External Energy Dissipation Research Articles

Variation characteristics and homology analysis of loaded coal-rock's non-stress signals

When loaded coal-rock is deformed, various non-stress signals, such as temperature-type, electromagnetic-type, and vibration-type, exhibit distinct characteristics as stress'. In order to clarify the relationship between various coal-rock's non-stress signals and establish the corresponding relationship between these characteristics and the damage degree, the study first analysed the generation and evolution mechanisms of the three types of non-stress signals from the perspective of physical mechanisms and energy, and then investigated the changing characteristics of loaded coal-rock's non-stress signals based on uniaxial experiments at different rates. Finally, the homology of non-stress signals is verified by comparing the characteristics of different non-stress signals. The findings indicate that the variation of the non-stress signal is connected to the status of the coal-rock fracture, which is a physical expression of external mechanical energy dissipation. Moreover, the degree of damage inside the coal-rock is proportional to the strength of each non-stress signal source, and the location of the measurement point has no effect on the details associated with coal-rock damage in the non-stress signal. All of the non-stress signals display changing features and fracture precursors connected to the coal-rock damage state. Among the three kinds of non-stress signals, the temperature-type non-stress signal exhibits the most obvious stationarity and stage, whereas the electromagnetic-type and vibration-type signals would fluctuate because of the stress stability. However, they differ greatly in terms of sensitivity to stress variations and difficulties in diagnosing fracture precursors. In addition, the maximum of the vibration-type and electromagnetic-type signals often corresponds with the “plateau” of the temperature-type signal, which means that three different non-stress signal features occur together. Furthermore, the homology of loaded coal-rock's non-stress signals can be efficiently verified by both evidence from theory and experiment. This research can offer a way to determine the loading condition of coal-rock by using non-stress signals, and it can theoretically promote future studies on the prevention of coal and rock dynamic disasters by multi-information fusion.

A novel resilient system of self-centering precast reinforced concrete walls with external dampers

The seismic vulnerability of concrete structures has prompted the development of innovative approaches to enhance earthquake resistance. Recent earthquakes have demonstrated the challenges of repairing concrete buildings damaged beyond feasible restoration. In response, research in structural engineering has increasingly focused on damage-resisting reinforced concrete walls, offering improved self-centering behavior and damage mitigation compared to traditional counterparts. Self-centering walls, employing a rocking mechanism, exhibit effective damage minimization and residual deformation reduction. This study introduces a robust approach to precast reinforced concrete walls, comprising a precast reinforced concrete shear wall integrated with an external energy dissipation component. The energy dissipation element, a reinforced concrete column attached externally on both sides of the wall, acts as a new damage-limiting component with enhanced energy dissipation capacity. Utilizing the general-purpose Finite Element (FE) software ABAQUS, a three-dimensional simulation of experimentally investigated self-centering precast reinforced concrete walls was developed. The finite element model was validated and subsequently employed to assess the performance of the proposed system under cyclic loading. Various design parameters of the reinforced concrete energy dissipation element, including cross-sectional area, wall height proportion, concrete strength, primary reinforcement yield strength, and reinforcement ratio, were investigated. Additionally, the suggested system underwent cyclic loading in multiple scenarios simulating subsequent earthquakes. The finite element analysis results indicate that the proposed method, with a well-designed energy dissipation element, ensures minimal damage, a controlled increase in lateral resistance, sufficient energy dissipation capacity, and the required resilience following successive seismic events.

Bioinspired ultra-tough, exceptionally stretchable, and self-recoverable bio-based coating for visual damage detection and self-healing

