A micromechanical damage model for concrete capable of taking into account the effect of highly time-varying load (time-varying stress) is outlined here. Giving primary consideration to concrete-type material, it is shown how an existing self-consistent rate-insensitive model can be modified and extended to induce rate dependency of concrete with pre-existing damage (cracks). The variations of several fracture mechanics parameters of concrete, viz., stress intensity factors, fracture toughness, etc., under the influence of high loading rates are investigated: the role of inertia of the material is explained and quantified. The process of crack evolution including crack kinking and nucleation under tensile and compressive stress-field has been thoroughly considered along with all possible situations that may arise. The resulting rate-sensitive model has been codified for high-speed computer and a few experiments have been replicated to validate it.
{"title":"Rate-Sensitive Micromechanical Model for Concrete","authors":"D. Chandra, T. Krauthammer","doi":"10.14359/5927","DOIUrl":"https://doi.org/10.14359/5927","url":null,"abstract":"A micromechanical damage model for concrete capable of taking into account the effect of highly time-varying load (time-varying stress) is outlined here. Giving primary consideration to concrete-type material, it is shown how an existing self-consistent rate-insensitive model can be modified and extended to induce rate dependency of concrete with pre-existing damage (cracks). The variations of several fracture mechanics parameters of concrete, viz., stress intensity factors, fracture toughness, etc., under the influence of high loading rates are investigated: the role of inertia of the material is explained and quantified. The process of crack evolution including crack kinking and nucleation under tensile and compressive stress-field has been thoroughly considered along with all possible situations that may arise. The resulting rate-sensitive model has been codified for high-speed computer and a few experiments have been replicated to validate it.","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122162709","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}
{"title":"Free Water in Concrete Pores: an Attempt of Physical Explanation of Concrete Dynamic Behavior","authors":"Francois Toutlemond, P. Rossi","doi":"10.14359/5926","DOIUrl":"https://doi.org/10.14359/5926","url":null,"abstract":"","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124093738","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 jpaper is concerned with the description and explanations of Hardened Cement Paste (HCP) response to dynamic (explosive) loading. An experimental testing technique has been developed to study the dynamic cracking of HCP samples, using cylindrical explosive microcharges. Following the initiation of the microcharge, radial cracks propagate and measurements of their growth may be conducted. Procedures to predefine the crack path have been investigated, like preparation of linear grooves along the sample. Predefining the crack path enabled relatively simple measurements of its propagation velocity. The dynamic crack propagation velocity was found to be relatively low, within the range of 70-200 m/sec. (about an order of magnitude lower than the theoretical value). The dynamic HCP failure process was found to be usually of multicrack type. Studies of microcharge intitiation near a samples boundary provided insight into the development of scabbing cracks and of their interaction with the radial cracks propagating towards the boundary. It has been found that crack interaction is strongly dependent on the relationship between the stress wave velocity and the crack propagation velocity.
{"title":"Experimental Studies on Dynamic Response of Hardened Cement Paste","authors":"D. Yankelevsky, Itzhak Avnon","doi":"10.14359/5923","DOIUrl":"https://doi.org/10.14359/5923","url":null,"abstract":"This jpaper is concerned with the description and explanations of Hardened Cement Paste (HCP) response to dynamic (explosive) loading. An experimental testing technique has been developed to study the dynamic cracking of HCP samples, using cylindrical explosive microcharges. Following the initiation of the microcharge, radial cracks propagate and measurements of their growth may be conducted. Procedures to predefine the crack path have been investigated, like preparation of linear grooves along the sample. Predefining the crack path enabled relatively simple measurements of its propagation velocity. The dynamic crack propagation velocity was found to be relatively low, within the range of 70-200 m/sec. (about an order of magnitude lower than the theoretical value). The dynamic HCP failure process was found to be usually of multicrack type. Studies of microcharge intitiation near a samples boundary provided insight into the development of scabbing cracks and of their interaction with the radial cracks propagating towards the boundary. It has been found that crack interaction is strongly dependent on the relationship between the stress wave velocity and the crack propagation velocity.","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121257757","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}
{"title":"Approach for Designing Civilian Structures Against Terrorist Attack","authors":"E. Hinman","doi":"10.14359/5913","DOIUrl":"https://doi.org/10.14359/5913","url":null,"abstract":"","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"192 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124328872","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 Naval Facilities Engineering Service Center (NFESC) is developing a new ordnance storage magazine that will reduce encumbered land and improve operational efficiency. Energy absorbing walls using lightweight concrete are being developed to prevent sympathetic detonation between cased munitions stored in adjacent cells. Design loads, wall response, and wall effectiveness are predicted and compared to test results from one-third scale development tests and full scale demonstration and certification tests. Specially designed lightweight concretes (or chemically bonded ceramics, CBC's) with high porosities in excess of 50% were used in the development program. The most efficient (cost and performance) barrier wall design utilizes a composite wall consisting of an exterior reinforced concrete cover and a heavy granular fill material. The CBC which makes up the cover has a strength of 2500 psi, a unit weight of 65 pef, and a porosity over 50%. This CBC cover mitigates initial shock on impact with acceptors while the heavy granular fill reduces wall velocity (and kinetic energy), disperses momentum, and stops fragments. The exterior magazine walls, also constructed with lightweight concrete, reduce shock loads on impact by acceptor munitions.
