Energy Dissipation Components Research Articles

Experimental study on seismic performance of reinforced concrete frames retrofitted with eccentric buckling-restrained braces (BRBs)

As a new type of energy dissipation component with excellent mechanical performance, the Buckling-Retrained Braces (BRBs) were gradually applied in retrofitting and improving seismic performance of reinforced concrete structures in China. In order to investigate the seismic performance of reinforced concrete structures retrofitted with BRBs, quasi-static test of two single-bay and 3-story reinforced concrete frames specimens was conducted and introduced in this paper. Two 1/2 scaled specimens were designed to reflect real prototype structure. For comparison, one control specimen was designed without BRBs, and the other specimen was retrofitted with BRBs. And particularly, for the specimen retrofitted with BRBs, the BRBs were eccentric layout instead of usually concentric or x-shaped layout, aiming to be more suitable for large-span frames. In the test, the failure mode, carrying capacity, deformability, ductility and energy dissipation ability of both two specimens were investigated. Based on the test results of the measured hysterical curves, skeleton curves, the seismic performances such as bearing capacity, plastic deformability, energy dissipation ability and ductility of two specimens were fully studied. And from the test results, it was indicated that the specimen retrofitted with BRBs showed much better seismic performance than the control specimen without BRBs, and the BRBs could effectively improve the seismic performance of the reinforced concrete frame. For the specimen retrofitted with BRBs, the BRBs firstly yielded before the beam-ends and the column-ends, and an expected yielding process or yielding mechanism as well as good seismic performance was obtained. For the specimens without BRBs, though the beam-ends yielded prior to the column-ends, the seismic performance was much poor than that of the specimen with BRBs.

Microfluidic Arrayed Lab-On-A-Chip for Electrochemical Capacitive Detection of DNA Hybridization Events.

A microfluidic electrochemical lab-on-a-chip (LOC) device for DNA hybridization detection has been developed. The device comprises a 3×3 array of microelectrodes integrated with a dual layer microfluidic valved manipulation system that provides controlled and automated capabilities for high throughput analysis of microliter volume samples. The surface of the microelectrodes is functionalized with single-stranded DNA (ssDNA) probes which enable specific detection of complementary ssDNA targets. These targets are detected by a capacitive technique which measures dielectric variation at the microelectrode-electrolyte interface due to DNA hybridization events. A quantitative analysis of the hybridization events is carried out based on a sensing modeling that includes detailed analysis of energy storage and dissipation components. By calculating these components during hybridization events the device is able to demonstrate specific and dose response sensing characteristics. The developed microfluidic LOC for DNA hybridization detection offers a technology for real-time and label-free assessment of genetic markers outside of laboratory settings, such as at the point-of-care or in-field environmental monitoring.

Investigations of the application of gyro-mass dampers with various types of supplemental dampers for vibration control of building structures

A gyro-mass damper (GMD) is an inertia-based passive control device. It has a gear assembly that amplifies the rotational inertias developed in the gears and generates a resultant resisting force that is proportional to the relative acceleration at the end terminals of the GMD. The amplification provided by the gear assembly can be adjusted by changing the gear masses or the gear ratios of the compound gears. Although similar inertia-based devices have been successfully used for vibration mitigation of motor vehicles and optical tables, there are only a few studies that investigated their application in building structures. This number is even lower for the particular type of inertial damper that has been considered in this study, i.e., GMD. Unlike other types of inertial dampers, the supplemental energy dissipation component of GMDs is not built-in to the device and can be independently attached as an external component. This allows the design engineers to use this cost-effective device and select any available energy dissipation device to use in parallel. In this study, using a small-scale GMD, by considering the rotational inertias of the intermediate gears, characteristic equation which describes the relationship between the applied relative acceleration and the resulting resisting force is derived and experimentally verified. For the introduction of GMDs into building structures, three different configurations are evaluated: (i) stand-alone GMD, (ii) GMD-brace system, and (iii) GMD–Viscous damper–Brace (GVB) system. The structure-GMD interaction, considering these three configurations, is investigated in frequency domain and in time domain through energy balance equations and time history analyses. It is shown that by selecting the system parameters properly, GVB systems with nonlinear viscous dampers can effectively improve the seismic behaviour of the structure. This is discussed in more detail when the effects of the damper nonlinearities, as well as the various GMD equivalent mass, brace stiffness, damping values and selected ground motions are investigated. The key findings related to the design, implementation and performance considerations of these systems are provided.

