Bending Moment Load Research Articles

Probability density functions of the DoB in tubular KT-joints of jacket-type platforms under out-of-plane bending loads

The degree of bending (DoB) has a profound effect on the fatigue behavior of tubular joints commonly found in offshore jacket structures. Probability density functions (PDFs) of the involved random variables are necessary for the fatigue reliability analysis of jacket structures. The objective of present research was the derivation of PDF for the DoB in tubular KT-joints commonly found in jacket-type platforms. A total of 243 finite element (FE) analyses were carried out on 81 FE models of KT-joints subjected to three types of out-of-plane bending (OPB) moment loading. Generated FE models were validated using experimental data, previous FE results, and available parametric equations. Based on the results of parametric FE study, a sample database was prepared for the DoB values. Thirteen theoretical PDFs were fitted to the developed histograms and the maximum likelihood (ML) method was applied to evaluate the parameters of fitted PDFs. In each case, the Kolmogorov-Smirnov test was used to evaluate the goodness of fit. After substituting the values of estimated parameters, six fully defined PDFs were presented for the DoB at the saddle positions of the central and outer braces in tubular KT-joints subjected to three types of OPB moment loading.

Analytical investigation on the development of adaptive infilled gabled frames

Reinforced concrete infilled frame with brick masonry panel is becoming more common in recent days. Now a days this type structural frame is implemented mostly on the high-rise building because those buildings should be able to resist the lateral loads such as wind and seismic force hence, infilled frames are one of the most common lateral loads resisting system. In this study, two-dimensional single-bay, single-storey gabled infilled specimens were analyzed under static loading. The behavior of the reinforced concrete (RC) bare frame, RC infill frame with cement mortar interface is used and analyzed. In particular, the paper discusses the lateral stiffness of the frames and gives a comparative study between gabled frame and rectangular frame under static lateral load with varying parameters based on the obtained results such as displacement, lateral stiffness, bending moment and lateral load are carried out.

Behavior of NSM CFRP reinforced concrete columns: Experimental and analytical work

This paper presents the results of experimental testing on fifteen reinforced concrete (RC) columns repaired or strengthened using Near Surface Mounted-Carbon Fiber Reinforced Polymer (NSM-CFRP) under concentric load, eccentric load with 125 mm eccentricity (balanced state), and pure bending moment load, while considering the effect of several configurations on the interaction diagram. Furthermore, this paper investigates the efficiency of these new configurations in the capacity of the RC columns by varying the direction of CFRP strips to be used as reinforcement. The specimens of RC columns, having cross-sectional dimensions 1200 mm × 200 mm × 200 mm (length × width × height) with 150 mm corbel at both ends (in the plane of bending moment) and 1.13 % steel reinforcement ratio, were used. The specimens were divided into five groups: control group, preloaded until 80 % transversely strengthened group, preloaded until 80 % longitudinally strengthened group, preloaded until 80 % transversely and longitudinally strengthened group, and un-loaded transversely and longitudinally strengthened group. Each group included three specimens with a different type of loading as described above. The overall response of the specimens was investigated in terms of axial load carrying capacity, axial displacement, toughness, and failure modes. Furthermore, the interaction diagram for each group was developed and investigated. The strengthened and retrofitted specimens showed a significant increase in axial capacity and significant enhancement in the interaction diagram for all groups. The study showed that the most improvement in the interaction diagram, for both tension and compression control region, occurred when specimens were strengthened in both directions (transversely and longitudinally). In addition, the interaction diagrams were modified to provide a direct solution for the NSM-CFRP ratio. The modified design model was found to be capable of predicting the axial load capacity of NSM-CFRP strips columns.

