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  • 1.
    Abbasiverki, Roghayeh
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Initial study on seismic analyses of concrete and embankment dams in Sweden2017Report (Other academic)
  • 2.
    Abbasiverki, Roghayeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Analysis of buried reinforced concrete pipelines subjected to seismic waves2014Conference paper (Refereed)
  • 3.
    Abbasiverki, Roghayeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Seismic response of buried concrete pipelines subjected to highfrequency earthquakesIn: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529Article in journal (Refereed)
    Abstract [en]

    Buried pipelines are tubular structures that cross large areas with different geological conditions. During an earthquake, imposed loads from soil deformations on concrete pipelines may cause severe damages. In this study, the use of two-dimensional finite element models of pipelines and surrounding soil for simulation of seismic waves that propagate from the bedrock through the soil are demonstrated. The models describe both longitudinal and transverse cross-sections of pipelines and the soil-pipe interaction is modelled as a nonlinear behaviour. The effects of uniform ground with different burial depths, soil layer thickness, soil stiffness and bedrock geometry on the seismic response of reinforced concrete pipelines is studied. Two earthquakes, with high and low frequency contents, are employed for the dynamic analysis. The results show that there is a much smaller risk of damage from high-frequency earthquakes, but that there is a significant effect on the response due to possible irregular ground with inclined bedrock.

  • 4.
    Abbasiverki, Roghayeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Analysis of shallowly buried reinforced concrete pipelines subjected to earthquake loads2014In: Nordic Concrete Research, ISSN 0800-6377, no 51, p. 111-130Article in journal (Refereed)
    Abstract [en]

    Buried reinforced concrete pipelines are widelyused in e.g. water and wastewater systems. Failure of these infrastructures mayresult in drastic effects and recently they have been brought into focus asvital components in safety systems for nuclear power installations. The highlevel of safety has here lead to a demand for reliable earthquake risk analyses.In this paper, methods are compared and the use of seismic design loadsdemonstrated. FE analysis in 2D of soil-pipe interaction under seismic wavepropagation is performed. The performance of concrete pipes subjected toseismic waves with different frequency content is evaluated with respect todifferent soil condition but also water mass effect.

  • 5.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    A comparison of models for shotcrete in dynamically loaded rock tunnels2010In: Shotcrete: Elements of a system / [ed] E. Stefan Bernard, Taylor & Francis Group, 2010, p. 1-10Conference paper (Refereed)
    Abstract [en]

    During blasting in tunnels and mines, the shotcrete-rock interaction is influenced by propagating stress waves. Shotcrete support in hard rock tunnels is here studied through numerical analysis and comparisons with previous numerical results, measurements and observations in situ. The stress response in the shotcrete closest to the rock when exposed to P-waves striking perpendicularly to the shotcrete-rock interface is simulated. The first model tested is an elastic stress wave model, which is onedimensional with the shotcrete assumed linearly elastic. The second is a structural dynamic model that consists of masses and spring elements. The third model is a finite element model implemented using the Abaqus/Explicit program. Two methods are used for the application of incident disturbing stress waves: as boundary conditions and as inertia loads. Results from these three types of models are compared and evaluated as a first step before a future extension to more detailed analyses using 3D models.

  • 6.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Behaviour of sprayed concrete on hard rock exposed to vibration from blasting operations2014Conference paper (Refereed)
  • 7.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Direct shear strength of high-strength fibre concrete2010In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 62, no 5, p. 379-390Article in journal (Refereed)
    Abstract [en]

    An experimental and theoretical study of the shear behaviour of steel-fibre-reinforced concrete is presented. Twenty-seven direct shear push-off tests were carried out on high-strength concrete, with and without steel fibre reinforcement. The test series contained uncracked and precracked specimens for the study of the slipping response and the shear stress that can be transferred across an open crack. The test variables were the fibre content and the reinforcement ratio. The test results were compared with information provided by the available codes and other, previous results. The test results indicated that incorporation of steel fibres and bars in concrete members subjected to shear leads to an improved mechanical behaviour before failure. Based on the presented experimental results, an equation governing the direct shear strength is proposed and verified against test results from other test series.

