Behavior Of Structural Systems Research Articles

A novel optimization‐based modal pushover analysis procedure for estimating the response of structures

AbstractIn recent years, studies have focused on the seismic behavior of various structural systems, including single‐ and double‐layered spatial structures. While nonlinear dynamic analyses are common for these studies, they are time‐consuming and complex. To address this, many pushover procedures have been developed, but their effectiveness in spatial structures remains underexplored. This study introduces an optimized lateral loading profile for evaluating the seismic response of walled bilayer spatial structures. By combining dominant inertial forces and optimizing their corresponding coefficients with the particle swarm optimization (PSO) algorithm, an optimal loading profile is derived. The method's accuracy was tested on models with varying arch height‐to‐span ratios and a constant wall height‐to‐span ratio, as well as a 15‐story frame structure. The results obtained showed that the proposed method closely matches incremental dynamic analyses (IDAs) in predicting base shear, initial stiffness, and displacements, especially for higher arch height‐to‐span ratios. Additionally, the method accurately estimates drift profiles and nodal displacements on roofs and walls, and performs better than similar mode‐based methods for frame structures.

A novel framework for effective structural vulnerability assessment of tubular structures using machine learning algorithms (GA and ANN) for hybrid simulations

Abstract Seismic vulnerability assessments are conventionally conducted by using sophisticated nonlinear analytical models, leading to aggressive computational demands. Previous attempts were made to reduce computational efforts for establishing vulnerability assessment of structures; however, the area of super tall and tubular structures still faces considerable lack. Advent of efficient machine learning (ML) has enabled engineering practitioners to automate the processes for fragility analysis; however, its application for high-rise tubular structures is not yet exploited, and most implementations are limited to basic ML. In this work, an attempt was made to reduce computational demand for the fragility assessment process for tubular structures by employing genetic algorithms (GAs) for nonlinear structural modeling, and development of artificial neural network (ANN) using deep learning for fragility development. Consequently, a simple lumped parameter model had been developed using open-source code of ZEUS-NL, containing parameters selected by GA to acutely account for convoluted interactive behavior of structural systems and dynamic demands. Subsequently, incremental dynamic analysis (IDA) was performed on the optimized model. A new framework has been established to develop and train ANN architecture by amalgamating Weka’s capability of data preprocessing with deep learning. The established ANN model resulted in correlation coefficient of 0.9972 and R 2 of 0.95, demonstrating adequate performance.

Study on seismic behavior and collapse risk of super high-rise braced mega frame-core tube structural system

The braced mega frame-core tube (BMFCT) structure could provide an efficient lateral-force resisting (LFR) system for high-rise or super high-rise buildings, especially for those higher than 500 m. The BMFCT structure is a dual LFR system, including the outer braced mega frame and the inner core tube. The seismic behavior and design method of this structural system is not clear. In this study, a parametric study based on collapse risk-targeted analysis is conducted to clarify seismic mechanism and performance and to make clear means of matching reasonable stiffness and setting energy-dissipation components. Five comparable BMFCT structures with different mega brace stiffness proportions and frame-tube stiffness ratios are designed. An efficient elasto-plastic modeling method is introduced to establish the accurate FE models. The corresponding collapse risks are calculated through Incremental Dynamic Analysis and fragility theory. The results show that the structural collapse risk increases with the increased frame-tube stiffness ratio. Therefore，the stiffness and bearing capacity of peripheral frames should be strengthened to ensure the structural collapse margin. On the other hand, the collapse resistance capacity gradually decreases with the increasing of the mega brace stiffness. Thus, the stiffness proportion of mega braces should be recommended to meet the basic lateral stiffness requirements, which shall not exceed 35 % of the overall structural stiffness. Moreover, the distribution feature and ideal arrangement of the energy dissipation components are proposed. The seismic design recommendation based on the uniform collapse risk is also proposed for the BMFCT system, which serves a reference for the structural design of super high-rise buildings.

