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Parametric study of hexagonal castellated beams in post-tensioned self-centering steel connections

Hassan ABEDI SARVESTANI

《结构与土木工程前沿（英文）》 2019年 第13卷 第5期   页码 1020-1035 doi: 10.1007/s11709-019-0534-6

摘要： The effects of important parameters (beam reinforcing plates, initial post-tensioning, and material properties of steel angles) on the behavior of hexagonal castellated beams in post-tensioned self-centering (PTSC) connections undergone cyclic loading up to 4% lateral drift have been investigated by finite element (FE) analysis using ABAQUS. The PTSC connection is comprised of bolted top and bottom angles as energy dissipaters and steel strands to provide self-centering capacity. The FE analysis has also been validated against the experimental test. The new formulations derived from analytical method has been proposed to predict bending moment of PTSC connections. The web-post buckling in hexagonal castellated beams has been identified as the dominant failure mode when excessive initial post-tensioning force is applied to reach greater bending moment resistance, so it is required to limit the highest initial post-tensioning force to prevent this failure. Furthermore, properties of steel material has been simulated using bilinear elastoplastic modeling with 1.5% strain-hardening which has perfectly matched with the real material of steel angles. It is recommended to avoid using steel angles with high yielding strength since they lead to the yielding of bolt shank. The necessity of reinforcing plates to prevent beam flange from local buckling has been reaffirmed.

关键词： finite element analysis     hexagonal castellated beam     parametric study     post-tensioned self-centering steel connection     steel moment-resisting frame    

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Secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams

Lizhao DAI; Wengang XU; Lei WANG; Shanchang YI; Wen CHEN

《结构与土木工程前沿（英文）》 2022年 第16卷 第3期   页码 388-400 doi: 10.1007/s11709-022-0809-1

摘要： An experimental study is performed on five post-tensioned concrete beams to explore the effects of different fracture positions on secondary transfer length and residual prestress of fractured strand. A numerical model is developed and used to predict the secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams. The model change interaction, which can deactivate and reactivate the elements for simulating the removal and reproduction of parts of the model, is used to reproduce the secondary anchorage of fractured strand. The numerical model is verified by experimental results. Results shows that the fractured strand can be re-anchored in concrete through the secondary anchorage, and the secondary transfer length of fractured strand with the diameter of 15.2 mm is 1133 mm. The residual prestress of fractured strand increases gradually in the secondary transfer length, and tends to be a constant beyond it. When the fractured strand is fully anchored in concrete, a minor prestress loss will appear, and the average prestress loss is 2.28% in the present study.

关键词： post-tensioned concrete beams     strand fracture     secondary transfer length     residual prestress    

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Seismic tests of post-tensioned self-centering building frames with column and slab restraints

Chung-Che CHOU, Jun-Hen CHEN

《结构与土木工程前沿（英文）》 2011年 第5卷 第3期   页码 323-334 doi: 10.1007/s11709-011-0119-5

摘要： Post-tensioned (PT) self-centering moment frames have been developed as an alternative to typical moment-resisting frames (MRFs) for earthquake resistance. When a PT frame deforms laterally, gaps between the beams and columns open. However, the gaps are constrained by the columns and the slab in a real PT self-centering building frame. This paper presents a methodology for evaluating the column restraint and beam compression force based on the column deformation and gap openings at all stories. The method is verified by cyclic tests of a full-scale, two-bay by one-story PT frame. Moreover, a sliding slab is proposed to minimize restraints on the expansion of the PT frame. Shaking table tests were conducted on a reduced-scale, two-by-two bay one-story specimen, which comprises one PT frame and two gravitational frames. The PT frame and gravitational frames are self-centering throughout the tests, responding in phase with only minor differences in peak drifts caused by expansion of the PT frame. When the specimen is excited by a simulation of the 1999 Chi-Chi earthquake with a peak ground acceleration of 1.87 g, the maximum interstory drift and the residual drift are 7.2% and 0.01%, respectively.

