Developing connection design rules in China

Yongjiu Shi 국제구조공학회 2005 Steel and Composite Structures, An International J Vol.5 No.2

The new version of Code for Design of Steel Structures (GB50017-2003) and other design standards in China were released over the last two years. Comparing with the previous version (GBJ17-88), many clauses covering the connection design have been revised. A number of additional provisions are supplemented to specify the design requirements for beam-column moment connections, as well as gusset plates for truss joints. In this paper, a summary on the design rules on connections specified in the current Chinese code is presented, and relevant commentary and background information is provided whenever appropriate. The design criteria governing weld and bolt resistance is examined and reviewed. Moreover, several issues such as detailing requirements for stiffeners and end-plate connections are discussed.

Loading capacity of simply supported composite slim beam with deep deck

Yongjiu Shi,Lu Yang,Yuanqing Wang,Qiuzhe Li 국제구조공학회 2009 Steel and Composite Structures, An International J Vol.9 No.4

The composite slim beam has become popular throughout Europe in recent years and has also been used on some projects in China. With its steel section encased in a concrete slab, the steel-concrete composite slim beam can provide the floor construction with minimum depth and high fire resistance. However, the design method of the T-shape steel-concrete composite beam is no longer applicable to the composite slim beam with deep deck for its special construction, of which the present design models are not available but mainly depend on experiences. The elevation of the flexural stiffness and bending capacity of composite slim beams with deep deck is rather complicated, because the influences of many factors should be taken into account, such as the variable section dimensions, development of cracks and non-linear characteristics of concrete, etc. In this paper, experimental investigations have been conducted into the flexural behavior of two specimens of simply supported composite slim beam with deep deck. The emphases were laid on the bonding force on the interface between steel beam and concrete, the stress distribution of beam section, the flexural stiffness and bending capacity of the composite beams. Based on the experimental results, the reduction factor of equivalent stress distribution in concrete flange is suggested, and the calculation method of flexural stiffness and bending capacity of simply supported slim beams are proposed.

Analysis on Shear Behavior of High-Strength Bolts Connection

Yongjiu Shi,Meng Wang,Yuanqing Wang 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.2

Because of high cost of tests and numerical calculation using solid element of high-strength bolts connection in steel frameworks, it is important to find an accurate and simplified approach to describe the shear behavior of high-strength bolts connection. The paper aims to find a spring element to simulate the shear behavior instead of solid element in structure. Firstly,solid element model of high-strength bolt connection is established, which is proved correct and applicable comparing with existing typical shear tests. Then, base on the reliability of finite element model, the shear behavior of bolts connection is further discussed through a large number of parameter analyses. The three feature points and four stages of the simplified shear model are calibrated according to tests and calculation results. A simplified shear behavior model and hysteretic criterion of highstrength bolts connection are proposed. According to cases study, feasibility of the proposed model is validated. The proposed model gives a simple process to provide quite accurate results, which provides a great tool for engineering applications.

Experimental and Analytical Study on Local Buckling Behavior of High Strength Steel Welded I-Section Beams

Yongjiu Shi,Kelong Xu 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.4

With the progress in metallurgical technique and steel production process, the strength of structural steels can be improved, along with other material properties, including higher toughness and better weldability. Meanwhile, there are numerous potential civil structural applications for high strength steel (HSS), such as large-span space frames, transfer truss in highrise buildings, as well as truss bridges. The mechanical behavior of structural members made up from HSS must be closely investigated and quantifi ed before HSS can be widely used in engineering structures. In this paper experiments on six Q550 HSS I-section beams under moment gradient (MG) and four Q550 HSS I-section beams under patch loading (PL) were carried out, to investigate the local buckling behavior of I-section beams subjected to diff erent loading conditions. The failure modes, critical local buckling strengths, ultimate strengths, load–deformation curves, load–strain curves and moment–rotation curves of the specimens were obtained. The test results of ultimate strengths were further compared with the design results in accordance with the available design methods in current specifi cations, ANSI/AISC 360-16, Eurocode 3, AS 4100-1998, AIJ LSD 2010 and GB 50017-2003. Accounting for material nonlinearity, geometric imperfection and residual stress, fi nite element models were established and verifi ed with the existing test results, which were used for the parametric analysis of two series of 240 beams. The parametric investigation focused on the eff ects of the material properties and component plate slenderness on the ultimate strengths of I-section beams under MG and the ones under PL. The comparisons between the parametric analysis results, test results and the design results from ANSI/AISC 360-16 and Eurocode 3 were also conducted.

