Deck Deflection Research Articles

Replacement of the deck and rehabilitation of the viaduct at the link between M-40 and M-607 in Madrid (Spain)

The existing concrete viaduct 560 m long at the link between M-40 ring road and M-607 expressway in Madrid (Spain) was subjected to a very comprehensive process of evaluation and testing after high deck deflections and surface cracking were detected. As conclusion of these studies very severe damages and a process of concrete degradations were confirmed which led to the decision of dismounting the existing deck structure and constructing a new one supported on the existing substructure which had to be repaired and reinforced. Grupo Puentes has carried out both the process of deck disassembly and the construction of the new deck in a record time of approximately nine months. The viaduct is in a very traffic congested link to approach Madrid and crosses over not only the main roads, M-40 ring road and M-607 expressway, but also two approach ramps and two railway lines, one of them high-speed line.

Evaluation of bridge load capacity using proof-load tests

A proof-load test is often necessary to accurately measure the field behavior of a bridge structure. A new segmental steel bridge has been constructed over the Tisza River in Hungary. The bridge comprises of two independent steel box girders assembled by a welding system. Engineers performed proof load tests before opening the structure to evaluate its load-carrying capacity and deck deflection. This paper presents several aspects of the load testing and evaluation of the bridge structure under static and dynamic loads using a rating factor (RF) approach compared to a baseline finite element model. The load test results helped to calibrate the model and verify the method. The study reveals that the tested bridge has an elastic behavior, a high capacity, and adequate dynamic performance.

Hot spot stress distribution and fatigue life evaluation of steel-UHPC deck in a long-span cable-stayed bridge

The steel-UHPC composite deck is an effective solution to fatigue cracks of orthotropic steel decks (OSD) in steel bridges. However, limited research has been reported on the hot spot stress distribution of the steel-UHPC composite deck. This study investigates the hot spot stress distribution and residual fatigue life evaluation of the steel-UHPC deck in a long-span cable-stayed bridge. The two extrapolation points' strain at fatigue-prone details were continuously measured under in-service traffic flow. The hot spot stress time history at each detail of the conventional OSD deck and steel-UHPC deck were analyzed and compared. The residual fatigue life of each detail was calculated. A three-dimensional finite element (FE) model was established and validated through experimental results. The bridge deck's deflection, the asphalt pavement's tensile stress, and the stress distribution at the floor beam cutout were numerically studied using the validated FE model. The results showed that the UHPC layer significantly reduced the hot spot stress and extended the fatigue life at each fatigue detail. The UHPC layer reduced the bridge deck's deflection and the asphalt pavement's tensile stress. Compared with nominal stress method, the hot spot stress method can better describe the large stress gradient distribution induced by the stress concentration at fatigue detail.

Hierarchical Bayesian calibration of deck deflection models using distributed fiber optic strain data

A naval hovercraft was outfitted with a distributed fiber optic sensing system (FOSS) on its cargo deck in which two fibers were placed along orthogonal axes. A series of trucks were loaded onto the cargo deck to simulate operational loading conditions and the resulting strain profiles were measured by the distributed FOSS. The aim of this study is to quantify the deck deflections that correspond to the measured strains under different vehicular loads. This is accomplished by idealizing the cargo deck as a rectangular plate and using the data to estimate the associated plate model parameters. In order to account for measurement noise and model prediction error, as well as the inherent variability of inferences made with different data sets, a hierarchical Bayesian scheme that considers both the model parameter uncertainty and the prediction error variance is utilized to derive the posterior distributions of the model hyper-parameters, i.e., their mean and variance. Given the volume of FOSS strain data available, different approaches were taken for incorporating the data into the hierarchical approach in order to determine whether the inclusion of all available strain data meaningfully reduced the uncertainty compared to using only time-averaged strain. Comparisons between the different approaches are explored in the context of 95% confidence intervals for strain profiles, deck deflection envelopes, and reliability indices based on allowable deflections.

Final-State Structural Behavior of the Long-Span Kömürhan Cable-Stayed Bridge under Torsional and Bending Loadings

Final-state field load testing is an effective method for understanding the real behavior of a bridge before it opens to traffic. The paper presents the procedure and the results of final-state static field tests on the new long span Kömürhan cable-stayed bridge with a single pylon and back span anchorage block under torsional and bending loadings. A total of six static loading cases were conducted to investigate real structural behavior of the bridge having a back span anchorage block and main span deck connected to the pylon with 42 tensioned cables in the deck center. Measured results have been obtained from the surveys and sensors while theoretical results have been calculated from the three-dimensional finite element model of the bridge final-state geometry. The results of final-state static load tests include the main span deck deflections, pylon horizontal displacements, the strains of the main span deck and the pylon, and the cable forces. A good agreement has been achieved between the experimental and theoretical results. Both experimental and theoretical results have shown that the real bridge behavior is in the elastic state under the planned test loads and supplies the design requirements. It is also observed that the results from the torsional and bending load cases positioned in the same sections are close to each other.

