• 한국지진공학회논문집
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• 제10권5호
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• pp.85-97
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• 2006

성능보장설계는 교각이 완전한 소성회전성능을 발휘할 때까지 다른 구조요소들과 교각 자체가 취성파괴 되지 않도록 설계하여 교량 전체 시스템의 연성파괴를 보장하기 위한 것으로서, 현행 도로교설계기준에는 명시적으로 규정되어 있지 않으나 대부분의 외국 교량내진설계기준에 채택되어 있다. 성능보장설계에서는 철근콘크리트 교각의 휨 초과강도를 구하고 이를 변환한 전단력을 교각, 기초, 말뚝에 작용하는 횡하중 설계전단력으로 결정하여 교각의 전단설계, 기초설계, 말뚝설계를 수행하도록 규정한다. 이 때 교각의 최대 소성모멘트를 결정하는 방법은 설계기준별로 각기 다른데, 이는 각 국의 재료 시공환경이 다르기 때문이다. 본 연구에서는 국내에서 사용하는 철근의 인장강도 측정치 3,407개와 콘크리트 압축강도 측정치 5,405개의 분석을 통하여 재료 초과강도계수를 제안하였고, 이를 적용하여 휨 초과강도를 결정하는 방법을 제시하였으며, 1,500개의 교각단면에 대한 모멘트-곡률 해석을 수행한 후 통계분석을 통하여 우리나라 실정에 적합한 초과강도계수를 제안하였다.

• Steel and Composite Structures
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• 제17권3호
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• pp.215-236
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• 2014

The flexural behaviour of steel beams significantly affects the structural performance of the steel frame structures. In particular, the flexural overstrength (namely the ratio between the maximum bending moment and the plastic bending strength) that steel beams may experience is the key parameter affecting the seismic design of non-dissipative members in moment resisting frames. The aim of this study is to present a new formulation of flexural overstrength factor for steel beams by means of artificial neural network (NN). To achieve this purpose, a total of 141 experimental data samples from available literature have been collected in order to cover different cross-sectional typologies, namely I-H sections, rectangular and square hollow sections (RHS-SHS). Thus, two different data sets for I-H and RHS-SHS steel beams were formed. Nine critical prediction parameters were selected for the former while eight parameters were considered for the latter. These input variables used for the development of the prediction models are representative of the geometric properties of the sections, the mechanical properties of the material and the shear length of the steel beams. The prediction performance of the proposed NN model was also compared with the results obtained using an existing formulation derived from the gene expression modeling. The analysis of the results indicated that the proposed formulation provided a more reliable and accurate prediction capability of beam overstrength.

• Steel and Composite Structures
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• 제43권4호
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• pp.447-456
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• 2022

Recent experimental studies showed that deep steel I-shaped profiles classified as high ductility class sections in seismic design international codes exhibit low deformation capacity when subjected to cyclic loading. This paper presents an innovative retrofit solution to increase the rotation capacity of beams using bonded carbon fiber reinforced polymers (CFRP) patches validated with advanced finite element analysis. This investigation focuses on the flexural cyclic behaviour of I-shaped hot rolled steel deep section used as beams in moment-resisting frames (MRF) retrofitted with CFRP patches on the web. The main goal of this CFRP reinforcement is to increase the rotation capacity of the member without increasing the overstrength in order to avoid compromising the strong column-weak beam condition in MRF. A finite element model that simulates the cyclic plasticity behavior of the steel and the damage in the adhesive layer is developed. The damage is modelled using the cohesive zone modelling (CZM) technique that is able to capture the crack initiation and propagation. Details on the modelling techniques including the mesh sensitivity near the fracture zone are presented. The effectiveness of the retrofit solution depends strongly on the selection of the appropriate adhesive. Different adhesive types are investigated where the CZM parameters are calibrated from high fidelity fracture mechanics tests that are thoroughly validated in the literature. This includes a rigid adhesive commonly found in the construction industry and two tough adhesives used in the automotive industry. The results revealed that the CFRP patch can increase the rotation capacity of a steel member considerably when using tough adhesives.