Application of steel equivalent constitutive model for predicting seismic behavior of steel frame

Meng Wang,Yongjiu Shi,Yuanqing Wang 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.5

In order to investigate the accuracy and applicability of steel equivalent constitutive model, the calculated results were compared with typical tests of steel frames under static and dynamic loading patterns firstly. Secondly, four widely used models for time history analysis of steel frames were compared to discuss the applicability and efficiency of different methods, including shell element model, multi-scale model, equivalent constitutive model (ECM) and traditional beam element model (especially bilinear model). Four-story steel frame models of above-mentioned finite element methods were established. The structural deformation, failure modes and the computational efficiency of different models were compared. Finally, the equivalent constitutive model was applied in seismic incremental dynamic analysis of a ten-floor steel frame and compared with the cyclic hardening model without considering damage and degradation. Meanwhile, the effects of damage and degradation on the seismic performance of steel frame were discussed in depth. The analysis results showed that: damages would lead to larger deformations. Therefore, when the calculated results of steel structures subjected to rare earthquake without considering damage were close to the collapse limit, the actual story drift of structure might already exceed the limit, leading to a certain security risk. ECM could simulate the damage and degradation behaviors of steel structures more accurately, and improve the calculation accuracy of traditional beam element model with acceptable computational efficiency.

Investigation of Ductility in Hybrid and High Strength Steel Beams

Mehdi Shokouhian,Yongjiu Shi 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.2

Compactness and lateral support configuration provisions for design of steel beams are formulated so as to ensure that theresulting beam exhibits adequate ductility. It appears from the current research that slenderness limitations are not valid forbeams made of the high strength steel grades. In this paper an attempt is made to study on influence of flange and webslenderness as well as lateral support spacing of homogenous and hybrid welded I-sections made of high strength steel onmember ductility. For this purpose an experimentally verified nonlinear numerical analysis of the local and overall stability wasperformed. These beams are subjected to constant moment loading a new theoretical method is proposed to calculate therotation capacity for this loading type. A comparative study was carried out between this method and numerical study resultsto ensure the accuracy of proposed method. In this research realistic material behavior and residual stresses were adopted infinite element models. Results have shown that using the high strength steel in cross sections subjected to bending has asignificant effect on flexural behavior of these members. Meanwhile, in present study, interaction between the flange and webslenderness ratios was evaluated in accordance to AISC criteria for compact sections.

Degradation and damage behaviors of steel frame welded connections

Meng Wang,Yongjiu Shi,Yuanqing Wang,Jun Xiong,Hong Chen 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.15 No.4

In order to study the degradation and damage behavirs of steel frame welded connections, two series of tests in references with different connection constructions were carried out subjected to various cyclic loading patterns. Hysteretic curves, degradation and damage behaviours and fatigue properties of specimens were firstly studied. Typical failure modes and probable damage reasons were discussed. Then, various damage index models with variables of dissipative energy, cumulative displacement and combined energy and displacement were summarized and applied for all experimental specimens. The damage developing curves of ten damage index models for each connection were obtained. Finally, the predicted and evaluated capacities of damage index models were compared in order to describe the degraded performance and failure modes. The characteristics of each damage index model were discussed in depth, and then their distributive laws were summarized. The tests and analysis results showed that the loading histories significantly affected the distributive shapes of damage index models. Different models had their own ranges of application. The selected parameters of damage index models had great effect on the developing trends of damage curves. The model with only displacement variable was recommended because of a more simple form and no integral calculation, which was easier to be formulated and embedded in application programs.

