Advances on Structural Engineering

Intuitive self-assembly devices are of great significance to the emerging applications of self-assembly theory. In this paper, a novel intuitive device with an aerodynamic system is fabricated for the self-assembly experiment. Table tennis balls were used as the objects to be assembled during the self-assembly process. To understand more about the system, two experiments were designed—the directed assembly experiment was conducted to organize a specific structure and to explore the influences of environmental variables, and the indirect assembly experiment repeated with the “bottom-up” self-organization process and expressed the characteristics of “the optimization” and “the emergence” in the self-organization process. This article expressed a novel self-assembly approach at a macroscale and created a new choice or idea for the structural design and the optimization method. Full article

In situ monitoring was conducted throughout the construction period to investigate the abnormal deformation of a bridge under construction subjected to sudden cooling by Typhoon Lekima. An FE model considering the temperature field based on measurement data was also established to reveal the exact causes of the bridge’s abnormal deformation and provide theoretical guidance for rehabilitation measures. The FE model simulation and measurement results showed that (1) the exact cause of the abnormal deformation of the bridge was the inconsistency of the temperature field between the top and bottom plates, and the sudden approach of the typhoon aggravated the inconsistency; (2) the abnormal deformation of the construction bridge caused by the typhoon could be addressed with rehabilitation before forming the bridge; (3) an extreme temperature field should be considered in the design of a beam–arch combination bridge. These results can provide a reference for the design and construction of similar bridges. Full article

In the process of cradle construction for high-pier, long-span, continuous, rigid-frame (HLCR) bridges, the strength failure and instability damage of the main pier will directly affect the bridge construction safety. Therefore, it is necessary to study the reliability of the main pier during the construction of HLCR bridges. This paper starts from the factors that easily affect the stability of the main pier during HLCR bridge cradle construction, establishes the resistance and load probability model of the main pier during the maximum cantilever stage and the maximum unbalanced load of the continuous, rigid-frame bridge’s hanging cradles, fully considers the influence of random factors on the reliability of the pier, and calculates and analyzes the reliability index β through calculation examples. The results show that the changes of various random factors during the construction process have different degrees of influence on the reliability of the bridge pier. Our work provides a basis for the safe control of hanging cradles in the construction of HLCR bridges. Full article

Composite girders with corrugated steel webs and concrete-filled steel tubular (CSW-CFST) truss chords are a new type of structure and have been used in bridges. To study the fatigue performance of these composite girders, model tests and numerical analysis were conducted, and the results compared with those for composite girders with corrugated steel webs and steel tubular (CSW-ST) truss chords. The results indicated that concrete-filling the chords constrained chord radial deformation and relieved hot-spot stress in the intersecting weld zones of composite girders with CSW-ST truss chords by 18.5–60.1%. The crack growth rates along both depth and length directions in composite girders with CSW-CFST truss chords were lower than those of composite girders with CSW-ST truss chords during the crack propagation and failure stages. Under the same fatigue load, concrete-filling the chords increased the fatigue life of composite girders with CSW-ST truss chords by 61.5%. Under the condition that there is no fatigue design S-N curve, the fatigue design S-N curve given in API can be used to evaluate the fatigue life of composite girders with CSW-CFST truss chords with a deviation of less than 17.4%. Full article

This paper presents the results of a parametric study on the response of unreinforced and retrofitted masonry specimens. The adopted strengthening technique is the steel-reinforced plaster, which is very commonly used but it is not supported by a proper theoretical and experimental characterization in the scientific literature. The aim was to investigate the main parameters that affect the structural performances of the walls. Several numerical models were implemented using the finite element method to analyze the influence of the bricks’ arrangements, the mechanical properties of the mortar joints, the number of connectors, and the mechanical properties and thickness of the plaster coating. A concrete damage plasticity model was adopted to describe the bricks, the mortar joints, and the plaster behaviors. For the unreinforced specimens, the outcomes confirmed that the mortar strength had a significant influence on the performance of the wall, together with the presence of potential weaknesses in the bricks, while the bond effect was negligible. For reinforced walls, the connectors do not have a significant influence on retrofitted wall capacity but may prevent instability if a proper number is considered. Furthermore, the strength of the plaster coating does not affect the collapse load significantly, while increasing the fracture energy, which can be produced, for instance, by using fiber-reinforced concrete, increases the capacity of retrofitted walls, with more limited damage. Finally, an increase in the plaster thickness may be beneficial in terms of collapse load, even though greater thickness may increase the seismic masses significantly. Full article

In order to meet residents’ demands for high sound insulation and thermal insulation performance in buildings, functional materials, such as non-adhesive extruded plastic panels, are added to floor slabs to form the bottom-up “structural layer-functional layer-levelling layer”, common in assembled buildings. The non-adhesive leveling system has gradually become a new floor structure. However, the strength of the functional layer is insufficient. How to determine the minimum thickness of the leveling layer is not fully considered in the current building ground design codes of various countries, which makes the engineering application ahead of the codes and the structural damage problems occur frequently. This must be considered, in order to ensure the safety of the system. Based on the layered elastic half-space theory, the effects of functional layer thickness, leveling layer thickness and leveling layer material on the maximum tensile stress of the system are compared. The results of this research lay a solid foundation for the popularization and application of non-adhesive flat extruded plate systems. Full article

Thick wall-thick slab structures are a newly-developed type of structural system comprising solely of structural floor slabs and shear walls, the former of which is thicker than that of slabs used in typical reinforced concrete frame structures. This study looks to develop a method to predict the initial stiffness of thick wall-thick slab joints under lateral loading by adopting the effective beam width method (EBWM). The height and length of the bearing wall, and the span length of the slab on effective beam width have been considered. Moreover, a correction coefficient that estimates the lateral force applied on the wall top, which is another crucial parameter for predicting the effective beam width and considered as the condition providing initial stiffness, is suggested based on experimental data from the literature. Additionally, by comparing values of the effective beam width obtained from the proposed model with those calculated using equations employed by the current code according to three wall-slab joint specimens, it has been demonstrated the usefulness and accuracy of the proposed method, which works better than the current code method for the wall-slab joints in TWTS cases. Full article

