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Seismic responses of utility tunnel-soil system were studied via shaking table model tests with considerations of two kinds of double box utility tunnels: with and without joint connections. These two testing utility tunnel models were made of galvanized iron wire and micro-concrete, and the ground was simulated by the dry standard sand through layered tamping treatment. The utility tunnel-soil system was subjected to horizontal vibration in uniaxial direction perpendicular to the longitudinal direction of tunnel model. Via instrumentations of earth pressure gauges, accelerometers and strain gauges, the earth pressure response, acceleration response and bending moment response were measured. The testing results show that the joint connections in the utility tunnel along the longitudinal direction play an important role in determining the characteristic of earth pressure response and bending moment response, whereas the effect of joint connections on acceleration response is less significant. In addition, the partition wall exhibits the consistent acceleration response with the side-wall of double box utility tunnel model under seismic condition. Based on the testing results, it is suggested that the joint connection should be taken reasonably into consideration during design and construction for engineering practice.

Buried pipelines are commonly damaged when laid across strike-slip faults, always leading to some level of destruction with fault movement. The moment of the neutral axis of a pipe section was obtained by integration, and the equations for the bending moment and the bending strain on a pipeline’s section were presented here, based on a trilinear stress–strain model. The calculation method for the lateral soil pressure and pipeline’s bending strain near the fault-crossing point was improved. Lateral soil pressure was regarded as being related to lateral pipeline movement and, for accurate calculation, this part of the pipeline was divided into finite element segments. An iterative process for solving for pipe bending strain was derived, and the algorithm and program for calculating bending strain and the potential damage position of the pipeline’s sections was compiled based on Matlab software. Compared with finite element method (FEM) results and the current standard method, in the situation of a pipeline being in tension under the action of a strike-slip fault (intersection angle

Excessive structural forces generated inside tunnel linings could affect the safety and serviceability of tunnels, emphasizing the need to accurately predict the forces acting on tunnel linings during the preliminary design phase. In this study, an anisotropic soil model developed by Norwegian Geotechnical Institute (NGI) based on the Active-Direct shear-Passive concept (NGI-ADP model) was adopted to conduct finite element (FE) analyses. A total of 682 cases were modeled to analyze the effects of five key parameters on twin-tunnel structural forces; these parameters included twin-tunnel arrangements and subsurface soil properties: burial depth H, tunnel center-to-center distance D, soil strength s u A , stiffness ratio G u / s u A , and degree of anisotropy s u P / s u A . The significant factors contributing to the bending moment and thrust force of the linings were the tunnel distance and overlying soil depth, respectively. The degree of anisotropy of the surrounding soil was found to be extremely important in simulating the twin-tunnel construction, and severe design errors could be made if the soil anisotropy is ignored. A cutting-edge application of machine learning in the construction of twin tunnels is presented; multivariate adaptive regression splines and decision tree regressor methods are developed to predict the maximum bending moment within the first tunnel’s linings based on the constructed FE cases. The developed prediction model can enable engineers to estimate the structural response of twin tunnels more accurately in order to meet the specific target reliability indices of projects.

As contemporary aerostructural research for aircraft design trends toward high-fidelity computational methods, aerostructural solutions based on theory are often neglected or forgotten. In fact, in many modern aerostructural wing optimization studies, the elliptic lift distribution is used as a benchmark in place of theoretical aerostructural solutions with more appropriate constraints. In this paper, we review several theoretical aerostructural solutions that could be used as benchmark cases for wing design studies, and we compare them to high-fidelity solutions with similar constraints. Solutions are presented for studies with 1) constraints related to the wing integrated bending moment, 2) constraints related to the wing root bending moment, and 3) structural constraints combined with operational constraints related to either wing stall or wing loading. It is shown that for each set of design constraints, the theoretical optimum lift distribution is consistently in excellent agreement with high-fidelity results. It follows that theoretical optimum lift distributions can often serve as a good benchmark for higher fidelity aerostructural wing optimization methods. Moreover, a review of solutions for the optimum wingspan and corresponding drag reveals important insights into the effects of viscosity, aeroelasticity, and compressibility on the aerodynamic and structural coupling involved in wing design and optimization.

The concrete elements undergo major physical and chemical changes when it gets in contact with high-temperature. The thermal effect will allow concrete elements to lose their strength and other structural parameters. In the case of reinforced concrete structural frame system, when reinforced concrete key elements undergoes thermal changes due to high-temperature, it leads to a major collapse as they are load-carrying elements. So, the key members of reinforced concrete structural frame must be analysed under high-temperature to understand their behaviour. In this study, a single-bay single-storey three-dimensional reinforced concrete prototype frame was analysed under high-temperature conditions using ABAQUS. A comparative study was made from the behaviour of reinforced concrete frame with slab and infill wall under high-temperature condition. The inclusion of slab and infill wall to the structural frame can improve the stiffness and overall structural performance. The major findings such as axial load, deformation, stiffness of the frame, bending moment and shear force can obtained from this analytical study.

Reinforced concrete infilled frame with brick masonry panel is becoming more common in recent days. Now a days this type structural frame is implemented mostly on the high-rise building because those buildings should be able to resist the lateral loads such as wind and seismic force hence, infilled frames are one of the most common lateral loads resisting system. In this study, two-dimensional single-bay, single-storey gabled infilled specimens were analyzed under static loading. The behavior of the reinforced concrete (RC) bare frame, RC infill frame with cement mortar interface is used and analyzed. In particular, the paper discusses the lateral stiffness of the frames and gives a comparative study between gabled frame and rectangular frame under static lateral load with varying parameters based on the obtained results such as displacement, lateral stiffness, bending moment and lateral load are carried out.

Coupled walls with replaceable steel shear link coupling beams are used to minimize the repair cost and downtime of buildings after major earthquakes. In this study, the direct displacement-based design (DDBD) method for coupled walls with steel shear link coupling beams using inelastic displacement spectra is developed. For capacity design, a continuum model of the coupled walls that accounts for the stiffness degradation due to expected damage in the first mode is adopted, to obtain equations to estimate the shear forces and bending moments generated due to higher modes. The effectiveness of the DDBD design method for coupled walls with steel shear link coupling beams is assessed by comparing the drift demands with nonlinear response history analysis (NLRHA) results and for capacity design purposes the shear force and bending moment profiles obtained from NLRHA are compared with the results obtained from the equations derived in this study and the weighted capacity design (WCD) method. The results obtained for 5-, 10-, and 15-story coupled walls with steel shear link coupling beams, show that the proposed design methodology is suitable to achieve the design objectives.

