Bearing capacity of composite columns reinforced by concrete filled steel tube

In this study, nine simplified short composite columns consisting of core CFST (concrete filled steel tube) of different diameters and outer reinforced concrete were constructed to study their compressive performance under axial or eccentric compression. The failure mode is characterized by the crush of the outer concrete. The bearing capacity increases at first and then decreases with further increase of the position coefficient. It can be concluded that position coefficient is an important structural parameter that has considerable influences on the ultimate bearing capacity of the composite columns. The outer concrete, steel tubes and longitudinal reinforcement are found to work in a cooperative manner under axial or eccentric compression when the position coefficient is about 0.5. An improved bearing capacity algorithm that takes the position coefficient into account has been proposed based on the experimental and simulation results and current technical specification in China. It has been proven to be precise and safe.     

预应力装配混凝土复合墙板抗震性能试验研究

结合砌体结构的发展现状和住宅产业化的发展趋势,提出一种“预应力装配混凝土复合墙板”,以期望在中小城镇低层建筑民用房屋中发展一种新的结构形式来对砌体结构进行补充。为了考察该复合墙板的抗震性能,对2块不同预应力度的试件进行了拟静力试验。得到了相应试件的抗震性能指标,显示该墙板具有较好的承载能力和变形性能,分析认为所提出的墙板可以达到8度区低层民用房屋的应用要求,可以作为砌体承重墙的一种替代形式,并且对该墙板相关构造提出了改进建议。     

等截面钢管混凝土格构柱骨架曲线的统一算法

介绍了斜缀管式和平缀管式等截面钢管混凝土格构柱骨架曲线的计算方法并进行评价分析。研究表明,不同缀管布置形式的钢管混凝土格构柱,其抗震性能具有共性。借鉴钢管混凝土单肢柱的计算框架,开展等截面钢管混凝土格构柱骨架曲线的统一算法研究,对弹性刚度、水平峰值荷载、峰值荷载位移、下降段刚度等主要参数的计算方法进行了深入探讨和算例分析,并以干海子大桥格构柱墩为研究对象,采用OpenSEES有限元程序,对骨架曲线算法进行工程实例验证。研究结果表明,计算值与试验值及有限元计算结果均吻合良好。最后提出了适合工程应用的等截面钢管混凝土格构柱骨架曲线的统一简化算法,为钢管混凝土计算理论的进一步完善和规程编撰提供参考。     

X形配筋增强高强钢筋异形柱边节点抗震性能试验研究

通过对核心区应用X形配筋增强的高强钢筋异形柱边节点和同等条件下未被增强的高强钢筋异形柱边节点进行拟静力试验研究,对比分析异形柱边节点的破坏特征、滞回曲线、承载能力、位移及延性、刚度退化、耗能能力等抗震性能指标。研究结果表明,配置HRB500高强钢筋异形柱边节点比配置600 MPa级的边节点承载能低,但滞回性能好,变形能力强,刚度退化推迟,耗能能力强;在核心区加入X形配筋,均可以改善高强钢筋异形柱边节点的破坏特征,使边节点抗剪能力、变形能力、耗能能力增强,刚度退化推迟,提高异形柱边节点抗震性能,配置HRB500高强钢筋的试件核心区应用X形配筋加强后抗震性能提高效果更好。     

柱失效方程中荷载相关特性对承载力抗震设计可靠度的影响

以竖向荷载和水平地震作用组合下的钢筋混凝土柱和钢柱为对象,研究了失效方程中荷载相关特性对柱承载力抗震可靠性的影响。根据现行《混凝土结构设计规范》和《钢结构设计规范》分析了不同柱弯矩轴力相关曲线的特性。结合多个框架结构实例,对比了柱失效方程中荷载相关曲线与规范考虑情形的异同。实例分析表明:水平地震和竖向荷载组合作用下,小偏压RC柱和工字型钢柱的荷载相关曲线与规范考虑的情形较为符合,均近似为负相关的直线;水平地震和竖向荷载组合作用下,大偏压RC柱的荷载相关曲线则与规范考虑的情形有较大出入,存在明显的正相关段部分。在此基础上,考虑失效方程复杂特性,依据已有的荷载和抗力变量概率模型,采用Monte Carlo法分析了水平地震和竖向荷载组合作用下柱的可靠性。结果表明:钢柱和小偏压RC柱的承载力抗震可靠度随轴压力荷载效应比值的变化幅度较小,与规范模式计算结果较接近;大偏压RC柱的承载力抗震可靠度随轴压力荷载效应比值的变化会有较大幅度波动,与规范模式计算结果差异较大;当轴压力荷载效应比值为负时,大偏压RC柱的承载力抗震可靠度会低于规范计算值较多,现行柱可靠性设计方法会偏于不安全。     