The significance of the dynamic interaction between bridge and trucks in the evaluation of the resonance structural frequencies

Bridges are key infrastructures that are built worldwide adopting different typologies, geometries, and construction materials. For these important infrastructures experimental proof tests before their opening to traffic are mandatory, as prescribed by many codes. In detail, static proof tests are performed to verify that the bridge behavior subjected to the design characteristic load conditions complies with that expected and does not exceed limits provided by codes (in terms of stresses and deck deflections). Nowadays, it is also often required in many countries to check the fundamental frequency of the real structure and to verify that it is in accordance with that obtained numerically during the design procedures. The fundamental frequency of the bridge is usually experimentally identified from ambient vibration tests on the unloaded structure through the operational modal analyses.This paper discusses about the dynamic identification of bridges performed during the loading phases of the static proof test, which is of interest to improve the control of the loading procedures, and to obtain frequency benchmarks that can be used as a support for the bridge structural health monitoring during its life. In detail, the paper addresses the problem of the dynamic interaction between the bridge and the stationed load (almost always provided by trucks) that affects the results interpretation and, sometimes, leads to erroneous conclusions on the bridge performance. Firstly, the bridge-truck interaction phenomenon is briefly exposed referring to a 2-dof dynamic system, then, an application to a real bridge case study dynamically tested during the proof load test day, is presented.

Comparison between Seismic Performance of Semi-Integrated Bridge and Conventional Bridge

The performance of a three-span integrated bridge is evaluated and compared with a conventional bridge for unidirectional and bi-directional excitation. The conventional bridge deck is connected to abutment through elastomers and the pinned connection is assumed at pier location. The height of the piers is 9.5 m, and the central and end spans are 38.0 m and 15.5 m respectively. A nonlinear time history analysis of the bridge is performed by using CSI Bridge software, for unidirectional and bi-directional excitation. The responses of the integrated bridge are compared with those of the conventional bridge in which bearings are provided between the deck and the support. The parameters varied are the major direction of the application of earthquake time history and PGA. The response quantities of interest include the maximum base shear of piers, maximum stresses developed at the critical sections of the deck, maximum deck deflection at the mid-span, and at the pier supports. The results of the numerical study show that as compared to the conventional bridge the integrated bridge has less base shear but has more stresses in the deck near pier supports; however, the stresses developed at the mid-span of the deck are significantly reduced.

Experimental and numerical analysis of ultimate compressive strength of long-span stiffened panels

Long-span stiffened panels, designed using girders with high webs and multi-web openings, are often used in the top of large spaces without inner columns, such as the theatre and the lounge in large passenger ships. This design, accompanied by in-tension pillars above the long-span stiffened panel, can decrease the deck deflection largely. In this paper, experimental and finite element analysis is performed of the ultimate compressive strength of two long-span stiffened panels subjected to combined uniaxial and lateral loads. The comparison of experimental results shows that the in-tension pillars only increase slightly the ultimate compressive strength of stiffened panel. The experimental results show agreement with the simulations performed by the ANSYS finite element solver. The validated numerical results illustrate the buckling and ultimate behaviour of long-span stiffened panels with their progressive collapse processes. The analysed ultimate loads are compared to the results calculated by seven existing empirical formulae. The finite element analysis also discusses the effect of girder openings on the ultimate compressive strength of the stiffened panel.

Methodology to account for the impact of stress history in layered soils for seismic vulnerability assessment of scoured bridges

Scour has been recognized as one of the leading causes of bridge collapse in the United States. Therefore, it is essential to be able to build models that accurately capture the response of bridges vulnerable to scour, including those located in layered rather than homogeneous soil deposits. Simple removal of soil springs due to scour ignores the effect of stress history for layered soils, which can lead to unconservative designs of foundations. This article proposes a methodology called the equivalent stress history and layered effects (ESHaLE) approach to capture the impact of soil stress history of layered soils on vulnerability assessment of scoured bridges. It utilises conservation of strength and mass to derive corresponding soil and depth parameters. Results show that neglecting to include stress history impacts in layered soils can lead to an underestimation of the single pile axial displacements by up to 35% in static analysis, and underestimation of the probability of exceeding bridge deck deflection thresholds by up to 25% in seismic fragility assessment. The study presents a method to include both soil stress history and layered effects in soil modeling and shows the importance of including these soil effects in the assessment of bridges vulnerable to scour.

