Small Span Bridges Research Articles

A spectrum correlation matrix-based rapid damage identification method for joints in hinged slab bridges by sparse measurement

Hinged slab bridges are widely used in the medium and small-span bridges on highways and the joints are highly susceptible to damage under the action of the increasing traffic. However, current methods for damage identification of hinged joints, whether rely on static or dynamic testing, typically require substantial manpower, resources and time, which presents challenges for the rapid evaluation of numerous bridges. In view of this, a novel damage index named spectrum correlation matrix (SCM) is proposed and its feature extraction technology is established as well as the potential for sparse measurement is theoretically explained. Furthermore, a rapid, robust, and convenient damage identification methodology using SCM and Levenberg-Marquardt algorithm is proposed. An optimal strategy for the layout of sparse measuring points has been explored, the sensitivity and the effectiveness of the proposed method is validated through both numerical simulations and the in-situ test of a bridge in service. The results indicate that the SCM contains abundant vibration information and shows a high sensitivity to damage. The strategy for the layout of measuring points is highly efficient and the proposed methodology greatly reduces the number of measuring points compared to previous vibration-based methods, which eases rapid identification of damage for joints in hinged slab bridges.

Comparative Study on the Seismic Vulnerability of Continuous Bridges with Steel–Concrete Composite Girder and Reinforced Concrete Girder

For medium- and small-span bridges, the weight of the superstructure in steel–concrete composite girder bridges is lighter than that of a reinforced concrete girder bridge. However, it is still uncertain whether steel–concrete composite girder bridges exhibit superior seismic performance compared to reinforced concrete girder bridges. This study quantitatively compared the seismic performance of the two types of bridges. Using the theory of probabilistic seismic demand analysis, the seismic vulnerability curves of bridges were derived. To conduct seismic demand analysis for probabilistic analysis on the OpenSEES platform, bridge samples were generated using the Latin hypercube stratified sampling method, which considers the uncertainties associated with the two types of bridges. The vulnerability curves of the piers, bearings, abutments, and the system of the two bridges were established using probabilistic analysis of the time history analyses. The results showed that the seismic vulnerabilities of components and the overall system of the steel–concrete composite girder bridge were both lower than those of the reinforced concrete girder bridge. When the peak ground acceleration (PGA) of the ground motion was 0.3 g, the moderate and serious damage probabilities of the piers in the steel–concrete composite bridge were only 54.61% and 60.89%, respectively, of those of the reinforced concrete bridge. Consequently, replacing the upper reinforced concrete girders with steel–concrete composite girders can significantly improve the seismic performance of a large number of existing bridges.

Optimization and fatigue assessment of girders with large-dimension corrugated steel webs

In recent years, large-dimension Corrugated Steel Webs (CSW) has increasingly become an available solution for long-span bridges to reduce deadweight and improve prestressing efficiency. Compared to conventional CSW used in small-span bridge girders, girders with large-dimension CSW in long-span bridges are more susceptible to fatigue cracking under repetitive traffic loads. However, the specifications aimed for small-dimension CSW may resulted in unsafe fatigue detail categories. This paper investigated the fatigue performance of large-dimension CSW girders for bridges. The reasonable corrugation angles of girders with CSW were obtained using Grey Relational analysis. The fatigue detail category corresponding to optimized corrugation angles was suggested based on the Theory of Critical Distance (TCD). The Finite Element Analysis (FEA) results indicate that the hot spot stress concentration factor (Ks) on the web-flange weld toe increases with the corrugation angle and decreases with the bend radius. When the corrugation angle and the bend radius are fixed, Ks increases with the corrugation wavelength. By developing a balanced fatigue and shear buckling performance scheme, the optimized corrugation angles of wavelength 1000 ∼ 2000 mm are between 30° and 45°. There is a negative correlation between the fatigue detail categories of CSW girders and corrugation wavelengths. In general, the fatigue detail category of wavelength 1600 ∼ 2000 mm under four-point bending can be classified into a range between 50 and 71 for Eurocode 3, Category D and Category E′ design curves for AASHTO, FAT 50 and FAT 71 for IIW respectively.

