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The mixing order of silica sand, clay (kaolinite), and water controls the microstructure of resulting artificial soil samples. Most homogeneous microstructures can be achieved by applying the mixing order “sand-water-clay.” The following methods were used to validate this statement: (1) optical observation, (2) X-ray tomography, (3) scanning electron microscopy, and (4) Mercury intrusion porosimetry. For all samples, clays are mainly organized in a homogeneous matrix but are also dispersed heterogeneously in micrometer-sized layers surrounding sand particles, particularly where sand grains show a greater roughness. At water contents ≥1.5 w L , the microstructures are visually similar from the mm to μm scale whatever mixing order is used. However, for water contents lower than 1.5 w L , the mixing order controls the distribution of the clay particles. This paper proposes a motivated choice of a preparation protocol of artificial clayey materials to be used in laboratory experiments. It might contribute to better understanding and modeling grain movements and arrangements in artificial muds, used for instance in underground mining, foundation settlement, hydraulic containment, road construction, soil stabilization, and in natural soils in the occurrence of soil liquefaction, industrial brick manufacturing, and in studying shear processes in tectonic fault zones.

The dynamic responses of a linear primary structure coupled with a nonlinear energy sink (NES) are investigated under harmonic excitation in the 1 : 1 resonance regime. In civil engineering, initial conditions are usually zero or approximately zero. Therefore, in this study, only these conditions are considered. The strongly modulated response (SMR), whose occurrence is conditional, is the precondition for effective target energy transfer (TET) in this system. Therefore, this study aims to determine the parameter range in which the SMR can occur. The platform phenomenon and other related phenomena are observed while analyzing slow-varying equations. An excitation amplitude interval during which the SMR can occur is obtained, and an approximate analytical solution of the optimal nonlinear stiffness is found. The numerical results show that the NES based on the optimal stiffness performs better in terms of control performance.

Y-shaped piles are a new type of pile whose cross-section is like the letter Y: they are often used in ground improvement for road or train subgrades in the eastern coastal region of China. To investigate the bearing behaviour of Y-shaped piles in saturated sand, a series of model tests under compressive and horizontal load for Y-shaped piles, C 1 circular pile (the same cross-sectional area of Y-shaped pile), and C 2 circular pile (the same perimeter of Y-shaped pile) were carried out. Comparative analysis was conducted on bearing capacity, axial force and side resistance distribution, load sharing ratio, bending moment, and lateral soil pressure distribution along the embedded length. The results show that the bearing capacity of a Y-shaped pile does not increase in proportion, and the shaft resistance is weakened to some extent in saturated sand; Y-shaped pile can effectively improve the compressive bearing capacity for the same amount of concrete. The lateral bearing capacity of a Y-shaped pile has directionality, and hanging a circular section into a Y-shaped section may improve the horizontal bearing capacity for the same amount concrete, but cannot give full play to the advantage of the larger side area for horizontal bearing capacity in saturated sand.

Bridge deterioration is affected by various factors. However, neither the relationships between these factors and deterioration are explicitly determined, nor the relative effect of each factor on deterioration is well understood. This study proposed a methodology to resolve these issues by integrating an artificial neural network (ANN) and sensitivity analysis method. The ANN was used to predict deterioration, and the sensitivity analysis method was applied to evaluate the influence of each factor on deterioration. Testing the methodology with 3,368 bridge inspection data pieces indicates that (1) the developed ANN obtained an accuracy of about 65%; and (2) seven factors were identified affecting deterioration. The established ANN model has equivalent performance for three deterioration grades and four types of bridges. Two sensitivity analysis (the Shapley value and the Sobol indices) methods were compared, and they identified the same five most important factors. Consequently, the methodology can effectively avoid the uncertainty of factors on deterioration by providing a relative importance list of factors. The methodology’s predictive ability and factor importance identification ability make it suitable for decision-makers to understand the deterioration situations and to schedule a further inspection and corresponding maintenance strategies.

A numerical investigation on the effects of separation ratios and Reynolds numbers on the flow around four square cylinders in diamond arrangement has been carried out using the lattice Boltzmann method. The separation ratios between the cylinders vary from g ∗ = 1 to 15. The Reynolds numbers based on the diameter of the square cylinder and the inlet uniform inflow velocity are selected from Re = 80 to 160. The computations show that a total of five different flow regimes are observed over the selected ranges: single bluff-body, quasi-unsteady, chaotic flow, in-phase synchronized vortex shedding, and antiphase synchronized vortex shedding flow regimes. It is found that the flow features significantly depend on both the separation ratio and Reynolds number, with the former’s influence being more than the latter’s. We found that the critical spacing for four square cylinders in diamond arrangement for selected Reynolds numbers (80 ≤ Re ≤ 160) is in the range of 2 ≤ g ∗ ≤ 5. The results reveal that the presence of secondary cylinder interaction frequencies indicates that, for chaotic flow regime, the wake pattern is not stable and there is a strong interaction of gap flows and continuous change in the direction of shed vortices behind the cylinders. The effects of the g ∗ and Re on fluid forces, vortex shedding frequency, and flow separation have been examined in detail.

This paper presents an innovative hollow concrete floor system comprising hollow precast panels and self-thermal-insulation infills. The precast panels are connected by welded reinforcement bars and cast-in-situ concrete joints. To study the vertical load-carrying capacity and the working mechanism of this innovative floor system, a static loading test was carried out on a 1/2 scale model. The specimen consists of six precast slab members, four precast reinforced concrete beams and columns, respectively. Experimental and simulation results related to the crack development and vertical load-carrying capacity were analyzed. It is found that the innovative floor system could meet the capacity requirements of the Chinese code. Furthermore, the crack development of the innovative system shows similar characteristics with the solid floor. To explore the feasibility of the existed analysis methods, the specimen was simulated and compared by nonlinear analysis in ABAQUS. The comparison illustrates that the analogue cross beam method is more accurate and suitable for the simulation of the innovative hollow concrete floor system.

Temperature is one of the factors affecting the safety operation of concrete arch dams. To accurately reconstruct the temperature field of the concrete arch dam online based on the temperature data of several typical dam sections, this paper proposes the AdaBoost-ANN algorithm. The algorithm uses artificial neural network (ANN) to establish a training set of the measured temperature data and the temperature field of the concrete arch dam obtained by the three-dimensional finite element model; these trained artificial neural networks are used as weak classifiers of the AdaBoost algorithm. Then, the AdaBoost-ANN algorithm is used to establish the mapping relationship between the measured temperature data and the temperature field, and the online reconstruction of the temperature field of the concrete arch dam is realized. The case study shows that the temperature field of the concrete arch dam can be accurately established by AdaBoost-ANN algorithm based on limited temperature observation data. The algorithm is more time-saving and labor-saving than the finite element method and is convenient for online reconstruction of the temperature field and assessment of the safety status of the concrete arch dam.

