Strength Design Criteria Research Articles

Structural design optimization and vibration assessment of a base frame for a 3 MW turbo compressor

This study focuses on the design and analysis of a base frame for a 3 MW turbo compressor, aiming to develop a robust and reliable structural framework. The design process included comprehensive simulations, incorporating static stress-strain and dynamic vibration analyses to assess the base frame’ performance under operational conditions. The static analysis evaluated the total deformation and strain behavior of the base frame, ensuring it can withstand the maximum load without yielding or excessive deformation. Dynamic vibration analysis was performed to identify the natural frequencies and potential resonance issues, minimizing the risk of vibrations that could compromise operational stability. Results from the static analysis revealed that the initial design exhibited a maximum total deformation of 0.24 mm, which was reduced to 0.09 mm in the final design—a 62.5% improvement. Elastic strain values were within safe operational limits for both designs. The effective mass ratio analysis showed significant results at frequencies close to 0 Hz, with negligible impact across the operating frequency range. Based on these analyses, an optimized base frame model was developed, meeting the design criteria for mechanical strength and vibrational stability. The results highlight the importance of integrating deformation, strain, and vibration assessments in the structural design of heavy-duty turbo compressor base frame, contributing to enhanced durability and performance.

A Simplified Approach to Determine Shear Strength for Corroded RC Beams

Corrosion damage, which can be considered as a construction or usage defect during the life of the structure, is an important parameter for the structural elements. Strength loss is observed in reinforced concrete (RC) elements due to corrosion, which is an important parameter affecting the performance of the building. Determining the shear strength of beams with corroded reinforcement is important in terms of strength loss, design, and reinforcement criteria in the structural element. In this context, the data of the corroded RC beam experimental tests carried out in the literature were collected and the ultimate shear strength values of the beams were determined depending on the test parameters. Strength estimation was performed with machine learning regression algorithms XGBoost and AdaBoost. The results obtained were evaluated with R2, RMSE and MAE performance metrics and high estimation success was achieved. The study shows that with these systems, which can perform learning based on experimental data, it is possible to estimate the shear strength values of corroded beams with known production parameters without the need for experimental measurements.

Improving aerodynamic response of tall buildings using smart morphing facades

Slender buildings are prone to vortex-induced vibrations and turbulence-induced buffeting. Usually, vortex-induced vibrations govern the strength and serviceability design criteria. The building's shape determines the aerodynamics of it; therefore, optimizing building shape can greatly reduce wind-induced vibrations. With a growing industry in adaptive and double-skin facades—mainly for energy saving purposes—there is an opportunity to innovate and implement smart, morphing facade modules (which we refer as Smorphacades) that actively modify their aerodynamic shape to alleviate flow-induced vibrations during high winds. This paper evaluates the performance of a 44-story tall building with the different configurations of the developed Smorphacade module system in mitigating building vibrations. Dynamic nonlinear time history analysis of the building under varying wind speeds ranging between 35 and 75 m/s are performed to evaluate the performance of building equipped with Smorphacade at low and high wind speeds. The performance measures chosen in the study are displacements and accelerations. Structural responses of building equipped with Smorphacade are compared against the bare building model responses to evaluate improvements in performance. Acceleration response comparisons at lower wind speeds provide insights into Smorphacade contributions to improving occupant comfort. Displacement comparisons at high wind speeds help understand the improvements in overall structural performance by reducing nonlinear response.

Similar simulation of overburden movement characteristics under paste filling mining conditions

The method of filling mining can solve the problem of surface subsidence caused by coal mining. Among them, it is crucial to study the mechanism of filler strength improvement timeliness and filler mining to control rock movement for filler mining. In this paper, by combining theoretical analysis and similar simulation experiments, compressive strength is used as the research parameter to conduct proportioning test research on paste filling similar materials such as coal gangue, fly ash, and cement. The results prove that the strengths of the test ratios can meet the strength design criteria and lay the foundation for the requirements of similar simulation experiments. In order to study the characteristics of overburden failure, stress and displacement in the process of filling mining, the key technical parameters of overburden movement are determined. Similar simulation experiments were conducted to study the movement and deformation of overburden rock and the displacement and stress distribution law of overburden rock in the coal mine under different filling rates and filling steps conditions. The results show that the filling rate and filling step are the keys to preventing the overlying rock from rupture and collapse, and the larger the filling rate is, the smaller the stress and displacement of the overburden; the larger the filling step is, the larger the displacement and stress change of the overburden, and vice versa. In addition, the displacement curve along the strike is basically an "arch" type distribution, and the stress variation trend is "large-small-large" with a "Z" type distribution. The research results are of great significance to guide the practice of filling mining and can provide the theoretical basis for its further promotion.

