Large-scale Bridge Research Articles

The study of wind effects on the bridge constructions

Construction of bridge structures occupies one of the leading positions in the construction industry. However, the design of these objects is a complex multi-factor task. Particular attention in the development of bridge structures must be paid to wind loads, since their dynamic loads can cause a number of adverse aeroelastic reactions. Large-scale bridge structures, which are flexible structures, are more susceptible to horizontal influence of the wind. This article presents a description of the study of wind impact on a bridge being built in the city of Moscow, according to a technique that was developed by employees of the UNPL AAISK (NRU MGSU). In this case, a test of the span section of the model on a specialized stand was conducted. The example of this object shows a graph of the dependence of the amplitude of oscillations of the bridge span on the wind speed without the use of fairings and their installation. According to the results of the work conclusions.

Non-contact fatigue crack detection in civil infrastructure through image overlapping and crack breathing sensing

Abstract Fatigue cracks are of critical structural safety concern in civil infrastructure. Many existing fatigue crack sensing methods are contact-based, hence extensive human operation is necessary for sensor and/or actuator deployment. In this study, we propose a vision-based non-contact approach to detect fatigue cracks through image overlapping. We treat crack breathing behavior, the small cyclic movement of the crack perpendicular to the crack path under repetitive fatigue loads, as a robust indicator for crack identification. The differential image features provoked by a breathing crack can be extracted, enhanced, and visualized through a series of image processing techniques. The performance of the proposed approach is experimentally validated through two laboratory setups including a small-scale steel compact specimen and a large-scale bridge to cross-frame connection specimen. Test results demonstrate the capability of the proposed approach in reliably identifying the fatigue crack, even the true crack is surrounded by other non-crack features.

Autonomous main-cable vibration monitoring using wireless smart sensors for large-scale three-pylon suspension bridges: A case study

Suspension bridges are supported by main cables that continue beyond the pillars to deck-level supports and must be anchored at each end of the bridge. The dynamic characteristics of the main cables are key indicators used to assess the structural health status of a bridge. In situ real-time health monitoring is an effective way to assess the dynamic characteristics. This paper presents a case study using vibration-based wireless smart sensors deployed on the main cables of a large-scale three-pylon suspension bridge to obtain its dynamic features. The methods of anti-aliasing filtering, statistical analysis and main cable tension force estimation were proposed and embedded into wireless smart sensors to provide autonomous data processing. According to the analysis of the vibration data from the main cables, the results demonstrate that the main cables have been in a stable state over time, and wireless smart sensors are promising for autonomous main-cable monitoring of large-scale three-pylon suspension bridges.

Large-scale testing of shrinkage mitigating concrete

Early-age cracking on concrete bridge decks is a major concern because it leads to premature deterioration of bridges. This study experimentally investigates the effects of restrained drying shrinkage on bridge decks using three 2 × 3 m experimental concrete slabs designed to simulate a portion of a bridge deck. The large-scale experimental bridge slabs used in this study were designed to closely replicate the restraint found in the field. Three different concrete mixtures are evaluated including (1) a mixture containing 100% portland cement, (2) a mixture incorporating Type-K cement, and (3) a mixture containing partially saturated lightweight fine aggregate to promote internal curing. As expected, the deck-containing Type-K cement had the highest initial expansion, but the internally cured concrete deck exhibited less shrinkage compared to both the control and the Type-K mixtures and adequately reduced the onset of cracking owing to restrained drying shrinkage.

Research on real time monitoring of prestressed concrete beam bridge

In order to ensure the safe operation of the bridge, it is very necessary to establish real-time monitoring system on some extraordinary large-scale bridges. In this paper, the prestressed concrete continuous bealm bridge is taken as the research object. Firstly, ANSYS is used to establish the initial finite element model according to the design data of the bridge, and then update the calculation model to conform to the actual state of the structure. After that, the analysis of mechanical performance under design load is carried out to provide a theoretical basis for the optimal placement of sensors. Finally, the bridge real-time monitoring system is set up and the collected monitoring data (displacement, strain, acceleration, etc.) is taken a statistical analysis, for the purpose of making a preliminary judgement on the actual operation of the bridge, and being considered as the theoretical basis and database of real-time monitoring system for follow-up study.

