Pub Date : 2021-09-01DOI: 10.5459/bnzsee.54.3.228-242
M. Tripathi, R. Dhakal
Bar buckling in RC structures is a commonly-observed failure mode that adversely affects their deformation capacity. To restrict bar buckling in ductile RC walls, design codes only emphasises on restricting the spacing of transverse reinforcement and does not recognise the importance of the effective stiffness of the ties (which is a combination of the tie leg axial stiffness and spacing) to restrict bar buckling. Therefore, in this paper the design requirements for anti-buckling transverse reinforcement are summarised, and improvements to the current design methodology for anti-buckling transverse reinforcement are proposed. To ensure that the transverse reinforcement detailing in plastic hinge regions is adequate to restrict bar buckling to single tie spacing and the compressive stress deterioration in bars due to buckling is controlled, refinements to the current detailing procedures are proposed. The buckling restraining ability of transverse reinforcement depends on the axial stiffness of the tie legs, while the compressive stress reduction in reinforcing bars due to buckling depends on their unsupported length (in bare bar tests) or buckling length that can include multiple tie spacing (inside RC members). Therefore, restrictions on both the axial stiffness of the tie legs and spacing of transverse reinforcement along the longitudinal reinforcing bars are proposed. The effective axial stiffness of tie legs is controlled by ensuring that the length of the tie legs in the direction of potential buckling is well below the critical length evaluated using a mechanics-based approach. Additionally, compressive stress degradation in reinforcing bars is controlled by limiting the ratio of the transverse reinforcement spacing and the longitudinal bar diameter such that any reduction of compressive stress carried by the longitudinal bars due to buckling at the limiting curvature recommended by New Zealand Concrete Standard is within an acceptable range. Furthermore, recommendations to avoid buckling of unrestrained reinforcing bars in the boundary zone and the wall web are proposed. Using the proposed design methodology, buckling of longitudinal reinforcing bars in ductile RC walls can be delayed and the detrimental effects of buckling on the lateral response of walls can be controlled until the design drift or curvature demands are met.
{"title":"Designing and detailing transverse reinforcement to control bar buckling in rectangular RC walls","authors":"M. Tripathi, R. Dhakal","doi":"10.5459/bnzsee.54.3.228-242","DOIUrl":"https://doi.org/10.5459/bnzsee.54.3.228-242","url":null,"abstract":"Bar buckling in RC structures is a commonly-observed failure mode that adversely affects their deformation capacity. To restrict bar buckling in ductile RC walls, design codes only emphasises on restricting the spacing of transverse reinforcement and does not recognise the importance of the effective stiffness of the ties (which is a combination of the tie leg axial stiffness and spacing) to restrict bar buckling. Therefore, in this paper the design requirements for anti-buckling transverse reinforcement are summarised, and improvements to the current design methodology for anti-buckling transverse reinforcement are proposed. To ensure that the transverse reinforcement detailing in plastic hinge regions is adequate to restrict bar buckling to single tie spacing and the compressive stress deterioration in bars due to buckling is controlled, refinements to the current detailing procedures are proposed. The buckling restraining ability of transverse reinforcement depends on the axial stiffness of the tie legs, while the compressive stress reduction in reinforcing bars due to buckling depends on their unsupported length (in bare bar tests) or buckling length that can include multiple tie spacing (inside RC members). Therefore, restrictions on both the axial stiffness of the tie legs and spacing of transverse reinforcement along the longitudinal reinforcing bars are proposed. The effective axial stiffness of tie legs is controlled by ensuring that the length of the tie legs in the direction of potential buckling is well below the critical length evaluated using a mechanics-based approach. Additionally, compressive stress degradation in reinforcing bars is controlled by limiting the ratio of the transverse reinforcement spacing and the longitudinal bar diameter such that any reduction of compressive stress carried by the longitudinal bars due to buckling at the limiting curvature recommended by New Zealand Concrete Standard is within an acceptable range. Furthermore, recommendations to avoid buckling of unrestrained reinforcing bars in the boundary zone and the wall web are proposed. Using the proposed design methodology, buckling of longitudinal reinforcing bars in ductile RC walls can be delayed and the detrimental effects of buckling on the lateral response of walls can be controlled until the design drift or curvature demands are met.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48506016","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}
Pub Date : 2021-09-01DOI: 10.5459/bnzsee.54.3.211-227
F. Dashti, R. Dhakal, S. Pampanin
Observations of out-of-plane (OOP) instability in the 2010 Chile earthquake and in the 2011 Christchurch earthquake resulted in concerns about the current design provisions of structural walls. This mode of failure was previously observed in the experimental response of some wall specimens subjected to in-plane loading. Therefore, the postulations proposed for prediction of the limit states corresponding to OOP instability of rectangular walls are generally based on stability analysis under in-plane loading only. These approaches address stability of a cracked wall section when subjected to compression, thereby considering the level of residual strain developed in the reinforcement as the parameter that prevents timely crack closure of the wall section and induces stability failure. The New Zealand code requirements addressing the OOP instability of structural walls are based on the assumptions used in the literature and the analytical methods proposed for mathematical determination of the critical strain values. In this study, a parametric study is conducted using a numerical model capable of simulating OOP instability of rectangular walls to evaluate sensitivity of the OOP response of rectangular walls to variation of different parameters identified to be governing this failure mechanism. The effects of wall slenderness (unsupported height-to-thickness) ratio, longitudinal reinforcement ratio of the boundary regions and length on the OOP response of walls are evaluated. A clear trend was observed regarding the influence of these parameters on the initiation of OOP displacement, based on which simple equations are proposed for prediction of OOP instability in rectangular walls.
