Ultimate Bending Moment Research Articles

Connection performance examination of a new bamboo-oriented strand board connector

Bamboo-oriented strand board (BOSB) with superior physical properties can be used in the furniture industry to alleviate wood shortages. Two types of plug-in connectors were designed in this paper: a splint-type connector and V-type connector. By cantilever bending, corner tension, and compression tests of L-type corner joints of BOSB and wood-oriented strand board (WOSB), the connection performance of the new connectors and six typical connectors was compared. The new connectors function like clamps, do not require that a screw or bolt pass into or through the board, and can be assembled repeatedly. The V-type connectors were more suitable for BOSB, and the joints exhibited the highest ultimate bending moment values (133.9 N·m, 86.8 N·m, 117.7 N·m). The splint connectors were more suitable for WOSB and their ultimate bending moment values (57.1 N·m, 45.3 N·m, 61.3 N·m) were greater than the joints fixed by V-type connectors (50.4 N·m, 35.4 N·m, 46.1 N·m). The results revealed that the connector performance affects the joint strength and that different plates were suitable for different connectors. A joint failure analysis revealed two simple failure modes for the two new connectors.

Study of hull girder ultimate strength at elevated temperatures

ABSTRACT Fire poses a significant threat in the shipping industry not only for humans (passenger, seafarers) but also for the ship structure. It is of great concern how elevated temperatures from a fire can influence the bending moment capacity of a hull girder due to the degradation of steel’s mechanical properties. The aim of the paper is to evaluate the ultimate bending moment capacity of a chemical oil/product carrier at ambient and elevated temperature conditions. The study defines the parameters and modelling that need to be considered in the finite element analysis (FEA) and proposes a modified incremental–iterative procedure for the bending moment capacity calculation at elevated temperatures. Smith Method was extended in order to incorporate neutral axis rotation and steel’s mechanical properties at elevated temperatures. The proposed modified Smith Method’s results present good agreement with the equivalent FEA results. It is concluded that with the proposed modified Smith Method, it is possible to determine the loading that can be carried by a hull girder with a specified temperature profile. The study also determines an analysis technique for the stiffened panel ultimate strength analysis at elevated temperatures.

The P-y Response of Laterally Loaded Flexible Piles in Residual Soil

This paper describes the main features related to lateral displacements with depth after successive lateral loading–unloading cycles applied to the top of reinforced-concrete flexible bored piles embedded in naturally bonded residual soil. The bored piles under study have a cylindrical shape, with 0.40-m in diameter and 8.0-m in length. Both bored piles types (P1 and P2) include an embedded steel pipe section in their center as longitudinal steel reinforcements: pile type P1 has another 16 steel rods as steel reinforcement to concrete while pile type P2 has no further steel reinforcement. Pile type P1 has three times as much stiffness (EI) and four and a half times the plastic moment (My) than pile type P2. A similar load–displacement performance was observed at initial loads as for small displacements of both piles. At this initial loading stage, the response of the reinforced concrete piles is a function of the soil characteristics and of a linear elastic pile deformation. During this stage, piles can even be understood as probes for evaluating soil reactions. For larger horizontal displacements, after the concrete section starts undergoing large deformations, approaching the ultimate bending moment, pile behavior and consequently the load–displacement relation starts to diverge for both piles. For pile P1 the values of relevant lateral displacements are extended to about 2.5-m in depth, while for pile P2 lateral displacements are mostly constrained to about 2.0-m in depth. Measurements of horizontal displacements of pile P1 against depth recorded with a slope indicator show that, after unloading, lateral loads at distinct stages (small and near failure loads), exhibits a much higher elastic phase of the system response. An analytical fitting model of soil reaction is proposed based on the measured displacements from slope indicator. The integration of a continuous model proposed for the soil reaction agrees fairly well with the measured displacements up to moments close to plastic limit. Results of load–displacement show that the stiffer pile (P1) was able to mobilize twice as much lateral load compared to pile P2 for a service limit displacement of about 20 mm. The paper shows results that enable the isolation of the structural variable through real scale pile load tests, thus granting understanding of its importance and enabling its quantitative visualization in examples of piles embedded in residual soil sites.

