Timber is a sustainable construction material having a higher strength to density ratio, lower embodied energy and a lower carbon footprint when compared with conventional construction materials such as steel and concrete. Furthermore, the advent of engineered wood products including glued laminated timber (Glulam), cross laminated timber (CLT) and laminated veneer lumber (LVL) with improved mechanical properties and dimensional stability has provided the opportunity to construct multi-storey timber buildings with robustness and reliability comparable to steel and reinforced concrete structures, but with far less environmental intrusion. This paper investigates the behaviour of CLT panels connected to LVL and/or Glulam timber joists by coach screws, creating a timber–timber composite (TTC) member. The load-slip behaviour and failure modes of the CLT–LVL and CLT–Glulam composite members are characterised by conducting push-out tests and the effect of the CLT lamellae orientation, screw size and inclination and the edge distance in conjunction with the type of timber joist (LVL, softwood/hardwood Glulam) on the structural behaviour of the TTC members are investigated. Finally, an empirical model for the load-slip response of the TTC members with dowel connections is developed and calibrated from non-linear regression of the push-out test data.
{"title":"EXPERIMENTAL STUDY OF TIMBER–TIMBER COMPOSITE MEMBERS","authors":"F. Nouri, M. Bradford, H. Valipour","doi":"10.2495/HPSM180091","DOIUrl":"https://doi.org/10.2495/HPSM180091","url":null,"abstract":"Timber is a sustainable construction material having a higher strength to density ratio, lower embodied energy and a lower carbon footprint when compared with conventional construction materials such as steel and concrete. Furthermore, the advent of engineered wood products including glued laminated timber (Glulam), cross laminated timber (CLT) and laminated veneer lumber (LVL) with improved mechanical properties and dimensional stability has provided the opportunity to construct multi-storey timber buildings with robustness and reliability comparable to steel and reinforced concrete structures, but with far less environmental intrusion. This paper investigates the behaviour of CLT panels connected to LVL and/or Glulam timber joists by coach screws, creating a timber–timber composite (TTC) member. The load-slip behaviour and failure modes of the CLT–LVL and CLT–Glulam composite members are characterised by conducting push-out tests and the effect of the CLT lamellae orientation, screw size and inclination and the edge distance in conjunction with the type of timber joist (LVL, softwood/hardwood Glulam) on the structural behaviour of the TTC members are investigated. Finally, an empirical model for the load-slip response of the TTC members with dowel connections is developed and calibrated from non-linear regression of the push-out test data.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124937650","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}
An attempt has been made to evaluate and predict the traffic-induced ground vibration using a hybrid optimized ANFIS-based model. Towards this aim, ground vibrations caused by traffic were monitored on a building located near the road. To investigate the appropriateness of this approach, the prediction by ANFIS was also compared with the most widely used vibration predictors. In this research, a hybrid of adaptive neuro-fuzzy inference system (ANFIS) optimized by particle swarm optimization (PSO) and genetic algorithm (GA) was proposed to predict traffic-produced ground vibration. The performance criterion selected for the comparison between the actual and the predicted data were the sum of squares due to error (SSE), the root mean square error (RMSE), and goodness of fit (R-square, adjusted R-square). It turns out that the hybrid GA-ANFIS prediction model outperforms the commonly used predictors and conventional ANFIS.
