Development of LRFD Design Procedures for Bridge Piles in Iowa – Field Testing of Steel H-Piles in Clay, Sand, and Mixed Soils and Data Analysis (Volume II), TR-583, 2011

In response to the mandate on Load and Resistance Factor Design (LRFD) implementations by the Federal Highway Administration (FHWA) on all new bridge projects initiated after October 1, 2007, the Iowa Highway Research Board (IHRB) sponsored these research projects to develop regional LRFD recommendations. The LRFD development was performed using the Iowa Department of Transportation (DOT) Pile Load Test database (PILOT). To increase the data points for LRFD development, develop LRFD recommendations for dynamic methods, and validate the results of LRFD calibration, 10 full-scale field tests on the most commonly used steel H-piles (e.g., HP 10 x 42) were conducted throughout Iowa. Detailed in situ soil investigations were carried out, push-in pressure cells were installed, and laboratory soil tests were performed. Pile responses during driving, at the end of driving (EOD), and at re-strikes were monitored using the Pile Driving Analyzer (PDA), following with the CAse Pile Wave Analysis Program (CAPWAP) analysis. The hammer blow counts were recorded for Wave Equation Analysis Program (WEAP) and dynamic formulas. Static load tests (SLTs) were performed and the pile capacities were determined based on the Davisson’s criteria. The extensive experimental research studies generated important data for analytical and computational investigations. The SLT measured load-displacements were compared with the simulated results obtained using a model of the TZPILE program and using the modified borehole shear test method. Two analytical pile setup quantification methods, in terms of soil properties, were developed and validated. A new calibration procedure was developed to incorporate pile setup into LRFD.

Development of LRFD Procedures for Bridge Pile Foundations in Iowa Volume III: Recommended Resistance Factors with Consideration of Construction Control and Setup, TR-584, 2012

The Federal Highway Administration (FHWA) mandated utilizing the Load and Resistance Factor Design (LRFD) approach for all new bridges initiated in the United States after October 1, 2007. As a result, there has been a progressive move among state Departments of Transportation (DOTs) toward an increased use of the LRFD in geotechnical design practices. For the above reasons, the Iowa Highway Research Board (IHRB) sponsored three research projects: TR-573, TR-583 and TR-584. The research information is summarized in the project web site (http://srg.cce.iastate.edu/lrfd/). Two reports of total four volumes have been published. Report volume I by Roling et al. (2010) described the development of a user-friendly and electronic database (PILOT). Report volume II by Ng et al. (2011) summarized the 10 full-scale field tests conducted throughout Iowa and data analyses. This report presents the development of regionally calibrated LRFD resistance factors for bridge pile foundations in Iowa based on reliability theory, focusing on the strength limit states and incorporating the construction control aspects and soil setup into the design process. The calibration framework was selected to follow the guidelines provided by the American Association of State Highway and Transportation Officials (AASHTO), taking into consideration the current local practices. The resistance factors were developed for general and in-house static analysis methods used for the design of pile foundations as well as for dynamic analysis methods and dynamic formulas used for construction control. The following notable benefits to the bridge foundation design were attained in this project: 1) comprehensive design tables and charts were developed to facilitate the implementation of the LRFD approach, ensuring uniform reliability and consistency in the design and construction processes of bridge pile foundations; 2) the results showed a substantial gain in the factored capacity compared to the 2008 AASHTO-LRFD recommendations; and 3) contribution to the existing knowledge, thereby advancing the foundation design and construction practices in Iowa and the nation.

