Transportation Research Record: Journal of the Transportation Research Board

A change in temperature causes a material to change length. Like most structures, bridges are subject to daily and seasonal thermal displacement cycles due to varying temperatures. In conventional bridges, expansion joints and seatings are used to accommodate these displacements. In integral bridges, the expansion joints are eliminated, and this results in rigid connections; hence, the superstructure, the bridge abutments, and the piles undergo varying displacements during each temperature cycle. To understand the temperature-induced soil–structure interactions, a realistic thermal displacement model that considers the realistic temperature variation cycles is necessary. This study discusses first the factors affecting bridge temperature variations and then a practical treatment of these effects in the design stage. The proposed mathematical model for thermal bridge displacement patterns considers the realistic changes in both daily and seasonal temperature cycles over time and the construction temperature. The usability, practicality, and importance of the model are verified by large-scale laboratory tests on segments of a bridge abutment supported by two pile types. The study shows that the proposed method is practical and capable of detecting detrimental effects induced by daily thermal displacement cycles. Potential uses of the proposed method are also discussed via a numerical example in which temperature and thermal displacement patterns measured for a real bridge are compared with estimates from the proposed model. This model was found to compare well with the measured data.

The AASHTO design provisions for barge impact on bridges spanning navigable waterways use a static force approach to determine structural demand on bridge piers. Recently, however, full-scale experimental dynamic tests of barge impact have indicated that consideration should also be given to additional forces generated from dynamic effects. Specifically, mass-related inertial forces generated by the superstructure of a bridge can restrain underlying pier columns and lead to dynamic amplification of column design forces. This paper presents an algorithm for performing simplified, coupled dynamic barge impact analysis for bridge structures. This type of analysis yields structural design forces, with dynamic amplifications included, on the basis of characteristics of the design impact condition (barge mass and speed). Results from the proposed simplified analysis method are validated using full-scale experimental test data and are compared with results obtained from full-resolution analyses for a variety of barge impact energies and bridge types.

Traffic barriers that can resist vehicle impact without being tied to a structure are needed at the top of mechanically stabilized earth walls. These barriers are usually constructed in an L-shape so that the impact load on the vertical part of the L can be resisted by the inertia force necessary to uplift the horizontal part of the L. The design load for such barriers has changed from 44.5 kN (10 kips) to 240 kN (54 kips) over the past decade. This increase has created concern about which load should be used. This paper contributes to answering that question. It shows the results of analytical solutions to the problem as well as one static load test and two impact tests on the same full-scale barrier. The conclusions are that 44.5 kN (10 kips) is an equivalent static load and that the 240 kN (54 kips) is a peak-impact load. Analytical and experimental approaches are used to provide better understanding of the behavior of the barrier–moment slab system. Guidelines for the dimensions of the barrier– moment slab system are presented and justified on the basis of the work described.

Aesthetic bridge railings that are Test Level 3 (TL-3) crashworthy have great appeal. As part of the project described here, the author worked closely with other designers from the Texas Department of Transportation to design, develop, and crash test an aesthetic and crashworthy bridge rail that meets NCHRP Report 350 TL-3 requirements. The aesthetic features of this bridge rail are easy to construct and repair. The bridge rail elements are mechanically attached to the posts and are not welded, to make the railing easier to construct and repair. The posts are fabricated from steel plate and are attractive and easy to construct. The rail elements, fabricated from high-strength aluminum, are attached to the steel posts after those are installed. The rail elements can be adjusted once in place and are also standardized highway barrier hardware. As a result of some simple and cost-effective curb reinforcement details developed as part of this project, damage to the concrete curb and deck was minimal from the crash testing. In addition, from previous testing, a TL-3 crashworthy transition had already been tested and approved for this new aesthetic bridge rail design. This bridge rail design is currently being implemented on new construction in Texas. This paper presents an overall review of the design of the aesthetic bridge rail, details of the design, aspects of construction, and results from the crash testing of the T-1F bridge rail.

