Transverse Frames Research Articles

A numerical procedure for calculating ice-induced fatigue damage for ship hulls in level ice

Ship hulls advancing in level ice are exposed to considerable cyclic ice loadings, which might cause fatigue damage, threatening the structural integrity and endangering the crews’ lives. Ice-induced fatigue problem is of significance to ice-going ships. In this paper, a fatigue analysis for ship structures in level ice is performed based on a dedicated 6-degree-of-freedom (6-DOF) numerical model of ice-ship interaction, founded on a circumferential crack assumption. The numerical procedure considers the time-varying instantaneous waterline and the couplings between ship motions and external forces. The local ice loads used for fatigue assessment can be obtained from numerical simulations, and the random load peaks are represented by Weibull distribution. A case study of fatigue calculation for designated transverse frames is carried out, of which the applied stress is converted from ice loads by means of structural beam theory. Eventually, according to a proper S-N curve, the fatigue damages are evaluated on the basis of Palmgren–Miner rule, respectively under the operational scenarios of laterally symmetrical and asymmetrical initial ice edges.

3D printing of beams with the possibility of transverse reinforcement, considering the peculiarities of the construction printer

3D printing of load-bearing structuresis creating rapid changes in the construction industry. New opportunities for building complex architectural forms are emerging, and the speed and quality of work is accelerating. But don't forget about the production specifics of this latest technology. An important detail that many people forget about is that 3D printing with concrete or mortar requires the use of some kind of reinforcement, and there are still nostandards for solving this issue. This is ensured by the use of construction 3D printers, which allow for complex operations both at industrial factories and directly at the construction site. However, despite all the advantages of this technology, there are also a number of challenges due to insufficient optimisation of new systems. The required stiffness of the structures is not achieved due to the absence of a spatial reinforcement structure, which should be provided by vertical reinforcement ties (transverse reinforcement). The article presents a solution to the problem of transverse reinforcement in 3D printing of load-bearing beams, proposed and performed by the authors. To implement the task, design drawings of test beam structures were developed. The article presents the design of the beams and the sequence of their production by 3D printing. The beams were manufactured, according to the sequence of work developed by the authors of the article, by the Ukrainian company 3D TECHNOLOGY UTU LLC. The work resulted in the development of a technology for manufacturing beams with the possibility of reinforcingthem with a vertical welded cage in the design position. To determine the physical and mechanical characteristics of the materials, samples of cubes andprisms, as well as reinforcement, were made. The proposed technology of printing beams using a construction 3D printer made it possible to producestructures that meet the previously developed design and technological solutions and made it possible toplace transverse frames in the design position, which allows the structure to take not only bending moments but also transverse forces.

Structural Analysis of Deck Reinforcement on Composite Yacht for Crane Installation

The crane installation on the deck of a yacht redistributes the stress field and affects the local structural integrity and performance. The safe operation of the yacht is associated with the optimal placement of the crane on the deck and the proper local structural reinforcement. Here, the structural analysis of the bow part of a yacht made of composite materials is studied, considering the retrofit installation of a crane, in three different cases of reinforcing the deck: (a) without any reinforcement, (b) with a T-type reinforcement, and finally, (c) with a longitudinal beam. The T-type connects the longitudinal bulkhead and the deck, reinforced locally with overlamination skin and adhesive-filler. The longitudinal beam works as a local longitudinal stiffener attached to the deck and connects the second, third, and fourth transverse frames. The structural analysis is performed using the finite element method following the classification societies’ rules. The local reinforcements are made from the same composite materials as the unreinforced deck. The maximum deformations, the principal stresses, and the safety factors following Tsai-Wu and Hashin criteria are calculated and compared for the three different cases. The T-type and longitudinal reinforcements reduce deck stresses by 33%, with longitudinal reinforcement reducing deck deformation by 17%. Composite failure analysis shows the structure was near failure, and the reinforcements enhance safety; T-type is better for multiaxial loads (Tsai-Wu), and longitudinal is superior for micromechanical failure (Hashin). By considering the structural performance and safety aspects, designers and engineers can make optimal decisions regarding yacht crane installation and proper reinforcement, leading to safer and more efficient structures.

