Straight Bridges Research Articles

Seismic performance of skewed bridges with uniform and non-uniform scour

Seismic safety of highway bridges is one of the critical issues for the functionality of transportation lifelines after severe earthquakes. Skewed highway bridges are found to be more vulnerable due to the irregular distribution of seismic demands on the bridge components. Moreover, scour induced loss of soil material and hence reduction in lateral support around the foundation piles can amplify the seismic effects on the structural components of water crossing bridges. A numerical study was conducted to investigate the seismic performance of skewed and straight highway bridges with varying scour depths and two different scouring types around the bridge piles. Analytical models of straight (0°) and 45° skewed bridges were created using the OpenSees program and a series of nonlinear response history analysis was carried out under the effect of recorded strong ground motions. In the first scouring type which was called as Case-1, scour depth was assumed the same around all piles and varied uniformly. In Case 2, two different non-uniform scouring types with linearly varying scour depth around the piles were investigated. The uncertainty in the earthquake ground motion excitation direction of the two horizontal components was also studied by considering the variable incidence angle of ground motion pairs. The maximum seismic demands of the members at different ground motion incidence angles were evaluated and compared to the demands obtained for the critical ground motion incidence angles suggested by Caltrans. Superstructure displacement, curvature demands of bridge column and shear force demands of pile elements are the seismic demand parameters examined within the scope of the study and were compared for each scour condition for both straight (0°) and 45° skewed bridge.

Shake Table Testing of Bidirectional Ductile Diagraphs with Buckling‐Restrained Braces in V-shaped configuration

The Bidirectional Ductile Diaphragm concept relies on Buckling Restrained Braces (BRBs) used at ends of spans in common multi‐span bridges to provide seismic resilient damage‐free bridges at low cost, while minimizing displacement demands to levels that can be easily accommodated by conventional expansions joints. This paper reports on the results of a shake-table testing program of Bidirectional Ductile Diaphragms designed with Buckling Restrained Braces (BRBs) deployed in a V-shaped layout. A single span taken from a scaled straight bridge with no skew, simply supported on slider bearings, and BRBs end connection details was subjected to: (1) earthquakes scaled to match the design level; (2) BRB deformation demands corresponding to 75 years of cycles of bridge thermal expansions, and: (3) earthquake scaled to levels exceeding the design level such as to bring the BRB to fracture upon repeated cycles of large inelastic deformations at extreme ductility demands. Results demonstrate that bridges using the bidirectional ductile end diaphragm concept with BRBs in a V-shaped configuration can develop a stable hysteretic response, with inelastic deformations concentrated in the BRBs. These bridges would experience no loss of functionality following an earthquake, resulting in fully resilient bridges that remain in service throughout and after the earthquake.

A Failure Analysis of the Long-Term Overturning Stability of Concrete Continuous Single-Column Pier Bridges Considering Creep and Overloaded Vehicles

Several single-column pier girder bridges have been involved in overturning accidents, resulting in significant economic losses and casualties, thus necessitating a risk assessment of the overturning stability. To date, the effect of structural degradation due to concrete creep on the long-term stability of bridges has not been demonstrated. In this study, a full-scale nonlinear analysis of the lateral overturning process of a collapsed concrete box girder based on the explicit dynamic finite element method (EFEM) was conducted to verify the reliability of the numerical method. An EFEM model incorporating concrete creep was developed to demonstrate the effect of structural degradation on the long-term stability of bridges. The synthesis overturning axis method (SOAM) was proposed to evaluate the long-term overturning stability of concrete continuous bridges, aiming to address the deficiencies in existing methods, particularly for curved bridges, and was compared with conventional methods. The results show that the variations in bearing reaction forces between curved and straight bridges under creep and self-weight are minimal, staying within 2%. An increase in the creep terminal coefficient results in the opposite trend in the ultimate vehicle weight of curved bridges and straight bridges, but fluctuations remain within 2%, indicating that long-term creep has a limited effect on the overall overturning stability. A failure analysis of 20 single-column pier bridges reveals significant differences in the ultimate vehicle weight between the rigid overturning axis method (ROAM) and folded overturning axis method (FOAM), with error ranges of −14.2% to 567.4% and −99.1% to −32.1%, respectively. The SOAM results have the smallest error range compared to those of the EFEM, with an error range of −38.8% to 33.9%. Despite these errors, the SOAM demonstrates a significant improvement in characterizing the trend and assessment accuracy of the overall overturning stability of single-column pier bridges.

