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Cement stabilization is a widely applied technique in improving the workability and geotechnical properties of soft clay. This paper investigated the influence of cement stabilization on the soil–water characteristic curve (SWCC) and the deformation behavior of unsaturated cement–stabilized soft clay. The combined effect of cementation and partial saturation on the hydromechanical behavior of cement-stabilized soils was discussed. The SWCC of stabilized soil was measured in the full suction range under drying and wetting paths using the pressure plate method, the filter paper method, and the vapor equilibrium technique. The deformation behaviors of cement-stabilized soft soil were investigated by conducting suction-controlled oedometer tests. Furthermore, scanning electron microscope micrographs and mercury intrusion porosimetry tests were performed to investigate the effects of cement content on the evolution of soil pore structures. The test results showed that the water retention capacity of the stabilized soft clay increased with increasing cement content. The SWCC showed a significant hysteretic behavior in the boundary effect zone and transition zone, whereas the hysteretic effect was unapparent in the residual zone. The increased cement content had a more significant hysteretic effect on the SWCC. The deformation resistance capacity increased as the cement content and matric suction increased. However, the effect of matric suction on deformation resistance capacity decreased as the cement content increased. With the increase in cement content, the macropores were converted to small interaggregate pores, the pore spaces were distributed more uniformly, and the particle surface became rougher, resulting in higher water retention capacity and significant hysteresis of the SWCC. [ABSTRACT FROM AUTHOR]

A simple analytical model for calculating the nonlinear deformations of a corrugated core (fluting) during out-of-plane compression is developed. The results from the analytical model are compared to a more comprehensive finite-element model and to experiments. A connection between the boundary conditions and the damage state of the corrugated board is discussed. Including a modified set of boundary conditions gives an almost perfect match of the initial stiffness to the experimental results, indicating that the core might be significantly damaged as a result of the manufacturing process. Possibly, the strength of corrugated boards might be increased about 20% if one could avoid damaging the fluting during the manufacturing process. [ABSTRACT FROM AUTHOR]

Wrinkling is a typical failure mode of sandwich structures with thin skins, where the bending deformation of face skins occurs simultaneously in conjunction with transverse stretching deformation of core layer. To analyze the three-dimensional (3D) deformation of wrinkling, a model is required to possess a capability describing completely different deformations at each ply. Therefore, by utilizing the Chebyshev polynomial at each layer of sandwich panels, this paper focuses on proposing a higher-order model to individually illustrate deformations of the skins and the core. By means of the proposed model, a refined triangular element has been constructed. By analyzing the stability of a sandwich plate without stiffeners, the finite-element formulation has been verified by comparing it to the quasi-3D elasticity solutions. In addition, it is anticipated that wrinkling failure can be effectively restrained by designing the stiffener layout. To this end, the influence of stiffener layouts on wrinkling behaviors of sandwich plates has been investigated in detail, and it is found that the capability of resisting the wrinkling deformation can be obviously improved by designing reasonable stiffener layouts. Moreover, the translation between buckling and wrinkling behaviors of sandwich panels with different stiffeners has been also explored, which can help to better understand wrinkling deformation mechanism. In summary, the proposed model can be used to design a reasonable arrangement of stiffeners to resist the wrinkling failure of sandwich panels. [ABSTRACT FROM AUTHOR]

A steel brace is effective to retrofit old reinforcement concrete (RC) buildings by increasing the horizontal load capacity of structures. However, concrete cracks that easily occur in the surrounding RC members under tension initiate early strength degradation, so this research aimed to develop a new self-centering brace (SCB) with the compression-only capacity such that no tension force is developed in the brace or to the adjoining RC members. Original SCBs have been developed to reduce the residual deformation of structures with a symmetrically flag-shaped hysteretic response. By altering the force transfer mechanism in the original SCB, a compression-only self-centering brace (C-SCB) can be developed under a symmetrically reversed cyclic loading, providing an alternative for the RC building retrofit. This paper first introduces the mechanics and deformation mechanism of the proposed C-SCB. A test program is then conducted on the cyclic tests of a buckling-restrained energy dissipating bar (EDB) to evaluate the energy dissipation. A 3,695-mm-long C-SCB is composed of posttensioning high-strength steel tendons, steel compression members, and buckling-restrained EDBs for the energy dissipation. The C-SCB in tests showed a good compression-only self-centering capability up to an axial displacement of 31 mm, with a maximum axial force of 1,530 kN. No damage of the steel tendons, compression members, or EDBs was found after three phase tests. Finite element analysis further validated the compression-only hysteretic response and mechanics of the C-SCB in a symmetrically reversed cyclic loading. [ABSTRACT FROM AUTHOR]

Self-centering braces are an attractive new type of brace able to reduce structural residual deformations after earthquakes, with no requirement of major modifications to structural joints. One primary challenge in widespread implementations of self-centering braces is their high demands of prestressing forces, in order to counteract the anti-recentering resistance induced by their energy-dissipation system. This paper introduces a novel self-centering (SC) brace, denoted as a viscoelastic low-prestressing self-centering (VE-LPSC) brace, that needs only a low level of prestressing force to achieve self-centering. The proposed brace incorporates a novel frequency-independent viscoelastic damper (VED) as its energy-dissipation system. The new VED behaves similarly to displacement-based dampers that provide stable stiffness and damping across various frequencies. Meanwhile, as loading ends, the VED does not generate residual anti-recentering forces, unlike conventional velocity-based dampers. Performance tests on the VEDs were first conducted using three specimens to examine the material's deformation capacity, frequency-independent characteristic, fatigue-resistance capacity, and recovery capacity. Then, six full-scale brace prototype specimens were manufactured and tested, considering three levels of prestressing forces (15, 50, and 100 kN). Test results revealed that the brace achieved complete self-centering and consistent stiffness and strength under various frequencies, even with a prestressing force of 15 kN. With conventional steel strand and Belleville springs as its prestressed elements, the new brace was able to elongate 2.27% (corresponding to a story drift of 4.54%) while maintaining its recentering capacity. The VE-LPSC brace may experience some strength degradation after loading lower to 90%, but its capacity can recover to 98% of the original strength after 2 weeks. [ABSTRACT FROM AUTHOR]

Pile-supported embankments, with advantages of high bearing capacity and effectiveness, have been widely used for constructing embankments on soft ground. The long-term load transfer and cumulative deformation mechanism caused by traffic loading are crucial to pile-supported embankment design and maintenance. A three-dimensional (3D) finite-element model of a pile-supported embankment to investigate its long-term load transfer and cumulative deformation mechanism under traffic loading is presented in this paper. The dynamic nonlinear behavior of the soft ground is considered by a simplified dynamic constitutive model that that has been effectively incorporated into the Abaqus program. In comparison with the results of published literatures, the applicability and accuracy of the proposed finite-element model are well verified at first. Then, the long-term load transfer and deformation mechanism are revealed by investing the soil arching and the cumulative deformation with a series of 3D numerical modeling. Furthermore, the influences of traffic loading type, speed of the vehicle, pile spacing, and total number of layers of grid on the long-term load transfer and deformation mechanism of the pile-supported embankment are investigated. [ABSTRACT FROM AUTHOR]

