Stiffness Of Bridge Research Articles

Analysis of Integral Abutment Bridge Static Load Test

In order to understand the form of deformation and stress characteristics of the integral abutment bridge structures under the loads, this paper bases on Fuyu industrial park crossing bridge, through test vehicle load simulating design load, does a static load test for the bridge, and with the aid of theoretical method to simulate the interaction of pile and soil, builds finite element model, compares between measured and theoretical values of deflection and stress, gets that, the bridge bearing capacity and stiffness is bigger, with sufficient safety reserves.

Monitoring of Changes in Bridge Response Using Weigh-In-Motion Systems

Weigh-In-Motion (WIM) and Bridge Weigh-In-Motion (B-WIM) are systems that allow obtaining the axle weights of road vehicles in motion, at normal traffic speeds. While WIM employs sensors embedded in the road pavement, B-WIM use the strain recordings of a bridge to infer the traversing vehicle axle weights. Both systems have been heavily improved over the past decades, and commercial versions are currently in operation. The two main applications of these systems are: (1) to assess the traffic loading on the infrastructure, and (2) to enforce the maximum weight limits. This paper suggests a novel application of these two systems to identify changes in bridge stiffness. It requires the bridge to be instrumented with a B-WIM system and a WIM system nearby. The principle is to use both systems to evaluate the gross weight of vehicles passing over the bridge and correlate their predictions. Changes in correlation of the predicted axle weights over time will indicate either structural damage or faulty sensor. A finite element model of a coupled vehicle-bridge system with different damage scenarios is used to test the approach numerically. Vehicle mechanical properties and speeds are randomly sampled within a Monte Carlo simulation. Results show how correlation changes as damage increases and how this correlation can be employed as a damage indicator.

Dynamic Test and Analysis of Double Curved Arch Bridge Based on Ambient Excitation

Dynamic test of double curved arch bridge based on environmental incentives. And Peak value method stochastic subspace identification method is used for modal analysis, and bridge modal parameters are obtained. The results were compared with the finite element software Midas civil, and results are consistent. The test shows that the bridge modal parameters can be identified in the environmental stimulus response. Measured frequency is lower than the finite element calculation of frequency; it means the bridge stiffness is lower. The identified dynamic properties can be served as the basis in the finite element model updating, damage detection, condition assessment and health monitoring of the bridge.

Wheel-Set Hunting Movement and its Contribution to Coupling Vibration of Vehicle-Bridge System

Wheel-set hunting is an important and random lateral movement when wheel-set running on the track. Firstly a vehicle-bridge dynamic interaction model is established, in which the lateral wheel-rail interaction is defined by Kalker linear creep theory with the calculation of detailed wheel-rail contact adhesion geometric parameters and creep force. Then with the case of a high speed train passing a 32 m simply-supported beam bridge, the wheel-set hunting movement is calculated according to the relative vehicle and bridge lateral movement. And the characteristics of wheel-set hunting with different train speed and bridge stiffness are discussed. Then a simple lateral wheel-rail interaction is defined with close contact and no elastic deformation, and the contribution of hunting movement to coupling vibration of vehicle-bridge system is summarized in this method. The results show that the wheel-set hunting movement could be neglected when analyzing the bridge response, but it should be considered when analyzing the vehicle response in the vehicle-bridge interaction.

Repair and Service Safety Evaluation of a Fire Damaged Concrete Bridge

The Yao Zhou downlink Viaduct damaged in a fire accident was repaired using steel plate and concrete composite strengthening (SPCCS) technique. After strengthening and servicing normally for 1.5 years, two loading tests, meanwhile, a three-day traffic information observation and dynamic strain monitoring were carried out. The static loading test and monitoring results all showed that the Yao Zhou downlink Viaduct had good service condition since reinforcement, which satisfying the safety requirement. In order to evaluate the effectiveness of the SPCCS technique in-depth, structural behaviour under the ultimate limit state (ULS) and the serviceability limit state (SLS) were analyzed. The SLS and ULC of the key sections before and after reinforcement were calculated using the simplified formula and the finite element models calibrated by filed test results. The post-evaluation results showed that the behaviour of the spans damaged in fire accident could be improved obviously under the SLS using SPCCS technique, as well as the bridge stiffness enlarged than the original bridge structure. The ultimate bearing capacity (UBC) of the key sections was improved about 75% using SPCCS technique, which was two times as the most disadvantageous load effect combinations. Whats more, the fatigue life of fire damaged box girders strengthened using SPCCS technique was evaluated based on monitoring strain data, and the further bridge maintenance suggestions were proposed based on the assessment results.

