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Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this phenomenon has been extensively reported for linear coastal defences like seawalls. However, no referenced study has treated the case of cylindrical structures typical of these applications to a similar extent. The aim of the present study is to define an empirical expression that portrays the relative overtopping rate over a vertical cylinder including a variety of bull-nose type mitigation structures to reduce the overtopping rate in the same fashion as for the linear structures characteristic of shoreline defences. Hydrodynamic interaction was studied by means of an experimentally validated numerical model applied to a non-impulsive regular wave regime and the results were compared with the case of a plain cylinder to evaluate the expected improvement in the overtopping performance. Four different types of parapets were added to the crest of the base cylinder, with different parapet height and horizontal extension, to see the influence of the geometry on the mitigation efficiency. Computational results confirmed the effectivity of the proposed solution in the overtopping reduction, though the singularity of each parapet geometry did not lead to an outstanding difference between the analysed options. Consequently, the resulting overtopping decrease in all the proposed geometries could be modelled by a unique specific Weibull-type function of the relative freeboard, which governed the phenomenon, showing a net reduction in comparison with the cylinder without the geometric modifications. In addition, the relationship between the reduced relative overtopping rate and the mean flow thickness over the vertical cylinder crest was studied as an alternative methodology to assess the potential damage caused by overtopping in real structures without complex volumetric measurements. The collection of computational results was fitted to a useful function, allowing for the definition of the overtopping discharge once the mean flow thickness was known. [ABSTRACT FROM AUTHOR]

Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this phenomenon has been extensively reported for linear coastal defences like seawalls. However, no referenced study has treated the case of cylindrical structures typical of these applications to a similar extent. The aim of the present study is to define an empirical expression that portrays the relative overtopping rate over a vertical cylinder including a variety of bull-nose type mitigation structures to reduce the overtopping rate in the same fashion as for the linear structures characteristic of shoreline defences. Hydrodynamic interaction was studied by means of an experimentally validated numerical model applied to a non-impulsive regular wave regime and the results were compared with the case of a plain cylinder to evaluate the expected improvement in the overtopping performance. Four different types of parapets were added to the crest of the base cylinder, with different parapet height and horizontal extension, to see the influence of the geometry on the mitigation efficiency. Computational results confirmed the effectivity of the proposed solution in the overtopping reduction, though the singularity of each parapet geometry did not lead to an outstanding difference between the analysed options. Consequently, the resulting overtopping decrease in all the proposed geometries could be modelled by a unique specific Weibull-type function of the relative freeboard, which governed the phenomenon, showing a net reduction in comparison with the cylinder without the geometric modifications. In addition, the relationship between the reduced relative overtopping rate and the mean flow thickness over the vertical cylinder crest was studied as an alternative methodology to assess the potential damage caused by overtopping in real structures without complex volumetric measurements. The collection of computational results was fitted to a useful function, allowing for the definition of the overtopping discharge once the mean flow thickness was known.

This paper experimentally investigates how parapets with varying heights can alter the flow pattern around a large aspect-ratio low-sloped gable roof building. We examine the benefits and challenges of existing methods and utilize an open-jet wind test section, to accurately simulate real-world atmospheric boundary layer conditions. A model of a low-rise building was fitted with solid parapets of varying heights and tested in a comparative study to understand their impact on roof pressures. The study compares the standard approach to the experimental results and suggests improvements to wind zones and pressure coefficients. The parapet of fourteen percent of the building height is the most efficient at reducing mean, peak, and area-averaged wind loads compared to other sizes. However, the standard provisions underestimate roof pressures for components and cladding design. [ABSTRACT FROM AUTHOR]

