Flange Wall Research Articles

Experimental insights into the seismic behaviour of flanged URM walls

Considerable attention has been given to understanding and modelling the seismic response of unreinforced masonry piers with rectangular cross-sections. However, the seismic performance of load-bearing masonry walls with flanges, commonly found in actual building configurations, remains less explored. This study investigates the behaviour of flanged walls through cyclic quasi-static tests on four full-scale C-shaped specimens comprising two primary seismic-resistant walls (webs) interconnected by a single flange. The construction of the specimens varied: two were built using standard solid calcium-silicate bricks with general-purpose mortar, while the other two utilised large-sized calcium-silicate blocks with tongue-and-groove interlocks and a thin layer of cement-based adhesive mortar. All specimens were subjected to cyclic horizontal loading parallel to the webs under consistent overburden load and double-fixed boundary conditions. The primary variable in testing the two walls of each type was the number of cyclic loading repetitions. This paper initially describes the key characteristics of the wall specimens, including geometry, construction details, and mechanical properties. Subsequently, it details the instrumentation plan and test protocol, and summarises the major observations from the tests, illustrating damage evolution and hysteretic force-displacement response. The results highlight the effect of the flange on initial stiffness and lateral force resistance, as well as the influence of block type and loading repetitions on failure mode, displacement capacity, and energy dissipation. Additionally, the study demonstrates the impact of floor slab uplift due to in-plane rocking of the webs on the top boundary conditions and the out-of-plane stability of the flange.

The Strength and Minimum Wall Thickness of Wellhead Equipment for Ultrahigh-Pressure Oil and Gas Wells

Summary As oil and gas wells are drilled to greater depths, wellhead pressure is expected to exceed the 20 ksi (138 MPa) limit specified by API SPEC 6A and other industrial standards, necessitating the development of 25 ksi (172.4 MPa) equipment. This paper focuses on the strength design and analysis of ultrahigh-pressure wellhead equipment, reviewing various wall-thickness calculation formulas and design criteria based on basic mechanical theory. It traces the flange wall thickness calculations in API SPEC 6A, discusses issues with 25-ksi equipment, and analyzes safety factors, methods, and allowable stresses in different standards. The findings of the research indicate that for high-pressure equipment with a pressure of 25 ksi (172.4 MPa), the optimal ratio of outer diameter to inner diameter is 2, and the structure can meet the requisite strength requirements. The wall thickness design method for structures such as flanges in traditional American Petroleum Institute (API) specifications uses the maximum principal stress criterion for calculation, which is not applicable to high-pressure equipment. For high-strength steel with high yield ratio used in high-pressure equipment, yield strength and tensile strength should be combined in design and use, fully utilizing the material’s properties. It is recommended to use finite element analysis for high- and ultrahigh-pressure complex structures, following the latest design concepts such as elastic-plastic ASME standards. The research provides a theoretical basis for designing ultrahigh-pressure wellhead equipment.

Prediction and optimization framework of shear strength of reinforced concrete flanged shear wall based on machine learning and non-dominated sorting genetic algorithm-II

Reinforced concrete (RC) flanged shear wall has good lateral strength and stiffness, which has been widely used in building structures. Due to the coupling effect of many factors such as wall section shape, shear span ratio, so the shear performance evaluation of flanged wall is still very limited. This paper proposed a prediction framework for the shear capacity of RC flanged shear walls. A database containing 14 input variables, 1 output variable and 153 samples was constructed to evaluate the prediction accuracy of 11 existing design methods. The Pearson coefficient was used to preliminarily analyze the correlation between variables. The grid search was used to optimize the hyperparameters of 4 machine learning models, and six statistical indicators ( R2, R, RMSE, SD, MAE, and MAPE) were used to comprehensively compare the prediction results of the ML models to determine the best model. On this basis, SHapley Additive exPlanations (SHAP) was used to enhance the interpretability of the prediction models, and the mechanism of the input variables on the shear capacity was quantified. A graphical user interface (GUI) was proposed to guide the engineering design. A multi-objective model (MOO) was established to analyze the trade-off between shear performance and cost, thereby determining the best optimal scheme. The results show that the prediction accuracy of the ML models is better than the existing design methods. The XGB model has the best prediction performance, with R2, R, RMSE are 0.99, 0.99, 118.96, respectively. The SHAP method can effectively enhance the interpretability of the ML models, and tw, lw and f ′c are the key parameters affecting the shear capacity of the flanged shear wall.