{"title":"A NEW APPROACH FOR THE PREDICTION OF TRAFFIC-INDUCED GROUND VIBRATION USING A HYBRID OPTIMIZED ANFIS-BASED MODEL","authors":"S. Lubej, A. Ivanič","doi":"10.2495/HPSM180201","DOIUrl":"https://doi.org/10.2495/HPSM180201","url":null,"abstract":"An attempt has been made to evaluate and predict the traffic-induced ground vibration using a hybrid optimized ANFIS-based model. Towards this aim, ground vibrations caused by traffic were monitored on a building located near the road. To investigate the appropriateness of this approach, the prediction by ANFIS was also compared with the most widely used vibration predictors. In this research, a hybrid of adaptive neuro-fuzzy inference system (ANFIS) optimized by particle swarm optimization (PSO) and genetic algorithm (GA) was proposed to predict traffic-produced ground vibration. The performance criterion selected for the comparison between the actual and the predicted data were the sum of squares due to error (SSE), the root mean square error (RMSE), and goodness of fit (R-square, adjusted R-square). It turns out that the hybrid GA-ANFIS prediction model outperforms the commonly used predictors and conventional ANFIS.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129416317","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}
To ensure safety of electric vehicles using green composites, this study examined the interlaminar shear strength, creep rupture strength, and useful life of plain woven jute fiber cloth reinforced polylactic acid after water immersion. The fiber volume fraction of the green composite was 40%. Water absorption tests were conducted of the green composite comprising jute fiber and polylactic acid (PLA). Tensile creep tests of green composite and jute fiber were conducted after water immersion. The maximum stress was 60–90% of tensile strength. The environmental temperature was room temperature. Short beam testing of double-notched green composite was also conducted after water immersion. Results show the following. When water absorption tests were conducted, the water absorption rates of green composite, jute fiber and PLA at 24 hr were 9%, 3.4% and 0.3%, respectively. The creep rupture strength of 9% water absorbed green composite was lower than that of non-water-absorbed (non-absorbed) green composite. However, the creep rupture strength of 3.4% water absorbed jute fiber was slightly higher than that of non-absorbed jute fiber. For maximum stress of 40 MPa, the creep rupture life of 9% water absorbed green composite was much shorter than that of the non-absorbed green composite. Interlaminar shear strength of 9% water absorbed green composite was lower by 11% than that of the non-absorbed green composite. Water penetrated to the fiber–resin interface when water absorption test of green composite was conducted until 24 hr. Therefore, the interlaminar shear strength, creep rupture life, and green composite strength were decreased mainly because of the decrease of fiber–resin interfacial adhesion as a result of water penetration.
{"title":"CREEP RUPTURE LIFE AND INTERLAMINAR SHEAR STRENGTH OF WATER-ABSORBED GREEN COMPOSITE WITH PLAIN WOVEN NATURAL FIBER CLOTH","authors":"H. Katogi, K. Takemura, Atsuhiro Hayamori","doi":"10.2495/HPSM180061","DOIUrl":"https://doi.org/10.2495/HPSM180061","url":null,"abstract":"To ensure safety of electric vehicles using green composites, this study examined the interlaminar shear strength, creep rupture strength, and useful life of plain woven jute fiber cloth reinforced polylactic acid after water immersion. The fiber volume fraction of the green composite was 40%. Water absorption tests were conducted of the green composite comprising jute fiber and polylactic acid (PLA). Tensile creep tests of green composite and jute fiber were conducted after water immersion. The maximum stress was 60–90% of tensile strength. The environmental temperature was room temperature. Short beam testing of double-notched green composite was also conducted after water immersion. Results show the following. When water absorption tests were conducted, the water absorption rates of green composite, jute fiber and PLA at 24 hr were 9%, 3.4% and 0.3%, respectively. The creep rupture strength of 9% water absorbed green composite was lower than that of non-water-absorbed (non-absorbed) green composite. However, the creep rupture strength of 3.4% water absorbed jute fiber was slightly higher than that of non-absorbed jute fiber. For maximum stress of 40 MPa, the creep rupture life of 9% water absorbed green composite was much shorter than that of the non-absorbed green composite. Interlaminar shear strength of 9% water absorbed green composite was lower by 11% than that of the non-absorbed green composite. Water penetrated to the fiber–resin interface when water absorption test of green composite was conducted until 24 hr. Therefore, the interlaminar shear strength, creep rupture life, and green composite strength were decreased mainly because of the decrease of fiber–resin interfacial adhesion as a result of water penetration.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128786857","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}
Nondeterministic optimization methods have been studied in depth from an academy and industrial point of view. The main drawback when implementing probabilistic optimization methods to complex structures is the computational cost. Many researchers have dedicated their efforts to the development of efficient algorithms to decrease the computational time required by the original formulation of the Reliability Based Design Optimization (RBDO) problems. Among these efficient methodologies the SORA (Sequential Optimization and Reliability Assessment) method has been widely used due to its decoupled formulation. Two application examples are presented with the objective to show the possibilities of taking into account uncertainty data into structural optimization for large-scale engineering problems.
