976 by dynamic deflection testing with a model 400 Road Rater. The Road Rater is used to determine structural ratings of flexible pavements. New pavement construction in Iowa has decreased with a corresponding increase of restoration and rehabilitation. A method to determine structural ratings of layered systems and rigid pavements is needed to properly design overlay thickness. The objective of this research was to evaluate the feasibility of using the Road Rater to determine support values of layered systems and rigid pavements. This evaluation was accomplished by correlating the Road Rater with the Federal Highway Administration (FHWA) Thumper, a dynamic deflection testing device. Data were obtained with the Road Rater and Thumper at 411 individual test locations on 39 different structural sections ranging from 10" of PCC pavement and 25" of asphalt pavement to a newly graveled unpaved roadway. A high correlation between a 9000 pound Thumper deflection and the 1185 pound Road Rater deflection was obtained. A Road Rater modification has been completed to provide 2000 pound load inputs. The basin, defined by four sensors spaced at 1 foot intervals, resulting from the 2000 pound loading is being used to develop a graph for determining relative subgrade strengths. Road Rater deflections on rigid pavements are sufficient to support the potential for this technique.

Dynamic Pavement Deflection Measurements, Progress Report, HR-178, 1977

The Road Rater is a dynamic deflection measuring appa-ratus for flexible base pavements. The basic operating principle of the Road Rater is to impart a dynamic loading and measure the resultant movement of the pavement with velocity sensors. This data, when properly adjusted for temperature by use of a nomograph included in this report, can be used to determine pavement life expectancy and estimate overlay thickness required. Road Rater testing will be conducted in the spring, when pave-ments are in their weakest condition, until seasonal correction factors can be developed. The Road Rater does not have sufficient ram weight to effectively evaluate load carrying capacity of rigid pavements. All rigid pavements react similarly to Road Rater testing and generally deflect from 0.65 to 1.30 mils. Research will be continued to evaluate rigid pavements with the Road Rater, however. The Road Rater has proven to be a reliable, trouble free pavement evaluation machine. The deflection apparatus was originally front-mounted, but was rear-mounted during the winter of 1977-78. Since that time, van handling has greatly improved, and front suspension parts are no longer overstressed due to improper weight distribution. The Road Rater provides a fast, economical, nondestructive test method to evaluate flexible pavements. Road Rater test data can be used to predict pavement life, set priorities for asphaltic concrete resurfacing, and design asphaltic concrete overlays. Temperature and seasonal variations significantly affect Road Rater deflection readings and must be considered. A nomograph included in this report adjusts for temperature, but does not correct for seasonal effect. Road Rater testing will be conducted in the spring until seasonal correction factors can be developed. The Road Rater has not successfully evaluated rigid pavements, but research will continue in this area. 1. Recommendations for continuing Road Rater research, evaluation and application are as follows:A computer program should be established to reduce Road Rater raw data (Range and Sensor reading) to HR-178 Road Rater Dynamic Deflections For Determining Structural Rating Of Flexible Pavements mean deflection (mils) and/or structural rating. This computer printout would be similar to present friction testing printouts, and would greatly reduce Road Rater data reduction manpower needs and costs. 2. Seasonal variation study should continue to develop seasonal correction factors. Seasonal test roads will be studied concurrently with routine testing during 1979 to develop this relationship. All Road Rater testing will be conducted in the spring until the seasonal relationship is established. 3. An asphaltic concrete overlay design method should be established based on Road Rater de-flection readings. The AASHTO Interim Guide for Design of Pavement Structures 1972 will be used as a base document for this study. 4. AASHTO Structural numbers should be compared to Road Rater Structural Ratings during 1979 on asphaltic concrete overlay projects. This analysis will enable us to refine Road Rater evaluation of flexible pavements. Roads will be tested before resurfacing and several months

Dynamic Tests of a Three-Span Continuous I-Beam Highway Bridge, HR-43, 1959

This paper presents the results of the static and dynamic testing of a three-span continuous I-beam highway bridge. Live load stress frequency curves for selected points are shown, and the static and dynamic load distribution to the longitudinal composite beam members are given. The bridge has four traffic lanes with a roadway width of 48 ft. Six longitudinal continuous WF beams act compositely with the reinforced concrete slab to carry the live load. The beams have partial length cover plates at the piers. Previous research has indicated that beams with partial length cover plates have a very low fatigue strength. It was found in this research that the magnitude of the stresses due to actual highway loads were very much smaller than those computed from specification loading. Also, the larger stresses which were measured occurred a relatively small number of times. These data indicate that some requirements for reduced allowable stresses at the ends of cover plates are too conservative. The load distribution to the longitudinal beams was determined for static and moving loads and includes the effect of impact on the distribution. The effective composite section was found at various locations to evaluate the load distribution data. The composite action was in negative as well as positive moment regions. The load distribution data indicate that the lateral distribution of live load is consistent with the specifications, but that there is longitudinal distribution, and therefore the specifications are too conservative.

