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Gerald Müller - One of the best experts on this subject based on the ideXlab platform.
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Wave effects on Blockwork structures: numerical models
Journal of Hydraulic Research, 2010Co-Authors: Gerald Müller, G WoltersAbstract:Transient or fluctuating pressures, generated for example by a wave impact on a sea wall or a water jet plunging into a pool, have been shown to propagate into water filled cracks or fissures of structures and rock. Model studies revealed the characteristics of impact generated pressure pulses, which were observed to travel at very low speeds of 60–160 m/s and to attenuate, whereby higher frequencies were preferentially damped out. Other effects, such as reflection and dynamic amplification also indicated that the pulses constituted waves propagating through an elastic 2-phase medium consisting of water and a small amount of air. Based on these observations, concepts for a numerical model of pressure pulse propagation in water were developed and implemented. It was found that the numerical model approximates the physical model test results well, both in the linear and the non-linear range and including the transition from an initial steep pressure pulse to wave-like forms. The damping coefficient was foun...
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Analysis of Blockwork coastal structures
Coastal Engineering 2004, 2005Co-Authors: R Marth, Gerald Müller, G Wolters, A. Klavzar, W. Alsop, Tom BruceAbstract:Blockwork coastal structures often suffer damages from breaking wave action. The type of damage observed suggests that wave impact induced pressure propagation into water filled cracks and the subsequent build-up of internal bursting pressures is the probable cause. A series of model tests was conducted to investigate structural aspects of this problem. The mechanism of seaward block removal was demonstrated for the first time, the internal stress distribution inside of Blockwork structures was analysed and the effect of wall inclination on internal pressures investigated. It was found that the structural characteristics and the geometry of Blockwork walls affect their load resistance significantly.
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Field and large scale model tests of wave impact pressure propagation into cracks
Coastal Engineering 2004, 2005Co-Authors: G Wolters, Gerald Müller, G. N. Bullock, Charlotte Obhrai, Howell Peregrine, Henrik BredmoseAbstract:Within a large & full scale study on wave impact induced pressures on coastal structures (BWIMCOST) an investigation of impact pressure propagation into structure cracks and fissures was carried out. The mechanism, which is held responsible for localized damage to existing Blockwork breakwaters, had previously been verified in small scale model tests and a numerical model had been developed. The current investigation is the first which describes the effect at full scale, with recorded pressures of up to 199 kPa found within the cracks. The experimental results are related to their possible impact on coastal structural integrity.
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Wellendruckschlagbelastungen auf historische Küstenbauwerke (Wave impact loads on historical coastal structures)
2004Co-Authors: Gerald Müller, G WoltersAbstract:During the 19th and the early 20th Century, many coastal structures were built from block-work, i.e. large granite or concrete blocks. A large number of these structures are still in use. The continuous damage to Blockwork structures, as well as a possible increase in wave loading due to increased storm activities, mean that coastal engineers occasionally have to develop repair and maintenance strategies or conduct risk assessments. The available information about this type of structures is however limited, and the interaction between waves and structure is not fully un-derstood. A number of observed cases of damage indicate that wave impact induced pressure pul-ses may propagate into water or air filled joints or cracks, generating high pressure fluctuations in-side of the structure. These pressures then push individual blocks out of their position into the sea. Several cases of damage to existing breakwaters illustrate this mechanism. Model tests showed that wave impacts can generate pressure pulses which then propagate into water and air filled cracks, whereby the speed of propagation increases with increasing crack width. Large scale tests and field measurements gave additional information about the characteristics of the pressure pulses. A si-milar damage mechanism is thought to be responsible for damage to sea dykes. photoelastic and numerical models of Blockwork walls showed that the stress distribution inside of such a wall de-viates considerably from standard assumptions. The analysis of damage events and model tests showed that not only the stability but also the integrity of the structure should be considered for the risk-assessment of Blockwork structures
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The propagation of wave impact induced pressures into cracks and fissures
Geological Society London Engineering Geology Special Publications, 2004Co-Authors: G Wolters, Gerald MüllerAbstract:Abstract Rock cliffs and Blockwork coastal structures often suffer a peculiar type of damage, whereby individual blocks are removed out of their location towards the sea. The location of damage suggests that breaking wave action is the main cause. It has been suggested that wave impact pressures travel into the water or air filled cracks and fissures of the structures, leading to large pressures acting inside of the structure or cliff and to the removal of blocks. This assumption was only recently confirmed for water filled cracks with a series of model tests at Queen9s University Belfast. Real cracks in rock cliffs are, however, often only partially filled with water. A new experimental study, also conducted at Queen9s University Belfast, revealed that wave impact generated pressures can ravel into both fully or partially water filled cracks or joints. In partially submerged cracks the pressure pulse was found to travel in the air, propagating fast and with little attenuation deep into the structure, signifying that partially filled cracks are potentially more dangerous for the integrity of the structure than completely water filled cracks. These pressure pulses may be the main cause for the seaward removal of Blockwork in coastal engineering structures or of rock cliff material.