关键词： post-tensioned frame     frame expansion     column restraint     sliding slab     frame test     shake table test    

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Self-centering steel plate shear walls for improving seismic resilience

Patricia M. CLAYTON,Daniel M. DOWDEN,Chao-Hsien LI,Jeffrey W. BERMAN,Michel BRUNEAU,Laura N. LOWES,Keh-Chuan TSAI

《结构与土木工程前沿（英文）》 2016年 第10卷 第3期   页码 283-290 doi: 10.1007/s11709-016-0344-z

摘要： As part of a Network for Earthquake Engineering Simulation research project led by researchers at the University of Washington with collaborators at University at Buffalo, and Taiwan National Center for Research on Earthquake Engineering, a self-centering steel plate shear wall (SC-SPSW) system has been developed to achieve enhanced seismic performance objectives, including recentering. The SC-SPSW consists of thin steel infill panels, referred to as web plates that serve as the primary lateral load-resisting and energy dissipating element of the system. Post-tensioned (PT) beam-to-column connections provide system recentering capabilities. A performance-based design procedure has been developed for the SC-SPSW, and a series of nonlinear response history analyses have been conducted to verify intended seismic performance at multiple hazard levels. Quasi-static subassembly tests, quasi-static and shake table tests of scaled three-story specimens, and pseudo-dynamic tests of two full-scale two-story SC-SPSWs have been conducted. As a culmination of this multi-year, multi-institutional project, this paper will present an overview of the SC-SPSW numerical and experimental research programs. This paper will also discuss innovative PT connection and web plate designs that were investigated to improve constructability, resilience, and seismic performance and that can be applied to other self-centering and steel plate shear wall systems.

关键词： self-centering     steel plate shear walls     large-scale experiment     post-tensioned connections     performance-based design    

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Calculation method of load distribution on pipe threaded connections under tension load

Shoujun CHEN, Lianxin GAO, Qi AN

《机械工程前沿（英文）》 2011年 第6卷 第2期   页码 241-248 doi: 10.1007/s11465-011-0219-x

摘要：

This paper presents a new calculation method that can calculate the load distribution on pipe threaded connections under tension load. On the basis of elastic mechanics, the new method was developed by analyzing each thread tooth, and a new deformation and covariant equation by making a mechanics analysis on each thread tooth was obtained. Compared with the traditional method proposed by the previous references, the new deformation and covariant equation could be used to describe the relation between the previous and the next thread tooth. By applying the new method on the sample of P-110S pipe threaded connection, the obtained results show that the load on thread tooth mainly concentrates on the four or five threads engaged and the middle teeth were not utilized well to bear the loads. The model offers a new way to calculate the loads carried on the thread teeth under tension load.

关键词： load distribution     calculation method     pipe threaded connections     tension load    

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Damage identification in connections of moment frames using time domain responses and an optimization

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 851-866 doi: 10.1007/s11709-021-0739-3

摘要： Damage is defined as changes to the material and/or geometric properties of a structural system, comprising changes to the boundary conditions and system connectivity, adversely affecting the system’s performance. Inspecting the elements of structures, particularly critical components, is vital to evaluate the structural lifespan and safety. In this study, an optimization-based method for joint damage identification of moment frames using the time-domain responses is introduced. The beam-to-column connection in a metallic moment frame structure is modeled by a zero-length rotational spring at both ends of the beam element. For each connection, an end-fixity factor is specified, which changes between 0 and 1. Then, the problem of joint damage identification is converted to a standard optimization problem. An objective function is defined using the nodal point accelerations extracted from the damaged structure and an analytical model of the structure in which the nodal accelerations are obtained using the Newmark procedure. The optimization problem is solved by an improved differential evolution algorithm (IDEA) for identifying the location and severity of the damage. To assess the capability of the proposed method, two numerical examples via different damage scenarios are considered. Then, a comparison between the proposed method and the existing damage identification method is provided. The outcomes reveal the high efficiency of the proposed method for finding the severity and location of joint damage considering noise effects.

关键词： damage identification     beam-to-column connection     time-domain response     optimization    

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Calculation method of radial stress and deformation on conic threaded connections with interference fit

Shoujun CHEN, Qiang LI, Qi AN,

《机械工程前沿（英文）》 2010年 第5卷 第3期   页码 302-307 doi: 10.1007/s11465-010-0018-9

摘要： This paper presents a calculation method for radial stress distribution and deformation on conic threaded connections with interference fit. Based on elastic mechanics, a new calculation model is established using the thick-walled-cylindrical theory. A sample calculation for API 88.9 mm conic threaded connection indicates that the method proposed in this paper is reasonable, and the finite element analysis (FEA) method is used to validate the proposed method. The results obtained by the proposed method and FEA method are identical. The model offers a new way of calculating the radial stress and deformation on conic thread connections with interference fit.