Research on Bridge Construction Control Technology Based on Mobile Formwork

After years of development and exploration of bridge construction technology, new construction methods have emerged. Relevant researchers continue to deepen the research and exploration of mobile formwork. The application of this method to bridge construction has only been developed in recent years. Because of this bridge construction method has many advantages, it is selected in modern bridge construction. The scope of application is more and more extensive. The construction method of the movable formwork construction method is procedural, which can greatly reduce the construction period, it has a relatively small impact on normal traffic, does not require a large amount of basic treatment work before the construction and can make the construction period to a large extent. shorten. These advantages make the construction method of mobile formwork developed and applied relatively quickly, especially in the construction of medium and small span bridges, the advantages of its application are more obvious. In the construction of large-scale bridges, large-scale movable formworks are needed. There are still many problems that need to be solved in the construction of large-scale movable formworks for construction bridges, such as crack control, faulty stage control, and construction safety guarantee. In the study of this paper, the application technology of mobile formwork in bridge construction was discussed from aspects of construction design, construction control, etc., through the moving formwork structure. In terms of force analysis, load, etc., the key technologies for control of construction box girders are studied. From the aspects of abutment structure processing, pre-compression of movable formwork and intermediate-outside formwork adjustment, the key construction technology of “one-mold double beam” movable formwork was studied. The passage provides practical reference for relevant technical personnel of bridge construction and provide method cases for researchers in the field of mobile formwork construction control technology.

Inelastic response analysis of bridges subjected to non-stationary seismic excitations by efficient MCS based on explicit time-domain method

This paper is devoted to stochastic response analysis of large-scale bridges with local plastic deformations under non-stationary random seismic excitations. A force-based fiber beam–column element is employed to simulate the inelastic behavior of bridges. By use of the explicit time-domain expressions of seismic responses, an effective dimension-reduced method is developed for fast inelastic time-history analysis of a structure with local nonlinearities. Only the nodal displacements that are associated with the inelastic elements need to be solved through iteration process, which leads to a significant reduction in computational cost for inelastic time-history analysis. With the merit of high efficiency, the dimension-reduced method is further used as a computational tool for repetitive inelastic time-history analyses in Monte Carlo simulation, and the statistical moments and mean peak values of critical responses can be readily achieved under random seismic excitations. To demonstrate the feasibility of the present approach, the nonlinear random vibration analysis of a long-span suspension bridge with a main span of 1200 m is carried out under rare earthquakes, in which the inelastic behaviors of the main towers are investigated with the use of inelastic fiber elements.

Research on the Precision Control Technology of Short - line Segmental Prefabricated Assembly Bridge

Short-line prestressed assembly bridge construction method has been widespread used for more than 10 years in China, unlike the “wysiwyg” cast-in-place beam, prefabrication and assembling construction process control is more important, especially for the virtual segment assembly. Due to the short line method commonly used in the large-scale bridge project, it is necessary to research intensive construction control, and improve the level of short line method. This article studied in two ways: the precast assembling error processing and precision control based on parametric analysis of the structure deformation.

Temperature insensitive curvature sensor based on cascading photonic crystal fiber

Abstract A temperature insensitive curvature sensor is proposed based on cascading photonic crystal fiber. Using the arc fusion splicing method, this sensor is fabricated by cascading together a single-mode fiber (SMF), a three layers air holes structure of photonic crystal fiber (3PCF), a five layers air holes structure of photonic crystal fiber (5PCF) and a SMF in turn. So the structure SMF-3PCF-5PCF-SMF can be obtained with a total length of 20 mm. During the process of fabrication, the splicing machine parameters and the length of each optical fiber are adjusted to obtain a high sensitivity curvature sensor. The experimental results show that the curvature sensitivity is −8.40 nm/m−1 in the curvature variation range of 0–1.09 m−1, which also show good linearity. In the range of 30–90 °C, the temperature sensitivity is only about 3.24 pm/°C, indicating that the sensor is not sensitive to temperature. The sensor not only has the advantages of easy fabricating, simple structure, high sensitivity but also can solve the problem of temperature measurement cross sensitivity, so it can be used for different areas including aerospace, large-scale bridge, architectural structure health monitoring and so on.

Performance analysis of simulation-based optimization of construction projects using High Performance Computing

Abstract The complexity and uncertain nature of bridge construction projects require simulation for analyzing and planning these projects. On the other hand, optimization can be used to address the inverse relationship between the cost and time of a project and to find a proper trade-off between these two key elements. In addition, the large number of resources required in large-scale bridge construction projects results in a very large search space. Therefore, there is a need for using parallel computing to reduce the computational time of the simulation-based optimization problem. Another problem in this area is that most of the construction simulation tools need an integration platform to be combined with optimization techniques. To alleviate these limitations, an integrated simulation-based optimization framework is developed within one High Performance Computing (HPC) platform, and its performance is analyzed by carrying out a case study. A master-slave (or global) parallel Genetic Algorithm (GA) is used to decrease the computation time and to efficiently use the full capacity of the computer. In addition, sensitivity analysis is applied to identify the promising configuration for GA and the best number of cores used in parallel and to analyze the impact of GA parameters on the overall performance of the simulation-based optimization model. Using NSGA-ΙΙ as the optimization algorithm resulted in better near-optimal solutions compared to those of fast-messy GA. Moreover, performing the proposed framework on multiple nodes using the cluster system led to 31% saving in the computation time on average. Furthermore, the GA was tuned using sensitivity analyses, which resulted in the selection of the best parameters of the GA.