{"title":"Design recommendations to prevent global out-of-plane instability of rectangular reinforced concrete ductile walls","authors":"F. Dashti, R. Dhakal, S. Pampanin","doi":"10.5459/bnzsee.54.3.211-227","DOIUrl":"https://doi.org/10.5459/bnzsee.54.3.211-227","url":null,"abstract":"Observations of out-of-plane (OOP) instability in the 2010 Chile earthquake and in the 2011 Christchurch earthquake resulted in concerns about the current design provisions of structural walls. This mode of failure was previously observed in the experimental response of some wall specimens subjected to in-plane loading. Therefore, the postulations proposed for prediction of the limit states corresponding to OOP instability of rectangular walls are generally based on stability analysis under in-plane loading only. These approaches address stability of a cracked wall section when subjected to compression, thereby considering the level of residual strain developed in the reinforcement as the parameter that prevents timely crack closure of the wall section and induces stability failure. The New Zealand code requirements addressing the OOP instability of structural walls are based on the assumptions used in the literature and the analytical methods proposed for mathematical determination of the critical strain values. In this study, a parametric study is conducted using a numerical model capable of simulating OOP instability of rectangular walls to evaluate sensitivity of the OOP response of rectangular walls to variation of different parameters identified to be governing this failure mechanism. The effects of wall slenderness (unsupported height-to-thickness) ratio, longitudinal reinforcement ratio of the boundary regions and length on the OOP response of walls are evaluated. A clear trend was observed regarding the influence of these parameters on the initiation of OOP displacement, based on which simple equations are proposed for prediction of OOP instability in rectangular walls.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45172342","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}
Pub Date : 2021-09-01DOI: 10.5459/bnzsee.54.3.197-210
D. Court-Patience, M. Garnich
Buckling-restrained braces (BRBs) form a bracing system that provides lateral strength and stiffness to a building. These systems have been shown to provide larger energy dissipation in severe earthquake events compared to concentrically and eccentrically braced frames (CBFs and EBFs). However, unlike CBFs and EBFs there is no guidance document or specific instructions in regulatory standards for the design of buckling-restrained braced frames (BRBFs) in New Zealand. This makes it difficult for structural engineers to be aware of all the strength and stability considerations required for the safe design of BRBFs. Currently, structural designs that include BRBFs require a peer-review to gain building compliance. The American standard ANSI/AISC 341-16 is the adopted document used in New Zealand for guidance in how to collect evidence showing a BRBF system will perform as intended. However, as ANSI/AISC 341-16 is not a governing document in New Zealand, instructions within the document are not enforced and can be made to fit within the constraints of a building project. By way of example, this paper presents the experimental test process and results acquired from pre-qualification testing of three different commercially available BRB architypes. Of the three BRB designs investigated, one failed prematurely due to global buckling. A manufacturing error was the likely cause of this premature failure. This failure highlights the need for strict quality control during fabrication. All remaining BRBs performed well, meeting the acceptance criteria set out in ANSI/AISC 341-16. Positive pre-qualification results meant the BRBs were installed in medium to high-rise buildings throughout New Zealand. The importance of sub-assemblage testing to assess the performance of a BRB and its frame components is also discussed. Finally, the capability of high fidelity modelling to supplemental physical testing is also presented.
