Search

Copyright of Space & Form / Przestrzeń i FORMA is the property of West Pomeranian University of Technology, Department of Architecture & Urban Planning and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the recent times, many huge concrete face rockfill dams (CFRDs) have been modelled and constructed in the world, and many of these dams are located on the strong earthquake zones. Examination of the seismic behaviour of a CFR dam built on the seismic zone is very important to assess the safety and future of the dam. For this reason, the nonlinear earthquake behaviour of these dams should be constantly observed taking into account the seismicity of the zone. In this study, three-dimensional (3D) seismic behaviour of the Ilısu dam built on the East Anatolian Fault (EAF) line is examined considering the effect of the important various far-fault earthquakes. The 3D finite difference model of the Ilısu dam is created using the FLAC3D software based on the finite difference method. The dam body, foundation, and concrete slab constantly interact during the lifetime of the CFRDs. Therefore, the special interface elements are defined between the dam body, concrete slab, and foundation to represent the interaction condition. The Mohr–Coulomb nonlinear material model is used for the rockfill materials and foundation. Moreover, the concrete slab is modelled considering the Drucker–Prager nonlinear material model to represent the nonlinearity of the concrete. Very special seismic boundary conditions rarely used for CFR dams in the past are used in this work. These boundary conditions are free-field and quiet boundary conditions. The free-field boundary condition that is a very important boundary condition for the nonlinear seismic analyses is considered for the lateral boundaries of the 3D model. In addition, the quiet artificial boundary condition is used for the bottom of the foundation. While defining these boundary conditions, the special fish functions are created and defined to the software. Moreover, the hysteric damping coefficients are separately calculated for all of the materials. These special damping values are defined to the FLAC3D software using the special fish functions to capture the effects of the variation of the modulus and damping ratio with the dynamic shear-strain magnitude. In the numerical analyses, a total of 7 various strong far-fault earthquakes are used for the 3D nonlinear earthquake analyses, and 7 different numerical analyses are performed for the full-reservoir condition of the Ilısu CFR dam. According to the seismic results, the principal stresses for the three critical nodal points on the dam body surface are examined and evaluated in detail. It is clearly understood that the nonlinear seismic behaviour of the Ilısu dam changes depending on the magnitudes and periods of the far-fault earthquakes. Each far-fault earthquake has different seismic effects on the nonlinear principal stress behaviour of the Ilısu CFR dam. [ABSTRACT FROM AUTHOR]

The concrete-face rockfill dam (CFRD) has become a preferred dam type, but its design remains largely based on past experiences. Understanding the behaviour of CFRDs is critical to the design and safety assessments of these dams. The main objective of this study is to review the behaviour of CFRDs from the perspective of statistical analysis. A set of monitoring records and construction details of 87 case histories of in-service CFRDs constructed in the past 50 years is collected. The analysed data that are presented are based on a review of the literature. Detailed statistical analyses of post-construction crest settlement and face slab behaviour, settlement of the dam body during construction and leakage after reservoir filling are conducted on the basis of the above-mentioned case histories. Several suggested empirical relationships are obtained by regression analysis to estimate the deformation and seepage behaviour of CFRDs. Findings offer reliable insights into dam behaviour and provide an engineering analogy and reference for the planning, design and construction of CFRDs in the future. The statistical analyses also attempt to identify quantitatively the major influencing factors of the deformation of CFRDs, such as intact rockfill strength, foundation characteristics, valley shape and seepage flow. Intact rockfill strength and foundation characteristics are found to be the main influencing factors of dam deformation behaviour. The results from the statistical analysis of the case histories and the analyses performed are also presented herein. [ABSTRACT FROM AUTHOR]

The thermal and mechanical performances of a simple thermal break are analysed. This thermal break can be used with external steel structures such as balconies and passageways attached on a concrete facade with external thermal insulation. The thermal barrier effect is obtained by a PVC and an acoustic insulation plates inserted between the end-plates of the attached steel beams and the support (floor slab, concrete wall). The thermal performances of the selected solutions were evaluated by numerical simulation. It shows that this simple solution reduces by up to 65% the thermal bridge at the attached steel beams connections. Besides, a parametric analysis showed that the reduction ratio depends on the configuration of thermal break (with or without additional thermal insulation around the steel beams at the connection), the thickness of PVC plate, the material of fastening systems (carbon steel or stainless steel) and the thickness of the facade thermal insulation. As deformable layers are used under the end-plates, the thermal break can be considered as unconventional steel connection with mechanical performances to be investigated. Thus, experimental program including static and cyclic tests is performed on various configurations of connections with thermal breaks to evaluate their mechanical behaviour considering the stiffness and the resistance. The results show that the solution of simple thermal break is efficient mainly for connections with extended end-plates. [ABSTRACT FROM AUTHOR]

