Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 21 Experimental and Numerical Investigation of Temperature Gradient in "Jenah" Concrete Box-Girder Bridge Experimental and Numerical Investigation of Temperature Gradient in "Jenah" Concrete Box-Girder Bridge 7 18 12668 A-10-54191-1 FA Farzad Raeesi Department of Civil Engineering, University of Tabriz, Tabriz, Iran. Hedayat Veladi Associate Professor at Tabriz Faculty of Civil Engineering, Tabriz, Iran Alireza Abbasnejad University of Tabriz Journal Article Air temperature variations due to daily, seasonal, and annual changes can affect the bridges. The deformation and stress caused under solar radiation should not neglected in bridge design and their effects can be compared with dead and live loads. Thus, the components of bridges such as bearings, dampers and so on, are seriously affected by the combination of external loads and thermal stress. Different countries have provided temperature gradients in their codes. Almost in all of the codes, the vertical temperature gradient is specified, but unfortunately in none of them, the lateral temperature gradient is presented. Furthermore, in the vertical gradient, there are numerous lacks exist in different codes. For an example, most of the codes do not involve either temperature variations due to annual changes, or not considered the longitude or latitude of the location of the designed bridges. These problems lead the engineers to do the precise study beside the codes provided by each country, for temperature effects on the bridge structures. This paper investigates the effect of vertical and lateral thermal gradient loads for concrete box girder designed based on Iranian Standard Loads for Bridge (ISLB) code, using experimental test and three-dimensional finite element analysis. The ISLB code has two main problems in the field of thermal gradients. Firstly, the vertical temperature gradient provided in ISLB code, cannot used for all bridges in Iran, because each bridge has its unique geographical environment, latitude, longitude, and axis of orientation. Secondly, it does not contain any models for the lateral temperature gradient. To handle these problems, the experimental test is done and thermocouples are installed in different parts of the segment to get the thermal gradients and investigate their effects. In the case of predicting vertical gradient, the recorded data show that, the maximum temperature difference occurs in 1430 hrs with the value of 8.8 °C , while by considering the lateral gradient, the maximum temperature difference occurs at 1130 hrs with the value of 2.9 °C . In this paper, comparison between vertical and lateral gradients leads to consider only vertical gradients in further investigations. Moreover, by applying vertical gradient in the finite element model of the Jenah bridge, maximum thermal stress is occurred in the intersection of the web and top flange with the value of 1.96 MPa and maximum deflection of 4.36 mm in the midspan of the bridge. As a solution for mitigating the negative effects of the thermal gradients, using polyurethane insulation is proposed and modeled in the FE model. Results of simulation reveal that utilizing insolation can reduce the top slab temperatures to 30.5 °C , 29.16 °C , 27.5 °C and 26.4 °C from 33.6 °C in the case of using 2, 3, 5 and 6mm polyurethane insulations, respectively, which results in stress reduction from 1.96 MPa to 1.65, 1.35, 0.63 and 0.38 MPa in the case of using 2, 3, 5 and 6 mm polyurethane insulations, respectively. Furthermore, using insulation can reduce the deflection of the bridge, which in this study, the maximum deflection of the 48 m span is reduced from 4.36mm to 3.57, 2.86, 1.63 and 1.07 mm, by utilizing 2, 3, 5 and 6 mm polyurethane insulations, respectively. Air temperature variations due to daily, seasonal, and annual changes can affect the bridges. The deformation and stress caused under solar radiation should not neglected in bridge design and their effects can be compared with dead and live loads. Thus, the components of bridges such as bearings, dampers and so on, are seriously affected by the combination of external loads and thermal stress. Different countries have provided temperature gradients in their codes. Almost in all of the codes, the vertical temperature gradient is specified, but unfortunately in none of them, the lateral temperature gradient is presented. Furthermore, in the vertical gradient, there are numerous lacks exist in different codes. For an example, most of the codes do not involve either temperature variations due to annual changes, or not considered the longitude or latitude of the location of the designed bridges. These problems lead the engineers to do the precise study beside the codes provided by each country, for temperature effects on the bridge structures. This paper investigates the effect of vertical and lateral thermal gradient loads for concrete box girder designed based on Iranian Standard Loads for Bridge (ISLB) code, using experimental test and three-dimensional finite element analysis. The ISLB code has two main problems in the field of thermal gradients. Firstly, the vertical temperature gradient provided in ISLB code, cannot used for all bridges in Iran, because each bridge has its unique geographical environment, latitude, longitude, and axis of orientation. Secondly, it does not contain any models for the lateral temperature gradient. To handle these problems, the experimental test is done and thermocouples are installed in different parts of the segment to get the thermal gradients and investigate their effects. In the case of predicting vertical gradient, the recorded data show that, the maximum temperature difference occurs in 1430 hrs with the value of 8.8 °C , while by considering the lateral gradient, the maximum temperature difference occurs at 1130 hrs with the value of 2.9 °C . In this paper, comparison between vertical and lateral gradients leads to consider only vertical gradients in further investigations. Moreover, by applying vertical gradient in the finite element model of the Jenah bridge, maximum thermal stress is occurred in the intersection of the web and top flange with the value of 1.96 MPa and maximum deflection of 4.36 mm in the midspan of the bridge. As a solution for mitigating the negative effects of the thermal gradients, using polyurethane insulation is proposed and modeled in the FE model. Results of simulation reveal that utilizing insolation can reduce the top slab temperatures to 30.5 °C , 29.16 °C , 27.5 °C and 26.4 °C from 33.6 °C in the case of using 2, 3, 5 and 6mm polyurethane insulations, respectively, which results in stress reduction from 1.96 MPa to 1.65, 1.35, 0.63 and 0.38 MPa in the case of using 2, 3, 5 and 6 mm polyurethane insulations, respectively. Furthermore, using insulation can reduce the deflection of the bridge, which in this study, the maximum deflection of the 48 m span is reduced from 4.36mm to 3.57, 2.86, 1.63 and 1.07 mm, by utilizing 2, 3, 5 and 6 mm polyurethane insulations, respectively.

