Steel-concrete Hybrid Structure Research Articles

Influence of continuous elastic lateral restraints on beams and beam-columns of steel-timber hybrid structures in fire

With the climate crisis and pursuit of efforts to reduce embodied carbon impacts in the built environment, steel-timber hybrid structures have emerged as a sustainable form of framed construction which offer numerous benefits over the widely used and well-established steel-concrete hybrid structures. However, there are major concerns about the structural fire performance of such systems among various stakeholders in the construction industry, particularly for the design implications in terms of the lateral-torsional buckling behaviour and the degree of lateral restraint mobilised in the steel-to-timber connections. The screws that connect cross-laminated timber slabs to steel beams may provide a certain degree of restraining action in fire. However, further investigations are required to quantify the slip characteristics of such connections. In this study, it was found from existing literature that at the fire limit state, the continuous elastic lateral stiffness available to restrain the beam varies between approximately 500 kN/m/m and 2000 kN/m/m. Relying entirely on the screws and using this practical range of stiffness, a parametric study using Eurocode 3 design buckling resistance equations on 9 m simply supported span steel beams and beam-columns with span-to-depth ratios of about 10, 15, 20 and 25 was performed. The results indicate that designing such members as fully restrained in fire conditions may lead to unrealistic assumptions and unsafe structures.

Experimental evaluation of the shear capacity of perfobond strips with steel fiber-reinforced mortar in narrow joint structures

Appropriate transfer of the shear force of a perfobond strip used as a shear connector in steel concrete hybrid structures depends on the restraining effect around the strip, and hence, the arrangement of the surrounding reinforcements is very important to improve the restraining effect. However, when the perfobond strip is arranged in narrow joint structures and when the rapid construction is also required, reinforcements are undesirable on the site. An alternate method to improve the restraining effect around the perfobond strip is to use steel fiber-reinforced mortar (SFRM). This study aims to evaluate appropriately the shear capacity of a perfobond strip with SFRM without surrounding reinforcements for narrow joint structures. Assuming these conditions, pull-out tests were conducted, and the data obtained were considered along with the results of push-out tests conducted in the previous study of the authors. Based on the results of both test series, the impacts of various factors on the shear capacity of the perfobond strip was analyzed comprehensively. The results showed that the shear capacity of a perfobond strip with SFRM increases with the perforation diameter, SFRM compressive strength, volume content of steel fibers in the mortar, and dimensions of the mortar block around the perfobond strip. Moreover, the plasticization of the perfobond steel plate and the difference in boundary conditions between the push-out and pull-out tests also affect the shear capacity of the perfobond strip. An equation was proposed for evaluating the shear capacity of the perfobond strip with SFRM without any surrounding reinforcements for narrow joint structures. The shear capacity obtained using the proposed equation has high correlation with the experimental value for both push-out and pull-out specimens.

Shear behavior of a perfobond strip with steel fiber-reinforced mortar in a condition without surrounding reinforcements

To sufficiently transmit the shear force of a perfobond strip shear connector in steel–concrete hybrid structures, the arrangement of the surrounding reinforcements is essential to improve the restraining effect around the perfobond strip. However, in cases of joint structures with small dimensions and rush work on site, because the arrangement of reinforcements in the joint is challenging, steel fiber-reinforced mortar (SFRM) can be used along with a perfobond strip to improve the restraining effect around the perfobond strip. This study investigates the shear behavior of a perfobond strip that uses SFRM without surrounding reinforcements. Push-out tests were conducted focusing on the effect of steel fibers inside the SFRM, SFRM compressive strength, perforation diameter, and dimensions of the mortar block around the perfobond strip. Findings of the study confirmed that the steel fibers inside the mortar contribute to the restraining effect around the perfobond strip, thus preventing a rapid drop in the shear force beyond the shear capacity of the perfobond strip. The shear capacity of the perfobond strip combined with SFRM increased with the perforation diameter, SFRM compressive strength, and dimensions of the mortar block around the perfobond strip. Several shear capacity evaluation equations proposed in previous studies are not applicable for evaluating the shear capacity of the perfobond strip that uses SFRM without surrounding reinforcements. Here, the shear capacity of the perfobond strip can be evaluated by considering the correlation between the experimental parameters of this study, but more test data are required.

Experimental Study on the Seismic Behavior of a Steel-Concrete Hybrid Structure with Buckling Restrained Braces

The damage to a concrete wall caused by a strong earthquake is generally concentrated at the bottom of the concrete wall, which seriously threatens the safety of the steel-concrete hybrid structure and is very difficult to repair after an earthquake. In this paper, a steel-concrete hybrid structure with buckling restrained braces at a scale of 1/10 is constructed and tested on a shaking table. First, the mechanical properties of the BRBs are obtained through a static reciprocating loading test. Then, the dynamic properties and seismic response of the steel-concrete hybrid structure with BRBs are obtained through shaking table tests. The results show that (1) the energy dissipation capacity of the BRBs is very good, and none of the BRBs buckle during the shaking table tests; (2) the steel beams and columns are basically in an elastic state; (3) all the cracks on the concrete wall are microcracks, which are widely distributed in floors 1–8 of the concrete walls; (4) the maximum interstory drift angle reaches 1/40, which indicates that the ductility of the steel-concrete hybrid structure is very good. In conclusion, BRBs can significantly improve the seismic performance of the steel-concrete hybrid structures.