Fracture Behavior Analyses of Welded Beam-to-Column Connections Based on Elastic and Inelastic Fracture Mechanics

Yuanqing Wang,Hui Zhou,Yongjiu Shi,Hong Chen 한국강구조학회 2010 International Journal of Steel Structures Vol.10 No.3

Detailed two-dimensional finite element models are applied to investigate the fracture behavior of welded beam-to-column connections which are widely used in steel structures in China. The elastic stress intensity factor (KI) and inelastic J-integral (JI) around the crack tip are calculated to provide quantitative estimates of fracture toughness requirements in the connections with different configurations. Four types of weld access holes are modeled after the full-scale connection tests. Subsequently,several connection details including weld flaw size and location, weld backing bar, fillet reinforcement and other modifications,are examined in the effectiveness of reducing the toughness demands on the weld. The analyses have confirmed the observations from connection cyclic tests that the fracture is more likely to occur at the beam flange weld heat affected zone (HAZ) which sustains extensive yielding and exhibits relatively low fracture toughness. The weld flaw size and location have shown significant effects on the toughness requirements both by elastic and inelastic analyses. The modification of removing backing bar and reinforcing a fillet weld shows the most effective approach to reduce the toughness demands. By inelastic analyses, the initial weld defect at HAZ (10 mm away from the column face) shows more toughness demands than that at the interface of the column flange and weld. The evaluated moment at column face when crack predicted to propagate, agrees well with the ultimate moment obtained from the connection tests.

Bearing Capacity of Non-linear Metallic Spiders Used in Point Supported Glass Facades

Yuanqing Wang,Huanxin Yuan,Yongjiu Shi,Yu Zou 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.2

Experimental and numerical investigations on bearing capacity of non-linear metallic spiders used in glass facades were presented. The non-linear metallic materials adopted in this study included two aluminum alloys (ZL105-T1 and ZL111-T6)and one austenitic stainless steel (AISI 302). A total of 21 spider specimens including three types of configurations were tested. Numerical simulation of the tests was conducted by virtue of sophisticated finite element (FE) models built up with ANSYS software. The test and FE predicted results were used to develop new design proposals for the spiders. Evaluation of the proposed design formulae revealed that a comparatively large safety margin would be appropriate in consideration of brittle glass panels. Finally, safety assessment of the spiders was conducted based upon a practical engineering application-the exhibition greenhouse in Beijing Botanical Garden.

Fracture Prediction of Welded Steel Connections Using Traditional Fracture Mechanics and Calibrated Micromechanics Based Models

Yuanqing Wang,Hui Zhou,Yongjiu Shi,Jun Xiong 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.3

Fracture resistance is of primary concern in the seismic design of beam-to-column connections in steel moment resisting frames (SMRFs). Micromechanics based fracture models such as the void growth model (VGM) and the stress modified critical strain (SMCS) model provide alternative approaches for ductile fracture prediction by relating micro-mechanisms of void nucleation, growth and coalescence to macroscopic stresses and strains. In this study, the VGM and SMCS models were calibrated for Q345 structural steel and the corresponding weld, through smooth notched tensile (SNT) tests and complementary continuum finite element models (FEMs). A series of seven local connections representing beam-to-column connections in SMRFs were tested under monotonic tensile loading and the specimen elongations at fracture critical point were obtained. The traditional J-integral based fracture mechanics and micromechanics based fracture models (VGM and SMCS) were applied to predict fracture in each tested local connection through refined three-dimensional FEM. Comparisons between these numerical approaches and experimental observations in prediction of fracture critical displacement, indicated that the VGM and SMCS models were able to predict fracture of welded connection with good accuracy, while the J-integral based approach resulted in quite conservative fracture prediction. This paper has bridged the gap between small-scale material tests and large-scale structural experiments in fracture evaluations