Mathieu Goron, B. Langrand, T. Fourest, N. Jacques, A. Tassin
During the emergency landing of an aircraft on water, the structure may experience critical forces and could eventually fail. The appropriate design of the structure should minimize the risk of occupant injuries. The recent progress in computation capabilities led to the increased use of numerical simulations in the certification process of aircraft. A specific challenge concerns the modelisation of suction forces that develop near the aircraft tail, where the first contact with water occurs. This phenomenon is due to the high horizontal velocity of the structure at impact and the longitudinal curvature of the fuselage. It can affect the overall aircraft kinematics during ditching. In this work, as an effort to improve aircraft ditching simulations and to assess the capabilities of numerical models to describe suction forces, the simple test case of the wedge water entry and subsequent exit is considered. Numerical simulations with the Eulerian formulation for the fluid and the Lagrangian formulation for the structure are used. The method used for the fluid–structure interaction is based on an immersed contact interface with penalty forces. The present work focuses on impact and suction forces modelling. Results show a satisfying capacity of the numerical approach to model negative hydrodynamic force (suction).
{"title":"ASSESSMENT OF COUPLED LAGRANGIAN–EULERIAN FINITE ELEMENT SIMULATIONS TO MODEL SUCTION FORCES DURING HYDRODYNAMIC IMPACTS","authors":"Mathieu Goron, B. Langrand, T. Fourest, N. Jacques, A. Tassin","doi":"10.2495/hpsu220101","DOIUrl":"https://doi.org/10.2495/hpsu220101","url":null,"abstract":"During the emergency landing of an aircraft on water, the structure may experience critical forces and could eventually fail. The appropriate design of the structure should minimize the risk of occupant injuries. The recent progress in computation capabilities led to the increased use of numerical simulations in the certification process of aircraft. A specific challenge concerns the modelisation of suction forces that develop near the aircraft tail, where the first contact with water occurs. This phenomenon is due to the high horizontal velocity of the structure at impact and the longitudinal curvature of the fuselage. It can affect the overall aircraft kinematics during ditching. In this work, as an effort to improve aircraft ditching simulations and to assess the capabilities of numerical models to describe suction forces, the simple test case of the wedge water entry and subsequent exit is considered. Numerical simulations with the Eulerian formulation for the fluid and the Lagrangian formulation for the structure are used. The method used for the fluid–structure interaction is based on an immersed contact interface with penalty forces. The present work focuses on impact and suction forces modelling. Results show a satisfying capacity of the numerical approach to model negative hydrodynamic force (suction).","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86403643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes a study on the mechanical response of concrete under high-velocity impact. It encompasses both experiments and numerical simulations. The aim is to validate an approach for building a concrete numerical model sufficiently robust and accessible to be used for designing civil or defense infrastructures. A conventional concrete (35 MPa compressive strength) has been chosen to apply the method. Experimental tests are conducted to characterize the material in compression and to measure its residual strength during compaction. Impact tests of a kinetic energy projectile (KEP) with an ogive shape nose are also conducted at velocities ranging from 200 to 900 m/s to reproduce both subsonic and supersonic impact conditions. The effect of the concrete confinement is investigated by varying the thickness of a metal jacket surrounding the impacted specimen. Regarding the numerical model, a Holmquist–Johnson–Cook (HJC) for concrete has been calibrated from the measured data. Simulations of the impact perforation are conducted with the γ-SPH solver available in IMPETUS AFEA TM . The numerical model has been able to reproduce the main damage in the concrete during the projectile penetration. Good correlation in terms of deceleration profile during penetration is obtained with the experiment. Moreover, the model is robust enough to reproduce the effects of the confinement variation in the projectile residual velocity. This methodology could be applied to other types of concrete materials subjected to various loadings such as near-field blast for example.