Structures on incline ground are vulnerable to earthquakes because of irregularities in plan and elevation. The structural configurations on slopes have been observed, with stepback and stepback-setback configurations being the most common. In mid to high rise buildings, shear wall and C-shaped shear wall cores are commonly used lateral load resisting components. The current research focuses on comparing the seismic performance of L-shear walls(LSW) at the corners, C shear-walls at core(CSW) and Reinforced concrete-filled steel tube column (RCFST) at corners and cores in stepback, and stepback-setback configurations buildings considering the base of the structures fixed designed for Indian codes using response spectrum analysis. The structural analysis tool ETABS 2017 was used to perform seismic analysis. Buildings on a hill slope with various configurations are studied: bare frame, concrete blockwork infill, LSW full bay at corners, LSW half bay at corners, CSW and RCFST column at corners and core. The characteristic parameters such as base shear, forces in the columns at the ground floor, storey drift, maximum storey displacement, time period, the bending moment in columns at every floor level and storey shear in structures will be determined and analysed for the different structures at the sloping ground. Structures with corner LSW perform better than buildings with centrally located shear walls at the core, whereas LSW at half bay in the corner and RCFST columns at corners and core serve the dual objective of space constraint and improved performance.

Many riveted joints bear the action of out-of-plane bending moments in steel truss bridges. The fatigue resistance of these joints isn’t stipulated in the current design criteria. Ensuring the safety of structures necessitates analysing the fatigue process of such riveted joints. This paper attempts to evaluate the fatigue life of riveted lap joints from the perspective of engineering applications. The study first found through fatigue tests with two types of fatigue details in riveted lap joints: plate surface cracking and rivet hole edge cracking. Then, the fatigue progression is divided into three stages: the microstructure short crack (MSC) stage, the physical short crack (PSC) stage and the long crack stage. The crack propagation model in the short crack stage is established by combining a scanning electron microscope test of the material and an empirical formula. The crack propagation model of the long crack stage is established by the crack propagation test and considering the crack closure effect. Results show that the fatigue life corresponding to the hole edge crack fatigue detail category is shorter than that to the plate surface crack. In each crack propagation stage, the crack propagation life decreases with increasing load and decreasing load ratio RL. For the two fatigue detail categories, the proportion of the long crack stage to the whole fatigue life is small, and the effect of the crack closure on the overall fatigue life is limited; therefore the effect of the load ratio RL on the fatigue life can be ignored.

In the present study, the flexural behavior of concrete-filled steel tube (CFST) beams strengthened by welding round steel at the soffit of the beam has been investigated. First, a total of six specimens were tested under four-point bending load, which includes one reference beam and five retrofitted beams strengthened by welding round steel of different diameters at the soffit of the beams. Then, the corresponding nonlinear finite-element models have been developed and calibrated against the experimental results. By combining indoor experiments and numerical simulations, the bending moment versus mid-span curvature curves, the flexural capacities, flexural stiffness, ductility, vertical deflection curves, strain distribution across the cross-section, and neutral axis offset of the test beams have been systematically analyzed. The results show that the welded round steel at the soffit can improve the flexural bearing capacity and stiffness of the CFST beams significantly. This can be attributed to the CFST beams benefitting from the flexural bearing effect of the round steel and the downward offset of the neutral axis which causes more core concrete to be in compression. Further, the larger the diameter of the round steel, the greater the benefit. Finally, comparisons have been made with the flexural stiffness calculated using the existing design codes, such as AIJ standard, BS5400, Eurocode 4 and AISC specification. The comparisons show that the flexural stiffness of the unstrengthened CFST beam can be predicted by AIJ and BS5400 perfectly, whereas those of the strengthened CFST beams can only be accurately calculated by AISC.

This paper proposes the use of a novel modular joint to overcome the shortcomings of existing aluminium alloy gusset joints. Bearing capacity tests are performed on the bearing capacity of four sets of joints in the early stage, and the force characteristics and failure mechanism of the novel modular joint are summarized. On this basis, this study conducts theoretical research on the design method of this new type of joint. According to the four failure modes that occurred in the experiment, namely, the bending failure of the aluminium alloy beam, the shear failure of the bolt group, the tensile and shear failure of the modular unit, and the local buckling failure of the unit bottom plate, a formula for calculating the ultimate bearing capacity of each component is provided. According to the working mechanism of modular joints, theoretical formulas for the ultimate flexural bearing capacity and initial stiffness of the joints are derived according to the three-part bending moments produced by each component. Based on a power function model, a prediction formula is fitted to the bending moment-rotation curve of the new joint and compared with the measured values of the joint and 22 numerical models. The results show that the average errors of the two sets of theoretical formulas are only 2.85% and 4.5%, fully verifying their validity and reliability. The results provide a theoretical basis for the engineering design and application of this type of joint.

Welded hollow spherical joints (WHSJs) are commonly used joints in reticulated shell structures. The WHSJs in actual projects are always subjected to tension force and moment. The appearance of tension force (TF) may affect the probability distribution of moment capacity for WHSJs with random corrosion. The stochastic FE analyses are conducted in this study to investigate the influence of TF on the probabilistic distribution of bending capacity of WHSJs. This study aims to investigate the influence of TF on bending capacity and construct a probabilistic distribution model of bending capacity considering the influence of TF. The proposed method for predicting probability distribution of reduction factor is also validated. Results show that the method has high accuracy in predicting the probabilistic distribution of bending capacity of WHSJs in complex force state. In addition, the proposed method is convenient for actual applications.

Partially encased composite (PEC) columns are efficient structural elements that offer ease and agility for prefabrication, requiring no molds for casting concrete. The manufacture of these elements involves anchoring the reinforcement to the metallic profile, which is a laborious process. Thus, alternative solutions capable of maintaining the column performance can propel PEC columns, providing more practical construction technics. One of these alternatives is substituting steel rebar with Fiber Reinforced Concrete (FRC), saving time. The benefits of such solutions were already proven with laboratory experiments. Therefore, this study aims to numerically analyze the structural behavior of PEC columns under different load conditions from available experiments based on a calibrated numerical model. The performance of the models was compared using two reinforcement configurations: conventional reinforcement and steel fiber reinforced concrete. Several cases of eccentric axial loads were evaluated, presenting the influence of the eccentricity and the skew angle relative to the major axis of inertia. Finally, simulations were carried out on columns subjected to non-uniform moments along with their height. The models showed a more abrupt rupture when bending around the minor axis of inertia when subjected to a constant moment on the length. Regarding non-uniform moments, the critical situation in all cases investigated occurs when the moment is constant along with the height. Results were favorable to FRC use because the two reinforcement configurations evaluated showed similar behavior in all the conducted analyses; the model of FRC showed higher ductility than the model with conventional reinforcement, mainly due to the confinement provided by fibers. Nevertheless, columns with FRC presented more significant lateral displacements, resulting in slightly lower maximum loads than those shown by columns with conventional reinforcement.