The Use of Fragility Curves in the Life-Cycle Assessment of Deteriorating Bridge Structures

Within the context of structure deterioration studies, we propose a new numerical method based on the use of fragility curves. In particular, the present work aims to theoretically study the degradation of concrete bridge structures subjected to aggressive environments. A simple probabilistic method based on fragility curves is presented which allows the forecasting of the lifetime of the considered structural system and the best monitoring time. The method was applied to investigate the degradation of a concrete bridge used as a case study. A Monte Carlo numerical procedure was used to simulate the variation over time of the residual resistant section and the ultimate bending moment of the deck of the case study. Within this context, fragility curves are used as reliable indicators of possible monitoring scenarios. In comparison with other methods, the main advantage of the proposed approach is the small amount of computing time required to obtain rapid assessment of reliability and deterioration level of the considered structure.

Theoretical analysis of the mechanical behavior of double-ring joints under pure bending, bending-shear and eccentric loading conditions

Taking double-ring joint as research object, the mechanical performances under pure bending, bending-shear and eccentric loading conditions of the joints were studied in this paper. Double-ring joints with different structural parameters were analyzed using finite element analysis and theoretical derivation methods and combined with experimental results. The following conclusions were obtained: 1) under the pure bending condition, the spring model of the double-ring joint was established, and the theoretical calculation formulas of the ultimate bearing capacity and initial rotational stiffness were derived; 2) under the bending-shear condition, the accuracy of finite element analysis models was verified by comparing the numerical with experimental results. The mechanical properties of double-ring joints under the bending-shear condition were similar to those under the pure bending condition; 3) based on the full-section plasticity criterion, the relationship between ultimate bending moment ratio η0N and axial force eccentricity δ was derived. With the exponential function for nonlinear fitting, the relationship between initial rotational stiffness ratio ξ0N and axial force eccentricity δ was derived.

Experimental and theoretical study of post-tensioned unbonded beams

Paper contains data obtained during a bending test of four post-tensioned unbonded beams as well as description of geometry of test specimens and strength properties of used materials. Midspan deflection, tendon stress increase, cracking moment and ultimate bending moment were measured during the test. Crack propagation pattern was assessed as well. Ultimate bending moment, cracking moment and midspan deflection were then estimated using reinforced concrete analysis methods widespread in Russia. Comparison of the test data and calculation results shows that nowadays there are not domestic analysis methods well enough to fully estimate the unbonded post-tensioned beams.

Analytical study of the section of the rc beams strengthened for flexure with FRP materials

Strengthening of concrete structures is applied as a solution for various deterioration problems in civil engineering practice. This paper presents an analytical study of the behaviour of cross-section of reinforced concrete (RC) beam, strengthened for flexure with fiber reinforced polymer (FRP) materials. Using the balance of internal forces in the cross section through all phases of stress through which the section passes, a program was written in the MATLsoftware, the execution of which produced a curve of dependence between bending moment and curvature, which is one of the most important indicators of cross section behaviour. The parameters varied in this study are the amount and type of FRP reinforcement and the obtained results indicate a significant influence of additional FRP reinforcement both on the yielding and ultimate bending moment, and on the bending stiffness of the strengthened cross section.

Comparison of the design of prestressed concrete hollow-core floor units with Eurocode 2 and ACI 318

A typical 1200 mm (48 in.) wide × 200 mm (8 in.) deep prestressed concrete hollow-core unit is analyzed and designed in order to make a comparison between Eurocode 2 and ACI 318-08. This includes calculations for serviceability limit state of stress and moment of resistance, ultimate moment of resistance, ultimate shear capacities, flexural stiffness (that is, for deflection), and cover to pretensioning tendons for conditions of environmental exposure and fire resistance. Concrete cylinder strength is 40 MPa (5.8 ksi), and concrete cube strength is 50 MPa (7.3 ksi). The hollow-core unit is pretensioned using seven-wire helical strands. Worked examples are presented in parallel formation according to Eurocode 2 and ACI 318. For uniformly distributed loads, the design criterion between the service moment to service moment of resistance (Ms/Msr for EC2 and Ms/Msn for ACI 318) and the ultimate design bending moment to ultimate moment of resistance (MEd/MRd for EC2 and Mu/φMn for ACI 318) is well balanced for this example. Usually the service moment is critical unless the amount of prestress is small. For EC2-1-1, flexurally uncracked shear capacity VRd,c is only limiting when the span-to-depth ratio in this example is less than about 35. For ACI 318, flexurally cracked shear capacity φVci is limiting when span-to-depth ratio is 42, showing that shear cracked in flexure will often be the governing criterion.