https://mcej.modares.ac.ir/article_12668_354680832fcea7e2b7057a5ac2c489f8.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 21 Effect of Endsill Shape on Scouring Depth and Index Downstream of USBR Type VI Stilling Basin Effect of Endsill Shape on Scouring Depth and Index Downstream of USBR Type VI Stilling Basin 19 29 12669 A-10-71142-1 FA Shokoufeh Kheirehdast Graduated MSc of Hydraulic Structures, Faculty of Civil Engineering and Environment, Tarbiat Modares University, Tehran, Iran. Masoud Ghodsian Professor, Faculty of Civil Engineering and Environment and Water Engineering Research Institute, Tarbiat Modares University, Tehran, Iran. Journal Article Stilling basins are used in the outlet of channels, chutes and culverts to dissipate the excess kinetic energy of incoming flow. One of the basins in which the energy of incoming flow is dissipated by impact, is USBR VI stilling basin. The USBR VI stilling basin was first introduced by Bradely and Peterka in 1995 and then was modified by Biechley in 1978. This structure consists of a middle wall and an endsill. Scouring around the structures that are located in the vicinity of erodible beds, such as stilling basins, has always been one of the most important problems related to these structures. Unlike other types of stilling basins, the studies carried out around this type of basin are limited, and there are still many hydraulics features of this type that have not been considered in previous researches. In this article, the effect of the shape of endsill on scour depth downstream of stilling basin is evaluated. Based on Beichley graph (Standard Design), the physical model of stilling basin was designed, constructed and installed in the hydraulic laboratory of Tarbiat Modares. Experiments were conducted in a 0.8 m wide, 0.9 m height, and 0.8 m length rectangular channel. The pump used in the experiments had a nominal flow rate of 400 cubic meters per hour (about 120 liters per hour), a head of 11.7 meters, a power of 22 horsepower, and an engine speed of 1450 rpm. In the design of experiments, the parameters including approach Froude number (i.e. 1, 1.5 and 2 times of standard Froude number on Beichley graph), the diameter of inlet pipe (i.e. De = 5, 8, and 12 centimeters), and endsill shapes (triangular, stepped and circular quadrant), in the form of 27 tests were assessed to study the dimensions of the scour depth. The observations revealed that in all three endsill shapes, the increase in Froud number has led to the decrease in scour index. the circular quadrant endsill had the lowest scour depth in the front of endsill and the least scour index, in the range of the Froude number of 2 to 6. In the range of the Froude numbers of 9 to 14, the triangular endsill causes the lowest scour index. In the relative diameter of inlet pipe equals to 10.16, for Froud numbers equal to 9.27 and 13.91, the triangular shaped endsill has the least scour index. in every endsills, decreasing the pipe’s diameter results in the maximum depth of the scour. Another important finding is that sediment bar is only formed in experiments conducted with inlet pipe’s diameter equal to 5cm for Froude number equal to Froude number on Beichley graph. The biggest amounts of the height of sediment bar and maximum scour depth are found for the stepped endsill and the smallest amounts of the height of sediment bar and maximum scour depth are found for the circular quadrant endsill. Subsequently, the non-dimensional equations according to the Froud number of incoming flow and the relative diameter of inlet pipe, were presented to estimate the maximum depth of the scour hole. Stilling basins are used in the outlet of channels, chutes and culverts to dissipate the excess kinetic energy of incoming flow. One of the basins in which the energy of incoming flow is dissipated by impact, is USBR VI stilling basin. The USBR VI stilling basin was first introduced by Bradely and Peterka in 1995 and then was modified by Biechley in 1978. This structure consists of a middle wall and an endsill. Scouring around the structures that are located in the vicinity of erodible beds, such as stilling basins, has always been one of the most important problems related to these structures. Unlike other types of stilling basins, the studies carried out around this type of basin are limited, and there are still many hydraulics features of this type that have not been considered in previous researches. In this article, the effect of the shape of endsill on scour depth downstream of stilling basin is evaluated. Based on Beichley graph (Standard Design), the physical model of stilling basin was designed, constructed and installed in the hydraulic laboratory of Tarbiat Modares. Experiments were conducted in a 0.8 m wide, 0.9 m height, and 0.8 m length rectangular channel. The pump used in the experiments had a nominal flow rate of 400 cubic meters per hour (about 120 liters per hour), a head of 11.7 meters, a power of 22 horsepower, and an engine speed of 1450 rpm. In the design of experiments, the parameters including approach Froude number (i.e. 1, 1.5 and 2 times of standard Froude number on Beichley graph), the diameter of inlet pipe (i.e. De = 5, 8, and 12 centimeters), and endsill shapes (triangular, stepped and circular quadrant), in the form of 27 tests were assessed to study the dimensions of the scour depth. The observations revealed that in all three endsill shapes, the increase in Froud number has led to the decrease in scour index. the circular quadrant endsill had the lowest scour depth in the front of endsill and the least scour index, in the range of the Froude number of 2 to 6. In the range of the Froude numbers of 9 to 14, the triangular endsill causes the lowest scour index. In the relative diameter of inlet pipe equals to 10.16, for Froud numbers equal to 9.27 and 13.91, the triangular shaped endsill has the least scour index. in every endsills, decreasing the pipe’s diameter results in the maximum depth of the scour. Another important finding is that sediment bar is only formed in experiments conducted with inlet pipe’s diameter equal to 5cm for Froude number equal to Froude number on Beichley graph. The biggest amounts of the height of sediment bar and maximum scour depth are found for the stepped endsill and the smallest amounts of the height of sediment bar and maximum scour depth are found for the circular quadrant endsill. Subsequently, the non-dimensional equations according to the Froud number of incoming flow and the relative diameter of inlet pipe, were presented to estimate the maximum depth of the scour hole.

https://mcej.modares.ac.ir/article_12669_51b7dae1031b20174cacc7e69d6e4bf0.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 01 Evaluation Possibility of Concrete Frames Rehabilitation with Off-Grade Steel Bracing Evaluation Possibility of Concrete Frames Rehabilitation with Off-Grade Steel Bracing 31 44 12670 A-10-64884-2 FA Ali Biglari Assistant Professor, Department of Civil Engineering, Golestan University. Saeed Nodeh Master of Civil Engineering Student, Department of Civil Engineering, Golestan University. Journal Article Steel bracing is known as one of the most effective systems resistant to lateral loads, and its use has been the subject of numerous studies to improve the lateral deformation tolerance of existing reinforced concrete frames. In this study, the seismic performance of steel bracing in the concentric plane in order to strengthen the existing reinforced concrete structures has been numerically investigated. A scaled reinforced concrete frame was modeled by finite element method by simple cross bracing. In the retrofitting of damaged reinforced concrete structures, attention should be paid to the continuity of service of the structure in structures of high importance. The important point in buildings of special importance such as hospitals and government buildings is that in such buildings the maintenance of the structure must be maintained at all hours. In addition, the implementation of in-plane bracing causes the destruction of intermediate frame components and can reduce the effective role of intermediate frame components in the seismic load of reinforced concrete frames. The interaction between the frame and the frame in seismic loading is an important issue that has been extensively focused on by various researches. Another important point is to pay attention to architectural issues and match the retrofit method with the aesthetic aspects of the structure. If there is an opening in the damaged frame, using the internal reinforcement method may cause problems in the opening space in the desired frame. According to the mentioned points, in order to continue the service of the structure during the retrofit operation and to reduce the destruction operation in the intermediate frame components, the reinforcement member can be externally connected to the damaged frame. Therefore, in this study, in order to achieve the mentioned goals, the implementation of steel bracing outside the plane was also investigated using the numerical method and its Possibility was verified. The studied sample was subjected to lateral load by displacement control method by ABAQUS software and analyzed by quasi-static method. This enables a better understanding of the performance of frames strengthened with in-plane and out-of-plane steel braces and the evaluation of the proposed method. In this study, the models were examined in terms of deformation and cracking characteristics, hysteresis, lateral stiffness reduction and energy absorption capability.The results of this study showed that after strengthening with braces, there was no local rupture due to the application of lateral load in the place of the plastic joints of the frames. As a result of the application of lateral load, the normal moment frame specimen showed a more fragile hysteretic behavior. The maximum resistance value of the reinforced concrete frame in a certain displacement after strengthening increased to 2.5 times of its original sample and resulted in less stress concentration in the boundary elements compared to in-plane bracing. The amount of hardness created in the sample increased to 1.35 times of the original sample and the amount of energy absorption increased to 2.25 times of the original sample. The results obtained in hysteresis, stiffness reduction and energy absorption sections indicate the effective performance