{"title":"Evidence collected for peer review of buckling-restrained braced frames in New Zealand","authors":"D. Court-Patience, M. Garnich","doi":"10.5459/bnzsee.54.3.197-210","DOIUrl":"https://doi.org/10.5459/bnzsee.54.3.197-210","url":null,"abstract":"Buckling-restrained braces (BRBs) form a bracing system that provides lateral strength and stiffness to a building. These systems have been shown to provide larger energy dissipation in severe earthquake events compared to concentrically and eccentrically braced frames (CBFs and EBFs). However, unlike CBFs and EBFs there is no guidance document or specific instructions in regulatory standards for the design of buckling-restrained braced frames (BRBFs) in New Zealand. This makes it difficult for structural engineers to be aware of all the strength and stability considerations required for the safe design of BRBFs. Currently, structural designs that include BRBFs require a peer-review to gain building compliance. The American standard ANSI/AISC 341-16 is the adopted document used in New Zealand for guidance in how to collect evidence showing a BRBF system will perform as intended. However, as ANSI/AISC 341-16 is not a governing document in New Zealand, instructions within the document are not enforced and can be made to fit within the constraints of a building project. By way of example, this paper presents the experimental test process and results acquired from pre-qualification testing of three different commercially available BRB architypes. Of the three BRB designs investigated, one failed prematurely due to global buckling. A manufacturing error was the likely cause of this premature failure. This failure highlights the need for strict quality control during fabrication. All remaining BRBs performed well, meeting the acceptance criteria set out in ANSI/AISC 341-16. Positive pre-qualification results meant the BRBs were installed in medium to high-rise buildings throughout New Zealand. The importance of sub-assemblage testing to assess the performance of a BRB and its frame components is also discussed. Finally, the capability of high fidelity modelling to supplemental physical testing is also presented.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48872808","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}
Pub Date : 2021-09-01DOI: 10.5459/bnzsee.54.3.184-196
M. Bikçe, M. M. Erdem
In the Sivrice, Elazığ, Turkey earthquake on January 24, 2020, 41 people lost their lives, more than 1600 people were injured, 672 buildings collapsed, and around 12600 buildings were severely damaged due to poor construction quality. After such devastating earthquakes, damage assessment and forensic investigations are normally carried out quickly for a judicial process, and material qualities are revealed. However, emotional sensitivity of the victims in the earthquake affected zone and disruptions in key lifeline services such as transportation, electricity supply often make these processes difficult. After the Elazığ earthquake, along with the conventional in-situ core sampling method, concrete pieces were collected from columns of collapsed and severely damaged buildings and transported out of the earthquake zone to overcome these adverse conditions. Unlike in the conventional method where the whole sampling process is carried out in the earthquake zone, the core extraction from the transported concrete pieces was carried out outside the earthquake-affected area. The extracted concrete samples were checked for compliance with the prevailing material standards. Moreover, multiple reinforcing bars of various diameters were also extracted and tested to check their compliance with the standards. Besides, the results of examination of the quality of materials and workmanship used in the construction are also discussed, along with the precautions required to minimize fatalities and damage from similar buildings.
