Bar Spacing Research Articles

Novel Screen System Improvement Methodology for Flood and Diffuse Pollution Control: Demonstration via a Case Study

Screen systems are often neglected in practice. This can lead to local flooding, pollution of receiving watercourses, blockages of channels by debris, and safety problems for children playing. The aim of this case study is therefore to protect below-ground channels and people, prevent flooding, improve water quality, and save personnel costs through a new screen system maintenance, repair, and upgrade methodology. The results show that repairing or enlarging the screens optimizes their functionality and reduces the risk of flooding. A particular focus is on increasing the screen dimension from one- and two-dimensional to three-dimensional screens. The new variable safety priority and the bar spacing increase with the passage area. Screens at large discharges should therefore be prioritized. Cleaning sand traps reduces the risk of pipe blockages and improves the water quality of receiving waters. Fine particles often have too high nutrient and oxygen demand values. The installation of pre-screens can increase the efficiency of the main screens. Optimization of travel routes for maintenance teams can be achieved by better planning maintenance routes. Adapting and maintaining screens to climate change by applying the novel prioritization method is likely to be successful. This should include prioritized inspections, repairs, and adjustments to screen structures.

A Case Study on Using the Concrete Cover Block in Steel Reinforcement Bar: Ghorahi Dang, Nepal

Cover block is one of the basic component on building structure like slab, column, beam, foundation. It is a multi- functionary engineering material. In maximum construction sites, bricks, stones, steel bars are used instead of cover block. This brings a lots of depraved consequences on building structures like lack of well spacing between surface and reinforcement bars, unbalance position of steel bars, reduce the lifespan of building and corrosion. Here, the main function of cover block is to reinforce the building structure by avoiding the corrosion on steel bar or avoiding the moisture with the steel bar, providing the resistive property, distributing an uniform load and managing space. In this way, the cover block is attached in a reinforcement bar in order to reinforce a building structure. When cover block was applied in a building structure, it made a building more durable as well as more attractive by maintaining the shape. This observation suggests that the use of cover block can contribute in strengthening a building structure and maintaining a position and space of a reinforcement bars as well as a structure. Key Words: Concrete cover block, Reinforcement bar, Potential failure of structure, Space maintaining, Corrosion activity.

Numerical and experimental analysis of structural optimization and flow resistance effect of safety barrier based on a pump device

The safety barrier is often positioned at the entrance of the inlet passage in large and medium-sized low-lift pump stations, to ensure the safety of people and animals. To elucidate the blocking effect of the safety barrier and its influence mechanism on the internal flow of the inlet passage, numerical simulation combined with the physical model test were employed to investigate the impact of the cross-section and bar spacing of the safety barrier on the head loss, and the impact mechanism was clarified. The results showed that the optimal cross-section form of the safety barrier was found to be circular from the standpoint of head loss. When the blockage ratio of the safety barrier exceeds 0.3; prompt clearance of the blockage is recommended.

Behavior of zero cement reinforced concrete slabs under monotonic and impact loads: Experimental and numerical investigations

Currently, there is a shift toward the use of low-carbon construction materials to reduce global carbon dioxide emissions. Zero-cement concrete (ZCC) synthesized from alkaline activated fly ash (FA) is a promising alternative for Portland cement in the construction industry to reduce global CO2 emissions, increase the consumption of waste materials, and save energy. A substantial amount of research on the impact load behavior of ordinary reinforced concrete (RC) structural components has been conducted. However, investigations on the behavior of zero cement concrete (ZCC) slabs under impact loads have not been reported. In this work, twenty simply supported two-way flat reinforced fly ash ZCC slabs (including two normal concrete (NC) slabs as reference samples) were tested under monotonic and impact loads. The test samples were categorized into eight groups on the basis of various parameters. Twelve RC slabs (1 NC and 11 ZCCs) were prepared for repeated impact tests, and eight slabs (1 NC and 7 ZCCs) were prepared for monotonic loading tests. Various parameters were investigated herein, including slab thickness, bar spacing, molarity concentration of alkali activators, hammer height, and hammer mass. Nonlinear finite element models were also developed and validated by using ABAQUS software for additional parametric study purposes. The results revealed that the behavior of ZCC slabs is approximately similar to that of NC slabs. The results also revealed that an increase in the ZCC slab thickness, reinforcement ratio, hammer height, and hammer mass has a noticeable effect on the dynamic response of the slab. However, increasing the molarity concentration of alkali activators has clearly a slight influence on the impact loadtime history. When the slab thickness was increased or the bar spacing was reduced, the static and impact energy absorption capacities were increased by 1.5 and 2.0 times, respectively. For impact load tests, the damage degree, penetration, and cracking pattern at failure were approximately typical for all test samples at the first hit except when the hammer mass and impact height were changed. For the samples subjected to monotonic loading, a flexural response was observed for almost all the slab samples at the first loading stage, and cracking started from the midpoint of the slab and propagated toward the slab edges; ultimately, punching shear failure was observed.