Model test study of bending moment and negative skin friction for batter rock-socketed piles under surface load

Batter rock-socketed piles (BRSP) foundation is one of common foundations, such as port engineering or cross-sea bridge, while there are few studies on negative skin friction for BRSP. A series of model tests are conducted to explore negative skin friction of BRSP which are embedded in thick soft clay. The effects of the inclined angle of piles and soil consolidation time to negative friction resistance and the bending moment of BRSP are analyzed. The test results show that: the development of negative friction and bending moment BRSP have pronounced time effect; the longer the consolidation time is, the slower the axial force and bending moment intensify. The ultimate pile shaft axial force and bending moment increases nonlinearly concerning the inclined angle of piles. And the “neutral point” position and peak point of bending moment is always located at 0.9~1.0 times soil depth.

Analysis of the mechanical properties of a fibreglass reinforced flexible pipe (FGRFP)

ABSTRACT Fibreglass reinforced flexible pipe (FGRFP) is a kind of composite thermoplastic pipe serving as a preferred application in the field of oil transportation. This paper studies the mechanical behaviour of FGRFPs under pure bending by experimental, numerical and theoretical methods. Full-scale four-point bending tests are conducted and the curvature-bending moment relations of specimens are recorded. In the numerical simulation method (NSM), a detailed finite element model considering both material and geometric nonlinear behaviour is established, and the composite is defined as an orthotropic elastic-plastic material. Based on the Euler–Bernoulli beam theory, a simplified theoretical method (STM) is proposed to predict the ultimate bending moment. In the parametric study, a simple formula is introduced to modify STM to make it more accurate. Good agreements proves the reasonability of the proposed NSM and STM. Additionally, STM could make a contribution to engineers in terms of a concise and relatively accurate way in ultimate status analysis.

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.

Numerical Investigation on the Ultimate Strength of Box Beams with Impact Damage

The objective of this paper is to study the residual ultimate strength of box beams with impact-induced damage, as a model of what may occur in ship hulls. The bottom and side plates of ship hulls can suffer denting or fracture damage due to grounding, collision and other contacts during the ship’s service life and these impact-induced damages could result in considerable strength degradation. Box beams are firstly subjected to impact loading and then four-point bending loading is imposed on the damaged structures to assess the residual strength using ANSYS/LS_DYNA. The ultimate moment and collapse modes are discussed considering the effect of impact location. The impact-induced deformation is introduced in the four-point bending simulation, and the impact-induced stress is included or not to determine the effect of residual stress and distortion after impact. It is shown that impact location has significant influence on the residual ultimate bending moment of the damaged box beam providing that the impact energy is kept constant. The collapse modes also change when the impactor strikes on different locations. Damaged hard corner and inclined neutral axes might explain the reduction of ultimate strength and diverse collapse modes. The residual stress in the box beam after impact may increase or decrease the ultimate strength depending on impact location.

Parametric Study of Different Unbonded Tendon Layouts in Pre-stressed Concrete Flat Plates

Post-tensioned unbonded tendons are widely used in flat slabs/plates when there is a demand for large span lengths, durable tendons and a reduction in the weight of structure. For post-tensioned flat slab/plates, different tendon layouts have been discussed in the literature. It is vital to compare the structural response (i.e., deflection and stresses) and the clashing of tendons of the proposed tendon layouts in the literature to select an appropriate layout. Hence, this study focuses on the analysis of three different six-panel flat plates (i.e., panel sizes: 6 m × 6 m, 9 m × 6 m and 11 m × 6 m) with five different tendon layouts, using computer programs ADAPT-Floor Pro and FEM-Design 17, based on linear finite element (FE) analysis. Short-term/long-term deflection and stress due to service load obtained from the computer programs has also been compared, to highlight the differences. Ultimate bending moment of resistance was calculated theoretically for different layouts and compared. Results from the analysis show that, when a higher portion of tendons is concentrated instead of distributed, stresses caused by other structural loads are counteracted best. The layout with all tendons concentrated also has the best results in terms of deflections.