Cyclic behavior of wood-frame shear walls with vertical load and bending moment for mid-rise timber buildings

In light wood-frame buildings, the gravitational and lateral force-resisting systems are composed of floor diaphragms and shear walls. During an earthquake, these walls are subjected to the simultaneous action of in-plane vertical force, shear force, and in-plane bending moment. In a mid-rise building, these internal forces can reach large magnitudes, especially on the lower stories, and could have an important influence on the lateral behavior of the walls. The historical use of light wood-frame construction has been in low-rise buildings. Consequently, few investigations have analyzed the effects of high gravitational forces or in-plane bending moment on the lateral behavior of wood shear walls designed for multi-story buildings. This paper presents an investigation of the cyclic lateral behavior of light wood-frame shear walls, designed for mid-rise buildings, subjected to large axial compressive load and in-plane bending moment. Eight wall specimens were experimentally tested with a cyclic lateral displacement protocol, a constant compressive load, and a cyclic in-plane bending moment. The effects of axial compressive load and in-plane bending moment were analyzed. Also, the wall length and the spacing of sheathing nails were varied to study the effects of these variables on the response. A numerical study was performed to show how these effects could influence the response of mid-rise timber buildings. An improvement in the lateral performance of the walls was observed compared to walls tested without compressive force nor bending moment, showing an increase in stiffness, load-carrying capacity, and dissipated energy.

Data for Interaction Diagrams of Geopolymer FRC Slender Columns with Double-Layer GFRP and Steel Reinforcement

This article provides data of axial load-bending moment capacities of plain and fiber-reinforced geopolymer concrete (GPC, FRGPC) columns. The columns were reinforced by double layers of longitudinal and transverse reinforcement using steel and/or glass-fiber-reinforced polymer (GFRP) bars. The concrete fiber-reinforcing materials included steel and synthetic fibers. The columns data included different parameters like the longitudinal reinforcement ratio, the applied load eccentricity, and the columns’ slenderness ratio. The data was collected from different analysis output files then sorted and tabulated in usable formatted tables. The data can support the development of design axial load-bending moment interactions. In addition, further processing of the data can yield analytical strength curves which are useful in determining the columns stability under different structural loading configurations. Researchers and educators can make use of these data for illustrations and prospective new research suggestions.

Study on Bending Performance of Epoxy Adhesive Prefabricated UHPC-Steel Composite Bridge Deck

UHPC has high strength, high toughness, and excellent durability. For orthotropic steel bridge deck pavement, UHPC can significantly increase the bridge deck’s stiffness and then solve the problems of fatigue cracking and pavement damage of the bridge deck. However, if UHPC adopts cast-in-place construction, its self-shrinkage can easily cause shrinkage cracks, and it requires high maintenance conditions. Meanwhile, the traditional stud connection will bring a great deal of welding work and cause welding fatigue. In contrast, prefabricated UHPC pavement and orthotropic steel bridge deck can greatly reduce the amount of welding of studs on the bridge deck through epoxy bonding, thus speeding up the construction process and avoiding the risk of cracking caused by UHPC self-shrinkage. In order to consider the influence of the surface state of interface and ratio of shear span to depth on flexural behavior of epoxy adhesive prefabricated UHPC-steel composite bridge deck, positive bending moment loading test with different ratios of shear span to depth was carried out, and the failure mode, load-deflection curve, interface slip, and strain distribution of the specimens were obtained. Finally, based on the cohesive interface element, the prefabricated UHPC-steel epoxy bonding interface was successfully simulated. The test results show that each specimen’s loading stage can be divided into the elastic stage, crack initiation stage, interfacial crack propagation stage, interface failure stage, and yield stage. The specimen’s ultimate failure is that the interface failure is prior to the yield at the bottom of the steel plate. During the loading process, the bending performance shows that the ultimate load P B i and growth deflection Δ δ B i C i of CD-ERA-P-λ4.44 are higher than those of other specimens in terms of the load-deflection curve. The ultimate load of CD-ERA-P-λ3.33 is lower than that of CD-ERG-P-λ3.33, which decreases by 4.6%, but the increasing deflection increases by 75%. Simultaneously, the interface slip of the specimen is similar, which further shows that the specimen has the best bending performance when the surface of the steel plate is rough (R) and the surface of the prefabricated UHPC plate is grooved (A). No matter what kind of surface is used at the interface, the reduction of the ratio of shear span to depth will aggravate the ultimate failure of the interface and the cracking of the precast UHPC slab. Finally, the bending performance of epoxy adhesive prefabricated UHPC-steel composite bridge deck is successfully simulated based on the cohesive interface element, which is verified by the test results.

