Eric P. Steinberg

Structural Reliability of Prestressed UHPC Flexure Models for Bridge Girders

Ultrahigh performance concrete (UHPC) has been used in several bridges and other structures throughout the world and is beginning to gain more exposure in the United States. For UHPC to continue to gain acceptance for bridge design in the United States, design specifications and procedures must be established for bridge engineers to utilize. The flexural behavior at the ultimate limit state for an UHPC girder is still a significant design concern. Therefore, this research examined three analytical approaches to evaluate the ultimate flexural strength of UHPC girders. In addition, Monte Carlo simulations were performed to account for the variability of several parameters and to determine reliability indices using the three analytical methods. The analysis results show that using typical AASHTO procedures, acceptable levels of reliability can be achieved while allowing the use of familiar and noncomplex equations.

Interfacial Properties of Ultrahigh-Performance Concrete and High-Strength Concrete Bridge Connections

AbstractRecently, ultra-high performance concrete (UHPC) has been utilized in highway bridge connections, where its superior strength and durability help to reduce joint cracking and enhance transverse load transfer. According to the load and resistance factor design (LRFD) bridge design procedure specified by AASHTO, the strength of the connections is dependent on the adhesion and friction between the connected materials. The objective of the present research is to identify the adhesion value between UHPC and high-strength concrete (HSC) with varying degrees of roughness. To this end, UHPC-HSC specimens were tested in direct tension according to ASTM protocols, and the maximum tensile stress at failure was obtained. Test results show that the average maximum tensile stress for the UHPC-HSC specimens with a smooth interface exceeds that determined from past research for any degree of roughness. Furthermore, the average maximum tensile stress increases with the degree of roughness. The results from the dir...

Modeling and Validation of a Passive Resettable Stiffness Damper

AbstractThe resetting semiactive stiffness damper (RSASD) has been shown to be effective at controlling vibrations in civil structures in the presence of near-field earthquakes. Although it has the advantages of being mechanically simple and relatively inexpensive, the RSASD requires a multicomponent feedback control system consisting of sensors, a microcontroller, a servo valve, and a battery to operate, rendering it less reliable during a seismic event. In the present work, the resetting passive stiffness damper (RPSD) is presented as an improvement to the RSASD, whereby the RSASD feedback control system is replaced by a novel mechanism to achieve resetting of the damper force. The results of laboratory studies on a small-scale RPSD demonstrate that the resetting mechanism performs as proposed. Results of numerical simulations performed for a five-story base-isolated building subject to four benchmark earthquakes indicate that the RPSD is capable of a similar control performance as the RSASD. Furthermor...

Damage Identification for Prestressed Adjacent Box-Beam Bridges

Structural health monitoring (SHM) has gained considerable attention as a tool for monitoring the health of civil infrastructure. For bridge infrastructure, previous methods have focused on the detection of localized damage through modal parameters extracted from the longitudinal direction of the structure. This paper investigates a new damage detection method based on the change in the first vertical mode extracted from the transverse direction of the bridge. The mode is determined through application of modal curve fitting to frequency response functions (FRFs) that are formed using vertical response data obtained in the direction perpendicular to the bridge’s longitudinal axis. Using this method, both local damage and global damage in the bridge reveal themselves as having a localized effect on the bridge response. Furthermore, damage is revealed in such a way that it enables differentiation of the damage types. To demonstrate the effectiveness of the method, modal parameters were extracted from acceleration data obtained from a finite element model of a full bridge. Analysis of the modal parameters showed that the proposed approach could not only detect both local and global bridge damage, but could also differentiate between damage types using only one mode shape. The proposed method was compared to a previously developed SHM method.

Reliability analyses of meteoroid loading on lunar structures

Abstract A distribution for the mass of the meteoroids is developed from flux equations assuming a homogeneous filtered Poisson process. Other random variable information required for analyses are derived from data or taken from literature. First-order, second-moment reliability analyses are performed for complete penetration of a meteoroid through exposed and covered lunar structures. Several failure functions are used to model this high speed impact event. Cumulative damage by meteoroid impacts to a radiation cover and an exposed structure are also examined. The results show cumulative damage may be a problem for structures with long design lives.

