Macromodeling Approach Research Articles

Macro-Modelling Approach for the In-Plane Cyclic Response of Cold-Formed Steel Partition Walls

Past earthquakes demonstrate that non-structural elements could be vulnerable to a relatively low intensity ground shaking which induces negligible structural damage. The study aims to improve previously developed macro-models of cold-formed steel (CFS) partition walls to properly capture their in-plane cyclic response and damage states of important components in a CFS partition wall under imposed excitation. An effective analytical modelling approach is adopted for a simple modelling procedure and less computational effort. The proposed analysis model of partition walls consisting of several lumped spring elements is verified using direct comparison with two full scale CFS partition wall tests. The analytical and experimental results are compared in terms of force–displacement relations, dissipated energy, and an influential damage mechanism of components consisting of partition walls. The comparison shows that the analytical model well captures the experimental response such as the overall strength and stiffness degradation and pinching behavior. Moreover, the damage mechanism predicted by the analytical model is in good agreement with that observed during the tests.

A Fast Macromodeling Approach to Efficiently Simulate Inhomogeneous Electromagnetic Surfaces

The full-wave simulation of complex electromagnetic surfaces such as reflectarrays and metasurfaces is a challenging problem. In this paper, we present a macromodeling approach to efficiently simulate complex electromagnetic surfaces composed of PEC traces, possibly with fine features, on a finite-sized multilayer dielectric substrate. In our approach, we enclose each element of the structure with a fictitious surface. By applying the equivalence principle on each surface, we derive a macromodel for each element of the array. This macromodel consists of a linear operator that relates the equivalent electric and magnetic current densities introduced on the fictitious surface. Mutual coupling between the elements of the structure is captured by the equivalent current densities in a fully accurate way. The crux of the proposed technique is to solve for equivalent current densities on the fictitious surface instead of directly solving for the actual current densities on the original scatterer. When simulating complex surfaces, this approach leads to fewer unknowns and better conditioning. We also propose a rigorous acceleration algorithm based on the fast Fourier transform to simulate electrically large surfaces. Numerical results demonstrate that the proposed approach is significantly faster and requires less memory than commercial solvers based on the surface integral equation method, while giving accurate results.

Numerical study of dynamic responses of reinforced concrete infilled frames subjected to progressive collapse

Recently, the contribution of infill walls on progressive collapse resistance of reinforced concrete (RC) structures attracts a great many research attentions, but the research interests are mainly concentrated on the static resistance and the macro-modeling approaches, which require predefined one-dimensional load paths through two-dimensional walls. However, the load transfer paths in dynamic loading regime are still not fully understood. To this end, high-fidelity finite element (FE) models of multi-story RC infilled frames are built and validated through quasi-static experimental results. Then the FE models are used to investigate the dynamic responses of infilled frames under different single and double CRS as well as the effect of the number of stories on the load transfer paths of full-height infill walls (FHIW) and infill walls having opening (IWHO). The results indicate that the load paths along the infill walls in static and dynamic loading regimes are similar prior to the peak resistance but different in post-peak resistance for single infilled story frames. Such difference results from the loading distribution pattern, in which the static loading is typically represented by a concentrated load whereas the dynamic loading involves the uniformly distributed load. Moreover, increasing the number of infilled stories with FHIW, trans-story load paths due to composite effect always exist to enhance resistance and such paths are scenario-dependent. In comparison, the load paths for multi-story frames with IWHO are relatively scenario-independent with minor composite effect. Therefore, to generalize the macro-modeling, it is conservative to ignore the trans-story load paths.

Seismic analysis of a masonry arch bridge using multiple methodologies

Masonry arch bridges form a noteworthy portion of road and railway networks in Europe and Turkey. Structural assessment of such bridges is often required because of their vulnerability to seismic actions. However, there are no standardized or widely accepted procedures, and the available assessment methods comprise significant uncertainties. This paper presents a seismic assessment of a stone masonry arch bridge using different methodologies by investigating the seismic behavior of masonry arch bridges and the uncertainties in the assessment methods presented. The Finite Element (FE) macro-modeling approach is used in modeling the behavior of the structure under investigation, after undertaking ambient vibration testing and dynamic identification study to determine the dynamic parameters of the structure. These experimental parameters were used to update the FE model before performing the seismic assessment using Nonlinear Static Analysis (NSA), Nonlinear Dynamic Analysis (NDA) and Incremental Dynamic Analysis (IDA). The IDA helped to depict the complete picture of the seismic behavior, whereas the comparison of the results highlighted the limitations of the NSA and enabled presenting recommendations for future work. In addition, the effects of the interaction of horizontal and vertical components of earthquake records in NDA underlined the necessity for their consideration in similar studies.