Bridge Rail and Approach Railing for Low-Volume Roads in Iowa, TR-592, 2010

Bridge rail and approach guardrails provide safety to drivers by shielding more hazardous objects and redirecting vehicles to the roadway. However, guardrail can increase both the initial cost and maintenance cost of a bridge, while adding another object that may be struck by vehicles. Most existing low volume road (LVR) bridges in the state of Iowa are currently indicated to not possess bridge rail meeting “current acceptable standards”. The primary objective of the research summarized in this report was to provide the nations bridge and approach rail state of practice and perform a state wide crash analysis on bridge rails and approach guardrails on LVR bridges in Iowa. In support of this objective, the criteria and guidelines used by other bridge owners were investigated, non-standard and innovative bridge and approach guardrails for LVR’s were investigated, and descriptive, statistical and economical analyses were performed on a state wide crash analysis. The state wide crash analysis found the overall number of crashes at/on the more than 17,000+ inventoried and non-inventoried LVR bridges in Iowa was fewer than 350 crashes over an eight year period, representing less than 0.1% of the statewide reportable crashes. In other words, LVR bridge crashes are fairly rare events. The majority of these crashes occurred on bridges with a traffic volume less than 100 vpd and width less than 24 ft. Similarly, the majority of the LVR bridges possess similar characteristics. Crash rates were highest for bridges with lower traffic volumes, narrower widths, and negative relative bridge widths (relative bridge width is defined as: bridge width minus roadway width). Crash rate did not appear to be effected by bridge length. Statistical analysis confirmed that the frequency of vehicle crashes was higher on bridges with a lower width compared to the roadway width. The frequency of crashes appeared to not be impacted by weather conditions, but crashes may be over represented at night or in dark conditions. Statistical analysis revealed that crashes that occurred on dark roadways were more likely to result in major injury or fatality. These findings potentially highlight the importance of appropriate delineation and signing. System wide, benefit-cost (B/C) analyses yielded very low B/C ratios for statewide bridge rail improvements. This finding is consistent with the aforementioned recommendation to address specific sites where safety concerns exist.

Autonomous Measurements of Bridge Pier and Abutment Scour using Motion-Sensing Radio Transmitters, TR-595, 2010

Two portable Radio Frequency IDentification (RFID) systems (made by Texas Instruments and HiTAG) were developed and tested for bridge scour monitoring by the Department of Civil and Environmental Engineering at the University of Iowa (UI). Both systems consist of three similar components: 1) a passive cylindrical transponder of 2.2 cm in length (derived from transmitter/responder); 2) a low frequency reader (~134.2 kHz frequency); and 3) an antenna (of rectangular or hexagonal loop). The Texas Instruments system can only read one smart particle per time, while the HiTAG system was successfully modified here at UI by adding the anti-collision feature. The HiTAG system was equipped with four antennas and could simultaneously detect 1,000s of smart particles located in a close proximity. A computer code was written in C++ at the UI for the HiTAG system to allow simultaneous, multiple readouts of smart particles under different flow conditions. The code is written for the Windows XP operational system which has a user-friendly windows interface that provides detailed information regarding the smart particle that includes: identification number, location (orientation in x,y,z), and the instance the particle was detected.. These systems were examined within the context of this innovative research in order to identify the best suited RFID system for performing autonomous bridge scour monitoring. A comprehensive laboratory study that included 142 experimental runs and limited field testing was performed to test the code and determine the performance of each system in terms of transponder orientation, transponder housing material, maximum antenna-transponder detection distance, minimum inter-particle distance and antenna sweep angle. The two RFID systems capabilities to predict scour depth were also examined using pier models. The findings can be summarized as follows: 1) The first system (Texas Instruments) read one smart particle per time, and its effective read range was about 3ft (~1m). The second system (HiTAG) had similar detection ranges but permitted the addition of an anti-collision system to facilitate the simultaneous identification of multiple smart particles (transponders placed into marbles). Therefore, it was sought that the HiTAG system, with the anti-collision feature (or a system with similar features), would be preferable when compared to a single-read-out system for bridge scour monitoring, as the former could provide repetitive readings at multiple locations, which could help in predicting the scour-hole bathymetry along with maximum scour depth. 2) The HiTAG system provided reliable measures of the scour depth (z-direction) and the locations of the smart particles on the x-y plane within a distance of about 3ft (~1m) from the 4 antennas. A Multiplexer HTM4-I allowed the simultaneous use of four antennas for the HiTAG system. The four Hexagonal Loop antennas permitted the complete identification of the smart particles in an x, y, z orthogonal system as function of time. The HiTAG system can be also used to measure the rate of sediment movement (in kg/s or tones/hr). 3) The maximum detection distance of the antenna did not change significantly for the buried particles compared to the particles tested in the air. Thus, the low frequency RFID systems (~134.2 kHz) are appropriate for monitoring bridge scour because their waves can penetrate water and sand bodies without significant loss of their signal strength. 4) The pier model experiments in a flume with first RFID system showed that the system was able to successfully predict the maximum scour depth when the system was used with a single particle in the vicinity of pier model where scour-hole was expected. The pier model experiments with the second RFID system, performed in a sandbox, showed that system was able to successfully predict the maximum scour depth when two scour balls were used in the vicinity of the pier model where scour-hole was developed. 5) The preliminary field experiments with the second RFID system, at the Raccoon River, IA near the Railroad Bridge (located upstream of 360th street Bridge, near Booneville), showed that the RFID technology is transferable to the field. A practical method would be developed for facilitating the placement of the smart particles within the river bed. This method needs to be straightforward for the Department of Transportation (DOT) and county road working crews so it can be easily implemented at different locations. 6) Since the inception of this project, further research showed that there is significant progress in RFID technology. This includes the availability of waterproof RFID systems with passive or active transponders of detection ranges up to 60 ft (~20 m) within the water–sediment column. These systems do have anti-collision and can facilitate up to 8 powerful antennas which can significantly increase the detection range. Such systems need to be further considered and modified for performing automatic bridge scour monitoring. The knowledge gained from the two systems, including the software, needs to be adapted to the new systems.