{"title":"EXPERIENCES ON STRUCTURAL OPTIMIZATION UNDER UNCERTAINTY IN AEROSPACE COMPONENTS","authors":"A. Baldomir, S. Hernández, C. López, C. Cid","doi":"10.2495/HPSM180121","DOIUrl":"https://doi.org/10.2495/HPSM180121","url":null,"abstract":"Nondeterministic optimization methods have been studied in depth from an academy and industrial point of view. The main drawback when implementing probabilistic optimization methods to complex structures is the computational cost. Many researchers have dedicated their efforts to the development of efficient algorithms to decrease the computational time required by the original formulation of the Reliability Based Design Optimization (RBDO) problems. Among these efficient methodologies the SORA (Sequential Optimization and Reliability Assessment) method has been widely used due to its decoupled formulation. Two application examples are presented with the objective to show the possibilities of taking into account uncertainty data into structural optimization for large-scale engineering problems.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125688998","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}
Codes of practice aim to assure structures have acceptable risks to the public and the minimum total costs over the working life of a design. However, current codified criteria for structural design correspond to a broad range of reliability levels, specified for dissimilar reference periods even though their recalculation for different periods is uncertain due to unknown dependence of failure events in time. In this contribution, target reliability levels are specified on the basis of probabilistic risk optimization considering the objective function as a sum of various costs including effects of time to failure and discounting. A case study presents probabilistic optimization of the roof of a stadium for 4,000 spectators and illustrates the effect of the considered input parameters. Failure consequences and relative cost of safety measure are shown to be major factors affecting the optimum reliability level. Less important factors are the discount rate and working life. Large uncertainty in failure cost estimates seems to have only a marginal effect on derived optimum reliability levels.
{"title":"ECONOMICALLY OPTIMUM STRUCTURAL DESIGN: METHODOLOGY AND CASE STUDY","authors":"M. Holicky, D. Diamantidis, M. Sýkora","doi":"10.2495/HPSM180151","DOIUrl":"https://doi.org/10.2495/HPSM180151","url":null,"abstract":"Codes of practice aim to assure structures have acceptable risks to the public and the minimum total costs over the working life of a design. However, current codified criteria for structural design correspond to a broad range of reliability levels, specified for dissimilar reference periods even though their recalculation for different periods is uncertain due to unknown dependence of failure events in time. In this contribution, target reliability levels are specified on the basis of probabilistic risk optimization considering the objective function as a sum of various costs including effects of time to failure and discounting. A case study presents probabilistic optimization of the roof of a stadium for 4,000 spectators and illustrates the effect of the considered input parameters. Failure consequences and relative cost of safety measure are shown to be major factors affecting the optimum reliability level. Less important factors are the discount rate and working life. Large uncertainty in failure cost estimates seems to have only a marginal effect on derived optimum reliability levels.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115818824","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}
The paper presents an optimal design of timber beams with non-uniform cross-section based on multiparametric mixed-integer non-linear programming (MINLP) optimization and Response Surface Optimization (RSO). For this purpose, the optimization model was developed with integrated requirements of Eurocode specifications. In order to get the variation of a given performance with respect to input parameters, the response surface optimization was performed as part of a finite element analysis. Using the deterministic analysis, we have been able to investigate the performance of the design over continuous ranges of the input parameters, using a limited number of simulations. From the response surface, we are able to identify the key parameters really influencing the design. In order to interpret the applicability of the response surface optimization and the recommended optimal design for the timber beam with non-uniform cross-section, the paper presents an example of determining the cheapest possible structure for the given design parameters.
