Creep deformation of clay masonry structures: a parametric study

1998 ◽  
Vol 25 (1) ◽  
pp. 67-80 ◽  
Author(s):  
Ezzeldin Y Sayed-Ahmed ◽  
Nigel G Shrive ◽  
Dan Tilleman
Keyword(s):  
Moisture Content ◽  
Creep Behaviour ◽  
Masonry Structure ◽  
Time Dependent ◽  
Masonry Structures ◽  
Moisture Condition ◽  
Test Setup ◽  
Elastic Part ◽  
Masonry Construction ◽  
Dependent Part

When loads are applied to a masonry structure, viscoelastic behaviour is exhibited where the response can be divided into two distinct parts: an instantaneous elastic part and a time-dependent part. With the change in masonry construction during the last century, the latter portion of the response is becoming more important in the design of masonry structures. The effects of mortar type, stress level, age at loading, moisture condition, and masonry strength on the creep behaviour of clay masonry structures are examined. The results of a continuing experimental programme, begun in 1988, were used to evaluate the variations in specific creep of clay masonry with the different parameters considered. The test setup and the effect of moisture content on the creep behaviour of clay masonry are also described briefly.Key words: masonry, creep, specific creep, creep ratio, mortar type, moisture condition.

scholarly journals In-Plane Strengthening Effect of Prefabricated Concrete Walls on Masonry Structures: Shaking Table Test

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Weiwei Li ◽  
Weiqing Liu ◽  
Shuguang Wang ◽  
Dongsheng Du
Keyword(s):  
Shaking Table Test ◽  
Masonry Structure ◽  
Shaking Table ◽  
Strengthening Effect ◽  
Masonry Structures ◽  
Dynamic Tests ◽  
Seismic Capacity ◽  
Concrete Walls ◽  
Improvement Effect ◽  
Scaled Models

The improvement effect of a new strengthening strategy on dynamic action of masonry structure, by installing prefabricated concrete walls on the outer facades, is validated by shaking table test presented in this paper. We carried out dynamic tests of two geometrically identical five-story reduced scaled models, including an unstrengthened and a strengthened masonry model. The experimental analysis encompasses seismic performances such as cracking patterns, failure mechanisms, amplification factors of acceleration, and displacements. The results show that the strengthened masonry structure shows much more excellent seismic capacity when compared with the unstrengthened one.

scholarly journals Effect of soil moisture condition on the conversion rate of oxamyl.

1979 ◽  
Vol 27 (3) ◽  
pp. 191-198
Author(s):  
J.H. Smelt ◽  
A. Dekker ◽  
M. Leistra
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Conversion Rate ◽  
Soil Moisture Content ◽  
Loamy Sand ◽  
Clay Loam ◽  
Moisture Condition ◽  
Soil Moisture Condition ◽  
Incubation Experiments ◽  
Wilting Point

The decomposition of oxamyl in four soils under moist conditions was measured in incubation experiments at 15 deg C. Half-lives of oxamyl in soils with moisture tensions of approx. -9.8 X 103 Pa were 13 days in a clay loam, 14 days in a loamy sand, 34 days in a peaty sand and 39 days in a humic loamy sand. The rate of oxamyl decomposition in the clay loam decreased with decreasing soil moisture content down to values for below wilting point. Oxamyl decomposition in the humic loamy sand decreased with decreasing soil moisture content, but increased sharply in the very dry range. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Charge Carriers Relaxation Behavior of Cellulose Polymer Insulation Used in Oil Immersed Bushing

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 336
Author(s):  
Yu Shang ◽  
Qiang Liu ◽  
Chen Mao ◽  
Sen Wang ◽  
Fan Wang ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Moisture Content ◽  
Charge Carriers ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Stable Operation ◽  
Polarization Current ◽  
Depolarization Current ◽  
Moisture Condition ◽  
Dc Voltage

Cellulose insulation polymer material is widely used in oil immersed bushing. Moisture is one of the important reasons for the deterioration of cellulose polymer insulation, which seriously threatens the safe and stable operation of bushing. It is significant to study the polarization and depolarization behavior of oil-immersed cellulose polymer insulation with different moisture condition under higher voltage. Based on polarization/depolarization current method and charge difference method, the polarization/depolarization current, interfacial polarization current and electrical conductivity of cellulose polymer under different DC voltages and humidity were obtained. Based on molecular-dynamics simulation, the effect of moisture on cellulose polymer insulation was analyzed. The results show that the polarization and depolarization currents become larger with the increase in DC voltage and moisture. The higher applied voltage will accelerate the charge carrier motion. The ionization of water molecules will produce more charge carriers. Thus, high DC voltage and moisture content will increase the interface polarization current. Increased moisture content results in more charge carriers ionized by water molecules. In addition, the invasion of moisture will reduce the band width of cellulose polymer and enhance its electrostatic potential, so as to improve its overall electrical conductivity. This paper provides a reference for analyzing the polarization characteristics of charge carriers in cellulose polymer insulation.