{"title":"ENGINEERING APPROACH TO CALIBRATE A CONCRETE MODEL FOR HIGH SPEED IMPACT APPLICATIONS","authors":"Hakim Abdulhamid, P. Deconinck, J. Mespoulet","doi":"10.2495/hpsu220111","DOIUrl":"https://doi.org/10.2495/hpsu220111","url":null,"abstract":"This paper describes a study on the mechanical response of concrete under high-velocity impact. It encompasses both experiments and numerical simulations. The aim is to validate an approach for building a concrete numerical model sufficiently robust and accessible to be used for designing civil or defense infrastructures. A conventional concrete (35 MPa compressive strength) has been chosen to apply the method. Experimental tests are conducted to characterize the material in compression and to measure its residual strength during compaction. Impact tests of a kinetic energy projectile (KEP) with an ogive shape nose are also conducted at velocities ranging from 200 to 900 m/s to reproduce both subsonic and supersonic impact conditions. The effect of the concrete confinement is investigated by varying the thickness of a metal jacket surrounding the impacted specimen. Regarding the numerical model, a Holmquist–Johnson–Cook (HJC) for concrete has been calibrated from the measured data. Simulations of the impact perforation are conducted with the γ-SPH solver available in IMPETUS AFEA TM . The numerical model has been able to reproduce the main damage in the concrete during the projectile penetration. Good correlation in terms of deceleration profile during penetration is obtained with the experiment. Moreover, the model is robust enough to reproduce the effects of the confinement variation in the projectile residual velocity. This methodology could be applied to other types of concrete materials subjected to various loadings such as near-field blast for example.","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91289414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Diego Villalba, J. París, I. Couceiro, F. Navarrina
The first formulation of topology optimization was proposed in the 1980s. Since then, many contributions have been presented with the purpose of improving its efficiency and expanding its field of application. The aim of this research is to develop a structural topology optimization algorithm considering minimum weight and stress constraints. Structural topology optimization with stress constraints has been previously formulated with several different approaches, mainly: local stress constraints, global stress constraints or block aggregation of stress constraints. In this research the overweight approach, an improvement of the so-called damage approach, is used. In this method, a virtual relative density (VRD) is defined as a function of the violation of the local stress constraints. VRD is increased as the stresses exceed the maximum allowable value, with the exception of the areas with the minimum value of the relative density, since full-void solutions are intended. The distribution of the material in the domain is modelled using two different approaches: a uniform relative density within each element of the mesh and a relative density defined by means of quadratic B-splines. For this reason, the structural analysis is performed by means of the finite element method (FEM) and the isogeometric analysis (IGA) respectively. The optimization is addressed by means of the sequential linear programming algorithm (SLP), which is driven by the information provided by a full first order sensitivity analysis extension of both FEM and IGA formulations. Finally, the overweight approach is tested by means of some two dimensional problems. The domain has been divided in an elevated number of elements to attain high spatial definition solutions. The results show that the overweight approach is a feasible alternative for the damage approach and the stress constraints aggregation techniques to solve the topology optimization problem. A comparison between both formulations of the material distribution is included.
{"title":"STRUCTURAL TOPOLOGY OPTIMIZATION WITH HIGH SPATIAL DEFINITION BY USING THE OVERWEIGHT APPROACH","authors":"Diego Villalba, J. París, I. Couceiro, F. Navarrina","doi":"10.2495/hpsu220071","DOIUrl":"https://doi.org/10.2495/hpsu220071","url":null,"abstract":"The first formulation of topology optimization was proposed in the 1980s. Since then, many contributions have been presented with the purpose of improving its efficiency and expanding its field of application. The aim of this research is to develop a structural topology optimization algorithm considering minimum weight and stress constraints. Structural topology optimization with stress constraints has been previously formulated with several different approaches, mainly: local stress constraints, global stress constraints or block aggregation of stress constraints. In this research the overweight approach, an improvement of the so-called damage approach, is used. In this method, a virtual relative density (VRD) is defined as a function of the violation of the local stress constraints. VRD is increased as the stresses exceed the maximum allowable value, with the exception of the areas with the minimum value of the relative density, since full-void solutions are intended. The distribution of the material in the domain is modelled using two different approaches: a uniform relative density within each element of the mesh and a relative density defined by means of quadratic B-splines. For this reason, the structural analysis is performed by means of the finite element method (FEM) and the isogeometric analysis (IGA) respectively. The optimization is addressed by means of the sequential linear programming algorithm (SLP), which is driven by the information provided by a full first order sensitivity analysis extension of both FEM and IGA formulations. Finally, the overweight approach is tested by means of some two dimensional problems. The domain has been divided in an elevated number of elements to attain high spatial definition solutions. The results show that the overweight approach is a feasible alternative for the damage approach and the stress constraints aggregation techniques to solve the topology optimization problem. A comparison between both formulations of the material distribution is included.","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83424390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A methodology to obtain the minimum weight of cables in cable-stayed bridges when a cable fails has been developed. To this end, a multi-model strategy is proposed that takes into account design constraints in both the intact and damaged models. The dynamic effect of the cable breakage is considered by the application of impact loads at the tower and deck anchorages. The methodology is applied to the Queensferry Crossing Bridge, a multi-span cable-stayed bridge with cross stay cables in the central section of each main span. The number of cables, anchorage position on the deck, cable areas and prestressing forces are considered as design variables into the optimization process simultaneously. The fail-safe optimum design results in a different cable layout than the optimized design of the intact structure, with minimum volume increase.
