Base Plate Thickness Research Articles

Investigating the effectiveness of concentric welded anchor rods in column base plate connections: A numerical and experimental study

This study presents a new strategy for column base plate connections, which involves the utilization of welded anchor rods positioned concentrically beneath the base plate, in alignment with the connected column. The objective was to remove the eccentricity between the anchor rods and the column, thereby excluding the base plate from the load-transferring chain. A numerical study was performed to compare the cyclic behavior and uplift response of the proposed connection with conventional column base connections. Additionally, different weld types were investigated to connect the anchor rods to the base plate, and their efficiency was evaluated based on a comprehensive dataset of nine tests on equivalent base-plate T-stub connections with different base-plate thicknesses, anchor-rod strengths, and anchor-rod diameters. The numerical results showed that using welded anchor rods could remove the pinching from the hysteresis loops, as the anchor rods can effectively resist cyclic loads in both compression and tension. Furthermore, removing the eccentricity between the anchor rods and the column enhanced the uplift stiffness by approximately 31 %. The experimental results indicated that the failure mode was the fracture of anchor rods for all specimens, while the other components remained elastic. The specimens with high-strength anchor rods showed a brittle failure accompanied by a sudden drop in load, which coincided with the fracture of anchor rod in the softened heat-affected zone. All developed weld types successfully withstood the ultimate tensile strength of anchor rods upon fracturing.

Environmental Microvibration Analysis Method for Vibration Isolation Research in High-Precision Laboratories

Environmental microvibrations, often originating from unidentified sources, pose a significant challenge for predicting and controlling their complex wave fields, potentially leading to measurement errors of sensitive instruments in high-precision laboratories and impacting the accuracy of experimental outcomes. Therefore, investigating effective control measures for environmental microvibrations under passive conditions is key to addressing such engineering issues. This paper presents a finite element analysis method tailored to address environmental microvibrations in the absence of apparent sources. This method involves obtaining the vibration time history at specific ground surface points through field measurements and combining the Rayleigh wave velocity attenuation character with depth at the center frequencies of one-third octave bands within the 1–100 Hz frequency range; the vibration time history at any depth in the soil is calculated. These calculated vibrations are then applied as input loads to the corresponding nodes on one boundary of the foundation–soil model, serving as the source of environmental microvibrations. The predicted results are compared with measured data and the empirical point source input method, indicating that this approach is more precise and efficient, providing valuable reference for the prediction and analysis of environmental microvibrations. In addition, utilizing this method, the study examines the effects of pile foundation parameters such as the pile length, burial depth, and concrete baseplate thickness on the vibration isolation performance of environmental microvibrations, providing guidance for designing pile foundation isolation.

Experimental and FE analysis of the behavior of steel column base connections under tension and bending moment

Most design procedures represent the steel base connection by assuming either a perfectly hinged or a fully rigid connection. However, these kinds of connections are, in fact, semi-rigid or flexible and their actual behavior is complicated. Most of the previous studies investigated these base connections experimentally under moments and axial compression only, which is completely different in the case of axial tension and moment. Therefore, experimental and numerical investigations with variable base plate thicknesses and diameters and arrangements of the anchor bolts were carried out to verify the behavior of this kind of base connection under axial tension and moment. Full-scale steel columns with hinged base plate connections were tested under the effect of two simultaneous actions, axial tension force and bending moment. Moreover, Finite Element (FE) models were developed and verified against the experimental results to conduct a parametric study. The investigated parameters were the base plate thickness and anchor bolt diameter and arrangement. The base plate connections under the effect of axial tension with moment instead of axial compression caused reductions in the rotational stiffness up to 99%. In addition, using only two bolts in this type of connection concentrated stresses on the base plate that led to big deformations. The small base plate thickness deformed easily under the effect of tension force which induced big initial gaps between the steel base plate and the Base beam and subsequently decreased the moment resistance and rotational stiffness of the base plate connection. The big elongation of the anchor bolts with small diameters increased the gap between the steel plate and the Base beam.

