Bore-like waves propagation and impact on a permeable slope over a dry bed: Impact loads, stress distribution, and run-up

The stress variations and stress distributions in stepped-lap adhesive joints of similar adherends under impact tensile loadings were analyzed in elastic range using three-dimensional finite element method (DYNA3D). The impact loadings were applied to the lower adherend by dropping a weight. The stress distributions in stepped-lap adhesive joints of similar adherends under static tensile loadings were also analyzed using FEM (MARC). The effects of Young’s modulus of the adherends, the adhesive thickness, and a number of steps in the adherends on the stress variations and the stress distributions at the interfaces between the adherends and the adhesive were examined under both impact and static loadings. As the results, it was found that (1) the maximum value of the maximum principal stress σ1 occured at the outside edge of the butted interface between the adhesive and the lower adherend to which impact loadings were applied; (2) The maximum value of stress σ1 increased as Young’s modulus of the adherends increased; (3) The maximum value of stress σ1 increased as the adhesive thickness decreased, and it increased at the butted parts of joints as the adhesive thickness decreased. The maximum value of stress σ1 increased at the lapped parts of joints as the adhesive thickness increased; (4) The maximum value of stress σ1 increased as the numbers of steps in the adherends increased. The characteristic of the joints under static loadings were also clarified. In addition, the experiments to measure the strain response of joints subjected to impact tensile loadings were carried out using strain gauges. A fairly good agreement was found between the numerical and the measured results concerning the strain responses.

Experimental studies in a wave basin are described with emphasis on wave impact on jacket platform decks and related structures in the Ekofisk field off Norway. The paper identifies a number of considerations related to the design of scaled physical models to be used in wave tests measuring impact loads. Special procedures for measurement of wave forces as well as techniques used for data analysis, specifically to remove extraneous effects introduced by the model's response to impact loads, are presented. Influence of the large protective barrier on wave crest characteristics around the structure are also provided in the paper. Results and discussion provide information on impact phenomena on various types of offshore structures, apart from the particular one used here. In view of the limited extent of information presently available, present results provide a useful addition to the engineering knowledge of such wave forces, their measurement and analysis. INTRODUCTION The Ekofisk complex, operated by Phillips Petroleum Company Norway, is located approximately 200 kilometers off the Norwegian coast near the UK border. The installation is characterized by a large circular shaped barrier housing a storage and processing facility, Within the near vicinity of this protective barrier are several jacket structures supporting production and accommodation facilities. A number of these jacket References and figures at end of paper. structures have access to the facility behind the protective barrier by means of connecting bridges. The primary concern with the Ekofisk field is subsidence. Since the mid-80's when this problem was discovered, the operators have taken various steps to ensure the continued safe operation of the complex, including raising a number of decks on jackets and installing the protective barrier around the storage and processing facility as it presently exists. However, subsidence is continuing and is consequently increasinghe effective water depth within the field beyond the design water depth, This raises concerns about waves vertopping the protective barrier wall, causing damage to the facility inside and impacting on the decks of the nearby structures. Therefore a requirement to investigate the probability of such an occurrence, as well as to quantify the resulting impact loads on various components of the installation, has been presented. A model study was commissioned at the Institute forMarine Dynamics in St. John's, Newfoundland by Phillips Petroleum Company Norway to measure and analyze wave impact loads resulting from predicted extreme wave conditions on various components of the Ekofisk facility. The model study involved design, construction and testing of 1:36 scale models of the protective barrier, 2/4 R jacket, connecting bridges and the 2/4 B jacket. Measurements included global and impact loads, water run up on the barrier wall and crest elevations in the surrounding field. The study generated a considerable amount of data, most of which is unique to the Ekofisk condition and is impractical to report here. However, the experimental techniques used to measure and interpret wave impact loads on the deck structures can be of widespread interest. These measured impact loads included resonant effects from the models.

Fracture behaviors of three-dimensional braided composites could be designed from braided preform structures. Here, we compare the fracture behaviors of three-dimensional four direction (3D4d) and five directional (3D5d) braided composites under impact loading. A drop weight impact tester combined with a high-speed photography system was employed to characterize the progressive damages and fracture behaviors, which include crack growth and crack mouth opening displacement. The two-dimensional digital image correlation method was utilized for evaluating deformation contours and strain field. A finite element analyses model was established to reveal impact damage evolution, crack growth, stress distribution, and energy absorption at microstructure level. We found that axial yarns had great effect on the crack propagation paths. The stress at the notch bottom caused yarn breakage and then resulted in a sharply growing crack. The axial yarns in the 3D5d braided composites impede the progress of cracks under transverse impact. The 3D5d braided composites have smaller crack mouth opening displacement than that of the 3D4d composites. The braided preform is the main energy absorption component. With the same volume fraction, axial yarns exhibit the highest energy absorption. Due to the existence of axial yarns, the resistance to the fracture and crack growth of the 3D5d braided composites is better than the 3D4d braided composites.