Evaluation of Transverse Tie Rods in a 50-Year-Old Adjacent Prestressed Concrete Box Beam Bridge

AbstractAdjacent prestressed concrete box beam bridges are one of the most popular bridges in the United States for short to medium spans. Recently, there has been concern about the structural capacity of these bridges as they age and show signs of deterioration. Unfortunately, limited research has been performed on the transverse ties because they are typically used for pulling the adjacent beam together during construction. Therefore, they are typically neglected in the overall performance of the bridge. Little, if any, information is known of the behavior and contribution of the transverse ties to load transfer and the ultimate capacity after failure of the longitudinal shear key joints. Instrumenting installed transverse tie rods has not been done in the past due to difficultly in accessing the rods, and no technique has been established to perform the installation of a sensor in the tie rods. In addition, instrumenting a tie rod that has already been installed from the fascia beam would only allow th...

Early-Age Behavior of an Adjacent Prestressed Concrete Box-Beam Bridge Containing UHPC Shear Keys with Transverse Dowels

AbstractAdjacent precast prestressed concrete box-beam bridges have been used in the United States for many years and have performed well. However, the shear keys between adjacent box beams are sus...

Evaluation of revised details of end zone of the prestressed concrete I-girders using finite element method

Abstract Prestressed concrete I-girders are becoming more widely used in bridges. However, the high prestressing force applied to these girders can lead to cracks in the end zone upon stress transfer. Recently, the standard drawing details for prestressed concrete I-girders were modified by the Ohio Department of Transportation (ODOT). The primary difference in the new drawings is the reinforcement details and usage of welded wire reinforcement at the end of the girders. In order to evaluate end cracking performance resulting from changes to the ODOT standard drawings, girders with various end reinforcement configurations were analysed using linear and non-linear finite element models. The strains and stresses at the end zone in the concrete and rebar were then evaluated. The non-linear finite element models were verified using available experimental data. After verification, the non-linear models were used to identify the location of the end zone cracks observed in the girders. The verified model was used to evaluate the revised details of end zone region. The results show that the modified details in the standard drawings meet the requirements of the AASHTO LRFD design specification. In addition, the end zone strains in the concrete and stresses in the reinforcement were reduced.

Laboratory Evaluation of Ultrahigh-Performance Concrete Shear Key for Prestressed Adjacent Precast Concrete Box Girder Bridges

AbstractPrecast adjacent box girder bridges have become a preferred solution in several states due to their simple structure, economy, and ease of construction. However, longitudinal cracks often appear along the shear keys between adjacent box girders. With its superior strength and durability, ultrahigh-performance concrete (UHPC) has been used as an alternative grout material to reduce shear key cracking and enhance load transfer. The objective of the present research was to evaluate the performance of UHPC in shear keys using direct shear, direct tension, and flexural tests. Also, this study determined the effectiveness and functionality of shear reinforcement bars by applying direct shear load on specimens with shear reinforcement. In the direct shear test, a steel frame was placed around the specimens to allow the shear key to experience pure shear force. The direct shear test established the cracking threshold and ultimate shear strength of each shear key with and without shear reinforcement bars. ...

Field Study of Ohio’s Structural Support Inspection Program for Overhead Signs, Traffic Signals, and High-Mast Lights

The Ohio Department of Transportation (DOT) undertook a field study to evaluate its overall structural inspection programs for overhead sign supports (including those mounted on bridges), high-mast light supports, and traffic signal supports. This paper describes the Ohio DOT’s current support inspection program, the field study performed, and the recommendations that resulted from the field study. This research evaluated the adequacy and frequency of the current structural support inspection program for the studied supports. To assess the current program, a detailed, hands-on inspection was conducted on 202 supports. The results were then compared with the Ohio DOT’s current ground-based, visual inspection process. The hands-on inspection process found almost 87% more deficiencies; some deficiencies detected during the hands-on inspections could not have been observed from the ground. In addition, the different inspection procedures used by each district often produced inspection reports that varied in the amount of information and level of details collected during inspection. Recommendations were made to address the inventory process and inspection procedures for each type of support. A long-term goal should be to establish the current structural adequacy of every support in the Ohio DOT’s inventory at the time of inspection.