Experimental Cyclic Behavior of Precast Hybrid Beam-Column Connections with Welded Components

Girgin, Sadik Can,Misir, Ibrahim Serkan,Kahraman, Serap Korea Concrete Institute 2017 International Journal of Concrete Structures and M Vol.11 No.2

Post-earthquake observations revealed that seismic performance of beam-column connections in precast concrete structures affect the overall response extensively. Seismic design of precast reinforced concrete structures requires improved beam-column connections to transfer reversed load effects between structural elements. In Turkey, hybrid beam-column connections with welded components have been applied extensively in precast concrete industry for decades. Beam bottom longitudinal rebars are welded to beam end plates while top longitudinal rebars are placed to designated gaps in joint panels before casting of topping concrete in this type of connections. The paper presents the major findings of an experimental test programme including one monolithic and five precast hybrid half scale specimens representing interior beam-column connections of a moment frame of high ductility level. The required welding area between beam bottom longitudinal rebars and beam-end plates were calculated based on welding coefficients considered as a test parameter. It is observed that the maximum strain developed in the beam bottom flexural reinforcement plays an important role in the overall behavior of the connections. Two additional specimens which include unbonded lengths on the longitudinal rebars to reduce that strain demands were also tested. Strength, stiffness and energy dissipation characteristics of test specimens were investigated with respect to test variables. Seismic performances of test specimens were evaluated by obtaining damage indices.

Effective lengths of braced frame columns

Girgin, Konuralp,Ozmen, Gunay Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.2

In several design codes and specifications, simplified formulae and charts are given for determining the effective lengths of frame columns. It is shown that these formulae may yield rather erroneous results in certain cases. This is due to the fact that, the code formulae utilise only local stiffness distributions. In this paper, a simplified procedure for determining approximate values for the buckling loads of braced frames is developed. The procedure utilises a fictitious load analysis of frames and yields errors less than 10%, which may be considered suitable for design purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range.

Effective lengths of braced frame columns

Konuralp Girgin,Günay Özmen 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.2

In several design codes and specifications, simplified formulae and charts are given for determining the effective lengths of frame columns. It is shown that these formulae may yield rather erroneous results in certain cases. This is due to the fact that, the code formulae utilise only local stiffness distributions. In this paper, a simplified procedure for determining approximate values for the buckling loads of braced frames is developed. The procedure utilises a fictitious load analysis of frames and yields errors less than 10%, which may be considered suitable for design purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range.

Experimental Cyclic Behavior of Precast Hybrid Beam-Column Connections with Welded Components

Sadik Can Girgin,Ibrahim Serkan Misir,Serap Kahraman 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.2

Post-earthquake observations revealed that seismic performance of beam-column connections in precast concrete structures affect the overall response extensively. Seismic design of precast reinforced concrete structures requires improved beamcolumn connections to transfer reversed load effects between structural elements. In Turkey, hybrid beam-column connections with welded components have been applied extensively in precast concrete industry for decades. Beam bottom longitudinal rebars are welded to beam end plates while top longitudinal rebars are placed to designated gaps in joint panels before casting of topping concrete in this type of connections. The paper presents the major findings of an experimental test programme including one monolithic and five precast hybrid half scale specimens representing interior beam-column connections of a moment frame of high ductility level. The required welding area between beam bottom longitudinal rebars and beam-end plates were calculated based on welding coefficients considered as a test parameter. It is observed that the maximum strain developed in the beam bottom flexural reinforcement plays an important role in the overall behavior of the connections. Two additional specimens which include unbonded lengths on the longitudinal rebars to reduce that strain demands were also tested. Strength, stiffness and energy dissipation characteristics of test specimens were investigated with respect to test variables. Seismic performances of test specimens were evaluated by obtaining damage indices.

Direct determination of influence lines and surfaces by F.E.M.

Orakdogen, Engin,Girgin, Konuralp Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.3

In this study, element loading matrices are defined for static application of classical M$\ddot{u}$ller-Breslau principle to finite element method. The loading matrices are derived from existing element matrices using Betti's law and known governing equations of F.E.M. Thus, the ordinates of influence lines and influence surfaces may be easily obtained from structural analysis for the loading matrices derived from governing equations, instead of through introduced unit force or displacement techniques. An algorithm for a computer program and comparative numerical examples are also presented to illustrate the procedure for determination of influence line and surface ordinates.

Buckling lengths of unbraced multi-storey frame columns

Ozmen, Gunay,Girgin, Konuralp Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.1

In several design codes and specifications, simplified formulae and diagrams are given for determining the buckling lengths of frame columns. It is shown that these formulae may yield rather erroneous results in certain cases. This is due to the fact that, the code formulae utilise only local stiffness distributions. In this paper, a simplified procedure for determining approximate values for the buckling loads of multi-storey frames is developed. The procedure utilises lateral load analysis of frames and yields errors in the order of 10%, which may be considered suitable for design purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range and on the safe side.

Predictability of second-hand bulk carriers with a novel hybrid algorithm

Duru Okan,Gulay Emrah,Girgin Sinem Celik 한국해운물류학회 2021 The Asian journal of shipping and Logistics Vol.37 No.4

This paper investigates the predictability of the asset prices of commodity transport (i.e. dry bulk carriers)by testing the shipping Q index as a leading indicator. We employ a comprehensive back-testing proce-dure with a broad spectrum of benchmark simulations. The shipping Q index (an adaptation of Tobin’s Qindex) has been introduced to benchmark models to observe predictive gain and interpret predictabilityfeatures. This study presents a novel hybrid model to forecast time series data. The forecasting abilityof the proposed hybrid algorithm is compared to specific univariate time series models, dynamic mod-els, nonlinear models, and widely used hybrid models in the literature. The findings document that notonly the proposed hybrid model performs better than the other competitive models in terms of hold outsample forecasting, but also using the shipping Q index improves the forecast accuracy by remarkablyreducing forecasting error.

Buckling lengths of unbraced multi-storey frame columns

Günay Özmen,Konuralp Girgin 국제구조공학회 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.1

In several design codes and specifications, simplified formulae and diagrams are given for determining the buckling lengths of frame columns. It is shown that these formulae may yield rather erroneous results in certain cases. This is due to the fact that, the code formulae utilise only local stiffness distributions. In this paper, a simplified procedure for determining approximate values for the buckling loads of multi-storey frames is developed. The procedure utilises lateral load analysis of frames and yields errors in the order of 10%, which may be considered suitable for design purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range and on the safe side.

A load increment method for ductile reinforced concrete (RC) frame structures considering strain hardening effects

M. Günhan Aksoylu,Konuralp Girgin 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.38 No.2

This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.

A load increment method for ductile reinforced concrete (RC) frame structures considering strain hardening effects

Gunhan Aksoylu, M.,Girgin, Konuralp Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.38 No.2

This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.