Bridge Section Research Articles

21.11: Asymmetrical cross sections in historic riveted bridges

ABSTRACTThe assessment of the load‐carrying capacity of two steel bridges dating from 1907 and 1912, showed that most of the heavily loaded cross‐sections were asymmetrical. The bridges are of the two‐hinged portal frame type. Compared to simple beam bridges, portal frames with clamped or hinged supports allow redistribution of bending moments from the span centre towards the frame nodes. Consequently, the beam height at the span centre can be reduced, which is exactly what is needed for obtaining maximum vertical clearance of the subjacent waterway. Both bridges show heavy corrosion, some parts of the flanges and angle profiles of the end portals being seriously weakened. Full inventory has been made of the corrosion damage, as it appeared mostly in the edge frames of both structures. Reduction or suppressing of flanges has been introduced in the FE‐models of both bridges to assess the remaining load‐carrying capacity for real traffic loading.A particular characteristic are the asymmetrical cross‐sections of the main portal frames. Because of this, the compression and tensile stresses in both flanges are of unequal magnitude, favouring the latter. The reason for this became evident rather quickly. In tensile parts of the riveted structure, weakening of cross‐sections by holes has been taken into account, whereas it is not considered in compressed areas. Older standards and literature confirm the fact that this was allowed at the time riveted structures were still being built.As today little is known about riveting, it was felt that this needed further underpinning. Apart from the longitudinal effects, lateral shrinkage of rivets during placing and plastic deformation also exist within the holes. The plastic deformation in the hole introduces a high compression between the rivet and the hole edge. As the heated rivet is cooling down and before further shrinking of the rivet diameter, this pressure must be reversed. Hence, cooling does not reduce the rivet diameter entirely, a portion being used to decompress the connection. Approximations of the process have been worked out and showed that the final reduction of the rivet section is less than the tolerance for fitting bolts. Hence, the assumptions made in the past may be underpinned to a certain extent.This surely was resourceful during assessment of historic structures, requiring considerably more detailed numerical modelling than new structures, thus having better chances to preserve these valuable bridges for continuing use.

Monitoring of orthotropic steel decks for experimental evaluation of residual fatigue life

Orthotropic steel decks, directly subjected to traffic loads, are very sensitive to fatigue: defects mainly appear as cracks, which affect the top plates, longitudinal ribs and cross-beams of the deck. In this kind of bridges, structural health monitoring can be effectively adopted in characterising the safety threshold of the ongoing fatigue damage. This paper estimates the residual fatigue life of an existing orthotropic box-girder bridge, using experimental data from long-term monitoring of real traffic-induced effects. The bridge in question, less than 25 years old, is located on one of Italy’s busiest toll highways and evidenced fatigue damage due to deficiencies in original design and detailing. After preliminary visual inspections, the dynamic identification of the bridge was investigated by operational modal analysis, and a long-term monitoring campaign of strain measurements was subsequently carried out, involving series of strain gauges located on the most critical bridge sections. According to stress cycles recorded at these points, unlimited life verification was carried out according to EN 1993-1-9, and estimates of the residual fatigue life of the various elements were then derived by extrapolation of the experimental data. The proposed method can effectively be applied to fatigued steel bridge decks so that residual fatigue life and the real urgency of retrofitting interventions can be evaluated in operational conditions.

Noise reduction research of high-speed railway U-shaped beam

Railway noise has become an important factor restricting the further development of railway and endangering human health. Because of the particularity of the structure of the railway bridge, the noise radiation source is strong, the noise varies with the distance and the noise reduction effect of the sound barrier is different from that of the railway section. Therefore, how to effectively control the impact of railway noise on residents on both sides of the bridge section has become the focus of environmental protection workers, research the influence of noise of railway bridge segment noise in residential area along the railway is very important. In the acoustic test program of high-speed railway u-shaped beam, we will select the most appropriate noise reduction scheme through the computer simulation and model test of HSR u-shaped beam with different structural forms of test, and provide reliable reference for practical engineering.

