Slab Bridge Research Articles

Thermally stressed state of asphalt concrete layer on a metal base

The results of a finite element study of the thermally stressed and deformed states of a fragment of a two-layer bridge structure, consisting of a bearing metal orthotropic slab with a layer of asphalt concrete applied on it, are presented. It is believed that the materials of the layers are characterized by different thermomechanical parameters, which determine the inhomogeneity of the stress and strain fields. An analogue of these phenomena can be the effect of transformation in electric thermal relays of thermal action on a bimetallic plate with different coefficients of thermal linear expansion into its mechanical displacements, which are used to actuate the switch and switches. Using the method of computer modeling, it was found that these factors lead to the concentration of stresses and strains and changes in the stress-strain state in all elements of the bridge structure end are not taken into account in the modern practice of designing and operating bridges, as well as are one of the reasons for the premature destruction of asphalt concrete pavements. To eliminate these shortcomings, on the basis of finite element algorithms, a theoretical analysis of the thermally stressed state of a metal bridge slab with an asphalt concrete pavement at various ratios of their thicknesses is carried out. It is shown that an increase in the thickness of the upper layer can lead to an increase in shear and normal tensile stresses initiated in it. Therefore, when designing bridge structures, these features should be additionally taken into account.

Flexural performance of UHPC-filled narrow joints between precast concrete bridge slabs

The deck slabs narrow joints in concrete bridges filled with Ultra-high performance concrete (UHPC) have the potential for wide application and high-efficiency promotion, but there is limited research available on this topic. This paper conducted flexural tests on the new joints. Ten precast concrete deck panels were designed and manufactured for concrete bridges. These panels were connected using UHPC-filled narrow joints. Combined with stress analysis, this study investigates the influence and mechanism of various factors on the mechanical performance of UHPC joints. These factors include the geometric shape of the joint, the roughness of the joint interface, the filling material used in the joint, the width of the joint, and the configuration of joint reinforcement (including the shape and length of lap reinforcement). The test results show that the panel with the UHPC joint filled with steel fibers has excellent flexural and bonding capacity. The jointed panel with a lap length of 140 mm and 120 mm has better flexural performance than the one with a lap length of 90 mm. The straight-jointed panel has a higher flexural capacity compared to the complex triangular-jointed panel. Additionally, reducing the joint width can achieve similar mechanical properties as before. A method has been proposed for calculating the flexural capacity of a jointed panel, utilizing the strut-and-tie model (STM). This method can accurately predict experimental results.

Review of the Analysis and Design of Foot Over Bridge by Using Steel Truss and Girder for Seismic and Wind Conditions with Identifications of Software Applications

A bridge is a structure that crosses a river, a valley, or a railway to connect one location to another. There are numerous kinds of bridges, including cantilever, cable-stayed, suspension, girder, deck slab, arch, and truss bridges. In any design, starting with a preliminary and detailed survey regarding bridge data, the loads that are primarily taken into account are dead load, live load, wind load, and seismic load. The methodologies that are accepted in software are modelling, material and section properties defined in software, assigning the material properties and section, boundary conditions applied, applied loading, analysis, and design. The software displays displacement, shear force, and moments. Starting with the deck slab, the loading mechanism moves up to the girder or steel truss, pier, and footing. There are various truss types accessible for design, including the K type, Howe, Pratt, and Warren. The review concludes that, while there are numerous materials available for bridge design, using cold-formed steel will lower project costs and FRP material, which will increase stiffness while reducing weight and strain. This review article applies to any study on the design of foot-over bridges, steel truss bridges, girders, and steel-truss bridges, materials suitable for bridges and their properties with experimental studies, software and load knowledge with codes, and additional research on this subject. The conclusion is that the steel truss may be replaced with a girder bridge when the steel truss is made with a tubular section and a Warren-type truss with material changes.