焊接加固热作用对工形截面压弯钢构件承载性能的影响

为研究焊接加固热作用及不同初始负载对工字形压弯钢柱承载性能的影响,基于考虑热影响的热结构耦合分析方法进行了热源模型热输入改进,并考虑初始几何缺陷、初始残余应力及摩擦等,完成了不同负载下焊接加固的3个工字形压弯钢柱的模拟分析。研究了焊接位移时程、腹板应力应变重分布及荷载位移关系,通过有限元分析与相应试验结果对比验证,进而获得了试验无法获得的焊接温度场、翼缘与加固板间的焊接应力应变重分布以及翼缘边缘屈服承载力等结果,并将承载力结果与规范计算结果对比,考察了现有设计方法。结果表明,焊接顺序决定焊接变形的发展过程,焊接热输入和初始负载共同决定持载焊接的位移变化范围和焊接残余变形的大小;初始负载越大,应力应变重分布往偏心受力方向发展更多,承载力越低,而初始残余应力不影响极限承载力;采用考虑热影响的有限元方法具有一定可行性和总体安全性,规范设计方法仍有可提升空间。     

Experimental studies on the energy absorption property of aluminum foam filled steel pipe under transverse compression

To understand the energy absorption property of aluminum foam-filled steel pipes and the energy absorption property affected by aluminum foam filler, the energy absorption ability and transverse compression property of steel pipes and aluminum foam-filled steel pipes are tested. The results show that the normal stress-strain curve of steel pipes is similar with that of cellular materials. The normal yield stress of a steel pipe with a large diameter under transverse compression is lower than that with the same wall thickness but a small diameter. The deformation mode of steel pipes can be changed by the filling of aluminum foam. The aluminum foam filler improve the energy absorption ability of steel pipes. The effect of aluminum foam density on the energy absorption ability of steel pipe is small, and the effect of pipe diameter on the energy absorption ability of aluminum foam-filled steel pipes is large.     

Experimental study on seismic behavior of beam-column sandwich joints with big beam-column eccentricity

Three specimens of sandwich joints with eccentricity being larger than a quarter of the column width in middle floor of frame are designed and loaded under cyclic loading. Their shear capacity, failure modes, and ductility, as well as energy dissipation are analyzed. The results show that the performance of sandwich joints with big eccentricity is good under cyclic loading. X-type reinforcements can be used to substitute for stirrups in the joint to bear shear forces. But the anchorage of longitudinal bars of beams in eccentric sandwich joints is relatively weak. Comparing to sandwich joints without eccentricity, the column longitudinal bars near the sandwich joints with big eccentricity are vulnerable to sudden change of strain.     

粉煤灰对高强混凝土收缩徐变的影响试验研究及其修正模型

粉煤灰对高强混凝土收缩徐变的影响直接关系到结构长期性能的合理确定。制作粉煤灰掺量分别为0、12%和24%的100 mm×100 mm×400 mm的C50混凝土棱柱体试件,在试验室条件下进行收缩及不同加载龄期的徐变试验,研究了粉煤灰对高强混凝土收缩徐变的影响。根据试验结果评估了目前常用的4种相关规范公式对高强混凝土收缩徐变的适用性,并引入粉煤灰影响系数以综合反映粉煤灰掺量和加载龄期对高强混凝土收缩徐变的影响,根据试验结果和现有研究成果提出了其修正模型。分析结果表明,JTG D 62和GL 2000推荐的收缩徐变预测模式与基准试件实测结果较为吻合,验证结论亦说明所引入的粉煤灰影响系数可应用于掺粉煤灰高强混凝土的收缩徐变预测。     

预应力CFRP布及预紧螺栓加固RC梁试验研究

为提高碳纤维布加固RC结构的效果及其可靠性,提出了预应力碳纤维布与预紧螺栓联合加固技术。结合在役RC梁的损伤特点及目前的RC梁加固方法,分别采用不同的碳纤维布加固技术对完整梁和破坏梁的抗弯性能进行了对比试验研究。针对目前碳纤维布张拉设备的缺陷,研发了便于现场应用的新型碳纤维布布张拉设备,分析了预应力大小对加固效果的影响。结果表明,预应力碳纤维布及预紧螺栓联合加固技术是一种更可靠的桥梁加固方法,不仅能够提高RC梁正截面的抗弯承载能力及正常使用阶段的截面刚度,而且螺栓预紧锚固碳纤维布能够很好地抑制其在混凝土表面的剥离,提高碳纤维布与混凝土表面之间粘结强度,对碳纤维布施加预应力能够充分发挥其高强性能,有效抑制混凝土裂缝开裂和开展。     