Pretensioned spun high-strength concrete (PHC) piles have been widely used in building foundations in many parts of the world. However, PHC piles are also known to have poor lateral deformation and ductility capacity and hence are not suitable for seismic regions. To improve the horizontal load bearing and deformation capacities, pretensioned centrifugal spun concrete piles with steel strands alone (hereafter referred to as PSC piles) or a combination of steel strands and mild steel deformed rebars (referred to as PSRC piles) have been developed. PSRC piles are expected to benefit on the one hand from steel strands with high deformation capacity, and on the other hand from deformed steel bars with good bond with concrete and hence better control of cracks. This paper presents a comprehensive study on the comparative flexural performance of PSC and PSRC piles. The bending tests of PSC piles and PSRC piles were firstly conducted on six full-scale pile specimens with three different pile diameters, respectively. The flexural performances are evaluated in terms of crack resistance, flexural and deformation capacities, as well as crack distribution. The results show that the cracking bending moment of PSRC piles is similar to that of PSC piles, but the ultimate bending moment is about 55% higher due to the addition of deformed rebars. The general cracking behavior of PSRC piles exhibit remarkable improvement comparing to PSC piles, with an extended crack region, denser distribution of cracks, and much reduced maximum crack width. Following the experimental study, a theoretical method is proposed for the calculation of the flexural strength and flexural stiffness of prestressed concrete piles considering the presence of both steel strands and deformed rebars. Furthermore, a finite element (FE) model has been developed to simulate the flexural performance of the piles. The accuracy of the FE model is validated through comparing with the experimental results, and subsequently parametric analyses are conducted to explore the influences of three parameters, including the prestressing level of the prestressing strands, prestressing strand ratio and deformed steel bar ratio, on the flexural performance of PSRC piles.

This paper assesses a number of direct strength methods (DSM) for thin-walled steel members under combined major axis bending and compression. These methods consist of two ways of calculating the compression – bending moment (P-M) interaction surface (plastic or first yield) of the cross-section, and the following three methods of operating on the P-M surface: using a compound value of the surface; converting a beam-column to an equivalent beam; and converting a beam-column to an equivalent column. The aim of this research is to identify the most consistently accurate and easy to implement DSM equations to calculate the resistance of thin-walled steel beam-column members, by comparison against numerical simulation results, obtained using a validated ABAQUS model. The numerical simulations investigated the effects of changing different design parameters to ensure a sufficient dataset for each failure mode, including section size, member length, flange restraint, load eccentricity and yield strength. Based on an evaluation of the mean and standard deviation of ratios of the calculated resistances to ABAQUS simulation results, it has been found that for global buckling, any of the methods can produce accurate results. For local buckling, the standard deviation values for all the methods are similar, about 0.05. However, when judging the mean values, the best methods are the equivalent beam method using plastic P-M surface, with a mean value of 0.995. For distortional buckling, upon modification of the existing DSM equations for pure bending using the plastic P-M surface, the equivalent beam method gave an average of 0.998 and a standard deviation of 0.102. Overall, the equivalent beam method using the plastic P-M surface is the most consistently accurate method.

This paper describes a simple analytical tool for the calculation of the shear strength of r.c. rectangular members with shear reinforcement and subjected to only truss mechanism. The proposed method considers simplified stress fields and evaluates the shear strength of members subjected to axial force, bending moment and shear force by means of the application of the static theorem of limit analysis. Unlike most of the formulations proposed in codes and in other research studies, the proposed method considers a single physical model to explain the resistance to axial force, bending moment and shear force, and simultaneously satisfies the equilibrium under all the above internal forces. The paper identifies basic points of the N-M-V ultimate domain and reports relations and procedures to calculate the values of the internal forces of these points as well as the internal forces of the points in between. The method is applied to a set of beam and column members and a comparison is drawn between the shear strength resulting from the simplified method and that from a more complex non-linear mathematical program proposed in the past by the same author. Finally, to prove the value of the method and define the field of reliable application, the proposed method is applied to members tested in laboratory by other researchers and characterised by different geometric and mechanical properties. The obtained results are also compared with those deriving from other methods present in the literature.

Even though aluminium latticed domes are widely used as roofing structures in case of very large areas, few researchers have focused their attention on the influence of the structural details on the overall structural behaviour and on the development of models to account for such influence in the design process. Conversely, the most significant part of the research efforts is devoted to steel structures. In particular, the semi-rigidity of joint behaviour can play an essential role in the structural response. In this paper, the behaviour of bolted Aluminium Alloy Gusset (AAG) joints under axial force and bending moment is investigated by developing a mechanical model based on the application of the component method which is currently codified for the analysis of steel connections. The experimental tests available in the technical literature have been analysed to gain insight into the actual behaviour of AAG joints. The proposed mechanical model is presented, leading to the evaluation of both the moment-rotation curve and the axial force versus axial displacement curve of AAG joints. Finally, the analytical results obtained from the mechanical model herein proposed have been compared with the experimental results showing the accuracy of the component method also for the modelling of non-conventional connections such as those used in the case of aluminium alloy latticed domes.

Reinforced concrete (RC) slabs of highway bridge decks are gradually deteriorated due to the traffic vehicle wheel-loading. Fatigue is one of a number of possible causes for the deterioration. Cantilever RC slabs of the bridge are also damaged by fatigue loading. To increase the fatigue durability of the bridge deck slab, the near-surface mounted (NSM) technique is used with carbon fiber reinforced polymer (CFRP) rods embedded in the RC slab as an effective strengthening method. This study presents the fatigue characteristics of cantilever RC slabs strengthened with CFRP rods with a high-modulus of elasticity. A cantilever RC slab specimen with embedded CFRP rods with high moduli was constructed on a moving-wheel load testing machine and tested for approximately 11 months. The slab had a minimum thickness of 160 mm (as stipulated by the Japanese design code), and the minimum number of steel reinforcements was embedded to ensure (negative) flexural failure of the RC slab where CFRP rods were not used. During the test, the CFRP strengthened slab specimen was subjected to a negative bending moment from repeated moving-wheel loads. Very limited experimental data are available for the evaluation of the structural behavior of cantilever bridge decks subjected to wheel loads. Therefore, the moving-wheel fatigue experiment of the cantilever RC slab with NSM CFRP rods would be useful information for strengthening. The moving-wheel loading test confirmed the increase in fatigue durability of the CFRP strengthened slab as the slab specimen endured approximately 3.56 million equivalent-cycles at an initial load of 60 kN, which was 32% higher than the designed service load. The experimental investigation revealed that the ultimate failure of the cantilever slab was punching shear failure attributed to the rupture of the CFRP rods.

The chapter reviews fundamental theories, formulas, solution methods, and a set (toolbox) of MATLAB functions for static analysis of Euler–Bernoulli beams. The system requirements for the MATLAB toolbox—a PC with Win 98SE/NT/2000 and XP or Mac with OS 9.x and up, and the software MATLAB (version 5.x and up) installed on the computer. A fundamental problem in the static analysis of Euler-Bernoulli beams is stated as the given external loads and boundary disturbances that determines the beam response (displacement, rotation, bending moment, and shear force), which is governed by a given equation and boundary conditions. There are many solution methods available for the static analysis of Euler-Bernoulli beams. The chapter presents three analytical solution methods for the beam problem—method of singularity functions, the boundary value approach, and distributed transfer function method (DTFM). The MATLAB functions are developed based on the distributed transfer function method, which is an exact analytical modeling and solution method for many one-dimensional distributed systems including bars, shafts, strings, and beams.