Seismic performance of rocking braced frames with double base plate connections

This paper presents a rocking system for concentrically braced frames (CBFs) to mitigate the seismic demands induced by seismic motions. The proposed system incorporates double base plate connections (DBPCs) at the base of the braced-bay columns, enabling them to uplift and initiate a rocking motion. The DBPC comprised two base plates: the upper one is thin, connected to the column and designed to yield under uplift loading, while the lower one primarily distributes compressive loads to the foundation. The DBPC was modeled using a combination of spring and gap elements in SAP2000 software. A comparative study was performed to investigate the seismic performance of the proposed rocking system against a conventional CBF system. Key parameters such as the thickness of the upper base plate and the arrangement of anchor rods were considered. Four prototype frames of different heights (3, 6, 9, and 12 stories) were investigated under the Sylmar-x record using the nonlinear time history analysis. The results demonstrated that utilizing rocking braced frames with double base plate connections can remarkably mitigate the base shear force by softening the structural response, decreasing the seismic damage experienced by the structure. The upper base plate acted similarly to a footing damper, absorbing a substantial amount of energy by yielding. Importantly, the residual drifts caused by the plastic deformations of the upper base plate remained within the acceptable performance limits for self-centering systems. Moreover, the self-centering mechanism was achieved solely through the structure’s self-weight, eliminating the need for additional re-centering devices.

Experimental and numerical analysis for the dry patch and thermal stress of one heating surface

In this study, an experiment to explore the surface temperature rise of an artificial dry patch at different heating powers was done. Then under specific sizes of the dry patches, the influences of these factors on thermal stress were thoroughly investigated through sensitivity analyses of factors such as the thickness of the heated wall surface, the location of the dry patch, and the thermal conductivity of the heating surface. It is found that in the case of CHF occurrence, even though the local maximum temperature inside the dry patch is much lower than the melting point of the material, the thermal stress caused by the dry patch exceeds the yield strength of the material, which triggers irreversible plastic deformation. Therefore, the heated wall fracture caused by thermal stress will occur prior to wall melting. At the same time, this study also found that changing the thickness of the stainless steel base plate and the thermal conductivity of the material both affect the maximum temperature in the dry patch region. Reducing the thickness of the heating plate makes the temperature in the dry patch region increase, which leads to a dramatic increase in the thermal stresses inside the material. Increasing the thermal conductivity of the material can flatten the temperature field, and the equivalent stresses also decrease.

An evaluation of the use of air cooling to enhance photovoltaic performance

The rapid rise in global energy consumption and its consequences on climate change has made incorporating renewable energy sources like solar photovoltaics into the building envelope easier. However, in spite of extensive uses and significant technological advances, the lower solar panel efficiencies caused by high temperatures remain a significant barrier to the viability of deploying photovoltaic technology in regions with hot climates utilizing computational fluid dynamics (CFD). This research examines the cooling effectiveness of air-cooled photovoltaic (PV) under the climate of Nablus - Palestine. This study presents a numerical model designed to cool solar panels using various air-cooled channel configurations. Rectangular fins made of high thermal conductivity materials such as copper were used in this study. The parametric study was based on the changing baseplate thickness, fin spacing, height, and thickness through a stepwise optimization process to enhance the heat transfer mechanism. The results show that the optimum design of average volume temperatures for the PV cell models in air-cooled channel configurations with and without fins were 40.28 °C and 42.58 °C, respectively. The optimum design was obtained at 3, 110, 60, and 4 mm for baseplate thickness, fin spacing, height, and thickness, respectively. This optimum design was responsible for the average PV panel temperature drop by 1.6 %, 1.3 %, 5.9 %, and 6.2 % for baseplate thickness, fin spacing, height, and thickness, respectively. The optimum design of an air-cooled cooling channel for PV is an important insight provided by this work, and it may help in the future development of more effective and affordable cooling methods.

