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This paper investigates the thermo-mechanical volume change behavior of municipal solid waste (MSW) by conducting drained heating–cooling tests at constant stresses and isothermal consolidation tests using a temperature-controlled triaxial apparatus. The experimental results show that the compression and swelling indexes of MSW specimen were temperature independent, and the heating-induced volumetric contraction was partially reversible upon cooling. Different from conventional soils, the thermally induced reversible and irreversible volumetric strains of MSW were much larger and stress level dependent. Apart from the experimental study, an isotropic thermo-elastoplastic constitutive model was developed in the framework of existing modified Cam-clay model, which allows the prediction of thermally induced volume changes of MSW. An important feature in this model was the derivation of thermally induced plastic volumetric strain based on the concept of equivalent stress. The capability of the proposed model was validated against the experimental results and showed good predictions. This paper serves as the first attempt to study the thermo-mechanical volume change behavior of MSW, and has provided additional data for the serviceability evaluation of existing pipes as well as settlement and capacity estimation of MSW landfills at elevated temperatures. [ABSTRACT FROM AUTHOR]

This paper presents a unified critical state parameter model for evaluating sand and overconsolidated clay, which is named as CASM-S. The model is formulated in terms of the modification of the clay and sand model, i.e., CASM, by incorporating the subloading surface theory with an overconsolidation state parameter R. Although the standard CASM proves to be useful in modelling overconsolidated clay and sand, the model (1) requires the rate of overconsolidated ratio to be constant which is in contrast to the observed behaviour of soils and (2) only allows elastic deformation to develop at the overconsolidated state that may underestimate the deformation corresponding to the peak stress or be unable to predict the actual stress path. By introducing a new material parameter u to those material properties of the standard CASM, the rate relationship of stress–strain for the CASM-S model is developed. The standard CASM can be either recovered or approximated as a special case of the overconsolidation state assumed in the CASM-S. The numerical integration of the newly proposed model is performed by the modified forward Euler method. Validation with undrained and drained overconsolidated clay and sand have demonstrated the capability of the CASM-S model to well predict the observed soil behaviours. [ABSTRACT FROM AUTHOR]

The p–y method as a simplified analysis tool has been widely used to analyze the behavior of laterally loaded piles. This paper develops a novel cyclic p–y elastoplastic model within the framework of the single-surface bounding surface theory. The model can capture the soil stiffness degradation during cyclic loading by incorporating the cumulative plastic displacement to an interpolation function of the elastoplastic resistance coefficient. The model is relatively simple with only four parameters that can be determined from standard soil properties and stress–strain responses measured in direct simple shear tests. The performance of developed model is validated by predicting the cyclic lateral response of piles installed in soft clay during field and centrifuge tests published in the literature. The model can reliably simulate monotonic and cyclic responses of piles under different lateral loading patterns, and capture main characteristics of the pile-head load–displacement curve, such as nonlinearity, hysteresis, displacement accumulation, and stiffness degradation. It can also predict the evolution of the lateral deflection and sectional bending moment along the pile during cyclic loading. [ABSTRACT FROM AUTHOR]

During the loading process of concrete members, the identification of characteristic damage states is not sensitive enough. This paper investigates the damage evolution of four concrete sandwich wallboards subjected to vertical compression by employing the strain energy density increment to enhance identification sensitivity. First, the equivalent elastic modulus model for a wallboard subjected to vertical compression is established based on the material stress–strain relationship. Then, the strain data of concrete, obtained from experiments and numerical simulations, are modeled as the normalized unit approximate strain energy density increments (NUASEDIs), which follow the damage evolution of the wallboard as a more sensitive index. The first cracking formation of wallboard corresponds to the first high NUASEDI. The failure damage state corresponds to the final high NUASEDI, which reflects the process changing from the local to the global failure. Finally, the strain energy density increment theory improves averagely the cracking identification sensitivity of concrete members by 13.32% and the failure identification sensitivity by 3.01%. [ABSTRACT FROM AUTHOR]

Resonant column (RC) devices have been widely used for estimating the shear modulus and damping ratio over a broad range of shear strain amplitudes. Although RCs significantly improve the assessment of soil dynamic properties, some challenges mainly associated with the calibration process still exist. This paper discusses the effect of the driving system rigidity on the measurements performed on a Hardin-type RC. It is shown that the use of a rigid connection between the soil specimen and the driving mass could significantly influence the obtained results. The findings of this study indicate that the apparatus resonant frequency of the Hardin-type RC device should be lower than the resonant frequencies likely to be measured during testing of the specimens. [ABSTRACT FROM AUTHOR]

A key challenge involving microbially induced carbonate precipitation (MICP) is lack of rigorous yet practical theoretical models to predict the intricate biological–chemical–hydraulic–mechanical (BCHM) processes and the resulting bio-cement production. This paper presents a novel BCHM model based on multiphase, multispecies reactive transport approach in the framework of poroelasticity, aimed at achieving reasonable prediction of the produced bio-cement, and the enhanced geomechanical characteristics. The proposed model incorporates four key components: (i) coupling of hydro-mechanical stress–strain alterations with bio-chemical processes; (ii) stress–strain changes induced due to precipitation and growth of bio-cement within the porous matrix; (iii) spatiotemporal variability in hydraulic and stiffness characteristics of the treated medium; and (iv) velocity dependency of the attachment rate of bacteria. The fully coupled BCHM model predicts key unknown parameters during treatment including concentration of bacteria and chemical solutions, precipitated calcium carbonate, hydraulic properties of the solid skeleton, and in situ pore pressures and strains. The model was able to reasonably predict bio-cementation from two different laboratory column experiments. The Kozeny–Carman permeability equation is found to underestimate permeability reductions due to bio-cementation, while the Verma–Pruess relation could be more accurate. A sensitivity analysis revealed bio-cement distribution to be particularly sensitive to the attachment rate of bacteria. [ABSTRACT FROM AUTHOR]

Several of the geotechnical structures constructed with unsaturated soils undergo a large deformation prior to reaching failure conditions (e.g., progressive failure of a soil slope). During this process, the shear stress in soils typically increases initially and then reduces with an increase in the shear strain. The prediction of the stress–strain relationship is critical for reasonable interpretation of the mechanical behavior of those geo-structures that undergo large deformation. This paper introduces a model based on the disturbed state concept (DSC) to predict the variation of shear stress in unsaturated soils during the strain-softening process under consolidated drained triaxial compression condition. In this model, the apparent stress–strain relationship is formulated as a weighted average of a hyperbolic hardening response extending the pre-peak state stress–strain curve and a linear response extending the critical state stress–strain curve with an assumed disturbance function as the weight. The prediction procedure is described in detail and the proposed model is validated using several sets of published data on unsaturated soils varying from coarse- to fine-grained soils. Finally, a comprehensive error analysis is undertaken based on an index of agreement approach. [ABSTRACT FROM AUTHOR]