The concentric pushing method was used to study the bonding properties between polymer and concrete. This paper studied the influence of polymer density, environmental temperature, and moisture content of concrete between polymer and concrete on the bond strength. The results indicated that the bond failure of specimens occurred mainly when the polymer was pushed out. Furthermore, increasing the polymer density increases the bond strength at the polymer-concrete interface but decreases as the moisture content of the concrete increases. The environmental temperature affects the curing time, and the bond strength increases with increasing temperature. Under the same condition, the bond strength was influenced by the roughness of the interface. This study provides references for the construction design and enhances polymer materials and matrix application for repairing cracks in concrete dams.

Due to many nondamage factors such as temperature, humidity, carbonation, and corrosion effects on natural frequency, the key problem of the application frequency-based method to detect damage is to reveal the rules of these factors affect natural frequency and further to eliminate their effects. The long-term characteristics of reinforced concrete structures require a lot of attention, especially in corrosive environment. In this paper, an experimental investigation was conducted to study the deflection and natural frequency of reinforced concrete beam in a marine environmental chamber for six corrosion stages (accelerated corrosion for 0, 20, 40, 70, 100, and 140 days). The experimental results demonstrated that deflection increases with corrosion time, while natural frequency decreases with corrosion time. Based on the accelerate corrosion test data of reinforced concrete beams, the general expression of the relationship between corrosion depth and natural frequency has been established through the fitting curve method. The polynomial model has been selected for establishing the relationship between steel corrosion depth (including the main reinforcement and stirrup) and natural frequency. The reason for selecting the polynomial model is that the sum of squares due to error (SSE) is closer to 0 and the coefficient of multiple determination (R-square) is closer to 1. This investigations help to discriminate the cause of reinforced concrete beams natural frequency change, to eliminate nondamage factors affects, and to apply many structural damage identification methods effectively.

Lately, Corrugated Steel Plate Shear Walls (CSPSWs) have gained significance and reputation for being effective lateral force-resisting systems. Corrugated plates are characterized by greater out-of-plane stiffness and buckling stability than flat plates, ensuring their enhanced hysteretic behavior. In ordinary Steel Plate Shear Walls (SPSWs), infill plates are fixed to beams and columns. But, detaching the infill plate from columns and connecting it to the beams only is assumed here as a method for reducing column demands. The current study explores the cyclic performance of CSPSWs with beam-only-connected infill plates. The design of a one-story single-bay specimen was done and its finite element model was developed. Parametric studies have targeted CSPSWs with different geometric variables, including orientation, thickness, and aspect ratio of the infill plate. Noteworthy responses were ultimate strength, initial stiffness, energy dissipation capacity, and force-deformation relationship. The obtained results indicated that selecting the right geometrical parameters could yield a desirable cyclic performance. Finally, an analytical method was proposed for calculating the ultimate shear strength of beam-only-connected CSPSWs.

The purpose of this study was to evaluate the effects of a shrinkage reducing agent (SRA) and Portland expanded cement (PEC) on the fluidity, mechanical properties, and shrinkage performance of ultrahigh-performance concrete (UHPC). The results indicated that the fluidity of the fresh UHPC mortar initially decreased and then increases along as a function of SRA dosage. When the dosage of SRA was 1%, the UHPC mortar fluidity was at its minimum. For dosages exceeding 1%, the additional water-binder ratio of the mortar increased, which in turn increased the UHPC fluidity. That is, the SRA delayed the cement hydration and increased the setting time, which is not conducive for early strength development of UHPC. As the SRA dosage was increased (i.e., 0%–2%), the autogenous shrinkage of UHPC decreased significantly such that even a small dosage of about 0.5% SRA was able to effectively reduce drying shrinkage. From the study results, it was also observed that PEC accelerated the loss of fluidity in the fresh UHPC and concurrently promoted the early strength development of UHPC. At 75% PEC content, the strength enhancement effects tended to be stable. This means that although the addition of PEC will potentially increase the autogenous shrinkage of UHPC, it has the positive effect of inhibiting drying shrinkage provided that the PEC dosage is controlled within the 25%–50% range. Furthermore, morphological analyses using a scanning electron microscope (SEM) indicated that an increase in the SRA dosage loosens the UHPC microstructure, with the formation of the hydration products remaining incomplete, thus ultimately causing the UHPC strength to decrease. Overall, the study findings indicated that 2% SRA and 25%–50% PEC can effectively reduce the shrinkage of UHPC and are, therefore, recommended as the optimum dosages.

Earthquakes are vibrations induced by the rapid releases of large quantities of energy from the crustal movements. During seismic excitation, there are kinetic energy, damping energy, and strain energy acting on the tunnel structure. Based on the indexes of the total energy, releasable elastic strain energy, and dissipated energy, this paper proposes three energy evaluation criteria for the tunnel structure, which are applied to the optimization of the aseismic design of the cross-sectional shape and material property of the tunnel structure. It can be concluded that the peak values and accumulated values of elastic strain energy at the spandrel and arch springing are significantly larger than other positions, which indicates that the strengths of the spandrel and arch springing are the most influential factor for the seismic damage of the tunnel structure. Considering this factor, the width-to-height ratio of 1.33 and Poisson’s ratio of 0.3 are determined as the most optimal cross-sectional shape and material property, respectively. Furthermore, by analyzing the relationship between the internal energy and the input energy of the tunnel structure with seismic excitation and proposing an equation for the evaluation of the dynamic stability of tunnel structure, the stabilities of the tunnel structure with different PGAs are analyzed; it can be concluded that the larger the peak value of seismic wave acceleration, the longer the instable period and the greater the degree of dynamic instability. The derived equations can be used as references for the seismic analysis of the tunnel structure, and the conclusions of this paper can contribute to the aseismic design of tunnel lining.

In this paper, a numerical study is presented to investigate wave force on the connections of main parts of a side-anchored straight floating bridge concept for the Bjørnafjorden fjord crossing. The floating bridge is supported by 18 pontoons, and three groups of mooring lines are employed to restrain the bridge against horizontal loads and increase its transverse stiffness. The created wave forces at the connections of pontoon-column and column-girder of the floating bridge considering the effects of short-crested and long-crested waves, varying wave direction, hydrodynamic interaction between pontoons, and mooring system are analyzed. It is found that short-crested and long-crested waves depending on their direction decrease or increase the wave forces on the joints. Considering that the effect of hydrodynamic interaction between pontoons can increase or reduce the wave forces and moments created in the joints, which means the neglect of the hydrodynamic interaction effects between the pontoons to simplify the modeling of this type of floating bridge, may be unacceptable. Moreover, the results showed that the bridge mooring system does not merely reduce the wave forces and moments at joints along the bridge.