Local and global loadings, which may cause the local damage and/or global failure and collapse of offshore structures and ships, are experimentally investigated in this study. The research question is how the elasticity of the structural section affects loading during severe environmental conditions. Two different experiments were undertaken in this study to try to answer this question: (i) vertical slamming impacts of a square flat plate, which represents a plate section of the bottom or bow of a ship structure, onto water surface with zero degree deadrise angle; (ii) wave impacts on a truncated vertical wall in water, where the wall represents a plate section of a hull. The plate and wall are constructed such that they can be either rigid or elastic by virtue of a specially designed spring system. The experiments were carried out in the University of Plymouth’s COAST Laboratory. For the cases considered here, elasticity of the impact plate and/or wall has an effect on the slamming and wave impact loads. Here the slamming impact loads (both pressure and force) were considerably reduced for the elastic plate compared to the rigid one, though only at high impact velocities. The total impact force on the elastic wall was found to reduce for the high aeration, flip-through and slightly breaking wave impacts. However, the impact pressure decreased on the elastic wall only under flip-through wave impact. Due to the elasticity of the plates, the impulse of the first positive phase of pressure and force decreases significantly for the vertical slamming impact tests. This significant effect of hydroelasticity is also found for the total force impulse on the vertical wall under wave impacts.Graphic abstractHydroelasticity effects on water-structure impacts: a impact pressures on dropped plates; b impact forces on dropped plates; c, d, e, f wave impact pressures on the vertical walls; g wave impact forces on the vertical walls; h wave force impulses on the vertical walls: elastic wall 1 vs. rigid wall (filled markers); elastic wall 2 vs. rigid wall (empty markers)

This paper reports an investigation on the relationship between the stress propagation and the span ratio of a sandwich beam of a hybrid composite under impact load. The stress distribution in the impact bending process is very complicated when the hybrid construction has a different mechanical impedance.Experimentally, the impact test was carried out with a three points bending method by using a falling elastic bar. The transient strain in the loading elastic bar and the dynamic flexural strain of the specimen at the backface against the impact point were measured.The results obtained show that the initial strain of the bar depends on the material charcteristics of the beam member of the impact side, and is not affected by those of the backface.In the case of a large span ratio, the value of the initial stress does not depend on the ratio and is always maximum during initial process. On the contrary, the maximum value of stress wave does not coincide with the initial one in the case of a small span ratio. The value of maximum stress depends on the modules of elasticity of the surface member laminated at the impact side. Therefore, the value of impact stress depends largely on the characteristics of the loading surface member, and it increases with increasing modules of elasticity.The deformation mode of the sandwich beam after a long time period has no connection with high frequency stress waves at the impact loading point. The impact load acts as a distributed load against the lower lamina. As the span length becomes smaller and the characteristics of the face member laminated at the impact side becomes harder, the strain produced at the backface against the impact point becomes smaller. In an extreme case an inverse bending strain is produced.

In this work, a finite element model of Ball Grid Array (BGA) package is established to predict the solder joint failure under the high-G drop impact test. To be deemed acceptable, the electronic packaging has to sustain the peak acceleration generated during the high-G drop impact test. Unlike the electronic devices intended for mass consumption, the electronic products designed specifically for military and aerospace industry must be capable of operating in very harsh environments, often involving high impact loading. Thus, the packaging encasing those electronic products must exhibit sufficient impact resistance. This has motivated the present study, comprising of finite element modeling and experimental testing. The proposed finite element model is used to simulate the stress distribution of electronic packaging during high-G impact loading. The simulation model is built using ANSYS LS-DYNA, which is also used to analyze the stress values recorded for the electronic packaging. The model not only simulates the high-G impact loading conditions, but also generates the resulting stress distribution. Its reliability is subsequently tested by comparing its output to the results of a high-G drop impact test. In the experiment, the BGA package failure primarily occurs due to the solder joint fracture, but may also involve copper trace cracking. Thus, the simulation results can be used in practice to reduce the impact loading on the solder joints and lower the probability of failure. Moreover, the thickness of the soft dielectric layer can be increased to absorb a greater amount of the impact force. Most importantly, the stress distribution generated by the proposed model can reveal any further weak points in the electronic packaging.

To quantify the loading due to breaking waves, model tests are currently the option of choice. However, it is suspected that scale effects lead to an overestimation of the prototype loading. As such, a typical question in impact load assessment is how conservative load measurements are. To understand how realistic model testing is in this respect, it is necessary to quantify scale effects in the measured loading due to breaking waves as well as to investigate to which extent entrapped air in the wave and during the wave impact is involved. To do so, the BreaKin Joint Industry Project was started in 2016. The objective of the BreaKin JIP was to get more insight into scale effects involved in wave-in-deck model tests and to take first steps towards linking wave kinematics with measured impact loads. During this JIP wave-in-deck model tests were carried out in MARIN’s Depressurized Wave Basin (DWB) at two scales (25 and 50) in atmospheric and depressurized condition. In previous work, a summary overview of these model test results was presented [1]. The current paper provides more in-depth insights into possible sources of scale effects involved in wave-in-deck type of loading, based on further analysis of the existing model test data. It includes a detailed review of a.o. local loads in correlation to the variability of measured (global) impact loads between repeat measurements.

