Wednesday, June 12, 2019
Time: 1:30 – 3:30 PM
Session Chair: Pat Kane
This Session presents three research studies and one bridge design. First are live load responses on seismic modelling of a simply-supported bridge. Second is mass redistribution in the superstructure of irregular bridges to address seismic response. Third is seismic loading and design for concrete filled steel tubes. Finally, is a seismic design for a bridge with integral abutment piles.
IBC 19-69: Novel Approach towards Improving the Seismic Response of Irregular Bridges: Tuned Structures
Samantha Chaudhari and Max Stephens, University of Pittsburgh, Pittsburgh, PA
Irregular bridge structures (e.g. bridges with large skew or bent-to-bent stiffness irregularities) are susceptible to greater damage from seismic loading due to increased displacement demands resulting from torsional effects. Current codes governing the design of bridges recognize the vulnerability of these structures, and impose stricter standards to improve performance, however these provisions have not always been effective in controlling deformations and reducing damage. To improve the seismic performance of irregular bridge structures, this research is focused on the concept of structural tuning, where the dynamic characteristics of irregular bridges are strategically modified to produce an aggregate behavior free of damaging irregular modes of response. First, practical methods to modify the dynamic characteristics of irregular bridges were identified. Two methods are introduced here including (1) strategic mass redistribution in the superstructure and (2) bent stiffness modification using post-tensioning and/or plastic hinge relocation. These methods were selected because they can be implemented without significantly altering the global geometry or column strengths. Next, two irregular case study bridges were re-designed using the aforementioned tuning methodologies; one with large skew and one with large variations in bent stiffness. Finally, validated modeling procedures were implemented in the opensource structural analysis software OpenSees to evaluate the seismic performance of the original and tuned case-study structures. Results from the numerical evaluation indicate that the structural tuning methodologies introduced here eliminate lateral responses dominated by irregular modes and result in decreases in overall bent drifts.
IBC 19-70: Repair of CFST Bridge Columns Subjected to Seismic Loading
James Bumstead and Max Stephens, University of Pittsburgh, Pittsburgh, PA
Concrete filled steel tubes (CFST) are frequently more efficient and economical than conventional reinforced concrete (RC) and/or structural steel in highway bridge construction. Recent research has resulted in practical and structurally robust connections between CFST columns and precast concrete sub and superstructure elements to facilitate accelerated bridge construction in moderate and high seismic regions. One such connection, referred to as the embedded ring (ER) connection, is a fully restrained, full-strength moment resisting connection which relies on an annular ring, welded to the end of the steel tube and embedded in the cap beam or foundation, to transfer forces from the CFST into the surrounding concrete. The readily identifiable damage state of the ER connection along with the accessibility to the steel tube provides a unique opportunity for repair which is more difficult in RC columns. That is the focus of this paper. Three practical repair strategies for the ER CFST connection where the damaged region of the CFST is encased in a concrete pedestal and headed bars are epoxied into the cap-beam or foundation have been evaluated. Each strategy utilizes a different force transfer method from the CFST column into the concrete pedestal; one using shear studs, one using a steel ring, and one using weld beads. Preliminary results indicate that all methodologies are effective in transferring force from the CFST into the pedestal, which shifts inelastic deformation away from the damaged region thereby restoring the stiffness, strength and deformation capacity of the CFST column.
