Irregular Frames Research Articles

Inverse Eigenmode Modeling and Multiscale Seismic Analysis of Irregular Frame Structure by Shear Spring–Multifloor Mass System

ABSTRACTA modeling method of an elastic shear spring–multifloor mass system (MF system) based on the fundamental eigenmode and natural circular frequency of a full‐scale structural frame is presented. MF system has plural lumped masses as representative of single floor, and the lumped masses are connected by interfloor shear springs. MF system focuses on both global and local responses of the original frame, namely, the total displacement, the non‐uniform displacements of an identical floor and the member force distributions. Therefore, the alternative use of MF system to the original full‐scale frame leads to the accurate and rapid evaluation of the responses of the frame. The introduction of the coupled shear springs to the modeling formulation provides the coupled horizontal responses in the two orthogonal directions. In addition, the interstory shear force distribution of the original frame and that of the equivalent MF system correspond. The accuracy of the proposed method is investigated through numerical examples for in‐plan irregular frames.

Low-Complexity Timing Correction Methods for Heart Rate Estimation Using Remote Photoplethysmography.

With the rise of modern healthcare monitoring, heart rate (HR) estimation using remote photoplethysmography (rPPG) has gained attention for its non-contact, continuous tracking capabilities. However, most HR estimation methods rely on stable, fixed sampling intervals, while practical image capture often involves irregular frame rates and missing data, leading to inaccuracies in HR measurements. This study addresses these issues by introducing low-complexity timing correction methods, including linear, cubic, and filter interpolation, to improve HR estimation from rPPG signals under conditions of irregular sampling and data loss. Through a comparative analysis, this study offers insights into efficient timing correction techniques for enhancing HR estimation from rPPG, particularly suitable for edge-computing applications where low computational complexity is essential. Cubic interpolation can provide robust performance in reconstructing signals but requires higher computational resources, while linear and filter interpolation offer more efficient solutions. The proposed low-complexity timing correction methods improve the reliability of rPPG-based HR estimation, making it a more robust solution for real-world healthcare applications.

Topology and size optimization of viscous dampers with discrete design variables by outer approximation

This article proposes a novel seismic retrofitting approach for the topology and size optimization of fluid viscous dampers using discrete design variables. The design variables are the damping coefficients of the dampers, and they are chosen from catalogues, leading to practical optimal design solutions. The optimization problems considered are formulated as 0–1 nonlinear programming problems. An algorithm based on outer approximation and that relies on first-order information is proposed to find optimized designs with modest computational resources and time. The effectiveness of the proposed approach is demonstrated through optimal seismic retrofitting of three-dimensional irregular frame structures. In the optimization problem formulation, the retrofitted structures are subjected to realistic seismic ground acceleration records with constraints on inter-storey drifts and total storey accelerations.

Some Conditions and Perturbation Theorem of Irregular Wavelet/Gabor Frames in Sobolev Space

Due to its potential applications in image restoration and deep convolutional neural networks, the study of irregular frames has interested some researchers. This paper addresses irregular wavelet systems (IWSs) and irregular Gabor systems (IGSs) in Sobolev space HsR. We obtain the sufficient and necessary conditions for IWS and IGS to be frames. By applying these conditions, we also derive the characterizations of IWS and IGS to be frames. Finally, we discuss the perturbation theorem of irregular wavelet frames (IWFs) and irregular Gabor frames (IGFs). We also provided some examples to support our results.

Seismic Response of Vertical Hybrid Concrete/Steel Frames Considering Soil–Structure Interaction

