Panel Aspect Ratio Research Articles

Evaluation of plastic hinge length in RC shear wall connected with floor slabs

Traditionally, seismic design focuses on inelastic behavior at the base of isolated shear walls. Yet, in multistoried RC wall-frame buildings with interconnected shear walls and floor slabs, significant inelasticity occurs at wall-slab junctions. This interaction greatly enhances the structure's seismic capacity. Previous studies overlooked this interaction, concentrating instead on isolated walls. The extent of inelastic action in a wall connected with floor slabs has not been studied extensively in the past. In the present study, the extent of the zone of inelastic behavior is studied at the wall-slab junction region by carrying out displacement based nonlinear static analysis of the wall-slab assemblages under monotonic as well as cyclic loads. A parametric study is carried out by varying the wall panel aspect ratio and axial load on walls. It is observed that this interaction using nonlinear static analysis, revealing increased curvature demand and localized damages at the junctions. It is observed that the extent of tensile damage at the junction region remains consistent across different axial load levels at the maximum drift level. Analytical expressions for plastic hinge length are proposed, crucial for refining seismic design strategies. The plastic hinge equation derived from pushover analysis yields values approximately 1.34 times higher than those obtained from cyclic loading.

Design and optimization of a household photovoltaic/thermal collector with serpentine tube: Energy and exergy analysis

Hybrid photovoltaic/thermal (PV/T) collectors that simultaneously generate electricity and heat have promise for sustainable energy production. However, their performance depends strongly on four key design parameters. These are: panel aspect ratio, serpentine tube pitch, solar intensity, and coolant flow rate. This study optimized these design parameters for a household serpentine-tube PV/T collector using energy and exergy analysis to enhance electrical and thermal efficiencies. Response surface methodology was employed to model the complex relationships between these parameters and the electrical and thermal efficiency responses. Increasing the panel aspect ratio from 0.125 to 8 resulted in 1.99 and 12.10 % improvements for electrical and thermal energy efficiencies along with 1.99 and 26.36 % improvements for electrical and thermal exergy efficiencies. Larger serpentine pitch from 80 to 400 mm decreased all four efficiencies. Higher radiation intensity from 200 to 1000 W/m2 reduced electrical efficiency by 8.36 % but increased thermal efficiency 75.33 %. Increasing the coolant flow rate from 0.1 to 1.4 L/min raised thermal and electrical efficiencies by 167.8 % and 12.4 %, respectively. Single-objective optimization yielded maximum electrical and thermal energy efficiencies of 11.8 % and 63.2 %, while multi-objective optimization gave lower responses. The study provides new insights into design trade-offs between electrical and thermal performance using comprehensive modeling and optimization. The model and methodology can guide significant PV/T design improvements.

Effect of facet gap on heliostat wind loading

Multi-facet heliostats are more versatile and advantageous in design compared to single facet heliostats, while generating new design challenges. Multi-facet designs can reduce manufacturing costs, allow for decentralisation of power supply, and bring the option of face down stow. Addition of a gap between two facets, changes the flow structure around the heliostat. The effect of gap between two heliostat facets is therefore investigated on wind loads through experimental investigation in a large wind tunnel. A heliostat model was placed in a simulated atmospheric boundary layer at The University of Adelaide wind tunnel. The investigation covered gap ratios between two panels (gap spacing/facet width) from 0 to 2, and panel aspect ratios (facet width/chord length) of 0.35 to 0.65, forming a complete heliostat aspect ratio of 0.7 to 1.3 with no gap. Wind load coefficients were determined using load cell measurements at the base, and application of differential pressure sensors on the surface, of the heliostat model. Findings indicate the presence of a gap, in general, increases the wind load on the heliostat, with facet aspect ratio exacerbating the results. The maximum load cases shift further into the operating range of heliostats where a change in centre of pressure, due to a change in gap ratio, shifts maximum coefficients from an elevation angle of 30° to 45° for lift force and hinge moment, and 90° to 75° for azimuthal moment. Increasing loads on elevation and azimuth drives potentially increases tracking deviations and beam misalignment, reducing concentrated solar power plant performance.

