scholarly journals Quasi-Static Nonlinear Seismic Assessment of a Fourth Century A.D. Roman Aqueduct in Istanbul, Turkey

Heritage ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 401-421
Author(s):  
Semih Gonen ◽  
Bora Pulatsu ◽  
Ece Erdogmus ◽  
Engin Karaesmen ◽  
Erhan Karaesmen
Keyword(s):  
Contact Stiffness ◽  
Point Contact ◽  
Structural Response ◽  
Fourth Century ◽  
Friction Angle ◽  
Stone Masonry ◽  
Seismic Capacity ◽  
Historic Masonry ◽  
Joint Friction ◽  
Modeling Approach

The majority of architectural heritage consists of load-bearing masonry components made up of stone units and relatively weak mortar joints, yielding potential weak planes for masonry structures where tension and shear failures are expected to occur. Advanced nonlinear analyses are required to simulate these phenomena and predict the corresponding nonlinear structural behavior of historic masonry constructions. In this context, this paper presents a model of a stone masonry Roman aqueduct (the Valens Aqueduct), constructed in the fourth century A.D. in Istanbul, Turkey, to explore the seismic capacity and behavior using the discrete element method (DEM). The employed modeling approach comprises distinct rigid blocks interacting along their boundaries based on the point-contact hypothesis. Thus, the discontinuous stone skeleton of the masonry aqueduct is represented explicitly in the computational model. First, a validation study was conducted on the laboratory experiment to demonstrate the capabilities of the adopted modeling approach. Then, a discontinuum model representing the Valens Aqueduct was used to assess the seismic capacity of the structure under gradually increasing lateral forces. The numerical simulations gave insight into the structural response of the aqueduct from the elastic range to total collapse. Additionally, parametric research was performed considering joint properties, namely the joint tensile strength, contact stiffness, joint friction angle, and compressive strength of the masonry, to quantify the effects of contact parameters on the displacement response of the DEM model. Further inferences were made regarding the modeling parameters, and practical conclusions were derived.

scholarly journals Static and Impact Response of a Single-Span Stone Masonry Arch

2021 ◽  
Vol 6 (12) ◽  
pp. 178
Author(s):  
Bora Pulatsu ◽  
Semih Gonen ◽  
Paulo B. Lourenço
Keyword(s):  
High Strain ◽  
Numerical Models ◽  
Contact Stiffness ◽  
Friction Angle ◽  
Masonry Wall ◽  
Impact Response ◽  
Sensitivity Analyses ◽  
Stone Masonry ◽  
Masonry Structures ◽  
Masonry Arch

Unreinforced masonry structures are susceptible to man-made hazards such as impact and blast loading. However, the literature on this subject mainly focuses on masonry wall behavior, and there is a knowledge gap about the behavior of masonry arches under high-strain loading. In this context, this research aims to investigate both quasistatic and impact response of a dry-joint stone masonry arch using the discrete element method. Rigid blocks with noncohesive joint models are adopted to simulate dry-joint assemblages. First, the employed modeling strategy is validated utilizing the available experimental findings, and then sensitivity analyses are performed for both static and impact loading, considering the effect of joint friction angle, contact stiffness, and damping parameters. The outcomes of this research strengthen the existing knowledge in the literature regarding the computational modeling of masonry structures that are subjected to usual and extreme loading conditions. The results highlight that applied discontinuum-based numerical models are more sensitive to stiffness parameters in high-strain loading than static analysis.

scholarly journals The Failure of Masonry Walls by Disaggregation and the Masonry Quality Index

Heritage ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 1162-1198
Author(s):  
Antonio Borri ◽  
Marco Corradi ◽  
Alessandro De Maria
Keyword(s):  
Quality Index ◽  
Failure Modes ◽  
Structural Response ◽  
Theoretical Models ◽  
Masonry Walls ◽  
Wall Panel ◽  
Seismic Capacity ◽  
Structural Behaviour ◽  
Historic Masonry ◽  
Type Of Failure

