Force Capacity Research Articles

Physics-based probabilistic capacity models and fragility estimates for light wood frame shear walls

Light wood frame buildings are common in the United States, and due to their prevalence, there has been significant damage to this type of building in previous earthquakes. For this building type, shear walls (typically sheathed with oriented strand board) are the main lateral force-resisting element. Probabilistic models and fragility estimates incorporating the prevailing uncertainties for shear walls are needed to make accurate predictions of the effects of future earthquakes on buildings of this type. This paper uses experimental data to develop probabilistic capacity models for the shear force and drift of light wood frame shear walls at the yield, peak, and ultimate performance levels. The proposed models are applicable to shear walls in low-rise buildings where the shear deformation is dominant. Moreover, the proposed models are applicable to walls that are similar to walls in the dataset. The probabilistic models are constructed starting from deterministic models. For the shear force, a new deterministic model is proposed. This model predicts the shear force capacity of the wall based on the capacity of individual nails. For drift, existing deterministic drift limits are used. The deterministic models are then improved by incorporating the effect of additional physical characteristics through explanatory basis functions that are shown to be significant in a probabilistic model selection procedure. Finally, fragility estimates are constructed for an example shear wall using the proposed capacity models and conditioning on the shear force and drift demands.

Development of P-M interaction chart for rectangular shear walls as per fundamental principles

Shear walls can act as excellent lateral load resisting system in multi-storeyed buildings, because of their high in-plane stiffness and strength. As per IS 13920:2016 reinforced concrete walls which carry lateral forces are termed as special shear wall and should be design accordingly. IS 13920:2016 proposes two closed form equations to calculate moment capacity of slender rectangular RC shear walls, which do not satisfy all the requirements IS456:2000. Equations provided in IS 13920:2016 are based on bilinear stress strain relation of HYSD steel bars. Vertical reinforcements which are distributed along the entire cross section of the wall are considered equivalent to a steel plate having the length of the wall and whose thickness is to be calculated so that the area of the plate is equal to the total area of the vertical reinforcement. Hence, stress blocks of steel along with stress block of concrete have been used to calculate force and moment capacities of the section. Shear wall sections are simultaneously subject to flexure along with axial forces and need to be design by using interaction charts. unfortunately, in our standard some shortcut design methodology has been provided in lieu of interaction charts, and these equations suffer from a number of limitations. In the present paper, a humble effort has been made to propose interaction charts to design using limit state philosophy as per IS 456–2000.

Shear Behavior of Low-Aspect-Ratio Precast Bridge Columns with Grouted Sleeve Connection Considering the Effect of Axial Load Ratios

To promote accelerated bridge construction (ABC), precast bridge columns are now being more widely used in engineering applications. Researchers have often studied the seismic performance of precast bridge columns, but the study of shear performance is quite limited. The main purpose of this study is to investigate shear behavior of low-aspect-ratio precast columns with grouted sleeve connections considering the effect of axial load ratios. Cyclic quasistatic tests of four 1/4-scaled reinforced concrete precast column specimens were conducted to investigate their seismic performance. The experimental results showed that large axial load reduced ductility factor of columns, but increased lateral force capacity. A predicting method for lateral force capacity of precast bridge columns based on a strut-and-tie model in the sleeve region was developed. The method can realistically predict the lateral force capacity and take into the influence of axial load on lateral force capacity of precast columns with grouted sleeve connection.

