Segmental Concrete Box Girder Research Articles

An Explicit Approach for Determining the Rational Length of Steel Portion in Steel–Concrete Hybrid Girder Bridges

The steel–concrete hybrid girder bridge structure is a combination of steel and concrete members in the direction of the bridge length. In long-span segmental concrete box girder bridges, the utilization of lightweight steel girders in the middle portion of the main span would greatly reduce the bridge self-weight while decreasing concrete creep and shrinkage effects. A critical parameter in the design of hybrid girder bridges is the rational length of the steel portion as a part of the main span (in other words, the rational location of the steel–concrete connection). Based on the concept of system equivalence, the steel–concrete hybrid system is equivalent to a full-concrete system with a reasonable span arrangement. The governing condition of the equivalence is that both systems have the same magnitude of self-weight hogging bending moments over the piers. Applying the system equivalence method, the rational length ratio of the steel portion to the main span (ξ) is explicitly solved, and its relationship with the length ratio of side span to main span (λ) is established. Finally, the proposed analytical approach is validated by five case studies, indicating that it is an effective and efficient method for the preliminary design of hybrid girder bridges.

Shear behavior of epoxy joints in precast segmental bridges under impact loading

As an essential component for transmitting shear forces, the epoxy joint of precast concrete segmental box girder bridges (PCSBs) is threatened by impact in their service life. This study experimentally and numerically investigated the impact responses of epoxy joints. Firstly, experimental tests were carried out on the epoxy joints with different confining stresses under static loading and the drop-hammer impact, respectively. Then, the numerical models of epoxy joints under impact loads were developed in LS-DYNA and carefully verified compared with the experimental results. Finally, the calibrated numerical model was applied to predict the dynamic shear capacity of the epoxy joint with different loading rates. The results show that the failure mode of epoxy joints under impact loading is the shear-critical mode. When the impact energy is relatively high, the concrete key will suffer compression damage and even be sheared off directly. The epoxy joints with high confining stresses exhibit little damage and less deformation. In addition, impact events with high mass but low velocity are severe in joint damage when the impact energy is equal. An improved analytical expression was proposed to predict the dynamic shear strength of epoxy joints under different strain rates. The derived formulas can generally predict the dynamic shear strength of epoxy joints of PCSBs.

The San Francisco–Oakland Bay Bridge, CA, USA – eastern span

With daily traffic of 260 000 vehicles, the San Francisco–Oakland Bay Bridge is a major connection in the San Francisco Bay area (CA, USA). The new bridge is a designated lifeline structure (to remain open for emergency traffic after a major seismic event) with a design life of 150 years. The new bridge is 3.6 km long and consists of four distinct structures: a low-rise post-tensioned concrete box girder near the Oakland shore; a 2.4 km long segmental concrete box girder (skyway); a first-of-its-kind self-anchored suspension (SAS) bridge with a 385 m main span over the navigational channel; and a post-tensioned concrete box girder that connects to the east portal of the Yerba Buena Island tunnel. Opened in 2013, the signature span of the bridge is the SAS bridge with a length of 624 m and a total deck width of 79 m accommodating ten lanes of traffic in addition to a bike/pedestrian path. The US$6.4 billion megaproject was procured under multiple contracts and was delivered using the traditional design–bid–build method. This paper describes the key design innovations and construction methods which address the unique challenges on this project.

Assessment of Temperature Evolution and Early-Age Thermal Cracking Risk in Segmental High-Strength Concrete Box Girder Diaphragms

Three-dimensional finite element (FE) thermal and stress models were created to compute the temperature evolution, thermal stress and potential of cracking in a segmental concrete box girder segment during construction. User-defined subroutines were developed in the ANSYS program to activate the degree of hydration-dependent heat rate and material properties, and creep behavior in the thermal and stress calculations. The developed FE model was verified with experimental measurements of a concrete cube. Adiabatic temperature rise, together with compressive strength and splitting tensile strength for a high-strength concrete mix typically used in construction of box girders were tested and incorporated in the subroutines. The effect of casting time and placement season (summer and winter), initial concrete temperature change, and insulation on the risk of cracking in a cast-in-situ box girder segment at early ages was investigated using the proposed model. The results indicate that the temperature difference between the segment's middle and the gate corner is very large leading to a high cracking risk. Use of an insulation material such as blankets along with casting concrete at the nighttime would significantly lessen the thermal tensile stress and thus could reduce cracking risk in the segment.