3D‐Printed Carbon Nanoneedle Electrodes for Dopamine Detection in Drosophila

AbstractIn vivo electrochemistry in small brain regions or synapses requires nanoelectrodes with long straight tips for submicron scale measurements. Nanoelectrodes can be fabricated using a Nanoscribe two‐photon printer, but annealed tips curl if they are long and thin. We propose a new pulling‐force strategy to fabricate a straight carbon nanoneedle structure. A micron‐width bridge is printed between two blocks. The annealed structure shrinks during pyrolysis, and the blocks create a pulling force to form a long, thin, and straight carbon bridge. Parameterization study and COMSOL modeling indicate changes in the block size, bridge size and length affect the pulling force and bridge shrinkage. Electrodes were printed on niobium wires, insulated with aluminum oxide, and the bridge cut with focused ion beam (FIB) to expose the nanoneedle tip. Annealed needle diameters ranged from 400 nm to 5.25 μm and length varied from 50.5 μm to 146 μm. The electrochemical properties are similar to glassy carbon, with good performance for dopamine detection with fast‐scan cyclic voltammetry. Nanoelectrodes enable biological applications, such as dopamine detection in a specific Drosophila brain region. Long and thin nanoneedles are generally useful for other applications such as cellular sensing, drug delivery, or gas sensing.

3D-Printed Carbon Nanoneedle Electrodes for Dopamine Detection in Drosophila.

In vivo electrochemistry in small brain regions or synapses requires nanoelectrodes with long straight tips for submicron scale measurements. Nanoelectrodes can be fabricated using a Nanoscribe two-photon printer, but annealed tips curl if they are long and thin. We propose a new pulling-force strategy to fabricate a straight carbon nanoneedle structure. A micron-width bridge is printed between two blocks. The annealed structure shrinks during pyrolysis, and the blocks create a pulling force to form a long, thin, and straight carbon bridge. Parameterization study and COMSOL modeling indicate changes in the block size, bridge size and length affect the pulling force and bridge shrinkage. Electrodes were printed on niobium wires, insulated with aluminum oxide, and the bridge cut with focused ion beam (FIB) to expose the nanoneedle tip. Annealed needle diameters ranged from 400 nm to 5.25 μm and length varied from 50.5 μm to 146 μm. The electrochemical properties are similar to glassy carbon, with good performance for dopamine detection with fast-scan cyclic voltammetry. Nanoelectrodes enable biological applications, such as dopamine detection in a specific Drosophila brain region. Long and thin nanoneedles are generally useful for other applications such as cellular sensing, drug delivery, or gas sensing.

Failure Analysis for Overall Overturning of Concrete Single-Column Pier Bridges Induced by Temperature and Overloaded Vehicles.

Several overloaded-induced overturning incidents of girder bridges with single-column piers have occurred in recent years, resulting in significant casualties and economic losses. Temperature, in addition to overloading, may also play a role in exacerbating bridge overturning. To investigate the association between temperature and bridge overturning, an explicit finite element model (EFEM) of a three-span concrete curved continuous bridge considering nonlinearities was developed to simulate overall collapse. The effects of uniform and gradient temperatures on the overall overturning stability of curved and straight bridges were evaluated based on the EFEMs. Furthermore, the temperature-bridge coupling model and temperature-vehicle-bridge coupling model were utilized to examine how gradient temperature influences bridge overturning. The results show that the overall overturning collapse of a bridge follows four stages: stabilization, transition, risk and overturning. Variations in uniform temperature from -30 °C to 60 °C had a negligible effect on the ultimate vehicle weight for bridge overturning, with a variation of less than 1%. As the gradient temperature ranged from -30 °C to 60 °C, curved bridges show less than a 2% variation in ultimate vehicle weights, compared to a range of -6.1% to 11.7% for straight bridges. The torsion caused by positive gradient temperature in curved bridges can exacerbate bridge overturning, while negative gradient temperature in straight bridges can lead the girder to 'upward warping', facilitating girder separation from bearings. Monitoring the girder rotation angle and vertical reaction force of bearings can serve as important indicators for comparing the stability of bridges.