In this study, a novel prefabricated light-steel beam–column connection consisting of a thin-walled rectangular hollow section column and two cold-formed steel truss beams is proposed and investigated by carrying out experimental tests. Eight cruciform beam–column connection specimens with different configurations are fabricated and tested to failure under monotonic static loading. First, failure mode and the loading–displacement curve of each specimen are investigated. Consequently, the effect of three variables, including truss-beam configuration, truss-beam type, and with or without sleeve tube reinforcing the column, on the static bearing capacity of the proposed connection and the deflection of the truss beams are investigated. It is found that plug welding the sleeve to the column can significantly increase the static bearing capacity of the proposed connection. In addition, fillet welding connecting the column and the channel connectors to accommodate the end of the truss beams is crucial to the static bearing capacity of the proposed beam–column connection. Because beam–column connections with single-truss beams have a higher load-bearing capacity and require less material and assembly work, it is recommended to adopt this type of configuration for the proposed connection. Full article

The Polish Air Force operates more than one hundred helicopters of the Mi family (manufactured by Mil Helicopters), equipped with metal main rotor blades. The main rotor blades are among the most stressed components of these structures. For this reason, they are subject to more frequent inspections during operation than other components. One type of damage detected during inspections is the local disbonding of fragments of the anti-erosion layer from the leading edge. This harmless-looking damage is very dangerous, since it quickly leads to the complete detachment of the layer. The leading edge, unprotected by the metal cover, erodes rapidly. The detached layer, when thrown away at high speed, endangers other parts of the helicopter, such as the tail rotor, and may cause damage to other helicopters if flying in formation. The technology supplied by the manufacturer to date has not encompassed the field repair of this type of damage. Therefore, efforts were made to develop repair technology for rapid repairs of blades in field conditions during missions of the Task Force White Eagle in Afghanistan. This article presents the concept of repair technology feasible in field conditions and presents the results of post-repair edge tests. Test results to identify the materials used in the construction of the trailing edge are also presented. The results of materials testing facilitated the development of technological processes, and, in the future, will aid the selection of a substitute bonding paste system with similar parameters that are essential for repairs. Full article

Negative skin friction (NSF) of piles in recent filling or soft area is an important effect factor of pile bearing capacity. Since field experiments on NSF are time consuming and it is difficult to large surcharge loads in experimental research, a unified calculation method of pile positive/negative skin friction was established based on the effective stress method for investigation. The closed-form analytical solutions for calculating the pile skin friction corresponding to the plastic and elastic state were derived respectively. Meanwhile, the axial load of a single pile under different distribution forms of the pile skin friction was deduced. The calculation method was verified by comparing with an in-situ test. Furthermore, a computer model, which was established by the finite element method, was used to study the effect of the friction coefficient, consolidation time, consolidation pressure, drainage condition, and pressure ratio on the distribution of NSF and the location of neutral point. The results show that the effect of the friction coefficient, consolidation time, and pressure ratio on the NSF were significant. The friction coefficient increased from 0.05 to 0.4, the position of the neutral point rose by 22%, and the drag load of pile shaft was obviously increased. The effect of consolidation pressure and drainage conditions on the neutral point were relatively less, but they had a great influence on the distribution and magnitude of NSF. Furthermore, under different consolidation pressures, the normalized maximum axial load, F_max/p, of the pile shaft had a good linear relationship with the pressure ratio, n, and the slopes were the same. Full article

In this paper, an inerter-based device for structural vibration control is proposed with which inertance can be altered relying on the frequency changes of the excitation. In this manner, a tuned mass damper is developed in such a way that it is assembled with a ball-screw inerter along with a new continuously variable transmission system. The device is termed an adaptive tuned mass inertance damper (ATMID). The ATMID is able to produce an alterable inertance, which gives rise to seamless variability in device frequency; consequently, the device frequency can be tuned to that of the excitation. To assess the efficiency of the device, the response amplitude of a single-degree-of-freedom harmonically induced structure controlled by the ATMID is compared with those of the passive-controlled and uncontrolled structures. Results show that in the frequency band where the effectiveness of the passive device with a mass ratio of 0.2 is degraded and even destructed, the adaptive device with a mass ratio of 0.1 and diverse inertance behaves impressively. As a result, notable oscillation suppression is obtained using the proposed adaptive device compared with passive-controlled (56%) and uncontrolled cases (21%). The presented extensive variability in the frequency of the device utilizing its transmission ratio of 0.45–2.2 leads the device to a superior level of oscillatory motion reduction in structural responses along an enlarged frequency band. Full article

This paper proposes a curved link-slab (CLS) structure, simplified into a hingeless arch model, to address the current cracking phenomenon of CLS concrete. The stress formula of the hingeless arch under various loads is derived based on the classical mechanic’s method. Based on an actual bridge example, the mechanical properties of CLS are analyzed under different loads and load combinations. The results show that: (1) the CLS stress is significantly lower than that of the flat link-slab structure (FLS), (2) its stress values are less than the concrete tensile limit, and (3) the CLS can effectively solve the concrete cracking phenomenon on the link-slab. The rationality of the stress formula derived from the simplified model of the hingeless arch is verified using the finite element method (FEM). The parametric sensitivity analysis shows that variation of the reinforcement ratio of the CLS has a limited impact on it. Considering both the concrete tensile and compressive limit, the thickness of the CLS should be 15 cm to 20 cm, and its design span should be about 5% to 7.5% of the main beam length. Full article

Prestressing of concrete structures using Fe-based shape memory alloys has been investigated extensively by experiments in the last decade. However, detailed investigations on the stress produced by the Fe-based shape memory alloys and its influence on concrete damage during deformation of concrete structure has not been investigated yet. In this study, the prestressing effect by Fe-based shape memory alloy bars on bending behavior of reinforced concrete beam was investigated numerically. A finite element simulation model was developed to investigated the bending responses of the beams including nonlinear material properties such as concrete cracking and crushing as well as the plastic deformation of the Fe-based shape memory alloy. The model is able to capture the bending behavior of the beam prestressed with the Fe-based shape memory alloy bars. Based on the numerical and experimental results, the prestressing effect by the shape memory alloy bars was investigated in detail. Although the developed model slightly overestimated the experimentally obtained bending load-deflection curves of the concrete beams, it was shown that the developed model can be used for an optimization study to select the best possible design parameters for prestressing the concrete beam with the Fe-based shape memory alloy bars. A possible reason for the overestimation is the idealized perfect bonding assumption between Fe-SMA and concrete used in the model, while slip at the interface occurred in the experiments. Full article

