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对中、美、欧现行规范关于钢结构截面类型及宽厚比限值的要求进行了归纳比较,利用ABAQUS有限元软件进行了单根H形钢梁考虑初始缺陷的屈曲承载力分析并与规范公式计算结果进行了对比。在此基础之上,以雄安站站房雨棚钢结构为背景,选取具有代表性的区域建立空间交叉H形钢梁精细有限元模型。对不同板件宽厚比的空间交叉H形钢梁进行了非线性屈曲承载力分析,研究了翼缘宽厚比及腹板高厚比对空间交叉H形钢梁局部稳定性和屈曲性能的影响。研究结果表明:ABAQUS模型对钢梁整体稳定性计算结果与规范公式吻合度较高,设计中采用杆件单元模型进行结构整体稳定性分析是安全合理的。考虑翼缘约束作用的H形钢梁腹板屈曲计算模型与该项目交叉钢梁有限元弹性屈曲分析结果吻合良好,结构起坡所引起的不均匀正应力是导致钢梁腹板失稳的主要因素。翼缘厚度确定后,根据上翼缘失稳与腹板局部屈曲临界值确定腹板厚度,依据S3级截面要求所控制的次梁腹板厚度是经济合理的。

当结构的高宽比较大时,在设防与罕遇地震作用下高烈度区的超高层结构的核心筒剪力墙可能承受倾覆力矩引起的巨大拉力,垂直于地震作用方向的核心筒翼墙受力状态接近于轴心受拉。由于混凝土抗拉强度较小,常采用钢板组合剪力墙来抵抗较大的墙肢拉力。采用非线性有限元法,对钢板组合剪力墙在轴心受拉作用下的开裂荷载、刚度变化、滞回性能与受拉承载力进行了较为全面的研究,表明混凝土对构件的轴拉承载力与刚度具有一定贡献。给出了钢板组合剪力墙在轴心受拉状态下最大裂缝宽度的计算方法,分析了墙体含钢率以及型钢、钢筋布置方式对裂缝宽度的影响。钢板组合剪力墙轴心受拉缩尺模型试验结果表明,有限元数值分析与模型试验吻合良好。在此基础上,提出了钢板组合剪力墙受拉状态下的设计建议。

开合屋盖结构属于复杂多重子结构体系,其动力特性非常复杂,活动屋盖在竖向地震作用下的响应远大于根据《建筑抗震设计规范》(GB 50011—2010)得到的结果。以国家网球馆(钻石球场)为例,对开合屋盖结构的振型模态与自振周期进行了深入分析,研究了质量参与系数的分布规律。高阶振型对开合屋盖结构动力响应的影响很大,尤其对于竖向地震作用,高振型起主要控制作用。在模态阻尼比的基础上,提出根据质量参与系数加权平均得到的一致阻尼比,物理意义明确,便于工程应用。计算分析表明,采用一致阻尼比算法得到结构各部位的内力及位移与按照模态阻尼比法的结果非常接近。

节点刚度与单层网壳结构的刚度与稳定性关系密切。采用了可以真实模拟相贯节点单层柱面网壳的多尺度计算模型,在节点域内采用精度较高的壳单元,在节点域外采用梁单元,节点域与杆端在连接面形心处位移与转角保持连续。该计算模型可以较为准确地反映相贯节点的力学性能,计算精度高、单元数量少,可同时进行结构整体与节点局部的计算分析。运用该模型全面考察了相贯节点刚度对单层柱面网壳跨中挠度、动力特性与屈曲性能的影响。通过对相贯节点进行补强,能够有效增强节点的刚度,采用梁单元模型即可进行单层网壳结构的计算分析,结构设计简便、结构效能较高。