SHEAR EXPERIMENTS ON STRAIGHT REINFORCED CONCRETE SLABS

As the existing bridge stock is aging, assessment of existing bridges becomes increasingly important. In the Netherlands, the shear capacity of reinforced concrete slab bridges is found to be insufficient. In particular, the shear and punching shear capacity of reinforced concrete slab bridges subjected to concentrated loads from the design tandem or truck is subject to discussion, as the shear behavior is situated in between one-way and two-way shear. Currently, an experimental program is being conducted at Delft University of Technology to determine the shear capacity of straight and skewed reinforced concrete slabs under point loads near to the support. This paper presents the results of the 25 tests conducted on six straight slabs of 5m × 2.5 m × 0.3 m subjected to a proof load testing loading protocol. The failure load and modes of the slabs are described in detail. Reinforced concrete slabs under concentrated loads can fail in shear, punching, and flexure, as well as a combination of these failure modes. The results of the experiments are compared to strength predictions obtained by using current design models and current methods for assessment. These experiments demonstrated that the Dutch guidelines, which are based on previous slab experiments, are an improvement as compared to the Eurocode for the assessment of existing reinforced concrete slab bridges. Ultimately, this work provides recommendations for bridge engineers tasked to assess reinforced concrete skewed slab bridges.

Distribution characteristics and prediction method of tire–road AE noise in the monitoring of prestressed hollow slab bridges

During the acoustic emission (AE) monitoring of bridge, the AE signal we need can be easily masked by tire–road noise. To find out how much this noise affects the AE monitoring results of the bridge. In this study, controlled pass-by tests were carried out to collect the tire–road AE signals made by cars, buses, and heavy trucks with different speeds, where AE sensors are placed at multiple positions on the pavement and bottom deck of the bridge. In each case, the intensity and spectrum of AE noise were analyzed. Results show that the intensity of the tire–road AE noise increases with the speed, and the bandwidth of the main frequency increases slightly with the increasing speed. The peak frequency of the tire–road AE noise produced by the vehicles is approximately 2 kHz, and the AE energy distributes between 0 and 25 kHz. The proposed prediction method based on the characteristics of tire–road AE noise can effectively predict noise.

Research on the Application of Impact Echo Method in the Detection of Grouting Compactness of Hollow Slabs in Bridges

Research on the Application of Impact Echo Method in the Detection of Grouting Compactness of Hollow Slabs in Bridges

Basic research on dry shotcrete materials for restoration of bridge slab lower section

Basic research on dry shotcrete materials for restoration of bridge slab lower section

Seismic Risk Analysis of Existing Link Slab Bridges Using Novel Fragility Functions

In this paper, a comprehensive probabilistic framework is proposed and adopted to perform seismic reliability and risk analysis of existing link slab (LS) bridges, representing a widely diffused structural typology within the infrastructural networks of many countries worldwide. Unlike classic risk analysis methods, innovative fragility functions are used in this work to retrieve more specific and detailed information on the possible failure modes, without limiting the analysis to the global failure conditions but also considering several intermediate damage scenarios (including one or more damage mechanisms), and providing insights on the numerosity of elements involved within a given damage scenario. Reliability analyses are performed on a set of LS bridges with different geometries (total lengths and pier heights) designed according to the Italian codes enforced in the 1970s. Accurate numerical models are developed in OpenSees and Multiple-Stripe nonlinear time–history analyses are carried out to build proper demand models, from which fragility functions are determined according to two limit states: damage onset and near-collapse. Mean annual rates of exceeding are thus estimated through the convolution between the hazard and the fragility. The results shed light on the main failure mechanisms characterizing this bridge typology, highlighting how different levels of risk (hence safety margins) can be associated with failure scenarios that differ in terms of elements/mechanisms involved and damage extension. Such a higher level of detail in the risk analysis may be useful to better quantify post-earthquake consequences (e.g., costs and losses) and define more tailored retrofit interventions. A comparison of the reliability levels associated with bridges of the same class with different geometries is finally presented.

