Optimal depth selection of composite tubular-floor trusses based on cost estimation
Authors : Hashem AlHendi, Mohammad Mahmoud and Murude Celikag
Abstract : The significance of this study initiates from the need to produce a selection guidance on the span range, span-to-depth ratio and scheme of the composite floor truss system to provide optimum performance and cost effectiveness for a particular application area. With this objective a parametric study was designed, based on three parallel chord trusses (Pratt, Howe, and Warren) using Rectangular Hollow Structural Shapes, a constant panel size of 2.5 m, four composite floor European-profiles and a range of load intensities. Hence, the span-to-depth ratios, RS/D, and dead-to-live load ratios, RDL/LL, were ranged from 3 to 27 and 0.84 to 3.22, respectively, for each truss type. The optimization was performed by using the design results of RFEM (2018) software for approximately 675 composite floor trusses with the objective of selecting optimal depth for each truss model. In addition, this paper attempts to introduce a cost function by considering the material, fabrication and painting costs and comparative figures allowing the design to be tailored with a focus on cost reduction. Accordingly, for all truss types, span-to-depth ratio of 9 to 12 with a span range of 7 to 23 m provides the most cost effective solution. Structural steel and the welding process are the two parameters that are found to have the highest impact on total cost
Keywords : composite floor truss, cost function, Howe, optimization, Pratt, Warren
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An experimental investigation into improving the performance of thermoelectric generators
Authors : Ali Alahmer, Mohammad Bani Khalid, Nabil Beithou, Gabriel Borowski, Sameh Alsaqoor, H. Alhendi
Abstract : Low-temperature heat sources have become increasingly popular in recent years, particularly for energy generation. The majority of thermal devices in the market (including devices using solar energy, geothermal energy, waste energy, and so on) transform heat into electricity indirectly, requiring mechanical work before producing power. Through the Seebeck effect, the technology that employs a thermoelectric generator (TEG) may directly transform heat energy into electricity. The TEG technology provides several advantages, including compactness, quietness, and the absence of moving components. TEGs have a low thermal and electrical efficiency, which is one of their main drawbacks. Therefore, the performance of a thermoelectric generator is improved by employing liquid evaporation heat transfer in this manuscript. The performance of the thermoelectric was examined experimentally and compared to the liquid evaporation mode under varied heat flux values and different modes of heat transfer in terms of free and forced convection with and without fins. The experimental results revealed that when compared to free convection without fins, adopting forced liquid evaporation convection would improve TEG voltage variation by 435.9%.
Keywords : thermoelectric generator, liquid evaporation, TEG performance, enhancing power generation, waste energy harvesting
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Numerical study of top-and seat-angle with double web-angle connection with high-strength steel
Authors : H. AlHendi, M. Mahmoud, M. Celikag
Abstract : Past experimental research on top-and seat-angle with double web-angle connection (TSACW) was limited by the rate and magnitude of actuator displacement and hence results did not give information on failure mode and ultimate capacities of connection. Furthermore, extensive literature review on TSACW revealed the need for developing an accurate finite element approach to represent the characteristics of the moment-rotation behavior. Therefore, this study examined the influence of connection parameters on flexural resistance, stiffness, rotation, ductility and failure modes obtained for such joints. Explicit Finite element (FE) analyses of connection models were carried out by using ABAQUS/CAE to explore the effect of material properties of bolts and angles on moment-rotation (M-ϕ) characteristics of TSACW under monotonic loading. Applicability of six currently available M-ϕ functions was assessed by comparing them with those obtained from FE analyses. In most cases, the ultimate flexural resistance of TSACW was increased whilst its rotational capacity was decreased with the use of A572 or A514 angles with less pronounced effect on the initial stiffness. The connection failure was controlled via large deformations achieved by the top angle. Among the six selected M-ϕ functions, Richard-Abbott model was found suitable for fitting the normalized moment-rotation curves for TSACW joints.
Keywords : Top-and seat-angle with double web-angle connection, HSS, Moment–rotation curve, Finite element analysis, ABAQUS/explicit, Richard-Abbott model
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Numerical investigation on the moment-rotation relationship of high strength steel semi-rigid connections
Authors : Hashem Al Hendi and Mohammad Adeeb Mahmoud
Abstract : The significance of this parametric study initiates from the need for further understanding of the behaviour of semi-rigid connections with high-strength steel components. This research attempted to gain a qualitative understanding of the influence of the material properties on the response of three types of semi-rigid connections: flush end-plate, top and seat angle and top and seat with double web angles. Hence, ABAQUS (v.6.17) software was used to develop three-dimensional (3-D) FE models. The FE models with different parameters drawn from previous experimental studies were generated in order to evaluate the effectiveness of this approach. Issues related to the stiffness, strength, sources of deformability, rotational capacity and failure mechanisms of joints were emphasized. In most cases, the use of HSS angles or HSS end-plate led to significant increase in moment capacity. Higher initial stiffness values were observed, especially when thick angles and plates were used. However, a decrease in rotational capacity of HSS joints was encountered.