In this study, air void contents and distributions of porous asphalt mixtures along the vertical and horizontal directions were quantitatively measured on planar images. Air void contents were determined using some image techniques; while the permeability was measured by the falling head test. Two aggregate gradations (G1 and G2) and three blow numbers (30, 40, and 50) were chosen to explore the effects of gradation and compaction effort on the porosity and permeability. Results showed that porosities and permeabilities are symmetrically distributed along the middle of the specimens; the porosities and permeabilities got the minimum values around the middle zone. A finer gradation or a significant compaction effort generally led to a lower porosity and permeability coefficient. In the horizontal direction, the air void content showed an increasing trend from the outside layer to the inner layer, indicating the nonuniformity of porosity distribution.

The use of cold-formed steel (CFS) channels with circular or rectangular web holes is becoming increasingly popular in building structures. However, such holes can result in sections becoming more susceptible to buckle and display lower load-carrying capacities. This paper presents a total of 42 axial compression tests of CFS lipped channel slender columns with and without circular and rectangular web holes, including different hole sizes and cross sections. The test results show that the axial members with a small ratio of width to thickness were governed by global buckling, while the members with a large ratio of width to thickness were controlled by the interaction of local, distortional, and global buckling. The axial strength decreased maximum by 20.48% and 22.98% for the member with circular holes and rectangular holes, compared to a member without a web hole. Then, a nonlinear elastoplastic finite element model (FEM) was developed, and the analysis results showed good agreement with the test results. The validated FE model was used to conduct a parametric study involving 36 FEMs to investigate the effects of column slenderness, dimension of the hole, and the number of holes on the axial strength of such channels. Furthermore, the formulas to predict the global buckling coefficient and the effective area were modified for such sections with holes by using the verified FEM. Finally, the tests and parametric study results were compared against the design strengths calculated in accordance with the developed method. The comparison results show that the proposed design method closely predicts the axial capacity of CFS channels with circular or rectangular web holes.

Expansive soils are found in numerous regions of the world explicitly in arid and semiarid zones. These soils expand when absorbed moisture and shrink when released water. Such soil is viewed as a characteristic risk for infrastructures due to the shrink and swell behavior. These soils become more problematic when lightly or moderately loaded structures are built on them. The swelling and shrinkage in these soils chiefly happen due to the presence of montmorillonite minerals. The mineralogical and swell behavior of foundation soils is playing a vital role in the overall stability of a structure. These parameters are often ignored in the geotechnical report writing stage specifically in small projects, due to which, the durability and service life of the facilities are reduced and the maintenance cost is increased. To mitigate the potential damages in structures constructed on expansive soil, it is necessary to assess the mineralogical and swelling characteristics of expansive soil. The current study aims to determine the geotechnical, mineralogical, and swell behavior of the local expansive soils. Based on the results, the Karak soil has the highest plasticity index (PI) of 37% with a clay fraction of 28%, while the D.I. Khan soil has the least PI of 23% with a clay fraction of 17%. Similarly, Karak’s soil contained a higher percentage of montmorillonite (Rp = 8.9%). The maximum values of swell pressure, swell potential, and 1D deformation are 280 kPa, 12.5%, and 1.92 mm for the Karak soil, 6.45% 150 kPa, and 1.38 mm for D.I. Khan soil, and 10.5%, 245 kPa, and 1.64 mm for Kohat soil, respectively. This concludes that Karak’s soil has high plasticity and swell characteristics than Kohat and D.I. Khan soil. The swell characteristic of expansive soils increases with the increase in the percentage of the fine specifically the clay fraction. Furthermore, the Karak soil is more critical than Kohat and D.I. khan soil for lightly loaded structures.

Based on analysis of the formation mechanism and characteristics of the negative friction in collapsible loess areas, this study investigates the load transfer law of a wall-soil system under a vertical load, establishes the vertical bearing model of a lattice diaphragm wall, and analyzes the vertical bearing capacity of an assembled latticed diaphragm wall (ALDW) in a loess area. The factors influencing the vertical bearing characteristics of the ALDW in a loess area are analyzed. The vertical bearing mechanism of the lattice diaphragm wall in the loess area is investigated. The failure modes of the ALDW in the loess area are mainly shear failure of the soil around the wall and failure of the wall-soil interface. In the generation and development of negative friction, there is always a point where the relative displacement of the wall-soil interface is zero at a certain depth below the ground; at this point, the wall and soil are relative to each other. The collapsibility of loess, settlement of the wall and surrounding soil, and rate and method of immersion are the factors affecting the lattice diaphragm wall. The conclusions of this study provide a reference for the design and construction of ALDWs in loess areas.

It is well known that the vertical vibrations of lightweight timber floors would cause discomfort to the occupants. As a new kind of flooring system, the metal-plate-connected timber truss joist floors were developed due to their larger spans and easier crossing of pipes and cables after sawn timber and I-joist floors. In this paper, the vibration modes and transfer functions of sixteen metal-plate-connected timber truss joist floors over a nominal span of 6 m were determined experimentally to measure the changes in vibration frequencies and transmissions obtained after the installation of strongbacks and strappings. The results showed that the fundamental natural frequencies of the metal-plate-connected timber truss joist floors at a 400 mm joist spacing were about 15 Hz, while the frequencies of the floors at a 600 mm joist spacing were about 12.5 Hz. The bracing elements of the strongbacks and strappings mainly enhanced the system stiffness in the across-joist direction of the flooring system, but they did not govern the fundamental natural frequencies of the floors and just changed the spacing of adjacent natural frequencies. The bracing elements as secondary elements of the floors also altered the vibration transmission paths in the across-joist direction. The frequencies where the stronger vibration transfers happened in the direction perpendicular to floor joists were generally above 15 Hz. Proper installation measurements of bracing elements in practical control need to be taken to alleviate the vibration response intensity at the targeted locations and frequencies.

The vortex-induced vibration may cause fatigue of a bridge structure, affecting the safety of vehicles and the comfort of pedestrians. Inerter is a two-terminal device, which has been applied in many areas. This paper studies the problem of suppressing the vortex-induced vibration of a bridge by using an inerter-based dynamic vibration absorber (IDVA). The performances in terms of the suspension travel and the vertical displacement of the bridge with different IDVAs in suppressing vortex-induced vibration are compared, and the effect of the installation position of IDVA on the performance of suppressing vortex-induced vibration is shown. The performance indexes for the vertical displacement of six IDVA arrangements are obtained by using an iterative method, where the performance indexes for the vertical displacement are minimized by using the optimization toolbox in a commercial software. The result shows that the optimal installation positions and the number of suitable installation positions are affected by the resonant mode. Among the six arrangements, one arrangement is identified to have the best performance of suppressing vortex-induced vibration. All the six arrangements have reduced the suspension travel performance.