The deployable bridge based on scissor structures is one of the effective methods to quickly restore traffic after natural and man-made disasters. Scissor structures have the advantages of high storage rate, lightweight, and convenient storage and transportation. However, when scissor structures are used as load-bearing structures, their stiffness and bearing capacity are low. In this study, a three-dimensional deployable bridge based on the cable-strengthened scissor structures was proposed. In addition to rapid expansion, steel cables were used to strengthen scissor structures to improve the stiffness and bearing capacity. Besides, the static loading comparative tests on cable-strengthened scissor structures and traditional scissor structures (cable-free scissor structures) were performed. The results show that the stiffness of the cable-free scissor structure is small, the bending moment of members is large, and the stress distribution is uneven. The stiffness of cable-strengthened scissor structure is significantly improved; the bending moment of members is significantly reduced; and the stress distribution in the member section is more uniform. It is proved that cables can be used to improve the stiffness and load-bearing capacity of scissor structures without affecting the deployability.

The core objectives of sustainable development are to develop access to renewable, sustainable, reliable, and cost-effective resources. Wind is an essential source of renewable energy, and monopile wind turbines are one method proposed for harnessing wind power. Offshore wind turbines can be vulnerable to earthquakes and liquefaction. This numerical study defined the effects of wind turbine weight on the seismic response of a wind turbine-monopile system located in liquefied multilayered soil with layer thicknesses of 5, 10, 15, and 20 m using four far-field records. OpenSees PL analysis indicated that if the liquefied sand had a lower density or a thickness of more than 10 m, then an increase in the earthquake acceleration beyond 0.4 g caused the pile to float like liquefied soil and to lose its vertical bearing capacity. Moreover, increasing the wind turbine power from 2 to 5 kW had no significant effect on the soil-structure interaction response. As the earthquake acceleration increased, the bending moment of the pile-column also increased as long as liquefaction did not occur and the pile-column deformation remained rotational-spatial in shape. As the acceleration and liquefaction increased and the pile began to float in response to its transverse motion, there was no significant difference in the pile-column displacement along the length, but there was a decrease in the pile-column bending moments. As this phenomenon increased and the pile continued to float, transformation of the pile increased the difference between the displacement of the pile-column along its length and further increased the bending moments. These results were derived from multiple correlation analysis, the bending moment relations, and lateral displacement of the pile-column of the wind turbine.

While metallic pipelines experience consistent deterioration due to aging, composite repair systems have become a method of interest over the recent decades. This study aims to deal with multiple failure modes of composite repaired pipes using probabilistic analysis. The failure modes—including bursting, adhesive debonding, and fracture—are all involved such that correlations among modes are considered to obtain the final system failure probability. The first passage probability method is applied to calculate the probability of failure in each failure mode. Additionally, the degradation process of the composite material is quantified by the Arrhenius relationship. It was found that adhesive debonding is the most influential failure mode, followed by bursting, then fracture due to internal pressure, and finally fracture induced by bending moment. The prominent input parameters were evaluated by carrying out a sensitivity analysis based on the FOSM reliability method. The results confirmed that composite repair parameters, including elasticity modulus, bonding strength, and thickness, noticeably impact the failure probability. The outcomes of this paper can help maintenance engineers better assess the reliability of composite repaired pipelines.

This paper studies the application of the inerter-based passive structural control in seismic response mitigation for a wind turbine. The inerter-based passive control system used here is called inerter-based dynamic vibration absorber (IDVA), in which a spring and an inerter-based mechanical network are connected in parallel. A multi-degree-of-freedom (MDOF) system is used to describe the wind turbine system with the consideration of the interaction between wind turbine structure and soil. For the purpose of mitigating seismic response, the inerter-based mechanical network is regarded as a controller to be designed using two different methods. Then, a variety of different network configurations are selected in the fixed-structure method, and only the low-order admittances are taken into account in the network synthesis method. By optimizing the controller parameters with $$H_{2}$$ optimization method, response parameters such as tower-top displacement are improved. The comparisons of the tower-top displacement performance corresponding to the traditional tuned mass damper (TMD) and the inerter-based dynamic vibration absorbers (IDVAs) show that the inerter-based control can use a smaller additional mass ratio to achieve the same tower-top displacement performance as the TMD control. Finally, the numerical simulation results obtained with different types of ground motions for a 5-MW NREL wind turbine also demonstrate the superiority of IDVAs compared to TMD, and a similar decreasing trend is observed for tower-top displacement performance and tower bottom bending moment performance.

This paper presents an analysis of the structural behavior of both tapered ring and parallel ring linings in a tunnel design project using a shell-spring approach. This is done to examine whether the tapered ring lining can be approximated as a parallel ring lining. The results show that, under the same load conditions, the maximum positive bending moment and axial force of the tapered ring model varies little compared with the parallel ring model. However, the maximum negative bending moment and maximum deformation in these two models vary significantly. Under conditions of different joint orientations, the maximum negative bending moment and deformation differ by as much as 19%, regardless of which lining model is used. Thus, the simplification of a tapered ring lining as a parallel ring lining for use in tunnel design is not sensible.

Based on the theoretical results obtained in the article [17], here the analysis of the influence of various design parameters on the own weight and cost of metal of truss beams with two posts is carried out. An optimal parameter has been obtained that makes it possible to reduce the calculated bending moment in the cross section of a truss beam with two struts.Method. By equalizing the bending moments in various design sections of the truss beam, the internal force factors are reduced. The corresponding equation for optimizing the parameters of the beam has been drawn up and a formula has been obtained to determine the optimal parameter of the structure as a whole.Result. Using the example of numerical calculations, a decrease in the calculated bending moment by 14% compared to truss beams without optimization is shown.Conclusion. The proposed method and algorithm testify to the efficiency and rationality of the obtained optimal parameter of the structure as a whole.

This paper investigates the structural behavior of the wing subjected to the aerodynamic loads during the flight using finite element analysis of wing flexure deformation. In this work, three different types of wing models are established. Material characteristics, the wing structure, and 1 design principle have been taken into account. The assembly of the wing model 2 consists of the thin skin, two spars, and the multi-ribs. The two spars consist of primary and secondary spars. For this study, NACA 23015 is chosen as the baseline airfoil as this airfoil is very similar to the customized airfoil being used in Airbus A320. Two spars mainly bear the bending moment and shear force, which are made of titanium alloy to ensure sufficient rigidity. The skin and wing ribs are made of aluminum alloy to lighten the structural weight; a static structural analysis is applied. Total deformation, equivalent elastic strain, and equivalent von Mises stress are obtained to study the wing’s structural behavior. Furthermore, the modal analysis is then applied. The natural frequencies and the modal shape of the wing for three orders are obtained through the pre-stress modal analysis. The modal analysis results help designers minimize excitation on the natural frequencies and prevent the wing from fluttering. According to the results, designers can emphasize strengthening and testing the stress concentration and large deformation area.

Taking the occurrence conditions of the hard main roof in the deep 13-1 coal mining roadway in Huainan mining area as the research object, based on the mechanical parameters of the surrounding rock and the stress state of the main roof obtained by numerical simulation, a simply supported beam calculation model was established based on the damage factor D, main roof support reaction RA, RB, and critical range C (9 m) and B (7 m) at the elastoplastic junction of the solid coal side and mining face side (hereinafter referred to as “junction”). Considering that the damage area still has a large bearing capacity, the vertical stress of the main roof at the junction is K1γH (0.05γh, 0.15γh, and 0.25γh) and K2γH (0.01γh, 0.10γh, and 0.2γh). The maximum deflection is 21 mm, 324 mm, and 627.6 mm, respectively. According to the criterion of tensile failure, the maximum bending moment of the top beam is 209 mN·m at the side of the working face 3.1 m away from the roadway side when K1 = 0.15 and K2 = 0.10, and the whole hard main roof is in tensile failure except the junction. To control the stability of the top beam and simplify the supporting reaction to limit the deformation of the slope angle, RC and RD are used to construct the statically indeterminate beam. By adding an anchor cable and advance self-moving support to the roadway side angle, the problem of difficult control of the surrounding rock with a large deformation of the side angle roof is solved, which provides a reference for roof control under similar conditions.