The freeze–thaw (F-T) cycle is one of the weathering factors that can cause rapid deterioration of the mechanical properties of rocks and threaten the stability and durability of rock engineering in cold regions. To study the influence of F-T action on the mechanical and deformation characteristics of sandstone, triaxial compression tests were performed under four confining pressures (0, 1, 3, and 5 MPa) and five F-T cycles (0, 40, 80, 120, and 160). The experimental results show that the stress–strain curves of the sandstone after F-T cycles can be divided into four phases: compaction, elasticity, strain-hardening, and postpeak failure. According to the deformation behaviors of the sandstone with various F-T cycles, an elastoplastic damage constitutive equation was established considering the compaction effect and F-T action. The model parameters were determined, and the theoretical curves were calculated. The comparisons with theoretical and experimental stress–strain curves demonstrate that the formulated constitutive equation can reflect the key deformation stages and mechanical behaviors of sandstone with different F-T cycles. Because the damage variable is introduced in establishing the model, the proposed model can also provide a quantitative description of the macrodamage, which agrees well with the microdamage of the sandstone after many F-T cycles measured by acoustic emission (AE) technology. The formulated constitutive equation in this paper can well describe the experimental deformation curves of sandstone with various F-T cycles and is easy to embed into numerical analysis software. The results can provide a certain theoretical reference for the evaluation of the durability and stability of rock engineering structures impacted by F-T-induced damage in cold regions. [ABSTRACT FROM AUTHOR]

Both cyclic loading on soil and intermittent periods come into play with the passing of trains. However, the existence of both cyclic deviator stress and cyclic confining pressure has already been observed in the stress field. In this paper, two types of cyclic triaxial tests, i.e., continuous cyclic loading and intermittent cyclic loading, were conducted to study the deformation behaviors of soft clay. The effects of cyclic confining pressure, duration of intermittent period (i.e., intermittent time), and loading cycles were analyzed. Compared to continuous cyclic loading, the intermittent period has a substantial influence on the deformation behavior of soft clay: the strain produced by intermittent cyclic loading is larger than that produced under undrained conditions, but less than that generated under partially drained conditions. The increment of accumulated axial strain corresponding to each loading stage under various factors was compared: an increase in intermittent time and loading cycles leads to greater degradation of the increment of accumulated axial strain, while the greater cyclic confining pressure corresponds to lower the increment of accumulated axial strain. The differences in the increment of accumulated axial strain for various loading cycles and cyclic confining pressures are significant in the cyclic loading period of the first loading stage, and can be ignored in subsequent cyclic loading periods. Besides, an empirical formula is provided to calculate the total accumulated axial strain caused by intermittent cyclic loading, and the predicted results accord well with the measured data. [ABSTRACT FROM AUTHOR]

In excavation engineering, most of the retaining structures are subjected to asymmetrical loads, including in asymmetrical excavation and asymmetrical overloading. However, a theoretical solution to, and deformation-controlling method for, this problem has remained elusive to date. In this work, a semianalytical solution for determining the deformation of retaining structures subjected to asymmetrical loads was derived based on the principle of minimum potential energy. The retaining structures were viewed as flexible, and the overall deformation of the retaining system was evaluated by our proposed theoretical model. This model was verified by comparing it with practical monitoring data. Subsequently, the theoretical solution was applied to analyze the stress and deformation characteristics under the conditions of asymmetrical excavation and asymmetrical overloading, which can be controlled to ensure the safety of a project. Finally, because of the requirement for a small amount of deformation in the foundation pit retaining piles, the earth pressure on the retaining piles is close to the static earth pressure. Reducing the length of the retaining pile on one side had a greater influence on the deformation on that side, but less of an influence on the other side. Thus, the proposed model can be used for optimizing the asymmetrical design of a retaining structure in order to balance the economy and safety of a project. Our design theory can be applied to a variety of engineering projects. A typical case is the Guangzhou Baiyun District Comprehensive Transportation Hub Project in China. The method was used to analyze the status of the subway foundation pit, offering a new design scheme to reduce the design length of the retaining piles, which resulted in great economic benefits in its practical application. The findings provided in this paper can be applied to the engineering of any long, narrow foundation pit that can be simplified into a two-dimensional plane–strain calculation model, being used to realize more accurate deformation control over the foundation pit envelope. The core of this calculation method is that it can accurately describe the magnitude of the earth pressure. The distribution of the earth pressure is worthy of further study. [ABSTRACT FROM AUTHOR]

In loess slopes, landslides are easily caused by rainfall and can be prevented by using retaining structures of stabilizing piles. This paper investigated the deformation and mechanical behaviors of the cantilever and fully buried stabilizing piles under complex pile–soil interactions. The deformation and mechanical behaviors, failure modes, and soil pressure distributions of two types of stabilizing piles were analyzed based on field model tests. Further, a calculation method for stabilizing piles considering nonlinear pile–soil interactions was proposed. Also, the numerical solution of the pile deformation and force was obtained by using the finite difference method and Newton's iterative method. The results showed that the deformation and mechanical behaviors of fully buried piles are superior to those of cantilever piles. Fully buried piles and cantilever piles have plastic double-hinged and single-hinged failure modes and undergo bending damage and shear damage, respectively. Besides, the landslide thrusts and soil resistances acting on the pile showed a parabolic distribution pattern. Compared to the model test results, the traditional calculation method overestimated the deformation and internal force of the stabilizing pile by 37.32%, and the newly proposed calculation model considering nonlinear pile–soil interactions was more consistent with the measured values. The study results help to guide the design and calculation of stabilizing piles under complex pile–soil interactions. [ABSTRACT FROM AUTHOR]

To objectively characterize the time-temperature-stress equivalence of viscoelastic properties of asphalt mixture, the triaxial compressive creep test was carried out on an AC-13 asphalt mixture under the conditions of different temperatures and stress states in this paper and the nonlinear variation law of creep deformation was obtained. According to the characteristics of similar creep curves and the principle of time-temperature equivalence, two methods were used to shift the creep compliance under different confining pressure, temperature, and axial stress conditions, and the change of temperature and stress shift factors with confining pressure were obtained; in addition, the creep compliance principal curve was fitted by the Prony series and its principal surface was established. On this basis, the multiple stress creep recovery test under different confining pressures was conducted to measure the parameters of Schapery's nonlinear viscoelastic model and their variation law with the triaxial stress ratio was obtained, which accurately characterized the synergistic effect of confining pressure and axial stress. [ABSTRACT FROM AUTHOR]

This paper presents a theory for the buckling of short beams considering cross-sectional distortions due to transverse shear (i.e., shear warping), based on the consistent linearization of a geometrically nonlinear planar beam. The proposed deformation field considers the warping amplitude as an independent kinematic field, and the hyperelastic material assumes that the stresses normal and tangent to the deformed cross section are linear with respect to their work-conjugate finite strains. An approximate closed-form solution to the resulting quartic equation for the critical load is provided to facilitate practical implementation. Theoretical differences giving rise to distinct buckling theories for higher-order shear beams are discussed in terms of (1) the assumed deformation field, (2) variational consistency, and (3) material constitutive relation. The proposed formulation is applied to evaluate the stability of infinite strip unbonded fiber-reinforced elastomeric isolators (FREIs) with moderate-to-high shape factor, for which shear warping is expected to have a major influence due to the flexural flexibility of the fiber reinforcement. A homogenization procedure is described to obtain effective isolator rigidities considering rubber compressibility and fiber extensibility. Next, a finite element parametric study of the buckling of unbonded infinite strip FREIs is presented, and the results are used as a benchmark to evaluate the adequacy of the proposed and existing formulations. The theory presented herein and its approximate solution exhibit the best match with the numerical results, and the latter is deemed adequate for practical application. [ABSTRACT FROM AUTHOR]

