Effect of Eccentric Shear Stiffness of Walls on Structural Response of RC Frame Buildings

Current research study consists of determining the optimum location of the shear wall to get the maximum structural efficiency of a reinforced concrete frame building. It consists of a detailed analysis and design review of a seven-story reinforced concrete building to understand the effect of shear wall location on the response of reinforced concrete structures when subjected to different earthquake forces. Three trail locations of shear walls are selected and their performance is monitored in terms of structural response under different lateral loads. Required objectives are achieved by obtaining design and construction drawings of an existing reinforced concrete structure and modeling it on Finite Element Method (FEM) based computer software. The structure is redesigned and discussed with four different configurations (one without shear wall and three with shear walls). Main framing components (Beams, Columns and Shear walls) of the superstructure are designed using SAP 2000 V. 19.0 whereas substructure (foundation) of RC building was?designed using SAFE. American Concrete Institute (ACI) design specifications were used to calculate the cracked section stiffness or non-linear geometrical properties of the cracked section. Uniform Building Code (UBC-97) procedures were adopted to calculate the lateral earthquake loading on the structures. Structural response of the building was monitored at each story level for each earthquake force zone described by the UBC-97. The earthquake lateral forces were considered in both X and Y direction of the building. Each configuration of shear wall is carefully analyzed and effect of its location is calibrated by the displacement response of the structure. Eccentricity to the lateral stiffness of the building is imparted by changing the location of shear walls. Results of the study have shown that the location of shear wall significantly affects the lateral response of the structure under earthquake forces. It also motivates to carefully decide the center of lateral stiffness of building prior to deciding the location of shear walls.

Effect of Bushen Hemai Decoction on vascular stiffness in elderly patients with isolated systolic hypertension

Objective: To investigate the effect of Bushen Hemai Decoction on the wall stiffness of middle-aged and elderly patients with isolated systolic hypertension. Methods: A total of 126 patients with middle and old systolic hypertension were selected from March 2017 to March 2018 in our hospital. According to the random table method, there were 63 cases in the observation group and 63 cases in the control group. The control group was treated with conventional western medicine, while the observation group was treated with kidney tonifying and pulse prescription hypothyroidism on the basis of the control group. The two groups were treated for 12 weeks. The changes of blood pressure, pulse conduction velocity and endothelium-dependent vasodilation function were compared between the two groups before and after treatment. Results: the systolic pressure in the two groups was lower than that before the treatment, but the diastolic pressure was not significantly changed, and the systolic pressure in the observation group was lower than that of the control group, while the diastolic pressure was not statistically significant. After treatment, the pulse conduction velocity of the two groups was lower than that before the treatment, and the pulse conduction velocity of the observation group was lower than that of the control group after treatment. After two groups of treatment, FMD was higher than before treatment, but there was no significant change in the diameter of vascular base, and FMD in the observation group was higher than that of the control group, but there was no statistical difference between the blood vessel base diameter. The total effective rate of the observation group (93.65%) was higher than that of the control group (74.60%). Conclusion: Bushen Hemai Decoction is effective in treating isolated systolic hypertension in middle-aged and old patients, and can reduce the stiffness of patients' tube wall, which is worthy of clinical reference.

Effect of Bushen Hemai decoction on vascular stiffness in elderly patients with isolated systolic hypertension

Objective: To investigate the effect of Bushen Hemai decoction on the wall stiffness of middle-aged and elderly patients with simple systolic hypertension. Methods: The 126 middle-aged and elderly patients with simple systolic hypertension admitted to our hospital from May 2010 to May 2015 were randomly divided into control group (63 cases) and observation group (63 cases). The control group was treated with conventional Western medicine, while the observation group was treated with Bushen Hemai decoction on the basis of the control group. The two groups were treated for 4 weeks. Results: The systolic blood pressure of the two groups decreased after treatment (observation group: T=16.165, control group: T=13.537, P<0.05);the systolic blood pressure of the two groups did not change significantly after treatment (observation group: T=1.857, control group: T=0.483, P>0.05);the systolic blood pressure of the observation group was lower than that of the control group after treatment (T=16.165, P<0.05). After treatment, the level of ST segment of ECG in the two groups was lower than that before treatment (observation group: T=22.145, control group: T=11.007, P<0.05);after treatment, the level of ST segment of ECG in the observation group was lower than that in the control group (T=8.130, P<0.05). After treatment, the pulse conduction velocity of the two groups was lower than that of the control group (observation group:T=8.694, control group: T=3.944, P<0.05);after treatment, the pulse conduction velocity of the observation group was lower than that of the control group (T=5.326, P<0.05). The total effective rate of the observation group (93.65%) was higher than that of the control group (76.19%) (P<0.05). Conclusion: Bushen Hemai Decoction has a significant clinical effect on middle-aged and elderly patients with simple systolic hypertension, and can improve the stiffness of the tube wall, which is worthy of clinical reference.

