Oblique Weir vs Plain and Labyrinth Side Weirs

Discuss about the Hydraulic Design of Weir and Traffic Bridge Design.

This study evaluates the advantages of oblique weir over plain and labyrinth side weirs. One of the maina advantages of oblique side weirs is that they have a greater effective length for overflowing, which diverts more discharge at the same opening of the channel. Their flow properties and weir height is also more. The researchers carried out over 200 test measurements and the results showed that the efficincy of oblque weirs is 2.33 times greater than that of other types of side weirs (plain and labyrnth) (Borghei & Parvaneh, 2011). They also presented flow and geometrical variables as a function of discharge coefficient, which can be used by desgn engineers when designing weirs for different structures, such as traffic bridge.

In this study, experimental studies were carried out to determine hydraulic flow characteristics of rectangular-crested weirs with different upstream angles. The effect of changing upstream angle was invested. The upstream slopes evaluated were 90, 75, 60, 45, 30, 22.5 and 10 degrees. The parameters determined were flow separation zone, approach velocity profile, discharge coefficient and flow surface pattern. The resarchers introduced a new corection factor for estimating discharge coefficient and a water surface mathematical relationhip. The results obtained from th study showed that an increase in upstream slope reduces discharge coefficient value. The highest and minimum  discharge coefficient values wwere recorded when upstream slope was 10 and 90 degrees respectively (Goodarzi, 2012).

In this study, researchers appled support vector machine (SVM) method to predict flow head loss on cascade weirs. The performance of this method was compared with other computing techniques by developing a multilayer perception neural network. The resuts showed that SVM is a reliable technique of predicting head loss of weirs and it is more accurate than the other techniques (Haghiabi, et al., 2017).

Even though side weirs are widely used to divert flows in channels, rivers, reservoirs and sewers, their hydraulic behavior is very dfficult and complex to predict using standard methods. This study presented a new design method of predicting side wers’ hydraulic behavior. The method was developed from vrious experimental studies carried out by the researchers. They came up with a numerical model that can predict hydruic behavior of the side weir. The new procedure presents results in form of simplified equations and graphs, making it easier for design engineers to establish hydraulic behaviors more easily and accurately (Rahimi, 2012).

Hydraulic Flow Characteristics of Rectangular-Crested Weirs

Side weirs are very common and useful devices in measuring flow of water. To design a more efficint weir, discharge coefficient has to be accuratey measured so as to create a precise flow model. In this study, researchers used two different machine learning techniques to predict discharge coefficient of rectagular and trapezoidal side weirs. The methods used were SVM (support vector machines) and GEP (gebe expression programming). The models’ perfoemance was evaluated using correlation coefficient, Nash-Sutcliffe index (NS) and mean normalize erro (MNE). The results obtained showed that SVM is a more accurate method that GEP (Roushangar, et al., 2016). Based on these results, designers and engineers should conider using modern technological tools such as artificial intelligence and machine learning to develop more accurate flow models of weirs. 

This study involved evaluation of open channel flow measurment of traverse weirs with finite crest length, sloping crest and downstream or upstream ramps. Broad-crested weir equation was used to develop correltions with discharge coefficient being used as the basis. Dowstream and upstream length scales were also introduced to investigate the effects of downstream and upstream ramps. The results obtained showed that an increase in downstream slope causes an increase in discharge coefficient while an increase in upstream slope causes a decrease in discharge coefficient (Azimi, et al., 2013). Design engineers can use this information to establish the most appropriate downstream or upstream slope for the weir.

In this study, researchers evauated flow of water over rectangular sharp-crested side weirs with different heights and widths. An acoustic Doppler velocity (ADV) meter was used to obtain 3D velocity of water flowing over the crest and within the side weir’s viscinity. The velocity distribution results showed that longitudinal velocity was highest close to the beginning of the side weir while velocity in spill flow’s direction was maximum at the weir’s end. The results also showed that discharge increased along the weir’s crest and it also increased with decrease in weir width. The researcher also developed an expression for estimating angle of spilling jet (Bagheri & Heidarpour, 2012).    