The aim of this study is to investigate the seismic behavior of concrete/steel mixed structures. In engineering praxis, many buildings consist of two parts: one made of reinforced concrete and the other made of steel. There are several difficulties in the code-based seismic design of these structures due to the different dynamic responses of each discrete part. Seismic design codes, such as the IBC and Eurocode 8, do not provide instructions for structures consisting of two parts. In addition, they use a single-loading scenario, but there are many locations that are affected by more than one earthquake in a short period. Another drawback is that recent provisions do not consider soil–structure interaction effects. The specific issue addressed here is the seismic response of mixed structures, which is evaluated through inelastic time–history analysis. More specifically, the response indices involve height-wise distributions for peak interstory drift ratios, maximum floor horizontal displacements, maximum floor accelerations, and plastic hinge formations in the frame elements when they are subjected to seismic sequences of earthquakes, as well as in far fault ground motions for different soil types. The results reveal that sequential ground motions lead to increased displacement demands, and they affect the permanent displacements. This phenomenon appears in both cases of stiff and flexible soil, as well as for both regular and irregular frames. It is found that soil–structure interaction generally leads to lower values of IDR, and maximum horizontal displacement and acceleration in comparison with the case of rigid soil assumptions.

Vibration control of steel frames with setback irregularities equipped with semi-active tuned mass dampers

This paper presents a pioneering study on the seismic vibration control of steel moment-resisting frames (MRFs) with setback irregularities using semi-active tuned mass dampers (SATMDs). The research investigates the efficiency and the location of the SATMDs and compares their efficiency with traditional tuned mass dampers (TMDs) for the vibration control of setback structures with different vertical irregularities. To assess the nonlinear seismic performance of buildings with setbacks, various engineering demand parameters such as inter-story drift ratio, story displacement, story velocity, story acceleration, and base shear factor were analyzed under earthquake excitations. The results reveal that the use of SATMDs reduced the seismic response of irregular frames with setbacks. In addition, the efficiency of SATMDs in the control of setback frames was more than the regular frames. Also, the investigations showed that placement of the control systems at the roof level of the structure significantly reduced the structural vibration of irregular structures. It is noticeable that the use of these control devices requires more attention for structures with significant setbacks because, in some cases, the response of a structure with SATMDs can be greater than an uncontrolled structure.

Seismic Performance of Vertical Irregular Steel Frame Structure under Mainshock-Aftershock

Abstract: The majority of the structures are involved with architectural importance and it is highly impossible to achieve uniform structural properties in all directions. Hence earthquake resistant design codes considered it as irregular frames based on relative difference in the story properties. In many cases these irregularities are responsible for structural collapse of buildings under earthquake ground motions. The seismic response of buildings with irregular distribution of stiffness along the height may be differentfrom that ofregular building. Also, past earthquakes showed that structure may be subjected to sequence of ground motions but current codes do not have guidelines for such cases. It is considered that aftershock do not cause any more damage to damaged structure by the preceding mainshock ground motion. In this study steel moment resisting frame buildings are evaluated to understand the seismic response of vertical stiffness irregular frames subjected to mainshock-aftershock ground motions. The 9-story steel moment resisting frame building situated in Los Angeles is used in this study was originally developed as part of the SAC steel project. In this study soft and stiff storey case was considered at three different locations along the height, i.e., at bottom storey, mid-height storey and top storey. The single modification factor is used for irregularity. For comparison purpose dynamic properties of regular and irregular frames are kept same. Two sets of 6 records were selected representing a seismic hazard level of 2% and 10% probability of exceedance in 50 years respectively as mainshock. Two sets of 30 mainshockaftershock ground motion are considered for the study. These ground motions were developed using randomized approach. A non-linear time history analysis of regular and irregular building is carried out separately under mainshock and mainshockaftershock. The effect of building irregularity was studied for single storey modification at bottom storey, mid-storey and top storey with comparison to regular building. The comparison of a regular and irregular building is carried out in terms of maximum roof displacement and interstorey drift ratio. Also, comparison of frames under mainshock and mainshock-aftershock is done.