A new experimental series on the highly plastic (plasticity index, IP = 34%) Lower Rhine clay (LRC) is presented. The study comprises tests on normally as well as overconsolidated samples under monotonic and cyclic loading. The loading velocity has been varied to evaluate the strain rate dependency of the LRC behaviour, testifying the well-known reduction of undrained shear strength with decreasing displacement rate. Isotropic consolidation followed by a cyclic loading with constant deviatoric stress amplitude leads to a failure due to large strain amplitudes with eight-shaped effective stress paths in the final phase of the tests. The inherent anisotropy has been additionally evaluated using samples cut out in either the vertical or the horizontal direction. Furthermore, the behaviour of LRC is compared with the behaviour of low plastic kaolin silt (IP = 12.2%). A new visco-hypoplastic-type constitutive model with a historiotropic yield surface has been used to simulate some of the experiments with cyclic loading. Even the eight-shaped stress loops at cyclic mobility are reproduced well with this model. The data of this paper can be also used by other researchers for the examination, calibration, improvement, or development of constitutive models dedicated to fine-grained soils under monotonic and cyclic loading. [ABSTRACT FROM AUTHOR]

During an earthquake, strain-rate effects affect both the stiffness and damping behaviour of soils, yet existing constitutive models for ground response analysis are typically formulated within a rate-independent framework. In this paper, a one-dimensional (1D) viscoplastic stress–strain model is presented to introduce strain rate effects in ground response analysis. Its constitutive equations are based on a model that uses a cubic spline fit of the modulus reduction curve and a coordinate transformation technique to match any input modulus reduction and damping curve. A viscous stress component is added to model the effect of strain rate on the mechanical behaviour of soils using a single input parameter. The model is able to reproduce the linear increase in shear strength with the logarithm of shear strain rate and allows the introduction of viscous effects in 1D ground response analysis with control over damping and modulus reduction behaviour. The model is implemented in a software for ground response analysis and used to predict the results of a centrifuge test modeling 1D wave propagation. The results show that the model accurately predicts the amplification and attenuation of shear waves, in a context where strain rates impact the response of the model significantly. [ABSTRACT FROM AUTHOR]

Methods of computation for soil heave based on an 'equivalent' net normal stress path approach often have built-in assumptions regarding the relationship between in situ matric suction, overburden stress, and swell pressure. The term 'matric suction equivalent' has been previously defined as the difference between in situ state of stress projected on the net normal stress plane (represented by swell pressure) and overburden stress. Correlations between matric suction, overburden stress, and swell pressure for matric suction values in excess of the air-entry value have not been well studied and are explored here for expansive soils. Filter paper (in-contact) and constant volume swell pressure tests were performed on undisturbed tube samples of expansive soils taken from Arizona, Colorado, and Texas. In general, the ratio of the matric suction equivalent to the matric suction decreases with increasing soil suction. An empirical relationship was established in which the matric suction equivalent was found to be proportional to the logarithm of the matric suction for in situ matric suctions greater than a certain value, termed as the 'intercept matric suction'. A correlation between the intercept matric suction and the soil's plasticity index (PI) was found for the clays of this study. The developed correlations represent a method for obtaining approximate estimates of in situ matric suction for expansive soils from PI and swell pressure data. Implications of the study findings for the use of an equivalent net normal stress approach for estimation of soil heave are explored. [ABSTRACT FROM AUTHOR]

The paper studies the behavior of axially loaded piles driven into inundated collapsible soils under compression and tension forces. Collapsible soils exhibit a considerable drop in the void ratio (i.e., significant changes in dry unit weight, friction angle, and shear strength) with the increase of water content. Several sandy and silty specimens of collapsible soils with different initial conditions are utilized to develop a correlation that evaluates the post-inundation soil properties and stress–strain relationship (as obtained from the conventional triaxial test). The developed model is integrated into a pile–soil model to predict the axial response of piles loaded after the inundation of the collapsible soils (i.e., no negative skin friction). The developed technique allows the assessment of the axial load transfer (t-z) and pile-head load–displacement curves. Comparisons between predicted and measured stress–strain curves of inundated collapsible soils and responses of axially loaded piles in such soils are presented for validation. [ABSTRACT FROM AUTHOR]

This paper presents the main results of a laboratory study of the use of shear wave velocity, Vs, to characterize hydraulically deposited tailings on the basis of density (void ratio), mean effective stress, and overconsolidation ratio. Tailings specimens from a gold mine in western Quebec were prepared in triaxial and oedometric cells in a manner that simulates hydraulic deposition. The specimens were consolidated isotropically and anisotropically (stress ratio, K of 0.38). Vs measurements were performed at each load increment using the piezoelectric ring-actuator technique (P-RAT). Correlations relating shear wave velocity to the void ratio, confining stress, and overconsolidation ratio of the tailings are presented. These laboratory correlations can be used for the characterization of the tailings by in situ Vs measurement. The application of these correlations to seismic cone penetration testing in an actual tailings impoundment is also presented. [ABSTRACT FROM AUTHOR]

The paper describes the anisotropic undrained stiffness behaviour of four medium-plasticity heavily overconsolidated UK stiff marine clays as revealed through hollow cylinder testing. The experiments contributed to two broader studies on stiff-to-hard London, Gault, Kimmeridge, and Oxford clay strata. They involved static and dynamic testing of multiple high-quality natural specimens sampled at similar depths from inland sites. This paper explores the directional dependency of the clays' highly nonlinear undrained stiffness characteristics. New data-analysis approaches are outlined that allow the stiffnesses associated with one-dimensional vertical, horizontal, or pure horizontal shear modes to be isolated in complex undrained stress paths. In the presented experiments, loading progressed from in situ stresses to reach ultimate failure at a range of final major principal stress orientation angles α (defined in the vertical plane) while keeping fixed values of the intermediate principal stress ratio, b. The tests reveal strong undrained stiffness anisotropy that can impact significantly on the prediction and understanding of ground deformation patterns in numerous geotechnical engineering applications. [ABSTRACT FROM AUTHOR]

This paper demonstrates reliability-based design for tensile rupture and pullout limit states for mechanically stabilized earth (MSE) walls constructed with geosynthetic (geogrid) reinforcement. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty due to the confidence (level of understanding) of the designer at the time of design. The reliability index is computed using a closed-form solution that is easily implemented in a spreadsheet. The general approach provides a quantitative link between nominal factor of safety, which is familiar in allowable stress design practice, and reliability index used in modern civil engineering reliability-based design practice. A well-documented MSE wall case study is used to demonstrate the general approach and to compare margins of safety using different load and resistance model combinations. A practical outcome from the case study example is the observation that the pullout limit state is much less likely to control design than the ultimate tensile rupture state for walls with continuous reinforcement coverage. The more accurate "simplified stiffness method" that is used to compute tensile loads in the reinforcement under operational conditions is shown to generate a more cost-effective reinforcement option than the less accurate American Association of State Highway and Transportation Officials (AASHTO) simplified method. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to determine the effect of deflection waveform on four-point flexural fatigue test results for hot mix asphalt. This paper reports how the waveform affects the fatigue resistance of an asphalt mixture and, consequently, the fatigue models of the material. The mix was tested at different strain levels under both haversine and sinusoidal deflection-controlled modes. The findings indicate that haversine displacement control testing results in a sinusoidal strain response of half the intended amplitude. This outcome was attributed to the viscoelastic nature of asphalt mixes. In the deflection controlled haversine test, permanent deformations lead to a new equilibrium neutral position of the beam and the force output follows a sinusoidal waveform. This produces erroneous fatigue results since the test assumptions do not match the actual test conditions. It is recommended to use a sinusoidal waveform to obtain consistent results. [ABSTRACT FROM AUTHOR]