{"title":"Investigation of construction material quality and workmanship defects of RC buildings collapsed and severely damaged in the 6.8 Mw Sivrice, Elazığ, Turkey earthquake, January 2020","authors":"M. Bikçe, M. M. Erdem","doi":"10.5459/bnzsee.54.3.184-196","DOIUrl":"https://doi.org/10.5459/bnzsee.54.3.184-196","url":null,"abstract":"In the Sivrice, Elazığ, Turkey earthquake on January 24, 2020, 41 people lost their lives, more than 1600 people were injured, 672 buildings collapsed, and around 12600 buildings were severely damaged due to poor construction quality. After such devastating earthquakes, damage assessment and forensic investigations are normally carried out quickly for a judicial process, and material qualities are revealed. However, emotional sensitivity of the victims in the earthquake affected zone and disruptions in key lifeline services such as transportation, electricity supply often make these processes difficult. After the Elazığ earthquake, along with the conventional in-situ core sampling method, concrete pieces were collected from columns of collapsed and severely damaged buildings and transported out of the earthquake zone to overcome these adverse conditions. Unlike in the conventional method where the whole sampling process is carried out in the earthquake zone, the core extraction from the transported concrete pieces was carried out outside the earthquake-affected area. The extracted concrete samples were checked for compliance with the prevailing material standards. Moreover, multiple reinforcing bars of various diameters were also extracted and tested to check their compliance with the standards. Besides, the results of examination of the quality of materials and workmanship used in the construction are also discussed, along with the precautions required to minimize fatalities and damage from similar buildings.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":"1 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42023859","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}
Pub Date : 2020-06-01DOI: 10.5459/BNZSEE.53.2.101-110
Rolando P Orense, L. Wotherspoon, M. Pender, S. V. Ballegooy, M. Cubrinovski
Pumice materials, which are problematic from an engineering viewpoint, are widespread in the central part of the North Island. Considering the impacts of the 2010-2011 Christchurch earthquakes, a clear understanding of their properties under earthquake loading is necessary. For example, the 1987 Edgecumbe earthquake showed evidence of localised liquefaction of sands of volcanic origin. To elucidate on this, research was undertaken to investigate whether existing empirical field-based methods to evaluate the liquefaction potential of sands, which were originally developed for hard-grained soils, are applicable to crushable pumice-rich deposits. For this purpose, two sites, one in Whakatane and another in Edgecumbe, were selected where the occurrence of liquefaction was reported following the Edgecumbe earthquake. Manifestations of soil liquefaction, such as sand boils and ejected materials, have been reported at both sites. Field tests, including cone penetration tests (CPT), shear-wave velocity profiling, and screw driving sounding (SDS) tests were performed at the sites. Then, considering estimated peak ground accelerations (PGAs) at the sites based on recorded motions and possible range of ground water table locations, liquefaction analysis was conducted at the sites using available empirical approaches. To clarify the results of the analysis, undisturbed soil samples were obtained at both sites to investigate the laboratory-derived cyclic resistance ratios and to compare with the field-estimated values. Research results clearly showed that these pumice-rich soils do not fit existing liquefaction assessment frameworks and alternate methods are necessary to characterise them.
{"title":"EVALUATING LIQUEFACTION POTENTIAL OF PUMICEOUS DEPOSITS THROUGH FIELD TESTING: CASE STUDY OF THE 1987 EDGECUMBE EARTHQUAKE","authors":"Rolando P Orense, L. Wotherspoon, M. Pender, S. V. Ballegooy, M. Cubrinovski","doi":"10.5459/BNZSEE.53.2.101-110","DOIUrl":"https://doi.org/10.5459/BNZSEE.53.2.101-110","url":null,"abstract":"Pumice materials, which are problematic from an engineering viewpoint, are widespread in the central part of the North Island. Considering the impacts of the 2010-2011 Christchurch earthquakes, a clear understanding of their properties under earthquake loading is necessary. For example, the 1987 Edgecumbe earthquake showed evidence of localised liquefaction of sands of volcanic origin. To elucidate on this, research was undertaken to investigate whether existing empirical field-based methods to evaluate the liquefaction potential of sands, which were originally developed for hard-grained soils, are applicable to crushable pumice-rich deposits. For this purpose, two sites, one in Whakatane and another in Edgecumbe, were selected where the occurrence of liquefaction was reported following the Edgecumbe earthquake. Manifestations of soil liquefaction, such as sand boils and ejected materials, have been reported at both sites. Field tests, including cone penetration tests (CPT), shear-wave velocity profiling, and screw driving sounding (SDS) tests were performed at the sites. Then, considering estimated peak ground accelerations (PGAs) at the sites based on recorded motions and possible range of ground water table locations, liquefaction analysis was conducted at the sites using available empirical approaches. To clarify the results of the analysis, undisturbed soil samples were obtained at both sites to investigate the laboratory-derived cyclic resistance ratios and to compare with the field-estimated values. Research results clearly showed that these pumice-rich soils do not fit existing liquefaction assessment frameworks and alternate methods are necessary to characterise them.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":"79 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84136149","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}
Pub Date : 2020-06-01DOI: 10.5459/bnzsee.53.2.83-100
M. Yazdanian, J. Ingham, Christopher Kahanek, Nicholas A. Cradock-Henry, J. Fountain, D. Dizhur
The 2013 Seddon earthquake (Mw 6.5), the 2013 Lake Grassmere earthquake (Mw 6.6), and the 2016 Kaikōura earthquake (Mw 7.8) provided an opportunity to assemble the most extensive damage database to wine storage tanks ever compiled worldwide. An overview of this damage database is presented herein based on the in-field post-earthquake damage data collected for 2058 wine storage tanks (1512 legged tanks and 546 flat-based tanks) following the 2013 earthquakes and 1401 wine storage tanks (599 legged tanks and 802 flat-based tanks) following the 2016 earthquake. Critique of the earthquake damage database revealed that in 2013, 39% and 47% of the flat-based wine tanks sustained damage to their base shells and anchors respectively, while due to resilience measures implemented following the 2013 earthquakes, in the 2016 earthquake the damage to tank base shells and tank anchors of flat-based wine tanks was reduced to 32% and 23% respectively and instead damage to tank barrels (54%) and tank cones (43%) was identified as the two most frequently occurring damage modes for this type of tank. Analysis of damage data for legged wine tanks revealed that the frame-legs of legged wine tanks sustained the greatest damage percentage among different parts of legged tanks in both the 2013 earthquakes (40%) and in the 2016 earthquake (44%). Analysis of damage data and socio-economic findings highlight the need for industry-wide standards, which may have socio-economic implications for wineries.