NEW INSIGHTS INTO THE WEB PANEL COMPONENT

AbstractThe column web panel is a fundamental component of beam‐column joints. This component has been thoroughly studied and codified in the past. In this paper, new insight on its behaviour is obtained using a large amount of high‐quality Finite Element (FE) models, covering a wide range of panel slenderness and aspect ratios. The study shows that the existing models in part 1‐8 of the current and forthcoming Eurocode 3 present a wide scatter in terms of resistance and stiffness, being unconservative in some specific cases.

Effect of Infills on the Response Modification Factor for Infilled Reinforced Concrete Frame Buildings

RC frames with unreinforced masonry infill walls are the most common type of building. Unreinforced masonry walls are often not considered by engineers in the design process, although walls and frames interact during strong ground motion, leading to structural responses deviating radically from what is expected in the design. Under lateral load, reinforced concrete confining members (frames) act in tension or compression, depending on the direction of the lateral seismic pressures. Meanwhile, masonry walls act as diagonal struts prone to compression. This research aims to develop the effect of masonry infills and their distribution on the value of the resulting response modification factor. For this purpose, a parametric study was performed on five, seven, and ten-story' buildings modeled as bare and infilled frames. Infill ratio, panel aspect ratio, unidirectional eccentricity, and bidirectional eccentricities were the parameters investigated. Each proposed model's resulting response modification factor was compared to the value cited in different international codes. It was concluded that this value differs depending on several parameters and cannot be constant for a certain structural system. The novelty of this research is the deduction of a general equation to calculate the response modification factor as a function of the percentage of infills and the eccentricity, while presenting two different methods to calculate it. Doi: 10.28991/CEJ-2023-09-12-09 Full Text: PDF

Investigating the deformation characteristics of balloon-type CLT shearwall

Balloon-type cross-laminated timber (CLT) shearwalls represent a valuable alternative to traditional platform-type construction for use as lateral load resisting systems in mid-rise mass timber buildings. Limited information is available on the behaviour of balloon-type shearwalls, and the system is not included in design codes and standards. The research aims to investigate the lateral deformation contribution and kinematic behaviour of balloon-type CLT shearwall system. A simplified analytical model to establish the lateral displacement of shearwalls is presented and discussed. The methodology involves a validated finite element model, and the result of sensitivity analysis is used to develop the analytical model. The study revealed that the stiffness of hold-downs and vertical joints, and aspect ratio of panels and vertical loads are contributing factors influencing lateral stiffness. The proposed analytical model was verified against 45 cases implemented in numerical models yielding an average error in the prediction of top lateral displacement of less than 4.7%.

In-plane, out-of-plane, and in-plane/out-of-plane interactional behavior of masonry-infilled steel MRFs with different frame components flexibilities and considering openings

In this paper, the in-plane (IP), out-of-plane (OOP), and IP/OOP interactional behavior of masonry-infilled steel moment-resisting frames (MRFs) are investigated through calibrated finite element modeling and analyses. Some of the key parameters influencing the response of masonry-infilled frames (MIFs), namely panel aspect ratio, size of central window opening, and steel frame components flexibility, are studied in a parametric study, covering a wide range of values for the parameters. The effect of each considered parameter on the IP and OOP response of MIFs are investigated. In addition, the suitability of various existing equations for predicting the IP and OOP strength of infills are evaluated, and based on the results obtained in this study, new formulae capable of predicting MIFs response characteristics are proposed. A novel non-uniform OOP force distribution pattern based on the first mode shape of free vibration of infilled frames is introduced and implemented, and OOP strength capacity of considered MIFs under this new force pattern are compared with those obtained from common uniform OOP force distribution method. For the IP/OOP interaction analyses, a novel loading protocol is introduced and adopted, and its suitability is compared with that of the common loading protocols used in the literature and discussed in detail. Finally, capacity of masonry infill walls subjected to simultaneous IP and OOP loadings were derived and, based on the results, a new interaction curve formulation was proposed. The results signified that the interaction curve formulation prescribed by ASCE/SEI 41-17 Standard is unconservative.

