Daniel G. Linzell

Nonlinear Seismic Response and Parametric Examination of Horizontally Curved Steel Bridges Using 3D Computational Models

AbstractThe seismic behavior of horizontally curved steel bridges is more complex than straight bridges because of their curvature and other parameters. Studies that attempt to develop methods to efficiently predict their seismic response have been somewhat limited to date. A computational modeling approach was examined to assist with understanding the seismic behavior of these bridges. The computational, three-dimensional (3D) bridge models consisting of the concrete deck, steel girders, cross-frames, pier columns and caps, and abutments and footings were created in OpenSees and examined for accuracy via application to a representative, three-span continuous curved steel plate girder bridge in Pennsylvania. Sensitivity studies in the form of tornado analyses were also carried out to investigate the influence of critical curved bridge parameters on the seismic response using a group of representative bridges. Each representative bridge was subjected to an ensemble of synthetic ground motions, and seismic ...

Cross-frame and lateral bracing influence on curved steel bridge free vibration response

Abstract Accurately quantifying the free vibration response of curved steel bridges has been a topic of interest for researchers and practitioners. This study examines the response of an experimental, single-span, noncomposite, curved I-girder bridge superstructure during free vibration. Finite element models of the experimental bridge system, which was tested for the FHWA Curved Steel Bridge Research Project (CSBRP), were constructed and calibrated against experimental data from dynamic investigations of the bridge by the Virginia Transportation Research Center (VTRC). Parametric studies of the experimental curved bridge system were conducted using these finite element models to investigate the effects of cross-frame and lateral bracing parameters on the structure’s free vibration response.

Effectiveness of Advanced Coating Systems for Mitigating Blast Effects on Steel Components

This work aimed to study the effectiveness of an advanced coating material, polyurea, as a blast mitigation tool for steel components. The response of polyurea-coated steel components under blast loads is studied using the explicit LS-DYNA code with appropriate loading time histories supplied by a computational fluid dynamics code developed at the Pennsylvania State University, PUMA2 (Parallel Unstructured Maritime Aerodynamics-2). Results presented from this ongoing research study are related to an application of polyurea onto armor grade steel plates and an examination of resulting failure modes and governing design parameters. Failure modes examined herein consist of fracturing in the polyurea/steel composite structure. Effects of thicknesses and locations of the polyurea on the blast mitigation are also studied. Explanations of selected strain-rate dependent material models for the steel and polyurea are provided. CFD blast simulations using PUMA2 are described and validated. Results obtained from numerical studies completed to date show that bare steel plates undergo severe fracturing and fragmentation under prescribed blast loads while polyurea coated plates are able to sustain prescribed pressures without fully fracturing.

EXAMINATION OF RESPONSE OF A SKEWED STEEL BRIDGE SUPERSTRUCTURE DURING DECK PLACEMENT

The response of a 74.45-m (244-ft 0-in.) skewed bridge to the placement of the concrete deck was monitored to compare measured and predicted behavior. This comparison was completed to (a) determine theoretical deflections and rotations with analytical models for comparison to actual deformations monitored during construction; (b) compare the results of various levels of analysis to determine the adequacy of the methods; and (c) examine variations on the concrete placement sequence to determine the most efficient deck placement methods. Two levels of analysis were used to achieve the objectives. Level 1 was a two-dimensional finite element grillage model analyzed with STAAD/Pro. Level 2 was a three-dimensional finite element model analyzed with SAP2000. These studies are discussed and findings are presented.

Probabilistic Vulnerability Scenarios for Horizontally Curved Steel I-Girder Bridges Under Earthquake Loads

Horizontally curved steel I-girder bridges are located in all seismic zones in the United States. Research has shown that damage can occur to steel bridge components under earthquake loads. Probabilistic-based techniques are one tool that can be used to assess more accurately the seismic vulnerability of curved bridges for various damage states and at various seismic hazard levels. To examine probabilistic-based vulnerability criteria efficiently, the study used response surface metamodels (RSMs) in conjunction with Monte Carlo simulations to generate horizontally curved steel I-girder bridge fragility curves. The generated curves were then used to evaluate bridge damage in terms of previously published structure damage states. The use of RSMs reduces the required number of computer simulations needed to generate the fragility curves. The paper summarizes the fragility curve generation procedure for a group of horizontally curved steel I-girder bridges using RSMs in association with Monte Carlo simulation. Probabilistic vulnerability scenarios are presented via application to existing horizontally curved steel bridges located in Pennsylvania, New York, and Maryland to estimate seismic demands for those bridges and to generate fragility curves.