Superposed perfobond connectors are a type of connector used in composite structures. When the construction conditions are limited to increase the diameter of the opening, the shear capacity of the connector can be improved by enhancing the confining effect of the concrete dowel. In this study, 12 superposed perfobond connectors were fabricated to investigate the influence of lateral constraints on their shear behavior. The effects of hole area and holes’ number, diameter of the perforating rebar, concrete compressive strength, and the number of transverse reinforcements were investigated via the failure modes and load–slip curves. The results indicate that double-sided shear failure occurs in connectors with perfobond rib thicknesses exceeding 9 mm, and the connectors featuring strong lateral constraints not only exhibited higher bearing capacities but also superior load-holding capacities after peak load. Finally, an equation for the shear capacity of multi-hole perfobond connectors, considering lateral constraints, was proposed according to the double-sided shear theory. Full article

Diversification of the optimum designs is practical for metallic dampers due to their advantages of low cost, stability, and ease of fabrication. Therefore, this paper presents a novel approach—dynamic optimization—to derive various optimum shapes of metallic dampers that will dissipate the greatest amount of seismic energy. Specifically, this study proposes a conceptual metallic damper for bridges as a target model to investigate and develop the optimization method. First, an optimizing system was constructed by combining an optimization algorithm (sequential quadratic programming, SQP) with finite element analysis. In a conventional optimization process, energy dissipation capability and stiffness of the metallic damper increases under given static loadings. However, the conventional process fails to diversify the optimized shapes and results in less energy dissipated in conditions with relatively small ground motions due to the increased stiffness. Therefore, a novel method with a simple numerical model for dynamic optimization was devised with additional spring sets and concentrated masses. By utilizing this model, the optimized results under relatively high acceleration conditions were similar to the statically optimized cases, while the other cases showed different trends of optimum shapes. These unconventional results demonstrate decreased stiffness in static analysis, but eventually exhibit higher energy dissipation during small earthquakes. Full article

The excavation depth of a deep and large foundation pit of a composite support system is 25.5 m, the minimum clear distance from the main structure of the station is 10.6 m and the closest distance to the entrance and exit structure is only 3.6 m. Relying on this project, numerical simulation, field monitoring and other methods are used to study the deformation law of the self-supporting system, the ground settlement and the subway station under construction. Then, the influence of different support parameters on the deformation of the subway station and track is analyzed, and the internal relationship between the deformation value of the station and track and the support parameters is further discussed. The main work and achievements are as follows: (1) Through field measurement and analysis, the deformation history of the station and track in the excavation is studied. The obtained results show that the interbracing + pile–anchor composite support structure has better control over the deformation of adjacent stations and tracks. Comparing the simulated value of station and track deformation with the measured data, it is concluded that the simulated and measured deformation trends remain consistent, and the maximum deformation value corresponds to the middle position of the foundation pit. This confirms the rationality and reliability of the composite support system model. (2) The analysis of the influence of different support parameters on the maximum deformation value of the subway station and track shows that the deformation of the station and track is less affected by the pile diameter of the retaining pile and the size of the interbracing section. It is greatly affected by the embedding depth of the retaining pile and the number of support channels. It is suggested that the optimal parameters should be a pile diameter of 1.0 m, embedding depth of 8 m, four interbracings and an interbracing section of 1.0 m × 1.0 m. Full article

The joint work of multiple subsystems in an active mass damper/driver (AMD) system solves the problems that the excessive weight and the insufficient driving capacity exist in the AMD system with an auxiliary mass. However, each subsystem has its own time delay, which is caused by inherent equipment defects. As a result, each subsystem works asynchronously, which reduces the performance of the whole system. It is necessary to take into account its multi-time-delay characteristics. Firstly, a four-layer frame is constructed for analyzing the impact of multi-time-delay on the output of control parameters. Then, a new compensation gain is designed by an H_∞ control law. Finally, the proposed methodology is used in the above experimental system, and the performance is verified by the control indexes. The results manifest that the proposed controller enhances the performance of the multi-time-delay control system. Full article

Non-cylindrical vectorial femtosecond lasers are employed to irradiate tungsten surfaces. Compound nanopatterns composed of periodic nanoholes and semi-circular curved ripples are produced by scanning the target relative to the laser beam. The tangential direction of the curved ripples is perpendicular to the local polarization direction of the vectorial femtosecond laser beam. Therefore, the formation mechanism of the curved ripples can be attributed to the interference between the incident femtosecond laser and the laser-induced surface plasmon polaritons (SPPs). We found that, in addition to the curved ripples, periodic nanoholes with an average diameter of 406 nm also appeared on the target surface, and they all tended to appear at the vertexes of the semi-circular curved ripples, i.e., the converging point of SPPs. Further experiments demonstrated that the location of the periodic nanoholes was totally determined by the polarization state of the incident femtosecond laser. Therefore, we deduced that the convergent SPPs induced by the non-cylindrical vectorial femtosecond laser interfered with the incident laser at the convergent point, leading to the generation of periodic nanoholes. The investigations in this work exhibited the important role of manipulating the propagation of SPPs in femtosecond laser surface structuring, which not only diversifies the surface patterns that can be produced by laser-induced periodic surface structuring (LIPSS) but also provides deep insights in the excitation and propagation dynamics of SPPs. Full article

This paper is concerned with determining the optimum conditions of steel cylindrical shells with technological limitations and one behavioral constraint, related to a specific constitutive law for limiting load-carrying capacity. The optimum structural design in the plastic range of circular cylindrical full shells composed of rings of variable thickness is given. A numerical procedure for determining the optimal dimensions of shell rings is given. A shell collapse mechanism is assumed in the kinematic part, which satisfies requirements. Within the optimum conditions, the power of the dissipation energy of rings assuming the hexagon Hodge condition of plasticity are derived. A series of numerical solutions and results of optimal structural designs for a shell that is simply supported at the ends are presented. In one example of optimally calculated shells, the length X₁ of one ring was varied. Full article