This study examines the effectiveness of parapets in preventing overtopping failures of small-scale homogeneous reservoir dams under seismic loads. In this study, a parapet covered the entire width of the dam crest and was designed to ensure its weight is transmitted to the dam crest. The test included four modes: initial mode, first seepage, seismic, and second seepage. The results show that without parapets the crack length and width expand significantly in the dam crest during the seismic mode, and the effect was large in the second seepage mode. The crack depth increased by 11.3–24 times during the seismic mode and expanded up to 73.3% of the dam height in the longitudinal direction along the axis of the crack formed in the dam crest during the second seepage mode. These findings suggest that the earthquake weakened the dam body, making it vulnerable to penetration. In contrast, the parapet structure effectively suppressed most of the tensile cracks by increasing the constraint force. Additionally, no crack expansion or tearing occurred during the second seepage mode post-earthquake, indicating improved seismic performance and suppression of seepage deformation. [ABSTRACT FROM AUTHOR]

A wind tunnel test was conducted to investigate the effects of parapets on the aerodynamic wind loads of roof-mounted solar arrays. The distribution of the mean wind pressure coefficient and the extreme wind pressure coefficient in the solar arrays were discussed in detail, and the results were compared with some national standards. Results show that the mean and extreme values of the wind pressure coefficient are larger at oblique wind angles. The presence of the parapet can reduce the mean and extreme area-averaged net pressure coefficients in some areas of the solar arrays, and both the most critical positive and negative shape factors reduce at the corner and outer rows while less change occurs at the inner zones. The experimental shape factors are much smaller compared to the values calculated by the standards. The guidelines for the design of wind pressure on roof-mounted solar arrays are very conservative, and more research is needed to make the standards applicable and complete. [ABSTRACT FROM AUTHOR]

The paper describes innovative parapet solution based on special shaped blocks made form textile-reinforced concrete - TRC. The blocks are designed for a placement at the parapet of building with a flat roof. The solution is appropriate for buildings with precast-concrete bearing structure by following the principle of precast technology (short construction time, minimal technological pauses). However, presented parapet TRC blocks can be used for energy efficient buildings as well in combination with thick layers of thermal insulation. The technical solution was registered as utility model no. CZ27642(U1).

Abstract The aerodynamic performance of a roof depends significantly on its shape and size, among other factors. For instance, large roofs of industrial low-rise buildings may behave differently compared to those of residential homes. The main objective of this study is to experimentally investigate how perimeter solid parapets can alter the flow pattern around a low-rise building with a large aspect ratio of width/height of about 7.6, the case of industrial buildings/shopping centers. Solid parapets of varied sizes are added to the roof and tested in an open-jet simulator in a comparative study to understand their impact on roof pressure coefficients. Roof pressures were measured in the laboratory for cases with and without parapets under different wind direction angles (representative of straight-line winds under open terrain conditions). The results show that using a parapet can alter wind pressures on large roofs. Parapets can modify the flow pattern around buildings and change the mean and peak pressures. The mean pressure pattern shows a reduction in the length of the separation bubble due to the parapet. The parapet of 14% of the building’s roof height is the most efficient at reducing mean and peak pressures compared to other parapet heights.

This study examines the effectiveness of parapets in preventing overtopping failures of small-scale homogeneous reservoir dams under seismic loads. In this study, a parapet covered the entire width of the dam crest and was designed to ensure its weight is transmitted to the dam crest. The test included four modes: initial mode, first seepage, seismic, and second seepage. The results show that without parapets the crack length and width expand significantly in the dam crest during the seismic mode, and the effect was large in the second seepage mode. The crack depth increased by 11.3–24 times during the seismic mode and expanded up to 73.3% of the dam height in the longitudinal direction along the axis of the crack formed in the dam crest during the second seepage mode. These findings suggest that the earthquake weakened the dam body, making it vulnerable to penetration. In contrast, the parapet structure effectively suppressed most of the tensile cracks by increasing the constraint force. Additionally, no crack expansion or tearing occurred during the second seepage mode post-earthquake, indicating improved seismic performance and suppression of seepage deformation.