Resilience in bridges is of paramount importance as bridges are important transport assets that maintain mobility after disasters. The most common cause of extreme stress development on structures and especially bridges is dynamic loads due to floods, earthquakes, strong winds, truck and ship collisions. In the international literature, there an ongoing research in support of adaptable and low-damage bridge connections for bridges and structures exposed to dynamic loads. This paper focuses on the design and assessment of a novel connection based on extensive numerical modelling of a 3D Finite Element (FE) model of the connections developed in Abaqus. The connection, which is essentially a resilient hinge, connects the foundation with the bridge pier and the latter with the deck, which are the positions where typically RC hinges are formed during extreme dynamic loads, e.g. earthquakes. A similar connection was designed before, however, this paper offers a design methodology and advances the connection by providing improvements to its mechanical characteristics, i.e. the geometry, resolving issues with regard to stress concentration by improving the contact surface geometry, the consideration of the friction and the optimization of its components. The paper concludes with a discussion on the connection constructability, therefore enabling further applications of the proposed design. The results also demonstrate that even though the rebars of the hinge undergo excessive elongation, the connection maintains a significant bending moment capacity, therefore not hindering the integrity of the bridge. Moreover, it is observed that the compressive zone of the hinge remains intact, thanks to the high strength of the steel, therefore no shortening of the RC column is expected.

To evaluate the seismic responses of bundled conductor interconnected electrical equipment, a model of the interconnected system was established. The bundled conductor model was incorporated into the interconnected model, and the electrical equipment was simplified as a 5-degrees of freedom structure. The bending stiffness of the sub-conductor and the constraint effects of the spacer, usually omitted in previous research, are considered in the paper. The iteration method was used to obtain the terminal forces and moments of the bundled conductor. Then, the model was validated by shaking table tests. We investigated the effects of the slackness and bending stiffness of the bundled conductor on the seismic responses of the interconnected system. Considering the bending stiffness of the sub-conductor and the effects of the spacer, the seismic response characteristics of the interconnected electrical equipment were much different from those connected by a flexible conductor without bending stiffness in previous research. Not only the terminal forces, but also the terminal bending moment should also be considered in the seismic performance evaluation of interconnected electrical equipment.

Gradual changes of weight and geometry of vehicles combined with traffic values sometimes leads to old existing bridges having to be strengthened and retrofitted. The optimal solution to follow is based on the resistance capacity reserves of each structure, on the existing traffic level at the moment of retrofitting works and on the estimated future traffic. Almost all existing road bridges in Romania were designed according to national provisions/standards. Starting with 2010, following the European Community’s decision, the projects should be designed according to the Eurocodes and the existing bridges, must also comply with the new European load models. The process of checking existing bridges for the action of load models described in Eurocodes is a complicated task. However, the process for the evaluation of the bearing capacity reserves can be significantly simplified using a probabilistic approach. The approach presented in this paper is based on the effects, in terms of bending moments and vertical displacements, produced by several types of vehicles on the bridge superstructure. For presenting the use of this proposed methodology, typical bridge superstructures with precast concrete girders of different lengths were analyzed. The proposed methodology allows to establish the “vulnerability” of existing bridges on live loads.

Rehabilitating the deteriorated deck of post-tensioned concrete box-girder bridges by ultra-high-performance concrete (UHPC) overlay is studied in this paper. Three post-tensioned concrete box-girder bridges in California were selected for the deck overlay analysis. Rehabilitation construction procedures for each bridge were described, including the practical lane closure and traffic re-routing. Detailed finite element models were established incorporating the staged construction modeling of the rehabilitation process, the time-dependent properties for existing concrete and prestressing tendon, and a “double-layer” modeling technique for the simulation of the deck. The time-dependent curves and equations of a specified UHPC were fitted based on experimental data, including creep, shrinkage, and elastic modulus, and this particular mix has been assumed in the FE analysis. How the thickness of the deck layer to be replaced affected the stress distributions in the UHPC overlay and the existing box girder was parametrically studied. Results indicated that stress variations in the existing box-girder were acceptable during the deck rehabilitation construction, but significant tensile stresses were developed in the newly placed UHPC deck overlay. Shrinkage-mitigation measures, such as adding the shrinkage-reducing admixture (SRA), should be considered during the placement of the UHPC overlay to control the shrinkage-induced tensile stress. Steel reinforcement may be adopted in the negative bending moment region to resist the flexural tensile stress by the live loads. The rehabilitation thickness of 3.8–5.1 cm (1.5–2.0 in.) is deemed appropriate for the bridges selected in this study.

This article presents a study to evaluate the structural response of a cable-stayed bridge under a novel system, partially earth-anchored system with crossing cables at the main span. Six side-to-main span ratios, ranging from 0.24 to 0.39 in increments of 0.03, are tested for different bridge response parameters for both the superstructure and substructure. The loads considered in the analysis are the dead load and traffic load. Three-dimensional finite element models of the bridge are developed using structural analysis software SAP2000 and are validated based on the data available in the literature. From this study, it is found that the side-to-main span ratios have a significant effect on girder axial force and anchorage forces while having a very minor effect on cable axial forces. The results also show that the ratio does not affect the bending moment of the main span, but that when a small ratio is considered particular attention needs to be paid to the pier farther from the pylon to avoid uplifting. Deck vibration and longitudinal movement, as well as pylon longitudinal displacement, are not to be an issue for this super-long bridge.

In order to study the cracking of prestressed reinforced concrete T-shaped beam structures, the authors planned and carried out a full-scale experiment with five variable factors. The following factors were chosen as variable factors: the relative span of the shear, the ratio of the table overhang width to the thickness of the beam rib, the ratio of the table overhang thickness to the working height of the beam section, the coefficient of transverse reinforcement, the level of prestressing in the working reinforcement. The article describes the cracking process and the destruction of test beams. It was found that the loading level of an opening of inclined cracks is 53% larger than the loading level of a normal crack opening. Mathematical models of bending moments and transverse forces of cracking were built using the “COMPEX” software. Also, the mathematical models of the crack opening width and the projection length of a dangerous inclined crack were obtained. These models are based on the experimental data. Analysing the obtained models, the complex influence of variable factors on the main parameters of crack formation and crack resistance was established. In particular, it was found that the prestress level in the working reinforcement has the greatest effect on the bending moment of cracking. In this case, the value of the shear force of cracking significantly depends on both the prestressing level in the reinforcement and the relative span of the shear. On the basis of the experimental data, the empirical expression is obtained for determining the projection of a dangerous inclined crack for prestressed reinforced concrete T-shaped beams. The resulting equation can be used to calculate a shear reinforcement.