  • 8.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Experimental and numerical investigation of stress wave propagation in shotcrete2011In: Nordic concrete research: Research projects 2011 / [ed] D.H. Bager, 2011, p. 59-62Conference paper (Refereed)
  • 9.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Laboratory investigation of stress waves in young shotcrete on rock2012In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 64, no 10, p. 899-908Article in journal (Refereed)
    Abstract [en]

    To study the behaviour of shotcrete under dynamic load, a non-destructive laboratory experiment was set up with P-wave propagation along a concrete bar, with properties similar to rock. Cement-based mortar with properties that resemble shotcrete was applied to one end of the bar with a hammer impacting the other. The shape of the stress waves travelling towards the shotcrete was registered using accelerometers positioned along the bar. Finite-element modelling was used to verify the test results, which showed that the laboratory model with an impacting hammer could be used to initiate the same type of stress waves that result from blasting in good-quality rock. Previously recommended maximum allowed peak particle vibration velocities were verified.

  • 10.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Structural dynamic and stress wave models for analysis of shotcrete on rock exposed to blasting2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 35, no 1, p. 11-17Article in journal (Refereed)
    Abstract [en]

    During blasting in tunnels and mines, the interaction between shotcrete (sprayed concrete) and rock is influenced by propagating stress waves. Shotcrete support in hard rock tunnels is studied here through numerical analysis using three different modelling approaches. The stress response in the shotcrete closest to the rock when exposed to P-waves striking perpendicularly to the shotcrete–rock interface is simulated. The first model tested is a structural dynamic model that consists of masses and spring elements. The second is a model built up with finite element beam elements interconnected with springs. The third is a one-dimensional elastic stress wave model. The models give comparable results, although the definition of the dynamic loads is different. The analysis results can be used to estimate whether the shotcrete will fail or not for a prescribed distance to detonating explosives inside the rock.

  • 11.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Vibration vulnerability of shotcrete on tunnel walls during construction blasting2014In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 42, p. 105-111Article in journal (Refereed)
    Abstract [en]

    The effect on shotcrete from blasting operations during tunnelling is studied, with focus on young and hardening shotcrete. A finite element model specially adapted for analysis of the shotcrete behaviour is tested, it is able to describe stress wave propagation in two dimensions which is important for cases where shear stresses are dominant. The modelling results are compared with in situ measurements and observations, from construction blasting during tunnelling through hard rock. The comparison shows that the model gives realistic results and can be used to investigate the vulnerability of shotcrete, aiming at compiling recommendations and guidelines for practical use. The given recommendations emphasize that blasting should be avoided during the first 12 h after shotcreting and that distance and shotcrete thickness are important factors for how much additional time of waiting is possibly needed.

  • 12.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Numerical modelling and evaluation of laboratory tests with impact loaded young concrete prisms2016In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, p. 1-14Article in journal (Refereed)
    Abstract [en]

    Numerical modelling in combination with in situ measurements, observations and laboratory testing will be important to future establishment of reliable guidelines for efficient civil and engineering work involving concrete casting close to e.g. blasting operations. Results from laboratory tests with impact loaded young concrete prisms are here evaluated using a 3D finite element model. Solid elements are used implementing a non-linear material model, capable of describing cracking during stress wave propagation. The position of cracks and measured particle vibration velocities are calculated and compared with laboratory test results. The damaging effect of impact vibrations is evaluated using crack width and fracture energy as damage criteria. Alternative geometry for the test prisms, with a notched section, is analysed. This will give one wide crack at the centre of the prism instead of two or three cracks distributed over its length which will make future laboratory test more efficient and reliable. Recommended damage limits at concrete ages of 4, 6, 8 and 12 h are given, based on numerical calculations for concrete strength class C25 and C50.