{"title":"ANALYSIS OF DAMAGE DATA COLLECTED FOR WINE STORAGE TANKS FOLLOWING THE 2013 AND 2016 NEW ZEALAND EARTHQUAKES","authors":"M. Yazdanian, J. Ingham, Christopher Kahanek, Nicholas A. Cradock-Henry, J. Fountain, D. Dizhur","doi":"10.5459/bnzsee.53.2.83-100","DOIUrl":"https://doi.org/10.5459/bnzsee.53.2.83-100","url":null,"abstract":"The 2013 Seddon earthquake (Mw 6.5), the 2013 Lake Grassmere earthquake (Mw 6.6), and the 2016 Kaikōura earthquake (Mw 7.8) provided an opportunity to assemble the most extensive damage database to wine storage tanks ever compiled worldwide. An overview of this damage database is presented herein based on the in-field post-earthquake damage data collected for 2058 wine storage tanks (1512 legged tanks and 546 flat-based tanks) following the 2013 earthquakes and 1401 wine storage tanks (599 legged tanks and 802 flat-based tanks) following the 2016 earthquake. Critique of the earthquake damage database revealed that in 2013, 39% and 47% of the flat-based wine tanks sustained damage to their base shells and anchors respectively, while due to resilience measures implemented following the 2013 earthquakes, in the 2016 earthquake the damage to tank base shells and tank anchors of flat-based wine tanks was reduced to 32% and 23% respectively and instead damage to tank barrels (54%) and tank cones (43%) was identified as the two most frequently occurring damage modes for this type of tank. Analysis of damage data for legged wine tanks revealed that the frame-legs of legged wine tanks sustained the greatest damage percentage among different parts of legged tanks in both the 2013 earthquakes (40%) and in the 2016 earthquake (44%). Analysis of damage data and socio-economic findings highlight the need for industry-wide standards, which may have socio-economic implications for wineries.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48018419","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}
Pub Date : 2019-09-30DOI: 10.5459/bnzsee.52.3.119-133
G. Morris, A. Thompson, J. Dismuke, B. Bradley
Nonlinear response history analysis (NLRHA), or so-called “nonlinear time history analysis”, is adopted by practicing structural engineers who implement performance-based seismic design and/or assessment procedures. One important aspect in obtaining reliable output from the NLRHA procedure is the input ground motion records. The underlying intention of ground motion selection and amplitude-scaling procedures is to ensure the input for NLRHA is representative of the ground shaking hazard level, for a given site and structure. The purpose of this paper is to highlight the salient limitations of the ground motion selection and scaling requirements in Sections 5.5 and 6.4 of the New Zealand (NZ) loading standard NZS 1170.5 (2004). From a NZ regulatory perspective; there is no specific framework for seismic hazard analysis and ground motion selection (thus self-regulation is the current norm). In contrast, NZS 1170.5 contains many prescriptive requirements for scaling and applying records which are challenging to satisfy in practice. Also discussed within, there are implications for more modern guidance documents in NZ, such as the 2017 “Assessment Guidelines” for existing buildings, which cite NZS 1170.5, a standard which is at least 16 years old (draft issued in 2002). To emphasize the above issues with NZS 1170.5, this paper presents a summary of the more contemporary approaches in the US standards ASCE 7-16 (new buildings) and ASCE 41-17 (existing buildings), along with some examples of the more stringent US requirements for Tall Buildings.
