초록 ▼

본 연구개발과제에서는 고강도로 제작된 휨재, 압축재, 그리고 휨과 압축의 조합력을 받는 보-기둥 부재들의 다양한 한계상태에서의 거동 규명을 통하여 설계목적에 부합되게 제어할 수 있는 설계기준 정립하기 위하여 기존의 관련 연구 및 기준 조사를 통하여 수치해석 및 실험연구 계획을 수립하고 연구를 수행하였다. 해석적 및 실험적 연구를 통하여 고성능 강재를 사용한 휨재, 압축재 및 보-기둥 부재가 현재 개정 작업 중인 관련 기준에 적용이 가능한 것으로 판단되어 관련 기준 위원회에 연구결과 적용을 제안하였고 위원회에서는 연구결과의 타당성을

본 연구개발과제에서는 고강도로 제작된 휨재, 압축재, 그리고 휨과 압축의 조합력을 받는 보-기둥 부재들의 다양한 한계상태에서의 거동 규명을 통하여 설계목적에 부합되게 제어할 수 있는 설계기준 정립하기 위하여 기존의 관련 연구 및 기준 조사를 통하여 수치해석 및 실험연구 계획을 수립하고 연구를 수행하였다. 해석적 및 실험적 연구를 통하여 고성능 강재를 사용한 휨재, 압축재 및 보-기둥 부재가 현재 개정 작업 중인 관련 기준에 적용이 가능한 것으로 판단되어 관련 기준 위원회에 연구결과 적용을 제안하였고 위원회에서는 연구결과의 타당성을 인정하여 개정된 기준에 연구결과가 반영될 예정이다. 또한 연구과제의 3년간의 연구결과 연구개발 초기에 설정한 양적 및 질적 목표 연구성과를 모두 초과 달성하는 성과를 거두었다.

Abstract ▼

Ⅲ. Research Contents and Results
∙ Research Process
The research processes to achieve the main purpose of this research and development project are as followings:
○ Step 1: Preliminary research
(1) Collection and classification for existing research and development outputs based on the r