In recent years, earthquake disasters have seriously damaged nonstructural components, so it is necessary to study their seismic performance. However, the existing scholarly research mainly concentrates on multistorey and high-rise buildings, and there are still deficiencies in the analysis of the seismic performance of the nonstructural components in large-span structures under seismic action. In this paper, the acceleration responses of a single-layer spherical reticulated shell structure are compared with those described in the current seismic design codes of the nonstructural components, and it is found that the current codes are not fully applicable to the seismic design of the nonstructural components in reticulated shell structures. The calculation formulas of the acceleration response spectra of single-layer spherical shell nodes are theoretically derived, and the shell node acceleration response spectra are affected by higher-order modes, orthogonal horizontal seismic input directions, and the membrane stiffness of the shell nodes. The variations in the acceleration responses of the shell nodes with node position and rise-to-span ratio are analysed, and a design method for the equivalent seismic action of the nonstructural components in a single-layer spherical reticulated shell with a roofing system is proposed. Full article

In Indonesia, infrastructure, such as port facilities, has been damaged by earthquakes. Therefore, evaluating rational earthquake ground motions (EGMs) for seismic design is necessary to mitigate earthquake disasters in the future. The EGMs in the Indonesian Seismic Code are stipulated based on the ASCE standards and not on site-specific ones. This study aims to propose site-specific EGMs for the seismic design of port facilities in Indonesia. The EGM records and ground data in Indonesia were used for analysis. The EGM incidents in the bedrock were evaluated with deconvolution analysis. The obtained EGMs were amplitude-adjusted to peak ground acceleration similar to that of the EGMs in the bedrock in the Indonesian Seismic Code. A seismic response analysis considering nonlinear soil characteristics was conducted, and 144 EGMs at port sites were obtained. Considering the variation in the obtained EGMs, we propose site-specific EGMs for the seismic design of port facilities. A comparison of the proposed EGMs with those in the design code reveals that the difference between them is significant. Full article

Natural disasters are unavoidable and can cause serious damage to bridges, which may lead to catastrophic losses, both human and economic. Therefore, the assessment of bridges exposed to these events is of paramount importance to identify possible mitigation needs. The objective of the present work is to present consistent tools that may allow us to obtain the failure probability of a masonry arch bridge under a flood event, leading to local scour. Surrogate models were implemented to ease the computational cost of the probabilistic analysis. Moreover, a stochastic parametric analysis based on the geotechnical properties of the soil components of masonry arch bridges located in Portugal was performed. The results show the failure mechanism of the masonry arch bridges when subjected to scour-induced settlements and the influence of soil density on the failure probability obtained for different flow discharge values and angles of attack. The presented methodology and derived fragility curves can be used to assess bridge performance under a flood event, thus providing useful information for bridge management and monitoring. Full article

Structural glass plays an important role in modern architecture, interior design, and building design. It has earned this title primarily because of its properties, such as transparency and its importance in lighting a space. Glass is a challenging building material because of its unpredictability and fragile behaviour. Its fragility, and the way it disintegrates, are the main reasons for using glass in collaboration with timber. The aim of this study is to provide researchers with a more detailed analysis of the influence of the cross-section of I-beams made of timber and glass on the load-bearing capacity and stiffness of each element, based on the research carried out as a basis for such a study. Special attention is focused on analysing the influence of different bonding line types. Composite materials are usually made of a combination of several materials. The goal in making composites is to create a synergy between these materials and combine the good properties of each part of the component. Full article

Fire-resistance experiments were conducted on two full-scale two-way reinforced concrete slabs with three simply supported edges and one clamped edge. This paper presents the design of the furnace, specimens and clamped-end device, the test plan, and the measuring contents and methods. The cracking and failure characteristics of the tested two-way reinforced concrete slabs were introduced. The temperature field distribution of the concrete and steel in the direction of the section thickness, out-of-plane deflections, in-plane deflections, and angle of the slab edges of the two-way concrete slab under fire conditions were analyzed. Cracks form on the slab surface, which is shaped similar to the bottom of a shallow bowl, with two transverse cracks in the mid-area of the medially clamped side and intensively annular diagonal cracks on the corner side. There were several main transverse cracks in the central area of the slab surface. The results indicate that there was a significant decrease in frequency under fire conditions. Relations between the frequency and the central vertical deflection of the two slabs were analyzed by the regression method. This research generates valuable test data that can be used to validate the numerical models developed by fellow researchers in the field of structural fire engineering. Based on the plate balance method and energy method, calculation formula of the limit carrying capacity calculation formula of reinforced concrete two-way slabs with four different boundaries under fire are given, which are simply supported on three sides and clamped on one side. The influence of membrane effect under large deflection is considered in the formula, and the calculated results are in good agreement with the experimental results. Full article

The paper presents an upgrade of the previously developed model for nonlinear 3D analysis of concrete structures extended with the possibility of simulation of the long-term effects (shrinkage and creep) under long-term static load. The origin model is based on the so-called multi-surface principle with modified Rankin criterion for dominant tensile influences (appearance and development of cracks) and the modified Mohr-Coulomb criterion for dominant compressive states (yielding and cracking of concrete). The material behaviour is described with elementary material parameters (modulus of elasticity, Poisson’s coefficient and uniaxial compressive and tensile strength of concrete) by standard tests. Sufficient accuracy along with a simple and effective description of the very complex behaviour of reinforced concrete structures, make this model advantageous. Creep and shrinkage are based on the procedure given by the fib Model Code 2010 and extended with a special extension for non-linear creeping. Two simple examples show the capabilities of the model, while a good agreement between numerical and experimental results indicates that the developed model can well describe long-term effects in reinforced concrete structures, and that the model is appropriate for standard engineering practice. Full article