Iowa Mass Concrete for Bridge Foundation Study - Phase II, Final Report, 2014

The early-age thermal development of structural mass concrete elements has a significant impact on the future durability and longevity of the elements. If the heat of hydration is not controlled, the elements may be susceptible to thermal cracking and damage from delayed ettringite formation. In the Phase I study, the research team reviewed published literature and current specifications on mass concrete. In addition, the team observed construction and reviewed thermal data from the westbound (WB) I-80 Missouri River Bridge. Finally, the researchers conducted an initial investigation of the thermal analysis software programs ConcreteWorks and 4C-Temp&Stress. The Phase II study is aimed at developing guidelines for the design and construction of mass concrete placements associated with large bridge foundations. This phase included an additional review of published literature and a more in-depth investigation of current mass concrete specifications. In addition, the mass concrete construction of two bridges, the WB I-80 Missouri River Bridge and the US 34 Missouri River Bridge, was documented. An investigation was conducted of the theory and application of 4C-Temp&Stress. ConcreteWorks and 4C-Temp&Stress were calibrated with thermal data recorded for the WB I-80 Missouri River Bridge and the US 34 Missouri River Bridge. ConcreteWorks and 4C-Temp&Stress were further verified by means of a sensitivity study. Finally, conclusions and recommendations were developed, as included in this report.

Implementation of a Pilot Continuous Monitoring System: Iowa Falls Arch Bridge, HR-1088, 2015

The goal of this work was to move structural health monitoring (SHM) one step closer to being ready for mainstream use by the Iowa Department of Transportation (DOT) Office of Bridges and Structures. To meet this goal, the objective of this project was to implement a pilot multi-sensor continuous monitoring system on the Iowa Falls Arch Bridge such that autonomous data analysis, storage, and retrieval can be demonstrated. The challenge with this work was to develop the open channels for communication, coordination, and cooperation of various Iowa DOT offices that could make use of the data. In a way, the end product was to be something akin to a control system that would allow for real-time evaluation of the operational condition of a monitored bridge. Development and finalization of general hardware and software components for a bridge SHM system were investigated and completed. This development and finalization was framed around the demonstration installation on the Iowa Falls Arch Bridge. The hardware system focused on using off-the-shelf sensors that could be read in either “fast” or “slow” modes depending on the desired monitoring metric. As hoped, the installed system operated with very few problems. In terms of communications—in part due to the anticipated installation on the I-74 bridge over the Mississippi River—a hardline digital subscriber line (DSL) internet connection and grid power were used. During operation, this system would transmit data to a central server location where the data would be processed and then archived for future retrieval and use. The pilot monitoring system was developed for general performance evaluation purposes (construction, structural, environmental, etc.) such that it could be easily adapted to the Iowa DOT’s bridges and other monitoring needs. The system was developed allowing easy access to near real-time data in a format usable to Iowa DOT engineers.

