Experimental research on mechanical properties of prestressed truss concrete composite beam encased with circular steel tube

Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.

Experimental Behavior of Recycled Aggregate Concrete Filled Steel Tubular Columns

During the modernization or rehabilitation activity,the demolished structural waste causes large soil pollution and unavailability of natural aggregate is the big concern for the construction industry.Therefore,this manuscript deals with the Composite Steel Circular Column(CSCC)with Recycled Aggregate concrete(RAC)as infill is partly used,with the replacement of 25%and 50%in M30 grade of Concrete.And internal reinforcement steel is fully replaced by rolled steel tubes(circular and square)with varied thickness,ISA-unequal angle.Around 14 specimens are cast and examined under axial load for analysis of the deflection characteristics,the load-bearing capacity along with its buckling behavior.The experimental values are estimated through LVDT(linear variable differential transducer)at 3-phase.The curve of load-deflection is drawn with the load pattern.From the date interpretation,it is found column made of 50%-RAC has more than 25%-RAC.

新型横向连接装配整体式榫卯剪力墙结构抗震性能模拟分析

为加强装配整体式剪力墙的竖向接缝性能和墙体的整体性,在传统榫卯接缝的基础上,研究提出一种采用新型横向连接的装配式榫卯剪力墙,设置横向凹槽处的封闭环形钢筋闭合连接,并与纵向孔洞处的竖向钢筋绑扎形成钢筋骨架,以提高剪力墙的整体稳定性。设置1组现浇剪力墙、1组传统装配式榫卯连接装配式剪力墙、1组采用新型横向连接的装配式榫卯剪力墙,使用ABAQUS有限元软件模拟在低周往复荷载作用下不同墙体的受力情况及破坏过程,并且对比分析不同竖向接缝对剪力墙工作性能和抗震能力的影响。研究结果表明,采用新型榫卯横向连接的装配式榫卯剪力墙的刚度和承载能力与现浇剪力墙基本一致,能够满足“等同现浇”的要求。

超深圆形基坑的力学监测与分析研究

在工业建筑的地下工程中,需开挖37.4 m深的圆形基坑,使用了内力与变形监测系统,以确保支护结构的稳定性。现场监测数据表明,以品字形分布的由排桩、冠梁、腰梁构成的支护结构措施与地下连续墙相似。由于该支护结构的刚度和强度均较高,因此由开挖基坑所造成的扰动在较小的变形范围内得到了控制。由于采取合理的加固措施并设置适当的施工工期,邻近的17m深矩形基坑对圆形基坑开挖带来的影响可控制在允许范围之内。

复合加固圆形木柱轴心受压承载力计算

内嵌钢筋外包纤维布的复合加固方法可以有效提高古建筑木柱的受压承载力和变形能力,大幅提升其工作性能。为提出内嵌钢筋外包碳纤维增强复合材料(carbon fiber reinforced polymer,CFRP)布复合加固圆形短木柱轴心受压承载力的计算公式,本文共完成12组42根复合加固试件的轴心受压试验。试验结果表明:木柱的破坏主要发生于初始缺陷较为集中的区段,且复合加固方法能够提升木柱的承载力和变形能力,加固效果显著。基于经典的纤维布约束混凝土柱抗压强度理论,对CFRP布约束木柱相关试验数据进行拟合分析,进而提出3个CFRP布约束木柱的抗压强度计算模型。通过对比理论计算值与试验值,比选出适用的CFRP布约束木柱顺纹抗压强度计算模型,继而给出复合加固圆形木柱的轴心受压承载力计算公式。依据补充试验结果和与既有文献研究中试验数据的对比可知,理论计算能够较好地预测相关试验结果,从而验证复合加固圆形木柱轴心受压承载力计算公式的可靠性。