One of the simples ways of improving side weir’s hydraulic performance is by incorporating guide vanes. This study investigated flow charcateristics of rectangular sharp-crested weirs installed with guide vanes. The researchers also determined flow behavior in the absence of guide vanes for comaprison reasons. 3D velocity distribution data showed that guide vanes significantly reduced longitudinal velocity and at the same time increased downward velocity magnitude. Additionally, lateral velocity was increased by the guide vanes thus causing more discharge. Last but not least, the guide vanes reduced spilling jet’s angle (Samiee, et al., 2016). 

Prediction of Flow Head Loss on Cascade Weirs by Support Vector Machine

This paper provides a solution to overcome one of the major problems that engineers face when designing rectangular side ways. The problem is that the designed length of these weirs is usually long making it quite difficult for engineer to design efficient rectangular weirs. To overcome this challenge, researchers in this paper reduces the length of weir by making the side weir to have a trapezoidal geometry. For this to be attained, discharge coefficient had to be determined. Discharge coefficient was calculated by conducting various experimetal tests for trapezoidal side weirs. The results showed that indeed the length of weirs can be reduced using trapezodal side weirs, which still attains th desired height of water (Nezami, et al., 2015).

This study involved invetigating the impact of using an oblique weir on flow discharge. The direction of flow was examined at five different angles (30, 45, 60, 75 ad 90 degrees). Numerical values of discharge were determined using ordinary differential equations while flow depth was determined using Eurler’s method. The results obtained showed that it is posisble to develop a numerical correlation between water depth, water surface profile and flow discharge by installing an oblique weir along the water stream. Therefore a side weir angle can be used to increase flow discharge. The researchers found that maximum discharge was recorded when the angle of flow direction was at 30 degrees while minimum discharge occurred at 90 degrees (Mohammed, 2015).

Establishng stage-discharge relationship of a weir flow is one of the major problems when designing a hydraulic structure. In this study, researchers applied Buckinghm’s theorem of dimensional analysis to determine simple and precise formulas for obtaining rating curves of different types of weirs: rectangular weir, elliptical weir, parabolic weir, triangular weir, circular weir, labyrinth weir and W-weir. The flow over different weirs was investigated. For rectangular weirs, which are the most common, it was found that the main parameters affecting flow over them are crest shape, obliquity, flow direction and approach channel width. The reserachers presented stage-discharge relationships of the different types of weirs and discussed their application limits. The results obtained in this paper can be used by designers and engineers to simply weir design procedure (Bijankhan & Ferro, 2017).    

Sharp-crsted weirs are one of the simplest and commonly used system of over-flow spillway for determining flow rate in hydraulic structures. In this paper, cubic and quadratic equations were used to fit experimental lower and upper thrust sheet profiles of rectangualr sharp-crested weirs respectively. Additionally, free-vortex theory was used for simulatio of flow over the weirs and their discharge coefficient determined.  Sharp-crested weirs’ physical models with different heights and widths were used. The findings obtained in this study, including proposed methods, were in agreement with experimental findings. The experimental data obatined also showed that the results presented by the equations were reasonable (Bagheri, 2009). Therefore it is possible to formulate and customize equations so as to determine various desgn parameters of different types of weirs.

New Design Method for Predicting Side Weirs’ Hydraulic Behavior

This study involved developing formulae for rehabilitated weirs, using El-Fayoum rehablitated weirs. The researchers took measurements (before and after the weirs were rehabilitated), analyzed them and used them to calibrate a mathemtical model called SOBEK. The field data collected and analyzed was verified using the SOBEK model them these data measurements were used to develop the formulae. The formulae developed can be used by engineers to design the required modfication of existing weirs to accommodate the increased discharge of the river (El-Belasy, 2013).