Developing intelligent materials with integrated ultra-high-performance damage monitoring and repair functions is of paramount significance for broadening the application of the latest generation of smart materials. Here, inspired by spider silk and biological skin, we embedded multiple hydrogen bonding motifs and rigid alicyclic groups with attached damage monitoring sensors in bio-based polyurethanes to create bio-based elastomers with exceptional mechanical properties combined with repair and damage monitoring functionalities. Benefiting from the abundance of multiple hydrogen bonding elements within the polyester backbone for fracture and remodeling as external energy dissipation, and the contribution of asymmetric alicyclic groups embedded in hard domains. The elastomer possesses exceptional toughness (583 MJ·m−3) and tensile strength (43 MPa), the elongation at break point is 2600 %, and self-healing (86 % at 60 °C for 6 h), environmental adaptability, and recyclability, thereby achieving the preparation of ultra-tough self-healing elastomeric materials. Simultaneously, the internally embedded sensors enable the localization and monitoring of damage through visually observable means, such as quenching and discoloration. The elastomer recovers well in 3.5 wt% NaCl solution and provides corrosion protection (9.23 × 107 Ω·cm2 even after 50 days of immersion), achieving the integration of ultra-high mechanical performance coating materials with damage warning and repair functions. Therefore, the molecular structure design scheme of the biomimetic elastomer provides constructive guidance for surface protection application of engineering equipment in service under harsh environments.

Seismic Performance of Self-reset Piers Assembled with External Replaceable Energy Dissipation Rings

In order to improve the shear and energy dissipation capacity, this paper proposes a kind of external replaceable energy dissipation ring segment assembly self-reset pier. The ABAQUS platform is used to simulate the refined model of pier and energy dissipation device. Then the influence of different energy dissipation modes on the seismic performance of bridge piers is studied by pseudo-static analysis. Finally, the influence of different parameters of energy dissipation ring on the seismic behavior of bridge piers is analyzed. The results show that the capacity of shear resistance and energy dissipation of the pier with two energy dissipation lines is significantly higher than that of the pier without energy dissipation devices. Reducing the radius of energy dissipation ring can effectively improve the lateral bearing capacity and cumulative energy dissipation of bridge piers. The thickness of energy dissipation ring has little effect on the seismic performance of bridge piers. Increasing a pair of energy dissipation rings can increase the cumulative energy dissipation of bridge piers by 31.1%. Although the residual displacement of pier top increases, the residual displacement angle is still less than 0.5%.

Experimental Assessment of Resilient Controlled Rocking Masonry Walls with Replaceable Energy Dissipation

In recent years, several studies have been conducted to evaluate the seismic response of controlled rocking masonry walls (CRMWs) that depend on unbonded post-tensioning (PT) tendons. The current paper describes the quasi-static cyclic testing of proposed controlled rocking masonry walls that omit PT but incorporate externally attached energy dissipation (ED-CRMWs). The proposed external energy dissipation (ED) is a flexural yielding device, named a flexural arm, that is bolted to the wall through a special steel hollow block to allow simple and fast replacement after an earthquake. As such, this wall system overcomes the limitation of internal ED devices (e.g., unbonded axial yielding bars) of being unreachable and unreplaceable after damage due to yielding or fracturing. In addition, the paper reports the retesting of the proposed controlled rocking wall after being repaired and subsequently compares the performance to that of the original wall in order to evaluate the wall resilience following seismic events. The experimental results are discussed in terms of the failure modes and damage pattern, force–displacement response, wall lateral load capacity, residual drifts, displacement ductility, and ED capacity. The results show that using a special hollow steel block at strategic locations produced a high displacement capacity of 5.0% drift without strength degradation and preserved the intended self-centering with residual drifts of less than 0.2% until at least 3.7% lateral drift. The flexural arm also had significant ductility capacity, where the walls reached 5.0% drift without buckling or fracturing of the arms. Both the original and the repaired walls exhibited limited and localized damage at the wall toes, thus positioning the proposed ED-CRMWs as a resilient system for masonry construction. Finally, the paper presents design recommendations that could be considered for introducing ED-CRMWs with flexural arms in future relevant standards.

Seismic Analysis of Posttensioned and Hybrid Bridge Bents with Buckling Restrained Braces

A numerical model is presented for a rocking bridge bent specimen consisting of two precast concrete columns with posttensioning (PT) bars, two footings, and a cap beam, with or without a buckling restrained brace (BRB). First, a numerical model of the posttensioned bridge bent specimen without a BRB is developed; emphasis is placed on modeling the rocking mechanism at the joint between precast concrete members joined only through PT bars. The numerical model is extended to a hybrid specimen consisting of a two-column posttensioned bridge bent with a BRB as an external energy dissipation device. Experimental results obtained from quasi-static cyclic tests of the posttensioned and hybrid specimens are compared with the numerical models. Satisfactory agreement of the numerical models with the experimental results is observed in terms of structural response, hysteretic energy, and PT-bar forces. The numerical models are subsequently extended to a previously tested three-column bridge bent for two configurations: (1) a posttensioned bridge bent with PT bars, and (2) a hybrid bridge bent with PT bars and two BRBs. A fiber-based bridge bent model is built, which includes soil–structure interaction (SSI) using simplified springs. A comparison of the posttensioned and hybrid bridge bents using far-field and near-field ground motions shows that the hybrid bridge bent displays superior performance compared with the posttensioned-only bridge bent.