G Wolters - One of the best experts on this subject based on the ideXlab platform.
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Wave effects on Blockwork structures: numerical models
Journal of Hydraulic Research, 2010Co-Authors: Gerald Müller, G WoltersAbstract:Transient or fluctuating pressures, generated for example by a wave impact on a sea wall or a water jet plunging into a pool, have been shown to propagate into water filled cracks or fissures of structures and rock. Model studies revealed the characteristics of impact generated pressure pulses, which were observed to travel at very low speeds of 60–160 m/s and to attenuate, whereby higher frequencies were preferentially damped out. Other effects, such as reflection and dynamic amplification also indicated that the pulses constituted waves propagating through an elastic 2-phase medium consisting of water and a small amount of air. Based on these observations, concepts for a numerical model of pressure pulse propagation in water were developed and implemented. It was found that the numerical model approximates the physical model test results well, both in the linear and the non-linear range and including the transition from an initial steep pressure pulse to wave-like forms. The damping coefficient was foun...
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Analysis of Blockwork coastal structures
Coastal Engineering 2004, 2005Co-Authors: R Marth, Gerald Müller, G Wolters, A. Klavzar, W. Alsop, Tom BruceAbstract:Blockwork coastal structures often suffer damages from breaking wave action. The type of damage observed suggests that wave impact induced pressure propagation into water filled cracks and the subsequent build-up of internal bursting pressures is the probable cause. A series of model tests was conducted to investigate structural aspects of this problem. The mechanism of seaward block removal was demonstrated for the first time, the internal stress distribution inside of Blockwork structures was analysed and the effect of wall inclination on internal pressures investigated. It was found that the structural characteristics and the geometry of Blockwork walls affect their load resistance significantly.
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Field and large scale model tests of wave impact pressure propagation into cracks
Coastal Engineering 2004, 2005Co-Authors: G Wolters, Gerald Müller, G. N. Bullock, Charlotte Obhrai, Howell Peregrine, Henrik BredmoseAbstract:Within a large & full scale study on wave impact induced pressures on coastal structures (BWIMCOST) an investigation of impact pressure propagation into structure cracks and fissures was carried out. The mechanism, which is held responsible for localized damage to existing Blockwork breakwaters, had previously been verified in small scale model tests and a numerical model had been developed. The current investigation is the first which describes the effect at full scale, with recorded pressures of up to 199 kPa found within the cracks. The experimental results are related to their possible impact on coastal structural integrity.
