Base Plate Thickness Research Articles

Determination of the flexural behavior of steel storage rack baseplate upright connections with eccentric anchor bolts

The baseplate upright connections of the steel storage racks are often attached to the concrete floor by anchor bolts possibly at an eccentric location. Currently available rack design specifications do not provide any guidelines to take account of the influence of eccentric anchor bolt location and do not consider the associated baseplate behavior in the design of such storage rack base connections. The first part of this paper experimentally established the flexural behavior of the baseplate upright connections with eccentric anchor bolts. The experiments considered an enhanced test setup and five groups of three nominally identical test specimens. Influencing parameters such as the baseplate thickness, anchor bolt size, the bracket thickness and the upright thickness were studied. The experimental observations revealed that the baseplate eccentric anchor bolt assembly plays a dominant role on the flexural behavior of the entire baseplate upright connections. The rotational stiffness, the failure mode and the moment capacity of the base connections are strongly intertwined with the eccentric anchor bolt location as well as the baseplate bending behavior. In order to further understand the behavior of such connections, in the second part of the paper, a component-based analytical model is established to predict the initial rotational stiffness and the progressive post yielding rotational stiffnesses of the baseplate upright connections. The moment capacity of the connections is also determined using a deformation limit-based method. The analytical model gives only a 3% underestimation of the initial stiffness and a 3% overestimation of the moment capacity compared with experimental results. The proposed model is suggested to be incorporated in future rack design specifications so that the model can be used by the rack designers to analytically determine the behavior parameters of the eccentric anchor bolted baseplate connections. The rack designers can also use the proposed model to identify the deformation contribution of each individual component and to develop a multi-linear moment-rotation relation of the baseplate upright connections without resorting to the physical experimental tests. Parametric studies were also performed using the proposed analytical model and the influence of relevant parameters had been quantified. Doubling of the baseplate thickness may result in a 11–37% increase in the initial rotational stiffness of the considered baseplate upright connections.

STUDY OF 7 BUILDING DEVELOPMENT PLANNING SPECIFICATION OF STEEL FRAMEWORK STRUCTURE (BASED ON SNI 1729 - 2015) (CASE STUDY: OFFICE BUILDING CONSTRUCTION PROJECT)

Steel is a material that is widely used in industrial development and buildings with functions as the main building frame. This plan aims to plan a building structure with 7 floors plus a ground floor that will function as an office building with analysis using a Structure Analysis Program (SAP 2000 v.19) combined with steel regulations on SNI 1729: 2015. Based on the results of SAP analysis 2000 v.19 produces a column structure using WF Steel 400x400x30x50 with the beam 1 using the profile of Steel WF 350x300x14x23 and for the beam 2 using the profile of Steel WF 200x200x9x14. For anchor and baseplate using anchor M-25 with a length of 400 mm, with baseplate thickness of 25 mm and for bolts using M-25 bolts with a total of 16 bolts.

Cold formed steel storage racks subjected to axial, shear and bending interactions

This research article aims to study the behaviour of expansion bolts under axial, shear and bending interaction of base plate connected cold form steel storage racks. The bilinear moment rotation relationship was adopted to identify the ultimate moment of resistance and stiffness of the base plate connected to a concrete block using M10 grade anchor bolt at different range of axial loads ranging from 25% to 100% there by the design strength of upright profile was studied. The dimension of the upright and the base plate thickness has to be changed so that the extreme stability under various ranges of axial and transverse loads had been studied. Using finite element analysis software (Abaqus), a model has been created and designed to observe moment rotation characteristics, behaviour of base plate under simultaneous axial, shear and bending interactions and compared with experimental analysis. Comparative studies reveal that there was no failure in the concrete block and when the upright thickness increases, the stiffness and moment of the base plate increases despite having a similar cross section. An interaction equation was developed to find the stiffness and ultimate moment of resistance of the base plate connection.

