Flange Wall Research Articles

Impact of concrete strength on seismic behavior of T-shaped double-skin composite walls

This study investigates the seismic performance of T-shaped double-skin composite walls (DSCWs), which are comprised of double-skin composite flange and web walls and concrete filled steel tubular (CFST) boundary elements, through experimental tests. Six T-shaped DSCW specimens, which are categorized into three groups, according to flange width and type of mechanical connectors (shear studs/tie bars), are tested under combined axial compressive loads and lateral cyclic loads. The DSCWs fail in a ductile flexural mode with similar damage patterns, characterized by buckling of steel tubes and faceplates, concrete crushing, and fracture of steel tubes at the wall base, and exhibit asymmetric hysteresis behaviors, with higher stiffness and strength but lower deformation capacities when the flange walls are under tension. Special focus should be placed on the design of CFST boundary element connected to the web wall, whose compressive failure triggers the loss of load carrying capacity of the specimens. The comparisons between the behaviors of two specimens in each group, which are infilled with high strength (C70) and normal strength concrete (C30) respectively, suggest that employment of high strength concrete improves the seismic behavior of T-shaped DSCW significantly regardless of the flange wall width when shear studs are used. Tie bars may impair the seismic behaviors of DSCWs by inducing premature local buckling of perforated steel faceplates. Numerical studies are conducted using detailed finite element models to investigate the buckling behaviors of steel faceplates which are connected to infilled concrete by tie bars and shear studs. The simulation results reveal that the former buckles earlier than the latter due to smaller critical stress. The slenderness ratio limits to prevent local buckling prior to yielding of steel faceplates are also suggested when these two types of mechanical connectors are used.

Effects of Variable Punch Speed and Blank Holder Force in Warm Superplastic Deep Drawing Process

A cylindrical deep drawing test was conducted for the purpose of improving the drawability, product accuracy, and quality in warm deep drawing using a superplastic material with large strain rate dependence. Then, the effects of blank holding force (BHF) and punch speed (SPD) on the flange wrinkle behavior and wall thickness distribution were investigated by experiments and theoretical analysis. A Zn-22Al-0.5Cu-0.01Mg alloy superplastic material SPZ2 with a sheet thickness of 1 mm was employed as the experimental material, and a cylindrical deep drawing experiment with the drawing ratio (DR) of 3.1 and 5 was performed at 250 °C. A good agreement was qualitatively obtained between the elementary theory on the flange wrinkle limit, the fracture limit, and the experimental results. In addition, the authors examined each variable BHF and SPD method obtained from the theory and experimentally demonstrated that the variable BHF method has a great effect on uniform wall thickness distribution and that variable SPD has a great effect on shortening the processing time for superplastic materials. Furthermore, the authors demonstrated the effectiveness of the variable BHF/SPD deep drawing method that varies both BHF and SPD simultaneously.

A dynamic small-sized hole flanging process driven by Lorentz-force for aluminum alloys

Lorentz-force-driven (LFD) stamping process is effective in formability enhancement and shape controlling in deep cup drawing. In this paper, LFD process was proposed for small-sized hole-flanging. A series of LFD flanging experiments under different diameters of pre-fabricated hole were carried out, and conventional flanging was implemented for comparison. Defect-free case with smaller prefabricated hole confirmed the potential of the LFD process in reaching higher flanged wall without fracture. Punch velocity captured during experiments reached the maximum value of around 10 m/s for both cases, four defect-free cases and the case of φ = 8.75 mm. A numerical model was established to investigate the deformation behavior and geometrical parameters during LFD flanging. Simulation results showed that excessive radial tensile strain in punch side led to the exceptional increase in thickness strain and thinning at the fillet. In addition, greater effective plastic strain along punch side elements resulted in higher hardening level than that in die side. Furthermore, bending moments would be generated when work-piece contacted with tools fillet, which formed the curved profile in die side and straight profile in flanged wall of punch side. More importantly, edge material attached to punch sidewall when slid through it and the diameter of straight profile there was totally controlled by the punch parameter.