Dynamic Shake-Table Testing and Analytical Investigation of Self-Centering Steel Plate Shear Walls

AbstractRecent research has shown that self-centering steel plate shear walls (SC-SPSWs) offer an enhanced seismic performance over conventional steel plate shear walls by providing an additional self-centering capability using steel frames detailed with posttensioned (PT) beam-to-column rocking connections. As with other previously proposed self-centering frames detailed with similar beam-to-column connections, this detailing facilitates the incorporation of replaceable energy dissipation components, as part of the lateral force resisting system (LFRS). In doing so, by design, the gravity frame components of the LFRS are also protected from damage during an earthquake. To investigate the dynamic seismic response of this proposed structural system, one-third scaled SC-SPSW specimens were subjected to ground motions during a series of dynamic shake-table tests. The experimental investigation results presented in this paper are the first shake-table tests conducted on SC-SPSWs. This test program was compose...

Shear Deformation and Sliding-Based Fiber Beam-Column Model for Seismic Analysis of Reinforced Concrete Coupling Beams

AbstractConventional RC coupling beams have been widely used as key energy-dissipation components in frame-core tube structural systems for high-rise buildings. A model with sufficient efficiency, accuracy, and practicality is urgently needed for the seismic analysis of high-rise structures. According to test results, both the shear deformation and shear sliding mechanisms are critical to assessing the seismic performance of coupling beams. However, available shear models for beams and columns cannot give satisfactory results in modeling both mechanisms in finite-element analysis (FEA). To address this problem, this study takes into account the section shear force–shear strain and shear sliding laws in the traditional displacement-based fiber beam-column element, which is implemented into a general FEA package. A new section shear force–shear strain law, which can consider the pinching effect, strength and stiffness deterioration, shear capacity degradation, and arbitrary complex loading path is first pro...

Cyclic behaviour of beam-to-column joints with cast steel connectors

This paper presents a comprehensive study on steel beam-to-column joints equipped with weld-free cast steel connectors used as replaceable energy-dissipating components. The basic idea was to use the connectors as the main source of deformation and energy dissipation, and to realize rapid repair of the joints by simple replacement of theses connectors after earthquakes. The research commenced with tests on five full scale specimens, including one specimen with conventional welded T-stub connectors and four specimens with the innovative cast steel connectors. The specimens with cast steel connectors were shown to have good energy dissipation capacity with stable and plump hysteretic curves, and the equivalent viscous damping could achieve up to 37.5%. These joints were also shown to meet the classification criteria of semi-rigid joints in terms of stiffness, and the ductility, which was governed by fracture of energy dissipating elements, was found to be satisfactory. The presence of shear tab connection was found to increase the initial stiffness and ultimate strength of the joints, but the energy dissipation was not significantly improved. Importantly, the yielding regions and main source of energy dissipation were limited to the cast steel connectors, while the adjacent structural members remained in the elastic range, indicating minimal repair work in the aftermath of earthquakes. For a further understanding of the proposed joints, finite element models were established, and based on test and numerical observations, preliminary design recommendations, including those on cast steel connector detailing and normal component-based joint design strategies, were finally outlined.

Tumbling asteroid rotation with the YORP torque and inelastic energy dissipation

The Yarkovsky–O'Keefe–Radzievskii–Paddack (YORP) effect and rotational energy dissipation due to inelastic deformations are two key mechanisms affecting rotation of tumbling asteroids in long term. Each of the effects used to be discussed separately. We present the first results concerning a simulation of their joint action. Asteroids (3103) Eger and (99942) Apophis, as well as their scaled variants, are used as test bodies. Plugging in the dissipation destroys limit cycles of the pure YORP, but creates a new asymptotic state of stationary tumbling with a fixed rotation period. The present model does not contradict finding Eger in the principal axis rotation. For Apophis, the model suggests that its current rotation state should be relatively young. In general, the fraction of initial conditions leading to the principal axis rotation is too small, compared to the actual data. The model requires a stronger energy dissipation and weaker YORP components in the nutation angle and obliquity.