This article presented the main principle guiding the design of long-span steel bridges in Chna made from asphalt surfacing system. The researchers cassified the deck pavements’ major distresses into structure-dependent and material-dependent groups. Th findings showed that the strength and stability of long-spanned steel bridges not only depends on reliable structures and materials but also on the wide-ranging understanding of the behaviour of the system, combination of material design and use of technology with strict system for quality control (Chen, et al., 2017). 

This article used  3-D finite element model to evaluate how pavement design parameters affect deck pavements behaviour of orthotropic steel bridge when subjected to traffic loading. The study was conducted by investgating the behaviour of four different types of materials: polymer concrete, mastic asphalt concrete, polymer-modified stone mastic asphalt concrete and epoxy asphalt concrete. Sensitvity analysis showed that with improved interface bonding between the pavement and deck plate, resistance to bottom-up fatiguue cracking increased significantly. Also, pavement temperature increase reuslted to a significant increase in critical tensile strain (Kim, et al., 2014).  

The researchers in this study performed an ideal design of a steel arch brdige so as to determine the effect of high performance steel for brdiges (HBS) and compared it with that of conventional rolled steel (SM520). Information obtained from the behaviors of these materials was used to determine appropriate sections of different members of the bridge then brdige members that experienced relatively high stress in relation to yield stress, including cross beam, main frame and arch rib, were selected. A genetic algorithm was applied with an aiim of reducing materia cost, with limit deflection and stress being applied as constraints. The results showed that HSB has higher allowable stress and that its cross sectional area of the entire structure and material cost of members decreased more than that of SM520 (Park, et al., 2016). 

This study involved investigation hon ow live loads affect simply supportd bridges by considering various parameters, including weight, venhicle occupancy ratio, longitudinal following space, axle space and speed of the vehicle. Different numerical models were used to determine the effect of the mentioned parameters. The researchers used Monte Carlo method to simulate random traffic flow. The study showed that the average live load for a simply supported bridge subjected to random traffic flow is less than the allowable design load based on American Association of State Highway and Transportation Officials (AASHTO), but t is more than the allowable design load based on BS5400, and it is 0.82 times greater than the Highway-I standard load (Liu, et al., 2016).

Predicting Discharge Coefficient of Trapezoidal Side Weirs Using Machine Learning Techniques

This study involved using a new method to determine structural parameters of a bridge and a vehicle’s dyamic axle loads from limited response measurements. Most of the available methods for identifying vehicle axle loads uses a model with identified system paramaters. The efficiency and accuracy of the proposed method was conducted using various numerical analyses. The final results obtained showed that it is posisble to accurately predict the bridge dynamic response using structural parameters and histories of identified axle load (Feng, et al., 2015).  

The objectiv of this study was establish the effect of traffic flow direction on bridge dynaic response. The researchers analyzed the statistical characterstics and critical traffic flow parameters of the bridge over a period of 24 hours, and used the findings to develop a random traffic flow simulation (RTF) program. They then presented a dynamic analysis module under random traffic flow entailing multi-lanes, arbitrary number of vehicles and random direction of traffic flow. The results showed that direction of traffic flow has very minimal influence on the dynamic response of the bridge. The mean responses are determined by the loads of moving vehicle. Also, it was found that the varying components tend to increase as wind speed increases (Wang, et al., 2014).

This paper emphasizes on the importance of proper bridge maintenance and management so as to ensure efficiency, durability and safety of the bridge. The researchers designed a comprehensive bridge maintenance and management intelligence aided decision support system (BMMS). They provided the structure of the system, function module, decision-making module and evaluation module. Therefore while designing a bridge, it is also very important to develop a comprehensive manintenance management plan (Yin, et al., 2011).

References

Azimi, A., Rajaratnam, N. & Zhu, D., 2013. Discharge charcateristics of weirs of finite crest length with upstream and downstream ramps. Journal of Irrigation and Drainage Engineering, 139(1).