Moment-rotation model of endplate blind bolted joints with CFST column

The moment-rotation curves can directly reflect the performance of H-shaped beam to concrete filled steel tube (CFST) column joints, which should be fully considered in structure analysis and design of such joints. However, the current determination of moment-rotation curves is mainly fitting results of experiments or simulations, which results considerable consumption of human and material resources. Hence, this paper proposes a new three-parameter exponential model for this type of joint to forecast the moment-rotation relation curve. Considering possible failure modes, a calculation method of ultimate bending moment for joints is proposed. An analysis model of initial rotational stiffness for joints is established according to component method. Based on the research results of this paper, the ultimate bending moment and initial rotational stiffness can be calculated straight by measurement factors and material properties. The values of the shape parameter for two kinds of the joint are derived by fitting the existing experimental data. Based on the established prediction model of moment-rotation, an accurate calculation method of ultimate bending moment, and analysis model of initial rotational stiffness, the prediction results are in good agreement with experimental results according to the comparison. The established moment-rotation model may be applied to the design of composite frames to predict the behavior of the joint with endplate and blind bolts simply and accurately. Moreover, it can save the workload of experiments and simulations.

Experimental study on the combined shear and bending behaviour of corbel joints in precast concrete segmental inverted-T caps

Precast construction of caps is adopted to reduce on-site construction time and facilitate installation. A corbel joint (CJ) is proposed as an innovative joint form to improve the mechanical behaviour and construction performance of precast concrete segmental inverted-T caps. To obtain a further understanding of the failure modes and resistance mechanisms of CJs subjected to combined shear and bending, eight cap specimens with different shear-span ratios (1.61, 2.37, and 3.89) and joint types (CJ, monolithic concrete, and straight joints with a single tooth or multiple teeth) were match cast and tested. The experimental results showed that the CJs achieved superior mechanical and deformation performance and higher bearing capacity compared to conventional straight joints. Owing to corbels intercepting cracks, the CJs were not fully opened similar to straight joints at the limit state. Furthermore, the reinforcement in the corbels reached the yield strength, which suggested that the CJs could transfer the shear force between two adjacent segments effectively and reliably. When the shear-span ratios changed from 1.61 to 3.89, the ultimate shear force in the joint plane reduced by 57.9%, while the ultimate bending moment increased by 5.2%. Therefore, the ultimate shear and bending moment of the CJs were correlated.

Flexural capacity of continuous reinforced concrete beams strengthened or repaired by CFRP/GFRP sheets

The flexural strengthening of reinforced concrete (RC) beams by bonding external composite materials has proved to be an effective and convenient technique. Several works, focus on mechanical behaviour of continuous reinforced concrete beam with two spans strengthened by composite materials, were reported in literature. This paper presents the flexural capacity of continuous RC beams with three spans strengthened or repaired by bonding carbon or glass fibre reinforced polymer (CFRP or GFRP) sheets. Experimental program consists of eight continuous RC beams strengthened by CFRP or GFRP sheets and one beam of reference. The dimension is the same for all beams with a length 9 m and a section 15x25 (cm). Experimental tests with monotonic loading were carried out by varying damaged level of the beams, composite material type and strengthening thickness. Five failure modes of strengthening beams were observed. The results show that the ultimate bending moment of the beam can be improved between 14.8 and 26.6% in case of the beams by bonding CFRP sheets and between 7.2 and 11.8% by bonding GFRP sheets. The beam, which was pre-damaged under pre-loading level 100% of the failure load, can be repaired as strengthened continuous RC beam. The optimal strengthening thickness in the positive and negative bending moment region was obtained. The variation of the strain in the positive and negative bending moment was analysed.

Hull Girder Ultimate Strength Assessment Considering Local Corrosion

The residual strength capacity of ship hull with full corrosion appearance in every structural member has been considered in a large number of research works; however, the influence of local corrosion on the ultimate strength and cross-section properties has not been taken into account and analyzed. Hence, this study aims to assess the effect of corrosion appearance in the flange section and web section on the ultimate vertical bending moment and several cross-section properties of a bulk carrier. To perform this task, a probabilistic corrosion rate estimation model and the common structural rule model are introduced and employed. The incremental-iterative method given by the International Association of Classification Societies-Common Structural Rules (IACS-CSR) is applied to determine the ultimate vertical bending moment, neutral axis position at the limit state, and other properties of the cross-section. The calculation results and discussions relative to the effect of corrosion on ship hull are presented.

