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A beam's Neutral Axis (NA) is a parameter that has been utilized to detect damage. Its position depends on the geometry of the cross-section and also a member's axial loads. Shifts in its position can indicate changes in either load distribution or geometric characteristics. When considering structures such as cable-stayed bridges where the inclined cables induce significant axial forces, the effect of axial loads on NA position is significant. In this research, a simplified analytical model was developed consisting of the key elements of a cable-stayed bridge (beam, cable, and bearing). The model was loaded with a vertical point load representing a vehicle load. The NA position was calculated beneath the load as it moves over the length of the beam. By changing element properties, one can observe how the NA position behaves in different locations of the beam, due to simulated damage in the beam, cable, or bearing. It was found that changes in NA position can capture not only whether damage has occurred, but also in which component of the structure the damage is located (beam, cable, or bearing). This ability to use NA position for damage identification renders it an excellent parameter for monitoring cable-stayed bridges. [ABSTRACT FROM AUTHOR]

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Damage to girders threaten a bridge's safety. They can be effectively detected by the neutral axis (NA) position of a girder. However, the NA position is inevitably affected by the nonlinear temperature gradient of girders, which could mask the damage-induced abnormality. Aiming at the practicality of the NA position, an improved thermal-varying NA model was scientifically derived by accommodating vertically distributed measurements of a nonlinear temperature gradient, followed by several simplified models. By eliminating the effect of the nonlinear temperature gradient on the NA position to the maximum, an abnormality alarming framework was then established for damage detection of girders. Finally, a girder model imposed by an actual nonlinear temperature gradient was developed to validate the advantages of the improved model and the effectiveness of the alarming framework. The proposed models are an improvement over the existing model in terms of prediction accuracy and stability. Additionally, the NA-based alarming method can effectively detect minor damage to the girder subjected to varying nonlinear temperature gradients. The optimal strain measurement is recommended at the lowest turning point of the temperature difference characteristic above the NA position, and the optimal temperature measurement should effectively represent the statistical outline feature of the temperature difference. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation revealing the effects of key design parameters on the behavior of disconnected piled raft (DPR) system. Large-scale model tests are conducted on instrumented foundations by varying the pile spacing, pile length, and the cushion thickness. From the test results, the load capacity improvement (LCI) factor of 3 × 3 DPR is found to increase with increasing pile spacing and length and decreasing cushion thickness. Interestingly, this factor is found to be higher at lower settlement of the raft irrespective of the length and spacing of the piles. The maximum axial load in a pile is found to occur 0.25 m below the pile head due to the generation of negative skin friction in the shallow depth. A significant downward shift of the neutral axis of the pile is observed with increasing cushion thickness resulting a higher difference between the pile head load and maximum axial load. The average load proportions of the piles and the raft in a DPR system are found 31% and 69%, respectively, when the raft settlement reaches 10% of its width. Based on the quantitative impact of these design parameters, recommendations are also provided regarding the design of the DPR system. [ABSTRACT FROM AUTHOR]

To investigate the development mechanism of sectional plastic stress and biaxial bending moments of H-section steel members prior to local buckling subjected to monotonic and cyclic loading, extensive parametric analysis models were established in ABAQUS. These models explicitly accounted for different axial force ratios, plate width-thickness ratios under different loading angles, verifying the applicability against existing experimental data. Based on the results of finite element analysis, the effects of various factors on the development of normal stresses in the cross-section were thoroughly investigated. A semi-empirical semi-theoretical calculation model was established to address biaxial loading in H-section steel members, considering bidirectional displacement, the form of normal stress distribution, and the relationship between the biaxial bending moments. By comparing the model with finite element results, it was observed that the model effectively predicted the progression of biaxial bending moments development subjected to biaxial loading in H-section steel members. This model provides a more convenient design approach for considering the partial plastic development of the cross-section in bidirectional flexural design. [ABSTRACT FROM AUTHOR]

