Steel-concrete Hybrid Research Articles

摩擦・付着を考慮した拘束応力下に於ける孔あき鋼板ジベルの終局せん断耐力

A perfobond strip is a shear connector comprising a flat steel plate with a number of holes punched through it. Concrete flows through the holes forming dowels that act as shear keys, providing resistance in both vertical and horizontal directions. This connector was proposed by Leonhardt in Germany, and the composite effect of steel and concrete is very high due to the shearing resistance of the concrete in the holes. In addition, it is recognized as having high fatigue strength. It is widely used as a validated shear connector in various steel-concrete hybrid civil engineering structures, since it has high shear resistance and fatigue strength, and it has better constructability than other types of shear connectors such as headed stud shear connectors. Strength evaluation formulas for the design of these shear connectors have been proposed by various investigators around the world. A design formula was specified in the JSCE (Japan Society of Civil Engineers) Standard Specification for Hybrid Structures in 2009. In view of their excellent features, they are expected to be increasingly applied to connections in building structures. However, these connections are much smaller than those in civil engineering structures, so there is a need for a strength formula that accurately evaluates their force transfer mechanism, such as their restraint stress. This paper proposes a modified formulation for ultimate shear strength considering the restraint stress of concrete in these connections, based on the new author's proposed formulations for ultimate and residual stresses under restraint stress to the contact surface under friction and the bonding behaviors of various contact surfaces between steel and concrete. This formulation provides ultimate shear strength by multiplying shear cracking strength by the ratio of ultimate shear strength to shear cracking strength, considering the effect of restraining concrete around the steel plate hole by reinforced concrete cover and penetrating rebar. This formulation includes a new effective area of restraint part and an effective width of RC-cover part. Predictions from the proposed formulation almost agree with test results.

Experimental studies into a new type of hybrid outrigger systemwith metal dampers

This paper presents the experimental investigation into a new type of steel-concrete hybrid outrigger system developed for the high-rise building structure. The steel truss is embedded into the reinforced concrete outrigger wall, and both the steel truss and concrete outrigger wall work compositely to enhance the overall structural performance of the tower structures under extreme loads. Meanwhile, metal dampers of low-yield steel material were also adopted as a „fuse‟ device between the hybrid outrigger and the column. The damper is engineered to be „scarified‟ and yielded first under moderate to severe earthquakes in order to protect the structural integrity of important structural components of the hybrid outrigger system. As such, not brittle failure is likely to happen due to the severe cracking in the concrete outrigger wall. A comprehensive experimental research program was conducted into the structural performance of this new type of hybrid outrigger system. Studies on both the key component and overall system tests were conducted, which reveal the detailed structural response under various levels of applied static and cyclic loads. It was demonstrated that both the steel bracing and concrete outrigger wall are able to work compositely with the low-yield steel damper and exhibits both good load carrying capacities and energy dispersing performance through the test program. It has the potential to be applied and enhance the overall structural performance of the high-rise structures over 300 m under extreme levels of loads.

Tests Study of a 1:20 Scale Steel-concrete Hybrid Structure

Abstract The seismic resistance of a 36-storey high-rise structure with the height of 149 m is studied in this paper. The simulated earthquake shaking table tests have been performed on 1/20 scaled model of the steel-concrete hybrid structure. The steel-concrete hybrid structure is composed of the surrounding diagrid, the reinforced concrete core tube, the floor slab, the beam of floor. The dynamic properties and the seismic behaviour have been analysed by the shaking table test based on the measurement method on the natural vibration frequency and the damage of the model structure. The test results have shown that the phenomena of failure occurred in some components after undergoing the earthquakes of the different fortification levels. The buckling failures occur in the inclined column of the diagrid on the higher floors, the horizontal cracks in the core walls of the higher floors has been appeared, and also the damages occur in the connection between the concrete core tube, the inclined beam of floor and the span beam. Since these inclined column and the key joints between the concrete core tube and the beam have been damaged seriously in the shaking table test, the detailed theoretical analysis is required to avoid the local structural damage.

Experimental investigation of the influence of steel joints upon the flexural capacity of precast concrete columns

Summary In previous studies, the authors have shown that successful modular construction depends on using the correct types of joint connections. In this experimental study, steel beam–column joint connections were shown to be very efficient in facilitating the construction of modular frames while ensuring sufficient flexural moment capacity at the joints to resist lateral loads. This research also included an investigation of the behavior, the crack pattern, and the flexural moment capacity of concrete columns with hybrid composite joints by means of structural experiments on three specimens. Three column specimens were subjected to cyclic loading under displacement control using an oil jack. The influence of including steel sections at the beam–column joint upon the flexural moment capacity of the column was studied, and the use of concrete–steel hybrid composite joints was found to increase the flexural structural performance of the concrete columns. The flexural moment capacity in the maximum load limit state of a concrete column with steel joints was 43.2% greater than that of a conventional reinforced concrete column without steel joints. The steel section in the joint was found to greatly contribute to the flexural moment capacity and to the modular construction technologies.