Seismic evaluation of vertically irregular RC frames subjected to mainshock-aftershock sequences of near-fault and far-fault ground motions

Sequential ground motions can significantly affect the seismic demands of reinforced concrete (RC) frames with irregularity along the height. In this paper, the effect of sequential near-fault and far-fault ground motion records with strong and weak aftershocks on the seismic demands of vertically irregular 10-story RC building frames is investigated. The vertically irregular frames with stiffness and mass irregularities were created by applying a modification factor of MF = 2 in three different locations along the height of the reference regular frame. Eigenvalue analysis was performed to evaluate the dynamic characteristics of the structures (i.e. the period and the effective modal participating mass ratio for different modes of vibration). In order to study the seismic demands of these structures, the non-linear response history analysis (NL-RHA), which is the most accurate method of seismic evaluation of structures, was carried out. The floor displacements, story drifts, plastic hinge rotations and residual story drifts obtained from the NL-RHAs were exhaustively studied, and the effect of seismic sequences on the seismic responses was investigated. Furthermore, the enhanced pushover analyses, including the modal pushover analysis (MPA), consecutive modal pushover (CMP) procedure, extended N2 (EN2) method, single-run multi-mode pushover (SMP) method and non-adaptive displacement-based pushover (NADP) procedure were implemented to consider the effect of higher modes in computing the seismic demands of the structures subjected to sequential near-fault and far-fault records as well as mainshocks. The results accentuate that the maximum seismic demands and damage of the structure for sequential near-fault and far-fault records with strong aftershocks are much greater than those for the corresponding mainshocks. Moreover, the enhanced pushover analyses in the case of sequential records have usually less accuracy in estimating the seismic demands in comparison with mainshocks only.

Young Women and Disgust in Contemporary Norwegian Comics: A Close Reading of Ane Barstad Solvang's Frykt & medlidenhet

Young Women and Disgust in Contemporary Norwegian Comics: A Close Reading of Ane Barstad Solvang's <i>Frykt</i> &amp; <i>medlidenhet</i>

Study on Dynamic Behavior of Shear Walls in Vertically Irregular Building Frames

Abstract: According to recent studies, the shear wall's construction is the most effective weight-restraining system in use today. Shear walls are of the most attainable and consequently usually utilized horizontal burden opposing parts in elevated structures. It is provided by progressing through the design levels starting at the foundational level. The extent of the ongoing work is to determine the ideal location of the shear walls in plans with erroneous shear wall placements, such as I frame, L packaging, and T frames for various zones in G+17 stories with each story level being 3.2 m. Shear walls are provided at the design's corners and edges. Additionally, the impact of seismic zone results according to IS CODE 1893(Part1): 2016 has been shown. Utilizing the striking assessment and plan programming ETABS 18.1.0, a novel reaction range investigation is done as part of the seismic assessment. Seismic execution of the design has been analyzed considering specific, for instance, story evacuating, Story float, Story Shear, Base shear

Seismic pre-dimensioning of irregular concrete frame structures: Mathematical formulation and implementation of a learn-heuristic algorithm

Irregular frame structures can exhibit an inefficient dynamic behavior, such as undesirable torsional effects and asymmetric displacements, that can severely affect structural performances in case of a seismic event. To mitigate the influence of geometric irregularities, the pre-dimensioning of structural elements is crucial to achieve the best possible seismic behavior. Identifying the optimal solutions in terms of elements’ cross-sections and orientations is a non-trivial problem that in general designers tackle following trial-and-error attempts which can become numerous in the most complicated cases.This paper formally describes the pre-dimensioning problem and presents a Learn-heuristic that hybridizes a Genetic Algorithm and a k-Means algorithm procedure for its solution. The algorithm is validated on a diverse set of 3D reinforced concrete structures and through a Structural Pre-dimensioning challenge, where the performances of the algorithm are compared against those accomplished by a group of Ph.D. candidates. The computational results evidenced that the proposed optimization framework achieves pre-dimensioning solutions that significantly improve the designs provided by the Ph.D. students, thus suggesting a favorable inclusion of the proposed solution method in classical pre-dimensioning processes.