Due to the high cost of laboratory testing, many researchers are considering developing methods to predict the behavior of unreinforced and reinforced wood beams. This work aims to create either numerical or analytical models useful for extrapolating already conducted tests to other schemes/materials used as reinforcement. In the case of timber structures, due to the complexity of timber, this task is difficult. The first part of the article presents an analysis of the suitability of using a simplified mathematical model based on the equivalent cross-section method to describe the behavior of unreinforced and reinforced with carbon-fibre-reinforced polymer (CFRP) composite full-size laminated veneer lumber (LVL) beams. The theoretical results were compared with the results of conducted experimental tests. The scope of the analysis includes the estimation of modulus of rupture, bending stiffness, and determination of the neutral axis position. The equivalent cross-section method showed good agreement in determining the bending stiffness and neutral axis position of the strengthened sections. However, the suitability of using the equivalent cross-section method to estimate the load-carrying capacity of a cross-section reinforced with fiber composites still needs to be confirmed, which, according to the authors, is due to the differences between the assumed (linear) and actual (nonlinear) strain distribution in the compression zone. The second part uses the equivalent cross-section method to estimate the predicted bending stiffness of LVL beams strengthened with aramid-fibre-reinforced polymer (AFRP), glass-fibre-reinforced polymer (GFRP), and ultra-high modulus carbon-fibre-reinforced polymer (CFRP UHM) sheets. The proposed method can be used for preliminary evaluation of strengthening effectiveness of LVL beams. [ABSTRACT FROM AUTHOR]

The traditional objective function (TOF) of bridge model updating is usually defined on the basis of the structural response residuals between numerically calculated and experimentally measured values. However, this model finds it difficult to determine the weighting factors, and the updated model lacks accuracy. To offset these disadvantages, this study proposes a novel objective function (NOF) for finite-element model updating of a long-span cable-stayed bridge using in situ static and dynamic measurements. The proposed NOF comprises the residual functions of the displacement assurance criterion, the position of the neutral axis, and the natural frequency. The global sensitivity analysis–based model updating uses the Kriging model as the surrogate model to save computational costs. The nondominated sorting genetic algorithm II is employed to find the Pareto solutions. The updating results with the TOF defined directly using displacement, stress, and frequency are listed for the purposes of comparison. The results show that the NOF avoids determining the weighting factors and provides more accurate results than the TOF. The updated displacement curves, the position of the neutral axis, and the frequencies obtained from the NOF are all closer to the experimentally measured ones than those obtained from the TOF. After model updating, the displacement's relative errors are around 5% without considering the displacement values under 10 mm. The relative errors of the first four frequencies are all less than 10%. The updated model can serve as the baseline finite-element model of the bridge. [ABSTRACT FROM AUTHOR]

Avian eggs represent a striking evolutionary adaptation for which shell thickness is crucial. An understudied eggshell property includes the neutral axis, a line that is drawn through any bent structure and whose precise location is characterized by the k‐factor. Previous studies have established that, for chicken eggs, mean k corresponds to the golden ratio (Φ = 1.618, or 0.618 in its reciprocal form). We hypothesized whether such an arrangement of the neutral axis conforms to the eggshell of any bird or only to eggshells with a certain set of geometric parameters. Implementing a suite of innovative methodological approaches, we investigated variations in k of 435 avian species, exploring which correspond to Φ. We found that mean k is highly variable among birds and does not always conform to Φ, being much lower in spherical and ellipsoid eggs and higher in pyriform eggs. While 21 species had k values within 0.618 ± 0.02 (including four falcon species) and the Falconinae subfamily (six species) revealed a mean of 0.618, it is predominantly domesticated species (chicken, ducks, and geese) that lay eggs whose neutral axis corresponds to the golden ratio. Thus, the study of the mathematical secrets of the eggshell related to the golden ratio of its neutral axis suggests its species‐specific signatures in birds. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of modulus of the base layer on the strain distribution for asphalt pavement, the modulus ratio of the base layer and the AC layer (Rm) is introduced as a controlled variable when keeping modulus of the AC layer as a constant in this paper. Then, a three-layered pavement structure is selected as an analytical model, which consists of an AC layer with the constant modulus and a base layer with the variable modulus covering the subgrade. A three dimensional (3D) finite element model was established to estimate the strains along the horizontal and vertical direction in the AC layer under different Rm. The results show that Rm will change the distribution of the horizontal strains along the depth in the AC layer; the increase of Rm could reduce the maximum tensile strain in the AC layer, but its effect is limited; the maximum tensile strain in the AC layer does not necessarily occur at the bottom, but gradually rises to the middle with the increase of Rm. Rm could significantly decline the bottom strain in the AC layer, and there is a certain difference between the bottom and the maximum strain when Rm is greater than or equal to one, which will enlarge with increasing Rm. Rm could change the depth of the neutral axis in the AC layer, and the second neutral axis will appear at the bottom of the AC layer under a sufficiently large Rm. The average vertical compressive strain in the AC layer will significantly enlarge with the increase of Rm.