{"title":"OPTIMUM DESIGN OF CABLE-STAYED BRIDGES CONSIDERING CABLE FAILURE","authors":"Noel Soto, C. Cid, A. Baldomir, S. Hernández","doi":"10.2495/hpsu220051","DOIUrl":"https://doi.org/10.2495/hpsu220051","url":null,"abstract":"A methodology to obtain the minimum weight of cables in cable-stayed bridges when a cable fails has been developed. To this end, a multi-model strategy is proposed that takes into account design constraints in both the intact and damaged models. The dynamic effect of the cable breakage is considered by the application of impact loads at the tower and deck anchorages. The methodology is applied to the Queensferry Crossing Bridge, a multi-span cable-stayed bridge with cross stay cables in the central section of each main span. The number of cables, anchorage position on the deck, cable areas and prestressing forces are considered as design variables into the optimization process simultaneously. The fail-safe optimum design results in a different cable layout than the optimized design of the intact structure, with minimum volume increase.","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85839724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Castedo, Anastasio P. Santos, C. Reifarth, M. Chiquito, Lina María López, A. Pérez-Caldentey, S. Martínez-Almajano, A. Alañón
Numerical simulation of reinforced concrete (RC) slabs with the addition of an external reinforced polymer (FRP) have been developed and compared with full scale real tests. The size of the slabs was 4.4 x 1.46 m, with a span of 4 m, and a thickness of 15 cm. The slabs were built using concrete of class C25/30, and B500C reinforcing steel. Seven tests were conducted, one at a scaled distance of 0.83 m/kg 1/3 , three at a scaled distance of 0.42 m/kg 1/3 , and three at 0.21 m/kg 1/3 . For the biggest scaled distance, the slab had no extra reinforcement. In the other two cases one of the slabs had no extra reinforcement, while the other two tests were performed with carbon fibre reinforcement (CFRP) and E-glass fibre reinforcement (GFRP) located on the face opposite to the blast. Numerical simulation was performed with LS-DYNA software. The study elements (concrete, steel and reinforcement) have been simulated in a Lagrangian formulation with solid elements, beam elements and shells, respectively. Three concrete models have been used and compared: CSCM, MAT72-R3 and RHT. As for the explosive, the CONWEP-based Load Blast Enhanced (LBE) card was used. Reinforcement with CFRP resulted in a generally reduced damage area on both surfaces. All models show a good correlation with the test results and a non-destructive damage estimation technique when comparing them in terms of damage area.
本文对外加FRP的钢筋混凝土(RC)板进行了数值模拟，并与实际试验结果进行了比较。石板的尺寸为4.4 x 1.46米，跨度为4米，厚度为15厘米。楼板采用C25/30级混凝土和B500C钢筋建造。共进行了7次试验，分别为0.83 m/kg 1/3、0.42 m/kg 1/3和0.21 m/kg 1/3。在最大比例尺处，楼板不加筋。在另外两种情况下，其中一种板没有额外的加固，而另外两种测试是在爆炸对面的面上使用碳纤维加固(CFRP)和e -玻璃纤维加固(GFRP)进行的。采用LS-DYNA软件进行数值模拟。研究单元(混凝土、钢和钢筋)分别用固体单元、梁单元和壳单元的拉格朗日公式进行了模拟。采用了CSCM、MAT72-R3和RHT三种具体模型并进行了比较。炸药采用基于conwep的负载爆炸增强(LBE)卡。用CFRP加固导致两个表面的损伤面积普遍减少。在损伤面积方面，各模型均与试验结果和无损损伤估计技术具有良好的相关性。
{"title":"FULL-SCALE REINFORCED CONCRETE SLABS WITH EXTERNAL REINFORCED POLYMER: FIELD TEST AND NUMERICAL COMPARISON","authors":"R. Castedo, Anastasio P. Santos, C. Reifarth, M. Chiquito, Lina María López, A. Pérez-Caldentey, S. Martínez-Almajano, A. Alañón","doi":"10.2495/hpsu220121","DOIUrl":"https://doi.org/10.2495/hpsu220121","url":null,"abstract":"Numerical simulation of reinforced concrete (RC) slabs with the addition of an external reinforced polymer (FRP) have been developed and compared with full scale real tests. The size of the slabs was 4.4 x 1.46 m, with a span of 4 m, and a thickness of 15 cm. The slabs were built using concrete of class C25/30, and B500C reinforcing steel. Seven tests were conducted, one at a scaled distance of 0.83 m/kg 1/3 , three at a scaled distance of 0.42 m/kg 1/3 , and three at 0.21 m/kg 1/3 . For the biggest scaled distance, the slab had no extra reinforcement. In the other two cases one of the slabs had no extra reinforcement, while the other two tests were performed with carbon fibre reinforcement (CFRP) and E-glass fibre reinforcement (GFRP) located on the face opposite to the blast. Numerical simulation was performed with LS-DYNA software. The study elements (concrete, steel and reinforcement) have been simulated in a Lagrangian formulation with solid elements, beam