关键词： conic threaded connections     interference fit     radial stress     deformation     finite element analysis (FEA)    

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Nonlinear analysis of pre-tensioned glass wall facade by stability function with initial imperfection

Siu-Lai CHAN, Yaopeng LIU, Andy LEE,

《结构与土木工程前沿（英文）》 2010年 第4卷 第3期   页码 376-382 doi: 10.1007/s11709-010-0086-2

摘要： Pre-tensioned high strength trusses using alloy steel bar are widely used as glass wall supporting systems because of the high degree of transparency. The breakage of glass panes in this type of system occurs occasionally, likely to be due to error in design and analysis in addition to other factors like glass impurity and stress concentration around opening in a spider system. Most design does not consider the flexibility of supports from finite stiffness of supporting steel or reinforced concrete beams. The resistance of lateral wind pressure of the system makes use of high tension force coupled with the large deflection effect, both of which are affected by many parameters not generally considered in conventional structures. In the design, one must therefore give a careful consideration on various effects, such as support settlement due to live loads and material creep, temperature change, pre-tension force, and wind pressure. It is not uncommon to see many similar glass wall systems fail in the wind load test chambers under a design wind speed. This paper presents a rigorous analysis and design of this type of structural systems used in a project in Hong Kong, China. The stability function with initial curvature is used in place of the cubic function, which is only accurate for linear analysis. The considerations and analysis techniques are believed to be of value to engineers involved in the design of the structural systems behaving nonlinearly.

关键词： tension system     glass wall     nonlinear analysis     pre-tensioning     second-order analysis    

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State-of-the-art on resistance of bearing-type bolted connections in high strength steel

Guoqiang LI, Yifan LYU, Yanbo WANG

《结构与土木工程前沿（英文）》 2020年 第14卷 第3期   页码 569-585 doi: 10.1007/s11709-020-0607-6

摘要： With the recent development of material science, high strength steel (HSS) has become a practical solution for landmark buildings and major projects. The current codes for design of bearing-type bolted connections of steel constructions were established based on the research of conventional steels. Since the mechanical properties of HSS are different from those of conventional steels, more works should be done to develop the appropriate approach for the design of bearing-type bolted connections in HSS. A review of the research carried out on bearing-type bolted connections fabricated from conventional steel and HSS is presented. The up-to-date tests conducted at Tongji University on four connection types fabricated from three grades of HSS with nominal yield strengths of 550, 690, and 890 MPa are presented. The previous research on failure modes, bearing resistance and the design with consideration of bolt hole elongation are summarized. It is found that the behavior of bolted connections in HSS have no drastic difference compared to that of conventional steel connections. Although the ductility is reduced, plastic deformation capacity of HSS is sufficient to ensure the load redistribution between different bolts with normal construction tolerances. It is also found that behavior of each bolt of multi-bolt connections arranged in perpendicular to load direction is almost identical to that of a single-bolt connection with the same end distance. For connections with bolts arranged in parallel to load direction, the deformation capacity of the whole connection depends on the minimum value between the end distance and the spacing distances in load direction. The comparison with existing design codes shows that Eurocode3 and Chinese GB50017-2017 are conservative for the design of bolted connections in HSS while AISC 360-16 may overestimate the bearing resistance of bolted connections.

关键词： High strength steel     bolted connection     bearing behavior     design codes    

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Seismic retrofitting of severely damaged RC connections made with recycled concrete using CFRP sheets

Yasmin MURAD, Wassel AL BODOUR, Ahmed ASHTEYAT

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 554-568 doi: 10.1007/s11709-020-0613-8

摘要： An experimental and numerical program is carried out in this research to investigate the influence of CFRP sheets on the cyclic behavior of unconfined connections made with recycled concrete. Cement is partially replaced by silica fume, iron filling and pulverised fuel ash using two different percentages: 15% and 20%. Each specimen is partially loaded at the first stage and then specimens are repaired using CFRP sheets. The repaired specimens are then laterally loaded until failure. In addition, a finite element model is built in ABAQUS and verified using the experimental results. The experimental results have shown that the repaired specimens have regained almost double the capacity of the un-repaired specimens and hence the adopted repair configuration is recommended for retrofitting seismically vulnerable RC connections. Increasing cement replacement percentage by silica fume, fuel ash or iron filling from 15% to 20% has reduced joint carrying capacity and weakened the joint. It is recommended using 15% pulverised fuel ash or silica fume as cement partial replacement to enhance the strength and ultimate drift of beam-column joints under cyclic loading. Iron filling concrete is also recommended but the enhancement is relatively less than that found with pulverised fuel ash concrete and silica fume concrete.