ТЕОРЕТИЧНЕ ДОСЛІДЖЕННЯ НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ БАЗОВИХ ПЛИТ УЗРП-16

Theoretical studies of the stress-strain state of base plates, which are the base of the UZRP-16 universal collapsible machines have been done. These machines are used for welding works in machine building industry. The finite element method was applied to solve the problems. Nature of influence of strength and structural parameters on the base plate stress-strain state in operation has been determined, namely: the relations between displacements and stresses arising in the base plates and the bending moment magnitudes have been recorded; the stress-strain state pattern of the base plates has been obtained depending on the place of bending moment application; influence of the conditions for bearing and fastening the plates on their stress-strain state has been investigated; influence of the plate geometric parameters on stress and displacement has been studied; The stress-material and displacement-material relations have been obtained for the plates. Based on the theoretical study results of the base plate stress-strain state, the following have been obtained: stress plots and patterns of deformed surfaces, which are symmetrical with respect to the plate central axes; maximum values of normal and tangential stress components arising in the field of bending moment application; stress on the rectangular base plate surface is 2.1 times higher than the stress on square plate surface under the same conditions of bearing and loading; stresses acting on the plate surfaces and being tensile stresses within the range of 10 to 70 MPa. It was found that the square shape of the plates, according to the stress state, is predominant in relation to the rectangular shape. The optimal condition for bearing is fixing the plates at nine points. For the first time, graphs were drawn for choosing the base plate thickness under action of various operational loads.

Monotonic Response of Exposed Base Plates of Columns: Numerical Study and a New Design Method

This paper describes a numerical study of the behavior of exposed base plates of columns under the action of axial and bending loads. The aim of this research is to evaluate numerically the failure mechanisms on stiffened and non-stiffened base plates and propose a new design method. The effects of base plate thickness, location of anchor rods, location of stiffeners and tensile strength of anchor rods were considered in the analysis. Sixteen finite elements simulations were performed considering different combinations of the above mentioned parameters. The results show a fragile response in the base plates when high resistance anchor rods are used. The anchor rods worked as fuse elements in base plates with a large thickness or many stiffeners. Additionally, the models with anchor bars located outside of the column flanges showed lower flexural strength and rotational stiffness compared to the models with anchor rods located between column flanges. The simulations showed that the base plate strength was determined by the simultaneous failure mechanisms of two or more components, different to what is stated in current design guides. Finally, the new method is suitable to design base plates with stiffened and not stiffened configurations, which unlike traditional design methods, show a good adjustment with numerical models.

Plastic limit analysis for eight-bolted base plate based on slip-line field theory

Eight-bolted base plates have gradually been employed in the UHV transmission lines. On the basis of slip-line field theory, this paper derived new calculation methods for predicting the uplift bearing capacities of rigid and flexible base plate, their reasonable accuracy has been validated by comparing with test observations and yield-line method results. The relevant parametric analysis demonstrated these two methods have consistent variation tendency and the thickness of base plates is of paramount impact on ultimate strength. Design suggestions considered four possible failure modes and their corresponding calculation formulae were presented for evaluating the controlling capacities of base plates, one of which associated with slip-line method adopted the least-square fitting to obtain correction coefficients so as to get explicit solutions for calculations. Their applicability and accuracy have been verified by comparing with the test and corresponding code.

Simulating the hot dip galvanizing process of high mast illumination poles. Part II: Effects of geometrical properties and galvanizing practices

Cracks that develop during galvanization of High Mast Illumination Poles (HMIPs), often at the pole-to-base plate connection, are an important concern to US fabricators and highway officials. If they are not detected during fabrication and are allowed to propagate during service, these cracks can pose a significant risk to the public due to the ubiquitous presence of HMIPs in close proximity to roads and highways. Economic losses caused by these cracks include the cost of detailed inspections to ascertain their presence and direct losses associated with discarded poles or repair of cracks that manifest while in service. Modifications to the design of HMIPs and/or the galvanization process to reduce the likelihood of galvanization cracks reduce economic loses, decrease fabrication costs, and improve public safety. This paper presents a parametric study evaluating the effects of geometric configuration and galvanization practices on thermally-induced stress/strain demands during the galvanization of HMIPs. Simulations were performed for poles with standard pole-to-base plate connection details adopted by the Texas DOT. Geometric parameters evaluated in the study included base plate-to-pole thickness ratio, pole shaft geometric shape, and bend radius. Galvanizing practice variables included dwell time, speed and angle of dipping, and cross-section orientation. Simulations were conducted using the commercial software Abaqus, following the methodology validated in a companion paper. In models having the same pole thickness, thermally-induced stresses and strains at critical locations increased with base plate-to-pole thickness ratio. In models with the same base plate thickness, stress and strain demands varied inversely proportional to pole thickness. Stress and strain demands were found to be lower for poles having circular shape than for multi-sided poles, and increases in bend radius led to reductions in localized strain demands. Dwell time was found to have a negligible effect on stress and strain demands, while increased dipping speed and dipping angle resulted in decreased stress and strain demands during galvanizing.