of the proposed method in strengthening damaged reinforced concrete structures. Steel bracing is known as one of the most effective systems resistant to lateral loads, and its use has been the subject of numerous studies to improve the lateral deformation tolerance of existing reinforced concrete frames. In this study, the seismic performance of steel bracing in the concentric plane in order to strengthen the existing reinforced concrete structures has been numerically investigated. A scaled reinforced concrete frame was modeled by finite element method by simple cross bracing. In the retrofitting of damaged reinforced concrete structures, attention should be paid to the continuity of service of the structure in structures of high importance. The important point in buildings of special importance such as hospitals and government buildings is that in such buildings the maintenance of the structure must be maintained at all hours. In addition, the implementation of in-plane bracing causes the destruction of intermediate frame components and can reduce the effective role of intermediate frame components in the seismic load of reinforced concrete frames. The interaction between the frame and the frame in seismic loading is an important issue that has been extensively focused on by various researches. Another important point is to pay attention to architectural issues and match the retrofit method with the aesthetic aspects of the structure. If there is an opening in the damaged frame, using the internal reinforcement method may cause problems in the opening space in the desired frame. According to the mentioned points, in order to continue the service of the structure during the retrofit operation and to reduce the destruction operation in the intermediate frame components, the reinforcement member can be externally connected to the damaged frame. Therefore, in this study, in order to achieve the mentioned goals, the implementation of steel bracing outside the plane was also investigated using the numerical method and its Possibility was verified. The studied sample was subjected to lateral load by displacement control method by ABAQUS software and analyzed by quasi-static method. This enables a better understanding of the performance of frames strengthened with in-plane and out-of-plane steel braces and the evaluation of the proposed method. In this study, the models were examined in terms of deformation and cracking characteristics, hysteresis, lateral stiffness reduction and energy absorption capability.The results of this study showed that after strengthening with braces, there was no local rupture due to the application of lateral load in the place of the plastic joints of the frames. As a result of the application of lateral load, the normal moment frame specimen showed a more fragile hysteretic behavior. The maximum resistance value of the reinforced concrete frame in a certain displacement after strengthening increased to 2.5 times of its original sample and resulted in less stress concentration in the boundary elements compared to in-plane bracing. The amount of hardness created in the sample increased to 1.35 times of the original sample and the amount of energy absorption increased to 2.25 times of the original sample. The results obtained in hysteresis, stiffness reduction and energy absorption sections indicate the effective performance of the proposed method in strengthening damaged reinforced concrete structures.

https://mcej.modares.ac.ir/article_12670_185afe2ab60395b0fb41349aa1469a7f.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 01 Probabilistic residual drift assessment of rocking buckling restrained braced frames under crustal and subduction ground motion records Probabilistic residual drift assessment of rocking buckling restrained braced frames under crustal and subduction ground motion records 45 63 12671 A-10-71318-1 FA Mehran Mirzaei Master of Science, Department of Civil Engineering, Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin, Iran Mansoor Yakhchalian Assistant Professor, Department of Civil Engineering, Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin, Iran Mahshid Tavakoli Master of Science, Department of Civil Engineering, Faculty of Engineering andTechnology, Imam Khomeini International University, Qazvin, Iran Mohammad Hosein Soltani Master of Science, Department of Civil Engineering, Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin, Iran Journal Article Buckling restrained braced frames (BRBFs) are widely used as a lateral force resisting system due to their advantageous characteristics such as elimination of brace buckling in compression, high ductility and energy dissipation. BRBFs may have damage concentration in one or few stories during severe seismic excitations, because buckling restrained brace (BRB) yields in a certain story and the stiffness of that story significantly decreases. Drift concentration is undesirable as it can lead to general instability resulting from P-Δ effects or residual drift. For controlling damage concentration in one or few stories and achieving a uniform distribution of drifts in all stories, a new system entitled rocking buckling restrained braced frame (RBRBF) can be used. RBRBF system generates uniform story drifts over the height of structure and prevents the damage concentration in one or few stories. Unlike conventional or suspended zipper braced frames, the braces on one side of the braced span along with the adjacent columns and ties are part of a vertical truss system that is hinged at the base and designed to remain elastic until the near collapse limit state is reached. This vertical truss system works as a strong support for preventing damage concentration in one or few stories of the braced frame. The braces on the other side of the braced span are BRBs and are designed to provide energy dissipation. RBRBFs are designed according to a displacement‐based approach. The novelty of this paper is investigating the residual drift performance of this new structural system under the effect of subduction ground motion records, which have higher significant durations compared with crustal ground motion records. In this study, 4-, 8-, and 12-story structures with RBRBF and BRBF systems are considered, and their residual drift capacity values given four maximum residual interstory drift ratio (MRIDR) levels of 0.2%, 0.5%, 1.0% and 2.0% are computed using incremental dynamic analyses (IDAs). IDAs are performed on two-dimensional models of the structures using 22 pairs of short-duration crustal and long-duration subduction ground motion records. After computing the capacity values given these four MRIDR levels, the residual drift margin ratios (RDMR), and the mean annual frequencies (MAFs) of exceeding different MRIDR levels (λRD) are obtained. The results demonstrate that all the RBRBFs have better residual drift performance than the BRBFs. Based on these results, the use of RBRBF dramatically reduces BRBF weaknesses including the concentration of damage in a certain story and low post-yield stiffness. For example, the ratios of the total λRD value given MRIDR= 2.0% for the BRBF system to its corresponding value for the RBRBF system for the 4-, 8-, and 12-story structures are 21.10, 4.06, and 3.21, respectively. In addition, for most of the structures, as the MRIDR level increases, the ratio of the RDMR value under crustal records to that under subduction records increases. Buckling restrained braced frames (BRBFs) are widely used as a lateral force resisting system due to their advantageous characteristics such as elimination of brace buckling in compression, high ductility and energy dissipation. BRBFs may have damage concentration in one or few stories during severe seismic excitations, because buckling restrained brace (BRB) yields in a certain story and the stiffness of that story significantly decreases. Drift concentration is undesirable as it can lead to general instability resulting from P-Δ effects or residual drift. For controlling damage concentration in one or few stories and achieving a uniform distribution of drifts in all stories, a new system entitled rocking buckling restrained braced frame (RBRBF) can be used. RBRBF system generates uniform story drifts over the height of structure and prevents the damage concentration in one or few stories. Unlike conventional or suspended zipper braced frames, the braces on one side of the braced span along with the adjacent columns and ties are part of a vertical truss system that is hinged at the base and designed to remain elastic until the near collapse limit state is reached. This vertical truss system works as a strong support for preventing damage concentration in one or few stories of the braced frame. The braces on the other side of the braced span are BRBs and are designed to provide energy dissipation. RBRBFs are designed according to a displacement‐based approach. The novelty of this paper is investigating the residual drift performance of this new structural system under the effect of subduction ground motion records, which have higher significant durations compared with crustal ground motion records. In this study, 4-, 8-, and 12-story structures with RBRBF and BRBF systems are considered, and their residual drift capacity values given four maximum residual interstory drift ratio (MRIDR) levels of 0.2%, 0.5%, 1.0% and 2.0% are computed using incremental dynamic analyses (IDAs). IDAs are performed on two-dimensional models of the structures using 22 pairs of short-duration crustal and long-duration subduction ground motion records. After computing the capacity values given these four MRIDR levels, the residual drift margin ratios (RDMR), and the mean annual frequencies (MAFs) of exceeding different MRIDR levels (λRD) are obtained. The results demonstrate that all the RBRBFs have better residual drift performance than the BRBFs. Based on these results, the use of RBRBF dramatically reduces BRBF weaknesses including the concentration of damage in a certain story and low post-yield stiffness. For example, the ratios of the total λRD value given MRIDR= 2.0% for the BRBF system to its corresponding value for the RBRBF system for the 4-, 8-, and 12-story structures are 21.10, 4.06, and 3.21, respectively. In addition, for most of the structures, as the MRIDR level increases, the ratio of the RDMR value under crustal records to that under subduction records increases.