Knowledge about soil behaviour in the near surface is fundamental to a broad range of military strategic research efforts. The prevailing mathematical representations of near-surface shear strength do not necessarily reflect the observed shear strengths. This paper presents an experimental procedure for testing self-supported, unconfined-drained specimens to investigate the shear strength of a poorly graded sand with the inferred unsaturated behaviour from typical effective stress expressions. The impact of soil suction is quantified from the soil–water characteristic curve obtained from a modified, unsaturated, one-dimensional oedometer device: Fredlund's device. Seventy-seven unconfined tests illustrate that while individual or discrete states can be explained by effective stress relationships, those expressions do not accurately quantify the observed shear strength from one state to the next. Saturation failure is observed when the degree of saturation is between 70.5% and 76.5%, well below the assumed threshold. The results show that the dry shear resistance is a function of the initial density state, but as the degree of saturation increases, the shear resistance becomes independent of the initial density, and converges to the saturation failure. These findings expose the limitations of effective stress expressions and suggest a revised nonlinear, three-dimensional, unconfined Mohr failure envelope based on an applied external stress. [ABSTRACT FROM AUTHOR]

The construction of an underground opening leads to changes in the in situ stress regime surrounding the excavation. The opening influences the rock mass owing to the redistribution of the stresses and results in the disturbance of the surrounding ground. At great depths, massive to slightly or moderately fractured rock masses are usually encountered, and under high stresses, they are more likely to behave in a brittle manner during an excavation. While constitutive models have been developed and proposed for the numerical simulation of such excavations using continuum mechanics, this brittle response cannot be simulated accurately enough, since the material behaviour is governed by fracture initiation and propagation. On the contrary, discontinuum approaches are more suitable in such cases. For the purposes of this paper, the brittle behaviour of hard, massive rock masses and the associated spalling failure mechanisms were simulated by employing a finite–discrete element method (FDEM) approach using Irazu software. The generated numerical model was utilized to replicate field conditions based on the observations at the Atomic Energy of Canada Limited (AECL) Underground Research Laboratory (URL) test tunnel located in Pinawa, Manitoba, Canada. The model results are compared with field observation data to explicitly demonstrate the suitability of the method. [ABSTRACT FROM AUTHOR]

This paper reports experiments with 102 mm diameter closed-ended instrumented Imperial College piles (ICPs) jacked into low- to medium-density chalk at a well-characterized UK test site. The "ICP" instruments allowed the effective stress regime surrounding the pile shaft to be tracked during pile installation, equalization periods of up to 2.5 months, and load testing under static tension and one-way axial cyclic loading. Installation resistances are shown to be dominated by the pile tip loads. Low installation shaft stresses and radial effective stresses were measured that correlated with local cone penetration test (CPT) tip resistances. Marked shaft total stress reductions and steep stress gradients are demonstrated in the vicinity of the pile tip. The local interface shaft effective stress paths developed during static and cyclic loading displayed trends that resemble those seen in comparable tests in sands. Shaft failure followed the Coulomb law and constrained interface dilation was apparent as the pile experienced drained loading to failure, although with a lesser degree of radial expansion than with sands. Radial effective stresses were also found to fall with time after installation, leading to reductions in shaft capacity as proven by subsequent static tension testing. The jacked, closed-ended, piles' ageing trends contrast sharply with those found with open piles driven at the same site, indicating that ageing is affected by pile tip geometry and (or) installation method. [ABSTRACT FROM AUTHOR]

This paper compiles the experimental and finite-element parametric study on member distortional buckling behaviour of new built-up metal hybrid double-I-box beams (HDIBBs). The cross-section of this built-up beam is unique and looks similar to the shape of a double-I-box fabricated using four channel sections. The flange plates were provided with an intermediate stiffener. In these built-up beams there is more material in the flange portions far away from the horizontal centroidal axis of their cross-section. Hence, there is an increase in the flexural rigidity that enhances the moment capacity of the beam, under major axis bending. The geometry consists of torsionally rigid closed-box web portion that provides high resistance to minor axis lateral-buckling. The varying parameters considered were the ratio of yield stresses of the flange to the web steel plates, the ratio of breadth to the depth of the section, and the flange plate thickness. In the experimental programme, all the HDIBB members failed due to kinds of distortional buckling which was identified by web buckling and flange twist along edges. The results revealed that when flange plate slenderness increases there is a drop in the moment resistance capacity of the beams. The numerical study was performed using ABAQUS software. In comparison, there was good agreement between experimental and numerical results. The validated finite element models were further extended to perform parametric studies on ideal HDIBB models. Both the experimental and parametric study results were compared with the predicted strengths using effective width method equations specified in the Euro code standards EN 3-1-3. It was found that the current Euro code design rules slightly over-estimate the distortional buckling resistance capacity of closed form built-up cold-formed steel members. A new design equation was formulated and recommended for estimating the reduction in distortional buckling moment resistance capacity for HDIBBs. [ABSTRACT FROM AUTHOR]

In various parts of the globe, carbonate sands are found at shallow sea water depth. These types of sands are very susceptible to large-scale particle breakage. Offshore structures like wind turbines and sea defences are constructed on these types of soils. From a design perspective, it is essential to assess the extent of particle breakage and the subsequent change in soil properties that occur under working load conditions. This paper presents the data obtained from a number of drained monotonic and cyclic triaxial tests on crushable carbonate sand ('Ballyconnelly sand') in conjunction with small-strain shear stiffness ( Gmax) measurements using the bender element technique. The soils were allowed to shear under three different loading patterns to understand the factors influencing the breakage of particles. The degree of crushing was quantified and analysed based on the total energy input. It was observed that, apart from applied stress, the total strain accumulation governs the amount of particle breakage. It was observed that Gmax increased significantly under high stress ratio. Gmax also increased noticeably during resting periods without any change in loading conditions as a result of creep, and subsequently during cyclic loading although at a reduced rate. [ABSTRACT FROM AUTHOR]