Ⅲ. Research Contents and Results
∙ Research Process
The research processes to achieve the main purpose of this research and development project are as followings:
○ Step 1: Preliminary research
(1) Collection and classification for existing research and development outputs based on the related projects supported by governmental bodies of Korea
(2) Collection and classification for material properties of HPS based on the data obtained from domestic and international steel companies
(3) Survey and analyses of design standards for HPS based on the data obtained from domestic and international public organizations and academic societies
○ Step 2: Numerical analyses and experimental programs
(1) Numerical analyses considering the material non-linearity, differences between tensile and compressive strength of material, effects of initial imperfection and residual stresses from fabrication
(2) Test program to verify the ultimate strengths of members
(3) Co-work with institution well equipped with the structural testing machines such as RIST for the efficiencies in experimental research
(4) Analytical research with various parameters to compensate the experimental results from the limited experimental study
(5) Suggestion of design equations through the statistical research
○ Step 3: Design standard
(1) The first draft of design standard from the research outcomes, after consulting with engineers and researchers
(2) Proposals based on the various opinions through the holding a public hearing with engineers, researches, competent authorities(MOLIT)
(3) Draft of design standard for HPS
∙ Research Contents
Research contents for flexural, compressive, and beam-column HPS members, which are most widely used structural members, are as followings:
○ Development of LRFD design equations for HPS flexural members
(1) Theoretical research on the compactness limits of HPS girders
(2) Analytical and experimental researches for the development of flexural design equations under positive and negative moments
(3) Development of shear strength design equations considering tension field action
(4) Development of design equations for resistance and hybrid factors
(5) Analytical and experimental researches on the serviceability
(6) Design equations on the flexural and shear design equations for LRFD standard
○ Development of LRFD design equations for HPS compressive members
(1) Basic research on the mechanical properties of HPS
(2) Analytical and experimental researches for the development of design equations for HPS compressive members
(3) Complementary research on design equations for HPS compressive members
(4) Design equations on the compression design equations for LRFD standard
○ Development of LRFD design equations for HPS beam-column members
(1) Analytical and experimental researches for the development of design equations for HPS beam-column members
(2) Complementary research on design equations for HPS beam-column members
(3) Design equations on the beam-column design equations for LRFD standard
∙ Research Results
The brief results from the research for LRFD standardization of flexural and compressive HPS members for the application to steel construction are as followings:¡ Development of LRFD design equations for HPS flexural members
(1) In AASHTO LRFD Specifications, the nominal flexural strength and ductility requirements of the composite I-girder using conventional steel in positive bending are specified by the plastic moment and ductility ratio. However, these are not suited for the composite girder made of high performance steel (HSB800) as a tension flange element because HSB800 has the properties that there is no certain fully-plastic region in the stress-strain curve. In this study, by assuming the fully-plastic region in the idealized stress-strain curves of HSB800, the plastic moment and ductility ratio are defined for the composite hybrid steel I-girder with HSB800 tension flange. By using the numerical analysis results of compact cross-sections with various dimensions, the nominal flexural strength and ductility requirements are proposed for a composite hybrid I-girder with HSB800 applied to tension flange and SM570 applied to web and compression flange.
(2) The ultimate flexural behavior of a composite HSB800 plate girder in negative bending is investigated by nonlinear FEA. Comparative analysis of the flexural strength from analyses and codes shows that strengths by AASHTO Appendix A6 were 12% less than those from FEA whereas AASHTO Article 6.10.8 and Eurocode 3 underestimate the strengths by 22% and 16%, respectively. KHBDC expected the strengths 14% smaller than FEA. It was observed that strength evaluation by KHBDC, Appendix A6 and Eurocode 3 correlate better to FEA than by Article 6.10.8.
(3) Flange local buckling (FLB) strength of plate girders with HSB 800 was evaluated by nonlinear finite element analysis. Parametric study of compression flanges with a compact, noncompact and slender web has shown that AASHTO LRFD Article 6.10.3 (2012) can be conservatively applicable to girders made with HSB 800. In case of AASHTO LRFD Appendix 6 and KHBDC LSD (2012), it has been found that care should be placed on applications of compact section compression flanges that are near the limit slenderness.
(4) Numerical analyses were performed to evaluate the LTB strength of doublyand mono-symmetric HSB800 steel girders with homogeneous and hybrid section. It was acknowledged that AASHTO LRFD appendix A6 can be applied to most sections with noncompact and compact web, but experimental study will be necessary for the monosymmetric sections with smaller compression flange than tension flange.
(5) The average flexural strength of I-girders fabricated from SM490, SM520, and HSB600 steels by nonlinear FEA was calculated to be 4% and 14% greater than those specified in AASHTO LRFD and Eurocode 3, respectively. In case of HSB800 I-girders with slender web, the average flexural strength by FEA was found to be 9% and 21% greater than those by AASHTO LRFD and Eurocode 3, respectively. Taking into account of relatively poor ductility characteristics of HSB800 steel, the nominal flexural strength formula in current AASHTO LRFD and KHBDC LSD can be applied to predicting the flexural strength of HSB800 I-girders with noncompact or slender web without modification.
(6) The HSB800 that is the high strength steel of the yield strength equal to 690MPa typically shows a lower ductility than the conventional steels. The recent limit-state-design method speculate the web compactness requirements for the effective plastic moment capacity, but these provisions shall be applicable to the steel section with specified minimum yield strength up to 485MPa. Thus, this study has investigated the ultimate bending moment and moment-plastic rotation behaviors numerically and experimentally for a series of prototype model girders. As a result, the applicability of the current provisions is examined for the prototype girders. Based on the study results, it is ascertained that the high moment capacity of HSB800 compact I-girders could be utilized.
(7) It appears that existing shear design equations developed for mild steels are not suitable for HSB800 steel. It was found that the shear design equation (Lee et al. 2008) derived for panels with aspect ratios greater than 3 are able to correctly predict the shear strength of HSB800 plate girders regardless of aspect ratio.
○ Development of LRFD design equations for HPS compressive members
(1) Coupon test results of HSA800 steel showed that most coupons were satisfied with tensile strengths and elongation of KD D 5994 limits, although the yield ratios of several coupons exceeded the limit of 0.85 due to residual stresses from fabrication.
(2) Experimental results of welded H-shaped stub columns showed that increased width-to-thickness ratios were resulted in increased maximum buckling strength. For the case of maximum average stress, specimens, whose maximum strengths were controlled by local buckling, showed decreases in maximum average stress as decrease in width-to-thickness ratios and specimens, whose maximum strengths were controlled by global buckling, vice versa.
(3) Experimental results of welded box-shaped stub columns showed that increased cross sectional areas were resulted in increased maximum buckling strength for the case of specimens with same thickness. However for the case of increases in width-to-thickness ratios due to increases in cross sectional areas, the compressive strengths were rapidly dropped after maximum strengths were reached due to local buckling. For the case of maximum average stress, the more slender showed the less maximum average stresses.
(4) Analytical results of welded H-shaped stub columns well predicted the maximum buckling strengths of experimental results with the average error of 5.3%. Analytical results also well predicted the initial stiffness, load-displacement curves, and stress-strain curves, stress concentration, and shapes of local buckling of experimental results. Analytical results of welded H-shaped stub columns showed that the larger width-to-thickness ratios, the more maximum compressive strengths, and the less average stresses. For the case of maximum average stress, specimens, whose maximum strengths were controlled by local buckling, the strength was rapidly dropped due to local buckling.
(5) Analytical results of welded box-shaped stub columns well predicted the maximum buckling strengths of experimental results with the average error of 2.3%. Analytical results also well predicted the initial stiffness, load-displacement curves, and stress-strain curves, stress concentration, and shapes of local buckling of experimental results. Analytical results of welded box-shaped stub columns showed that the larger width-to-thickness ratios, the more maximum compressive strengths, and the less average stresses.
(6) Generally, analytical results showed higher strength than required strength by the current design standard. Specifically welded H-shaped stub columns with larger width-to-thickness ratio of web were satisfied with current design standard with enough margins. Welded box-shaped stub columns with slender section were barely satisfied with current design standard.
○ Development of LRFD design equations for HPS beam-column members
(1) Coupon test results of HSA800 steel showed typical characteristics of high strength steel with uncertain yielding point and high yielding ratio. The yield and tensile strength and elongation of all coupons were satisfied with required criteria by KS.
(2) As the width-to-thickness ratio of both flange and web, maximum compressive strengths were decreased. The maximum average stresses of the specimens decreased as with width-to-thickness ratio increased, for the case of maximum average stress, for the cases that maximum strengths were controlled by local buckling.
(3) The stub column specimens, fabricated with HSA800 and designed with non-compact section of flexural stress, were satisfied with P-M interaction requirements of standard with large margins as axial strength ratios decreased. Welded box-shaped column specimens showed larger margins than welded H-shaped column specimens.
(4) In all specimens, local buckling was observed after global buckling except for the H-shaped specimens whose local buckling was observed after flexural buckling. Local buckling of all the H-shaped specimens was observed after 90% of maximum strength was reached except for SCH-HSA800-8-25-E0.8 specimen.
(5) Decreased stresses by local buckling were observed after yields were reached for both analytical and experimental results and the shapes stress-strain curves of analytical results were generally well matched up with experimental results. As axial strength ratios increased the maximum stresses were increased and rapid stresses decrease were observed after local buckling. Analytical results well predicted the maximum compressive strengths of experimental results with the average error of 1.65%.
(6) P-M interaction curves obtained from the parametric studies showed that compressive strength of non-slender specimens were satisfied with current design standard with enough margins especially for the case with lower axial strength ratio. However compressive strength requirement of the current design standard for slender section specimens was not satisfied.