Unsteady State Water Level Analysis for Discharge Hydrograph Estimation in Rivers with Torrential Regime: The Case Study of the February 2016 Flood Event in the Crati River, South Italy

Discharge hydrograph estimation during floods, in rivers with torrential regime, is often based on the use of rating curves extrapolated from very low stage–discharge measurements. To get a more reliable estimation, a reverse flow routing problem is solved using water level data measured in two gauged stations several kilometers from each other. Validation of the previous analysis carried out on the flood event of February 2016 at the Europa Bridge and Castiglione Scalo sections of the Crati River (Cosenza, Italy) is based on the use of ‘soft’ discharge measurement data and the comparison of the water level data computed in the downstream gauged section by three different hydraulic models with the ‘hard’ available water level measures. Results confirm that the 1D diffusive model provides more reliable results than the 1D complete one and no significant improvement is gained by the use of a more computationally demanding 2D model.

Optimal safety valuation of high-speed railway bridges based on reliability assessment and life-cycle cost concept

This study was intended to evaluate the dynamic performance high-speed railway bridges (HSR bridges) of composite box girder type so as to propose the rational safety level and optimal design method using reliability assessment (RA) and expected life-cycle cost (LCC) concpet. To that end, a various design alternatives were created considering the variation of member section based on a standard design section (current Korean code) of HSR bridges and then the static analysis, natural frequency analysis and time history analysis using time series of traffic load were implemented on each design alternative. Based on finite element analysis (FEA) results, the dynamic amplification factor (DAF) of the standard design section was evaluated in a way of comparing with related alternatives. RA depending on design strength limit state function was carried out considering the effect of external uncertainty contained in FEA results by each design alternative. Furthermore, the expected LCC of HSR bridges was evaluated using RA results and the optimal design method was determined through the calculated minimum LCC. To review the effect of internal uncertainty included in the safety index, failure probability and minimum LCC of selected optimal design method, sensitivity assessment was implemented and, consequently, a frequency-histogram (cumulative-percentage) was illustrated. The outcomes of research, along with the dynamic performance assessment of HSR bridges, will be expected to provide the basic information in determining the structural safety and optimal design method.

宜兴百渎港桥断面污染源解析及水体达标研究

百渎港桥断面为国控断面，2018年水质考核目标为Ⅲ类，2015年十二个月水质监测结果显示，百渎港桥断面氨氮和总磷尚不能达标。对百渎港桥断面水环境现状进行调查，分析污染物入河量及其构成，诊断和识别主要水环境问题，通过水文水质模型构建及模拟计算，提出保障断面达标的污染物削减方案。 The section of Baidu-port bridge is state-controlled section, and the water quality assessment ob-jective for 2018 is class III. Water quality monitoring results of twelve months in 2015 showed that the water quality indexes of ammonia nitrogen and total phosphorus could not achieve standards. The present water environment situation of Baidu-port bridge section is investigated; the amount of pollution into river and its constitution are analyzed, and the main water environmental problems are diagnosed and identified. Through construction and simulation calculation of hydrology and water quality model, the pollutant reduction plan is put forward to ensure attaining standards of the section.

Two – Dimensional Mathematical Model to Study Erosion Problem of Tigris River Banks at Nu’maniyah

The high and low water levels in Tigris River threaten the banks of the river. The study area is located on the main stream of Tigris River at Nu’maniyah City and the length of the considered reach is 5.4 km, especially the region from 400 m upstream Nu’maniyah Bridge and downstream of the bridge up to 1250 mwhich increased the risk ofthe problemthat itheading towardsthe streetand causingdanger tonearbyareas.
 The aim of this research is to identify the reason of slope collapse and find proper treatments for erosion problem in the river banks with the least cost. The modeling approach consisted of several steps, the first of which is by using “mini” JET (Jet Erosion Test) device provides a simple method of measuring scour depth with the time for the riverbank and finding values of critical shear stress and erodibility factor for ten soil samples taken from right bank and bottom of Tigris River; the second of which involved setting up a static BSTEM software for two models (with and without treatment), then calculating the erosion amounts and factor of safety for the ten soil samples; the third approach involved implementing a two dimensional RMA2 to simulate four scenarios to find the velocity, water depth, and water surface elevation distributions for two models (with and without treatment). Therefore, observed erosion in other discharges in natural case near the right bank [especially at cross section that are located in Tigris River at Nu’maniyah City from 500 m upstream Nu’maniyah Bridge and cross section that are located from 1800 m downstream Nu’maniyah Bridge] is high because of high erodibility coefficient in those cross sections that causes high erosion. Also, failure occurs in natural case of Tigris River at Nu’maniyah City because of erosion near the right bank and does not occur because of slope stability failure for right bank where the range of the velocities near the right bank for the study area for most discharges is between 0.67 and 0.91 m/s. In addition to experimental work using "mini" JET device shows high erodibility coefficient in those cross sections and (2+900) which confirms that this device is very good indicator for the possibility of bank scour. The velocities upstream of the island and near the right bank in the study area are between 0.64 and 1.47 m/s, while downstream of the island is between 0.64 and 1.04 m/s. In addition to soil of Tigris River right bank at Nu’maniyah is silty soil, the scour velocity is higher than 0.5 m/s, therefore the right bank is safe against scour only when the discharges of Tigris River are less than 500 m3/s. Thus, vegetation is unsafe treatment on right bank of Tigris River at Nu’maniyah City. The velocity causes removal of plants since treatment for river bank is 0.61 m/s where velocities near bank at most discharges are higher than this limit. Thus, treatment by riprap is the proper choice on the right bank of Tigris River at Nu’maniyah City because its cost with maintenance is 2 billion IQD less than gabion treatment in addition to velocity reduction ratio along the right bank by riprap ranges from 15% to 85%, while velocity reduction ratio along the right bank by gabion ranges from 8% to 25%, respectively.