Dissimilar Friction Stir Lap Welding of Aluminium to Steel: Influence of Alloy Type and Sheet Thickness on Strain Distribution and Failure Location

Dissimilar joining through solid-state welding is an important engineering tool to address the transportation industry’s sustainable goals. The dissimilar friction stir lap welding (FSLW) of two different aluminium alloys (AA5182 and AA5052 with two different thicknesses) to steels AISI1010 and DP1000 was performed in this work, in order to analyse the effect of the mismatch in base material properties and plate thickness on the joint strength and fracture location. The mechanical behaviour and the strength of the welds were assessed using transverse tensile–shear testing and hardness measurements. Strain data acquisition through Digital Image Correlation (DIC) was used. The differences in fracture location registered for the different joints are explained based on the alloy’s plastic properties and on the mismatch in thickness between the plates. Local stress–strain curves were plotted, using the strain data acquired through DIC, to highlight the mechanisms resulting in the differences in tensile behaviour among the joints. It is concluded that despite the differences in failure location and tensile behaviour, the strength of the joints was very similar, irrespective of the base material combinations.

Impact of Plate Thickness and Joint Geometry on Residual Stresses in 347H Stainless Steel Welds

Weldments of 347H stainless steel are potentially susceptible to stress relaxation cracking at elevated service temperatures. Mitigation of stress relaxation cracking susceptibility within a multipass weld requires a good understanding of welding practices and manufacturing techniques to control high tensile residual stresses. In this work, the dependence of residual stress distribution in 347H stainless steel on base plate thickness, joint geometry design, and preheating condition was systematically investigated by using three-dimensional finite element models. The finite element models were validated through good agreement between neutron diffraction measurements and calculated elastic strains. The single-V-groove welds with and without a preheating step all produced similar peak von Mises residual stresses, above 450 MPa, within both the fusion zone and heat-affected zone (HAZ). In plates thicker than 0.5 in. (12.7 mm), high tensile residual stress could be observed in a relatively large area, from the middle of the plate thickness to underneath the top surface. A double-V groove shifted the high tensile stress area to the middle thickness of the weld. A single-J-groove weld was able to confine the residual stress to a very small region near the middle thickness within the fusion zone and suppressed the von Mises residual stress within the HAZ to below 400 MPa.

An assessment method to ensure applicability of concrete capacity method for design of anchorages: Linear force distribution approach

AbstractThe concrete capacity design (CCD) method for the design of anchorages comes with a pre‐requisite that the base plate connecting the anchors of a group should be “sufficiently stiff.” This article addresses a frequently and vastly discussed topic in fastening technology, namely “What a sufficiently stiff base plate actually means?” The qualitative definition used by the codes requires that the deformation of the base plate should be small compared to the anchor displacements, in addition to the requirement that the base plate should remain linear elastic. This requirement indirectly ensures that the forces among the anchors of the group are distributed in a linear manner, which is the primary requirement to apply the CCD method for design of anchorages. Such a qualitative definition has raised more questions than answers and haunts the fastening technology community. Perhaps the possible solution to this problem requires asking the question differently, that addresses the problem directly: How can it be ensured that the tension forces among the anchors of a group are distributed in a linear manner? This paper first discusses the problem in detail highlighting several issues in the current approach and later provides an overview of an assessment method in form of a set of criteria that can be used to evaluate whether the tension force distribution is linear for an anchorage with a given anchor pattern, baseplate, attachment, and load case. The principle of the approach is based on a combination of simple mathematical formulations and the evaluation of finite element calculations performed on anchorages modeled with base plate, attachment, and anchors. The proposed formulations are described, and it is explained why they are adequate to find practical and safe general solutions to the problems. The application of the set of criteria allows the calculation of an optimum base plate thickness, sufficient to distribute the forces linearly among the anchors, without being overly conservative.

Development of Novel Inter‐module Connection for Composite Modular Tall Buildings

AbstractThe emerging modular building construction technique is gaining attention by researchers and investors because of its benefits such as short construction time, better quality control, minimal environmental effect and more economical. Composite modules have many advantages, including size reduction and improved fire resistance, over the steel modules, which encourage the application of modular construction on tall buildings. Current state‐of‐art lacks the proper connection technique for composite modular tall buildings. This paper presents novel inter‐module connection for composite modular tall buildings. Purposed inter‐module connection is very simple in geometric design, adequately strong to bear loads for tall buildings, easy to connect and disconnect, and applicable with internal joints and composite modules. Bolts through bolt holes connect modules vertically whereas gusset plate connects horizontally. Firstly, prototype is developed, and workability is confirmed. Performance and failure mechanism of proposed connector under tensile load are evaluated considering the effect of different parameters such as thickness of base plate, size and material of bolt. Results can be used to develop the design guideline for proposed inter‐module connection.