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Damages of Blockwork Coastal Structures due to Internal Wave Impact Induced Pressures
WIT Transactions on the Built Environment, 2005Co-Authors: R Marth, G Muller, G WoltersAbstract:During the 19th and the early 20th centuries, many coastal structures (breakwaters and sea walls) were built from Blockwork made up of natural stone or concrete blocks. Some Blockwork coastal structures that are still in use suffer recurrent damages from wave action. It is generally assumed that wave impact pressures enter water filled cracks and generate pressures acting inside of the structure, causing the seaward removal of blocks. This removal of a single block by wave impacts will disrupt the integrity of the Blockwork, potentially leading to progressive failure of the structure. In recent years, several physical model tests have been conducted at the Queen’s University of Belfast and the Technical University of Berlin in order to analyze the damages of Blockwork coastal structures due to internal wave impact induced pressures. In this paper an overview of the most important results of these model tests are given. In order to assess a structures vulnerability to pressure inside cracks, important aspects concerning crack dimensions, ventilation of cracks and the inclination of the sea face of a Blockwork structure are presented. The results should be considered as a basis for the definition of improved maintenance and repair strategies.
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Wellendruckschlagbelastungen auf historische Küstenbauwerke (Wave impact loads on historical coastal structures)
2004Co-Authors: Gerald Müller, G WoltersAbstract:During the 19th and the early 20th Century, many coastal structures were built from block-work, i.e. large granite or concrete blocks. A large number of these structures are still in use. The continuous damage to Blockwork structures, as well as a possible increase in wave loading due to increased storm activities, mean that coastal engineers occasionally have to develop repair and maintenance strategies or conduct risk assessments. The available information about this type of structures is however limited, and the interaction between waves and structure is not fully un-derstood. A number of observed cases of damage indicate that wave impact induced pressure pul-ses may propagate into water or air filled joints or cracks, generating high pressure fluctuations in-side of the structure. These pressures then push individual blocks out of their position into the sea. Several cases of damage to existing breakwaters illustrate this mechanism. Model tests showed that wave impacts can generate pressure pulses which then propagate into water and air filled cracks, whereby the speed of propagation increases with increasing crack width. Large scale tests and field measurements gave additional information about the characteristics of the pressure pulses. A si-milar damage mechanism is thought to be responsible for damage to sea dykes. photoelastic and numerical models of Blockwork walls showed that the stress distribution inside of such a wall de-viates considerably from standard assumptions. The analysis of damage events and model tests showed that not only the stability but also the integrity of the structure should be considered for the risk-assessment of Blockwork structures
An Fried - One of the best experts on this subject based on the ideXlab platform.
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Flexural strength of low density Blockwork
Construction and Building Materials, 2012Co-Authors: Ash Ahmed, An FriedAbstract:Abstract The characteristic flexural strength of low density aircrete wallettes (2.8 and 2 N/mm 2 ) incorporating both conventional and thin layer mortar is verified. The wallettes are tested in accordance with British and European standards. The flexural strength of aircrete wallettes is derived from the strength of small specimens tested to destruction under four-point loading. The strengths of the wallettes are high with impressive repeatability with the maximum strength being reached for thin layer wallettes within 7 days curing time. In general the strengths of both conventional mortar and thin layer mortar wallettes compare favourably to values reported in the standards.
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Flexural behaviour of thin joint concrete Blockwork: Experimental results
Construction and Building Materials, 2011Co-Authors: O.j. Kanyeto, An FriedAbstract:Abstract This paper presents a report of an experimental investigation of the behaviour of thin joint concrete Blockwork in flexure. Two concrete block types and one thin layer mortar type were used to build wallettes and wall panels, which were then tested to failure. Graphs plotted from the test data revealed a combination of linear and non-linear relationships between the load and displacement. The investigation also revealed that the transverse lateral load capacity of masonry built using solid dense concrete blocks with thin joint mortar is considerably higher (up to 3.5 times) than that of similar Blockwork constructed using conventional mortar. Both the mortar properties and the constituents of the parent material forming the block appear to alter the joint strength resulting in enhancements to flexural tensile bond strength. The results also indicate that when thin joint technology is employed, in conjunction with solid dense concrete blocks, the masonry behaves more as a concrete plate than conventional Blockwork.