Progressive Collapse of Typical and Atypical Reinforced Concrete Framed Buildings

This paper investigates the progressive collapse potential of eight-story reinforced concrete framed buildings with several atypical structural configurations and compares results with a typical structural configuration. The alternative load path mechanism, the linear-static analysis procedure amplified by dynamic increase factors, and the demand capacity ratio criterion limits from the U.S. General Services Administration guideline were used to evaluate the vulnerability of the different atypical and typical framed structures. Variations in bay size, plan irregularity, and closely spaced columns were used to represent the atypical structural configurations. The extracted demand-capacity ratio (DCR) of the global structural response showed that the demand-capacity ratio for the longitudinal frame with short-span beams had a larger DCR than the transverse frame with longer beam spans with significant potential for progressive collapse. Furthermore, atypical building configurations with closely spaced columns failed by shear and showed the highest DCR limits. In addition to the global structural response, the local member end actions were also evaluated. The evaluation showed that the critical atypical frame configuration with closely spaced columns had a 91% and 127% maximum shear force and support bending moment value difference, respectively, when compared to a baseline typical frame configuration.

Automatic Diagnosis of Carotid Atherosclerosis Using a Portable Freehand 3-D Ultrasound Imaging System.

The objective of this study is to develop a deep-learning-based detection and diagnosis technique for carotid atherosclerosis (CA) using a portable freehand 3-D ultrasound (US) imaging system. A total of 127 3-D carotid artery scans were acquired using a portable 3-D US system, which consisted of a handheld US scanner and an electromagnetic (EM) tracking system. A U-Net segmentation network was first applied to extract the carotid artery on 2-D transverse frame, and then, a novel 3-D reconstruction algorithm using fast dot projection (FDP) method with position regularization was proposed to reconstruct the carotid artery volume. Furthermore, a convolutional neural network (CNN) was used to classify healthy and diseased cases qualitatively. Three-dimensional volume analysis methods, including longitudinal image acquisition and stenosis grade measurement, were developed to obtain the clinical metrics quantitatively. The proposed system achieved a sensitivity of 0.71, a specificity of 0.85, and an accuracy of 0.80 for diagnosis of CA. The automatically measured stenosis grade illustrated a good correlation ( r = 0.76) with the experienced expert measurement. The developed technique based on 3-D US imaging can be applied to the automatic diagnosis of CA. The proposed deep-learning-based technique was specially designed for a portable 3-D freehand US system, which can provide a more convenient CA examination and decrease the dependence on the clinician's experience.

Determination of stress state and deformations that can appear in tranversal frames of a 48309 dwt bulk carrier

The main objective of this study case is to analyze the response in terms of stress and deformation of transversal frames of a bulk carrier that occur due to the applied loads. This assessment helps ensure the safety of the vessel in terms of structural strength and resistance and to determine the best solutions to apply in unfavorable scenarios. The analysis will be performed on a cargo tank, for three static stress cases, the vessel being placed on still water, on sagging and hogging.

A Study on the Movement Characteristics of Fuel in the Fuel Tank during the Maneuvering Process

To investigate the movement characteristics of fuel within an aircraft’s fuel tank during maneuvering, this study employs numerical simulations using the Finite Pointset Method (FPM) with specific boundary conditions and excitation. The simulation results successfully capture the complex phenomena of fuel free surface fluctuations, surging, rolling, and breaking, along with the corresponding changes in the center of gravity induced by fuel movement. Throughout the aircraft’s maneuvering process, the longitudinal center of gravity experiences minimal variations, whereas the aerodynamic center of gravity exhibits significant fluctuations, reaching a range of 0.47 m. The longitudinal center of gravity consistently shifts backward with a displacement of 0.41 m. The maximum height attained by the liquid’s free surface during aircraft maneuvering measures approximately 0.22 m, reaching the upper panel’s height of the wing fuel tank, resulting in a certain level of impact on the upper panel. The maximum impact force generated during the aircraft maneuvering process amounts to 2.3 × 105 pascals, with the point of action located at the junction of the transverse frame and the upper panel. The findings of this work provide support for the safe design of aircraft fuel tank systems.