Numerical evaluation of a non-ductile RCFMI building subjected to the Canterbury, New Zealand Earthquakes: A case study of the St Elmo Courts building

The 2010/2011 Canterbury, NewZealand earthquakes resulted in minor to severe levels of damage to a number of high-rise Reinforced Concrete Frame with Masonry Infill (RCFMI) buildings that were constructed before the establishment of the first New Zealand seismic code in 1935. Because a ductile design philosophy was not adopted in the NewZealand structural seismic design process until the release of the 1976 NewZealand Seismic Code, these high-rise RCFMI buildings can be considered to be non-ductile and potentially earthquake-vulnerable buildings. The seismic performance of these NewZealand non-ductile high-rise RCFMI buildings has received little research attention previously, and the reported study was consequently conducted to investigate the appropriateness of employing a macro-modelling approach using commercial software. The level of modelling accuracy was first established by correlation against previously reported experimental studies and the adopted numerical model was then applied to numerically assess a case study non-ductile high-rise RCFMI building that was severely damaged during the Canterbury earthquakes. It was shown that the numerical modelling results were well-matched with the observed earthquake damage. As a result, it was concluded that the adopted numerical modelling approach can be implemented for the seismic assessment of existing non-ductile RCFMI buildings across NewZealand.

Seismic Collapse Assessment of Composite Plate Shear Walls

Collapse evaluation of composite plate shear walls (C-PSWs) under seismic loading requires a reliable analytical model that can accurately capture deterioration in the strength and stiffness of the system. In this study, research was carried out to develop a macromodeling approach for C-PSWs. Nonlinear time history analyses of six multistory (7-, 10-, and 13-story) C-PSWs (traditional and innovative) located in Western Canada were performed. It was observed that a significant portion of the story shear was resisted by the boundary members, while the RC panel resisted less than 10% of the total story shear. To estimate the seismic response parameters (i.e., ductility-related and overstrength-related force modification factors) for designing C-PSWs, incremental dynamic analysis (IDA) was performed for all archetypes following a standard procedure. It was observed that all archetypes provided significant safety margin against collapse (large collapse margin ratio). In addition, a sensitivity study was conducted and the effects of postyielding parameters (ductility capacity and postcapping stiffness) adopted for the deterioration model for infill plate and postcracking parameters (shear strain corresponding to maximum shear stress, yielding shear strain, and residual stress) adopted for the deterioration model for RC panel on seismic collapse capacities of traditional C-PSWs were investigated. It was observed that postyielding parameters for the steel infill plate can affect the seismic response of C-PSWs. On the other hand, variation of postcracking parameters for the concrete panel had a minor effect on seismic collapse capacity of the C-PSW system.

A unified macro-modelling approach for masonry-infilled RC frames strengthened with composite materials

Non-structural masonry infills in existing reinforced concrete (RC) frame structures are known to affect their seismic behaviour significantly with potential detrimental effects. Increasing experimental evidence is available for the use of composite materials, such as fibre-reinforced polymers (FRP) and textile reinforced mortars (TRM), for in-plane retrofitting of brittle masonry infills. In order to apply such strengthening solutions in practice, adequate analytical models for predicting the behaviour are needed, however the large variation in infill properties already makes modelling the behaviour of non-retrofitted infills a challenge. Based on existing experimental and numerical studies on retrofitted infills, a macro-model is proposed, comprising a tie to account for the tensile strength of the composites materials, but also an increased compressive strut width due to the composite materials improving connection of the infill to the frame. After compiling a database of experimental data for composite retrofitted specimens tested in the literature, empirical equations for tie and strut strength was obtained. These equations constitute the first unified approach for FRP- and TRM-strengthened infills and were verified against the largest database of experimental results to date. The strut model was calibrated for the increase in strut width in terms of experimentally obtained stiffness increase, while the tie model was determined based on the remaining increase in strength. The empirical equations were shown to achieve a relatively high correlation with experimental results and to represent the mechanics of tested specimens well in terms of observed damage, hence indicating their potential for use as design-oriented equations for composite strengthened infills.