Research on fatigue damage correction coefficient of main truss members of railway suspension bridges

Steel truss girder suspension bridges are gradually applied to long-span railway bridges. The fatigue damage correction factor is an important parameter for fatigue calculation, however the research on the coefficient is limited to small-span bridges. This paper analyzes force characteristics of main truss members, calculates the fatigue damage correction coefficient of truss members, and studies the influences of train loading length, annual traffic level of fatigue damage correction coefficient. The main conclusions are as follows: (1) The influence line and fatigue stress characteristics of the main truss members were studied; the stress range of members under tension or mainly under tension is analyzed, and the stress ranges and ratios between dead and live loads in main truss members are investigated. The results show that the maximum stress range of the bottom chord is 182 MPa, the ratios of dead to live loads of about 90 % of bottom chords and diagonal web members exceed the current specifications, and stress ratios of about 10 % of bottom chords and diagonal web members exceed the current specifications. (2) The fatigue damage correction coefficients of main truss members under different train loading lengths and annual traffic levels are calculated and recommended. The research results provide a basis for updating and supplementing the railway steel bridge code.

Analysis on the stress mechanism of the exposed steel anchor box composite cable–pylon anchorage structure

For the exposed steel anchor box cable–pylon anchorage structure, there is a good application prospect in urban bridges of medium and small span due to its good mechanical behavior, easy construction and beautiful overall appearance. This paper reveals the stress-transfer mechanism of the exposed steel anchor box cable–pylon anchorage structure through a segmental model test with a scaled-down ratio of 1:2, and focused on the effect of prestress in the pylon. Three calculation modes for the anchorage structure are proposed, and simplified calculation equations of the horizontal load distribution relationship and the vertical shear force of the stud are derived. The effects of various design parameters on the load distribution ratio, the pylon wall tension caused by shrinkage and the vertical shear force of the studs are discussed by using the simplified calculation equation. The research results show that the exposed steel anchor box cable–pylon anchorage structure has good applicability in medium and small span bridges. Prestress can significantly reduce the tensile stress of the pylon wall concrete, and improve its crack resistance. There is no significant difference between the results of the simplified calculation equations and the finite element calculation, and the simplified calculation equations meet the design requirement.

A rapid evaluation method based on natural frequency for post-earthquake traffic capacity of small and medium span bridges

To improve the efficiency of evaluating the traffic capacity of bridges after the earthquake, a rapid method based on natural frequency for evaluating post-earthquake traffic capacity of small and medium-span bridges is proposed. Firstly, OpenSees software is selected to establish the seismic numerical analysis model of the pier, and the pressure of the main girder on the pier is equivalent to concentrated mass to extract the dynamic characteristics of the pier. The horizontal thrust on the pier top is adopted to simulate seismic action by the pseudo-static method, and the horizontal thrust is controlled by the maximum horizontal displacement. The value range of pier parameters is determined according to the definition of the regular bridge and relevant design data, then the design parameters and maximum horizontal displacement of each pier are sampled by the Latin hypercube sampling method to obtain various combined working conditions. Subsequently, the natural frequency, residual displacement and bearing capacity of the pier under different working conditions are obtained through numerical simulation. The relationship between natural frequency and residual bearing capacity of the pier after the earthquake is established in light of the simulation results of pier models. Then, the vehicle load is arranged on the basis of the most unfavorable loading principle, and the bearable maximum vehicle weight of the bridge is estimated from the bearing capacity of each pier, so that the traffic capacity of the bridge after the earthquake can be quickly evaluated by the change of natural frequency of piers. Finally, the reliability of the pier numerical model and residual displacement calculation method are verified by the test results of piers. The application process of the evaluation method proposed in this paper is illustrated by two typical examples of a simply supported beam bridge and a continuous beam bridge, which proves the feasibility of this method.

Structural Damage Identification System Suitable for Old Arch Bridge in Rural Regions: Random Forest Approach

A huge number of old arch bridges located in rural regions are at the peak of maintenance. The health monitoring technology of the long-span bridge is hardly applicable to the small-span bridge, owing to the absence of technical resources and sufficient funds in rural regions. There is an urgent need for an economical, fast, and accurate damage identification solution. The authors proposed a damage identification system of an old arch bridge implemented with a machine learning algorithm, which took the vehicle-induced response as the excitation. A damage index was defined based on wavelet packet theory, and a machine learning sample database collecting the denoised response was constructed. Through comparing three machine learning algorithms: Back-Propagation Neural Network (BPNN), Support Vector Machine (SVM), and Random Forest (R.F.), the R.F. damage identification model were found to have a better recognition ability. Finally, the Particle Swarm Optimization (PSO) algorithm was used to optimize the number of subtrees and split features of the R.F. model. The PSO optimized R.F. model was capable of the identification of different damage levels of old arch bridges with sensitive damage index. The proposed framework is practical and promising for the old bridge’s structural damage identification in rural regions.