Nonstationary elastoplastic response analysis of curved beam bridges under spatial variability of earthquake ground motion using absolute displacement method

Current studies indicate that curved beam bridges are more sensitive to the spatial variability of earthquake ground motion (SVEGM) than straight bridges. However, research methods used currently typically disregard the nonlinear characteristics of bridges or use only deterministic excitations for analysis. Furthermore, the sensitivity of curved beam bridges with different curvature radii to the SVEGM has not been investigated comprehensively. Hence, in this study, a nonlinear finite element model of curved beam bridges is established using the ANSYS platform and the MATLAB is then employed to reduce and decouple the non-stationary seismic evolutionary power spectral density (EPSD) matrix. The absolute displacement method is employed for the multidimensional and multipoint nonlinear time-history analysis of the bridges. Considering different wave velocities, site conditions, and coherence types, this study comprehensively analyses the random response and frequency domain characteristics of curved continuous beam bridges under different SVEGMs. The analysis includes a verification of curved beam bridges with different curvature radii based on 48 cases (six SVEGMs with eight curvature radii). The results indicate that the presence of curvature renders curved beam bridges more sensitive to the SVEGM. The SVEGM significantly affects the random response and response frequency domain distribution of curved beam bridges, with smaller curvature radii contributing more significantly to the response. Therefore, the SVEGM must be considered in the seismic analysis of curved beam bridges, particularly those with smaller radii, to avoid an inaccurate estimation of the seismic performance of the bridges. The findings of this study can improve the seismic design and evaluation of curved beam bridges as well as enhance their seismic performance and reliability.

Haofa dog – An indigenous canine germplasm from Manipur, India

A study on Haofa dog was carried out at its breeding tract in Ukhrul and Kamjong districts of Manipur to find out its origin, distribution and phenotypic characteristics. A total of 100 adult Haofa dogs (50 male and 50 female) were recorded for studying physical characters and body measurement. Further, 69 number of observation were also recorded for studying body weights of adult male and female. In addition, 100 Haofa owners were interviewed to study the reproductive characteristics, management practices followed and their utility, etc. The study revealed that Haofa were of medium size with a compact body, broad chest, straight top line and slightly tucked up abdomen. The coat colour is usually black with grey skin while some dogs have black coat colour with white markings in ventral parts and tips of legs. The head of a Haofa dog is medium in size with a slightly trapezoid shape, while the forehead is usually prominent with the straight nasal bridge. Eyes are oval shaped with golden colour. Ears are erect and usually cropped at an early age. The dogs have short coats and their tails are usually semi-curved and docked usually at a young age. The adult body weight and average litter size at birth ranges from 22-31 kg and 3-8, respectively. Haofa is morphologically different from the other exotic breeds, crossbreeds or local dogs found in the state. Hence, it deserves to be recognized as a distinct breed of dog.

Digital simulation of distortion-induced fatigue in steel bridges with different geometrical configurations

Distortion-induced fatigue cracks at web gaps often occur in multi-girder steel bridges under vehicle loads. This paper presents full size digital simulations of steel girder bridges with different geometrical configurations, to explore the distortion-induced fatigue cracking performance. In the digital simulations, four geometrics are considered, in addition to two web gap details, namely the vertical stiffener web gap and the horizontal gusset plate web gap. Introducing multi-layer and multi-pass welds residual welding stress fields, digital fatigue simulation results show that the distortion-induced fatigue cracks at both web gaps are Mode I-II-III combined cracks dominated by Mode I. The coupling of the three modes is more prominent at the vertical stiffener web gap compared to the horizontal gusset plate web gap. In the skewed bridge, curved bridge, and skewed-curved bridge, the significant bending-torsional coupling effect, the structural asymmetry, and the stress deformation asymmetry cause an increment in distortion ranges, fatigue crack growth rates, and the proportions of Mode II and III cracks. The fatigue strength categories for vertical stiffener web gap and horizontal gusset plate web gap in straight, skewed, curved and skewed-curved bridges are category 125, 112, 110 and 110, and category 160, 140, 100 and 100 of the Chinese specification and Eurocode, respectively. Therefore, the geometrical configuration is an important factor affecting the distortion-induced fatigue behavior, which should be considered in the fatigue design and maintenance of steel girder bridges.