Optimization of steel-reinforced wooden purlins

A new structural typology of a Steel-Reinforced Wooden (SRW) purlin made of rectangular laminated wood and C-section type cold-formed steel is presented in this article. The steel C-section profile is fitted onto the wooden purlin so that both work together as a composite unit. Although the wooden sections are weaker and have a lower elastic modulus than the steel sections, the overall dimensions of the SRW purlins are no larger than the steel C-section purlin sizes. The SRW purlins also form lighter structures than either plain steel or wooden purlins and they therefore have lower CO2 emissions. In addition, lighter purlins reduce the load on the main structure, which in turn reduces the material needed for the main structure of the building. So, reinforcement of the wooden purlin with steel sections within certain areas notably improved performance when compared with ordinary single-material purlins. The use of the SRW purlins can, therefore, improve the overall sustainability of a building. The improvements were analyzed in terms of sustainability and lower weight, as a function of span length and design load. The behaviors of the single material purlins and the SRW purlin were also compared. Both material strength and deformation design criteria and their influence were studied using an analytical approach based on loading and span length. The simple, innovative, and reliable design procedure described in this study ensured compliance with all technical requirements. Moreover, the savings relating to material weight were evaluated, neutralizing the carbon footprint in all cases under analysis.

Determination method of fatigue strength of cement-stabilized Macadam under three-dimensional stress state using equivalent stress as index

The cement-stabilized macadam (CSM) material is in a three-dimensional (3D) complex stress state in the pavement structure. It is difficult for the conventional test method to characterize the 3D fatigue strength characteristics of the CSM. In order to establish a 3D fatigue strength design criterion through simple strength methods, this work conducted the conventional unconfined compressive (UC), direct tensile (DT), and indirect tensile (IT) tests. The corresponding 3D strength model, including three parameters, was determined based on three strength testing methods. In addition, a normalized fatigue model including one parameter was obtained by three fatigue tests. Finally, the fatigue strength model under a 3D stress state was established by combining fatigue and the 3D strength model. The results indicate that the 3D strength model effectively characterized the CSM strength under any stress state, and the difference between the IT strengths predicted by the 3D strength model and obtained by the test is 18.43%. Moreover, the fatigue normalization model reflected the 3D fatigue failure of CSM in a complex stress state. The proposed fatigue strength of CSM based on the equivalent stress has clear physical meaning. This work provided a practical technology to obtain 3D fatigue strength resistance of CSM, which solved the technical problem of inaccurate measurement of pavement structure resistance.

Durability-Aimed Design Criteria of Cement-Stabilized Loess Subgrade for Railway

The subgrade is the foundation of railway construction, so its strength and stability are very important to ensure the safety and stability of a train. Loess is widely distributed in northwestern China, and it must be stabilized before being used in railway subgrade construction because loess is sensitive to water. Railway subgrade withstands not only the train load but also repeated attacks from the environment and climate because it has to be exposed to natural environment after construction. Therefore, the strength of cement-stabilized loess deteriorates continuously because of the above factors. Taking account of long-term stability, the influences of load on the cement-stabilized loess as well as the strength reduction laws of cement-stabilized loess under wet–dry cycling and freeze–thaw cycling were analyzed in this study. Additionally, the respective reduction coefficients were obtained. Finally, the strength design criteria of cement-stabilized loess subgrade were put forward based on railway subgrade durability by analyzing the obtained reduction coefficients and the critical dynamic strength of railway subgrade.

Risk-based ultimate strength design criteria for very large floating structure

Very large floating structures (VLFSs) are novel offshore structures without direct reliability design criteria available currently. Target reliability, as a critical safety indicator, could be used to evaluate the ultimate strength reliability of VLFSs. Therefore, it is necessary to establish acceptable risk criteria to determine the structural design target reliability of VLFSs and to calculate partial safety factors (PSFs) for use as ultimate strength design criteria. This paper developed a reliability assessment process in order to achieve the ultimate strength design criteria of VLFS. A reasonable target reliability range for VLFS was determined by risk assessment methods and principles considering the structure failure probability and consequences. The longitudinal ultimate strength for the typical sections of VLFS was calculated by applying the simplified progressive failure method. The vertical extreme wave bending moments and their uncertainties for the corresponding typical sections of VLFS were analysed based on wave scatter diagram of the South China Sea. Finally, the ultimate strength reliability was assessed based on the reasonable target reliability range established within this paper. Results have shown that the reasonable target reliability range is found to be applicable for identifying the weak structural components of VLFS and some typical sections of VLFS should be redesigned to satisfy the criteria. This paper can provide a reference for the safe design and compilation of relevant guidelines for VLFS.