elements and shells, respectively. Three concrete models have been used and compared: CSCM, MAT72-R3 and RHT. As for the explosive, the CONWEP-based Load Blast Enhanced (LBE) card was used. Reinforcement with CFRP resulted in a generally reduced damage area on both surfaces. All models show a good correlation with the test results and a non-destructive damage estimation technique when comparing them in terms of damage area.","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85257024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since the Paris Agreement was established, great interest has arisen in evaluating the sustainability performance of our structures along with their life cycles. The remarkable economic expenses, the important environmental impacts associated with the construction sector, and the great social benefits that might be derived from a well-designed infrastructure system have put the design of essential infrastructures in the spotlight of many researchers. One of today’s main challenges is the derivation of adequate sustainability indicators that aid designers when deciding on the most sustainable design alternative. The sustainability performance of infrastructures is based on various indicators that are often conflicting given their different nature. Consequently, the obtention of such indicators usually needs to be addressed using multi-criteria decision-making methods. The present communication shows the analytic hierarchy process (ANP) for the sustainability assessment of a concrete bridge exposed to a coastal environment, involving several decision-makers. A set of nine quantitative criteria, covering the economic, environmental, and social dimensions of sustainability, has been considered here.
{"title":"GROUP ANALYTIC NETWORK PROCESS FOR THE SUSTAINABILITY ASSESSMENT OF BRIDGES NEAR SHORE","authors":"Ignacio J. Navarro, J. Martí, V. Yepes","doi":"10.2495/hpsu220131","DOIUrl":"https://doi.org/10.2495/hpsu220131","url":null,"abstract":"Since the Paris Agreement was established, great interest has arisen in evaluating the sustainability performance of our structures along with their life cycles. The remarkable economic expenses, the important environmental impacts associated with the construction sector, and the great social benefits that might be derived from a well-designed infrastructure system have put the design of essential infrastructures in the spotlight of many researchers. One of today’s main challenges is the derivation of adequate sustainability indicators that aid designers when deciding on the most sustainable design alternative. The sustainability performance of infrastructures is based on various indicators that are often conflicting given their different nature. Consequently, the obtention of such indicators usually needs to be addressed using multi-criteria decision-making methods. The present communication shows the analytic hierarchy process (ANP) for the sustainability assessment of a concrete bridge exposed to a coastal environment, involving several decision-makers. A set of nine quantitative criteria, covering the economic, environmental, and social dimensions of sustainability, has been considered here.","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73137583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Arm-Z is a concept of a hyper-redundant manipulator based on linearly joined sequence of congruent units. Each unit has only one degree of freedom (1-DOF), namely a twist relative to the previous unit in the sequence. Since each module is identical, Arm-Z has a potential of being economical and robust: the modules can be mass-produced and, in case of failure, easily replaced. However, the control of Arm-Z is nonintuitive and difficult, thus it usually requires application of computational intelligence methods. This paper presents a number of concepts for kinetic street furniture based on Arm-Z: a spiral column of adjustable height, a sun-tracking shade/solar energy harvester, bio-mimicry sculpture, kinetic sprinkler/fountain. The proposed concepts are low-tech in principle. Therefore in each case, the first module in the sequence is fastened to a solid base (ground). For simplicity, the drive is applied directly to the first module and transferred to subsequent units by internal gears. Each module is equipped with a set of cylindrical and bevel gears with straight teeth with involute profile (for connecting the modules).
