A Cost-Effective Integral Bridge System with Precast Concrete I-Girders for Seismic Application

To promote accelerated bridge construction in seismic regions, a large-scale experimental investigation was conducted to examine the seismic sufficiency of precast concrete I-girders in integral bridge super-structures. Such structures are not frequently used in high seismic regions due to lack of design guides and overly conservative design approaches. A half-scale,17.8 m (58.5 ft) long test unit modeling a portion of a prototype bridge incorporating a concrete column, ten I-shaped precast concrete girders, and an inverted-tee concrete cap beam was used to experimentally verify that precast concrete members employing accelerated construction techniques can be used in integral super-structures and provide excellent seismic performance. Comparison of an as-built girder-to-cap connection detail with an improved detail shows that the as-built detail in existing bridges will satisfactorily resist positive and negative seismic moments and allow plastic hinges to develop at the column tops, though this was not the original design intent. However, the improved detail, which exhibited excellent seismic moment resistance, is recommended for new bridges to avoid potential deterioration of the girder-to-cap connection

A cost-effective integral bridge system with precast concrete I-girders for seismic application

To promote accelerated bridge construction in seismic regions, a large-scale experimental investigation was conducted to examine the seismic sufficiency of precast concrete I-girders in integral bridge superstructures. Such structures are not frequently used in high seismic regions due to lack of design guides and overly conservative design approaches. A half-scale, 17.8 m (58.5 ft) long test unit modeling a portion of a prototype bridge incorporating a concrete column, ten I-shaped precast concrete girders, and an inverted-tee concrete cap beam was used to experimentally verify that precast concrete members employing accelerated construction techniques can be used in integral superstructures and provide excellent seismic performance. Comparison of an as-built girder-to-cap connection detail with an improved detail shows that the as-built detail in existing bridges will satisfactorily resist positive and negative seismic moments and allow plastic hinges to develop at the column tops, though this was not the original design intent. However, the improved detail, which exhibited excellent seismic moment resistance, is recommended for new bridges to avoid potential deterioration of the girder-to-cap connection

Section, Member and System Level Analyses for Precast Concrete Hybrid Frames

This report presents the research conducted as part of an investigation for the California Department of Transportation (Caltrans) regarding the seismic response and overall moment capacity of precast I-girder to inverted-T bent cap bridge connections for seismic applications. The current design practice, as outlined by Caltrans’ Seismic Design Criteria, assumes that the connection between the precast I-girders and the inverted-T bent cap will degrade in a seismic event and shall therefore be designed as a pinned connection, making the precast girder option for seismic bridges inefficient. A prototype I-girder to inverted-T bent cap bridge and a 50% scale test unit was designed in order to investigate the behavior of the as-built girder-to-cap connection region. Additionally, per the request of Caltrans, an improved girder-to-cap connection detail was developed in order to ensure a fully continuous moment connection between the I-girders and inverted-T bent cap. A finite element grillage model was developed using ABAQUS and SAP2000 and was used to predict the global and local responses of various aspects of the test unit. The test unit was constructed and tested in two phases of quasi-static cyclic testing. The first phase was a horizontal load test phase, which simulated the effects of gravity and seismic loads on the entire test unit. The second phase was a vertical load test phase, which specifically focused on the positive and negative moment capacity of the connections. Both the results of the finite element grillage model and the testing were used to make conclusions regarding the performance of Igirder to inverted-T bent cap bridges. It was concluded that the current I-girder to inverted-T bent cap bridge connection is capable of acting as a fully continuous connection for both positive and negative moments during both gravity and seismic loading, contrary to the design assumptions stated in Caltrans’ Seismic Design Criteria. The improved connection detail demonstrated the ability to ensure a fully continuous moment connection between the I-girders and inverted-T bent cap. Both connection details also exhibited a significant moment resistance beyond what was expected during the vertical load test although the as-built connection eventually failed under positive moments at moderate to large displacements

Seismic Performance of an I-Girder to Inverted-T Bent Cap Connection

This report presents the research conducted as part of an investigation for the California Department of Transportation (Caltrans) regarding the seismic response and overall moment capacity of precast I-girder to inverted-T bent cap bridge connections for seismic applications. The current design practice, as outlined by Caltrans’ Seismic Design Criteria, assumes that the connection between the precast I-girders and the inverted-T bent cap will degrade in a seismic event and shall therefore be designed as a pinned connection, making the precast girder option for seismic bridges inefficient. A prototype I-girder to inverted-T bent cap bridge and a 50% scale test unit was designed in order to investigate the behavior of the as-built girder-to-cap connection region. Additionally, per the request of Caltrans, an improved girder-to-cap connection detail was developed in order to ensure a fully continuous moment connection between the I-girders and inverted-T bent cap

A cost-effective integral bridge system with precast concrete I-girders for seismic application

To promote accelerated bridge construction in seismic regions, a large-scale experimental investigation was conducted to examine the seismic sufficiency of precast concrete I-girders in integral bridge superstructures. Such structures are not frequently used in high seismic regions due to lack of design guides and overly conservative design approaches. A half-scale, 17.8 m (58.5 ft) long test unit modeling a portion of a prototype bridge incorporating a concrete column, ten I-shaped precast concrete girders, and an inverted-tee concrete cap beam was used to experimentally verify that precast concrete members employing accelerated construction techniques can be used in integral superstructures and provide excellent seismic performance. Comparison of an as-built girder-to-cap connection detail with an improved detail shows that the as-built detail in existing bridges will satisfactorily resist positive and negative seismic moments and allow plastic hinges to develop at the column tops, though this was not the original design intent. However, the improved detail, which exhibited excellent seismic moment resistance, is recommended for new bridges to avoid potential deterioration of the girder-to-cap connection.This article was published as Vander Werff, J., Snyder, R., Sritharan, S., Holombo, J. 2015. A Cost-Effective Integral Bridge System with Precast I-Girders for Seismic Application. PCI Journal 60 (5) 76 - 95. Posted with permission.</p

Mirtazapine-Induced Pancreatitis—A Case Report

Acute pancreatitis has numerous etiologies, with the most common including gallstones, alcohol abuse, and medications such as angiotensin-converting enzyme (ACE) inhibitors, statins, and diuretics. Mirtazapine has been associated with increased serum cholesterol and serum triglyceride levels. However, few studies have reported dangerously elevated triglyceride levels resulting in acute pancreatitis. This report discusses a case of mirtazapine-induced pancreatitis in a 46-year-old African American female. The patient presented to the emergency department with pancreatitis, presumably alcohol-induced as with a prior admission, but she denied any recent alcohol use. Mirtazapine then became the suspected cause of her hypertriglyceridemia-induced pancreatitis and was discontinued. After discontinuing mirtazapine, and utilizing an insulin infusion, her triglyceride levels normalized and symptoms of pancreatitis resolved. Using the Naranjo Adverse Drug Reaction Probability Scale, a total score of 5 was calculated indicating a probable adverse drug reaction of acute pancreatitis from mirtazapine. </jats:p