A novel subdiscipline of bionics is emerging in the form of ‘egg-inspired engineering’ through the use of egg-shaped ovoids as thin-walled tanks and building structures. Hügelschäffer’s and Narushin’s models of egg geometry are highly applicable within this proposed subdiscipline. Here we conducted a comparative analysis between the two models with respect to some of the most important egg parameters. These included contents volume, shell volume, and the location of the neutral axis along the shell thickness. As a first step, theoretical studies using the Narushin’s model were carried out due to the lack (or limited amount) of data on the geometric relationships of parameters and available calculation formulae. Considering experimental data accumulated in the engineering and construction industries, we postulate a hypothesis that there is a correlation between location of the neutral axis and the strength of the walls in the egg-shaped structure. We suggest that the use of Narushin’s model is preferable to Hügelschäffer’s model for designing thin-walled shelled vessels and egg-shaped building structures. This is due to its relative simplicity (because of the requirement for only two initial parameters in the basic equation), optimal geometry in terms of material costs per unit of internal capacity, and effective prerequisites for shell strength characteristics.

The loads in the deep beams are transmitted diagonally from the load area to the support area by means of the strut and the tie. It is characterized by having a small span to depth ratio. which causes the distribution of stresses to be non-linear within the beam, which motivates researchers to study the effect of the placing of longitudinal hollows and the extent to which these holes affect the behavior and distribution of stresses for these types of beams. In addition to the advantages added by longitudinal hollow to the beam such as reducing weight and passing various electrical and mechanical services...etc. This study investigated the effect of making longitudinal circular holes (with a diameter of 50mm) with a slope on the structural behavior of three deep beams with a solid sample as a reference where the slope used was 0%, 4.3%, and 7.8%. The results showed that making holes reduces the load capacity of the deep beam, a decrease in the failure load was observed by 7.56%, 8.96%, and 11.2% for hollow beams with a slope of 0%, 4.3%, and 7.8%, respectively. Also, the appearance of flexural cracking increased by 2.66%, 2.66%, and 6.66%.and 2.14%, 3.52%, and 7.14%, respectively, for shear cracks. While the effect was small for the neutral axis location as well as for the vertical deflection.

A surface nanocrystalline was fabricated by ultrasonic shot peening (USSP) treatment at AZ31 Mg alloy. The effect of nanocrystalline thickness and its placed side (external or internal) on the bendability was studied by a V-bending test. Three durations, 5, 10, and 15 min, were applied to form the surface nanocrystalline with thicknesses of 51, 79, and 145 µm, respectively. Two-side treatment led to a similar bendability as that of as-received. One-side internal treatment for 5 min resulted in an improved bendability while the improvement was limited and degenerated for longer treatment. The improvement was related to the drawing back of the neutral axis. The one-side external treatment also improved the bendability, and the improvement was due to the redistribution of strain and stress during bending. With nanocrystalline at external side, it resulted in a larger stress but a smaller strain at the convex, which prevented the happening of crack during bending. [ABSTRACT FROM AUTHOR]

Ultimate strength is an important design consideration for the safety of intact or damaged ship structures. The simplified progressive collapse method is a commonly used iterative method to obtain the accurate ultimate strength of ships. Since the accuracy of the neutral axis position directly affects the accuracy of the ultimate strength, the force equilibrium criterion and the force vector equilibrium criterion are adopted to search for the height and angle of the neutral axis, especially for damaged ships. However, the search for the neutral axis position based on the two criteria requires iterative computation which decreases the calculation efficiency. In this paper, the relationship between the results of the iterative process and the neutral axis position is studied, and it is found that the relationship is approximately linear. Then a new iterative method based on the linear equation is proposed to obtain the neutral axis position and is adopted to improve the simplified progressive collapse method. Finally, the new method is used to calculate the neutral axis position of a damaged VLCC. The comparison of the ultimate strength results shows that the improved simplified progressive collapse method based on the linear equation has improved efficiency and good accuracy. • It is found that the results of the equilibrium criterion vary approximately linearly for small movements of neutral axis. • An improved method based on the derived linear equation is proposed for the search of the location of neutral axis. • Comparison of the proposed method with existing methods shows that it is accurate and more computationally efficient. [ABSTRACT FROM AUTHOR]