Iowa System of Bridge Deck Rehabilitation with Cathodic Protection, HR-1044, 1986

Bridge deck and substructure deterioration due to the corrosive effects of deicing chemicals on reinforcing steel is a problem facing many transportation agencies. The main concern is protection of older bridges with uncoated reinforcing steel. Many different methods have been tried over the past years to repair bridge decks. The Iowa system of bridge deck rehabilitation has proven to be very effective. It consists of scarifying the deck surface, removing any deteriorated concrete, and overlaying with low slump dense concrete. Another rehabilitation method that has emerged is cathodic protection. It has been used for many years in the protection of underground pipelines and in 1973 was first installed on a bridge deck. Cathodic protection works by applying an external source of direct current to the embedded reinforcing steel, thereby changing the electrochemical process of corrosion. The corroding steel, which is anodic, is protected by changing it to a cathodic state. The technology involved in cathodic protection as applied to bridge decks has improved over the last 12 years. One company marketing new technology in cathodic protection systems is Raychem Corporation of Menlo Park, California. Their system utilizes a Ferex anode mesh that distributes the impressed direct current over the deck surface. Ferex mesh was selected because it seemed readily adaptable to the Iowa system of bridge deck rehabilitation. The bridge deck would be scarified, deteriorated concrete removed, Ferex anode mesh installed, and overlaid with low slump dense concrete. The Federal Highway Administration (FHWA) promotes cathodic protection under Demonstration Project No. 34, "Cathodic Protection for Reinforced Concrete Bridge Decks."

Iowa Bridge Backwater Software User Manual, Version 2.0, TR-564, 2010

This manual describes how to use the Iowa Bridge Backwater software. It also documents the methods and equations used for the calculations. The main body describes how to use the software and the appendices cover technical aspects. The Bridge Backwater software performs 5 main tasks: Design Discharge Estimation; Stream Rating Curves; Floodway Encroachment; Bridge Backwater; and Bridge Scour. The intent of this program is to provide a simplified method for analysis of bridge backwater for rural structures located in areas with low flood damage potential. The software is written in Microsoft Visual Basic 6.0. It will run under Windows 95 or newer versions (i.e. Windows 98, NT, 2000, XP and later).

Scour Around Bridge Piers and Abutments, HR-30 and Iowa Highway Research Board Bulletin No. 4, 1956

Man’s never-ending search for better materials and construction methods and for techniques of analysis and design has overcome most of the early difficulties of bridge building. Scour of the stream bed, however, has remained a major cause of bridge failures ever since man learned to place piers and abutments in the stream in order to cross wide rivers. Considering the overall complexity of field conditions, it is not surprising that no generally accepted principles (not even rules of thumb) for the prediction of scour around bridge piers and abutments have evolved from field experience alone. The flow of individual streams exhibits a manifold variation, and great disparity exists among different rivers. The alignment, cross section, discharge, and slope of a stream must all be correlated with the scour phenomenon, and this in turn must be correlated with the characteristics of the bed material ranging from clays and fine silts to gravels and boulders. Finally, the effect of the shape of the obstruction itself-the pier or abutment-must be assessed. Since several of these factors are likely to vary with time to some degree, and since the scour phenomenon as well is inherently unsteady, sorting out the influence of each of the various factors is virtually impossible from field evidence alone. The experimental approach was chosen as the investigative method for this study, but with due recognition of the importance of field measurements and with the realization that the results must be interpreted so as to be compatible with the present-day theories of fluid mechanics and sediment transportation. This approach was chosen because, on the one hand, the factors affecting the scour phenomenon can be controlled in the laboratory to an extent that is not possible in the field, and, on the other hand, the model technique can be used to circumvent the present inadequate understanding of the phenomenon of the movement of sediment by flowing water. In order to obtain optimum results from the laboratory study, the program was arranged at the outset to include a related set of variables in each of several phases into which the whole problem was divided. The phases thus selected were : 1. Geometry of piers and abutments, 2. Hydraulics of the stream, 3. Characteristics of the sediment, 4. Geometry of channel shape and alignment.