IBC 19-71: Seismic Design of Integral Abutment Bridge
Mohamed Zawam, Trevor Small, and Xiaocen Jia, WSP Canada Inc., Oakville, ON, Canada
This paper discusses challenges associated with the design of Highway 401 underpass at 3rd line road, Bainsville, Ontario. The superstructure was an integral abutment type structure with cast-in-place reinforced concrete deck composite with five (5) precast prestressed concrete NU 1600 girders. The integral abutments were founded on steel H-piles driven to bedrock. The piers comprise a reinforced concrete bent supported by two circular columns. The seismic design was according to the new provisions in CHBDC 2014. The abutments were subjected to high deformations due to thermal effects, concrete shrinkage, and creep. Such deformations created a challenge for optimizing the piles design to ensure sufficient flexibility at the abutments, while achieving adequate strength to resist the seismic forces. The high mass of the concrete superstructure in addition to the seismic class of the site (class E) have led to significant design seismic forces. The seismic design was carried out using a multi-mode response spectrum analysis on a three-dimensional, linear elastic finite element model. Non-linear soil springs were utilized for the model using P-Y iteration method in order to account for the large deformations at the abutments. Seven HP 310×179 piles were used at each abutment. The pile was a class 1 section which allowed the piles to undergo plastic deformations under non-seismic ultimate loading conditions. Corrugated steel pipes around the piles, which was filled with loose sand, was increased to 900mm diameter compared with conventional 600mm diameter to accommodate the larger movements. The construction is scheduled to finish in spring 2019.
IBC 19-72: Preliminary Analytical Study of Live Load Effect on Seismic Responses of Simply Supported Bridge
Cunyu Cui and Professor Yan Xu, Tongji University, Shanghai, Shanghai China
With the massive transport infrastructure projects developed nationwide in China in recent years, large numbers of viaducts were constructed. The chance when vehicles are crossing a viaduct while an earthquake happening is considerably higher than the past, especially in the urban areas with increasing congestion. However, despite live load may or may not be included in bridge seismic design according to current codes, the realistic effect of live load on bridge seismic response is still unclear, especially when considering the complicated contact behavior between vehicle and bridge. In this study, preliminary analysis of live load effect on seismic response of simply supported bridge is carried out. Vehicles and bridge in the vehicle-bridge system are both simplified as mass-spring systems and the contact behavior between vehicle and bridge is modeled by Hertz law of contact. The responses of vehicle-bridge system under various excitations including sinusoidal and realistic seismic records are analyzed. Conditions of beneficial and adverse effects of live load on seismic responses of simply supported bridge are distinguished, and the analytical results are helpful to the seismic design of simply supported bridges.
Inspection & Analysis Session
Time: 1:30 – 3:30 PM
Session Chair: Ray Hartle
Room: Woodrow Wilson A
IBC 19-73: A New View for Bridge Inspectors
Joe Campbell, P.E., M.S.C.E, FHWA – MN, St Paul, MN
This presentation is based on the work the FHWA Minnesota Division has been working on to advance the opportunity for Local Program Agancy’s and their use of drones to supplement bridge inspections. The MN Division focus has been on recreational/affordable drone options that could be tools for the Team Leaders and inspection staff. This work has led to the identification of a cost effective drone system that can be readily purchased for around $3,000. This work also identified, how first person vision goggles, an accessory for many recreational drones, has the opportunity to greatly improve the field capabilities of a drone supplemented inspection. The field improvements are accomplished by giving the wearer of the FPV goggles the ability to see the drones video images at high definition on a very large screen format. Connected directly to a drone’s video feed, FPV goggles give bridge inspectors a first -person visual that is equivalent to being 3 feet away from the components they are inspecting. With the combination of optical and digital zoom capabilities of some recreational drones, this up-close field of view can be provided with the drone being 12 feet away. The FPV visual images can be so clear and immersive it can give the inspector ability to see hairline cracks in the field, all without standard costly and hazardous inspection techniques. The affordability of recreational drones and FPV goggles gives every bridge owner the opportunity to add a drone to their toolbox that any bridge owner can afford.