Design and verification of the loading system and boundary conditions for wind turbine foundation model experiment

Previous studies show that the wind turbine foundation is subjected to the coupling effect of torque-vertical load-horizontal load-bending moment load (i.e., T-V-H-M). In a large-scale model experiment of wind turbine foundation, the existing methods cannot accurately simulate the complex loads, counterweights, or foundation boundary conditions. In this paper, a novel method for simulating the loads and boundary conditions of wind turbine foundation model experiments was introduced, and a series of related confirmatory research was conducted, showing that the proposed multi-point composite loading system can resolve the problem of increasing shear force caused by the conventional single-point bending moment control loading method. Meanwhile, it can satisfy the load matching requirements of T-V-H-M loads under ordinary laboratory conditions. The regional counterweight system provided a simulation method for the weight of the foundation and overburdens soil under the gravity field, which can accurately restore the distribution of the foundation resistance. The stiffness of ground soil had a significant impact on the force characteristics of the foundation structure. It is concluded that the proposed method can achieve an excellent accuracy at a reasonable computational expense.

Validation of the dynamic load characteristics on a Tidal Stream Turbine when subjected to wave and current interaction

A comparison of a tidal turbine's performance and structural loads is conducted using lab-scale numerical models and experimental testing under multiple current-only and wave-current conditions at the IFREMER wave-current flume. Experimental testing, used to validate CFD models, was accomplished using a 0.9 m diameter, 3-bladed tidal turbine and had a blockage ratio of 8% while the turbine was submerged. Initial investigations analysed the performance and loads on the turbine under uniform and profiled current-only conditions. The presence of a profiled velocity gradient was found to have a negligible effect on the average performance characteristics; however, transient thrust, torque and out of plane bending moment loads experienced much greater variations. These load fluctuations were further increased with increasing levels of shear in the velocity profile, while peaks in the turbine loads coincided with its rotational frequency. The addition of regular, Stokes 2nd Order Theory waves added to the complexity of the flow conditions experienced by the turbine. The effect on the average performance characteristics were negligible while the total turbine thrust and torque fluctuations increased by 35 times that of the current-only cases. Peaks in the loads aligned with the wave surface elevation, indicating the importance of transient analyses of dynamic loads.

Characterization and nonlinear models of bending extensile/contractile pneumatic artificial muscles

Pneumatic artificial muscles (PAMs) are compliant fluidic actuators, usually consisting of a tubular bladder, a braided sleeve and end fittings. PAMs have been studied extensively by researchers; however, most previous researches are focused on the axial PAMs. Herein, a pair of nonlinear models were developed based on the principle of virtual work and the force balance analysis. And the two models are applicable to both bending extensile PAMs (BE-PAMs) and bending contractile PAMs (BC-PAMs). In this study, a cyclic bending moment loading experimental method were proposed and conducted with BE-PAMs and BC-PAMs to characterize their deformation and actuation performance and draw their overall relationships of actuation moment to bending curvature and inner pressure. With the experimental results, the validation analysis was carried out to demonstrate the validity of the two models. The energy model can get higher accuracy, while the force balance model could provide more details of the interior and interaction stress conditions. The combination of both can promote the comprehension of non-axial bending PAMs. Moreover, two three-finger soft grippers and a humanoid hand based on BE-PAMs and BC-PAMs were built and tested to investigate their performance on gripping objects. The BE-PAM gripper showed more accommodative gripping performance, whereas, the BC-PAM gripper owned higher gripping force. The humanoid hand combining the merits of both showed excellent flexibility, adaptability and decent load capability in gripping object with various sizes, shapes and materials.