The visual method for assessment of the structural behaviour of historic masonry walls, known by the acronym MQI (Masonry Quality Index) was introduced in 2002 by a team of researchers from the University of Perugia, Italy. This is based on a visual survey of the faces and the cross section of a wall panel, and it aims at verifying if a wall complies with the “rules of the art”. Based on this analysis, it is possible to calculate a numerical index: numerous tests, carried out on site by the authors to validate the method, have demonstrated that the index is able to provide useful information about the mechanical characteristics and structural response, in general, of the analysed wall panel. The failure mode of a wall panel under the action of an earthquake is a critical aspect. In general, the failure modes can be categorized in two classes: masonry disaggregation and the development of a local or global mechanism of wall elements (macroelements). Several theoretical models and numerical simulations only consider the latter. In this paper, application of the MQI method is further investigated, with particular emphasis to those masonry typologies which are more prone to collapse by disaggregation during a seismic event. Under the action of an earthquake, some types of masonry are typically unable to deform and to split in macroelements, and another type of failure occurs: this is the so-called “masonry disaggregation” or “masonry crumbling”. This type of failure anticipates the ones resulting from macroelement methods or stress analysis. As a conclusion, these latter methods become completely inappropriate and potentially hazardous, as they overestimate the seismic capacity of the building under investigation. The MQI method has been adapted to assess the structural response of different types of masonry under the action of an earthquake. In detail, the aim was to verify when the phenomenon of masonry disaggregation is likely to occur.

Simple Contact Stiffness Model Validation for Tie Bolt Rotor Design With Butt Joints and Pilot Fits

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Aaron M. Rimpel ◽  
Matthew Leopard
Keyword(s):  
Natural Frequencies ◽  
Contact Stiffness ◽  
Butt Joint ◽  
Design Stage ◽  
Design Calculation ◽  
Butt Joints ◽  
Modeling Approach ◽  
Stiffness Model ◽  
Joint Location ◽  
Simple Contact

Abstract Tie bolt rotors for centrifugal compressors comprise multiple shaft components that are held together by a single tie bolt. The axial connections of these rotors—including butt joints, Hirth couplings, and Curvic couplings—exhibit a contact stiffness effect, which tends to lower the shaft bending frequencies compared to geometrically identical monolithic shafts. If not accounted for in the design stage, shaft bending critical speed margins can be compromised after a rotor is built. A previous paper had investigated the effect of tie bolt force on the bending stiffness of stacked rotor assemblies with butt joint interfaces, both with and without pilot fits. This previous work derived an empirical contact stiffness model and developed a practical finite element modeling approach for simulating the axial contact surfaces, which was validated by predicting natural frequencies for several test rotor configurations. The present work built on these previous results by implementing the same contact stiffness modeling approach on a real tie bolt rotor system designed for a high pressure centrifugal compressor application. Each joint location included two axial contact faces, with contact pressures up to five times higher than previously modeled, and a locating pilot fit. The free-free natural frequencies for different amounts of tie bolt preload force were measured, and the frequencies exhibited the expected stiffening behavior with increasing preload. However, a discontinuity in the data trend indicated a step-change increase in the contact stiffness. It was shown that this was likely due to one or more of the contact faces becoming fully engaged only after sufficient tie bolt force was applied. Finally, a design calculation was presented that can be used to estimate whether contact stiffness effects may be ignored, which could simplify rotor analyses if adequate contact pressure is used.

Simple Contact Stiffness Model Validation for Tie Bolt Rotor Design With Butt Joints and Pilot Fits

2019 ◽  
Author(s):  
Aaron M. Rimpel ◽  
Matthew Leopard
Keyword(s):  
Natural Frequencies ◽  
Contact Stiffness ◽  
Butt Joint ◽  
Design Stage ◽  
Design Calculation ◽  
Butt Joints ◽  
Modeling Approach ◽  
Stiffness Model ◽  
Joint Location ◽  
Simple Contact