The Efficiency of Using Machine Learning Techniques in Fiber-Reinforced-Polymer Applications in Structural Engineering

Sustainable solutions in the building construction industry have emerged as a new method for retrofitting applications in the last two decades. Fiber-reinforced polymers (FRPs) have garnered much attention among researchers for improving reinforced concrete (RC) structures. The existing design guidelines for FRP-strengthened RC members were developed using empirical methods that are based on specific databases, limiting the accuracy of the predicted results. Therefore, the use of innovative and efficient prediction tools to predict the behavior of FRP-strengthened RC members has become essential. During the last few years, efforts have been progressively focused on the use of machine learning (ML) as a feasible and effective technique for solving various structural engineering problems. Its capability to predict the behavior of complex nonlinear structural systems while considering a wide range of parameters offers a distinctive opportunity to make the behavior of RC members more predictable and accurate. This paper aims to evaluate the current state of using various ML algorithms in RC members strengthened with FRP to enable researchers to determine the capabilities of current solutions as well as to find research gaps to carry out more research to bridge revealed knowledge and practice gaps. Scopus databases were searched using predefined standards. The search revealed ninety-six articles published between 2016 and 2023. Consequently, these articles were analyzed for ML applications in the field of FRP retrofitting, including flexural and shear strengthening of RC beams, flexural strengthening of slabs, confinement and compressive strength of columns, and FRP bond strength. The results reveal that 32% of the reviewed studies focused on the application of ML techniques to the flexural and shear strengthening of RC beams, 32% on the confinement and compressive strength of columns, 6.5% on the flexural strengthening of slabs, 22% on FRP bond strength, 6.5% on materials, and 1% on beam–column joints. This research also revealed that the application of various ML algorithms has shown a significant improvement in resistance prediction accuracy as compared with the existing empirical solutions. Supervised learning techniques were the most favorable learning method due to their good generalization, interpretability, adaptability, and predictive efficiency. In addition, the selection of suitable ML algorithms and optimization techniques is found to be mainly dictated by the nature of the problem and the characteristics of the dataset. Nonetheless, selecting the most appropriate ML model and optimization algorithm for each specific application remains a challenge, given that each algorithm is developed with different principles and methodologies.

An implicit Material Point Method for micropolar solids undergoing large deformations

Modelling the mechanical behaviour of structural systems where the system size approaches that of the material microstructure (such as in MEMS) presents challenges to the standard continuum assumption and classical models can fail to predict important phenomena. Of the various non-conventional continuum frameworks developed to tackle this issue, the micropolar (Cosserat) continuum is widely acknowledged as a suitable and rigorous alternative for its ability to naturally predict size effects by introducing characteristic length scales. This work proposes an implementation of geometrically non-linear micropolar theory using an implicit Material Point method, for the purpose of simulating nanoscale large-deformation problems involving Hookean materials. The framework employs an analytically-derived consistent tangent, and is verified with a novel benchmark problem derived using the Method of Manufactured Solutions. Due to similarities between the methods, many aspects of the formulation could be used to construct an Updated Lagrangian Finite Element Method.

Earthquake response control effects of coupled structural systems incorporating a negative stiffness connector: Experimental and numerical investigation

Coupled vibration control (CVC) systems, which typically consist of two frames and connectors, such as stiffness and damping elements, can be used for the seismic protection of coupled or adjacent structures. This study aims to experimentally and numerically elucidate the response behavior and control effects of CVC structural systems comprising a mainframe and subframe incorporating passive negative stiffness (PNS) at the connection subjected to earthquakes. Shake table experiments were conducted using CVC system specimens incorporating a PNS device (PNSD) consisting of curved-leaf springs under dynamic excitations. A significant seismic response reduction for the mainframe of the CVC specimen under simulated waves was achieved by incorporating the PNSD at the connection. Moreover, a response simulation was performed using six-story CVC structure models connected by negative stiffness and viscous damping elements subjected to simulated and observed seismic wave inputs. The displacement and acceleration peak response of the mainframe using the numerical CVC models was lower than that of the uncontrolled model. Therefore, incorporating negative stiffness and viscous damping connectors into CVC systems can reduce the seismic response. This study contributes to the advancement of aseismic technologies for coupled or adjacent buildings utilizing the PNS.

