Research on the mechanical properties of the castellated lightweight steel portal frame

Transcription

1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Research on the mechanical properties of the castellated lightweight steel portal frame Yisheng Su 1, a, Qiliang Li 1,b, Yibin Yang 1,c, Xianghua Chen 2,d 1 College of Civil Engineering and Architecture, Guangxi University, Nanning , China 2 XingJian college of Science and Liberal Arts, Guangxi University, Nanning , China a suyisheng@sina.com, b feel1986@126.com, c yangtuobaye@163.com, d yangyu840301@163.com Keywords: Castellated component, portal frame, bearing capacity, rigidity. Abstract. Based on the ANSYS, castellated lightweight steel portal frames are modeled to analysis the stress destruction process and stress distribution rule under horizontal and vertical loads. The comparative analysis with the original solid-webbed portal frame in yield load, ultimate load, the mid-span deflection is pursued. The results show that: there are some differences in failure mode between the castellated lightweight steel portal frame after expansion and the original solid-webbed portal frame. The former bearing capacity and rigidity increase by a large scale than the latter. Introduction A Castellated steel component (castellated steel beam and castellated steel column) has the following characteristics: reasonable section forms, high bearing capacity, large bending rigidity, beauty and significant economic benefits. Castellated steel beam can be used as frame beam, platform beam, hydraulic steel gate and the steel beam of the steel-concrete composite structure, etc. At present, research and application on castellated steel beam are more and more mature at home and abroad [1,2]. Based on ANSYS, single-layer single-span castellated lightweight steel portal frame is proposed. One of the main researches is the castellated portal frame s bearing capacity, deflection and other features under horizontal and vertical loads simultaneously. The other is the comparative analysis between the castellated lightweight steel portal frame and the original solid-webbed portal frame. Finite element analysis model The frame models in this article [3] take three different kinds of span into account. Circular hole is used in castellated beam and castellated column, designed with the production method in the literature [4].The circular-hole radius is 182.4mm, hole s spacing is 116.8mm and the center distance of circular hole is 481.6mm. The dimensions of the original solid-webbed portal frames are shown in Tab.1. The castellated portal frames whose the dimension shown in Tab.2 obtain by expanded the original solid-webbed portal frame columns and beams at the ratio of The schematic diagram of section of solid-webbed component and castellated component are showed in Fig.1. Tab.1 Dimension of the solid-webbed portal frames Number Node connections Height SFMJ-1 rigid solid-webbed columns h b t w t(mm) solid-webbed beams H b t w t(mm) Span SFMJ-2 rigid SFMJ-3 rigid Notes: h- Section height of solid-webbed component; b- Flange width of solid-webbed component; t w -Web thickness of solid-webbed component; t-flange thickness of solid-webbed component. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-21/02/16,07:29:15)

2 1268 Advances in Civil Engineering and Architecture Number Node connections Tab.2 Dimension of the castellated portal frames Height castellated columns castellated beams h b t w t(mm) H b t w t(mm) FWMJ-1 rigid FWMJ-2 rigid FWMJ-3 rigid Notes: h- Section height of solid-webbed component; b- Flange width of solid-webbed component; t w -Web thickness of solid-webbed component; t-flange thickness of solid-webbed component. The castellated portal frame model is shown in Fig.2. The joint of the left and right column foot is rigid connect. Four stiffeners, whose thickness is equal to that of the beam flange, are set in contract area between beams and columns (shown in Fig.3). Span (a) solid-webbed I-shaped section (b) castellated beams empty web section Fig.1 Schematic diagram of sections SHELL181 three-dimensional 4-node shell element shell in ANSYS element library is used to model [5-7]. Mapped meshing is used in the flange of beams and columns, and free meshing is used in the web. In order to consider the problem of stress concentration, the units in the orifice edge partly are refined (shown in Fig.4). Considering the geometric and material nonlinearity, the influence of welding residual stress of the web in the modeling process is neglected. The material is isotropic. Modulus of elasticity is 206,000MPa. Yield stress is 235MPa. Poisson s ratio is 0.3. Steel density is 7850kg/m 3. Steel is set as perfectly plastic material, subjecting to Misses yield criterion. q 3kN/m 2kN/m Fig.2 Castellated portal frame Fig.3 Region of node Fig.4 Meshes in ANSYS Loading process analysis of castellated frames FWMJ-1: First, wind load of 3kN/m on the left column and 2kN/m on the right column are imposed respectively. And then, vertical uniform load is imposed on frame s beam gradually. When the load on frame s beam is up to 9.152kN/m, the area in five o clock and twenty minutes direction of the first hole edge on the left of the castellated beam reaches the yield strength first (shown in Fig.5). Then, beam deflection of the mid-span is 82.6mm, and column cap s displacement is 18.85mm. After 9.776kN/m, the area in six o clock and forty minutes direction of the first hole edges on the right of the castellated beam reach the yield strength.as the load is up to kN/m, the area in two o clock and fifty minutes direction of the first hole edge on the top reaches the yield strength. While the load on frame s beam is up to 12.48kN/m, yield region including several hole edges in the mid-span of beam and column caps extend to the flange (shown in Fig.6, Fig.7). At the same time, equivalent stress in the joint region is about 200MPa.