Due to the high cost of laboratory testing, many researchers are considering developing methods to predict the behavior of unreinforced and reinforced wood beams. This work aims to create either numerical or analytical models useful for extrapolating already conducted tests to other schemes/materials used as reinforcement. In the case of timber structures, due to the complexity of timber, this task is difficult. The first part of the article presents an analysis of the suitability of using a simplified mathematical model based on the equivalent cross-section method to describe the behavior of unreinforced and reinforced with carbon-fibre-reinforced polymer (CFRP) composite full-size laminated veneer lumber (LVL) beams. The theoretical results were compared with the results of conducted experimental tests. The scope of the analysis includes the estimation of modulus of rupture, bending stiffness, and determination of the neutral axis position. The equivalent cross-section method showed good agreement in determining the bending stiffness and neutral axis position of the strengthened sections. However, the suitability of using the equivalent cross-section method to estimate the load-carrying capacity of a cross-section reinforced with fiber composites still needs to be confirmed, which, according to the authors, is due to the differences between the assumed (linear) and actual (nonlinear) strain distribution in the compression zone. The second part uses the equivalent cross-section method to estimate the predicted bending stiffness of LVL beams strengthened with aramid-fibre-reinforced polymer (AFRP), glass-fibre-reinforced polymer (GFRP), and ultra-high modulus carbon-fibre-reinforced polymer (CFRP UHM) sheets. The proposed method can be used for preliminary evaluation of strengthening effectiveness of LVL beams.

Conocer el comportamiento real de una estructura de hormigón armado es difícil. debido a los múltiples factores que influyen en el mismo. La heterogeneidad del hormigón y la evolución de sus características mecánicas y físicas a lo largo de la vida útil del material, hace que podamos obtener valores aproximados de su comportamiento. El objetivo de este trabajo de investigación es evaluar de una manera más precisa este comportamiento, mediante la inclusión en las estructuras de sensores de fibra óptica. Estos sensores nos proporcionan valores precisos de deformación en tiempo real, durante toda la vida de la estructura. Para obtener estos resultados, se han embebido los sensores en una viga de hormigón armado y se ha analizado realmente lo que le ocurre cuando la solicitamos a diferentes escalones de carga. Los resultados obtenidos los hemos comparado con los teóricos obtenidos del cálculo de resistencia de materiales, llegando a la conclusión de que, en efecto, las estructuras de hormigón armado son elementos complejos, pero que, con este sistema de monitorización, podremos obtener resultados más precisos de su comportamiento. Abstract Knowing the real behavior of a reinforced concrete structure is a difficult task due to the multiple factors that influence it. The heterogeneity of the work and the evolution of its mechanical and physical characteristics throughout the useful life of the material, makes it possible to obtain approximate values of its behaviour. The objective of this research work is to evaluate this behavior in a more precise way, through the inclusion of fiber optic sensor structures. These sensors provide us with precise values of deformation in real time, throughout the life of the structure. I have embedded the sensors in a reinforced concrete beam and I have really analyzed what happens when we request it at different load stages. The obtained results have been compared with the theoretical ones obtained from the calculation of resistance of materials, arriving at the conclusion that, in fact, reinforced concrete structures are complex elements, but that, with this monitoring system, we can obtain more precise results of his behavior

The intersection of neutral layer and the transverse section is called neutral axis. The position of neutral-axis will be changed when the corresponding beam structure is damaged. In this work, the static loading test of recycled concrete beam is carried out to verify the damage detection method based on neutral axis position. Experimental results show that structural damage can be detected by the change of the neutral-axis position.

Structural Health Monitoring (SHM) has enabled the condition of large structures, like bridges, to be evaluated in real time. In order to monitor behavioral changes, it is essential to identify parameters of the structure that are sensitive enough to capture damage as it develops while being stable enough during ambient behavior of the structure. Research has shown that monitoring the neutral axis (N.A.) position satisfies the first criterion of sensitivity; however, monitoring N.A. location is challenging because its position is affected by the loads applied to the structure. The motivation behind this research comes from the greater than expected impact of various load characteristics on observed N.A. location. This paper develops an indirect way to estimate the characteristics of vehicular loads (magnitude and lateral position of the load) and uses a data mining approach to predict the expected location of the N.A. Instead of monitoring the behavior of the N.A., in the proposed method the residuals between the monitored and predicted N.A. location are monitored. Using actual SHM data collected from a cable-stayed bridge, over a 2-year period, the paper presents the steps to be followed for creating a data mining model to predict N.A. location, the use of monthly sample residuals of N.A. to capture behavioral changes, the ability of the method to distinguish between changes in the load characteristics from behavioral changes of the structure (e.g. change in response due to cracking, bearings becoming frozen, cables losing tension, etc.), and the high sensitivity of the method that allows capturing of minor changes.