Experimental investigation of the hysteretic behaviour of single-story single- and coupled-panel CLT shear walls with nailed connections

The impact of wall-to-floor hold-downs, vertical spline joints, shear connectors, panel aspect ratio, and gravity loading on the performance of single storey cross-laminated timber (CLT) shear walls was experimentally investigated. The shear walls consisted of 191 mm thick 7-ply CLT panels with nail connected hold-downs, shear brackets, and plywood surface splines. First, the strength and stiffness of the hold-downs, vertical spline joints, and shear brackets were determined. Then, a total of 27 single and coupled shear walls with panel aspect ratios of 2.5 and 3.5, gravity loading of 20 kN/m and 30 kN/m, different hold-down strength as well as different nail spacing in the splines were tested under monotonic and reversed cyclic loading. The connector tests showed that the presence of washers, even with reduced nailing, significantly increased overall connection stiffness, capacity, and ductility. The shear wall tests demonstrated that the wall aspect ratio had the most significant influence on the shear wall performance. Increasing the number of shear brackets also resulted in higher capacity, deformation, and energy dissipation, while tighter nail spacing in the spline joints resulted significant higher capacity and stiffness in coupled shear walls.

Experimental behaviour of plate girders in steel – Internal forces in intermediate transverse stiffeners

Economical design of steel plate girders usually adopts slender web panels sometimes combined with large panel aspect ratio, which determines the elastic stability of the web panel. The adoption of transverse stiffeners is one efficient strategy to retard the web buckling due to shear. The primary role of intermediate transverse stiffener is clear: divide the web into panels providing lateral support to the web plate along the span – This increases the shear strength of the web. However, FprEN 1993-1-5: 2022 [1] stiffener design approach is based mainly on direct compressive forces resulting from the tension filed action in post buckling phase. According to multiple investigations, this area requirement is much higher than that found in laboratory testing and numerical simulations. The findings of experimental testing on eight plate girders with thin webs and two configurations of transverse stiffeners under ultimate load are presented. Using the web and stiffener measure strains, the internal stiffener forces are calculated past the shear failure of the plate girders. These results show that the axial compression and bending moment measured in the intermediate transverse stiffeners are considerably lower than those specified for the design by the FprEN 1993-1-5: 2022 [1].

Flutter of carbon-based nanohybrid composite panels

Recently, carbon-based composite aerospace and mechanical structures have considerable attention due to their great material and mechanical properties. Carbon nanotubes (CNTs) or graphene platelets (GPLs) reinforcements for different matrices are common for the design of modern multilayer structures. In the present paper, the supersonic flutter of nanohybrid composite multilayer panels is examined and discussed. The nanohybrid multilayer panel is made of different technologically justified configurations of polymer layers reinforced by CNTs and GPLs The effective material properties of each CNTs and GPLs layer are determined according to two well-established homogenization techniques: the Mori–Tanaka scheme and the modified Halpin–Tsai model, respectively. Reddy’s third-order shear deformation theory is applied to avoid determining shear correction factors for different distributions of material properties. Hamilton’s principle and the first-order piston theory are applied to formulate aeroelastic coupled equations of motion of the panel. The numerical meshless method is employed to discretize dynamic equations and find generalized multi-parametric characteristic equations functionally dependent on the parameters of the structure with different boundary conditions. The accuracy of the obtained solution and results is examined by comparing the determined natural frequency and critical aerodynamic pressure with those obtained in previous studies. Then, a comprehensive parametric study is carried out to show the effects of hybridization of different distribution patterns of CNTs and GPLs, weight fractions, total layer number, and aspect ratio of hybrid composite panels on the flutter bounds. Results show that the present method provides a highly effective general numerical model for flutter analysis of hybrid nanocomposite panels with different boundary conditions for all thickness categories including thick plates. Moreover, an optimization nanoparticles distribution for the flutter of the nanohybrid composite panel has been obtained.

Free Vibration Analysis of Functionally Graded Porous Cylindrical Panels Reinforced with Graphene Platelets.