钢板剪力墙延性好、耗能能力强,是一种新型的高层抗侧力构件。工程实践中为满足开窗洞和开门洞的要求,需要采用带大矩形洞口的带肋钢板剪力墙作为抗侧力构件的方案。目前国内外对于此类钢板剪力墙尚未见到系统的研究,设计规范中缺乏可操作的具体规定。通过试验研究和数值分析方法对带大矩形洞口钢板剪力墙的受力性能进行了较为深入的研究,结果表明水平边框梁和竖向边框柱的面外刚度对结构的整体性能影响较大,薄钢板剪力墙开洞后刚度有所降低,根据开洞薄钢板墙的力学特点,提出了矩形洞口周边的边框梁和边框柱设计方法。

根据国家体育场大跨度钢结构柱脚的受力特点,提出一种适用于大型钢结构的新型半埋入柱脚形式。在柱脚-混凝土承台模型的有限元分析与柱脚锚固件的锚固性能试验的基础上,形成了大型柱脚-混凝土承台的设计方法。该类柱脚在国家体育场钢结构中的实际应用情况表明,本文提出的柱脚形式与设计方法对于大型钢结构具有很好的适用性和广泛的应用前景。

焊接薄壁箱形构件板件的宽厚比较大,受压板件出现局部屈曲,可以采用有效宽度的概念确定构件的正截面承载力。本文在参照国内外钢结构设计规范的基础上,根据板件的应力状态,提出焊接薄壁箱形构件有效截面的计算方法,同时考虑受压较小板件应力值较低对有效宽度的有利影响和有效截面形心与箱形构件形心之间的偏移量,给出构件在拉、压、双弯、双剪、扭作用下的构件承载力计算公式,供结构设计人员参考。

宁波国际会议展览中心主展厅大跨度屋盖支承条件复杂,风荷载效应显著。通过风洞试验确定屋盖的风压分布情况,在网壳结构的部分钢管中填充混凝土以平衡部分风吸力。采用抗震球形钢支座克服支座相对位移对屋盖结构产生的影响。小展厅和东、西展厅大跨度屋盖采用了主、次空间管桁架结构体系,在展厅中部设置了四肢钢管组合柱,从而有效地减小了屋盖的跨度与高度。为了适应大跨度屋面温度变形的要求,采用了滑板式聚四氟乙烯橡胶支座。

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Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Anhui Agricultural Sciences is the property of Journal of Anhui Agricultural Sciences Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: After osteoarthritis, chondrocyte autophagy is inhibited. Autophagy is an important physiological mechanism to maintain cell homeostasis, which reduces injury of macromolecules and organelles. Improving autophagy may alleviate the progression of osteoarthritis. OBJECTIVE: To explore the mechanism of chondrocyte autophagy in osteoarthritis and the regulation of related factors in chondrocyte autophagy. METHODS: Relevant literatures were searched in PubMed, CNKI, and WanFang from January 2001 to present, using the keywords of “osteoarthritis, chondrocyte, autophagy, treatment, signaling pathways, traditional Chinese medicine, miRNA.” RESULTS AND CONCLUSION: The progression of osteoarthritis is related to the changes of autophagy in chondrocytes. In the early stage of cartilage degeneration, autophagy in chondrocytes is activated to protect chondrocytes against various environmental changes. However, with the aggravation of cartilage degeneration, autophagy in chondrocytes cannot maintain, resulting in cell damage and even death. Protein kinases such as mammalian target of rapamycin, nuclear factor-κB, p53 and signaling pathways are involved in autophagy and its related processes. Rapamycin, diazoxide, resveratrol and microRNAs can increase the autophagy activity of chondrocytes, which is a feasible method to inhibit the progression of osteoarthritis. [ABSTRACT FROM AUTHOR]