Methane gas recovery from gas hydrate-bearing sands requires dissociation of the hydrate. Understanding changes in the stiffness of the sand is essential if future production scenarios are to be modelled realistically. This paper reports the results of resonant column tests conducted to measure changes in shear and flexural Young's modulus (stiffness) of sand specimens during the formation and dissociation of hydrate within the pore space. Factors such as hydrate saturation, effective stress, and dissociation method (thermal stimulation and depressurization) were evaluated. Results show a nonlinear relationship between stiffness and hydrate volume, with hydrate formation and dissociation giving markedly different changes in stiffness. Stiffness increases more slowly during the initial stages of hydrate formation, compared to later stages, with the eventual stiffness being independent of the effective stress applied at the start of formation. In contrast, the onset of dissociation leads to a rapid reduction in stiffness, with thermal stimulation giving a greater reduction compared to depressurization for similar changes in hydrate volume. These results highlight the impact of hydrate morphology on changes in stiffness during the hydrate formation process or its dissociation. We present and discuss a conceptual model to explain the differences observed. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution for drained expansion in both spherical and cylindrical cavities with a unified state parameter model for clay and sand (CASM). The solution developed here provides the stress and strain fields during the expansion of a cavity from an initial to an arbitrary final radius. Small strains are assumed for the elastic region and large strains are applied to soil in the plastic region by using logarithmic strain definitions. Since its development, the unified CASM model has been demonstrated by many researchers to be able to capture the overall soil behaviour for both clay and sand under both drained and undrained loading conditions. In this study, the CASM model is used to model soil behaviour whilst a drained cavity expansion solution is developed with the aid of an auxiliary variable. This is an extension of the undrained solution presented by the authors in 2017. The parametric study investigates the effects of various model constants including the stress-state coefficient and the spacing ratio on soil stress paths and cavity expansion curves. Both London clay and Ticino sand are modelled under various initial stress conditions and initial state parameters. The newly developed analytical solution highlights the potential applications in geotechnical practice (e.g., for the interpretation of cone penetration test data) and also provides useful benchmarks for numerical simulations of cavity expansion problems in critical state soils. [ABSTRACT FROM AUTHOR]

Lateral loads often control the design of deep foundations. This paper focuses on improving the understanding of soil-structure interaction (SSI) of laterally loaded piles and developing p- y curves based on simultaneous direct measurements of the soil-pile interaction pressure ( p) and lateral pile displacement ( y) along the length of the pile. This paper summarizes the methodology, instrumentation, soil-pile interaction measurements, and procedure used to investigate the soil-pile interaction and to develop the directly measured p- y curves. A 102 mm diameter, 1.42 m long precast concrete pile was fully instrumented with advanced sensors and installed in well-graded sand. The digital image correlation (DIC) data indicated that the soil movement in front of the pile extended up to 6.3 pile diameters (6.3 D) from the pile center. The normalized measured maximum soil-pile interaction pressures closely matched the normalized pressures provided in the literature for short, stiff laterally loaded piles installed in cohesionless soils. In addition, the direct measurement-based p- y curves at different depths showed nonlinear behavior, in which the initial stiffness and ultimate soil reaction increased as the depth increased. When compared to p- y curves calculated from measured strain along the pile length, the directly measured p- y curves showed differences of ultimate soil reaction ranging from 8% to 33%. When compared to p- y curves calculated using the procedures available in the literature, the measurement-based p- y curve ultimate soil reactions have differences ranging from 5% to 189%. The differences in ultimate soil reaction could be mainly attributed to the installation method. [ABSTRACT FROM AUTHOR]

One of the main requirements of designing perpetual pavements is to determine the endurance limit of asphalt mixtures. The endurance limit is the strain below which no fatigue damage occurs or can be healed during unloading. If the pavement thickness is controlled so that the strain at the bottom of the asphalt layer is kept below the endurance limit, the pavement would endure indefinite load repetitions and would not experience bottom-up fatigue cracking. Field observation shows that an endurance limit for hot mix asphalt (HMA) does exist. The endurance limit values were previously determined in the laboratory in the NCHRP Project 9-44A for conventional HMA at different conditions. The purpose of this paper was to determine the endurance limit values for asphalt rubber (AR) mixtures using laboratory beam fatigue tests. The paper discusses the results of a study that produced a preliminary estimation of the endurance limit for an asphalt rubber mixture placed in Sweden. This study included 24 beam fatigue laboratory tests conducted according to the AASHTO T321-03 test procedure with rest periods between loading cycles. Two factors that affect the fatigue response of asphalt mixtures were evaluated, which are the applied strain and the rest period between loading cycles. A model was developed to determine the stiffness ratio as a function of strain and rest period. The endurance limit was determined using the developed model by setting the stiffness ratio as one, indicating no accumulated damage or complete healing. Endurance limit values for the AR mixture ranged from 150 to 175 microstrain at 20 °C, which are significantly higher than those of conventional HMA. This indicates that a thinner asphalt rubber layer can be used to reach the endurance limit as compared to the HMA layer. Determining the endurance limit of asphalt rubber has significant design and economic implications. [ABSTRACT FROM AUTHOR]

Backfill is commonly used world-wide in underground mines to improve ground stability and reduce solid waste disposal on the surface. Practical solutions are required to assess the stress state in the backfilled stopes, as the stress state is influenced by the fill settlement that produces a stress transfer to the adjacent rock walls. The majority of existing analytical and numerical solutions for the stresses in backfilled openings were developed for two-dimensional (plane strain) conditions. In reality, mine stopes have a limited extension in the horizontal plane so the stresses are influenced by the four walls. This paper presents recent three-dimensional (3D) simulations results and a new 3D closed-form solution for the vertical and horizontal stresses in inclined backfilled stopes with parallel walls. This solution takes into account the variation of the stresses along the opening width and height, for various inclination angles and fills properties. The numerical results are used to validate the analytical solution and illustrate how the stress state varies along the opening height, length, and width, for different opening sizes and inclination angles of the footwall and hanging wall. Experimental results are also used to assess the validity of the proposed solution. [ABSTRACT FROM AUTHOR]

A test fill at Onsøy, close to the town of Fredrikstad in Norway, was built on a very soft marine clay with in situ vane strength as low as 11 kPa and a plasticity index varying from 34 to 50. The dimensions at the bottom of the long test fill were 20 m × 60 m with a height of 2.3 m. The fill, as placed in the first stage, had a computed factor of safety against foundation failure of 1.35 based on in situ vane strength. The fill was allowed to sit for about 3 years (from 1972 to 1975) before it was, in a second stage, brought to failure in about 4.3 days by raising the height. This second stage is the subject of this paper. Back-calculation of the failure by undrained stability analysis based on in situ vane tests performed shortly before the start of the second stage, based on undrained triaxial and constant volume direct simple shear tests on specimens from tube samples taken shortly before the start of the second stage and reconsolidated to the in situ effective stresses, gave factors of safety varying from 0.88 to 1.45 depending on type of analysis. Settlement values computed at the centreline of the fill for the second stage based on the results from undrained compression triaxial tests agreed reasonably well with the field measurements. [ABSTRACT FROM AUTHOR]