The diaphragm wall is widely used in deep excavation engineering to guarantee the safety of the foundation pit and surrounding environment during excavation. An accurate prediction of the lateral deformation of the diaphragm wall is the basis of the design and optimization of the diaphragm wall structure. In this paper, we apply the third-order shear deformation plate theory to develop an analytical method for predicting the lateral deformation of the diaphragm wall to take into account the effects of shear stress distributed along the thickness direction on the lateral deformation. By using the Pb-2 Ritz method, combined with the minimum potential energy concept, the analytical solution for the deformation of the diaphragm wall is obtained under certain simplifications. Three types of boundary conditions for the bottom side of the diaphragm wall are considered to meet different geological conditions. The proposed method is verified by comparing the results predicted in this study with the monitoring data obtained from the practical pit engineering of Dinggong south road metro station of Metro Line 2 in Nanchang, Jiangxi province, China. Finally, the effects of the thickness and the embedded depth of the diaphragm wall and the lateral support patterns are analyzed, and the optimized design parameters for the diaphragm wall are also suggested. The proposed method can theoretically provide preliminary parameter optimization guidance for the design and construction of a diaphragm wall. [ABSTRACT FROM AUTHOR]

Ground fissure is the most common geological catastrophe phenomenon in Xi'an, posing a major security threat to the currently developing urban cloud rail transit system. In this paper, a 3D-FEM calculation model is established to study the influence of the intersection angles between the hidden ground fissure and the cloud rail on the deformation and failure characteristics of the structure. The findings indicate that the pile foundation is under tension in the main deformation area of the hanging wall of the ground fissure, and the negative friction zone (NFZ) appears below the neutral point (buried depth 18 m for intersection angle 30°). The pile foundation is under compression in the footwall, and the pressure it bears is less than the tensile force sustained by the hanging wall pile, and the NFZ is above the middle point. The NFZ of the pile foundation in the hanging wall and footwall increases as the intersection angle decreases. The pile foundation mainly undergoes vertical settlement, and the horizontal displacement is relatively small. The 3D movement of the pile foundation results in settlement and inclination of the superstructure of the cloud rail simply supported beam bridge, such as the pier and track beam. Therefore, the cloud rail bridge should span the ground fissure at a large angle as far as possible, and 3D adjustable support should be adopted to adjust the offset of the track beam caused by the ground fissure. [ABSTRACT FROM AUTHOR]

To calculate a more accurate flow number (FN) to evaluate the effects of temperature, long-term aging, and salt freeze-thaw cycles on the high-temperature creep deformation characteristics of warm-mix recycled asphalt mixture (WRAM). This paper uses WRAM with different recycled asphalt pavement (RAP) old material contents (0%, 30%, 50%, and 70%) as the research object. The shortcomings of the cut line minimum method were analyzed, and based on this, a two-step slope of the cut line minimum method based on different interval coefficients (P) was proposed. In addition, this method was also compared with the four common methods. The results show that all five methods can solve the FN accurately, but the two-step slope of the cut line minimum method is better than the four common methods. When the P value is 0.99, 0.97, and 0.95, the method can find the accurate and unique FN , which is easy to operate and practical. According to the high-temperature evaluation indexes (creep rate b and improved FN), temperature and salt freeze-thaw cycles reduce the high-temperature creep deformation resistance of WRAM, while long-term aging will promote the high-temperature creep deformation resistance ability. Compared with traditional hot-mix asphalt mixture (HAM), WRAM is more excellent in high-temperature creep deformation resistance, aging resistance, and salt freeze-thaw cycles damage resistance. [ABSTRACT FROM AUTHOR]

Deformations in dam structures can have a critical impact on dam safety and life. Accurate methods for dam deformation prediction and safety evaluation are thus highly needed. Dam deformations can be predicted based on many factors. The analysis of these influences on the deformation of the dam reveals a problem that deserves further attention: dam deformation lags behind environmental factors of the water level and temperature as well as the time lag of the temporal dam deformation data. In this paper, a hybrid deep learning model is proposed to enhance the accuracy of dam deformation forecasting based on lag indices of these factors. In particular, dam deformations are predicted using deep networks based on gated recurrent units (GRUs), which can effectively capture the temporal characteristics of dam deformation. In addition, an improved particle swarm optimization (IPSO) algorithm is used for optimizing the GRU hyperparameters. Furthermore, the complete ensemble empirical mode decomposition with adaptive noise algorithm (CEEMDAN) and the partial autocorrelation function (PACF) are exploited to select the lag factor indices. The accuracy and effectiveness of the proposed CEEMDAN–PACF–IPSO–GRU hybrid model were evaluated and compared with those of other existing models in terms of four different evaluation indices (MAE, MSE, R2 , and RMSE) and using 9-year historical data for the case of a pulp-masonry arch dam in China. The experimental results show that our model outperforms other models in terms of the deformation prediction accuracy (R2 increased by 0.16%–9.74%, while the other indices increased by 14.55% to reach 96.69%), and hence represents a promising framework for general analysis of dam deformations and other types of structural behavior. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on the evaluation of the seismic performance of a new hybrid buckling restrained brace (HyBRB) under cyclic load. Detailed design steps adopted for the HyBRB design are reported in this paper. The analytical method for estimation of critical loads corresponding to buckling mode formation of the steel core inside the restrainer has been presented. The design targets achieved for the HyBRB are ease of inspection of the detachable BRB core to facilitate replacement of the steel core after a seismic event, if necessary, and enhanced energy-dissipation capacity through restrained buckling about both weak and strong axes of the core. The proposed HyBRB has displayed stable hysteretic behavior with good energy-dissipation capacity in low to high levels of the core strain range. Permanent deformation about the strong axis of the core was observed on unfastening of the restrainers, although restrained buckling of the core was observed about the weak axis in lower displacement amplitudes. Analytical simulation was carried out using a phenomenological model to simulate the experimental behavior. The simulated axial force-deformation hysteresis loops were found to be in close agreement with those obtained from experimental investigation. [ABSTRACT FROM AUTHOR]

Although steel single angle sections are commonly used as beams to support distributed loads which cause biaxial bending and torsion, their behavior may be extremely complicated, and the accurate prediction of their strengths very difficult. Further, many design codes do not have any design rules for torsion, while some recommendations are unnecessarily conservative, or are of limited application, or fail to consider some effects which are thought to be important. This paper is one of a series on the behavior and design of single angle section steel beams. Two previous papers have studied the biaxial bending behavior of restrained beams, a third has studied the lateral buckling of unrestrained beams, and a fourth the biaxial bending of unrestrained beams. In each paper, simple design methods have been developed. In this present paper, an approximate method of predicting the second-order deflections and twist rotations of steel equal angle beams under major axis bending and torsion is developed. This method is then used to determine the approximate maximum biaxial bending moments in such beams, which are then used with the section moment capacity proposals of the first paper of the series and the lateral buckling proposals of the third paper to approximate the member capacities. This method is extended to steel unequal angle beams in a companion paper. [ABSTRACT FROM AUTHOR]

