Structural Behaviour of Single Layer Space Frame with Member Arrangement Following Spiral Phyllotaxis

Choong, Kok Keong,Kim, Jae Yeol Trans Tech Publications, Ltd. 2013 Advanced materials research Vol.842 No.-

<P>The regular arrangement of the plant organs is botanically known as phyllotaxis. Among the types of phyllotaxis found in nature, spiral phyllotaxis is the most frequently found pattern. The unique arrangement of this pattern in plants has benefited most of the plant structure as it enables them to grow more efficiently and compatible for physical constraints such as moisture and amount of light falls. In this research, the unique spiral phyllotaxis pattern has been adopted as idea for member arrangement pattern for structural space frame system. Two type of spiral phyllotaxis pattern and one regular model are generated. Analysis using finite element software LUSAS has been carried out in order to determine the effect of member arrangement following spiral phyllotaxis on stresses and displacement in the space frames.</P>

Linear Form Finding Approach for Regular and Irregular Single Layer Prism Tensegrity

Mohammad Moghaddas,Kok Keong Choong,김재열,강주원 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.5

In an irregular prism tensegrity, the number of force equilibrium equations is less than the number of unknown parameters of nodal coordinates and member force ratios. As a result, the form-fi nding process normally becomes nonlinear with additional conditions or needs to be carried out with the use of iterative procedures. For cases of irregular prism tensegrity which involves large number of members, it was found that previously proposed methods of form-fi nding are not practical. Moreover, there is a need for a form-fi nding approach which is able to cater to diff erent requirements on fi nal confi guration. In this paper, the length relation condition is introduced to be used in combination with the force equilibrium equation. With the combined use of length relation and equilibrium conditions, a linear form-fi nding approach for irregular prism tensegrity was successfully formulated and developed. An easy-to-use interactive form-fi nding tool has been developed which can be used for form-fi nding of irregular prism tensegrities with large number of elements as well as under diverse specifi c requirements on their confi gurations.

Finite Element Analysis of Buckling Behavior for Cold-Formed Steel Hat Purlins with Openings

Fatimah De’nan,Kok Keong Choong,Jin Ying Ling,Nor Salwani Hashim 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.4

In urban building design, introducing openings in the webs of structural members allows the fl exible installation of ductwork and piping. This study investigated the eff ects of the shape, location, and spacing of web openings on the buckling behavior of cold-formed steel hat purlins. Eigenvalue analysis shows that the existence of web openings reduced the buckling moment of a section by up to 24%. The shape and location of the web openings also aff ected the buckling behavior. In particular, the buckling moment decrease when the web opening was located at mid-span. It was found that, the buckling moment increase when the web opening spacing increases. The section with diamond web openings shows the highest buckling moment and the section with elongated circle openings shows the smallest buckling moment compared to other web opening shapes. The results of this study should provide guidance on hat purlins with openings design to meet structural performance requirements.

Perforation Effect on the Bending Behaviour of Cold-Formed Steel Hat-Purlin Section

Fatimah De’nan,Kok Keong Choong,Jin Ying Ling,Nor Salwani Hashim 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.1

Many structural members, for example, cold-formed steel members, hot-rolled steel members, and composite beams were extensively used in steel construction due to economic development in cities building design. This was to allow fl exible installation of ductwork, piping and other systems. Substantial research has been performed on Channel and Zee cold-formed steel sections, but the papers on Hat section steel purlins turned out to be few only, especially Hat-purlin with perforations. Hence, numerical study on cold-formed Hat section steel purlin with perforation was carried out to investigate the eff ect of perforation to bending behaviour of such sections. Finite element method using LUSAS software was chosen to carry out the research study. Five diff erent perforation shapes were selected, which were circle, diamond, C-hexagon, square and elongated circle. Perforation depth was fi xed at 0.5D2, where D2 is the inclined web depth of the section. The results showed that perforated section had lower bending moment than that of the section without perforation, with a percentage diff erence of not more than 4%. Most of the perforated sections had similar bending characteristic despite of the diff erence in perforation shapes, where the yield moment diff erence was less than 2%. Critical opening length played a crucial role in aff ecting the bending behaviour of section. Furthermore, the location of perforation also infl uenced the bending behaviour of Hat-purlin. Regardless of perforation spacing, the perforated sections with equal number of perforations behaved similar elastic characteristic before yielding. Section with diamond perforation had higher bending moment than other perforated section whereas section with elongated circle perforation had the lowest bending moment. The presence of perforations gives minor eff ect on the bending behaviour of cold-formed steel Hat-purlin.

Prediction of Ultimate Torque of Reinforced Concrete Box Beam Bonded with CFRP Strips

Shengqiang Ma,N. Muhamad Bunnori,Kok Keong Choong 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11

One control and three strengthened Reinforced Concrete (RC) beams with box-section were subjected to pure torsion. The proposed strengthening schemes were U-jacketing or U-jacketing with longitudinal strips of fiber-reinforced polymer (CFRP). The U-jacketing strips exhibited a reasonable improvement to the ultimate torque from the experimental investigation. The CFRP strengthening schemes, failure modes, cracking angles, and strain in fibers were investigated and recorded. Besides, three models used for computing the torque of RC members and two for FRP torsional contribution were carefully reviewed and discussed. Based on these models, six combinations were formed by the two-part models addition for predicting the torsional capacity of the strengthened members. The database of 25 strengthened beams was collected from the literature for evaluating prediction of the ultimate torque of the specimens by these six combinational models. In comparison with the laboratorial numbers of the ultimate torque of specimens, the combination of Comb 2 (ACI and fib Bulletin 14 models) and Comb 6 (Chinese and Ghobarah models) presented rational prediction in the ultimate torque of retrofitted beams. However, Comb 6 is a more suitable combination for calculating the ultimate torsional capacity of strengthened beams with rectangular or box-section by FRP entirely wrapping or Uwrap.

Models Reviewed for Predicting CFRP Shear Contribution of Strengthened Reinforced Concrete Box Beam

Shengqiang Ma,N. Muhamad Bunnori,Kok Keong Choong,Rui Zhao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.8

Eight various models for calculating the FRP (fiber-reinforced polymer) contribution to shear from different codes and studies were reviewed and discussed. From all the models, it is found that the effective strain is the most important parameter which lies in all equations except JSCE model. Besides, the six models from guidelines and two from latest literature with different parameters were discussed and applied for calculating shear contribution of 181 FRP shear strengthening specimens collected from existing literature. It reveals that all ratios of calculation related to experimental results showed distributions around the bisector in all equations of models. From the values of total members, the predictions of FRP shear contribution of the beam with a T-section or rectangular section using two models (fib Bulletin 14 and Sayed et al.) were very close to the experimental values and also stood safe sides. Furthermore, one control and four strengthened reinforced concrete (RC) box beam by carbon fiber-reinforced polymer (CFRP) were tested for shear strength. Compared with the experimental results, all theoretical values predicted by the reviewed models overestimated the FRP shear contribution of strengthened members, because the effective strain was overestimated. A coefficient of 1.31, therefore, was also proposed, which divided the formula of the effective strain in the fib Bulletin 14 model according to the experimental effective strain in fiber. The model with the modified effective strain presented a rational prediction in CFRP shear contribution of strengthened RC box beams.