Measured Deflection Data Research Articles

Stiffness degradation analysis of reinforced concrete beams under corrosion-fatigue coupling action based on experimental research

In order to study the effect of corrosion-fatigue coupling action on the stiffness degradation of reinforced concrete beams, a novel corrosion-fatigue coupling experimental device is designed, eleven reinforced concrete T-shaped test beams are made, in which a set of static load test, then seven sets of simple fatigue tests under different stress amplitudes and three sets of corrosion-fatigue coupling tests under different stress amplitudes are conducted respectively. The test phenomenon, load-deflection relationship, and fatigue life of the simple fatigue test beams and the corrosion-fatigue coupling test beams are compared. The test results show that the deflection development of the corrosion-fatigue coupling test beams includes three stages of sudden increase-stable-sudden increase, as the same as the simple fatigue beams. The deflection growth rate of the corrosion-fatigue coupling beams in the second stage is greater than that of the simple fatigue beams. Fatigue cyclic loading significantly increases the residual deflection of the test beams compared to the static load test beam. Then a new calculation method of the midspan deflection of the simple fatigue beam and the corrosion-fatigue coupling beam is developed according to the measured deflection data and the fatigue life test results. In this method the influence factors such as fatigue loading times, fatigue stress amplitude, concrete elastic modulus degradation, steel corrosion and other factors are systematically considered, and this method is verified by experimental data.

Effect Of Creep On The Long-Term Deflection Of Box Girder Balanced Cantilever Bridge Structure Using B3 Model and CEB 2010

Creep significantly affects the long-term deflection of the prestressed concrete bridge structure. Some models often used in predicting creep do not consider the water-cement ratio. The water-cement ratio is a factor in the magnitude of creep. If the water-cement ratio is excessive, the creep will also be significant. B3 Model uses the water-cement ratio in predicting creep in prestressed concrete bridge structures and has provided good accuracy with measured deflection data. This study compares B3 Model with Model CEB 2010 to predict the effect of creep on the long-term deflection. The author modeled the bridge structure using Midas Civil 2022 v1.2 software by utilizing the construction stages analysis facility to idealize the balanced cantilever and the effect of creep on the long-term deflection. Envelope displacement of bridge B3 Model is more significant than CEB 2010. The prediction deflection of the B3 Model in 100 years of service life of the bridge is -16.34 cm, while CEB 2010 is -11.90 cm. Creep affects total deflection by 84% to 88%. Creep affects the deflection significant because, in the construction process, each box girder segment is stressed and loaded at the age of 3 days. At the age of 3 days, the elastic modulus of the concrete is still not entirely, and the cement paste on the concrete is still in the hydration process. The results showed a significant difference between B3 Model and CEB 2010. B3 Model predicts that the long-term deflection of the bridge until the end of the bridge's service life is 44% to 49% greater than the CEB 2010 model. Prediction of total deflection until the end of 100 years of bridge service life does not exceed the limit determined by SNI and CEB codes.

Missing data imputation framework for bridge structural health monitoring based on slim generative adversarial networks

In structural health monitoring (SHM) systems, sensors are important to collect structural responses to assess the load-resistant capacity and health status of structures. However, data loss of these sensors is sometimes inevitable due to communication outages and malfunction, which will result in incorrect diagnosis of structural health status. Conventional lost data imputation methods fundamentally have low implementing efficiency owing to incompact neurons network structures. This paper proposed a slim generative adversarial imputation network (SGAIN) to recover the missing deflection data for bridge SHM systems. This framework uses slim neural networks with a generator-discriminator architecture to capture the valuable information from the non-missing parts of fault sensor and other normal sensors. Based on analysis on the long-term measured deflection data under the ambient and dynamic excitation of a highway-railway dual-purpose bridge, the proposed method shows the efficient and accurate imputation performance under the input scenarios with different correlation levels. The comparative results show the proposed SGAIN significantly outperforms the conventional GAIN model for all three scenarios with different missing rates. The execution velocity of SGAIN model also outperforms GAIN with 10–20% increment for three type scenarios. Such improvement is significantly valuable and it is believed that SGAIN could also have a good imputation capability when transferred to other valuable scenarios.