The middle rock pillar in ultra-small-spacing tunnels is significantly narrow, and the stability of the primary support and lining are easily influenced by the blasting vibration wave from an adjacent tunnel. Therefore, understanding the vibration frequency characteristics is essential for the blasting vibration control. Based on the blasting works on a double-track roadway tunnel (Jiuwuji tunnel in Guizhou, China), this study investigates the dominant frequency attenuation in the preceding tunnel with the middle rock pillar spacing ranging from 4.0 m to 9.4 m. The results show that the ranges of the dominant frequency distributions on the primary support and lining are widely within 200 Hz, but there are varieties in their propagation laws. The distribution of the dominant frequencies on the primary support is broader than that on the lining; and the dominant frequencies are concentrated on a specific range when the lining is far from the blast face beside a particular value, which is not present on the primary support. As the presence of cavity and changing medium between the lining and the primary support, it made a significant contribution to the filtering the vibration waves. Furthermore, on the primary support, the high-frequency part of the vibration waves attenuates rapidly with distance, and then, the practical prediction equations describing dominant frequency attenuation were proposed. The comparison on frequency characteristics per delay for the millisecond delay blasting shows that multiple delay sequences blast contributes to a multi-structured amplitude spectrum of blast vibration waves; and the varies of the equivalent explosion sources dimensions and numbers of free surfaces in each blast delay resulting in diverse vibration waveforms. Finally, the dominant frequencies determined by different methods were compared, and the results show a nonlinear relationship between the ZCFs and DFs. The above research conclusion expands the understanding of blasting vibration in tunnel engineering, particularly in the frequency distribution. Full article

An innovative passive energy damper is introduced and studied experimentally and numerically. This damper is designed as the main plate for energy absorption which is surrounded by an octagon cover. In addition to simplicity in construction, it can be easily replaced after a severe earthquake. Experimental test results, as well as finite element results, indicated that, by connecting the cross-flexural plate to the main plate, the mechanism of the plate was changed from flexural to shear. However, the cross_flexural plate always acts as a flexural mechanism. Changing the shear mechanism to a flexural mechanism, on the other hand, increased the stiffness and strength, while it reduced the ultimate displacement. Comparing the hysteresis curve of specimens revealed that models without cross_flexural plates had less strength and energy_dissipating capability than other models. Adding the flexural plate to the damper without connecting to the main plate improved the behavior of the damper, mainly by improving the ultimate displacement. Connecting the cross plate to the web plate enhanced the ultimate strength and stiffness by 84% and 3.9, respectively, but it reduced the ductility by 2.25. Furthermore, relationships were proposed to predict the behavior of the dampers with high accuracy. Full article

In view of the stick-slip phenomenon in deep and hard rock drilling, a new type of torsional impactor that can provide torsional impact vibration was designed. According to the working principle and structural characteristics of the designed torsional impactor, this paper theoretically analyzes the influences of different structural parameters and motion parameters on the impact frequency, impact force, and impact torque of the torsional impactor. The results show that the impact frequency f is directly proportional to the rotational speed V_Z of the transmission shaft and the installed number n of torsional impact generating devices. Additionally, the impact force F is directly proportional to sine value of the impact angle α (i.e., sinα), impact hammer mass m, impact hammer rotation speed V_Z (i.e., transmission shaft rotation speed), and impact hammer rotation radius r and is inversely proportional to action time Δt of the impact hammer and impact anvil. Furthermore, the impact torque M is directly proportional to the impact force F and rotary radius r of the impact hammer. This article lays a foundation for further theoretical and experimental research of torsional impactors and provides a reference for the design and testing of torsional impactors. Full article

In an effort to improve impact energy-absorption characteristics, this study introduces a cylindrical crash absorber (CAP) with discontinuous protrusions and a continuous local-expansion plastic-forming method for its manufacture. The mechanical properties of the cylindrical energy-absorption structure were modified by installing multiple particle protrusions on the cylinder sidewall to reduce the initial pickup load and improve the impact energy-absorption performance. To facilitate manufacture of the proposed CAP, a cylindrical rubber piece was placed into a cylindrical tube and pressure was applied to the rubber from both ends of the tube. The CAP was formed by the bulging force of the rubber. The formability was verified by developing a successive local bulge-forming experimental device and comparing the manufactured CAP with the results of numerical simulations. Testing of quasi-static collapse conducted on a CAP manufactured using this device verified the effectiveness of the proposed CAP design and its plastic-forming method. It was determined that this design reduced the initial peak load, and the crash absorber could maintain stability over a long, continuous distance during crushing deformation. Full article

This study proposes a new damage identification method for hangers of arch bridges using the static deflection difference at the anchorage point of the hanger and the tie-beam. The relationship between the ratio of cable tension loss and the deflection difference at the anchorage point is studied. For the first time, the deflection difference influence matrix for hanger damage identification is defined. The static deflection change parameter is formulated as a function of the deflection difference influence matrix and the ratio of cable tension loss. The study shows that the percentage of cable tension loss can be obtained from the changes in static deflection at the anchorage point and the deflection difference influence matrix. Therefore, by observing a plot of the ratio of cable tension loss, the damage locations can be identified conveniently. Numerical and laboratory studies show that this method can accurately locate the damaged hanger of through-arch bridges under various scenarios. The proposed damage detection method has a clear theoretical base and is simple to operate, and it is suitable for practical engineering. Full article

This research identifies the significant optimal intensity measures (IM) for seismic performance assessments of the fixed offshore jacket platforms. A four-legged jacket platform for the oil and gas operation is deployed to investigate the seismic performance. The jacket platform is applied with nonlinearly modeled using finite element (FE) software OpenSees. A total of 80 ground motions and 21 different IMs are incorporated for numerical analyses. Nonlinear time-history analyses are performed to obtain the jacket structure’s engineering demand parameters (EDP): peak acceleration and displacement at the top of the structure. Four important statistical parameters: practicality, efficiency, proficiency, and coefficient of determination, are then calculated to find the significant IMs for seismic performance of the jacket structure. The results show that acceleration-related IMs: effective design acceleration (EDA), A95 parameter, and peak ground acceleration (PGA) are optimal IMs, and the acceleration-related IMs have good agreements with the acceleration-related EDP. Full article