Synthesis of Cyclodextrin-based MOFs incorporating amino acid chiral ligands for chiral separation of naproxen enantiomers

The design of adsorbent materials capable of efficiently separating chiral molecules were a promising way to achieve selective recognition and separation of racemic enantiomers. Here, a γ-Cyclodextrin (γ-CD) based metal–organic framework (MOF) with D-Histidine (D-His) as a chiral ligand was synthesized for the first time to construct a functional chiral adsorption separation material (D-His@γ-CD-MOF), which can be used as an adsorbent for Naproxen enantiomer (S-/R-Npx). D-His@γ-CD-MOF provided a large number of chiral recognition sites for the selective enrichment of S-Npx based on the realization of the spatial advantage of the MOF structure, and the e.e. % value of a single separation of Npx racemates could reach 20.0 %. Meanwhile, the intermolecular binding patterns were predicted by computer simulations, and the chiral adsorption was attributed to the difference in affinity due to the difference in π-lone pair miscellaneous and hydrogen bonding force capacities of D-His@γ-CD-MOF and S-/R-Npx. Therefore, considering the stereospecific structure of D-His@γ-CD-MOF as well as the lone pair electron and hydrogen bonding coordination ability, it has great prospects for application as a chiral resolution agent.

Shear Force Capacities of H-Type Furniture Joints Constructed of Various Heat-Treated Wood Species

The aim of this study was to investigate the effect of wood species, heat treatment, adhesive type and joint technique on shear force capacity of H-type furniture joints. For this purpose, an experimental design that consisted of 3 wood species, 2 treatment processes (untreated, heat-treated), 2 adhesive types (polyurethane (PUR), polyvinyl acetate (PVAc)) and 2 joint techniques (dowel, mortise-tenon (MT)) and 5 replications for each group were prepared, and accordingly, a total of 120 specimens were tested under static shear loads. Siberian pine (Pinus sibirica), Iroko (Chlorophora excelsa), and common ash (Fraxinus excelsior), which are commonly used in furniture constructions, were used as wood species. In general, iroko showed the highest shear force capacity between the wood species. The specimens constructed of heat-treated wood species showed lower shear force capacity by approximately 15 % in comparison to the same untreated specimens. MT joints showed better performance than dowel joints higher by approximately 21 %. PVAc adhesive gave higher values than PU adhesive by around 5 %. According to the results of four-way interactions, highest shear force capacities of H-type joints were obtained from “Common ash-PVAc-MT” combination in groups of untreated specimens and from “Iroko-PU-MT” combination in groups of heat-treated specimens.

Determinants of FDI inflows: Aggregate versus country-specific evidence from ASEAN-6

This paper seeks to explore the determinants of foreign direct investment (FDI) inflows into six countries of the Association of Southeast Asian Nations (ASEAN), namely Indonesia, Malaysia, the Philippines, Singapore, Thailand and Vietnam, from 1995 to 2019. Estimations for the aggregate model are conducted with the Driscoll–Kraay standard errors panel regression approach, while the country-specific analyses are based on the fully modified ordinary least squares (FMOLS) approach. At the aggregate level, gross domestic product (GDP) growth, trade openness, unemployment, working-age population and interest rate spread are the main drivers of FDI inflows into the ASEAN-6, while per capita GDP, real interest rate and the global financial crisis have no significant impact. The empirical analysis for the specific-country cases yields mixed results, implying that international corporations may have various criteria to evaluate before making investment decisions depending on the development stage of the host country. Our research findings offer several implications for policymakers to attract quality FDI: (i) fostering trade and investment liberalization through taking down trade barriers and tariffs across nations; (ii) enhancing the quality and capacity of the labor force through management policy renovations; (iii) stabilizing interest rates through monetary policy management to ensure macroeconomic stability.

Experimental and Analytical Investigation of Flexural Behavior of Carbon Nanotube Reinforced Textile Based Composites

In this study, the main goal of this study was to understand the effect of carbon nanotube (CNT) additives on the elastic behaviors of textile-based composites. The materials have three phases: carbon fiber fabric, epoxy matrix, and carbon nanotubes. Different weight fractions of CNTs were used (0% as a reference, 0.3%). Mechanical tests were performed, such as tension and three-point bending beam tests. In addition, the composite material damages were examined in detail. The experimental results show that the samples with CNT carried 9% and 23% more axial tensile force and bending capacity on average than those with NEAT. Besides, it was understood that adding 0.3% by weight of MWCNT increases the tensile modulus by approximately 9%. Finally, the mechanical tensile and bending tests are supported by analytical solutions successfully applied in the literature.

