Energy Dissipation Capability Research Articles

Nonlinear dynamics of earthquake-resistant structures using shape memory alloy composites

Earthquake-resistant structures have been widely investigated in order to produce safe buildings designed to resist seismic activities. The remarkable properties of shape memory alloys, especially pseudoelastic effect, can be exploited in order to promote the essential energy dissipation necessary for earthquake-resistant structures. In this regard, shape memory alloy composite is an idea that can make this application feasible, using shape memory alloy fibers embedded in a matrix. This article investigates the use of shape memory alloy composites in a one-story frame structure subjected to earthquakes. Different kinds of composites are analyzed, comparing the influence of matrix type. Both linear elastic matrix and elastoplastic matrix with isotropic and kinematic hardening are investigated. Results indicate the great energy dissipation capability of shape memory alloy composites. A parametric analysis allows one to conclude that the maximum shape memory alloy volume fraction is not the optimum design condition for none of the cases studied, highlighting the necessity of a proper composite design. Despite the elastoplastic behavior of matrix also dissipates a considerable amount of energy, the associated residual strains are not desirable, showing the advantage of the use of shape memory alloys.

Post-yield Damping Ratio Estimation Studies for Masonry-Infilled Reinforced Concrete Frames

Damping ratio is an important and central parameter for the dynamic analysis of structures. The present study focuses on the estimation of the equivalent damping ratio in a post-yield region for RC frames, both with and without infills. One-story one-bay RC frames casted non-integrally with fly ash (FA) bricks and autoclaved aerated concrete (AAC) blocks infills are considered and are tested under monotonic lateral half-cycle loading. Post-yield behavior parameters, displacement ductility and maximum drift ratio, are used to estimate the equivalent damping ratio at each cycle of lateral loading, and empirical relationships are established. Secant stiffness and stiffness degradation for RC frames are also extracted to determine the contribution and effectiveness of type of infills. Free vibration tests on RC frame specimens are conducted subsequent to each cycle of monotonic lateral loading, and the damping ratio is evaluated. It is found that the equivalent damping ratio substantially increases for RC frames with the onset of damage in the post-yield region. The major advantage of the infilled RC frame is a drastic reduction in the maximum drift ratio. However, types of infill are found to yield equivalent damping ratio at par, suggesting similar energy dissipation capabilities. RC frame infilled with AAC block is recommended due to its higher initial as well as secant stiffness vis- $$\grave{a}$$ -vis FA brick-infilled RC frames and higher stiffness degradation that allows it to behave similar to RC frame without infill.

Experimental and numerical study of the spring-asphalt 3D isolation structures under multi-component ground motions

A low-cost spring-asphalt bearing for the 3D seismic base isolation of low-rise residences is presented in this paper. Its dynamic response under horizontal, vertical and rocking ground motions is studied by shaking table test. Different types of excitations such as horizontal excitation only, horizontal and vertical excitation, horizontal, vertical and rocking excitations with different peak ground accelerations are input. A numerical model is developed to further study the dynamic characteristics of buildings with spring-asphalt 3D isolation bearing under multi component ground motions. Frequency domain and time domain analysis are conducted to research dynamic responses of the model. The function of asphalt is also researched by contrast experiments. Research results show that the 3D isolation bearing could efficiently reduce horizontal and vertical acceleration response of upper structures. Furthermore, asphalt makes the structure possess good energy dissipation capability. In addition, the asphalt could provide considerable damping and reduce the displacement while does not add so much stiffness.

Experimental study on component performance in steel plate shear wall with self-centering braces

Steel plate shear wall with self-centering energy dissipation braces (SPSW-SCEDB) is a lateral force-resisting system that exhibits flag-shaped hysteretic responses, which consists of two pre-pressed spring self-centering energy dissipation (PS-SCED) braces and a wall plate connected to horizontal boundary elements only. The present study conducted a series of cyclic tests to study the hysteretic performances of braces in SPSW-SCEDB and the effects of braces on the overall hysteretic characteristics of this system. The SPSW-SCEDB with PS-SCED braces only exhibits excellent self-centering capability and the energy loss caused by the large inclination angle of PS-SCED braces can be compensated by appropriately increasing the friction force. Under the combined effect of the two components, the SPSW-SCEDB exhibits a flag-shaped hysteretic response with large lateral resistance, good energy dissipation and self-centering capabilities. In addition, the wall plate is the primary energy dissipation component and the PS-SCED braces provide supplementary energy dissipation for system. The PS-SCED braces can provide up to 90% self-centering capability for the SPSW-SCEDB system. The compressive bearing capacity of the wall plate should be smaller than the horizontal remaining restoring force of the braces to achieve better self-centering effect of the system.