Bagheri, S., 2009. Flow over rectangular sharp-crested weirs. Irrigation Science, 28(2), pp. 173-179.

Bagheri, S. & Heidarpour, M., 2012. Characteristics of Flow over Rectangular Sharp-Crested Side Weirs. Journal of Irrigation and Drainage Engineering, 138(6), pp. 541-547.

Bijankhan, M. & Ferro, V., 2017. Dimensional analysis and stage-discharge relationship for weirs: a review. Journal of Agricultural , 48(1).

Borghei, S. & Parvaneh, A., 2011. Discharge characteristics of a modified oblique side weir in subcritical flow. Flow Measurement and Instrumentation, 22(5), pp. 370-376.

Chen, X., Huang, W., Qian, Z. & Zhang, L., 2017. Design principle of deck pavements for long-span steel bridges with heavy-duty traffic in China. Road Materials and Pavement Design, 18(3), pp. 226-239.

El-Belasy, A., 2013. Developing formulae for combined weir and orifice (case study: El-Fayoum weirs). Alexandria Engineering Journal, 52(4), pp. 763-768.

Feng, D., Sun, H. & Feng, M., 2015. Simultaneous idntification of bridge structural parameters and vehicle loads. Computers & Structures, Volume 157, pp. 76-88.

Goodarzi, E. F. J. &. S. N., 2012. Flow Characteristics of Rectangular Broad-Crested Weirs with Sloped Upstream Face. Journal of Hydrology and Hydromechanics, 60(2), pp. 87-100.

Haghiabi, A., Azamathulla, H. & Parsaie, A., 2017. Prediction of head loss on cascade weir using ANN and SVM. ISH Journal of Hydraulic Engineering, 23(1), pp. 102-110.

Kim, T., Baek, J., Lee, H. & Lee, S., 2014. Effect of pavement design parameters on the behaviour of orthotropic steel bridge deck pavements under traffic loading. International Journal of Pavement Engineering, 15(5), pp. 471-482.

Liu, Y., Zhang, H., Deng, Y. & Jiang, N., 2016. Effect of live load on simply supported brdiges undera random traffic flow based on weigh-in-motion data. Advances in Structural Engineering, 20(5).

Mohammed, A., 2015. Numerical analysis of flow over side weir. Journal of King Saud University – Engineering Sciences, 27(1), pp. 37-42.

Nezami, F., Farsadizadeh, D. & Nekooie, M., 2015. Discharge coefficient for trapezoidal side weirs. Alexandria Engineering Journal, 54(3), pp. 595-605.

Park, J., Chun, Y. & Lee, J., 2016. Optimal design of an arch bridge with high performance steel for brdiges using genetic algorithm. International Journal of Steel Structures, 16(2), pp. 559-572.

Rahimi, A., 2012. Hydraulic design of side weirs by alternative methods. Australian Journal of Basic and applied Sciences, 6(6), pp. 157-167.

Roushangar, K., Khoshkanar, R. & Shiri, J., 2016. Predicting trapezoidal and rectangular side weirs discharge coefficient using machine learning methods. ISH Journal of Hydraulic Engineering, 22(3), pp. 254-261.

Samiee, S., Heidarpour, M. & Bagheri, S., 2016. Flow characteristics of rectangular sharp-crested side weirs in the presence of guide vanes. ISH Journal of Hydraulic Engineering, 22(1), pp. 109-114.

Wang, T., Han, W., Yang, F. & Kong, W., 2014. Wind-vehicle-bridge coupled vibration analysis based on random traffic flow simulation. Journal of Traffic and Transportation Engineering, 1(4), pp. 293-308.

Yin, Z., Li, Y., Guo, J. & Li, Y., 2011. Integration research and design of the bridge maintenance management system. Procedia Engineering, Volume 15, pp. 5429-5434.