Papers by Keyword: Energy Dissipation

Abstract: The previous research on beam and column connections made of laminated bamboo with steel brackets has been tested under static loads. Furthermore, these connections need to be studied for their performance in terms of energy dissipation. The test specimens will be subjected to two-way lateral (cyclic) loading treatment. The testing and analysis standards used include ASTM E2126-11, AISC 360-16, Eurocode 1993-1-8, and Eurocode 1998-1. The results showed that the configuration of the number of thread rods used and the size of the thread rod cross-sectional area affected the moment values achieved. In addition, the trends formed in the curves show that the first loading cycle has a greater bending moment capacity than the second loading cycle. The results show that loading history, bracket usage, configuration, and thread rod cross-sectional area affect the dissipation energy values; the highest dissipation energy value is 527.89kJ for 10.6 configuration specimen and the smallest dissipation energy value is 159.80 kJ for 6.4 configuration specimen. Additional results show that test specimens with six thread rod configurations are classified as medium energy dissipation class (DCM), and test specimens with four thread rod configurations are classified as low energy dissipation class (DCL). Test specimens with configurations 6.4, 8.4, 8.6, 10.4, and 10.6 showed service failure.

Abstract: This study evaluates hybrid fluid viscous damper (FVD) layouts for seismic control of a 20-storey reinforced-concrete tower. Two retrofit configurations (C1, C2), each employing 120 FVDs with a combined damping capacity of approximately 60,000 kN·s/m per configuration, were modelled in ETABS as nonlinear link elements and subjected to nonlinear time-history analyses using representative ground motions. Device constitutive behavior was represented by a velocity-dependent law and model verification included explicit link spring/area settings to prevent silent unit-scaling of damper properties. Both hybrid layouts substantially reduce peak inter-story drifts and increase system energy dissipation, though performance varies by direction: relative to the undamped frame, C1 reduced peak drift by ≈28.7% in X and ≈44.6% in Y, while C2 reduced peak drift by ≈26.2% in X and ≈53.9% in Y. Damper contribution to seismic energy dissipation reached ≈47.3% for C1 and ≈45.6% for C2, with total (structural plus device) dissipation of ≈52.4% and ≈55.6%, respectively. Directional asymmetry is attributed to modal shapes and damper distribution. The results indicate that carefully arranged hybrid FVD systems can deliver significant, orientation-aware improvements to seismic resilience.

Abstract: Beam-column joint is the most vulnerable location of a moment-resisting reinforced concrete frame structure. The joint region experiences the maximum shear stress both in vertically and horizontally which is generated due to the shear transfer mechanism from the adjoining beams and columns. The shear capacity and bond stress capacity are the two major factors affecting the strength of a joint core in RC structure. An important discovery recently is the ductile behaviour of the whole structure under repeated loading. The behaviour of the concrete beyond elastic limit which is in the concrete hardening zone can drastically influence the ductility of the concrete. The non-linear stress-strain behaviour after the onset of the initial crack and up to ultimate compressive strength plays an important role in improving ductility. Beyond the ultimate compressive strength, concrete will undergo softening which is neglected in this study as once concrete reaches ultimate stress it is unsafe for service. This material ductility can be fulfilled with the application of high-strength fibres with ductile behaviour. However, the hybridization of two or more fibres can incorporate two different characteristics of the fibre used. The use of ordinary-grade of concrete moreover reduces the shear-resisting capacity of the joint. A hybrid mix of hooked-end steel fibre with basalt fibre and crimpled steel fibre with polypropylene fibre are used with a volume fraction of 1% to 1.4% of the concrete. In this study, ordinary M25 grade concrete and fibre mixed M25 grade concrete is employed under static and cyclic loading. The laboratory tests are also conducted to evaluate the compressive strength, split-tensile strength, and flexural strength of the hybrid mix fibre-reinforced concrete at the age of 28^th days. Five full-scale models of the beam-column joint are designed as per the Bureau of Indian Standards. Numerical models of concrete and steel reinforcement are developed. Numerical analysis is carried out using finite element software ANSYS-v21. The behaviours of the beam-column joint are observed under static as well as cyclic loading. Crack patterns, first crack load, initial displacement, ultimate load, and ultimate displacement are observed under static conditions. And under cyclic loading, hysteresis load vs displacement, energy dissipation, and stiffness degradation are observed. The hybridization of hooked steel with basalt fibre gives better results in mechanical strengths and the hybrid effect of crimpled steel with polypropylene fibre gives better results in mechanical strengths. And also under numerical study, the above specimens show an improvement in energy dissipation capacity. Keywords beam-column joint, hybrid fibre reinforced concrete, numerical concrete model, ANSYS, static, reverse cyclic, energy dissipation, stiffness, crack

Abstract: The response of the bulkhead type of blast wall under deflagration blast pulse was studied using finite element modelling software. The behavior of unstiffened and stiffened panels was analyzed. The study aimed at determining the effect of plate and stiffener thicknesses on energy dissipation and distribution of reaction forces. This was carried out in order to optimize the response of the primary steelwork through typological and geometrical modifications of the local element. Furthermore, novel strategies for the improvement of the blast response were introduced with a focus to use alternative materials and innovative connections. The latter was assessed numerically using a simplified model and its benefits were analyzed by comparing with the traditional approach.