Experimental investigations on concrete cone failure of rectangular and non-rectangular anchor groups

The current recommendations given in the codes and guidelines for design of anchorages to concrete are limited in scope to rectangular and regular anchor groups with a maximum of three anchors in a row. Furthermore, several assumptions are made, which may render the designs conservative but may also lead to unconservative results such as the required base plate thickness and the cracked concrete assumption. The aim of this experimental study was to investigate the load-displacement behaviour of tension loaded anchor group configurations that are either only partly covered or not covered by the current design provisions. Furthermore, this work aimed to generate an experimental database on the concrete cone failure of anchor groups under tension loading. The results of a comprehensive experimental program carried out on diverse anchor group configurations within and beyond the scope of the European Standard EN1992-4 are discussed focusing on several aspects such as (i) different geometric configurations, (ii) varying stiffness of the base plate, and (iii) influence of eccentricity. The experimental program contains tests on single anchors and on anchor groups in normal- and high-strength concrete. The testing concept, test setup and the test results are discussed in detail in this paper. Based on the evaluation of the test results presented here, a new analytical model is being developed for the concrete cone failure mode of tension loaded anchor groups that will be presented in a future paper.

Shear behavior of lap connection using one-side bolts

Experimental and numerical investigations on the basic shear behaviors of the lap connections connected by the threaded-fixed one-side bolts were presented. The threaded-fixed one-side bolt in the connection was clamped by internal threads on the wall of a bolt hole, instead of the traditional nut. 36 test specimens with different thicknesses of screwed shear plate and different bolt pre-tension forces were conducted. The failure mode of the shear connection obtained from tests were perfectly consistent with those predicted by EC3-1-8 design equations and the ultimate shear predicted resistance was conservative compared with the test result, both of which differed by 4.6%. A finite element model was built and verified to further investigate effects of the thickness of base plate and the bolt diameter on the shear behavior of the lap connection. The simulated results concluded that the bolt would tilt if the thickness of base plate was smaller than the bolt diameter. The lap connection using the threaded-fixed one-side bolts and the traditional bolts with nut were compared. Difference in the ultimate shear resistance is 0.24% as only the bolt shear fracture failure occurred, however, difference in the ultimate shear resistance is 2.5% as the bolt shear fracture accompanied by the bolt tilting occurred. This paper proved that the screwed shear plate could replace the traditional nut in engineering applications.

Rotational behavior of exposed column bases with different base plate thickness

Exposed column base connections are used in low- to mid-rise steel moment resisting frames. This paper is to investigate the effect of the base plate thickness on the exposed column base connection strength, stiffness, and energy dissipation. Five specimens with different base plate thickness were numerically modelled using ABAQUS software. The numerical model is able to reproduce the key characteristics of the experimental response. Based on the numerical analysis, the critical base plate thickness to identify the base plate and anchor rod yield mechanism is proposed. For the connection with base plate yield mechanism, the resisting moment is carried by the flexural bending of the base plate. Yield lines in the base plate on the tension side and compression side are illustrated, respectively. This type of connection exhibits a relatively large energy dissipation. For the connection with anchor rod yield mechanism, the moment is resisted through a combination of bearing stresses of concrete foundation on the compression side and tensile forces in the anchor rods on the tension side. This type of connection exhibits self-centering behavior and shows higher initial stiffness and bending strength. In addition, the methods to predict the moment resistance of the connection with different yield mechanisms are presented. And the evaluated moment resistances agree well with the values obtained from the FEM model.

Effect of Heat Sinks on Cooling Time to Weld Interpass Temperature

In high- and ultrahigh-strength steel welding, interpass cooling time is an important factor affecting productivity and welding costs. Usually, welding heat input is restricted to meet the relatively short recommended cooling times between 800 and 500 °C (t8/5), which are prescribed by the need to meet weld strength and toughness properties. This, in turn, leads to the need for multipass welding with the interpass waiting times needed for the weld to cool to a sufficiently low interpass temperature. Welding productivity is affected by both the number of passes and the interpass waiting time. With a view to minimizing the total number of passes needed for a given preparation, it is beneficial for the interpass temperature to be as low as possible as this permits higher heat input for a given t8/5. On the other hand, low interpass temperature requires longer interpass waiting times. Therefore, this research concerns the potential of introducing copper heat sinks adjacent to the weld to reduce the time it takes for the weld to cool down to the interpass temperature. It is demonstrated that, in the case of a butt weld in a 6 mm thick base plate MAG welded with a weld energy of 1 kJ/mm and an interpass temperature of 100 °C, copper heat sinks almoust halve the interpass waiting time. This can have a marked effect on the overall productivity when welding highand ultrahigh-strength steels and increase their attractiveness for steel construction.