Laboratory Investigation of Grouted Coupler Connection Details for ABC Bridge Projects, RB07-013, 2015

With an ever increasing desire to utilize accelerated bridge construction (ABC) techniques, it is becoming critical that bridge designers and contractors have confidence in typical details. The Keg Creek Bridge on US 6 in Iowa was a recent ABC example that utilized connection details that had been utilized elsewhere. The connection details used between the drilled shaft and pier column and between the pier column and the pier cap were details needing evaluation. These connection details utilized grouted couplers that have been tested by others with mixed results—some indicating quality performance and others indicating questionable performance. There was a need to test these couplers to gain an understanding of their performance in likely Iowa details and to understand how their performance might be impacted by different construction processes. The objective of the work was to perform laboratory testing and evaluation of the grouted coupler connection details utilized on precast concrete elements for the Keg Creek Bridge. The Bridge Engineering Center (BEC), with the assistance of the Iowa Department of Transportation (DOT) Office of Bridges and Structures, developed specimens representative of the Keg Creek Bridge connections for testing under static and fatigue loads in the structures laboratory. The specimens were also evaluated for their ability to resist the intrusion of water and chlorides. Evaluation of their performance was made through comparisons with design assumptions and previous research, as well as the physical performance of the coupled connections.

Investigation of Negative Moment Reinforcing in Bridge Decks, TR-660, 2015

Multi-span pre-tensioned pre-stressed concrete beam (PPCB) bridges made continuous usually experience a negative live load moment region over the intermediate supports. Conventional thinking dictates that sufficient reinforcement must be provided in this region to satisfy the strength and serviceability requirements associated with the tensile stresses in the deck. The American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications recommend the negative moment reinforcement (b2 reinforcement) be extended beyond the inflection point. Based upon satisfactory previous performance and judgment, the Iowa Department of Transportation (DOT) Office of Bridges and Structures (OBS) currently terminates b2 reinforcement at 1/8 of the span length. Although the Iowa DOT policy results in approximately 50% shorter b2 reinforcement than the AASHTO LRFD specifications, the Iowa DOT has not experienced any significant deck cracking over the intermediate supports. The primary objective of this project was to investigate the Iowa DOT OBS policy regarding the required amount of b2 reinforcement to provide the continuity over bridge decks. Other parameters, such as termination length, termination pattern, and effects of the secondary moments, were also studied. Live load tests were carried out on five bridges. The data were used to calibrate three-dimensional finite element models of two bridges. Parametric studies were conducted on the bridges with an uncracked deck, a cracked deck, and a cracked deck with a cracked pier diaphragm for live load and shrinkage load. The general conclusions were as follows: -- The parametric study results show that an increased area of the b2 reinforcement slightly reduces the strain over the pier, whereas an increased length and staggered reinforcement pattern slightly reduce the strains of the deck at 1/8 of the span length. -- Finite element modeling results suggest that the transverse field cracks over the pier and at 1/8 of the span length are mainly due to deck shrinkage. -- Bridges with larger skew angles have lower strains over the intermediate supports. -- Secondary moments affect the behavior in the negative moment region. The impact may be significant enough such that no tensile stresses in the deck may be experienced.

Evaluation of the Need for Longitudinal Median Joints in Bridge Decks on Dual Structures, TR-661, 2015

The primary objective of this project was to determine the effect of bridge width on deck cracking in bridges. Other parameters, such as bridge skew, girder spacing and type, abutment type, pier type, and number of bridge spans, were also studied. To achieve the above objectives, one bridge was selected for live-load and long-term testing. The data obtained from both field tests were used to calibrate a three-dimensional (3D) finite element model (FEM). Three different types of loading—live loading, thermal loading, and shrinkage loading—were applied. The predicted crack pattern from the FEM was compared to the crack pattern from bridge inspection results. A parametric study was conducted using the calibrated FEM. The general conclusions/recommendations are as follows: -- Longitudinal and diagonal cracking in the deck near the abutment on an integral abutment bridge is due to the temperature differences between the abutment and the deck. Although not likely to induce cracking, shrinkage of the deck concrete may further exacerbate cracks developed from thermal effects. -- Based upon a limited review of bridges in the Iowa DOT inventory, it appears that, regardless of bridge width, longitudinal and diagonal cracks are prevalent in integral abutment bridges but not in bridges with stub abutments. -- The parametric study results show that bridge width and skew have minimal effect on the strain in the deck bridge resulting from restrained thermal expansion. -- Pier type, girder type, girder spacing, and number of spans also appear to have no influence on the level of restrained thermal expansion strain in the deck near the abutment.