Abstract: This paper aims to explore the low velocity impact response of glass fiber composite/aluminum hybrid laminates (GLAREs). Puck’s criterion with an efficient algorithm and damage evolution laws based on equivalent strain are used for intralaminar damage models, and the interface delamination is simulated by the bilinear cohesive model in ABAQUS, besides, the Johnson-Cook model is applied to describe the mechanical properties of aluminum layers. Numerical analysis is performed on GLAREs with different impact energy based on simplified finite element model in order to study the damage evolution behaviors of composite layers and interface. In addition, the energy dissipation mechanisms due to damage of composite layers including fiber tension, fiber compression, matrix tension and matrix compression, interface delamination and plastic deformation of aluminum layers are also explored. Meanwhile, the simulation results with simplified model have a good agreement with the experimental results.

Abstract: Classical ring springs are mechanical elements used in industrial applications and in transport for shock absorption and energy dissipation. They are constituted by a stack of internal and external metal rings (typically high strength steel), with tapered surfaces in contact with one another. Under the action of an axial load these surfaces slide, the rings are deformed circumferentially and energy is dissipated due to friction. The main advantages of these springs are the high specific energy stored and the large damping capacity due to sliding friction. Furthermore, the stiffness and damping are independent on the strain rate and the temperature, which limits or avoids the occurrence of any resonance problems. The superelastic materials, characterized by an almost flat stress plateau and large reversible deformation, can be used to replace traditional steels in ring springs giving a significant performance increase. Compared to the traditional version where energy is dissipated only due to friction, in superelastic ring springs there is an increase of the dissipated energy thanks to the internal hysteresis of the material. This paper studies analytically the ring springs in traditional material and in superelastic material, providing equations to dimension these mechanical elements, which enable the designer to customize this useful structural element.

Abstract: When analyzing the seismic response of a very long elevated structure such as a Shinkansen viaduct, it is common practice to analyze a cutout of the structure under consideration and treat its both ends as free boundaries. This is attributable to the assumption that seismic response analysis assuming free boundary conditions is more conservative than one assuming non-free boundary conditions. In this study, after finding out that response to harmonic ground motion can be greater than under free-boundary conditions if outward energy dissipation occurs from the analysis domain, a series of numerical experiments was performed to determine whether such phenomena occur in seismic response. Then, after confirming that the frequency components of ground motion that satisfy the wave propagation condition greatly affect seismic response, the study showed that the area of the wave propagation condition region of the Fourier spectrum can be used as an indicator by which to judge the likelihood of occurrence of such phenomena.

Abstract: Higher seismic performance can be achieved by localizing the inelastic deformation in the connections (fuses) and minimizing the residual drift that are often a determining factor in whether a structure can be repaired or re-occupied after an earthquake. This paper introduces the self-centering damage avoidance steel Moment Resisting Frames (MRFs) using innovative Resilient Slip Friction Joints (RSFJs). The RSFJ provides self-centering and energy dissipation in one compact package requiring no post-event maintenance. In this concept, the beam is connected to the column through a pinned joint at the top, an RSFJ at the bottom and a slotted web plate for transferring the shear forces, when required. The RSFJ allows for gap opening in the connection upon loading and then re-centers the system when unloading. Furthermore, a secondary fuse within the RSFJ is considered to keep maintaining a ductile behavior in the system in case of an earthquake larger than the design earthquake. The conducted experimental tests confirmed the outcomes of this study.

Abstract: This paper describes quasi-static testing of Asymmetrical Friction Connection (AFC) and Symmetrical Friction Connections (SFC) in steel braces. It is shown that stable energy dissipation mechanisms have been achieved in braces using Bisalloy 500 shims on the sliding surface. When incorporated into a moment frame, the braces and the moment resisting frames underwent large displacements without significant frame yielding. The effective coefficient of friction is shown to be dependent on prying.

Abstract: Buckling-restrained braces (BRBs), which were first applied in 1989 in Japan, are now widely used worldwide as ductile seismic-proof members in seismic zones, such as those in Japan, USA, Taiwan, China, Turkey, and New Zealand. Although the design procedures of BRBs and their applications are described in the design codes and recommendations of several countries, they do not necessarily cover all the required aspects. Moreover, various new types of BRBs are still under investigation by many researchers. In this paper, the early history of BRB research and development and state-of-the-art views on the items required to design BRBs for obtaining stable hysteresis are briefly overviewed. This is followed by a summary of various representative application concepts and up-to-date investigations.