Shake Table Tests on a Masonry Structure Retrofitted with Composite Reinforced Mortar

2019 ◽  
Vol 817 ◽  
pp. 342-349
Author(s):  
Stefano de Santis ◽  
Gianmarco de Felice ◽  
Garis Lorenzo Di Noia ◽  
Pietro Meriggi ◽  
Marika Volpe
Keyword(s):  
Seismic Vulnerability ◽  
Masonry Structure ◽  
Shake Table ◽  
Masonry Structures ◽  
Shake Table Tests ◽  
Reinforced Polymer ◽  
Glass Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Glass Fibre Reinforced ◽  
Recent Earthquakes

Recent earthquakes have dramatically shown the seismic vulnerability of existing masonry structures and highlighted the urgent need of developing suitable strengthening solutions. In order to gain an improved understanding of the seismic response of masonry constructions and of the most appropriate technologies for their retrofitting, a shake table test was performed on a full-scale U-shaped tuff masonry structure, provided with an asymmetric plan with openings and with an inclined roof. The specimen was tested unreinforced and then repaired and retrofitted with composite reinforced mortar (CRM), comprised of a glass fibre reinforced polymer mesh applied with a lime mortar. Natural accelerograms were applied with increasing scale factor to collapse. Results provided information on the dynamic behaviour of masonry structures strengthened with CRM and on the enhancement of seismic performance provided by the retrofitting work.

Properties of thermally modified medium-density fibreboards

Holzforschung ◽  
2012 ◽  
Vol 66 (1) ◽  
Author(s):  
Jürgen Bonigut ◽  
Detlef Krug ◽  
Beate Stephani
Keyword(s):  
Thermal Treatment ◽  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Phenol Formaldehyde ◽  
Creep Behaviour ◽  
Modulus Of Rupture ◽  
Medium Density ◽  
Thickness Swelling ◽  
Short Term ◽  
European Standards

Abstract Thermal treatment of solid timber and oriented strandboards (OSB) improves durability against fungal decay and dimensional stability (swelling and shrinking). It is not clear whether thermal treatment of medium-density fibreboards (MDF) has the same effects. In this work, four variants of phenol-formaldehyde (PF)-bonded MDF with varying contents of resin and hydrophobing agent were thermally post-treated according to the Mühlböck procedure at three different maxi-mum temperatures. The short-term properties internal bond, modulus of rupture, modulus of elasticity, thickness swelling and equilibrium moisture content and the long-term property creep behaviour of treated variants and of one untreated variant have been tested. The results are presented and discussed in comparison with the respective European standards. Altogether, the thermal treatment had a positive effect on most of the tested mechanical short-term properties. The moisture-related properties, i.e., thickness swelling and equilibrium moisture content, were also positively influenced. The creep behaviour of heat-treated MDF could also be improved by thermal modification.

scholarly journals Numerical Study on Crack Distributions of the Single-Layer Building under Seismic Waves

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Fenghui Dong ◽  
Zhipeng Zhong ◽  
Jin Cheng
Keyword(s):  
Seismic Waves ◽  
Numerical Study ◽  
Single Layer ◽  
Experimental Tests ◽  
Masonry Structure ◽  
Original Model ◽  
Dynamic Responses ◽  
Masonry Structures ◽  
Reinforced Masonry ◽  
Longitudinal Cracks

This paper conducts a numerical simulation of the antiseismic performance for single-layer masonry structures, completes a study on crack distributions and detailed characteristics of masonry structures, and finally verifies the correctness of the numerical model by experimental tests. This paper also provides a reinforced proposal to improve the antiseismic performance of single-layer masonry structures. Results prove that the original model suffers more serious damage than the reinforced model; in particular, longitudinal cracks appear on bottoms of two longitudinal walls in the original model, while these cracks appear later in the reinforced model; a lot of cracks appear on the door hole of the original model, and no crack appears in the reinforced model till the end of seismic waves; seismic damage of walls in the reinforced model is obviously lighter than that in the original model; dynamic responses at all observed points of the reinforced masonry are obviously less than those of the original model. Strains at all positions of the reinforced model are obviously smaller than those of the original model. From macroscopic and microscopic perspectives, the computational results prove that the reinforced proposal proposed in this paper can effectively improve the antiseismic performance of the masonry structure.

