Slab Bridge Research Articles

Equivalent Solution Method for the Analytical Transverse Modal Shape of Hollow Slab Bridges

Hollow slab bridges are the most widely used form of small- and medium-span bridges. The existing research on the dynamic characteristics of hollow slab bridges is mostly based on numerical models, but there is a lack of theoretical analyses of their dynamic characteristics. In this paper, the relationship between the dynamic characteristic parameters and structural parameters of a hollow slab bridge is explored theoretically. Firstly, the solid model of a hollow slab bridge was established, and a modal analysis was carried out on it as a reference. Then, an orthotropic plate was used as an equivalent dynamic analysis model, and the analytical form of the transverse modal shape was deduced based on Kirchhoff thin plate theory. Furthermore, one hinge joint was considered as being equivalent to the elastic support boundary, and the local structure and the equivalent elastic support boundary were used to reflect the transverse modal shape of the original structure. The analysis shows that the influence of hinge joints on the transverse modal shape is mainly reflected in the transmission of bending deformation. Through comparison and verification, the results show that the analytical expression of the transverse modal shape can well describe the low-order transverse modal shape of a hollow slab bridge.

Construction Technology of Underpinning and Pre-supporting Pile Foundation of Special-shaped Slab Beam in Urban Interchange

<p>With the rapid development of China's urbanization process, the original transportation plan cannot fail to meet the needs of urban economic development, and the transformation and upgrading of the urban transportation system is imminent. Urban rail engineering has become the only way to solve traffic problems in major core cities. However, conflicts between subway shield tunnels and existing building foundations occur from time to time, especially when some important buildings and public facilities cannot be demolished, underpinning technology is required. This paper relies on the Shijiazhuang Metro Line 2# underpassing the urban overpass special-shaped slab beam construction and bridge project built in 1994, combined with the past pile foundation underpinning and current intelligent construction technology, in the multi-support prestressed concrete special-shaped slab beam substructure pile foundation Intelligent pre-supporting technology is adopted in the underpinning construction process, which solves the problem of synchronous control of multi-supporting special-shaped slab girder under complex environment, and ensures the safety of construction and bridge operation.</p>

Transfer Matrix Method for Calculating the Transverse Load Distribution of Articulated Slab Bridges

Articulated slab bridges have been widely used by transportation administration for short-to-medium span bridges because of their good economy, convenient construction, and environmental advantages, while the presence of shear keys increases the complexity of structural behavior. Developing more reasonable analysis approaches of quick assessment, pre-design, and hand calculations for the articulated slab bridges is a challenge because of the peculiar shear key mechanism. This paper is devoted to presenting a recursive algorithm, based on the force equilibrium conditions of each individual slab, thus resulting in simultaneous equations of the transfer matrix method (TMM). In this procedure, the state vector is an array composed of vertical displacement, shear force, unit constant; and the transfer matrix contains the bending and torsional stiffness parameters of simply supported slabs. Then, the influence line of transverse load distribution (TLD) is calculated for each slab by introducing boundary conditions. To validate and verify the efficiency of the TMM algorithm, a transversely prefabricated void slab bridge with a span of 20 m is considered as a case study. The traditional force (FM) and finite element (FEM) methods are used for comparison and validation. It is demonstrated that the TMM can provide good results with higher algorithm efficiency by exempting the modeling tasks in FM and FEM and capture variations in TLD along the bridge’s span. In addition, the influence of the span length and relative stiffness coefficient of slabs on the TLD of articulated slab bridges are analyzed from the parametric analysis.

ВИПРОБУВАННЯ МОДЕЛЕЙ ПЛИТ ПРОЇЗНОЇ ЧАСТИНИ МОСТІВ ІЗ ЗАЛІЗОБЕТОННИМИ НЕЗНІМНИМИ ОПАЛУБКАМИ МЕТОДОМ ОПТИКО-ЦИФРОВОЇ СПЕКЛ-КОРЕЛЯЦІЇ ЗОБРАЖЕНЬ