Separation efficiency of a wastewater bar screen based on a 3D computational fluid dynamics modeling

The wastewater screening process is a crucial step in the majority of wastewater treatment plants, frequently using mechanical bar screens as the first filtration step to remove heavy debris from the wastewater flow. In the present study, two 3D geometries of bar screens with different screen openings were presented to investigate the effect of the variation in screen spacing of bars on the separation efficiency of debris. Based on the Ansys Fluent CFD code within the Eulerian-Lagrangian approach, the particle trajectories were tracked, and the retention efficiency of these two bar screens was evaluated. The results show that a higher particle separation efficiency is favored for small bar spacing and coarse particle sizes. Actually, despite the impact of bar spacing on the separation efficiency of particles, the adequate choice of this parameter is related to particle properties and the fluid flow inlet velocity. These parameters also have a great influence on the separation efficiency of bar screens. The study can help for more structural improvements in the shape of the screening media, which leads to enhanced performance of wastewater screening facilities.

Research on the Right of Women in the Bar Space

In China, the current behavior of going to bars shows a trend of degendering, and women also begin to enter bars to consume. In recent years, many female-friendly or female-only bars have emerged. As the emerging consumers of bar-related industries, female groups are growing, putting forward their needs to society, in order to let society hear their voices and give women equal rights and space to men. Based on Chinas current bar culture and gender-related social background and phenomena, this paper adopts the participatory observation method and semi-structured interview method to analyze the observed phenomena and interview contents, and finds that women are subjected to many explicit or implicit unequal treatment in bars, and further discusses the main causes of gender discrimination in bars. Through the analysis of the unequal treatment faced by women in bars, it is concluded that the cause of the discrimination against women is the deep-rooted pressure of male power in China, and the social root of this pressure is the inequality of gender rights and the shackles of traditional Chinese concepts. This paper finally attempts to discuss the solution of this inequality: female self-consciousness against traditional ideas.

Experimental Study on Bond and Force Transmission Properties of Steel Reinforcement in Non-Contact Lap Splice Encased in Calcium Sulphoaluminate Cement-Based Micro Steel Fiber Concrete

CSMSFC (Calcium Sulphoaluminate Cement-based Micro Steel Fiber Concrete) possesses the advantages of early strength, high strength, exceptional toughness, minimal shrinkage, and excellent bond performance with bars. When applied to NLSB (Non-contact Lap Splice of Bars) in prefabricated structures, CSMSFC enhances mechanical performance while preventing shrinkage cracking and reducing seismic damage. Additionally, it shortens construction periods for prefabricated structures and achieves a comprehensive improvement in seismic performance and construction efficiency. However, there is a lack of systematic testing of factors influencing the bond strength between CSMSFC and NLSB and the effect of CSMSFC on the force transfer performance between NLSB. Therefore, the axial tensile tests of NLSB were conducted on 51 non-contact lapping specimens to investigate the bond properties and force transfer mechanism between lapping bars and CSMSFC. The effects of lapping length, volume fraction of steel fibers, spacing of bars, and concrete cover thickness on the lapping characteristics were examined, and the comparison with OPMSFC (Ordinary Portland Cement-based Micro Steel Fiber Concrete) was also considered. The experimental results demonstrate that the bond strength between bars and CSMSFC increased by 36.8%, 42.3%, and 43.3% respectively, with volume fractions of steel fiber at 1.5%, 3%, and 4.5% compared to the absence of steel fiber. The bonding effect between CSMSFC and bars is similar to that of OPMSFC and bars. The bond strength between CSMSFC and the bars improved by 4.3% and 6.6% with the increases of the spacing of bars from 0 to 20 mm and the concrete cover thickness from 10 to 30 mm. Conversely, with the increases of the lapping length from 50 mm to 100 mm, 200 mm, and 300 mm, the bond strength decreased by 46.8%, 72.2%, and 82.0%, respectively. Finally, based on the force transmission mechanism of the non-contact lapping bars, a calculation model is proposed for determining the lapping length while considering the reinforcing effect of steel fiber “stirrups.” A formula is derived from the model to calculate the minimum lapping length of HRB400 bars in CSMSFC, considering the volume fraction of steel fibers, which can assist in designing the minimum lap length of NLSB in practical applications.