关键词： retrofitting     CFRP sheets     recycled concrete     pulverised fuel ash     silica fume     cyclic     beam-column connections    

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Fragility assessment of wood sheathing panels and roof-to-wall connections subjected to wind loading

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 867-876 doi: 10.1007/s11709-021-0745-5

摘要： The performance of the wood-frame buildings after tornadoes has shown that the majority of the wind damage resulted from building envelope failure most typically due to the loss of the roof. To assess the performance and the reliability of low-rise wood-frame residential buildings with a focus on the roofs, fragility analysis can be used to estimate the probability of failure of a roof when constructed with specified nails and sheathing sizes. Thus, this paper examines the fragility of specific types of nails, roof-to-wall (RW) connection details, and sheathing sizes based on the damaged roofs that were previously assessed in the Dunrobin area in Ottawa (Ontario) that was hit with an Enhanced Fujita (EF3) tornado on September 21, 2018. The presented fragility analysis considers four scenarios, including different sheathing and nail sizes. Dead loads, wind loads, and resistance on the sheathing panels were compiled and analyzed to determine the failure of the examined roofs. The eight fragility models suggest that the safest roof sheathing (RS) is the 1.22 m × 1.22 m sheathing panel with 8 d nails, and the safest RW connections is achieved by using H2.5 hurricane clips.

关键词： tornadoes     wind loads     low-rise buildings     fragility analysis     risk assessment     structural failures    

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Efficacy and safety of JAK inhibitor INC424 in patients with primary and post-polycythemia vera or post-essential

null

《医学前沿（英文）》 2016年 第10卷 第4期   页码 437-443 doi: 10.1007/s11684-016-0472-9

摘要：

A phase II study (A2202) was performed to evaluate the efficacy and safety of JAK inhibitor ruxolitinib in 63 Chinese MF patients. Ruxolitinib was given twice a day (bid) at a starting dose of 15 mg (n=25) or 20 mg (n=38) based on a baseline platelet count. About 94.7% of the patients achieved a reduction in spleen size, 27.0% of which exhibited significant reduction (≥35%) at week 24. Significant improvement in debilitating constitutional symptoms, as assessed by MFSAF v2.0, was observed in patients treated with ruxolitinib. Ruxolitinib treatment was generally well tolerated by Chinese patients. Although the treatment was associated with an increase in certain adverse events (AEs) that were established as identified risks (anemia and thrombocytopenia), these AEs were considered manageable in this clinical setting. Ruxolitinib provided substantial reductions in splenomegaly and improvements in symptoms, and was well-tolerated by Chinese patients with MF.

关键词： JAK     ruxolitinib     Chinese patients     myelofibrosis    

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Influence of loading ratio on flat slab connections at elevated temperature: A numerical study

Rwayda Kh. S. AL-HAMD, Martin GILLIE, Safaa Adnan MOHAMAD, Lee S. CUNNINGHAM

《结构与土木工程前沿（英文）》 2020年 第14卷 第3期   页码 664-674 doi: 10.1007/s11709-020-0620-9

摘要： For reinforced concrete members subjected to high temperature, the degree of in-service loading, commonly expressed as the loading ratio, can be highly influential on the structural behavior. In particular, the loading ratio may be pivotal in relation to the phenomenon of load-induced thermal strain. Despite its potentially pivotal role, to date, the influence of the loading ratio on both material and structural behavior has not been explored in detail. In practice, real structures experience variation in imposed loading during their service life and it is important to understand the likely response at elevated temperatures across the loading envelope. In this paper, the effect of the loading ratio is numerically investigated at both material and structural level using a validated finite element model. The model incorporates a proposed constitutive model accounting for load-induced thermal strain and this is shown to outperform the existing Eurocode 2 model in terms of accuracy. Using the validated model, the specific case of flats slabs and the associated connections to supporting columns at various loading ratios are explored. For the cases examined, a marked difference in the structural behavior including displacement direction was captured from low to high loading ratios consistent with experimental observations.

关键词： concrete     finite elements     fire     load-induced thermal strain     punching shear    

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Dynamic modelling and simulation of a post-combustion CO capture process for coal-fired power plants

《化学科学与工程前沿（英文）》 2022年 第16卷 第2期   页码 198-209 doi: 10.1007/s11705-021-2057-7

摘要： Solvent-based post-combustion capture technologies have great potential for CO2 mitigation in traditional coal-fired power plants. Modelling and simulation provide a low-cost opportunity to evaluate performances and guide flexible operation. Composed by a series of partial differential equations, first-principle post-combustion capture models are computationally expensive, which limits their use in real time process simulation and control. In this study, we propose a first-principle approach to develop the basic structure of a reduced-order model and then the dominant factor is used to fit properties and simplify the chemical and physical process, based on which a universal and hybrid post-combustion capture model is established. Model output at steady state and trend at dynamic state are validated using experimental data obtained from the literature. Then, impacts of liquid-to-gas ratio, reboiler power, desorber pressure, tower height and their combination on the absorption and desorption effects are analyzed. Results indicate that tower height should be designed in conjunction with the flue gas flow, and the gas-liquid ratio can be optimized to reduce the reboiler power under a certain capture target.