The main cables of the Ambassador Bridge—carrying four lanes of traffic over the Detroit River between Detroit, Michigan, and Windsor, Ontario, Canada—have recently been inspected internally for the first time, after 78 years of service. The bridge has a suspended main span of 1,850 ft, with back spans consisting of trusses supported on steel bents. The main cables comprise 37 strands of 218 wires each, protected with red lead paste. The wires are No. 6 gauge, cold drawn and double galvanized, with a specified minimum tensile strength of 215 ksi. Cable strength was calculated by means of the procedures of NCHRP Report 534: Guidelines for Inspection and Strength Evaluation of Suspension Bridge Parallel Wire Cables. Four locations were inspected along the length of each cable, and wire samples removed for testing. All three models presented in NCHRP Report 534 were used to estimate cable strength: the simplified strength model, the brittle wire model, and the limited ductility model. Modifications to the NCHRP procedure were required for the unloaded backstay locations. The results of the evaluation showed the cables to be in very good condition, with a calculated factor of safety of 2.70, which was based on the limited ductility model. The reduction in strength from the as-built condition was less than 10% at the worst location.

The suspended superstructure of the new Tacoma Narrows Suspension Bridge in Washington State consists of twin welded steel trusses with a continuous and integral orthotropic steel deck measuring over 1 mi in length. AASHTO M270 Grade 50 HPS 50W and HPS 70W steels are the materials of choice. The truss elements are fabricated of both closed-box and open I-sections. The bridge, including major components of the stiffening truss, was designed to allow for a future lower roadway or light-rail transit system. This paper discusses the design aspects of this 5,400-ft suspended superstructure, including the development of design details to satisfy performance requirements for serviceability, fatigue, wind, and seismic loading. Global superstructure and local component computer modeling techniques are presented as they relate to force, fatigue, and displacement demands and overall structural performance for the 150-year design service life. Fabrication and lessons learned are also discussed.

As the design challenges faced by bridge engineers become more complex, the importance of properly analyzing steel girder bridges is increasing dramatically. Improper modeling of steel girder bridges can result in misleading analysis results, which can lead to constructability problems or, worse still, problems with structures in service. This paper broadly outlines the various methods of analysis and presents key modeling issues for consideration in steel girder bridge analysis. Some recent comparisons of modeling techniques demonstrate the variability in analysis results for identical bridges modeled in different ways.

For the past 30 years, it has been common practice to use AASHTO standard design specifications for underground precast concrete structures. Today, the bridge engineering profession is making the transition from the standard AASHTO load factor design bridge specifications to the load and resistance factor design (LRFD) specifications. The FHWA has mandated that all culverts, retaining walls, and other standard structures designed after October 2010 be designed according to the AASHTO LRFD bridge design specifications for a project to receive federal funding. This paper compares related provisions from both specifications used in designing underground concrete structures, such as underground utility structures, drainage inlets, three-sided structures, and box culverts. Although many provisions of these two codes are the same, important differences could have a significant impact on the amount of reinforcement, member geometry, and cost to produce buried reinforced concrete structures. Many AASHTO LRFD code provisions that differ from the standard specifications include terminology, load factors, implementation of load modifiers, load combinations, multiple presence factors, design vehicle live loads, distribution of live load to slabs and earth fill, live load impact, and live load surcharge. This study demonstrates that greater reliability and a more uniform factor of safety are obtained when the LRFD specifications are used.

This paper presents the results of field load tests on four spans of a post-tensioned, prestressed concrete road bridge over a reservoir water plant on the Nysa Klodzka River in Topola, Poland, under static loads. The spans were especially designed for B-class loads (400 kN) according to Polish load standards. They underwent a whole range of research, which included testing bridge deck slab deflections under trial static (and dynamic) loads. The tests were performed on October 28, 2002.

Structural health monitoring using sensor technology is one of the most promising ways that can provide an excellent means for protecting important structures such as bridges, dams, and nuclear reactors. These sensors provide real-time information about structural conditions such as strain, temperature, and vibration. The information obtained from these sensors can later be analyzed and compared with the design data; the process allows the early detection of problems. This paper presents experimental results on two types of sensors to verify their behavior, accuracy, and applicability for strain monitoring of concrete applications. The investigation included concrete curing-behavior test, thermal test, accuracy test, and other tests to assess the mechanical properties of concrete with embedded sensors.