Research Progress on Fire Resistance of Steel-concrete Composite Structures

The 1930s was an important period of development in the design theory of bridge technology in Europe and the United States. Among them was the invention of welding technology, which created more favorable conditions for the development of combined structures, i.e., the connection between reinforced concrete slabs and steel girders could be welded instead of the initial connection method. In China, for more than thirty years, on the one hand, large span bridges have been able to develop rapidly and set new world records, driven by the huge technical demand seeking span breakthroughs. On the other hand, concrete bridges dominate the large number of small span bridges. In short, in China, steel-concrete (SC) structures have also developed accordingly. This paper first introduces the steel-concrete combination structure, and then analyzes the steel-ability concretes to withstand fire from both theoretical and experimental perspectives. Valid data are provided by graphs and equation analysis. Finally, a method that can measure the fire resistance of SC composite structures in fire is obtained.

Life cycle dynamic sustainability maintenance strategy optimization of fly ash RC beam based on Monte Carlo simulation

Small and medium span bridges account for 86% of the bridges in China, and maintenance is necessary to ensure their safety and serviceability. The infrastructure sector causes substantial CO2 emissions, and it is one of the most polluting sectors. Fly ash (FA) is often used in bridges to reduce CO2 emissions. Moreover, the lack of temporal information is an important limitation of the life cycle CO2 assessment of bridges. Taking the upper structure of small and medium span bridges as the research object, this paper proposes a Monte Carlo simulation-based life cycle multi-objective dynamic maintenance strategy optimization model to analyze the life-cycle carbon emissions, costs, and life cycle reliability of different preventive maintenance (PM) and essential maintenance (EM) methods of FA reinforced concrete (RC) beams. Considering the continuous effect of carbon emissions and the net present value of the cost, the time effect of carbon emissions and costs of maintenance and reinforcement at different times is analyzed. Through 50,000 simulations of the case beam, the parameter characteristics of different optimal reinforcement schemes and the relationship between the reliability, life cycle CO2 emissions, and costs are studied. When introducing the discount rate, the essential maintenance with higher carbon emissions and costs has a marginal effect, i.e., the longer that future carbon emissions and costs occur, the smaller the net present value. The proposed method is demonstrated to be effective at supporting decision making for bridge managers. It would be helpful for identifying the effectiveness of PM and EM, selecting optimal maintenance time interval, and providing a rational estimate of the CO2 emissions and costs of bridges.

Comparative study of microimage strain sensing system and FBG sensing system for strain measurement

Strain is one of the conventional parameters that evaluate structural performance in the field of bridge health monitoring. Among the various techniques that have been utilized to measure strain, fiber Bragg grating (FBG) sensing system has been broadly applied for long-term strain monitoring in civil engineering, whereas microimage strain sensing (MISS), with its corresponding sensors designed and fabricated, is a new technology for strain measurement. Furthermore, the MISS system is developed to monitor the strain of small and medium span bridges. To verify the performance of the MISS system in strain measurement, a comprehensive and comparative study of the MISS system and FBG strain sensor system is provided. First, the technical features of the two technologies were described. Moreover, more details were expounded in terms of service life, deployment, coverage, cost, and temperature dependence. Then, assisted data comparisons were carried out through component testing. Results show that the proposed MISS system is effective and robust. Therefore, the proposed MISS system will serve as a promising strain measuring alternative in the field of bridge structural health monitoring.

Damage Identification Method for Medium- and Small-Span Bridges Based on Macro-Strain Data under Vehicle-Bridge Coupling.

