Thin End Plates Research Articles

Stack-level analysis of the performance variation in air-cooled PEMFC with Z-type anode manifold

Air-cooled proton exchange membrane fuel cell (PEMFC) stack holds significant promise due to its potential to reduce system complexity. The anode manifold type leads to gas maldistribution in an air-cooled stack, and affects the efficiency and life span of the stack. In this study, 3D multi-physics model of stacks ranging from 10 to 40 cells are established to investigate the gas distribution characteristic of Z-type anode manifold. Considering the heat dissipation aspects only, it is advisable to keep a thin endplate while meeting the required stress tolerances. The core temperature of the stack with 20 mm endplates measures 43.8 °C, while the stack with 6 mm endplates reaches a core temperature of 45.5 °C. Under a cathode air flow velocity condition of 4 m‧s−1, the maximum net oxygen consumption reaches 1.69 mol‧s−1 in Cell-4. Furthermore, the electrochemical reaction intensity decreases sequentially from Cell-4 and Cell-5 in the middle to Cell-1 and Cell-10 in the edges of the stack. Additionally, cells near the anode inlet and outlet are prone to have the insufficient gas supply in the Z-type anode manifold stack.

Validity of models for frictional heating in sliding isolators

AbstractThis paper investigates the validity of theories for the prediction of the temperature increase at the sliding interfaces of sliding isolators. The prevailing theory considers the isolator to be indefinite in depth and the heat flux generated at the sliding interface(s) to be infinite in extent. In reality, the depth is finite and small, and bounded by an insulating boundary, whereas the heat flux is bound by the circular area of contact. New theories are presented in which the restrictions of the past theory are relaxed. The resulting solutions have been implemented in program OpenSees for single and for triple friction pendulum isolators but are very complex and time‐consuming to be used in response history analysis with many isolators. Analysis of the response of sliding isolated structures with these models demonstrates that consideration of the finite depth of the isolators and of the limited extent of the heat flux does not have any important effects on the calculated isolator displacement demands in either short‐duration or long‐duration ground motions. It is shown that the finite depth has some effect on the peak temperature at the sliding interface and, more importantly, on the duration of the high temperature in long‐duration ground motions. This is of some importance in the use of these theories for the development of testing specifications for isolators with unusually thin end plates.

Numerical analysis of a prefabricated concrete beam-to-column connection with bolted end plates

Precast concrete structures have been widely used in China in recent years because of the obvious advantages in construction speed, labor saving and quality control. Many experimental and numerical studies have been performed to investigate the seismic behavior of the precast concrete structures. However, the numerical analysis on prefabricated concrete beam-to-column connection with bolted end plates (PCC) under cyclic loading is still limited. Therefore, in this paper, the developed finite element models (FEM) were established to further study the seismic performance of the PCC specimens. The sensitivity analysis were conducted to ensure the reliability and validity of the FEM. Then, the FE models of the typical specimens were validated by test data such as failure modes, hysteresis curves and steel strain. Parametric analysis was carried out to investigate the effect of the end plate thickness, preload of bolt, concrete strength, etc. The key parameters affecting the seismic behavior of the connections were obtained. Eventually, based on the numerical simulation results, the law between the responses of the connections and the key parameters was determined quantitatively by response surface methodology. According to the yield line theory, the theoretical formula on the bending capacity of the connection with thin end plate was derived. Meanwhile, the formulas on the bending capacity of the unbonded prestressed concrete beam were also obtained. The results indicated that the bearing capacity and initial stiffness of the connection were improved with the increase of end plate thickness and bolt preload. The steel box significantly enhanced the shear capacity of joint region of the PCC specimens. Although the bending capacity of the beam can be improved by increasing the concrete strength, high strength concrete significantly reduced the ductility. The calculated value of the connection matched well with the test or simulation data which may provide a reference for predicting the bending capacity of specimens with different failure modes in subsequent studies.