The present study proposes a practical yet reliable model for stay cables in cable-stayed bridges considering large force variation under seismic actions. The proposed model is capable of approximating the nonlinear equivalent stress-strain relationship of cables, taking into account the variation of equivalent modulus of cables during the earthquake as well as possible cable loosening. The cable performance based on the proposed method shows an overall good agreement with the actual response of cables. Then, the model is applied to a case cable-stayed bridge under seismic actions and the structural response is compared with the conventional method which models the cables with a constant equivalent modulus derived at dead load state. Comparing to the proposed model, the conventional method fails to accurately describe the cable force at the low stress level and shows discrepancies in time histories of the structural response in terms of amplitude and phase angle. Moreover, conventional method might lead to underestimation of the bending moment at the tower bottom and longitudinal displacement at deck end for most cases, resulting in unconservative seismic design. Such result highlights the importance of applying the proposed model in seismic design of cable-stayed bridges.

Eurocode (EC3) bending moment design model of mono-symmetric corrugated web girders (CWGs) is based on the critical failure mode among the tension flange yielding, the compression flange yielding and the lateral-torsional buckling (LTB) of the compression flange. Recently, LTB behaviour of S460 laterally-unrestrained mono-symmetric CWGs with fully-effective flanges has been investigated by the authors, from which EC3 design model has been modified to better represent their actual strength. Nevertheless, the effect of the local buckling (LB) of slender compression flanges on the flexural strength and behaviour of such long girders has not been examined. While the corrugated web potentially makes large contribution to the out-of-plane stiffness, LB of the compression flange is expected to reduce LTB resistance of such girder significantly. Principally, this paper is devoted to exploring such effect on the accuracy of EC3 bending moment design model. Currently, virtual tests, by using ABAQUS software, are generated based on accurate validation. Then, parametric studies, intentionally designed to eliminate the tension flange yielding, are carried out on simply supported girders considering mainly the influences of the flange and web dimensions on the behaviour of S460 mono-symmetric CWGs. The strengths of such girders are compared with EC3 design model, from which it is found to provide unsuitable predictions. Hence, new formula has been proposed to accord better with the FE results. Additionally, several conclusions are provided at the end to assist design engineers in suggesting efficient cross-sections.

Gusset joints connect only the upper and lower cover plates to the flange of aluminium alloy beams through bolts, and there is no connection to the web. To compensate for this deficiency of gusset joints, a new aluminium alloy flower-gusset composite joint (FGC joint) is proposed in this paper. In this paper, compression, shear and bending tests are performed on new FGC joints. The test results show that (1) compared with those of gusset joints, the compressive stiffness and bearing capacity of FGC joints increase by 2.1 and 1.36 times; (2) the shear capacity and shear stiffness of FGC joints are 1.47 times and 1.74 times higher than those of gusset joints; and (3) the bending capacity of FGC joints is 1.2 times higher than that of gusset joints, but the bending stiffnesses of the two kinds of joints are similar. Then, a numerical model is established to analyse the load transfer mechanism of FGC joints. Numerical analysis shows that the FGC joint passes axial compression through the cover plates and the flower body, shear is transmitted mainly through the flower body, and the bending moment is mainly transferred by the cover plates. Finally, based on the test and numerical analysis, the bearing capacity design method of the new joint is proposed through theoretical analysis.

Stress concentration factors (SCF) in steel tubular joints have gained considerable attention since it is the crucial parameter for fatigue design of steel tubular structures. Meanwhile, among various strengthening methods, Fiber Reinforced Polymer (FRP) wrapping has shown to be an effective scheme for reinforcing steel structures. This study is dedicated to the numerical investigation of SCF values in FRP-strengthened tubular KT-joints under the action of In-Plane Bending (IPB) and Out-of-Plane Bending (OPB) moments on the central as well as outer braces with three various practical loading patterns per each moment. The Finite Element (FE) modeling methodology for joint geometry and FRP generation was validated against the available data in the literature and well-known codes. The effects of different geometrical parameters along with the FRP parameters on the SCF values were studied through post-analyzing a total of 2920 FE models. The numerical parametric studies indicated that FRP strengthening could lower the SCF values in KT-connections by about 30 and 55 percent under IPB and OPB moments, respectively. Using the driven data, practical fatigue design formulas were developed for predicting SCF in FRP-strengthened KT-joints under bending moments, and reliability of the proposed equations was examined using Fatigue Guidance Review Panel recommendations.

The impact of ground motion duration often arises when investigating buildings’ performance in regions susceptible to strong earthquakes, where reinforced concrete (RC) shear walls are typically used as a lateral force-resisting system. Although the seismic performance of these reinforced walls has been improved by the use of self-centering devices and materials, the influence of ground motion duration on self-centering RC walls is not yet well understood. This paper, therefore, examines the effect of ground motion duration on seismic performance and the damage scheme of the self-centering shear wall reinforced with three different types of superelastic shape memory alloy (SE-SMA) in the plastic hinge. A ten-story case study building was analyzed and designed according to the current ASCE 7-16 and ACI-318 practice codes. The maximum inter-story drift ratios (IDR), residual drift ratios (RIDR), shear forces, bending moments, material damages, and collapse margin ratios were examined. The results indicate that IDR and RIDR significantly increased as ground motion duration increased. Meanwhile, the shear forces increased by about 24% on average, which induced only a 6% increase in the bending moments. It was also observed that ground motion duration significantly influenced the scaling factor required to reach the collapse level. Among the examined SE-SMA RC walls, the results indicate that Cu-based SMA RC wall exhibits superior performance in terms of IDR, RIDR, shear forces, and bending moments and performs fairly well in terms of material damage and collapse margin ratio compared to other SMA RC walls. Thus, using Cu-based SMA material in seismically active regions prone to short and long duration ground motions is generally recommended.

The hybrid coupled wall (HCW) system consists of steel coupling beams that connect adjacent reinforced concrete (RC) wall piers. In order to minimize or even eliminate the lengthy design iterations of conventional performance-based seismic design method and directly account for inelastic structural behavior, the modified energy-balance based plastic design (EBPD) method is proposed and developed for the seismic design of HCW systems with the consideration of influences of the degradation of hysteretic behavior and pinching effects. The design base shear can be obtained by solving the modified energy balance equation analytically. Twelve HCW prototype structures with different structural heights and coupling ratio (CR) were designed and evaluated by conducting a series of push-over analyses and nonlinear dynamic time-history analyses with the proved-reliable program of PERFORM-3D. The analysis results indicate that all HCW prototype structures exhibit the favorable yield mechanism and satisfactory seismic performance. Particularly, the influences of CR on the deformation characteristics, bending moment distribution among wall piers and vertical distribution of overturning moment are revealed. Suggestions are made in terms of the appropriate selection of CR for different structural heights.