Analysis of Vehicle-Bridge Coupling Vibration Characteristics of Curved Girder Bridges

When vehicles move on a bridge, the coupling effect between vehicles and bridges can affect driving safety and comfort, especially for curved bridges, therefore, choosing reasonable design parameters for curved bridges is crucial. In this article, a three-span curved continuous box-girder bridge was taken as the research object; the entire process of vehicle-bridge coupling vibration of highway curved girder bridges was conducted via numerical simulation and the vehicle-bridge coupling vibration analysis program Cmck 1.0 was developed. Then, the influence factors such as curvature radius, constraint mode, and vehicle characteristics on the vehicle-bridge coupling vibration of curved girder bridges were explored. The results showed that as the curvature radius increased, the dynamic response of the bridge offered a gradually decreasing trend and compared to the vertical dynamic response, the torsional response was more sensitive to the influence of the curvature radius. Different constraint methods significantly impacted the dynamic response of bridges, and the vertical and torsional dynamic responses of bridges under general constraint arrangement of straight bridges were increased compared to those under boundary conditions for curved beam bridges. As the axle load of the car decreases, the bridge mid-span vertical and torsional dynamic responses showed a decreasing trend. In contrast, the lateral dynamic response gradually increased.

Comparison of Linear and Nonlinear Procedures for the Analysis of the Seismic Performance of Straight Multi-Span RC Bridges

The assessment of the seismic performance of transportation infrastructures is of primary importance for the management of the aftermath of an earthquake. To perform such an assessment, various modeling approaches characterized by different levels of accuracy are available and modern seismic design codes provide recommendations about their use. Non-linear time-history analysis (NLTHA) is acknowledged as the most reliable method, but is difficult to implement and is computationally expensive. This paper aims to investigate the viability of less complex methods, but with low computational cost, for the assessment of straight, multi-span bridges and compare their performance against the results of NLTHA in order to quantify the expected accuracy. The study is developed considering three bridge archetypes with either simply-supported or continuous-deck layouts, representative of typical features of the Italian bridge stock. The bridges are analyzed first through nonlinear dynamic analyses, to define the benchmark solution; then linear dynamic analyses, such as Linear Time-History and Response Spectrum Analysis, nonlinear static analyses, such as MPA (Modal Pushover Analysis), and Equivalent Static Analysis are considered. A comparison among the examined procedures is eventually proposed, highlighting the strengths and weaknesses of each approach.

Refined Analysis of Spatial Three-Curved Steel Box Girder Bridge and Temperature Stress Prediction Based on WOA-BPNN

Bridges often improve the visual appeal of urban landscapes by incorporating curve elements to create iconic forms. However, it is noteworthy that curved bridges have unique mechanical properties under loads compared to straight bridges. This study analyzes a spatial three-curved steel box girder bridge based on an actual engineering case with a complex configuration. Initially, the finite element software Midas/Civil 2021 is utilized to establish a beam element model and a plate element model to examine the structural responses under dead loads in detail. Then, two different temperature gradient distribution models are employed for the temperature effect analysis. The backpropagation neural network (BPNN) optimized by the WOA algorithm is trained as a surrogate model for finite element models based on the results of temperature stress simulation. The results reveal that the bending–torsion coupling effect in the second span of the spatial three-curved steel box girder bridge is pronounced, with the maximum torque reaching 40% of the bending moment. The uneven distribution of cross-section stress is particularly significant at the vertices, where the shear lag coefficient exceeds 3. Under the action of temperature gradients, the bridge displays a warped stress state; the stress results obtained from the exponential model exhibit a 21% increase compared to BS-5400. Optimization of the weights by the WOA algorithm results in a significant improvement in prediction accuracy, and the convergence speed is improved by 30%. The coefficient of determination (R2) for predicting temperature stress can reach as high as 0.99.