Separation of the Temperature Effect on Structure Responses via LSTM—Particle Filter Method Considering Outlier from Remote Cloud Platforms

Structural health monitoring (SHM) has been widely applied in the field of Mechanical and Civil Engineering in recent years. It is very hard to detect damage, however, using the measured data directly from the remote cloud platform of on-site structure, owing to changing environmental conditions. At the same time, outlier data from the remote cloud platform often occurs due to the harsh environmental conditions, interferences in the wireless medium, and the usage of low-quality sensors, which can greatly reduce the accuracy of structural health monitoring. In this paper, a novel temperature compensation method based on a long-short term memory (LSTM) network and the particle filter (PF) is proposed to separate the temperature effect from long-term structural health monitoring data. This method takes LSTMs as the state equation of PF, which solves the problem whereby PF cannot accurately derive the state equation for complex structures. A feedback model using the probability distribution generated by PF is developed to filter the observed value, thus measurement outliers can be successfully reduced. A numerical simulation and the measured deflection data from an SHM system are utilized to verify the proposed method. Results from the numerical simulation show that the LSTM-PF method can satisfactorily compensate for the temperature effect even when the nonlinear temperature effect is considered. Moreover, outputs from the SHM system of a large-scale suspension bridge indicate the temperature effect can be compensated and outliers can be appropriately reduced at the same time using the measured deflection data.

Vertical compressive strain-based method for setting the rigid layer depth based on falling weight deflectometer test

A new method has been proposed to set the rigid layer depth using the field measured deflection data of some different pavements. First, the effect of the rigid layer depth on the backcalculated subgrade modulus was analyzed. Then, the setting model named controlled strain method based on the consistency of the backcalculated subgrade moduli was established. Finally, the feasibility of the proposed method was validated by the comparison with the regression formula setting method. It was found that with an increase in the rigid layer depth, the backcalculated subgrade moduli progressively became larger. The rigid layer depth can be set by controlling the vertical compressive strain at the bottom of the subgrade. The corresponding vertical compressive strains obeyed a normal distribution with a mean value of 7.64 με. The new setting method worked well for backcalculating the layer moduli of the pavement structure.

Investigation of Live Load Deflection Limit for Steel Cable Stayed and Suspension Bridges

Long span bridges such as steel cable stayed and suspension bridges are usually more flexible than short to medium span bridges and expected to have large deformations. Deflections due to live load for long span bridges are important since it controls the overall heights of the bridge for securing the clearance under the bridge and serviceability for securing the comfort of passengers or pedestrians. In case of sea-crossing bridges, the clearance of bridges is determined considering the height of the ship master from the surface of the water, the trim of the ship, the psychological free space, the tide height, and live load deflection. In the design of bridges, live load deflection is limited to a certain value to minimize the vibrations. However, there are not much studies that consider the live load deflection and its effects for long span bridges. The purpose of this study is to investigate the suitability of live load deflection limit and its actual effects on serviceability of bridges for steel cable-stayed and suspension bridges. Analytical study is performed to calculate the natural frequencies and deflections by design live load. Results are compared with various design limits and related studies by Barker et al. (2011) and Saadeghvaziri et al. (2012). Two long span bridges are selected for the case study, Yi Sun-Sin grand bridge (suspension bridge, main span length = 1545 m) and Young-Hung grand bridge (cable stayed bridge, main span length = 240 m). Long-term measured deflection data by GNSS system are collected from Yi Sun-Sin grand bridge and compared with the theoretical values. Probability of exceedance against various deflection limits are calculated from probability distribution of 10-min maximum deflection. The results of the study on the limitation of live load deflection are expected to be useful reference for the design, the proper planning and deflection review of the long span bridges around the world.

Modification Research of Pavement Deflection Representative Value Formula Based on Wavelet Transform

Because the measured deflection of expressway asphalt pavement does not obey the normal distribution, the calculation formula of deflection representative value can’t be used. In order to solve it, in the premise of keeping original characteristics of the measured deflection data, by using the two times standard deviation method, the specific data of the original measured deflection data were eliminated and then furthermore the noise of the deflection data was managed through wavelet transform. The normal distribution ratio of the measured deflection data of asphalt pavement were increased from 20.0% to 86.7%, the requirement of the original formula of deflection representative value was meet, so according to the method, the original formula of the deflection representative value can be modified. Engineering Practice shows that the revised deflection representative value calculation formula that was applied to evaluate the pavement structural strength was suitable. Its evaluation result can reflect the actual technical condition of roads.