Keywords : High-strength steel, Finite element analysis, Moment–rotation curve, Flush endplate, Top and seat angle, Top and seat with double web angles
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Finite element prediction of reverse channel connections to tubular columns behaviour
Authors : H. Alhendi and M Celikag
Abstract : This paper attempts to introduce a standardized moment-rotation function for reverse channel flush end-plate connection (RCC). This function is expressed in terms of the geometric parameters for the purposes of either predicting the connection behavior or incorporating the behavior into a frame analysis computer program. With this objective a parametric study was carried out, based on modeling of 140 RCC under monotonic loading by using the general finite element package ABAQUS. Out of the six currently available functions, the Kishi–Chen and Richard–Abbott models were proved appropriate for fitting experimental M–/ data for RCC. The two functions were successfully used in this parametric study to express the relationships for 140 specimens, where the analytical and predicted data are in very good agreement. However, the results of the fitted functions indicate that the dimensionless form of Richard–Abbott function provides more accuracy than Kishi–Chen function. Furthermore, the comparison of Eurocode 3 model with numerical M–/ curves illustrated a significant overestimation of the knee region behavior for most of the cases, particularly for RCC with low initial stiffness.
Keywords : Reverse channel, Tubular column, Moment–rotation curve, Standardized function, Kishi–Chen and Richard–Abbott
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Behavior of reverse-channel and double-reverse-channel connections to tubular columns with HSS
Authors : H. Alhendi and M Celikag
Abstract : This paper reports on the possible achievements on moment–rotation (M–ϕ) characteristics of reverse channel flush end-plate connections (RCC) by using HSS reverse channel under monotonic loading. It also introduces a double reverse channel connection (DRCC), where the reverse channel is split into two pieces, by leaving a gap in between, for better access to bolts. The investigations were based on parametric studies performed by using a general finite element package ABAQUS. In most cases, the use of HSS reverse channel led to noticeable increase in ultimate flexural resistance and the rotational capacity of RCC and DRCC. The key for the failure of RCC was the ratio of wall thickness of channel to the thickness of flush end-plate. When the behavior of DRCC with HSS (S690) reverse channel was compared to RCC, there was an increase in ultimate flexural resistance and rotational capacity by up to 38.7% and 53.1% respectively, without compromise to the initial stiffness. It was also noted that the clear distance between the split reverse channels had effect on the deformation of DRCC. This distance should be kept to a minimum, 20% of the beam depth, and at the same time it should be practically adequate for bolt accessibility.
Keywords : Reverse channel, Double reverse channel, Moment–rotation curve, Tubular column, HSS
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Parametric study on moment-rotation characteristics of reverse channel connections to tubular columns.
Authors : H. Alhendi and M Celikag
Abstract : The significance of this parametric study initiates from the need for further understanding of the behavior of semi-rigid/partial-strength I-beam to tubular column connections. This research attempted to gain a qualitative understanding of the influence of the geometrical configurations of reverse channel connections (RCC) on the moment–rotation (M-ϕ) response. Hence, ABAQUS (v.6.12) software was used to develop three-dimensional (3-D) FE models for thirty specimens. The FE models developed were validated against the experimental results available from literature where 268 FE models were used for sensitivity analysis. The main emphasis of this research was on the stiffness, strength, sources of deformability, rotational capacity and failure mechanisms of the RCC. All tests were able to achieve a rotational capacity beyond the minimum 0.03 rad, in most cases more than 0.06 rad and in one case reached 0.16 rad. For the same configuration of RCC, it was found that the channel wall thickness to the flush end-plate thickness ratio is the key to the rotational capacity of RCC. In addition, the deformability of the column face was mainly dependent on the ratio of channel depth to square hollow section (SHS) width and the minimum value of this ratio is recommended to be kept equal to 0.72.
Keywords : Reverse channel, Moment–rotation curve, Tubular column, Stiffness, Moment capacity, Rotational capacity
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