Investigation of Reinforced Concrete Bridge Substructures under Extreme Flood Hazards
Presented By: Amir Gheitasi
Affiliation: WSP USA
Description: Minnesota Department of Transportation (MnDOT) tasked WSP to provide engineering
services for inspection and evaluation of series of pier caps on approach spans of two
sister bridges that carry Trunk Highway (TH) 77 bridge over the Minnesota River. These pier
caps were relatively shallow supported on two rectangular columns. The initial load rating
analysis performed using traditional Strut-and-Tie Method (STM) resulted in poor ratings
(given the geometrical restraints for STM analysis set forth by AASHTO LRFD (i.e., minimum
angle between struts and ties). The sectional method gave better results, but it was still
unsatisfactory to pass shear.
The WSP team developed a full 3D Finite Element modeling framework for these caps that
leveraged solid elements to simulate concrete and discrete modeling of all internal
reinforcement. Based on observed state of stresses in the as-designed model, cracks were
then introduced into the model to approximate the state of non-linearity. Presence of these
discontinuities in the concrete continuum allowed for development of a realistic stress
field and shear transfer mechanism within concrete by e6ectively engaging internal
reinforcement. The refined analysis indicated presence of a viable load path through
evaluation of 3D state of stresses, which resulted in satisfactory shear load ratings
according to LRFR methodology.
Investigation of Reinforced Concrete Bridge Substructures under Extreme Flood Hazards
Presented By: Tahereh Torabi
Affiliation: Iowa State University
Description: Floods pose a significant threat to the safety and functionality of reinforced concrete (RC) bridge structures, causing severe damage or collapse. This study focuses on the RC bridge substructures, evaluating their structural response under extreme flood hazards. Refined intensity measures (IMs), with emphasis on hydraulic loading and scour-induced foundation instability, are incorporated to assess system vulnerability. A modeling framework is introduced to capture the response of various RC bridge substructures across a set of representative flood scenarios, integrating nonlinear soil–structure interaction and component-level details. Engineering demand parameters, such as pier ductility, drift, settlement, stress, and pile stability, are employed to quantify performance and define damage states over a range of hazard intensities. The results highlight the urgent need to update current RC bridge risk assessment frameworks to explicitly address service life hazards, thereby advancing resilient design practices.
Influence of Elastomeric Bearing Pads on the Rollover Stability of Prestressed Concrete Bridge Girders
Presented By: Matthew Whelan
Affiliation: University of North Carolina At Charlotte
Description: Elastomeric bearings are widely used to support prestressed concrete bridge girders during handling, transportation, and erection. Although widely used in bridge construction, their influence on girder behavior during temporary support stages is often underestimated or omitted from current design methodologies. This study investigates the influence of elastomeric bearing deformation on the rollover response of girders with geometric imperfections such as horizontal sweep. A detailed three-dimensional nonlinear finite element (FE) model is developed to simulate girder–bearing interaction, incorporating geometric and material nonlinearity, concrete and elastomer behavior, and compression-only contact at the support interface. The model is validated using published full-scale rollover test data from a BT-54 bulb-tee girder with initial sweep subjected to vertical midspan loading. Results highlight that bearing deformation significantly alters boundary conditions, affecting rotation and lateral displacement at critical stages. These effects are typically neglected in conventional analytical approaches, which rely on idealized supports and may lead to inaccurate rollover predictions. The validated model provides a platform for future parametric studies on the combined influence of bearing response, sweep magnitude, and girder geometry. The findings support more accurate safety assessments and refined design recommendations to reduce rollover risk during bridge construction.
Large-Scale Precast Prestressed Concrete Bent Cap Design Program
Presented By: Nestor Rubiano
Affiliation: Decon LLC
Description: A 20-mile elevated highway design-build project required the design of hundreds of bridge
piers to support prestressed precast concrete girder simple spans. A considerable number
of caps were hammerheads, mostly concentric. All hammerhead caps had rectangular
cross sections, constant width, and variable depth on both sides of the column. To lower
construction costs and reduce construction time, the contractor proposed the use of
precast prestressed concrete caps as an alternative to conventionally reinforced cast-inplace
concrete caps. A direct, well-organized, and highly automated design method was
developed to consider all stages of construction (fabrication, transportation, and erection)
and operation, including long-term e=ects.
Typical materials were used for design including Grade 270 low-relaxation 0.6-in strands,
Grade 60 reinforcing steel and high strength concrete with 28-day strength of up to 8.5 ksi.
Material behavior included time-dependent models and prestressing losses.