{"title":"DETERMINING OPTIMAL DESIGNS OF TIMBER BEAMS WITH NON-UNIFORM CROSS-SECTION","authors":"P. Jelušič","doi":"10.2495/HPSM180171","DOIUrl":"https://doi.org/10.2495/HPSM180171","url":null,"abstract":"The paper presents an optimal design of timber beams with non-uniform cross-section based on multiparametric mixed-integer non-linear programming (MINLP) optimization and Response Surface Optimization (RSO). For this purpose, the optimization model was developed with integrated requirements of Eurocode specifications. In order to get the variation of a given performance with respect to input parameters, the response surface optimization was performed as part of a finite element analysis. Using the deterministic analysis, we have been able to investigate the performance of the design over continuous ranges of the input parameters, using a limited number of simulations. From the response surface, we are able to identify the key parameters really influencing the design. In order to interpret the applicability of the response surface optimization and the recommended optimal design for the timber beam with non-uniform cross-section, the paper presents an example of determining the cheapest possible structure for the given design parameters.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124289297","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}
M. Bogataj, L. Čuček, T. Zula, S. Kravanja, Z. Kravanja
The solutions to engineering systems should not only be feasible but should also be beneficial to all the pillars of sustainable development (economic, environmental and social) to the greatest possible extent. However, due to the inherent trade-offs among the three components of sustainable development, identifying such solutions is not a straightforward task. In this manuscript, we present a simultaneous approach for sustainable synthesis and optimization of engineering systems based on a mixed-integer (non)linear programming MI(N)LP. The approach aims at providing sustainable solutions and an insight into the trade-offs among the economic, environmental and social component of sustainable development. Maximization of a sustainability profit, which is a composite criterion comprised of economic, ecoand social profits, is applied in order to obtain the optimal sustainable solutions. The solutions are compared to those obtained by maximizing either pure economic profit or minimizing Green House Gas emissions. The approach is tested on two case studies and the results are compared. The first example is a simple example from the field of civil engineering. The example presents the synthesis/optimization of a 5.5 meters long cantilever beams. The second example represents supply chain synthesis/optimisation of a biogas production plant in Slovenia. The results for the first case study indicate that 23% increase in sustainability profit causes slight decrease in economic profit (6%). On the other hand, the results for the second case study indicate that a slight increase in sustainability profit (6%) causes a 27% decrease in economic profit. Nevertheless, the solutions obtained by maximizing the sustainability profit remain economically viable due to its composite nature that properly captures and reflects the trade-offs.
{"title":"SUSTAINABLE SYNTHESIS AND OPTIMIZATION OF ENGINEERING SYSTEMS","authors":"M. Bogataj, L. Čuček, T. Zula, S. Kravanja, Z. Kravanja","doi":"10.2495/HPSM180191","DOIUrl":"https://doi.org/10.2495/HPSM180191","url":null,"abstract":"The solutions to engineering systems should not only be feasible but should also be beneficial to all the pillars of sustainable development (economic, environmental and social) to the greatest possible extent. However, due to the inherent trade-offs among the three components of sustainable development, identifying such solutions is not a straightforward task. In this manuscript, we present a simultaneous approach for sustainable synthesis and optimization of engineering systems based on a mixed-integer (non)linear programming MI(N)LP. The approach aims at providing sustainable solutions and an insight into the trade-offs among the economic, environmental and social component of sustainable development. Maximization of a sustainability profit, which is a composite criterion comprised of economic, ecoand social profits, is applied in order to obtain the optimal sustainable solutions. The solutions are compared to those obtained by maximizing either pure economic profit or minimizing Green House Gas emissions. The approach is tested on two case studies and the results are compared. The first example is a simple example from the field of civil engineering. The example presents the synthesis/optimization of a 5.5 meters long cantilever beams. The second example represents supply chain synthesis/optimisation of a biogas production plant in Slovenia. The results for the first case study indicate that 23% increase in sustainability profit causes slight decrease in economic profit (6%). On the other hand, the results for the second case study indicate that a slight increase in sustainability profit (6%) causes a 27% decrease in economic profit. Nevertheless, the solutions obtained by maximizing the sustainability profit remain economically viable due to its composite nature that properly captures and reflects the trade-offs.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116097068","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}