{"title":"Shock Absorbing Structural Elements","authors":"L. Malvar, K. Hager, J. Tancreto","doi":"10.14359/5921","DOIUrl":"https://doi.org/10.14359/5921","url":null,"abstract":"The Naval Facilities Engineering Service Center (NFESC) is developing a new ordnance storage magazine that will reduce encumbered land and improve operational efficiency. Energy absorbing walls using lightweight concrete are being developed to prevent sympathetic detonation between cased munitions stored in adjacent cells. Design loads, wall response, and wall effectiveness are predicted and compared to test results from one-third scale development tests and full scale demonstration and certification tests. Specially designed lightweight concretes (or chemically bonded ceramics, CBC's) with high porosities in excess of 50% were used in the development program. The most efficient (cost and performance) barrier wall design utilizes a composite wall consisting of an exterior reinforced concrete cover and a heavy granular fill material. The CBC which makes up the cover has a strength of 2500 psi, a unit weight of 65 pef, and a porosity over 50%. This CBC cover mitigates initial shock on impact with acceptors while the heavy granular fill reduces wall velocity (and kinetic energy), disperses momentum, and stops fragments. The exterior magazine walls, also constructed with lightweight concrete, reduce shock loads on impact by acceptor munitions.","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123487499","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}
Department of Defense (DoD) facilities which may be subjected to blast effects from accidental explosions are required to satisfy the safety requirements delineated in DoD 6055.9-STD, "DOD Ammunition and Explosives Safety Standards."(1) In the safety standard, Army Technical Manual 5-1300, "Structures to Resist the Effects of Accidental Explosions,"(2) is referenced for specific criteria to be used in the analysis, design, and construction of blast resistant structures. In this paper, available data from dynamic tests of mechanical splicing systems will first be reviewed. The current research effort will then be outlined, and initial findings will be examined. Finally, recommendations for future work will be detailed and discussed.
{"title":"Development of Design Criteria for Reinforcing Steel Splices in Blast Resistant Concrete Structures","authors":"W. Zehrt, P. M. LaHound","doi":"10.14359/5920","DOIUrl":"https://doi.org/10.14359/5920","url":null,"abstract":"Department of Defense (DoD) facilities which may be subjected to blast effects from accidental explosions are required to satisfy the safety requirements delineated in DoD 6055.9-STD, \"DOD Ammunition and Explosives Safety Standards.\"(1) In the safety standard, Army Technical Manual 5-1300, \"Structures to Resist the Effects of Accidental Explosions,\"(2) is referenced for specific criteria to be used in the analysis, design, and construction of blast resistant structures. In this paper, available data from dynamic tests of mechanical splicing systems will first be reviewed. The current research effort will then be outlined, and initial findings will be examined. Finally, recommendations for future work will be detailed and discussed.","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121794371","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}
{"title":"Protecting Petroleum Process Plant Buildings from Vapor Cloud Explosions","authors":"D. J. Forbes","doi":"10.14359/5916","DOIUrl":"https://doi.org/10.14359/5916","url":null,"abstract":"","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125558213","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 accidental release of combustible materials is not an infrequent event in our highly industrialized society. Such a release has the potential to cause an associated explosion which can produce severe consequences to nearby workers, equipment and structures. This paper describes a computer program (HALL) which was developed for evaluating the consequences of internal accidental explosions on structures, equipment and people. This computer program was designed to help analyze the effects of blast waves which travel along a single axis, i.e., it analyzes one-dimensional propagation and reflections of blast waves within structures. In order for a HALL analysis to be sufficiently realisitic, the structure must be relatively long compared to its width. Structures or components of structures falling into this category include two- to three-story chemical process cells or hallways in process facilities. The program is illustrated by its application to a process cell which contains a chemical reactor vessel. The process cell is equipped with a blow-out panel and a blow-out wall. In this illustration the reactor vessel experiences a leak which produces a local vapor cloud which subsequently explodes. The solution focuses on the blast environment within the process cell and the response of the blow-out panel and a blow-out wall in mitigating the effects of the accidental blast.