Experimental Research on the Seismic Behavior of the Interior Joint with High Shear - Compression Ratios in the Frame

The reversed cyclic loading tests of 5 nearly full-scale beam-column assembly specimens with high shear-compression ratio under different axial loads in reinforced concrete plane frames have been completed,which cover the shortage in the field of high shear-compression parameter among seismic joint experiments in the world.Based on relatively complete measuring and analyses of the law for the bond and slip of the beam bar through the joint,the stress of the level stirrup legs and hysteretic dissipated energy and the change of rigidity,the characteristic of shear transfer mechanisms and damage development and comprehensive seismic behavior of the assembly are proposed in this paper.It makes it possible to improve design codes and to establish relatively reasonable analytic modes and hysteretic modes in inelastic dynamic response analyses of the frame.     

Experimental study on vibration and structure noise of marine gear box with heavy load

The performance requirements of marine gear box are much higher than that of other gear boxes due to its special working conditions. The structure and transmission principle of a high-power marine gearbox are analyzed, and the experimental test is carried out for the analysis and calculation of its vibration characteristics and intensity. Measured by FFT analysis of vibration signals, the main peak is caused by its octave and the engagement frequency of input stage and middle-class transmission. The vibration severity of high-power marine gearbox reached 4.47 mm/s. In addition, the calculated structure noise of the measuring points is at the 1/3 octaves, and the largest structure noise is 131.27 dB which occurred in the frequency of 329 Hz.     

不同建筑热工分区办公建筑外围护结构负荷指标影响因素权重

为研究多因素对不同热工分区办公建筑总负荷指标的综合影响,在分析了单一因素对建筑总负荷指标影响规律的基础上,采用层次分析法对分别位于哈尔滨、兰州、重庆、广州的办公建筑负荷指标进行了评价。得到了窗户传热系数K_w、玻璃遮阳系数S_c、窗墙比R在不同热工分区办公建筑总负荷指标影响因素中的权重值,并对此进行了一致性检验。结果表明：对于严寒地区的哈尔滨和寒冷地区的兰州节能建筑,各因素重要程度为R > K_w > S_c;对于夏热冬冷地区的重庆和夏热冬暖地区的广州节能建筑,各因素重要程度为S_c > R > K_w。在建筑结构优化设计中应根据各热工分区负荷影响因素的比重不同进行优先控制相应因素。     

Experimental Investigation on the Aseismic Behavior of Seismic Damage Masonry Wall Retrofitted with Grouting and Steel Hoops

In order to accurately evaluate the aseismic behavior of the seismic damaged masonry pagodas destroyed by Wenchuan earthquake and strengthened after the earthquake, a test was conducted to acquire related parameters on seismic performance from the specimens made by masonry and retrofitted with grouting and steel hoops. Taking a seismic damaged ancient masonry pagoda in Sichuan as a case study, four kinds of primitive specimens are fabricated by simulating the conformation of the masonry pagoda. Then the primitive specimens are destroyed under cycle loads and the damaged specimens are repaired by grouting and steel hoops. Cycle controlling tests are conducted with the specimens and relevant data are acquired. Experimental results showed that grouting combined with steel hoops could improve the ductility and energy dissipation capacity of a seismic damage of brick masonry structure, but it do a little to improve the stiffness of a seismic damage structure. And the cracking load of the repaired masonry is much lower than the original undamaged structure.     

融合慕课和虚拟仿真实验项目训练的“食品工艺原理”课程教学设计

以提高课程教学效果为出发点,以培养有专业知识素养和实践能力的创新型人才为目标,通过线上-慕课和虚拟仿真训练项目与线下-课堂与实验操作相结合的"食品工艺原理"课程教学设计,能极大地提升学生独立思考、自主学习获得高阶性知识和解决复杂工程问题的能力,实现课程教学目标。     

Management System of the Tender and Bidding for Power Projects with a Valuation Based on the Bill of Quantities

Valuation based on the bill of quantifies will change the existing valuation mode of tender and bidding. For the standardized management of tender and bidding for power projects and the inteUigentized information management of power enterprises, it is an inevitable trend of reform to apply the valuation mode based on the bill of quantifies. According to the characteristics of power projects, this paper expounds the working process of the valuation mode based on the bill of quantities and analyzes the goal and function need of the tender and bidding management system. Considering the calculation procedure of the valuation and the quote strategy of quantities bill, the composition of fees for the valuation is settled and the calculation method is designed. To establish the management system of tender and bidding with a valuation based on the bill of quantities is beneficial for the costing reform of power projects and the perfection of the tender and bidding market. Therefore it is of great significance to spread the new management mode of project costing with a valuation based on the bill of quantities.