Introduction. The article examines the testing method of monolithic slabs of bridges deck with permanent reinforced concrete formwork [1] using the method of optical-digital speckle-correlation of images [2]. Problem statement. A promising direction in cast-in-situ bridge construction is using of various types of permanent formwork during slab concreting. However, using of such formworks has not been studied much till today. Therefore, it is advisable to conduct a test of full-scale models of slabs. In domestic practice, mechanical devices, strain gauges, optical microscopes, etc. are used during laboratory studies and field tests of building structures to measure relative deformations and movements, as well as to visually observe the formation and development of cracks. All these devices require constant checking and maintenance and it is not always possible to do this. However, for the needs of laboratory tests with the method of optical-digital speckle correlation of images, a digital image of the object at different load levels is mostly sufficient. It is only necessary to choose the right optics according to the experimental area and ensure sufficient lighting. Purpose. The purpose of the work was in experimentally determining of the expediency of using the optical-digital speckle-correlation method of images in the models testing. Metods of study. According to the results of exploratory researches, it is proposed to apply the method of optical-digital speckle correlation of images. Results. The expediency of using the method of optical-digital speckle-correlation of images in the investigation of bridges deck models has been established. Conclusions. Using the method of optical-digital speckle-correlation of images makes possible to investigate the change of relative deformations and the movement of individual points or areas during the study of concrete surfaces. This, in turn, allows to investigate the places and nature of the formation of cracks and enables practical use - during the examination of existing structures, it is possible to record the places of future cracks and the relative deformations of individual areas.

Efficient Bayesian model selection and calibration using field data for a reinforced concrete slab bridge

In this work, a reinforced concrete slab bridge (instrumented and tested in 2018) is investigated. Based on field data, a finite element model of the bridge is calibrated. Model selection is performed both based on log evidence and posterior predictive capabilities. It is investigated if the models selected based on the log evidence also induce the most accurate posterior predictions. The influence of different assumptions on modelling the spatial distribution of the stiffness and different possible suggestions on how to include prediction errors and model bias are investigated. Comparing the conclusions based on log evidence and posterior predictions, only using the log evidence for model selection could be debated. Models performing best when considering the log evidence led to the least accurate posterior predictions, and models rejected based on the log evidence could still have good predictive capabilities. Considering the different model classes, introducing spatial variation of the stiffness leads to a posterior prediction closer to the measurements. Introducing a global model bias leads to a better match between predictions and measurements compared to not including this model bias. Even better posterior predictions are achieved if this model bias is quantified locally for the different considered datapoints.

Parametric Evaluation on Reinforced Concrete Solid Slab Bridges by Staad-Pro Software

Abstract: Designing with economy, grace, and sturdiness is the art and science of structural planning and analysis. To compete in the highly competitive market, structural designing necessitates a thorough structural analysis on which the planning is predicated. The use of software can reduce the number of man hours and efforts required for structural analysis, and an effort was made in the current study to accomplish this goal. This study's objective is to assess and design a solid-deck slab bridge using STAAD-Pro and a manual process under various loading circumstances. Additionally, STAAD-Pro, which runs through numerous load combinations, was used to check the analysis results in terms of shear, bending moment, axial force, and deflection. The highest design moments produced by the fusion of different loading scenarios.

A study of multi-target image-based displacement measurement approach for field testing of bridges

ABSTRACT As the demand for field testing of bridges grows, so does the need to optimize field testing procedures to allow for a simplified testing strategy that can be employed more effectively. With the advent of computer vision, there has been limited research exploring Feature-Based Image Registration (FBIR) methods for structural testing of bridges. In this paper, the potential of a simple FBIR approach to accurately capture submillimeter displacements using consumer-grade cameras will be demonstrated through a field test on a reinforced concrete slab bridge and on a full-scale bridge deck specimen in the laboratory. The internal and external parameters that influence the results of this measurement strategy were investigated by using various camera positions during the laboratory tests and applying different threshold parameters to the Speeded-Up Robust Features algorithm used for the feature detection and matching. The FBIR method demonstrates great potential, producing an average measurement accuracy within 1.6% of conventional displacement sensors during the field test and 3.3% during the laboratory tests. Altogether, the advantages to this image-based measurement approach enhance the load testing strategy to be implemented by bridge owners at much lower costs and with minimal complication and field setup.