Comparison of efficiency for steel and combined frames

Recently, in the practice of design, customers of design works and investors of various projects have a dilemma regarding the choice of building material for load-bearing building structures. At the same time, the choice is usually limited to two types of materials – steel and reinforced concrete. Each of these materials has its advantages and disadvantages, which results in their different efficiency of application for various types of building structures. At the same time, the main attention is paid to the estimation side, because in modern complex and dynamic conditions, it turns out to be dominant in many cases. 
 The article presents the results of research of the completed master's thesis on the comparative analysis of the effectiveness of steel and combined frames (steel-reinforced concrete) on the example of the filter station building. The building has dimensions in plan of 54 × 36 m with a total height of about 22 m. Its supporting frame is a statically nondefined flat frame consisting of columns and crossbars in the form of trusses. In the longitudinal direction of the building, the frames are united into a spatial system by means of covering structures. The building is craneless and has three floors, each about 6.5 m high. 
 In the course of research, the considered variants of the transverse frame were analyzed using the finite element method on the basis of the LIRA-CAD multifunctional design complex. As a result, appropriate cross-sections for loads according to the climatic conditions of Ukraine were obtained. A comparison of variants showed that the first design variant is 9 % cheaper. Taking into account the additional technological advantages in its manufacture, the steel frame can be considered more effective for the given construction conditions and be recommended for practical implementation. Separately, it should be noted that such a frame also has an average of 5 times less total mass, which should be considered its additional advantage.

A Polar Integrated Alignment Assisted by DVL Under Large Azimuth Misalignment

The gravity tends to coincide with the earth’s rotation vector in the polar region, degrading the coarse alignment azimuth of the strapdown inertial navigation system (SINS) to a large misalignment. Under a large azimuth misalignment, the linear error model inevitably renders unacceptable theoretical errors in the integrated alignment. In addition, polar region challenge such sensors as a star sensor of celestial navigation, which fails to provide high-precision attitude reference for integrated alignment. Therefore, in allusion to the misalignment mentioned above based on SINS for the polar region, an integrated alignment algorithm is proposed, assisted by the Doppler Velocity Log (DVL). Notably, the work first investigates the extent to which azimuth accuracy deteriorates in the polar region. On the premise of large azimuth misalignment, the nonlinear error model under the transverse frame is derived from the ellipsoid earth model. Additionally, the state and measurement models are constructed, combined with the velocity of DVL as an observation. An adaptive measurement variance matrix is designed for the unscented Kalman filter (UKF) to estimate the attitude error. Eventually, the semi-physical experiments demonstrate that the proposed algorithm significantly improves the initial alignment accuracy of the polar region.

Assessment and Rehabilitation Solutions for an Industrial Hall Affected by Extreme Actions

The original structure of the industrial hall consisted of longitudinal reinforced concrete frames with columns and beams and 133 timber roof trusses (33.5 m span each), which were supported on longitudinal beams. Owing to the extreme action of snow, many trusses in the timber roof crashed down and fell onto the auxiliary structure. This led to the occurrence of a 200 mm distance between two elements in the bottom flange connection area, a 150 mm displacement in the upper part of the reinforced concrete (RC) columns, and many transversal cracks. The main causes that led to the collapse of the timber roof trusses were the high level of stress applied on the structure by snow loads in December 2018, as compared with the provisions of the Romanian code, the fact that the structure was designed for a rigid transversal frame instead of a deformable structure, and the insufficient dimensions of the cleats used on the bottom flange. The rehabilitation solution chosen consisted in lifting the timber roof trusses, after their crashing down, to near their initial level. The degraded structure was strengthened by: (1) consolidating each timber roof truss using a steel tension rod at the bottom flange of the truss, with the timber truss anchored at both ends by being inclined and perforated; and (2) for the RC columns, the strengthening solution was based on carbon fiber reinforced polymer (CFRP) lamellas and wraps.

Analysis on the causes of cracking and excessive deflection of long span box girder bridges based on space frame lattice models

Long-span prestressed concrete box girder bridges (continuous girder and rigid frame bridges) tend to have some apparent diseases. On the one hand, cracks in various directions appear in different positions of different slabs of the box girder; on the other hand, the deflection of the structure develops for a long time, which significantly exceeds the design expectation eventually. This paper intends to use the space frame lattice model, combined with the complete stress index system, to analyze the causes of cracks in different forms in an actual bridge. Unlike the single beam model and the transverse frame model under the guidance of the existing code system, the space frame lattice model that discretizes an entire box girder section into individual slabs can more precisely simulate the load that exceeds the code but exists. In addition, the complete stress index system enriches the design of box girder bridges and can well explain the cracking causes of old bridges. This paper also discusses the effect of the difference in creep and shrinkage caused by the difference in thickness among slabs on the deflection.