{"title":"KINETIC STREET FURNITURE WITH ARM-Z","authors":"Ela Zawidzka, M. Zawidzki","doi":"10.2495/hpsu220021","DOIUrl":"https://doi.org/10.2495/hpsu220021","url":null,"abstract":"Arm-Z is a concept of a hyper-redundant manipulator based on linearly joined sequence of congruent units. Each unit has only one degree of freedom (1-DOF), namely a twist relative to the previous unit in the sequence. Since each module is identical, Arm-Z has a potential of being economical and robust: the modules can be mass-produced and, in case of failure, easily replaced. However, the control of Arm-Z is nonintuitive and difficult, thus it usually requires application of computational intelligence methods. This paper presents a number of concepts for kinetic street furniture based on Arm-Z: a spiral column of adjustable height, a sun-tracking shade/solar energy harvester, bio-mimicry sculpture, kinetic sprinkler/fountain. The proposed concepts are low-tech in principle. Therefore in each case, the first module in the sequence is fastened to a solid base (ground). For simplicity, the drive is applied directly to the first module and transferred to subsequent units by internal gears. Each module is equipped with a set of cylindrical and bevel gears with straight teeth with involute profile (for connecting the modules).","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86429899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Because of its relevance in civil infrastructures, the analysis of the dynamic behaviour of concrete has increased exponentially in recent years. This is motivated by the new type of threats that have to be taken into consideration nowadays when designing these types of structures. The growing interest in the dynamic response of concrete arises from the enhancement of its mechanical properties when the material is subjected to high strain rates. In this research, the traditional Split Hopkinson Pressure Bar developed by Kolsky, with a standard compression configuration (including incident and transmitted bars) was modified into a version in which the transmission bar was removed, so that the specimen’s response is dominated by tensile stresses inside it. Spalling tests on cylindrical samples were carried out to measure the tensile strength and the fracture energy of conventional concrete. Results for strain rates ranging from 60 to 130 s –1 are presented and compared to the respective quasi-static values. As the key point of the research, two different projectile shapes (cylindrical and conical) have also been evaluated, presenting a qualitative and quantitative analysis regarding the variations in tensile stress evolution of the pulses. a deeper analysis should be done to clarify this point. From the tests, a mean value of 1.264 N/mm was obtained. Similar values of G (cid:3007) were obtained between cylindrical and conical projectiles, just a small difference in the higher strain rate produced by the cylindrical projectile. DIF parameter for the fracture energy show that even when the strain rate is kept within a narrow range, a common increasing trend can be seen.
由于其与民用基础设施的相关性，近年来对混凝土动力性能的分析呈指数级增长。这是由于现在在设计这些类型的结构时必须考虑到的新型威胁。混凝土在高应变率下力学性能的增强引起了人们对混凝土动态响应的兴趣。在本研究中，将由Kolsky开发的具有标准压缩配置(包括入射杆和透射杆)的传统分离式霍普金森压杆修改为去除透射杆的版本，使试件的响应由其内部的拉应力主导。对圆柱形试样进行了剥落试验，测定了常规混凝土的抗拉强度和断裂能。给出了应变率范围为60 ~ 130 s -1的结果，并与相应的准静态值进行了比较。作为研究的重点，还对两种不同形状的弹丸(圆柱形和锥形)进行了评估，对脉冲拉应力演化的变化进行了定性和定量分析。为了澄清这一点，应该进行更深入的分析。试验得到的平均值为1.264 N/mm。圆柱形和锥形弹丸的G值(cid:3007)相似，圆柱形弹丸产生的应变率较高，相差不大。断裂能的DIF参数表明，即使应变率保持在较窄的范围内，也有共同的增大趋势。
{"title":"INFLUENCE OF THE PROJECTILE SHAPE ON THE DYNAMIC TENSILE CHARACTERIZATION OF CONCRETE USING A SPLIT HOPKINSON BAR","authors":"M. Ruiz-Ripoll, Victor Rey DE PEDRAZA, C. Roller","doi":"10.2495/hpsu220141","DOIUrl":"https://doi.org/10.2495/hpsu220141","url":null,"abstract":"Because of its relevance in civil infrastructures, the analysis of the dynamic behaviour of concrete has increased exponentially in recent years. This is motivated by the new type of threats that have to be taken into consideration nowadays when designing these types of structures. The growing interest in the dynamic response of concrete arises from the enhancement of its mechanical properties when the material is subjected to high strain rates. In this research, the traditional Split Hopkinson Pressure Bar developed by Kolsky, with a standard compression configuration (including incident and transmitted bars) was modified into a version in which the transmission bar was removed, so that the specimen’s response