Feasibility of optimising bicycle helmet design safety through the use of additive manufactured TPE cellular structures

Bicycle helmets are designed to attenuate forces and accelerations experienced by the head during cycling accidents. An essential element of bicycle helmet design is, therefore, the appropriate manufacturing of energy-dissipating components. The focus of this study was to evaluate the feasibility of using thermoplastic elastomer (TPE) cellular structures (Duraform® Flex), manufactured via a laser sintering (LS) process, as the energy-dissipating inner liner of the bicycle helmet. This study is presented in two sections; the optimisation of the LS process capabilities for the manufacture of cellular structures and an evaluation of the effects of cellular structure density on helmet impact kinematics. Through the fabrication and testing of tensile and compressive specimens, each process parameter (laser power, scanning exposure, build temperature and part orientation) was optimised to maximise compressive strength. The energy-dissipating characteristics of helmet cellular structures, made from this optimised material, were evaluated during simulated helmeted headform impact tests. Reduced accelerations and increased pulse durations were reported for decreased structural densities, demonstrating improved energy-dissipating characteristics for this novel technique. This study demonstrates that cellular structure-based inner liners, manufactured via additive manufacturing processes, have exciting potential towards improving bicycle helmet safety.

Study on Seismic Performance of a Stiffened Steel Plate Shear Wall with Slits

To determine the force mechanism for the steel plate shear wall with slits, the pushover analysis method was used in this study. An estimated equation for the lateral bearing capacity which considered the effect of edge stiffener was proposed. A simplified elastic-plastic analytical model for the stiffened steel slit wall composed of beam elements was presented, where the effects of edge stiffeners were taken into account. The wall-frame analysis model was established, and the geometric parameters were defined. Pushover analysis of two specimens was carried out, and the analysis was validated by comparing the results from the experiment, the shell element model, and a simplified model. The simplified model provided a good prediction of the lateral stiffness and the strength of the steel slit wall, with less than 10% error compared with the experimental results. The mutual effects of the bearing wall and the frame were also predicted correctly. In the end, the seismic performance evaluation of a steel slit wall-frame structure was presented. The results showed that the steel slit wall could prevent the beams and columns from being damaged by an earthquake and that the steel slit wall was an efficient energy dissipation component.

Seismic behavior of suspended building structures with semi-rigid connections

A method is presented in this paper to analyze the dynamic response behavior of suspended building structures. The effect of semi-rigid connections that link suspended floors with their supporting structure on structural performance is investigated. The connections, like the restrains in non-structural suspended components, are designed as semi-rigid to avoid pounding and as energy dissipation components to reduce structural response. Parametric study is conducted to assess the dynamic characteristics of suspended building structures with varying connection stiffness and suspended mass ratios. Modal analysis is applied to identify the two distinct sets of vibration modes, pendulum and bearing, of a suspended building structure. The cumulative modal mass is discussed to ensure the accuracy in applying the method of response spectrum analysis by SRSS or CQC modal combination. Case studies indicate that a suspended building having semi-rigid connections and proper suspended mass ratios can avoid local pounding failure and reduce seismic response.

Development of steel dampers for bridges to allow large displacement through a vertical free mechanism

Isolation bearings and dampers are often installed between piers and superstructures to reduce the seismic responses of bridges under large earthquakes. This paper presents a novel steel damper for bridges. The damper employs steel plates as energy dissipation components, and adopts a vertical free mechanism to achieve a large deformation capacity. Quasi-static tests using displacement-controlled cyclic loading and numerical analyses using a finite element program called ABAQUS are conducted to investigate the behavior of the damper, and a design methodology is proposed based on the tests and numerical analyses. Major conclusions obtained from this study are as follows: (1) the new dampers have stable hysteresis behavior under large displacements; (2) finite element analyses are able to simulate the behavior of the damper with satisfactory accuracy; and (3) simplified design methodology of the damper is effective.