{"title":"Ground motion input for nonlinear response history analysis","authors":"G. Morris, A. Thompson, J. Dismuke, B. Bradley","doi":"10.5459/bnzsee.52.3.119-133","DOIUrl":"https://doi.org/10.5459/bnzsee.52.3.119-133","url":null,"abstract":"Nonlinear response history analysis (NLRHA), or so-called “nonlinear time history analysis”, is adopted by practicing structural engineers who implement performance-based seismic design and/or assessment procedures. One important aspect in obtaining reliable output from the NLRHA procedure is the input ground motion records. The underlying intention of ground motion selection and amplitude-scaling procedures is to ensure the input for NLRHA is representative of the ground shaking hazard level, for a given site and structure. \u0000The purpose of this paper is to highlight the salient limitations of the ground motion selection and scaling requirements in Sections 5.5 and 6.4 of the New Zealand (NZ) loading standard NZS 1170.5 (2004). From a NZ regulatory perspective; there is no specific framework for seismic hazard analysis and ground motion selection (thus self-regulation is the current norm). In contrast, NZS 1170.5 contains many prescriptive requirements for scaling and applying records which are challenging to satisfy in practice. Also discussed within, there are implications for more modern guidance documents in NZ, such as the 2017 “Assessment Guidelines” for existing buildings, which cite NZS 1170.5, a standard which is at least 16 years old (draft issued in 2002). To emphasize the above issues with NZS 1170.5, this paper presents a summary of the more contemporary approaches in the US standards ASCE 7-16 (new buildings) and ASCE 41-17 (existing buildings), along with some examples of the more stringent US requirements for Tall Buildings.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2019-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48567186","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}
Pub Date : 2019-09-30DOI: 10.5459/bnzsee.52.3.134-140
H. Tjahjanto, G. MacRae, A. Abu, C. Clifton, T. Beetham, N. Mago
This paper evaluates external diaphragm axial capacity in moment frame structures with square concrete-filled steel tubular (CFST) columns considering bidirectional loading. Three design methods were considered: (1) the CIDECT method; (2) the equivalent beam method; and (3) the tie method. Finite element analyses were conducted to investigate the behaviour of an external diaphragm plate connected to a square CFST column under varied bidirectional diaphragm axial forces. It is shown that the perpendicular diaphragm axial forces did not reduce the diaphragm axial capacity significantly, which is consistent with the assumptions made by the CIDECT method and the tie method. The CIDECT method, in some cases, was not conservative. Among the considered methods, the tie method was the most justifiable method, although in some cases the capacity predictions were too conservative. The tie method was later modified by considering the contribution of the steel tube in addition to the diaphragm plate in calculating the diaphragm axial capacity. The modified tie method was shown to accurately predict a lower bound estimate of the capacity of an external diaphragm connection.
{"title":"Diaphragm axial capacity for external diaphragm connections (EDCs) in square CFST column structures","authors":"H. Tjahjanto, G. MacRae, A. Abu, C. Clifton, T. Beetham, N. Mago","doi":"10.5459/bnzsee.52.3.134-140","DOIUrl":"https://doi.org/10.5459/bnzsee.52.3.134-140","url":null,"abstract":"This paper evaluates external diaphragm axial capacity in moment frame structures with square concrete-filled steel tubular (CFST) columns considering bidirectional loading. Three design methods were considered: (1) the CIDECT method; (2) the equivalent beam method; and (3) the tie method. Finite element analyses were conducted to investigate the behaviour of an external diaphragm plate connected to a square CFST column under varied bidirectional diaphragm axial forces. It is shown that the perpendicular diaphragm axial forces did not reduce the diaphragm axial capacity significantly, which is consistent with the assumptions made by the CIDECT method and the tie method. The CIDECT method, in some cases, was not conservative. Among the considered methods, the tie method was the most justifiable method, although in some cases the capacity predictions were too conservative. The tie method was later modified by considering the contribution of the steel tube in addition to the diaphragm plate in calculating the diaphragm axial capacity. The modified tie method was shown to accurately predict a lower bound estimate of the capacity of an external diaphragm connection.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2019-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43022676","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}
Pub Date : 2019-09-30DOI: 10.5459/bnzsee.52.3.109-118
T. Sullivan
The peak storey drift demands that an earthquake imposes on a building can be assessed through a detailed engineering seismic assessment or recorded if a building is instrumented. However, for the rapid seismic assessment of a large number of buildings, it is desirable to have a simplified means of estimating storey drift demands. Consequently, this paper proposes a simplified means of quickly estimating storey drift demands on reinforced concrete (RC) frame buildings. Expressions for peak storey drift demand as a function of ground motion intensity are developed by utilising concepts and simplifications available from displacement-based seismic design and assessment methods. The performance of the approach is gauged by comparing predicted storey drift demands with those obtained from rigorous non-linear time-history analyses for a number of case study buildings. The promising results suggest that the approach proposed will be useful for rapidly assessing the likelihood of damage to a range of drift-sensitive elements in modern RC frame buildings.