A dynamic stiffness-based two-step method for damage identification of joints in hinged slab bridges using support vector machine

As critical components of hinged slab bridges, joints are of great importance to the bearing capacity and serviceability of bridges. The existing model-based joint damage detection methods are based on precise finite element models, and their identification accuracy is significantly affected by construction uncertainty. In this paper, dynamic stiffness is introduced into joint damage detection and a two-step framework is proposed for the damage localization and quantification of joints in hinged slab bridges. The dynamic stiffness-based data-driven method is suitable for the evaluation of bridges with incomplete information or bridges with serious damage. Firstly, the second-order difference of dynamic stiffness (SDDS) calculated by slabs’ responses is used an indicator to locate the damage. Secondly, Bayesian optimization is utilized to optimize the model hyperparameters of the support vector machine (SVM), where the dynamic stiffness serves as the characteristic vector for training the optimized SVM network. The applicability of this method was numerically validated using a grillage model of a hinged slab bridge, taking into consideration factors such as noise interference, impact location, sensor placement, and impact force characteristics. Additionally, on-site experiments were conducted on an in-service bridge to verify the effectiveness of the proposed method. Analysis results demonstrate that the proposed two-step method can properly evaluate joint damage with less dependence on the impact locations, force amplitude and environmental factors, and thus can be used for rapid damage identification of in-service hinged slab bridges and quantitative evaluation of repair effect.

Damage identification of hinge joint in hollow slab bridge based on model updating and orthogonal matching pursuit algorithm

Hinge joints are crucial for transverse force transfer in prestressed hollow slab bridges. Damages to hinge joints cause overall instability, load distribution changes, and reduced bearing capacity of the bridge. A new method using model updating and the orthogonal matching pursuit (OMP) algorithm is proposed to accurately assess the damage of hinge joints in such bridges using a single measurement point. The hinge joint damage index obtained by the OMP algorithm is assigned to the corresponding hinge joint in the FE model to complete the model update. Results show that this method can accurately identify hinge joint damage locations and degrees with a single measurement point. The damage identification of 12 hinge joints of an in-service hollow slab bridge is carried out, and the findings reveal that the damage occurred on the fourth, fifth, and seventh hinge joints.

Retrofitting of Bridge Slabs for Safety Railing Refurbishment in Italy: A State-of-the-Art Review

The recent accident of Mestre (northern Italy), which caused 21 fatalities due to a bus falling from a bridge, strongly highlighted the safety problem related to the presence of old railings along Italian roads. Bridge railings, also known as guardrails or parapets, serve the crucial function of preventing vehicles from accidentally driving off the edge of a bridge. Performance requirements of safety railings have been recently increased due to laws and technical standards enforced in Italy and Europe. However, many bridges along important roads, such as motorways and highways, are currently equipped with outdated safety railings since they were built before these regulations came into force. Therefore, many people are daily exposed to the risk of heavy accidents due to railing failures as well as vehicles and people eventually present below such structures. This paper aims to outline the technical problems and solutions in bridge refurbishment interventions devoted to increasing traffic safety as, for example, the installation of code-conforming railings, which often require the structural retrofit of bridge elements supporting the railing. To this end, several technical solutions are described and critically compared, and, finally, an economic analysis is reported to highlight the slab retrofit influence on the total intervention cost.

Embodied Energy Optimization of Prestressed Concrete Road Flyovers by a Two-Phase Kriging Surrogate Model.

This study aims to establish a methodology for optimizing embodied energy while constructing lightened road flyovers. A cross-sectional analysis is conducted to determine design parameters through an exhaustive literature review. Based on this analysis, key design variables that can enhance the energy efficiency of the slab are identified. The methodology is divided into two phases: a statistical technique known as Latin Hypercube Sampling is initially employed to sample deck variables and create a response surface; subsequently, the response surface is fine-tuned through a Kriging-based optimization model. Consequently, a methodology has been developed that reduces the energy cost of constructing lightened slab bridge decks. Recommendations to improve energy efficiency include employing high slenderness ratios (approximately 1/28), minimizing concrete and active reinforcement usage, and increasing the amount of passive reinforcement.