Finite element analysis for built-up steel beam with extended plate connected by bolts

Abstract Extended end-plate type connections are widely utilized in steel assemblies for easy production and assembly. The proper end-plate and bolt selection is paramount to confirming safety and economy in all connections and, consequently, steel buildings. This study presented an approach for refined parametric three-dimensional finite element analysis of bolted steel beam-to-beam extended end-plate connections. The model considers geometrical and material non-linearity to determine the impact of various factors on the connection’s performance. The proposed model was used to construct a parametric study. The study variables were bolt diameter and end-plate thickness, focusing on how thick and thin end plates affect connection conductivity. Numerical outcomes demonstrate that the connection's flexural strength and stiffness capability improved by increasing the end-plate thickness and bolt diameter. Finally, the analysis results were assessed, and the main conclusions were presented.

Static behavior of TOBs bolted endplate connection to strengthened HSST with fixed thread length

Five thread-anchored one-side bolts connected endplate connections to Hollow Square Steel Tube (TOBEC-HSSTs) with various strengthening measures were tested to investigate the structural performance under monotonic loads. The thread anchored length was 1.2 times the bolt diameter for all specimens. The connection behaviour were influenced by the endplate thicknesses and the strengthening measures (i.e. the internal polygonal tube, the internal polygonal tube with infilled concrete, and the cross-H section stiffener with infilled concrete). The failure patterns, moment-rotation curves, and strain response of joints were obtained through tests. It was found that (1) 1.2 times the bolt diameter was taken as the safe thread assembled length, which can avoid the premature failure of hole threads not before the fracture of other components under monotonic loads. (2) The presence of the infilled concrete can improve the rigidity and strength of the connection by 84% and 23%, respectively, compared to the reference joint without the infilled concrete, and the thickness of the column wall can be reduced when the concrete was infilled into hollow steel tube. (3) For the connections with thin endplates, the cross-H section stiffener exhibited 8.8% and 3.5% higher preliminary stiffness and yield bending moment than the inner polygonal tube, but the cross-H section stiffener had 14.3% lower rotation capacity. (4) Thickening endplates can change the failure modes of the connections to beam plastic hinge formation, enhance the preliminary stiffness and yield bending moment of joints by 2.4% ∼11%, but decrease the rotation capacity of joints by 54% compared to thin endplates. Based on experimental results, the calculation methods of the bending moment bearing capacity for TOBEC-HSSTs considering the strengthening effect of internal stiffeners and infilled concrete under different failure patterns were proposed with errors no greater than 15%.

Cyclic and monotonic performance of unstiffened extended end-plate connections having thin end-plates and large-bolts

This study presents the findings of comprehensive numerical and experimental programs on unstiffened extended end-plate connections (UEECs) having thin plates and large sized bolts. The main goal of the research program is to analyze the effects of variables influencing the capacity of these connections. Six specimens were subjected to cyclic and monotonic loading to achieve this goal. For the experimental part, the thickness of end-plate was chosen as the variable. The thickness of end-plates was selected to ensure failure modes governed by the bending capacity of end-plates. A comprehensive numerical study consisting of 156 finite element models where the parameters are I-section types, width and thickness of end-plate, edge distance, distance from flange to bolt row, bolt diameter and weld thickness was performed. The results showed that the connections with thin end-plates can perform high ductility and strength. Moreover, the design methods given by AISC 358-16 and EN1993-1-8 conservatively predict the plastic moment capacity of UEECs. According to numerical findings, the average ratios of actual to estimated plastic moment capacity by AISC 358-16 and EC3:1-8 are 2.77 and 3.13, respectively. These ratios alter to 3.70 and 3.93 for the experimental results. The yield line mechanism and the spacing between the plastic hinges are to cause this underestimate. An expression for the observed yield line pattern is developed to estimate the plastic moment capacity more correctly. The actual to estimated plastic moment capacity ratios according to proposed expressions are averagely 1.23 and 1.29 for the outcomes of the experimental and numerical study, respectively.