Experimental and Analytical Study on Shear Lag Effect of T-Shaped Reinforced Concrete Shear Walls

Because of the flanges on T-shaped shear walls (TSSWs), the shear force acting on such walls results in a shear lag effect, making it impossible to forecast with accuracy the normal stresses of the flanges using the Bernoulli–Euler assumption. Shear lag (SL) in flanged walls has, however, received less attention from researchers, particularly in experimental studies. Understanding the SL in T-shaped reinforced concrete shear walls under shear and axial force is the main goal of this work. First, a SL model is suggested for TSSWs. In this model, the SL deflection is considered to be the generalized displacement and the SL warping deformation, and it is assumed to be a quadratic nonlinear function. Then, experimental and numerical simulation studies are, respectively, conducted to investigate SL effect of TSSWs, and also to evaluate the accuracy of the SL method. Finally, the parameter analysis is conducted to investigate the influence of axial load, shear force, and flange length on the SL effect of TSSWs. The results show that the SL of the TSSW is significant, the normal stress distribution (NSD) of the flange is uneven, and the normal stresses near the web are higher, according to the results of the analytical, simulated, and experimental results. The SL model can accurately predict the normal stresses of the flange of TSSWs, and the quadratic parabola assumption of the SL warp displacement of TSSWs is reasonable. Parameter analysis shows that axial force has little effect on the SL effect of TSSWs. The TSSWs under larger shear force have the more obvious SL effect. A more obvious SL effect occurs in the TSSWs with longer flanges.

Mechanical performance of elliptical one-sided bolted joints for T-stub and hollow section members under tension

This paper presents experimental and numerical investigations on the tensile performance of the elliptical one-sided bolted joints in building applications. Two types of joints are examined including the T-stub joints and T-hollow joints, where T-stub joints are formed by two T-stubs connected together through elliptical one-sided bolts at their flanges; and T-hollow joints are formed by two T-stubs connected to a square hollow section (SHS) member with the help of the elliptical one-sided bolts. A group of T-stub joints with ordinary bolts is also comparatively studied. Similar failure modes were observed for either elliptical one-sided or ordinary bolted joints while the yield capacity for elliptical one-sided joints was 9% lower than that of ordinary bolted joints for the T-stub joints. Parametric studies are further carried out on the key parameters such as flange thickness of the T-stubs and wall thickness of the hollow section members in the T-stub and T-hollow joints. It is found that the joint stiffness and strength can be improved with the increase of flange thickness or wall thickness for T-stub and T-hollow joints. Analytical models based on the yield line mechanisms are then presented, providing mechanism-based understanding for such elliptical one-sided joints in structural assembly. Detailed finite element (FE) models were constructed with considerations of bolt pre-tensioning and contact behaviours such as those between T-stub flange and bolt head. The deformed configurations of specimens can be successfully described by the FE modelling and the differences on initial stiffness and yield capacity between experimental and FE results are within about 10%.

An analytical investigation into the lateral load response of curved RC shear walls

SummaryCurved structural elements can extensively be employed in engineering applications, to which structural designers and architects can resort in order to cope with the existing structural limitations and architectural challenges. In this regard, the current study is an attempt to provide insight into the overall performance of curved reinforced concrete (RC) shear walls (CRCSWs) due to the gaps existing in the literature. In order to fulfill this purpose, a CRCSW with general cross‐section has been considered subjected to the applied bi‐lateral and axial loadings. Equivalent non‐rectangular T‐, U‐, and L‐shaped sections are then introduced in lieu of a curved section. Thereafter, the stress and displacement distributions of CRCSWs have been analytically established. In order to highlight the structural merits of CRCSWs, a comparative study is performed based on the six non‐dimensional parameters defined in this study. According to the comparative study conducted between the CRCSWs and the equivalent non‐rectangular flanged walls, unlike latter wall types, the shear‐lag effects do not make serious issues for the performance of CRCSWs. Furthermore, to make a more realistic judgment on the response of CRCSWs, a numerical investigation has been carried out utilizing the finite element (FE) software Abaqus. On the strength of the data obtained from the FE simulation of 90 CRCSWs in three categories of short, squat, and slender walls, a regression model has been established, which is advantageous in that it can supply a means for the initial estimation of the shear strength of CRCSWs. The average R‐factor of 0.88 indicates that the established formulations can potentially well predict the shear strength of CRCSWs. The findings of this study divulge that, in addition to the inherent aesthetical advantages of CRCSWs, these structural elements can effectively resist against bi‐directional loadings as compared with the equivalent RC walls with flanged sections.