Effect of Temperature on the Modal Variability in Short-Span Concrete Bridges

The dynamic characteristics of bridges are known to be affected by damages as well as by environmental factors such as temperature. Therefore, the changes in the dynamic characteristics caused by damages and environmental factors should be considered when evaluating the health of the structure. Accordingly, this study conducted long-term monitoring and modal identification of short-span concrete bridges, i.e., a RC (reinforced concrete) slab bridge a RC rahmen (rigid-frame) bridge. The investigation revealed that temperature is the factor having the greatest influence on the variability of the dynamic characteristics as the natural frequencies of the bridge decrease with higher temperatures. Model updating verified that such modal change resulted from the temperature dependency of the elastic modulus of concrete. The RC slab bridge showed higher temperature dependency than the RC rahmen bridge owing to the presence of elastomeric bearings. Apart from the effect of temperature, non-negligible modal changes caused by other environmental factors were also identified. The results of this study are expected to provide valuable data for the health evaluation of bridges.

Temperature distribution simulation and thermal properties investigation of hollow slab beam based on meteorological data

Natural environment has a great impact on the performance of bridge structures, such as the ambient temperature, solar radiation, climate extremes and so on. Due to the lack of regional pertinence in the provisions of the existing specifications on the temperature load standard, and the lack of verification of its adaptability of hollow slab beam bridge in the reconstruction and expansion project, it is necessary to study the temperature load of the beam based on the temperature data of the area where the bridge site is located. Based on the measured meteorological data, the cross-section temperature distribution characteristics of the hollow slab beam and the temperature load effect were investigated. The vertical temperature load model of the short and medium-span hollow slab beam was proposed according to the simplified temperature curve. Firstly, based on the annual measured meteorological data, the plane model was established to analyze the temperature distribution characteristics of the hollow slab beam. Secondly, according to the temperature field distribution of the beam cross-section, the solid model of 16 m hollow slab beam was established to analyze the distribution of the temperature load effect. Finally, based on the preliminarily proposed temperature curve, vertical temperature load models were proposed by introducing the theory of extreme value extrapolation. The studies have shown that the temperature of the hollow slab beam is approximately horizontal distributed, and temperature extreme value appear at the location of the beam web. The roof and floor of the hollow slab beam are compressed and the webs are tensioned in the positive temperature difference state, the stress condition is opposite under the negative temperature difference state. The positive and negative temperature load models can meet the extrapolation requirements of the bridge design reference period. This study innovatively proposed a temperature load model based on the temperature curve corresponding to the most unfavorable effect of the beam. The extrapolation idea in the derivation of vehicle load model is introduced as well. And a temperature load model suitable for the extension of hollow slab bridges in Guangdong is established in this study.

Theoretical analysis of stress of asphalt mixture bridge deck pavement based on design index

At present, the specification for the design of asphalt mixture bridge deck pavement is missing, so it is of great significance to research on it. In order to study the design theory of asphalt mixture bridge deck pavement, the bottom tensile strain of asphalt mixture layer and the permanent deformation of asphalt mixture layer as the design index of asphalt mixture bridge deck pavement have been selected. Combined with a specific simply supported slab bridge, the mechanical properties and influencing factors of asphalt mixture bridge deck pavement based on the design index have been analyzed. Firstly, the section characteristic calculation basis of fatigue checking calculation is proposed by using the standard method, and the fatigue section characteristic of simply supported solid slab bridge is analyzed. Considering different load positions, the calculation method of fatigue stress under design load and ultimate load is proposed, and the fatigue stress is calculated. According to the equal strain principle, the bottom stress of asphalt mixture is calculated. Secondly, based on the assumption of plane section, the strain calculation formula of rectangular section with two parameters under temperature load is deduced. Using the derivation formula, the stress distribution of the section under the action of uniform temperature and gradient temperature is calculated, and the general stress distribution law is obtained. Finally,take Specification for design of highway asphalt pavement (JTG D50-2017) for reference to calculate the permanent deformation of asphalt mixture bridge deck pavement; Compared with the field measured value, the theoretical calculated value is less than the field measured value, which may be related to the insufficient compaction of asphalt on the bridge deck.