Cyclic and monotonic performance of stiffened extended end-plate connections with large-sized bolts and thin end-plates

Cyclic and monotonic performance of stiffened extended end-plate connections with large-sized bolts and thin end-plates

Bolt stripping failure and ductility of end plate beam-column connections at ambient and elevated temperatures

PurposeThe effect of bolt stripping failure on the ductility of steel end plate beam-column connections has received relatively little investigation to date. The objective with the present work is to establish a validated numerical model of end plate connections at elevated temperatures, which predicts the mechanical behaviour and failure modes observed in the experimental tests including the bolt stripping failure. Furthermore, the validated FE model was used to investigate the effect of stripping failure on both the rotational and load-bearing capacity of end plate connection.Design/methodology/approachThe analysis was conducted on a validated numerical model of end plate connections at elevated temperatures, which predicts the mechanical behaviour and failure modes observed in the experimental tests including the bolt stripping failure. The material was modelled considering ductile damage initiation and evolution featured in ABAQUS/Standard.FindingsThis study demonstrates that thick end plates can prevent stripping failure which significantly improves the rotational capacity of the connection. This failure mode can develop readily with thin end plates; however the effect is often unrealistically mitigated through idealised experimental tests. The rotational capacity of a connection can be 5.0 times higher if stripping failure is avoided, particularly at elevated temperatures. Eurocode 3 part 1.8 does not consider the possibility of stripping failure when discussing the requirements for plastic analysis. It is concluded in the present study that by allowing for the possibility of bolt stripping, the mode of failure can often shift from end plate failure to bolt stripping, this in turn significantly reduces the connection rotational capacity.Originality/valueThe effect of bolt stripping failure on the ductility of steel end plate beam-column connections has received relatively little investigation to date.

Behaviour of thin flush end-plate connections in a 3D bare steel frame under fire loading: experimental study

PurposeThe paper aims to report a fire test conducted on a three-dimensional frame in order to investigate the behaviour of bare steel flush end-plate connections with relatively low thickness at elevated temperatures.Design/methodology/approachA half-scale model was fabricated and exposed to modified (scaled) ISO 834 heating curve using a semi-open furnace. The maximum temperature inside the furnace reached 1,026 °C.FindingsThe rotations of connections are reported and compared with those of a previous study on an exactly the same model with thick end-plates. Various modes of failure such as local buckling of the beams flanges and lateral-torsional buckling of beams were observed during the test. Finally, the structure collapsed after 29 min of heating due to the fracture of weld between one of the beams and one of its attached end-plates whilst the other beam had undergone a maximum deflection of 35 cm (≈ 1/6 span length). Other observed failure modes included bolt fracture, bolt thread stripping and large inelastic deformation of the end-plates.Originality/valueAlthough the adoption of thin end-plates increased the rotational capacity of the connections, it did not improve the robustness of the structure under fire conditions.

Comparative Analysis of Circular and Square End Plates for a Highly Pressurized Proton Exchange Membrane Water Electrolysis Stack

End plates are located at both ends of a proton exchange membrane water electrolysis (PEMWE) stack. If the end plates are thin, clamping pressure is not uniform and the performance of PEMWE can deteriorate from leakage and high electrical contact resistance caused by the deformation of the thin end plates. In this study, end plates were designed to reduce the weight while clamping the stack uniformly by finite element analysis (FEA). The weights of the circular and square end plates were reduced compared to conventional end plates by 22.9% and 23.3%, respectively. The stress and strain distribution of square and circular end plates are analyzed using topology optimization. This analysis can improve the performance of the PEMWE by using new end plate designs verified by dummy cell stack simulation to maintain uniform pressure.

Seismic Behavior of a Novel Blind Bolted Flush End-Plate Connection to Strengthened Concrete-Filled Steel Tube Columns

Modified blind bolts (Hollo-Bolt) and a locally strengthened steel tube column in the panel zone were created to overcome the moment-resisting problem for the bolted connections between concrete-filled hollow section columns and open section beams and to enhance the performance of connections. The cyclic loading was conducted on a total of six modified anchored blind bolted flush end-plate connections to concrete-filled steel tube (CFST) columns. The key parameters investigated were the tube wall thickness, end-plate thickness, blind bolt anchorage method, and beam section. The failure mode, hysteretic behavior, strength, stiffness, ductility, and energy dissipation capacity of the connections were analyzed and evaluated with all details. The results indicated that connections with modified anchored blind bolts and locally strengthened steel tubes could avoid the premature failure of CFST column and exhibit an improved behavior with a favorable strength, stiffness, and stiffness degradation. The test observations reveal two representative failure modes, and the tube wall thickness and blind bolt anchorage method have a significant effect on the resultant failure mode. Moreover, the use of thin endplate and weak beam can effectively enhance the hysteretic behavior of joints, ductility, and energy dissipation capacity; and the change in anchoring method has little effect on the stiffness. Finite element (FE) analysis models were established for the aforementioned connections. The numerical models were validated against the experimental results and exhibited good agreement. Finally, based on the component method, an initial stiffness calculation method was established for the connections.