IBC 19-74: Seeing beyond the Surface – Underwater Visualization using 3D Sonar
Nicole Bartelt, MnDOT, Oakdale, MN; Barritt Lovelace, Collins Engineers
How can you adequately inspect and maintain things that are hard to see? Bridge inspectors often have to find out what lies beneath the surface of rivers. Typically, we turn to professional divers to provide information about what’s underwater. But diving inspections don’t always deliver precise information about bridge damage, debris and riverbed topography. To overcome these limitations MnDOT has incorporated innovative 3D sonar equipment to provide detailed underwater imaging. Thanks to this inspection technology, we now have a way to see previously hidden riverbed floors and underwater bridge structures. The difference is like night and day, the data is totally scalable, with real-world elevations and dimensions. It’s like the difference between a paper map and Google Earth. MnDOT recently completed an implementation research project to generate both stationary and mobile scanning techniques, outline the setup of both systems, discuss field operations, summarize the data analysis and post-processing of images, and review lessons learned. The report included several case studies to frame a discussion of the capabilities and limitations of 3D acoustic imaging for underwater bridge inspection. The case studies provide examples of different applications of this technology. Underwater acoustic imaging has been shown to have real value to bridge inspectors and owners for a variety of applications. This presentation will review the variety of projects the technology can be used on, a number of recent examples, and how we use social media to share this information.
IBC 19-75: Inspection of the Glen Canyon Dam Access Tunnel in Page, Arizona
Steve Brandon, P.E., P.G., Schnabel Engineering Inc., Sterling, VA ; Matthew Koziol, Schnabel Engineering Inc., Dallas, TX ; Lee Renegar, Underground Support Services, LLC
The Glen Canyon Dam Tunnel, owned by the Bureau of Reclamation (USBR), is a two mile long, 24-ft high, and 22-ft wide horseshoe shaped tunnel; the project is located in Page, Arizona. The tunnel was completed in 1958 and was driven through massive Navajo Sandstone by the drill-and-blast method. The tunnel has limited access and is used by the USBR on a daily basis to access the power plant at the base of the dam, summertime sees an increase in daily traffic by commercial whitewater rafting enterprises using the tunnel to access the Colorado River. The paper describes the on-site inspection of the tunnel to document the physical and functional conditions of the tunnel structure. The approach to the inspection and documentation of results was based on methods described in the Federal Highway Administration (FHWA) Tunnel Operations, Maintenance, Inspection, and Evaluation (TOMIE) Manual. The inspection team performed an in-depth inspection, including full arch perimeter geologic mapping of the entire tunnel including a cast-in-place concrete section. The inspection included mapping of all rock bolts that appeared deteriorated, loose, or noted to be in poor condition by previous USBR maintenance team inspections. Geologic characterization included mapping structural rock features such as bedding planes, joints, fractures, and faults. All geologic and ground support features were recorded and documented on full perimeter mapping sheets.
IBC 19-76: Improved Structural Assessments Assisted by Digital Image Correlation
Chris Hendy, FREng, MA CEng FICE Eur Ing, Atkins SNC-Lavalin, Epsom, Surrey United Kingdom; Jan Winkler, Atkins SNC-Lavalin
As our transportation infrastructure ages and the challenge of keeping it serviceable grows, the need for improved condition information on which to make good cost-effective maintenance decisions becomes ever more vital. Gathering this condition information requires structural health monitoring and inspection on a grand scale and, for it to be useful, it must be accurate, inexpensive, easy to interpret and avoid interfering with traffic flows – whether rail or highway. Digital image correlation (DIC) is a non-contact photogrammetry technique that can be used for monitoring by imaging a bridge periodically and computing strain and displacement from images recorded at different times or operating conditions. This paper discusses the use of DIC for monitoring a variety of bridges in service with the primary objective of better understanding the real behavior and avoiding the need for strengthening when appropriate or designing earlier interventions before problems become more serious. In the majority of cases, the structures were left untouched throughout the monitoring and were in full service operation.
Pedestrian & Special Bridges Session
Time: 1:30 – 3:30 PM
Session Chair: Bill Detwiler
Room: Woodrow Wilson B/C/D
Ever wonder what makes a bridge iconic? Explore the context sensitive design strategies deployed for the 2nd Street Bridge over the Shoal Creek in Austin, TX and the type selection process that lead to this gleaming structural solution. Not crazy about vibrating pedestrian bridges? Learn how pedestrian induced vibrations can be mitigated before construction through parametric analysis or after through the use of novel tuned mass dampers on several projects throughout North America. Prefabricated temporary bridges not giving you enough load capacity? Check out how precast bulb tee beams provided a temporary solution for moving 1.5 million cubic yards of dirt and rock and saved one contractor a heap of cash.