Study on the Test System of Yunluo Long-life Asphalt Experimental Road

In order to grasp the mechanical response of the asphalt concrete pavement structure, on the basis of the layer theory of the asphalt pavement structure and the measurement system, the measured data post-processing application of the asphalt pavement structure was developed. Based on the Yunluo expressway experimental section of Guangdong Province, according to the calculation theory of road structure, the finite element analysis model of the pavement structure was established, and the mechanical properties of the asphalt pavement structure of the experimental section were analysed. It was determined that the layout scheme of the asphalt pavement corresponding structure layer temperature and strain sensor and the road test plan based on FWD. By using FWD as the loading tool, the resistance strain sensor were used to dynamically monitor the transverse and longitudinal strains of the road structural layers in order to grasp the dynamic response of the asphalt pavement. By using the FWD's own deflection detection system, the measured deflection data of the pavement structure were obtained. At the same time, taking into account the processing difficulties of mass measurement data, the postprocessing application of the measured data was developed. The results show that according to the theoretical analysis, the measured system was reasonable, the layout scheme and the test plan were proper. The measured data postprocessing applications can offer a better analysis platform for analysts.

Static and Dynamic Backcalculation Analyses of an Inverted Pavement Structure

A crucial part of any maintenance strategy is an intricate understanding of the material characteristics of the pavement, so that the current level of damage may be accurately assessed and an appropriate plan implemented. Advances in the precision to which these parameters can be determined, as well as improvements in how these results are interpreted under varying conditions of measurement and analysis, are essential in the effective execution of a maintenance strategy. Results from Falling Weight Deflectometer (FWD), which is a Non-Destructive Testing (NDT) device, can be used to predict elastic modulus of any layer by comparing measured deflection data to calculated values through an iterative process referred to as back-calculation. This paper presents a comparison between static and dynamic back-calculation procedures, specifically with regard to typical South African inverted pavements. The analysis indicates a dynamic analysis provides results of greater accuracy than a static analysis, although the effect of the difference requires further investigation.

Experimental Testing of a Cross-Entropy Algorithm to Detect Damage

Cross-entropy optimization has recently been applied to the damage detection in structures subject to static loading. The optimization procedure minimizes the error between the measured deflection data and theoretical deflection data obtained from artificially generated finite element models based on assumed statistical distributions of stiffness for each discretized element. Following a number of iterations, the finite element model with stiffness properties producing deflections closer to reality is established as the mathematical model closest to the true structure. However, while previous testing of the algorithm has been relatively successful, it has been limited to theoretical simulations. Therefore, this paper conducts lab experiments on a beam loaded statically to test the accuracy of the algorithm. Deflections are measured for beam scenarios under different loading levels. The accuracy of the results is discussed and recommendations are made to improve the performance of the algorithm when implemented in practice.

Study on the Axle Load Conversion Formula for Asphalt Pavement Based on Actually Measured Deflection Equivalent

Vehicle load is one of the most important factors influencing service performance and service life of pavement. In the pavement design and analysis, different axle loads need be conversed to the standard axle load based on the equivalent deterioration principle of pavement. Pavement surface deflection values under different axle loads have been measured on several expressways in this paper. The correlation relationships between deflection and axle loads are analyzed. The regularity of deflection and axle conversion index based on deflection equivalent are analyzed, too. The axle conversion formula based on deflection equivalent for asphalt pavement is regressed according to the actually measured deflection data. This research achievement can provide us with a reliable axle load conversion method for asphalt pavement design.

Two-Step Indirect Static Deflection Estimation of Bridges Based on Ambient Acceleration Measurements

For the static deflection measurement of a bridge, which is carried out for bridge rating and load-carrying capacity evaluation, sensor inaccessibility due to the fixed reference point can cause significant inconvenience and can increase installation cost and time. Therefore, an alternative indirect static deflection estimation method is proposed utilizing finite element (FE) model updating with measured acceleration data obtained from an ambient vibration test. For fast and stable optimization during model updating, a two-step model updating approach is additionally proposed. To investigate the effects of used modal quantities and their weighting factors, several cases of extensive model updating were carried out by applying several types of data sets: using only natural frequencies, using only mode shapes, and using both of them. By simulating the load test on each of the updated models, deflections were estimated and compared with the real measured deflection data in the load test. It is concluded that the static deflection can be reasonably estimated using updated FE model which is obtained by using the measured ambient acceleration data.