Gravity Modulation of Thermal Instability in a Viscoelastic Fluid Saturated Anisotropic Porous Medium

2012 ◽  
Vol 67 (1-2) ◽  
pp. 1-9 ◽  
Author(s):  
Beer S. Bhadauria ◽  
Atul K. Srivastava ◽  
Nirmal C. Sacheti ◽  
Pallath Chandran
Keyword(s):  
Porous Medium ◽  
Gravity Field ◽  
Viscoelastic Fluid ◽  
Thermal Instability ◽  
Time Dependent ◽  
Periodic Part ◽  
Gravity Modulation ◽  
Dependent Part ◽  
Anisotropic Porous Medium ◽  
The Stability

The present paper deals with a thermal instability problem in a viscoelastic fluid saturating an anisotropic porous medium under gravity modulation. To find the gravity modulation effect, the gravity field is considered in two parts: a constant part and an externally imposed time-dependent periodic part. The time-dependent part of the gravity field, which can be realized by shaking the fluid, has been represented by a sinusoidal function. Using Hill’s equation and the Floquet theory, the convective threshold has been obtained. It is found that gravity modulation can significantly affect the stability limits of the system. Further, we find that there is a competition between the synchronous and subharmonic modes of convection at the onset of instability. Effects of various parameters on the onset of instability have also been discussed.

Orthotropic mechano-sorptive creep behavior of Chinese fir during the moisture adsorption process determined in tensile mode via dynamic mechanical analysis (DMA)

Holzforschung ◽  
2019 ◽  
Vol 73 (3) ◽  
pp. 229-239 ◽  
Author(s):  
Hui Peng ◽  
Jiali Jiang ◽  
Jianxiong Lu ◽  
Jinzhen Cao
Keyword(s):  
Moisture Content ◽  
Elastic Strain ◽  
Adsorption Process ◽  
Wood Cell Wall ◽  
Mechanical Analysis ◽  
Chinese Fir ◽  
Time Dependent ◽  
Unstable State ◽  
Viscoelastic Creep ◽  
Constant Moisture Content

AbstractThe orthotropic viscoelastic creep (VEC) at a constant moisture content (MC) and mechano-sorptive creep (MSC) during the adsorption process were examined for Chinese fir (Cunninghamia lanceolata) under tension at 20, 40, 60 and 80% relative humidity (RH) (30°C). Free swelling was performed on matched specimens based on the strain partition assumption to better understand the characteristics of the mechano-sorptive (MS) phenomenon. Expansion, elastic and time-dependent creep behaviors of radial (R) and tangential (T) specimens were affected by the MC to a higher degree than those of the longitudinal (L) specimen. A higher proportion of elastic strain in total strain was found in the L specimen as compared with transverse specimens, regardless of VEC and MSC. The RH level had a greater effect on relaxation behavior in the L specimen for MSC. According to the three tests, expansion mainly dominated the creep strain during adsorption, especially for the L specimen. The MS strain exerted more influence on transverse specimens and had less contribution to the L specimen. Moreover, under all RH isohume (RHI) conditions, the unstable state contributed to MS strain diminishing as MC approached equilibrium moisture content (EMC). A shorter adsorption time to a new equilibrium state was achieved at the expense of intensifying the unstable state of the wood cell wall.

scholarly journals The Influence of Moisture Content on the Time-Dependent Characteristics of Rock Material and Its Application to the Construction of a Tunnel Portal

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Xiaojun Liu ◽  
Chao Yang ◽  
Jing Yu
Keyword(s):  
Moisture Content ◽  
Deformation Behaviour ◽  
Creep Behaviour ◽  
Three Dimensional ◽  
Viscosity Coefficient ◽  
Guizhou Province ◽  
Creep Model ◽  
Low Grade ◽  
Saturation Degree ◽  
Moisture Contents

Uniaxial compression creep experiments were carried out for low-grade metamorphic slate samples (located in the southeastern area of Guizhou province, China) with different moisture contents, using an Instron electric-fluid servo-compression machine. Based on the experimental results, a detailed analysis was made of the effect of moisture content on the strength and deformation behaviour of the slate specimens. The three-parameter generalised Kelvin model was identified to describe the creep behaviour of the low-grade metamorphic slate with different moisture contents. There is an approximately linear negative correlation between the elastic modulus and the saturation degree, and the viscoelastic modulus and viscosity coefficient show a negative exponent correlation with the saturation degree. The Kelvin creep model considering the moisture degradation effect was established and a three-dimensional finite difference model was developed with the softwareFLAC3Dto validate the creep model. A three-dimensional numerical analysis was then performed to simulate the tunnel excavation process. The results show that the influence of moisture and creep of the surrounding rocks is needed for estimating the deformation of complex tunnel portals.

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