A comparative study of multi-mode cable vibration control using viscous and viscoelastic dampers through field tests on the Sutong Bridge

This study reports a comprehensive performance comparison of two types of widely used dampers, i.e., viscoelastic dampers (VEDs) and viscous dampers (VDs), for multi-mode vibration control of long cables. Cables of three different lengths (334.2 m, 454.1 m and 546.9 m respectively) in the Sutong Bridge were chosen for investigation. The VED is of viscous-shear type and it consists a housing box containing viscous medium and shear plates immersed in the viscous medium. When attached to the cable, the shear plates and the housing are respectively connected to the cable with a clamp and to a support using flange connections. The VD under study is a typical fluid damper which uses two ball joints to respectively connect to the cable and the support. The manufactured dampers were first tested in laboratory for mechanical properties based on which the damper design was adjusted for maximizing multi-mode cable damping effects. The dampers were eventually attached to the respective cable on the bridge for field tests when the bridge was in operation. Field test results show that the VED provides comparable damping effects for all tested modes while the VD provided damping decreases considerably for higher cable modes. For cable modes with frequency approximately ranging from 1.4 Hz to 3.0 Hz their performances are comparable. Comparisons have then been performed between the measurements and analytical analyses based on a model of a shallow cable with a Kelvin-Voigt damper using damper parameters identified from laboratory tests. It is found that for the VEDs theoretical predictions agree well with the measurements suggesting no efficiency loss from damper support or connections while the measured damping ratios provided by the VD are about 33% to 80% of the corresponding theoretical estimates which is probably attributed to the joints required for the VDs. In addition, measurements on damper deformation in the field tests show that the damper for such long cables experiences continuous cyclic deformation with large amplitude and low frequency due to heavy traffic load induced bridge deck deflections. This deformation could cause severe fatigue problems of the damper and its connections and hence needs to be considered in damper design.

Structural Audit of Sadhu Vaswani Pul using Institutionally Developed Displacement Sensors.

The main aim of this study is to conduct the structural audit of the Sadhu Vaswani Pul which is a Rail Over Bridge, situated in Koregaon Park, Pune and to establish the displacement sensors developed in the institution as a reliable test for structural auditing of the bridge decks. Traditional methods of auditing like the Rebound Hammer test and the Ultrasonic pulse velocity tests have been considered in this study. Very few methods are available for testing the deck displacement and this problem has been tackled here. The novelty of this research is that the institutionally developed displacement sensors are used for determining the deck displacement of the selected bridge. These sensors have not been used before and no on-site techniques are available to obtain the deck deflections under real-time loading. The displacement test on the decks was conducted. The critical decks which were determined during the Visual Inspections were tested by the displacement sensors. A two-axle truck of 18.5 tonnes was passed over the bridge deck and the displacement readings were recorded at the same time. The displacement reading thus obtained indicated the deflection of the deck under a uniform rolling load. The displacements obtained were then validated by the standards given in AASTHO-LFRD. After conducting the above tests, the overall condition of the bridge was determined and the critical sections which should be repaired were mentioned.

Exterior girder rotation of skew and non-skew bridges during construction

In bridge design, bridge decks regularly overhang past the exterior girders in arrange to extend the width of the deck whereas constraining the specified number of girders. The overhanging part of the deck comes about in uneven eccentric loads to the exterior girders which are by and large most prominent. These eccentric loads are primarily a result of bridge construction operations as well as the weight of new concrete and other construction live loads. These unbalanced loads can lead to a differential edge deflection of overhang deck and a rotation of the exterior girders. The girder rotation or differential deck deflection can also affect local and global stability of the entire bridge. The objective of this study is to enhance the knowledge and understanding of external girder behavior due to unbalanced eccentric construction loads and to identify the critical factors affecting their rotation. In this article, field data obtained during the construction of two skewed (one with a small skew (3.8°) and the second with a severe skew (24°)) and one non-skewed steel girder bridges are described, and a detailed comparison is presented. The three bridges experienced maximum outward exterior girder rotation during construction which subsequently decreased following construction operations. The field results were used to validate and calibrate the finite element models. The numerical and field-monitored data showed good agreement and can be used to assist bridge designers and construction engineers to design appropriate systems to limit girder rotation during construction.