Experimental and numerical investigation on the vibro-acoustic characteristics of periodic rib stiffened plate based on band gap theory

This study presents a novel method for analyzing the vibration and noise from the periodic rib stiffened plate (PRSP). For the first time, the band gap theory was combined with hybrid finite element-boundary element method (FE-BEM) to predict the vibro-acoustic characteristics of this structure and guide its vibration and noise reduction design from the perspective of bending wave propagation. The excitation test was carried out simultaneously to verify the rationality and accuracy of the proposed method. Then, the acoustic contribution analysis was conducted and the influence of structural design parameters on bending wave bandgap and noise reduction effect was discussed in detail. The results show that there are alternating passbands and stopbands for bending waves propagating in PRSP, making the vibro-acoustic responses in different frequency bands exhibit distinct differences as well. Increasing the base plate thickness and decreasing the rib spacing are conducive to widen the bandgaps and reduce the noise radiation, which are the decisive factors affecting the vibro-acoustic characteristics of PRSP. While the rib thickness has little effect, this provides a new approach for vibration mitigation and acoustic optimization in steel bridges.

A numerical study integrated with RSM for hydrothermal and entropy performance of porous jet impingement

AbstractThe thermohydraulic and thermodynamic performance of porous jet impingement under pressure drop effect has not yet been jointly published. Thus, the novelty of this work computationally along with the response surface methodology (RSM) optimization approach considers the porous jet impingement performance linked with a pressure drop simultaneously. Also, the current study used a novel multiobjective optimum design study for various design parameters, such as porosity (ε), Darcy number (Da), and pore per inch (PPI), under numerical simulation assessment of forced laminar convection of jet impingement with full and partial metal foam. The influence of various base plate thicknesses (t = 0, 1, 2, and 3 mm), various nanofluids (Al2O3, CuO, SiO2, and ZnO), and the metal foam size percentage (W/L = 0, 0.25, 0.5, 0.75, and 1) on the improvement of the thermohydraulic and thermodynamic performance is also simulated. Results indicated that utilizing pure water and a metal foam size (W/L) of 1 along with a base plate thickness of 0 mm produced the preferable thermohydraulic and thermodynamic performance. Furthermore, according to an optimization analysis, the current study's objective for the thermohydraulic and thermodynamic performance of jet impingement can be achieved using the parameters porosity ε = 0.1, Darcy number, Da = 1, and the PPI = 15. Therefore, this investigation integrating computational fluid dynamics and RSM offers considerable innovation and useful reference for the optimum design of a porous jet impingement cooling.

Numerical and analytical study of pinned column base plate connections

Gravity system column base plate connections are generally classified as pinned connections with no to minimal moment capacities. A low rotational stiffness value is recommended by the New Zealand Steel Structures Standard, NZS 3404, to represent pinned connections. However, numerous past research studies have shown that these so-call pinned connections possess significant rotational stiffness which could attract large moment demand and potentially lead to yielding of the column base. Furthermore, the constant axial load on the gravity column in conjunction with column base yielding could result in axial shortening of the column, which would significantly increase the cost and difficulty of post-earthquake rehabilitation. With the aim to minimize column base yielding and column axial shortening, a numerical parametric study was conducted to examine the influences of various parameters, including base plate thickness, anchor rod diameter, axial load magnitude, foundation depth and anchor rod pitch distance, on the connection behaviour. It was found that the applied axial load greatly affected the moment resistance as well as the rotational stiffness of the connection. Results also showed that the rotational stiffness of pinned column base plate connections was significantly higher than the value suggested in NZS 3404. An analytical model was developed and validated against numerical and experimental studies to predict moment-rotation response of pinned column base plate connections. Satisfactory results were observed.