Study of stainless steel bolted extended end-plate joints under seismic loading

Bolted stiffened extended end-plate (BSEP) joint is a commonly used beam-to-column joint in steel frames. In this paper, five full-scale stainless steel BSEP joints were tested under cyclic loading. The tested joints were made of Grade S31608 (EN 1.4401) stainless steel welded I-sections, assembled by four types of bolts, including galvanized high strength bolts of Grades 10.9 and 8.8, and austenitic stainless steel bolts of Grade A4-70 and A4-80. Variations of end-plates of different thicknesses (16 mm and 20 mm) were also considered in the design of the test specimens. Material properties of the plates were tested and the slip-resistant behaviour of the bolts with surface treatments were obtained prior to the joint tests. The test setup, loading protocol and instrumentation employed in the tests are described herein. The obtained test results are reported, including the full moment-rotation curves and the failure modes of the joints. It is observed from the seismic tests that hysteresis curves of all specimens show some sliding and pinching, especially for connections with stainless steel bolts or thin end-plates. The test results were used to validate finite element (FE) models, which can be employed for further numerical investigations. The test results were also employed to assess the stiffness and moment resistance capacity predictions according to the current European design provisions.

Seismic behavior of outrigger truss-wall shear connections using multiple steel angles

An experimental investigation on the seismic behavior of a type of outrigger truss-reinforced concrete wall shear connection using multiple steel angles is presented. Six large-scale shear connection models, which involved a portion of reinforced concrete wall and a shear tab welded onto a steel endplate with three steel angles, were constructed and tested under combined actions of cyclic axial load and eccentric shear. The effects of embedment lengths of steel angles, wall boundary elements, types of anchor plates, and thicknesses of endplates were investigated. The test results indicate that properly detailed connections exhibit desirable seismic behavior and fail due to the ductile fracture of steel angles. Wall boundary elements provide beneficial confinement to the concrete surrounding steel angles and thus increase the strength and stiffness of connections. Connections using whole anchor plates are prone to suffer concrete pry-out failure while connections with thin endplates have a relatively low strength and fail due to large inelastic deformations of the endplates. The current design equations proposed by Chinese Standard 04G362 and Code GB50011 significantly underestimate the capacities of the connection models. A revised design method to account for the influence of previously mentioned test parameters was developed.

Evaluation of the Energy Dissipation Capacity of an Unstiffened Extended End-plate Connection

확장단부판(extended end-plate) 접합부는 보-기둥 모멘트 접합부의 한 형태로 접합부를 구성하는 단부판(end-plate)의 두께 및 길이, 고장력볼트의 개수 및 직경, 고장력볼트의 게이지 거리, 용접부의 치수 및 길이 등에 따라서 상이한 거동특성과 에너지소산능력을 발현한다. 이러한 확장단부판(extended end-plate)는 미국 및 유럽 등지에서는 다양한 기하학적 형상으로 기둥-보 접합부에 적용되고 있다. 그러나 현재 우리나라에서는 강구조 보-기둥 접합부에 적극적으로 적용되고 있지 못한 상황이다. 이렇게 적용성이 높지 않은 이유로는 기하학적 형상변화에 따른 설계강도식 제안, 에너지소산능력 평가 및 시공지침의 제공이 적절하게 이루어지지 못하고 있기 때문이다. 따라서 이 연구에서는 단부판(end-plate) 두께가 상대적으로 얇은 기하학적 형상을 갖는 비보강 확장단부판(unstiffened extended end-plate) 접합부의 에너지소산능력을 평가하여 에너지소산능력 예측모델을 제안하기 위한 기초자료를 제공하기 위하여 진행하였다. 이를 위하여 비보강 확장단부판(unstiffened extended end-plate) 접합부에 대한 3차원 비선형 유한요소해석을 단부판(end-plate)의 두께를 변수로 하여 수행하였다. An extended end-plate connection displays different behavioral properties and energy dissipation capacity based on the thickness and length of the end-plate comprising the connection in the form of a beam-to-column moment connection, the number and diameter of the high strength bolt, the gauge distance of the high strength bolt, and the size and length of the welds. Such extended end-plate is applied to beam-to-column connections in various geometric forms in the US and European regions. Currently in Korea, however, the extended end-plate beam-to-column connection is not actively applied due to the lack of proper design formulas, the evaluation of the energy dissipation capacity, and the provision of construction guidelines. Accordingly, this study was conducted to provide the basic data for the proposal of a prediction model of energy dissipation capacity by evaluating the energy dissipation capacity of unstiffened extended end-plate connections with relatively thin end plate thicknesses. To achieve this, a three-dimensional nonlinear finite element analysis has been conducted on unstiffened extended end-plate connections, with the thickness of the end plate as the set variable.

