Dynamic performance of high supporting formwork under horizontal impact load

A fully nonlinear numerical wave tank (NWT) is set up for extreme wave modelling and wave impact simulation. As a first step, a focused wave train was model and the focal location where the steep focused wave is close to breaking was determined. Subsequently, an in-depth investigation is performed on the wave impact loads on the wave-ward side of a deck box of a semi-submersible subject to this extreme wave. The numerical results are also compared with the predictions in accordance to the DNVGL technical guide. It is concluded that the severe horizontal impact loads are caused by the “strike” action of the rushing water mass from near-breaking waves rather than the run-up jets. The predictions based on the technical guide are conservative and in general overestimate the impact loads. These findings could contribute to a more comprehensive understanding and a more accurate algorithm with respect to the horizontal impact loads.

Discrete element modeling and simulation study on cutting rock behavior under spring-mass-damper system loading

Dynamic behavior of RC columns confined with CFRP grid-reinforced ECC subjected to lateral low-velocity impact

To evaluate the biomechanical stability of a newly-designed Y type pedicle screw (YPS) in osteoporotic synthetic bone. The osteoporotic synthetic bone were randomly divided into 3 groups ( n=20). A pilot hole, 3.0 mm in diameter and 30.0 mm in deep, was prepared in these bones with the same method. The YPS, expansive pedicle screw (EPS), and bone cement-injectable cannulated pedicle screw (CICPS) were inserted into these synthetic bone through the pilot hole prepared. X-ray film examination was performed after 12 hours; the biomechanical stability of YPS, EPS, and CICPS groups was tested by the universal testing machine (E10000). The test items included the maximum axial pullout force, the maximum running torque, and the maximum periodical anti-bending. X-ray examination showed that in YPS group, the main screw and the core pin were wrapped around the polyurethane material, the core pin was formed from the lower 1/3 of the main screw and formed an angle of 15° with the main screw, and the lowest point of the inserted middle core pin was positioned at the same level with the main screw; in EPS group, the tip of EPS expanded markedly and formed a claw-like structure; in CICPS group, the bone cement was mainly distributed in the front of the screw and was dispersed in the trabecular bone to form a stable screw-bone cement-trabecular complex. The maximum axial pullout force of YPS, EPS, and CICPS groups was (98.43±8.26), (77.41±11.41), and (186.43±23.23) N, respectively; the maximum running torque was (1.42±0.33), (0.96±0.37), and (2.27±0.39) N/m, respectively; and the maximum periodical anti-bending was (67.49±3.02), (66.03±2.88), and (143.48±4.73) N, respectively. The above indexes in CICPS group were significantly higher than those in YPS group and EPS group ( P<0.05); the maximum axial pullout force and the maximum running torque in YPS group were significantly higher than those in EPS group ( P<0.05), but there was no significant difference in the maximum periodical anti-bending between YPS group and EPS group ( P>0.05). Compared with EPS, YPS can effectively enhance the maximum axial pullout force and maximum rotation force in the module, which provides a new idea for the design of screws and the choice of different fixation methods under the condition of osteoporosis.

The structural behavior of a tensile fabric structure, known as hypar, is investigated. Seismic-induced stresses in the fabric and axial forces in masts and cables are obtained using accelerograms recorded at different regions of the world. Time-history analysis using each recording are performed for the hypar by using finite element simulation. It is found that while the seismic stresses in the fabric are not critical for design, the seismic tensile forces in cables and the seismic compressive forces in masts should not be disregarded by designers. This is important, because the seismic design is usually not considered so relevant, as compared for instance with wind design, for these types of structures. The most relevant findings of this study are: 1) dynamic axial forces can have an increase of up to twice the static loading when the TFS is subjected to seismic demands, 2) large peak ground accelerations seem to be the key parameter for significant seismic-induced axial forces, but not clear trend is found to relate such forces with earthquakes and site characteristics and, 3) the inclusion or exclusion of the form-finding in the analysis procedure importantly affects results of seismic stresses in the fabric, but not in the frame.

By using the ABAQUS finite element (FE) model, which has been verified by experiments, the deformation and internal force changes of RC columns during the impact process are investigated, and a parametric analysis is conducted under different impact kinetic energies Ek. According to the development path of the bottom bending moment-column top displacement curve under impact, the member is in a slight damage state when the curve rebounds before reaching the peak and in a moderate or severe damage state when the curve exceeds the peak, in which case the specific damage state of the member needs to be determined by examining whether there is a secondary descending stage in the curve. Accordingly, a qualitative method for evaluating the bending failure of RC column members under impact is obtained. In addition, the damage state of RC columns under impact can also be quantitatively evaluated by the ratio of the equivalent static load Feq and the ultimate static load-bearing capacity Fsu.