Cell suspension culture and plant regeneration of a Brazilian plantain, cultivar Terra

The objective of this study was to establish cell suspension culture and plant regeneration via somatic embryogenesis of a Brazilian plantain, cultivar Terra Maranhão, AAB. Immature male flowers were used as explant source for generating highly embryogenic cultures 45 days after inoculation, which were used for establishment of cell suspension culture and multiplication of secondary somatic embryos. Five semisolid culture media were tested for differentiation, maturation, somatic embryos germination and for plant regeneration. An average of 558 plants per one milliliter of 5% SCV (settled cell volume) were regenerated in the MS medium, with 11.4 µM indolacetic acid and 2.2 µM 6-benzylaminopurine. Regenerated plants showed a normal development, and no visible somaclonal variation was observed in vitro. It is possible to regenerate plants from cell suspensions of plantain banana cultivar Terra using MS medium supplemented with 11.4 µM of IAA and 2.2 µM of BAP.

Mississippi Drive (Iowa 92) from Main Street to the Norbert F. Beckey Bridge in Muscatine, Iowa, STP-U-5330(614)—27-70, Muscatine County, 2015

The proposed action consists of upgrading Mississippi Drive (Iowa Highway 92) through downtown Muscatine, Iowa. The Mississippi Drive Corridor Project begins south of the Main Street/Grandview Avenue intersection, continuing to the East 2nd Street/Norbert F. Beckey Bridge intersection, which marks the end of the project. It passes through a mix of commercial, residential, Central Business District and industrial land uses. The total length of the project is approximately 1.6 miles, including 19 intersections (6 with traffic signals). Refer to the vicinity map on Figure 1. The current roadway is a 3- to 4-lane, urban facility with both divided and undivided medians. The roadway, ranging from 40 to 64 feet wide, is considered difficult to cross for pedestrians, especially for small children or elderly. The width of this roadway is being considered to be narrowed to improve the accessibility to the downtown from the Mississippi River riverfront area by pedestrians. This project also includes accommodations for bicycles and pedestrians and measures to reduce flooding on the roadway.

Evaluation of Post-Tension Strengthened Steel Girder Bridge Using FRP Bars, 2003

Many state, county, and local agencies are faced with deteriorating bridge infrastructure composed of a large percentage of relatively short to medium span bridges. In many cases, these older structures are rolled or welded longitudinal steel stringers acting compositely with a reinforced concrete deck. Most of these bridges, although still in service, need some level of strengthening due to increases in legal live loads or loss of capacity due to deterioration. Although these bridges are overstressed in most instances, they do not warrant replacement; thus, structurally efficient but cost-effective means of strengthening needs to be employed. In the past, the use of bolted steel cover plates or angles was a common retrofit option for strengthening such bridges. However, the time and labor involved to attach such a strengthening system can sometimes be prohibitive. This project was funded through the Federal Highway Administration’s Innovative Bridge Research and Construction program. The goal is to retrofit an existing structurally deficient, three-span continuous steel stringer bridge using an innovative technique that involves the application of post-tensioning forces; the post-tensioning forces were applied using fiber reinforced polymer post-tensioning bars. When compared to other strengthening methods, the use of carbon fiber reinforced polymer composite materials is very appealing in that they are highly resistant to corrosion, have a low weight, and have a high tensile strength. Before the post-tensioning system was installed, a diagnostic load test was conducted on the subject bridge to establish a baseline behavior of the unstrengthened bridge. During the process of installing the post-tensioning hardware and stressing the system, both the bridge and the post-tensioning system were monitored. The installation of the hardware was followed by a follow-up diagnostic load test to assess the effectiveness of the post-tensioning strengthening system. Additional load tests were performed over a period of two years to identify any changes in the strengthening system with time. Laboratory testing of several typical carbon fiber reinforced polymer bar specimens was also conducted to more thoroughly understand their behavior. This report documents the design, installation, and field testing of the strengthening system and bridge.