is dominated by tensile stresses inside it. Spalling tests on cylindrical samples were carried out to measure the tensile strength and the fracture energy of conventional concrete. Results for strain rates ranging from 60 to 130 s –1 are presented and compared to the respective quasi-static values. As the key point of the research, two different projectile shapes (cylindrical and conical) have also been evaluated, presenting a qualitative and quantitative analysis regarding the variations in tensile stress evolution of the pulses. a deeper analysis should be done to clarify this point. From the tests, a mean value of 1.264 N/mm was obtained. Similar values of G (cid:3007) were obtained between cylindrical and conical projectiles, just a small difference in the higher strain rate produced by the cylindrical projectile. DIF parameter for the fracture energy show that even when the strain rate is kept within a narrow range, a common increasing trend can be seen.","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76583386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
One of the major barriers for municipalities responsible for mitigation of sewage exfiltration is locating grossly leaking sections of the sewage conveyance system in a time-, labor- and cost-efficient manner. In this study, water samples were collected from the dense network of manholes overlying the storm drain systems in the tourist area of Waikīkī and inland residential areas on the island of O‘ahu, Hawai‘i. The majority of the sewage conveyance infrastructure in this coastal area is submerged and the storm drains are routinely subject to backflow during high tide. Exfiltration of sewage from the aging conveyance system in this coastal area contaminates the surrounding shallow brackish aquifer, which then enters leaking pipe joints and cracks in the storm water conveyance system. Samples collected from the storm drains were analyzed for the presence of carbamazepine, a commonly prescribed anticonvulsant, pain relief and bipolar disorder treatment drug, which behaves as a conservative tracer in the environment (> 50 days half-life, low sorption). Samples were also analyzed for the more labile anthropogenic tracer caffeine (~4 day half-life). The higher stability of carbamazepine enables detection of this compound at greater distances from sewage release sites while caffeine serves as a better tracer for detecting recent, proximal releases of sewage, given its ephemeral nature and relatively high and ubiquitous presence. The concentration levels and spatial distribution of detection of these two anthropogenic biomarkers were successfully used to identify areas of ongoing sewage exfiltration in Waikīkī and surrounding residential communities. The variation in carbamazepine and caffeine concentrations measured in Waikīkī storm drains over a 1 year period generally correlate with daily visitor arrivals to O‘ahu.
负责减少污水外溢的市政当局面临的主要障碍之一是以时间、劳动力和成本效益高的方式找到污水输送系统中严重泄漏的部分。在这项研究中，从夏威夷O’ahu岛旅游区和内陆住宅区的雨排水系统上密集的沙井网络中收集水样。这个沿海地区的大部分污水输送基础设施都被淹没，在涨潮时，雨水渠经常会回流。沿海地区老化的输水系统所排放的污水污染了周围的浅咸淡水含水层，然后进入雨水输水系统漏水的管道接头和裂缝。分析从雨水沟收集的样本是否存在卡马西平。卡马西平是一种常用的抗惊厥、缓解疼痛和治疗双相情感障碍的药物，在环境中表现为保守的示踪剂(半衰期> 50天，吸附性低)。样品也分析了更不稳定的人为示踪剂咖啡因(~4天的半衰期)。卡马西平的高稳定性使人们能够在距离污水排放点较远的地方检测到这种化合物，而咖啡因则是一种较好的示踪剂，可以检测最近的、近距离的污水排放，因为咖啡因的性质短暂，含量相对较高且无处不在。利用这两种人为生物标志物的浓度水平和检测的空间分布，成功地确定了waik k ā及其周围居民社区正在进行的污水外溢区域。在waik ki雨水渠中测量的卡马西平和咖啡因浓度在一年内的变化通常与每天到欧胡岛的游客人数有关。
{"title":"IDENTIFICATION OF SEWAGE EXFILTRATION IN COASTAL AREAS THROUGH THE MONITORING OF DRUGS AND STIMULANT CONCENTRATIONS IN URBAN STORM DRAINS","authors":"S. Spengler, M. Heskett","doi":"10.2495/friar220061","DOIUrl":"https://doi.org/10.2495/friar220061","url":null,"abstract":"One of the major barriers for municipalities responsible for mitigation of sewage exfiltration is locating grossly leaking sections of the sewage conveyance system in a time-, labor- and cost-efficient manner. In this study, water samples were collected from the dense network of manholes overlying the storm drain systems in the tourist area of Waikīkī and inland residential areas on the island of O‘ahu, Hawai‘i. The majority of the sewage conveyance infrastructure in this coastal area is submerged and the storm drains are routinely subject to backflow during high tide. Exfiltration of sewage from the aging conveyance system in this coastal area contaminates the surrounding shallow brackish aquifer, which then enters leaking pipe joints and cracks in the storm water conveyance system. Samples collected from the storm