Program Midas Civil and Excel spreadsheets were used for the structural analysis and
design of the piers. Midas APIs were used to automate model creation, analysis and design
data extraction, as well as to post-process the results. Advanced analyses were needed to
evaluate stress concentrations at utility openings and column connections. Validation of
short- and long-term vertical deflections helped the accurate definition of girder bearing
support elevations, girder camber, and girder haunch thickness.
BIM models of the caps were created to ensure accurate reinforcement detailing and to
confirm the constructability of precast caps by considering the prestressed and nonprestressed
reinforcement, column connections, utility lines, and other elements required
in the caps.
Development of a Precast Column Solution Using Precast Prestressed Concrete Piles Filled with Cast-In-Place Concrete
Presented By: Emmanuel Montero Carvajal
Affiliation: The University of Texas At Austin
Description: A novel construction method utilizing Precast Prestressed Concrete Piles (PCP) filled with concrete
cast-in-place, working as one complete column to evaluate their structural performance under
varying levels of eccentricity, is presented with the goal of introducing a new precast column system.
A control specimen was constructed cast-in-place following traditional methods according to current
bridge design standards and tested, establishing a baseline for comparison. The specimens built
according to the proposed construction methodology were designed to investigate the effects of the
internal roughness of the precast elements (PCP) and the embedment length for the connectors to the
foundation and the bent cap. The specimens underwent testing using the same procedures as the
control specimen to evaluate their performance and the influential factors. Test results indicated that
precast specimens with a sufficiently long embedment length exhibited performance comparable to
the control specimen, despite differences in internal roughness among the specimens. Conversely,
precast columns featuring an intentionally roughened interior and a shorter embedment length
displayed a decrease in load-carrying capacity. A composite section was achieved between the PCP
and the cast-in-place core without employing shear connectors, resulting in a satisfactory noncontact
splice of the connectors in the core and prestressed strands in the pile section.
From Design Manual to Field Reality: Integrating Curved Geometry, Micropiles, and Staged Construction in Substructure Design
Presented By: Anjan Babu
Affiliation: Auburn University
Description: The replacement of the Route 8 Bridge over the Mayo River in Patrick County, Virginia, required substructure innovations that extended beyond conventional VDOT and AASHTO practice. The project replaced a straight, two-lane bridge with a wider (40'-6"), curved, jointless concrete bridge constructed in stages while maintaining traffic and pedestrian access. The substructure system—comprising conventional cantilever abutments with deck extensions, a wall-type pier, and micropile foundations—was developed to balance curved geometry, environmental sensitivity, and constructability within a confined, remote site.
Analytical refinements addressed micropile group behavior under eccentric and unbalanced loads, interaction between non-parallel superstructure elements and jointless abutments, and vibration control during phased demolition adjacent to existing retaining walls and utilities.
This case study demonstrates how collaborative, performance-based refinement of standard substructure guidance can achieve constructability, resilience, and minimal environmental impact in complex bridge geometries. The resulting framework translates design manuals into practical, field-proven strategies for future curved, staged, and micropile-supported concrete bridges.
Design of Footing Hybrid Socket Connection for Innovative Hollow-Core Bridge Columns
Presented By: Mohanad Abdulazeez
Affiliation: University of Missouri - Kansas City
Description: To promote the development of Accelerated Bridge Construction (ABC) in high-seismic areas,
this study explores an innovative prefabricated column-to-footing socket connection aimed at
enhancing resiliency, ease of construction, and cost-effectiveness. The socket connection utilizes
hollow-core fiber-reinforced polymer (FRP)-concrete-steel (HC-FCS) columns with embedded
corrugated steel pipes (CSPs). The composite HC-FCS column consists of a concrete shell
sandwiched between an outer FRP tube and an inner steel tube. The inner steel tube is embedded
in the footing connection of the HC-FCS column. The same authors tested the innovative socket
connection experimentally on a large HC-FCS column under seismic loads, showing high ductility,
strong moment and drift capacities, and promising potential for future design use. Building on
previous experimental findings that demonstrated excellent seismic performance, this study
employs finite element (FE) modeling in LS-DYNA to conduct a parametric analysis of 51 largescale
column-to-footing connections. The FE models were used to critically assess the effect of
seven parameters on the seismic behavior of such a novel column-to-footing connection.
Consequently, design equations based on mechanical analysis of a simplified strut-and-tie model
were proposed to determine the essential characteristics of the CSP in HC-FCS column-to-footing
connections for practical implementation.