Energy Harvesting with Piezoelectric Element Using Vibroacoustic Coupling Phenomenon

This paper describes the vibroacoustic coupling between the structural vibrations and internal sound fields of thin structures. In this study, a cylindrical structure with thin end plates is subjected to the harmonic point force at one end plate or both end plates, and a natural frequency of the end plates is selected as the forcing frequency. The resulting vibroacoustic coupling is then analyzed theoretically and experimentally by considering the dynamic behavior of the plates and the acoustic characteristics of the internal sound field as a function of the cylinder length. The length and phase difference between the plate vibrations, which maximize the sound pressure level inside the cavity, are clarified theoretically. The theoretical results are validated experimentally through an excitation experiment using an experimental apparatus that emulates the analytical model. Moreover, the electricity generation experiment verifies that sufficient vibroacoustic coupling can be created for the adopted electricity generating system to be effective as an electric energy-harvesting device.

G101043 音振動連成現象を利用した発電システム([G101-04]機械力学・計測制御部門,一般セッション(4))

This paper describes the vibroacoustic coupling between the structural vibrations and internal sound fields of thin structures. In this study, a cylindrical structure with thin end plates is subjected to a harmonic point force at one end plate and a natural frequency of the end plates is selected as the forcing frequency. The resulting vibroacoustic coupling is then analyzed by theoretically and experimentally by considering the dynamic behavior of the plates and the acoustic characteristics of the internal sound field as a function of the cylinder length. The length and phase difference between the plate vibrations, which maximize the sound pressure level inside the cavity, are clarified theoretically. The theoretical results are validated experimentally through an excitation experiment using an experimental apparatus that emulates the analytical model.Moreover, the electricity generation experiment verifies that sufficient vibroacoustic coupling can be created for the adopted electricity generating system to be effective as an electric energy-harvesting device.

Experimental Modal Analysis Of A Water-filledCircular Cylindrical Tank

Experimental modal analysis has been performed on an empty and water-filled, circular cylindrical tank horizontally suspended. The tank is composed of a circular cylindrical shell with a longitudinal butt seam welding and two end annular plates. A rubber disk was glued to each annular plate to close the tank. The boundary conditions imposed to the circular cylindrical shell by the thin end plates can be considered very close to simply supports. Two little pipe fittings, used for supplying water, were welded to one of the end plates in such a position that they do not affect shell vibrations. The tank was hung to a truss with its axis kept horizontal by a compliant suspension, by using cables connected to the end plates. The Frequency Response Functions (FRFs) between 100 response points and one single excitation point (SIMO test) have been measured. Burst random has been used as excitation input. Natural frequencies and mode shapes are in very good agreement with theoretical data computed using the Fliigge theory of shells and potential and incompressible fluid model.

Strength criteria for bolted beam-column connections

Abstract This paper describes an experimental investigation into the strength parameters of bolted beam-to-column connections. Fifteen specimens of beam-column connections were tested with 16 mm, 20 mm and 24 mm diameter bolts and 12 mm, 16 mm and 20 mm endplates for a constant beam and a constant column cross section using both pulsating and gradually increasing ‘static’ loads. Test connections were designed to the Australian specifications. All connections, except one, met the strength requirements by transferring the nominal plastic moment of the beam across the connection. According to the design criteria, the bending of the endplate was the predicted mode of failure, but experiments revealed different phenomena. Specimens failed generally with the yielding of column flanges/web and welds around the beam tension flange. High factors of safety were obtained for specimens tested with thin endplates.