To select a seismic resistant system, in addition to strength and stiffness, ductility and energy dissipation are important to be considered. Structures have nonlinear behavior under the influence of moderate and strong earthquakes. One of the primary aims in designing seismic resistant structures is to prevent the formation of undesirable collapse mechanisms such as the collapse in only a few storeys of the structure that leads to low energy dissipation. In order to achieve a global collapse mechanism, modern seismic codes provide simple rules for design, which is called the hierarchy criteria. Although these simple criteria could prevent the formation of a soft storey mechanism, they could not lead to an optimal global collapse mechanism. In these mechanisms, the energy dissipation zones include all the yielding zones such as beams, while all other parts of the structure have remained in the elastic range. TRF (T-resisting frame) is an innovative lateral resistant system introduced for architectural reasons and to provide more energy dissipating capability. This system has several collapse mechanisms due to the moment, shear, or moment-shear behavior of its members. In this paper, within the framework of the theory of plastic mechanism control, the rigid-plastic analysis of the TRF system to achieve the desired collapse mechanism is used by considering the moment-shear interaction. According to these analyses, which are performed on a single storey frame, simple hierarchy criteria are developed to create the desired collapse mechanism. Also, these criteria prevent undesired collapse mechanisms in order to have more energy dissipation and more ductility. Finally, the validity of the proposed criteria has been verified by the pushover analysis.

Aimed at the characteristics of aeolian sand under rapid construction conditions in desert geotechnical engineering, a series of the true triaxial undrained test were carried out on the GDS apparatus. The 3D deformation, failure, and other characteristics of the dense sand are obtained. Under the condition of same p c , the state transition point where the void water pressure changes from increasing to decreasing appears earlier and leads to enhanced dilatancy with the increase of b, which means the enhanced dilatancy of dense sand caused the increase in strength. The results of the same b shows that the void water pressure generally indicates a decrease at low confining pressure and an increase at high confining pressure, indicating that the aeolian sand shows dilatancy at low confining pressure and contraction at high confining pressure. The state transition point increases with the increase of p c , but all points tend to the same critical state line and state transition line. When b = 0, the critical state line is q = 1.57 p ′ , and the state transition line is q = 1.23 p ′ . When b = 1, the critical state line is q = 1.24 p ′ , and the state transition line is q = 1.04 p ′ . The results at same b obtained the unified critical state line and the state transition line. Therefore, the true triaxial test can obtain the unified relationship of void ratio, p c and b, which overcomes the fact that the existing test cannot consider the influence of b. The test results provide a basis data for the design, construction, and maintenance of geotechnical engineering in Tengger Desert.

Investigations were carried out to study the mechanical performance under uniaxial load of unplastered and plastered straw bales. Results from tests on 30 rice straw bales indicated nonlinear load-bearing properties with large deformations and anisotropy. Since the deformations observed did not conform to the current building code requirements, the evaluation of ultimate bearing capacity through the maximum axial vertical load was not possible. To obtain the design strength of rice straw bales in composite walls, further 21 specimens of plastered straw bales were also tested in compression. The permissible deformation of the straw bales was evaluated. It is noteworthy that the large deformability of straw bales can reduce the damage to structures after an earthquake. Consequently, the straw bale use can widely enhance the seismic performance of low-rise buildings.

The objective of this study is to examine the performance of the shallow reinforced concrete foundation of a large-scale wind turbine under the influence of environmental loads. A 2 MW horizontal-axis onshore wind turbine supported by a shallow concrete foundation was considered. The foundation stresses, foundation settlements, and static and dynamic contact pressures at various positions of the shallow foundation were monitored from the construction phase to the operation phase in the field. Numerical simulations were also performed to further analyze the behavior of the wind turbine foundation in different cases. The results demonstrate that the responses of the reinforced concrete foundation, i.e., foundation stresses, contact pressures, and foundation settlements, were variables closely related to the wind direction and wind speed. The distribution of foundation stresses suggested that a reasonable design of steel reinforcement cages around the foundation steel ring is important. The dynamic contact pressure of the foundation could reach 5 kPa, so the influence of dynamic wind loads on the foundation response could not be always neglected, particularly for the foundations seated on weak soils. The foundation settlement during the operation phase could be characterized by the logistic model, but its distribution was uneven due to the presence of eccentric upper weight and wind load. The findings would provide guidance for the foundation design of onshore wind turbines in hilly areas.

Magnetorheological (MR) dampers, as an intelligent vibration damping device, can quickly change the damping size of the material in milliseconds. The traditional semiactive control strategy cannot give full play to the ability of the MR dampers to consume energy and reduce vibration under different currents, and it is difficult to control the MR dampers accurately. In this paper, a semiactive control strategy based on reinforcement learning (RL) is proposed, which is based on “exploring” to learn the optimal value of the MR dampers at each step of the operation, the applied current value. During damping control, the learned optimal action value for each step is input into the MR dampers so that they provide the optimal damping force to the structure. Applying this strategy to a two-layer frame structure was found to provide more accurate control of the MR dampers, significantly improving the damping effect of the MR dampers.

Seismic demand and performance of bridges are highly dependent upon the level of irregularity. Although previous studies have proposed methodologies so as to quantify the irregularity of the bridges in terms of global regularity index, it still remains unclear how to determine the distribution of irregularity along a bridge, as well as to discover the irregularity sources. This research project is intended to develop a quantitative vector regularity criterion for single- and multiframe bridges based on the modified correlation function for spatial locations of scaled mode shapes of deck-alone and whole bridge. The proposed criterion calculates two types of regularity indices, namely, local (LRI) and global regularity indices (GRI). The GRI is a scalar value representing the overall regularity of the entire bridge, whereas the LRI highlights vector irregularity distribution along the bridge. Since the deck discontinuity due to the in-span hinges is one of the leading causes for irregularity, the proposed index has been employed in case of multiframe bridges as well. Furthermore, the current study aims to investigate the correlation between the proposed irregularity indicators and the nonlinear to linear demand ratio. Therefore, the appropriate analysis method can be chosen based on irregularity extent of bridges. Obtained results of the proposed indices reveal that in-span hinge is one of the main parameters affecting the distribution of local irregularity along a bridge. Therefore, multiframe bridges need to be investigated in detail so as to validate the special design requirements recommended by design codes.

