The simplification of fuzzy control algorithm and hardware implementation

The conventional interface composition algorithm of a fuzzy controller is very time and memory consuming. As a result, it is difficult to do real time fuzzy inference, and most fuzzy controllers are realized by look-up tables. Here, researchers derive a simplified algorithm using the defuzzification mean of maximum. This algorithm takes shorter computation time and needs less memory usage, thus making it possible to compute the fuzzy inference on real time and easy to tune the control rules on line. A hardware implementation based on a simplified fuzzy inference algorithm is described

Beam element verification for 3D elastic steel frame analysis

The paper describes the attributes that should be possessed by a benchmark example for verifying the beam elements used to carry out 3D linear buckling analysis and 3D second-order elastic analysis of steel frames. Based on the attributes described, the paper proposes a suite of benchmark examples selected from the literature. The necessary features of a beam element required to pass the proposed benchmark problems are given, and beam elements that possess these features are cited. The paper also explains the merits of linear buckling analysis examples, and provides a commentary on two well-known examples

Cubic beam elements in practical analysis and design of steel frames

This paper discusses various issues in the use of cubic beam elements for computer structural analysis/design of steel frames. It is pointed out that the concern expressed in recent literature regarding the number of cubic elements required to model a steel member is not justified, and that the inaccuracy of one cubic element in Euler buckling analysis of a simply supported column is largely irrelevant to the second-order elastic analysis/design or advanced analysis of steel frames. The sources of inaccuracy of the cubic element are elucidated. It is also explained that the plastic-zone analysis method is not so inefficient as was previously believed. The spatial cubic element is shown to be capable of accurately accounting for the coupling between axial, flexural and torsional deformation modes. It is concluded that for the purposes of second-order elastic analysis/design and advanced analysis of 2D and 3D steel frames, the well-documented cubic element is a versatile and efficient choice

Limitations of current design procedures for steel members in space frames

The use of more advanced methods of analysis to design steel frames may lead to substantial material savings, in addition to simplicity in the design procedures. However, these benefits do not yet appear to be a powerful incentive for many structural engineers to abandon the familiar linear elastic analysis (LEA) based design procedures, even when dealing with steel structures that are not regular rectangular frames. This paper uses a heuristic example to demonstrate the serious limitations of the LEA based design procedures, whether alignment charts or system buckling analysis is used to determine the effective lengths of the compression members. It is shown that LEA based design procedures may lead to unsafe structures due to their inability to account for bending moment amplification in the rigidly connected tension members of a space frame. Furthermore, there is no allowance for the amplification of axial forces due to changes in the structure geometry, which is significant for the space frame example. Confidence in the system buckling analysis method for determining the effective lengths of compression members, based on linear buckling analysis, is shown to be potentially dangerous for certain types of frames. For the space frame example, the elastic buckling load is overestimated by over 200%. The conservatism inherent in the member capacity check equations specified in steel design standards is also illustrated

A novel electrochemical technique for mineral scale coverage and scaling tendency quantification

Mineral scaling poses a far greater problem to any industry that uses or produces water. The quality of water used by industry varies widely and gives rise to numerous scaling problems. Mineral scale formation and deposition on equipment surface causes major flow assurance concerns particularly apparent in the offshore oil and gas industry. An improper of scale management programmes could lead to a rapid mineral scale build up and subsequently significant reductions in productivity and compromises the operational safety of process equipment (i.e. safety valves) as a result of blockage. The result is costly workovers increasing project operating costs (OPEX) due to the need for scale dissolver treatments and significant production losses. As part of scale management programme, it is desirable to be able to quantify the extent of the mineral scale that has deposited on component surface and also to be able to monitor the changes of likelihood that a production fluid will precipitate out mineral scale. The nature of this research is focus on exploring a simple approach or a methodology to detect the mineral scale formed specifically for calcium carbonate on the electrode surface. The application of a submerged impinging jet (SIJ) in conjunction with an electrochemical technique was developed. The development of this technique has been taken into the consideration of advantages and disadvantages of the current available scale detection techniques. Not only has the complexity of equipment and facilities been considered during the development stage, but the data interpretation of the existing technologies has been considered. In general, efforts have concentrated upon strategies to develop and to validate this methodology for the scale coverage on the electrode surface as well as monitoring the scaling tendency through the electrochemical technique measurement. Various verifications and experiments were undertaken to ensure the reliability of the use of electrochemical measurement and SIJ geometry configurations. The influence of surface condition on the sensitivity of this technique were also assessed This technique clearly demonstrated that various levels of mineral deposition on the surface could be quantified. This included the calcium carbonate deposition in the presence and absence of magnesium ions. In this study, a similar SIJ set up configuration was used for scaling tendency measurement to quantify and predict whether scaling will occur in water or brine solution. The scaling tendency results illustrated that there was a good correlation between the saturation ratio and the scaling tendency slope measurement by an electrochemical analysis. The contribution main of this research contributes to a better understanding of the used of SIJ for scale detection, monitoring and quantification of calcium carbonate scale formation

Effect of loading direction on the bearing capacity of cold-reduced steel sheets

This study is concerned with double-shear bolted connections in cold-reduced steel sheets that undergo the pure bearing failure mode of the inside sheet. Compared to the published test results of bolted connections failing in the net section fracture, those involving the bearing failure mode had very wide scatter in the ultimate test loads of specimens having seemingly similar configurations. This technical note presents the laboratory test results of 51 specimens composed of G2 and G450 steel sheets, which have very different ductility properties. One new and significant finding is that the absolute bearing capacity can be considerably higher in the rolling direction of the cold-reduced steel sheet than in the perpendicular direction, even though the tensile strength has the opposite trend. Another result is that material ductility has a much greater effect on the bearing capacity than on the net section tension capacity. It was also found that snug tightening had little effect on the bearing capacity of specimens thicker than 1.5 mm. For the inside sheet of a double-shear bolted connection, the current American Iron and Steel Institute provision for bearing capacity is reasonably accurate if the load is applied in the rolling direction of G2 steel sheet, but is overoptimistic in the perpendicular direction

Block shear capacity of bolted connections in hot-rolled steel plates

This paper extends the research previously conducted at the University of Wollongong on block shear failure of bolted connections in cold-reduced steel sheets with low ductility to hot-rolled steel plates. It examines the applicability of the basic approach employed for cold-reduced sheet steel bolted connections, which makes use of the so-called active shear planes, to hot-rolled steel plate connections. The active shear planes lie midway between the gross and the net shear planes defined in the steel structures specifications. The paper shows that shear yielding leading to the block shear failure of a bolted connection in a hot-rolled steel gusset plate is typically accompanied by full strain hardening. The paper proposes a design equation that provides more accurate and consistent results compared to the American, Australian, Canadian and European code equations in determining the block shear capacities of bolted connections in hot-rolled steel gusset plates. A resistance factor of 0.85 is recommended in order to achieve a target reliability index of 4.0 or greater