As the anti-seepage bodies in concrete-faced rockfill dams (CFRDs), face slabs play a vital role in ensuring dam reliability; thus, the stresses acting on face slabs should be analysed in detail. Considering the importance of the hydrodynamic pressure on high CFRD, the hydrodynamic pressure should be calculated with accurate methods when assessing the safety of high (approximately 300 m) CFRDs in strong ground motion zones. The principal objective of this paper is to investigate the effects of hydrodynamic pressure on the face slab response of a 300 m high CFRD under seismic loads in different directions. A dynamic coupling method for the modelling of CFRD-reservoir systems based on an approach combining the finite-element method (FEM) and the scaled boundary finite-element method (SBFEM) is developed. The hydrodynamic pressure of an incompressible fluid, based on a semi-analytical SBFEM approach, is expressed in the form of a full added-mass matrix. Moreover, the distribution of the hydrodynamic pressure and the mechanism by which it influences the dynamic stresses in the slabs are investigated. It is revealed that hydrodynamic pressure influences the dynamic stress in face slabs through the frictional force between the cushion and the slabs and cannot be neglected in the dynamic analysis of a high CFRD. [ABSTRACT FROM AUTHOR]

This paper combined with the adaptive principle to improve the genetic algorithms (GA) and applied it to optimal design of the shape of the concrete face rock-fill dam (CFRD). Based on the improved GA, a mathematical model was established for the design optimization of CFRD. CFRD utilizes dam cost as objective function and dam slope and geometries of the dam material partition as design variables. Dam stability, stress, displacement, and stress level are used as the main condition constraints. The calculation procedures were prepared, and the GA was used to optimize the design of Jishixia CFRD. Results show that the GA could solve the global optimal solution problem of complex optimization design, such as the high degree of nonlinearity and the recessiveness of constraint conditions, and using the GA to optimize the CFRD design can reduce the quantities of projects and engineering safety costs. [ABSTRACT FROM AUTHOR]

The revision task on technical specification for application of autoclaved aerated concrete products JGJ/T17 is under way, which was assigned in November 2013.The framework, thoughts and contents of revision on the specification are presented in this paper. [ABSTRACT FROM AUTHOR]

The deformation characteristics of a concrete-faced rock-fill dam (CFRD) during the dam's construction and initial reservoir filling phases were investigated. A detailed examination of behavior of a CFRD during the construction stage was conducted for the CFRD-type Daegok Dam located in Korea, where a well-designed monitoring program was planned. The monitoring record obtained during the dam construction and initial impoundment is presented. The vertical displacements during dam embankment are compared with other CFRD cases in Korea. Two-dimensional finite element analyses were performed to assess the displacements during both the construction and initial reservoir filling stages, using the model parameters estimated based on large-scale triaxial tests. A nonlinear and inelastic constitutive soil model was used to represent the behavior of the rock materials. In addition, the monitoring results for 29 CFRDs were analyzed. The observed and predicted values on the normalized maximum displacement and the location of maximum values during the dam construction stage agree well. Also, the limitations of numerical analysis on the reservoir filling stage are addressed. [ABSTRACT FROM AUTHOR]

Abstract: The aseismic design of concrete faced rock-fill dams (CFRDs) has become vitally important in recent years. A series of 1-g large-scale shaking table model tests were conducted, applying similitude laws to evaluate the effectiveness of various aseismic measures. The following four reinforcing measures are discussed in this study: reinforcing the top zone with geogrid, protecting the downstream slope surface using stone block, replacing the top zone of the dam with cemented rock-fill material or concrete layers. The failure developments were visualised using the particle image velocimetry (PIV) technique. The mechanisms of these reinforcement measures were analysed in detail. The effectiveness of these measures was evaluated by comparing the crest settlement rates and key accelerations corresponding to surface grain yield, slab fracture and slab dislocation. Based on the model test results, a combination of reinforcement measures was proposed for the prototype CFRDs. [Copyright &y& Elsevier]

Highlights: [•] Experimental study to assess the initial shear strength of brickwork facades. [•] Experimental results differ from the provided by EC 6 for brick masonry. [•] More conservative values might be considered in the EC 6 for brickwork. [•] The brickwork facade - concrete slab contact plane has been studied. [•] EC 6 might take into account the shear strength in the brick-concrete interface. [Copyright &y& Elsevier]

Abstract: The primary goal of this study was to examine the cracking behavior of the face plate of a CFRD during earthquake excitation. Analyses of the impounding stage and earthquake loading were conducted in sequential phases using a 2-D plane-strain model with the appropriate non-linear constitutive relationships for the dam constituents. The effect of rockfill stiffness and the face plate design properties on the seismic performance of the face plate was investigated. The crack widths on the plate increased with earthquake shaking. Settlement of the fill during intense seismic excitation counteracted this phenomenon by causing compression on the plate at some locations. [Copyright &y& Elsevier]