Experimental investigation on the horizontal impact response of precast RC bridge piers with grouted sleeve connections considering defects

Active fault is the most dangerous natural hazards of buried steel pipelines, as large stress and strain induced by ground movement can lead to pipe failure, which may cause severe accidents. Based on nonlinear finite element method, local buckling behavior of buried high strength X80 steel pipelines under compression strike-slip fault was studied systematically. Accuracy of the numerical model was validated by previous full scale experimental results. A baseline analysis was performed to elucidate the local buckling phenomenon of pipe. Parametric analysis was also performed to investigate the effects of influence factors of pipe’s buckling behavior. Results shows that, when local buckling occurs, axial section force decreases abruptly. When pipe-fault intersection angle equals 135°, the maximum axial section force peaks and the critical fault displacement is the smallest. With the increase of pipe wall thickness, the maximum axial section force and the critical fault displacement increases. With the increase of pipe internal pressure, the maximum axial section force and the critical fault displacement decreases. When p = 0MPa, inward-diamond buckling occurs in the pipe. While p≥4MPa, elephant-foot buckling occurs in the pipe.

To compare the use of cannulated screws in an inverted triangular configuration, medial buttress plates, and the combination of these 2 fixation methods in the treatment of Pauwels type 3 femoral neck fractures. Twenty-eight anatomical composite third-generation femoral bone models were divided into 4 groups. The control group (group 1) was formed with 7 third-generation intact bone models. The fracture model was created with a 70° cutting block to fit 21 Pauwels type 3 fracture configurations. Seven models were fixed with an isolated 3.5 mm one-third semi-tubular medial buttress plate (group 2), 7 were fixed in an inverted triangular configuration with 6.5 mm cannulated screws (group 3), and 7 were fixed using a combination of 6.5 mm cannulated screws and a medial buttress plate (group 4). Cyclic loading was applied using axial forces ranging from 60 N to 600 N and moments ranging from 0.7 Nm to 7.0 Nm for 500 cycles. Once the cyclic loading stage was completed, the loads were removed from the system, and the quasi-static loading stage was employed to determine the stiffness and failure forces of the system under both axial and torsional forces. Quasi-static tests were performed with an axial speed of 1.8 mm/min and a torsional speed of 4.5°/min. The biomechanical properties of all groups were examined in terms of axial stiffness, torsional stiffness, and maximum axial force parameters. The stiffness values of groups 1, 2, 3, and 4 were 303 ± 35.8 N/mm, 159.6 ± 25 N/mm, 232 ± 35.9 N/mm, and 366.9 ± 58 N/mm, respectively, under axial forces (P < .01); 2172.7 ± 252.1 Nmm/°, 1225.3 ± 238.6 Nmm/°, 2123 ± 359.4 Nmm/°, and 2721.85 ± 304 Nmm/°, respectively, under torsional moments (P < .01); and 2072.1 ± 256.1 N, 1379.9 ± 290.6 N, 2099.1 ± 454.2 N, and 2648.4 ± 364.6 N, respectively, under the maximum force (P < .01). This study showed that in the fixation of Pauwels type 3 fractures formed on third-generation bone models, the utilization of half-thread cannulated screws in an inverted triangle configuration, along with a medial buttress plate, provided stronger fixation compared to the remaining implant groups and the control group. According to the evaluation of the parameters, the isolated application of a medial buttress plate had poorer biomechanical properties than other fixation methods.

In-situ horizontal cyclic loading tests on composite foundation composed of soilbags and piles

To study the failure of conventional packers in the fracturing and stimulation of low-porosity and low-permeability reservoirs and reduce the failure accidents of packers in the fracturing process, a suitable integrated string packers was selected in the process of fracturing and stimulation in an oilfield in the Middle East as a case study. Three different well types have been established. The wellbore temperature distribution and the axial force of the string can be calculated under the conditions of various wellhead pressures and different displacement, and it is found that the temperature at the bottom of the well can reach 130 °C, and the maximum axial force at the wellhead is 500 kN. At the same time, the applicability of retrievable tubing testing squeeze (RTTS) and hydraulic-set retrievable (RH) packer in different working conditions was evaluated, and it was found that only RTTS packers can meet the needs of the oil field. According to the calculated temperature field and axial force distribution, the stress on different components of the packer under different working conditions is established during the fracturing-stimulation operation. In the worst working conditions, the maximum stress of the packer occurs at the lower part of the central pipe, reaching 303.83 MPa, which is in a safe state. The contact stress on rubber rings can reach 30 MPa, indicating that the sealing performance can meet the requirements of on-site use. The temperature and axial force data calculated by the model provide a theoretical basis for safe well control. Through model evaluation, it was found that the RTTS packer can be suitable for the fracturing and stimulation needs of the oilfield. The research methods and achievements in the article provide theoretical guidance for evaluating the applicability of packers in the fracturing and stimulation process of low porosity and low permeability reservoirs.