Development of a simplified model and seismic energy dissipation in a super-tall building

The seismic design of super-tall buildings has become an important research topic in earthquake engineering. Limited research has been conducted on the distribution of plastic energy dissipation among the different components of super-tall buildings when subjected to strong earthquakes. A simplified two-dimensional (2D) nonlinear model is developed based on the analysis of Shanghai Tower, an actual super-tall building with a total height of 632m. The accuracy of the simplified model is validated by comparing the results from modal analyses, and static and dynamic time-history analyses of the refined finite element model. Then, the proposed simplified model is used to determine the plastic energy dissipation of different components and the distribution of the total plastic energy dissipation over the height of the Shanghai Tower under different seismic intensities. The analysis indicates that the total plastic energy is mainly concentrated in the upper four Zones of the building and that the outrigger is the major plastic energy dissipation component in the Shanghai Tower.

Application of Buckling-Restrained Braces in Prefabricated Reinforced Concrete Frame

The old prefabricated reinforced concrete buildings have been designed with old standards that are lower than the present design code provisions. These buildings are likely to be vulnerable to severe damage or total collapse under strong seismic excitations. Hence, it is necessary to evaluate these buildings seismic performance and to retrofit them using appropriate methods. Buckling-restrained brace (BRB) is a kind of prospective energy dissipation component. As a brace, it is also a lateral force resistant member. Based on the characteristics of prefabricated frame and BRB, the time history analysis of a prefabricated frame strengthening by BRB is carried out by using software ANSYS to input the seismic wave. Then, the seismic behavior of this kind of frame is studied. It is observed that the seismic response of the retrofitted structures reduces significantly in comparison with the corresponding original structure without any retrofit measures.

Recentering Shape Memory Alloy Passive Damper for Structural Vibration Control

This paper presents a preliminary study on the evaluation of an innovative energy dissipation system with shape memory alloys (SMAs) for structural seismic protection. A recentering shape memory alloy damper (RSMAD), in which superelastic nitinol wires are utilized as energy dissipation components, is proposed. Improved constitutive equations based on Graesser and Cozzarelli model are proposed for superelastic nitinol wires used in the damper. Cyclic tensile-compressive tests on the damper with various prestrain under different loading frequencies and displacement amplitudes were conducted. The results show that the hysteretic behaviors of the damper can be modified to best fit the needs for passive structural control applications by adjusting the pretension of the nitinol wires, and the damper performance is not sensitive to frequencies greater than 0.5 Hz. To assess the effectiveness of the dampers for structural seismic protection, nonlinear time history analysis on a ten-story steel frame with and without the dampers subjected to representative earthquake ground motions was performed. The simulation results indicate that superelastic SMA dampers are effective in mitigating the structural response of building structures subjected to strong earthquakes.

A simplified design procedure for seismic retrofit of earthquake-damaged RC frames with viscous dampers

The passive energy dissipation technology has been proven to be reliable and robust for recent practical applications. Various dampers or energy dissipation devices have been widely used in building structures for enhancing their performances during earthquakes, windstorm and other severe loading scenarios. This paper presents a simplified seismic design procedure for retrofitting earthquake-damaged frames with viscous dampers. With the scheme of designing the main frame and the supplemental viscous dampers respectively, the seismic analysis model of damped structure with viscous dampers and braces was studied. The specific analysis process was described and approach to parameter design of energy dissipation components was also proposed. The expected damping forces for damped frame were first obtained based on storey shear forces; and then they were optimized to meet different storey drift requirements. A retrofit project of a RC frame school building damaged in the 2008 Wenchuan earthquake was introduced as a case study. This building was retrofitted by using viscous dampers designed through the simplified design procedure proposed in this paper. Based on the case study, it is concluded that this simplified design procedure can be effectively used to make seismic retrofit design of earthquake-damaged RC frames with viscous dampers, so as to achieve structural performance objectives under different earthquake risk levels.