https://mcej.modares.ac.ir/article_12671_a7ba7390e92513e12fc5fe070e40ee7e.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 01 Investigating the effect of Velocity on Water Column Separation using CFD Methods Investigating the effect of Velocity on Water Column Separation using CFD Methods 65 77 12672 A-10-11309-2 FA Mehdi Azhdary Moghaddam Professor, Department of Civil Engineering, University of Sistan and Baluchistan, Zahedan, Iran Sakineh Safari PhD student, Department of Civil Engineering, University of Sistan and Baluchistan, Zahedan, Iran Abdul Hamid Bahrpeyma Associate Professor, Department of Civil Engineering, Sistan-Baluchistan University, Zahedan, Iran Mohammad Givehchi Assistant Professor, Department of Civil Engineering, Sistan-Baluchistan University, Zahedan, Iran Journal Article The Water Column Separation phenomenon is one of the transient flow regimes, which is created under conditions such as the sudden closing of the valve or the shutdown of the pump in the water supply network. Hard pressure fluctuations and damages caused by the mentioned phenomenon require identifying and providing a solution to prevent it. By this purpose, the present article investigates the possibility of Water Column Separation in a Loop Water Supply Network using Computational Fluid Dynamics method. Next, the Effect of the inlet velocity on the pressures created due to the Water Column Separation was investigated. For software validation, the Loop system provided by Wang et al. (2017) was selected. After ensuring the efficiency of the software to model the phenomenon of Water Column Separation, simulation was performed at different speeds. Checking the simulation results indicated the occurrence of Water Column Separation in the Intended Network. Also, the Results indicated that with the increase of the input Velocity, the maximum value of the Pressure in the Network increases and its minimum value decreases. In such a way that with a 12% increase in the input velocity, the maximum pressure value changes by 11.8% and the minimum value by 14.26%. In general, it can be said that by controlling the Velocity as an effective factor on the pressure fluctuations of the Water Column Separation, this phenomenon and the resulting damages are prevented. The Water Column Separation phenomenon is one of the transient flow regimes, which is created under conditions such as the sudden closing of the valve or the shutdown of the pump in the water supply network. Hard pressure fluctuations and damages caused by the mentioned phenomenon require identifying and providing a solution to prevent it. By this purpose, the present article investigates the possibility of Water Column Separation in a Loop Water Supply Network using Computational Fluid Dynamics method. Next, the Effect of the inlet velocity on the pressures created due to the Water Column Separation was investigated. For software validation, the Loop system provided by Wang et al. (2017) was selected. After ensuring the efficiency of the software to model the phenomenon of Water Column Separation, simulation was performed at different speeds. Checking the simulation results indicated the occurrence of Water Column Separation in the Intended Network. Also, the Results indicated that with the increase of the input Velocity, the maximum value of the Pressure in the Network increases and its minimum value decreases. In such a way that with a 12% increase in the input velocity, the maximum pressure value changes by 11.8% and the minimum value by 14.26%. In general, it can be said that by controlling the Velocity as an effective factor on the pressure fluctuations of the Water Column Separation, this phenomenon and the resulting damages are prevented.

https://mcej.modares.ac.ir/article_12672_d5542ec466d3f3446d5be39e42606a61.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 21 Identification and Ranking of Effective Factors on Accepting Trenchless Technology Identification and Ranking of Effective Factors on Accepting Trenchless Technology 79 97 12673 A-10-54948-2 FA S.H. Afzali.Borujeni Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran M.R. Zare Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran L. Adelzade Saadabadi Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran. 0000-0002-9152-1340 Journal Article In today’s society, pipelines as vital arteries play a significant role in maintaining people’s peace and satisfaction. According to growing developments in societies, the necessity of constructing, refurbishing, repairing, and maintaining underground installations such as petrol pipelines, gas, water, wastewater, runoffs, and connections is considered as the indispensable part of civil and installation operations. Regarding problems stemming from the open trench excavation methods and growth of underground installations, using trenchless technologies in the construction industry is increasing in order to solve the problems more economically and effectively. The present project aimed at recognizing and ranking the most important effective factors in accepting the trenchless technology in Iran. This research has a practical target and has been performed by the survey and the describing method. The statistical population of this research includes middle managers, contractors, and civil projects engineers of Isfahan province. In this regard, a sample of 87 people was randomly selected and the questionnaire was distributed among them. Eventually, a total of 68 questionnaires were collected with favorable consistency. This questionnaire has been designed by the investigator according to the Likert scale with high stability. Accordingly, the factors were grouped in the form of 28 criteria and 8 major groups as the effective factors on accepting the trenchless technology in Iran. Descriptive and inferential methods and the Friedman test were used to rank the effective factors, and the SPSS software was applied to analyze the data. Among the 8 major groups of executive management, environmental, demographics, technology, economically, project productivity (construction management), organizational, and individual had the first to the 8th rank, respectively. In addition, control system, risks, environment, budget, chief executive officer (CEO), special and geographical performance, and direct costs ranked the top among the 28 factors. In today’s society, pipelines as vital arteries play a significant role in maintaining people’s peace and satisfaction. According to growing developments in societies, the necessity of constructing, refurbishing, repairing, and maintaining underground installations such as petrol pipelines, gas, water, wastewater, runoffs, and connections is considered as the indispensable part of civil and installation operations. Regarding problems stemming from the open trench excavation methods and growth of underground installations, using trenchless technologies in the construction industry is increasing in order to solve the problems more economically and effectively. The present project aimed at recognizing and ranking the most important effective factors in accepting the trenchless technology in Iran. This research has a practical target and has been performed by the survey and the describing method. The statistical population of this research includes middle managers, contractors, and civil projects engineers of Isfahan province. In this regard, a sample of 87 people was randomly selected and the questionnaire was distributed among them. Eventually, a total of 68 questionnaires were collected with favorable consistency. This questionnaire has been designed by the investigator according to the Likert scale with high stability. Accordingly, the factors were grouped in the form of 28 criteria and 8 major groups as the effective factors on accepting the trenchless technology in Iran. Descriptive and inferential methods and the Friedman test were used to rank the effective factors, and the SPSS software was applied to analyze the data. Among the 8 major groups of executive management, environmental, demographics, technology, economically, project productivity (construction management), organizational, and individual had the first to the 8th rank, respectively. In addition, control system, risks, environment, budget, chief executive officer (CEO), special and geographical performance, and direct costs ranked the top among the 28 factors.