Integrated learning model for water intake capacity of Tyrolean weirs under supercritical flow

ABSTRACT Tyrolean weir can be used as an effective solution to address floatation and sediment deposition in runoff hydropower stations. To improve the efficiency and accuracy of calculating this structure's water intake capacity. The integrated learning algorithm random forest (RF), the firefly algorithm (FA), and the exponential distribution algorithm (EDO) are utilized to develop the algorithm that can be used for the Tyrolean weir Cd and (qw)i/(qw)T prediction models. Sobol's method and SHAP theory are introduced to analyze the above parameters quantitatively and qualitatively. It is shown that EDO-RF is the optimal prediction model for the Tyrolean weir's discharge coefficient and the Froude number Fr has the greatest influence on the Cd prediction results; when Fr < 30, the greater the negative influence of Fr on the model prediction results. When Fr > 30, the greater the positive influence of Fr on the model prediction results. FA-RF is the optimal prediction model for the Tyrolean weir water capture capacity (qw)i/(qw)T, with the ratio of bar length to bar spacing L/e being the largest; When L/e < 20, the greater the negative influence of L/e on the model prediction results. When L/e > 20, the more significant the positive impact of L/e on the model prediction results.

Sorting grid usage to reduce the catch of undersized narrow‐clawed crayfish (Pontastacus leptodactylus Eschscholtz, 1823) in fyke net fisheries

AbstractSustainability of natural stocks of crayfish is critical because of their economic and ecological importance. Crayfish (Pontastacus leptodactylus), one of the most important species in Turkish inland fisheries, has been facing serious threats recently. One threat the species faces is high landed bycatch of undersized crayfish because of selective fishing gear, such as fyke nets. We estimated size‐selectivity of sorting grids with various bar spacings for crayfish to reduce bycatch. Six bar spacings (15.0, 17.5, 20.0, 22.5, 25.0, and 30.0 mm) were tested alongside commercial crayfish fyke nets. Mean selectivity (L50) (±95% CI) was 6.90 (6.63–6.99) cm for 15.0 mm bar spacing, 7.52 (7.16–8.02) cm for 17.5 mm, 8.52 (8.32–8.71) cm for 20.0 mm, 9.70 (9.28–9.90) cm for 22.5, 10.75 (10.34–11.17) cm for 25.0 mm, 11.80 (11.31–12.24) cm for 30.0 mm, and 8.79 (8.05–9.29) cm for commercial fyke nets. The proportion of undersized specimens caught be reduced from 32.27% for commercial fyke nets to as low as 2.46% by using sorting grids. The codend of 22.5 mm bar spacing was more selective, with significantly lower discard rates, and more effective for individuals above the minimum conservation reference size than commercial fyke nets.

Morphometric characteristics of Antarctic krill (Euphausia superba) and finfish bycatch in the krill fishery in the waters of South Orkney Islands during the 2022/23 fishing season

Determination of bar spacing of bycatch reduction devices (BRDs) should consider species composition and morphometric characteristics (particularly width) of target species krill and bycatch. This study conducted a scientific investigation of the finfish bycatch in the Antarctic krill (Euphausia superba) trawl fishery by the fishing vessel SHEN LAN in the waters surrounding the South Orkney Islands from December 24, 2022, to February 20, 2023. The results show that scientific observers sampled 676 individuals of finfish bycatch. Of these, 665 were identified to species (17 species from 8 families), while the remaining 11 specimen were juveniles of the Nototheniidae family that could not be identified to the species level. IRI (index of relative importance) calculations showed three dominant (IRI value greater than 1,000) finfish bycatch species (Champsocephalus gunnari, Pseudochaenichthys georgianus, and C. aceratus from the Channichthyidae family) and four important (IRI value between 1,000 and 100) finfish bycatch species (Electrona carlsbergi and Gymnoscopelus nicholsi from the Myctophidae family, Gobionotothen gibberifrons from the Nototheniidae family, and Notolepis coatsi from the Paralepididae family). Our study provides morphometric data (particularly body width) that is crucial to model the potential for bycatch reduction by use of bycatch reduction devices (BRDs) and to determine the appropriate candidate bar spacings for BRD sea trials. Predictions suggest that a 10 mm (the maximum body width of krill) bar spacing releases a significant amount of dominant and important bycatch species (93.94% of C. gunnari, 53.99% of P. georgianus, 76.25% of C. aceratus, and 100% of G. gibberifrons). Reduced fishing pressure would reduce the risks to dominant and important bycatch species to make the krill fishery sustainable. We recommend that future BRD sea trials should initially test a 10 mm bar spacing. If marked loss of krill is observed, wider spacings (e.g. 15 mm) must be tested.