TARİHİ YIĞMA BİR KÖPRÜNÜN DEPREM DAVRANIŞININ DEĞERLENDİRİLMESİ

Tarihi yığma kemerli köprüler eski dönemlerden beri geçmiş uygarlıkların kültürel mirasını günümüze aktaran en önemli yapılardan biridir. Tarihi yığma kemerli köprüler geçmişte ulaşım, ticaret ve mimarinin en önemli unsurlarından biridir. Ancak yeni yapı malzemelerinin ve yapım yöntemlerinin gelişmesiyle günümüzde artık yığma kemerli köprüler inşa edilmemektedir. Bu yapılar deprem, sel, yangın ve savaşlar gibi dış etkenlerle zarar görebilmektedir. Ülkemizde de tarihi köprüler gibi geçmişi günümüze bağlayan önemli mühendislik yapılarının mevcut durumlarının tespit edilerek geleceğe güvenle devredilmesi amacıyla çeşitli çalışmalar yapılmaktadır. Bu çalışmanın temel hedefi tarihi yığma kemerli bir köprünün lineer dinamik analizlerini gerçekleştirerek köprünün deprem etkisi altındaki davranışını incelemektir. Bu amaçla tek açıklıklı yığma kemerli bir köprü sayısal örnek olarak ele alınmıştır. Köprünün 3 boyutlu sonlu elemanlar modeli ANSYS sonlu elemanlar programı ile makro modelleme yaklaşımı dikkate alınarak oluşturulmuştur. Lineer dinamik analizlerde köprünün bulunduğu konum da göz önünde bulundurularak 2011 Simav ve 2002 Sultandağı depremlerine ait ivme kayıtları sismik etki olarak kullanılmıştır. Yapılan analizlerden köprüye ait yer değiştirmeler ve maksimum-minimum asal gerilmeler elde edilmiş ve köprünün sismik tepkileri değerlendirilmiştir.

Design of an 8‐bit time‐mode cyclic ADC based on macro modeling

SummaryThis work presents a macro modeling approach for the time‐mode cyclic ADC. The proposed ADC macro model is realized using the time‐to‐voltage converter (TVC) and the voltage‐to‐time converter (VTC) that are the key building blocks of time‐mode ADCs. In addition, the effect of circuit nonidealities and error sources of the time‐mode ADC including parasitic capacitance, current source output resistance, switch on‐resistance, capacitor mismatch, and comparator offset are incorporated in the macro model. The simulation time of the proposed ADC macro model showed 87.1% reduction compared to the all transistor level ADC circuit. As a result, the proposed ADC macro model can facilitate the ADC design and leverage the ADC nonideality analysis. Furthermore, the proposed macro model can be used for ADC calibration scheme development. As a practical design example, the macro model for an 8‐bit time‐mode cyclic ADC has been realized, where the nonideality analysis, design optimization, and calibration scheme development based on the proposed macro model have been demonstrated.

Numerical study on masonry infill wall by using in-plane element and joint interface with RC frame

Commonly house’s damage under earthquake is because their capacity inadequate to prevent from collapse, and the masonry wall system is not designed to resist the earthquake force. However, masonry infill wall is commonly used as partition and to separate large area with a purposed. Interaction between frame and masonry infill wall are not good connected to prevent building damage from earthquake. To understand the interaction between frames and infill wall can be simulated by numerical method or by Macro-modelling approach. The purpose of this numerical study is modelled a frame as a single element, a masonry infill wall as a plate element, and an interface between frame and masonry infill wall as an elastic spring. The concept of modelling depends on material parametric provided and the number of elements. Modelling with computational software facilitate to create material element and model and this modelling is conducted by Tohoku-coast NS time history seismic. The result shows the frequency parameter expressively increase from frequency on frame model to frame with infill wall model, or the time period parameter significantly reduce with the addition of infill wall. By the addition of mortar thickness which increased the stiffness also affect the frequency parameter and maximum displacement. The thickness of mortar brought the optimal value to good response is recommended with thickness of 0.5 cm to 1.5 cm. The finding is that infill wall gives significant influence on frame response if the interface of frame and infill wall designed with good material characters.

Seismic vulnerability assessment of confined masonry structures by macro-modeling approach

As seen during numerous earthquakes, confined masonry exhibited a reliable anti-seismic response due to a number of factors. To understand the effect of these factors, a case study of full scale confined masonry (CM) structure is considered and results of its numerical assessment are described. It focus mainly on the evaluation of factors such as masonry strength, wall density, pre-compression level and properties of the confining elements. The numerical study is performed using advanced numerical simulations in ATENA environment. A rigorous analysis of the nonlinear behavior of CM structures involves advanced nonlinear finite element models and a stable computational cost, making these procedures inappropriate for everyday applications. Therefore, in recent times, several researchers have offered simplified methodologies. In this study a macro-element simplified model based on smeared crack and total stress–strain models is applied to a benchmark CM prototype structure. Results are presented as force–displacement curves, types of failure modes, ductility and damage index. From the parametric studies it was revealed that material strength play a central role on the behavior of confined masonry subjected to lateral loading and determine the effect of other parameters such as pre-compression level, wall density and properties of confining elements.