목차 Contents

• 표지 ... 1
• 제 출 문 ... 2
• 보고서 요약서 ... 3
• 요 약 문 ... 4
• SUMMARY ... 12
• CONTENTS ... 21
• 목 차 ... 22
• 제1장 연구개발과제 개요 ... 23
• 1.1 연구개발의 필요성 및 목적 ... 23
• 1.2 연구개발의 정의 및 범위 ... 26
• 1.3 관련분야의 국내외 기술개발 현황 ... 28
• 1.4 연구개발결과가 관련분야에서 차지하는 위치 ... 34
• 제2장 연구개발 수행 내용 및 결과 ... 37
• 2.1 연구수행 전략 및 방법론 ... 37
• 2.2 연구수행과정 및 내용 ... 39
• 2.3 연구수행결과 및 결과의 검증 방법 ... 64
• 제3장 최종연구성과 및 적용실적 ... 72
• 3.1 최종 연구성과 ... 72
• 3.2 연구성과 적용 ... 73
• 제4장 연구목표 달성 및 효과 ... 76
• 4.1 연구개발 최종목표 달성도 ... 76
• 4.2 기대성과 및 파급효과 ... 77
• 제5장 연구성과의 활용 및 추가연구 필요성 ... 79
• 5.1 연구성과의 활용방안 ... 79
• 5.2 추가연구 필요성 ... 79
• 참고문헌 ... 81
• 끝페이지 ... 86