Performance assessment of aerospace sandwich secondary structure panels using thermoelastic stress analysis

Full scale tests carried out on polymer composite sandwich panels, which model the loads experienced by aircraft secondary wing structure, are described. The results from the tests form the basis of a performance assessment of the sandwich construction. The sandwich panel face sheets were manufactured from five different carbon fibre material architectures and were consolidated with epoxy resin using a variety of approaches. In previous work, it was shown that it was possible to significantly reduce the manufacturing costs of producing the sandwich structure by replacing the standard certificated process of unidirectional prepreg cured in an autoclave with a method that used non-crimp fabric infused in a conventional oven. In the present paper, thermoelastic stress analysis (TSA) is used during the full scale tests to obtain stress data from the five different panel types. The TSA data and measured deflection data are used to validate finite element (FE) models of each panel. The experimental validation highlighted some interesting features in the modelling approach. The face sheet materials were treated as homogeneous orthotropic blocks, which resulted in a conservative prediction of deflections. The models did not consider the woven and stitched material face sheet material configurations and therefore, omitted some of the features apparent in the experimental work. However, the validation showed that this did not affect the performance evaluation and most importantly, the validated FE showed that using different face sheet materials had little effect on the stresses in the panels.

Evaluation of Structural Integrity of Asphalt Pavement System from FWD Test Data Considering Modeling Errors

This study examines the structural integrity assessment technique used for the asphalt pavement system that considers the modeling errors introduced by material uncertainties. To this end, the artificial neural network is utilized to estimate the elastic modulus of soil layers by using the measured deflection data from the Falling Weight Deflectometer test. A wave analysis program for a multi-layered pavement system is developed based on the spectral element method for more accurate and faster calculation. The developed program is applied for the numerical simulation of the Falling Weight Deflectometer tests, specifically for the reliability analysis and the generation of training and testing patterns for the neural network. The effects of uncertainties in the material properties for modeling a given pavement system such as Poisson ratio and layer thickness are intensively investigated using the Monte Carlo Simulation. Results reveal that the amplitude of impact loads is most significant, followed by the layer thickness and the Poisson ratio, which are more significant on the max deflections than other parameters. The evaluation capability of the neural network is also investigated when the input data is corrupted by the modeling errors. It is found that the estimation results can be significantly deviated due to the modeling errors. To reduce the effect of the modeling error, (to improve the robustness of the algorithm), we proposed an alternative scheme in order to generate the training patterns taking into consideration any modeling errors. The study then concludes that the estimation results can be improved by using the proposed training patterns from an extensive numerical simulation study.

Interpreting the behavior of laterally loaded drilled shaft from measured deflection data

AbstractThe drilled shafts have been widely used to support lateral loads (active load case) or as a means to stabilize an unstable slope (passive load case) due to their large lateral load resistance and structural capacity for shear and bending moments. However, there is a need to develop an analytical procedure that can use the actual measured deflection data of a drilled shaft subject to either active or passive load case to interpret the soil‐drilled shaft interaction behavior. The mathematical formulation and the accompanied numerical procedure based on the principle of superposition were developed in this paper to allow for deducing the relevant soil‐drilled shaft interaction behavior under the applied lateral load (i.e. net soil reaction force on the drilled shaft, the shear and bending moment in the shaft) from the measured deflection data. Both compatibility and force equilibrium conditions were utilized in formulating the mathematical equations for common single drilled shaft boundary conditions (free head and fixed bottom). The current application is limited to small deformation to meet the requirement that the drilled shaft responds in a linear elastic range. A total of three theoretical cases, along with two actual field cases, were used to demonstrate the validity of the proposed method and its engineering applications. Copyright © 2009 John Wiley & Sons, Ltd.

Finite-Element Modeling of Short-Term Field Response of Composite Wood-Concrete Floors/Decks

A finite-element model (FEM) is developed to predict the load-displacement behavior of a composite wood-concrete floor/deck system under short-term loading. The interlayer connection was modeled with link elements dedicated for connection modeling. Results of past tests of two full-scale layered floor/deck specimens are employed to confirm the FEM model. The specimen had a layer of solid sawn lumber overlaid by concrete and interconnected to it with a pattern of notched shear key/anchor details. The FEM results agreed closely with the measured deflection data for the loadings considered. The efficiency of composite behavior achieved by each of those specimens is quantified by a conventional and three improved approaches based on the computer modeling and measured test results. The new approaches better capture the overall efficiency of the entire floor/deck.