Design and Field Monitoring of Horizontally Curved Steel Plate Girder Bridge

Bridge 207 is a two-span horizontally curved steel plate girder bridge near Port Matilda, Pennsylvania. Although the curvature is not severe, the curvature combined with the unequal span balance caused an unusual distribution of force effects in the girders. A global twisting of the superstructure was caused by the unequal vertical deflections in the two spans. The computer program BSDI-3D was used to analyze the curved superstructure. To account for the out-of-plumb condition of the girders in their final condition, additional lateral flange bending moments were calculated. The magnitude of the additional lateral moments was a function of the vertical bending moments and the degree of twist in the girder. Field monitoring of the structure is focusing on the effects of curvature during construction. This is being accomplished by developing a detailed time line of superstructure erection and deck placement and through monitoring of the bridge by using vibrating wire strain gauges and tiltmeters positioned at critical locations on the girders and cross-frames. Field data were recorded before and after critical construction events, such as girder erection, cross-frame and formwork placement, and the deck pour. This information is being used to determine the effects of curvature on the cross-frames during construction by using axial stresses and strains and on the girders by using warping stresses and strains.

Field Tests and Numerical Modeling of Vehicle Impacts on a Boulder Embedded in Compacted Fill

Landscape Vehicular Anti-Ram (LVAR) systems are a group of protective barriers, which are designed using natural materials (e.g., boulders) and have proven to both effectively protect sensitive structures against threats and be aesthetically pleasing. This paper presents two consecutive vehicular crash tests hitting the same single boulder embedded in AASHTO coarse aggregate fill. A LS-DYNA model was developed to simulate the field-scale tests, which were instrumented with high-speed cameras and pressure cells. A readily available truck model from the National Crash Analysis Center was modified and implemented in the LS-DYNA model. The boulder and surrounding soil were modeled using the Mohr-Coulomb failure criteria. The model parameters were calibrated using results from the first field-scale test with a truck traveling at 48.3 km/hr (30 mph) impacting the LVAR system. The calibrated model was then used to simulate the second field-scale test, which involved a truck traveling at 80.5 km/hr (50 mph) impacting the same LVAR system without resetting the boulder or soil. The calibrated model was able to provide the global response of the system, including the time-history of the translational displacement and rotation of the boulder, and was in good agreement with field-scale test results. This suggests that the overall global response was dominated by the dynamic behavior of the truck and boulder system upon impact. Hence, a simple material model for soil and boulder is sufficient for simulating the tests conducted.

Optimization of Design Details in Orthotropic Steel Decks Subjected to Static and Fatigue Loads

In recent decades, orthotropic steel decks (OSDs) have been routinely incorporated into long-span bridges. The most widely used method to reduce stress concentration, improve fatigue performance, and control crack propagation is to cut out the diaphragms (or subfloor beams) into which the OSDs frame. However, the capital cost of cutout fabrication in the United States is high and may not be economically feasible. Study is required of cost-effective modified design details without cutouts as well as comparisons with their corresponding flexural and fatigue performance against current design details that use cutouts. Alternative design details (e.g., deck ribs welded directly to the transverse diaphragms using full-penetration welds) with thicker deck plates, but without cutouts, were investigated for potential improvements in fatigue resistance and capital cost. A parametric study was conducted with calibrated finite element models of a portion of the Bronx–Whitestone Bridge in New York City to study the effects of cutouts, deck plate thickness, and other important parameters on fatigue performance. Various traffic load combinations and truck types were considered with the use of an elaborate weigh-in-motion database. Results detail the equivalent stress ranges at critical locations in the OSDs that were calculated to quantitatively estimate fatigue lives for two OSD models: one with cutouts and one without. On the basis of these comparisons, recommendations related to overall structural performance were made to ensure a safe and rational design for various OSD options in long-span bridges.

Optimizing Horizontally Curved, Steel Bridge, Cross-Frame Arrangements to Enhance Construction Performance

AbstractUnlike straight bridges where cross frames and diaphragms are considered secondary members that predominantly stabilize the compression zones of noncomposite girders during construction, the interaction of bending and torsion in horizontally curved, steel, I-girder bridges renders these components primary load-carrying members. The effect of curvature on horizontally curved bridge behavior has been shown to be more critical during construction owing to a lack of a large, hardened, concrete deck that helps to stiffen and stabilize the entire system. Therefore, cross frames play important roles with respect to stabilizing the girders and distributing loads in curved bridges during construction. This work examined the effects of a bracing system that involved skewing cross frames relative to a normal to the girder’s web, termed skewed cross frames, on the construction behavior of horizontally curved, I-girder bridges having radially oriented substructure units (abutments and piers). The performance o...

Effect of Temporary Shoring Location on Horizontally Curved Steel I-Girder Bridges during Construction

Temporary shoring supports are used in construction of horizontally curved bridges to help ensure that the final constructed geometry is maintained by mitigating excessive girder deformations. Limited guidance currently exists in available design specifications and guidelines with respect to optimal placement of shoring towers because the number and locations of these supports are often site specific. However, if preliminary information could be provided to bridge designers and constructors with respect to shoring tower placement as a function of global curved bridge parameters, such as number of spans and radius of curvature, the amount of time required to specifically locate and proportion the towers could be reduced. This research aimed to examine the effects of shoring tower positioning on curved bridge behavior at different stages of construction. Sequential analyses of multiple idealized double-span curved bridges with varying radii were conducted using nonlinear finite-element models and vertical deformations and rotations of the girders, and shoring tower reactions were compared for different shoring support locations and different erection sequences. On the basis of the results, optimal shoring locations were obtained for the curved girders at different construction stages.