The build-up of earthquake-induced excess pore-water pressure may be viewed as analogous to the cumulative damage of saturated granular materials caused by cyclic loading, and consequently as a damage metric when converting an irregular earthquake loading to an equivalent number of uniform cycles, Neq. In this paper, a comprehensive series of strain-controlled tests have been conducted using the new combined triaxial simple shear (TxSS) apparatus developed at Institute de Recherche d'Hydro-Quebec (IREQ) in collaboration with the geotechnical group at the Université de Sherbrooke to verify the hypothesis of adopting the pore-water pressure ratio, Ru, as a damage metric when converting earthquakes to an equivalently damaging number of uniform strain cycles. Different reconstituted saturated samples of Baie-Saint-Paul, Carignon, and Quebec sands have been tested under undrained conditions up to liquefaction. The experimental results from this study have been utilized to develop an empirical expression to compute Neq γ from both the number of cycles required to trigger liquefaction, Nliq, and the material parameter, r. The parameter r had been experimentally calibrated a priori from a separate set of tests using uniform strain cycles following the theoretical framework outlined by Green and Lee in 2006. The present results reveal that the measured pore-water pressure ratio, Ru, is in agreement with predicted cumulative damage using the Richart and Newmark (R-N) hypothesis. However, the Palmgren-Miner (P-M) hypothesis underestimates the cumulative damage (i.e., the generated pore-water pressure) during cyclic loading. [ABSTRACT FROM AUTHOR]

In this paper, time-dependent clogging is studied considering a unit cell consisting of a single stone column interacting with the surrounding soft clay. Clogging is assessed quantitatively and the corresponding void space of the column is determined using computed tomography. It is observed that the extent of clogging is substantial in the upper part of the column, but diminishes rapidly with depth. The soil properties in the clogged zone are determined indirectly through additional tests of clay-aggregates mixtures with various clay fractions. An equal strain consolidation model based on the principle of unit cell analysis is developed to capture both the initial and time-dependent clogging. The model accounts for a reduction in permeability and an increase in compressibility of the column. This current model, as expected, offers identical results to some previous studies if clogging is ignored, while the comparison with other selected models demonstrates the influence that clogging of the stone column can have on the consolidation of the surrounding soil. Furthermore, load-settlement predictions from the proposed 'equal strain' model are also compared with the consolidation response of a previously developed 'free strain' model. [ABSTRACT FROM AUTHOR]

Air permeability is one of the key parameters in performing consolidation analysis of unsaturated soil. Few data are available regarding the air permeability for intact loess under different applied stresses. The work reported in this paper evaluated the air permeability at isotropic stress using data obtained from laboratory investigations for intact loess. Air permeability tests were performed on specimens of intact loess at various water contents and isotropic stresses. Stress remarkably affected air permeability as a function of both liquid saturation and volumetric air content. There were all unique relationships not only between relative air permeability and liquid saturation as well as relative volumetric air content, but also between air permeability and modified air saturation for different stresses. The relative air permeability against liquid saturation could be well described by the Parker-van Genuchten-Mulaem (P-vG-M) model in terms of total liquid saturation. The relationship between relative air permeability and relative volumetric air content could be more conveniently expressed by the reference point power law (RPL) model, using the reference point values at natural water content rather than that at air-dried water content. Compared with the other two models, the proposed modified air saturation power law (MAPL) model was more appropriate to predict the air permeability. [ABSTRACT FROM AUTHOR]

The high-cycle accumulation (HCA) model proposed by the authors can be used to predict permanent deformations or stress relaxation due to a large number (e.g., several millions) of load cycles with relative small strain amplitudes (<10−3). The predicted stress relaxation depends on the isotropic 'elastic stiffness', , used in the HCA model. To calibrate the bulk modulus, K, the rate of pore pressure accumulation obtained from an undrained cyclic test and the rate of volumetric strain accumulation measured in a drained cyclic test are compared. Poisson's ratio, ν, can be determined from the shape of the stress relaxation path measured in an undrained test with anisotropic consolidation stresses and strain cycles. Unfortunately, the calibration of K shown for a medium coarse sand in a previous paper by Wichtmann et al. in 2010 was affected by membrane penetration effects. Consequently, all further studies have been performed on a fine sand for which membrane penetration is negligible. The present paper reports on the new results. The strong pressure dependence of K and its independence from amplitude found in the previous study could be confirmed by the new tests. In addition, the new experimental results reveal a density dependence of K, while the bulk modulus is rather independent of stress ratio. Furthermore, for the first time Poisson's ratio, ν, used in the HCA model has been calibrated based on tests performed with different amplitudes, densities, and initial stresses. [ABSTRACT FROM AUTHOR]

The build-up of friction on seabed pipelines is an important design consideration, affecting their stability and the resulting in-service strain and fatigue. The consolidation beneath a partially embedded pipeline has been investigated in the past and linked to the build-up of axial pipe-soil resistance. This paper extends previous work by providing solutions for consolidation around a new class of shallow penetrometer, to provide a basis to scale from site investigation results directly to the build-up of pipeline friction. Small-strain finite element analyses, using the Modified Cam Clay soil model, are presented for the novel toroid and ball penetrometers. The effects of initial penetrometer embedment, device roughness, strength gradient, and overload ratio have been explored in a comprehensive manner, and are compared with pipe results. The toroid penetrometer shows excellent agreement with an element of an infinitely long pipe, simplifying the scaling process. The ball penetrometer shows a faster consolidation response, typically by a factor of three, reflecting the more effective drainage mechanisms of a three-dimensional device compared to a plane strain device. The dissipation responses are fitted by simple equations to aid application in design. [ABSTRACT FROM AUTHOR]

In this work, the flow of a fractional Maxwell fluid is discussed. The velocity function and time-dependent shear stress of a Maxwell fluid with fractional derivatives are calculated. It is considered that the fluid in the infinitely long circular cylinder is moving with a velocity ft. The fluid in the infinitely long circular cylinder of radius R is initially at rest and at t = 0+, because of shear, it instantly starts to move longitudinally. To obtain the solutions, we have employed Laplace transformation and modified Bessel equation. The solutions are in series form, which are expressed in terms of modified Bessel functions and , and satisfy all given conditions. In this paper, Laplace inverse transformation has been calculated numerically by using MATLAB. The behavior of the following physical parameters on the flow are investigated: relaxation time, dynamic viscosity, kinematics viscosity, similarity parameters of fractional derivatives and radius of the circular cylinder. Finally, the impact of the fractional parameter and material elements is shown by graphical demonstration. [ABSTRACT FROM AUTHOR]

Thermal-induced strains caused by daily temperature fluctuations are considered to be a direct impact of environmental factors on flexible pavements. This paper investigates thermal-induced strains in the longitudinal, transverse, and vertical directions at the bottom of hot mix asphalt (HMA) during a 16 month monitoring period. This study was conducted at the Integrated Road Research Facility (IRRF), which is a fully instrumented test road in Edmonton, Alberta, Canada. Noticeable variations for horizontal and vertical strains were observed as a function of ambient air temperature change. Results showed that the highest strains occurred in winter and spring, while the most pronounced strain fluctuations were captured during the spring-thaw period. Using the obtained data, coefficients of thermal contraction and expansion were determined during different seasons. It was found that thermal coefficients are different in three directions, illustrating the anisotropic properties of HMA. [ABSTRACT FROM AUTHOR]