Analytical Behavior of Conventional and Virtual Outrigger Structural Systems by Using Modal Pushover Analysis

Analytical Behavior of Conventional and Virtual Outrigger Structural Systems by Using Modal Pushover Analysis

Structural Analysis of the Performance of the Diagrid System with and without Shear Wall

Abstract: The objective of the present work is to study, behaviour and performance of diagrid structural system with and without shear wall under lateral loads i.e. wind and earthquake that may occur during the lifespan of the building. In this present work a particular G+70 storey geometrically irregular C-shaped high-rise Diagrid building with and without Shear wall are modelled using ETABS software. These models are analysed for Static and dynamic behavior in three different zones i.e, Zone III, Zone IV and Zone V with basic wind speed 44 m/s, 47 m/s and 50 m/s respectively. Equivalent Static analysis, Response Spectrum Method (dynamic analysis) and Static Wind analysis is carried out

Lateral deformation behaviour of structural internal replacement pipe repair systems

Structural internal replacement pipe (SIRP) systems are emerging composite technologies for the repair of circumferentially cracked host pipes or pipes with joints subject to lateral deformation caused by the surface loads from vehicular traffic. However, laboratory experiments to investigate the suitability of different SIRP systems in repairing full-scale pipes are a very costly and time-consuming process. This paper investigated numerically the behaviour of SIRP repair systems under lateral deformation using the three-dimensional finite element analysis (FEA). The FEA model was validated from the results of the full-scale experimental test. The effect of the crack width of the host pipe, thickness, and material properties of the SIRP, on the bending behaviour of the pipe repair system, was evaluated. The results of the analyses show that the effect of the thickness and elastic modulus of the SIRP on the lateral deformation behaviour is dependent on the width of the circumferential crack in the host pipe. A simplified analytical model based on Fibre model analysis (FMA) and incorporating an average stress factor for host pipes with a narrow crack width was developed to reliably describe the lateral deformation behaviour of the SIRP systems.

Generalized yield surface for sheet-based triply periodic minimal surface lattices

Triply periodic minimal surfaces (TPMS), which are a class of architected cellular materials, have attracted significant attention lately, due to their prevailing mechanical, electrical and chemical properties, to name a few, and due to the advancements in additive manufacturing technologies that make it possible to print such materials. However, simulating the elastic-plastic mechanical behavior of structural systems (e.g., beams, plates, cores of sandwich panels, structural systems with various levels of geometric complexity) that are latticed with thousands of TPMS lattices are computationally expensive to model explicitly, and hence the need to develop accurate yield surfaces in order to capture their plastic behavior in a homogenized approach. In this work, a generalized initial yield criterion is proposed for sheet-based TPMS lattices, which incorporates the Lode parameter L. The initial yielding of five different sheet-based TPMS lattices are investigated in five different loading conditions. These lattices are Schoen's I-WP (IWP-s), Gyroid (GYR-s), Diamond (DIA-s), F-RD (FRD-s) and Primitive (PRIM-s). The proposed yield criterion accurately predicts the initial yielding of all these lattices in all the loading conditions considered, outperforming other yield criteria currently proposed in literature.

Experimental and Numerical Study on the Collapsing Behavior of Structural Systems with Steel Members Arranged in Parallel Under Tension

Experimental and Numerical Study on the Collapsing Behavior of Structural Systems with Steel Members Arranged in Parallel Under Tension

Numerical Analysis of Single Lap Pretension Bolted Joint

Due to their superiority, bolted connections are commonly utilized to join numerous building components. When evaluating the impacts of the connections on the behavior and load-bearing capacity of structural systems, it is crucial to understand the parameters that govern the load-carrying capacity of bolted joints. The bearing capacity of single lap and single bolt friction-effect joints are examined numerically in this paper. Through numerical analysis, the variation in the bearing capacity of the joint as a function of the parameters affecting joint capacity, the pre-tension force, and the surface friction coefficient between the joining plates, was analyzed. Accordingly, it has been observed that the pre-tensioning force and friction coefficient both increase the joint's capacity in a comparable manner. The results demonstrate that the bearing capacity of a slip-critical joint can be enhanced by applying roughening techniques to the friction surfaces of the plate.