Distinct genetic origins of eumelanin levels and barring patterns in cichlid fishes.

Pigment patterns are incredibly diverse across vertebrates and are shaped by multiple selective pressures from predator avoidance to mate choice. A common pattern across fishes, but for which we know little about the underlying mechanisms, is repeated melanic vertical bars. To understand the genetic factors that modify the level or pattern of vertical barring, we generated a genetic cross of 322 F2 hybrids between two cichlid species with distinct barring patterns, Aulonocara koningsi and Metriaclima mbenjii. We identify 48 significant quantitative trait loci that underlie a series of seven phenotypes related to the relative pigmentation intensity, and four traits related to patterning of the vertical bars. We find that genomic regions that generate variation in the level of eumelanin produced are largely independent of those that control the spacing of vertical bars. Candidate genes within these intervals include novel genes and those newly-associated with vertical bars, which could affect melanophore survival, fate decisions, pigment biosynthesis, and pigment distribution. Together, this work provides insights into the regulation of pigment diversity, with direct implications for an animal's fitness and the speciation process.

Development of an overlaid concrete median barrier: Numerical studies and full-scale field tests

This study aims to develop an overlaid CMB(Concrete Median Barrier) with a containment level of SB5 (230 kJ of impact severity) based on a series of numerical simulations and full-scale field tests. The 810-mm CMB (CMB810) currently in service on roads, should be overlaid up to height of 1370 mm (CMB1370) with containment level of SB5 to prevent vehicles from traveling over it. From a series of numerical simulation, the effects of dowel/longitudinal bars on structural adequacy and occupant risk were quantitatively assessed in order to develop the CMB1370. Numerical analyses indicate that decreasing the spacing of dowel bars and the proximity of longitudinal bars from the top of the CMB1370 can significantly lessen the volume loss incurred during vehicle-to-barrier collisions. The numerically proposed CMB1370 underwent full-scale field tests in compliance with three evaluation criteria: (1) structural adequacy, (2) occupant risk, (3) vehicle's post-impact trajectory. The full-scale field test results demonstrated that the CMB1370 effectively contained and redirected the vehicle without any instance of damages, penetration or overriding. The measured deformation of CMB1370 by several LVDTs was within acceptable limits for use on the road. Previous full-scale field tests, the primary focus was on the structural adequacy of the CMB and the resulting damage it sustained. However, these findings provide new insights into the behavior and rehabilitation of the CMB, as well as the damage sustained at impact. Moreover, no significantly fragmented debris larger than 2.0 kg was observed from the barrier. Thus, the proposed CMB1370 meets all the requirements specified in the crash test guidelines in Korea.

Study on seismic performance of reinforced concrete shear wall with diagonally distributed reinforcement

AbstractReinforced concrete shear walls in multistory buildings often undergo the combined action of vertical and horizontal loads, with their failure primarily attributed to localized damage of the concrete at the bottom of edge elements, leading to premature loss of wall functionality. To enhance the performance of shear walls, this study explores the optimization of shear wall design from the perspective of the stress path within the wall, introducing a diagonally distributed reinforcements in shear walls (referred to as DDR shear walls). To investigate the seismic performance of DDR shear walls, we consider the effects of axial compression ratio, the inclination angle of distributed reinforcing bars, reinforcing bar spacing, and shear span ratio. We design 27 shear wall models with various parameter combinations and employ ABAQUS finite element analysis software to simulate the seismic performance. The simulation results reveal that the inclined distribution of reinforcing bars significantly enhances the seismic performance of shear walls. To achieve optimal structural performance, the inclination angle of reinforcing bars should be adjusted for different floor levels, with higher floors requiring a greater angle and lower floors a smaller one. Additionally, increasing the reinforcing bar spacing and altering the shear span ratio will have varying degrees of impact on the seismic performance of shear walls, necessitating rational design adjustments based on specific circumstances. Furthermore, the application of DDR shear walls in prefabricated construction can be considered to optimize construction processes.