The slope ratio of hard rock Concrete Face Rock-fill Dam (CFRD) has already been determined in the code, but the slope ratio of soft rock CFRD must be calculated. Considering the difference of linear and nonlinear strength envelope, an appropriate strength envelope should be chosen to ensure the safety and economy of the dam. Take a one-hundred- meter soft rock CFRD for example, in order to get linear and nonlinear strength envelope, a large-scale tri-axial test has been carried on for dam material. A slope analysis has also been made for downstream slope. The results show that the safety factor calculated by nonlinear strength envelope is bigger than the safety factor calculated by the linear strength envelope. Through arguing the rationality of using non-linear strength envelope and referring to other one-hundred- meter soft rock high CFRD that has been built, and also Cook's advice about the dam slope ratio, it is not hard to see that nonlinear strength envelope of CFRD is more appropriate for the slope stability analysis. [ABSTRACT FROM AUTHOR]

Abstract: The seismic behavior of tall concrete face rockfill dams in narrow canyons is investigated, based on numerical simulation of the staged construction, creep settlements, reservoir impoundment and seismic shaking of the dam. The study takes into account the flexibility of the canyon rock, the hydrodynamic effects and potential dynamic rockfill settlements. The static analysis uses a hyperbolic model for the rockfill, whereas the dynamic analysis uses a nonlinear hysteretic model, which accounts for the initial dynamic stiffness and produces hysteresis loops in agreement with the experimental data regarding the shear modulus and damping ratio. A damage plasticity model is used for the reinforced concrete, whereas frictional contact behavior is considered at the base and vertical walls of the concrete slab panels. An existing 150-m-high dam is used to investigate some key issues on the seismic behavior of such dams subjected to upstream−downstream and vertical excitation. Emphasis is placed on the evaluation of the tensile stresses within the slab panels, the compressive stresses at the slab-to-slab vertical interfaces and the opening of the joints. Moreover, the effect of potential dynamic settlements on both the slab stresses and joint openings is investigated. Recommendations for increasing the dam safety and reducing the water leakage through the dam body are given. [Copyright &y& Elsevier]

Abstract: Based on the law of equi-width joint steady flow, a seepage computational model was established. This model permits use of finite element method in seepage simulation and analysis. In addition, rock-fill dam seepage characteristics under an unusual condition with massive face slab cracks was obtained via a computational example. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an experimental study of a steel–concrete composite bridge deck slab with profiled sheeting and perfobond shear connectors. Two full-scale deck slab specimens cast onto three concrete blocks were fabricated and tested under static loading to examine the ultimate load-carrying capacity of the proposed deck slab system under sagging and hogging bending actions. The ultimate behaviour of the full-scale deck slab specimens is also compared with that of simply supported deck specimens under hogging bending only. In addition, the load–deflection behaviour of the proposed deck system is compared with that of a reinforced concrete (RC) deck slab. The test results indicate that the ultimate load-carrying capacity of the proposed deck system is at least 220% greater than that of the RC deck system and that the deck weighs about 23% less than the RC deck system. The paper summarizes the test results, findings, and recommendations for future study. [Copyright &y& Elsevier]

Abstract: This paper presents a theoretical study of the flexural behaviour of indeterminate concrete beams reinforced with fibre reinforced polymer (FRP) bars using a local deformation model developed by the authors. The model is firstly presented and its performance compared with tests on simply supported and continuous concrete beams reinforced with FRP bars. A detailed theoretical investigation is then conducted by applying the model to continuous beams reinforced with FRP bars in order to predict the bending moment distribution, as well as the progressive formation of flexural cracks and associated crack spacings and crack widths. Of particular interest is the ability of the model to determine the deformations in highly stressed regions in the beam. Based on the theoretical results, comments are made as to the ductility and overload behaviour of concrete beams reinforced with FRP bars in comparison to concrete beams reinforced with steel bars. All results and associated comments are dependent on certain assumptions and are dependent on the input parameters used in the model. The results are found to be particularly dependent on the bond characteristics between the FRP bar and surrounding concrete. [Copyright &y& Elsevier]

Concrete face rockfill dams (CFRDs) are considered to be fundamentally safe, especially against leakage, and to be a low-cost alternative at many sites. Their design is based on empirical experiences rather than theory. The present paper describes post-construction deformation and leakage using 27 CFRD case studies. The analysis shows that deformation normal to the face slab is larger than the post-construction crest settlement when the dam height exceeds 100 m and that the long-term leakage rate increases rapidly when the dam height exceeds 125 m. On considère que les barrages en enrochements avec face amont en béton (« CFRD ») possède une sécurité fondamentale, particulièrement contre les fuites et ont été une alternative à bon marché pour plusieurs sites, de plus leur conception est basée sur des expériences empiriques plutôt que sur la théorie. Le présent article décrit la déformation après construction, et les fuites au moyen de 27 études de cas de CFRD. L’analyse montre que la déformation normale à la face de la dalle est plus grande que le tassement de la crête après construction lorsque la hauteur du barrage dépasse 100 m, et le taux de fuites à long terme augmente rapidement lorsque la hauteur du barrage excède 125 m. [ABSTRACT FROM AUTHOR]

The article discusses the methods used to tie wythes of brick, concrete block, brick face and stud walls. It describes the English bond and Flemish bond methods of tying wythes of brickwork together. An analysis of the face bricks of a college building is presented, along with the actions taken to examine and reinstall displaced bricks on the building. The author concludes that English bond ties brickwork together more effectively than other bonds.