Comparative evaluation of two simulation approaches of deck-abutment pounding in bridges

The present paper compares two simulation methods of the deck-abutment pounding in bridges: the commonly adopted gap element (or compliance) approach and a nonsmooth dynamics approach. Specifically, the study evaluates these two approaches with respect to their ability to predict the measured response of a straight, large-scale bridge model from an independent experimental study. The paper also investigates the sensitivity of the deck response to critical assumptions of the compliance approach, i.e., the stiffness of the gap element, the presence of friction during contact, the occurrence of sticking during frictional contact, and the constitutive law of the contact elements. The results show that the deck rotation predicted by these two approaches might differ notably, and highlight the dominant role of friction and its modelling on the seismic response of bridges involving pounding at the deck level.

An iterative order determination method for time-series modeling in structural health monitoring

Statistical time-series modeling has recently emerged as a promising and applicable methodology to structural health monitoring. In this methodology, an important step is to choose robust and optimal orders of time-series models for extracting damage-sensitive features. In this study, an iterative order determination method is proposed to determine optimal orders based on residual analysis. The proposed technique consists of identifying the best time-series model, determining the maximum orders, and selecting the optimal orders that enable the model to extract uncorrelated residuals. The application of low-pass signal filters to the process of order determination is also evaluated. In a comparative study, the influence of optimal orders on damage is assessed to perceive whether features extracted from optimal models, with and without using low-pass filters, are sensitive to damage. Experimental data of a three-story laboratory frame and a large-scale bridge are applied to demonstrate the performance and capability of the proposed method. Results show that the proposed iterative method is an efficient tool for the determination of optimal orders along with the extraction of uncorrelated residuals.

Conductance of Junctions with Acetyl-Functionalized Thiols: A First-Principles-Based Analysis

Thiol-based contacts are widely used in fabrication of molecular junctions but are associated with several drawbacks due to their chemical reactivity. In particular, their tendency to dimerize by forming sulfur–sulfur bonds is viewed as a barrier for large scale bridge fabrication. Instead, the use of functionalized sulfur end groups in the fabrication of the junctions is promoted. We analyze the effects of thiol functionalization by acetyl on the transport properties of porphyrin based bridges. In scanning tunneling microscopy (STM) experiments, where the conductance is measured as the tip is retracted, we observe molecular conductance steps due to junctions with acetyl protected thiols that are significantly lower than observed for junctions with deprotected thiols (by a factor of ≈5). Using a first-principles based computational approach, we explain the lower conductance of junctions with acetyl functionalized thiol and associate it to chemical changes of the sulfur, where essentially a tunneling barri...

Spiral strand cables subjected to high velocity fragment impact

Structural cables are widely adopted around the world in offshore construction, sports stadia, large scale bridges, Ferris wheels and suspended canopy and fabric structures. However, the robustness of such structures to blast or impact is uncertain with a particular concern related to the loss of a primary structural cable when damaged by high velocity blast fragmentation. This paper presents the first ever numerical and experimental study on commonly used high-strength steel spiral strand cables subjected to high velocity fragment impact. Spiral strand cables were impacted by 20mm fragment simulating projectiles travelling at velocities between 200 and 1400m/s. Complex 3D non-linear finite element models were developed and carefully compared with experimental tests. The penetration resistance of the cables and resultant damage were studied with respect to fragment impact velocity. It was found that for all the impact velocities, the fragment penetration depth was less than half of the cable diameter demonstrating a considerable amount of resilience. Considering the damage caused, the residual cable breaking strengths were estimated and found to be still higher than the minimum breaking load of an un-damaged cable. The numerical models were also able to reproduce the main features of the impact tests, including the extent of localised damage area, the fragment penetration depth and mode of individual wire failures, thus demonstrating their potential to be widely used in industry for structural resilience and robustness assessments by structural engineers.

Effects of Geometric Imperfections on the Bracing Performance of Cross Beams during Construction of Composite Bridges

Steel girders require stability controls for different construction stages before the lateral-torsional support from the concrete deck occurs. The load-carrying capacity of bridge girders and bracing forces generated in their bracings are very sensitive to the girders' initial imperfections in terms of both the magnitude and distribution along the span. Relatively little knowledge is available in this matter; however, decisions on the worst shape of imperfections that gives a conservative resistance and/or maximizes the bracings forces is often not an easy task in practice. The present paper reports the test results (in terms of the load-carrying capacities and bracing forces) of a large-scale bridge of twin I-girder type in which the location of the intermediate cross beam was varied across the depth of the main girders. Moreover, extensive numerical investigations were performed to study the effects of some relevant shape of imperfections on both the load-carrying capacities of the studied bridges and the magnitude of bracing forces generated in the cross beams that were involved. The test results showed that the load-carrying capacity of steel girders can exceed their lowest theoretical eigenvalue because of the presence of initial imperfections. In the finite-element analyses of the studied bridge cases, in some cases, the girders followed their shape of geometric imperfections and reached a load value that was greater than the lowest eigenvalue of the systems.