Behaviour and Design of Innovative Connections of Prefabricated CFST Columns under Tension

This paper investigates the tensile behaviour of prefabricated concrete-filled steel tube (PCFST) columns with bolted connections. Innovative bolted column-column (BCC) connections are developed using standard structural bolts to simplify the construction process for the connection of two PCFST columns, especially for the corner, edge, and interior columns. The behaviour of BCC connections in PCFST columns under tension has been investigated, adopting the finite element (FE) modelling approach. Parametric studies are carried out to understand the influence of bolt arrangements (TB = 4, 6, 7, 8), base plate thickness (tbp = 8, 10, 14, and 18 mm), bolt diameters (db = 16, 18, 20, 24 mm), vertical stiffeners (ths = 4, 6, 8, 10 mm), horizontal stiffeners (ths = 10, 12, 13, 15 mm), and yield strength of steel tube (fy,t = 380, 450, and 550 MPa) on the behaviour of PCFST columns with developed BCC connections. The results show that the PCFST columns with the developed BCC connections can attain sufficient tensile strength and satisfy the tensile strength requirements recommended in AS5100 and the robustness requirements in AS1170. The outcome of this paper will be useful to practising structural engineers to design prefabricated CFST columns with BCC connections under tension.

Finite Element Analysis of Restraint Intensities and Welding Residual Stresses in the Ti80 T-Joints

The restraint intensity of Ti80 T-joints was investigated using finite element analyses. The influence of slit height, vertical plate thickness and base plate thickness was studied, respectively. Results show that the slit height and vertical plate thickness have a significant impact, while the effect of base plate thickness is negligible. A prediction model of restraint intensity was constructed through binary linear regression; the error was estimated at about 10%. Then, finite element simulations were carried out to study the welding residual stresses of specimens with different restraint intensities. The results show that residual stresses on the backing weld surface are higher in the middle and lower at both ends, while the weld root shows opposite results. In general, stresses at the weld root are greater than those on the weld surface. The mean value of the residual stress at the weld root increases with the increase in restraint intensity but not uniformly, i.e., it is slow at first and then it increases rapidly. A prediction model of the residual stress was produced through cubic fitting, and the errors between the finite element simulations and predictions were about 8%. Using the prediction model, the residual stress of actual Ti80 alloy workpieces can be estimated before welding, and a corresponding strategy for avoiding cracks can be generated.

Design and optimisation of heat sinks to enhance the thermal conductivity through simulations

A Pin-Fin is a component of heat sink, in a thermal system that aids in the dissipation of heat produced. The efficiency of the system is determined in large part by the design of the pin fin. The goal of the study was to use the Taguchi method of optimization to construct a Pin-fin with certain geometry and analyse it using computational simulations. To study the numerous tests to be undertaken on the performance characteristics, an orthogonal array was used. Base Plate Thickness, Fin Height, Fin Width, and Fin Spacing were all considered when designing the heat sink's pin–fin. As a result, the L-9 orthogonal array was chosen, and testing was carried out using commercial simulation software. The simulation testing took place in a Steady-State environment. For efficiency, heat flux, and temperature difference V/s heat sink characteristics, the Signal to Noise ratio was shown. Various iterative trials were compared using the produced graphs and the temperature dissimilarity that exists between the base and the fin tip to determine the most optimum design. In comparison to the other models with inconsistent response characteristics, the study found that heat sink models with a mid-range of thermal efficiency proved to be of reliable design.

Rapid calculation of part scale residual stress – Powder bed fusion of stainless steel, and aluminum, titanium, nickel alloys

A novel analytical model is developed to compute the part scale through-thickness longitudinal residual stress distributions and applied for laser powder bed fusion of four commonly used powder alloys. An important input for the analytical modeling calculations is the peak residual stress for a deposited layer, which is estimated using a unique functional relationship and presented as a function of important process conditions for laser powder bed fusion of different powder alloys. The analytically calculated results of longitudinal residual stress distributions through the part and baseplate thickness are tested rigorously with the corresponding numerically computed and experimentally measured results in the literature for laser powder bed fusion of small and large parts involving the deposition of several thousands of layers. It is shown further that the analytical model can serve as a fast and practical design tool to estimate the through-thickness longitudinal residual stress distribution, which is along the length of the part, for part scale laser powder bed fusion using inexpensive computational resources and with appreciable accuracy. The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations. • An analytical model for residual stresses in 3D printed parts is extensively tested. • The model is validated with experimental data and numerically computed results. • Residual stresses in large 3D printed parts of 5 alloy compositions were examined. • Powder-specific process maps of peak tensile residual stresses are presented.