关键词： CO2 capture     post-combustion capture     simulation     dominant factor    

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Adiponectin: mechanisms and new therapeutic approaches for restoring diabetic heart sensitivity to ischemic post-conditioning

null

《医学前沿（英文）》 2013年 第7卷 第3期   页码 301-305 doi: 10.1007/s11684-013-0283-1

摘要：

Systemic inflammatory response following myocardial ischemia-reperfusion injury (IRI) to a specific organ may cause injuries. Ischemic post-conditioning (IPostC) has emerged as a promising method for myocardial protection against IRI both in experimental and in clinical settings. Enhancement of endogenous nitric oxide (NO) is one of the major mechanisms by which IPostC confers cardioprotection. However, the sensitivity of the diabetic heart to IPostC is impaired and the underlying mechanism is unknown. Adiponectin (APN) is an adipocyte-derived plasma protein with anti-diabetic and anti-inflammatory properties. Plasma levels of APN are decreased in obese subjects and in patients with type 2 diabetes. APN supplementation has been shown to increase NO production and attenuate myocardial IRI in normal (non-diabetic) animals. However, the effect of APN on myocardial injury in diabetic subjects, especially its potential in restoring the sensitivity of the diabetic heart to IPostC has not been investigated. In the current paper, we discussed the possible reasons why the myocardium of diabetic subjects loses sensitivity to IPostC and also highlighted the potential effectiveness and mechanism of APN in restoring IPostC cardioprotection in diabetes. This review proposes to conduct studies that may facilitate the development of novel and optimal therapies to enhance cardioprotection in patients with severe diseases such as diabetes.

关键词： adiponectin     ischemic post-conditioning     ischemia reperfusion injury     diabetes    

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标题 作者 时间 类型 操作

Parametric study of hexagonal castellated beams in post-tensioned self-centering steel connections

Hassan ABEDI SARVESTANI

期刊论文

Secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams

Lizhao DAI; Wengang XU; Lei WANG; Shanchang YI; Wen CHEN

期刊论文

Seismic tests of post-tensioned self-centering building frames with column and slab restraints

Chung-Che CHOU, Jun-Hen CHEN

期刊论文

Self-centering steel plate shear walls for improving seismic resilience

Patricia M. CLAYTON,Daniel M. DOWDEN,Chao-Hsien LI,Jeffrey W. BERMAN,Michel BRUNEAU,Laura N. LOWES,Keh-Chuan TSAI

期刊论文

Calculation method of load distribution on pipe threaded connections under tension load

Shoujun CHEN, Lianxin GAO, Qi AN

期刊论文

Damage identification in connections of moment frames using time domain responses and an optimization

期刊论文

Calculation method of radial stress and deformation on conic threaded connections with interference fit

Shoujun CHEN, Qiang LI, Qi AN,

期刊论文

Nonlinear analysis of pre-tensioned glass wall facade by stability function with initial imperfection

Siu-Lai CHAN, Yaopeng LIU, Andy LEE,

期刊论文

State-of-the-art on resistance of bearing-type bolted connections in high strength steel

Guoqiang LI, Yifan LYU, Yanbo WANG

期刊论文

Seismic retrofitting of severely damaged RC connections made with recycled concrete using CFRP sheets

Yasmin MURAD, Wassel AL BODOUR, Ahmed ASHTEYAT

期刊论文

Fragility assessment of wood sheathing panels and roof-to-wall connections subjected to wind loading

期刊论文

Efficacy and safety of JAK inhibitor INC424 in patients with primary and post-polycythemia vera or post-essential

null

期刊论文

Influence of loading ratio on flat slab connections at elevated temperature: A numerical study

Rwayda Kh. S. AL-HAMD, Martin GILLIE, Safaa Adnan MOHAMAD, Lee S. CUNNINGHAM

期刊论文

Dynamic modelling and simulation of a post-combustion CO capture process for coal-fired power plants

期刊论文

Adiponectin: mechanisms and new therapeutic approaches for restoring diabetic heart sensitivity to ischemic post-conditioning

null

期刊论文