Site-Specific Seismic Analysis of Buildings Supported by Lightly Reinforced Precast Concrete Walls

This paper aims to show the application of site-specific response spectra in the analysis of buildings that are supported by lightly reinforced precast concrete walls. Previous surveys on load-bearing precast reinforced concrete walls in multi-storey buildings in low-to-moderate seismic regions have found that many existing precast walls are lightly reinforced with a connection reinforcement ratio less than the wall reinforcement ratio. When these precast walls are subjected to reversed cyclic loads, the lateral response is typically controlled by rocking and the ultimate performance is governed by the ruptures of connection dowels. This paper uses moment–curvature analyses in combination with plastic hinge analyses to evaluate the force–displacement capacity of planar lightly reinforced load-bearing precast walls. The seismic performance of a building supported by these lightly reinforced precast walls can then be assessed by superimposing the capacity curve and the inelastic site-specific response spectra developed for the building site. The proposed analytical approach is illustrated through a case study building. By comparing a lightly reinforced precast wall with a comparable limited ductile reinforced concrete wall, it is also found that, although these two walls exhibit similar force capacities, the ultimate displacement capacity of the lightly reinforced precast wall is significantly lower. This finding highlights the potential seismic vulnerability of lightly reinforced precast walls in some existing buildings.

Effect of synthetic zeolite on tobermorite synthesis

Chemical anchors are widely used in additional installations of construction irons, repair and reinforcement work. Due to the increasing diversity of materials and the improved awareness of waste products, it has become possible to produce different kinds of concrete, with various properties. In this study, class B420C ribbed bars with 16 mm diameter, were installed in four different concretes by using four different chemical adhesives, and a tensile force was applied. The stiffness, displacement ductility ratio, energy-dissipation capability and tensile force values were determined and the failure modes were interpreted from the load-displacement curves, obtained as a result of the experiments. It was found that the tensile force and energy-dissipation capacity, had increased as a result of installing anchor and applying a tensile force to the concrete, that was obtained by adding admixture materials, to the reference concrete. In the analytical part of the study, the formulation provided in ACI 318 was used, capacity and design strengths were identified, and their safety levels were determined in comparison with the test results.

Effect of out-of-plane displacements on the in-plane capacity of lightly precompressed rocking unreinforced masonry piers

Unreinforced masonry (URM) buildings subject to bidirectional seismic excitation are under the effects of simultaneous in-plane and out-of-plane actions. Seismic assessment carried out without considering the combined effects due to these actions could result in non-conservative capacity estimates and inadequate strengthening requirements. Bidirectional effects are not explicitly considered in the seismic assessment of existing URM buildings, owing to the limitations in existing protocols and analytical models and the simplicity achieved in performing the assessment. The current work attempts to quantify the effect of out-of-plane displacements on the in-plane capacity of masonry walls undergoing a flexural rocking mechanism of failure, thereby improving the existing understanding of bidirectional interaction in masonry structures. Response of lightly precompressed masonry piers with different aspect ratios in the presence of out-of-plane displacements, were studied experimentally and replicated using numerical and analytical studies. Results indicate that the interaction problem in URM structures should not be considered only from a force capacity reduction perspective. The force capacity reduction predicted using the interaction equations employing an exceedance of net tensile stress-based approach shall be applicable only for the flexural cracking strength and not the ultimate flexural capacity. The in-plane flexural cracking capacity reduces in proportion to the applied out-of-plane displacements when the applied out-of-plane displacements are in the elastic range. In the inelastic range of out-of-plane displacements, the ultimate flexural capacity corresponding to toe-crushing and also the initial stiffness of the pier was observed to decrease due to the reduction in net area available for compression. Also, even small range of out-of-displacements could result in inelasticity in a URM pier leading to a reduced toe-crushing capacity. Hence, it may not be conservative to define the in-plane restoring shear as the failure capacity for rocking URM piers under bidirectional loading. Accordingly, modifications are proposed for the response of masonry walls undergoing rocking mechanism.