Seismic behaviour of irregular steel frames with beam and joint energy dissipation

This paper investigates the seismic performance of steel moment resisting frames, exploring the potential for energy dissipation not only in the beams but in the beam-to-column joints too. Such an approach practically doubles the possible locations for dissipative zones in the structure but on the other hand places requirements for ductile behaviour on the connections. A design methodology that facilitates the formation of plastic hinges in the beam-to-column joints and the beams at the same time, is presented and examined in comparison to typically designed frames with rigid joints. A number of 24, 2D regular and irregular frame configurations are studied numerically, employing both nonlinear static and dynamic analyses. The examined configurations involve either irregular mass distribution across the floors or stiffness discontinuities of the framing across the floors and the bays. The results indicate a great reduction in ductility demands for the frames with energy dissipation in the beams and the joints concurrently, while other metrics of their seismic response, such as interstorey drifts and lateral capacity remain practically unaffected.

Column-to-beam flexural strength ratio for performance-based design of RC moment frames

The concept of strong column – weak beam is frequently used in seismic design to secure the safety of framed buildings, and for RC special moment frames, current design codes require the minimum column-to-beam flexural strength ratio at joints to reduce the likelihood of yielding in columns. However, the requirement for the strength ratio may not be satisfactory to prevent column hinging due to inelastic moment distributions and higher mode effects of dynamic response. In the present study, to investigate the required strength ratio, a numerical study was performed considering various parameters (plastic rotations of beams and columns, design earthquake loads and vertical distributions, gravity loads, stiffness ratios, design methods for beam strength, joint locations, and frame heights). The numerical study results showed that the strength ratio varies with the parameters and its vertical distribution is generally in a wine-glass shape along the frame height. On the basis of the numerical investigation, a design method for the strength ratio was developed as a function of the height ratio for performance-based design. For verification, nonlinear static and dynamic analyses were performed for regular and irregular frames designed by the developed method, and the results showed that the use of the developed method can improve seismic performance in a more economical way.

Rectangling irregular videos by optimal spatio-temporal warping

Image and video processing based on geometric principles typically changes the rectangular shape of video frames to an irregular shape. This paper presents a warping based approach for rectangling such irregular frame boundaries in space and time, i.e., making them rectangular again. To reduce geometric distortion in the rectangling process, we employ content-preserving deformation of a mesh grid with line structures as constraints to warp the frames. To conform to the original inter-frame motion, we keep feature trajectory distribution as constraints during motion compensation to ensure stability after warping the frames. Such spatially and temporally optimized warps enable the output of regular rectangular boundaries for the video frames with low geometric distortion and jitter. Our experiments demonstrate that our approach can generate plausible video rectangling results in a variety of applications.

Perturbation of Wavelet Frames of Quaternionic-Valued Functions

Let L2(R,H) denote the space of all square integrable quaternionic-valued functions. In this article, let Φ∈L2(R,H). We consider the perturbation problems of wavelet frame {Φm,n,a0,b0,m,n∈Z} about translation parameter b0 and dilation parameter a0. In particular, we also research the stability of irregular wavelet frame {SmΦ(Smx−nb),m,n∈Z} for perturbation problems of sampling.

Am I Playing Better Now?

G-SYNC technology matches formerly regular display refreshes to irregular frame updates, improving frame rates and interactive latency. In a previous study of gaming at the 30Hz frame rates common on consoles, players of Battlefield 4 were unable to discern when G-SYNC was in use, but scored higher with G-SYNC and were affected emotionally. We build on that study with the first examination of G-SYNC's effects at the 60Hz frame rate more common in PC gaming and on emerging consoles. Though G-SYNC's effects are less at 60Hz than they were at 30Hz, G-SYNC can still improve the performance of veteran players, particularly when games are challenging. G-SYNC's effects on emotion and experience were limited.

Strain evolution of L-shaped precast columns spliced by laminated metal plates, part I

ABSTRACT Mechanical joints for both irregular steel-concrete composite precast frames and reinforced concrete precast frames were developed to replace conventional cast-in-place concretes in the previous study of the authors. Novel connections modified from conventional steel joints having fully restrained moment connections offer rapid and facile erections. This study aims to numerically identify microscopic strain evolution and failure modes of the laminated metal plates splicing L-shaped precast composite columns. Numerical parameters including material properties of structural components of mechanical joint were implemented to determine damages and strength degradations with associated fractures. Comprehensive numerical results agreed well with test data, which explored structural behavior and contribution of each structural element of mechanical joint to flexural capacity. Strain evolution showed that degradation of the mechanical joints was retarded by interior bolts to a level similar to monolithic columns, resulting in contribution of mechanical joint to flexural capacity of columns. Influence of axial loads on the behavior of columns with mechanical joints was also evaluated to provide design recommendations.