The free vibration of functionally graded porous cylindrical shell panels reinforced with graphene platelets (GPLs) was numerically investigated. The free vibration problem was formulated using the first-order shear deformation shell theory in the framework of the 2-D natural element method (NEM). The effective material properties of the GPL-reinforced shell panel were evaluated by employing the Halpin-Tsai model and the rule of mixtures and were modified by considering the porosity distribution. The cylindrical shell surface was transformed into the 2-D planar NEM grid to avoid complex computation, and the concept of the MITC3+shell element was employed to suppress shear locking. The numerical method was validated through benchmark experiments, and the free vibration characteristics of FG-GPLRC porous cylindrical shell panels were investigated. The numerical results are presented for four GPL distribution patterns (FG-U, FG-X, FG-O, and FG-Λ) and three porosity distributions (center- and outer-biased and uniform). The effects of GPL weight, porosity amount, length-thickness and length-radius ratios, and the aspect ratio of the shell panel and boundary condition on the free vibration characteristics are discussed in detail. It is found from the numerical results that the proposed numerical method accurately predicts the natural frequencies of FG-GPLRC porous cylindrical shell panels. Moreover, the free vibration of FG-GPLRC porous cylindrical shell panels is significantly influenced by the distribution pattern as well as the amount of GPLs and the porosity.

Development and testing of knife-plate connected steel panel dampers

Steel panel dampers (SPDs), consisting of the inelastic panel and elastic connecting segments, have been widely used in steel building structures commonly with brace- or stub-column-type configurations, especially in high seismic regions. The elastic connecting segments of stub-column-type SPDs were usually significantly enlarged to ensure their elasticity under the associated extreme loads of the inelastic panel. With the aim of improving the structural efficiency and ductility capability of SPDs, a novel design, named as knife-plate-connected SPD (KSPD), was proposed in the study. The proposed KSPD consisted of one steel panel and two boundary-columns on the horizontal sides with pinned column ends, which were achieved by knife-plate details, connecting to the framing systems. The designed configuration of KSPDs potentially reduced the aspect ratio of the steel panels for easily achieving shear yielding while remaining the stud-column appearance, and mitigated the deformation amplification of the steel panels usually occurred in conventional stub-column-type SPDs. Five full-scale KSPD specimens with various configurations of the panel stiffeners have been experimentally examined and compared under cyclic loadings including fatigue cycles. The feasibility of the KSPD design was experimentally validated, and the developed KSPDs were verified to achieve stable energy dissipation and significant ductility of approximate ten and cumulative plastic deformation (CPD) value up to 796. For the design purpose of the members, the width-to-thickness limits of the steel panel were established to prevent panel buckling and the sub-panel edge fracture upon the test results, respectively, and a design inequality of the knife plates upon strengths was developed to prevent the fracture of the knife plate. Finally, the design suggestions of the proposed KSPD were summarized upon the experimental results and findings of the study.

Experimental and numerical investigation on patch loading capacity of longitudinally stiffened hybrid titanium-clad bimetallic steel plate girder

Plate girders are important load-bearing components of bridge and industrial structures. Corrosion significantly affects durability and service life of plate girders. Bimetallic steel consisting of corrosion-resistance metal and metal with superior mechanical properties provides an engineering solution for the mitigation of corrosion. The titanium-clad bimetallic steel (TCBS) was innovatively introduced into the plate girder as the web to solve the corrosion issue, where the nonlinear resistance performance and failure mode of a longitudinally stiffened hybrid TCBS plate girder under patch loading were investigated experimentally. The test results prove that the longitudinally stiffened hybrid TCBS plate girder has stable load-bearing performance, which is similar to that of the conventional mild steel plate girder. Effects of the shape and magnitude of the initial geometric imperfection on the resistance behavior of the longitudinally stiffened hybrid TCBS plate girder were investigate numerically. A parametric study on the effects of the material properties, longitudinal stiffener location, relative flexural rigidity of the longitudinal stiffener, web panel aspect ratio, and web height-to-thickness ratio on the resistance and critical buckling behaviors of a longitudinally stiffened hybrid TCBS plate girder was performed. Considering the strain strengthening properties of TCBS, the ultimate resistance and ductility of longitudinally stiffened hybrid TCBS plate girders can be significantly improved without affecting the buckling performance. The effect of key parameters on the longitudinally stiffened hybrid TCBS plate girder is consistent with that of the conventionally stiffened mild steel plate girder. Therefore, it is a feasible solution to apply TCBS to the plate girder web, which performs a beneficial effect on the durability of the plate girder.