低刚度薄壁件铣削加工刀具破损及表面质量分析

为分析低刚度薄壁在切削过程中的情况,进行了低刚度薄壁的小径向浸入比切削试验,通过实时监测的方式同步采集薄壁厚度方向的加速度信号和XYZ三个方向的切削力信号,并且通过超景深显微镜对刀具的磨损破损状况及加工表面质量进行观测。试验发现:薄壁刚度较低时,切削振动剧烈,加速度值和X方向的切削力随着进给速度的增大而快速增大;薄壁振动会导致刀具刀刃部分破损现象早于磨损发生,出现多处块状掉落;薄壁顶部因其更弱的刚度导致大量的长条状凸起,严重影响表面质量,且薄壁表面下部加工质量明显优于上部;低刚度时采用逆铣比顺铣更能适当降低切削力并减少毛刺的出现。

三水河特大桥桥墩温度场及温度效应研究

为研究温度效应对连续刚构桥空心薄壁墩受力行为的影响,以(98+5×185+98)m变截面预应力混凝土连续刚构桥——三水河特大桥主桥为背景,通过现场温度场测试,研究桥墩垂直温度场和水平温度场的分布规律,并以实测温度场为依据,选取对桥墩刚度影响较大的桥墩高度、顺桥向宽度和壁厚作为关键参数,分析整体均匀温度T和梯度温度ΔT对空心薄壁墩受力的影响。结果表明:实测桥墩垂直温度场随着墩高的变化分布差异较小,水平温度场受日光照射影响较大,桥墩夏季的梯度温度值约为冬季的2倍。墩高对桥墩温度应力的影响基本呈反比关系,顺桥向宽度对墩底温度应力的影响呈线性增长趋势,壁厚与温度应力呈反比关系。对于长联刚构桥,为减小桥墩的温度效应,建议边主墩高度不宜小于60 m,桥墩顺桥向宽度宜尽量减小,桥墩壁厚宜取80~100 cm。

薄壁型钢混凝土梁抗弯性能试验研究

为研究薄壁型钢混凝土(thin-walled steel reinforced concrete,TSRC)梁试件的抗弯性能,设计制作了5根TSRC梁并进行四点弯曲试验,探究不同抗剪螺杆布置方式、截面形式、剪跨比以及混凝土保护层厚度对TSRC梁试件抗弯性能的影响。研究结果表明:TSRC梁的失效模式为薄壁钢管加载点处发生局部屈曲,外围混凝土保护层出现贯通斜裂缝,混凝土保护层沿抗剪螺杆开裂;TSRC梁试件在加载过程中未发生脆性破坏,表现出较好的延性;TSRC梁开裂荷载较小,在0.11P_(u)~0.15P_(u)之间,裂缝总数较少,稳定在6~10条;满跨布置螺杆、增大钢管截面尺寸、减小剪跨比以及增加保护层厚度均可提高TSRC梁试件的承载力。基于试验结果,建立适用于TSRC梁的极限抗弯承载力和抗弯刚度计算公式,可为该构件在实际工程中的应用提供参考。

装配式冷弯厚壁型钢半刚性梁-柱节点抗震性能试验研究

冷弯型钢在装配式结构中应用具有天然的优势,为了扩展冷弯厚壁型钢结构的使用范围,克服冷弯厚壁钢的缺点,设计6个新型分层装配式“十字型”梁-柱节点,进行循环加载试验,对梁-柱节点的破坏模式、初始刚度、骨架曲线、等效黏滞阻尼系数、能量耗散系数、割线刚度、滞回曲线和关键部位应变分布进行研究,主要得到以下结论:通过螺栓和节点板的滑移,半刚性节点具有一定的耗能能力。增设高强螺栓可以提高梁柱节点的承载力,初始刚度和耗能能力也得到提高,避免梁端与连接板孔壁承压。增加可更换节点翼缘板,对梁-柱节点的破坏模式没有明显影响,承载能力、耗能能力、初始刚度分别得到较大提高。

连续刚构箱形-双薄壁组合式主墩及其刚度匹配设计方法

文章针对因受到建设条件制约而不得不采用主墩高度相差较大的连续刚构桥梁,应用箱形-双薄壁组合式桥墩作为主墩结构,提出了对应的主墩刚度匹配设计方法,并对刚度计算过程进行了推导,得到了组合式桥墩墩顶顺桥向抗推集成刚度的计算公式,用实桥计算示例对提出的主墩设计和传统设计的结果进行了对比。结果表明,文章提出的箱形-双薄壁组合式主墩刚度匹配设计方法能有效地避免主墩高度差引起的内力不均匀分配问题,从而改善高、低主墩连续刚构桥梁在温度、制动力等水平荷载下的力学表现,提高结构的抗震性能。