A novel experiment-based approach on nonlinear bending analysis of thermoplastic composite laminates

A novel experiment-based approach, in which we proposed a new physical model for the carbon fibre reinforced thermoplastic (CFRTP) composite with stress-strain nonlinearity and material bimodularity, is presented for the nonlinear bending analysis of CFRTP composite laminates. The nonlinear stress-strain curves in tension, compression and shear are determined by experiments. The bimodular nonlinear model is validated through comparisons of tensile, compressive and three-point bending experimental data against the finite element analysis results firstly. Numerical investigations are then carried out for the symmetric angle-ply CFRTP composite laminates. The effects of the material nonlinearity, bimodularity, fibre orientation, plate aspect ratio, width-to-thickness ratio, boundary conditions and load distributions on the nonlinear bending load-central deflection and load-bending moment curves of CFRTP laminate plates are discussed in detail.

Analysis of concrete columns with high-performance concrete jackets and polymer wraps

Cross-sectional analyses of circular and square reinforced concrete (RC) columns strengthened with reactive powder concrete jacketing and fibre-reinforced polymer (FRP) wrapping were undertaken. The stress block method was used to determine theoretical axial load–bending moment (AL–BM) interactions of the columns. These were then compared with experimental results and found to be in very good agreement. A parametric study was also undertaken to investigate the most important factors that influence the AL–BM capacity of circular and square strengthened columns. Finally, a group of theoretical AL–BM interactions for circular and square strengthened columns was produced. These can be used in a wide range of applications for strengthening RC columns with high-performance concrete jackets and FRP wraps.

Investigation of BFRP bar reinforced geopolymer concrete filled BFRP tube columns

An experimental investigation was carried out on a novel type of concrete-filled tube column, which used geopolymer concrete and basalt-fibre-reinforced-polymer reinforcing bars and confinement tube. Geopolymer concrete was used in place of ordinary Portland cement concrete to counter the sustainability challenges of conventional cement manufacture. Longitudinal basalt-fibre-reinforced-polymer bars were used to replace steel reinforcement to avoid corrosion, while basalt-fibre-reinforced-polymer tube confinement was used to replace the conventionally used steel helix to enhance strength and ductility. Compressive load–deformation behaviour of 200 mm dia., 800 mm high specimens under concentric, 25 mm eccentric, 50 mm eccentric and four-point bending loads was experimentally investigated. Experimental axial load–bending moment diagrams were then produced. Although geopolymer concrete is normally considered to be more brittle than Portland cement concrete, the test results showed that the specimens with geopolymer concrete were more ductile compared to those with Portland cement concrete. It was also found that increased load eccentricity resulted in ductility enhancement in specimens with both types of concrete with basalt-fibre-reinforced-polymer bars and tubes, while steel-reinforced specimens suffered loss of ductility with increased load eccentricity.

Research on the Law of Bearing Capacity of the Bucket Foundation for Offshore Wind Turbines in Clay Soil

Xing, Z.; Fu, P., and Huang., L., 2020. Research on the law of bearing capacity of the bucket foundation for offshore wind turbines in clay soil. In: Liu, X. and Zhao, L. (eds.), Today's Modern Coastal Society: Technical and Sociological Aspects of Coastal Research. Journal of Coastal Research, Special Issue No. 111, pp. 43–48. Coconut Creek (Florida), ISSN 0749-0208.The bucket foundation can be used as the foundation of high-rise buildings. An in-depth understanding of the bearing capacity of the foundations is critical to ensure reliable design and safe operation of foundation. Based on the load characteristics of high-rise buildings and the parameters of soil, the authors explore the law of the bearing capacity of bucket foundations in clay soil and summarize the impacts of the ultimate horizontal load and the ultimate bending moment load on the failure of the bucket foundation. The research found that the failure mode of bucket foundations in clay soil was mainly caused by rotation, the optimal height-diameter ratio of the bucket foundation was about 0.57, and the envelope curve of horizontal load-bending moment failure was roughly an ellipse.