A comparative study of self-centering precast concrete walls with replaceable buckling-restrained yielding plates or friction dissipation components

Two new unbonded post-tensioned (PT) self-centering precast concrete wall systems with excellent reparability and seismic resilience are investigated in this paper through cyclic loading testing of four large-scale precast walls. As major innovative features, reparability and seismic resilience of the structures are achieved by using externally connected replaceable buckling-restrained yielding plates (Type I) or friction components (Type II), and steel jackets to confine concrete at wall toes. Both types of wall specimens showed excellent self-centering, energy dissipation, and ductile behavior over 3.5–4% lateral drift without significant strength reduction, demonstrating remarkable advantages over monolithic cast-in-place (CIP) walls and self-centering precast concrete walls with yielding reinforcing bars. The damage in the proposed walls concentrated in the external energy dissipation components, with minor concrete cracking and no concrete crushing at the completion of testing, making repairs feasible by replacing the damaged components. The energy dissipating capacity for the Type II wall was significantly greater than those for the Type I walls at relatively small drift levels due to the large initial stiffness of friction-based damping. As there was no significant damage in the friction damping components throughout testing, the energy dissipation for the Type II wall was much more stable than those for the Type I walls. Comprehensive finite element models were also developed for both types of walls, which satisfactorily captured the global and local behaviors, including prediction of minor concrete damage, steel and concrete strains, and nonlinear behavior of the energy dissipation components. A parameter study was subsequently conducted to investigate the effects of losses in the friction bolt force and PT force on the wall behavior. Overall, both types of walls can be used in the life-line structures that have great demand for fast reparation and restoration of their original lateral resistance and energy dissipation after a major earthquake.

Quasistatic Analysis of Precast Segmental Concrete-Filled Steel-Tube Bridge Pier with External Arched Energy Dissipation Device

In order to further promote the application of segment-assembled bridge piers in medium- and high-intensity areas, and to reduce the post-earthquake damage and repair cost of bridge piers, in this paper, a precast segmental concrete-filled steel-tube bridge pier (PSCFSTBP) with an external arched energy dissipation device (AEDD) is proposed. Firstly, the effectiveness of the finite-element analysis software ABAQUS 6.14-4 is proved by the test results of the PSCFSTBP and the corresponding finite-element model analysis results. Secondly, ABAQUS 6.14-4 was used to establish four-segment PSCFSTBP models with four different structural forms (non-energy dissipation device, external arch steel plate, external vertical steel plate, and external AEDD), and the seismic performance of each model was compared and analyzed under reciprocating displacement loading. The results show that compared with the PSCFSTBP with an external AEDD, the lateral bearing capacity of the PSCFSTBP with an external vertical steel plate is increased by about 11.9%, and the initial stiffness is increased by about 2.5%. Compared with the PSCFSTBP with an external arch steel plate, the lateral bearing capacity, initial stiffness, and energy dissipation capacity are increased by 28.8%, 4.6%, and 13 times, respectively. Compared with the PSCFSTBP without an energy dissipation device, its lateral bearing capacity, initial stiffness, and energy dissipation capacity are increased by 39.4%, 10.4%, and 18 times, respectively. The residual displacement of the PSCFSTBP with an external AEDD is kept within 1 mm in the whole displacement loading stage, the offset rate is less than 1%, and the pier damage is controllable, which can realize rapid repair after an earthquake. Finally, the multi-level energy consumption and local replacement of the AEDD are also explored.

Molecular Origin of Internal Friction in Intrinsically Disordered Proteins.