https://mcej.modares.ac.ir/article_12673_fffb8ef15de06d87e6ba6c830f3b6284.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 21 The effect of electric field on membrane bioreactors performance and membrane fouling reduction The effect of electric field on membrane bioreactors performance and membrane fouling reduction 99 110 12674 A-1-21318-6 FA َAsieh Mahdizadeh Babol Noshirvani University of Technology Journal Article Rapid growth of population is leading to high water consumption and producing large amount of waste water which needs to be treated and being reutilized for reusing purposes. Among sewage treatment methods, the use of integrated activated sludge and membrane separation is increasing due to advantages such as higher quality effluents, lower ecological footprint, less sludge production, and lower operational costs. Despite the many benefits, the problem of membrane fouling due to deposition and adsorption of colloidal and soluble material on the surface of membrane has limited the use of this method. There are several methods for eliminating and mitigating membrane fouling, each with disadvantages such as increasing costs, producing secondary pollutants, increasing sludge production, reducing the membrane life and durability, etc. In recent years, the use of electrical coagulation as a method to reduce membrane fouling in the MBR system has been taken into account. Submerged Membrane Electro Bioreactors (SMEBR) is a new approach that reduces clogging of the membrane by combining the MBR system with the electric field. In the forthcoming research, the effects of electric field on the system were investigated by applying a low voltage electric field (1.5 volts per cm) in the MBR reactor. The results of the experiments showed that applying the electric field in this case improves the characteristics of the wastewater (reducing the concentration of COD, nitrate and phosphate) and reducing the concentration of external polymeric substance (EPS) and soluble material product (SMP) protein. Also, the application of an electric field in MBR reactors reduces fouling and improves the output flux more than the conventional membrane. Key words: Membrane bioreactor, Electric Field, Biofouling Rapid growth of population is leading to high water consumption and producing large amount of waste water which needs to be treated and being reutilized for reusing purposes. Among sewage treatment methods, the use of integrated activated sludge and membrane separation is increasing due to advantages such as higher quality effluents, lower ecological footprint, less sludge production, and lower operational costs. Despite the many benefits, the problem of membrane fouling due to deposition and adsorption of colloidal and soluble material on the surface of membrane has limited the use of this method. There are several methods for eliminating and mitigating membrane fouling, each with disadvantages such as increasing costs, producing secondary pollutants, increasing sludge production, reducing the membrane life and durability, etc. In recent years, the use of electrical coagulation as a method to reduce membrane fouling in the MBR system has been taken into account. Submerged Membrane Electro Bioreactors (SMEBR) is a new approach that reduces clogging of the membrane by combining the MBR system with the electric field. In the forthcoming research, the effects of electric field on the system were investigated by applying a low voltage electric field (1.5 volts per cm) in the MBR reactor. The results of the experiments showed that applying the electric field in this case improves the characteristics of the wastewater (reducing the concentration of COD, nitrate and phosphate) and reducing the concentration of external polymeric substance (EPS) and soluble material product (SMP) protein. Also, the application of an electric field in MBR reactors reduces fouling and improves the output flux more than the conventional membrane. Key words: Membrane bioreactor, Electric Field, Biofouling

https://mcej.modares.ac.ir/article_12674_217ffec3caf17a44bf340fc11d93e8ab.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 21 Optimization of location and diversion angle of lateral intakes in U shaped channel Optimization of location and diversion angle of lateral intakes in U shaped channel 111 123 12675 A-1-14528-7 FA Journal Article Lateral intake and stream diversion facilities, which are widely used in irrigation, land drainage and municipal sewage systems, deal with sediment transport. In this research, using a numerical discrete phase model, simulation of the sediment transport phenomenon is carried out in a 180-degree channel bend with a lateral intake that is located at a position of 115 degrees outside the arc and with a 45-degree diversion angle. The numerical model was calibrated with laboratory data. Then, in 31 positions of the channel bend from the 10 to 140 degrees with 5 degrees' intervals and with 5 diversion angles of 10, 30, 50, 70 and 90 degrees, and for three diversion discharge ratios of 20%, 30% and 40%, the calibrated numerical model has been implemented and the percentage of sediment entered to the lateral intake were determined for each model. The results were used as the data necessary for training and validation of Artificial neural network (ANN) model. The inputs of ANN model were location of lateral intake in outer bank of channel bend (φ) and diversion angle of lateral intake (θ), diverted water discharge ratio (Qr). The output is diverted sediment ratio into the lateral intake (Gr). The data were used for training and validation of the ANN model and the best structure was obtained for the neural network models using R2, SSE and MARE criteria and compared to regression models. The best structure of ANN model was obtained as a 5-layer model with 3 membership functions for each input variable and 27 conditional rules. The accuracy of the results obtained from the models in terms of the mean absolute relative error (MARE) indicates the ability of the neural network models to predict the amount of sediment diverted to the lateral intake with respect to regression models. Then, by developing a new simulation-optimization method based on the Multi-Objective Genetic Algorithm Optimization model (NSGAII), the FLUENT numerical model and neural network models, the optimal position and diversion angle of the lateral intake in the U-shaped channel is determined to minimize the amount of sediment inflow into the lateral basin and maximize the rate of dewatering discharge. By connecting the best model obtained from the ANN model, to NSGA-II model, the Pareto Front contains a list of optimal positions and optimal diversion angle of lateral intake are obtained with respect to the objective function and its limitations in the U-shaped channel. Finally, to determine the optimal position and angle of the lateral basin in the U-shaped channel by connecting the Pareto front obtained from the Multipurpose Genetic Algorithm (NSGA-II) to the TOPSIS multi-criteria decision-making method, the best option is found among the Pareto front options. The results include the optimum position and optimum angle of lateral intake dewatering along with diversion discharge and sediment rates corresponding to these values. The results show that the optimum diversion angle obtained is 38-degree and the optimum position obtained is 127-degree Lateral intake and stream diversion facilities, which are widely used in irrigation, land drainage and municipal sewage systems, deal with sediment transport. In this research, using a numerical discrete phase model, simulation of the sediment transport phenomenon is carried out in a 180-degree channel bend with a lateral intake that is located at a position of 115 degrees outside the arc and with a 45-degree diversion angle. The numerical model was calibrated with laboratory data. Then, in 31 positions of the channel bend from the 10 to 140 degrees with 5 degrees' intervals and with 5 diversion angles of 10, 30, 50, 70 and 90 degrees, and for three diversion discharge ratios of 20%, 30% and 40%, the calibrated numerical model has been implemented and the percentage of sediment entered to the lateral intake were determined for each model. The results were used as the data necessary for training and validation of Artificial neural network (ANN) model. The inputs of ANN model were location of lateral intake in outer bank of channel bend (φ) and diversion angle of lateral intake (θ), diverted water discharge ratio (Qr). The output is diverted sediment ratio into the lateral intake (Gr). The data were used for training and validation of the ANN model and the best structure was obtained for the neural network models using R2, SSE and MARE criteria and compared to regression models. The best structure of ANN model was obtained as a 5-layer model with 3 membership functions