Segmental Bridge Construction Research Articles

Gravity-triggered rotational connecting method for automated segmental bridge construction

Gravity-triggered rotational connecting method for automated segmental bridge construction

Investigations on the fatigue loading of thin-walled and resource-efficient UHPFRC segmental bridges

Many reinforced concrete and prestressed concrete bridges are defective or can no longer withstand the increased traffic loads for a sufficiently long time. In the long term, they will have to be replaced by new structures. In previous reinforced concrete and prestressed concrete bridges, fatigue loading (e.g. traffic, wind) is rarely a problem with regard to the concrete, especially since the cyclic traffic loads are relatively low compared to the static dead loads due to a solid construction method. However, for reasons of sustainability and compliance with climate targets, future structures and bridges should be built in a resource-efficient and materials-compatible manner, while at the same time fast and durable. A target-oriented approach to this is segmental bridge construction with keyed dry joints made of ultra-high-performance fiber-reinforced concrete (UHPFRC). In these bridge structures the fatigue loads could become more relevant due to the slenderness of the thin-walled UHPFRC bridges superstructure and fatigue problems could occur. In order to investigate this in more detail, FE investigations on segmental box girder bridges under variation of the concrete strength (NSC, HSC and UHPFRC) were carried out, while optimising the cross-section dimensions. It was shown that due to the performance of UHPFRC and the associated cross-section optimisation, an exponential increase in the ratio of cyclic live loads to static dead loads and thus an exponential increase in fatigue loading occurs at thin-walled and resource-efficient UHPFRC segmental bridges compared to NSC and HSC bridges and that this can become relevant for the design of such bridges.

CONSTRUCTION STAGE ANALYSIS OF SEGMENTAL BOX GIRDER BRIDGE

Segmental bridge construction is very common in Pakistan. However, the impact ofstructural system changes before and after the completion of segmental bridge construction is achallenge and major concern for construction stakeholders. Therefore, in this study, construction stageanalysis was performed for balanced cantilever construction technique to check the safety andserviceability of the bridge. Through time dependent analysis, considering the construction sequenceand creep deformation of concrete, structural responses related to the member forces were reviewed.Moment reversal was observed in the cantilever segments near the face of the pier. Therefore,maximum compressive and tensile stresses were observed in the top and bottom fibers of the girder,respectively. These stresses were within the AASHTO LRFD limits for construction stage loads.Results demonstrated that the creep moment redistribution started when the structural system changedfrom statically determinate to indeterminate stage. Furthermore, it was concluded that the timedependent deformation of concrete was the governing factor in order to achieve the final designmoments.

(Digital Presentation) Bipolar Electrochemical Impedance Spectroscopy for Corrosion Monitoring of Steel Reinforced Cementitious Structural Components

Bipolar electrochemical impedance spectroscopy (BPEIS) was previously explored as a potential nondestructive method for detecting corrosion of steel in post-tensioned tendons which are used as reinforcing structural elements in segmental bridge construction. The tendons are composed of a grout-filled cylindrical plastic duct that contains high-strength steel strands. A proof of concept was demonstrated by experiments performed on tendons with passive and corroded strands and through finite-element simulations of the indirect impedance response1. Further work showed that bipolar impedance was sensitive to local corrosion in field tendons if the measurement is obtained near the corroding region2. This work further scrutinizes BPEIS as a corrosion monitoring method for reinforced cementitious structural components with direct comparison between corrosion damage estimates and actual metal loss.Bi-polar electrochemistry is a noncontact method in which a conducting material placed within an electric field induced by two feeder electrodes is indirectly polarized while maintaining charge neutrality such that the conducting material forms two poles, a positively charged pole which acts as the anode and negatively charge one that acts as the cathode. If the electric field is applied between the feeder electrodes under alternating current, the poles fluctuate between anode and cathode extremes corresponding to the direction of the induced field. Under such polarization conditions, the opportunity to assess the electrochemical impedance between the feeder electrodes is provided. The measured impedance includes the interfacial impedance of the feeder electrodes, the conducting material interface impedance, and the impedance of the conductor itself which can be assumed to be negligible. By placing two reference electrodes between the feeder electrodes, the interfacial impedance of the feeder electrodes can be eliminated from the measurement, thus allowing one to obtain an impedance reflective of the electrolyte impedance between the reference electrodes and the impedance of the conducting material interface.A finite element model is used to relate the measured impedance response to the impedance of the steel and cement interface and therefore the corrosion rate. The ability to accurately monitor the corrosion rate will be assessed by comparing the estimated corrosion damage obtained by integration of periodic estimates of corrosion rate to the actual damage. The role of a corrosion product layer, reinforcement geometry, and electrode configuration to the sensitivity of the measurement to corrosion rate will be described.[1] Alexander, C. L., & Orazem, M. E. (2020). Indirect electrochemical impedance spectroscopy for corrosion detection in external post-tensioned tendons: 1. Proof of concept. Corrosion Science, 164, 108331.[2] Alexander, C. L., & Orazem, M. E. (2020). Indirect impedance for corrosion detection of external post-tensioned tendons: 2. Multiple steel strands. Corrosion Science, 164, 108330.