Protein folding and dynamics are controlled by an interplay of thermal and viscosity effects. The effect of viscous drag through the solvent molecules is described by the classic Kramers theory in the high friction limit, which considers the dampening of the reactant molecules in the solution and quantifies the dependence of the reaction rate on the frictional drag. In addition to the external energy dissipation originating from the surrounding solvent molecules, there is an additional mode of internal energy dissipative force operative within the polypeptide chain reflecting the internal resistance of the chain to its conformational alterations. This dry, solvent-independent intrinsic frictional drag is termed internal friction. In the case of natively folded proteins, the physical origin of internal friction is primarily attributed to the intrachain interactions or other nonnative interactions in their compact states. However, the molecular origin of internal friction in intrinsically disordered proteins (IDPs) remains elusive.In this Account, we address this fundamental issue: what are the principal drivers of viscosity-independent (dry) friction in highly solvated, expanded, conformationally flexible, rapidly fluctuating IDPs that do not possess persistent intrachain interactions? IDPs exhibit diffusive conformational dynamics that is predominantly dominated by the segmental motion of the backbone arising due to the dihedral rotations in the Ramachandran Φ-Ψ space. The physical origin of friction in a complex biopolymeric system such as IDPs can be described by classic polymer models, namely, Rouse/Zimm models with internal friction. These one-dimensional models do not invoke torsional fluctuation components. Kuhn's classic description includes the connection between internal friction and microscopic dihedral hopping. Based on our time-resolved fluorescence anisotropy results, we describe that the sequence-dependent, collective, short-range backbone dihedral rotations govern localized internal friction in an archetypal IDP, namely, α-synuclein. The highly sensitive, residue-specific fluorescence depolarization kinetics offers a potent methodology to characterize and quantify the directional decorrelation engendered due to the short-range dihedral relaxation of the polypeptide backbone in the dihedral space. We utilized this characteristic relaxation time scale as our dynamic readout to quantify the site-specific frictional component. Our linear viscosity-dependent model of torsional relaxation time scale furnished a finite nonzero time constant at the zero solvent viscosity representing the solvent-independent internal friction. These results unveil the effect of the degree of dihedral restraining parameter on the internal friction component by showing that a restrained proline residue imparts higher torsional stiffness in the chain segments and, therefore, exhibits higher internal friction. This Account sheds light on the molecular underpinning of the sequence-specific internal friction in IDPs and will be of interest to unmask the role of internal friction in a diverse range of biomolecular processes involving binding-induced folding, allosteric interaction, protein misfolding and aggregation, and biomolecular condensation via phase separation.

Reliability-based optimization of multiple nonlinear PTMDs for seismic retrofitting of buildings

Recent Probabilistic Seismic Hazard Analysis (PSHA) for Chile has indicated a significant increase in PGA values currently adopted in the country. Thus, assessing the reliability of existing buildings and developing tools for seismic retrofitting purposes have become relevant. Adding external passive energy dissipation systems to attenuate seismic oscillations is usually cost-effective. Among the options, pendulum-tuned mass dampers (PTMDs) are attractive due to their performance and simplicity for installation and maintenance issues. Even so, a comprehensive literature survey reveals that reliability-based optimization (RBDO) studies of single and multiple PTMDs cannot be found, to the best of the authors’ knowledge. Hence, this paper aims at performing the RBDO of single and multiple PTMDs of a steel building based on Chilean seismicity. For this purpose, uncertainties in both ground motion and parameters of the mechanical model are considered through seismic vulnerability analysis, which is integrated into an optimization problem. Because strong ground motion must be included, leading the oscillators to sway at large angles, the PTMDs’ non-linear behavior is considered. The results show that for single PTMDs, the classical closed-form expressions can also be successfully employed, but only for higher mass ratios. Furthermore, the optimization for double PTMDs scenario leads to similar performance (as for the single PTMD), but with the associated advantages in installation and maintenance processes, due to their lower masses.

Seismic performance of precast CFDST segmental column with hybrid energy dissipation devices

Precast segmental column has various advantages as compared to traditional cast in-situ monolithic column. The major issues of such column are the concrete compressive damages at the toes of the segments and limited energy dissipation due to the rocking mechanism. This study explores a new design of precast segmental column with damage resistant features and hybrid energy absorption system. Super elastic shape memory alloy (SMA), external energy dissipation devices and concrete-filled double-skin steel tubes (CFDST) segments are used to form a seismic resilient precast segmental column. Specifically, the SMA rebars provide the column with good self-centring ability; the external replaceable energy dissipation devices provide extra energy dissipation capacity; the use of CFDST segments mitigates the concrete damage. It is found that the proposed column performs well with small residual displacement, satisfying energy dissipation and minor damage.