复合加固圆形短木柱轴心受压应力-应变关系

内嵌钢筋外包CFRP(carbon fiber reinforced polymer)布复合加固方法可以有效提升古建木柱的承压和变形能力,加固效果显著。为了建立复合加固木柱轴心受压应力-应变模型,同时考虑内嵌钢筋数量以及CFRP布加固量等因素的影响,该文完成了42根复合加固木柱的轴心受压试验。试验结果表明:复合加固方法能够提高木柱的受压承载力、改善木柱的延性;由于木材存在有不可避免的初始缺陷,木柱的破坏主要发生于初始缺陷较为集中的区域。相同测点处,木材、CFRP布和钢筋的荷载-应变曲线分布相近,表明木材与CFRP布和钢筋黏结性能良好,三者能够协调变形、共同工作。基于既有的相关研究,通过对试验数据的拟合分析,给出了复合加固木柱轴心受压峰值应力和峰值应变的计算公式,进而提出了三折线型和多项式型复合加固木柱的轴心受压本构模型。考虑到木材材质的离散性,加固木柱的模型计算曲线与试验曲线基本吻合,验证了所得应力-应变模型的可靠性。

空调用无刷直流电机一种新的定子工程设计探讨

本文介绍了一种空调用无刷直流电机一种新的定子关键部分设计,对两种定子优点和缺点做了一个比较。可以为从事此工程设计的技术人员提供一些参考。

Stress-strain relationship of recycled self-compacting concrete filled steel tubular column subjected to eccentric compression

As a typical compression member,the concrete-filled steel tube has been widely used in civil engineering structures.However,little research on recycled self-compacting concrete flled circular steel tubular(RSCCFCST)columns subjected to eccentric load was reported.In this study,21 specimens were designed and experimental studies on the stress-strain relationship of were carried out to study the mechanical behaviors.Recycled coarse aggregate replacement ratio,concrete strength grade,length to diameter ratio and eccentric distance of specimens were considered as the main experimental parameters to carry out eccentric compression tests.The corresponding stress-strain relationship curves were used to analyze the influence of concerned parameters on ecentric load-bearing capacity of RSCCFCST columns.The experimental results show that the strain of the eccentric compression stress-strain curves increase with the increase of recycled coarse aggregate replacement ratio and concrete strength grade.With increase of eccentric distance,the ductility of specimens increases while the bearing capacity decreases.Moreover,a phenomenological model of RSCCFCST columns is proposed,which exhibits versatile ability to capture the process during loading.The present study is expected to further understanding the behaviors and to provide guidance of RSCCFCST columns in design and engineering applications.

广州市交通信息指挥中心结构设计关键技术

主要介绍广州市交通信息指挥中心结构设计的关键技术,对钢管混凝土核心柱的相关设计问题、环梁的计算及构造、菱形钢筋的设计及构造、牛腿的设计、屋顶大跨度设计、现浇混凝土空心楼盖设计等核心问题进行了详尽描述。针对剪力墙平面外抗弯承载能力的计算及锚固长度不够的问题,给出设置环梁的设计方法,并给出了设计公式。结果表明,采用单向布置的结构方案能解决荷载较大的大跨度结构受力问题;采用牛腿的转换方式能有效地解决上下错位的框架柱结构的传力问题。

配置环形钢筋的梁桥湿接缝承载力计算方法比较研究

为研究配置环形钢筋的梁桥湿接缝承载力计算方法,系统收集该类湿接缝承载力试验资料和计算方法,发现:1)现有的接缝承载力计算方法均以试件的抗拉承载力为基础,主要区别在于核心混凝土区域抗拉强度的计算及试件抗拉承载力的控制因素;2)由Joergensen提出的塑性功模型计算方法得到的理论值与试验值更为接近,且数据离散性小,更为稳定;3)HE Z-Q拉压杆模型比其他模型更好地反映了环形钢筋湿接缝的破坏模式与受力机理。由于目前的计算方法与实际情况仍有一定的误差,建议今后仍然应从破坏模式及受力机理出发,推导出更适用于环形钢筋湿接缝承载力的计算方法。