冷弯薄壁C型钢-混凝土组合梁抗弯性能试验研究及有限元分析

为探究冷弯薄壁C型钢-混凝土组合梁受弯性能,制作并设计了5个不同断面组合形式的组合梁试件,并对其进行抗弯性能试验研究,分析其承载性能、破坏机理。在试验基础上,通过有限元分析软件ABAQUS对此组合梁进行非线性分析,对其进行参数分析,研究材料、尺寸对组合梁性能的影响。基于试验研究与有限元模拟分析,建立冷弯薄壁C型钢-混凝土组合梁的承载力模型,对其承载力、刚度进行理论分析。结果表明:各组合梁的主要破坏形式均属于延性破坏;采用ABAQUS建立的组合梁有限元模型能较好地模拟冷弯薄壁C型钢-混凝土组合梁的受力过程。随着C型钢屈服强度的增加,极限荷载最高提高56.5%;C型钢厚度每增加1mm,极限荷载平均提高28.5%;截面高度每增加50mm,极限荷载提高20%左右。但是提高混凝土的强度等级对组合梁的承载力影响较小;推导出了适用于此种冷弯薄壁C型钢-混凝土组合梁的抗弯承载力及其刚度计算方法,发现计算结果与试验结果吻合较好。

四边连接圆形压痕钢板剪力墙的抗侧能力分析

为合理调节或优化传统钢板剪力墙(steel plate shear wall,SPSW)的抗震性能,本文提出了一种新型的带圆形压痕的钢板剪力墙结构(steel plate shear wall with circle dents,SPSW-CD)。基于有限元方法系统研究了压痕孔径、压痕孔距、压痕深度、钢板厚度和钢材强度等参数对SPSW-CD抗侧性能的影响,提出了四边连接SPSW-CD抗侧刚度及水平承载力的简化计算公式。分析结果表明随着压痕孔径增加,SPSW-CD的初始抗侧刚度及水平承载力均呈降低趋势;压痕孔距及钢板厚度越大,SPSW-CD抗侧性能越优。随着钢材强度增加,SPSW-CD水平承载力呈明显的增大趋势,但对其抗侧刚度影响不明显。压痕深度对SPSW-CD抗侧性能的影响可忽略。SPSW-CD抗侧刚度及水平承载力计算公式计算误差均小于10%,研究成果可用于此类结构的工程设计。

地连墙内撑支护体系支撑有效刚度计算方法

针对地连墙内撑支护体系,综合考虑内支撑的初始挠曲、支撑杆件压弯二阶效应、支撑与地连墙的相互作用和地连墙变形等因素,建立内支撑的有效刚度计算方法.以北京地铁某车站基坑工程为背景,在ABAQUS有限元建模中分别引入现行规范支撑刚度和支撑有效刚度,进行基坑开挖与支护的数值模拟,并将模拟结果与实测结果进行对比分析.研究结果表明:内支撑有效刚度计算方法能更真实地反映基坑支护体系的实际受力、变形状态.

框架刚度计算方法对箱梁畸变效应分析的影响

研究了用位移法和力法计算的框架刚度对箱梁畸变效应分析结果的影响.首先分别用位移法和力法推导出了箱梁的抗畸变惯性矩解析式,然后建立了畸变控制微分方程,并给出箱梁同时承受偏心均布和集中荷载时该方程的初参数解.利用这2种解析法和有限元软件对悬臂梁模型和简支梁算例的畸变效应进行了研究.结果表明:2种解析法计算的矩形截面箱梁的畸变翘曲正应力、畸变横向正应力和畸变角一致,与实测值和有限元结果均吻合良好;2种解析法计算的梯形截面箱梁的畸变矩、畸变双力矩基本一致,与有限元结果均吻合良好,但二者计算的梯形截面箱梁的畸变角、单位宽度横向弯矩存在明显差异,其中力法计算的单位宽度横向弯矩更接近有限元结果;随着腹板倾斜度的增大,2种解析法计算的畸变框架刚度和畸变框架刚度之差均增大,而畸变翘曲刚度先减小再增大.