A Review on Infilled frame Structure with respective of various Interface Materials

During major earthquakes, existing buildings have collapsed or suffered serious damage, resulting in number of losses, severe injuries, and deaths. Based on literature, the influence of this work reviewed the effects of interface with different materials and also to find how infilled frames behave in framed structure. This study's primary goal is to strengthen RC-framed structures and increase the ductility of infilled frames by using interface materials. The research offers a full range and points relevant to ductile parameters for more results in the field of infilled frames using interface materials. In parametric investigation the interface material with interface thickness and the combination of interface material with a particular frame, from that optimum value to be identified. This research benefits researchers, professionals, and specialists the behaviour of various structural systems, as well as innovative mitigation techniques that have been used in the literature to build progressive collapse resistance experimentally.

Boundary continuity effect on performance of composite beam-slab sub-assemblages at elevated temperature

The behaviour of composite beam-slab structural system under fire condition has been investigated in the past few decades. However, previous research works mainly focused on isolated beam-slab sub-assemblages. In this paper, the boundary continuity effect on structural behaviour of composite beam-slab sub-assemblages subject to fire is investigated, where three different boundary continuities are considered, namely, internal, edge, and corner composite slab. Six specimens with a single unprotected interior beam were tested to failure, and two aspect ratios of 1 and 1.5 for each boundary condition were included. A total vertical load of 100 kN was applied to each specimen, which was heated by an electrical heating furnace from ambient temperature to 1000 °C within 1 h and maintained at 1000 °C until failure of the specimen occurred. The internal composite slab panel with an aspect ratio of 1 had the longest failure time and the edge composite slab panel with an aspect ratio of 1.5 sustained the longest duration. Finite Element (FE) models of the specimens validated by the experimental results were adopted to study membrane forces in the beam-slab sub-assemblage. Numerical simulations showed that different boundary continuities resulted in different membrane forces, and both the axial and rotational stiffness values in the direction of continuous edges were much greater than those of discontinuous edges for typical composite slabs. Moreover, the authors proposed minor amendments to Bailey-BRE method for calculating the enhanced load capacity at ultimate limit state and showed that the predictions were conservative when compared with test results.

Experimental Evaluation of the Cyclic Behaviour of Scaled (1:3) Reinforced Concrete Frames

This paper presents laboratory test results for two-column one-bay reinforced concrete (R/C) bare frames with or without masonry infills for 1:3 scale prototypes when the top beam is subjected to horizontal cyclic loading using 50kN axial load per column. It is well documented that infills affect the dynamic characteristics of building structures. At the same time, their uncertain behaviors have also been recorded. Many parameters, such as the infill materials, reinforcing of infills, connection to the surrounding frame by means of surrounded joint contact, local techniques, and others affect structural system behavior. The masonry infills increase the overall horizontal lateral strength and stiffness and partially structural strength; hence, proper use can positively affect the general seismic behavior. Masonry infill benefits were tested using several specimens: one virgin bare frame, one virgin bare frame with masonry infills, and one virgin frame with masonry infills and reinforced cement plaster. In this experimental series, the aim was to investigate and study the following parameters concerning the general problem of the frames and masonry infills under the influence of cyclic horizontal loading: the frame type, the masonry infill type and, the strength of mortars and coating used to construct the brick walls. The obtained results align with the results of similar studies in Greece. All results address the influence of the infills concerning stiffness, strength, and energy dissipation of the infilled R/C frames, which are significant parameters that should not be neglected.