Seismic behavior investigation of the steel multi-story moment frames with steel plate shear walls

Steel plate shear walls are recently used as efficient seismic lateral resisting systems. These lateral resistant structures are implemented to provide more strength, stiffness and ductility in limited space areas. In this study, the seismic behavior of the multi-story steel frames with steel plate shear walls are investigated for buildings with 4, 8, 12 and 16 stories using verified computational modeling platforms. Different number of steel moment bays with distinctive lengths are investigated to effectively determine the deflection amplification factor for low-rise and high-rise structures. Results showed that the dissipated energy in moment frames with steel plates are significantly related to the inside panel. It is shown that more than 50% of the dissipated energy under various ground motions is dissipated by the panel itself, and increasing the steel plate length leads to higher energy dissipation capability. The deflection amplification factor is studied in details for various verified parametric cases, and it is concluded that for a typical multi-story moment frame with steel plate shear walls, the amplification factor is 4.93 which is less than the recommended conservative values in the design codes. It is shown that the deflection amplification factor decreases if the height of the building increases, for which the frames with more than six stories would have less recommended deflection amplification factor. In addition, increasing the number of bays or decreasing the steel plate shear wall length leads to a reduction of the deflection amplification factor.

Seismic performance and design approach of unbonded post-tensioned precast sandwich wall structures with friction devices

The unbonded post-tensioned (PT) precast sandwich wall structure with friction devices is a combination of the precast sandwich wall structure with friction devices and with PT tendons. The friction devices provide the energy dissipation capability and PT tendons provide the self-centering capability. The mechanical behavior of unbonded PT precast sandwich wall structures with friction devices are investigated theoretically and experimentally. The experimental results verify the effective of the theoretical analysis on predicting the hysteretic responses. It is shown that the structures with rigid joints dissipate energy through plastic damage, and the structures are destroyed finally with the bottom concrete crush; the structures with friction devices have lower stiffness and moment capacity than that of structures with rigid joints, but the friction devices can effectively protect the main concrete walls from damage; additional PT tendons can improve the self-centering capabilities of structures with friction devices. In addition, the multi-layer shell and truss element are adopted to simulate the sandwich wall and the friction devices in finite element analysis (FEA) model. The simplified procedures are proposed to simplify the smooth experimental hysteresis curves into idealized flag-shape curves. The effectiveness of the numerical and simplified results is experimentally verified. Finally, the performance-based design approach suitable for unbonded PT precast sandwich wall structure with friction devices is proposed and confirmed by dynamic time-history analysis.

Effective base isolation combining low-friction curved surface sliders and hysteretic gap dampers

The re-centering capability represents a fundamental property of any effective isolation system. Indeed, a potential residual displacement after an earthquake, besides affecting the serviceability of the construction, may also result in increased peak displacements during aftershocks and future events. In curved surface sliders (CSSs), energy dissipation and re-centering capability are two competing aspects influenced by the friction coefficient and the state of lubrication of the sliding pad. On the one hand, the large energy dissipation capability of high-friction CSSs contributes to mitigate the displacement demand during strong events but negatively affects the re-centering behavior. On the other hand, low-friction CSSs exhibit a better re-centering behavior, but are expected to undergo large displacements that, in turn, imply large dimensions in plan and pose problems of possible pounding between adjacent buildings and damage of nonstructural elements, lifelines and utilities crossing the isolation joint. The present study proposes an efficient base-isolation system that combines low-friction CSSs with hysteretic gap dampers. The latter device introduces supplemental energy dissipation only when the displacement of the isolation system exceeds a threshold or initial gap while not being engaged otherwise. The mechanical properties of the gap damper are designed to provide a target energy dissipation such that the displacement demand of low-friction CSSs can be kept to the same level as that of high-friction CSSs. A parametric study comprising a series of nonlinear response history analyses and different CSS characteristics demonstrates that the supplemental dissipative mechanism of the gap damper does not impair the re-centering capability of the CSS isolators. These outcomes are additionally validated by comparing numerical simulations of a 3D base-isolated case-study frame with shake-table test results. The proposed base-isolation system efficiently combines satisfactory energy dissipation, which reduces the displacement demand, with high re-centering capability resulting in negligible residual displacements.