A comparative study of the novel externally-attached precast SRC braced-frames for seismic retrofitting under near-field spectrum-compatible non-stationary stochastic earthquake

Seismic retrofitting is a hot issue in the field of earthquake engineering, and the externally-attached substructure approach is a well-known solution due to its no-disturbing construction and high-efficiency improvement. In this paper, a comparative study of a novel externally-attached precast steel-reinforced-concrete (SRC) braced-frames for seismic retrofitting is performed, and the near-field spectrum-compatible non-stationary stochastic earthquakes are generated as the excitation to reflect the input uncertainty. The construction and simulation approaches of the novel substructure are first introduced, and then the generation theories of near-field spectrum-compatible non-stationary stochastic earthquake are explained. The comparative study of five scenarios is conducted, via a 3-span-5-story existing reinforced concrete frame, and a series of performance indices are adopted for analysis, including the inter-story deformation, inter-story shear force, section-mechanical performance, and energy-consumption capacity. In general, the comparison study verifies the effectiveness of the novel externally-attached SRC braced-frames for retrofitting, and the external frame obviously reduces the axial force of the existing beams and columns, which indicates that the shear demand is transferred to the external substructures and the damage accumulation is well controlled after retrofitting. Although the inter-story performance and energy-dissipation capacity of the external substructures are not as direct as the bare brace scenarios, the external frames alleviate the potential premature damage of the existing joints and avoid the infills or facades of the existing building to place external braces, which provides a practical reference for the engineering application and future research.

Convergent Validity between Electromyographic Muscle Activity, Ultrasound Muscle Thickness and Dynamometric Force Measurement for Assessing Muscle.

Muscle fatigue is defined as a reversible decline in performance after intensive use, which largely recovers after a resting period. Surface electromyography (EMG), ultrasound imaging (US) and dynamometry are used to assess muscle activity, muscle morphology and isometric force capacity. This study aimed to assess the convergent validity between these three methods for assessing muscle fatigue during a manual prehension maximal voluntary isometric contraction (MVIC). A diagnostic accuracy study was conducted, enrolling 50 healthy participants for the measurement of simultaneous changes in muscle thickness, muscle activity and isometric force using EMG, US and a hand dynamometer, respectively, during a 15 s MVIC. An adjustment line and its variance (R2) were calculated. Muscle activity and thickness were comparable between genders (p > 0.05). However, men exhibited lower force holding capacity (p < 0.05). No side-to-side or dominance differences were found for any variable. Significant correlations were found for the EMG slope with US (r = 0.359; p < 0.01) and dynamometry (r = 0.305; p < 0.01) slopes and between dynamometry and US slopes (r = 0.227; p < 0.05). The sample of this study was characterized by comparable muscle activity and muscle thickness change between genders. In addition, fatigue slopes were not associated with demography or anthropometry. Our findings showed fair convergent associations between these methods, providing synergistic muscle fatigue information.

Macroscale Superlubricity with Ultralow Wear and Ultrashort Running-In Period (∼1 s) through Phytic Acid-Based Complex Green Liquid Lubricants.

Liquid superlubricity has attracted much attention, due to its ability to significantly reduce friction on the macroscale. However, the severe wear caused by the long running-in period is still one of the bottlenecks restricting the practical application of liquid superlubricating materials. In this work, the obtained polyethylene glycol-phytic acid (PEG-PA) composite liquid lubricants showed outstanding superlubricating properties (μ ≈ 0.006) for Si3N4/glass friction pairs with an ultrashort running-in period (∼1 s) under high Hertzian contact pressure of ∼758 MPa. More importantly, even after up to 12 h (∼700 m of travel), only about 100 nm deep wear scars were found on the surface of the glass sheet (wear rate = 2.51× 10-9 mm3 N-1 m-1). From the molecular point of view, the water molecules anchored between the two friction pairs have extremely low shear force during the friction process, and the strong hydrogen bond interaction between PEG and PA greatly improves the bearing capacity of the lubricant. This work addresses the challenge of liquid superlubricant simultaneously exhibiting low shear force and high load-carrying capacity and makes it possible to obtain liquid superlubrication performance with an extremely short running-in time.