Cost-effective methods for flexural strengthening of one-way RC precast flat slab bridges in South Carolina

In South Carolina, there are one-way precast RC flat slab bridges that were constructed in the 1950 s for H-10 and H-15 design trucks (lower than the current design standards) and have deteriorated over time. To ensure public safety and continued usage, strengthening the bridges is imperative. Various methods exist for flexural strengthening, including application of UHPC from above and strengthening from below with FRP, steel plates, and external prestressing. However, these methods may compromise the ductile behavior of the slabs and they are also challenging, labor-intensive, and expensive to apply. The innovation of this paper lies in investigating the methods for strengthening from above that have the potential to improve both the flexural strength and ductility of slabs, while offering advantages in terms of ease of implementation and cost-effectiveness compared to existing methods. Five slabs obtained from decommissioned bridges in South Carolina were tested under monotonic loading to failure: one reference slab; one slab strengthened with steel channel sections from above; one slab strengthened with steel plate sections from above, and two slabs connected at the joint by near surface mounted steel rebars for strengthening. Strengthening the slabs with steel channel sections from above effectively improved the flexural strength and ductility of the slabs while being more economical and easier to implement than other methods of strengthening. Following strengthening, some slabs may require overlays to cover the steel sections and ensure that bridge traffic may go on them. Even after accounting for reduction in strength gain due to the deadload of the overlay, a positive net strength gain in measured peak moment was observed in the strengthened slabs. The moment capacities of the slabs, as determined through design calculations following the ACI 318–19 code, exhibit a good agreement with the measured peak moment observed in experimental tests, thus validating their reliability as a dependable alternative to solely relying on experimental tests.

A study on the deflection and crack layout in a hollow slab bridge

A study on the deflection and crack layout in a hollow slab bridge

Damage modes and mechanism of steel-concrete composite bridge slabs under contact explosion

The steel-concrete (SC) composite bridge slab is widely used in long-span bridges. With the increasing threat of explosive attacks on bridges, understanding the blast-resistant performance of composite bridge slabs is important. In this paper, SC composite slabs with different types of interfaces between concrete slab and steel plate, and different steel plate thickness, were tested under contact explosion. The damage modes and dynamic responses were carefully observed and measured. Refined FE models were developed to investigate the damage mechanism by analyzing and comparing the detailed damage process of slabs and characteristics of stress wave propagation. The results revealed that the damage modes of SC composite slabs varied significantly depending on the type of interface. For slabs with stud connectors, the compressive stress wave propagated within the composite slab in a spherical pattern and finally induced a circular concrete crater and steel plate deformation. Increasing the thickness of steel plate significantly reduced steel plate deformation. For slab with PBL connectors, the stress wave in the concrete was attenuated when it propagated across the PBL ribs, while the stress of concrete between the ribs nearest to the explosion was much large than that outside the ribs. Stress reflection on the top of PBL ribs increased the damage degree of concrete, potentially leading to induced cracks along the ribs. The overall response of composite slabs could be divided into the combined phase and separated phase. The PBL ribs could better restrain the interface detachment compared to studs.

Applications of Machine Learning to Predict the Flexural Bearing Capacity of Hollow Core Slabs After Fire Exposure

Conventional evaluation of the overall mechanical properties and ultimate flexural capacity of prestressed hollow core slabs after a fire exposure depends heavily on the inversion of fire scene temperature. To avoid this drawback, this paper presents a new methodology which combines a generalized regression neural network (GRNN) with conventional non-destructive testing technology. Thereby, a neural network model for predicting the material performance parameters after fire exposure is obtained based on conventional testing indices. A hollow core slab bridge is used as an example, and the applicability of the trained network model is confirmed using numerical simulation and a field failure test. Results show that the overall relative error of GRNN in predicting the key performance parameters of the bridge after fire exposure is less than 10%. Further, because of the good thermal inertia of the concrete, the relative error in predicting the material performance parameters of steel after a fire is less than 5%. Moreover, the ultimate flexural capacity of the prestressed hollow core slab after a fire can be accurately evaluated by feeding the material performance parameters predicted by GRNN neural network into the finite element (FE) model.