Experimental study on the global behaviour of jack-up unit reinstalled near a footprint

Spudcan is the foundation of the jack-up unit, and the depression on the seabed left by previous spudcan penetration and extraction was called the footprint. Footprint-spudcan interaction is one of the causal sources of jack-up unit accidents. The depression creates a localized eccentric loading and bending moment on the spudcan and platform legs that invariably cause the tilting of the platform. This paper presents a set of experiments carried out at 1g with a three-legged jack-up unit model equipped with a flat-based spudcan in clay. A rotary joint connection was adopted, and results were compared against the responses of fixed head condition. In all of the experiments, an initial footprint was created at the outside of the forward leg. The global dynamic behaviour, induced bending moment and horizontal loads on three legs and pressure distribution under the spudcan were recorded. It is found that the peak moment on the forward leg occurs at the spudcan base level, but the maximum on the stern leg is just under the hull. The leg failure is most prone to occur at the top of the stern leg at a shallow penetration depth due to excessive stress. The critical reinstallation location was found to be at 0.5 times the equivalent diameter of the spudcan and the influence of the footprint can be negligible when the offset distance larger than 1.5D. The non-uniform pressure distribution under the spudcan can intuitively reflect the eccentric loading at the bottom of the spudcan, and the pressure discrepancy on the two sides of the spudcan during the penetration process is highlighted.

Effect of bolted shear connectors on the axial load-bending moment interaction capacity of CFT columns

In Concrete-Filled Tubular (CFT) columns under the influence of compressive loading, an omnilateral confinement pressure is exerted upon the concrete core which leads to increase in the strength, stiffness, and ductility of the column. This paper investigates the influence of bolted shear connectors on the behavior of circular and square CFT columns. Also, a comparison is made between the interactional axial load-bending moment (P–M) curves obtained from the numerical analyses and the P–M relationships put forth by different design standards. For this purpose, 18 circular and 9 square CFT columns, categorized into six groups, are subjected to eccentric compressive loading. The investigated parameters include concrete compressive strength, diameter of the steel tube, load eccentricity, and the presence of bolted shear connector. In most cases, the presence of bolted shear connectors in the column causes strength and ductility to increase, leading to an improvement in the axial load-bending moment (P–M) interaction. The employment of bolted shear connectors at 12.5 cm to 25 cm intervals results in a minimum of 5% and a maximum of 45% increase in the strength of the column.

Geosynthetic as Sustainable Materials for Earthquake resistant of Masonry Structures

When exposed to simultaneous in-plane and out-of-plane behaviour generated by earthquakes or high wind pressure, unreinforced masonry (URM) walls are vulnerable to failure. The paper presents the performance of brick masonry panels using non-woven geotextile in-plane shear and out-of-plane bending experimentally tested. The panels were reinforced with a diagonal geometric pattern on both sides. From the laboratory assessment, it was determined that geosynthetic enhancement significantly improved the capacity of load carrying, displacement capacity, bending moment, stiffness, diagonal shear, in-plane shear, and flexural strength with higher performance for both cases in the case of the cross pattern. In contrast to the un-strengthened panel, experimental findings have demonstrated a less fragile behaviour. Geosynthetics can therefore be preferably suited for strengthening the brick masonry panel in order to defend brick constructions in seismic populated places.

A closed form procedure for the design of longitudinal bars in RC sections subjected to axial load and biaxial bending

AbstractThis paper presents an analytical procedure for the design of the longitudinal reinforcement in reinforced concrete rectangular sections subjected to axial load and biaxial bending moment. The integration of the equilibrium equations is performed in analytical form for the case of uniaxial moment, including the effect of the reinforcement placed on the sides of the section and adopting code‐based constitutive laws for steel and concrete. The strength domain of the section is calculated in closed form for the case of only main steel and in simplified form when including the reinforcement disposed on the side. Additionally, a formulation is proposed for the interaction domain of the two components of the bending moment for constant axial load, in which the uniaxial moment capacities are calculated including all the rebars within the section. The proposed method is adopted for setting a design procedure of the steel bars of rectangular sections subjected to biaxial bending. Comparisons with numerical results and code provisions show the reliability of the approach, which reduces computational costs and give useful indications for practitioners and designers.