3 Advanced Materials Research Vols Fig. 5 Equivalent stress around 1st circular hole of the left end of beam under yield load Fig. 6 The stress in top flange of beam Fig. 7 Equivalent stress on top inside flange FWMJ-2: The loading method is same to FWMJ-1. When the load on frame s beam is up to 5.624kN/m, the area in eight o clock and fifty minutes direction of the first hole s edge on the top of the right castellated column reaches the yield strength first. Then, beam deflection of the mid-span is 97.83mm, and column cap s displacement is 19.6mm. As the load is up to 6.993kN/m, the area in three o clock and ten minutes direction of the first hole s edge on the top of the left castellated columns reach the yield strength. After 7.144kN/m, the area in six o clock and fifty minutes direction of the first hole edge on the right of the castellated beam reaches the yield strength. Yield region appear in the area of several hole edges in the mid-span of beam and column caps, and part of them extend to the flange, when the load is up to ultimate load 7.448kN/m. At the same time, equivalent stress in the joint region has not yet reached the yield strength. FWMJ-3: The loading method is same to FWMJ-1. When the load on frame s beam is up to 4.811kN/m, the area of nine o clock direction of the first hole edge on the top of the right castellated column reaches the yield strength first. Then, beam deflection of the mid-span is mm, and column cap s displacement is 20.2mm. As the load is up to 5.749kN/m, the area of three o clock and ten minutes direction of the first hole edges on the top of the left castellated columns reach the yield strength. After 6.336kN/m, yield region appear in the area of several hole edges in the mid-span of beam and column caps, and part of them extend to the flange. From the stress development process of the castellated lightweight steel portal frame above, conclusion can be drawn as follows: the yield point of the castellated frame appears in the first hole edge of beam ends and column cap. With the load increasing, several hole edges of beam ends and column cap appear yield area and the yield area expends to the flange gradually, after ultimate load, there are several areas from circular hole edges to the flange of the beam and column yield. But the largest equivalent stress in the joint region has not yet reached the yield strength. From the loading beginning to ultimate load, the curve of beam deflection and column cap displacement show the linear growth basically. Mechanical properties of two portal frames forms To further analyze mechanical properties of the castellated portal frames, the ultimate bearing capacity, mid-span deflection and the lateral displacement of the original solid-webbed portal frame in the same height, span, load form and constraint condition are analyzed. All of SFMJ-1 SFMJ-3 first yield in the node field, and then the yield area expands with the load increasing. When the flange and some web of the mid-span cross-section of the beam yielded, portal frame damaged. Bearing capacity comparison. Yield load and ultimate load comparison (shown in Table.3) between the castellated and original solid-webbed portal frames which are simultaneously bearing load of uniformly distributed load on beam and column. Results in Table.3 show that, compared with the yield load and the ultimate load of original solid-webbed portal frame, those of the castellated portal frames have sharply increased. The yield load increases by 41% - 52% and the ultimate load increased by 42% - 54%.