This paper, which is the second of two companion papers, presents the results of a large-scale testing program on a novel bridge column design, termed polyurethane (PU)-enhanced rocking column with energy dissipation (ED) links. The experimental program included cyclic testing of large-scale (approximately 1∶2.5) cantilever bridge columns, including (1) a rocking-only precast concrete column, which served as the reference column, (2) a PU-enhanced rocking column with a solid PU segment, and (3) a PU-enhanced rocking column with an axisymmetrically bilayered segment with an exterior PU layer to withstand seismic loads, an internal reinforced concrete core to sustain long-term gravity loads, and external ED links to provide energy dissipation and flexural stiffness and strength. The specimens were subjected to displacement-controlled lateral cyclic loading of increasing amplitude (exceeding a 10% drift ratio) at several drift ratio rates (up to 1 s−1). The tested PU column with ED links was further repaired via ED link release and retightening—the yielding of the ED links was small and did not justify replacement—to demonstrate its rapid reparability characteristics. The repaired column was subsequently retested to demonstrate that the original column properties had been practically recovered. This second companion paper experimentally quantifies the performance of all designs in terms of strength, ductility capacity, self-centering and energy dissipation capabilities, posttensioning losses, and ED link fracture capacity. It also quantifies the capability of ED link release and retightening (and, by extension, ED link replacement) in eliminating residual deformations and recovering the mechanical properties of the original/undamaged system. Compared to conventional RC rocking-only columns, the proposed PU-enhanced column design with ED links demonstrated higher energy dissipation and self-centering capabilities, while release and retightening of the ED links eliminated the residual deformations and resulted in the recovery of the mechanical properties of the original/undamaged column. While ED link release and retightening (i.e., ED link reuse) is adopted in this study, because the yielding of the ED links was small, as verified herein by the practically identical response of the original and repaired column, it can be deduced that ED link replacement (i.e., use of new/pristine ED links) would also restore the original column properties and eliminate residual deformations. [ABSTRACT FROM AUTHOR]

To more accurately describe the mechanical behavior of prestressed steel strands with symmetrical wires breaking in unbonded post-tensioned concrete beam, this paper establishes the equilibrium equation after the bending deformation of the broken wire, taking into consideration bending deformation of the broken wires and the friction between wires and duct. The results derived from this equation fit well with the experimental data. The increase of friction between the center and outer wire and the friction between the broken wire and duct can reduce the recovery length and the strain ratio of the unbroken wire within the recovery length. The increase of axial force before wires breaking will increase the recovery length and the strain ratio of the unbroken wire within the recovery length. The rise in the number of broken wires can reduce the strain the broken wire fully recovers to and recovery length and increase the strain ratio of unbroken wires within the recovery length. In addition, we find that the stress of the unbroken wires near the breaking end becomes greater after symmetrical wires breaking, which is harmful to the structural safety. If there is corrosion in the unbroken wires near the breaking ends, these wires are likely to break immediately following the symmetrically broken wires. [ABSTRACT FROM AUTHOR]

Some theoretical criteria are set forth to study the onset of a strong and/or a weak discontinuity in hypoplastic granular materials under some simple motion fields. The theoretical criteria were based on direct analysis, considering both kinematical and dynamical conditions necessary to be satisfied in order to make a discontinuity of either type possible. We mean by simple motion fields those motion fields that are typically observed in standard laboratory tests, including homogeneous motion fields. A series of comparisons with available experimental data have been made for a simple hypoplastic constitutive equation. In geomechanics and other fields related to granular or porous materials, it is of particular importance to see whether the material is stable while deforming under applied loads. The phrase stability means, in a general sense, an ability to sustain the applied loads or remain in a particular form, without further deformation, following total loss of strength. Examples are the stability of underground tunnels or deep excavations prior to the construction of, say, a high-rise building. In both cases, deformation occurs while tunnel boring or ground excavation takes place, resulting in the alteration of the stress state followed by possible instabilities. A good example of instability is the catastrophic failure of tunnels in rock that takes place by sliding and falling of heavy blocks of rock along cracks and joints, in general, along planes of discontinuity. A plane of discontinuity often indicates the onset of instability in most materials. The results of this paper are expected to be useful in performing stability analysis in terms of assessing the possibility of the formation of such planes of discontinuity in a particular class of materials called hypoplastic materials. [ABSTRACT FROM AUTHOR]

Conventionally, the pressure coefficients of tensile membrane structures are determined in wind tunnels on rigid models and the effect of the typically large deformations of the membranes on the pressure coefficients is not taken into account. The aim of the current research is to analyze the effect of the displacements of membrane structures on the pressure coefficients. A more precise wind analysis is introduced in this paper. Two rigid models were analyzed in a wind tunnel: the model of the unloaded construction shape, and the model of the deformed shape of the membrane under wind loads. The deformed shape was determined with the dynamic relaxation method on the basis of the pressure coefficients obtained from the construction shape subjected to wind loads. The two pressure coefficient fields, the corresponding membrane stresses and displacements are introduced and compared in this paper. Results show that the displacements of the membrane under wind load can result in significant differences of the pressure coefficients maximum values. Conversely, the introduced analysis and the determination of the pressure coefficients of the deformed shape improve the accuracy of the wind analysis of tensile membrane structures. [ABSTRACT FROM AUTHOR]

The research reported in this paper investigates the coefficient of thermal contraction (CTE) and coefficient of thermal expansion (CTE) of asphalt concrete (AC) under different conditions in the laboratory. As a first step, the CTC and the CTE of AC at different temperatures ranging between -20 and 55°C were measured using field samples to examine the temperature effect. Then, the difference in the CTC and the CTE values in the vertical and horizontal directions (cross anisotropy) were evaluated using field samples. The influences of air void (AV), aggregate type, and aggregate gradation on the CTC and the CTE values were also investigated using laboratory prepared SuperPave gyratory samples. The deformation measuring devices, LVDTs, were calibrated using a zerodur to eliminate the temperature effect on the LVDTs. Results show that the CTC and the CTE values of AC are nonlinear with temperature and vary with aggregate type. However, gradation of aggregate and AV of sample do not affect the CTC and the CTE values significantly. The findings of this paper are highly expected to be useful in calculating the temperature-induced stress in AC using any design/analysis tool. [ABSTRACT FROM AUTHOR]

In accordance with the advancement of technological development, access to all types of digital data is becoming increasingly important. Various problems are commonly faced when obtaining digital data from existing maps. These include errors caused by the imperfection of the digitizing device, deformations in paper maps, errors in matching the data along the edges of adjacent paper maps, and systematic errors caused by the operator. Although the data obtained from photogrammetric methods are affected by pointing errors by the operator and errors occurring when analog photos are scanned, these errors are independent of the deformations that occur in paper maps. This study compared the raster maps produced from aerial photos with the data acquired from digitized vector maps. The statistical distributions of the discrepancies obtained as a result of this comparison were analyzed. The data from the scanned map and photogrammetric map were found to be consistent with each other, but the scanned map and newly produced map were not consistent with each other. [ABSTRACT FROM AUTHOR]