Formation of post-buckling shear mechanisms in stiffened web panels of slender steel plate girders

A series of validated finite element models are used to investigate the formation of mechanisms in stiffened slender web panels of steel plate girders under pure shear. The prototype girder is based on the seminal tests by Basler and has a web slenderness of 267. Six model cases are analyzed with variations in web panel aspect ratio (1, 1.5, and 3), steel yield strength (Grades 36 and 50), initial imperfection magnitude, and flange thickness. When loaded in shear, the web panels exhibit a 3-stage response: (1) elastic behavior, (2) web mechanism formation, and (3) panel mechanism. In Stage 1, the web initially exhibits an elastic in-plane shear response with no distinct buckling bifurcation. During this stage, the web’s initial out-of-plane imperfections become engaged in second-order bending along its compression diagonal. Concurrently, tension develops in the opposite diagonal as a non-uniform membrane stress field, with highest intensities at locations where second-order bending is low. In Stage 2, a web mechanism is formed when connected bands of thru-thickness von Mises yielding develop across the tension diagonal. These bands emerge at locations where tension membrane stresses interact with locations of maximum second-order bending stress in the buckled shape. The shear load at the end of web mechanism formation is recommended as a target for plastic limit state design because it marks a significant decrease in shear stiffness. In Stage 3, von Mises yielding continues to saturate the web panel, and the bounding flanges and transverse stiffeners become increasingly engaged in load redistribution from the plastified web. Any hardening increase in shear resistance during the panel mechanism stage is modest in magnitude (up to ∼10% for some cases in this study) and is heavily dependent on the sizing of the flanges and stiffeners to carry redistributed forces.

Macro vs Micro Limit Analysis models for the seismic assessment of in-plane masonry walls made with quasi-periodic bond types

Masonry bond patterns can considerably affect the seismic performance of in-plane walls. Although several numerical and experimental works addressed this topic, few attempts tried to investigate such an issue using analytical formulations. This paper aims to compare macro and micro limit analysis models investigating masonry walls arranged with different bond types, namely Running, Flemish and English. A dataset involving 81 combinations is generated by varying geometrical (panel aspect ratio, block aspect ratio, bond type) and mechanical (friction coefficient) parameters. Finally, one-way and two-way factor interactions are used to evaluate how each parameter affects the horizontal load multiplier and assess matching among the two adopted formulations.

In-plane shear behaviour of prefabricated modular wall system assembled of fibre reinforced polymer composites

Fibre reinforced polymer (FRP) composites could be an alternative of traditional materials for modular construction due to their superior strength to weight ratio, corrosion resistance and immunity from biological degradation. This paper investigates the in-plane shearing behaviour of full-scale modular wall system made from all glass FRP (GFRP) rectangular hollow section (RHS) frames and GFRP sheathing. Monotonic in-plane shear load was applied to understand the effect of important parameters such as sheathing height offset from bottom of wall panel, wall opening, customised angle brackets for additional shear resistance, and comparison between single and double frame wall system. The results show that the wall panel with 10 mm sheathing offset from bottom deformed under shear and avoided high compression stress with significant higher loading capacity than panel with full sheathing. The stiffness of wall panel with opening can be estimated from the wall opening ratio of opening to total wall area. Furthermore, the installation of customised angle brackets can improve the loading capacity and stiffness of the wall panel. Finally, high height-to-width panel aspect ratio increased the loading capacity but reduced the overall panel stiffness in both single and double wall panels. Overall, this study presented that the structural parameters alter the ultimate failure modes which increased the overall loading capacity and impacted the panel stiffness.