A Localized Fire Model for Predicting the Surface Temperature of Box Girder Bridges Subjected to Tanker Truck Fire

The quantification of thermal action is important to the analysis of structural-fire performance of bridges. This study evaluates the parameters for the localized fire model adopted in SFPE Handbook for application to the fire scenario of a tanker truck burning beneath a bridge. Modification is applied first to the flame length and then to the distribution of gauge heat flux using the simulation results of various fire models established in Fire Dynamics Simulator considering parameters, including the sectional dimensions of bridge, bridge headroom, truck size and heat release rate. Spatially varied gauge heat flux or adiabatic surface temperature of the bridge can be predicted with this fire model. Implementation of this modified fire model in structural-fire analysis is illustrated with a sequentially coupled thermo-mechanical modelling of a post-tensioned segmental concrete box girder bridge exposed to tanker truck fire. The adiabatic surface temperature calculated from the modified fire model is applied as thermal boundary to the bridge. Simulation results show that, although the global structural responses are seldom influenced by fire, localized damage in concrete and tendon may result. The prestress in tendons near mid-span may be reduced even after the bridge is cooled down to ambient temperature, which may adversely affect its load-carrying capacity. The damage to concrete may also induce localized separation between adjacent segments, possibly affecting the durability of tendons.

Stresses, deformations and damages of various joints in precast concrete segmental box girder bridges subjected to direct shear loading

Precast segmental concrete bridges involve multiple concrete segments joined together by posttensioning, and have the advantages of rapid construction, low-cost, and excellent quality control. Joints that represent locations of discontinuity are prominent factors affecting overall structural behavior of segmental bridges. In this study, a comprehensive analysis is performed for thirteen tested specimens with different joint types, subjected to direct shear loading, to assess the shear behavior of joints in precast box girder segmental bridges. The analysis focused on understanding the role of prestressing force, concrete compressive strength, presence of epoxy, and number of shear keys on: the stress and strain level in reinforcing bars, prestressing strands, displacements, type, time and mechanisms of sequential cracking and of damage level in the joints. The results showed that increasing of the confining pressure to 4.5 MPa and/or number of shear keys from 6 to 10, can highly improve both of the elastic stiffness and the plastic ductility of the segmental bridges, and changes the brittle behavior of the epoxied joints to a gradual strength degradation mode; the relative displacement of the dry joints is double of that in their identical epoxied joint; and the strains in the top layer reinforcement of the top slabs for keyed joints are ten times higher than that in the flat joint specimens.

Shear behavior of dry and epoxied joints in precast concrete segmental box girder bridges under direct shear loading

Precast segmental concrete bridge construction involves multiple concrete elements joint together by post-tensioning. The joints that represent locations of discontinuity are the prominent factors affecting the overall behavior of segmental bridges. In this study, a series of single cell, box shaped specimens, with a geometry closely resembling the keyed joint of actual segments, were subjected to direct shear test. The joints are flat and keyed, dry and epoxied, having web and flange keys. Tests were carried out to assess the shear capacity, shear behavior, crack propagation and deformations of different kinds of joints. It was found that epoxy can minimize joint imperfections and letting shear stresses to be distributed uniformly. Perfect joint closure and shear transfer was observed for epoxied joint when fully posttensioned immediately. Shear capacity of epoxied joints had consistently higher than dry joints by 25–28%; while, the failure of the epoxied joints was found to be sudden and brittle. The average shear transfer of a single key is higher for specimens with less number of keys. Four flange shear keys are capable to increase shear capacity by 14% and the elastic stiffness of the joints by 73%. It was determined that, the AASHTO design criterion can conservatively predict shear capacity of all kinds of epoxied joints and flat dry joints; however, it is greatly overestimating the shear capacity of multi-key dry joints.

Construction of precast segmental box girder bridge

New road segmental bridge have been built near the city of Žilina, aligned on European highway corridor. The use of segmental concrete box girder was chosen as the flexible system and appropriate method in a municipal zone. The same parallel precast post-tensioned box girder structures were used with main spans of 60.5 m for total length of 1042m. The balanced cantilever method, with the self-launching gantry was used for erection. The shorter end spans, adjacent to the abutment, had to be built by employing falsework. Generally, the early segmental bridges have not been realized without problems following to the structure collapse. In order to assure the safety under construction stage of bridges and subsequently in service, the data was collected during casting and erection of the bridges since August 2016 to November 2017. The experimental research was divided into the laboratory testing and continuous in-situ strain and temperature monitoring of the bridge superstructure. The paper illustrates fabrication and erection process of the bridge and some results of superstructure testing.