Large-magnitude mining-induced seismic events can occur as a result of local rock mass stress increase. High apparent stress events can be used as a proxy to identify increases in local rock mass stress conditions. This paper proposes a relative apparent stress ratio (ASR) for quantifying apparent stress of a seismic population. Variations in ASR are analysed over time with reference to seismic hazard inferred from the magnitude of seismic events. The proposed ratio is examined through examples of seismic populations from a single deep Canadian mine. [ABSTRACT FROM AUTHOR]

Estimation of undrained uplift capacity is essential for the determination of optimal burial depth of buried offshore pipelines. However, a generalized prediction model that incorporates various factors influencing this capacity is scarce in the literature. In this paper, results from a series of small-strain finite element analyses are presented that explore the effects of pipe embedment, pipe-soil interface roughness, interface tensile capacity, soil shear strength, and unit weight on pipe uplift response. From the study, a simple method to predict the undrained upheaval resistance of buried pipelines for any practical range of pipeline and soil parameters is proposed. Factors associated with transition in failure mechanism with embedment are also examined. The numerical model is validated by comparing the results with available analytical and experimental data. Large-deformation finite element analyses have also been performed independently for a few cases to justify the applicability of small-strain methods in modelling pipe upheaval. Accuracy of the model for generalized shear strength profile is then examined by considering practical values of parameters over broad ranges. The proposed methodology gives results with maximum error less than 8% for all ranges of parameters and hence can be adopted in design practices. [ABSTRACT FROM AUTHOR]

This paper describes the instrumentation, execution and performance of two full-scale tests where a braced steel sheet pile wall interacting with rows of overlapping dry deep mixing columns was excavated and then loaded to failure. The purpose of these tests was to provide knowledge of the behavior of deep mixing column rows located in the passive zone and interacting with a retaining structure. Both tests were extensively instrumented on the active as well as on the passive side of the retaining structure. In both conducted tests a stability failure of the retaining structure occurred, resulting in heave at the bottom of the excavation and large settlements of the ground surface behind the sheet pile wall. For a spacing between lime-cement (LC)-panels of 3.0 m, a very brittle failure developed suddenly in the clay between the panels with small deformations prior to failure. In the second test, with a spacing of 1.5 m between LC-panels, the failure developed in the LC-panels as well as in the clay between the panels. Even if a similar failure mechanism developed, measured horizontal displacements, horizontal stresses, and pore pressure response prior to failure differed between the tests. [ABSTRACT FROM AUTHOR]

Concrete manholes are widely used in sanitary sewer and storm water systems in Canada. However, technical information regarding their structural aspects is limited. The main objective of this paper is to evaluate the effect of main parameters that impact the design of precast concrete manholes. A three-dimensional finite element model for circular precast concrete manholes was developed using Plaxis 3D and was calibrated against the experimental results presented in an earlier paper by the authors. The calibrated numerical model was used to analyze different configurations of concrete manholes and to conduct a parametric study on the parameters that govern its design including: type of native soil around the manhole; trench width ( Tw); water table elevation ( Wt); effect of manhole stage installation; and effect of soil compaction. The critical conditions were identified based on the change in the pressure underneath the centre of the manhole base and the bending moments within the manhole base. It was found that the trench width, stage installation of manhole, and filling soil compaction had marginal effects on the total vertical pressure beneath the centre of the manhole base. The presence of the water table at the top of the manhole resulted in the most critical contact pressure at the manhole base. [ABSTRACT FROM AUTHOR]

Many studies show that the propagation of a breakup water surge in impeded rivers (ice cover present) differs from the unimpeded case. Some of the differences are due to ice sheet breaking into pieces as the wave travels downstream while others are due to the effect of a fissured but otherwise intact ice cover's resistance to motion. This is the subject of this paper: water waves that are sufficiently strong to break the cover away from the banks but not strong enough to create transverse cracks. Although some analytical solutions exist for the propagation of these transients for simple cases, for the first time in the literature, this paper introduces numerical solutions using a FEM model (HYDROBEAM) that simulates this interaction using the one-dimensional Saint-Venant equations appropriately written for rivers having an intact fissured floating ice cover coupled with a classic beam equation subject to hydrostatic loads (often referred to as a beam on an elastic foundation). The governing equations are numerically expressed and are solved using a finite element method (FEM) for the hydrodynamic and ice beam equations separately. A coupling technique is used to converge to a unique solution at each time step (for more information on the numerical characteristics of the model, see companion paper presented by the authors in this issue). The coupled model, gives a first and unique opportunity to compare the simplified analytical solutions to the full numerical solutions. A parametric analysis is herein presented that quantifies the impact of the ice cover's presence and stiffness on wave attenuation and wave celerity as well as to quantify tensile stresses generated in the ice sheet as a function of ice properties (thickness and strength) and channel shape (rectangular and trapezoidal). In general, for rectangular channels, it was found that the simplified analytical solutions are quite representative of the phenomenon namely that short wave transients are affected by the cover's stiffness but long waves (>400 m) are not. [ABSTRACT FROM AUTHOR]

High-cycle accumulation (HCA) models may be used for the prediction of settlements or stress relaxation in soils due to a large number of cycles (N > 103) with a relatively small-strain amplitude (εampl < 10-3). This paper presents a discussion of the elastic stiffness, [IMG], used in the basic constitutive equation of an HCA model, εεε[IMG], where [IMG] is the trend of effective stress, ε[IMG] is the trend of strain, ε[IMG] is the rate of strain accumulation, and ε[IMG] is the plastic strain rate. [IMG] interrelates the “trends” of stress and strain evolution. For the experimental assessment of the bulk modulus, ε[IMG], the rate of pore-water pressure accumulation, [IMG], in undrained cyclic triaxial tests and the rate of volumetric strain accumulation, ε[IMG], in drained cyclic tests have been compared. The pressure-dependent bulk modulus, K, was quantified from 15 pairs of drained and undrained tests with different consolidation pressures and stress amplitudes. It is demonstrated that both the curves ε[IMG] in the drained tests and u(N) in the undrained tests are well predicted by the authors’ HCA model if the elastic stiffness is determined using the method described in the present paper. A simplified determination of K from the unloading and reloading curve in an oedometric compression test is discussed. Les modèles d’accumulation à cycles élevés (HCA) peuvent être utilisés pour la prédiction des tassements ou de la relaxation des contraintes dans les sols en raison du nombre élevé de cycles (N > 103) ayant une amplitude relativement petite (εampl < 10–3). Cet article présente une discussion de la rigidité élastique, [IMG], utilisée dans l’équation constitutive de base du modèle HCA, εεε[IMG], où [IMG] est la tendance de la contrainte effective, ε[IMG] est la tendance de déformation, ε[IMG] est le taux d’accumulation des déformations et ε[IMG] est le taux de déformation plastique. [IMG] relie les « tendances » de l’évolution des contraintes et des déformations. Afin d’évaluer expérimentalement le module de compressibilité, ε[IMG], on a comparé le taux d’accumulation de pression interstitielle, [IMG], avec le taux d’accumulation de déformation volumique, ε[IMG], dans les essais triaxiaux cycliques non drainés. Le module de compressibilité, K, dépendant de la pression a été quantifié à partir de 15 paires d’essais drainés et non drainés ayant des pressions de consolidation et des amplitudes de contrainte différentes. Il a été démontré que les courbes ε[IMG] dans les essais drainés et u(N) dans les essais non drainés sont bien prédites par le modèle HCA développé, lorsque la rigidité élastique est déterminée de la manière décrite dans cet article. Une méthode de détermination du K à partir de la courbe de déchargement et de rechargement obtenue par un essai en compression oedométrique est discutée. [ABSTRACT FROM AUTHOR]