  • 13.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Numerical modelling and evaluation of laboratory tests with impact loaded young concrete prisms2016In: Materials and Structures, ISSN 1359-5997Article in journal (Refereed)
    Abstract [en]

    Numerical modelling in combination with in situ measurements, observations and laboratory testing will be important to future establishment of reliable guidelines for efficient civil and engineering work involving concrete casting close to e.g. blasting operations. Results from laboratory tests with impact loaded young concrete prisms are here evaluated using a 3D finite element model. Solid elements are used and a non-linear material model implemented, capable of describing cracking during stress wave propagation. The position of cracks and measured particle vibration velocities are calculated and compared with laboratory test results. The damaging effect of impact vibrations is evaluated using crack width and fracture energy as damage criteria. Alternative geometry for the test prisms, with a notched section, is analysed. This will give one wide crack at the centre of the prism instead of two or three cracks distributed over its length which will make future laboratory test more efficient and reliable. Recommended damage limits at concrete ages of 4, 6, 8 and 12 h are given, based on numerical calculations for concrete strength class C25 and C50.

  • 14.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Finite element simulation of shotcrete exposed to underground explosions2012In: Nordic Concrete Research, ISSN 0800-6377, no 45, p. 59-74Article in journal (Refereed)
    Abstract [en]

    An elastic finite element model is used tosimulate theinducedstress waves from blasting, propagating in rock towards shotcrete on a tunnel wall. Due to the inhomogeneous nature of the rock, the stress wavesattenuate onitsway from the point of explosiontowardsthe shotcrete on the rock surface. Material damping for the rock-mass is estimated from in-situ measurements. The vibration resistance of the shotcrete-rock support system depends on the material properties of the shotcrete. Age-dependent material properties are varied to investigate the behaviour of young shotcrete subjected to blast loading. Finally, finite element analysis results are presented and verified through comparison with other numerical models, measurements and observations.

  • 15.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Sjölander, AndreasKTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.Ansell, AndersKTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Evaluation and analysis of laboratory tests of bolys-anchored, steel-fiber-reinforced shotcrete linings2017Conference proceedings (editor) (Refereed)
  • 16.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    3D- modellering av samverkan mellan berg och sprutbetongförstärkning. Förstudie2009Report (Other academic)
  • 17.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    A finite element model for dynamic analysis of shotcrete on rock subjected to blast induced vibrations2004In: Shotcrete: More Engineering Developments: Proceedings of the Second International Conference on Engineering Developments in Shotcrete, October 2004, Cairns, Queensland, Australia / [ed] E. Stefan Bernard, London: Taylor & Francis Group, 2004, p. 15-26Conference paper (Refereed)
  • 18.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    A literature review on the shear capacity of dynamically loaded concrete structures2005Report (Other academic)
  • 19.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    A Literature Review on the Vibration Resistance of Young and Early age Concrete2002Report (Other academic)
  • 20.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Axiell provbelastning av BAT Mk III filterspets2000Report (Other academic)
  • 21.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Dragprovning av nitar från Forsmobron2000Report (Other academic)
  • 22.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Dragprovning av stål från Forsmobron2000Report (Other academic)
  • 23.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Dynamic finite element analysis of young shotcrete in rock tunnels2007In: ACI Structural Journal, ISSN 0889-3241, E-ISSN 1944-7361, Vol. 104, no 1, p. 84-92Article in journal (Refereed)
    Abstract [en]

    The problem with shotcrete on rock subjected to vibrations has previously been studied in place and through numerical modeling. Within the present project, an elastic finite element model is presented that consists of beam elements used to model the flexural stiffness and mass of the shotcrete lining and a section of rock. Spring elements are added for elastic coupling between shotcrete and rock. The loads on the model are acceleration-time series. Scaling laws for the magnitude of vibration velocities in rock as a function of distance and amount of explosives are used to study the damage to shotcrete at various. distances from the source of an explosion. Age-dependent shotcrete material properties are varied to investigate the vulnerability of young shotcrete exposed to explosion-induced vibrations. Recommended minimum shotcrete ages, based on the numerical results, are given for practical use.