Breast muscle white striping and serum corticosterone reduced in broilers exposed to laser environmental enrichment

Genetic selection for breast yields and fewer days to market has inadvertent effects on broiler meat quality. Woody breast (WB) and white striping (WS) are pectoralis major myopathies prevalent in commercial broilers. Effects of voluntary exercise on these disorders, specifically, are unknown. A second-generation laser enrichment device shown to induce activity in Ross 308 and 708 birds was implemented using 1,360 Ross 708 broilers randomly assigned to laser enrichment or control for 49 d. Laser-enriched birds were exposed to 6-min laser periods 4 times daily. Seventy focal birds were gait and contact dermatitis scored weekly. Blood was collected wk 5 to 7 from 56 broilers for serum corticosterone, myoglobin, and troponin. Seventy broilers were sampled for breast muscle width, fillet dimensions, and WB and WS at wk 6 and 7. One and 2-day postmortem, fillet compression force and water-holding capacity were measured. Serum corticosterone was reduced by up to 21% in laser-enriched birds wk 5 to 7 (P < 0.01). Serum myoglobin was increased in laser-enriched broilers by 5% on wk 5 (P < 0.01) but increased in control birds wk 6 to 7 by up to 13% (P < 0.01). Serum troponin was reduced in laser-enriched broilers by 9% at wk 5 (P < 0.01). Laser exposure increased breast width and fillet weight at d 42 by 1.08 cm (P < 0.05) and 30 g (P < 0.05). At d 49, fillet height was increased 0.42 cm in laser-enriched birds (P < 0.05). Laser enrichment reduced severe WS incidence at d 42 by 24% (P < 0.05) and on d 49 by 15% (P < 0.10). Severe WB score was numerically reduced by 11% in laser enrichment on d 42 and 18% on d 49 (P > 0.05). Water-holding capacity was improved in laser-enriched breasts (P < 0.01) and expression of myostatin and insulin-like growth factor 2 were increased on d 49 (P ≤ 0.01. Laser enrichment reduced markers of stress and muscle damage while improving breast muscle quality and is therefore a potential effective enrichment for commercial broilers.

Effects of Dietary Supplementation of Chinese Yam Polysaccharide on Carcass Composition, Meat Quality, and Antioxidant Capacity in Broilers.

The study aimed to evaluate the influences of the dietary supplementation of Chinese yam polysaccharide (CYP) on the carcass performance, antioxidant capacity, and meat quality of broilers. Three hundred and sixty healthy 1-day-old broilers with similar body weight (39 ± 1 g, gender balanced) were randomly divided into four groups (control, CYP1, CYP2, and CYP3 groups). In the control group, broilers were fed a basal diet with CYP, and the CYP1, CYP2, and CYP3 groups were fed diets supplemented with 250, 500, and 1000 mg/kg CYP, respectively. There were three replicates in each group, 30 birds in each replicate, and the feeding trial lasted for 48 days. Statistical analysis was performed using SPSS 17.0 (SPSS Inc., Chicago, IL, USA) by one-way analysis of variance. The results showed that compared with the control group, dietary supplementation with 500 mg/kg CYP can improve live weight, half-eviscerated carcass percentage, eviscerated carcass percentage, and thigh muscle percentage. Moreover, dietary supplementation with 500 mg/kg CYP can improve the contents of total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD), glutathione peroxidase (GPX), and glutathione s-transferase (GST) in serum (p < 0.05). Meanwhile, the mRNA expression levels of nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), quinone oxidoreductase (NQO1), superoxide dismutase 1 (SOD1), glutathione peroxidase 1 (GPX1), and catalase (CAT) in the liver; the mRNA expression levels of HO-1, NQO1, GPX1, and CAT in the breast muscle; and the mRNA expression levels of NQO1, SOD1, and CAT in the thigh muscle of broilers in the CYP2 group were significantly increased (p < 0.05). In addition, the yellowness and shear force of the thigh and breast muscles and the content of malondialdehyde (MDA) in the serum of broilers in the control group were higher than that in the CYP2 groups (p < 0.05). The results demonstrated that the CYP2 group had the best effect on improving meat quality. In conclusion, dietary supplementation with 500 mg/kg CYP can improve the meat quality of broilers by improving carcass quality, meat color, shear force, and antioxidant capacity.

