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圆端形钢管混凝土柱局压力学性能研究
Local Compression Mechanical Properties of Circular-ended Concrete-filled Steel Tubular Columns
刘华东;汤永强; LIU Huadong;TANG Yongqiang;采用有限元软件ABAQUS对圆端形钢管混凝土柱局压力学性能及受力机理进行数值模拟,对试件受力全过程、接触力及参数进行分析。结果表明:同一截面钢管圆弧段相比平直段约束作用更强,接触力更大,且自端部向下,截面各点处的接触力逐渐减小;当局压面积比由1.44分别增大至4、9、16时,圆端形钢管混凝土柱局压承载力分别降低33.6%、54.7%、66.1%;钢管屈服强度由235 MPa增加至345、390、420 MPa时,试件刚度无明显变化,局压承载力分别提高33.7%、47.3%、56.4%;当混凝土立方体抗压强度由30 MPa分别增加至35、40、45、50 MPa时,试件刚度逐渐增大,局压承载力分别提高2.2%、4.1%、6.4%、11.2%;含钢率由0.05增加至0.1、0.15、0.2时,试件刚度增大,局压承载力分别提高57.7%、114.6%、165.3%。
A numerical simulation of the local compressive mechanical properties and force mechanism of concrete-filled steel tubular(CFST) columns with rounded ends was conducted using the finite element software ABAQUS.The entire loading process,contact forces,and relevant parameters of the specimens were analyzed.The results indicate that,within the same cross-section,the circular arc segment of the steel tube provides stronger confinement and experiences greater contact forces compared to the straight segment.Moreover,the contact forces gradually decrease from the end downwards along the column.When the local compressive area ratio increases from 1.44 to 4,9,and 16,the local compressive bearing capacity of the CFST columns with rounded ends decreases by 33.6%,54.7%,and 66.1%,respectively.As the yield strength of the steel tube increases from235 MPa to 345,390,and 420 MPa,there is no significant change in the stiffness of the specimens,but the local compressive bearing capacity increases by 33.7%,47.3%,and 56.4%,respectively.When the compressive strength of the concrete cube increases from 30 MPa to 35,40,45,and 50 MPa,the stiffness of the specimens gradually increases,and the local compressive bearing capacity improves by 2.2%,4.1%,6.4%,and 11.2%,respectively.As the steel ratio increases from 0.05 to 0.1,0.15,and 0.2,the stiffness of the specimens increases,and the local compressive bearing capacity enhances by 57.7%,114.6%,and 165.3%,respectively.
基于标准球的直线运动2D激光雷达标定
Linear Moving 2D LiDAR Calibration Based on Standard Sphere
刘昶;罗寅;王彦博;孙丽梅; LIU Chang;LUO Yin;WANG Yanbo;SUN Limei;在利用安装在直线运动机构上的2D激光雷达对场景进行3D扫描任务中，需对2D激光雷达的运动方向提前标定，针对该标定问题提出一种以已知直径的标准球作为标定装置的标定方法。首先利用激光雷达在直线运动机构上的不同位置对标准球进行扫描，利用扫描点和最小二乘法拟合扫描圆的方程，估计出球心在雷达坐标系下的坐标，得到雷达运动方向的初步估计；再以所有扫描点共球面作为约束，通过一个迭代过程对运动方向进行优化，得到标定的最终结果。真实实验中采用篮球作为标准球标定装置，对安装在直线运动机构上的2D激光雷达进行标定，结果显示扫描点到拟合的球面距离的平均误差为0.75 mm；采用相同装置对已知尺寸的长方体仪表箱进行测量实验，得到仪表箱高度的误差为0.13mm，角度的平均误差为0.87°，验证了本文方法的有效性。
In the 3D scene scanning task using a 2D LiDAR(light detection and ranging) mounted on a linear motion mechanism， the moving direction of the 2D LiDAR needs to be calibrated in advance. To address the calibration problem， a method using a diameter known standard sphere as calibration instrument was proposed. Firstly the standard sphere was scanned by the LiDAR at different positions of the linear motion mechanism. The coordinates of the sphere center in the LiDAR frame were estimated by fitting the scanning circle equation by Least Square Method using the scanning points. Then the moving direction was estimated initially. Secondly using the constraint that all scanning points were on the sphere， the moving direction was optimized by an iterative process. Then the final calibration results were obtained. In the real experiment， a basketball was used as the standard sphere calibration instrument. A 2D LiDAR mounted on a linear motion mechanism was calibrated using the proposed method. The results showed that the average error of the distance among the scanning points and the fitted sphere was 0.75mm. Using the same device to measure a size known cuboid instrument box， the results showed the height error of the box was 0.13mm， and the average angle error was 0.87°. The experimental results verified the effectiveness of the proposed method.