Damage index of reinforced concrete members based on the energy dissipation capability degradation

SummaryBased on the estimation method of the energy dissipation capacity of reinforced concrete members under variable amplitude displacement cycles, the damage quantitative index of reinforced concrete members based on the energy dissipation capacity degradation is proposed. This index can establish a quantitative relationship with the energy dissipation capacity requirements and material parameters (yield force, yield displacement, and stirrup ratio). To understand the performance classification criteria of reinforced concrete members under variable amplitude displacement cycles based on the damage quantitative index, nine reinforced concrete members with different reinforcement conditions were tested. It was found that the reinforced concrete members can be classified as undergoing no damage (0 < Dk ≤ 0.3), mild damage (0.3 < Dk ≤ 0.6), moderate damage (0.6 < Dk ≤ 0.7), severe damage (0.7 < Dk ≤ 0.8), and destruction (0.8 < Dk ≤ 1), where the five performance states are based on the damage quantitative index. The performance classification criteria were verified by 18 flexural failure specimens in the Pacific Earthquake Engineering Research Center database.

Experimental evaluation of seismic performance of unbonded prestressed reinforced concrete column

Unbonded prestressed reinforced concrete column (UBPRC column) has become an attractive approach in the field of bridge seismic design due to its superior self-centering behavior. Unbonded prestressing bar in a UBPRC column functions as a self-centering element and longitudinal mild reinforcement functions as an energy dissipator. Quasi-static cyclic test was carried out in this study to compare the seismic performance of reinforced concrete column (RC column), UBPRC column and fully prestressed concrete column (FPC column). The result shows that the UBPRC column has higher post-yield stiffness and smaller quasi-static residual displacement, but lower energy dissipation capability than the RC column. The FPC column suffers from the least quasi-static residual displacement, but has the lowest energy dissipation capability, the least ultimate displacement and the most severe prestress loss. The quasi-static residual displacement and residual crack width of the UBPRC column are around 66% and 73% of those of the RC column, respectively. The failure patterns of the RC column and the UBPRC column are similar, while the failure pattern of the FPC column is similar to that of a rocking column. The self-centering behavior of the three columns was analyzed and quantified using a self-centering index, which can be recommended for use in the seismic design of bridge columns.

Failure mechanism of silica coated polypropylene fibres for Fibre Reinforced Concrete (FRC)

This work investigates the effect of a fast, acid-catalysed sol-gel silica nano-coating on the mechanical performance of draw-wire Polypropylene (PP) fibres used as dispersed reinforcement in Fibre Reinforced Concrete (FRC). The failure mechanism is investigated. To this aim, the role of curing time is also considered. Mechanical performance is assessed in pull-out and three-point bending tests of un-notched beams. Coating deeply affects the post-cracking behaviour of FRC, which shifts from brittle (plain concrete), to softening (uncoated) and finally to plastic-softening (coated fibres). Remarkably, 28-day curing improves over 8-day curing in terms of energy dissipation capability for coated fibres only. This suggests that fibre-to-matrix bond enhancement moves the failure mechanism from delamination at the interface to failure in the interphase zone. In the former case, failure is inconsistent and occurs independently from the curing time while in the latter failure depends on the matrix quality.

Experimental study on seismic behaviour of adobe wall reinforced with cold–formed thin–walled steel

Abstract Currently, adobe is one of the building material commonly used in towns and villages. However, the damage of the adobe houses during earthquakes is severe. To reduce the severe damage, this study aimed to improve the seismic behaviour of the rural adobe houses. A series of tests were conducted on the seismic behaviour of the adobe walls. The material property tests were performed on raw materials and the particle size distribution, liquid–plastic limit, optimum moisture content and maximum dry density of soil were analyzed. The mechanical behaviour of the adobe and mud bricks was characterized by conducting the axial compression test. The stress–strain curves of the bricks were analyzed. The elastic modulus was obtained and the relationship between the modulus of elasticity and compressive strength of adobe bricks and mud bricks was established. The quasi–static loading tests were performed on an unreinforced adobe wall and an adobe wall reinforced with 1 mm thick cold–formed thin–wall steel. A comparative analysis of the failure mode, hysteretic performance, stiffness, ductility and energy dissipation capability was performed. Besides, strains at key locations of the reinforced adobe wall were studied. It indicated that the seismic behaviour of the reinforced wall was much better than that of the unreinforced wall. The cracking load, ultimate load, ductility coefficient and energy consumption were increased by 43.34%, 79.10%, 440% and 560%, respectively. The results indicated that the application of cold–formed thin–walled steel enhanced the seismic performance of the adobe wall significantly.