Damage detection of damaged beam by constrained displacement curvature

Structural damage detection technique involves the problem of how to locate and detect damage that occurs in a structure by using the observed changes of its dynamic and static characteristics. The objective of this study is to present an analytical method for damage detection by utilizing displacement curvature and all static deflection data to be expanded from the measured deflection data. Utilizing the measured displacements as displacement constraints to describe a damaged beam, minimizing the change of the displacement vector between undamaged and damaged states, and neglecting the variation between the test data and the analytical results, the deflection shape and displacement curvature of the damaged beam can be estimated, and the damage can be detected by the curvature. The validity and effectiveness of the proposed method are illustrated through comparison with the experimental results of a simple cantilever beam test.

Simulation studies of internal mechanisms in the static deflection of a cellulose electroactive paper actuator

Studies of voltage-induced deflections in electroactive paper (EAPap) have been carried out. On the experimental side, measurements of bias-dependent deflections and strain, water absorption as a function of time, and relative humidity were obtained for the cellulose EAPap actuator. In addition, model simulations have also been carried out to probe and quantify the role of the various internal mechanisms responsible for the deflection. Our simulation predictions yield good agreement with the measured deflection data for the EAPap. The modeling suggests that internal ion content and its migration, water absorption leading to a nonuniform permittivity, random variations in the transverse piezoelectric-coupling coefficient d31,i, and the modulus of elasticity all collectively contribute to the EAPap deflection electrophysics. It also appears that higher sensitivity, with a minimal bias dependence, could be achieved by deliberately adding ions during EAPap processing.

Molecular mechanics modelling and simulation of the adsorption-induced surface stress in micro-nano-cantilever sensors

Micro-nano-cantilevers have the exclusive potential to be an extremely sensitive sensor for chemical and biological detections. The mechanism of the sensor is that the adsorption-induced surface stresses cause the cantilever to bend, which can be measured by electronic or optical methods. In this paper, molecular mechanics method and theoretical energy minimization method are developed to study this bending behaviour. Molecular mechanics simulations were carried out on a homoepitaxy copper nano-cantilever to investigate the dependence of adsorption-induced surface stress on adatom concentration. Noneven pattern of development of adsorption-induced surface stress as adatom concentration increases was observed in the present atomistic simulations. To study the bending of microcantilever induced by adsorption, e.g. mercury adsorption on gold-coated cantilevers, the total energy consisting of atomic interaction energy of elastic bending energy is minimized. The Lennard–Jones model is employed to represent the interaction between mercury and gold atoms. Based on Dareinga's model, we developed a model with more atoms and considered the periodic boundary conditions. Calculated deflections with the proposed new model agree better with measured deflection data. This discussion can contribute to our knowledge base about mechanisms of surface stress and micro-nano-cantilever bio-sensor.

Consideration of Finite Slab Size in Backcalculation Analysis of Jointed Concrete Pavements

The effects of finite slab size and load transfer across joints usually are ignored in the backcalculation analysis of jointed concrete pavements when the test load is applied on an interior point of the slab concerned. Although correction factors have been proposed to take these effects into consideration, the benefits of doing so have yet to be established, and their use has not been accepted in routine backcalculation tests. A study was conducted to assess whether significant improvements in the accuracy of backcalculation analysis could be achieved by considering finite slab size and load transfer at joints in the backcalculation analysis of jointed concrete pavement systems. Five backcalculation methods were evaluated with measured deflection data extracted from the Long-Term Pavement Performance database, and comparisons were made with the measured pavement properties. The analysis based on the measured field data offered affirmative evidence of the theoretical lower- and upper-bound estimates provided by backcalculation solutions based on the infinite slab model and one-slab model, respectively. An error analysis was presented to show that the infinite slab model gave superior solutions as compared with the one-slab model. A nine-slab model that considered finite slab size and joint load transfer effects resulted in only marginal improvements in the backcalculation results. Two finite slab size models that applied correction factors to infinite-slab solutions were found to produce the largest errors among the five backcalculation models studied.