Accurate assessment of the condition of bridges leads to their economic management. Ultrasonic seismic methods can be successfully used for this purpose through evaluation of changes in material characteristics and detection of the development of defects and zones of deterioration. The impact echo (IE) method is of special benefit in evaluation of corrosion-induced deck delamination, due to the method's nondestructive nature, speed of evaluation, and ability to detect delaminated zones at various stages of deterioration: from initial to progressed and developed. The traditional approach in condition assessment of bridge decks by IE on the basis of review of individual test point records and a new automated approach based on three-dimensional (3-D) data visualization are presented. The developed 3-D visualization platform allows both the advanced presentation and interpretation of IE data. The data presentation is provided as 3-D translucent visualizations of reflectors in a bridge deck section and horizontal and vertical cross sections through all distinctive zones, including a zone of delamination. The associated interpretation platform allows both (a) the overall assessment of the condition of the deck, through cumulative distributions and histograms of reflection intensity, and (b) identification of deteriorated zones of the deck for repair or rehabilitation in an efficient and intuitive way. The visualization platform effectively enables an IE device to be used as a type of bridge deck sonar device.

The impact echo method is a nondestructive testing method that is based on the use of elastic waves. It has been widely used in the nondestructive evaluation of concrete. With the identification of the peak frequency observed in the frequency spectrum, the depth of a reflector can be estimated when the longitudinal wave velocity is known. However, in most applications, an empirical correction factor (β) is used because the frequency observed in the spectrum is not in good agreement with the frequency calculated by the given equation in the impact echo. This paper presents determination of the empirical shape factor, β, in impact echo for different rectangular shapes. Two-dimensional dynamic boundary element analysis was conducted as a frequency sweep to simulate the impact test. The deformation modes of the first-mode resonance were examined for each shape by applying boundary element method analysis.

Impact echo (IE) is successfully applied for the nondestructive evaluation of concrete structures. Its principle is based on the use of longitudinal waves generated by the elastic impact of a steel sphere. However, this impact creates other wave types such as Rayleigh and shear waves. Especially when IE is applied on structures with compact dimensions, the effects of these waves become crucial. The separation of the different signal components and the definition of effective criteria to distinguish between them are therefore highly relevant. In this study, the duration and attenuation of the different signal components are explained and used to distinguish between the actual measurement information and interfering effects caused by reflections at the boundaries. An explanation is offered for why the different components of an IE signal have different characteristics in regard to their duration over time. Furthermore, a procedure is introduced that makes use of the relation between the signal duration in the time domain and the bandwidth in the frequency domain. It therefore avoids the application of a rather complex time– frequency analysis. This characteristic is demonstrated on simple sinusoidal signals in a first step and then applied to data collected from IE measurements. Because of the low computation effort and the fact that only few input parameters have to be chosen, this method is also applicable to whole scan lines composed of a large number of measurement points and the imaging of the results.

This paper deals with seismic design and ductility evaluation of thin-walled steel bridge piers of box sections supporting highway bridge superstructures. The basic characteristics of the thin-walled steel box section structures are noted. A seismic design method for ultimate strength and ductility evaluation of thin-walled steel bridge piers of box sections is presented. The application of the method is demonstrated by comparing the computed strength and ductility of some bridge piers with test results. The method is applicable to both the design of new, and the retrofitting of existing, thin-walled steel bridge piers of box sections. The effects of some important parameters, such as width-to-thickness ratio, column slenderness ratio, and residual stress, on the ultimate strength and ductility of thin-walled steel bridge piers of box sections are presented and discussed.