for each input variable and 27 conditional rules. The accuracy of the results obtained from the models in terms of the mean absolute relative error (MARE) indicates the ability of the neural network models to predict the amount of sediment diverted to the lateral intake with respect to regression models. Then, by developing a new simulation-optimization method based on the Multi-Objective Genetic Algorithm Optimization model (NSGAII), the FLUENT numerical model and neural network models, the optimal position and diversion angle of the lateral intake in the U-shaped channel is determined to minimize the amount of sediment inflow into the lateral basin and maximize the rate of dewatering discharge. By connecting the best model obtained from the ANN model, to NSGA-II model, the Pareto Front contains a list of optimal positions and optimal diversion angle of lateral intake are obtained with respect to the objective function and its limitations in the U-shaped channel. Finally, to determine the optimal position and angle of the lateral basin in the U-shaped channel by connecting the Pareto front obtained from the Multipurpose Genetic Algorithm (NSGA-II) to the TOPSIS multi-criteria decision-making method, the best option is found among the Pareto front options. The results include the optimum position and optimum angle of lateral intake dewatering along with diversion discharge and sediment rates corresponding to these values. The results show that the optimum diversion angle obtained is 38-degree and the optimum position obtained is 127-degree

https://mcej.modares.ac.ir/article_12675_b3d5c779237614a9cef5305b85a28273.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 21 Analytical Solution for Multi-well System of Groundwater Remediation in the vicinity of a Permanent Stream Analytical Solution for Multi-well System of Groundwater Remediation in the vicinity of a Permanent Stream 125 138 12676 A-10-12232-4 FA Abdollah Ramezani-Charmahineh PhD Student of Water Resources, Department of Water Engineering, Shahrekord University Mahdi Asadi-Aghbolaghi Associate Professor, Department of Water Engineering, Shahrekord University Rasoul Mirabbasi Najafabadi Associate Professor, Department of Water Engineering, Shahrekord University Sayyed-Hassan Tabatabaei Associate Professor, Department of Water Engineering, Shahrekord University Journal Article Human civilizations have always depended on freshwater to form, develop and fulfillment of various needs. With increasing urbanization, not only has the need for freshwater not diminished, but also some new technologies and industries have increased water consumption, and the pollution of water sources has increased significantly. Since groundwater resources are far from surface pollution and have their natural remediation ability, protection and remediation have not been given sufficient and appropriate attention. This issue and the overexploitation of aquifers have resulted in the quantitative and qualitative balance of groundwater resources being unsustainable. These issues show that further research is needed on various aspects of groundwater remediation. By developing the equations for water movement in porous media and analyzing them, it is possible to simulate groundwater flow. In this study, the double-well pumping system has been investigated analytically as one of the effective methods for aquifer remediation. In this system, pumping wells provide a return to natural conditions by draining polluted water and preventing it from spreading in the aquifer. For this purpose, the equations of the groundwater potential function and the stream function were determined for two pumping wells near a permanent stream. In other words, the real part of the complex potential equation represents the potential function and its imaginary part specifies the stream function; using the image well theory, the effect of the stream was also applied in the problem relations. By determining the coordinates of the stagnation points, the capture zone of the multi-well system was delineated in various configurations and the amount of stream withdrawal was also calculated. The capture zone describes the behavior and capability of the multi-well system by indicating the capture domain of discharge wells for different distances and different pumping rates. Three configurations of the remediation system are presented for two types of critical pumping rates. Under these conditions, it is possible to control the capture zone without intercepting the stream boundary and creating gaps in the extraction region at different distances of the wells with certain pumping rates. At the first critical pumping rate, the capture zone of the double-well system is tangent to the permanent stream boundary, and at a pumping rate below this threshold, groundwater pollution does not reach the surface waters. At the second critical pumping rate, capture zones of two wells merge together. Indeed, in discharges less than this critical rate, there is a distance (gap) between capture zones of the wells and pollution can enter the surface water through this gap. Also, the distance between two wells was determined in the state that both types of critical pumping rate are equal. This case shows a state of capture zone whose boundary is tangent to the stream boundary, and the capture zones of two wells are merged together. In the mentioned state, the dimensionless distance between two pumping wells (the distance between the two wells divided by their distance from the stream boundary) and the dimensionless critical pumping rate are equal to 2×0.58 and 0.33, respectively. Human civilizations have always depended on freshwater to form, develop and fulfillment of various needs. With increasing urbanization, not only has the need for freshwater not diminished, but also some new technologies and industries have increased water consumption, and the pollution of water sources has increased significantly. Since groundwater resources are far from surface pollution and have their natural remediation ability, protection and remediation have not been given sufficient and appropriate attention. This issue and the overexploitation of aquifers have resulted in the quantitative and qualitative balance of groundwater resources being unsustainable. These issues show that further research is needed on various aspects of groundwater remediation. By developing the equations for water movement in porous media and analyzing them, it is possible to simulate groundwater flow. In this study, the double-well pumping system has been investigated analytically as one of the effective methods for aquifer remediation. In this system, pumping wells provide a return to natural conditions by draining polluted water and preventing it from spreading in the aquifer. For this purpose, the equations of the groundwater potential function and the stream function were determined for two pumping wells near a permanent stream. In other words, the real part of the complex potential equation represents the potential function and its imaginary part specifies the stream function; using the image well theory, the effect of the stream was also applied in the problem relations. By determining the coordinates of the stagnation points, the capture zone of the multi-well system was delineated in various configurations and the amount of stream withdrawal was also calculated. The capture zone describes the behavior and capability of the multi-well system by indicating the capture domain of discharge wells for different distances and different pumping rates. Three configurations of the remediation system are presented for two types of critical pumping rates. Under these conditions, it is possible to control the capture zone without intercepting the stream boundary and creating gaps in the extraction region at different distances of the wells with certain pumping rates. At the first critical pumping rate, the capture zone of the double-well system is tangent to the permanent stream boundary, and at a pumping rate below this threshold, groundwater pollution does not reach the surface waters. At the second critical pumping rate, capture zones of two wells merge together. Indeed, in discharges less than this critical rate, there is a distance (gap) between capture zones of the wells and pollution can enter the surface water through this gap. Also, the distance between two wells was determined in the state that both types of critical pumping rate are equal. This case shows a state of capture zone whose boundary is tangent to the stream boundary, and the capture zones of two wells are merged together. In the mentioned state, the dimensionless distance between two pumping wells (the distance between the two wells divided by their distance from the stream boundary) and the dimensionless critical pumping rate are equal to 2×0.58 and 0.33, respectively.