A Finance Approach to Climate Stress Testing

There is increasing interest in assessing the impact of climate policies on the value of financial sector assets, and consequently on financial stability. Prior studies either take a black box macro-modelling approach to climate stress testing or focus solely on equity instruments - though banks' exposures predominantly consist of debt. We take a more tractable finance (valuation) approach at the industry-level and use a Merton contingent claims model to assess the impact of a carbon tax shock on the market value of corporate debt and residential mortgages. We calibrate the model using detailed, proprietary exposure data for the Dutch banking sector. For a €100 to €200 per tonne carbon tax we find a substantial decline in the market value of banks' assets equivalent to 4-63% of core capital, depending on policy choices.

A Macromodeling Approach for Analog Behavior of Digital Integrated Circuits

A macromodeling technique for digital cells is presented. The proposed macromodel allows fast and accurate signal approximation, as well as delay estimation for CMOS digital circuits. To verify its accuracy, the technique is implemented on different logic gates, a half-adder, and a flip-flop. The simulation results are compared with those obtained with SPICE for a 65-nm CMOS technology with a 1.0-V power supply. The results show the delay offset and amplitude deviation are within 5% of SPICE values for an exponential input with maximum $10^{9}$ V/s slope. The execution time of the experimental simulator implemented in MATLAB was more than 1000 times faster than SPICE in all cases.

System-level seismic resilience assessment of reinforced masonry shear wall buildings with masonry boundary elements

The concept of seismic resilience plays an important role in seismic assessment of structures as it assesses the capability of a system to withstand an unwanted event, such as earthquakes, by estimating the losses and determining the system’s functionality and sustainability during and after such event. In this study, a framework was utilized to assess the seismic resilience of Reinforced Masonry Shear Wall (RMSW) buildings as well as studying the impact of incorporating Masonry Boundary Elements (MBEs) at the ends of RMSW. To achieve this goal, a ten-story RMSW building was numerically modelled in OpenSees to assess the seismic performance and resilience of the system when adding confined MBEs. The selected building is located in Montreal, Canada, and initially designed to be built having rectangular walls. Subsequently, the walls were redesigned to integrate MBEs at their outermost fibre to help increase the ductility and strength of the RMSWs. A full 3D wide-column macro-modelling approach was used to simulate the dynamic response of the archetype building. Validation of the modelling approach was done against available experimental tests as an initial step to ensure the robustness of the model in predicting the inelastic response of the building. Subsequently, the models were analyzed against multiple ground motion records using Incremental Dynamic Analysis to identify the initiation of collapse alongside developing the fragility curves of the building. The system-level seismic performance of the building was assessed after incorporating MBEs. The resilience of the building was assessed using the developed fragility functions, and a comparison was made to highlight the effect of using MBEs on the response of the studied RMSW building. The results showed a significant enhancement in the seismic resilience of the building by using confined MBEs at the shear walls’ extreme.

LOCALIZATION ANALYSIS OF AN ORTHOTROPIC MULTI-SURFACE PLASTICITY MODEL UNDER UNIAXIAL STRESS

Numerical simulations of masonry structures are often based on continuum macromodelling approaches that need constitutive laws able to phenomenologically reproduce the behavior of the material. To capture the deformation process up to failure, appropriate softening laws are needed to take into account the contraction of the yield stress domain caused by cracking and crushing. It is well known that softening may lead to localization of inelastic strain. This paper focuses on localization analysis of an orthotropic macro-scale model in the framework of multi-surface plasticity, which describes the in-plane behavior of masonry structures. Preliminary results reported in this short paper are limited to uniaxial stress states. Analytical localization conditions are first derived for uniaxial stress states with principal axes aligned with the material axes of orthotropy. Then, localization analysis is extended to an arbitrary angle between the principal stress axes and the axes of orthotropy.

Numerical Modeling Approaches of FRCMs/SRG Confined Masonry Columns

The Fabric Reinforced Cementitious Matrices (FRCMs) and Steel Reinforced Grout (SRG) are a promising strengthening solution for existing masonry since inorganic matrix is considerably compatible with historical substrates. The present paper is focused on a Finite Element (FE) analysis of masonry columns confined with FRCM composites developed by Abaqus-code. The masonry columns were modelled using a macro model approach. The model was performed by using the following functions Concrete Damage Plasticity (CDP) and the Plastic (P) in order to describe the constitutive laws of material for masonry columns and external reinforcement, respectively. Typical failures of FRCM-systems are slippage of the fibers within the embedding matrix, instead for SRG-systems are detachment of the composite strip at the fabric-matrix interface and fiber rupture. In addition, perfect bond was considered for the interaction between the masonry column and in the overlap zone the bond slip law was modelled on the base of the failure mode. Results of an experimental investigation on FRCM and SRG clay brick masonry columns are used to calibrate the numerical model.