Even though high-strength steel has been widely used across the world, the global buckling behaviour of high-strength steel beams has yet to be systematically investigated through experimental tests and numerical simulations. This paper describes an experimental and numerical study of the lateral-torsional buckling resistance of welded Q690 steel beams. Eight beams with doubly-symmetric cross-sections and different height-to-width ratios were tested under a concentrated point load. To allow free lateral deflections, a special loading system was designed and erected at the mid-span of steel beams. The applied load remained in the vertical direction during the whole loading process, despite significant rotations and lateral deflections of the beam. The critical bending moment of steel beams was quantified in the experimental tests. Besides, numerical models were established by using ABAQUS and initial imperfections were properly defined in the model. Direct comparisons were made among numerical results of steel beams of different steel grades and design curves in different standards. Based on experimental and numerical results, recommendations were provided for the lateral-torsional buckling design of Q690 steel beams. It was suggested that GB50017-2003 and GB50017-201X can predict the buckling resistance of Q690 steel beams with slightly conservative results, Eurocode 3 yields rather conservative estimations, but ANSI/AISC360-10 significantly overestimates the buckling resistance.

Suspension bridge’s main cable under live load undergoes deformation depending on its gravity stiffness, i.e., work done against gravity under the initial dead load. In three-tower suspension bridges (3TSB), the middle tower's effect on the main cable's gravity stiffness is crucial but hard to assess. In this paper, the 3TSB model was simplified to the 2TSB with elastic constraints. The main cable shape was then calculated via the ratio between the simply supported beam's bending moment and the horizontal force component. The 2TSB model results were used to derive the 3TSB main cable's deflection using the middle tower's stiffness under vertical load. The analytical formula for gravity stiffness of 3TSB was derived by matching the latter with the simply supported beam's deflection formula. For a case-study 3TSB with main spans of 248 m + 1060 m + 1360 m + 380 m, analytical predictions were verified by FEM numerical results obtained via ANSYS. Linear relationships between live load and increments of the main cable's deflection and horizontal force component were derived. Besides, the main cable's deflection under live load can be reduced by increasing its sag-to-span ratio and cross-sectional area.

Software users concerning seismic analysis of buildings usually use the concentrated mass (ML) matrix and the Rayleigh damping matrix (C). Similarly, the initial stiffness matrix (KO) and the first two modes are commonly used to calculate C. In addition, it is commonly believed that damping forces are small so there are no significant errors if the Rayleigh model is used. The evaluation of the accuracy of these practices for the case of steel buildings constitutes the main objective of this research. To this aim the seismic responses of three models, representing steel buildings of low-, mid- and high-rise are considered. If ML is used, shears and bending moments in columns are underestimated by up to 31% and 65%, respectively. If the first two modes are used, shears, drifts, and bending moments in beams are underestimated by up to 27%, 50%, and 55%, respectively, while for axial loads and bending moments in columns the underestimation can be up to 78%. Similarly, damping forces and damping moments are underestimated by up to 350% and 325%, respectively. Damping moments represent a considerable fraction (0.47) of plastic moments in beams. If KO is used in C, axial loads in columns are underestimated by up to 80%. The results of this study give rise to state that the consistent mass matrix should be used in the structural modelling of the structural system under consideration. Similarly, first mode and one superior, and the tangent stiffness matrix should be used to formulate the Rayleigh damping matrix.

This paper investigates the behaviour of two popular structural systems subjected to overheating and column removal cases, which may follow fire incidents. A typical 15–storey steel building is designed with two types of structural system framed-tube and moment-resisting frame. The nonlinear behaviour of these structures under different fire scenarios is investigated using OpenSees Software. The results indicate that deflection of heated beams is insignificant below 400 °C but after that, degrading mechanical properties of steel material leads to large deflection and runaway of heated beams at temperatures below 600 °C. Also, heating the beams of structures initially induces large axial forces in the beams due to restraints on thermal expansion. Thermal expansion of heated floors induces large horizontal displacement and consequently causes additional bending moments in the exterior column. So columns reach their elastic limit at the early stages of fire. Columns of the framed-tube system reach their elastic limit at lower temperatures (130 °C) but fail at higher temperatures (380 °C) compared to columns of the moment-resisting frame system (210 °C). In addition, the lower storey and interior columns are more vulnerable to progressive collapse and fail at lower temperatures (330 °C) due to carrying more gravity loads. In most fire scenarios, beams and columns of framed-tube systems fail at higher temperatures and perform well in the fire than moment-resisting frame systems. In column removal scenarios, mid-span displacement of the heated beam increases significantly, leading to downward movement of upper stories. Also, column removal in the framed-tube system is more destructive than in the moment-resisting frame system. In general, in both structural systems, column removal scenarios, which may follow fire, induce more damage to the structures than general temperature rise in considered fire scenarios.

The shear lag of the box girder section of a wide box bowstring arch bridge was investigated in this study. The finite element analysis software Midas Civil was used to discretize the bridge into separate entities, establish its spatial model, and analyze the law of shear lag effect in the longitudinal direction during the main construction stage and the completion stage separately. The shear lag effect is more prominent at certain key points due to the influence of the tension of the boom and the weight of the arch foot during the construction stage. After the bridge is completed, the axial pressure of the arch foot drives the shear lag effect near the midpoint of the main girder section to its maximum; the axial force is transmitted along the longitudinal bridge direction in a V shape along which it gradually decreases. Under the action of uniformly distributed load, the cross-section of the box girder near the middle fulcrum is affected by the axial force of the arch foot; there is both a positive and negative shear lag effect. Under the eccentric load, the positive and negative shear lag effects appear simultaneously at the end fulcrum. The shear lag coefficient is higher in the web on the eccentric load side than the non-load side. There is obvious and widely fluctuating positive/negative shear lag effect in the vicinity of the middle fulcrum. There is significant tensile stress on the roof under the action of the middle fulcrum. The cross-sectional stress of a single-box seven-cell box girder under compression-bending load action was analyzed according to the finite element analysis results. The stress was decomposed into a superposition of bending moment action and axial force action. The shear lag coefficient λ M under the action of bending moment was also solved via energy variation method. Assuming that the axial force is only borne by the compressed area, the shear lag coefficient λ N under the action of the axial force was obtained; λ M and λ N were superimposed to determine the comprehensive shear lag effect coefficient λ .

In this paper experimental results of investigation on reinforced concrete (RC) beams strengthened with the near surface method (NSM) are analyzed considering the response under bending tests on two beams. One of the RC beams was damaged by bending until the yield of reinforcement and successively strengthened with carbon fiber polymer (CFRP) rod, while the second beam was strengthened with glass-FRP rod. Both the beams have been subjected to bending tests until failure. Experimental diagrams and discussion on static response are presented in the paper. It also places a particular emphasis on the non-linear response of RC sections strengthened with CFRP and GFRP rods under bending moment beyond the first elastic behavior.