The longitudinal deformations of the pipe roof in the entrance of a shallow multiarch tunnel of Tujiangchong were monitored by a series of strain gauges, and the working mechanism of the pipe roof was analyzed according to the field test results. A three-dimensional finite difference code, FLAC^3D, was adopted to simulate the deformation of the pipe roof and to evaluate its effect on ground surface settlement. Both the calculated and numerical results fit the field observations quite well. The numerical results indicated that a double-layer pipe roof provided a restraining effect on ground movement and helped to reduce the tunnel deformation and corresponding ground surface settlement. Ground settlement directly above the crown could be reduced by 40% to 50% compared with the settlement induced by tunneling without any pipe roof reinforcement. This project provided a successful case history of using double-layer pipe roof reinforcement in a shallow multiarch tunnel construction.

The development and the use of finite element analyses in the 1970s and 1980s changed the nature of culvert assessment because they permitted consideration of the geometrical and material details of the burial condition, as well as the construction process, culvert geometry, and earth and vehicle loads. While these procedures have been used to study a wide range of new culvert and pipe structures, there has been little consideration of the structural deterioration that is precipitating most current infrastructure investments. This study therefore examines the influence of corrosion on the stability of corrugated steel culverts. Corrosion in the lower half of the structure is considered, including a range of losses in wall thickness and lateral extents. Changes in the factor of safety against yield are assessed as corrosion develops, as are changes in culvert resistance to buckling failure. For the five specific design cases considered, the governing design criterion was stability against yield, and the factor of safety against yield was found to decrease almost in proportion to wall thickness (when maximum wall thrust within the corroded zone was considered). This decrease occurred because the corroded metal culverts experienced little change in the distributions of thrust or moment as a result of local losses in wall thickness. While the results presented are purely theoretical, they provide a starting point for an appreciation of the influence of metal culvert deterioration and can guide future research, including physical test programs.

Maine's first cable-stayed bridge opened to traffic on December 30, 2006. Designed as an emergency replacement for the Waldo–Hancock Bridge, the new bridge uses an innovative cradle system to carry the stays from the bridge deck through the pylon and back to the bridge deck. Each strand is anchored independently; thus, strands may be removed, inspected, and replaced while the bridge carries traffic. This advantage, coupled with Maine Department of Transportation concerns for the premature loss of the Waldo–Hancock Bridge due to corrosion, created interest in an opportunity to install and monitor representative carbon fiber-reinforced polymer (CFRP) strands in the cable stays of this bridge. CFRP strands were installed for the purposes of assessing their performance in a service condition and evaluating them for use on future bridges. Three representative stays in the bridge were designed to include two reference strands each, which may be removed and not replaced without change to the bridge's structural integrity. Six epoxy-coated steel strands were removed and successfully replaced with CFRP strands in June 2007. Data are being collected from the monitoring equipment installed on all of the strands (both traditional steel and CFRP strands) in the bridge to evaluate CFRP strand performance for future bridge cable stay and post-tensioning installations. The bridge location ensures that the test strands will be evaluated under a wide range of temperatures and variety of wind loads.

An integrated monitoring system for carbon fiber composite cable (CFCC) strands recently implemented in the Penobscot Narrows Bridge in Maine is presented. This cable-stayed bridge features a cradle-stay system in the pylons that provides a continuous cable stay between the main span bridge deck anchorage and the back span bridge deck anchorage. The cradle-stay system allowed for replacing epoxy-coated steel strands with CFCC strands. The monitoring system installed in the bridge is composed of a set of sensors and devices that provide complementary structural information: (a) load cells supported on steel anchorage chairs, (b) linear voltage differential transformers (LVDTs) mounted on the steel anchorage chairs, (c) fiber-optic strain (FOS) sensors embedded in composite sleeves, and (d) temperature sensors. The monitoring system was designed to detect variations over time in individual carbon fiber strand force and strains at the anchorage locations and to correlate the measurements with ambient temperature. Laboratory tests were conducted to proof-load the steel anchorage chairs and to calibrate the LVDTs and embedded FOS strain measurement systems. The baseline response of the CFCC strands that was based on load cell, FOS sensors, and LVDTs measurements after the strand stressing operation is presented. The CFCC strands experienced changes in tensile force between +3% and −5% over the first 4 months in service, which were consistent with ambient temperature fluctuations. The FOS measured strand strains and the LVDT deflections of the anchored chair exhibited trends consistent with the variations in CFCC strand force.