Estimation of Crash Severity on Mountainous Freeways in Chongqing

Mountainous freeways always suffer from accidents due to special terrain, weather conditions, driving environment, and so on. Based on the records of 898 accidents that occurred on mountainous freeways in Chongqing during the past 6 years, the partial proportional odds model is used to identify the factors affecting the accident severity. The time of the accident, season, involvement of trucks, accident characteristics, speeding, maximum driving experience of involved drivers, and weather and road conditions are found to be important for the levels of accident severity. Zero to 6 a.m. and 19 to 24 p.m. are the times prone to serious traffic accidents. The probability of serious traffic accidents in summer and autumn is greater than that in spring and winter. Once a truck is involved in an accident, the consequence is often more severe. Turnover and speeding will result in a grave accident. When there is an experienced driver, the probability of serious traffic accidents is low. The fog is extremely unfavorable weather conditions. The probability of serious accident happening in the downgrade, ramp, curve, bridge, and tunnel sections is greater than the others. The results aim to provide valuable reference for traffic safety on mountainous freeways.

Solution of the Problem of Providing Railway Track Stability in Joint Sections Between Railroad Facilities and Subgrade

The paper presents the results of design, implementation and operational observations of nonstandard track structures with variable stiffness in joint sections of bridges and tunnels with regular subgrade. Technical and economic efficiency evaluation based on long-term real data analysis was carried out.It was experimentally confirmed that the sub-rail base stiffness changes reach 5-8 times, force unevenness exists and intensive residual deformations accumulate on the approaches to bridges and tunnels under passing trains. Several designs of reinforced concrete slabs, frames and monolithic concrete were developed to smoothly change the stiffness, reduce intensive accumulations of residual deformations. Empiric relationships between the development of settlements within the structures of variable stiffness and the tonnage passed were found. Additional technical decisions were proposed to improve the performance of the structures invented. Maintenance of track approaches to bridges and tunnels cost reduction was proven.

Analysis of T-bolts Abnormal Fracture of DTⅥ2 fastener Based on Metro Pass-by Dynamic Monitoring

For the problem of T-bolts abnormal fracture in DTⅦ2 fastener at a bridge section of Beijing metro line, dynamic monitoring is done which includes vibration acceleration and rail corrugation. The monitoring results indicate that there exists short-wave corrugation of 25mm at this section. And in the fracture section rail and T-bolts vibration increase abnormally. The vibration resonance peak is around 700-800 Hz. There is a significant correlation between characteristic wavelength, resonance frequency and train speed. Rail and T-bolts vibration transfer ratio shows that there exist the phenomenon of vibration amplification and asynchronous phase at 700-800 Hz. Further analyses indicate that the main reason of T-bolts abnormal fracture is fastener system abnormal matching. It causes vibration transfer ratio amplification at 700-800 Hz, and the vibration asynchrony of rail and T-bolts which causes abnormal interaction force. The short wave corrugation of 25mm leads to wheel-rail vibration, which inputs too much vibration energy to the fastener system.