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THIN LAYER CONCRETE Blockwork IN FLEXURE
2011Co-Authors: An Fried, Kanyeto OAbstract:The adhesion between polymer modified mortars and concrete block masonry was examined to determine any enhancement to the bond. A test programme was undertaken to evaluate this trend. Two concrete block types and one thin layer mortar type were used to build wall panels which were then tested to failure. The results showed that both the mortar properties and the constituents of the parent material forming the block alter the joint strength, resulting in enhancements to flexural tensile bond strength. The transverse lateral load capacity of masonry built using solid dense concrete blocks with thin joint mortar is up to 3.5 times that of similar Blockwork constructed using conventional mortar. This means that when thin joint technology is used, in conjunction with solid dense concrete blocks, the masonry behaves more as a concrete plate than conventional Blockwork. Graphs plotted from the test data reveal a bi-linear relationship between the load and displacement, from initial application of the load until failure
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Micro-chemical/structural characterisation of thin layer masonry: A correlation with engineering performance
'Elsevier BV', 2009Co-Authors: Marrocchino E, An Fried, Koulouris A, Vaccaro CAbstract:Masonry is one of the most ancient methods of construction. The types of blocks and mortars used over the centuries have developed considerably with the introduction of various types of materials. A multidisciplinary investigative approach, involving both engineering and material sciences expertise, will be necessary for a complete evaluation of the behaviour of masonry elements. From the engineering point of view, the transverse lateral load capacity of masonry built using solid dense concrete blocks with thin layer mortar, is up to four times that of similar Blockwork constructed using conventional mortar. Both the mortar and block constituent material's properties alter the joint strength with enhancements to tensile flexural bond strength. When thin layer masonry technology (TLMT) is employed, in conjunction with solid dense concrete blocks, the masonry behaves more as a concrete plate than conventional Blockwork. The engineering properties of masonry elements are not only related to the engineering properties of the blocks and mortars used, but also to how the bond at their interface interacts. Testing on two different block types, and one mortar was undertaken to verify this hypothesis. Engineering testing was carried out to determine the flexural strength of the material. This approach was combined with petrographical examination of the two different types of block and the bond zone using micro-analytical techniques, (OTLM, SEM and EMPA). Observations using SEM and EMPA techniques revealed that these differences depend on the composition of both blocks and mortar, and in particular they are related to the petrographical composition of the parent material of the block. These aspects affect how the bond layer forms and influence the mechanical properties of the joint. (C) 2007 Elsevier Ltd. All rights reserved
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Micro-chemical/structural characterisation of thin layer masonry: A correlation with engineering performance
Construction and Building Materials, 2008Co-Authors: E Marrocchino, An Fried, A. Koulouris, Carmela VaccaroAbstract:Abstract Masonry is one of the most ancient methods of construction. The types of blocks and mortars used over the centuries have developed considerably with the introduction of various types of materials. A multidisciplinary investigative approach, involving both engineering and material sciences expertise, will be necessary for a complete evaluation of the behaviour of masonry elements. From the engineering point of view, the transverse lateral load capacity of masonry built using solid dense concrete blocks with thin layer mortar, is up to four times that of similar Blockwork constructed using conventional mortar. Both the mortar and block constituent material’s properties alter the joint strength with enhancements to tensile flexural bond strength. When thin layer masonry technology (TLMT) is employed, in conjunction with solid dense concrete blocks, the masonry behaves more as a concrete plate than conventional Blockwork. The engineering properties of masonry elements are not only related to the engineering properties of the blocks and mortars used, but also to how the bond at their interface interacts. Testing on two different block types, and one mortar was undertaken to verify this hypothesis. Engineering testing was carried out to determine the flexural strength of the material. This approach was combined with petrographical examination of the two different types of block and the bond zone using micro-analytical techniques, (OTLM, SEM and EMPA). Observations using SEM and EMPA techniques revealed that these differences depend on the composition of both blocks and mortar, and in particular they are related to the petrographical composition of the parent material of the block. These aspects affect how the bond layer forms and influence the mechanical properties of the joint.
Tom Bruce - One of the best experts on this subject based on the ideXlab platform.