The damage identification method based on macro-strain modality has shown good results for large-span flexible bridges. However, medium- and small-span bridges have a high stiffness, and the axle system is embodied. The strong time-varying vibration characteristics, coupled with the non-stationary characteristics of vehicle loads, make it difficult to accurately determine the stable strain modes of such bridges. To solve this problem, a damage localization index in the form of an amplitude vector matrix of the mutual energy density spectrum based on macro-strain was constructed using wavelet transform de-noising and reconstruction technology and cross-correlation function. The macro-static strain and macro-dynamic strain data obtained from a vehicle–bridge coupling experiment were reconstructed through wavelet transform, and the factors influencing the damage indices were analyzed. The results showed that the proposed indicators could help realize an accurate damage localization for medium- and small-span bridge systems with different damage degrees under the action of vehicle–bridge coupling.

Measurement research on vibro-acoustic characteristics of large-span plate-truss composite bridge in urban rail transit

Large-span plate-truss composite bridge (LPCB) is developing more and more rapidly in urban rail transit. Nevertheless, the bridges are often close to residential buildings, and some even pass through residential areas directly. Compared with small span bridges and ordinary concrete viaducts, the train-induced vibration and noise of LPCB are larger and last longer, and have a greater impact on the residents along the line. Therefore, it is necessary to study the train-induced vibro-acoustic characteristics of LPCB. However, the current research on LPCB mainly focuses on the aspects of bridge structure design, construction, traffic safety and comfortable capability etc, and usually only cares about the global mechanical behavior of bridge structure and train-track-bridge coupling vibration. In order to study the vibro-acoustic characteristics of large-span and complex bridge structures such as LPCB, it is extremely important to obtain and analyze the field measured data. In this paper, the vibration and noise filed measurement of LPCB has been carried out by the authors. The vibration characteristics of track and bridge system have been measured by means of acceleration sensors, which were arranged on the rails, track slab, the center of bridge deck, longitudinal web and transverse web. The noise characteristics of wheel-rail and bridge structure system have been measured by mans of noise sensors, which were arranged beside the track structure and under the bridge structure. Based on the measurement date, the vibro-acoustic characteristic of the LPCB were analyzed in the present paper. It is found that the response of track structures are mainly affected by wheelsets periodic excitation, while the response of bridge structures are determined both by wheelsets periodic excitation and wheel-rail irregularity; the rail and slab are decoupled after beyond the natural frequency of the rail-fastener system (100 Hz); the vibration energy in high frequency band can be effectively suppressed to downward transmission by damping pad floating slab track; the overall vibration level of rail, track slab and bridge are about 130 dB, 114 dB and 118 dB respectively, the overall sound pressure level of track-side and bridge structure are approximately 82 dB(A) and 83 dB(A) respectively.

Static aerodynamic force coefficients for an arch bridge girder with two cross sections

Aiming at the wind-resistant design of a sea-crossing arch bridge, the static aerodynamic coefficients of its girder (composed of stretches of π-shaped cross-section and box cross-section) were studied by using computational fluid dynamics (CFD) numerical simulation and wind tunnel test. Based on the comparison between numerical simulation, wind tunnel test and specification recommendation, a combined calculation method for the horizontal force coefficient of intermediate and small span bridges is proposed. The results show that the two-dimensional CFD numerical simulations of the individual cross sections are sufficient to meet the accuracy requirements of engineering practice.

Reliability Evaluation of Hinged Slab Bridge Considering Hinge Joints Damage and Member Failure Credibility

The hinged slab bridge is widely used in medium- and small-span bridges because of its simple structure and convenient construction. However, hinge joints damage is the main defect of this kind of bridge, and it is difficult to express the deterministic damage degree of hinge joints in the detection process. A system reliability evaluation method considering fuzzy detection information of hinge joints damage and member failure credibility is proposed in this paper. Firstly, the membership function is used to quantitatively express the fuzzy detection information of hinge joints, and the fuzzy variable is transformed to an equivalent random variable. Secondly, the functional relationship between the transverse distribution coefficient and hinge joints damage is constructed by the modified hinge-jointed plate method and response surface method, and the reliability of the member considering the fuzzy detection information of hinge joints damage is calculated by the first-order second-moment method (FOSM). Then, the failure credibility is introduced to represent the different possibilities of system failure caused by member failure, and a system reliability assessment method of different failure criteria considering member failure credibility is established based on copula theory. Finally, the applicability of the proposed method is verified by taking the reinforced concrete hinged slab bridge as a numerical example.