A Novel Framework for Parametric Loewner Matrix Interpolation

The generation of black-box macromodels of passive components at the chip, package, and board levels has become an important step of the electronic design automation (EDA) workflow. The vector fitting (VF) scheme is a very popular method for the extraction of such macromodels, and several multivariate extensions are now available for embedding external parameters in the model structure, thus enabling model-based variability analysis and design optimization. The Loewner matrix interpolation framework was recently suggested as an effective and promising alternative macromodeling approach to VF. In this article, we propose a parametric version of Loewner interpolation, which embeds orthogonal polynomials as an integral part of the parameterization framework. This approach is shown to be efficient and accurate and presents various advantages with respect to competing multivariate rational interpolation methods. These advantages include better control of model smoothness in the parameter space and a particularly efficient implementation of the singular value decomposition, which is the core of the model extraction scheme. These advantages are confirmed through several examples relevant for signal and power integrity applications.

System Identification and Seismic Performance Assessment of a Stone Arch Bridge

ABSTRACT This paper presents system identification and seismic performance assessment of a masonry arch bridge located on the railway route which is on the northeastern part of Turkey. Forty-one masonry arch bridges were registered as historical and needed to be preserved on the route. On the other hand, the railway line passes through North Anatolian Fault, resulting in high seismic demand on bridges. Therefore, seismic assessment of the bridges was carried out by finite element analysis; however, masonry structures such as stone arch bridges have significant uncertainties in terms of material properties, boundary conditions, and modeling assumptions. As a result, it becomes almost unavoidable to perform dynamic identification tests to validate finite element models (FEM). Modal properties of 12 bridges such as modal frequencies, mode shapes, and modal damping ratios were identified through vibration measurements collected under ambient conditions, impact loading, and train passage. Based on identified modal parameters, FEM of the bridges were updated to obtain actual values of Young’s modulus of masonry and soil. FEM updating procedure was performed by minimizing the difference between experimental and analytical modal properties. Afterwards, seismic performance assessment of a representative bridge was carried out using ANSYS software. Two different nonlinear approaches were considered, namely, pushover and nonlinear time history (NLTH) analyses. In the analyses, macro-modeling approach was followed to develop homogenized behavior of stone and mortar. It was found that mass proportional pushover analysis gave similar results to NLTH in terms of seismic performance. The other significant point was that modeling soil medium reflects the actual behavior of the bridge in the sense that artificial stress concentrations do not occur at the pier base. It was also observed that tensile strength capacity was reached on spandrel walls which may result in a probable failure.

Pushover analysis of confined masonry walls using a 3D macro-modelling approach

This paper shows a novelty way to simulate the nonlinear behaviour of confined masonry walls subjected to in-plane lateral loading by using a 3D macro-modelling approach. For this purpose, the finite elements method implemented in ABAQUS software was used. All the 3D solid finite elements were modelled as a single part, which allowed avoiding modelling the contact interfaces between concrete and masonry elements. The nonlinear behaviour of the concrete and masonry were governed by two main types of failures: crushing and cracking, which were properly represented by the Concrete Damage Plasticity (CDP) model. Steel rebars were modelled as elastic–plastic with hardening and were assumed to have a perfect adhesion with the surrounding concrete by means of the embedded constraint. Prior to the modelling process, experiments were carried out whose results were used as patterns to validate the proposed model. A calibration process of the tensile properties of masonry was conducted for properly fitting the experimental patterns. As a result, there were good agreements between the numerical and experimental outcomes in terms of capacity curves and cracking patterns.

Shaking table testing and numerical simulation of the seismic response of a typical China ancient masonry tower

Ancient masonry towers are an important cultural heritage and particularly vulnerable to damage during earthquakes. To investigate the dynamic characterization and the seismic performances of historical masonry towers, a 1/8-scale masonry model representative of an ancient Chinese tower was studied by shaking table tests. The experimental model was subjected to four scaled earthquake ground motion in two directions, the dynamic characteristics, the seismic response as well as the failure mechanism were analyzed. In addition, a nonlinear finite element model was also established with macro-modeling approach to further study its seismic response, the results between the tests and the model were compared and agreed well.