In-Plane Behaviour of Unreinforced Masonry Strengthened with a Structural Glass Window: A Proof of Concept

Innovative solutions for seismic-retrofitting existing structures are currently required, as often traditional strategies are expensive, non-reversible, highly invasive, and/or fail to address both serviceability and ultimate limit states together. The present paper describes a preliminary experimental campaign performed at TU Delft to investigate an innovative structural glass window for strengthening masonry buildings. To this purpose, a prototype composed of a timber frame, a semi-rigid adhesive, and a 20 mm thick structural glazing layer was designed. The prototype aimed to improve the structure’s behavior against minor but more frequent service vibrations (SLS), as well as against ultimate ones (ULS). Specifically, an increase in the structure’s in-plane capacity and stiffness was targeted to reduce cracking at low drifts/displacements, while at larger drifts, the adhesive’s tearing and timber crushing were used to activate damping. To evaluate the prototype’s performance, a quasi-static, cyclic, in-plane test on a strengthened full-scale wall was performed and compared with available data on a similar, yet unstrengthened, wall. Although the benefits were not pronounced in terms of cracking and energy dissipation, the implementation of the proposed strategy provided an increase in terms of initial stiffness (18%), force capacity (8%, 36%), and ductility (220%, 135%). This outcome provides the ground for numerical studies that will help better delineate the proposed strategy and improve the current design.

Peran Training Dan Coaching Dalam Pengembangan Kinerja Karyawan Perusahaan Padat Karya

This review plans to test: (1) know the expected set of responsibilities of Work Preparing (Training) and representative execution at PT. Surya Satria Timur Banjarmasin, (2) realizing that Occupation Preparing (Training) affects representative execution at PT. Surya Satria Timur Banjarmasin. The plan of this study is a quantitative report and is an overview study, where information is gotten from a poll. The review test is 43 representatives of PT. Surya Satria Timur Banjarmasin with basic straight regresie information examination. The consequences of the review show that: 1) There is a halfway impact of Occupation Preparing (Training) on representative execution at PT. Surya Satria Timur Banjarmasin (0.000 &lt; 0.05). 2) There is a semi-persuasive impact on worker execution at PT. Surya Satria Timur Banjarmasin Area, Tanah Bumbu Rule (0.000 &lt; 0.05). 3) There is a concurrent impact of Occupation Preparing (Training) and work inspiration on representative execution at PT. Surya Satria Timur Banjarmasin (0.000 &lt; 0.05). An idea that can be recommended is the need to normalize and facilitate the time of Occupation Preparing (Training) to the capacity of the labor force to get Work Preparing (Training) materials, ideally great representatives are given Work Preparing (Training) and inspiration through advancements and motivators so they can work on their inspiration and execution.