Structural Performance and Strength Prediction of Steel-to-Concrete Box Girder Deck Transition Zone of Hybrid Steel-Concrete Cable-Stayed Bridges

AbstractBecause a large longitudinal force exists in hybrid girder cable-stayed bridges due to the cable tension, its transfer mechanisms on the steel-concrete combination segment would be an important issue. In this study, experiments and theoretical analysis were conducted to characterize the longitudinal force transfer mechanisms of the steel-concrete combination segment in hybrid girder cable-stayed bridges. Five full-scale local structure specimens were designed and manufactured based on the original design of the steel-to-concrete transition zone according to a completed cable-stayed bridge in China. The specimens were subjected to monotonic loading and tested up to complete failure. The load-slip curves; stress distribution and failure modes, which varied with the thickness of the bearing plate; and the shear connector distribution were obtained. To simulate the test properly, calculation methods for predicting the shear connector capacity and corresponding load-slip curves were proposed based on t...

Perforated FRP ribs for shear connecting of FRP-concrete hybrid beams/decks

The primary consideration of FRP-concrete hybrid beams/decks is to handle the connection for FRP girder and concrete slab. This paper presents the results of push-out tests developed to characterize the shear behavior of perforated FRP rib (PFR) as a solution for shear connection of FRP-concrete hybrid beam. Tests reveal that PFRs provide two advantages when compared with traditional steel bolts, related to at least 2.5 times the shear capacity and approximately 10 times the slip modulus. Theoretical analysis indicated that: (i) PFRs are capable of meeting the shear capacity requirement of load transferring between FRP and concrete; (ii) the slip modulus of PFR increases proportionally with the area of the concrete wedge and second orderly with the thickness of the perforated plate; (iii) shear failure occurs in the perforated FRP plate prior to the failure of the concrete wedge, which governs the design of PFR and is the main difference from PBL (perfobond leist) in steel–concrete hybrid beams. Finally, calculation equations for shear capacity and slip modulus of PFR are developed to facilitate the design.

Seismic damage evolution of steel–concrete hybrid space-frame structures

This paper presents a study on the seismic damage evolution and failure process of steel–concrete hybrid structures through simulation and tests. For steel members, the Krieg–Key constitutive model with a plasticity damage model is used to simulate the damage of steel. For concrete members, the improved Faria–Oliver model is adopted to analyze the damage of concrete. After that, these material models are assigned to fiber elements. The fiber element is adopted to establish a finite element model of steel–concrete hybrid structures. In order to evaluate the effectiveness of this modeling method, shaking table tests are conducted on a scaled test model of a three-storey steel–concrete hybrid structure. The test result shows that the proposed damage model and fiber elements are effective to simulate the seismic damage evolution and failure process of steel–concrete structures.

Uniform Damping Ratio For Non-Classically Damped Hybrid Steel Concrete Structures

Steel–concrete hybrid systems are used in buildings, in which a steel structure has been placed on a concrete structure to make a lighter structure and have a faster construction. Dynamic analysis of hybrid structures is usually a complex procedure due to various dynamic characteristics of each part, i.e., stiffness, mass and especially damping. Dynamic response of hybrid structures has some complications. One of the reasons is the different stiffness of the two parts of structure and another reason is non-uniform distribution of materials and their different features such as damping in main modes of vibration. The available software is not able to calculate damping matrices and analyze these structures because the damping matrix of these irregular structures is non-classical. Also an equivalent damping should be devoted to the whole structure and using the available software. In the hybrid structures, one or more transitional storeys are used for better transition of lateral and gravity forces. In this study, an equation has been proposed to determine the equivalent uniform damping ratio for hybrid steel–concrete buildings with transitional storey(s). In the proposed method, the hybrid structure containing concrete, steel and transitional storeys appropriately substituted with 3-DOF structure. A wide range of eigenfrequency and mass ratios is examined for each ratio pair, and given the characteristics of the primary system, the complete 3-DOF structure can be formed. Equivalent uniform damping ratio is derived by means of a semi-empirical error minimization procedure. The multiple nonlinear regressions are used for determination of equations of modal damping ratios of hybrid buildings.