This paper proposes a novel mitigation approach to improve the safety and structural integrity of buried steel transmission pipelines subjected to ground deformation. This method involves altering the boundary condition of buried pipelines with adjacently installed special geomaterial blocks (SGBs) consisting of a set of expanded polystyrene geofoam and polypropylene squared plastic boxes. The proposed SGB allows accommodating ground deformation while significantly reducing the ground-induced forces in the pipe. The mitigation technique is first presented, followed by the experimental test program developed to evaluate the beneficial effects of SGB on the pipe response when subjected to lateral and oblique displacements. Furthermore, a simplified spring-based analytical modeling approach is proposed for predicting the force-displacement response of the pipe–SGB–soil assembly with emphasis on the interaction between the pipe and soil under the new boundary condition. The analytical model is validated using experimental test data. The results of the experimental tests confirm the efficiency of the proposed remediation and feature the relationship between the applied displacement and the force developed in the pipe. Furthermore, it is found that the proposed simplified analytical model can appropriately predict the expected reaction of the pipe equipped with the SGB. [ABSTRACT FROM AUTHOR]

The deformations of Kirchhoff–Love plate elements are usually characterized by three components describing the strains in the middle plane and three components describing the bending of the plate element. It is shown that alternatively one may consider pure bending deformations about two neutral axes that generally are not in the same plane and skew to each other. This interpretation provides an intuitive understanding of the plate deformations and is particularly useful when analyzing the behavior of reinforced concrete plate elements subjected to combined bending moments and membrane forces. After a recapitulation of the conventional interpretation of Kirchhoff–Love plate deformations and their implications on the strain distribution in plate elements, this paper presents the alternative interpretation and illustrates its application for a special case with orthogonal neutral axes. [ABSTRACT FROM AUTHOR]

The trapdoor/trapdoor-like model test has been widely utilized to investigate the evolution of soil arching. However, the primary focus of previous studies has been on the mechanical and deformation behaviors of the arching field under the single-trapdoor condition, while the interaction of soil arching between adjacent trapdoors has not been well understood. In this paper, a series of discrete numerical models based on the plane–strain laboratory trapdoor test were established to investigate the interaction effect, with respect to stress redistributions, particle movement, anisotropy of contact forces, and energy regime. The effects of motion mode, namely the simultaneous and nonsimultaneous movement, and the spacing (B) between adjacent trapdoors on the arching performance were examined. The numerical results revealed that the simultaneous movement of twin trapdoor slightly influences earth pressures resting on the surface of both trapdoors. The deformation pattern is deeply influenced by a narrow spacing of 0.25B and characterized by two arching fields interacting with each other, resulting in a noticeable subsidence at the crest. The subsequent lowering of the second-lowered trapdoor under the nonsimultaneous movement condition increases pressures resting on the first-lowered trapdoor, yields additional settlement within the former arching field, and distorts adjacent arched force chains. An increase in spacing from 0.25B to 1B is beneficial for reducing the pressure increment, decreasing the arching deformations, minimizing the rotation of the major principal direction, and decreasing the friction energy distribution density above the stationary supports. [ABSTRACT FROM AUTHOR]

Ultrasonic guided-wave technology has been successfully applied to detect multiple types of defects in pipes. However, cross-sectional deformation, which is a common defect, is less studied when compared with structural discontinuity defects in pipes. In this paper, the guided wave is employed to detect cross-sectional deformation. First, the effect of sectional deformation parameters on the reflection of guided waves is analyzed using a series of three-dimensional (3D) finite-element (FE) models, and the deformation parameters affecting the reflection are examined in light of the physics of the guided waves based on the FE results. The results show that the reflection occurs at the start of the cross-sectional deformation, while the subsequent gradual deformation region does not cause reflection. The reflection coefficient is dependent on the axial deformation severity, and the mode conversion ratio is dependent on the circumferential deformation extent. Second, an experimental study was conducted to evaluate guided-wave reflection characteristics due to pipe cross-sectional deformation in a realistic situation. Test pipes with local and overall deformations were manufactured, and the reflection from both types of deformation was investigated experimentally. The results show good agreement between the experimental measurement and the FE prediction. Two quantitative parameters, axial deformation rate δ and circumferential deformation rate β , are defined to represent the cross-sectional deformation, and are found to correlate well with the reflection coefficient and mode conversion ratio. The ratio of δ/β is suitable to be used to judge the deformation type. [ABSTRACT FROM AUTHOR]

A fundamental understanding of the mechanical properties and the failure mechanism of hybrid fiber-reinforced polymers (FRP) is required for the effective application of FRP in construction. This paper presents a new methodology for predicting the tensile behavior of hybrid FRP tendons by considering the interfacial stress transfer between the resin and the fibers in hybrid FRP. Subsequently, the authors utilize the fundamental concepts of fracture mechanics to derive a model capable of predicting the mechanical properties of hybrid FRPs. For this paper, the authors conducted an experimental study on the tensile properties of hybrid basalt/carbon FRP tendons and hybrid glass/carbon FRP tendons. They identified the effects of resin type, fiber fraction, and fiber arrangement over the cross section. The results show that the stress-strain relationship of hybrid FRP can be modified from the linear behavior of FRP to a ductile behavior with a steady pseudoyielding plateau and a high ultimate failure strain. Meanwhile, the load drop in hybrid FRP, which is attributable to the fracture of the fibers with low elongation capacity, can be controlled effectively by the proper design of the hybrid fiber proportions, resin type, and volume fraction. The proposed hybridization results in improving the deformation ability of fibers with low elongation capacity. Moreover, the proposed model for the description of failure progression and prediction of mechanical properties is verified by good agreement with the experimental results of this paper and those from prior studies by others. [ABSTRACT FROM AUTHOR]

This paper focuses on the analysis and design of foundations on clayey (elastic) soils in the San Francisco/San Pablo Bay area. Many of these soils have mild to moderate expansive properties that still allow the use of shallow T-footings (strip footings). Although suitable for strip footings, the clayey soils deform under structural loads, causing settlement. This deformation causes internal forces in the reinforced T-footing which need to be properly accounted for in design. Three local methods are examined and compared with respect to their assumptions, conservatism, and appropriateness of use. These methods are the spanability method, the bearing capacity method, and the FEM. Although the spanability and bearing capacity methods are deemed adequate by local building officials and design engineers, this paper recommends the use of a more accurate method for design and analysis such as FEM to properly account for structural loads within the T-footings. [ABSTRACT FROM AUTHOR]