https://mcej.modares.ac.ir/article_12676_32cfba8a13694631a8418e4d246e55fa.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 01 the effect of matric suction changes on the behavior of Anchored excavations in expansive soil the effect of matric suction changes on the behavior of Anchored excavations in expansive soil 139 156 12677 A-10-11849-4 FA Maryam Mansoori Ferdowsi University of Mashhad, Faculty of Engineering, Department of Civil Engineering Aliye Labib Ferdowsi University of Mashhad, Faculty of Engineering, Department of Civil Engineering Ali Akhtarpour Ferdowsi University of Mashhad, Faculty of Engineering, Civil Engineering Department 0000-0003-1654-0194 Journal Article Due to the increase in population and the increasing need for construction, the issues related to excavation and stability of the excavation have been given importance. The stability of excavations can be controlled and improved by various methods such as anchoring, retaining walls, shielding, etc. that in each project, according to the characteristics of that project and the type of factors threatening the stability of that excavation, one or more stabilization methods can be used. The excavation investigated in this research is stabilized by two pile-anchor and concrete pile methods. One of the factors leading to the instability of the excavation is the infiltration of water into the excavation. Water infiltration into the excavation can be due to various reasons such as rainfall, rise of the underground water level, pipe burst, etc.; Therefore, the possibility of water infiltration into the excavation should be checked in each excavation, and necessary measures should be taken in case of water infiltration. matric suction is defined as the difference between pore air pressure and pore water pressure, which plays a major role in the shear resistance behavior of unsaturated soils; Now, water infiltration reduces matric suction and as a result reduces shear resistance and increases soil volume in expansive soils. The excavation studied in this research has been exposed to factors that change matric suction such as pipe burst, absorption well and climate conditions. The boundary conditions of pipe bursting and absorption well are assumed for a period of one year; Also, the weather conditions have been obtained from the meteorological data of the two rainy months of Sarakhs city. Using sigma/W software and Couple analysis, the simultaneous effect of change in matric suction and change in stress and strain has been investigated. Also, the Penman-Monteith method has been used for the calculation of evaporation and transpiration to model the climate conditions. In this research, a comparison was made between different excavation stabilization situations (pile-anchor and pile method) under different conditions of matric suction (pipe burst, absorption well and weather conditions). Also, in this research, the effect of the location of the burst pipe and absorption well (distance from the excavation wall) on factors such as deformations, the moment created in the pile and the forces created in the anchors (behavior of the excavation) was investigated. Considering the destructive behavior of expansive soils in unsaturated conditions, the soil studied in this research is of expansive type. The characteristics of the modeled soil are related to the area of Sarakhs city. In order to consider the effect of soil swelling, the used elasticity modulus is related to the effective stress and as a result matric suction, which is called the swelling modulus. The results showed that the increase in moisture in the soil and as a result the decrease in matric suction in the swelling soil increases the force in the anchors and the bending moment in the pile. Also, the increase in the force of the anchors and the displacement created in the case of pipe bursting and absorption well modeling is much more than the conditions of the climate boundary effect for the two rainy months of the year. By increasing the distance of the absorption well and the bursting of the pipe from the excavation, the increase in the force created in the anchors decreases. climate conditions affect the upper 6 meters of the excavation, i.e. the active zone. Due to the increase in population and the increasing need for construction, the issues related to excavation and stability of the excavation have been given importance. The stability of excavations can be controlled and improved by various methods such as anchoring, retaining walls, shielding, etc. that in each project, according to the characteristics of that project and the type of factors threatening the stability of that excavation, one or more stabilization methods can be used. The excavation investigated in this research is stabilized by two pile-anchor and concrete pile methods. One of the factors leading to the instability of the excavation is the infiltration of water into the excavation. Water infiltration into the excavation can be due to various reasons such as rainfall, rise of the underground water level, pipe burst, etc.; Therefore, the possibility of water infiltration into the excavation should be checked in each excavation, and necessary measures should be taken in case of water infiltration. matric suction is defined as the difference between pore air pressure and pore water pressure, which plays a major role in the shear resistance behavior of unsaturated soils; Now, water infiltration reduces matric suction and as a result reduces shear resistance and increases soil volume in expansive soils. The excavation studied in this research has been exposed to factors that change matric suction such as pipe burst, absorption well and climate conditions. The boundary conditions of pipe bursting and absorption well are assumed for a period of one year; Also, the weather conditions have been obtained from the meteorological data of the two rainy months of Sarakhs city. Using sigma/W software and Couple analysis, the simultaneous effect of change in matric suction and change in stress and strain has been investigated. Also, the Penman-Monteith method has been used for the calculation of evaporation and transpiration to model the climate conditions. In this research, a comparison was made between different excavation stabilization situations (pile-anchor and pile method) under different conditions of matric suction (pipe burst, absorption well and weather conditions). Also, in this research, the effect of the location of the burst pipe and absorption well (distance from the excavation wall) on factors such as deformations, the moment created in the pile and the forces created in the anchors (behavior of the excavation) was investigated. Considering the destructive behavior of expansive soils in unsaturated conditions, the soil studied in this research is of expansive type. The characteristics of the modeled soil are related to the area of Sarakhs city. In order to consider the effect of soil swelling, the used elasticity modulus is related to the effective stress and as a result matric suction, which is called the swelling modulus. The results showed that the increase in moisture in the soil and as a result the decrease in matric suction in the swelling soil increases the force in the anchors and the bending moment in the pile. Also, the increase in the force of the anchors and the displacement created in the case of pipe bursting and absorption well modeling is much more than the conditions of the climate boundary effect for the two rainy months of the year. By increasing the distance of the absorption well and the bursting of the pipe from the excavation, the increase in the force created in the anchors decreases. climate conditions affect the upper 6 meters of the excavation, i.e. the active zone.

https://mcej.modares.ac.ir/article_12677_8c0f24a304f10044bcb756fd2ab2370f.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 01 Experimental Investigation of Energy Loss in Crump Spillways in Free Flow and Submerged State Experimental Investigation of Energy Loss in Crump Spillways in Free Flow and Submerged State 157 167 12678 A-10-45699-2 FA Mohammad Hasan Hashemi Fesharaki Ph.D. student, Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran Ali Khoshfetrat . Assistant Professor, Faculty of Civil Engineering, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran. Elham Izadinia Assistant Professor, Engineering College, Department of Civil Engineering, Shahid Ashrafi Esfahani University, Isfahan, Iran Ehsan Delavari Assistant Professor, Faculty of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran. Journal Article Dams are one of the best ways to store water in the long term. In general, it is important to increase the coefficient of water passage, more energy loss, and of course, to reduce scour downstream of dams and hydraulic structures and overflows. Weirs are part of hydraulic structures that allow more flow to pass over them during floods. Crump spillway also improves and protects the body of dams and spillway by passing excess flow during floods. Increasing the energy loss prevents the flow rate and scour or reduces the scour and prevents cracking and overturning of the crump weir. Many people have done valuable studies on the water transfer coefficient of crump weirs, but a review of previous research shows that few researchers have investigated the energy dissipation of crump weirs. Also, the energy dissipation in free flow and submerged states in Crump weirs has not been investigated. One of the conditions that can lead to an increase in energy loss is the presence of obstacles in the downstream slope of crump spillways. To better understand these cases, in this research, Crump spillways with different heights and slopes upstream and downstream were used. Also, the existence of the block (baffle) and the free and immersed states of the flow were investigated to estimate the energy losses. Experiments were carried out in a flume 10 meters long, 0.6 meters wide and 1.2 meters high. The flow is supplied by a pool tank and a pump. The flow is calmed down by flow relaxers and then reaches the overflow