A machine learning-based formulation for predicting shear capacity of squat flanged RC walls

The squat flanged reinforced concrete (RC) walls have been widely utilized in nuclear power plant and building structures. Nevertheless, the empirical equations in current design codes and published studies show a significant discrepancy in calculating the shear strength of the walls. The purpose of this study is to develop an effective machine learning model, namely artificial neural network (ANN), for predicting the shear strength of squat flanged RC walls. A total of 369 test results of squat flanged RC walls were collected from the literature and used to develop the ANN model. The results of the proposed model were compared with those of existing design codes and published studies. The comparisons emphasized that the developed ANN model in this paper can predict the shear capacity of squat flanged RC walls more accurately than the existing equations. Moreover, the effect of input parameters on the predicted shear capacity of the walls was sufficiently investigated. A predictive formula based on the ANN model, which can cover thirteen input parameters, was then proposed to compute the shear strength of the squat flanged walls. Additionally, an efficient graphical user interface (GUI) platform has been established for facilitating the practical design process of the squat flanged RC walls.

Interaction equations of composite walls with T-section under axial compression and biaxial bending

This paper studies the load-carrying capacity of concrete-infilled double steel corrugated-plate walls with T-section (T-CDSCWs) under axial compression and biaxial bending. T-CDSCWs are composed of flange and web walls and boundary elements. The T-section is mono-symmetric and exhibits different interaction curves of load-carrying capacity when subjected to axial load and different direction bending. Based on the finite element (FE) model established by the previous study, the local buckling of the steel corrugated-plates is considered in the load-carrying capacity. Subsequently, this paper investigates the behaviours of T-CDSCWs under axial compression and uniaxial bending, including stress distribution, load–displacement curves, and interaction curves. Based on the numerical results, the pure moment capacity is found to be evaluated by reducing the plastic moment capacity, and the interaction equations of N–positive Mx, N–negative Mx, and N–My are proposed in the bilinear, linear, and parabolic form. For biaxial bending, the shape of the interaction curves is almost exclusively related to the axis compression ratio. Accordingly, this paper proposes the interaction equations of Mx–My subjected to certain axial compression. Moreover, the local buckling of steel corrugated-plates has no significant influence on the shape of the interaction curves no matter the bending direction. The global stability of T-CDSCWs is not involved in the study, and with the interaction equations obtained above, the global stability design of T-CDSCWs can be investigated by introducing the magnification factor of the bending moment caused by the secondary effect.

Effect of weld zone and corner with cold bending effect on wrinkling of rectangular welded tube in rotary draw bending

Wrinkling of QSTE700 high strength steel thin-walled rectangular welded tube is easy to occur in rotary draw bending (RDB) process due to the existence of non-homogeneous weld zone and corner with cold bending effect. So the FE model of RDB of QSTE700 rectangular welded tube considering weld zone and corner with cold bending effect was established. Based on this FE model, the effect of weld zone and corner with cold bending effect on wrinkling of inner flange and side wall of rectangular welded tube in RDB was researched. The results showed that: when weld zone and corner with cold bending effect were studied separately, weld zone both increased the wrinkling height of inner flange and side wall. However, the influence of corner with cold bending effect on wrinkling height of side wall and inner flange was inconsistent, it reduced the wrinkling height of inner flange, but increased the wrinkling height of side wall. When the weld zone and corner interacted, the coupling effect between weld zone and corner with cold bending effect on wrinkling resulted in the decrease of wrinkling height of inner flange and increase of wrinkling height of side wall of rectangular welded tube in RDB.

Flexural buckling of axially loaded concrete-infilled double steel corrugated-plate walls with T-section

This paper investigates the flexural buckling behaviour of axially loaded concrete-infilled double steel corrugated-plate-walls with T-section (T-CDSCWs). The T-CDSCW is composed of flange and web wall elements and vertical boundary elements. The wall element consists of two bolted-connected steel corrugated-plates with concrete infilled. The composite effect of the components in the wall element improves the load-bearing capacities of the T-CDSCW efficiently and leads to a thinner wall. Therefore, the failure mode of the T-CDSCW may be governed by global instability. With the web breadth relatively less than the flange breadth, the first-order elastic buckling mode of the T-CDSCW is flexural buckling about the asymmetric axis. The design issue of the flexural instability of the axially loaded T-CDSCW is investigated experimentally and numerically in this paper. The load-bearing and deformation behaviours were investigated by an experiment of the axially loaded T-CDSCW, based on which refined finite element (FE) models of T-CDSCWs are established and validated. The FE buckling analysis is carried out to investigate the elastic buckling behaviour of the T-CDSCW and propose the elastic flexural buckling load and the borderline between flexural and flexural-torsional buckling. Then, the inelastic flexural instability of the T-CDSCW is investigated by the FE nonlinear analysis, and influences of initial geometric imperfection are discussed. The normalized flexural slenderness ratio derived from elastic flexural buckling load delineates flexural instability pretty well and bases the design formulas of strength reduction factor. The design formulas proposed in this paper help to understand the axial load-bearing behaviour of the T-CDSCW.