In this study, a polynomial higher-order shear deformation theory is introduced and developed for static analysis of functionally graded material (FGM) beams. The presented theory has strong similarities with Timoshenko beam theory in some aspects, such as equations of motion, boundary conditions and stress expressions. The developed theory does not require shear correction factor and satisfies the stress-free boundary conditions, such that the transverse shear stress varies parabolically through the beam thickness. The mechanical properties of the FGM beam are assumed to vary continuously in the thickness direction based on power-law distribution in terms of the volume fractions of the constituents. The influences of material distribution, boundary conditions, aspect ratio and neutral axis on the mid-plane deflection, normal stress and shear stress are figured out. The results obtained are compared with the data available in the literature to verify the correctness and the accuracy of the developed theory. The presented theory can provide a reference which other researchers can use for their studies. [ABSTRACT FROM AUTHOR]

Due to unphysical coupling induced by the material inhomogeneity, FG (functionally graded) nanobeam problems were formulated in a very complex way so that they cannot be analytically solved. In this paper, an uncoupled theory is proposed for FG nanobeams considering their small size effects. First, with the aid of the neutral axis, the axial displacement is expressed in terms of generalized displacements for FG nanobeams. Based on the nonlocal strain gradient theory, the generalized stresses and strains are accordingly defined and uncoupled constitutive relations are derived. Based on the principle of virtual work, an uncoupled theory is eventually established, including governing equations and boundary conditions. Within the present framework, analytical solutions to FG nanobeams are obtained for the first time for general boundary conditions. These solutions not only re-evaluate the previous results but shed light on the small size effects of FG nanobeams. [ABSTRACT FROM AUTHOR]

The results of an extensive experimental program into the location of the neutral axis in cracked fiber‐reinforced concrete (FRC) are reported. In total, 74 prisms are tested in a monotonic (51 specimens) and cyclic (23 specimens) bending test in accordance with EN 14651. In the program, 13 different FRCs are considered with 9 different fiber types and dosages. A normal strength concrete with residual strength values between 1b and 2d, cf. Model Code 2010 (MC10), is considered. The deformation profile in the cracked section is measured by side‐mounted linear variable displacement transducers on the prisms, and the position of the neutral axis is calculated. The experimental results are compared against predictions of the MC10. Based on a simplified stress diagram, the MC10 predicts that the location of the neutral axis depends on the residual strength of the FRC at the serviceability limit state: increasing the strength results in a larger compressive zone and vice versa. However, the results obtained within this study do not confirm this relation. The cyclic results indicate that the neutral axis shifts upward during unloading and subsequent reloading decreases the neutral axis again to preunloading levels. Finally, for all reported FRC types, the neutral axis lies very high in the cracked section, even at very small crack mouth opening displacement values. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to evaluate the ductility of reinforced concrete beams longitudinally reinforced with hybrid Fiber Reinforced Polymer (FRP)–steel bars. The specimens were fourteen reinforced concrete beams with and without hybrid reinforcement. The test variables were bar positions, ratio of longitudinal reinforcement, and type of FRP. The beams were loaded until failure using a four-point bending test. The performance of the tested beams was observed using the load–deflection curve obtained from the test. Numerical analysis using the fiber element model was carried out to examine the growth of neutral axis due to the effects of the test variables. The neutral axis curves were then used to estimate the neutral axis angles and displacement indices. The test results showed that the reinforcement position did not significantly affect the flexural capacity of beams with a higher ratio of hybrid reinforcement, but was quite significant in beams with a lower ratio of hybrid reinforcement. It was observed from the test that the flexural capacity of beams with hybrid reinforcement was 15–45% higher than that of beams with conventional steel bars, depending on bar positions and the ratio of longitudinal reinforcement. The ductility of beams with hybrid reinforcement was significantly increased compared to that of beams with FRP, but decreased as the hybrid reinforcement ratio (Af/As) increased. This study also showed that the developed numerical model could predict the flexural behavior of beams with hybrid reinforcement with reasonable accuracy. Based on the test results, parametric analysis, and data obtained from the literature, the use of the neutral axis angle and displacement index value to evaluate the ductility of cross-sections with hybrid reinforcement is proposed.