Studies on T-shaped one-side bolted connection to hollow section column under bending

A novel T-shaped One-side Bolted endplate Connection (TOBC) for steel beam to Hollow Square Steel Tube (HSST) was proposed and the behavior of TOBC under static bending moment was investigated through Finite Element Model (FEM). The FEM was verified by test results on Standard High-strength Bolted Connection (SHBC) in terms of the failure mode, the bending moment-rotation curve and the yield bending moment. Parametric analysis of TOBC was carried out. Studied parameters included both the general parameters of an endplate connection, such as the endplate width, the endplate thickness, the endplate strength, the bolt diameter, the bolt pretension force, the axial compression ratio of the column and the beam length, and the unique parameters of the TOBC, such as the direction of slotted bolt hole, the gap between infill block and bolt hole, the angular deviation of the T-head and the two-bolt hole of T-shaped One-side Bolt (TOB). A total of six failure modes were found namely: the beam yielding failure, the bolt failure, the endplate yielding failure, the column wall yielding failure, the column wall yielding accompanied with endplate yielding failure and the column wall yielding accompanied with bolt failure. The TOBC with slotted bolt hole in vertical direction had better performance than that in horizontal direction in terms of the initial stiffness, the yield bending moment and the ultimate bending moment. The gap between infill block and bolt hole had no effect on the bending performance of TOBC in moment connection. The angular deviation of the T-head had little influence on the bending performance of TOBC, if it was less than 30 degrees. The initial stiffness and yield bending moment of TOBC could be greatly increased by using two-bolt holes in the connection tension region.

Flexural behavior of concrete-filled double-skin steel tubular beams after subject to high temperature

Concrete-filled double-skin steel tubular (CFDST) specimens that exhibit lightweight, good ductility, and better bending resistance, can be used for beams. However, fire often causes great damage, and the flexural behavior of CFDST beams after subject to high-temperature has not been studied. To investigate the flexural behavior of CFDST beams after subject to high temperature, seven CFDST specimens after subject to high temperature were carried out four-point bending tests. The main parameters explored in the test include hollow ratio (0.31, 0.52, 0.72) and temperature (300 °C, 500 °C, 800 °C). The corresponding finite-element analysis (FEA) models were established, and the results showed good agreement with the test. The in-depth mechanism and systematic analysis including the influence of different hollow ratio, material property, and temperature on the whole process curve of CFDST after subject to high temperature are carried out using FEA models. It is found that the ultimate bending moment of CFDST after subject to high-temperature increases with hollow ratio and material property, but decreases with the temperature. The outer steel tube contributes the most to the ultimate bending moment, and the inner steel tube improves the ductility at a later stage. Specimens with a large hollow ratio (χ ≥ 0.52) have better bending capacity, and the ultimate bending moment of specimens with a small hollow ratio (χ < 0.52) decrease the least with the change of temperature due to the protection of concrete. Based on the findings from the test and numerical studies, a temperature effect coefficient kr is proposed to represent the residual bearing capacity after subject to high temperature, and combined with three different codes to evaluate the ultimate bending moment. A comparison of test results showed the calculated results following the T/CCES 7–2020 (2020) had a good agreement.

Strength and stiffness analyses of standard and double mortise and tenon joints

This paper investigated the effect of the tenon length on the strength and stiffness of the standard mortise and tenon joints, as well of the double mortise and tenon joints, that were bonded by poly(vinyl acetate) (PVAc) and polyurethane (PU) glues. The strength was analyzed by measuring applied load and by calculating ultimate bending moment and bending moment at the proportional limit. Stiffness was evaluated by measuring displacement and by calculating the ratio of applied force and displacement along the force line. The results were compared with the data obtained by the simplified static expressions and numerical calculation of the orthotropic linear-elastic model. The results indicated that increasing tenon length increased the maximal moment and proportional moment of the both investigated joints types. The analytically calculated moments were increased more than the experimental values for both joint types, and they had generally lower values than the proportional moments for the standard tenon joints, as opposed to the double tenon joints. The Von Mises stress distribution showed characteristic zones of the maximum and increased stress values. These likewise were monitored in analytical calculations. The procedures could be successfully used to achieve approximate data of properties of loaded joints.