Pile buckling is infrequent, but sometimes it can occur in slender piles (i.e., micropiles) driven into soils with soft layers and/or voids. Buckling analysis of piles becomes more complex if the pile is surrounded by multi-layered soil. In this case, the well-known Timoshenko’s solution for pile buckling is of no use because it refers to single-layered soils. A variational approach for buckling analysis of piles in multi-layered soils is herein proposed. The proposed method allows for the estimation of the critical buckling load of piles in any multi-layered soil and for any boundary condition, provided that the distribution of the soil coefficient of the subgrade reaction is available. An eigenvalue-eigenvector problem is defined, where each eigenvector is the set of coefficients of a Fourier series describing the second-order displaced shape of the pile, and the related buckling load is the eigenvalue, thus obtaining the effective buckling load as the minimum eigenvalue. Besides the pile deformed shape, the stiffness distribution in the multi-layered soil is also described through a Fourier series. The Rayleigh–Ritz direct method is used to identify the Fourier development coefficients describing the pile deformation. For validation, buckling analysis results were compared with those obtained from an experimental test and a finite element analysis available in the literature, which confirmed this method’s reliability. Full article

This study proposes an analytical model applicable to the shear analysis of reinforced high-strength concrete beams. The proposed model satisfies the equilibrium and compatibility conditions and constitutive laws of the materials. The proposed model is based on the fixed angle theory and allows the principal stress to rotate as the load increases, so that the RC beams can be analyzed more realistically. High-strength material models were used in the proposed model to consider the characteristics of high-strength concrete. The concrete shear contribution at crack surfaces was calculated from Mohr’s circle. The proposed model considers the effect of bending moment on shear by reducing the amount of longitudinal reinforcement resisting shear. To verify the accuracy of the proposed model, a total of 64 experimental results were collected from the literature. A comparison with previous experimental results confirmed that the proposed model can be predicted relatively accurately with an average of 0.98 and a coefficient of variation of 12.1%. Full article

Vertical deflection of a frame beam is an important indicator in the limit-state analysis of frame structures, particularly for steel–concrete composite beams, which are usually designed with large spans and heavy loads. In this study, the equivalent flexural stiffness of composite frame beams is analysed to evaluate their vertical deflection. A theoretical beam model with a spring constraint boundary and varied stiffness segments is established to consider the influence of both the rotation restraint stiffness at the beam ends and the cracked section in the negative moment region, such that the inelastic bending deformation of the composite beams can be elaborately described. By an extensive parametric analysis, a fitting formula for evaluating the equivalent flexural stiffness of the composite beams, including the effects of the rotational constraint and the concrete cracking, is obtained. The validity of the proposed formula is demonstrated by comparing its calculation accuracy with those of existing design formulas for analysing the equivalent flexural stiffness of the composite beam members. Moreover, its utility is further verified by conducting non-linear finite element simulations of structural systems to examine the serviceability limit state and the entire process evolution of beam deflections under vertical loading. Finally, to facilitate the practical application of the proposed formula in engineering design, a simplified method to calculate the deflection of composite beams, which utilises the internal force distribution of elastic analysis, is presented based on the concept of equivalent flexural stiffness. Full article

The design of a manipulator arm, which is built from a construction kit, is presented in this article. The procedure is based on the results of the discrete optimization of a truss structure and its application to a simple component system (assuming a predefined shape and material of components). A genetic algorithm is used to optimize the truss structure, and the results of the solution are verified on a simple task used in literature (the code was written in the Python language). The construction kit was inspired by Merkur^®, and the article proposes several components with different shapes and materials. The construction kit and the optimization of the truss structure were used to design the manipulator arm. The truss topology has been predefined with respect to the construction set. The finite element method (software ANSYS^®) was used to analyze the components (shell elements) and truss structures (linear analysis, buckling analysis, etc.). To validate the presented approach, the arm designed by topological optimization was used. The comparison shows that the use of components may be an alternative to topology optimization and additive manufacturing. The next step will be the modification of the presented method in order to minimize the differences between the simplified task used for optimization (truss structure-rod element) and the simulation composed of components (components assembly-shell element). Full article

The development of a carbon-fiber-reinforced plastic (CFRP) part is carried out by utilizing many experimental results in deciding the design. For this reason, the development period of a CFRP structure is long and an obstacle for commercialization. In this paper, multiple regression analysis is used to derive a response surface that estimates the generated load using the shape parameters of a corrugated collision energy absorbing structure to shorten the development period. To obtain the response surface, we conducted a quasistatic crushing experiment by using the length of linear portions (pitch) and the number of stacks (thickness) of a corrugated shape as parameters. When progressive crushing mode is observed, energy absorption efficiency decreases with the increase in pitch, and increases with the increase in the number of stacks. To discuss how energy absorption efficiency changes, a comparison examination is conducted using the derived response surfaces. Results indicate that specifications with high energy absorption efficiency can be accurately selected using the response surface of primary expression. In addition, differences in deformation mode were due to the influence of the stress at the corner portion of a part. Full article

In a flexoelectric sensing element using bending mode, estimation of the flexoelectric coefficient was investigated using 3-D stress/strain analysis and experiments. The proposed method uses the results (deformation and strain) from the finite element analysis (FEA). The estimated flexoelectric coefficients were compared with those obtained via the conventional method (Euler’s beam theory) under the assumption of the quasi 1-D stress field. The results show that the RMS value and standard deviation of the estimated flexoelectric coefficient for the 3-D stress field case of the sensing element are 31.51 µC/m and 0.24%, respectively. In addition, we found that the flexoelectric coefficient obtained from the results of the 3-D stress analysis is 1.8% smaller than that of the quasi-1-D stress analysis. Therefore, in order to obtain a more reliable flexoelectric coefficient in the sensing element, the results of the 3-D numerical stress analysis should be used for accurate estimation of the flexoelectric coefficient. Full article

The concept of city information modeling (CIM) has become increasingly popular in recent years. A literature review of previous CIM studies is presented in this paper. First, a bibliometric analysis of the current global CIM research is described, revealing that CIM has become a significant research hotspot. Next, three main research areas of the current CIM technique, namely data collection, integration, and visualization, are summarized to describe the characteristics of CIM research. Furthermore, some widely used CIM platforms are compared, and typical application cases of the CIM technique at different stages of the city life cycle are summarized. Finally, the current issues in CIM research are discussed, and future development directions are proposed. The findings of this study are expected to help researchers understand the current state of CIM and identify future development directions, thereby promoting CIM research development. Full article