BACKGROUND: Although some risk factors related to osteoarthritis have been proposed, including genetic susceptibility, aging, obesity, joint structure and force line abnormalities, the pathogenesis of osteoarthritis is still unclear to a large extent. OBJECTIVE: To review the related literature worldwide, and summarize the mechanism of proinflammatory factors and matrix metalloproteinases in osteoarthritis as well as relevant therapeutic advances. METHODS: With the key words of “osteoarthritis, interleukin-1, interleukin-6, interleukin-17, C-reactive protein, tumor necrosis factor-α, matrix metalloproteinase, treatment” as the key words in English and Chinese respectively, the first author searched for the basic and clinical research in PubMed and CNKI databases in the period from January 1990 to present. RESULTS AND CONCLUSION: Osteoarthritis is a kind of joint disease caused by many factors. The pathogenesis is complex, mainly regulated by a variety of signal pathways, among which the role of inflammatory cytokines and matrix metalloproteinases in the pathogenesis of osteoarthritis has become increasingly obvious. However, in-depth investigations on regulating the occurrence and development of osteoarthritis are still required. It is believed that in the near future, clarifying the pathogenic mechanism of osteoarthritis and developing new treatments, especially introducing stem cell therapy and gene therapy, are expected to greatly target the treatment and prevention of osteoarthritis. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Beijing Olympic Tower consists of five slender single towers, of which the maximum aspect ratio is 33. The sightseeing platform on the top of the towers hangs out and the building shape is very complicated. The girders of the base hall which has a very high indoor architectural requirement are large span and heavily loaded. Through setting multiple connection trusses along the vertical direction，five single towers were united to form a bundled tower system， and the lateral stiffness and overturning resisting capacity of the structure were improved significantly. The adverse effects of uneven vertical deformation and differential settlement were avoided by using temporary horizontal trussprestressed bracing system between the individual towers. The test precision problem of the complex model was solved successfully by using the sectional wind tunnel test technology. By developing reentrant hoisting mechanism combined with high-place fire protection water tank, the problem of insufficient TMD installation space was addressed. The natural vibration frequency of the mass block could be adjusted according to the measured condition. After applying the vertical TMD devices at the end of the large cantilever at the tower crown，the resonance caused by the dense stream of people was significantly mitigated. The roof of the base hall adopted an intercross clear water concrete beam-plate system，which could effectively transfer the internal force at the missing part of the roofing slabs，ensuring the integrity of the structure and embedded effect of the tower body. Considering the interior architectural effect of the building，a long-span arch girder was adopted，thus the force transfer capability of the girder could be effectively improved，the section size of the components could be optimized, and the structural cost could be reduced. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A practical calculation method for apparent wave velocity was proposed for traveling wave effect analysis of super-long structures, and the influences of apparent wave velocity were analyzed in this paper. A multi-support excitation model taking account of both horizontal and rotational stiffness of the pile foundation was established. Taking a multistory super-long terminal structure with a large span roof as an illustrative example, the displacements, horizontal seismic forces, and internal forces of members under earthquake travelling along the longitudinal direction were analyzed comprehensively. The results show that，the apparent wave velocity is mainly affected by the shear wave velocity of bedrock, hypocenter depth and epicenter distance，where a faster bedrock shear wave velocity，a smaller epicenter distance，or a deeper focal depth could all lead to a larger the apparent wave velocity. The story shear forces caused by multi-support excitation is less than that caused by uniform excitation. With a decrease in apparent velocity, the differences between multi-support excitation and uniform excitation are more obvious. When under multi-support excitation along the longitudinal direction, the change of apparent wave velocity and foundation stiffness has a significant influence on the inter-story drift angle of the lower floor； when under multi-support excitation along the transverse direction, the apparent velocity has a great influence on the inter-story drift angle of the upper floor, but the effect of the foundation stiffness is small. When the symmetrical structure is excited in the direction parallel to earthquake propagation, torsional effect is insignificant ； but when excited in the direction perpendicular to earthquake propagation, an obvious torsional effect would occur. When under multi-support excitation along the longitudinal direction，the internal force of some frame columns on the bottom floor increases ； when under multi-support excitation along the transverse direction, the internal force of a small number of frame columns becomes critical. With an increase in apparent wave velocity, the internal force of the frame columns decreases gradually. After considering the foundation stiffness, the internal force of the frame columns can be reduced significantly. The internal forces of several members in the long-span roof are controlled by multi-support excitation G as the apparent velocity decreases, the internal forces of the long-span roof members gradually decrease, and the effect of the foundation stiffness is negligible. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the effect of diameter-thickness ratio (D/t) on seismic behavior of concrete filled steel tubular (CFST) columns, two specimens with diameter 600 mm were tested under constant vertical loads and cyclic horizontal loads. The failure phenomenon, hysteretic curves, strains developing procedure on steel tubes and core reinforcement of the specimens with D/t of 37. 5 and 50 were analyzed. The test results show that, the hysteretic curves of CFST columns with large diameter are very full. The energy dissipation performance is superior. The deformation capacity is excellent. With the increase oiD/t, the maximum deformation angle and the equivalent damping ratio of the specimens are slightly reduced. The concrete crushing and tube wall buckling occur mainly in the region between the bearing plate and the first row of studs which have a clear constraint effect on the tube wall of the specimens. When D/t is relatively small, the steel pipe wall has stronger constraint effect on the core concrete, and the residual deformation is smaller. The core longitudinal reinforcement is basically in the elastic state. The stirrups are far from the yield strain, even they have less constrain effect on concrete. But there is obvious slip between reinforcement and concrete. The bending bearing capacity of concrete filled steel tubular columns with large diameter in the test is significantly higher than calculation results according to the relevant specifications in China, which means the Chinese specification is conservative. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Axial compression ratio is closely related to the seismic behavior of steel plate concrete composite shear walls (SPCW). Effects of axial compression ratio on the lateral stiffness, hysteretic behavior, energy dissipation capacity, ductility and bearing capacity of SPCW were analyzed by elasto-plastic finite element software. The results show that SPCW normal section bearing capacity changes along with axial compression ratio and reaches the maximum when the axial compression ratio is 0.4. SPCW has the maximum ductility and energy dissipation capacity when the axial compression ratio is in the range of 0.2 to 0.4. The deformation capacity, ductility and energy dissipation capacity decrease if the axial compression ratio exceeds 0.6. Meanwhile, axial compression ratio influences the initial lateral stiffness of SPCW. Lateral stiffness decreases with the cycles of reversed loading. To verify the reliability of the finite element analysis, a scaled compression-bending SPCW specimen test was carried out. The finite element analysis results agree well with the test results. While the normal section bearing capacities calculated by formula of JGJ 138--2012 ' the code for design of composite structure ' and the fiber finite element model are conservative. In order to ensure good seismic behaviors of SPCW,the axial compression ratio should not be too high. [ABSTRACT FROM AUTHOR]