Energy dissipation models of soil nails for 3D upper bound analyses of steep reinforced slopes

Analytical energy dissipation models of nail-soil systems under the ultimate limit state are rare. In this study, a rigorous plastic energy dissipation model (RPEDM) is employed and a pseudo-plastic energy dissipation model (PPEDM) of nails is proposed to analyze the stability of nailed slopes. In the RPEDM, the energy dissipation rate of nails was assumed to be independent of nail-grout interaction. However, in the PPEDM, the nail-soil interaction was analytically accounted for. Based on the upper bound of the plastic theorem, the RPEDM and PPEDM are then incorporated into a three-dimensional discretized failure mechanism to analyze the stability of steep nailed slopes. External work rates and energy dissipation rates are computed to formulate the work rare balance equation, followed by a global search of the critical factors of safety (FS). A comparison with numerical simulations and existing solutions demonstrated that: (1) the RPEDM obeyed the basic principle of the plastic theorem but the estimated FSs had a significant discrepancy with numerical simulations; (2) the PPEDM could predict more accurate FSs and variation of axial forces mobilized within nails compared with the RPEDM but the FSs obtained by PPEDM did not provide rigorous upper bound solutions since “elastic energy dissipation” was factored in the analysis; (3) the PPEDM can degrade into RPEDM if the width of the nail-soil interaction zone is equal to zero. In the end, the RPEDM and PPEDM were used to explore the effects of the layout and the size of nails on the FSs of steep nailed slopes.

Seismic Performance Analysis of Segmental Assembled Concrete-Filled Steel Tubular Pier with External Replaceable Energy Dissipation Ring

In order to develop a new type of prefabricated bridge structure system with green, efficient and recoverable function, which complies with the new requirements of rapid repair of pier function after earthquake, and improves the applicable performance of prefabricated assembled pier in medium and high-intensity seismic areas, a precast segmental concrete-filled steel tubular (PSCFST) pier with an external energy dissipation ring is proposed. Based on ABAQUS analysis software, a four-segment PSCFST pier model is established, and the pseudo-static comparative analysis is carried out between the traditional PSCFST pier and the PSCFST pier with the external energy dissipation ring. The results show that compared with the traditional PSCFST pier, the lateral bearing capacity of the PSCFST pier with an external energy dissipation ring is increased by 60%, the energy dissipation capacity is increased by about 20 times, and the damage is concentrated in the energy dissipation ring, the damage is controllable, and the rapid repair after the earthquake can be realized by replacing energy dissipation devices and other measures. At the same time, the seismic performance of pier models with three different control parameters (initial prestress, material strength of energy dissipation ring and section width of energy dissipation ring) under reciprocating loading is analyzed. The results show that the initial prestress does not affect the cumulative energy consumption of the pier; the increase in the material strength of the energy dissipation ring improves the overall stiffness and improves the energy dissipation capacity of the PSCFST pier; the reduction in section width will affect the overall equivalent stiffness and unloading stiffness of the segmental pier, and the energy dissipation capacity will be significantly reduced.

Evaluating the Vertical Extension Module of a Building with Installed Rotary Dampers at Joints

In this study, the shape of a vertical expansion module with a rotary-type damping device is proposed. The external energy dissipation capacity is confirmed through experiments and the performance of the module is simulated. It can be easily applied to high-rise structures, as the module is directly supported by the bearing walls without the need for a separate base system. Additionally, as the damper can be replaced, it is possible to enhance seismic performance even after construction. The simulation results show that the rotary-type damper is more effective in reducing the displacement, shear force, and moment than free and fixed joints. In the pushover analysis of a system modeled using the moment hinge of the rotary damper of the joint, the best response reduction effect is obtained when the yield moment of the hinge is defined as 1% of the frame plastic moment. As a result of the analysis of the multi-degree-of-freedom system considering a harmonic load, we determined that it is efficient for the hinge to yield after the displacement, and the acceleration response of the resonant structure reaches steady state during the installation. In the multi-degree-of-freedom system with slab joints added to the analytical model, the displacement response decreased gradually as the natural period of the structure decreased and the joint increased. This provides evidence that the damper does not affect the overall behavior of the structure. The most important design factor of the rotary-type friction damper, shown through the experiment, is the relationship between the frictional surface and the tightening force of the bolt.