drains were analyzed for the presence of carbamazepine, a commonly prescribed anticonvulsant, pain relief and bipolar disorder treatment drug, which behaves as a conservative tracer in the environment (> 50 days half-life, low sorption). Samples were also analyzed for the more labile anthropogenic tracer caffeine (~4 day half-life). The higher stability of carbamazepine enables detection of this compound at greater distances from sewage release sites while caffeine serves as a better tracer for detecting recent, proximal releases of sewage, given its ephemeral nature and relatively high and ubiquitous presence. The concentration levels and spatial distribution of detection of these two anthropogenic biomarkers were successfully used to identify areas of ongoing sewage exfiltration in Waikīkī and surrounding residential communities. The variation in carbamazepine and caffeine concentrations measured in Waikīkī storm drains over a 1 year period generally correlate with daily visitor arrivals to O‘ahu.","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84867997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quiriatjaryn M. Ortega-Samaniego, Andres Fraíz, A. Dominici, A. Ramos‐Merchante, M. Pachés, I. Romero
The Pacora River is one of the priority basins of the Republic of Panama since it provides water for human consumption therefore its conservation is of great importance; the country has laws that protect the integrity of the basins from their ecological nature to that for use for economic activities. This basin has great potential not only for agricultural activities but also a buffer for population development in the urban area of the country. This study was carried out in the middle and lower upper parts of the Pacora River during the wet, dry and transitional season, the data obtained was used to calculate the water quality index and the fluvial habitat index and the elaboration of an impact–pressure matrix, in order to evaluate the levels of influence that anthropogenic activities have in the area, based on established laws regulating water quality levels and forest legislation. The results obtained indicate that the Pacora River are among the ranges of little polluted, acceptable and uncontaminated for the water quality index and for the habitat fluvial index in the range of not reaching very good, good and very good. Regarding the analysis of pressures and impacts, the values are between probable impact, checked and non-apparent impact and medium to high risk. These data indicate a shift in the use of native forest land to industrial, agricultural and urban activities.
{"title":"PRESSURES–IMPACT ANALYSIS OF THE PACORA RIVER, PANAMA","authors":"Quiriatjaryn M. Ortega-Samaniego, Andres Fraíz, A. Dominici, A. Ramos‐Merchante, M. Pachés, I. Romero","doi":"10.2495/friar220101","DOIUrl":"https://doi.org/10.2495/friar220101","url":null,"abstract":"The Pacora River is one of the priority basins of the Republic of Panama since it provides water for human consumption therefore its conservation is of great importance; the country has laws that protect the integrity of the basins from their ecological nature to that for use for economic activities. This basin has great potential not only for agricultural activities but also a buffer for population development in the urban area of the country. This study was carried out in the middle and lower upper parts of the Pacora River during the wet, dry and transitional season, the data obtained was used to calculate the water quality index and the fluvial habitat index and the elaboration of an impact–pressure matrix, in order to evaluate the levels of influence that anthropogenic activities have in the area, based on established laws regulating water quality levels and forest legislation. The results obtained indicate that the Pacora River are among the ranges of little polluted, acceptable and uncontaminated for the water quality index and for the habitat fluvial index in the range of not reaching very good, good and very good. Regarding the analysis of pressures and impacts, the values are between probable impact, checked and non-apparent impact and medium to high risk. These data indicate a shift in the use of native forest land to industrial, agricultural and urban activities.","PeriodicalId":23773,"journal":{"name":"WIT Transactions on the Built Environment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76720935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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