Experimental study on bond performance of staggered lap rebars in ultra-high performance concrete (UHPC)

Ultra-high performance concrete (UHPC) has received extensive attention worldwide due to its ultra-high mechanical properties and durability. The bond performance between steel bars and UHPC is crucial for the design of Reinforced-UHPC structures. To study the bond performance of overlapping steel bars in UHPC, a total of 13 groups of 39 pull-out tests were conducted with overlapping lengths, cover thickness, steel bar diameter, and clear spacing of steel bars as influencing variables in this study. According to the results, when the lap length increased from 4 times the bar diameter (4db) to 5db and 6db, the maximum bond strength decreased by 10% and 20%, respectively. Moreover, with an increase in the cover thickness from 25 mm to 35 mm and 45 mm, the maximum bond strength increased by 6% and 14%, while the residual bond strength increased by 15% and 48%, respectively. When the diameter of the reinforcing bars increased from 16 mm to 20 mm and 25 mm, the ultimate load capacity increased by 50% and 70%, respectively, while the bond stress decreased by 16% and 27%. Additionally, the bond strength showed less sensitivity to the clear spacing of steel bars, with a decrease of 3% and 10% in bond strength when the clear spacing increased from 1.5db to 2db and 3db, respectively. The ductility of the specimen decreases when the bar diameter or the clear distance between bars is too large. A theoretical calculation formula for splitting bond strength was established, which yielded accurate results. Furthermore, a bond-slip model was fitted based on the test results, providing reference for finite element analysis of steel bar-UHPC structures.

Downstream passage performance of silver eel at an angled rack: effects of behavior and morphology

The European eel is critically endangered due to heavy impact of anthropogenic factors, such as habitat fragmentation, overexploitation and climate change. During downstream migration, silver eels may encounter hydropower plants, which often result in delay or mortality from impingement on trash-racks or turbine passage. These problems can be mitigated with downstream passage solutions, such as angled racks that guide downstream-migrating eels to safe passage routes. The importance of bar spacing and phenotypic diversity for passage performance is, however, largely unknown. In this study, we investigated how morphological parameters (body mass, eye and fin indices) and behavioral score (open field test) influenced passage rate at an experimental intake equipped with a bypass and angled racks with either 15 or 30 mm bar spacing. Both racks were efficient in guiding eels into a bypass. There was a strong positive effect of body mass and a weak positive effect of open field test score on passage rate. Other factors such as eye and fin indices played a minor role. These results demonstrate the performance of angled racks with bypasses and form a useful starting point for further research regarding the relationships between individual variation in behavior, morphology and passage solutions for silver eels.

Splice Length of Large Diameter Reinforcing Bars in Ultra-High-Performance Concrete

Potential exists for construction time savings through replacement of cast-in-place substructure columns, piers, or both, with prefabricated bridge elements and systems. Cast-in-place substructure construction requires forming, placing steel, and pouring concrete at the construction site. Using prefabricated elements would decrease the extent of work required at the site and potentially reduce concrete curing time. This research furthers the effort to use ultra-high-performance concrete (UHPC) as a joining material for prefabricated bridge substructure elements. UHPC has a high early strength, requires less development or splice length than conventional concrete, and has been used previously for accelerated construction projects, such as bridge deck replacement with precast units. UHPC also has a discontinuous pore structure that reduces liquid ingress, significantly enhancing durability compared to conventional concrete. Although UHPC has been researched extensively, previous research for reinforcing bar splice and development lengths has focused on #9 and smaller diameter bars. Typically, larger diameter bars are used for substructures. This research determined the required splice lengths for large diameter steel deformed reinforcing bars embedded in UHPC based on 127 individual tests. Three primary variables were included in the testing matrix: bar size, bar spacing, and concrete cover. To achieve at least 75 kips per square inch (ksi) (517 MPa) reinforcing bar stress in UHPC with an early age strength of 14 ksi (97 MPa), the required embedment length ranges from 8 to 13 times the bar diameter and the corresponding splice length varies from 6 to 11 times the bar diameter, depending on the bar size and concrete cover.