Behavior of Fiber Reinforced Key Joints in Precast Concrete Segmental Bridge: Experimental and Numerical Analysis

Abstract Fiber reinforced concrete (FRC) has been gradually applied to the construction of precast segmental bridges, but due to the discontinuity of the joint structure and the existence of keys, ...

The Application of Indirect Impedance to Monitor Corrosion Rates of Inhibitor-Impregnated External Post-Tensioned Tendons

An indirect electrochemical impedance spectroscopy method was previously explored as a potential nondestructive method for detecting corrosion of steel in post-tensioned tendons which are used as reinforcing structural elements in segmental bridge construction. The tendons are composed of a grout-filled cylindrical plastic duct that contains high-strength steel strands. A proof of concept was demonstrated by experiments performed on tendons with passive and corroded strands and through finite-element simulations of the indirect impedance response.1 Further work showed that the indirect impedance method was sensitive to local corrosion in field tendons if the measurement is obtained near the corroding region.2 This work expands the application of the indirect impedance methodto corrosion monitoring of inhibitor-impregnated post-tensioned tendon sections. A corrosion inhibitor that is injected into the tendons through the interstitial space of the strands may be capable of preventing or stopping corrosion. The sensitivity of indirect impedance measurements to changes in both electrical properties of the grout and the corrosion rate of the steel is assessed by comparison to traditional measurements of the impedance in which direct contact is made to the steel. Additionally, further assessment of the indirect impedance method is made by relating the analysis results to the actual corrosion damage obtained by autopsies of the tendon sections. C. L. Alexander and M. E. Orazem. "Indirect Impedance for Corrosion Detection of External Post-tensioned Tendons: 2. Multiple Steel Strands." Corrosion Science 164 (2020): 108330.C. L. Alexander and M. E. Orazem. "Indirect electrochemical impedance spectroscopy for corrosion detection in external post-tensioned tendons: 1. Proof of concept." Corrosion Science164 (2020): 108331.

Indirect electrochemical impedance spectroscopy for corrosion detection in external post-tensioned tendons: 1. Proof of concept

An indirect electrochemical impedance spectroscopy method, previously applied to corrosion detection in reinforced concrete structures, was explored as a potential nondestructive method for detecting corrosion of steel in post-tensioned tendons used as reinforcing structural elements in segmental bridge construction. A proof of concept is demonstrated by experiments performed on tendons with passive and corroded strands and through finite-element simulations of the indirect impedance response. The numerical simulations, used to explore the influence of non-uniform current distributions on the indirect impedance response, demonstrate how frequency dispersion influences the impedance measurement. Validation of the model is shown through comparison to experimental measurements.

A Laser-Based Noncontact Vibration Technique for Health Monitoring of Structural Cables: Background, Success, and New Developments

Structural cables are susceptible to the effects of high stress concentrations, corrosion, and wind-induced and other vibrations. Cables are normally the most critical elements in a cable-supported structure and their well-being is very important in the health of the structure. The laser-based vibration technique discussed in this paper is a means for health monitoring of cables and therefore the entire cable-supported structure. This technique uses a noncontact remote sensing laser vibrometer for collecting cable vibration data from distances of up to several hundreds of feet and determines its dynamic characteristics including vibration frequencies and damping ratios. A formulation specifically developed for structural cables capable of accounting for important cable parameters is then used to calculate the cable force. Estimated forces in the cables are compared to previously measured forces or designer’s prediction to detect patterns associated with damage to the cable itself and/or changes to the structure elsewhere. The estimated damping ratios are also compared against predefined criteria to infer about susceptibility against wind-induced vibrations and other vibrations. The technique provides rapid, effective, and accurate means for health monitoring of cable-supported structures. It determines the locations and elements with potential damage and the need for detailed and hands on inspection. To date, the technique has been used successfully for evaluation of twenty-five major bridges in the US and abroad. Though originally devised for condition assessment of stay cables, it has been developed further to include a variety of systems and conditions among them structural hanger ropes in suspension, truss, and arch supported bridges, ungrouted stay cables, cables with cross-ties, and external posttensioning tendons in segmental bridge construction. It has also found a valuable place in construction-phase activities for verification of forces in tension elements with minimal efforts. Future endeavors for automation and aerial delivery are being considered for this technique.