Finite Element Analysis on Reinforced Concrete Columns Strengthened by ECC Jacketing under Eccentric Compressive Load

Engineered cementitious composite (ECC) can be used for strengthening of concrete columns due to its similar structure and suitable connection to normal concrete and its special tension behavior. In this study, to analyse the columns, finite element (FE) method was used after verification by experimental results. Reference column was strengthened by normal concrete and ECC jacketing. The effects of type of jacket material, longitudinal reinforcement, compressive stress and ultimate tensile strain of ECC on variations of eccentric load-bending moment (P-M) interaction curves were investigated. Results showed that the use of ECC instead of normal concrete can increase load carrying capacity of strengthened column, due to tensile strain hardening behavior of this material. It was found that, amount of this increase depends on eccentricity of eccentric load and varying from 0.4-23%. In ECC jacketing, tensile cracks are continuous, but in concrete jacketing, there were discrete cracks and more quantity of damages. Due to higher load carrying capacity and better distribution of tensile cracks in ECC jacketing than normal concrete jacketing, the use of ECC is suitable for strengthening of reinforced concrete columns. Load carrying capacity of columns under concentric load and pure bending moment were calculated by theoretical method and the results were compared with FE.

Semi-analytical model development for preliminary study of 3D woven Composite/Metallic flange bolted assemblies

This research deals with the development of a new semi-analytical model for composite-metal eccentric tensile bolted joints of casing structures. The model is based on a direct stiffness method considering structural elements, where flanges are modeled with axisymmetric shell elements, the bolt with a beam element and contact behavior with a specific number of compressive linear springs, identified by means of convergence tests. A hybrid element is added in order to set the link between flange and bolt. Since the model is intended for the preliminary design of bolted joints including composite materials, we propose an extension of the stiffness matrix formulation of isotropic axisymmetric shell elements to orthotropic ones. This formulation is validated with respect to a 2D FE axisymmetric model. Then, a semi-analytical model is established for a casing assembly approximately corresponding to a real casing of an aircraft engine. Design criteria such as normal stress on the bolt, bending moment and axial load at a specific section of the composite flange, given by the semi-analytical model are compared to a 3D FE computation. Results are in very good agreement and the semi-analytical model offers considerable time saving where the computation time was 120 times faster than the 3D FE model. Moreover, relative error does not exceed 2% for normal stress of the bolt and 9% for the flange bending moment which is satisfactory in a preliminary design approach. However, due to the formulation of hybrid element, less accurate results were observed for axial displacement of the composite flange and it would be advisable to consider a new formulation. This will be detailed in future work. Finally, a parametric study showed the ability of the semi-analytical model to predict the physical behavior of joints and proved its usability for running optimization studies and its reliability as a preliminary design tool.

Higher order adhesive effects in composite beams

Composite adhesive bonded joints are widely used in various industrial and technological applications, including aerospace, electronics, biomedical, automotive, ship building and construction. In this paper, the attention is focused on layered structures consisting of two adherent beams bonded together by an adhesive layer. For such structures, a modeling approach based on the classical Timoshenko beam theory in conjunction with an adhesive model of imperfect interface is introduced. This imperfect interface approach, recently proposed by the authors in the contest of linear elastic adhesive and adherents materials, small strains and small displacements theory, models the asymptotic behavior of a thin interphase at higher orders for both the cases of hard and soft interface materials in a unified approach (Rizzoni et al., 2014). Accounting for higher order terms of the asymptotic expansions in the adhesive, the proposed approach generalizes simpler models based on the classical spring-type interface law or on the case of perfect contact between the adherent layers.The proposed methodology is used to evaluate stresses in two adhesive bonded joint configurations subjected to bending moment and transverse shear loading. Numerical simulations are produced and the results show good agreements with those obtained through finite element analysis.