Effect of Pressing Parameters on the Quality of Joint Formation of Heat Exchanger Fins with the Base Plate

In this paper, the results of experimental and numerical studies on joining the thin fins to the thick base plate of a heat exchanger are presented. The elements of the heat exchanger were joined by using developed method of press forming. The joining technology consists in clamping the sheet metal into the channel of the base plate using a punch with specific geometry. The effect of different configurations of the punch geometry (shape, radius and distance between fin and punch) and the indentation depth on the depth of the interface between the fin and base plate is analysed. Furthermore, the effect of different combinations of fin-base plate materials has been numerically studied. The plate material was the AA2219 -T851 aluminium alloy, while the fins were made of the AA5251 aluminium alloy. The elastic-plastic numerical computations of the joining process have been carried out using the finite element-based MSC.Marc program. It was found that the area of the contact of the fin with the base plate can be optimised by choosing the right parameters of the tool geometry and technological parameters. Experimental research has shown that increasing the punch indentation causes the material to flow in the transverse direction to the punch and the indirect extrusion in the region between the punches.

Cyclic loading tests on exposed column-base plate weak-axis connections of small-size steel structures

Research on evaluating the seismic performance of exposed column-base plate weak-axis connections of small-size steel structures is substantially limited. Therefore, in this study, six exposed column-base plate weak-axis connection specimens with L-shaped anchor bolts under cyclic loading were tested. The primary test variables were the thickness of base plates, the presence of rib plates, and the number and embedment length of anchor bolts. Furthermore, round and threaded rods with L-shape were used as anchor bolts to assess the effect of bond performance. It was found that the structural performance of the connections was influenced by the thickness of base plate and the bond performance of anchor bolts. It should be noted that although base plate meets the minimum thickness requirements by the current design code, if the base plate yields before the moment capacity of steel column reaches the plastic moment, the structural performance of the connection will decrease. The connection details in this study can be considered semi-rigid connections. Threaded anchor bolts with L-shape are more preferred over the smooth round anchors for increased bond strength. Furthermore, equations for required tensile capacity and cross-sectional area for anchor bolts were derived in this study.

Exposed column-base plate strong-axis connections for small-size steel construction

Experimental study on exposed steel column-base plate connections subjected to both axial and lateral loadings is quite limited. Therefore, based on the intensive field investigation, nine specimens were tested to appraise the seismic performance of various column-base plate strong-axis connections of small-size steel structures in this study. The main parameters were the thickness of base plates, the embedment length of anchor bolts, and the presence of hook and rib plates. Flexural strength, deformation capacity, energy dissipation, and stiffness of the test specimens were investigated. Based on the test results, the hysteretic behaviour of exposed column-base plate strong-axis connections was significantly influenced by the base plate thickness as well as the number and embedment length of anchor bolts. However, the effect of rib plates on the flexural performance of column-base plate connections was negligible. The flexural stiffness of the specimens was approximately 15% of the flexural stiffness by the New Zealand Standard with the assumption that the supports were fixed. It was found that although column-base plate strong-axis connections were properly designed in accordance with design guides, the flexural performance of the connections could be unreliable without sufficient bond capacity between concrete and anchor bolts.

Strain energy density based fatigue cracking assessment of load-carrying cruciform welded joints

This paper presents fatigue failure crack initial points and the fatigue failure mode transition relationship between the weld toe and root of load-carrying cruciform welded joints on the basis of LEFM and Williams’ notch stress intensity theory. The notch stress intensity factors (NSIFs) of different failure locations were calculated quantitatively. The averaged strain energy density (SED) in a control volume near the notches is used to unify the scalar quantity and rectify inconsistencies of NSIFs units for the weld toe and root. The failure mode transition relations of different geometrical parametric models (such as main plate thickness, attachment plate thickness, weld length, and penetration size) were compared and analyzed based on the SED values from weld toe and root locations, and the effect of unequal main plate thickness ratio in a cruciform joint on failure mode was also investigated. The results show that SED approach can be used to accurately predict the transition region of equal base plate thickness. The weld length and penetration size are related to significant changes in the fatigue failure location of cruciform joints. The SED approach effectively reflects failure characteristics and can be used to assess fatigue failure behaviors for load-carrying cruciform welded joints.