Abstract Tie bolt rotors for centrifugal compressors comprise multiple shaft components that are held together by a single tie bolt. The axial connections of these rotors — including butt joints, Hirth couplings, and Curvic couplings — exhibit a contact stiffness effect, which tends to lower the shaft bending frequencies compared to geometrically identical monolithic shafts. If not accounted for in the design stage, shaft bending critical speed margins can be compromised after a rotor is built. A previous paper had investigated the effect of tie bolt force on the bending stiffness of stacked rotor assemblies with butt joint interfaces, both with and without pilot fits. This previous work derived an empirical contact stiffness model and developed a practical finite element modeling approach for simulating the axial contact surfaces, which was validated by predicting natural frequencies for several test rotor configurations. The present work built on these previous results by implementing the same contact stiffness modeling approach on a real tie bolt rotor system designed for a high pressure centrifugal compressor application. Each joint location included two axial contact faces, with contact pressures up to five times higher than previously modeled, and a locating pilot fit. The free-free natural frequencies for different amounts of tie bolt preload force were measured, and the frequencies exhibited the expected stiffening behavior with increasing preload. However, a discontinuity in the data trend indicated a step-change increase in the contact stiffness. It was shown that this was likely due to one or more of the contact faces becoming fully engaged only after sufficient tie bolt force was applied. Finally, a design calculation was presented that can be used to estimate whether contact stiffness effects may be ignored, which could simplify rotor analyses if adequate contact pressure is used.

Mechanical Properties of Rocks Used for the Construction of Vehicular Bridges Supported by Pier Masonry

2012 ◽  
Vol 535-537 ◽  
pp. 1881-1888 ◽  
Author(s):  
Gustavo Mendoza-Chavez ◽  
Luis Horacio Martínez-Mártinez ◽  
David Joaquin Delgado-Hernandez ◽  
David De León Escobedo ◽  
Elia Mercedes Alonso Guzmán ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Risk Assessment ◽  
Mechanical Behavior ◽  
Poisson Ratio ◽  
Friction Angle ◽  
Masonry Structure ◽  
Stone Masonry ◽  
Wide Availability ◽  
Density Values ◽  
Ongoing Project

In Mexico, since the early stages of the civilization, the stone masonry has assumed an important role in construction due to the wide availability of this kind of material. Masonry is a material composed by bricks, carved or even rubble stones jointed without (dry joint) or with mortar (mortar joints); which is principally formed with sand, water and cementitiuos materials. The research presented in this paper deals with the procedure of obtaining the mechanical properties of rocks placed on piers of four vehicular bridges located in the south of the state of Mexico, these mechanical properties are compressive strength, modulus of elasticity, Poisson ratio, Cohesion and Internal friction Angle of the rocks as independent units, also are reported the Density values. All of these properties are necessary to conduct further research regarding the mechanical behavior of the pier as a structure since this piece of research is part of an ongoing project concerning risk assessment of vehicular bridges developed in Mexico. The identified rocks in masonry were volcanic igneous materials such as dacites, basalts, rhyolites, andesites and rusted andesites. The materials with the highest and the lowest mechanical properties are the basalt and the dacite respectively. It is recommended to use the dacite’s properties in order to perform a conservative analysis of the mechanical behavior of any masonry structure, located near the selected sample studied herein.

Test Rig for Extraction of the Contact Parameters for Plane on Plane Contact

2012 ◽  
Author(s):  
D. Botto ◽  
M. Lavella ◽  
M. M. Gola
Keyword(s):  
Contact Area ◽  
Contact Stiffness ◽  
Point Contact ◽  
Real Plane ◽  
Operational Environment ◽  
Test Rig ◽  
Friction Forces ◽  
Plane Contact ◽  
Wide Range ◽  
Contact Parameters

The modelling of the friction interfaces has received much attention in recent years from the aerospace industry. In order to obtain reliable prediction of the nonlinear dynamic behaviour of the disc and blades in the aerospace engine the friction forces at interfaces, such as in under-platform dampers, blade and fir tree roots or shrouds, must be modelled accurately. Two contact parameters, namely the contact stiffness and the coefficient of friction, are sufficient to model, with good accuracy, the friction contact. The contact parameters are obtained experimentally, and are of interest for the designer only if representative of the operational environment of the engine. To pursue this aim a test rig has been designed to perform experiments in a wide range of temperatures, with different combinations of normal and tangential load, frequencies and mating materials, representative of the real operating condition of the engine. Most of the rigs found in literature perform most likely point contact even if the two bodies have plane mating surfaces. The design of a real plane-on-plane contact test rig is not an easy task but despite the difficulty a solution was found in the design shown in this work. The core of the rig is a tilting mechanism enabling one surface to lies down on the other so that the plane-on-plane contact is achieved, at least within the flatness geometrical tolerance of the surfaces. The results of the experiments are the hysteresis loops, namely the tangential contact force against the relative displacement, from which the contact parameters can be calculated. Measurements of displacements are taken very close to the actual contact area and are performed by means of two laser interferometers. Localized heating is achieved by means of an induction heating machine while a thermocouple measures the temperature at points close to the contact area.