This paper systematically investigated the axial compression behavior of circular concrete-filled high-strength thin-walled steel tubular (CFHTST) columns with out-of-code diameter-to-thickness (D/t) ratios. The axial compression test was first conducted to examine the failure mode, load-displacement curves, and composite mechanism effect. The finite element (FE) model was thereafter established to perform full-range analysis on the load versus displacement curve as well as the interaction behavior, where the parametric study was performed to investigate the influences of the material strengths and geometric sizes. Subsequently, the applicability of typical design methods was evaluated, and a revised equation for determining strain εscy corresponding to ultimate strength was established to assess the plastic deformation capacity of CFHTST columns. Finally, a theoretical model for calculating axial bearing capacity was derived based on unified twin-shear strength theory by considering the influence of intermediate principal stress. The research results indicate that a relatively high confine effect can be guaranteed for CFHTST columns under out-of-code D/t ratios, given that the ratio Nu/Nnom between the measured capacity (Nu) and nominal cross-sectional capacity (Nnom) mainly distributes within 1.179∼1.292; the full-range analysis reflects that the axial load-deformation curve can be distinguished by four various loading stages; the scope b = 0.3∼0.55 of intermediate stress coefficient is generally suggested for predicting axial strength of circular CFST columns within an error of ±5%. The abovementioned study can provide the meaningful design reference for the analysis and application of CFHTST columns.

Bridges in a marine environment have been suffering from the chloride attack for a long period of time. Due to the fact that different sections of piers may be exposed to different conditionals, the chloride-induced corrosion not only affects the scale of the deterioration process but also significantly modifies over time the damage propagation mechanisms and the seismic damage distribution. In order to investigate the seismic damage of existing RC bridges subject to spatial chloride-induced corrosion in a marine environment, Duracrete model is applied to determine the corrosion initiation time of reinforcing steels under different exposure conditionals and the degradation models of reinforcing steels, confined concrete, and unconfined concrete are obtained based on the previous investigation. According to the seismic fragility assessment method, the damage assessment approach for the existing RC bridges subject to spatial chloride-induced corrosion in a marine environment is present. Moreover, a case study of a bridge under two kinds of water regions investigated the influence of spatial chloride-induced corrosion on the seismic damage of piers and other components. The results show that the spatial chloride-induced corrosion may result in the section at the low water level becoming more vulnerable than the adjacent sections and the alteration of seismic damage distribution of piers. The corrosion of pier will increase the seismic damage probability of itself, whereas it will result in a reduction of seismic damage probability of other components. Moreover, the alteration of seismic damage distribution of piers will amplify the effect. Due to the fact that the spatial chloride-induced corrosion of piers may alter the yield sequence of cross section, it then affects the seismic performance assessment of piers. A method to determine the evolution probability of yield sequence of corroded piers is proposed at last. From the result, the evolution probability of yield sequence of piers in longitudinal direction depends on the relationship between the height of piers and submerged zone. Moreover, the height of piers, submerged zone, and tidal zone have a common influence on the evolution of yield sequence of piers in transversal direction.

This paper is presented to develop the hydrodynamic performance of double-row floating breakwater (FBW) by changing cross-sectional geometry in the high wave periods. The ANSYS-AQWA software is employed for the present calculations, which is a potential-based boundary element method (BEM). The rectangular moored pontoons in the single- and double-row types are selected, and the results of the wave transmission coefficient and response amplitude operator (RAO) are presented and compared. The numerical results showed good agreement with experimental data at different wavelengths, wave height, and the distance between double-row FBWs. Then, the performance results of FBWs for five shapes (rectangular, π-shaped, plus-shaped, triangular-shaped, and box-shaped) in the wave transmission coefficient, RAO, and mooring line tension are presented and compared to each other. The results showed that the plus-shaped FBW has a better performance in reducing wave transmission than other shapes. In waves with long periods, the performance of π-shaped, triangular-shaped, and box-shaped FBWs is reduced, and the rectangular FBW loses its efficiency. Overall, the plus-shaped FBW has preferable performance regarding RAO response, mooring tension, and wave transmission.

Dynamic modulus is a key evaluation index of the high-modulus asphalt mixture, but it is relatively difficult to test and collect its data. The purpose is to achieve the accurate prediction of the dynamic modulus of the high-modulus asphalt mixture and further optimize the design process of the high-modulus asphalt mixture. Five high-temperature performance indexes of high-modulus asphalt and its mixture were selected. The correlation between the above five indexes and the dynamic modulus of the high-modulus asphalt mixture was analyzed. On this basis, the dynamic modulus prediction models of the high-modulus asphalt mixture based on small sample data were established by multiple regression, general regression neural network (GRNN), and support vector machine (SVM) neural network. According to parameter adjustment and cross-validation, the output stability and accuracy of different prediction models were compared and evaluated. The most effective prediction model was recommended. The results show that the SVM model has more significant prediction accuracy and output stability than the multiple regression model and the GRNN model. Its prediction error was 0.98–9.71%. Compared with the other two models, the prediction error of the SVM model declined by 0.50–11.96% and 3.76–13.44%. The SVM neural network was recommended as the dynamic modulus prediction model of the high-modulus asphalt mixture.

Based on the monotonic tensile test of grouted sleeve specimens conducted, this paper uses multifactor regression analysis to construct the equivalent constitutive relationship of grouted sleeve specimens under uniaxial tension. The study based on this constitutive relationship of grouted sleeves and the effect of bond and slip between steel and concrete were considered. The prefabricated reinforced concreted beam-column joints with grouted sleeves were presented with finite element software ABAQUS. The seismic behavior of prefabricated reinforced concreted beam-column joints with grouted sleeves under low-frequency cyclic loading was then investigated. In addition, parametric studies via finite element analysis were performed to examine the influence of various parameters on the strength and energy dissipation capacity of the specimens. The simulation results show that plastic deformation was mainly observed near the beam-column interface; the hysteretic curve of this joint was plump. The test results showed that good energy dissipation and displacement ductility capacities can be achieved. The error of yield load between the numerical simulated and experimental result was 7.11%, the error of peak load was 6.88%, the error of ultimate load was 3.76%, and the error of displacement ductility was 7.84%. Results showed that the calculated results obtained in the paper agree well with test results from the references. The finite element model adopted in this paper can reflect the seismic behavior of the prefabricated reinforced concrete beam-column joints with grouted sleeves by using equivalent constitutive relation.

Potential earthquake-induced damage to overlapped tunnels probably occurs during the operation and maintenance of mountain tunnel engineering, especially in the seismically active zone. This study investigated the dynamic response and the failure characteristics of the parallel overlapped tunnel under seismic loadings by employing shaking table tests. The failure mode of the parallel overlapped tunnels was analyzed through macroscopic test phenomena. The dynamic responses of the surrounding rock and tunnel lining were evaluated by acceleration and dynamic strain, respectively. In particular, wavelet packets were used to investigate the spectrum characteristics of the tunnel structure in depth. The failure process of the model can be divided into three stages. The upper-span and the under-crossing tunnels showed different failure characteristics. Additionally, the lining damage on the outer surface of the tunnel mainly occurred on the right side arch waist and the left side wall, whereas the lining damage on the inner surface of the tunnel mainly appeared on the crown and invert. Wavelet packet energy results showed that the energy characteristic distributions of the upper-span and the under-crossing tunnels were not consistent. Specifically, the energy eigenvalues of the crown of the upper-span tunnel and the invert of the under-crossing tunnel were the largest, which should be considered to be the weak parts in the seismic design.