The paper describes innovative parapet solution based on special shaped blocks made form textilereinforced concrete - TRC. The blocks are designed for a placement at the parapet of building with a flat roof. The solution is appropriate for buildings with precast-concrete bearing structure by following the principle of precast technology (short construction time, minimal technological pauses). However, presented parapet TRC blocks can be used for energy efficient buildings as well in combination with thick layers of thermal insulation. The technical solution was registered as utility model no. CZ27642(U1). [ABSTRACT FROM AUTHOR]

This paper will discuss the variations in wave loads on a vertical seawall structure due to the addition of parapets. A 1:8 model scale experiments on a wall with parapets will be carried out. The models will be tested for monochromatic waves that have different breaking characteristics that are identified based on the amount of air entrapped during breaking. These include slightly-breaking waves (SBW), breaking waves with small air trap (BWSAT), and breaking waves with large air trap (BWLAT). The relative reduction in impact pressure will be used to quantify parapet performance. This paper revealed that with the addition of a parapet, wave force increases compared to a vertical wall (VW) until incident wave height [(Hi < 0.125 m)]. However, with further increases in wave height (H), the wave force reduces for large (LP) and medium parapets (MP) compared with a small parapet (SP). The exit angle of the parapet plays a vital role to decrease the wave loads for higher H; the extent of the decrease is dictated by the movement of deflected water. Based on the tested parapets and wave characteristics, an LP (45°) attracted less load on the overall structure compared with other parapet types for higher Hi (Hi > 0.125 m). [ABSTRACT FROM AUTHOR]

The installation of guardrails around a roof perimeter is an efficient way to protect construction workers against falls from heights, provided the guardrails are strong enough to arrest a fall. A guardrail's strength relies heavily on its fastening to the roof parapets, and an improper fastening could lead to unsafe guardrails. This article investigates the in situ strength of temporary steel guardrails installed on the flat roof parapets of two existing buildings, respectively built in 2008 and 2013. Thirty-six strength tests were conducted on three different guardrails and four different parapets, considering different methods of fastening the vertical posts to the parapets and varying the fastening hardware. The results show that some guardrails are not easily installed on smaller roof parapets, which could lead to improper installation on some work sites. Fastening using only one plane of the parapet often resulted in guardrails failing before reaching the regulatory strength requirement. Fastening using two planes of the parapets gave satisfactory results in comparison, and that should be the preferred fastening method to guarantee workers' safety. [ABSTRACT FROM AUTHOR]

Summary: The results of an investigation of the probability of earthquake damage to nonstructural unreinforced masonry (URM) components are presented. The components include parapets, chimneys, and out‐of‐plane loaded facades typical of low‐rise pre‐1940 construction in Australia and New Zealand. The study is based on a street survey of component geometry, in situ data on material strength, and simplified mechanical models. Uncertainties in capacity and demand were quantified based on, respectively, stochastic and deterministic approaches. The damage probabilities were compared with relevant guidelines and empirical damage data from three earthquakes. The study established a link between the qualitative damage states reported in existing guidelines and the quantitative URM component damage states. While some median damage state thresholds correlated well with the data from the guidelines, a larger dispersion value was found in the current study due to the large variations in component properties. Comparisons with empirical data suggest that the developed fragility data provide a realistic estimate of nonstructural component damage that occurred in similar buildings, with a reasonable level of conservatism. The outcome is useful in rapid assessment of the seismic risks due to nonstructural component collapse in URM precincts. [ABSTRACT FROM AUTHOR]

In the calculation of the snow load on the roof with parapets, standards of Japan, America, and Europe have given full consideration to the erosion effect on the snow load of the fully exposed roof caused by wind field, the movement of snow induced by wind, the supplementation of upstream snow to snow heaped up around downstream obstruction. In addition, factors such as the indoor heating and the combined effect of rain and snow are introduced to realize an accurate estimation of snow load on building roofs. By contrast, the Chinese code only considers the influence of the parapet height. Therefore, based on the measured snow distribution on an actual parapet roof on ages and the influencing factors in foreign codes introduced above, the snow distribution characteristics on the parapet roof were analyzed. The results show that: more snow is blown downstream towards the parapet; the peak snow depth close to the downstream parapet is proportional lo the upstream roof width, and with an increasing wind velocity, the drifting effect is enhanced; the upstream roof width and the ground snow load have a great influence on the peak snow depth at the parapet, and the influence of wind velocity depends on the ground snow load; the larger the ground snow load is, the greater influence the wind velocity has ; the ratio of the snowdrift length to the parapet height is around 3. 75, and it is suggested to adopt a value of 4.0 in Chinese code. [ABSTRACT FROM AUTHOR]