Steel-concrete hybrid bridge decks: design models for connection regions

Steel-concrete hybrid bridge decks: design models for connection regions

鉄道構造物等設計標準・同解説 （鋼とコンクリートの複合構造物）改訂の概要

鉄道構造物等設計標準・同解説 （鋼とコンクリートの複合構造物）改訂の概要

EXPERIMENTAL STUDY ON SHEAR RESISTANCE EVALUATION OF PERFOBOND STRIP WITHOUT PENETRATING REBAR

In steel-concrete hybrid members and structures, to ensure required stress transmission between the steel and the concrete members, shear connectors are generally arranged between the two. A perfobond strip is widely used as the shear connector in various hybrid structures, and when applying the perfobond strip it is important to confirm its shear resistance. In this study, the shear resistance of the perfobond strip without the penetrating rebar is investigated experimentally by employing a simple push-out specimen. As a result, a design formula is proposed for evaluating the shear resistance of the perfobond strip, taking into account the dimensions of concrete block and the thickness of the perfobond plate, as well as the perforation diameter, and the concrete compressive strength.

A study on the design and material costs of tall wind turbine towers in South Africa

The aim of this project was to study the structural design and material costing of various designs of tall wind turbine towers and the associated foundations in a South African context. Design guidelines are proposed for the design of tubular steel, concrete and concrete-steel hybrid towers and foundations for hub heights of 80, 100 and 120 m. The results indicate that concrete and hybrid towers become viable alternatives to the conventional steel towers at hub heights equal to and above 100 m. Three heights - 80 m, 100 m and 120 m - of each type of tower (steel, concrete and hybrid) and their foundations were designed according to the relevant design standards. The designs were verified using the Abaqus CAE finite element software (SIMULIA 2010). The material costs of the designs were calculated for a South African environment, according to the increases in material cost with increasing hub height. In this paper, the required foundation sizes for the concrete and hybrid towers were found to be smaller than for the steel towers. The material costs of the concrete and hybrid towers were shown to be lower than for the steel towers, especially at hub heights above 100 m. An increase in hub height caused an increase in energy generation of 3.52% and 6.28% for 80 m to 100 m, and for 80 m to 120 m hub heights, respectively. It is postulated that the concrete and hybrid towers become viable alternatives to the conventional steel towers at hub heights above 100 m.

Improved design of tubular wind tower foundations using steel micropiles

The constant increase in the wind power production leads to the need of higher wind towers, which brings up some questions regarding the effectiveness of tubular towers and respective foundations. This work focuses on the comparative structural design, life cycle behaviour and costs of onshore concrete shallow foundations for tubular wind towers (WT) when steel micropiles are used to improve resistance of the soil–structure interface (hybrid foundation). Typical wind loading for Turbine Class II and moderate seismicity (.25 g peak ground acceleration) is used to design and analyse 18 WT foundation case studies. This allows the comparison between shallow and hybrid foundations designed for three different hub heights and respective turbine rated power (80 m/2 MW, 100 m/3.6 MW and 150 m/5 MW) and for three different tubular tower solutions (steel, concrete and hybrid steel–concrete). The possible benefits of the solution using steel grouted micropiles are discussed in terms of potential environmental and economic impacts using life cycle analysis. The use of micropiles reveals to be an interesting solution to improve common shallow WT foundations since it allows the reduction of the dimensions of the foundation leading to significant environmental and cost benefits.

Connection between Concrete Layers with Different Strengths

As part of a research intending to develop steel-concrete hybrid girder using ultra high performance concrete with compressive strength of 80 MPa, this study conducts loading test on this girder to investigate the methods for its composition with a slab using 30 MPa-concrete and the corresponding interfacial behavior. Prior to the loading test, the design formula of the Eurocode for the shear resistance developed in concrete-to-concrete interface is examined for the interface between concrete layers of different strengths. The effect of the surface roughness on the shear resistance is examined using this formula and finite element analysis to verify the applicability of the formula. Based upon the results, loading test is conducted on girder specimens to evaluate the actual behavior with respect to the interfacial surface condition. The test results reveal that the specimen with rough interface could not develop perfectly composite behavior and experienced adhesive failure. In case of simultaneous action of flexure and shear, it appears that conservative design should be applied without consideration of the interfacial condition when determining the arrangement of shear reinforcement.

Seismic Reduction and Control Analysis of Hybrid Structure with Viscous Dampers under Strong Earthquake

This article focuses on the effect of viscous damper on seismic performance of steel-concrete hybrid structure under strong earthquake. The result shows that viscous damper has effect on seismic reduction and control. The story lateral displacement, story drift rotation and energy dissipation-seismic can be reduced effectively by viscous dampers. The maximum value of vibration-reduction ratio is 36.0%, 67.9%, 36.9%. It is different effect on seismic reduction by different earthquake ground motion. Response of earthquake amplifies under Pasadena earthquake wave than the others.