4 1270 Advances in Civil Engineering and Architecture Table.3 Bearing capacity comparison between the castellated and solid-webbed portal frames Number FWMJ-1 SFMJ-1 FWMJ-2 SFMJ-2 FWMJ-3 SFKJ-3 Span Yield load 1(kN m -1 ) Increase the percentage of yield load (%) Ultimate load (kn m -1 ) Increase the percentage of ultimate load (%) Notes: Yield load is the vertical load imposed on the structure when the first yield of the structure appear. Mid-span deflection and lateral displacement comparison. All the load mid-span deflection curve and load lateral displacement curve of the castellated portal frame and the original solid-webbed portal frame are shown in Figs. 8 and 9 respectively. Since the cross-section rigidity of beam and column of the castellated portal frame has increase considerably compared with that of original solid-webbed portal frame, the mid-span deflection decrease by 57% - 61% under horizontal and vertical uniformly load, and the castellated frame lateral displacement of column growth is slow and linear, while the original solid-webbed is quick and increases faster beyond yield load. Conclusions Based on ANSYS, under the horizontal and vertical uniformly load force on beam and column simultaneously, the single-layer single-span castellated portal frame and original solid-webbed portal frame are simulated and analyzed in order to study their mechanical properties. From the result of this study, the following conclusions can be drawn: Under the horizontal and vertical uniformly load force on beam and column simultaneously, the castellated portal frame yield at the first circular hole edge of either ends of the beam or the column cap. With load increasing to ultimate load, several areas between circular hole edge and the flange of the beam and column (the region of the beam-bridge) yield, while the maximum equivalent stress of the node region has not reached the yield strength yet. What is noteworthy is that, the first yield shifts from circular hole edge of the beam to the inside edge of the column cap with the span increasing. As for the original solid-webbed, first yield appears at the region of the complicated force field and both

5 Advanced Materials Research Vols node region and the mid-span cross-section of the beam have a larger of the range in yield under the ultimate load. Compared with the ultimate load and the yield load of original solid-webbed portal frame, that of the circular hole castellated portal frame improve greatly. The yield load increases by 41% - 52% and ultimate load increases by 42% - 54% as well. The lateral displacement of the column cap and the mid-span deflection of the beam are much smaller than the original solid-webbed frame, which reduces by 57% - 61%. The main reason of this result is that castellated components which get from the unique way to produce have great improved in section s rigidity. Therefore, to promote the use of castellated components to lightweight steel portal frame will bring economic benefit significantly. From the analysis of the failure process, the stress distribution rule and failure mode have been studied about the castellated portal frame, the circular holes which are near the ends of the beam, mid-span and column cap are prone to damage. Therefore, to take some certain measures to reinforce the region at the ends of beam and column will make the bearing capacity of castellated portal frame further improve in practical projects. Acknowledgment The authors would like to thank the Science Foundation of Guangxi (NO ), for their generous support to the research projects. References [1] Yisheng Su. The experiment and analysis of the circular and polygon holes honeycombed steel beams [J]. Journal of Guangxi University (Nat Sci Ed), 2003, 28(1):5-9. In Chinese. [2] Wen Huang, Qiangang Chen. Elasto-plastic Behavior Analysis of Castellated Beams [J]. Journal of Chongqing University (Natural Science Edition), 2006, 29(4): In Chinese. [3] Xianghua Chen. Finite element analysis of the mechanical properties for the castellated portal frame of light-weight steel [D]. Nanning: Guangxi University College of Civil Engineering & Architecture, In Chinese. [4] Yisheng Su. Study on the Application of Steel Castellated Beams [D]. Nanning: Guangxi University College of Civil Engineering & Architecture, In Chinese. [5] Tan Yang, Xiyuan Sun, Liangping Liao. Load characteristics analysis of the circular hole castellated beam based on ANSYS [J]. Journal of Guangxi University (Nat Sci Ed), 2006, 31(4): In Chinese. [6] Yisheng Su, Xingguo Yu, Feng Liu, Xianghua Chen. Analytical studies bearing capacity of two models for cellular steel column [J]. Journal of Guangxi University (Nat Sci Ed), 2009, 34(3): In Chinese. [7] Yisheng Su, Xiang Lin, Yilu Wu. Research on the mechanical properties of light-weight castellated portal steel frame [J]. Journal of Guangxi University (Nat Sci Ed), 2011, 36(1): In Chinese.

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