Flutter suppression of long-span suspension bridge with truss girder

Section model wind tunnel test is currently the main technique to investigate the flutter performance of long-span bridges. Further study about applying the wind tunnel test results to the aerodynamic optimization is still needed. Systematical parameters and test principle of the bridge section model are determined by using three long-span steel truss suspension bridges. The flutter critical wind at different attack angles is obtained through section model flutter test. Under the most unfavorable working condition, tests to investigate the effects that upper central stabilized plate, lower central stabilized plate and horizontal stabilized plate have on the flutter performance of the main beam were conducted. According to the test results, the optimal aerodynamic measure was chosen to meet the requirements of the bridge wind resistance in consideration of safety, economy and aesthetics. At last the credibility of the results is confirmed by full bridge aerodynamic elastic model test. That the flutter reduced wind speed of long-span steel truss suspension bridges stays approximately between 4 to 5 is concluded as a reference for the investigation of the flutter performance of future similar steel truss girder suspension bridges.

Numerical analysis on the difference of drag force coefficients of bridge deck sections between the global force and pressure distribution methods

To analyze the difference of drag force coefficients of bridge sections obtained by the global force and pressure distribution methods, three-dimensional numerical simulations on the drag force coefficients of three typical sections are carried out. Firstly, after the numerical simulation method is validated, the percentage contribution of the friction drag force coefficient of the three sections under varying wind attack angles are investigated. Furthermore, the effect of the Reynolds number and handrails on the percentage contribution of the friction drag force coefficient is analyzed, and the results show that while the Reynolds number has an insignificant effect, the handrails’ effect is significant. Due to the importance of the contribution of the friction drag force for streamlined sections, more cases are simulated to investigate the percentage contribution of the friction drag force coefficient by varying the aspect ratio and fairing angle using the Sutong Bridge’s cross section as an example. The correction coefficients of the drag force coefficients obtained by the pressure distribution method for streamlined sections are obtained by the least square principle. The research conclusions can provide a reference for the differences of the drag force coefficient measured by the global force and pressure distribution methods for engineering practice.

AN INVESTIGATION OF CORROSION ENVIRONMENT OF A BRIDGE CONSTRUCTED IN MOUNTAINOUS AREA

Corrosion occurred on steel bridges which were constructed in mountainous area. However, few studies have investigated the corrosive environment of steel bridge in mountainous area. In this research, Temperature, humidity, wind conditions and amount of airborne salt have been observed at bridge site. In order to comprehensively assess corrosive condition, exposure test was also performed. Observation and exposure test were conducted at the steel plate girder bridge with 60m length and three main girders. During observation period, anti-freezing agent (Na-Cl) is sprayed in winter. From the observation, time of wet on the bridge is longer than bridges those were constructed at coastal area. It was clearly observed that flying behavior of anti-freezing agent around superstructures is influenced by the prevailing wind. Furthermore, distribution of amount of adhesion salt at the surface of steel in the bridge section was also clarified. Rust thickness of exposure specimen was revealed that the influence of anti-freezing agent, and at lower flanges becomes larger than that of web. These results can be applied to corrosive environmental simulation of steel bridges.

Study of vibrations in a short-span bridge under resonance conditions

Resonance is a phenomenon of utmost importance in railways engineering, leading to vast damages both in track and vehicles. Thus, to avoid the undesired effect of resonance, it must be studied, understood and predicted. To this aim, in the current study a FE model able to reproduce the dynamic behavior of a real stretch of track has been developed and its correct behavior has been calibrated with real data. Furthermore, different measures of mitigation have been proposed and its effect on displacements and vibrations in the mid-span section of a railway bridge have been evaluated.

Magnetic resonance imaging of flow and mass transfer in electrohydrodynamic liquid bridges

Here, we report on the feasibility and use of magnetic resonance imaging-based methods to the study of electrohydrodynamic (EHD) liquid bridges. High-speed tomographic recordings through the longitudinal axis of water bridges were used to characterize the mass transfer dynamics, mixing, and flow structure. By filling one beaker with heavy water and the other with light water, it was possible to track the spread of the proton signal throughout the total liquid volume. The mixing kinetics are different depending on where the light nuclei are located and proceeds faster when the anolyte is light water. Distinct flow and mixing regions are identified in the fluid volumes, and it is shown that the EHD flow at the electrodes can be counteracted by the density difference between water isotopes. MR phase contrast imaging reveals that within the bridge section, two separate counter-propagating flows pass one above the other in the bridge.