Feasibility Study of Dynamic Overload and Ultimate Load Tests of Full-Scale Highway Bridges, HR-160, 1973

As a result of the construction of the Saylorville Dam and Reservoir on the Des Moines River, six highway bridges are scheduled for removal. Five of these are old high-truss single-lane bridges, each bridge having several simple spans. The other bridge is a fairly modern (1955) double 4-span continuous beam-and-slab composite highway bridge. The availability of these bridges affords an unusual opportunity for study of the behavior of full-scale bridges. Because of the magnitude of the potential testing program, a feasibility study was initiated and the results are presented in this two-part final report. Part I summarizes the findings and Part II presents the supporting detailed information.

Dynamic Deflections for Determining Structural Rating of Flexible Pavements, HR-178, 1979

The Road Rater is a dynamic deflection measuring apparatus for flexible base pavements. The Road Rater replaces the Benkelman Beam which was last used by the Iowa DOT in 1977. Road Rater test results correlate reasonably well (correlation coefficient = 0.83) with Benkelman Beam test data. The basic differences between the Road Rater and Benkelman Beam are as follows: 1. The Benkelman Beam uses a static 18,000 lb. load while the Road Rater uses a dynamic 800 to 2,000 lb. loading. 2. The Road Rater tests much faster and more economically than the Benkelman Beam. 3. The Road Rater better simulates a moving truck than the Benkelman Beam. The basic operating principle of the Road Rater is to impart a dynamic loading and measure the resultant movement of the pavement with velocity sensors. This data, when properly adjusted for temperature by use of a nomograph included in this report, can be used to determine pavement life expectancy and estimate overlay thickness required. Road Rater testing will be conducted in the spring, when pavements are in their weakest condition, until seasonal correction factors can be developed. The Road Rater does not have sufficient ram weight to effectively evaluate load carrying capacity of rigid pavements. All rigid pavements react similarly to Road Rater testing and generally deflect from 0.65 to 1.30 mils. Research will be contined to evaluate rigid pavements with the Road Rater, however. The Road Rater has proven to be a reliable, troublefree pavement evaluation machine. The deflection apparatus was originally front-mounted,but was rear-mounted during the winter of 1977-78. Since that time, van handling has greatly improved, and front suspension parts are no longer overstressed due to improper weight distribution.

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.

Development of Asphalt Dynamic Modulus Master Curve Using Falling Weight Deflectometer Measurements, TR-659

The asphalt concrete (AC) dynamic modulus (|E*|) is a key design parameter in mechanistic-based pavement design methodologies such as the American Association of State Highway and Transportation Officials (AASHTO) MEPDG/Pavement-ME Design. The objective of this feasibility study was to develop frameworks for predicting the AC |E*| master curve from falling weight deflectometer (FWD) deflection-time history data collected by the Iowa Department of Transportation (Iowa DOT). A neural networks (NN) methodology was developed based on a synthetically generated viscoelastic forward solutions database to predict AC relaxation modulus (E(t)) master curve coefficients from FWD deflection-time history data. According to the theory of viscoelasticity, if AC relaxation modulus, E(t), is known, |E*| can be calculated (and vice versa) through numerical inter-conversion procedures. Several case studies focusing on full-depth AC pavements were conducted to isolate potential backcalculation issues that are only related to the modulus master curve of the AC layer. For the proof-of-concept demonstration, a comprehensive full-depth AC analysis was carried out through 10,000 batch simulations using a viscoelastic forward analysis program. Anomalies were detected in the comprehensive raw synthetic database and were eliminated through imposition of certain constraints involving the sigmoid master curve coefficients. The surrogate forward modeling results showed that NNs are able to predict deflection-time histories from E(t) master curve coefficients and other layer properties very well. The NN inverse modeling results demonstrated the potential of NNs to backcalculate the E(t) master curve coefficients from single-drop FWD deflection-time history data, although the current prediction accuracies are not sufficient to recommend these models for practical implementation. Considering the complex nature of the problem investigated with many uncertainties involved, including the possible presence of dynamics during FWD testing (related to the presence and depth of stiff layer, inertial and wave propagation effects, etc.), the limitations of current FWD technology (integration errors, truncation issues, etc.), and the need for a rapid and simplified approach for routine implementation, future research recommendations have been provided making a strong case for an expanded research study.

Dynamic Speed Feedback Signs, 2014

Dynamic speed feedback sign (DSFS) systems are traffic control devices that are programmed to provide a message to drivers exceeding a certain speed thresh¬old. A DSFS system typically consists of a speed-measuring device, which may be loop detectors or radar, and a message sign that displays feedback to drivers who exceed a predetermined speed threshold. The feedback may be the driver’s actual speed, a message like “SLOW DOWN,” or activation of a warning device such as beacons or a curve warning sign. For more on this topic by these authors, see also "Evaluation of Dynamic Speed Feedback Signs on Curves: A National Demonstration Project": http://www.trb.org/main/blurbs/172092.aspx