Investigation of Steel Column–Baseplate Connection Details Incorporating Ductile Anchors

It is widely accepted that the behavior of steel column–baseplate connections will profoundly impact the seismic response of steel buildings and other structures. Previous investigations into moment-frame steel column–baseplate connections have focused on the relationship between global metrics such as connection strength and stiffness to basic design parameters such as anchor arrangement and size, baseplate thickness, and column size. However, there is growing recognition that other details, such as the column setting method, baseplate hole size, anchor material selection, and anchor stretch length may significantly affect connection performance. This paper describes nine full-scale connection tests exploring the effects of such details on strength, rotation capacity, and postyield behavior. A comparison of the present with a prior test program on the basis of physical damage evolution and moment-rotation behavior is undertaken. The baseplate setting arrangement and anchor stretch length were found to have the most pronounced impact on the connection cyclic moment-rotation response. Suggestions for connection details that promote connection robustness, ductility, and strength are presented.

Analysis and design of demountable embedded steel column base connections

This paper describes the finite element model for predicting the fundamental performance of embedded steel column base connections under monotonic and cyclic loading. Geometric and material nonlinearities were included in the proposed finite element model. Bauschinger and pinching effects were considered in the simulation of embedded column base connections under cyclic loading. The degradation of steel yield strength and accumulation of plastic damage can be well simulated. The accuracy of the finite element model is examined by comparing the predicted results with independent experimental dataset. It is demonstrated that the finite element model accurately predicts the behaviour and failure models of the embedded steel column base connections. The finite element model is extended to carry out evaluations and parametric studies. The investigated parameters include column embedded length, concrete strength, axial load and base plate thickness. Moreover, analytical models for predicting the initial stiffness and bending moment strength of the embedded column base connection were developed. The comparison between results from analytical models and those from experiments and finite element analysis proved the developed analytical model was accurate and conservative for design purposes.

Fatigue of titanium weldments: S-N testing and analysis for data transferability among different joint types

Fatigue testing of both TIG and MIG welded titanium components were first carried out using fillet welded cruciform specimens. A mesh-insensitive traction structural stress method is then introduced for establishing data transferability from one joint geometry to another and one base plate thickness to another. In addition, available test data from literature are also analyzed using the traction stress parameter proposed. Major findings are:(a) There exist no noticeable differences in S-N curve behaviors between Ti-CP and Ti-6-4 weldments.(b) The proposed traction stress parameter with a thickness correction term can be used to effectively correlate lab specimen test data in the form of a single S-N curve with a narrow scatter band regardless of joint types and base plate thicknesses, which has been demonstrated for both MIG and TIG welded specimens.(c) By using both the S-N curve and traction stress parameter developed, satisfactory fatigue life estimates for a series of full-scale MIG-welded structural component fatigue tests have been achieved.

Numerical Thermal Analysis and Optimization of Multi-Chip LED Module Using Response Surface Methodology and Genetic Algorithm

In this paper, the heat transfer performance of the multi-chip (MC) LED module is investigated numerically by using a general analytical solution. The configuration of the module is optimized with genetic algorithm (GA) combined with a response surface methodology. The space between chips, the thickness of the metal core printed circuit board (MCPCB), and the thickness of the base plate are considered as three optimal parameters, while the total thermal resistance ( $R_{\mathrm {tot}})$ is considered as a single objective function. After optimizing objectives with GA, the optimal design parameters of three types of MC LED modules are determined. The results show that the thickness of MCPCB has a stronger influence on the total thermal resistance than other parameters. In addition, the sensitivity analysis is performed based on the optimum data. It reveals that $R_{\mathrm {tot}}$ increases with the increased thickness of MCPCB, and reduces as the space between chips increases. The effect of the thickness of base plate is far less than that of the thickness of MCPCB. After optimization, three types of MC LED modules obtain lower $T_{j}$ and $R_{\mathrm {tot}}$ . Moreover, the optimized modules can emit large luminous energy under high-power input conditions. Therefore, the optimization results are of great significance in the selection of configuration parameters to improve the performance of the MC LED module.

Influence of base plate bending stiffness on the seismic performance of liquid storage tanks

In the past, a number of investigations have been performed on the seismic behaviour of storage tanks. At the University of Auckland, a number of shake table experiments on tanks with different aspect ratios have been recently performed. The earthquake ground excitation was simulated based on a design spectrum from the New Zealand code NZS 1170.5, classification D for soft soils. The results show that the base plate stiffness of storage tanks may play a significant role in the magnitude of hoop stresses caused by the passage of the earthquake. To incorporate a low-damage seismic design philosophy, the tank is allowed to separate partially at the base. This temporary separation initiates rigid body like motion of the tank and thus reduce the wall local deformations. Consequently, the stress development along the wall can be reduced from that occurring with full base plate contact. This research focuses on the effect of the base plate thickness on the hoop stress development along the height of the tank wall for five radial directions.