  • 24.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Dynamic testing of steel for a new type of energy absorbing rock bolt2006In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 62, no 5, p. 501-512Article in journal (Refereed)
    Abstract [en]

    Rock bolts of steel are the most frequently used components in systems for rock reinforcement. Special types are used as energy absorbing elements in systems exposed to dynamic loads and these must yield plastically under high loading velocities. A new type of energy absorbing rock bolt of soft steel has been suggested and tested. To investigate the strain rate effects on the yield stress and ultimate strength of the steel were bars dynamically loaded in a high speed testing machine. The observed tensile forces can be divided into one part from impact and another from quasi-static straining. The tests showed that there was a considerable strain rate effect on the yield stress of the steel. It is recommended that higher dynamic yield stresses are utilized in the dynamic design which has to incorporate the risk of high peak forces from impact loading.

  • 25.
    Ansell, Anders
    KTH, Superseded Departments, Structural Engineering.
    Dynamically loaded rock reinforcement1999Doctoral thesis, monograph (Other scientific)
  • 26.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Dynamiskt belastad ung sprutbetong2000Report (Other academic)
  • 27.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    En förstudie i modellering av vibrationsutsatt sprutbetong på berg med finita element-metoden2000Report (Other academic)
  • 28.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Finite element models for dynamic analysis of shotcrete on rock2002Report (Other academic)
  • 29.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Frequency Dependent Matrices for Dynamic Analysis of Frame Type Structures1996Licentiate thesis, monograph (Other academic)
  • 30.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    In situ testing of young shotcrete subjected to vibrations from blasting2004In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 19, no 6, p. 587-596Article in journal (Refereed)
    Abstract [en]

    A criterion for how close, in time and distance, to young shotcrete blasting can take place will be an important tool in planning for safe and economical tunnelling projects. As a first step, in situ tests with young, plain un-reinforced shotcrete have been conducted in a Swedish mine. Shotcrete panels were projected on tunnel walls and exposed to vibrations from explosive charges detonated inside the rock at shotcrete ages between I and 25 h. The shotcrete was tested to investigate growth of compressive strength and also to determine final compressive and adhesive strengths. The response of the rock was measured with accelerometers, giving signals that were later numerically integrated to particle vibration velocities. An average scaling relation of distance between explosive charges and the point of observation and weight of explosives was also derived. The recorded vibration levels showed that the shotcrete had withstood high particle velocity vibrations without being seriously damaged, even when the rock material was fragmented and ejected. Drumminess of shotcrete appeared, indicating that the major failure mechanism was sudden loss of adhesion at the shotcrete-rock interface. No differences in performance between shotcrete of different ages were observed. It was, thus, confirmed that young shotcrete without reinforcement can also survive high vibration levels without being seriously damaged.

  • 31.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Investigation of shrinkage cracking in shotcrete on tunnel drains2010In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 25, no 5, p. 607-613Article in journal (Refereed)
    Abstract [en]

    The presented investigation combines in situ observations, measurements, testing and theoretical modelling. The in situ work was done to map and evaluate the shrinkage related cracking of shotcrete on short and long sections of soft, plastic drains. The occurrence of variation in shotcrete thickness and crack widths were of particular interest. The theoretical analysis focuses on the stresses that can occur due to uneven drying shrinkage in the two-layered shotcrete. The models used include variation in shotcrete thickness and in time of waiting between turns of spraying, with or without watering of the shotcrete. Watering will delay the shrinkage but has no effect on the strength development. Long times of waiting without watering before spraying a second layer will increase the tensile stresses in the shotcrete. It is recommended that the further work is directed towards establishing guidelines for the design of future drain constructions with shotcrete. Different methods for repair and strengthening of cracked shotcreted drains must be developed, tested and evaluated.