Experimental research on the seismic properties of shear wall reinforced with high‐strength bars and magnetorheological dampers

Magnetorheological (MR) damper was a kind of smart instrument, and it was very suitable for the semi-active control. In this research, a large-scale MR damper working in the shear mode of the MR fluid was developed to enhance the mechanical properties of the shear wall. The influence of MR damper on the mechanical properties of the shear walls, such as stiffness, strength, ductility, and the energy dissipation capacity, had been researched. Firstly, both the model of MR damper and shear wall were established to optimize the properties of the MR damper and shear wall. Then, three different concrete shear walls were fabricated, which were reinforced by carbon fiber-reinforced polymer (CFRP) bars (W-1), CFRP bars and MR dampers (W-2), and steel strands and MR dampers (W-3), respectively. The mechanical properties of the specimens were experimentally researched and analyzed. The experimental results showed that the ductility, the ability to bear external loads, stiffness, and energy dissipation capacity of the shear walls could be enhanced by the MR damper simultaneously. Compared with W-1, the ductility, the ability to bear external loads, ultimate deformation, and energy-dissipation capacity of W-2 increased by 4.1%, 26.8%, 83.9%, and 35.8%, respectively. The residual deformation of the three shear walls was almost the same. The results indicated that the MR damper could enhance the mechanical properties of the shear walls and had no influence on the self-centering capacity of the shear walls at the same time.

Seismic performance of bridge with unbonded posttensioned self-centering segmented concrete-filled steel-tube columns: An underwater shaking table test

As one of the prefabricated structures, precast segmented bridges can be used to shorten construction time, reduce traffic delays, improve quality control, and minimize environmental impact. Despite the numerous advantages of segmented pre-fabricated rapid assembly technology, it is not widely used in high seismic hazard zones nor applied to complex water-abundant situations because of the lack of knowledge on its seismic performance. Through experimental and numerical studies, researchers have studied the seismic performance of such type of column under quasi-static testing. The behaviors of the column or bridge under desired strong ground motions (GMs) have been rarely investigated. This paper presents the major findings of an underwater shaking table testing program conducted on a 1/4 scaled single-span bridge with novel self-centering segmented concrete-filled steel tube columns. This study focuses on the performance of the bridge subjected to different GMs under 4 water conditions, which are with water at a height of 1.2 m, 1.5 m, 1.8 m, and without water. The bridge model incorporated two post-tensioned precast self-centering segmented concrete-filled steel tube (PSCFST) single columns with fixed and sliding supports connected to a single span steel box-girder superstructure. The internal unbonded PT tendons are installed at the center of the segment section, and external energy dissipation (ED) bars are installed on the outside of the bottom segment. The bridge model was then subjected to a sequence of natural and artificial GMs with different amplitudes. The well-designed PSCFST bridge demonstrated a desirable seismic performance, and no significant damage was observed. Concerning the overall response of the structure, the maximum drift ratio reached 2.14%. Moreover, a maximum residual drift of 0.09% was observed after the tests, which indicates that the test model demonstrated a desirable self-centering capability after a sequence of GMs. The cumulative energy dissipation and equivalent viscous damping ratio of the bridge were calculated. A comparison is made for the seismic performance of the bridge especially in terms of the displacement and acceleration of the whole structure under the cases of with and without water.

Numerical Study on Hysteretic Behaviour of Horizontal-Connection and Energy-Dissipation Structures Developed for Prefabricated Shear Walls

This study proposed a developed horizontal-connection and energy-dissipation structure (HES), which could be employed for horizontal connection of prefabricated shear wall structural system. The HES consists of an external replaceable energy dissipation (ED) zone mainly for energy dissipation and an internal stiffness lifting (SL) zone for enhancing the load-bearing capacity. By the predicted displacement threshold control device, the ED zone made in bolted low-yielding steel plates could firstly dissipate the energy and can be replaced after damage, the SL zone could delay the load-bearing and the load-displacement curves of the HES would exhibit “double-step” characteristics. Detailed finite element models are established and validated in software ABAQUS. parametric analysis including aspect ratio, the shape of the steel plate in the ED zone and the displacement threshold in the SL zone, is conducted. It is found that the HES depicts high energy dissipation ability and its bearing capacity could be obtained again after the yielding of the ED zone. The optimized X-shaped steel plate in the ED zone exhibit better performance. The “double-step” design of the HES is a potential way of improving the seismic and anti-collapsing performance of prefabricated shear wall structures against large and super-large earthquakes.