Comparative life cycle assessment of tubular wind towers and foundations – Part 1: Structural design

The use of tubular towers made of steel, concrete or hybrid steel–concrete has become standard in the wind energy industry. However, more powerful wind energy generators are leading to the need for increasing the towers height. This implies rethinking of existing solutions for the support onshore structure composed of tower and foundation, including design concept, life cycle and environmental repercussion. The need for transportation of larger prefabricated elements and more complex processes of assembling on site become important issues. This paper addresses the comparative study concerning the influence of increasing height on the structural design and outcome of different structural solutions. Steel, concrete and hybrid steel–concrete wind towers with heights of 80, 100 and 150m supporting multi-megawatt turbines of 2, 3.6 and 5MW power respectively are addressed. The design of the towers is made in accordance with the structural Eurocodes. Two different scenarios are addressed, the first considering common lifetime of 20years and the second considering increased lifetime of 40years with reuse of tower parts. In-situ erection of steel tubular parts is achieved using flange connections or newly developed friction connections. Conclusions point out that, for towers up to 80m, the use of steel tubular sections and flange connections are the most suitable. Friction connections are suitable for higher towers, leading to less material consumption. The use of concrete towers, particularly for heights above 100m, is penalized when seismic risk is considered in special in the dimensions of the slab foundations

Performance-Based Seismic Design Principles and Structural Analysis of Shanghai Tower

Shanghai Tower is a 632 m high super tall building adopting innovative steel-concrete hybrid mega frame-core tube-outrigger lateral structural system. Since both of the height and irregularity of Shanghai Tower are far beyond the current Chinese design code provision, non-prescriptive performance-based seismic design (PBSD) approach is required to employ in the seismic design of this super tall building. The general PBSD methodologies of code-exceeding tall buildings are briefly introduced at first. According to PBSD principles of code-exceeding tall buildings, the seismic performance objectives are selected for Shanghai Tower. The design criteria for structural components and systems consistent with the performance objectives are established. The elasto-plastic time-history analysis of the structure under frequent, basic and rare earthquakes, respectively, is carried out with the aid of ABAQUS program. Seven sets of ground motions are selected as the input motions. The detailed numerical simulation results, such as the structural dynamic characteristics, the displacement responses, the base shear, the overturning moment, and the damage conditions, are presented. The structural analysis results indicate that the structure can meet the predetermined performance objectives with relatively large safety margin.

Evaluation Method of Shear Capacity of Steel Reinforced Concrete Beam Considering Shear-span Ratio and Support Condition

A number of calculation equations for the design shear capacity of steel reinforced concrete (SRC) members with simple support are given in the Design Standards for Railway Structures and Commentary (Steel-Concrete Hybrid Structures). However, there are some equations that are applicable to a certain member because the scope of application for these equations is unclear. In addition, support conditions for transverse beams on railway viaducts are different from simple supports because both transverse beam ends are fixed. In this study, the scope of application for existing equations was clarified, and an equation to calculate the shear capacity of SRC beams under antisymmetric moment distribution was proposed.

Study on Rational Position of Joint Section of Steel-Concrete Hybrid Girder Bridge

Taking Wei River Bridge with span combination of 69m+7×90m for example, the method of determining the steel-concrete joint section for variable cross-section steel-concrete hybrid continuous box girder bridge were investigated by finite element and parameter sensitivity analysis. The results show that it was an effective method for hybrid girder highway beam bridge from the view of mechanical property that the bending moment under dead load combination was employed as the main parameters, considering the negative bending moment in the pier top and the amplitude of bending moment in the joint section under live load. But based on reasonable structure stress conditions, the length of steel box girder that the host material of the bridge was concrete could determined by economy principle.

Nonlinear time history analysis of China Pavilion for Expo 2010 Shanghai China

SUMMARYThe peculiar building style and special structural system of the National Hall of China Pavilion for Expo 2010 Shanghai is a long‐span and large cantilevered steel–concrete hybrid structure with a shape of an inverted trapezoid in elevation and local discontinuity of floor slabs in plan for esthetic and functional considerations. Because of these characteristics, the building is classified as an irregular and complex structure. To investigate the seismic behavior of the structure, a refined finite element model was established by using NosaCAD. To simulate the nonlinear behavior of the members, the fiber section model was chosen for compression‐flexure frame members, and nonlinear flat shell element was chosen for tube wall. Nonlinear analysis was carried out to study the seismic behavior of the structure under the minor and major earthquakes at the level of intensity 7. With the analysis, the deformations, internal forces and damage states of the structure were investigated. Analysis results show that there is no damage on structure under minor earthquake, the structural system has sufficient capacity and ductility to resist major earthquake, and seismic performance objective of no damage under minor earthquake and no collapse under major earthquake can be reached. The deformation of the structure is less than the limit of the Chinese code. The order and distribution of damages on components of the tubes are reasonable, which can dissipate some dynamic energy. Finally, weak points were identified, and some corresponding suggestions were put forward to improve the overall seismic performance of this structure. Copyright © 2013 John Wiley & Sons, Ltd.