The paper presents the experimental and numerical study of a mild steel replaceable dissipation device. The dissipater is made of a milled-down mild steel bar that is confined by a steel tube filled with either grout or epoxy. The use of a reduced area concentrates yielding and plastic straining over a defined length while the tube prevents buckling. The device has been widely adopted in posttensioned rocking systems, and extensive experimental research was carried out on wall and beam-column subassemblies using this external dissipater. As part of those experimental programs, some component testing was carried out; nevertheless, a more comprehensive study was necessary to cover a wider range of geometric and mechanical parameters. The main objective of this research was to calibrate and suggest design parameters to support the design of the dissipation device. The paper shows a comprehensive experimental program under quasi-static cyclic loading carried out with varying geometrical parameters. This work forms the basis for the development of more refined analytical and numerical models to simulate the behavior of the device. In particular, the onset of the dissipater interaction with the confining tube and its buckling mechanism were targeted. Further numerical simulations made use of a fiber element–based model that was capable of capturing the full range of deformation mechanisms highlighted in the experimental program. Using this model, an extensive parametric analysis was carried out to determine significant design parameters, such as the maximum force in the dissipater and the buckling onset strain. Analytical models were also presented to predict the monotonic behavior of the dissipater and provide calibration of the hysteretic force-displacement rule proposed in the final part of the paper. [ABSTRACT FROM AUTHOR]

Cemented paste backfill (CPB) is a novel cementitious construction material that is used extensively for underground mine support and/or mine waste management worldwide. CPB consists of a mix of tailings (mine waste), water, and binder. In other words, tailings are transformed into construction materials. Key engineering properties required for the geotechnical design of CPB structures include strength and deformation behavior. However, there is a paucity of technical data and information about the effect of sub-zero temperatures on these properties. This paper presents an experimental study that focuses on the investigation of the influence of sub-zero curing temperatures on the strength, deformation behavior, and microstructure (e.g., pore structure, porosity, and binder hydration products) of CPB. Several CPB samples with various combinations of compositions (e.g., binder type, cement amount, and water content) cured at different temperatures (sub-zero and room temperatures) and times (7–90 days) are tested with regard to strength, stress–strain behavior, and microstructural characteristics. It is found that frozen CPB (FCPB) exhibits remarkable strength compared with unfrozen CPB and has a great resemblance to frozen soil. No obvious peak stress is observed from FCPB samples during compression, and strain hardening phenomena are commonly seen after the initial yield point. Factors that may affect the behavior of FCPB are thoroughly examined. Binder contents and types are found to be irrelevant; in contrast, water content plays a dominant role. This negligible effect of binder on the properties of FCPB is due to the inhibition of the binder hydration by sub-zero curing temperatures. FCPBs show coarser pore structure than unfrozen CPBs. The results obtained in this study have significant practical engineering applications for mines located in permafrost or cold regions. [ABSTRACT FROM AUTHOR]

Large deformation of the surrounding rock may also occur in hard rock tunnels under certain circumstances. Taking the construction of the jointed and altered granite stratum in the Zangga Tunnel, China, as a case study, the paper analyzes the surrounding rock deformation characteristics and influencing factors in the jointed and altered granite stratum, and explores the control measures for the large deformation by the numerical analysis and the field application test. The results show that the accumulated deformation value and the deformation rate have large values, and the horizontal convergence is larger than the crown settlement. Geological reasons, such as an active fault and alteration, are the internal factors of large deformation, whereas the high in situ stress situation and other reasons are the external factors. The numerical analysis results show that the optimized support structure has the capability to control the deformation. Numerical analysis results show that the optimized structure can control the deformation and the plastic zone range. The field test results show that the deformation rate and value are well-controlled after adopting the control measures, and the field construction efficiency is significantly enhanced, indicating that the control measures presented have a good construction effect in this stratum. [ABSTRACT FROM AUTHOR]

A slab-column joint in a flat plate structure may exhibit upward or downward punching shear (UPS and DPS) failure when subjected to different abnormal loading conditions. This can cause distinct residual deformations of the slabs, which in turn influences the behavior of the consequent progressive collapse of the entire structure. This paper presents two experimental tests on two 2×2-bay , 1/3-scaled flat plate substructure specimens. Both tests were conducted in two loading phases. In the first loading phase (LP-1), the interior column of specimens UPS-Sub and DPS-Sub was subjected to a gradually increased upward and downward concentrated load, respectively, until punching failure occurred at the interior slab–column joint. In the second loading phase (LP-2), an incremented downward uniformly distributed load was applied on the slab of both specimens up until the ultimate state just before a complete collapse of the slab. After LP-1, local and global damage patterns were observed respectively from UPS-Sub and DPS-Sub. The punching shear strength and the corresponding displacement of the interior joint in UPS-Sub were found to be 58.2% higher and 53.6% lower, respectively, than the corresponding ones in DPS-Sub. In LP-2, due to the upward residual deformation of the slab in UPS-Sub as a result of LP-1, its first peak load, vertical displacement, and horizontal displacement under compressive membrane action were, respectively, 8.4%, 91.1%, and 57.1% larger than those in DPS-Sub. On the other hand, the postpunching peak load of the two specimens under tensile membrane action were identical. To offer an in-depth understanding of the mechanical behavior that resulted from upward or download punching shear failure, the punching shear strengths of the interior slab–column joints and collapse resistance of the substructures were also analytically investigated. [ABSTRACT FROM AUTHOR]

Large deformation analyses of structures are of great importance to the evaluation of structural performance under extreme environmental loads, but currently available methods are time-consuming because of the requirement of factorizing large-scale matrices. The inelasticity-separated finite-element method (IS FEM), which can keep the global stiffness matrix unchanged and uses the Woodbury formula as the solver, was presented recently to provide a highly efficient tool for local material nonlinear analysis. To extend the high efficiency advantage of the IS FEM to large deformation analyses, in which the material nonlinearity may be nonlocal and the geometric nonlinearity should be considered, this paper proposes a novel numerical solution scheme by incorporating the updated Lagrangian (UL) formulation into the IS FEM framework. Within this scheme, a Woodbury approximation method (WAM) is introduced as an efficient solver, in which the changing global stiffness matrix is approximated as a constant matrix within a short time period, and a linear equation related to the Schur complement matrix is solved by the combined approximations (CA) method. To eliminate the additional error induced by the approximation, an adaptive iteration strategy (AIS) is presented, in which the approximation error involved in WAM solution is evaluated based on energy norm concept, and the global stiffness matrix is required to be updated adaptively according to the calculated error. The high efficiency and accuracy of the proposed method are finally demonstrated by the time complexity analysis and numerical examples. [ABSTRACT FROM AUTHOR]

The rotation and shear property theory of rubber bearings is researched in the paper. On the basis of the nonlinear rotational stiffness and Haringx elastomer model, a simple mechanics model is provided to analyze the rotation, compression, and shear property for rubber isolators. The rotational stiffness analysis theories corresponding to different shear deformation state are established on the basis of the properties of rubber material and isolators. The tests of natural rubber bearings (RB) and lead plug rubber bearings (LRB) were conducted to testify the nonlinear rotational stiffness analysis model and the shear hysteretic model proposed in the paper. The test results show that both nonlinear rotational stiffness analysis model and shear hysteretic model proposed in the paper could be used effectively to analyze the mechanics properties. [ABSTRACT FROM AUTHOR]

A methodology is developed in this paper for the design and proportioning of interventions for seismic upgrading of substandard reinforced-concrete (RC) buildings. The retrofit approach is presented in the form of a simple design tool that aims toward both demand reduction and enhancement of force and deformation supply through controlled modification of stiffness along the height of the building. This objective is achieved by engineering the translational mode-shape of the structure, so as to optimize the distribution of interstory drift. Results from the proposed approach are summarized in a spectrum format in which demand, expressed in terms of interstory drift, is related to stiffness. Design charts, which relate the characteristics of commonly used global intervention procedures to influence drift demands, are developed to facilitate the retrofit design. The intervention procedures considered in this paper are reinforced-concrete jacketing, the addition of reinforced-concrete walls, and the addition of masonry infills. The proposed methodology is also amenable to adaptation to other strengthening methods, such as the addition of cross-bracing. [ABSTRACT FROM AUTHOR]