This paper presents the background experimental and analytical research that was carried out to develop the provisions for the seismic design of high-strength concrete structures in the 2004 Canadian standard CSA A23.3-04. It is noted that the 1994 Canadian standard CSA A23.3-94 limited the concrete compressive strength to 55 MPa for the seismic design of nominally ductile and ductile structures, while the 1995 New Zealand Standard limited the concrete compressive strength to 70 MPa. In contrast, the 2008 American Concrete Institute (ACI) code ACI 318M has no upper limit on concrete strength, even for the seismic design of ductile structural elements. This tremendous variation in these limits indicated that more experimental evidence was needed. This paper presents experimental results of reversed cyclic loading tests on large-scale structural components as well as simulated seismic loading tests of a frame structure constructed with high-strength concrete. The goal of this collaborative research program at the University of Sherbrooke and McGill University was to determine the seismic design and detailing requirements for high-strength concrete structures to achieve the desired level of ductility and energy dissipation. The experimental programs include full-scale testing of the following: columns subjected to a pure axial load (square and circular columns); columns subjected to flexure and axial loads; beam-column subassemblages (square and circular columns); coupling beams in coupled wall structures; shear walls and a two-storey, three-dimensional frame structure. The results of the responses of the high-strength concrete structural specimens are compared with the responses of companion specimens constructed with normal-strength concrete. [ABSTRACT FROM AUTHOR]

In this paper the behaviour of two “standard research sands”, widely used for experimental purposes, is compared in a torsional hollow cylinder apparatus under monotonic and cyclic loading conditions. Both sands are fine and uniform with D50 = 0.22 and 0.29 mm, respectively. However, their response to undrained monotonic loading at similar void ratios is dramatically different, with the finer sand showing strength reduction after peak and the coarser sand showing continuous increase in strength with torsional shear. The difference in response is mainly attributed to grain angularity and to a lesser degree to their grading. The results of drained torsional hollow cylinder tests show initial contraction followed by dilation. The stress ratio at phase transformation is uniquely defined by both drained and undrained tests for each sand. Cyclic loading instability is manifested by a sudden increase in shear strain and excess pore-water pressure leading to initial liquefaction. The instability initiates across the instability line for the sand showing strength reduction and across the phase transformation line for the sand showing continuous increase in strength with shearing. Both lines are defined under monotonic loading conditions. The liquefaction, stiffness, and damping characteristics of the sands are given in this paper. Dans cet article, le comportement de deux « sables de recherche standard »très utilisés à des fins expérimentales est comparé dans l’appareil de torsion sur cylindre creux sous des conditions de chargement monotonique et cyclique. Les deux sables sont fins et uniformes avec des D50 = 0.22 mm et 0.29 mm respectivement. Cependant, leurs réactions sous un chargement monotonique non drainé sont dramatiquement différentes, avec le sable plus fin montrant une réduction de résistance après le pic, et le sable plus gros montrant un accroissement continu de la résistance dans le cisaillement en torsion. La différence dans la réaction est attribuée principalement au caractère anguleux des grains et à un moindre degré à leur granulométrie. Les résultats des essais de torsion drainée sur cylindre creux montrent une contraction initiale suivie d’une dilatation. Le rapport de contraintes à la transformation des phases est uniquement défini tant par les essais drainés que non drainés pour chaque sable. Durant le chargement cyclique, une instabilité manifestée par un accroissement soudain de la déformation en cisaillement et de l’excédent de pression interstitielle menant à une liquéfaction initiale, se développe en travers de la ligne d’instabilité pour le sable montrant une réduction de résistance, et la ligne de transformation de phase pour le sable montrant un accroissement continu de résistance avec le cisaillement. Les deux lignes sont définies dans des conditions de chargement monotonique. Dans cet article, on donne les caractéristiques de liquéfaction, de rigidité et d’amortissement des sables. [ABSTRACT FROM AUTHOR]

This paper deals with the application of under-deck cable-staying systems and combined cable-staying systems to prestressed concrete road bridges with multiple spans of medium length. Schemes using under-deck cable-staying systems are not suitable for continuous bridges, as they are not efficient under traffic live load and only allow for the compensation of permanent load. However, combined cable-staying systems are very efficient for continuous bridges and enable the design of very slender decks (1/100th of span) where the amount of materials used is halved in comparison with conventional schemes without stay cables. In this paper, the substantial advantages provided by combined cable-staying systems for continuous bridges (such as high structural efficiency, varied construction possibilities, both economic and aesthetical benefits, and landscape integration) are set out. Finally, design criteria are included. Cet article étudie l’application des systèmes à haubans sous pont et des systèmes à haubans combinés pour des ponts autoroutiers en béton précontraint de plusieurs portées de longueur moyenne. Les systèmes utilisant les systèmes à haubans sous pont ne conviennent pas aux ponts à travées continues puisqu’ils ne sont pas efficaces sous des charges de roulage dynamiques et ne permettent que la compensation de la charge permanente. Toutefois, les systèmes à haubanage combiné sont très efficaces pour les ponts à travées continues et permettent la conception de tabliers très effilés (1/100 de la portée) dans lesquels la quantité de matériaux utilisés dans le tablier est réduite de moitié par rapport à ceux des ponts conventionnels sans haubans. Dans cet article, les plus importants avantages des systèmes à haubanage combiné pour les ponts à travées continues sont énoncés : la grande efficacité de la structure, de meilleures possibilités de construction, les aspects économiques et esthétiques ainsi que l’intégration au paysage). Les critères de conception sont également inclus. [ABSTRACT FROM AUTHOR]

Although a number of constitutive models for unsaturated soils exist in the literature, some fundamental questions have not been fully answered. There are questions related to (i) the change of the yield stress with soil suction, (ii) modelling slurry soils, and (iii) the smooth transition between saturated and unsaturated soil states. This paper addresses these questions by proposing an alternative modelling approach. The paper first presents a volumetric model for unsaturated soils. This volumetric model is then used to derive the yield surface in the suction – mean stress space. Hysteresis associated with soil-water characteristic curves is then formulated in the same framework of elastoplasticity. It is shown that volume collapse during wetting and plastic shrinkage during initial drying are both direct results of a suction-dependent hardening law. The proposed model seems to be more flexible in modelling different types of unsaturated soils than most models in the literature. The model can be applied to soils that are dried or loaded from initially slurry conditions, for soils that have low to high air-entry values, and for compacted soils as well. [ABSTRACT FROM AUTHOR]

The article presents a response to the discussions made by Robert K. Barrett and Dov Leshchinsky on the authors' paper "The influence of facing stiffness on the performance of two geosynthetic reinforced soil retaining walls." They appreciate the comments raised by Barrett and Leshchinsky. In doing so, they clarify and elucidate a number of points related to the details and contingents of the test program described in the referring paper. Moreover, they provide various implications to current practice.