Nature-Inspired Nacre-Like Composites Combining Human Tooth-Matching Elasticity and Hardness with Exceptional Damage Tolerance.

Making replacements for the human body similar to natural tissue offers significant advantages but remains a key challenge. This is pertinent for synthetic dental materials, which rarely reproduce the actual properties of human teeth and generally demonstrate relatively poor damage tolerance. Here new bioinspired ceramic-polymer composites with nacre-mimetic lamellar and brick-and-mortar architectures are reported, which resemble, respectively, human dentin and enamel in hardness, stiffness, and strength and exhibit exceptional fracture toughness. These composites are additionally distinguished by outstanding machinability, energy-dissipating capability under cyclic loading, and diminished abrasion to antagonist teeth. The underlying design principles and toughening mechanisms of these materials are elucidated in terms of their distinct architectures. It is demonstrated that these composites are promising candidates for dental applications, such as new-generation tooth replacements. Finally, it is believed that this notion of bioinspired design of new materials with unprecedented biologically comparable properties can be extended to a wide range of material systems for improved mechanical performance.

Cyclic behavior of moment-resisting frames strengthened with steel curved dampers

Steel moment frames have been widely used for earthquake-resistant purposes. These systems possess significant ductility, however, excessive deformation due to the lower structural stiffness. In order to improve the behavior of moment-resisting frames when subjected to cyclic loads, a new design that combined steel curved damper and brace member was proposed in this study. The curved damper was cut from steel plate and was placed in the center portion of the brace member. The new device was attached to the frame and was used to dissipate energy throughout the load application. A series of loading tests on steel frames strengthened with the proposed design were carried out. The strength and energy dissipation capabilities of frames with and without the strengthening device were compared. It was found from the comparisons that the behavior of framed structures was significantly improved, thus justified the effectiveness of the proposed design.

Investigation of the flexural and thermomechanical properties of nanoclay/graphene reinforced carbon fiber epoxy composites

Abstract

Ultra-thin-ply CFRP Bouligand bio-inspired structures with enhanced load-bearing capacity, delayed catastrophic failure and high energy dissipation capability

In this work, we demonstrate for the first time that the inherent low performance to out-of-plane loading of thin-ply Carbon Fibre Reinforced Plastics (CFRPs) can be overcome with tailored bio-inspired Bouligand microstructures. To this end, we designed, manufactured ultra-thin-ply CFRP Bouligand laminates and conducted an original study which combines full-penetration quasi-static indentation tests, in situ three-point bending tests conducted under a SEM and detailed analytical modelling. We investigated a wide range of mismatch (pitch) angles [2.5°, 5°, 10°, 20°, 45°], showing that decreasing pitch angles simultaneously achieved a larger (i) load-bearing capability, (ii) delay in catastrophic failure and (iii) total dissipated energy. We then investigated the role of the pitch angle on the activation of the highly dissipative sub-critical failure mechanisms responsible for the high mechanical performances achieved by small pitch angles laminates. Our investigation clearly shows that, with ultra-thin-ply CFRP, smaller pitch angles achieve higher damage tolerance and structural integrity.

Characterizations of flow over stepped spillways with steps having transverse slopes

The top and downstream face of the embankment dams must be protected from overtopping damages happen due to extreme floods. This can be achieved by providing one of the overtopping protection systems. The most common overtopping protection systems are those which have stepped fashion. This type of protection systems consists of a series of continues steps mostly made of concrete. In this study, the effects of the transverse slope of steps on flow properties over the overtopping protection systems were explored experimentally. Steps with transverse slopes are those which have inclinations from one spillway wall towards the other spillway wall in a zigzag way. To achieve the goals of the study, three physical models, stepped spillways, were made of wood and tested in a prismatic flume. The width, depth, and length of the wooden models were 0.6 m, 0.96 m and 1.92 m respectively. Sixteen steps (with three different transverse slopes ranging from zero to 5.7°) were cut into the surface of the models from the crest to the toe. The models were then tested under various flow rates ranging from 0.003 to 0.05 m3/s. The results showed that the models with steps having transverse slope had higher energy dissipation capability compared to the model with steps having zero transverse slopes (flat steps); up to 14% higher. In addition, for the models with steps having the transverse slope, the onset of the skimming flow occurred at higher ratios of critical depth (yc) to step height (h); greater than 1.37. However, the distances of the inception points from the first step brink (inception point locations) were reduced by half, on average, for the model with steps having a transverse slope of 5.7°.