Rough Surface Contact of Curved Conformal Surfaces: An Application to Rotor–Stator Rub

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Rough Surface ◽  
Contact Force ◽  
Contact Stiffness ◽  
Point Contact ◽  
Contact Model ◽  
Industrial Society ◽  
Real Surface ◽  
Linear Elastic ◽  
Surface Contact ◽  
Rough Surface Contact

Rotating machines and associated triboelements are ubiquitous in industrial society, playing a central role in power generation, transportation, and manufacturing. Unfortunately, these systems are susceptible to undesirable contact (i.e., rub) between the rotor and stator, which is both costly and dangerous. These adverse effects can be alleviated by properly applying accurate real-time diagnostics. The first step toward accurate diagnostics is developing rotor–stator rub models which appropriately emulate reality. Previous rotor–stator rub models disavow the contact physics by reducing the problem to a single esoteric linear contact stiffness occurring only at the point of maximum rotor radial deflection. Further, the contact stiffness is typically chosen arbitrarily, and as such provides no additional insight into the contacting surfaces. Here, a novel rotor–stator rub model is developed by treating the strongly conformal curved surfaces according to their actual nature: a collection of stochastically distributed asperities. Such an approach is advantageous in that it relies on real surface measurements to quantify the contact force rather than a heuristic choice of linear contact stiffness. Specifically, the elastoplastic Jackson–Green (JG) rough surface contact model is used to obtain the quasistatic contact force versus rotor radial deflection; differences and similarities in contact force between the linear elastic contact model (LECM) and JG model are discussed. Furthermore, the linear elastic model's point contact assumption is assessed and found to be inaccurate for systems with small clearances. Finally, to aid in computational efficiency in future rotordynamic simulation, a simple exponential curve fit is proposed to approximate the JG force–displacement relationship.

Grasp Stiffness Matrix for Soft Finger Contact Model in Robotic Applications

2000 ◽  
Author(s):  
Abdul Ghafoor ◽  
Jian S. Dai ◽  
Joseph Duffy
Keyword(s):  
Stiffness Matrix ◽  
Contact Stiffness ◽  
Point Contact ◽  
Point Contacts ◽  
Rigid Object ◽  
Equivalent Point ◽  
Line Spring Model ◽  
On Line ◽  
Soft Finger

Abstract This paper proposes a practical and analytical model for soft finger grasp. It presents a contact stiffness matrix by applying congruence transformation and mapping stiffnesses from a line spring model onto translational and rotational stiffnesses. The contact that is realised in this paper is in the form of a patch contact with evenly distributed finite number of equivalent point contacts. An analytical approach is hence proposed based on line springs and screw representation of the frictional elastic point contacts that provides a direct correlation between the equivalent point contact and soft finger contact of a rigid object and gives a procedure to complete the analysis. The grasp achieved with the analysis provides both translational and rotational restraint. The approach and its use for finite manipulation are supported by a case study.

scholarly journals Rheology of Natural Hydraulic Lime Grouts for Conservation of Stone Masonry—Influence of Compositional and Processing Parameters

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 13 ◽  
Author(s):  
Luis Baltazar ◽  
Fernando Henriques ◽  
Maria Cidade
Keyword(s):  
Processing Parameters ◽  
Stone Masonry ◽  
Hydraulic Lime ◽  
Historic Masonry ◽  
Natural Hydraulic Lime ◽  
Extrinsic Parameters ◽  
Scientific Papers ◽  
Significant Research ◽  
Intrinsic And Extrinsic Parameters ◽  
Measuring Instrumentation

This review provides an overview of the recent progress in the field of the rheology of grouts for historic masonry consolidation. During the last two decades, significant research has been devoted on the grouting technique for stone masonry consolidation but most results are scattered by scientific papers, congress communications, and thesis. This paper compiles and briefly demonstrates the effect of several intrinsic and extrinsic parameters, such as admixtures, additions, pressure, temperature, and measuring instrumentation, on the rheological performance of natural hydraulic lime-based grouts.

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