Masonry component products are increasingly made industrially with reduced variation in mechanical properties. The joint is the only part of the masonry that is affected by manual action and so the load bearing capacity is not only determined by the quality of the bricks and mortar used but moreover by the way the masonry has been built and cured. As a result, it may be expected that the largest material variations are at the brick–mortar interfaces. This has been observed as irregular interface bonding with a bonded central area surrounded by fissures. As a consequence of the final shape of the joint, forces concentrate in the central part of the joint and strain variations occur near fissure tips which result in spalling of bricks in experiments. This paper demonstrates the need for detailed deformational measurements in the brick–mortar interface region. To overcome the limitations with traditional measuring instruments, a refined methodology based on the laser speckle technique is introduced in a companion paper [Canadian Journal of Civil Engineering, 34(11), 1467 (2007)] by the authors of this paper. [ABSTRACT FROM AUTHOR]

The brick–mortar interaction is important in the mechanical behaviour of masonry. It affects the load transfer considerably, as shown by detailed deformation measurements taken using electronic speckle pattern interferometry (ESPI), a laser speckle interference technique. A companion paper [Canadian Journal of Civil Engineering, 34(11), 1475 (2007)] by the authors of this paper argues that the joint is the only part of contemporary masonry significantly affected by manual action, which is why large material variations appear at the brick–mortar interface. To evaluate this phenomenon, ESPI measurements were performed and compared with accompanying linear variable differential transformer (LVDT) results. The behaviour of specimens loaded with various eccentricities was relatively soft in the brick–mortar interface area when compared with the behaviour shown in the surrounding stiff brick and mortar. The brick–mortar interface was characterized by a central part surrounded by fissures. Most of the load was transmitted in the central part. Because of this, the axial strain curve over the width of the specimens was U-shaped for concentrically loaded specimens (i.e., those with zero eccentricity). Over the height of the two-brick one-joint specimen, a smooth, B-shaped lateral strain curve was observed, in which the largest strains were found in the bricks. [ABSTRACT FROM AUTHOR]

This paper outlines the static and fatigue behavior of cast-in-place, second-generation steel-free bridge decks. Although cast monolithically, the first bridge deck was divided into three segments. The first segment was reinforced with steel, according to conventional design. The other two segments were steel-free designs with internal crack-control grids, one consisting of carbon-fibre-reinforced polymer (CFRP) and the other consisting of glass-fibre-reinforced polymer (GFRP). This hybrid CFRP or GFRP and steel strap design is called the second generation of the steel-free concrete bridge deck. The hybrid system limits the width of any longitudinal cracks that develop and eliminates corrosion from within the deck slab. All three segments were tested under cyclic loads of 222 and 588 kN to investigate fatigue behavior. The second bridge deck comprises an internal panel and two cantilevers and also incorporates a complete civionics system. The static tests outlined in this paper are useful in the development of the fatigue theory, which was derived from the fatigue testing of the first bridge deck. [ABSTRACT FROM AUTHOR]

Externally bonded fibre-reinforced-polymer (FRP) laminates and fabrics have been successfully used for strengthening damaged or deficient concrete members, whereas internal FRP reinforcements are becoming an efficient alternative to steel reinforcement, particularly in corrosive environments. Despite the enormous progress that has been observed in the last decade, further research is still required to consolidate recent developments and expand the scope of application of FRPs for structural uses. Nonlinear finite element analysis combined with laboratory testing constitutes an efficient approach for pursuing this objective. The scope of this paper is to illustrate, through a selection of a wide variety of typical applications, the contribution of a refined three-dimensional (3-D) constitutive model for investigating the nonlinear response of concrete structures reinforced with internal and external FRPs. The analyses are carried out using a general and portable constitutive concrete model implemented as a user-defined subroutine at Gauss integration point level in commercial finite element software. The constitutive law follows a 3-D hypoelastic approach that models the nonlinear behaviour of concrete using a scalar damage parameter that accounts for the anisotropic behaviour of partially confined concrete and the inelastic volume expansion upon reaching the peak strength. In tension, the model adopts a macroscopic approach that is directly integrated into the concrete law. It simulates implicitly the reinforcing bar – concrete interaction using tension-stiffening factors modified according to the nature of reinforcement that vary as a function of the member strain. The applications include results of well-known test series published in the literature on beams with external and internal FRP reinforcement, slabs with internal reinforcements, bond failure analysis of external FRP, and the effect of confinement on the behaviour in compression of circular and square elements. The paper demonstrates the ability of the concrete model to correctly simulate the behaviour of structural elements reinforced with FRPs at service load level and reproduce failure mechanisms and loads that are consistent with the experimental observations. [ABSTRACT FROM AUTHOR]

The aim of this paper is to develop two- and three-dimensional stability charts for slopes susceptible to translational failure. An extensive parametric study was conducted using a slope model that is designed to simulate field conditions with respect to configurations of the sliding mass, and unit weight and shear strength of the involved materials. Slopes subjected to different conditions of pore-water pressures and seismic forces were considered in the study. The study shows the special importance and difficulties of considering the end effects in the analysis of translational slope failures and suggests a method for quantifying and incorporating them. Charts presented in this paper do not require an iterative procedure in determining factor of safety. They give the practicing geotechnical engineer a fast and reliable method to estimate the two and three-dimensional factors of safety for slopes susceptible to translational mode of failure and to back-calculate the mobilized shear strength of materials involved in slope failures following such mode. Numerical examples are given to illustrate different uses of these charts. [ABSTRACT FROM AUTHOR]

This paper presents a study on the interfacial behavior of carbon fiber reinforced polymer (CFRP) sheets when applied to concrete members as external reinforcement. Two bond test methods that are detailed in the paper were used in separate test series to study the bond behavior and failure mechanism of CFRP sheets bonded to concrete. A modified push-apart test method was proposed and tested. It was concluded that there existed an effective length beyond which there will be no increase in the ultimate capacity of the joint. An experimental test method to determine the effective bond length was also proposed and tested. The strains at the edge of the CFRP sheets are consistently higher than those at the center. The anchorage requirements for the CFRP sheets were also investigated in this study. Anchor sheets placed at 90° to the primary test sheets and bonded underneath the tested sheet showed better or equivalent overall bond behavior compared with those bonded on top of the tested sheet. The distance at which the anchor sheet is placed from the crack does not appear to change the bond behavior. [ABSTRACT FROM AUTHOR]