Deformation characteristics analysis of the fineblanking-extrusion flanging process

Nowadays, lots of flanging parts formed with the sheet metal have been widely used in the automotive industry. The fineblanked-extrusion flanging process can be used to fabricate the sheet metal flanging parts with high surface quality, high dimensional accuracy and production efficiency when compared with the conventional hole flanging process. In this paper, the process parameters were mathematically analyzed firstly, and the relationship between the punch displacements in fineblanking process H1 and in extrusion process H4 was presented. Then, a finite element model was created and verified by comparing with the experimental result. Using the valid finite element model, the forming load, metal flow, and damage distributions during the forming process were comprehensively analyzed, and the relationship between the workpiece thickness, flange wall thickness and the flange height has been revealed. Based on these simulation results, the deformation mechanism of the fineblanked-extrusion flanging process was revealed.

Effect of Process Parameters and Preheating Temperature on Surface Roughness and Thickness Distribution in Hole Flanging using Incremental Sheet Metal Forming

Incremental Sheet metal forming is a die less method of forming which offers high formability. In this research work; effect of step depth, tool rotation speed and preheating temperature on surface roughness and thinning of flange wall is investigated in hole flanging using incremental forming. The parameter optimization is carried out by Taguchi method. Grey relational analysis is carried out to obtain best parameter combination.

Effect of process parameters and preheating temperature on surface roughness and thickness distribution in hole flanging using Incremental Sheet metal Forming

Incremental Sheet metal forming is a die less method of forming which offers high formability. In this research work; effect of step depth, tool rotation speed and preheating temperature on surface roughness and thinning of flange wall is investigated in hole flanging using incremental forming. The parameter optimization is carried out by Taguchi method. Grey relational analysis is carried out to obtain best parameter combination.

Seismic Fragility Assessment and Resilience of Reinforced Masonry Flanged Wall Systems

AbstractSeveral experimental and analytical studies have evaluated the seismic response of reinforced masonry (RM) shear walls either as a component (i.e., planar rectangular walls) or as a system ...

Experimental study of lateral load behavior of H‐shaped precast reinforced concrete shear walls with bolted steel connections

SummaryThis paper presents an experimental study of H‐shaped precast reinforced concrete shear walls involving vertical connections under combined vertical and lateral loading. The H‐wall is composed of two prefabricated flange wall panels: one prefabricated web wall panel and vertical bolted steel connections between the flange and web panels. The assembling of the H‐wall is completely dry without any in situ casting. Three H‐wall specimens were constructed and tested to investigate the mechanical behavior and seismic performance of them. The lateral load‐bearing capacity, ductility, energy dissipation, lateral stiffness, strain in the connecting steel frame, and sliding within the bolted steel connections are presented and discussed to evaluate the effectiveness of the vertical connections. The ultimate shear‐resistance mechanism of the precast H‐wall assembly is also analyzed. The H‐wall assemblies generally possess high load‐bearing capacity, favorable ductility, and good energy‐dissipating capacity. The thickness of the steel plates in the connecting steel frame affects the lateral stiffness and the ultimate load‐bearing capacity of the H‐walls. Furthermore, the encasing steel plates for the web wall panel not only helps transfer the stress in the wall steel bars but also confines the concrete resulting in improved ductility.

Decoupling and analysis of the deformation of flanged reinforced concrete shear walls

SummaryCompared with rectangular walls, a relatively large proportion of shear deformations are expected for flanged walls due to their larger flexural capacity. As few well‐documented experimental data are available to assess the attributes of the various deformation components of flanged walls, the feasibility of using established models to predict the deformation capacity of flanged walls is debatable. This study presents experimental results for three large‐scale T‐shaped reinforced concrete walls under cyclic loading to examine the relative contributions of flexural, shear, and sliding deformations to lateral displacement. By using a high‐precision and noninterference measurement method based on particle image velocimetry, the deformation components were decoupled to investigate the variation in each deformation component with the total deformation corresponding to the damage evolution process. For flexure‐dominant T‐shaped walls, the ratio of shear‐to‐total deformations in the plastic hinge region slowly increases over the entire plastic range, whereas the ratio of shear‐to‐total top displacements remains approximately constant. When predicting the deformation capacity of flanged walls, shear deformations but not the contribution of sliding deformations should be considered. Based on the proportional relationship between shear strain and curvature, a simple model for estimating the shear deformations of flexure‐dominant flanged walls is proposed.