The development of composite bridges with corrugated steel webs in China

The prestressed concrete girder with corrugated steel webs is one of the most promising steel–concrete hybrid structures applied to highway and railway bridges, owing to its excellent mechanical properties and efficient material utilisation. Composite bridges with corrugated steel webs (CBCSWs) have undergone rapid development in China since 2005, resulting in remarkable technical progress in many aspects. A state-of-the-art review of CBCSWs in China is presented. Based on data collected for over 90 CBCSWs built in China during the years 2005–2018, characteristics relating to bridge span, structural type and construction methods are comprehensively analysed. Some mechanical issues regarding the design and construction of typical CBCSWs are elaborated to understand fully their structural performance and promote their development. Furthermore, a few representative CBCSWs are expounded in relation to their innovative structural design and construction techniques; their respective characteristics are highlighted. Finally, several conclusions are drawn and future research directions are predicted: the CBCSW is a competitive bridge solution when 80–200 m main spans are required; advanced materials, innovative structure types and advanced construction methods making good use of corrugated steel web are the source of its development. The experiences in this study can serve as a useful base for constructing more excellent and impressive CBCSWs.

Pseudo-dynamic and cyclic loading tests on a steel-concrete vertical hybrid structure

This paper presents the experimental investigations on the seismic performance of a peculiar steel-concrete vertical hybrid structural system referred to as steel truss-RC tubular column hybrid structure. It is typically applied as the supporting structural system to house air-cooled condensers in thermal power plants (TPPs). Firstly, pseudo-dynamic tests (PDTs) are performed on a scaled substructure to investigate the seismic performance of this hybrid structure under different hazard levels. The deformation performance, deterioration behavior and energy dissipation characteristics are analyzed. Then, a cyclic loading test is conducted after the final loading case of PDTs to verify the ultimate seismic resistant capacity of this hybrid structure. Finally, the failure mechanism is discussed through mechanical analysis based on the test results. The research results indicate that the steel truss-RC tubular column hybrid structure is an anti-seismic structural system with single-fortification line. RC tubular columns are the main energy dissipated components. The truss-to-column connections are the structural weak parts. In general, it has good ductile performance to satisfy the seismic design requirements in high-intensity earthquake regions.

Seismic Vulnerability Analysis of High-Rise SRCFrame-RC Core Tube Hybrid Construction

With the development of the modern building, the steel-concrete hybrid structure is more and more widely used. However, the study on the seismic behavior of steel reinforced concrete composite structures is not fully studied. Using a 30-storey steel reinforced concrete (SRC) frame-reinforced concrete core tube hybrid structure (RC) analyze the seismic performance and seismic fragility by theoretical analysis and numerical simulation methods. The PUSHOVER method is used to obtain the capacity spectrum curve, the seismic demand spectrum curve and the performance control points. According to the development of plastic hinge of typical structure, the limit value of quantitative index of structure and the division of structural failure grade is determined. According to the data obtained from finite element analysis, the fragility curve. Provide the basis for earthquake disaster prediction and evaluation.

Numerical Study on the Seismic Performance of a Steel–Concrete Hybrid Supporting Structure in Thermal Power Plants

This paper presents the numerical investigation on the seismic performance of a steel–concrete hybrid structure consisting of reinforced concrete (RC) tubular columns and steel braced truss with A-shaped steel frames, which is a novel supporting structural system to house air-cooled condensers (ACC) in large-capacity thermal power plants (TPPs). First, the finite element (FE) modeling approach for this hybrid structure using the software ABAQUS was validated by a range of pseudo-dynamic tests (PDTs) performed on a 1/8-scaled sub-structure. The failure process, lateral displacement responses, changing rules of dynamic characteristic parameters and lateral stiffness with increase of peak ground acceleration (PGA) were presented here. Then, nonlinear time-history analysis of the prototype structure was carried out. The dynamic characteristics, base shear force, lateral deformation capacity, stiffness deterioration and damage characteristics were investigated. Despite the structural complexity and irregularity, both experimental and numerical results indicate that the overall seismic performance of this steel–concrete hybrid supporting structure meets the seismic design requirements with respect to the high-intensity earthquakes.

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.