Thermal Field Characteristics of Reinforced Concrete Box Girder during High-Temperature Asphalt Pavement Paving

During high-temperature asphalt pavement paving, the bridge is subjected to significant temperature variations, and thereby the nonlinear thermal field distribution that occurs in the box girder might threaten the safety and serviceability of the bridge structures. Therefore, this study aims to investigate the thermal field characteristics of reinforced concrete box girder with steel fiber-reinforced concrete leveling layer during asphalt pavement paving. Firstly, a three-dimensional thermal field model of a reinforced concrete segmental box girder was developed and validated using the transient thermal field theory, and the dynamic paving process was simulated by the element deletion method. Secondly, the thermal field model was applied to analyze the vertical, transversal, and longitudinal temperature distribution during asphalt pavement paving. Thirdly, the effects of various sensitive factors on the thermal field of bridge components during asphalt pavement paving were evaluated. Finally, the extreme temperature load model was established through the statistical analysis method, in which the sensitive factors were introduced. Results demonstrate that the proposed numerical simulation method is feasible for thermal field characteristic analysis of reinforced concrete box girder during asphalt pavement paving. In addition, the research results can provide the theoretical foundation for temperature load selection and structural safety design of the concrete box girder during asphalt pavement paving.

Numerical Analysis of Shear-Off Failure of Keyed Epoxied Joints in Precast Concrete Segmental Bridges

© 2016 American Society of Civil Engineers. Precast concrete segmental box girder bridges (PCSBs) are becoming increasingly popular in modern bridge construction. The joints in PCSBs are of critical importance, which largely affects the overall structural behavior of PCSBs. The current practice is to use unreinforced small epoxied keys distributed across the flanges and webs of a box girder cross section forming a joint. In this paper, finite-element analysis was conducted to simulate the shear behavior of unreinforced epoxied joints, which are single keyed and three keyed to represent multikeyed epoxied joints. The concrete damaged plasticity model along with the pseudodamping scheme was incorporated to analyze the key assembly for microcracks in the concrete material and to stabilize the solution, respectively. In numerical analyses, two values of concrete tensile strength were adapted: one using a Eurocode formula and one using the general assumption of tensile strength of concrete as 10%f cm . The epoxy was modeled as linear elastic material because the tensile and shear strength of the epoxy were much higher than those of the concrete. The numerical model was calibrated by full-scale experimental results from literature. Moreover, it was found that the numerical results of the joints, such as ultimate shear load and crack initiation and propagation, agreed well with experimental results. Therefore, the numerical model associated with relevant parameters developed in this study was validated. The numerical model was then used for a parametric study on factors affecting shear behavior of keyed epoxied joints, which are concrete tensile strength, elastic modulus of epoxy, and confining pressure. It has been found that the tensile strength of concrete has a significant effect on the shear capacity of the joint and the displacement at the ultimate load. A linear relationship between the confining pressure and the shear strength of single-keyed epoxied joints was observed. Moreover, the variation in the elastic modulus of epoxy does not affect the ultimate shear strength of the epoxied joints when it is greater than 25% of the elastic modulus of concrete. Finally, an empirical formula published elsewhere for assessing the shear strength of single-keyed epoxied joints was modified, based on the findings of this research, to be an explicit function of the tensile strength of concrete.

Barrier Effect on Transverse Load Distribution for Prestressed Concrete Segmental Box Girder Bridges

AbstractBarriers are purposely omitted from the structural analysis for bridge design or load rating. They are not considered as primary structural members because, after a forceful collision, they may sustain some structural damage and would no longer strengthen the bridge deck. However, when completely intact, these secondary structural members do affect the distribution of applied loads, which is of interest to permitting agencies, such as the Florida Department of Transportation (FDOT). For a prestressed concrete segmental box girder bridge, both design and load rating (for oversized load permits) are determined by longitudinal and transverse analyses without considering the influence of the barriers. For the transverse analysis, the maximum moment generated from the live load is traditionally calculated from Homberg charts. These influence surfaces are based on plate behavior and idealized support conditions and are generally conservative. This moment estimation and the lack of consideration for the ...