The influence of parapets on crown walls of mound breakwaters on wave forces has not been extensively analyzed in the literature. In this study, numerical experiments were carried out using the open-source platform OpenFOAM® to evaluate the influence of nine crown wall geometries with and without parapets. The OpenFOAM® model was validated with laboratory experiments. Dimensionless horizontal forces and overturning moments due to horizontal forces increase when there is a parapet. Dimensionless up-lift forces provide similar results, regardless of the existence of a parapet. Crown walls with parapets increase the horizontal wave forces and overturning moments due to horizontal wave forces by a factor of two.

This paper explores the use of a cyber-physical systems (CPS) “loop-in-the-model” approach to optimally design the envelope and structural system of low-rise buildings subject to wind loads. Both the components and cladding (C&C) and the main wind force resisting system (MWFRS) are considered through multi-objective optimization. The CPS approach combines the physical accuracy of wind tunnel testing and efficiency of numerical optimization algorithms to obtain an optimal design. The approach is autonomous: experiments are executed in a boundary layer wind tunnel (BLWT), sensor feedback is monitored and analyzed by a computer, and optimization algorithms dictate physical changes to the structural model in the BLWT through actuators. To explore a CPS approach to multi-objective optimization, a low-rise building with a parapet wall of variable height is considered. In the BLWT, servo-motors are used to adjust the parapet to a particular height. Parapet walls alter the location of the roof corner vortices, reducing suction loads on the windward facing roof corners and edges, a C&C design load. At the same time, parapet walls increase the surface area of the building, leading to an increase in demand on the MWFRS. A combination of non-stochastic and stochastic optimization algorithms were implemented to minimize the magnitude of suction and positive pressures on the roof of a low-rise building model, followed by stochastic multi-objective optimization to simultaneously minimize the magnitude of suction pressures and base shear. Experiments were conducted at the University of Florida Experimental Facility (UFEF) of the National Science Foundation’s (NSF) Natural Hazard Engineering Research Infrastructure (NHERI) program.

This paper explores the use of a cyber-physical systems (CPS) approach to optimize the design of rigid, low-rise structures subjected to wind loading, with the intent of producing a foundational method to study more complex structures through future research. The CPS approach combines the accuracy of physical wind tunnel testing with the ability to efficiently explore a search space using numerical optimization algorithms. The approach is fully automated, with experiments executed in a boundary layer wind tunnel (BLWT), sensor feedback monitored by a computer, and actuators used to bring about physical changes to a mechatronic structural model. Because the model is undergoing physical change as it approaches the optimal solution, this approach is given the name “loop-in-the-model” optimization. Proof-of-concept was demonstrated for a low-rise structure with a parapet wall of variable height. Parapet walls alter the location of the roof corner vortices, reducing suction loads on the windward facing roof corners and edges and setting up an interesting optimal design problem. In the BLWT, the parapet height was adjusted using servo-motors to achieve a particular design. Experiments were conducted at the University of Florida Experimental Facility (UFEF) of the National Science Foundation's (NSF) Natural Hazard Engineering Research Infrastructure (NHERI) program. [ABSTRACT FROM AUTHOR]

In order to study the destructive mechanism of superstandard storm surge caused by typhoon, we studied the overtopping rate and overtopping flow of the sloped seadike with parapet under superstandard tide and wave through physical experiments. The empirical formulas between the relative crest ultra-height, relative wall-top ultra-height, relative parapet height and the overtopping rate were established based on experimental data of regular waves. In addition, the appropriate dimensionless parameter was proposed for the research on the relation between overtopping flow thickness and overtopping rate. The proper relative position parameter was also defined to study the overtopping flow thickness on the dike crest. [ABSTRACT FROM AUTHOR]