The giant truss arch of the Ordos Dongsheng Stadium has an inclination angle of 6. 1° from the vertical plane. Using the concept of half through arch bridge, 23 sets of wire cables are used to draw-off the roof. This design method could improve the stiffness of the large span roof, reduce the depth of the trusses significantly, and make the structural system more reasonable. Based on the analysis and comparison of the bending moment distribution of the circular arc, the quadratic parabola, eight parabola and three hinged arch axis, three hinged arch axis is chosen as the initial axis of the arch. Based on the study of the moving roof's position, the average value of the cable forces according to moving roof fully opened and fully closed state is used as the loading force system to make the eccentric bending moment of the giant arch smallest. After the iterative calculation and spline interpolation, the axis of the arch is finally determined. The truss arrangement of the roof is harmony and unity with the arch and wire cables. The wire cables formed multi-point support on the roof and meet the requirements of the track rigidity for the retractable roof's moving. Structural deformation and stress of the structural member are satisfied with the requirement of the design specifications and wire cables will not fail or relax under different load cases, and the overall stability of the structure is superior. Concrete filled steel tube members are adopted in the arch feet to improve seismic performance. The results of cable breaking analysis show that the adjacent cable's force on the same side increases obviously. The forces of the other cables, the giant arch as well as the roof have little influence. The safety of the structure and cable replacing requirements can be satisfied. [ABSTRACT FROM AUTHOR]