Special Issue on Design, Analysis, and Construction of Segmental Bridges

Special Issue on Design, Analysis, and Construction of Segmental Bridges

Behavior of Concrete Segmental Box Girder Bridges with Open Webs

AbstractThe prestressed concrete (PC) box girder bridge with open webs, whose mechanical behavior is halfway between that of the traditional plain web and the lattice box girder bridges is a relatively new bridge form. The concept depends on new structural developments considering complex geometry that combines cast in situ and prefabricated elements. In this paper, the Abra Bridge (or Tavaro Viaduct) in France was measured and analyzed by using the so-called space frame lattice model. The paper discusses the advantages of this bridge type. The paper also presents the use of a space frame lattice computational method for structural analysis. Given the calculated results, to reduce the principal stresses in the webs, the shear stresses are reduced by the vertical preshear force provided by the external prestressed tendons along the whole bridge, which is proposed by the authors. At the same time, the vertical internal prestressed tendons in the webs can be designed to increase the vertical compressive stre...

Evaluation of Cracks in a Large Single-Cell Precast Concrete Segmental Box Girder Bridge without Internal Struts

The Hathaway Bridge, an eastbound and westbound bridge pair, is located in Panama City, Florida. Each of the pair consists of a single-box precast concrete segmental girder with a deck width of 24.4 m (80 ft). The lengths of the eastbound and westbound bridges are 1,031.43 and 1,162.93 m (3,384 and 3,815 ft), respectively. To date, these are the largest single-cell precast segments without internal struts fabricated in the United States. During construction, many web cracks developed in the external anchorage areas. The purpose of this investigation is to identify the main causes of the cracks and provide some design recommendations for large precast concrete segmental box girders. First, a brief description of the bridge is given. Then, analytical models for the bridge, posttensioning forces, and construction forces are presented. The analytical results show that the external longitudinal posttensioning forces can cause significant high-tensile stresses in the interior face of the web around the anchorages. The information presented in this paper can assist bridge engineers in the design of concrete segmental box girder bridges.

Fault-Tree Model for Risk Assessment of Bridge Failure: Case Study for Segmental Box Girder Bridges

Over the past few decades, the design capacity and service condition of many bridges, which are vital components of the surface transportation infrastructure reliability and functionality, have been challenged by rapid traffic growth and scarce maintenance funds. Numerous incidents of bridge collapse call for an urgent need to develop a systematic method of assessing the failure risks and identifying the initiating events that can lead to a bridge collapse. This paper presents a process of bridge failure risk analysis through fault-tree modeling for a common type of bridge known as segmental concrete box girder bridge. The process was applied to a segmental box girder bridge in South Carolina and was found to effectively identify causal factors of bridge failure and estimate overall failure risk. However, to comprehensively assess the probability of bridge failure, fault-tree analysis can best be used in combination with current risk assessment methods, such as visual inspections and structural health monitoring sensors.

Experimental monitoring of the strengthening construction of a segmental box girder bridge and field testing of external prestressing tendons anchorage

Prestressed concrete segmental box girder bridges are composed of short concrete segments that are either precast or cast in situ and then joined together by longitudinally post-tensioning internal, external, or mixed tendons. The objectives of this study are to monitor the construction process of the external prestressing tendons to strengthen the bridge structure and perform a field load test to measure the strain and the deflection of the anchorage devices of the external prestressing tendons to determine the state of these devices after tension forces are applied. The monitoring process of the external prestressing tendons construction includes inspecting the cracks in the diaphragm anchorage and the deviation block devices before the tension forces are applied to the external tendons; measuring the deformation of the steel deviation cross beam during the tension process; measuring the deformation of the box girder after different levels of tension forces are applied; measuring the elongation of the external tendons in each level of the tension; and measuring the natural frequency of the external tendons after the tension process is complete. The results of the monitoring process show that the measured values of the deformation, the elongation, and the natural frequency meet the requirements. Therefore, there is no damage during the construction and the tensioning of the external prestressing tendons. A field load test is performed to the anchorage beam, the steel deviation block devices, and the steel deviation cross beam. The field load test results of the anchorage devices show that the values of the strains, the stresses, and the deflection are less than the respective allowable limit values in the requirements. Therefore, the anchorage devices have sufficient strength, and the working state is good after the tension forces are applied to the external prestressing tendons.

Design and construction of Bukit Panjang LRT, Singapore

The Bukit Panjang light rapid transit (LRT) system, a groundbreaking project for the Land Transport Authority of Singapore, was designed to serve as a feeder to the existing mass rapid transit network and the Bukit Panjang bus interchange. The main civil engineering elements consist of 7·8 km of twin-track elevated guideway, 14 stations and a maintenance depot with an operation control centre. The system was completed and opened to the public in November 1999. This paper discusses the design and construction of the LRT guideway, which consists mainly of precast prestressed concrete segmental box girder bridges with epoxy glued joints and internally prestressed tendons. The bridge decks are predominantly simply supported spans ranging from15 to 34 m; however, a few special decks are made continuous due to stability requirements. Two overhead launching girders were employed for erecting the guideway. Due to specific site constraints and system requirements, the alignment was characterised by numerous tight curves with a minimum horizontal radius of 60 m. The geometry control method and construction equipment, such as the casting cells and the launching girders, were tailor-made in order to tackle the unconventional situation. Some operation and maintenance aspects of the system are also covered in this paper.