Non-Linear Analysis of Cable Stayed Bridges

The concept of cable-stayed bridges dates back to the seventeenth century. Due to their aesthetic appearance, efficient utilization of material, and availability of new construction technologies, cable-stayed bridges have gained much popularity in the last few decades. After successful construction of the Sutong Bridge, a number of bridges of this type have been proposed and are under construction, which calls for extensive research work in this field. Nowadays, very long span cable-stayed bridges are being built and the ambition is to further increase the span length using shallower and slender girders. In order to achieve this, accurate procedures need to be developed which can lead to a thorough understanding and a realistic prediction of the bridge’s structural response under different load conditions.In the present study, an attempt has been made to analyze the seismic response of cable stayed bridges with single pylon and two equal side spans. This study has made an effort to analyze the effect of both static and dynamic loadings on cable-stayed bridges and corresponding response of the bridge with variations in span length, pylon height and pylon shape. Comparison of static analysis results have been made for different configuration of bridges - their mode shapes, time period, frequency, pylon top deflection, maximum deck deflection; and longitudinal reaction, lateral reaction and longitudinal moment at pylon bottom. Time history analysis results have been investigated for different configuration of bridges under the effects of three earthquakes response spectrum (Bhuj, El Centro and Uttarkashi) - axial forces in stay cables, deck deflections and stress diagrams at maximum peak ground acceleration of the above mentioned earthquakes.

Design and experimental verification of easily constructible bamboo footbridges for rural areas

The present study examines a new approach for low-cost footbridges as a remedy to the overwhelming lack of bridges in underprivileged rural areas. The proposed truss footbridges can be rapidly assembled, by non-experienced personnel from pre-fabricated full culm bamboo members and steel gusset plate type connections. This paper addresses the challenges of the design and the construction, and highlights important knowledge gaps in the process. Firstly, it evaluates experimentally the physical and mechanical properties of bamboo culms from two species (namely, Kao Jue and Mao Jue). Then, it develops an analytical model and performs the structural design of the bridge. Importantly, the present study introduces a new three-dimensional gusset plate type truss connection for full culm bamboo members. The proposed connection overcomes the assembly problems due to the non-standardized bamboo geometry. The study also reports the construction of full scale bridge prototypes and their experimental testing. The measured deck deflections under vertical loads are reasonably well captured by the analytical model. However, the bridge collapse is due to a local mode failure peculiar to bamboo; longitudinal splitting. The results reveal that the connections and the associated local failure modes of bamboo, are the most sensitive part of the examined structures, and highlight several directions for further experimental and theoretical research.

Probabilistic analysis of a twin deck curved cable-stayed footbridge subjected to multiple inputs and corrosion

In order to investigate the benefits of Circular Hollow Section (CHS) structural members to a complex cable-stayed footbridge, this paper presents a simulation-based probabilistic assessment of this type of structures when erected in an aggressive environment. The footbridge studied is located in Pescara, Italy, next to the Adriatic sea. We validated a Finite Element (FE) model of this bridge, and then, we performed a probabilistic study. Owing to corrosion during the bridge design life, both general and localized corrosion models capable of evaluating the reduced load bearing section were adopted; and appropriate probability distributions were assigned to input model parameters. Afterwards, the probabilistic evaluation of the bridge deck response was conducted using non-linear simulations based on Monte Carlo Sampling, where the convergence was accelerated by using Latin Hypercube Sampling (LHS). Serviceability limit state for stresses was satisfied for the footbridge service life for both wind and pedestrian loads. However, for the limit states referred to maximum deck deflection and rotation, the probabilities of failure crossed limiting values suggested in Eurocodes. As a result, for the twin deck curved cable-stayed footbridge with CHS members, the probabilistic analysis was able to predict the exceeding time of limit states’ thresholds. Thus, both repair and a retrofit plan within its design lifetime could be set.

Stress-laminated-timber decks: state of the art and design based on Swedish practice

Stress-laminated-timber (SLT) bridge decks are a valid alternative to conventional short- and medium-span bridges in terms of cost and performance. SLT decks are made from a number of planks or glulam beams positioned side by side and stressed together using high-strength steel bars. A concentrated load can therefore be distributed from the loaded beams onto adjacent beams due to the resisting friction caused by the pre-stressing of all beams in the deck. This paper describes the state of the art of SLT bridge decks, with special emphasis on Swedish practice. The effect of butt joints on deck deflection and solution applied to accommodate the loss of pre-stress are shown. Simple design tools for the preliminary design of road bridges are illustrated. Best practice with regard to some detailing, water protection and durability is also discussed. Finally, possible developments of SLT bridges are discussed.