IBC 19-77: Dynamic Analysis Evaluating Human Induced Vibrations in a Lightweight Suspension Bridge
Martin Hudecek, Ph.D., Stantec Consulting Ltd., Victoria, BC, Canada; Eduardo Arellano, P.Eng., Stantec Consulting Ltd., Kamloops, BC, Canada
In lightweight slender bridges, human induced vibrations can result in significant discomfort and yet compromise structural integrity if frequency of passing load, represented by walking or running pedestrians, synchronizes with the natural frequency of the bridge. This paper discusses a method of advanced dynamic analysis considering human induced vibrations in a suspension bridge. The method is demonstrated on the Bear River Siphon Suspension Bridge situated south of Grass Valley, CA. Predicted structural response is compared with the actual response obtained from onsite testing. Although the vital function of the bridge in question is to carry a water line (54-inch in diameter), the deck comprises also two walkways for maintenance crew. Therefore, with the main span of 200 ft and cable sag-to-span ratio of 0.12, this structure qualifies under category of slender bridges and may be susceptible to human induced vibrations. The presented analysis method, utilizing finite element analysis software, is developed to obtain dynamic accelerations of the deck. Accelerations of the deck represent the main concern affecting comfort of walking at serviceability limit state. The developed method considers frequency and load magnitude of walking or jumping pedestrians crossing the structure in various groups. Natural frequencies, serving as main input, were calculated and verified against onsite dynamic testing. Ritz and Eigen vectors and structural damping factors are employed in the developed method to simulate load imposed on a real structure. The developed method is described in detail and accompanied with flowcharts to provide a practical guideline for industrial applications.
IBC 19-78: Heavy Haul Adjacent Bulb Tee Bridge
Aaron Craig, P.E., P. Joseph Lehman, Inc., Duncansville, PA ; Russell Dickson, Pennstress, Roaring Spring, PA
This paper details the challenges faced and solutions developed in design, fabrication, and construction of a contractor’s temporary bridge used by off-road heavy haul trucks over 4 traffic lanes on S.R. 0015 in Union County, Pennsylvania. Through its 8-month life, more than 1 million cubic yards of dirt crossed this 140’ single span. Construction was completed in less than 15 days, primarily during nighttime traffic shutdowns. This project demonstrates collaborative efforts between the contractor, fabricator, and design engineers to bring a simple, innovative, cost-effective solution. Construction of the Winfield Interchange portion of the Central Susquehanna Valley Throughway involves movement of 1.5 million cubic yards of dirt and rock, transferring large volumes across the existing highway. To accomplish this while maintaining the congested roadway, PennDOT proposed use of a temporary bridge. Since most pre-fabricated temporary bridges are designed for highway traffic, use by 200-ton trucks presented a challenge and a cost. The contractor, New Enterprise Stone and Lime, turned to local precaster, Pennstress, and Lehman Engineers for help. Could a precast concrete structure provide a viable solution? Simplicity and robustness were paramount to provide adequate capacity plus quick installation and removal of the structure. The substructure utilized precast post-tensioned abutments and wingwall panels. The superstructure employed adjacent bulb-tee beams with match-cast precast post-tensioned diaphragms and an integral wearing surface. TL-4 bridge railings with debris shields were also provided. Implementation was successful but not without obstacles. The temporary bridge served its purpose and saved the contractor over $650,000 over conventional approaches.