Plastic Hinge Length for Flanged Reinforced Concrete Shear Walls with Asymmetric Sections

ABSTRACT This research investigates the determination method, spreading mechanism and influencing factors of the plastic hinge length for asymmetrical flanged walls using the finite element method. The plastic hinge length of flanged walls under flange-in-compression loading is generally greater than that under flange-in-tension loading. Based on the results, simple equations for predicting the plastic hinge length of flanged walls and which consider the contributions of the moment gradient, diagonal shear cracks, and strain penetration are proposed. Through comparison with the existing equations and design codes, the predicted plastic hinge lengths obtained from the proposed equations accord better with the test results.

Database of flanged reinforced concrete squat walls and its utilization based on machine learning

Flanged reinforced concrete (RC) squat walls are widely used in conventional buildings, owing to their capability of meeting certain architectural demands and providing significant lateral strength and stiffness in both principal directions. Despite their popularity and advantages, understanding of these walls is still limited due to the complexities brought by the non-rectangular cross-section and the relatively small shear span ratio. To facilitate future investigations through, a database containing comprehensive information about 182 flanged RC squat walls is presented in this paper. The criteria for selecting data and relevant sources are first introduced. Then items in the database are categorized into five groups, with histograms to assist understanding. The characteristics of these items are also discussed, and suggestions for future research are proposed. Furthermore, potential uses of this database are suggested, and the peak shear strength of these walls is explored based on machine learning as an example of utilization of this database. Compared with the mainstream building codes, this data-based approach produces much better predictions. Researchers are also encouraged to explore the use of this database through other data-driven approaches.

Cold resistance of steel beam prestressed by wall drawing

Introduction. The purpose of the article is a generalized analysis of existing methods for determining of structural steel elements behaviour in extreme conditions of subzero temperatures and their use to assess the cold resistance of steel beams prestressed by drawing of a thin wall. Subject of study is structural steel. Object of study is bimetallic steel beam prestressed without rods.Materials and methods. The study is based on the mechanics of deformable solid bodies, studies of the mechanical characteristics of steel and its behaviour at considerable subzero temperatures, taking into account stress concentrators and the probability of brittle cracks in the beam elements.Results. The impact strength analysis of steels C440 and C245 used in the flange plates and wall of prestressed beam was carried out. It is found that during the structure operation in the temperature range from minus 45°C to minus 55°C, cold resistance of the beam elements is ensured. It is proved that actual normal stresses in the extreme fibers of the prestressed beam web section are lower than the allowable stresses during plastic deformation of the wall material and, according to the theory of M. Huber, R. Mises and H. Hencky, the probability of brittle cracks in stress concentrators zone is low. It is found that the absence of stiffeners along the beam wall reduces plastic deformations caused by welding, reduces the number of extra elements in the structure and increases the material’s cold resistance.Conclusions. The high stability of prestressed beam wall enables designing it quite thin and increasing its cold resistance. The stressed state of the structure, reduction of its weight, thinning of wall, absence of welding stress concentrators, and reduction of the number of extra elements in the beam testify to the cold resistance of the material of the beam pre-stressed by wall drawing.

Analysis of Reinforced Concrete Shear Walls with Different End Configurations for Seismic Design