Seasonally frozen soil effects on the dynamic behavior of highway bridges

Frozen ground is significantly stiffer than unfrozen ground. For bridges supported on deep foundations, bridge stiffness is also measurably higher in winter months. Significant changes due to seasonal freezing in bridge pier boundary conditions require additional detailing in order to ensure a ductile performance of the bridge during a design earthquake event. This paper reports the latest results obtained from a project that systematically investigated the effects of seasonally frozen soil on the seismic behavior of highway bridges in cold regions. A bridge was chosen and was monitored to study its seismic performance and assess the impact of seasonally frozen soil on its dynamic properties. A Finite Element (FE) model was created for this bridge to analyze the impact of seasonal frost. It was found that when frost depth reaches 1.2 m, the first transverse modal frequency increases about 200% when compared with the no-frost case. The results show that seasonal frost has a significant impact on the overall dynamic behavior of bridges supported by pile foundations in cold regions, and that these effects should be accounted for in seismic design.

Lateral Load Distribution of Articulated Hollow Slab Beam Bridge Strengthened by Transverse Prestressed Force

Abstract. Aiming at the features of the articulated hollow slab beam bridges with transverse prestressed force, an assumption that regards the reinforced slab beam bridges as analogy orthotropic plate was proposed. The lateral flexural stiffness and torsional stiffness of the plate bridges per meter width can be calculated approximately as an average value of those of the solid section and the minimum hollow section. The longitudinal flexural stiffness and torsional stiffness per meter width remain the same as the original ones. The modified G-M method for calculating the strengthened bridge was proposed. Example as a typical hollow slab bridges, the lateral load distribution influence-line after strengthening bridge obtained by using modified G-M method. The numerical analysis before and after strengthening bridge by using FEM was complete to gain lateral load distribution influence-line. It shows that the values predicted by the proposed modified G-M were matched with the results by the FEM after strengthening bridge. It shows that the method strengthening articulated hollow slab beam bridges by exerting transverse prestress steel wire on them proved to be effective and the presented modified G-M theory to be right.

Lateral Load Distribution of Articulated Hollow Slab Beam Bridge Strengthened by Transverse Prestressed Force

Aiming at the features of the articulated hollow slab beam bridges with transverse prestressed force, an assumption that regards the reinforced slab beam bridges as analogy orthotropic plate was proposed. The lateral flexural stiffness and torsional stiffness of the plate bridges per meter width can be calculated approximately as an average value of those of the solid section and the minimum hollow section. The longitudinal flexural stiffness and torsional stiffness per meter width remain the same as the original ones. The modified G-M method for calculating the strengthened bridge was proposed. Example as a typical hollow slab bridges, the lateral load distribution influence-line after strengthening bridge obtained by using modified G-M method. The numerical analysis before and after strengthening bridge by using FEM was complete to gain lateral load distribution influence-line. It shows that the values predicted by the proposed modified G-M were matched with the results by the FEM after strengthening bridge. It shows that the method strengthening articulated hollow slab beam bridges by exerting transverse prestress steel wire on them proved to be effective and the presented modified G-M theory to be right.

Analysis of Multi-Pylon Cable-Stayed Bridges with Intersecting Cables

For the intermediate pylons of multi-pylon cable-stayed bridges can’t be connected by backstays to fixed points, it is possible to produce greater horizontal displacements in the top of towers under the action of external loads. Therefore, it is an important problem to obtain adequate structural stiffness in the design of multi-pylon cable-stayed bridges. In this paper, methods of improving stiffness of multi-pylon cable-stayed bridges are discussed. Multi-pylon cable-stayed bridges with intersecting cable are studied. Some useful recommendations were given for the design of multi-pylon cable- stayed bridges by numerical calculation.

Cable Deflection and Gravity Stiffness of Cable-Stayed Suspension Bridge

The paper studye the cable deflections of cable-stayed suspension bridge subject to living load. in addition, an analytical formula of the gravity stiffness of the cable-stayed suspension bridge is derived. Duo to the dead load state in the cable-stayed part is more differ from that in the suspension part, the research aim at different parts of the cable in the cable-stayed suspension bridge. Using the energy relation principle associated with deformation of the cable, the cable deflections and gravity stiffness of cable-stayed suspension bridge are derived.

Structure and behavior of floor system of two super high-speed railway Changjiang composite bridges

Wuhan Tianxingzhou Changjiang (WTC) Bridge and Nanjing Dashengguan Changjiang (NDC) Bridge are two super high-speed railway 3-trusses composite bridges. This is the first time of using three trusses in such large bridges in the world. These two types of railway floor systems of the two bridges have never been used in China before. The problem how to conform the deformations and stress levels of the railway floor system of WTC Bridge was studied. After finite element analysis and comparison, the plan of arranging one expansion stringer every two panels in railway floor system were proposed and good effect was obtained. Because of the application of three trusses, the allocation of the loads acted on the deck in three trusses is different and varies in different places of NDC Bridge. This problem was studied by model experiment and 3D finite element analysis. The results of 3D FEM analysis coincide with the model test results. The allocation rule of the loads acting on the deck in three trusses was presented. Because of the application of monolithic decks, the stiffness and structural integrity of NDC Bridge are high.