考虑填充墙平面刚度分布的RC框架结构抗地震倒塌能力研究

为研究填充墙对RC框架结构抗震性能的影响,以汶川地震中发生倒塌的漩口中学教学楼A为原型,基于ABAQUS软件建立了有限元模型,对结构底层各柱的剪力进行分析,发现由于填充墙的布置使得结构平面刚度分布不均,造成地震剪力在各榀框架之间分布不均匀。为了定量地考虑平面各轴线刚度分布对结构抗震性能的影响,设计了4个沿轴线各榀填充墙框架不同刚度分布的结构模型,通过IDA(增量动力分析)分析对比评估4个模型的抗地震倒塌能力。结果表明:平面刚度均匀分布的结构模型倒塌概率最低,具有良好的地震韧性;当某轴线的刚度高于平面各轴线平均刚度的30%时,结构的倒塌概率大幅提高,抗倒塌安全储备不足,建议在设计中平面各轴线的刚度不应超过此限值。

拼合式带翼缘冷弯薄壁型钢十字形构件抗扭刚度试验研究

拼合式带翼缘冷弯薄壁型钢十字形构件在轴心压力作用下的主要破坏形式为扭转失稳,其扭转失稳极限承载力取决于抗扭刚度,而拼合效应对构件抗扭刚度的影响没有明确的计算方法。为研究拼合式带翼缘十字形构件的抗扭性能及拼合效应对抗扭刚度的影响,对10个不同截面尺寸和拼合螺栓分布的带翼缘十字形冷弯薄壁构件进行了扭转试验,得到扭转全过程的扭矩-转角曲线和扭矩-应变曲线。设计了专用加载装置使构件在加载初期发生自由扭转,据此得到该拼合构件的自由扭转刚度。试验结果表明:减小螺栓间距能增强拼合效应,对于单列螺栓构件,螺栓间距的变化对拼合效应的影响更明显;拼合效应主要作用于构件的腹板,腹板尺寸增大,单位面积的螺栓数量减少,拼合效应对抗扭刚度的贡献相对减少;相较于非拼合构件,拼合构件抗扭刚度的提升可能是因为螺栓在一定程度上约束了相邻腹板的相对翘曲,提升程度可能与拼合节点间腹板的翘曲刚度有关。

某部分框支剪力墙结构等效刚度比控制分析

转换层下部结构刚度对部分框支剪力墙结构的竖向刚度规则性和地震剪力传递突变程度有较大影响,等效刚度比是衡量转换层下部结构相对刚度的重要设计指标。本文对8度区某部分框支剪力墙结构等效刚度比的控制进行分析讨论。首先,通过转换层下部结构高度线性插值对等效刚度比进行修正,其次,通过调整转换层层高和转换层下部结构剪力墙厚度两种方式,分析不同等效刚度比对结构整体指标、构件受力和结构整体抗震性能的影响。结果表明,等效刚度比越大,转换层与其上一层的层间位移角比和有害层间位移角比越小,等效刚度比小于1.0时,转换层与其上一层的有害位移角比突变增大;设置转换层对转换层以上3层的地震剪力分配产生了较大影响;框支框架的相对刚度比越大,水平力传递突变程度越小;随着等效刚度比增加,结构主要屈服部位由结构底部转移至转换层以上部位。

HDPE双壁波纹管-CIPP内衬复合结构受力特性研究

原位固化法(CIPP)可用于修复高密度聚乙烯(HDPE)双壁波纹排水管,但目前没有合适的模型来量化评估修复后整体结构的承载特性,修复设计无据可依。为此,首先基于叠合曲梁模型和复合曲梁模型对修复结构整体的受力特性进行理论分析,然后结合室内平板荷载试验对理论模型开展验证分析,最后通过室内土箱试验研究,探明了CIPP内衬对既有管道承载能力的提升作用,揭示了复合结构的破坏模式,以及既有管道的椭圆缺陷对CIPP修复效果的影响。研究结果表明:(1)自然固化CIPP内衬体系应采用叠合曲梁模型,紫外光固化CIPP内衬体系应采用复合曲梁模型;(2) CIPP内衬-柔性管道复合结构在外荷载作用下可能发生界面剥离,导致承载能力和刚度降低;(3) CIPP内衬可以提高复合结构的环刚度,增强其抵抗外荷载的能力,有效降低土体承受的荷载,减小土体变形程度。研究成果可为HDPE双壁波纹管的CIPP修复设计提供数据支撑。

高层框架剪力墙隔震结构剪力墙合理刚度研究

针对高层框架剪力墙隔震体系,基于隔震层上部框架剪力墙协同工作原理,建立了高层框架剪力墙基础隔震结构在倒梯形荷载作用下的简化模型,推导了倒梯形荷载作用下结构的最大层间弹性位移角表达式。采用弯剪型三质点模型,进一步推导了三质点模型的质量矩阵和柔度矩阵,利用振型分解反应谱法,根据底部剪力相等原理,得到了以层间位移角为限值约束条件下的剪力墙合理刚度表达式。提出了高层框架剪力墙隔震体系的剪力墙合理刚度交互设计方案。最后以一栋12层的框架剪力墙隔震结构为数值算例,按照剪力墙合理刚度的理论推导和交互设计方案,进行剪力墙合理刚度的计算和设计,通过数据分析验证了本文提出的算法和设计方案是可行的,可以为结构设计提供参考。

混凝土结构设计中常见的稳定问题

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