Segmental Construction in the Cold: Bridging the Grand River

In cold climates, special consideration needs to be given to the design and construction of segmental post-tensioned concrete girder bridges. This article presents the special considerations that enabled winter construction of the Fairway Road/Grand River Bridge in Canada at a location where temperatures commonly drop below −20°C. The four-span crossing is a high-level, variable depth, post-tensioned, cast-in-place, twin box-girder segmental bridge, 237 m in length with a main span of 95 m over the Grand River. During the winter months, the form traveler was enclosed and heated to protect the cast-in-place concrete. Cold weather concrete protection to enable winter construction is common practice in Canada, but to enable segmental post-tensioned construction during the winter months a method to protect the tendons after stressing was necessary. Standard specifications require tendons to be grouted within 14 days of tensioning. However, post-tensioning grout typically requires a minimum temperature of 5°C. Therefore, a method of applying a corrosion inhibitor powder was implemented during winter construction to provide temporary protection of the stressed tendons until temperatures permitted the grouting to be completed. This article also presents special design features that include the use of glass fibre reinforced polymer reinforcing and high performance concrete.

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

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

Experience Curve Effects in Bridge Construction

Learning is an essential part of life through which we accumulate experience, which then can help us to improve our ability to solve problems. In economics experience can improve productivity. The concept of the experience curve as a form of organizational learning was developed during the second half of the 20th century. It was especially promoted by the Boston Consulting Group and found its way into most textbooks on management and strategic planning; empirical data have been published for a number of industries. In the construction industry, however, very few data areavailable to support the concept. The largest obstacle for all researchers is to obtain the cost information as these are typically not shared by companies. Consequentially we have gathered cost data from four very large expressway bridges to study experience effects in construction projects. These were built in Bangkok, Thailand, by the same joint venture for the same owner during the periodfrom 1990 to 2000 using segmental bridge construction technology. The square meters of bridge deck serve as basic units and the four projects comprise some threemillion of these, so that impacts of increasing experience could be observed. The data for all four projects have been evaluated and adjusted for inflation. They support the idea that a costreduction of 20% can be achieved. The cost reductions must be actively pursued, there exists no automatic process.

Collapse mechanism and robustness of precast segmental bridges

In the construction of multi-span precast concrete segmental bridges, in situ stitches are often cast to connect together adjacent cantilevers assembled from precast segments. Since the stitches are often lightly reinforced, the robustness of a segmental bridge could be adversely affected by the capability of the stitches to resist any large variations in moment during extreme events. While most previous studies have focused on methods to measure robustness, there has been little systematic examination of the effects of strength and behaviour of structural components on robustness of structures. As prestressed concrete is relatively non-ductile, finite-element analyses are carried out taking into account the full-range non-linear moment–curvature relationship to examine the formation of plastic hinges and possible collapse mechanisms. Three classes have been proposed for the evaluation of robustness, namely superb, adequate and inadequate. Recommendations to achieve good robustness are also put forward.

MIDAS-Based Finite Element Analysis of the Short Line Method of the Precast Segmental Bridge Construction

This paper studies the precast and cantilever erection process of pre-stressed concrete continuous beam bridge alignment control in short line method, basis on the construction of a light rail. Various stages of bridge construction performed on simulation analysis and calculated by the finite element software MIDAS, concluded the ultimate internal force and deformation values, and the maximum deformation are within the scope of design elevation deviation 20 mm allowed, as to achieve the target of bridge assembly.

New Structural Joint by Rebar Looping Applied to Segmental Bridge Construction: Fatigue Strength Tests

The objective of this research has been to design, develop, and evaluate experimentally a modified type of construction joint of limited length between concrete slab segments. The design concept is based on an anchorage hook of reduced development length stiffened by transverse reinforcement bars. The purpose of this paper is to investigate the mechanical behavior of the joint in terms of stiffness and strength for an application that requires high durability, which often leads to serviceability problems such as cracking and water leakage at transverse joints. This can regularly appear in bridges. Additionally, bridge decks are structures that are subjected to repeated loading such as traffic loads, making it necessary to evaluate the behavior of joints under fatigue load. Therefore, studies focusing on the strength, stiffness, and serviceability of the joints must be carried out. This paper investigates experimentally the fatigue behavior and strength of loop joints with regard to the loop bar diameter, loop joint width, and applied load ranges. These results were compared with the behavior of RC slabs without joints. A total of eight slabs were fabricated for fatigue loading tests, and the failures of the different specimens (with loop joints and without) were obtained. From the test results, the mechanical behavior of the slabs with loop joints was confirmed to be similar to that of the slabs without joints. The experimental loop joint design was found to perform correctly under fatigue loads.