This paper introduces an analytical method to calculate the interfacial shear and normal stresses in reinforced concrete (RC) beams strengthened by a fiber reinforced polymer (FRP) sheet or a steel plate (i.e., a soffit plate). The maximum interfacial shear and normal stresses are localized at the end of the soffit plate, and as a result, a debonding phenomenon develops at this position and may produce a sudden failure of the structure. The effects of the shear deformations are calculated in an RC beam, an adhesive layer, and a soffit plate. Thus, the composite RC beam is assumed to be a Timoshenko beam. Application of shear deformations to a Timoshenko beam results in a pair of simultaneous second-order and fourth-order ordinary differential equations. In the engineering literature, these equations are called coupled differential equations. These coupled equations are solved analytically considering all terms. The present paper illustrates the effects of interfacial stresses on the behavior of RC structures strengthened by FRP sheets or steel plates. Finally, the agreement of the results obtained from the analytical solution and the results available in the literature confirms the accuracy of the proposed approach in predicting both interfacial shear and normal stresses. [ABSTRACT FROM AUTHOR]

The initial rotational stiffness of connections is important for the design of semirigid frames. However, most current studies on steel beam to concrete-filled steel tube column connections with bidirectional bolts are based on experimental tests, and theoretical analysis and numerical analysis are rarely reported. As a result, there is no suitable analytical model for calculating the initial stiffness of the connection. Based on the component method, this paper proposes an analytical model to predict the initial stiffness of the connection. It is considered that the connection rotation is mainly induced by deformations of the endplate in bending, column flange in bending, bolts in tension, and panel zone in shear. Moreover, the effects of the endplate in bidirectional bending and bolt pretension are taken into consideration. Then, the prediction results based on the proposed analytical model are compared with experimental results to verify its accuracy, and comparison results indicate that the proposed analytical model can predict the initial rotational stiffness of steel beam to concrete-filled steel tube column connection well. In addition, bolt diameter and endplate thickness are the most influential parameters that affect the initial stiffness of the connection. It also provides a way for such connections to be designed as rigid connections. Finally, the proposed analytical model can be applied with good precision in elastic analysis and serviceability calculations in the design of semirigid steel-concrete composite frames. It can be applied to four types of connections: stiffened extended endplate connections, nonstiffened extended endplate connections, flush endplate connections, and T-stub connections. The proposed analytical model saves substantial resources and workload in experiments and simulations. DOI: 10.1061/(ASCE)ST.1943-541X.0002187. ' 2018 American Society of Civil Engineers. [ABSTRACT FROM AUTHOR]

This paper presents an empirical methodology that allows calculation of ground displacements behind corners of retained cut excavations. The increased stiffness of a retaining wall at the corner of an excavation normally leads to a corresponding reduction in ground movements behind the retaining wall. These 'corner effects' derived from retained cut excavations can only be assessed at present by using three-dimensional numerical analysis or empirical methods. Significant cost and time can be taken carrying out three dimensional analysis, which, additionally, is not normally carried out at an early stage of the design of a project. Furthermore, numerical analysis must be undertaken by a competent person with appropriate training. An inappropriate analysis can yield to misleading and counterproductive results. This constitutes an expensive requirement on practitioners that often resort to more conservative designs which ignore corner effects. The methodology of adjusting calculated ground movements around corners of excavations described in this paper is simple to use and easy to program into software or spreadsheets. It can be used in conjunction with two-dimensional numerical analysis and also for calculating displacements in early stages of projects when numerical analysis has not yet been undertaken. This allows for more informed early discussion with third parties where approvals are sought on a given project. [ABSTRACT FROM AUTHOR]

The tensile stiffness and deformation model of rubber bearings are systemically researched in the paper, a series of basic concepts, such as origin tensile longitudinal elastic modulus, tensile stiffness factor, origin tensile stiffness, offset tension origin stiffness, etc. are suggested corresponding to the theoretical formula and the experimental estimation method. Based on the origin tensile stiffness and offset tension origin stiffness, the deformation calculating theories related to pure tensile state and tension-shear state of isolated bearing are established. The double stiffness model and original stiffness model are proposed to describe the tension properties of rubber isolators after the bearings yield. The vertical tensile stiffness, offset tension origin stiffness, and deformation tests are performed with nature rubber bearings and lead plug rubber bearings to verify the new concepts and computation model of rubber isolators. All test results show that the theories established in the paper are suitable to analyze the tensile stiffness and tensile deformation for rubber isolators. [ABSTRACT FROM AUTHOR]

The vertical stiffness and deformation theories of rubber isolators in compression and compression-shear states are systemically researched in the paper, a series of basic concepts, such as origin compression stiffness, origin compression longitudinal elastic modulus, offset vertical stiffness, etc. are suggested with corresponding theoretical formula and experimental estimation method. Based on the basic concepts and newly suggested calculating theories, the deformation calculating theory related to pure compression state and compression-shear state of isolating bearing is established. The vertical stiffness, offset vertical stiffness and deformation tests are performed with nature rubber bearings and lead plug rubber bearings total 16 original specimens to verify the new concepts and computation model of rubber isolators. All test results show that the theories established in the paper are suitable for analyzing the vertical stiffness and deformation of rubber isolators. [ABSTRACT FROM AUTHOR]

This paper presents three plasticity models that can be applied to numerically simulate pipe–soil interaction. They can be applied individually to evaluate the force–displacement response of a small plane-strain pipe section or in combination to simulate a long pipeline system. In the latter, numerous pipe–soil elements are attached to structural finite elements, each simulating localized foundation restraint along the pipeline. The three models are increasing in sophistication, mainly due to the manner in which they account for the behavior within an allowable combined loading surface. The first is based on traditional strain-hardening plasticity theory and therefore assumes a purely elastic response inside a single expandable yield surface. The second allows some plasticity due to the use of a bounding surface, and the third accounts for kinematic hardening through the introduction of a second smaller surface. The models are detailed in this paper, allowing for simple numerical implementation. Importantly, they are incorporated within the structural analysis of a pipeline and their potential to investigate generic pipeline system behavior is demonstrated. The applicability of the three models is interpreted theoretically and their differences shown through application for (1) a one pipe–soil interaction element and along (2) a 100 m segment of pipeline. The latter shows the practical application of these models to offshore pipeline engineering examples, with the influence of a free span behavior investigated. The ability to model complex cyclic loading is also shown. [ABSTRACT FROM AUTHOR]