The fatigue damage behavior of bone has attracted significant attention in both the mechanical and orthopedic fields. However, due to the complex and hierarchical structure of bone, describing the damage process quantitively or qualitatively is still a significant challenge for researchers in this area. In this study, a nonlinear bi-modulus gradient model was proposed to quantify the neutral axis skewing under fatigue load in a four-point bending test. The digital image correlation technique was used to analyze the tensile and compressive strains during the fatigue process. The results showed that the compressive strain demonstrated an obvious two-stage ascending behavior, whereas the tensile strain revealed a slow upward progression during the fatigue process. Subsequently, a theoretical model was proposed to describe the degradation process of the elastic modulus and the movement of the neutral axis. The changes in the bone properties were determined using the FEM method based on the newly developed model. The results obtained from two different methods exhibited a good degree of consistency. The results obtained in this study are of help in terms of effectively exploring the damage evolution of the bone materials.

Composite action between steel girders and concrete slab is an important mechanical feature that needs to be maintained so that bridges can carry the applied load safely. This mechanical feature is maintained through the shear studs installed at the top flange of the steel girders. These shear studs keep the steel girders and the concrete slab working as one unit, resulting in a stronger section than if each element works separately. The composite action can be investigated using several methods of which one is the study of the position of the neutral axis (NA). The variation of the position of the NA over time gives an indication about the structural performance of the composite section. In this study, the variation of the position of the NA over time is investigated. Two bridges located in Manitoba were investigated in this study. The variation of the NA is observed as a result of variation of ambient temperature (temperature). Regression models are suggested to relate variation of the NA to the temperature that was measured beside the web of one of the bridge girders. Repeatability analysis over 4 years was conducted, confirming that the NA varies cyclically over years. It is suggested that this variation indicates that there is a change in the degree of composite action assuming that cold temperatures will induce more connection between the steel girders and the concrete slab as a result of thermal contraction of the shear studs. In addition, the stiffness of the material could be affected due to change of temperature. The other possibility is that an axial force develops in the beam as a result of the bearing restraint during the passing of vehicles on the bridge. The results found in this study will eventually lead to enhancements of the design procedures that currently assume a fixed position of the NA over time of composite sections of bridges, similar to the bridges presented in this study. [ABSTRACT FROM AUTHOR]

Recently, the problem faced by the construction industry is a significant shortage of raw materials of concrete. Thus, the main idea of this research is to replace the use of concrete at the middle area of neutral axis of beam with voided system by incorporating PVC pipe. This research aims to reduce the concrete usage; structure's self-weight without neglecting its strength performance. The experimental work consists of casting and testing the 1200 x 160 x 160 mm beams with (Ø40 mm, Ø50 mm, and Ø100 mm) and without void at the neutral axis. The test results indicated that the strength performance of all RC beams with voided section is stronger than the ordinary RC beam where the V50 RC beam is able to withstand loads up to 38.25 kN and has a strength increment of 49.2% compared to the ordinary RC beam. By this material optimization, the reduction of concrete usage and self-weight of the V100 RC beam recorded a reduction of up to 35.14% but in terms of its strength is relatively low compared to the V40 RC beam and V50 RC beam. This findings show a positive result in reducing the dead load without affecting the strength of the structure. Besides aiming to the reduction of concrete usage and structure's self-weight, the idea of this research could be used and implemented in producing a lightweight structure with easy handling and installing, and at the same time focusing to meet the IBS system. [ABSTRACT FROM AUTHOR]

Bending is a conventional manufacturing process of sheet forming. This process induces reasonable residual stress through the thickness. Prediction of this residual stress profile is more difficult in bilayer sheet bending due to different material properties and thickness of layers. In this article, the residual stress distribution will be derived analytically for a bilayer sheet. The induced stress profile due to loading and released stress after unloading has been derived by integration along with the thickness. Also, the neutral axis movement due to non-uniform plastic deformation has been involved in the solution. The stress distribution has been derived analytically for elastic–perfect plastic, elastic–linear plastic and elastic–power law hardening material behavior. The results obtained from the proposed equation are compared by a finite element analysis. The finite element analysis contains bending a bilayer sheet to a specified curvature radius by a three-roll bending process. Comparing the results of the analytical solution and finite element analysis shows good agreement. The location of the neutral axis and the maximum of residual stresses in the thickness have been predicted very well with the proposed equation. [ABSTRACT FROM AUTHOR]