This paper presents an experimental investigation on the flexural behavior of ultra-high-performance concrete (UHPC) beams prestressed with external carbon fiber-reinforced polymer (CFRP) tendons. A total of eight T-shaped beam specimens were fabricated and tested, and the effects of the effective prestressing stress, partial prestressing ratio, deviated angle, and loading condition on the flexural behavior were analyzed. The experimental results indicate that the fully prestressed beams experienced a brittle failure, and the shear capacity of these beams was mainly controlled by the effective prestressing stress in CFRP tendons and the ultimate tensile strength of UHPC, whereas the partially prestressed beams failed in a ductile manner. The presence of internal steel reinforcement could significantly improve the flexural capacity and deformation ability. Thus, internal reinforcements should not be omitted from UHPC beams with CFRP tendons. A higher effective prestressing stress resulted in enhanced cracking load and flexural capacity. The deviated angle enhanced the utilization efficiency of high strength CFRP tendons. The loading condition exerted a slight influence on the flexural behavior of the specimens. Moreover, a method considering the effect of steel fibers was proposed and verified to predict the flexural capacity of UHPC beams prestressed with external CFRP tendons. Full article

A membranous shaped Ni/Zn layered double hydroxide based nanohybrid was obtained using a low-cost template-free hydrothermal process at optimized growth conditions of 180 °C for 6 h. The synthesized nanohybrid was structurally, texturally and morphologically characterized using different techniques such as X-ray diffraction, FTIR, XPS spectroscopy, BET analysis and FESEM microscopy. The adsorption performance of our product was estimated through the Azorubine dye removal from synthetic wastewater. We therefore studied the synergic effects of Ni/Zn adsorbent dosage, contact time, pH, adsorbate concentration, stirring speed and temperature on the Azorubine adsorption efficiency. In this investigation, we obtained bi-structure based nanoadsorbent with 54% crystallinity order composed of nickel hydrate and zinc carbonate hydroxides in irregular nanoflake-like mesoporous nanohybrid morphology. Interestingly, it was also revealed to have high specific surface area (SSA) of around 110 m² g⁻¹ with important textural properties of 18 nm and 0.68 cm³ g⁻¹ average pore size and volume, respectively. Moreover, the adsorption results revealed that this novel Ni/Zn layered double hydroxide (Ni/Zn LDH) was an efficient adsorbent for Az molecule and possesses an adsorptive ability exhibiting a short equilibrium time (60 min) and a high Az adsorption capability (223 mg g⁻¹). This fast removal efficiency was attributed to high contact surface area via mesoporous active sites accompanied with the presence of functional groups (OH⁻ and CO₃²⁻). In addition, the Langmuir and Freundlich isotherms were studied, and the results fitted better to the Langmuir isotherm. Full article

The behaviour of dry-joint masonry arch structures is highly nonlinear and discontinuous since they are composed of individual discrete blocks. These structures are vulnerable to seismic excitations. It is difficult for traditional methods like the standard finite element method (FEM) to simulate masonry failure due to their intrinsic limitations. An advanced computational approach, i.e., the combined finite-discrete element method (FDEM), was employed in this study to examine the first-order seismic capacity of masonry arches and buttressed arches with different shapes subjected to gravity and constant horizontal acceleration. Within the framework of the FDEM, masonry blocks are discretised into discrete elements. A finite element formulation is implemented into each discrete element, providing accurate predictions of the deformation of each block and contact interactions between blocks. Numerical examples are presented and validated with results from the existing literature, demonstrating that the FDEM is capable of capturing the seismic capacities and hinge locations of masonry arch structures. Further simulations on geometric parameters and friction coefficient of masonry buttressed arches were conducted, and their influences on the seismic capacities are revealed. Full article

This study aims to investigate the ultimate bearing capacity of a novel tubular K-joint used for light-steel structures consisting of thin-walled square hollow section members, a U-shape connector and self-drilling screws, and the effect of three patterns of stamping indentation fabricated on the U-shape connector on the ultimate bearing capacity of the proposed K-joint. Firstly, a total of 12 K-joint specimens were tested to failure under monotonic brace axial compressive loading. Secondly, failure mode and the ultimate bearing capacity of each specimen were investigated and analyzed. Finally, finite element analyses were carried out to study the effect of three key parameters, including chord axial stress ratio, half width-to-thickness ratio of the chord and brace-to-chord wall thickness ratio, on the ultimate bearing capacity of the proposed K-joints using the recommended U-shape connector. It was found that failure mode of the proposed K-joint is governed by both the deformation of the U-shape connector and the chord local plastification. Besides, the K-joint specimen using a U-shape connector with the strip stamping grooves in the horizontal direction generally has a higher bearing capacity and a much smaller connector deformation. Similar to the welded tubular joints, chord axial stresses may also significantly reduce the ultimate bearing capacity of the proposed K-joint. Full article

This paper describes the Field Boundary Element Method (FBEM) applied to the fracture analysis of a 2D rectangular plate made of Functionally Graded Material (FGM) to calculate Mode I Stress Intensity Factor (SIF). The case study of this Field Boundary Element Method is the transversely isotropic plane plate. Its material presents an exponential variation of the elasticity tensor depending on a scalar function of position, i.e., the elastic tensor results from multiplying a scalar function by a constant taken as a reference. Several examples using a parametric representation of the structural response show the suitability of the method that constitutes a Stress Intensity Factor evaluation of Functionally Graded Materials plane plates even in the case of more complex geometries. Full article

Loading rates affect the behavior of concrete specimens from the beginning of the loading process until failure. At rather high loading rates, longitudinal deformations in concrete specimens under a compressive load are practically elastic up until the ultimate limit state. It has been previously demonstrated that transverse deformations effectively indicate high-strength concrete behavior in the entire static loading process range. A theoretical model for cylindrical concrete specimen failure under compressive load, based on a structural phenomenon, has also been proposed. The aim of the present research is experimental verification of using transverse deformations in addition to longitudinal ones for investigating high-strength concrete behavior at the non-elastic stage. This research is based on testing normal-strength concrete cylindrical specimens under compression at relatively high loading rates. The theoretical model of the cracking and failure scheme of the cylindrical specimens are experimentally confirmed. The obtained results demonstrate that it is possible to use transverse deformations for the interpretation of initiation and development of inelastic deformations in high-strength concrete up to class C90 based on the data for normal-strength concrete specimens of class C30 subjected to relatively high loading rates. Full article