Vulnerability to traffic loads of typical Italian bridges in relation to the evolution of the code framework

AbstractOver the last century, the definition of the design traffic loads for Italian road bridges has undergone a continuous evolution, starting from the first code in 1933 up to the current code. The changes in the arrangement and in the intensity of the design loads that have occurred over the years resulted in significant variations, both decreasing and increasing the overall static demand required to the bridges compared to previous codes.As part of a broader study on the structural risk of existing bridges with respect to traffic loads, it is certainly of interest to investigate the influence of the adopted design code on the risk itself. The paper presents some of the results of a study conducted with this purpose, regarding Prestressed Concrete beam‐and slab bridges with simply supported spans, one of the most common typology among bridges with medium‐small span.The comparison between historical codes and current one is carried out in terms of internal forces of the most stressed girder, taking into account the transverse distribution of loads. The study can provide useful elements for the definition of a fast procedure for the preliminary assessment of typical existing Italian bridges based on the geometric characteristics of the decks and their design age.

Orthotropic composite slabs for road bridges

AbstractLarge increases in traffic loads led to extensive fatigue damages to existing orthotropic steel deck slabs of road bridges. Reinforced concrete bridges and conventional composite bridges are less susceptible to fatigue but considerably heavier. The ortho‐composite slab is a lightweight and robust alternative construction method, which retains the advantages of the previously mentioned construction methods, but eliminates their disadvantages. Within the framework of the AiF‐FOSTA research project P1265 [1], the construction of the bridge deck was developed using dowel strips as composite elements with high load‐bearing capacity and fatigue resistance. The principle of area composite with loading of the dowel strips in longitudinal and transverse direction was used. Extensive experimental and structural mechanics studies were conducted, particularly investigating the load‐bearing capacity and fatigue strength of the ortho‐composite slab under local load application. The following article describes the load‐bearing structure of the ortho‐composite slab and the motivation for the research project P1265. It gives an overview of the experimental investigations carried out. Finally, the article presents pilot projects that were carried out to apply the construction method. In further articles on Eurosteel, the experimental investigations and structural‐mechanical calculations are described in more detail (see [2] and [3]).

Experimental Investigation of the Shear Resistance Mechanism on Hybrid NSC-UHPC Predamaged and Undamaged Unidirectional Bridge Slabs

Experimental Investigation of the Shear Resistance Mechanism on Hybrid NSC-UHPC Predamaged and Undamaged Unidirectional Bridge Slabs

Range Image-Aided Edge Line Estimation for Dimensional Inspection of Precast Bridge Slab Using Point Cloud Data

The accurate estimation of edge lines in precast bridge slabs based on laser scanning is crucial for a geometrical quality inspection. Normally, the as-designed model of precast slabs is used to match with laser scan data to estimate the edge lines. However, this approach often leads to an inaccurate quality measurement because the actually produced slab can be dimensionally different from the as-designed model or the inexistence of the as-designed model. In order to overcome this limitation, this study proposes a novel algorithm that generates and utilizes range images generated from scan points to enhance accuracy. The proposed algorithm operates as follows: first, the scan points are transformed into a range of images, and the corner points of these range images are extracted using a Harris corner detector. Next, the dimensions of the precast bridge slab are computed based on the extracted corner points. Consequently, the extracted corner points from the range images serve as an input for edge line estimation, thereby eliminating the matching errors that could arise when aligning collected scan points to an as-designed model. To evaluate the feasibility of the proposed edge estimation algorithm, a series of tests were conducted on both lab-scale specimens and field-scale precast slabs. The results showed promising accuracy levels of 1.22 mm for lab-scale specimens and 3.10 mm for field-scale precast bridge slabs, demonstrating more accurate edge line estimation results compared to traditional methods. These findings highlight the feasibility of employing the proposed image-aided geometrical inspection method, demonstrating the great potential for application in both small-scale and full-scale prefabricated construction elements within the construction industry, particularly during the fabrication stage.