Three variants of the engineering solution of inverse problems regarding the strength of pipeline sections bent as a result of ground movements or during an earthquake are proposed. The feature of this approach consists in calculation of stresses not by the forces acting on the pipe, but by the displacements or deflections. Therefore, full-scale measurements of the detected deviation of the pipe position from the planned pipeline route should be taken as initial data for estimating the values of additional bending stresses. The first problem considered is the assessment of the risk of pipeline malfunction upon sagging or bulging of the supports of aboveground pipelines. The problem is solved in the beam approximation. The pipeline is considered a statically indeterminate beam, one of the supports of which is forcibly moved to a given distance. For a once statically indeterminate beam, a system of four equations — two equilibrium equations and two integral equations for deflections — was solved numerically. The calculated values of three reactions of the supports and the angle of rotation of the pipe section on the first support are used to calculate bending moments, stresses and deflection lines. The problem for a thrice statically indeterminate beam under strain loading was also solved. The second goal is to model the stress-strain state of the pipeline proceeding from the tables of experimental data on the values of pipe deflections and their coordinates. The problem was also solved numerically, using the procedures of smoothing, linear interpolation and sequential differentiation. It is shown that taking into account the possible ambiguous solution of the inverse problem, we should not rely on the calculated values of transverse forces and distributed loads. It is enough to limit ourselves to the second coordinate derivative of the deflection. The third goal is to prevent accidents at the design stage. It is proposed to create a list of normalized deflection functions for modeling possible emergency situations for pipeline sections placed in difficult ground-geological conditions and seismically dangerous zones. The examples of such functions are given.

У статті описано підхід до оцінки ступеня небезпеки ерозійно-корозійного зносу елементів трубопроводів АЕС із вуглецевих сталей. З метою апробації запропонованого підходу проведено комплекс розрахунково-аналітичних робіт, зокрема: а) проаналізовано існуючий підхід до оцінки ступеня небезпеки ерозійно-корозійного зносу на АЕС України; встановлено його недоліки; б) розроблено алгоритм оцінки ступеня небезпеки ерозійно-корозійного зносу з використанням експрес-оцінки та уточненої процедури; в) верифіковано розрахункові моделі співставленням з іншими існуючими розрахунковими моделями та експериментальними даними з метою демонстрації їх коректності; г) за розробленим підходом виконано оцінку ступеня небезпеки ерозійно-корозійного зносу систем трубопроводів енергоблоків №№ 1 та 4 Відокремленого підрозділу «Запорізька атомна електростанція», виявлених у період експлуатації з 2012 року по 2016 рік. Розроблений підхід дозволяє: 1) оцінювати ступінь небезпеки ерозійно-корозійного зносу не тільки в окружному напрямку поперечного перерізу труби внаслідок дії внутрішнього тиску (підхід, що базується на вимогах ПНАЭ Г-7-002-86, щодо визначення допустимої товщини стінки бездефектного трубопроводу), але й уздовж осі трубопроводу від одночасної дії внутрішнього тиску, осьового зусилля та моментів згину. Такий підхід особливо актуальний для трубопровідних систем, які, переважно, мають складну просторову конфігурацію, що призводить до виникнення в них осьових зусиль та моментів згину внаслідок дії масових характеристик трубопроводів та арматури, температурних, сейсмічних впливів тощо; 2) оцінювати ступінь небезпеки ерозійно-корозійного зносу не тільки за його глибиною (підхід ИН-Т.0.03.190-14), а й з урахуванням довжини та ширини ерозійно-корозійного зносу. На відміну від існуючого підходу, це дозволяє коректніше оцінювати ступінь небезпеки ерозійно-корозійного зносу.

The counterweight-balanced column bending test (CWB-CBT) was developed by Fernandez and Murphey [1] to counter the gravity sag issue of column bending test and generate a better uniform bending stress state in characterizing thin composites’ bending behavior at large curvatures. When analyzing the test data the original processing method assumes that the specimen is under constant curvature deformation, but the sample is still subjected to small variable flexure moment and curvature due to concentrated compressive load. Aims to evaluate the simplified processing method accuracy and provide comprehensive guidelines for CWB-CBT. Euler’s elastica large deflection theory was applied to evaluate the curvature and moment error in the simplified solution. Laminate [0]4 and woven composites were selected to investigate the result accuracy by experimental validation and finite element model. Within the elastic range, the accuracy is independent of load and bending rigidity, but is related to the geometry. The simplified method tends to present higher stiffness results due to constant curvature assumption. A decreasing trend is exhibited for errors as the ratio of fixture arm span to coupon length increases. When the ratio reaches two, the curvature error is less than 5.7085%, and the bending moment error is under 3.2173‰. The error correction method is also provided. The CWB-CBT can evaluate thin composites’ elastic bending behavior when considering the error correction. Attention should be paid to results reliability after material enters the nonlinear behavior stage.

This paper presents a Fiber Bragg Grating (FBG)-based torque sensor with high sensitivity and miniature size for MIS instruments and multi-finger hands. The proposed sensor design mainly consists of a torque-sensitive flexure structure and two diagonally arranged optical fibers embedded with FBG sensing elements. An improved hollow hexaform structure with flexible hinges has been utilized to design the torque-sensitive flexure with an excellent linear measurement range and a solid capacity to resist non-torsion loading. Two optical fibers with an FBG inscribed each adopt a two-point gluing configuration with a tightly stretched status, and they are arranged diagonally along the hyperboloid surface. This configuration can obtain improved sensitivity and resolution and avoid the drawbacks of FBG chirping and low repeatability. Finite element modeling (FEM)-enabled simulation has been implemented to perform design optimization for further sensor sensitivity improvement and performance investigation. The prototyped sensor has been calibrated and achieves a high resolution of 0.062N $\cdot $ mm within [−100, 100N $\cdot $ mm] and excellent linearity with a small linearity error of 0.68%. The crosstalk experiments on the bending moment of Mx and My and the axial force have been conducted to validate the anti-interference capacity on the basis of the small values of 0.47%, 0.31%, and 1.78%. The proposed design also supports convenient customization to achieve the adjustable measuring range and torque sensitivity, which has been validated by another sensor version with a resolution of 0.26 $\text{N}\cdot $ mm within [−500, 500N $\cdot $ mm].

Buried pipeline is threatened from the soil displacement due to earthquake and other causes, which leads to the formation of unexpected external forces such as bending moment. The problem can be worse with the appearance of defects, resulting in the reduction in pipe capacity. The paper focuses on the overall problem of defected pipe crossing the strike-slip fault. A full-scaled FE model can be very complicated with the large-scale and micro-scale levels corresponding to the strike-slip fault and defect on pipe problems, respectively. To ease this difficulty, the macro and micro problems are solved separately with two types of FE models and their corresponding databases. To be specific, one FE model is used for predicting external moment due to strike-slip fault and the other is for predicting the moment capacity of defected pipe. Data-driven models are consequently developed with artificial neural network (ANN) for each database generated from these types of models: ANN1 evaluating moment capacity of defected pipe (R2 is 0.9943 on test set) and ANN2 predicting both moment and axial force appeared in pipe due to strike-slip fault (R-squares are 0.9883 and 0.9929 on test set, respectively). Consequently, the stress–strength analysis for the overall problem is solved. Accounting for the unavoidable uncertainty of the models, the paper proposed an approach which assumes that the actual distribution of residual of a model is equivalent to this of the test set. The distributions of residuals on test set of these ANNs are tested to be normally distributed and generated by the conventional Monte Carlo simulation. To the end, the deterministic problem leads to the failure probability. The proposed framework has been investigated, and the final results on this selective parametric study are reasonable.