Corrugated paperboards are used for packaging because of their high strength-to-weight ratio, recyclability, and biodegradability. Corrugated paperboard consists of a liner and a corrugated medium and has an orthotropic sandwich structure with unique characteristics for each direction owing to its flute shape. In this study, finite element analysis (FEA) was performed on the flat crush behavior of the corrugated paperboard based on the flute type. The stress-strain (SS) curve and shape change of the flute were analyzed during the flat compression. In addition, it was compared with the FEA results through various experiments. The restraints and boundary conditions applied during FEA were used to properly describe the conditions during the experiment. Specifically, the horizontal translation motion of the top and bottom surfaces of the modeled test specimen was constrained during FEA to correspond to the effect of sandpaper attached to the upper and lower plates of the testing machine. This was done to prevent the specimen from sliding in one direction during the flat crush test. The change in the flute shape of the corrugated paperboard by flute type analyzed through experiments and FEA was very similar; although there was a difference in the absolute value between the two methods of the SS curve, the flute type exhibited a similar trend. Therefore, a qualitative comparative study on the flat crush behavior by flute type was possible with the FEA method, as in this study. Further studies on the material properties of the corrugated paperboard components and the modeling methods of the corrugated paperboard will enable the FEA-based simulation technique to be an alternative tool that can replace the flat crush test. Full article

Wet clutch transmits its power by the friction torque between friction and separate disks. Conical groove friction disk is a new attempt in Wet clutch. Its configurations allow significant enhancement of torque delivery performances, compared with the traditional plane friction disk. In order to study the frictional performances of the conical groove friction configuration, the friction coefficient calculation model of conical groove friction disk was established, and experimental investigation was used to measure the friction coefficient under sliding velocity conditions. The influence of configuration parameters: cone heights and angles on friction coefficients were evaluated in a typical variable speed test. The results indicated that configuration parameters can affect friction performance in a constant speed period. The equivalent radius can directly describe the friction region of a conical groove friction disk. The constant speed test can be a useful method. Full article

In this study, a method for detecting the railway surface defects called “squats” using the ABA (Axle Box Acceleration) measurement of trains was proposed. ABA prototype design, implementation, and field tests were conducted to derive and verify the results. The field test was performed using a proven precision measurement system, and the measured data were signal-processed using a Matlab program. The algorithm used to determine the position of the squats was developed based on wavelet spectrum analysis. This study was verified for a section of a domestic general line and, following field verification for the section, squats was detected with a hit rate of about 88.2%. The main locations where the squats occurred were the rail welds and the joint section, and it was confirmed that in some sections, unsupported sleepers occurred at the locations where the squats occurred. Full article

According to the change characteristics in the toughness of the metal material during the fatigue damage process, the fatigue tests were carried out with the standard 18CrNiMo7-6 material. Scanning the fracture with an electron microscope explains the lack of linear cumulative damage in the mechanism. According to the obtained results, a nonlinear damage accumulation model which considered the loading sequence state under the toughness dissipation model was established. The recursive formula was devised under two-level. The fatigue test data verification of three metal materials showed that using this model to predict fatigue life is satisfactory and suitable for engineering applications. Full article

This paper presents a study about the buckling behavior of thin stainless-steel lining (SSL) for trenchless repair of urban water supply networks under negative pressure. The critical buckling pressure and displacement (p–δ) curves, temperature changing curves, hoop and axial strain of the lining monitoring section and the strain changes with system pressure (p–ε) of the lining under the action of different diameters, different lining wall thickness and different ventilation modes were obtained through five groups of full-scale tests. The variation principles of the post-buckling pressure and the reduction regularity of the flowing section of the lining were further investigated. By comparing different pipeline buckling models and introducing thin-shell theory, the buckling model of liner supported by existing pipe was established. The comparison between the test results and thin-shell theory indicates that one of the significances of the enhancement coefficient k value is to change the constraint condition of the aspect ratio, l/R, thus increasing the critical buckling pressure of the lining. Finally, an improved lining buckling prediction model (enhancement model) is presented. A previous test is used as a case study with the results showing that the enhanced model is able to predict critical buckling pressure and lobe-starting amount of the liner, which can provide guidance for trenchless restoration of the liner with thin-walled stainless steel. Full article

Three types of connectors were proposed and tested for a modular double-skinned composite tubular (DSCT) wind turbine tower, which is composed of two concentric steel tubes filled with concrete between them. The three proposed types were a socket type connector, an H-type connector, and a bolted–welded with shear key connector. Using the proposed connectors, three modular DSCT tower specimens and a single-body specimen were built. Then, quasi-static tests were conducted to evaluate the performance of the three types of connectors, and their behavioral characteristics and failure modes were analyzed. The test results showed that the bolted–welded with shear key connector specimen exerted an almost equal moment resisting capacity as the single-body specimen; however, the other modular specimens exerted only half the moment resisting capacity of the single-body specimen. Moreover, the results showed that the bolted–welded with shear key connector is applicable in a modular DSCT wind turbine tower as it has equal ductility, maximum lateral displacement, and energy dissipation as the single-body specimen. Full article

This article addresses the process to optimally select safety factors and characteristic values for the Eurocodes. Five amendments to the present codes are proposed: (1) The load factors are fixed, γ_G = γ_Q, by making the characteristic load of the variable load changeable, it simplifies the codes and lessens the calculation work. (2) Currently, the characteristic load of the variable load is the same for all variable loads. It creates excess safety and material waste for the variable loads with low variation. This deficiency can be avoided by applying the same amendment as above. (3) Various materials fit with different accuracy in the reliability model. This article explains two options to reduce this difficulty. (4) A method to avoid rounding errors in the safety factors is explained. (5) The current safety factors are usually set by minimizing the reliability indexes regarding the target when the obtained codes include considerable safe and unsafe design cases with the variability ratio (high reliability/low) of about 1.4. The proposed three code models match the target β₅₀ = 3.2 with high accuracy, no unsafe design cases and insignificant safe design cases with the variability ratio 1.07, 1.03 and 1.04. Full article