Experimental Aerodynamic Control of a Long-Span Suspension Bridge Section Using Leading- and Trailing-Edge Control Surfaces

We experimentally investigate the suppression of flutter in long-span suspension bridges. A rigid sectional model of a long-span suspension bridge is mounted in a wind tunnel on a suspension system. Control surfaces, which are used to suppress flutter, are movable flaps that are fitted to the bridge section’s leading and trailing edges. The flaps are responsive to the deck’s heave and pitch motions. In this paper, the aerodynamic force is modeled using a thin aerofoil theory, although other modeling techniques can be used. The controller has a second-order passive transfer function with inputs of a combination of the deck’s pitch angle and heave position, and outputs of the flaps’ angular positions. The control system design problem is solved as an ${\mathcal{ H}}_\infty $ optimization problem.

Collapse mechanisms and load–deflection curves of unstiffened and stiffened plated structures from bridge design

Cross sections of modern bridges are generally build with stiffened plated elements. The verification methods given in Eurocode EN 1993-1-5, to obtain the ultimate buckling resistance of plated structures, result in a time consuming procedure. In addition, the methods are mainly based on the elasticity theory and reduction factors from e.g. experiments are needed. Therefore, an alternative approach to obtain the ultimate resistance of unstiffened and stiffened plates is used. The method is based on a strain-dependent and geometric nonlinear yield-line theory including imperfections. This theory makes it possible to approximate the decreasing part of the load–deflection curve of such stability sensitive structures. The ultimate resistance, as maximum of the load–deflection curve, is approximated by a defined limit value. Therefore, the use of additional reduction factors is not necessary. Collapse mechanisms, which have been determined with the Finite Element Method (FEM) beforehand, are needed in order to apply the yield-line theory.

Wake control of vortex shedding based on spanwise suction of a bridge section model using Delayed Detached Eddy Simulation

In this paper, the DDES (Delayed Detached Eddy Simulation) is applied to study the spanwise suction control effect on wind-induced effect of a static bridge deck. Isolated suction holes are arranged on the lower surface of the test model in spanwise direction, and based on previous studies of similar bluff body, a proper distance of spanwise suction was chosen to trigger or amplify the most unstable secondary instability (i.e. Mode A) in wake. The simulation results show that the suction arranged close to the wake has the best control effect on reducing the fluctuating aerodynamic forces. Due to the mean-velocity modification by isolated spanwise suction, the virtual aerodynamic shape modification is generated, which could act as spanwise perturbation to suppress spanwise vortexes. The results indicate that the spanwise suction could trigger or amplify the Mode A instability, and hence lead to the dislocation of the spanwsie vortex or even completely suppress the spanwise vortex. In addition, the spanwise suction control can surpress spanwise vortex shedding in a wide Re range.

The effect of artificial light on wildlife use of a passage structure

Barriers to animal movement can isolate populations, impacting their genetic diversity, susceptibility to disease, and access to resources. Barriers to movement may be caused by artificial light, which is known to disrupt bird, sea turtle, and bat behavior, but few studies have experimentally investigated the effects of artificial light on movement for a suite of terrestrial vertebrates. Therefore, we studied the effect of ecological light pollution on animal usage of a bridge under-road passage structure. On a weekly basis, sections of the structure were subjected to different light treatments including no light added, followed by a Reference period when lights were off in all the structure sections. Sand track data revealed use by 23 mammals, birds, reptiles and amphibians, nine of which had >30 tracks for species-level analysis. Columbia black-tailed deer (Odocoileus hemionus columbianus) traversed under unlit bridge sections much less when neighboring sections were lit compared to when none were, suggesting avoidance due to any nearby presence of artificial light. Similarly, deer mouse (Peromyscus maniculatus) and opossum (Didelphis virginiana) track paths were less frequent in the lit sections than the ambient. Crossing was correlated with temporal or spatial factors but not light for three of the other species. These findings suggest that artificial light may be reducing habitat connectivity for some species though not providing a strong barrier for others. Such information is needed to inform mitigation of habitat fragmentation in the face of expanding urbanization.

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.