  • 32.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Kompletterande provning av BAT Mk III filterspets2000Report (Other academic)
  • 33.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Laboratory testing of a new type of energy absorbing rock bolt2005In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 20, no 4, p. 291-300Article in journal (Refereed)
    Abstract [en]

    Energy absorbing rock bolts are used as part of rock support systems in underground constructions that are exposed to e.g., rock bursts and detonating explosives. A rock bolt capable of absorbing kinetic energy from these loads must be able to yield with the ground movements and also deform plastically over large distances, at high displacement rates. A new type of energy absorbing rock bolt has been developed and tested in laboratory. The bolt is without a casing and consists of a steel bar that has an inner ribbed-like anchorage section and an outer nut that transfers the load from the rock via a circular disc. When subjected to a dynamic load, the lengthening of the steel bar leads to a decrease in diameter whereby the adhesive bond between bar and grout is lost and the outer end of the bolt is free to yield. The rock bolt is given a very good protection from corrosion when fully grouted in cement. In a laboratory, rock bolts in concrete cylinders were subjected to free fall tests to achieve a loading velocity of 10 m/s. The tests demonstrated that the distribution of plastic strain along the length of a grouted rock bolt is not constant when dynamically loaded. The sections where plastic yielding was allowed were not fully utilized in any of the cases, opposite to that in previous static tests which show almost constant elongation of the bolts. The tests also verified that the load-carrying components of the bolt, the nut and the anchorage, are reliable when dynamically loaded. Elastic and plastic waves will start to propagate through the rock bolt as it is suddenly loaded, resulting in permanent deformation along a section of the bolt. This yield process is demonstrated through a combined graphical and numerical method.

  • 34.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Material properties for dynamic analysis of shotcrete on rock2002Report (Other academic)
  • 35.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Modelling of shotcrete on rock subjected to blast induced vibrations2002In: Nordic Concrete Research: Research projects 2002 / [ed] D.H. Bager, Oslo: The Nordic Concrete Federation , 2002, p. 48-50Conference paper (Refereed)
  • 36.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Numerical study of shotcrete as rock support on irregular tunnel surfaces2011In: Nordic Concrete Research: Research projects 2011 / [ed] D.H. Bager, Oslo: The Nordic Concrete Federation , 2011, p. 225-228Conference paper (Refereed)
  • 37.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Numeriska beräkningar med Markovkedjor i tillståndsutvecklingsmodeller för broelement2001Report (Other academic)
  • 38.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Provning av belysnings- och kontaktledningsstolpe2000Report (Other academic)
  • 39.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Recommendations for shotcrete on rock subjected to blasting vibrations, based on finite element dynamic analysis2005In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 57, no 3, p. 123-133Article in journal (Refereed)
    Abstract [en]

    Shotcrete is sprayed concrete applied pneumatically on, for example, a rock surface to prevent fallout of rock blocks and thereby securing the arch-shape of a tunnel profile. A finite element model, especially adapted to the dynamic analysis of shotcrete on rock that is subjected to vibrations from blasting, has been developed and tested. The model consists of spring and beam elements that are used to simulate the behaviour of an elastic concrete area, bound to a rock surface through adhesion. This facilitates the calculation of a two-dimensional displacement field, using mode superposition and Duhamel integral. The loads applied on the model are accelerations that give rise to inertia forces on the system. The accelerations are calculated from given weights of explosives, geometrical conditions and rock properties. The presented numerical examples demonstrate the response of shotcrete to vibrations, based on material data from an extensive literature survey. A series of calculations are compiled to give recommendations for how close to shotcrete blasting in rock can be allowed.

  • 40.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Shotcrete on rock exposed to large-scale blasting2007In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 59, no 9, p. 663-671Article in journal (Refereed)
    Abstract [en]

    Shotcrete sprayed on rock is vulnerable to stress waves from large-scale blasting in tunnels and mines. Shotcrete support in a Swedish underground mine is studied through numerical analysis and comparisons with previous results, measurements and observations in situ. A previously developed finite-element model that consists of beam and spring elements is used to calculate the response of shotcrete to vibrations from production blasts in the mine. The modelling approach is similar to that of a building during an earthquake, with accelerations measured in situ used as loads. The analysis shows that the calculated bond stresses exceed the strength in the interface between shotcrete and rock close to the blasts. The results show that it is possible to optimise the scheme of the blasting so that shotcrete is protected from damaging vibrations. Also recommended, for practical use, are minimum distances to large amounts of explosives given. This set of recommendations is a supplement to previously given guidelines valid for small amounts of explosives at short distances from shotcrete on rock.