Long-term performance of rubber bearing considering solar radiation effect

The equivalent shear stiffness of a rubber bridge bearing increases over time due to the deterioration of rubber. It was assumed in the past aging estimation that rubber in the bearing and at the surface had the same temperature as its surrounding ambient temperature because rubber bearings were thought to be usually in the shadow as they are installed between the superstructure and the substructure. However, in the actual environment, there are many bearings that are exposed to solar radiation that causes bearing temperature to increase. To evaluate the effect of solar radiation on the bearing temperature, bearing surface temperatures were measured for a bearing installed on an elevated highway in Nagoya, Japan. In addition, to understand a temperature variation in a bearing, a bearing model was manufactured, and a temperature measurement of internal temperature was carried out. Long-term performance of rubber bearing by considering solar radiation effect on bearing temperature was investigated.

Behavior of instrumented prestressed high performance concrete bridge girders

A comprehensive monitoring of the behavior of four prestressed high performance concrete (HPC) bridge girders, with higher compressive strength, during construction and while in-service, is presented. The monitoring program covered instrumentation and monitoring of a series of four girders during the casting operation, after construction, under the effects of traffic and thermal loads, as well as under controlled load conditions. Information regarding transfer length, prestress loss, heat of hydration, compressive strength, modulus of elasticity (MOE), modulus of rupture (MOR), creep, shrinkage, coefficient of thermal expansion, and chloride permeability of the concrete used is obtained and presented. Furthermore, the in-service monitoring and controlled load tests and details regarding thermal expansion, bridge stiffness, and load distribution factors are also presented. This paper provides details of testing of the concrete properties and field instrumentation of the bridge girders as well as a discussion of service level monitoring and controlled load testing. Comparisons are made between experimental and theoretical results.

Finite-Element Modeling and Development of Equivalent Properties for FRP Bridge Panels

Fiber-reinforced polymer FRP composite materials are increasingly making their way into civil engineering applications. To reduce the self-weight and also achieve the necessary stiffness, sandwich panels are commonly used for FRP bridge decks. However, due to the geometric complexity of the FRP sandwich deck, convenient analysis and design methods for FRP bridge deck have not been developed. The present study aims at developing equivalent properties for a complicated sandwich panel configuration using finite- element modeling techniques. With equivalent properties, the hollowed sandwich panel can be transformed into an equivalent solid orthotropic plate, based on which deflection limits can be evaluated and designed. A procedure for the in-plane axial properties of the sandwich core has first been developed, followed by developing the out-of-plane panel properties for bending behavior of the panel. An application is made in the investigation of the stiffness contribution of wearing surface to the total stiffness of bridges with FRP panels. The wearing surface contribution is not usually accounted for in a typical design of bridges with traditional deck systems.

Long-Term Monitoring and Analysis of a Curved Concrete Box-Girder Bridge

Curved bridges are important components of a highway transportation network for connecting local roads and highways, but very few data have been collected in terms of their field performance. This paper presents two-years monitoring and system identification results of a curved concrete box-girder bridge, the West St. On-Ramp, under ambient traffic excitations. The authors permanently installed accelerometers on the bridge from the beginning of the bridge life. From the ambient vibration data sets collected over the two years, the element stiffness correction factors for the columns, the girder, and boundary springs were identified using the back-propagation neural network. The results showed that the element stiffness values were nearly 10% different from the initial design values. It was also observed that the traffic conditions heavily influence the dynamic characteristics of this curved bridge. Furthermore, a probability distribution model of the element stiffness was established for long-term monitoring and analysis of the bridge stiffness change.

Low-Cycle Fatigue Testing of High-Performance Concrete Bonded Overlay–Bridge Deck Slab Systems

Plain and fibrous latex modified concrete and microsilica concrete overlays with acceptable laboratory strength and durability characteristics were installed on a full-scale prototype bridge deck for field performance evaluation. After 1 year of exposure to drying shrinkage, temperature variations, and freeze-thaw cycles, no cracking or debonding were observed in the overlays. The bond strengths at 28 days and at 1 year were acceptable for all overlay types due to the excellent curing and surface preparation using water-jet blasting. The prototype bridge was then statically tested before and after applying low-cycle fatigue loading simulating AASHTO HS20 truck service load, overload, and ultimate load. Minor bond strength deterioration at the maximum negative moment region and slight bridge stiffness degradation were observed after each load case. Significant enhancement in the bridge stiffness was observed after installation of the overlays. Also, the overlay with synthetic fibers showed better crack bridging action than the overlay with steel fibers.