Parallel strand bamboo (PSB) is an engineered bamboo product fabricated using crushed bamboo fiber bundles. Recently, this product finds applications in the civil engineering field. It is expected that the use of this composite will continue to grow because of its excellent mechanical performance, relatively low variability in material properties, and shape standardization. Modern bamboo structures made from PSB composites may be subjected to temperature variations during service. So far, however, there has been little discussion about the temperature-dependent creep. In this study, an investigation was carried out on the short-term behavior of the compressive property of PSB. A stress range of 8 to 64 MPa over a temperature range of 25°C to 75°C was considered in the 24-hour creep tests. In addition, Burgers model was adopted to describe the short-term creep behavior of PSB. Temperature and stress effects on the creep compliance of the Burgers model were also discussed.

Aiming at the existing heavy-haul railway, bridges hardly meet the transportation requirements. Based on the spatial vibration calculation model of the freight train–track–bridge (FTTB) system, the FTTB spatial vibration model under the condition of auxiliary steel beam reinforcement is established. Besides, according to the random analysis method of train derailment energy, coming up with an evaluation method of auxiliary steel beam reinforcement is based on safety and dynamic response, which is used to discuss the train safety and the change law of FTTB system vibration response. The results show that the derailment resistance of the FTTB system is increased by 22.6% after the auxiliary steel beam is reinforced. Compared with the previous speed (115.56 km/h), the speed is 132.73 km/h after the auxiliary steel beam reinforcement; at the same time, the allowable limit speed increases from 92.49 km/h to 106.18 km/h. In addition, the reinforcement of the auxiliary steel beam can not only effectively reduce the lateral vibration response of the FTTB system under the action of empty wagon but also effectively decline the vertical vibration response of the FTTB system under the action of the loaded wagon, which can meet the stability requirement for running at the speed of 90 km/h. In summary, the reinforcement of auxiliary steel beams can improve the running safety of trains, reduce the vibration response of the FTTB system, and meet the requirements of operation stability.

Galloping of an iced transmission line subjected to a moderating airflow has been analysed in this study, and a new form of galloping is discovered both theoretically and experimentally. The partial differential equations of the iced transmission line are established based on the Hamilton theory. The Galerkin method is then applied on the continuous model, and a discrete model is derived along with its first two in-plane and torsional modes. A trapezoidal wind field model is built through the superposition of simple harmonic waves. The vibrational amplitude is generally observed to be more violent when the wind velocity decreases, except in the 2nd in-plane mode. Furthermore, the influence of the declining wind velocity rates on galloping is analysed using different postdecline wind velocities and the duration of the decline in wind velocities. Subsequently, an experiment has been carried out on a continuous model of an iced conductor in the wind tunnel dedicated for galloping. The first two in-plane modal profiles are observed, along with their response to the moderating airflow. Different declining rates of the wind velocity are also verified in the wind tunnel, which show good agreement with the results simulated by the mathematical model. The sudden increase in the galloping amplitude poses a significant threat to the transmission system, which also improves the damage mechanism associated with the galloping of a slender, a long structure with a noncircular cross-section.

Under complex seismic forces, the failure characteristics of the plastic hinge region at the bottom of the pier column and the methods improving the ductility have attracted extensive attention. In this study, steel fiber-reinforced concrete with fine aggregate (SFRC-FA) was applied to locally replace the conventional concrete in the potential plastic hinge region at the bottom of the pier column. Five SFRC-FA pier column specimens with different stirrup ratios and different replacement lengths and one conventional reinforced concrete pier column specimen were produced. Using the seismic behavior tests under the combined bending-shear-torsion-axial force, the failure mode, torsional bearing capacity, energy dissipation, and the torsional plastic hinges of the pier columns were investigated. In addition, an equation for calculating the torsional bearing capacity of the new composite pier columns was proposed. The results showed that (1) compared with the reinforced concrete pier column, the plastic hinge was shifted from the bottom of the pier column to the middle of the height of the pier column due to the application of SFRC-FA at the bottom of the pier column, which improved the torsional bearing capacity; (2) the effect of reducing the stirrup ratio of the SFRC-FA replacement region on the torsional bearing capacity, cracking mode, energy dissipation, and ductility was not obvious; (3) the accuracy of the new equation based on the space truss model proposed in this article was verified by comparison with the experiments of this study and other researches.

Herein, numerical predictions of the dynamic response of an existing floating pontoon bridge are compared with the measured dynamic response. Hydrodynamic coefficients that describe the fluid-structure interaction and the wave transfer functions are obtained by applying linear potential theory. The results obtained from the hydrodynamic analysis are combined with a beam model of the bridge in a finite element method (FEM) framework to enable stochastic response prediction through the power spectral density method. The standard deviations of the predicted accelerations are compared with the standard deviations of the measured accelerations, and the overall quality of the prediction model is discussed. Predictions with sea states related to the serviceability limit state (SLS) and ultimate limit state (ULS) conditions used in design of the bridge are emphasized. To investigate the behaviour more in depth, a measurement segment is chosen and predictions of the displacement response power spectral density due to excitation characterized by the recorded sea surface elevation are compared with those obtained from the corresponding response measurements. A decent agreement is obtained for both cases when using the model as it is and with waves as the only excitation source, but significant discrepancies are present, in particular, for the torsional components. By including preliminary contributions from wind action and relying on a model optimized against measured modal parameters, a satisfactory agreement is obtained. The effect on the response of an uncertain structural damping is also quantified and concluded to be significant within realistic damping levels.

Liquid sloshing under coupled surge and heave excitations in a rectangular tank has been numerically investigated by applying a Navier–Stokes solver. Fieriest coupled sloshing was further considered, and the internal baffle was expected to suppress the violent sloshing wave. After getting fully validated against available results from the literatures, the numerical model was applied to research coupled sloshing, and both vertical baffle and horizontal baffle have been considered. Due to the strong vortexes created by the sharper corners of the baffles and the reduction of the effective water bulk climbing through the tank walls, the sloshing was dramatically reduced. The increase of the baffle distance away from the tank bottom led to a decrease in the sloshing wave. It was noted that the baffle near the free surface caused the maximal dissipation. The frequency response of the sloshing wave was accordingly illustrated.