Theoretical analysis of stress of asphalt mixture bridge deck pavement based on design index

At present, the specification for the design of asphalt mixture bridge deck pavement is missing, so it is of great significance to research on it. In order to study the design theory of asphalt mixture bridge deck pavement, the bottom tensile strain of asphalt mixture layer and the permanent deformation of asphalt mixture layer as the design index of asphalt mixture bridge deck pavement have been selected. Combined with a specific simply supported slab bridge, the mechanical properties and influencing factors of asphalt mixture bridge deck pavement based on the design index have been analyzed. Firstly, the section characteristic calculation basis of fatigue checking calculation is proposed by using the standard method, and the fatigue section characteristic of simply supported solid slab bridge is analyzed. Considering different load positions, the calculation method of fatigue stress under design load and ultimate load is proposed, and the fatigue stress is calculated. According to the equal strain principle, the bottom stress of asphalt mixture is calculated. Secondly, based on the assumption of plane section, the strain calculation formula of rectangular section with two parameters under temperature load is deduced. Using the derivation formula, the stress distribution of the section under the action of uniform temperature and gradient temperature is calculated, and the general stress distribution law is obtained. Finally,take Specification for design of highway asphalt pavement (JTG D50-2017) for reference to calculate the permanent deformation of asphalt mixture bridge deck pavement; Compared with the field measured value, the theoretical calculated value is less than the field measured value, which may be related to the insufficient compaction of asphalt on the bridge deck.

Damage mechanism of conventional joints and proposal of a novel joint for hollow-core slab bridges

Damage mechanism of conventional joints and proposal of a novel joint for hollow-core slab bridges

Corrosion evaluation of steel bars in steam-cured concrete under chloride attack and alkali–silica reaction

One of the challenges to reinforced concrete slabs in bridges is deterioration due to rebar corrosion by deicing salts. In order to simulate a concrete slab subjected to deicing salt penetration from the top surface of the bridge slab during winter, high-strength steam-cured concrete with double-layer reinforcements was exposed to 10% sodium chloride solution to investigate rebar corrosion. Five concrete mix proportions were prepared, including high early strength concrete and concrete containing fly ash and blast furnace slag as supplementary cementitious materials (SCMs). For both the high early strength and fly ash concretes, alkali active andesite in the pessimum proportion was mixed with coarse aggregates to investigate the effect of alkali–silica reaction (ASR) on rebar corrosion. It was found that the combined effects of chloride attack and ASR adversely affected the corrosion resistance of high early strength concrete. Fly ash concrete had excellent performance as to corrosion resistance and ASR mitigation. Results also showed that a widely used electrochemical technique known as the half-cell potential test can satisfactorily diagnose corrosion of double-layer reinforced concrete. Concrete specimens containing SCMs with no ASR threat showed no signs of steel bar corrosion and significantly low chloride diffusion coefficients after 3 years.

Investigation on the crack formation in carbon concrete for the use in deck caps on cantilever slabs of bridges

AbstractDeck caps of bridges—in Germany shortly known as “bridge caps”—are usually made of steel reinforced concrete to form the anchoring area for the guardrail of bridge deck edges on existing cantilever slabs. Combined with protective devices, the outside arranged deck caps provide safety against lateral breaking or crashes of vehicles. Due to their exposed position in the cross section of bridges and the particularly intensive stresses, the deck caps are considered as wear parts and have to be renewed several times during the service life of a bridge. The decisive factor here is the discrepancy between the frost resistance of the concrete and the crack width restriction. On the one hand, only very small cracks (<0.2 mm) can be accepted to prevent corrosion of the rebars under the strong exposure of these elements. To confine crack widths without applying an excessively high degree of reinforcement, a low concrete compressive strength is advantageous. On the other hand, a sufficient frost resistance requires a correspondingly high compressive strength. With carbon reinforcement, these contrary points could be defused and simultaneously the needed durability could be provided. Therefore, slightly modified deck cap concretes combined with a carbon reinforcement mesh were tested to examine the bond behavior with and without freeze–thaw attack. To prove the characteristics of this combined system, the crack formation and crack distribution were investigated experimentally. The test results were compared to calculated values from a mathematically tool to be able to develop different reinforcement concepts in future that can ensure an optimized crack formation and crack width for deck caps.