IBC 19-79: Pedestrian Bridges and Walkways – Controlling Vibration Through Tuned Mass Damper Design
Pierre-Oliver Dallaire, M.A.SC., ING, Trevor Haskett and Shayne Love, RWDI, Guelph, ON, Canada
Pedestrian bridges are often unique, lightweight and flexible. As such they are susceptible to vibrations from wind, seismic and from pedestrians themselves. This paper focuses on the pedestrian-induced vibrations which result from pedestrians walking across a bridge. RWDI studies performed on many pedestrian bridges include prediction of the force, simulation of the bridge response and the design and installation of tuned mass dampers (TMDs) to mitigate vibrations. RWDI has developed custom time domain routines to solve the response of a structure to pedestrian-force inputs. Pedestrian forcing depends on crowd density, walking frequency, stride length, jumping etc. This paper examines the use of TMDs to reduce the vibration response of pedestrian bridges and walkways. A TMD is an auxiliary spring-mass-damper system that opposes the motion of the primary structure to which it is attached. Simple formulae exist to determine the optimal TMD frequency and damping; however, these often-used TMD design formulae may be inappropriate in some instances. This paper illustrates that for optimal design, consideration must be given to the TMD mass ratio and the length of the bridge. For short to medium span bridges, the ability of a TMD to reduce vibration amplitudes may be significantly overestimated if steady-state harmonic excitation is assumed for TMD design. The results of this study can be used to ensure TMD design is optimal resulting in realistic performance and pedestrian comfort. Examples of completed bridges and walkways in North America will be discussed.
IBC 19-80: Design and Construction of the 2nd Street Bridge – Austin, Texas
Robert Anderson, P.E., S.E. and Trevor Kirkpatrick, AECOM, Tampa, FL
As part of the revitalization of a decommissioned water treatment plant site in down town Austin, Texas, the new 2nd Street Bridge provides a vital link for vehicles and pedestrians over Shoal Creek between the new city library to the west and residential/retail areas to the east. The new bridge is designed, proportioned and detailed to offer an elegant solution to connect the two sides of the 2nd Street over Shoal Creek with an iconic structure that is friendly to vehicles and pedestrians, and integrated with the future vision for this location. Through a series of design charrettes, a tiered process was used to elicit input and obtain decisions from key stakeholders. During those workshops the team analyzed and evaluated the following full spectrum of options against a comprehensive list of project goals. The preferred bridge type was a canted network arch concept spanning approximately 160 ft. The over deck supporting elements of the arch bridge are a pair of trapezoidal shaped steel ribs each with a network arrangement of galvanized wire rope hangers connected above deck to the girder framing. A central utility corridor between the box girders will accommodate the multiple utility lines which cross the bridge. The bottom soffit of the utility corridor will be screened by a metal deck bar grating. Outrigger beams carry a curved pedestrian sidewalk, varying from 12 to 14 ft wide. The thrust of the arch ribs is resisted by a foundation system with 6-foot diameter drilled shafts anchored to bedrock.
W-12: Moving Forward for MASH Implementation of Bridge Railing Systems – Research and Practice
Time: 1:30 – 4:30 PM
The Workshop objective is 1) to provide comprehensive information on policy guidance and practice of MASH implementation for bridge railing in the wake of 2016 AASHTO/FHWA Joint Implementation Agreement for MASH; 2) to provide opportunity for DOTs, researchers and bridge practitioners to exchange information in this topic; 3) to ensure bridges are designed to protect both highway bridge and vehicle drivers.
Speakers: Xiaohua Cheng, New Jersey DOT, Trenton, NJ; Richard W. Dunne, P.E., Rutgers, The State University of New Jersey, Piscataway, NJ; Robert Bielenberg and Scott Rosenbaugh, University of Nebraska, Lincoln, NE
W-13: Bridge Scour Prevention
Time: 1:30 – 4:30 PM
Bridge failures from scour can occur quickly during peak flood events, so the Physics of Scour need to be understood and applied in cost-effective permanent Scouring-Vortex-Preventing Bridge Designs for all flow speeds, rather than statistical correlations with large uncertainties. Specific examples of Bridge Failures Due to Scour and government Regulations on Designing for Scour will be briefly reviewed. Designing to Prevent Bridge Scour During Extreme Events keeps high speed flow away from scourable surfaces.
Speaker: Roger Simpson, Ph.D., AUR, Inc., Blacksburg, VA