The free vibration characteristics of steel-concrete composite continuous beams (SCCCBs) are analyzed based on the Euler–Bernoulli beam theory. A modified dynamic direct stiffness method has been developed, which can be used to analyze the SCCCBs with some lumped masses and elastic boundary conditions. The results obtained by the proposed method are exact due to the elimination of approximated displacement and force fields in derivation. The proposed method is verified by comparing its results with those obtained by ANSYS software and laboratory tests. Then, the influencing factors on the reduction of natural frequency are analyzed and discussed in detail using the proposed method. The results show that stronger interfacial interaction results in higher values of natural frequency as well as larger steel subbeam and thinner concrete slab. The smaller the natural frequency of the SCCCBs is, the more significant effect the interfacial interaction on the natural frequency is. The reduction of natural frequency is not affected by the different numbers of spans but the equal single-span length and various ratios of the side span to the main span but equal total length, but it is influenced by the extra single-span length and different ratios of the side span to the main span but equal main span length. And it is only affected by bending stiffness. Furthermore, the reasonable ratio of the side span to the main span is 0.9∼1.0.

The state-of-the-art review of hybrid GFRP-concrete systems for bridge decks is presented in this study. Previous research on the experimental work, analytical modeling, and field application on hybrid GFRP-concrete deck systems are presented, along with a variety of deck systems are discussed. Then, seven typical types of connection technology between FRP and concrete are introduced and compared. Besides, the current progress on the performance of shear connections via beam tests, pushout tests, and pullout tests are probed, respectively. Finally, general conclusions are made, identifying the need for future research.

Pounding may occur between the main girders under the action of strong earthquakes, so as between main girders and abutments. This causes excessive longitudinal displacement of the main girder and unseating damage to bridges. Because long bridges in mountainous areas with high intensity are easy to unseat, the authors studied the influence of restrainer piers, expansion joint spacings (EJSs), and the span on the seismic performance of long bridges. The ABAQUS finite element software was used to simulate a bridge dynamic analysis model considering the elastoplasticity of the pounding effect of the pier and the beam. By inputting El-Centro, Northbridge, and Taft seismic waves, the time-history analysis of the seismic response of long bridges was carried out. The results indicated that a reasonable number of restrainer piers, an appropriate EJS, and a span could effectively reduce the maximum relative displacement of pier-beams. This behavior will improve the seismic performance of bridge structures. Moreover, for a 24-span equal-height beam bridge, the optimum seismic effect was obtained when 3 restrainer piers, an EJS of 70 mm, and a 50 m span were used.

Among vibration-based damage detection methods, one of the effective approaches for damage localization is the modal strain energy method. In this paper, the modal strain energy method is developed for damage detection in plate-like structures with various boundary conditions. Firstly, the theory of the modal strain energy method is briefly outlined. In order to overcome the limitation of measuring points, a central difference method is newly employed to compute the partial differential terms in the modal strain energy formula. Finite element analysis is conducted on an aluminum thin plate to obtain the mode shapes before and after the occurrence of damage. Feasibility of the proposed method is verified by investigating plates with different types of boundary conditions. A damage index is presented to identify the location and extent of crack in the plate-like structures. The analytical results show that the proposed method accurately identifies the crack in the plate structure with various types of boundary conditions by using appropriate mode shapes and damage threshold.

To efficiently and accurately predict the effects of twin tunneling on adjacent buried pipelines, the effects of upward and downward relative pipeline-soil interactions were considered. A series of numerical parametric studies encompassing 8640 conditions were performed to investigate the responses of a pipeline to twin tunneling. Based on the dimensionless analysis and normalized calculation results, the concept of equivalent relative pipeline-soil stiffness was proposed. Additionally, expressions for the relative pipeline-soil stiffness and relative pipeline curvature and for the relative pipeline-soil stiffness and relative pipeline settlement were established, along with the related calculation plots. Relying on a comparison of prediction results, centrifuge model test results, and field measured results, the accuracy and reliability of the obtained expressions for predicting the bending strain and settlement of adjacent buried pipelines caused by twin tunneling were validated. Based on the calculation method, the maximum bending strain and maximum settlement of pipelines can be calculated precisely when the pipeline parameters, burial depth, soil parameters, and curve parameters of ground settlement due to tunneling are provided. The proposed expressions can be used not only to predict the maximum bending strain and maximum settlement of pipelines caused by single and twin tunneling but also to evaluate the effects of single and twin tunneling on the safety of existing buried pipelines. The relevant conclusions of this article can also provide a theoretical basis for the normal service of buried pipelines adjacent to subway tunnels.

Two kinds of layered double hydroxides (LDHs), MgAl-NO2 (N-LDH) and MgAl-CO3 (C-LDH), were incorporated to study the durability of mortar and concrete. The LDH contents of mortar were 1%, 2%, and 4% by mass and the LDH contents of concrete were 0.5%, 1%, 2%, 4%, respectively. The effect of LDHs on sulfate resistance of mortar was studied through dry-wetting cycle test, compressive strength test, and flexural strength test. In addition, the effects of LDHs on pore structure, chloride resistance, carbonation resistance, shrinkage, and creep of concrete were investigated by SEM, mercury injection test, XRD, chloride ion diffusion coefficient test, chloride salt corrosion depth test, carbonation depth test, shrinkage test, and creep test. The results showed that LDHs can improve the ability of resisting ion corrosion, carbonization, shrinkage, and creep, reduce the pore content, and optimize the pore structure of mortar and concrete to some extent. Moreover, 4% LDHs had a better effect on improving the durability of mortar and concrete compared to 0.5%, 1%, and 2% LDHs, and the effect of C-LDH was better than N-LDH.

This research aims to evaluate the calculation accuracy and efficiency of the artificial neural network-based important sampling method (ANN-IS) on reliability of structures such as drum brakes. The finite element analysis (FEA) result is used to establish the ANN sample in ANN-based reliability analysis methods. Because the process of FEA is time-consuming, the ANN sample size has a very important influence on the calculation efficiency. Two types of ANNs used in this study are the radial basis function neural network (RBF) and back propagation neural network (BP). RBF-IS and BP-IS methods are used to conduct reliability analysis on training samples of three different sizes, and the results are compared with several reliability analysis methods based on ANNs. The results show that the probability of failure of the RBF-IS method is closer to that of the Monte-Carlo simulation method (MCS) than those of other methods (including BP-IS). In addition, the RBF-IS method has better calculation efficiency than the other methods considered in this study. This research demonstrates that the RBF-IS method is well suited to structure reliability problems.