Three-Dimensional Fracture Analysis of Large Opening Box Girder With Crack Damage Under Bending and Torsion Loads

Abstract This work aims to investigate the complex fracture behavior of a large opening box girder (LOBG) using three-dimensional (3D) finite element method (FEM). A numerical model is developed to simulate the fracture of LOBG under individually or jointly applied torsion and bending loads. The crack damage is introduced into the side plate and bottom plate of LOBG. The influencing factors such as crack angles, crack locations, and load types are emphatically discussed. Additionally, the crack growth angles are also predicted during the analysis. The results present that the large opening can generate significant effects on the crack growth of the side plate crack (SPC) and the bottom plate crack (BPC). Under the condition of torsion or hogging, SPC grows more easily than BPC, while BPC is relatively prone to grow under sagging condition. Compared with the torsion condition, the initial crack angle can significantly reduce the stress intensity factor (SIF) under the bending condition. Furthermore, the cracks that gradually approach transverse frames are also more likely to induce mode I fracture under torsion conditions. These findings from the present study can reveal insights for a better understanding of fracture behavior for LOBG.

Experimental study on the damage characteristic and assessment of transverse bent frame of high-piled wharf under impact load

Several studies have demonstrated that ship collision is the key reason that leads to the damage of the wharf. In order to examine the damage characteristics and assessment method of the bent frame under the impact load, a model test with four conditions is conducted in this paper. The experimental results highlight that: (1) The damage of the bent frame promotes the characteristics of three stages: micro-damage appearance, crack development, crack penetration; (2) The aggravation of the overall damage of the bent frame results in an increase in the frequency and damping ratio of the structure, but they are not sensitive to low damage; (3) The efficiency of converting kinetic energy into structural deformation energy increases with higher impact energy; (4) Damage degree is a discriminating index of the bent frame performance can represent the current health status of the structure.

Effect of local cut-out on fatigue strength assessment in ship structures

The aim of the work is to evaluate different design alternatives to obtain criteria for the selection of the most effective design by fatigue strength assessment of the local cut-out as a result of the connection between the longitudinal or ordinary stiffener and the transverse web frame (longi-web) in the side hull structure (upper wing torsional box), very important area due to its high stress concentration, of a container vessel, one of the most important ships in terms of its influence on the world economy. Structural solutions and design guidelines are established, by means of numerical models validated by experimental tests, which allow alternative designs to be obtained that improve their fatigue behaviour. Standard cut-out geometries are studied under the presence of different variables (radius of curvature, longitudinal spacing, longitudinal stiffener cross-section, and flange arrangement) that are evaluated to determine their effect in the structural assessment (fatigue damage, stress concentration, and fracture mechanics) and the weight comparison between alternatives.

The fatigue enhancement of Gade valley viaduct box girders due to distortional effects

In this paper, a case study is examined in which a bridge structure with fatigue critical details was successfully managed and remediated without extensive traffic closures. Severe theoretical fatigue life shortfalls have been identified at the transverse stiffener frames of the box girder due to distortional effects in the steel box. Gade valley viaduct was the final link in the M25 London orbital motorway, constructed in 1986 at Kings Langley, UK. It is a composite box girder viaduct 440 m long with typical spans of 42 m and carries 180 000 vehicles daily. A series of cracks and original sub-standard weld quality issues were discovered in the transverse stiffener frames of the box girder. The fatigue shortfall that was a significant contributor to the identified fatigue cracking was confirmed by assessment and strain-gauge monitoring. A fatigue enhancement bracing system was deployed at all spans and boxes to provide a full 120 year fatigue life. The use of off-structure testing in a mock-up girder before the application on the live structure was a key feature of this project, where several lessons were learned from weld trials. This case study illustrates how heavily used structures with theoretical fatigue life shortfalls can be successfully rehabilitated to ensure safety.