Kazuto Tanaka, M. Kaetsu, T. Katayama, T. Ishikawa
The use of carbon fiber reinforced thermoplastic (CFRTP) contributes to weight reduction of automobiles and offers better gasoline mileage. Recently, to mold CFRTP with high-strength and highstiffness for complex shaped products with ribs and bosses, the hybrid molding system has been developed by combining press molding and injection molding. Although rib root shape is the important factor in the press and injection hybrid molding, the effect of rib root shape on the rib root strength has not been clarified yet. In this study, carbon fiber reinforced polyamide 6 composites were molded by press and injection hybrid molding. Rib root tensile test of T-shaped specimen cut out from the hybrid molded products and in-plain tensile test of the outer shell laminate were conducted to clarify the effect of rib root shape (radius of curvature R = 0 and 2.5). For rib root tensile test of T-shaped specimens, higher strength was obtained in the molded products with R = 0 than those with R = 2.5. On the other hand, in the case of in-plain tensile strength of outer shell laminate, higher tensile strength was obtained in the molded products with R = 2.5 than those with R = 0.
{"title":"EFFECT OF RIB ROOT SHAPE ON THE TENSILE STRENGTH OF PRESS AND INJECTION HYBRID MOLDED PRODUCTS MADE WITH CF/PA6 RANDOM PREPREG SHEET","authors":"Kazuto Tanaka, M. Kaetsu, T. Katayama, T. Ishikawa","doi":"10.2495/HPSM180101","DOIUrl":"https://doi.org/10.2495/HPSM180101","url":null,"abstract":"The use of carbon fiber reinforced thermoplastic (CFRTP) contributes to weight reduction of automobiles and offers better gasoline mileage. Recently, to mold CFRTP with high-strength and highstiffness for complex shaped products with ribs and bosses, the hybrid molding system has been developed by combining press molding and injection molding. Although rib root shape is the important factor in the press and injection hybrid molding, the effect of rib root shape on the rib root strength has not been clarified yet. In this study, carbon fiber reinforced polyamide 6 composites were molded by press and injection hybrid molding. Rib root tensile test of T-shaped specimen cut out from the hybrid molded products and in-plain tensile test of the outer shell laminate were conducted to clarify the effect of rib root shape (radius of curvature R = 0 and 2.5). For rib root tensile test of T-shaped specimens, higher strength was obtained in the molded products with R = 0 than those with R = 2.5. On the other hand, in the case of in-plain tensile strength of outer shell laminate, higher tensile strength was obtained in the molded products with R = 2.5 than those with R = 0.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127170264","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}
Serviceability limit states including cracking are of increasing importance and often dominate the design of reinforced concrete structures. Furthermore, actual crack widths and their shape play an important role in the assessment of service life of existing reinforced concrete structures. Crack width is inherently a random variable of considerable scatter due to randomness of material properties, geometry of the structure, loading and model uncertainty in crack width estimates. The state-of-the-art concepts for serviceability verifications were recently presented in fib Model Code 2010 that is jointly with Eurocode EN 1992-1-1 considered as key background materials in this study. To assess the sufficiency of code requirements and design procedures, crack widths of water retaining structures are investigated in detail using probabilistic methods of structural reliability. The current codes seem to be well calibrated to reach a target reliability index of 1.5 in the serviceability limit states. The two variables dominating structural reliability are uncertainty in crack width model and concrete cover. Numerous topics need to be further investigated including revision of crack width limits, improvements of mechanical models, quantification of model uncertainty, methodology for load combinations, treatment of spatial variability for large structures, and optimisation of target reliabilities.