Lateral Capacity of URM Walls: A Parametric Study Using Macro and Micro Limit Analysis Predictions

This research investigates the texture influence of masonry walls’ lateral capacity by comparing analytical predictions performed via macro and micro limit analysis. In particular, the effect of regular and quasi-periodic bond types, namely Running, Flemish, and English, is investigated. A full factorial dataset involving 81 combinations is generated by varying geometrical (panel and block aspect ratio, bond type) and mechanical (friction coefficient) parameters. Analysis of variance (ANOVA) approach is used to investigate one-way and two-way factor interactions for each parameter in order to assess how it affects the horizontal load multiplier. Macro and micro limit analysis predictions are compared, and the differences in terms of mass-proportional horizontal load multiplier and failure mechanism are critically discussed. Macro and micro limit analysis provide close results, demonstrating the reliability of such approaches. Furthermore, results underline how the panel and block aspect ratio had the most significant effect on both the mean values and scatter of results, while no significant effect could be attributed to the bond types.

Ultimate strength prediction of cracked panels under extreme cyclic loads considering crack propagation

The objective of this study is to gain insights on the failure mechanism and behavior of cracked panels under cyclic loading. Numerical analyses were performed to investigate the ultimate strength of cracked panels. The prefabricated crack is assumed to be transverse and through-thickness, the relevant three types of crack location models are studied. Crack propagation arisen out of extreme cyclic loads is taken into consideration and the element erosion approach is adopted to simulate the process of crack growth. The influences of the amplitude of cyclic loads, the crack location, the panel thickness and the aspect ratio of panel on the ultimate strength of cracked panels under extreme cyclic loads are discussed in detail. Based on numerical results, the prediction formulae for dimensionless ultimate strength considering crack propagation are derived to estimate the ultimate strength of cracked panels under cyclic loads.

Experimental research on seismic performance of cold-formed thin-walled steel frames with braced shear panel

The traditional cold-formed thin-walled (CFTW) steel sheathed walls are prone to have misalignment at the joints of wall panels and the damage of self-tapping screw connections under earthquake, resulting in obvious pinching of the hysteretic curves. In order to improve the energy dissipation and shear bearing capacity of the lateral resisting member in CFTW steel structures, an innovative structure called CFTW steel structure with braced ductile shear panel (CFTW-BSP) was proposed in this paper. Four full-scale one-story one-bay CFTW-BSP specimens containing two X-shaped and two K-shaped brace specimens were designed and tested under horizontal cyclic loads. The effects of configuration types, shear panel aspect ratios and slotted holes were investigated by comparing the lateral performance. In addition, the replaceability of the shear panel damper was analyzed. In general, the specimens performed well with a stable and plump energy dissipation capacity. The plastic deformation concentrated on the shear panel before 2% interstory drift, and then the end stud bases yielded and cracks propagated near the hold-downs at the ultimate stage. The braces always remained elastic during the tests. For X-shaped brace specimens, the slotted holes on shear panel can improve the ductility but decrease the energy dissipation capacity of the structure. For K-shaped brace specimens, the lateral resistance of the structure can be improved by decreasing the shear panel aspect ratio.

A Numerical Investigation on the Limitations of Design Equations for Steel Plate Shear Walls

In previous studies various design issues on steel plate shear wall (SPSW) systems under lateral loading were investigated using analytical and experimental methods. However, these studies tried to examine the interactive effect of only a few of design parameters, such as panel aspect ratio, column flexibility parameter, axial load ratio on the boundary frame columns, web plate thickness, stiffness of horizontal and vertical boundary elements and top anchor beam, etc., on the drift capacity and shear force distribution among frame and panel components of SPSWs at a time. This study investigates the effect of all of these parameters in the same framework. A parametric study is conducted on finite element models of 292 3-story SPSWs with rigid beam-to-column connections and designed for specified parameters. By evaluating failure forms from finite element analyses, the limiting (undesired) cases resulting from different combinations of specified geometric properties are identified. A column flexibility factor of 2.2 is proposed instead of the current limit value of 2.5 for satisfactory column performance, improved drift capacity and balanced strength distribution among frame and panel of SPSW. The value of 0.75 for the ratio of plate shear force to total shear force has emerged as a critical threshold value for the strength distribution among plate and frame components in order to conform capacity design principles. This study provides a comprehensive look on the behavior of SPWS for determining the most suitable combination of various parameters in the design of SPSW structures.