Sectional strength design of concrete-infilled double steel corrugated-plate walls with T-section

This paper presents the sectional strength design method of concrete-infilled double steel corrugated-plate walls with T-section (T-CDSCWs). The T-CDSCW is composed of flange and web wall elements and concrete-filled steel tubes, where the former are formed by bolt-connected steel corrugated-plates and infilled concrete while the latter behave as vertical boundary elements. Load bearing capacities of T-CDSCWs are significantly improved by the favorable combination effect between bolt-connected steel corrugated-plates and infilled concrete in the wall elements. The failure mechanism and the sectional strength design of T-CDSCWs under combined axial compression and bending moment are focused analytically, experimentally and numerically, with an assumption of no consideration of overall instability of T-CDSCWs and local buckling of the steel corrugated-plates in the wall elements. An experiment of the T-CDSCW for sectional strength prediction was carried out, and a refined finite element (FE) model of the T-CDSCW was validated by the experimental results. Based on the FE model, parametric analyses of T-CDSCWs are performed to further investigate the effects of steel ratio and sectional geometry on the load-bearing capacities. It is found that T-CDSCWs under axial compression have completely different values of load-bearing capacities when they incorporate different bending direction moments. Based on experimental and numerical results, design formulas for predicting the sectional strength of T-CDSCWs under axial compression and bending moments are proposed, providing a preliminary structural design method of T-CDSCWs.

Variability in Seismic Collapse Probabilities of Solid- and Coupled-Wall Buildings

Reinforced concrete walls are a common lateral load–resisting system for buildings. Common wall configurations are solid planar or solid flanged (H, I, T, L, or C-shaped cross sections) and coupled planar or flanged walls. A coupled-wall system comprises two solid walls linked at most floors by coupling beams that typically have length-to-depth ratios ranging from 2 to 4. In low- to midrise buildings, solid walls are expected and designed to form a single plastic hinge at the base of the wall; in mid- to high-rise buildings, a second hinge is expected in the upper half of the buildings. In coupled walls, plastic hinges are expected at the ends of the coupling beams and at the base of the wall. Because coupled walls offer a more distributed plastic mechanism, they are considered to provide superior earthquake performance to solid walls. This study employs nonlinear incremental dynamic analysis with the suite of ground motions from crustal earthquakes and a set of six idealized wall buildings of varying height to test the hypothesis that coupled walls provide reduced earthquake collapse risk over solid walls; to establish the sensitivity of collapse to modeling decisions and model parameters; and to identify design decisions that can reduce earthquake collapse risk.

The length of plastic hinge area in the flanged reinforced concrete shear walls subjected to earthquake ground motions

Past earthquakes have shown that appropriately designed and detailed buildings with shear walls have great performance such a way that a considerable portion of inelastic energy dissipation occurs in these structural elements. A plastic hinge is fundamentally an energy diminishing means which decrease seismic input energy through the inelastic deformation. Plastic hinge development in a RC shear wall in the areas which have plastic behavior depends on the ground motions characteristics as well as shear wall details. One of the most generally used forms of structural walls is flanged RC wall. Because of the flanges, these types of shear walls have large in-plane and out-of-plane stiffness and develop high shear stresses. Hence, the purpose of this paper is to evaluate the main characteristics of these structural components and provide a more comprehensive expression of plastic hinge length in the application of performance-based seismic design method and promote the development of seismic design codes for shear walls. In this regard, the effects of axial load level, wall height, wall web and flange length, as well as various features of earthquakes, are examined numerically by finite element methods and the outcomes are compared with consistent experimental data. Based on the results, a new expression is developed which can be utilized to determine the length of plastic hinge area in the flanged RC shear walls.