A novel method and validation for obtaining the optimal interference fit of round-end mortise-and-tenon joint

ABSTRACT To determine the optimal interference fit of mortise-and-tenon (M&T) a novel method is proposed. To validate its effectiveness, compression tests were conducted considering the effects of wood species (beech and western hemlock), tenon widths (30, 40, 50 mm), and grain orientations (radial, diagonal, and tangential) to obtain the optimal interference fit and contact force (CF). Furthermore, the mounting force (MF) and withdrawal force capacity (WFC) of T-shaped M&T joints constructed by the control and optimal interference fit were evaluated by compression and withdrawal tests, respectively. The results indicated that (1) all three evaluated factors had significant effects on the tenon compression behavior and CF; (2) the derived optimal fits showed that the tenon with a larger width required a higher fit value based on regression equations; (3) the MF and WFC were significantly affected by the three evaluated factors and proportional to the tenon fit; (4) the maximum WFC occurred at the M&T joints made of western hemlock with 50-mm tenon width in tangential orientation with 0.99-mm interference fit, and the beech with 30-mm tenon width in diagonal orientation with 0.78-mm interference fit. The proposed method will assist the wood product manufacturers to design M&T joints rationally.

Experimental investigation on the dynamic behavior of grouted splice sleeve connector under fast tensile loading

This paper presents an experimental program designed to investigate strain rate effects on the bond behavior of grouted splice sleeves connected with deformed steel bars. Thirty-six grouted splice sleeve specimens with different anchorage lengths were designed and tested under direct dynamic tensile loads with four loading strain rates (10−3, 10−1, 10° and 10+1 s−1). Strain gauges were employed to record the strain of the sleeve and rebar. The failure modes and the dynamic bond-slip relationships of specimens were obtained. The results show that the bond force capacity increases with an increase in the strain rate. However, the failure mode shifts from the steel bar fracture towards steel bar pullout as the strain rate increases. The mechanisms of a dynamic load transmission are described based on the experimental results. A dynamic analytical procedure incorporating the strain rate effects was developed to predict the bond force-slip relationships and was validated by comparing the experimental bond force-slip curves. The shifting of failure modes was attributed to the damage aggravation effects of the grouted mortar, which led to a reduced effective anchorage length and a steel bar pullout failure mode at high strain rates. In addition, based on the proposed analytical model, the required anchorage length of grouted splice sleeves at different strain rates was calculated and an empirical model was developed to determine the critical embedment length to facilitate engineering design.

Design, manufacturing, and testing of a hybrid self‐centering brace for seismic resilience of buildings

AbstractThis study explores the development of a shape memory alloy (SMA)‐based hybrid self‐centering brace that combines NiTi superelastic cables with viscoelastic dampers. First, the behavior of individual components of the hybrid self‐centering brace, that is, SMA cables and viscoelastic damper is characterized under various experimental conditions. Then, three prototype hybrid self‐centering braces with a maximum force capacity of 172 kN are designed and fabricated. The experimental tests are conducted to reveal the response of the hybrid self‐centering braces under increasing loading displacement amplitude. The effect of loading rate and training loading cycles on the mechanical response of the braces are also analyzed. Furthermore, the low‐cycle fatigue behavior of the hybrid self‐centering braces is evaluated by testing two of the braces for up to 30 loading cycles at a relatively large displacement amplitude. For each experimental condition, the variation of certain mechanical properties such as equivalent stiffness and equivalent viscous damping are evaluated and analyzed. Three case‐study frames with various bracing systems (i.e., SMA brace, viscoelastic brace, and hybrid self‐centering brace) are designed and modeled in OpenSees. Nonlinear dynamic analyses are carried out under 44 far‐field ground motion records to illustrate the advantages of hybrid self‐centering brace on structural seismic performance. The results indicate that the developed SMA‐based hybrid self‐centering braces provide an average of 9% equivalent viscous damping at different loading amplitudes with a complete self‐centering characteristic. The response of the bracing system is not affected considerably by loading rate, but it is found to be sensitive to cyclic loading. The steel frame with hybrid self‐centering braces is capable of leveraging the benefits of self‐centering ability and energy dissipation capacity.