Influencing Factors and Prediction Model for the Antierosion Performance of Cement‐Improved Loess Compacted Using Different Compaction Methods

To analyze the antierosion performance of cement‐improved loess (CIL), several influencing factors have been investigated based on two different compaction methods, which include the quasi‐static compaction method (QSCM) and the vertical vibration compaction method (VVCM). Then, a prediction model for the cumulative erosion mass loss (CEML) has been established. The effects of erosion on the strength deterioration of CIL were also studied. The results show that, compared with QSCM, specimens compacted using the VVCM have better antierosion performance. As the cement content and the compaction coefficient are increased by 1%, the antierosion performance is increased by 16% and 6.2%, respectively. The eroding time has a significant effect on the antierosion performance of CIL, and the CEML increases linearly with an increase in the eroding time. The compressive strength of CIL decreases significantly due to erosion, and based on the average deterioration degree of the specimens, the design criteria for strength of CIL are proposed, which can provide reference for the design of CIL.

The influence of hydrogen sulfide on internal pressure strength of carbon steel production casing in the gas well

The production casing strength design of gas well containing hydrogen sulfide is deeply complicated because of corrosion and hydrogen damage increase. In general, API 5C3: 2018 yield strength design criterion is the main standard to calculate casing string strength that satisfies casing materials selection. There are two kinds of production casing materials C110 and P110SS in the experiment, according to API 5C3: 2018 yield strength design criterion combining with fracture toughness measured by NACE TM0177: 2016 method D (Double Cantilever Beam Test) to evaluate casing string internal pressure strength. The relationship between fracture toughness and internal pressure strength is discussed in the room environment, NACE Standard TM0177-2016 Test Solution D and the special sour environment containing hydrogen sulfide with annuals protection solution. The results show that the fracture toughness of production casing string decreases with the severity of harsh environments. Thus, annulus protection fluid has a positive effect on improving the internal pressure strength of the production casing that enhances wellbore integrity performance to resist the sour environment risk. These research results can provide an important reference for strength design and specification optimization of carbon steel production casing in the gas well with hydrogen sulfide.

Strength design of welded high-strength steel beams considering coupled local and global buckling

Abstract High-strength steel (HSS) is gaining increasing use in modern building construction for several reasons, the most notable being that its increased strength can lead to a reduction in self-weight and correspondingly reduced emissions and waste during its manufacture. However, there is little guidance available in design standards when the steel grade exceeds 690 MPa. Such guidance is needed, because the use of thinner plate elements than would normally be encountered in mild steel members leads to an increased importance in local plate buckling participating in the strength limit state, and its interaction with yielding and residual stresses that are germane to HSS members. This paper investigates the buckling strength of welded HSS I-beams numerically, and based on the results of the study it proposes a corresponding strength design criterion that incorporates local buckling and lateral-torsional buckling and their interaction at the ultimate limit state. The finite element model used for the analysis is based on ABAQUS software, and it incorporates the interaction of elastic buckling, yielding, residual stresses induced by welding and geometric imperfections. The numerical formulation is validated against test results reported by several investigators, and it is then used to produce a substantive set of data to investigate the buckling strength of welded HSS beams. It is shown that the buckling strength depends primarily on two parameters: the generalised (or member) slenderness and the section slenderness. It is also demonstrated that coupled modes of failure are possible for slender sections that incorporate the interaction of local and lateral-torsional modes, which traditionally are treated simplistically in current steel design standards by using effective section properties. To overcome the limitations on guidance for the strength design of HSS beams, a set of new strength design equations are proposed from the numerical data, based on the generalised and section slendernesses.