The Seismic Response Analysis of Damaged Slip Component of Sliding Isolated Structure

In the service of sliding isolated structure, the slip component damage degree determines the safety of sliding isolated structure. The seismic response analysis about a sliding isolated frame structures was obtained by the finite element analysis software SAP2000 at various loads and compared with the traditional structure. Seismic response differences between slip component of the different forms and number damage was studied. According to Teflon invalid and the displacement-limited of energy dissipation component invalid, the impact of seismic response owing to slip component damage was analyzed. It will provide a reference for the isolated building design, the effective maintenance and damage detection.

Multiple dissipation components of excess light energy in dry lichen revealed by ultrafast fluorescence study at 5 K

A time-resolved fluorescence study of living lichen thalli at 5 K was conducted to clarify the dynamics and mechanism of the effective dissipation of excess light energy taking place in lichen under extreme drought conditions. The decay-associated spectra obtained from the experiment at 5 K were characterized by a drastically sharpened spectral band which could not be resolved by experiments at higher temperatures. The present results indicated the existence of two distinct dissipation components of excess light energy in desiccated lichen; one is characterized as rapid fluorescence decay with a time constant of 27 ps in the far-red region that was absent in wet lichen thalli, and the other is recognized as accelerated fluorescence decay in the 685-700 nm spectral region. The former energy-dissipation component with extremely high quenching efficiency is most probably ascribed to the emergence of a rapid quenching state in the peripheral-antenna system of photosystem II (PS II) on desiccation. This is an extremely effective protection mechanism of PS II under desiccation, which lichens have developed to survive in the severely desiccated environments. The latter, which is less efficient at 5 K, might have a supplementary role and take place either in the core antenna of PS II or aggregated peripheral antenna of PS II.

Selection of real earthquake accelerograms for structural dynamic analysis and energy evaluation

Real earthquake accelerograms are used in structural dynamic analysis. The criteria for record database establishment, record screening, selection principle, scaling adjustment, and sampling size are discussed in the present paper. An optimized selection method using coupled genetic and greedy algorithms is proposed, and energy input characteristics for the records which are selected only through matching acceleration design spectrum are analyzed. Using the proposed method, the mean and target spectra can reach a good agreement within a period range of interest. The dispersion among the response spectra of the different records is small, and the tolerance of the spectrum value corresponding to each period in the important period scope can be controlled more strictly than the specified limit. If the structural cumulative damage or structures with energy-dissipation components are considered, the records selected using the method that only match the acceleration design spectrum are not applicable. In this case, the selection method that considers the energy input demand is recommended.

Experiment Research and Numerical Simulation of an Innovative Seismic Isolating System Designed for Long-Span Continuous Girder Bridges

To enhance the earthquake resistance capacity of long-span continues bridge, theory and design of a new seismic isolating system are proposed based on the utilization of improved carbon structural steel material. Pseudo-static test result of the damping tenon, one essential energy dissipation component, proved the system’s excellent characteristic of consuming earthquake energy. Comparative experiments of three models reflect the working stability of the damping tenon confronted with different stimulation. Finite Element simulation further validates accuracy of the experiment and helps analyzing the material’s elastic and plastic developing status due to different load steps. Finally, this new seismic isolating system is recommended to long-span continues girder bridge designed on the basis of high level earthquake resistant standard.

Research on Seismic Performance Objectives of High-Rise Diagrid Tube Structures

Diagrid tube structures have advantages on constructing high-rise buildings for its great lateral stiffness, but its seismic design methodology researches are limited. The two-stage design method in Chinese code is not specific enough for the seismic fortification objectives of this kind of structures. It is necessary to propose some specific seismic performance objectives for the key components. Typical CFST diagrid tube-concrete core tube structures are studied by dynamic elastic-plastic time-history analysis using Perform-3D program. The structure plasticity developing process is summarized and the distribution characteristics of seismic fortification lines between tubes are discussed. The influences of main structure lateral stiffness related factors on the plasticity developing process are researched. The key components of structure lateral stiffness and plastic energy dissipation are studied. The seismic performance objectives of the key components are proposed for the three-level seismic fortification objectives.