in 6 meters. To evaluate the effect of the slope and height of the spillway, three spillway models with a height of 0.15 meters and one spillway with a height of 0.2 meters and with different slopes upstream and downstream of the spillway were used. The flow rates used are 0.03, 0.035, 0.04, 0.045 and 0.05 cubic meters per second. By setting the appropriate engine speed for the pump, the flow rate entered the laboratory flume through the tank and the water depth was measured with the sensors installed on the top of the flume. The results showed that with the increase in the height of the overflows, the amount of energy loss decreases. The amount of energy loss in free flow mode with baffle is higher than the amount of energy loss in free flow mode without baffle. The amount of energy loss in submerged flow mode is lower than the amount of energy loss in free flow mode. As the downstream angle of the overflow decreases, the energy loss increases. By reducing the upstream angle of the overflow, energy loss is reduced. The amount of energy loss in free flow mode in type A, B, C and D spillways is 33.29, 33.83, 39.77 and 27.32% respectively. A general relationship was presented to calculate the amount of energy loss in crump weirs. In this relationship, there is a coefficient that is a function of free flow without baffle, submerged flow and free flow with baffle. Dams are one of the best ways to store water in the long term. In general, it is important to increase the coefficient of water passage, more energy loss, and of course, to reduce scour downstream of dams and hydraulic structures and overflows. Weirs are part of hydraulic structures that allow more flow to pass over them during floods. Crump spillway also improves and protects the body of dams and spillway by passing excess flow during floods. Increasing the energy loss prevents the flow rate and scour or reduces the scour and prevents cracking and overturning of the crump weir. Many people have done valuable studies on the water transfer coefficient of crump weirs, but a review of previous research shows that few researchers have investigated the energy dissipation of crump weirs. Also, the energy dissipation in free flow and submerged states in Crump weirs has not been investigated. One of the conditions that can lead to an increase in energy loss is the presence of obstacles in the downstream slope of crump spillways. To better understand these cases, in this research, Crump spillways with different heights and slopes upstream and downstream were used. Also, the existence of the block (baffle) and the free and immersed states of the flow were investigated to estimate the energy losses. Experiments were carried out in a flume 10 meters long, 0.6 meters wide and 1.2 meters high. The flow is supplied by a pool tank and a pump. The flow is calmed down by flow relaxers and then reaches the overflow in 6 meters. To evaluate the effect of the slope and height of the spillway, three spillway models with a height of 0.15 meters and one spillway with a height of 0.2 meters and with different slopes upstream and downstream of the spillway were used. The flow rates used are 0.03, 0.035, 0.04, 0.045 and 0.05 cubic meters per second. By setting the appropriate engine speed for the pump, the flow rate entered the laboratory flume through the tank and the water depth was measured with the sensors installed on the top of the flume. The results showed that with the increase in the height of the overflows, the amount of energy loss decreases. The amount of energy loss in free flow mode with baffle is higher than the amount of energy loss in free flow mode without baffle. The amount of energy loss in submerged flow mode is lower than the amount of energy loss in free flow mode. As the downstream angle of the overflow decreases, the energy loss increases. By reducing the upstream angle of the overflow, energy loss is reduced. The amount of energy loss in free flow mode in type A, B, C and D spillways is 33.29, 33.83, 39.77 and 27.32% respectively. A general relationship was presented to calculate the amount of energy loss in crump weirs. In this relationship, there is a coefficient that is a function of free flow without baffle, submerged flow and free flow with baffle.

https://mcej.modares.ac.ir/article_12678_e99ce0cdd4f46110c2497ea4f5ead1f1.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 2 2024 06 21 A new method for damage detection minor damages in the piers of straight bridges using fragility curves of harmonic forces A new method for damage detection minor damages in the piers of straight bridges using fragility curves of harmonic forces 185 201 12679 A-10-79063-1 FA Mohammad Mohammadi Tarbiat Modares University Farhad Daneshjoo Tarbiat Modares University 0000-0003-2636-5967 Journal Article Due to the increase in the age of bridges, the explanation and use of effective methods for detecting partial damage with the help of health monitoring systems are crucial since they provide the conditions for repairing the damage before the damage increases. One of the primary goals of this article is to provide an effective and efficient method for health monitoring and detect partial damage in the pier of a straight bridge using fragility curves of harmonic forces, and provide a criterion to show the correlation of fragility curves in healthy and damaged states. To achieve these goals, a complete model of a straight bridge that includes 8 piers, each 10 meters high and its deck includes 5 openings, the length of each is 15 meters, and the total length of the deck of 75 meters was modeled in the CSI Bridge software, and then, was validated. To detect the most vulnerable column for damage modeling for health monitoring operations, three earthquake records corresponding to the soil of the construction site were successively applied to the model. By examining the decrease in the slope of the moment-rotation graphs, the level of damage that occurred at the bottom of the column was detected. Finally, it was found that the middle piers were more prone to seismic damage and health monitoring operations were performed on one of the middle columns. To draw the fragility curves of harmonic forces, harmonic forces were first applied to the top of the column, and then, the rotations created at the bottom of the column were measured. Based on the obtained data and using the relevant relations, the fragility curves were drawn. The index of the maximum intensity of force, the index of rotation damage that occurred at the bottom of the column, and the defined performance level of exceedance from the linear state are the characteristics of these fragility curves. To draw the fragility curve in the damaged state, the desired earthquake (seismic) force was first applied to the bridge, and then, harmonic forces were applied to the top of the desired column. The results of this study revealed that the fragility curves of harmonic forces have been drawn well in healthy and partially damaged states according to the defined characteristics, and partial damages with different intensities have been correctly detected. To examine the correlation of the fragility curves of harmonic forces in both damaged and healthy states, two new criteria PCOMAC and PDI were introduced. The results of this article indicate that the PCOMAC criterion is very suitable for examining the correlation of fragility curves of harmonic forces. Due to the increase in the age of bridges, the explanation and use of effective methods for detecting partial damage with the help of health monitoring systems are crucial since they provide the conditions for repairing the damage before the damage increases. One of the primary goals of this article is to provide an effective and efficient method for health monitoring and detect partial damage in the pier of a straight bridge using fragility curves of harmonic forces, and provide a criterion to show the correlation of fragility curves in healthy and damaged states. To achieve these goals, a complete model of a straight bridge that includes 8 piers, each 10 meters high and its deck includes 5 openings, the length of each is 15 meters, and the total length of the deck of 75 meters was modeled in the CSI Bridge software, and then, was validated. To detect the most vulnerable column for damage modeling for health monitoring operations, three earthquake records corresponding to the soil of the construction site were successively applied to the model. By examining the decrease in the slope of the moment-rotation graphs, the level of damage that occurred at the bottom of the column was detected. Finally, it was found that the middle piers were more prone to seismic damage and health monitoring operations were performed on one of the middle columns. To draw the fragility curves of harmonic forces, harmonic forces were first applied to the top of the column, and then, the rotations created at the bottom of the column were measured. Based on the obtained data and using the relevant relations, the fragility curves were drawn. The index of the maximum intensity of force, the index of rotation damage that occurred at the bottom of the column, and the defined performance level of exceedance from the linear state are the characteristics of these fragility curves. To draw the fragility curve in the damaged state, the desired earthquake (seismic) force was first applied to the bridge, and then, harmonic forces were applied to the top of the desired column. The results of this study revealed that the fragility curves of harmonic forces have been drawn well in healthy and partially damaged states according to the defined characteristics, and partial damages with different intensities have been correctly detected. To examine the correlation of the fragility curves of harmonic forces in both damaged and healthy states, two new criteria PCOMAC and PDI were introduced. The results of this article indicate that the PCOMAC criterion is very suitable for examining the correlation of fragility curves of harmonic forces.

https://mcej.modares.ac.ir/article_12679_fcf059b3a04a642eca4c21bd3fa5e9e3.pdf