Seismic Performance Assessment of the Historical Reggio Calabria Cathedral

Background: Italy's church buildings' cultural and architectural significance cannot be overstated. Objective: This paper addresses the seismic vulnerability of the cathedral located in Reggio Calabria, Italy. The analysis of this building is interesting as it was retrofitted after the destructive 1908 Messina-Reggio Calabria earthquake. Methods: The original design illustrating the static schemes and the considered actions of the church are described. Structural drawings of that time are also reported, which proved to be fundamental for the numerical modelling of the building. The issues and assumptions made during the modelling phase of the structure with the seismic actions are also illustrated. All the transverse and longitudinal frames were analysed using nonlinear analysis to evaluate the seismic capacity and vulnerability indicators in terms of accelerations and periods. Results: The results provided by the modal analysis are presented and discussed to highlight the global dynamic behaviour of the church. Conclusion: The seismic vulnerability indicators have been calculated by considering the seismic actions recommended by the current technical standards and concerning the 1975 Messina earthquake, which represents the most severe earthquake experienced by the church.

Fire resistance evaluation for a steel hall transverse frame depending on the simplification degree of the computational model applied

Fire resistance evaluation for a steel hall transverse frame depending on the simplification degree of the computational model applied

A fast simulation tool for ship grounding damage analysis

This paper presents a numerical tool based on analytical formulations for rapid assessment of damage in ship grounding accidents. Through a step-by-step solution, the ship resistant force is assessed by the super-element method and transferred to a 6-DoF external dynamics solver, which updates the global ship motion by taking into account the action of hydrodynamic forces. The two-way coupled solver is first confronted to finite element simulations considering a 34-kTons cruise ship in bottom and side grounding situations. It is then used to simulate thousands of scenarios, varying the rock shape, the ship impact location, initial penetration and velocity as well as rock/hull friction coefficient. In this way, the influence of ship structural properties (shell thickness, material grade, etc.) on the breach size is investigated. The highest breach reductions are obtained by increasing either the outer shell thickness or the material grade, while acting on transverse frames marginally affects the damage extent. It also appears that a bottom impact is systematically more damaging than a side impact, all else being equal. Likewise, a structural reinforcement is demonstrated to be more efficient in bottom grounding than in side grounding. This is because in side grounding situation, the ship is pushed away by rock and thus undergoes significant sway, yaw and sometimes roll motions that limit the damage extent. Finally, friction is shown to be of primary importance in bottom grounding, while its effect is rather limited in side grounding.

Effect of the Torsion Box Dimensions on Local Stress Distribution and Fatigue Strength Assessment of a Container Ship

The aim of this paper is to estimate the influence of the dimensions of the torsion box (height and width), of a 2400 TEU feeder-class container ship, on local stress distribution and assessment of local fatigue strength by using a numerical approach based on the fatigue limit-state and ultimate limit-state in the midship region. In terms of the fatigue limit-state, the effect of the dimensions of the torsion box is obtained by geometrical modifications, in the connection between the side shell longitudinal stiffeners with the transverse web frame for nine structural details, referring to different arrangements of strengthening elements (brackets and flat bars). The process of comparing the different elements determines the most effective combination. This structural influence on the local stress distribution is assessed, along the longitudinal plates between ordinary stiffeners bounding the perimeter of the torsion box, by calculating the hull girder stresses, local buckling stresses and shear stress distribution induced by vertical and horizontal shear forces, Saint Venant and warping torques, and finally the shear stresses induced by a warping moment. Scantling criteria are obtained allowing for a better design of this very important region in container ships.

Study on seismic performance of transverse frame of prefabricated elevated subway station

This paper presents an assembly scheme of double bridge column-elevated subway stations. The scheme can help to realize the assembly construction of urban elevated subway stations. A 1/6-scaled precast assembly transverse frame of elevated subway station was designed and fabricated to verify the scheme. The pseudo-static loading test was performed to investigate the bearing capacity, failure mode and hysteretic behavior of the precast assembly transverse frame. Test results showed no joint connection failure occurred during the test, and the test specimen had good ductility, indicating that the assembly scheme proposed in this paper was feasible. Finally, the finite element model was established by calling PQ-Fiber subroutine developed by Tsinghua University with ABAQUS to study the seismic performance of test specimen. And numerical simulation results were in good agreement with test results.