EWM-based design method for distortional buckling of cold-formed thin-walled lipped channel sections with holes

<abstract> <p>The distortional buckling is easy to occur for the cold-formed steel (CFS) lipped channel sections with holes. There is no design provision about effective width method (EWM) to predict the distortional buckling strength of CFS lipped channel sections with holes in China. His aim of this paper is to present an proposal of effective width method for the distortional buckling strength of CFS lipped channel sections with holes based on theoretical and numerical analysis on the partially stiffened element and CFS lipped channel section with holes. Firstly, the prediction methods for the distortional buckling stress and distortional buckling coefficients of CFS lipped channel sections with holes were developed based on the energy method and simplified rotation restrained stiffness. The accuracy of the proposed method for distortional buckling stress was verified by using the finite element method. Then the modified EWM was proposed to calculate the distortional buckling strength and the capacity of the interaction buckling of CFS lipped channel sections with holes based on the proposal of distortional buckling coefficient. Finally, comparisons on ultimate capacities of CFS lipped channel sections with holes of the calculated results by using the modified effective width method with 347 experimental results and 1598 numerical results indicated that the proposed EWM is reasonable and has a high accuracy and reliability for predicting the ultimate capacities of CFS lipped channel section with holes. Meanwhile, the predictions by the North America specification are slightly unconservative.</p> </abstract>

Experimental Study and Proposal to Improve the EWM Design of Cold-Formed Steel Lipped Channel Columns with Circular Holes under Axial Compression

The cold-formed steel (CFS) lipped channel section with circular holes has been widely used in low-rise and multistory building structures as the column. However, the circular hole in the web makes the lipped channel column become susceptible to buckle. A total of 54 CFS lipped channel axial compression columns with and without circular holes were used to study the buckling behavior and the effective width design method. The interaction of the local buckling and the distortional buckling were observed for the short and intermediate columns, while the slender columns were controlled by the interaction of the local buckling, distortional buckling, and flexural buckling or flexural-torsional buckling. The experimental failure loads were gradually decreased with the increase in the diameter of the circular hole for the specimens with the same section. The failure loads of the specimens with two holes were lower than those of the specimens with one hole with same section and same diameter of holes. Then, the experimental results were used to validate a nonlinear finite element model (FEM) previously developed by the authors. The validated FEM was subsequently used to obtain additional 36 numerical failure results concerning the effects of the length, the section, and the diameter and the number of the circular holes. Furthermore, the proposal to calculate the distortional buckling coefficient of the CFS lipped channel section with circular holes were put forward based on numerical analysis considering the reduction of effect of holes. Finally, a proposal to improve the effective width method (EWM) design approach for CFS lipped channel sections with circular holes under axial compression was presented. The comparisons between experimental and numerical capacities and their calculations provided by the proposed EWM design method illustrate a great application of the proposed approach.

Study on the Performance of the Hydraulics System Planning of Swampy Irrigation Area of Dadahup, Kapuas District, Central Kalimantan Province

Swampy Irrigation Area (DIR) Technical Implementation Unit (UPT) Dadahup is a swampy irrigation area that needs serious handling of flood control. This flood is resulting in crop failure in several blocks. Furthermore, the malfunctioning of the main gates in controlling the entry and exit of water resulted in a long-standing inundation for the land. This paper presents the hydraulic system of the irrigation network of DIR UPT Dadahup by reviewing secondary data and documentation of field observations. Based on these parameters, the authors simulate the main primary channel using HEC-RAS to perform hydraulic analysis. The flow simulation results show that water entering the land inundated the three canal segments. One has the highest embankment elevation of 1,778 m, with the highest tide on the channel section of 2.25 m. Other results showed that water entering the land also inundated one channel section. The highest embankment elevation was 1,233 m, with the highest tide on the channel section being 1.4 m. From these results, the overflow of water was then eliminated by the heightening of the embankment.

Research on the Characteristics of Turnout Flow Based on the Eccentricity Index of Maximum Flow Velocity

On the one hand, the characteristics of the turnout flow in the river are related to the stability of the turnout flow, and on the other hand, it is related to the safety of the flowing buildings near the bend turnout river. To observe the characteristics of the flow field in the chaotic river, the open channel surface layer digital particle image velocity (DPIV) system is used to measure the data in the physical model of the curved turnout river, and the maximum flow eccentricity (MFE) of the channel section is established. The flow pattern of the turnout flow is analyzed. The results show that the MFE index can effectively evaluate the flow pattern of the turnout flow. The MFE of the upper stream section of the curved river changes with the sudden change position of the flow between twice to 3.5 times the water surface width from the center point, and moves upstream with the increase of the flow rate, and moves downstream with the increase of the water level. This characteristic has guiding significance for the adjustment of the flow pattern of the front pool of the building.

Vane induced two phase flow mixing

Micromixers are used for mixing of multiphase fluids in microchannels. Passive micromixers help in mixing of fluids by having a designed periphery in their structure. In the current study, a Y micro-channel section of 25 mm length with an inlet diameter of 2 mm is considered. Vane shaped micromixers are placed inside the channel to mix fluids of two different concentrations. The vanes are positioned at specific places inside the channel to enhance mixing in the stratified flow stream. The presence of vanes during the flow induces mixing of the stratified fluids without requiring additional components. The study is carried out using COMSOL Multiphysics. The mixing index increases with increase in the number of vanes and no considerable change in velocity is observed downstream of the last vane. Further, when the thickness of the vane is increased, it is found that the mixing index also increases.