  • 41.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Shrinkage cracking in sprayed concrete on soft drains in traffic tunnels2011In: Sprayed concrete: Modern use of wet mix sprayed concrete for underground support / [ed] T. Beck, O. Woldmo & S. Engen, Oslo: Norwegian Concrete Association , 2011, p. 27-38Conference paper (Refereed)
  • 42.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Structural behaviour of shotcrete on irregular hard rock surfaces2010In: Shotcrete: Elements of a system / [ed] E. Stefan Bernard, London: Taylor & Francis Group, 2010, p. 11-20Conference paper (Refereed)
  • 43.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Testing and modelling of an energy absorbing rock bolt2000In: Structures under shock and impact IV / [ed] N. Jones & C.A. Brebbia, Southampton: WIT Press, 2000, p. 417-426Conference paper (Refereed)
  • 44.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    The dynamic element method for analysis of frame and cable type structures2005In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 27, no 13, p. 1906-1915Article in journal (Refereed)
    Abstract [en]

    With the dynamic element method (DEM), results more accurate than with the conventional finite element method (FEM) are obtained with the same number of degrees of freedom. This is due to the introduction of shape functions of polynomial type, introducing frequency dependence into the mass matrix expressions. It is demonstrated how this affects free vibration analysis, including the solution of nonlinear eigenvalue problems. Various numerical techniques for solving these polynomial problems are discussed. The polynomial matrix formulations for stiffness and mass matrices are given for a beam, a bar and a cable element. Numerical examples demonstrate how the DEM can be implemented for modelling of frame type structures and its efficiency is compared to that of the conventional FEM

  • 45.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    The dynamic shear capacity of concrete structures2007In: Structural Concrete, ISSN 1464-4177, E-ISSN 1751-7648, Vol. 8, no 3, p. 147-154Article in journal (Refereed)
    Abstract [en]

    For shear capacity, the current design procedure used for concrete structures has been found to be inaccurate for some dynamic design load cases. Loads traditionally believed to be highly dynamic are only within the quasi-static range, but it is known that the combination of a high impact velocity and a hard, stiff impact will lead to shear failure. Load cases on concrete structures which can be classified as dynamic are, for example, those relating to weapons and hard impacts from steel objects. The characteristic of a dynamic load has great influence on the overall response and mode of failure of concrete structures. When structures which have been designed to fail in flexure under static loads fail in shear when loaded dynamically, the reason is probably the changing frequency content of the load. On the basis of a literature review, some important conclusions and recommendations are presented in this paper. The results will be used in further evaluation of existing design tools, aiming at accurate and reliable routines for the design of safe and cost-efficient concrete structures.

  • 46.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Towards practical guidelines for shotcrete on rock exposed to blasting2008In: Sprayed concrete: Modern use of wet mix sprayed concrete for underground support / [ed] K. Berg, C. Hauck & R. Kompen, Oslo: Norwegian Concrete Association , 2008, p. 7-16Conference paper (Refereed)
  • 47.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Tryck- och böjprovning av gängskarvade stålkärnepålar2001Report (Other academic)
  • 48.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Töjningsmätning vid tågpassage över Forsmobron2000Report (Other academic)
  • 49.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Töjningsmätning vid tågpassage över gamla Lidingöbron2003Report (Other academic)
  • 50.
    Ansell, Anders
    KTH, Superseded Departments, Structural Engineering.
    Töjningsmätning vintertid vid tågpassage över gamla Lidingöbron2004Report (Other academic)
123 1 - 50 of 128
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