Quantitative Expression of the Modified Bragg's Law for Bragg resonances of water waves excited by five types of artificial bars

For Class I Bragg resonance excited by five types of finite periodic array of widely spaced bars (rectangular, parabolic, rectified cosinoidal, trapezoidal, and triangular bars), the average phase velocity between any two adjacent bars in each type of bar field has been specifically calculated by employing a mathematical transformation, and therefore, the excitation condition of Class I Bragg resonance excited by each bar field is clarified and the modified Bragg's law established by Xie and Liu becomes a quantitative form. On one hand, if the incident surface wavelength, L, is fixed in advance, then according to the excitation condition, we can directly obtain the critical bar spacing, d, at which Class I Bragg resonance occurs. On the other hand, if the bar spacing, d, is fixed, then according to the excitation condition, we can use an iteration scheme to find out the critical surface wavelength, L, at which Class I Bragg resonance will be excited. In comparison with existing experimental, numerical, and analytical results of Bragg resonance excited by the five types of bar fields, it is shown that the modified Bragg's law is much more accurate than the Bragg's law, and the phenomenon of phase downshift can be well explained. In the linear long-wave limit, owing to the simple dispersion relation, the modified Bragg's law becomes an explicit expression and coincides with Liu's approximate law very well, although the former is a straight line segment while the latter is a curved line segment. Finally, it is shown that the phase downshift of Bragg resonance becomes more significant as the cross-sectional area of bars increases.

The Effect of Air Pressure and Nozzle Distance on the Quality of Water-Based Painting Using a Gravity-Feed Spray Gun

Environmental influences can cause corrosion or damage to materials, which is why paint coating is used to protect them. Some of the factors that affect the quality of the paint are technical, such as setting the air pressure and spray gun nozzle spacing. The experimental research aims to determine how air pressures of 1.5, 2, and 2.5 bar and nozzle spacings of 10–15–20 cm affect the gloss and thickness of the water-based paint layer. A gravity-feed spray gun was used for this purpose. The luster test method uses an AMTAST AMN60 glossmeter with the ASTM D523-08 standard, and the thickness test uses a coating thickness gauge with the ASTM E 376-96 standard. The air pressure and the distance of the spray gun nozzle affect the gloss and thickness of the paint layer. Parameter 2 bar/15 cm yielded the highest gloss of 92.77 GU, while parameter 2.5 bar/10 cm resulted in the highest coating thickness of 0.26 mm.

Cyclic behavior of UHPC corner beam-column joints under bi-directional bending

Design codes contain special provisions for anchorage lengths of flexural reinforcement and amount of transverse reinforcement in beam-column joints, to safeguard against joint failure and possible structural collapse. However, those stipulations could lead to congested joints with construction problems such as segregation. This study leverages experimental testing of eight corner beam-column joints under constant axial and cyclic bi-directional bending loads. In addition to being one of few on corner joints under a complex and practical loading, the study’s main aim is to evaluate the effectiveness of ultra-high-performance concrete (UHPC) as a joint fill in lieu of normal strength concrete (NSC). Brittle failure, either by pure shear or shear combined with yielding of beam reinforcement occurred in all NSC joints and varied in shape and intensity depending on the column depth-to-beam longitudinal bar diameter (hc ⁄db) ratio and spacing of transverse beam/column reinforcement. Ductile failure characterized by the yielding of beam reinforcement and plastic hinge at the beam-joint interface occurred in all UHPC joints and was independent of the two aforementioned variables. The application of UHPC in the joint region resulted in increasing the joint ultimate strength by 27.6–54.8%, energy dissipation by 24–163%, and stiffness by 20 to 50%, compared to NSC joints. Such results were obtained when no transverse reinforcement is used in the joint, and only half transverse reinforcement is used in the beam/column members, and with hc ⁄db relaxed to 38% of the code recommended ratio, highlighting the advantages of UHPC joints. Predictions of ACI-ASCE 352R code were found to be overly unconservative and in need of future improvement.

Bragg reflection of linear shallow-water waves by an array of widely spaced trapezoidal bars on a fringing reef flat

A closed-form solution to the linear shallow-water wave equation for wave reflection by a finite periodic array of widely spaced trapezoidal bars on a fringing reef flat is presented. It is shown that, when the total number, height, or top width of the trapezoidal bars increases, the strength of the Bragg resonance increases but the downward shift of the resonance phase becomes more pronounced. When the width of the reef face increases or when the reef face changes from a concave profile to a convex profile, the strength of the Bragg resonance decreases and the downward shift of the resonance phase also becomes more pronounced. Especially, it is found that the location of trapezoidal bars plays an important role in the strength and occurrence condition of the Bragg resonant reflection. Finally, the optimal collocation of the location and width of trapezoidal bars is investigated. Considering both construction cost and reflecting capacity, the relative width is recommended to be within 0.4≤wb/d≤0.6 and the distance from the reef edge to trapezoidal bars is suggested to be equal to the spacing of trapezoidal bars.