Concrete bridge deck stresses induced by stay-in-place forms

In this study, the restraining actions induced by stay-in-place metal forms to concrete bridge decks are examined. A comparison between the behaviour of a concrete deck section constructed with regular stay-in-place metal forms and that constructed on a flat-bed geometry where the corrugations in the stay-in-place forms are filled with extruded polystyrene foam is conducted. Data consisting of three-dimensional concrete deck strains, thermal gradient profiles through the deck thickness, deck deflection profiles and reinforcement strains were recorded through a long-term sensory system consisting of 340 sensors embedded within the deck since construction. Analysis of stresses developed in the concrete deck material indicates that using the foam material to fill the corrugations proved to be successful in reducing the concrete shrinkage stresses at early age and also in reducing the constraining effects of the stay-in-place forms on deck expansion and contraction within the monitoring period of about 1 year.

유한요소해석을 이용한 응력적층 바닥판의 구조성능평가

본 연구에서는 유한요소해석을 이용하여 응력적층 바닥판의 구조성능을 평가하였다. 바닥판의 구조성능은 처짐과 응력, 압체력의 변화로 평가할 수 있다. 하중 재하 후 바닥판의 처짐 형상을 확인한 결과 하나의 판처럼 거동하는 것을 확인하였다. 이는 압체력에 의해 각 부재 사이에 마찰력이 작용했기 때문이다. 또한 초기 압체력과 산출된 압체력을 비교한 결과 바닥판의 처짐과 함께 압체력이 감소했다. 이는 하중에 의해 바닥판의 변형이 발생하면서 작용하는 힘이 줄어듦에 따라 압체력이 감소한 것으로 판단된다. 그러나 재료의 소성 특성이 제대로 반영되지 않았기 때문에 잔류응력과 잔류변형이 고려되지 않았으므로 추후 이에 대한 연구가 필요하다. This paper represented the finite element analysis to estimate structural performance of stress-laminated deck, which is determined by deflection, stress, and aging characteristics of tensioning. After loading, the deflected shape showed plate behavior because pre-stressing make frictional force between each member. Compared between initial post-tension and the results, pre-stressing forces were decreased with deck deflection. This is because deflection occurred in the deck so that pre-stressing decreased due to load reduction. However, material plasticity was not considered so that advanced researches should be performed.

Optimization of the economic practicability of fiber-reinforced polymer (FRP) cable-stayed bridge decks

This paper aims to find the optimum cable spacing and the optimum FRP deck stiffness in terms of vertical deformation. To achieve the objective of this study eighteen models are developed using ABAQUS; three different deck stiffness and six different cable spacing. Firstly, a non linear static finite-element analysis is performed on the models; then pre-tensioning forces are applied to cables, after that the shape modes for each model are presented. Secondly, a nonlinear dynamic analysis is performed on the models, the results obtained from the finite-element analysis are used in the optimization. The results show that for certain cable spacing the deflection decreased, and the cable stress increased as the deck stiffness increased. Furthermore, for certain deck stiffness, the cable stresses and the maximum deck deflection increased as the spacing between cables increased. Secondary, a relationship is performed to find the optimum cable spacing for each deck stiffness and optimum deck stiffness for each cable spacing. Finally, new twelve models are developed in order to study the effect of deck types (FRP, Concrete and steel) on the static and dynamic behavior. The results show that the using FRP deck instead of the concrete deck will lead to vertical deformation and cable stress less than the allowable proposed values by the design code because of the light weight of the FRP materials.

Field Monitoring and Repair of a Glass Fiber-Reinforced Polymer Bridge Deck

This paper reports on the monitoring and repair of a pilot field deployment of a glass fiber-reinforced polymer (GFRP) deck on a small steel girder bridge in the Washington State. Deck deflections were monitored periodically over a 10-month period and were found to increase significantly over that time. The GFRP deck is an adhesively bonded assembly of GFRP tubes and top and bottom plates. After 9 months of service, wearing surface cracking was observed, and upon closer inspection, the top GFRP plate was found to be delaminated from the tubes over a fairly large area. Deck deflections in the area of delamination were found to be considerably larger than those observed during previous monitoring in undamaged locations. A retrofit solution was employed where the top plate was reconnected to the tubes using screws coated with a two-part epoxy that mixed when they were driven. At the time of writing the retrofit was successful in reattaching the delaminated top plate.