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Orphan breakwaters – what protection is given when they collapse?
Proceedings of the Institution of Civil Engineers - Maritime Engineering, 2018Co-Authors: William Allsop, Adrian Pearson, Tom BruceAbstract:Around the UK, many coastal harbours have reduced in importance and/or lost the original sources of income against which to defray maintenance or refurbishment. Their breakwaters may however still protect harbour-side properties against wave overtopping, and thus flooding. This paper presents results from an exploratory study to identify how Blockwork breakwaters common in many smaller UK coastal harbours may collapse due to storm action, and in this paper, how much wave protection is given by collapsed breakwaters. The companion paper by Pearson & Allsop (2017) describes initial work to estimate the failure of Blockwork walls, and presents results of wall collapse tests.
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Analysis of Blockwork coastal structures
Coastal Engineering 2004, 2005Co-Authors: R Marth, Gerald Müller, G Wolters, A. Klavzar, W. Alsop, Tom BruceAbstract:Blockwork coastal structures often suffer damages from breaking wave action. The type of damage observed suggests that wave impact induced pressure propagation into water filled cracks and the subsequent build-up of internal bursting pressures is the probable cause. A series of model tests was conducted to investigate structural aspects of this problem. The mechanism of seaward block removal was demonstrated for the first time, the internal stress distribution inside of Blockwork structures was analysed and the effect of wall inclination on internal pressures investigated. It was found that the structural characteristics and the geometry of Blockwork walls affect their load resistance significantly.
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Wave effects on Blockwork structures: model tests
Journal of Hydraulic Research, 2002Co-Authors: Gerald Müller, Tom Bruce, Mark J. Cooker, W. Allsop, P. Hull, Leopoldo FrancoAbstract:Up to the middle of this century many coastal structures were built from Blockwork, using either natural stone blocks or concrete blocks. Those Blockwork structures subjected to breaking wave impacts often show a particular damage type, whereby individual blocks are shifted out of their position and moved into the sea. Engineers have suspected for a long time that wave impact pressures can travel into the water filled cracks and joints of such structures, building up pressures inside of the structure and thus destroying the structure from within. In order to verify the damage mechanism, and to investigate the characteristics of impact induced pressure pulses, model tests on the propagation of wave impact pressures into water filled cracks were conducted. It was found that impact generated pressure pulses can enter water filled cracks and that they exhibit wave-like characteristics such as finite propagation speed, reflection, superposition and attenuation. Changes in cross section were found not to affect...
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How safe are Blockwork breakwaters and seawalls against wave attack
Coastal Engineering 2000, 2001Co-Authors: Tom Bruce, William Allsop, Mark J. Cooker, Leopoldo Franco, Gerald MüllerAbstract:Coastal structures have been constructed of Blockwork since ancient times. Although there exists a very large number of more modem Blockwork seawalls and breakwaters, some of which are of very great commercial importance, there is little or no guidance available for the monitoring of the condition of such structures, nor for their maintenance and repair. This paper begins by presenting an overview of a range of Blockwork seawalls and breakwaters. Evidence of damage is presented, and loading / damage initiation mechanisms are reviewed. The possibility of new methods of stability analysis based upon block revetment experience is noted. It is concluded that progress will rest upon both the further analysis of historical records, and progress in methods of assessing the internal state of Blockwork seawalls and breakwaters.
N. W. H. Allsop - One of the best experts on this subject based on the ideXlab platform.
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Reservoir dams: Wave conditions, wave overtopping and slab protection
1996Co-Authors: A.j. Yarde, L.s. Banyard, N. W. H. AllsopAbstract:This report describes research to simplify and consolidate the prediction of wave action in reservoirs; to calculate wave induced discharges on embankments; and to extend work on Blockwork and slabbing protection for dam faces presented by Herbert et.al (1995) in the companion report SR 345. The report should be used by engineers involved in the inspection, analysis, design and construction of block revetmetments and slabbing protection against wave attack of faces of embankment dams or similar revetments.