Molecular Adhesion Model for the Bridged State of a Magnetic Recording Slider

Frictional hysteresis loops are measured with a pico-slider on typical desktop media to illustrate the bridged state with a chemisorbed perfluoropolyether lubricant. Our new molecular adhesion model calculates the mean spacing and bridge stiffness from the experimental friction force, surface topography, and dispersive surface energy. An increase in friction force with increasing pressure is consistent with molecular bond orientation by the adhesion stress

Stiffness and Damping of Thin PFPE Lubricant Bridging Between Magnetic Disk and Diamond Probe Tip

Spring constants and damping coefficients of a thin lubricant bridge of a perfluoropolyether (PFPE) lubricant intervening between a diamond probe tip and a diamond-like carbon (DLC) surface of a magnetic disk are identified through regression analysis of tip damping vibration. PFPE lubricants with functional end groups were used to form a lubricant bridge between the DLC surface and a probe tip with a notably small curvature radius of 0.1μm. The tip was both retracted from and extended toward the disk surface at four different progressive distances to attain varied elongation of the bridge. It was also vibrated at each step to provide damping waveforms. By applying regression analysis to the observed waveforms, the spring constant and the damping coefficient of the lubricant bridge were identified within an elongation range from 50nm to 800nm. Spring constant of the lubricant bridge kb had a negative value varying from −0.15N∕m to −0.1N∕m. The damping value expressed in the form of frequency-multiplied damping cb×ω ranged from 0.02N∕m to 0.06N∕m. Note that both the absolute value of spring constant ∣kb∣ and frequency-multiplied damping cb×ω exhibited U-shaped variation with lubricant bridge elongation; that is, those values decrease with bridge elongation and they begin to increase after reaching the minimum. The variation in the spring constant was found to be in good accordance with the quasi-static stiffness of the lubricant bridge, and variation in the damping coefficient was explained by energy loss arising in the vibrating lubricant bridge.

The efficiency of bridges in a crack

Bridges are cross connections in a crack that contract its faces behind the crack tip. They appear because of the inhomogeneity of the material or differences in the kinematics of fracture. We obtained a general solution to the nonlinear singular integral equation that relates the crack opening h(x) to the stress caused by bridges p(x) and determined the stress-intensity factor F(B) (degree of unloading of the crack tip due to the presence of bridges) depending on the dimensionless stiffness of bridges B. As the measure of the efficiency of bridges, we suggest the ratio of the stress for crack start in a matrix without bridges σm to that in the presence of bridges σ∞. When bridges with a strength σu occupy a fraction f of the fracture area, their efficiency Y(ζ, B) depends on the degree of reinforcement ζ = fσu/σm and on their stiffness B. The Y(ζ, B) dependences have been obtained in an explicit form for the limiting cases of brittle and fully ductile bridges.

에너지 소산장치를 장착한 사장교의 지진 취약도 해석

이 논문에서는 에너지 소산장치가 장착된 사장교의 지진 취약도 해석 방법을 제시하고 에너지 소산장치의 장착 및 주탑-보강형 연결 조건에 따른 지진 취약도 변화를 살펴본다. 입력지반운동, 에너지 소산장치 특성값 및 사장교 강성 모형에 확률 변수를 도입하여 불확실성을 고려하고 에너지 소산장치의 비선형 이력거동을고려하여 시간이력 해석을 수행한다. 해석결과의 회귀분석을 통한 최대 응답과 입력지반운동 세기(intensity) 사이의 관계식으로부터 취약도 해석을 위한 소요 역량(demand)을 수립한다. 역량(capacity)에 해당하는 한계상태는 주탑 하부의 전단력, 보강형의 교축방향 변위, 케이블 장력의 변동량 그리고 강주탑의 좌굴이 고려된다. 해석 예제로서 강주탑 사장교인 제 2 진도대교 모형에 대하여 취약도 해석을 수행하였다. 취약도 해석결과 에너지 소산장치의 사용을 통하여 구속 또는 비구속 연결조건시 높은 손상확률을 보이던 한계상태에 대하여 그 손상확률을 크게 줄일 수 있음을 확인하였다. This paper presents a seismic fragility analysis method for a cable-stayed bridge with energy dissipation devices. Model uncertainties represented by random variables include input ground motions, characteristics of energy dissipation devices and the stiffness of cable-stayed bridge. Using linear regression, we established demand models for the fragility analysis from the relationship between maximum responses and the intensity of input ground motions. For capacity models, we considered the moment and shear force of the main tower, longitudinal displacement of the girder, deviation of the stay cables tension and the local buckling of the main steel tower as the limit states for cable-stayed bridge. As a numerical example, fragility analysis results for the 2nd Jindo bridge are presented. The effect of energy dissipation devices is also briefly discussed.