Analysis of the Condition of Tendons in Prestressed Concrete Structures

Prestressing Steel Fracture Detection Bernd Hillemeier, Simon Knapp, Thomas Luther Abstract The earliest possible non-destructive location of a prestressing steel fracture is a challenge of our time. The endangerment of prestressing steels through stress cor-rosion cracking and hydrogen embrittlement is not visible from the outside. The estimated service life of existing prestressed concrete structures must take into account the construction plans as well as the construction year. The design criterion "crack before break" did not always have priority. Magnetic fields open up a view of the interior of the supporting structure. They show the condition of the prestressed reinforcement in a picture document. The method is practicable and has already developed so far that the DGZfP published the position paper „Magnetische Verfahren zur Spannstahlbruchortung" ("Magnetic methods for prestressing steel fracture location") in 2017. The know-how of prestressing steel fracture detection is to imprint magnetic fields into the prestressed reinforcement. This happens with electromagnets or permanent magnets. The smaller and more manageable the devices, the less their depth effect. The specific advantage of those devices lies in measuring prestressed concrete gird-ers with direct bond and low concrete cover. How do you guide the magnets, how do you interpret the data? Transverse tendons in carriageway slabs are tested at pe-destrian speed to a width of 3.5 m with a 3 t heavy self-propelled electromagnet, preferably at night due to traffic conditions. Despite the fact that our many years of practical experience from Germany, Switzerland, GreatBritain and the USA lead to the constant further development of the process steps, more and more specific measuring tasks are carried out more practically and economically. shows that the probability of failure without early announcement is low. The answer to the question of whether there are cracks in tendons and, if so, in what number and how they are spatially distributed, significantly increases the reliability of the in-formation concerning safety. The non-destructive testing method based on rema-nence magnetism localizes fractures in prestressing steels in a direct bond or in ducts. The presentation will show examples from the areas of prestressed concrete girders of bridge structures, carriageway slabs of road and motorway bridges with a tested area of around 4000 m² per day, floor slabs of parking garages, prestressed con-crete girders in swimming, sports and industrial halls, VT folds of hall structures and Tank container in prestressed concrete construction. Nevertheless, if the complexity of a structure with regard to the arrangement and concentration of the mild and prestressed concrete reinforcement is great, the labor-atory test with the simulated reinforcement situation is recommended. In the case of the shell roof of the town hall in Biel (Switzerland), in addition to the laboratory repro-duced structure in Berlin, the client manufactured another test element for experi-mental verification. The presentation also reports on this.

Damage modes and residual deflections of multi-beam hollow slab bridge under car explosions

The purpose of this study is to investigate the damage modes and residual deflection of multi-beam hollow slab bridges under car explosions. To comprehensively estimate the blast response, the failure process of the bridge with different beam numbers are cautiously simulated and compared. With the experimentally validation of the constitutive laws and the fluid–structure interaction parameters, the impact analysis software Autodyn is adopted to capture the damage mechanisms and the vibration histories. After cautious numerical simulations, local punching shear failure and global flexural failure dominate the damage modes of multi-beam hollow slab bridges. Due to the oversized impact energies and the insufficient structural resistance, overall collapse is observed in bridge with 4 or 6 beams in middle and acentric explosions. For bridge with 8 or 10 beams, the formed plastic hinges imply the large residual deflection and possible overall collapse during middle explosions. Owing to the easier energy dissipation and the smaller impact areas, limited flexural damage are discovered in bridge with 8 or 10 beams under acentric explosions. Due to the limited flexural damage and the small residual deflection of the distant beams, these beams can maintain great bearing capacity and can be repaired after explosions.