In conventional RC beam, the transition from compression to tension zone of the beam when load applied producing ineffective region at the middle area of the neutral axis. This is because, the area experiencing less compression and tension compare to the region above and below the neutral axis. Thus, the purpose of this research is to replace the use of concrete at the middle of the neutral axis by incorporating 4 PVC pipes to reduce cost and the self-weight of the structure. 4 pipes with a diameter of 20mm, 25mm and 50mm will be combined together to form a continuous voided square beam of V40, V50 and V100. The size of RC beam specimens is 1200mm x 160mm x 160mm, these beams were test with 3-point load test to identify the flexural strength. From the test, the ordinary beam recorded lowest maximum load, which is 15,35kN and VRB 100mm is the strongest beam with the maximum load 33.75kN and has the highest strength increment compared to another voided rectangular beam. Besides that, VRB 100mm also can reduced until 42.69% self-weight of RC beam and reduce until 37.5% of the concrete usage. From this study, it shows that the Voided Square Beam can reduce the self-weight of beam and reduce the concrete usage. Besides that, this idea also can implement to produce the lightweight structure that meet the standard of Industrialized Building System (IBS). [ABSTRACT FROM AUTHOR]

This paper uses long-term bridge monitoring data to quantitatively assess the composite action exhibited in slab-on-girder highway bridges and investigates the potential relationship between composite action and deck deterioration over negative bending regions. A three-span highway bridge in Michigan is instrumented with a structural monitoring system to observe the flexural response of the spans to vehicular loads. The monitoring system is designed to offer data for quantitative assessment of the degree of composite action in composite and noncomposite sections of the bridge spans using the position of neutral axis and the magnitude of slip strain as key response parameters correlated to composite action. It is shown that unintended nonlinear partial composite action exists in negative bending regions of the bridge. A calibrated analytical model and a finite-element model are developed based on empirical observation allowing tensile strains in the deck to be estimated under load. Estimated surface strains are compared with those with the design assumption of no composite action at the slab–girder interface. It is concluded that the observed partial composite action results in higher tensile strains in the deck which is a likely culprit to accelerated deck deterioration. [ABSTRACT FROM AUTHOR]

Carbon Fiber Reinforced polymer (CFRP) bars are weak in yielding property which results in sudden failure of structure at failure load. Inclusion of non-pretensioned steel reinforcement in the tension side of CFRP based prestressed concrete beam will balance the yielding requirements of member and it will show the definite crack failure pattern before failure. Experimental investigation has been carried out to study the deflection behavior of partially prestressed beam. Experimental works includes four beam specimens stressed by varying degree of prestressing. The Partial Prestressing Ratio (PPR) of specimen is considered for experimental works in the range of 0.6 to 0.8. A new deflection model is recommended in the present study considering the strain contribution of CFRP bar and steel reinforcement for the fully bonded member. New deflection model converges to experimental results with the error of less than 5% .

The continual increase of truck weights on our transportation system is a growing concern among bridge engineers. The load carrying capacity of the structures within the system must withstand this ever-growing demand. For multi-girder steel bridges, the load carrying capacity is heavily influenced by the presence of composite action between the girders and the concrete deck slab. While detailing to ensure reliable composite action is typically included in new designs, for many existing structures, the owner may not fully know the level of composite action. This may be due to administrative issues like insufficient original construction drawings or mechanical issues like breakdown of the shear transfer components. Even in situations where composite action was not intended there exists some partial interaction due to chemical bond and friction. Clearly understanding the presence and reliability of composite action in multi-girder structures is key to managing these structures effectively. This paper explores how load testing has been utilized to identify the level of composite action for existing bridges. The challenges associated with field identification of composite action are presented. In addition, three case studies of truck load testing are discussed. The first case utilized uncontrolled ambient truck measurements of an instrumented structure to field determine the composite behavior. The second and third cases perform a controlled load test with variations in truck weights and positions. Overall, the paper illustrates the advantages and disadvantages of truck load testing for identification of composite action and provides recommendations for future studies.