Design and construction of Bukit Panjang LRT, Singapore

The Bukit Panjang light rapid transit (LRT) system, a groundbreaking project for the Land Transport Authority of Singapore, was designed to serve as a feeder to the existing mass rapid transit network and the Bukit Panjang bus interchange. The main civil engineering elements consist of 7·8 km of twin-track elevated guideway, 14 stations and a maintenance depot with an operation control centre. The system was completed and opened to the public in November 1999. This paper discusses the design and construction of the LRT guideway, which consists mainly of precast prestressed concrete segmental box girder bridges with epoxy glued joints and internally prestressed tendons. The bridge decks are predominantly simply supported spans ranging from 15 to 34 m; however, a few special decks are made continuous due to stability requirements. Two overhead launching girders were employed for erecting the guideway. Due to specific site constraints and system requirements, the alignment was characterised by numerous tight curves with a minimum horizontal radius of 60 m. The geometry control method and construction equipment, such as the casting cells and the launching girders, were tailor-made in order to tackle the unconventional situation. Some operation and maintenance aspects of the system are also covered in this paper.

Proof testing in support of the new San Francisco–Oakland Bay Bridge

AbstractFollowing the Loma Prieta earthquake, Caltrans (California Department of Transportation) started a multi‐year seismic vulnerability assessment and retrofit project of all major bridges in California, including the San Francisco–Oakland Bay Bridge (SFOBB) East Bay Span. First, a retrofit of the East Span Steel Truss structure was evaluated. However, owing to the high cost and the questionable reliability in terms of performance of the retrofit and owing to its difficult implementation under full traffic, a replacement structure was determined to provide a seismically more reliable alternative, resulting in the SFOBB East Span Replacement Project.The new bridge consists of four distinct structures: (1) the Oakland landing or touchdown structures; (2) a segmental concrete box girder crossing called the Skyway; (3) a self‐anchored suspension (SAS) signature span; and (4) a series of multi‐cell post‐tensioned concrete box girder bridges providing the transition to the tunnel on Yerba Buena Island. The new bridge will feature parallel roadways and will be built next to the existing bridge, which will be dismantled after the new bridge is opened to traffic.This paper focuses only on the seismic safety aspects in the RC elements of three of the four segments of the new SFOBB East Span Bridge, namely the Skyway, the SAS bridge and the Oakland touchdown. Analytical and numerical models were developed to assess the seismic behavior of the Bay Bridge and a large‐scale proof‐testing program was conducted at the Charles Lee Powell Structural Research Laboratories at the University of California, San Diego. In the framework of this program, two steel shear links at 100% scale were tested, two concrete piers of the Skyway at 25% scale, a 25% scale model of the West Anchor Pier W2, and two column 35% scale piers of the Oakland Touchdown were also tested.The large‐scale tests on all structural elements of the new East Span of the San Francisco–Oakland Bay Bridge with expected inelastic performance characteristics proved that the design fully meets all performance requirements. The large‐ or full‐scale tests were able to identify performance issues, resulting in design improvements and considerable cost savings. Alternative detailing and construction procedures were validated, leading to a more economic construction of the new bridge. Copyright © 2005 John Wiley & Sons, Ltd.

Design of California's New San Francisco—Oakland Bay Self-Anchored Suspension Bridge

The seismically vulnerable east span of California's San Francisco—Oakland Bay Bridge will be replaced with a dual eastbound and westbound parallel structure 3.6 km long. The Bay Bridge lies between the Hayward and the San Andreas Faults, which can generate magnitude 7.5 and 8.1 M earthquakes, respectively. Performance criteria require that the bridge be operational immediately after a 1,500-year-return-period earthquake from either of these two faults. Four distinct structures will make up the bridge crossing: a low-rise posttensioned concrete box girder near the Oakland shore, a segmental concrete box girder 2.4 km long, a self-anchored suspension signature span, and a posttensioned concrete box girder that connects to the east portal of the Yerba Buena Island tunnel. The single-tower asymmetric self-anchored suspension bridge was selected from a total of four design alternatives that were developed for the signature main span; these included two cable-stayed bridges and two self-anchored suspension bri...