A hybrid method for damage detection and condition assessment of hinge joints in hollow slab bridges using physical models and vision-based measurements

The simply supported slab bridge is a typical perfricated reinforced concrete bridge. Under the influence of increasing vehicle loads and natural environmental erosion, the hinge joints between slabs suffer from damage that cannot be easily evaluated, which brings negative effects on the load carrying capacity of bridges. In the present study, a hybrid method for damage detection and condition assessment of hinge joints in hollow slab bridges using physical models and vision-based measurements was proposed. The stiffness reduction of hinge joints is taken as the damage degree and condition level of the inspected hinge joints. An analytical model of a simplified spring-mass system was firstly built to demonstrate the applicability of using the relative displacement ratio as the damage index of hinge joints. The relationship between the relative displacement ratio and the stiffness reduction of hinge joints was then studied thoroughly through a parametric study on finite element models considering different damage levels of hinge joints. Thresholds of the relative displacement ratio were defined to classify the damage states of hinge joints. The damage index of target hinge joints can be calculated from the actual data provided by using computer vision-based multi-camera and multi-point displacement measurements. Lastly, the application of a real-life bridge under normal traffic was demonstrated to verify the feasibility of the quantitative evaluation of the service status of joints in hinged-slab bridges. It indicated that the proposed method could evaluate the damage degree of joints quantitatively, effectively and economically.

CO2-Optimization of Post-Tensioned Concrete Slab-Bridge Decks Using Surrogate Modeling.

This paper deals with optimizing embedded carbon dioxide (CO2) emissions using surrogate modeling, whether it is the deck of a post-tensioned cast-in-place concrete slab bridge or any other design structure. The main contribution of this proposal is that it allows optimizing structures methodically and sequentially. The approach presents two sequential phases of optimization, the first one of diversification and the second one of intensification of the search for optimums. Finally, with the amount of CO2 emissions and the differentiating characteristics of each design, a heuristic optimization based on a Kriging metamodel is performed. An optimized solution with lower emissions than the analyzed sample is obtained. If CO2 emissions were to be reduced, design recommendations would be to use slendernesses as high as possible, in the range of 1/30, which implies a more significant amount of passive reinforcement. This increase in passive reinforcement is compensated by reducing the measurement of concrete and active reinforcement. Another important conclusion is that reducing emissions is related to cost savings. Furthermore, it has been corroborated that for a cost increase of less than 1%, decreases in emissions emitted into the atmosphere of more than 2% can be achieved.

Effect of blast load on the structural integrity of steel arch bridge slab

In order to know the safety margins and the critical zone of an important infrastructure such as a bridge, the response of the construction typology to extreme forces must be investigated. In this sense, in the literature, few numerical and experimental data are available concerning the response of steel bridges under explosive loads. The purpose of this work is to develop a coherent model, using the finite element analysis method, to verify the behaviour of such a structure and to focus on the collapse mechanism. As a case study, a typical network arch bridge was defined and meshed. Information about stresses, strains and displacement were collected as a function of the position and intensity of the slab damage. Finally, some useful observations were collected regarding the slab response, damage mechanisms and the role of the concrete class.

Research of strength and condition of cement-concrete pavement on bridges by non-destructive methods

The article presents the results of determining the strength of non-destructive methods of cement concrete pavement on bridges. According to the results of the research, a differential curve, a reliability curve and the inverse value of the accumulated frequency of compressive strength of cement concrete are constructed. It is established that the cement concrete of the investigated objects corresponds to the strength class according to the normative documents. However, the results of visual, instrumental and thermal imaging inspection of areas on the bridges revealed a number of defects in the cement-concrete pavement and pavement slabs, which can lead to loss of the pavement structure strength. In particular, it was found that the destruction of the inspected reinforced concrete slabs of bridges mainly occurs under the influence of corrosion and loss of the working part volume of the steel reinforcement, unsatisfactory condition of the compensation seams on the supports. It is determined that cracks in reinforced concrete slabs occur due to low resistance of concrete to bending loads, due to which steel reinforcement is exposed to aggressive environments. In turn, it was proved that structural cracks in concrete occurred due to excessive loading, which led to overstrain of the structure, and non-structural cracks - due to internal stresses caused by thermal loads and various linear expansions of materials. Thermal imaging study revealed a significant difference in temperature in the pavement structural elements, which in the future leads to the destruction of cement-concrete pavement. It was found that the peeling of the protective layer of metal reinforcement on the studied bridges is caused by the phenomenon of electro-chemical corrosion.
 The experience analysis of cement-concrete pavement of the studied objects allows to prepare proposals for the construction of cement-concrete pavement of bridges and overpasses using modern materials, in particular, non-metallic reinforcement.