Simplified Data‐Driven Model for the Moment Curvature of T‐Shaped RC Shear Walls

Sectional deformation quantities, such as curvature and ductility, are of prime significance in the displacement‐based seismic design and performance evaluation of structural members. However, few studies on the estimates of curvatures at different limit states have been performed on asymmetric flanged walls. In this paper, a parametric study was performed for a series of T‐shaped wall cross‐sections based on moment‐curvature analyses. By investigating the effects of the axial load ratio, reinforcement content, material properties, and geometric parameters on curvatures at the yield and ultimate limit state, we interpret the variation in curvature with different influencing factors in detail according to the changes of the neutral axis depth. Based on the regression analyses of the numerical results of 4941 T‐shaped cross‐sections, simple expressions to estimate the yield curvature and ultimate curvature for asymmetric flanged walls are developed, and simplified estimates of the ductility capacity including curvature ductility and displacement ductility are further deduced. By comparing with the experimental results, we verify the accuracy of the proposed formulas. Such simple expressions will be valuable for the determination of the displacement response of asymmetric flanged reinforced concrete walls.

Numerical modeling of a two story third-scale reinforced masonry shear wall building subjected to quasi-static lateral loading

This paper presents numerical modeling of a two-story third-scale reinforced concrete masonry building composed of walls in orthogonal directions and subjected to quasi-static cyclic lateral loading up to failure. OpenSees and Response-2000 were used to capture the behavior at the section level as well as that at the element and system levels. The results of ten experimentally tested individual walls were used to verify the modeling approach that was used to generate the building model. The models were able to accurately capture the response of individual walls and that of the tested building. Force based elements were used to represent the walls and values for the factors controlling the cyclic behavior of masonry and steel material models used were recommended. The maximum error obtained for the strength of all wall models and for the building model was 4% and 12% respectively. Numerical results showed that overall ductility of the building was higher than that of its constituent walls especially under eccentric load which was consistent with experimental results. The torsional response of flanged walls was found to be essential for the accurate representation of the building behavior under eccentric lateral loading.

Influence of blank thickness fluctuation on flange state and final thickness distribution in the power spinning of thin-walled head

The initial blank exists unavoidable thickness fluctuation. In the spinning process of head parts, this fluctuation affects the flange state and final wall thickness distribution of the parts, which seriously deteriorates the forming quality. To research the blank thickness fluctuation on flange and spun head thickness distribution, three-dimensional (3D) finite element (FE) models considering blank fluctuation for the spinning process of 2219 aluminum head parts were established. The blank fluctuation was characterized using the Latin hypercube sampling method (LHS), and three fluctuation ranges and three fluctuation types were adopted (type 1, the average blank wall thickness is approximately equal to 1.0 mm, 1.0 mm is defined as the ideal standard blank thickness (ST); type 2, the average blank wall thickness is bigger than ST; type 3, the average blank wall thickness is smaller than ST). Then, flange fluctuations and the variations of wall thickness deviation were analyzed. The results showed that the maximum flange fluctuation appears within the 20% spinning process; the maximum flange fluctuation of type 1 is larger than those of type 2 and type 3. In the top zone of the spun head, the maximum wall thickness deviation of type 3 is the largest. While in the middle and edge zones, the maximum wall thickness deviation of type 2 is the largest. Simultaneously, a greater initial blank fluctuation leads to the bigger thickness frequency deviation. The research provides an in-depth understanding of the effects of blank wall thickness fluctuation on the forming quality in the head spinning process, and thus lays a basis for choosing the blank.

Natural Period Formula of a Reinforced Concrete Shear Wall Structure Considering Flange Wall Effect

In this study, natural period formular is presented for a RC shear wall structure with H-, T-, and L-shaped wall sections. The natural period formular proposed by Goel and Chopra and adopted in ASCE 7-10 was modified by using the ratio of the flange and web wall area. The natural periods of structures with H-shaped wall were numerically obtained, the results indicated that the ASCE 7-10 could not consider the natural period variation according to the length of the flange wall, but the proposed formula could do. Especially, ASCE 7-10 estimated much longer periods than eigenvalue analysis, and this implies that conservative seismic design is difficult. The periods by eigenvalue analysis exist between the upper and lower bounds given by the proposed formula, and conservative design is possible by using the proposed lower bound value. In order to verity the effectiveness of the proposed method, actual residential buildings with various types of flange walls are considered. Ambient vibration tests, eigenvalue analyses, and nonlinear dynamic analyses were conducted and the periods were compared with the values by ASCE 7-10 and the proposed formula. The results showed that the proposed formula could estimate more accurately the periods than ASCE 7-10.