Optimal design of flax fiber reinforced polymer composite as a lightweight component for automobiles from a life cycle assessment perspective

AbstractThe present study combines the generalized rule‐of‐mixture (ROM) model and the Ashby material selection method for the life cycle assessment (LCA) of flax fiber reinforced polymers (FRPs) and glass FRPs (GFRPs). The ROM model allows life cycle environmental impact predictions according to specific parameters of flax FRPs such as fiber format, volume fraction, manufacturing technique, and load‐bearing capacity. The comparisons applied in this study are constructed on two common composite structures: mat panels and injection molded struts with equal stiffness and strength as the design criteria. On the one hand, the parametric LCA predicts that the equal strength design criterion for flax FRPs contributes to consistent mass increases, subsequently resulting in higher life cycle environmental impacts compared to the reference GFRPs; on the other hand, under the equal stiffness criterion the flax mat polypropylene (flax mat‐PP) film helps with mass reduction in reference to the glass mat‐PP composite, leading to the 20–50% life cycle environmental impact reductions for most impact categories. The subsequent evaluation of the influences of the fiber volume fraction on flax FRPs shows different patterns. For the short flax fiber‐PP composite, a steady decrease of the life cycle CO2 emissions can be observed with the increasing fiber volume fraction. However, for the flax mat‐PP composite, depending on the tensile modulus of the flax fiber, the optimal volume fractions of the fiber change from 28 to 32% v/v, whereby the lowest life cycle greenhouse gas (GHG) emissions can be achieved.

Study on strength design criteria due to introduced defects in Inconel 718 fabricated by metal 3D printer

Study on strength design criteria due to introduced defects in Inconel 718 fabricated by metal 3D printer

Structural behaviour of an all-composite road bridge

Fibre reinforced polymer composites have become an integral part of the bridge industry because of their versatility, high strength-to-weight ratio and enhanced durability. The novel idea of an all-composite structural system for road bridges has been proposed for the first time in Poland. The FRP bridge is a simply supported structure with 10.0 m long span and 7.66 m wide deck. The superstructure consists of four U-shaped girders bonded with sandwich deck slab, fabricated by means of a vacuum infusion. The bridge configuration, a finite element model developed for design and the proof test results are described in this paper. The test has shown that an all-composite bridge can meet the relevant strength and deflection design criteria. To develop an understanding of the long-term performance of the FRP bridge, a monitoring scheme utilizing distributed fibre-optic sensors was implemented to assess any changes in the bridge structural behaviour.

19.04: Diagrid: the renaissance of steel structures for tall buildings geometry, design, behavior

ABSTRACTStructural configurations best addressing the traditional requirements of strength and stiffness for tall buildings are the ones employing the tube concept, whose efficiency, however, is strictly related to the involved shear‐resisting mechanism. In this perspective, diagrid structures – the latest mutation of tube structures – show an extraordinary efficiency, related to the adopted geometrical pattern: thanks to the triangle tessellation of the façades, internal axial forces are largely prevalent in the structural members, thus shear lag effects and racking deformations are minimized. Being also adaptable to whatever surface, diagrid is becoming the most used structural solution for tall buildings of complex form. In this paper some specific design issues for diagrid structures are identified, namely: the relative importance of strength and stiffness design criteria, as well as to the need of secondary bracing systems for counteracting the inter‐module flexibility effects. Simplified procedure for dealing with such issues are proposed and design implications are discussed.

Requirements for intermediate ring stiffeners placed below the ideal location on discretely supported shells

Silos in the form of a cylindrical metal shell are commonly supported by a few discrete columns to permit the contained materials to be directly discharged. The discrete supports produce a circumferential non-uniformity in the axial membrane stresses in the silo shell. A combination of a ring beam and an intermediate ring stiffener can be used for large silos to redistribute the stresses from the local support into uniform stresses in the shell. Previous work done by the authors has identified the ideal location and the stiffness and strength requirements for the intermediate ring stiffener placed at this location. In cases where a shell with a large radius rests on a few supports, the ideal location can be quite high and the option of placing the intermediate ring stiffener below the ideal location may provide a viable solution. This paper explores strength and stiffness requirements for intermediate ring stiffeners placed below the ideal location. Pursuant to this goal, the cylindrical shell below the intermediate ring stiffener is analyzed using the membrane theory of shells. The reactions produced by the stiffener on the shell are identified. Furthermore, the displacements imposed by the shell on the intermediate ring stiffener are obtained. These force and displacement boundary conditions are then applied to the intermediate ring stiffener to derive closed form expressions for the variation of the stress resultants around the circumference to obtain a strength design criterion for the stiffener. A stiffness criterion in the form of a simple algebraic expression is then developed by considering the ratio of the circumferential stiffness of the cylindrical shell to that of the intermediate ring stiffener. These analytical studies are then compared with complementary finite element analyses that are used to identify a suitable value for the stiffness ratio for ring stiffeners placed at different locations.