The Canterbury earthquake royal commission report highlighted that, despite being well-detailed, several reinforced concrete (RC) shear walls did not achieve their anticipated ductility capacities. In order to enhance the performance of such walls during future seismic events, the report recommended the use of concentrated and confined rebars at the wall toes coupled with high reinforcement ratios within the wall to initiate secondary cracks and extend the inelastic wall regions, thus minimizing the corresponding seismic demands. In this respect, the current study evaluates the seismic performance of RC walls with flanged and boundary element configurations compared with their typical rectangular counterparts, when different reinforcement ratios are incorporated. Specifically, the study presents a detailed analysis of six three-story half-scaled RC shear walls tested under quasi-static cyclic loading representing different seismic demands. The six walls were originally tested in two phases, where each phase had three different wall types (i.e., rectangular, flanged, and boundary element configurations). Walls in both phases had the same overall dimension and cross-section area; however, Phase II walls had 2.4 times the vertical reinforcement ratios used in Phase I walls. Following a summary of the experimental program and results, the current study presents the analytical results of the walls in terms of their load-strain relationships, curvature profiles, stiffness degradation trends, energy dissipation capacities, and equivalent viscous damping ratios. A comparison between the theoretical and experimental curvatures is also presented for the test walls at different drift levels. The results show that flanged and boundary element walls had low yield curvatures and high ultimate curvatures which resulted in enhancing their displacement ductility capacities. Flanged and boundary element walls also exhibited higher stiffness degradation rates when compared with their rectangular counterparts, leading to reduced seismic demands. Moreover, flanged and boundary element walls with high vertical reinforcement ratios (1.58%–1.63%) had higher energy dissipation capacities than their counterparts with low vertical reinforcement ratios (0.66%–0.69%). However, rectangular walls with low vertical reinforcement ratios (1.17%) showed higher ultimate curvature capacities than rectangular walls with high vertical reinforcement ratios (2.80%). Overall, the results demonstrate that future editions of relevant design standards (e.g., CSA A23.3 and ACI 318-19) should consider assigning different seismic design parameters (e.g., ultimate compressive strains, equivalent viscous damping ratios, and ductility-related modification factors) for RC shear walls based on their end configurations that can significantly alter the performance of such walls under seismic events.

Analytical Modeling of Posttensioned C-Shaped CLT Core Walls

Post-tensioned (PT) timber technology, also referred to as Pres-Lam (prestressed laminated timber) provides a low damage seismic design solution. So far PT timber research and practical implementation have focused on moment resisting frames, planar shear walls and coupled planar shear wall—or column-wall-column—systems and their analytical prediction models were adapted and extended from precast concrete to account for the unique characteristics of engineered timber. Following a recent experimental study on a PT cross-laminated timber (CLT) C-shaped core-wall system aiming to enhance lateral strength and stiffness, this paper presents an analytical framework/model to capture three unique kinematic rocking mechanisms for a PT C-shaped CLT core-wall system connected primarily with self-tapping screws. Depending on the relative stiffness of the screwed connections to the PT and the energy dissipaters, the model considers different kinematic responses, and that a staged kinematic response could occur at different imposed core-wall base connection rotations. It also accounts for the material inhomogeneity of CLT with nonedge glued lamella and implements a nonlinear spring model for the screwed connections calibrated from component testing and expected elastic core-wall deformations. The study showed that, for the given specimen configurations presented, the compressive flange wall could be neglected for a PT C-shaped CLT core wall. The analytical model was verified against three large-scale 8.6 m high PT C-shaped core-wall experimental tests and the model prediction error was within 10%. The analytical model was limited to capturing the envelope (push-over) curve of a four wall PT C-shaped CLT core-wall system.

Seismic performance of flanged RC walls under biaxial cyclic loading

Flanged RC walls are frequently utilized to provide strength and stiffness in two horizontal directions, yet the coupling of the bidirectional horizontal components of ground motion are bound to have large impact on the seismic response of flanged walls. However, few data exist characterizing the performance of flanged walls subjected to biaxial cyclic loading. Aiming to provide an insight into the influence of the biaxial coupling effect on the seismic behavior of flanged RC walls, three T-shaped and two L-shaped walls were tested under uniaxial and biaxial loading. Subsequently, a finite element model was employed for parametric studies and generating numerical data for a detailed comparison of the seismic performance of the flanged walls under uniaxial and biaxial loading. The results showed that the coupling of alternating loadings in orthogonal directions intensified the cracking and damage of flanged walls, resulting in the reduction of the bearing and deformation capacities, an increase in the proportion of flexural deformation in the plastic hinge area, acceleration of the energy dissipation process, and a more significant shear lag effect as opposed to uniaxial loading. Furthermore, the damage aggravation as well as reduction in seismic performance of L-shaped wall due to the biaxial coupling effect were more obvious than that of T-shaped wall. Based on the test and numerical results, the reduction of the ultimate inter-story drift ratio caused by biaxial loading was quantified through statistical analysis and the derived reduction factors can provide reference for the performance-based seismic design and anti-collapse design of flanged RC walls under multi-dimensional seismic action.