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Pub Date : 2019-09-30DOI: 10.5459/bnzsee.52.3.141-149
J. Hare
Seismic risk has traditionally been approached using probabilistic analysis. This dilutes the potential impact of low probability, extreme events that may lead to severe consequences including excessive land damage, building damage, injuries and death. The communication of risk in probabilistic terms is also not clearly understood by most audiences. Further, it is evident that few building developers, owners and users have a good understanding the implications of this and the capacity design of buildings, which may not be repairable after a severe event. There is also an adverse impact on planning and land use, where decisions that may affect many people are based on a limited view of adverse outcomes such as liquefaction, lateral spread and slope stability in severe earthquakes. A different way of thinking about seismic risk is proposed. An approach of using scenarios derived from a combination of deterministic as well as probabilistic thinking would prompt consideration of impacts over a range of events. This would allow full consideration of which outcomes are clearly not acceptable and which are. This may facilitate planning for both private and public sector, with a common understanding that is relatively easily communicated to both experts and lay people. This risk evaluation framework would also facilitate consideration of mitigation, by bringing focus on unacceptable outcomes of severe events that are currently obscured by pure probabilistic analysis. This was missing in Christchurch, which experienced the sort of event we can readily anticipate and should actively plan for in other parts of New Zealand. This would help us avoid future red zones and excessive damage and demolition. It will inform development of building codes and standards and will help us evaluate risk and provide resilience and redundancy across the range of interconnected infrastructure networks. Informed debate is needed with key decision makers to discuss the underlying objectives of our regulation and how these may be better met by such an approach, without engineers allowing themselves to be trapped in past thinking and assumptions.
{"title":"A different way of thinking about seismic risk","authors":"J. Hare","doi":"10.5459/bnzsee.52.3.141-149","DOIUrl":"https://doi.org/10.5459/bnzsee.52.3.141-149","url":null,"abstract":"Seismic risk has traditionally been approached using probabilistic analysis. This dilutes the potential impact of low probability, extreme events that may lead to severe consequences including excessive land damage, building damage, injuries and death. The communication of risk in probabilistic terms is also not clearly understood by most audiences. Further, it is evident that few building developers, owners and users have a good understanding the implications of this and the capacity design of buildings, which may not be repairable after a severe event. \u0000There is also an adverse impact on planning and land use, where decisions that may affect many people are based on a limited view of adverse outcomes such as liquefaction, lateral spread and slope stability in severe earthquakes. \u0000A different way of thinking about seismic risk is proposed. An approach of using scenarios derived from a combination of deterministic as well as probabilistic thinking would prompt consideration of impacts over a range of events. This would allow full consideration of which outcomes are clearly not acceptable and which are. This may facilitate planning for both private and public sector, with a common understanding that is relatively easily communicated to both experts and lay people. \u0000This risk evaluation framework would also facilitate consideration of mitigation, by bringing focus on unacceptable outcomes of severe events that are currently obscured by pure probabilistic analysis. This was missing in Christchurch, which experienced the sort of event we can readily anticipate and should actively plan for in other parts of New Zealand. \u0000This would help us avoid future red zones and excessive damage and demolition. It will inform development of building codes and standards and will help us evaluate risk and provide resilience and redundancy across the range of interconnected infrastructure networks. \u0000Informed debate is needed with key decision makers to discuss the underlying objectives of our regulation and how these may be better met by such an approach, without engineers allowing themselves to be trapped in past thinking and assumptions.","PeriodicalId":46396,"journal":{"name":"Bulletin of the New Zealand Society for Earthquake Engineering","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2019-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47467890","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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