Modeling the Cyclic Response of Perfobond-rib Shear Connectors

In order to predict the shear-slip behavior of steel-concrete hybrid structures under cyclic load, a constitutive model of the unloading and reloading of shear connectors is required. The aim of this study is to develop a constitutive model of perfobond-rib shear connectors (PBL) that includes the description of unloading and reloading paths under single shear force. Static push-out tests with unloading-reloading cycles were carried out under several different restraint conditions to examine the load-displacement relations. The unloading-reloading process was repeated by increasing the maximum load and gradually accumulating the residual displacement and then the total shear displacement of PBL was increased. The experimental results clarified that the relations of load and displacement under cyclic loading can be modeled independently of restraint conditions. Empirical models for unloading and reloading, starting from arbitrary displacements, were successfully formulated.

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.

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.

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.

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.

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.

Numerical Study on Nonlinear Semiactive Control of Steel-Concrete Hybrid Structures Using MR Dampers

Controlling the damage process, avoiding the global collapse, and increasing the seismic safety of the super high-rise building structures are of great significance to the casualties’ reduction and seismic losses mitigation. In this paper, a semiactive control platform based on magnetorheological (MR) dampers comprising the Bouc-Wen model, the semi-active control law, and the shear wall damage criteria and steel damage material model is developed in LS-DYNA program, based on the data transferring between the main program and the control platform; it can realize the purpose of integrated modeling, analysis, and design of the nonlinear semi-active control system. The nonlinear seismic control effectiveness is verified by the numerical example of a 15-story steel-concrete hybrid structure; the results indicate that the control platform and the numerical method are stable and fast, the relative displacement, shear force, and damage of the steel-concrete structure are largely reduced using the optimal designed MR dampers, and the deformations and shear forces of the concrete tube and frame are better consorted by the control devices.

Experimental studies on nonlinear seismic control of a steel–concrete hybrid structure using MR dampers

This article presents experimental studies on the feasibility of nonlinear seismic control of a 3-story steel–concrete hybrid structure using magnetorheological (MR) dampers. The control strategies included passive-on control, passive-off control and semi-active control, and strains gathered at the bottom of the steel columns were used as feedbacks to build the semi-active controller. For each control type, the control efficacy on structural response and damage was verified for the El Centro, Taft and Tianjin earthquake with specified peak ground acceleration (PGA) of 0.2g, 0.4g, 0.9g and 1.2g respectively. The test results show that (1) it is feasible to control the seismic response of the steel–concrete hybrid structure using MR dampers; (2) structure with semi-active control and passive-on control perform better in the shaking table test considering the maximum inter-story drift, displacement time history and energy dissipation capacity, compared to uncontrolled structure and structure with passive-off control; (3) there is also more structural damage in the passive-off and uncontrolled cases, proving the effectiveness of MR dampers in damage control. In addition, an inverse calculation method for strain is proposed to effectively utilize the strains measured during the shaking table test to obtain the stress and material damage process at measured positions, using damage model of the steel and concrete material.

Study on seismic performance of a super‐tall steel–concrete hybrid structure

SUMMARYMany steel–concrete hybrid buildings have been built in China. The seismic performance of such hybrid system is much more complicated than that of steel structure or reinforced concrete (RC) structure. A steel–concrete hybrid frame‐tube super‐tall building structure with new type of shear walls to be built in a district of seismic intensity 8 in China was studied for its structural complexity and irregularity. Both model test and numerical simulation were applied to obtain the detailed knowledge of seismic performance for this structure. First, a 1/30 scaled model structure was tested on the shaking table under different levels of earthquakes. The failure process and mechanism of the model structure are presented here. Nonlinear time‐history analysis of the prototype structure was then conducted by using the software PERFORM‐3D. The dynamic characteristics, inter‐story drift ratios and energy dissipation conditions are introduced. On the basis of the comparison between the deformation demand and capacity of main structural components at individual performance level under different earthquake level, the seismic performance at the member level was also evaluated. Despite the structural complexity and code‐exceeding height, both experimental and analytical results indicate that the overall seismic performance of the structure meet the requirements of the Chinese design code. Copyright © 2012 John Wiley & Sons, Ltd.

Mechanical Behavior Research of a High-Rise Hybrid Structure Based on Shaking Table Test

In order to establish the systematic design method of performance-based earthquake engineering for steel-concrete hybrid structure tall buildings, a 1/15 scale model shaking table test is conducted in State Key Laboratory for Disaster Reduction in Civil Engineering of Tongji University. The dynamic property, acceleration and displacement response of the model structure under different earthquake levels are investigated from the test. The failure mode of structure is analyzed and the seismic response of the prototype structure is interpreted according to the similitude relation. The conclusions drawn from this investigation show that the prototype structure can basically satisfy the requirements of no damage under frequent earthquakes and no collapse under rare earthquakes; steel frame- concrete core structural system has good seismic performance under rare earthquake; and the damage of the connection between the steel frame beam and the core wall is the main failure pattern of the structure.