An experimental and numerical study on the impact of various parameters in improving the heat transfer performance characteristics of a water based photovoltaic thermal system

The hybrid photovoltaic thermal system (PV/T) has been developed to harvest solar energy's electrical and thermal forms. However, effective heat evacuation from the backside of photovoltaic panels remains difficult, limiting their thermal and electrical performance. The current study presents a numerical and experimental examination of various parameters for improving a photovoltaic thermal system's heat transfer performance. The influence of flow parameters, tube diameters, and base plate thickness on the heat transfer, electrical, and overall performance characteristics of the water-based PV/T has been investigated. According to the current research, the water-based PV/T with a 16 mm tube diameter and a water flow rate of 1.02 L per minute has the highest average thermal, electrical, and overall efficiency of 44.5%, 14.8%, and 59.3%, respectively. The findings show that the photovoltaic thermal (PV/T) system's thermal and electrical efficiency increase when Reynolds numbers increase. The heat transfer rate of the PV/T system may increase by 15% with an increased Reynolds number. A maximum decrease in cell temperature is obtained by increasing the tube diameter and decreasing the backplate thickness of the photovoltaic thermal (PV/T) system. An increase in the tube diameters of the PV/T system results in a maximum reduction of 6 °C in cell temperature. The experiment and numerical findings were in better agreement in this study, with the highest relative error of 3.96%.

Design of steel transmission pole base plates using yield line method

Steel transmission poles are widely used for their strength, ease of construction, small footprint, and aesthetic appearance. These poles can be either directly embedded into their foundations or supported on based plates which are connected to the reinforced concrete footings via group of anchor bolts.There are few available published methods for the analysis and design of this type of base plate connection. These methods are not widely used in the industry as they are either complex, lack solid theoretical background, or yield results that are not consistent with manufacturer's time-tested proprietary design methods. Therefore, there is a need for an accurate method suitable for technical or design office for designing these connections when subjected to axial loads, bending moments or the combined effect of both.This paper presents a numerical study performed on the base plates of polygonal steel poles that are supported directly on anchor bolts with levelling nuts and subjected to bending moment and axial load. The Finite Element (FE) analysis part of the work is carried out using ADINA software and the results obtained from the analyses are compared with published experimental results from which it is concluded that the finite element model can accurately predict the behaviour of these connections.Parametric investigation is then conducted to gain more insight into the behaviour of these base plate connections and to use the obtained data the validation of the proposed design method. The parametric investigation covered the behaviour of these connections under pure axial load and pure bending moment while the varying parameters considered included number of shaft sides, base plate thickness, number of anchor bolts and anchor bolt diameter.Design formulae based on the yield line theory are then proposed and a comparison between the yield loads calculated using the proposed expressions and finite element results is presented. The yield loads resulting from using the proposed design method agreed with the finite element results with a maximum calculated difference of 13%.

Reliability assessment method for tank bottom plates based on hierarchical Bayesian corrosion growth model

For effectively predicting the tank failure time and analyzing the key elements influencing the reliability of corroded bottom plates, this article presents a model for calculating the reliability of corroded tank bottom plates based on a hierarchical Bayesian corrosion growth model. Firstly, the growth of corrosion defect depth is expressed by the gamma process, and the hierarchical Bayesian model is used to calculate the corrosion depth growth. After that, the reliability calculation model of the corroded tank base plate is established by combining the results of the hierarchical Bayesian model with the stress-strength interference theory, and the three uncertain factors of the base plate thickness, radius, and yield strength are considered in the model. Finally, the reliability assessment and sensitivity analysis of corroded bottom plate are carried out. The results show that the proposed reliability calculation model can provide more accurate failure state prediction results than the reliability calculation model which only considers the influence of corrosion depth, and can provide reference for reducing the failure rate of tank floor and reasonably formulating the maintenance plan of tank floor.