The “M and P” Technique for Damage Identification in Reinforced Concrete Bridges

The seismic damage in reinforced concrete bridges is identified in this study using the “M and P” hybrid technique initially developed for planar frames, where M signifies “Monitoring” and P denotes “Pushover analysis”. The proposed methodology involves a series of pushover and instantaneous modal analyses with a progressively increasing target deck displacement along the longitudinal direction of the bridge. From the results of these analyses, the diagram of the instantaneous eigenfrequency of the bridge, ranging from the health state to near collapse, is plotted against the inelastic seismic deck displacement. By pre-determining the eigenfrequency of an existing bridge along its longitudinal direction through “monitoring and frequency identification”, the target deck displacement corresponding to the damage state can directly be found from this diagram. Subsequently, the damage can be identified by examining the results of the pushover analysis at the step where the target deck displacement is indicated. The effectiveness of this proposed technique is evaluated in the context of straight multiple span bridges with unequal pier heights, illustrated through an example of a four-span bridge. The findings demonstrate that the damage potential in bridge piers can be successfully identified by combining the results of a monitoring process and pushover analysis.

Investigation of seismic behavior of horizontally curved bridges in comparison with equivalent straight bridges accordıng to the AASHTO LRFD specifications

Investigation of seismic behavior of horizontally curved bridges in comparison with equivalent straight bridges accordıng to the AASHTO LRFD specifications

Equivalent static methods for seismic design of straight integral abutment bridges

AbstractIntegral abutment bridges (IABs) are becoming the solution of choice in the low to mid‐length ranges because of their low cost compared with traditional solutions and their good performance under seismic actions. The main drawback of these bridges is the need to consider soil‐structure interaction to assess their performance, a problem that is more pronounced for actions implying horizontal deck movements, such as temperature or the specific focus of this paper, that is, seismic action. In IAB design, simplified models are often used, where soil‐structure interaction is modeled by means of beams on non‐linear Winkler springs for the evaluation of seismic behavior. This paper, starting from an existing non‐linear dynamic model (NLDM) that describes IABs longitudinal seismic response, derives two equivalent static models: one non‐linear and the other linear, for displacement‐ or force‐based design respectively. A parametric study is carried out to assess the static models performance in terms of the main design internal actions versus the NLDM. Finally, the assessed model errors are discussed in the context of partial factors safety format.

Parametric study on prestressed skewed box-girder bridge

This study employs the finite element-based CSiBridge v.20.0.0 software to examine the response of a single-cell prestressed box-girder bridge subjected to Indian loading conditions. The analyses is carried out on a simply supported bridge considering the specifications of Indian Road Congress (IRC) 6:2017, IRC 18:2000 and IRC 21:2000. An existing model of prestressed skewed bridge is validated with the published one. A convergence study is conducted for determining the model’s mesh size. An extensive parametric study is carried out to gain a better understanding of the response of a skewed prestressed bridge. The parameters variables are: Skew angle (0°, 10°, 20°, 30°, 40°, 50°, and 60°); Span (35, 40, 45, 50, 55, and 60 m); and Span-depth ratio (10, 12, 14, 16 and 18). The results of this study are presented as ratios of Bending moment, Shear force, Torsional moment, and Vertical deflection. Finally, equations for estimation of these ratios for different span and span-depth ratio are also deduced from the statistical approach so that the results of skewed bridges may be evaluated directly. It is determined that the skewed bridge outperforms the straight bridge because of its higher span-depth ratio, which results in less bending moment development. Evidence suggests that the skewness may help to lessen the prestress load’s dominance. The findings of this study may be helpful to engineers and designers in the analysis and design of prestresssed skewed box-girder bridges.