Evaluation of seismic performance of steel frames with stiffness irregularity subjected to mainshock–aftershock using equivalent single-degree-of-freedom system

Many buildings in the present-day scenario have irregularities due to the discontinuity of their mass, stiffness, and geometry through their height. Buildings with vertical irregularities suffer severe damage as observed in past records. Structures situated in earthquake-prone regions are subjected to multiple earthquakes, occurring at a short interval of time, due to the mainshock–aftershock (MS–AS) sequence. This study investigates the effects of stiffness irregularities on the seismic performance of the 9-storey steel moment-resisting frame (SMRF) subjected to mainshocks and MS–AS. Nonlinear time-history analysis (NTHA) was conducted to compare the height-wise variation of maximum inter-storey drift ratio (IDR) demands of the regular and stiffness irregular frames. The results show that stiffness irregularity through the height of the frame influences the height-wise variation of inter-storey drift. Also, the structural responses of regular and irregular frames subjected to MS–AS are increased compared to mainshocks. This study also evaluates the accuracy of previously proposed three different equivalent single-degree-of-freedom systems (ESDOF) for obtaining seismic demands of multi-degree-of-freedom (MDOF) systems of regular and irregular frames subjected to mainshocks and MS–AS. The mean values of the height-wise variation of IDR obtained from MDOF and ESDOF systems are compared. The effectiveness of ESDOF systems for estimation of IDR is examined by mean bias and standard deviation of the ratio of mean values of IDR determined by NTHA of MDOF systems to the values determined by ESDOF systems. The study concludes ESDOF systems are useful for estimating the height-wise variation of IDR for regular and stiffness irregular frames subjected to mainshocks and MS–AS.

Performance-Based Seismic Design for buildings

Structures are designed using current seismic design codes which are mostly based on Force-Based Design approach. The aim of the work is to implement the Performance-Based Seismic Design (PBSD) approach in concrete buildings. PBSD, which is a new concept in seismic design of structures, is a reliable approach capable of providing more detailed information on the performance levels of both structural and non-structural elements. Methods. In this study Performance-Based Seismic Design has been utilized on reinforced concrete irregular frame. In order to do this pushover analysis was done. Story drift ratios were chosen as deformation limits to define the performance levels for specific earthquake hazard levels. The results of this study show that Performance-Based Seismic Design gives a structure with better seismic load carrying capacity, thereby achieving the objective of performance as well as economy. It is also possible to conclude that PBSD obtained by above procedure satisfies the acceptance criteria for immediate occupancy and life safety limit states for various intensities of earthquakes.

Mass irregularity effect on seismic response of moment‐resisting steel frame by nonlinear time history analysis using force analogy method

SummaryNonlinear time history analysis (NTHA) is widely considered to be the most accurate and robust method of seismic analysis and, when performed with force analogy method (FAM), can result in significant reduction in computational time, as compared to the conventional displacement‐based finite element (FE) solution technique. Taking this advantage of efficient FAM, this paper investigates the effects of location (along building height) and intensity (150–225%) of single‐floor mass irregularity on seismic response of mid‐rise moment‐resisting steel frames. Three building heights (6, 8, and 10 storeys) have been considered, and the analysis results are presented in the form of floor displacements, storey drift ratio, and plastic energy dissipation. Based on the analysis, it has been observed that critical location (for the maximum seismic response) of mass‐irregular floor corresponds to the level that exhibited the maximum seismic response (i.e., storey drift ratio) in the reference mass‐regular frame. Further, criticality of the irregular frame to seismic excitation has been found to decrease when mass‐irregular floor moves towards the top of the building. The criticality of the irregular frame has been found to increase with the increase in mass‐irregular intensity. Collapse of the irregular frame has been seen to initial first near the storey level where mass‐irregular floor is located.