{"title":"The Nature of Airblast Loads and Effects of a Process Cell Due to a Vapor Cloud Explosion","authors":"A. Longinow, A. Wiedermann, F. Calabrese","doi":"10.14359/5918","DOIUrl":"https://doi.org/10.14359/5918","url":null,"abstract":"The accidental release of combustible materials is not an infrequent event in our highly industrialized society. Such a release has the potential to cause an associated explosion which can produce severe consequences to nearby workers, equipment and structures. This paper describes a computer program (HALL) which was developed for evaluating the consequences of internal accidental explosions on structures, equipment and people. This computer program was designed to help analyze the effects of blast waves which travel along a single axis, i.e., it analyzes one-dimensional propagation and reflections of blast waves within structures. In order for a HALL analysis to be sufficiently realisitic, the structure must be relatively long compared to its width. Structures or components of structures falling into this category include two- to three-story chemical process cells or hallways in process facilities. The program is illustrated by its application to a process cell which contains a chemical reactor vessel. The process cell is equipped with a blow-out panel and a blow-out wall. In this illustration the reactor vessel experiences a leak which produces a local vapor cloud which subsequently explodes. The solution focuses on the blast environment within the process cell and the response of the blow-out panel and a blow-out wall in mitigating the effects of the accidental blast.","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"23 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133238744","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 number of blast resistant facilities planned, designed, and constructed recently in petrochemical plants points to an increased interest in this specialized type of design. This paper deals with the numerous decisions to be made in designing blast resistant buildings. First, the need for a blast resistant design must be evaluated. Then design objectives and relative cost must be balanced to produce an optimal design. Design practices must be established as there are various company, military, and professional publications available. Detailing practices also require careful consideration as there are differences in the implementation of shear reinforcing, precast elements, penetrations, and exterior doors. Several actions would greatly benefit the design of petrochemical blast facilities. A clear definition from government and insurance sources is needed on what facilities need to be protected from explosions. Improvements are needed in the evaluation of blast loads within petrochemical facilities. A consensus on engineering calculations and construction details would help unify design approaches.
{"title":"Industrial Blast Resistant Facilities: an Engineer’slConstructor’s Viewpoint","authors":"W. Bounds, M. Nene, Hsitoung Ko","doi":"10.14359/5914","DOIUrl":"https://doi.org/10.14359/5914","url":null,"abstract":"The number of blast resistant facilities planned, designed, and constructed recently in petrochemical plants points to an increased interest in this specialized type of design. This paper deals with the numerous decisions to be made in designing blast resistant buildings. First, the need for a blast resistant design must be evaluated. Then design objectives and relative cost must be balanced to produce an optimal design. Design practices must be established as there are various company, military, and professional publications available. Detailing practices also require careful consideration as there are differences in the implementation of shear reinforcing, precast elements, penetrations, and exterior doors. Several actions would greatly benefit the design of petrochemical blast facilities. A clear definition from government and insurance sources is needed on what facilities need to be protected from explosions. Improvements are needed in the evaluation of blast loads within petrochemical facilities. A consensus on engineering calculations and construction details would help unify design approaches.","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130015104","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}
{"title":"Role of Physical Testing in Impact Analysis of Concrete Structures","authors":"P. Bischoff","doi":"10.14359/5925","DOIUrl":"https://doi.org/10.14359/5925","url":null,"abstract":"","PeriodicalId":296155,"journal":{"name":"SP-175: Concrete and Blast Effects","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122510058","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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