{"title":"TOWARDS OPTIMUM DESIGN FOR CRACK WIDTH LIMIT STATES: THE NEED FOR FURTHER DEVELOPMENTS","authors":"M. Sýkora, M. Holicky, J. Marková","doi":"10.2495/HPSM180141","DOIUrl":"https://doi.org/10.2495/HPSM180141","url":null,"abstract":"Serviceability limit states including cracking are of increasing importance and often dominate the design of reinforced concrete structures. Furthermore, actual crack widths and their shape play an important role in the assessment of service life of existing reinforced concrete structures. Crack width is inherently a random variable of considerable scatter due to randomness of material properties, geometry of the structure, loading and model uncertainty in crack width estimates. The state-of-the-art concepts for serviceability verifications were recently presented in fib Model Code 2010 that is jointly with Eurocode EN 1992-1-1 considered as key background materials in this study. To assess the sufficiency of code requirements and design procedures, crack widths of water retaining structures are investigated in detail using probabilistic methods of structural reliability. The current codes seem to be well calibrated to reach a target reliability index of 1.5 in the serviceability limit states. The two variables dominating structural reliability are uncertainty in crack width model and concrete cover. Numerous topics need to be further investigated including revision of crack width limits, improvements of mechanical models, quantification of model uncertainty, methodology for load combinations, treatment of spatial variability for large structures, and optimisation of target reliabilities.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126833544","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}
Liang Zhongyang, W. Zhou, Xuan Wang, D. Northwood, Cheng Liu
The key way of achieving sustainability of a product is to design a manufacturing process that increases the mechanical properties of traditional materials, e.g. steel, whilst also increasing processing efficiency, and diminishing energy consumption. A novel process has been developed that allows for a traditional spring steel (60Si2Mn) to be produced with a high level of strength (tensile strength is over 2100 MPa, bending strength is 4100 MPa, yield strength is 1700 MPa as well as hardness of 59 HRC), also retaining reasonable ductility on an industrial scale. It is shown that a triple-phase microstructure comprising lenticular prior martensite, nano-scaled needle/lath-like bainitic ferrite and film retained austenite, is obtained. The excellent combination of strength and ductility is attributed to a synergistic multi-phase strengthening effect. The nano-scaled structure exhibits a good balance between strength and toughness. The presence of prior martensite provides the kinetics of subsequent nano-scaled bainitic transformation by bainitic laths nucleating at the martensite–austenite interfaces. This design methodology potentially broadens the application of spring steel to components that experience more demanding service environments, such as heavy loads.
{"title":"A 2.1 GPA TRIPLE-PHASE SPRING STEEL","authors":"Liang Zhongyang, W. Zhou, Xuan Wang, D. Northwood, Cheng Liu","doi":"10.2495/HPSM180011","DOIUrl":"https://doi.org/10.2495/HPSM180011","url":null,"abstract":"The key way of achieving sustainability of a product is to design a manufacturing process that increases the mechanical properties of traditional materials, e.g. steel, whilst also increasing processing efficiency, and diminishing energy consumption. A novel process has been developed that allows for a traditional spring steel (60Si2Mn) to be produced with a high level of strength (tensile strength is over 2100 MPa, bending strength is 4100 MPa, yield strength is 1700 MPa as well as hardness of 59 HRC), also retaining reasonable ductility on an industrial scale. It is shown that a triple-phase microstructure comprising lenticular prior martensite, nano-scaled needle/lath-like bainitic ferrite and film retained austenite, is obtained. The excellent combination of strength and ductility is attributed to a synergistic multi-phase strengthening effect. The nano-scaled structure exhibits a good balance between strength and toughness. The presence of prior martensite provides the kinetics of subsequent nano-scaled bainitic transformation by bainitic laths nucleating at the martensite–austenite interfaces. This design methodology potentially broadens the application of spring steel to components that experience more demanding service environments, such as heavy loads.","PeriodicalId":340058,"journal":{"name":"High Performance and Optimum Design of Structures and Materials III","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133964465","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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