Pipe elbows are essential connection components between the storage terminal and conveying pipelines in the petrochemical industry, which are prone to rupture and perforation under various potential impact loads. In this paper, the rupture and perforation responses of pressurized pipe elbows subjected to transverse impact loads were systematically investigated. Perforation phenomena of pipe elbows were qualitatively analyzed to identify the failure modes and features. Perforation mechanisms of mode transition, transient deflection, velocity variation, and stress distribution were systematically discussed. Extensive parametric studies were performed to investigate the deflection and mechanical responses. Parametric equations were established to describe the critical impact resistance. These results revealed the perforation phenomena and impact limits of pipe elbows subjected to impact loads, which are informative for protection design and damage assessment of pressurized pipe elbows.

Experimental and numerical investigation of reinforced concrete beams with variable material properties under impact loading

Shear lag is the phenomenon that occurs when a supported slender member undergoes deformation from lateral loading, causing in-plane non-uniform distribution of stresses that results in reducing the member’s minimum strength capacity. This paper investigates the behaviour of shear distribution in steel I-section and box girders when subjected to both static and impact loadings. Three-dimensional finite element analysis models were prepared in Strand7 and validated against experimental results providing a basis for further comparison research into shear lagging effects. A parametric study was conducted comparing the effects of impact loading through certain specified velocities at the midspan of restrained ends. It provided new insights into the distribution of shear lag and prevalence of loading locality when considering unique impact scenarios. Impact loads provided different shear-lag results compared to static loads as the material’s properties absorb energy through deformation and distribution of stress. Furthermore, the study highlights the need for additional investigation into a variety of impact scenarios and possible factors for designers to consider when implementing members in structures.

Mechanical-electric response characteristics of 1–3 connectivity pattern cement-based piezoelectric composite sensors with varying functional phase parameters under impact loading

Low-velocity impact behavior of two-way RC slab strengthening with carbon TRM strips

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.

To enhance the impact resistance of hydraulic columns, a theoretical analysis method was employed to develop a dynamic characteristic analysis model for conventional columns under impact loads. This model facilitated the derivation of key parameters such as equivalent stiffness, maximum retraction amount, and impact duration. A fluid-solid coupling model for the conventional column was constructed using finite element and coupled Eulerian-Lagrangian (CEL) methods. Subsequently, numerical simulation results were compared and analyzed against theoretical predictions. Based on this analysis, an energy-absorbing column was designed, and its fluid-solid coupling model was established to investigate its mechanical response under static and dynamic impact loads.The findings indicate that under a static load of 2000 kN, when superimposed with impact loads of 200 kJ, 400 kJ, and 800 kJ respectively, the peak impact forces on energy-absorbing columns are 89.20%, 91.72%, and 98.42% lower than those on normal columns. The yield displacements of energy-absorbing columns increase by 142.26%, 109.15%, and 108.41% compared to normal columns. Energy absorption in energy-absorbing columns is 152.11%, 171.80%, and 145.18% higher than in normal columns. Furthermore, initial velocities of energy-absorbing columns are consistently lower compared to normal columns. After reaching initial velocity, energy-absorbing columns exhibit reduced oscillations due to interactions between the energy absorber, column, and hydraulic fluid system under impact loads. Unlike normal columns, energy-absorbing columns mitigate stress concentration at the column head through interactions between the energy absorber, emulsion, and column. Additionally, the impact resistance time of energy-absorbing columns is 2.19, 1.64, and 1.85 times longer than that of normal columns.Energy-absorbing columns outperform conventional columns across six metrics: peak impact force, column yield displacement, energy absorption, column movement speed, stress distribution, and impact resistance time, demonstrating superior mechanical properties in impact resistance.

The paper presents the results of experiments at Colorado School of Mines in subjects related to the mechanics of rock failure. A brief review of Fenner's hypothesis of the distribution of stress around circular and elliptical openings is presented and field evidence cited which supports the hypothesis.An impact loading device useful in studies of rock failure is described, and the attitudes of strain lines in a brittle, lacquer‐coated tunnel model as obtained with the impact loading device are compared with the directions and magnitudes of the principal stresses obtained using an interferometer. The distribution of the strain lines is compared with the stress distribution around the opening, and a strain pattern produced by impact loading is compared with one produced by static loading. Results indicate that the apparatus and techniques can be used to determine the direction of principal stress and to compare static and impact loads producing similar strain patterns.