Effect of flanges on the in-plane behavior of the masonry walls

In unreinforced masonry buildings, load bearing walls are not of only rectangular shape in the plan, but the cross walls connected to them make the walls of either I shape, T shape, C shape, etc. The presence of the cross walls can significantly change the behavior of the masonry walls in terms of strength and the failure modes of the walls. In this paper, a parametric study has been performed to investigate the effect of different parameters, namely pre-compressions, material properties, aspect ratios, and boundary conditions on the in-plane behavior of the masonry walls. The masonry walls have been modeled using the simplified micro-modeling approach in the standard finite element software Abaqus without any user-defined subroutine. It has been found that the strength and damage pattern of the flanged walls are different from the rectangular walls, which needs to be considered in the analysis of masonry walls using a numerical approach or while conducting experiments.

An Analytical and Numerical Approach for Shear Failure of Pier-Wall Connections in Typical Dutch URM Buildings

ABSTRACT Since the 1980s, calcium silicate element masonry has been commonly used in Dutch buildings, and vertical continuous joints have been usually located at the corner of perpendicular walls. Since the shear failure of these joints may significantly reduce the seismic performance of the flanged wall and therefore of the entire building, the assumption of rigid connection may be inaccurate, unlike for the traditional interlocking of bricks in running bond textures. In this paper, analytical and numerical approaches to study the failure of vertical joints in the seismic assessment of URM buildings are presented. The first part of the work focuses on two different numerical models to study the nonlinear behaviour of the vertical connection; the related critical numerical issues are then discussed. The second part introduces an analytical method able to estimate the lateral force–displacement curve of a flanged wall, which considers the possible failure of the connection. In particular, the method is derived from the section analysis approach developed for controlled rocking deformable systems. The comparison between the numerical simulations and the analytical method proves the capacity of the latter to provide a quick but sufficiently accurate estimate of the force–displacement curve of a URM U-Shaped wall.

Experimental study and finite element analysis of T‐shaped precast shear walls with H‐shaped shear keys

AbstractTo achieve an effective horizontal connection between the flange and web of a prefabricated T‐shaped shear wall and ensure the seismic performance of the joint, a prefabricated T‐shaped reinforced concrete (RC) shear wall with H‐shaped shear keys (HSKs) is developed in this study through tests of full‐scale specimens, finite element (FE) parametric analysis, and deriving design equations. To facilitate transportation and installation, the flange and web of this T‐shaped shear wall are composed of several precast wall panels without protruding parts. The HSKs are welded between these wall panels to transfer the out‐of‐plane load of the flange wall and the in‐plane load of the web wall. The target mechanical properties of the HSK can be accurately designed by adjusting its geometric parameters such as the shape, height, thickness, and the core area width. Based on the test results, a FE model of the HSK shear wall is established, and parametric analysis is carried out to optimize its design. Finally, based on the design target of both yield force and yield displacement, a double‐target design approach is proposed to meet the different seismic requirements of HSK shear walls at different storeys.

Molecular mechanisms of maize endosperm transfer cell development.

Endosperm transfer cells function as the nutrient transporter, antimicrobic barrier, and signal mediator between filial and maternal tissues. Sugar supply of maternal tissues, sugar demand of filial tissues, and requirement for defence against pathogens are three elemental factors inducing differentiation of endosperm transfer cells. Epigenetic factors, especially MEG1, moderate the key genetic factor ZmMRP-1 to activate endosperm transfer cell-specific genes that control the flange wall ingrowth formation and defensin-like protein secretion in maize. Auxin and cytokinin are primary hormones involved in development of maize endosperm transfer cells. Crosstalk between glucose and hormone signaling regulates endosperm transfer cell development via modifying ZmMRP-1 expression. This review summarizes the current knowledge on maize endosperm transfer cell development, and discusses its potential molecular mechanisms. It is expected to strengthen the theoretical basis for structural and functional optimization of endosperm transfer cells, and yield improvement of kernels in maize.