Energy dissipating joint can effectively strengthen the connection of prefabricated buildings. In the present study, a new slotted mild steel damper was installed at the beam end of the prefabricated structure to form as the energy-dissipating joint of the beam-column. By using ABAQUS software, a finite element (FE) analysis was conducted for the single-story-and-span of the single-frame structure with a slotted damper as energy-dissipating joint. The result shows that the damper was the first to yield in the structure and performed well in energy dissipation, indicating its reasonable design of structure and connection. The energy dissipation mainly occurred at the flange of the variable cross sections, between which beam-ribbed webs ensured the required bearing capacity and stiffness and provided a reliable connection. The hysteretic curves were obtained by analyzing the mechanical properties of the slotted damper under pure bending and pure shearing. In the OpenSees platform, the Steel02 Material model and the twoNodeLink element were used to fit the hysteretic curves; this method was employed for the parametric simulation of the slotted energy dissipation. The dynamic characteristics and seismic response of the controlled structure with slotted energy dissipating joint were also analyzed and compared with those of the uncontrolled structure in the OpenSees platform. The results show that the period of the controlled structure was prolonged and the top story acceleration decreased, indicating its effect in reducing seismic response. The shear-dependent seismic reduction ratio was about 35%, while the drift-dependent seismic reduction ratio was about 10%. The seismic performance of bottom story was better than that of the top story, and the damper has good energy dissipation performance in the bending direction. Some detailed design criteria are put forward and consequences for design on the basis of the performed simulations are shown.

An innovative precast connection (the precast connection installed in the middle of the shear wall) was proposed for the shear wall. To verify the effectiveness of the proposed precast connection, two cast-in-situ shear walls (RCW1 and RCW2) and three precast shear walls (PCW1, PCW2, and PCW3) were manufactured and investigated. The construction joints were inserted in the bottom and the middle for RCW1 and RCW2; and the structural glue horizontal connection, structural glue cogged connection, and cast-in-situ plug grouting connection were utilized for PCW1, PCW2, and PCW3, respectively. The failure mode, loading capacity, ductility, stiffness degradation, and energy dissipation of specimens were analyzed under the horizontal low-frequency cycled loading. Simultaneously, a numerical simulation was carried out on the ABAQUS software, and simulation results were consistent with experimental results. The result showed that the moment-shear failure occurred in all the specimens except PCW1; the bottoms of PCW2 and PCW3 were still vulnerable regions. The bearing capacity and the ductility of RCW2 were improved to different degrees by installing the construction joint in the middle of the shear wall. Specifically, the structural glue cogged connection and the cast-in-situ plug grouting connection have no obvious effect on the reduction of bearing capacity but can improve the ductility of the specimen; the stiffness degradation and energy dissipation of RCW1, RCW2, PCW2, and PCW3 were basically the same.

To study the heterogeneous nature of lifetimes of certain mechanical or engineering processes, a mixture model of some suitable lifetime distributions may be more appropriate and appealing as compared to simple models This paper considers a mixture of the Marshall–Olkin extended Weibull distribution for efficient modeling of failure, survival, and COVID-19 data under classical and Bayesian perspectives based on type-II censored data We derive several properties of the new distribution such as moments, incomplete moments, mean deviation, average lifetime, mean residual lifetime, Renyi entropy, Shannon entropy, and order statistics of the proposed distribution Maximum likelihood and Bayes procedure are used to derive both point and interval estimates of the parameters involved in the model Bayes estimators of the unknown parameters of the model are obtained under symmetric (squared error) and asymmetric (linear exponential (LINEX)) loss functions using gamma priors for both the shape and the scale parameters Furthermore, approximate confidence intervals and Bayes credible intervals (CIs) are also obtained Monte Carlo simulation study is carried out to assess the performance of the maximum likelihood estimators and Bayes estimators with respect to their estimated risk The flexibility and importance of the proposed distribution are illustrated by means of four real datasets [ABSTRACT FROM AUTHOR] Copyright of Mathematical Problems in Engineering is the property of Hindawi Limited and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission However, users may print, download, or email articles for individual use This abstract may be abridged No warranty is given about the accuracy of the copy Users should refer to the original published version of the material for the full abstract (Copyright applies to all Abstracts )

In order to explore the influence of internal water on the seismic response of hydraulic tunnel, the combined mechanical analysis models of multimaterial including surrounding rock, lining structure, and internal water are built. Based on the explicit central difference method, the dynamic finite element analysis methods for rock, lining, and water are discussed, respectively. The dynamic contact force method is used to simulate the rock-lining contact interaction, and the arbitrary Lagrange-Euler (ALE) method is used to simulate the lining-water coupling interaction. Then a numerical simulation analysis method for combined seismic response of rock-lining-water system in hydraulic tunnel is proposed, and the detailed solving steps are given. This method is used to study the seismic stability characteristics of the water diversion tunnel in a hydropower station, and the displacement, stress, and damage failure characteristics of the lining structure under the conditions of no water, static water, and dynamic water are comparatively analyzed. The results show that the hydrostatic pressure restricts the seismic response of the lining, while the hydrodynamic pressure exacerbates its seismic response and leads to damage, separation, and slip failure appearing on the haunch, which can provide a scientific reference for the seismic design of hydraulic tunnel with high water head and large diameter.

In order to solve the problem of poor antiimpact ability of hydraulic support under rock bursting, a kind of thin-walled cylinder crushing component used in the composite spiral antiimpact device was developed, and different structural models were proposed and simulated. On this basis, the model was verified by experiments. The results show that the arrangement of the hollow structure can restrain the ring mode deformation and Euler instability of the tube member in the crushing yield and can carry out the buckling deformation according to the expected crushing force during the compression deformation process and effectively reduce the initial peak force. The arrangement of guide grooves can make the buckling deformation more stable and regular, which can effectively reduce the initial peak force and elastic displacement. With the smaller wall thickness and the smaller wall thickness of the induced groove, the effective deformation yield stroke of the crushing member increases, and the initial peak force, total energy absorption, average reaction force, and elastic displacement decrease. The simulation results are consistent with the experimental results which will be used in the future works.

Owing to the desirable bond strength and excellent workability, spiral hoop and bolted steel connectors are introduced to enhance the connecting performance of superimposed reinforced concrete shear wall (SRCSW) system. In order to investigate the seismic performance of SRCSWs, applying such connecting methods under flexure-shear interaction and flexural dominated status, two groups of precast (PC) specimens were constructed: one-story and two-story specimens. Seismic behavior in terms of crack patterns, load-displacement response, ductility, stiffness degradation, strain response, and deformation results of SRCSWs is evaluated by the quasistatic cyclic test. It is shown that the wall specimens with the proposed connectors exhibited similar failure mode to that of the cast-in-place (CIP) walls and possessed adequate seismic performance such as lateral resistance, ultimate drift ratio, and lateral stiffness besides the ease of erection. The strain responses and deformation results of the PC specimens under reversed cyclic loading were presented to evaluate the effectiveness of the introduced connections. The test results indicated that the PC walls adopting bolted steel connectors behaved better in force transmission and exhibited greater integrity characteristic compared with the specimens having spiral hoop connectors. Lastly, simplified finite element models considering the nonlinear slip behavior within the connection joint of SRCSWs were established and verified, which could provide sufficient accuracy and efficiency to predict the seismic response of the proposed wall system.