A new type of beam-column connection for large diameter concrete filled tubular column was proposed on the basis of traditional inner ring plate connections. In order to avoid the difficulty of pouring concrete and using more steel due to the wider inner ring plate, welding reinforcing bars on the inner ring plate were used, which could reduce the amount of steel and be convenient for setting reinforcing bar cage in the steel pipe column. In order to avoid the lamellar tearing of the surface of steel pipe column, flange at the beam end needs to be widened. The width and angle of flange were reasonably determined by analysis. The relationship between connection detail and stress distribution was fully analyzed by nonlinear finite element software. The rigid zone length of beam-column connection was obtained by comparative analysis. The relationship between rigid zone length and bending stiffness of frame beam was researched. In order to verify the rationality of the new type connection, experimental studies on the scale model of concrete filled tubular column and H-section beam connection were conducted. The results of finite element analysis and scaled model tests indicate that the steel bar can improve the force-transfer by inner ring plate and the stress of connection is reduced effectively. When the flange width is expanded 1. 5 times and the widened angle is 1:6, the maximum stress on connection zone is significantly lower than H-section beam and the earthquake-resistant design philosophy of 'strong-joint and weak-member' is satisfied. The connection stiffness has remarkable effect on the lateral stiffness of frame structure which has concrete filled tubular column and H-section beam connections. The bending stiffness of the frame beam can be increased by more than 40 percent when the rigid zone length is about 0. 4 times the diameter of steel pipe. The seismic behavior of the connection is good and the seismic design concepts of 'strong-joint and weak-member' can be realized. [ABSTRACT FROM AUTHOR]

High-frequency-pressure-integration tests were carried out in a wind tunnel to investigate wind load characteristics on smooth cantilevered roof and wavy-shaped cantilevered roof, both of which have the same size. The effects of wavy-shaped roof surface have been evaluated in wind tunnel test. Wind pressure distribution shows that, wavy shape does not change the main mechanism of wind load, but intensifies the separation on the front edge of the roof. Bending moment coefficient is a controlling factor for the wind-resistance design of the main roof structure, and can be derived from integration. Relative to the smooth surface cantilevered roof, the mean bending moment coefficient of the wavy-shaped cantilevered roof is increased by 23% and the RMS (root mean square) of bending moment coefficient of the wavy-shaped cantilevered roof is increased by 20%, under the most unfavorable wind direction angle. But wavy shape decreases the energy concentration of the fluctuating wind load when reduced frequency is between 0.1 and 0.2. Wavy shape has strong influence on the extreme wind pressure, since wind uplift on wavy-shaped cantilevered roof is 13% larger than that on smooth surface cantilevered roof, which is the controlling factor of the wind-resistant design of cladding structures. The influence of wavy shapes should be considered for the wind-resistant design of the wavy-shaped cantilevered roof to ensure safety. [ABSTRACT FROM AUTHOR]

The shape factors of wind loads for the complex-shaped and important buildings are not specified in GB 50009-2012 4Load code for the design of building structures * . The wind loads of these buildings are frequently determined by wind tunnel tests. A method of determining the design wind loads for cladding and components based on the wind tunnel tests was presented in this paper. In this method, the peak pressure coefficient of wind load is expressed as the summation of shape factor and the peak fluctuating pressure coefficient, instead of the product of the gust factor and the shape factor in GB 50009-2012. The method can not only be applied to the windward cladding and components, but also to the leeward cladding and components which are located in the flow separation zones. After the non-Gaussian characteristics of wind pressure histories are considered, the peak fluctuating pressure coefficient can be simply calculated using the reduced formulae of non-Gaussian peak factor. As an example, the design wind loads on cladding and components of a large-span flat roof were investigated using both the presented method and the method in GB 50009-2012. The recommended peak pressure coefficients on cladding and components of flat roof were presented for the wind-resistant design. It is clear that the problem of design wind loads on cladding and components is solved effectively by the presented method and that the load panels specified in AIJ-RLB-2004 code are reasonable. It is illustrated that the design wind loads on cladding and components located in the flow separation zones may be underestimated by the national code if the shape factors are obtained by wind tunnel test. [ABSTRACT FROM AUTHOR]