Analysis of in-situ stitches in precast concrete segmental bridges

In the construction of precast concrete segmental bridges, in-situ stitches are often cast to connect together adjacent cantilevers assembled from precast segments. Except for some continuity tendons near the bottom, there is normally no longitudinal reinforcement through the stitches, and they are usually provided with little or no shear reinforcement. Hence the stitch is a potential weakness. This article presents the numerical results from finite element models calibrated with available experimental data. Parametric study shows that the ultimate shear capacity of keyed stitch increases with the prestress and aspect ratio. Comparing the numerical results with various design formulae shows that the codes generally underestimate the ultimate shear capacity of keyed stitches. The shear strength of keyed stitch is mainly contributed by the strength of shear keys located in the compression zone. A design equation is proposed considering the aspect ratio and stress concentration.

International perspective: Extending the service lives of bridges

Future demands for service-life performance of concrete bridges pose multidisciplinary challenges on the designer and the contractor to master structural, materials, construction, and maintenance properties. The growing demand for environmental awareness is an additional element of such designs. The demands for long service lives also reflect on the owner through new challenges regarding service-life-design basis and corresponding acceptance criteria. For segmental bridge construction, the drive toward reduced materials comsumption and self-weight has led to the adoption of more complex, high-performance materials and more sophisticated member geometries. This raises the demand for high-quality workmanship and execution competence, which is not always fully recognized and respected by owners and designers or the supervision teams. Hence, such high-performance materials can easily lead to low-performance structures. The challenge of providing factual service-life designs of 100 to 150 years or more can be achieved, and at times this is surprisingly easy. This new integrated approach identifies a new focus in our design procedures; an important change in design paradigm is needed. Such a changed design focus may lead to dramatically improved service-life performance and will greatly increase the competitiveness of structural concrete. This new perspective will also reflect on revised engineering university curricula.

Field calibration of time-dependent behavior in segmental bridges using self-learning simulation

The construction of segmental bridges often shows unexpected deflections, mainly due to the complex time-dependent behavior of concrete. The control of excessive deflections is important for the successful completion of their construction. It is difficult to accurately predict these deflections purely by conventional numerical simulations, and often the preferred method is field calibration. The quality of the calibration is dependent on the experience of the engineers involved. Therefore, it is difficult to systematically quantify and benefit from the gained experience, and to accumulate it. We employ a novel method called Self-learning Simulation (SelfSim), which integrates numerical simulations and field observations. SelfSim “learns” the time-dependent behavior of concrete in the field from displacement measurements. The gained knowledge is retrieved using extracted stresses, strains, rates of stresses and strains, and a neural network-based constitutive model. SelfSim is able to provide predictions about the remaining or future construction with the gained knowledge. Deflections can be controlled systematically by using the information provided by SelfSim. As a demonstration, the proposed method is applied to the field calibration of the Pipiral Bridge, a concrete segmental bridge built by the balanced cantilever method.

Fundamentals of Launching a Precast Concrete Segmental Operation for Bridge Construction Projects

Construction of precast concrete segmental bridges is continuously evolving to keep pace in a competitive environment. As segmental bridge construction grows in popularity, many precasters will consider upgrading plant facilities to handle this relatively new product. Historically, general contractors have produced most precast concrete segments for existing precast concrete segmental bridges, and it has been the exception when a contractor has purchased segments from a precast concrete manufacturer. This article examines the necessary facility upgrades a precaster would need to successfully undertake the comprehensive planning, coordination, and transformation process needed to enter the field of segmental bridge production, also listing sources for industry technical support in this area. While the challenges of upgrading operations to include precast concrete segmental bridge components are numerous, innovation and risk management and system integration can establish this product line as a true precaster product.

Modified Skew Bending Model for Segmental Bridge with Unbonded Tendons

Segmental bridges with unbonded prestressed tendons have some advantages over conventional concrete bridges, such as weather-independent construction and the corrosion protection of the prestressing tendons. This paper analyzes the behavior of a prestressed segmental bridge with unbonded tendons under combined loading of torsion, bending, and shear. According to experimental research, a modified skew bending model was developed to calculate the load-carrying capacity of segmental bridges subjected to combined bending, shear, and torsion. A finite element method (FEM) was used to investigate the deflection behavior of such a structure and to check the theoretical model. The theoretical and FEM research results compared favorably with test results. Finally, suggestions for the design and construction of segmental bridges with external prestressing were made.

Practical crack control during the construction of precast segmental box girder bridges

Cracks that occurred in the bottom slab of a precast segmental bridge were investigated through a construction sequence analysis, which revealed that the cracks were caused by excessive deformation during temporary post-tensioning while joining the segments. In addition, a parametric study was performed to evaluate the effects of the prestressing sequence, bottom slab thickness, and position of the prestressing anchors. The structural behavior of the girder sections was greatly affected by the thickness of the bottom slab and the position of prestressing anchors, but not by the prestressing sequence. Based on the results, a construction method that prevents the cracks is proposed.