Study on the damping efficiency of continuous beam bridge with constant cross-section applied by lead rubber bearings and fluid viscous dampers

Bridges are the lifelines of disasters in earthquake areas. Therefore, it is very necessary to ensure the safety and traffic function after earthquake. Seismic isolation refers to install external energy dissipation devices or external energy input devices in specific parts of engineering structures. There are certain differences in longitudinal and transverse seismic responses of multi-span continuous beam bridges by changing the seismic dynamic characteristics or dynamic effects of structures. It is difficult to achieve the purpose of seismic isolation in both horizontal directions using isolation devices alone. The rubber deformation ability of lead rubber bearings can effectively insulate, and the yield energy consumption ability of its lead core can effectively consume the seismic energy for damping. The horizontal resistance is very small under the creep load, and the stiffness decreases rapidly after yielding under the strong dynamic earthquake load; meanwhile, the seismic energy is dissipated by the hysteresis of bearing. Fluid viscous damper is a velocity-dependent energy dissipation device, which produces viscous damping force, provides strong restoring force for components, and has a good limit function. This process will also dissipate the seismic energy, so as to reduce the structural earthquake response. Using these two methods together, the horizontal seismic responses of multi-span continuous beam bridges can be effectively controlled at the same time. Based on this idea, this article takes a high-speed multi-span continuous beam bridge with equal section as the engineering background, and uses dynamic time history analysis method to discuss the seismic isolation effect of lead rubber bearings and fluid viscous dampers.

Upper Bound Limit Stability Analysis for Soil Slope with Nonuniform Multiparameter Distribution Based on Discrete Algorithm

Slope stability analysis is a core issue in geotechnical engineering. This paper proposes a method of upper bound limit stability analysis for a slope with multiparameter coordinated variation based on the comprehensive consideration of the nonuniform distribution of slope soil parameters. This method starts from the perspective of energy balance, establishes a slope failure mechanism which meets velocity separation requirements, deduces its calculation formula for external force power and internal energy dissipation power, develops a cycle program for the most dangerous slip surface searching and stability coefficient calculation through computer programming technology, and finally forms a calculation method of upper bound limit stability analysis for the soil slope with nonuniform multiparameter distribution. At the same time, this method takes a dump slope in an open‐pit mine as the engineering background, considers the nonuniformity of density, cohesion, and internal friction angle of the slope soil under subsidence, applies upper bound limit analysis to analyze the slope stability, and evaluates the accuracy of analysis results by using the residual thrust method. The results show that upper bound limit analysis has highly accuracy in stability coefficient calculation; compared with the residual thrust method, the stability coefficient calculation result by upper bound limit analysis is a strict upper bound solution, and the calculation error is easy to be estimated and eliminated. Simultaneously, the most dangerous slip surface obtained by upper bound limit analysis can fully satisfy the velocity separation requirement and has a greater engineering reference value.

Effect of damage and support damping mechanisms on unimorph piezoelectric energy harvester

Damping plays a critical role in power generation by piezoelectric energy harvesting, and yet there is a lack of sensitivity studies on different sources of damping. In this paper, two damping sources in unimorph piezoelectric energy harvesters, namely support loss and damage damping mechanisms, are experimentally investigated. Variations of the power generation are evaluated with respect to the sources of damping. Accordingly, the power generation model is developed according to the experimental results in this work and using a single degree of freedom analytical model. This study focuses on the debonding effect, as an internal damping source, and support loss, as a critical source of external energy dissipation. The results show that the debonding reduces the output power dramatically at resonance and, particularly, at anti-resonance frequencies. Moreover, investigation of the support loss shows that the material of clamp as well as installation torque have an impact on the support loss and, consequently, affect the output power.