Structural Improvements for Tall Buildings under Wind Loads: Comparative Study

The behavior of a very slender building is investigated under wind loads, to satisfy both strength and serviceability (comfort) design criteria. To evaluate the wind effects, wind tunnel testing and structural analysis were conducted, by two different procedures: (i) Pressure Integration Method (PIM), with finite element modeling, and (ii) High Frequency Force Balance (HFFB) technique. The results from both approaches are compared with those obtained from Eurocode 1 and the Italian design codes, emphasizing the need to further deepen the understanding of problems related to wind actions on such type of structure with high geometrical slenderness. In order to reduce wind induced effects, structural and damping solutions are proposed and discussed in a comparative study. These solutions include (1) height reduction, (2) steel belts, (3) tuned mass damper, (4) viscous dampers, and (5) orientation change. Each solution is studied in detail, along with its advantages and limitations, and the reductions in the design loads and structural displacements and acceleration are quantified. The study shows the potential of damping enhancement in the building to mitigate vibrations and reduce design loads and hence provide an optimal balance among resilience, serviceability, and sustainability requirements.

Strength Criteria Versus Plastic Flow Criteria Used in Pressure Vessel Design and Analysis1

This paper presents a critical comparison of the traditional strength criteria and the modern plastic flow criteria used in the structural design and integrity assessment of pressure vessels. This includes (1) a brief review of the traditional strength criteria used in the ASME Boiler and Pressure Vessel (B&PV) Code, (2) a discussion of the shortcomings of the traditional strength criteria when used to predict the burst pressure of pressure vessels, (3) an analysis of challenges, technical gaps, and basic needs to improve the traditional strength criteria, (4) a comparison of strength theories and plasticity theories for ductile materials, (5) an evaluation of available plastic flow criteria and their drawbacks in prediction of burst pressure of pressure vessels, (6) a description of a newly developed multiaxial yield criterion and its application to pressure vessels, and (7) a demonstration of experimental validation of the new plastic flow criterion when used to predict the burst pressure of thin-wall pressure vessels. Finally, recommendations are made for further study to improve the traditional strength design criteria and to facilitate utilization of the modern plastic flow criteria for pressure vessel design and analysis.

Structure improvement and strength finite element analysis of VHP welded rotor of 700°C USC steam turbine

The optimized structure strength design and finite element analysis method for very high pressure (VHP) rotors of the 700°C ultra-super-critical (USC) steam turbine are presented. The main parameters of steam and the steam thermal parameters of blade stages of VHP welded rotors as well as the start and shutdown curves of the steam turbine are determined. The structure design feature, the mechanical models and the typical position of stress analysis of the VHP welded rotors are introduced. The steady and transient finite element analysis are implemented for steady condition, start and shutdown process, including steady rated condition, 110% rated speed, 120% rated speed, cold start, warm start, hot start, very hot start, sliding-pressure shutdown, normal shutdown and emergency shutdown, to obtain the temperature and stress distribution as well as the stress ratio of the welded rotor. The strength design criteria and strength analysis results of the welded rotor are given. The results show that the strength design of improved structure of the VHP welded rotor of the 700°C USC steam turbine is safe at the steady condition and during the transient start or shutdown process.

Design method of the pinned external integrated buckling-restrained braces with extended core. Part I: theoretical derivation

The contact force distribution between the core member and the external member of a buckling-restrained brace (BRB) is closely related to its deformation mode, and it directly affects the working state of the extended core and external restraining member. This study focuses on a pinned BRB with extended core as a research object and investigates the stress state of a BRB. Based on the specified core deformation modes and contact force distributions, the contact force and the bending moment distribution in the external member are deduced. Lastly, by considering the mechanical characteristics of the external member and extended strengthened core region (ESCR), their strength design criteria are established. In the theoretical derivation of the design method, the influence of some parameters is considered, including the initial geometrical imperfection of the external member, the gap between the core and the external member, the rigidity reduction of the restrained strengthened core region (RSCR), and the change of contact position. Finite element numerical verification of the corresponding theoretical derivation is discussed in detail in another paper as Part II (Jiang et al., 2015).