The effect of different strain quantities on behavior of pin-jointed structural systems

The effect of different strain quantities on behavior of pin-jointed structural systems

Investigation of the Effects of Different Types of Traditional Timber Load-Bearing Systems Used in Turkey on Building Behaviour

Recently historic timber structures in Turkey are unfortunately not given the value they deserve. Although timber structures are unique symbols of our cultural heritage, they are forgotten for natural and human reasons. On the other hand, when traditional timber structures standing today to repairs and / or reinforcements and restorations are examined, it is seen that timber elements according to the knowledge and skill of construction foreman are constructed with different types of structural systems. This matter reveals that choosing the right timber structural system is very important. This study the effects of their behaviour of traditional timber structural systems of different types widely used in the construction of timber structures in Turkey were comparatively examined. With this purpose, teen different structural system models with the Sta-stell program of the timber-framed (with Çatkı) Safran mansion which is widely used in Turkey were created and the findings were compared with each other by carried out structural analyses. The findings obtained reveal that buttresses are important in meeting, distributing and transferring the loads acting on the structural system, especially earthquake loads, to the foundation and the displacement distributions in the storey levels of the buttressed building models are less. In addition, the findings obtained show that buttresses that increase the lateral rigidity of timber structures increase the performance of the structure in question and reduce the internal forces of the structural elements. Turkey's widely used timber structural systems (in accordance with the Safran mansion architecture, which received the best restored mansion award) were modelled and analysed. The results presented are aimed to design recommendations and better understanding of the behaviour of different timber structural systems in today’s architectural practice.

An adaptive PC-Kriging method for time-variant structural reliability analysis

The practical application of time-variant reliability analysis is limited by its computationally expensive models which describe the structural system behavior. This paper presents a new adaptive PC-Kriging (APCK) approach to accurately and efficiently assess the time-variant reliabilities. Time interval is firstly discretized with a series of time instants and then the stochastic process is reconstructed by standard normal random variables and deterministic function of time. PC-Kriging (PCK) models are built at each time instant to predict the instantaneous responses of performance function. To improve the accuracy and efficiency, a new update strategy based on the integration of U- and H- learning functions is developed to refine the PCK models of instantaneous responses. One or two best samples are identified by the proposed learning criterion for updating the PCK models. Finally, Monte Carlo simulation (MCS) is used to estimate the time-variant reliability based on the updated PCK models. Four examples are used to validate the accuracy and efficiency of the proposed method.

Seismic Design and Performances of Frame Structures Connected to a Strongback System and Equipped with Different Configurations of Supplemental Viscous Dampers

The paper investigates the dynamic behavior of structural systems obtained by connecting a moment-resisting frame structure with a vertical rigid truss pinned at the base, known in literature as “strongback,” and equipped with added fluid-viscous dampers. The strongback, designed in order to remain in the elastic field under strong seismic ground motion, acts as a mast by imposing to the structure a linear lateral deformed shape. By regularizing the lateral drift profile of the structure, the strongback limits undesired effects such as weak-storey mechanisms, damage concentration and residual drifts. In addition, when supplemental dampers are inserted in the structure, a considerable amount of energy can be dissipated, thus reducing the peak seismic response. The aim of the work is twofold: i) to provide analytical formulations for the preliminary design of added dampers based on the Generalized Single Degree Of Freedom (GSDOF) concept, and ii) to evaluate the increase in energy dissipation capabilities for selected dampers configurations thanks to the presence of the strongback. The formulas are developed for different configurations of added viscous dampers: dampers inserted within the frame between all or selected consecutive storeys (inter-storey placement) and dampers located at the base of the strongback to realize a rigid “dissipative tower.” The effectiveness of the dampers configurations is evaluated through dynamic time-history analyses.

Parameter identification and dynamic response analysis of a modified Prandtl–Ishlinskii asymmetric hysteresis model via least-mean square algorithm and particle swarm optimization

Hysteresis is a nonlinear phenomenon observed in the dynamic response behavior of numerous structural systems under high intensity cyclic or random loading, as well as in numerous mechanical and electromagnetic systems. For several decades, hysteretic response analysis of structural systems has been widely studied and numerous hysteresis models have been proposed and utilized in order to reproduce and better understand the complex hysteretically degrading behavior of structural systems. An important area of research in this regard has been the parameter identification of hysteretic systems. In this paper, we propose a modified Prandtl–Ishlinskii model to simulate the asymmetric hysteresis, which is the complex behavior in structural systems. In addition, a new approach based on particle swarm optimization and least-mean square algorithm is utilized for parameter identification of this hysteresis model. Finally, the model is applied in structural dynamic response analysis of a base isolated structural model under seismic load.