Strain Data Analysis of Small and Medium Bridge Structures Based on Finite Element

Structural health monitoring technology is increasingly used in the operation and management of small and medium span bridge structures, which also brings the problem that it is difficult to fully interpret and utilize the mass monitoring data. In this paper, the Sanyang Bridge is used as the engineering background, based on the strain monitoring data, combined with the finite element calculation software MIDAS/civil, to evaluate and analyze the operating state of the bridge structure. The results show that the overall operation status of Sanyang Bridge is good, the evaluation method combining finite element calculation and monitoring data is reasonable, this method can be applied to data processing and condition assessment of small and medium span bridges.

Rsearch on Load Adaptability of Existing Hollow Slab Bridge of Ji-Qing Highway

Throughout the reconstruction and expansion process of the Jinan and Qingdao Expressway, there is a need for the existing Bridge to be demolished first and then reinforced for a better utilization. In order to better evaluate the load capability of the Level 1 lane, the load ability of the Seven-Ministry loads adaptability model and the current Ji-Qing traffic model, this paper examines three models of the load adaptability of existing small span Bridges. The load adaptability of the three load models on the old bridge of Jiqing existing line is analysed by comparing the bearing capacity level of the three load models in the three spans of 5m, 8m, and 13m of the hollow slab bridge.

Proposal of Sustainability Indicators for the Design of Small-Span Bridges.

The application of techniques to analyze sustainability in the life cycle of small-span bridge superstructures is presented in this work. The objective was to obtain environmental and economic indicators for integration into the decision-making process to minimize the environmental impact, reduce resource consumption and minimize life cycle costs. Twenty-seven configurations of small-span bridges (6 to 20 m) of the following types were analyzed: steel–concrete composite bridges, cast in situ reinforced concrete bridges, precast bridges and prestressed concrete bridges, comprising a total of 405 structures. Environmental impacts and costs were quantified via life cycle environmental assessment and life cycle cost analysis following the boundaries of systems from the extraction of materials to the end of bridge life (“from cradle to grave”). In general, the results indicated that the environmental performance of the bridges was significantly linked to the material selection and bridge configuration. In addition, the study enabled the identification of the products and processes with the greatest impact in order to subsidize the design of more sustainable structures and government policies.

The effect of rise-span ratio on the rigid-framed arch bridges

The rigid-framed arch structure is a popular bridge structure on medium and small span bridge such as flyover. Rise-span ratio affects the rigid-framed arch structure performance, in order to analyse the influence on the rigid-framed arch structure of different rise-span ratio, a calculation model of the rigid-framed arch structure on the basis of the project established using the large general finite element software, by adjusting the rise value to change the rise-span ratio, analysing and comparing the structural internal force and deformation condition of the rigid-framed arch in different rise-span ratio under the action of constant live load, temperature change, and foundation settlement. The influence of different rise-span ratio on the rigid-framed arch stress summarized.

Structural Rationality Research on Integrated Prefabricated I-Shaped Steel-Concrete Composite Girder Bridges

In order to promote the use of steel-concrete composite bridges in small and medium span bridges, and improve industrial construction of bridge and assembling degree of the composite girder bridge, an integrated prefabricated steel-concrete composite girder bridge was proposed. Considering the requirements of small and medium span bridges and the condition of highway transportation, the basic unit of the integrated prefabricated steel-concrete composite girder was constructed, and the connection way of units was put forward so as to further form the whole bridge. According to the result of calculation and analysis, the mechanical behaviour of the integrated prefabricated steel-concrete composite girder is superior to the traditional separated prefabricated steel-concrete composite girder, and it also performs better than the existing prefabricated concrete box girder and prefabricated concrete T-shaped girder in economy from the prospective of cycle. Besides, by comparing with the existing prefabricated concrete box girder, the prefabricated concrete T-shaped girder and the separated prefabricated steel-concrete composite girder, the integrated prefabricated steel-concrete composite girder would significantly improve the construction efficiency and shorten the construction period, and the construction quality could be guaranteed. All in all, the integrated prefabricated steel-concrete composite girder is a rational structure with convenient construction for bridge engineering.

Middle displacement monitoring of medium–small span bridges based on laser technology

Middle displacement monitoring of medium–small span bridges based on laser technology