A review of the most recently published literature suggests that the prediction of service life of corrosion affected concrete structures remains at the stage of parametric studies, in spite of intensive research on reinforcement corrosion in concrete structures for the past three decades or so. The intention of this paper is to present a performance-based methodology for service life prediction of corrosion affected concrete structures and apply it to flexural members in marine environments. Reliability methods are employed to determine the time period for each phase of service life. It is found that corrosion induced concrete cracking would occur in reinforced concrete flexural members at about 18% of its total service life, and that, once reinforced concrete flexural members become unserviceable due to corrosion induced excessive deflection, there is about 13% of the service life remaining before the structures finally become unsafe. It is concluded that the methodology presented in this paper can serve as a rational tool for decisionmakers with regard to repairs and strengthening of corrosion affected concrete structures. Accurate prediction of each phase of service life of corrosion affected structures can assist structural engineers and asset managers in achieving a cost-effective strategy in the management of reinforced concrete infrastructures. [ABSTRACT FROM AUTHOR]

In this paper, the inelastic response of rigid-plastic and elastic-plastic systems subjected to pulse-type excitations is revisited with dimensional analysis. Starting from Newmark’s result on the maximum displacement of a sliding mass resting on a base that is subjected to a rectangular acceleration pulse, the paper introduces an energetic length scale of the excitation and the relevant dimensionless Π-products that govern the response of yielding structures. The introduction of Buckingham’s Π-theorem reduces the number of variables that govern the response of the elastic-plastic system from five (5) to three (3). The proposed dimensionless Π-products are liberated from the associated elastic system response and are consistent with the incremental evolution from the rigid-plastic to the elastic-plastic system. When the response is presented in terms of the dimensionless Π-terms remarkable order emerges. It is shown that for a given value of dimensionless yield displacement the response curves (maximum relative dimensionless displacements) become self-similar and follow a single master curve. The self-similar solutions show clearly how the inelastic response amplifies as the normalized yield displacement increases and that an increase in strength may lead to an increase in inelastic displacements. The main advantage of the analysis presented in this paper is that it brings forward the concept of self-similarity—an invariance with respect to changes in scale or size—which is a decisive symmetry that shapes nonlinear behavior. [ABSTRACT FROM AUTHOR]

Understanding the mechanical properties of membrane materials in two-dimensional (2D) stress space is critical for structural design and mechanical analysis of membrane structures. In this paper, an experimental study of the warp-knitted fabric PVDF8028 subjected to biaxial loads was performed to expose the detailed mechanical behaviors and determine proper elastic parameters for the fabrics under multiple stress ratios. The least-square method was adopted to calculate the elastic parameters for different stress states, and response surfaces of strain and elastic parameters were used to reveal the mechanical behaviors in detail. Comparison between coated plain-woven and warp-knitted fabrics was used for exhibiting the influences of microstructures and deformation mechanisms on the macroscopic mechanical properties of materials. The results show that the stress–strain behaviors exhibit significant nonlinearities, and could be characterized by appropriate response surfaces. The elastic stiffness response surfaces of loading and unloading processes could form an unbalanced X-shaped cross, and detailed elastic parameters in those two processes could be obtained by corresponding response surfaces. Compared with plain-woven fabrics, warp-knitted fabrics could exhibit more obvious nonlinear characteristics due to the existence of their coiled yarns and lower Poisson's ratios because of the special noncrimp yarn structure. The differences in macroscopic mechanical properties for these two materials result from the corresponding differences in microstructures and deformation mechanisms. [ABSTRACT FROM AUTHOR]

Groundwater seepage and an increased lateral earth pressure coefficient at rest (K0) increase the potential for triggering large-scale landslides in sensitive clays. After the failure is triggered, the successive retrogressive failure of soil blocks in the undrained condition is influenced highly by K0. This paper presents the numerical techniques for modeling seepage and K0 using an Eulerian-based large deformation finite-element method. The finite-element simulation was performed first for a drained condition to calculate the in situ effective stresses and seepage forces, which then were used to model subsequent undrained retrogressive failure in total stress, triggered by toe erosion. A strain-softening- and strain-rate-dependent undrained soil strength model, which captures the behavior of soil failure from its intact condition to the fluidlike remolded material flow, was adopted in the retrogressive failure analysis. The simulation covered different phases of the landslide, including the initiation and retrogression of failure, and debris flow. Using the developed numerical technique, the 2010 Saint-Jude landslide in Quebec, Canada, was simulated. [ABSTRACT FROM AUTHOR]

The large deformation issue in soft rock mass is a worldwide difficulty that has puzzled tunnel engineering for a century and a half. Previous studies have mainly focused on a large deformation mechanism, prediction, and control of soft rock with single lithology, while there are limited studies on the tunneling-induced large deformation in monoclinic and soft-hard interbedded rock strata. This paper studies the deformation law, evolution process, and failure mechanism of a tunnel excavated in monoclinic and soft-hard interbedded rock mass by onsite measurements in the No. 3 inclined shaft of the Muzhailing Tunnel, which is a key control project of the Lanzhou-Haikou National Expressway. The achieved results indicated that the tunnel deformation was characterized by significant asymmetry, the maximum deformation in the cross section was observed to occur in the normal direction of the bedding plane, and the side of the larger deformation was consistent with the dip direction of the strata. The vertical displacements were greater than the horizontal displacements except for the right foot of the middle bench, and the primary lining at the upper left of the tunnel had intruded into the space of the secondary lining and had to be demolished and reconstructed. The displacement speed and amount mostly reached the peak in the construction stage of the middle bench, and its displacement amount accounted for about half of the total displacement. The spatiotemporal curves of large deformation could be divided into four stages according to the excavation time and the distance from the tunnel face. Two types of exponential functions were used to fit and predict the tunnel displacement, which displayed good applicability. The disaster evolution process of large deformations was summarized into five stages on a macro scale: premise, gestation, development (including four substages), occurrence, and treatment of large deformation. The failure mechanism of monoclinic and soft-hard interbedded rock mass is mainly the bending-tensile failure of thin-layered strata. [ABSTRACT FROM AUTHOR]

Past researchers have introduced performance-based methods to simultaneously account for the various sources of uncertainty in the prediction of lateral spread displacements through the incorporation of a probabilistic analytical framework. Although these methods can effectively handle the various sources of uncertainty associated with empirical lateral spread displacement prediction, they are difficult for engineers to perform without the use of specialized numerical tools. This paper introduces a simplified procedure that approximates the results of the performance-based method through the use of lateral spread reference parameter maps. Equations are provided to correct mapped reference parameter displacements for site-specific geotechnical and topographical information to produce hazard-targeted estimates of lateral spread displacement. The simplified performance-based procedure is validated through a comparative study using several soil profiles across several cities in the United States. Results show that the simplified procedure approximates the results from the full performance-based procedure at all evaluated return periods within 3% and/or 4.0 cm. [ABSTRACT FROM AUTHOR]

The longitudinal stiffness of multispan suspension bridges plays an important role in load-resisting systems. In this paper, a model defined as the kinematic multispring (KMS) model is proposed for simulating the longitudinal deformation behavior of multispan suspension bridges. Tower springs and cable springs constitute a series-parallel system in the KMS model. The stiffness formulas for cable springs were derived on the basis of the energy principle. The elastic elongation of the cable was considered and proved to be nonnegligible, especially for long-span bridges. The effect of the inclined angle of the cables wasfirst considered in the formulas for the cable elastic stiffness. The elastic stiffness and the geometric stiffness of the cables were found to be relevant.Compared withnumericalmodels, theKMSmodel proposed in this paper was proven to be accurate and applicable. [ABSTRACT FROM AUTHOR]