Experimental seismic behavior of T-shaped double skin composite wall with steel truss

The double skin composite wall (DSCW) with steel truss is an innovative lateral load resisting member which composed of two steel plates, core concrete, concrete-filled steel tubes (CFSTs) as boundary members, and steel truss connectors. The effects of the aspect ratio and the flange wall width on the seismic performance are investigated based on the quasi-static test of full-scale T-shaped DSCWs with steel truss. The failure mode, load-displacement response, shear strength, ductility, energy dissipation, shear deformation, and stress distribution of the specimens were analyzed. The test results showed that the failure mode of the T-shaped DSCW with steel truss specimens with aspect ratios of 2.0 and 2.5 was flexure-shear failure, which was characterized by shear buckling of the steel plate, local buckling, and fracture of the boundary members, and of crushing of core concrete. The T-shaped specimens with a small aspect ratio have a higher shear strength, ductility, energy dissipation capacity, and shear deformation proportion. The T-shaped specimen with a long flange wall also has a higher shear strength, but the ductility, energy dissipation capacity, and shear deformation proportion are small. The stress distribution indicates that the T-shaped specimen is more likely to failure due to the insufficient flexural strength of the boundary member. The theoretical formula for the flexural strength of T-shaped DSCW with steel truss is established, and the validation results show that the formula is accurate and safe.

Effects of press-forming parameters on the dimensional stability of paperboard trays

The dimensional stability of press-formed paperboard trays was investigated during heating and cooling of trays packed with oatmeal. Female mold tool temperature, dwell time, pressing force, and blank holding force were altered in the press-forming of the trays to observe their impacts on the dimensional stability. Dimensional measurements of the trays showed reduced tray width, and the trays exhibited distortions on the tray flange and outer wall. The results showed smaller effects on the tray length, parallel to the machine direction of the material. Improved dimensional stability of the trays was found with a 180 °C female mold tool temperature, a 600-ms dwell time, a 150-kN pressing force, and a 1.44-kN blank holding force. The optimal press-forming parameters were concluded to enhance bonding of the paperboard fibers during the press-forming. The optimization of the press-forming parameters was found necessary to reduce the observed negative response of the material to the challenging environmental conditions in the production of prepared food.

PEAK SHEAR STRENGTH OF H-SHAPED REINFORCED CONCRETE SQUAT WALLS

Flanged RC squat walls are widely used in conventional buildings and nuclear facilities owing to the significant lateral strength and stiffness in both principle directions. The building codes are found to have some problems in predicting the peak shear strength of flanged RC squat walls, such as insufficient parameters and the exclusion of the influence of the flanges. Moreover, calculated values are more discrete than experimental values. In this paper, we established a database of the comprehensive information of 152 flanged RC squat walls. The performance of popular building codes in predicting the peak shear strength of this kind of walls was compared and analyzed. Based on the crack patterns on the web, a model of flanged RC squat walls considering the influence of the flanges was built, based on which the equation for the peak shear strength was deduced. The results reveal that the proposed equation can calculate the peak shear strength of the shear walls in the database with a mean value of 1 and a small variation coefficient. These results can provide guidance for the design of structural walls and the revision of building codes.

DEVELOPMENT OF TECHNOLOGICAL PROCESS OF FORMATION OF WIDE FLANGES ON SHEET PROCUREMENTS BY ROLLING STAMPING METHOD

The article presents the results of development and research of the technological process of forming wide outer flanges of lids of malt and distillation columns on sheet blanks by rolling stamping. For this purpose, equipment has been developed in the form of a rolling device for a lathe and an autonomous rolling unit, which allow to form the outer flanges with a conical roll. The rolling unit to the lathe provides the presence of coil springs for pressing the roll to the workpiece with the mandrel. Both settings provide the ability to change the angle of the axis of the rolling unit relative to the axis of the mandrel with the workpiece. Studies have shown that the technological capabilities of the process are limited by the corrugation of the flange wall. The power calculation of flanging of external flanges by a conical roll by the SHO method is carried out and formulas for determination of deformation forces are received. The acceptable accuracy of these formulas has been experimentally confirmed, and there is a tendency to increase the error with increasing geometric dimensions of the workpiece. To assess and expand the technological capabilities of the process, an analysis of the formation and deformed state of the workpieces. Since the main danger in the formation of external flanges by the SHO method is the loss of stability in the form of corrugations, the paper obtained an expression for determining the maximum width of the flange under the condition of a stable process. If it is necessary to obtain more developed flanges, it is proposed in the second stage to provide thinning of their wall by drawing with the use, if necessary, heating the workpiece by induction method.