Computational modeling of nickel–titanium orthopedic staples in the treatment of a fractured scaphoid: Effects of staple bridge configuration

Internal fixation devices made of nickel-titanium (NiTi) staples have the advantage of producing compressive stress at the fracture site due to their unique shape memory effect and superelasticity. In the present study, a comparison was made between two commercial NiTi staples of the same size but with different bridge configurations, used for scaphoid fracture fixation. The staple and scaphoid anatomical configurations were modeled using SolidWorks, while ABAQUS software was used to analyze the stress and displacement caused by staples and distributed in the scaphoid waist. In the staple with a straight bridge, the regions under the tips of the staple legs underwent the largest stress, whereas there was negligible stress in the regions closer to the staple bridge. In the staple with an S-shaped bridge, the stress concentration was highly localized in the region close to the staple bridge, with a maximum stress that was over eight times higher than in the staple with a straight bridge. Considering the amount and distribution of stress in both staples, neither of the staples was able to create the ideal healing condition on the fracture surface.

Finite element analysis of reinforced concrete curved box-girder bridges

The study presents the design forces of simply supported single-cell reinforced concrete (RC) curved box-girder bridges using a finite element method (FEM) based CSiBridge v.20 software. An existing model has been used to validate the present modelling approach. Models subjected to vertical loading, i.e., dead load (DL) and Indian road congress live load (LL), are considered for investigation. An intensive parametric study examines the maximum values of bending moment (BM), shear force (SF), torsional moment (TM), and vertical deflection (VD) in both girders of bridges. The influences of curve angle and span are considered in the study. The effect of curve angle, up to 12°, is negligible on forces and deflections, and thus such bridges can be analysed as a straight one. Finally, non-dimensional equations are derived for evaluating forces and deflections, so that one may predict these quantities for curved bridges based on straight bridge’s results. Engineers and designers may consider present work valuable in analysing, and designing curved box-girder bridges.

Influence of Skewnesson Flexural Response of RC Slab Bridges

Normally, straight slab bridges are preferred in any road network due to simplicity in design and construction. However, in some circumstances, it becomes necessary to provide the skew slab bridges owing to geometrical considerations. The structural behaviour of skew slab bridges differs significantly as compared to right slab bridges unless the skew angle is small. In this paper, attempts have been made to investigate the influence of skewness on flexural response of two-lane slab bridges of different spans ranging between 4 m to 8 m at in interval of 1 m and the skew angle has been varied from 0° to 45° in the multiple of 15°. In this study, the linear-elastic three-dimensional finite element analysis of slab bridges has been carried out using the STAAD_Pro. In order to investigate the effect of skewness on flexural response five different span slab bridges, the longitudinal moment, transverse moment, twisting moment, and the maximum deflection produced in skew slab bridges are normalized with the corresponding parameters in the right slab bridges. The study showed that the normalized longitudinal moment decreases significantly with the increase in angle of skew from 15° to 45°, in contrast, an excessive rise in the normalized transverse moments was observed.

Analysis and design optimization approach of vibration characteristics of an I shaped straight steel girder bridge

Bridges are subjected to environmental exposure like corrosion which may induce cracks. These cracks may cause change in natural frequency of bridge. The current study's goal is to explore the effect of crack on the vibration characteristics of bridge the design and modal analysis of bridge is conducted by ANSYS 21 simulation package. Two different designs of bridges are evaluated i.e. without crack and with crack.The effect of crack on natural frequency and mode shape is evaluated. The vibration characteristics of bridge structure changed with artificially induced transverse elliptical crack on girder.Techniques of optimization could help in determining the behaviour of the damage and extent to which it could be controlled via simulation technique without conducting tests on the actual model. Analysing the frequencies using ANSYS software, the validity of the presented numerical formulation is studied. Response spectrum methodology is used in studying the crack characteristic and optimization of crack variables. Sensitivity analysis showed the individual effect of each variable on the output parameters. Moreover, the response surface plots generated showed the peak and least deformation values of natural frequencies. Invaluable information which help practicing engineers better understand the vibration characteristics is provided.