Experimental and three-dimensional finite element method studies on pounding responses of bridge structures subjected to spatially varying ground motions

Pounding and unseating damages to bridge superstructures have been commonly observed in many previous major earthquakes. These damages can essentially attribute to the large closing or opening relative displacement between adjacent structures. This article carries out an experimental study on the pounding responses of adjacent bridge structures considering spatially varying ground motions using a shaking table array system. Two sets of large-scale (1:6) bridge models involving two bridge frames were constructed. The bridge models were subjected to the stochastically simulated ground motions in bi-direction based on the response spectra of Chinese Guideline for Seismic Design of Highway Bridge for three different site conditions, considering three coherency levels. Two types of boundary conditions, that is, the fixed foundation and rocking foundation, were applied to investigate the influence of the foundation type. In addition, a detailed three-dimensional finite element model was constructed to simulate an experimental case. The nonlinear material behavior including strain rate effects of concrete and steel reinforcement is included. The applicability and accuracy of the finite element model in simulating bridge pounding responses subjected to spatially varying ground motions are discussed. The experimental and numerical results demonstrate that non-uniform excitations and foundation rocking can affect the relative displacements and pounding responses significantly.

Retraction Notice: Resistance Analysis of Open Caisson Towing on Water in the Construction of the Large Scale Bridge

Retraction Notice: Resistance Analysis of Open Caisson Towing on Water in the Construction of the Large Scale Bridge

Performance-based design methodology for inundated elevated coastal structures subjected to wave load

This paper presents the method and results of a numerical study to develop a performance-based design methodology for elevated coastal structures with a focus on bridges. However, the methodology is applicable to other elevated coastal structures. A combined Eulerian–Lagrangian method for fluid–structure interaction was applied in order to compute forces on elevated coastal structures. The numerical results are in good agreement with test results of a large scale bridge section tested previously at the O.H. Hinsdale Wave Research Laboratory at Oregon State University. Specifically, a 5-m section of a prototype I-10 bridge section was used to demonstrate the fragility approach for performance-based design using four different levels of elevation. By introducing fragility modeling, a variety of design options can be considered consisting of either raising the elevation of the bridge or strengthening the structure itself in order to obtain the desired probability of failure for a specific intensity of hurricane surge and waves.

ENHANCED FINITE ELEMENT ANALYSIS OF COMPOSITE BEAMS WITH INTERLAYER SLIPS

An enhanced finite element model considering interface slips of composite beams was developed in this study by separating mathematical and physical meshes and introducing zero thickness interface elements to simulate discontinuous deformation of the interfaces. With separated mathematical and physical meshes, the overlapping of mathematical and physical elements in space was no longer required, and the sizes and shapes of mathematical elements can be chosen according to the mechanical descriptions of the physical elements. In each mathematical element, the physical area can be divided into multiple sub-domains. Each sub-domain can have different materials and geometry shapes, and can also have different mechanical characteristics, thus greatly reducing the number of mesh elements. Deflections, interface slips and the stress distribution of controlling cross-sections corresponding to a slip modulus increasing from zero to infinite can be easily obtained. In addition, a slip modulus range with a maximum extent of contribution to the composite beams can be directly determined. The proposed method is of high computational efficiency, and can be used in engineering practice involving complex structures, especially large-scale bridges subject to complicated loadings.

Structural damage alarming and localization of cable-supported bridges using multi-novelty indices: a feasibility study

This paper presents a feasibility study on structural damage alarming and localization of long-span cable-supported bridges using multi-novelty indices formulated by monitoring-derived modal parameters. The proposed method which requires neither structural model nor damage model is applicable to structures of arbitrary complexity. With the intention to enhance the tolerance to measurement noise/uncertainty and the sensitivity to structural damage, an improved novelty index is formulated in terms of auto-associative neural networks (ANNs) where the output vector is designated to differ from the input vector while the training of the ANNs needs only the measured modal properties of the intact structure under in-service conditions. After validating the enhanced capability of the improved novelty index for structural damage alarming over the commonly configured novelty index, the performance of the improved novelty index for damage occurrence detection of large-scale bridges is examined through numerical simulation studies of the suspension Tsing Ma Bridge (TMB) and the cable-stayed Ting Kau Bridge (TKB) incurred with different types of structural damage. Then the improved novelty index is extended to formulate multi-novelty indices in terms of the measured modal frequencies and incomplete modeshape components for damage region identification. The capability of the formulated multi-novelty indices for damage region identification is also examined through numerical simulations of the TMB and TKB.