Decorin Regulates the Aggrecan Network Integrity and Biomechanical Functions of Cartilage Extracellular Matrix.

Joint biomechanical functions rely on the integrity of cartilage extracellular matrix. Understanding the molecular activities that govern cartilage matrix assembly is critical for developing effective cartilage regeneration strategies. This study elucidated the role of decorin, a small leucine-rich proteoglycan, in the structure and biomechanical functions of cartilage. In decorin-null cartilage, we discovered a substantial reduction of aggrecan content, the major proteoglycan of cartilage matrix, and mild changes in collagen fibril nanostructure. This loss of aggrecan resulted in significantly impaired biomechanical properties of cartilage, including decreased modulus, elevated hydraulic permeability, and reduced energy dissipation capabilities. At the cellular level, we found that decorin functions to increase the retention of aggrecan in the neo-matrix of chondrocytes, rather than to directly influence the biosynthesis of aggrecan. At the molecular level, we demonstrated that decorin significantly increases the adhesion between aggrecan and aggrecan molecules and between aggrecan molecules and collagen II fibrils. We hypothesize that decorin plays a crucial structural role in mediating the matrix integrity and biomechanical functions of cartilage by providing physical linkages to increase the adhesion and assembly of aggrecan molecules at the nanoscale.

Theoretical study of tensegrity systems with tunable energy dissipation

This letter centers on the study of novel structures with tunable energy dissipation based on the tensegrity system known as the D-bar. Through an analytical approach, it is found that the geometry and topology of D-bar systems can be designed to tune the ratio of the stress experienced by the overall D-bar systems to that of their internal members. Pseudoelastic shape memory alloy (SMA) wires are then incorporated as the tensile members of the D-bars to introduce energy dissipation capabilities, and the formulas to determine the energy dissipation of these SMA-based D-bars are provided. The global–local stress formulas are used to design the properties of the D-bars such that a target maximum stress which the SMA wires experience in a loading/unloading cycle is obtained. Our results show that this target maximum stress can be tuned such that it is large enough to allow the SMA wires to undergo full pseudoelastic phase transformations and thus provide maximum energy dissipation, while being below their failure stress value.

Experimental Test of Novel Honeycomb Structural Fuse

ABSTRACTThis paper proposes a novel type of metallic damper, named Honeycomb Structural Fuse (HSF), a modified version of the previously developed Welded Wide Flange Fuse (WWFF). Based on the commonly available welded wide flange section, honeycomb‐shape perforations were laser cut on web. The HSF is designed to dissipate earthquake energy through plastic deformation of the web in shear, while the flanges remain elastic. To investigate the seismic behaviour of HSF, a total of 9 specimens with different honeycomb cell wall aspect ratios (cell wall thickness to cell wall centre length) and honeycomb cell combinations (number of cell rows and columns) were manufactured and tested to examine the influence of different parameters on its performance including force‐drift relationship, working mechanism and buckling modes etc., are summarized. The experiment shows that the newly proposed HSF exhibits stable energy dissipation capability, which can be used as an efficient metallic damper for seismic applications.

Experimental study of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joint

The functional structure of earthquake-resilient has become a frontier issue in the field of structural seismic performance. For researching the performance of seismic and post-earthquake resilience of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joint (PSCWJ) previously proposed by the author, the low frequency cyclic loading test and the finite element (FE) numerical verification have been carried out on eight specimens in this paper. The hysteretic curve, skeleton curve, strain variation curve, ductility, energy dissipation and other seismic performance indexes of this joint have been obtained. The impact of weakend form, thickness and strength of the flange cover plate (FCP), and the gap between beams on the joint seismic performance as well as the post-earthquake repair performance have been investigated. The results indicate that: the reasonably designed joint does well in bearing capacity, ductility and energy dissipation capability; the quick repair of joint can be realized by installing a new connection device, and the repaired joint can still meet the seismic performance requirements; the FCP weakened by a straight dog-bone profile is better for the joint plastic development and the relocation of plastic hinge at the beam end; the gap properly set between beams can effectively promote the rotation capability of the joint; the yield load of joint is directly decided by the thickness and the strength of the FCP.