Numerical modelling of wave interaction with rock-armoured rubble mound breakwaters has been performed to study wave overtopping. The influences of the slope angle, a berm in the seaward slope, a protruding crest wall, a recurved parapet, and the wave steepness have been studied using a validated CFD model (OpenFOAM). The numerical modelling confirms trends that have been observed in physical model tests while the validity of earlier developed guidelines has been examined outside the ranges of the physical model tests on which the guidelines are based. The numerical model results confirm that wave overtopping at rubble mound breakwaters depends on the wave steepness, that the influence of a berm is affected by the wave steepness, and that an earlier developed influence factor to account for the effects of a protruding crest wall can be applied to even larger crest walls than the tested crest walls on which the guidelines are based. The results indicate that the influence of the applied core material of the berm on the discharges is very limited. The numerical model also indicates that applying a recurved parapet on a crest wall of a rubble mound breakwater only has an effect for very small overtopping discharges. The numerical model results show that wave overtopping at rubble mound breakwaters strongly depends on the slope angle. Since this effect is so large that it cannot be neglected, while present guidelines for non-breaking waves do not include the effect of the slope angle, modified guidelines have been proposed. The observed effects of the slope on wave overtopping discharges at rubble mound structures still need to be verified based on physical model tests. • Effects of slope angle, crest wall, recurved parapet, and berm have been studied using OpenFOAM. • The modelling confirms trends observed in physical model tests, even outside ranges of the tests. • Applying a recurved parapet on a crest wall only has an effect for very small overtopping discharges. • Wave overtopping at rubble mound breakwaters strongly depends on the slope angle. • A method to account for the effects of the slope angle on wave overtopping has been proposed. [ABSTRACT FROM AUTHOR]

Over the time period 2002 - 2010 many of the bridges crossing the Bega Channel in Timisoara city were rehabilitated. The analyzed bridge, the Traian Bridge, is approximately 100 years old and is realized out of reinforced concrete as Gerber solution. The works had different complexity degrees depending on the degradation level of the crossing structure and of its age. The bridge assures a gauge which includes a combined traffic, vehicles and tram. This particularity required specific rehabilitation solutions. In order to bring the crossing structure to an appropriate viability level, structural rehabilitation works and an anticorrosive protection of the concrete elements were executed, but also new solutions for the execution of the footway and the tram railway were adopted. The paper analysis the behaviour in exploitation of the rehabilitated elements and of the adopted technical solutions for the above mentioned structure. [ABSTRACT FROM AUTHOR]

Fragility curves have proved to be an efficient tool for the seismic vulnerability assessment of buildings made of stone masonry such as those located in historic districts of Eastern Canadian cities. However, most studies do not take into consideration the case of collapse in the out-of-plane direction. This failure mode may be critical for elements such as chimneys, firewalls, and front walls. This study focuses on the assessment of seismic vulnerability of stone masonry buildings sensitive to out-ofplane failure. A model of out-of-plane capacity showing the degree of damage in terms of displacements was developed as well as a calculation method for displacements in the out-of-plane direction taking into account the filter effect of the building in plane direction. Fragility curves derived are used to estimate the probability of damage in different seismic scenarios. [ABSTRACT FROM AUTHOR]

The formula to quantify the average wave overtopping discharge of non-breaking waves over a dike according to the TAW-report (2002) and included in the EurOtop Manual (2007), only contains the influence of the roughness of the dike slope and the obliqueness of the waves on wave overtopping. Unlike the formula for breaking waves, the reductive effect of a storm wall or a berm is not included in this formula. Over 1000 scale model tests with non-breaking waves on a wide variety of structures have been carried out for this paper. The crest of the dike slope has been modified with a storm wall, a storm wall and parapet, a stilling wave basin, a promenade, and a combination of a promenade and storm wall with or without parapet. For all these modified crests, a reduction factor has been deducted to include in the wave overtopping formula of non-breaking waves. This paper presents the results of all investigated measures to reduce wave overtopping over a smooth dike slope in an easy and logical way to serve as a guidance for use by designers. An example is given where all presented measures are compared to each other, and to other well-known structures. [ABSTRACT FROM AUTHOR]