In this paper, the radial and axial forces due to inrush and short circuit currents on both inner and outer surfaces of low voltage (LV) and high voltage (HV) windings are calculated. Static and dynamic aspects of these forces which are related to the variation of forces versus winding height and time are analyzed. Power transformer in the start-up mode and under short circuit fault is modeled using two-dimensional (2D) time stepping finite element method (TSFEM). This approach leads to the precise determination of the required signals including current, magnetic flux density, radial and axial forces. Calculated forces are analyzed significantly to compare impacts of the mechanical forces due to inrush and short circuit currents on the windings of the transformer. Three-dimensional (3D) TSFEM is utilized to evaluate aforementioned forces and compare with 2D TSFEM results. In the 3D TSFEM, geometrical and physical characteristics of the all components of the transformer, nonlinearity of the core materials and distribution of the primary and secondary windings are taken into account. 2D TSFEM results are verified by 3D TSFEM results.

Purpose. Research of the influence of the process parameters on the quality of threaded connections, notably, thread formation axial force on the opposite sides of the roots. Determination the thread formation axial force for screws with a wide groove. Design/methodology/approach. In a paper it is shown, that action of uncompensated thread formation axial force increases the defects and imperfectness of the strengthened layer. Proposed the theory about changes in the traditional self-stretching thread-formation method on the implementation process with a constant axial force. The external axial load must be equal to the largest axial component force of the thread-formation. The method uses the slip-line method with a model taking into account the interaction between two consecutive formed threads and enables the mean pressure on the thread flank to be obtained as a function of the formed thread height. From these results and a knowledge of the forming screw end geometry, an analytical method is proposed for the maximum axial force, the physical phenomena of the displacement of material in the tapping process is illustrated and the significantly influential parameters highlighted. Findings. This study proposes an analytical model based on a previous study concerning radial penetration of a rigid acute wedge into a perfectly plastic material. An experimental study seeks to determine the optimal lead hole on the work piece for an M8 screw. The experimental results are compared favorably with the results of the analytical study in order to validate the forming screw model. Originality/value. It is shown the influence of the geometrical parameters of the thread forming screw and of the work-piece on the axial force, and the influence of the process parameters on the quality of threaded connections. This sets limits on the forming axial force and conserves a sufficiently well formed thread shape for good stripping resistance. The experimental results are compared favorably with the results of the analytical study in order to validate the forming screw model.

ABSTRACTIn this work a probabilistic structural analysis of a container terminal wharf is presented. Through the application of the Monte Carlo Simulations in a finite element structural model, the statistics of the axial forces at the pile heads were evaluated. Considering only ship berthing conditions, but varying equipment type, number and positions, ten external load combinations were analyzed and compared. Both finite element model and probabilistic analysis were performed in ANSYS software, v.16, on its APDL Mechanical and Probabilistic Design System packages respectively. The random input parameters considered were the concrete structure, pavement and rear landfill self-weight, live loads and ship sizes, for which statistical parameters were attributed based on bibliography or data collection. PIANC’s berthing energy method for fender systems design was applied for the evaluation of ship berthing forces acting on the structure. Considering the axial forces as the main parameters in the design of partially embedded piles, the random output parameters obtained were the minimum and maximum axial forces on each simulation. That approach, applied due to the possibility of ANSYS to be programmed through its Parametric Design Language (APDL), proved to be a powerful tool for probabilistic analysis of complex structural systems. The results present a comparison between the statistical parameters and probability density curves for the ten cases analyzed, by which the worst combinations from a probabilistic point of view could be defined. Keywords: Container terminal berth; Probabilistic Analisys; Monte Carlo Method; Finite Element Method; ANSYS.

The risk of applying compression to a sliding-screw-plate osteosynthesis in the treatment of femoral neck fractures was evaluated in an experimental study of 40 femoral neck osteotomies. Ten pairs of bones from autopsied women between 70 years and 79 years of age were compared to 10 pairs of bones from autopsied women of more than 80 years of age. The compression was applied intermittently but measured continuously. The results showed a diphasic curve. When the maximum axial compression force was reached, any attempt to apply further compression resulted in a rapid fall in pressure at the site of the osteotomy. The median of the maximum axial compression force was 971 N, ranging from 275 N to 1756N. The maximum axial compression forces were significantly lower in bones from women of more than 80 years of age compared to bones from women in the seventh decade. The clinical implication of the study is that compression of femoral neck fractures by a sliding-screw-plate system may be hazardous in patients with brittle bone, e.g. women over 80 years of age.