Tube Structural System Research Articles

Seismic fragility assessment of eccentric gravity column-core tube structures subjected to pulse-like ground motions

The effects of pulse-like ground motion and structural eccentricity on the seismic fragility and anti-collapse behavior of the new gravity column-core tube structural system are investigated. Numerical models of the gravity column-core tube structure are first established employing the CANNY program and validated against the shaking table test results. Subsequently, reference symmetric gravity column-core tube structures with 10-, 20- and 30-stories are designed, and then their eccentric structures are established by changing the nodal mass distribution. Ten pulse-like and ten corresponding non-pulse-like ground motion records are selected as the seismic excitations. The seismic fragility and anti-collapse analysis of these eccentric structures are conducted. The results show that the pulse-like ground motion significantly affects the seismic response and fragility of the gravity column-core tube structures, with an apparently higher probability of exceeding the limit states (Pf) for the pulse cases than those for the non-pulse cases. With increasing eccentricity, the Pf shows an increasing trend. Besides, both the pulse-like ground motion and the increase of eccentricity lead to a decline in structural anti-collapse capacity. The results are expected to provide a reference for the seismic design of the new gravity column-core tube structures.

Seismic fragility of vertically irregular gravity column-core tube structure subjected to pulse-like ground motions

The effects of the pulse-like ground motion and structurally vertical irregularity on the seismic fragility of the new gravity column-core tube structural system are investigated. Based on the shaking table test, the finite element parameters are verified. By changing the stiffness ratio of the first story to the second story, the typical vertically irregular gravity column-core tube structure models of 20-, 30- and 40-stories are established. Selecting 10 pulse-like and 10 corresponding non-pulse-like ground motion records, the incremental dynamic analysis and seismic fragility analysis are performed to these structures employing CANNY program. The results show that the maximum inter-story drift ratio (θmax) and the probability of exceeding the limit state (Pf) of each structure under pulse-like cases are significantly greater than those under non-pulse-like cases. From slight damage to approaching collapse state, the difference in seismic fragility curves between pulse-like cases and non-pulse-like cases is gradually amplified. It is suggested that the seismic strength reduction factor of these new type of structures be reduced properly to consider the pulse-like ground motion effect. With the stiffness ratio decreases, θmax and Pf have an increasing trend. However, the increasing quantity is small, which may be due to the effect similar to the isolation in the first story. As a limit value of vertical irregularity in the first story, the stiffness ratio of 1.5 provisioned in the code is conservative. To give consideration to both the safety and the economy, it is recommended to lower the limit value to about 1.2 for the gravity column-core wall structures with stiffness irregularity at the first story.

Experimental study on exterior precast concrete beam-to-CECFST column joints with wet connections under cyclic loading

Concrete-encased concrete-filled steel tube (CECFST) structural system has gained popularity in recent years due to its several advantages over conventional structures. Additionally, precast technology has become an effective way of improving construction efficiency and environmental performance. Therefore, it is essential to investigate the structural behaviour of precast concrete (PC) beam-to-CECFST column joints to ensure their optimal performance in applications. In this regard, this paper presents an experimental study of 4 precast exterior joints subjected to lateral cyclic loading. The study investigated the effect of replacing normal concrete with steel fibre-reinforced concrete at the joint region and the presence of axial load on PC composite joints. Based on the test results, cyclic load-carrying resistance, failure modes and crack patterns of the PC specimens were recorded and analysed. In addition, a Digital Image Correlation (DIC) system was adopted to show the crack evolution of joint specimens and calculate shear strains of concrete encasement at the joint region. Further comparisons were conducted in terms of ductility, energy dissipation, stiffness and strength degradation to investigate the joint performance. Finally, existing American and European design code provisions were modified and used to predict joint shear strength. Their predictions were reasonably close to the test results.

Study on seismic behavior and collapse risk of super high-rise braced mega frame-core tube structural system

The braced mega frame-core tube (BMFCT) structure could provide an efficient lateral-force resisting (LFR) system for high-rise or super high-rise buildings, especially for those higher than 500 m. The BMFCT structure is a dual LFR system, including the outer braced mega frame and the inner core tube. The seismic behavior and design method of this structural system is not clear. In this study, a parametric study based on collapse risk-targeted analysis is conducted to clarify seismic mechanism and performance and to make clear means of matching reasonable stiffness and setting energy-dissipation components. Five comparable BMFCT structures with different mega brace stiffness proportions and frame-tube stiffness ratios are designed. An efficient elasto-plastic modeling method is introduced to establish the accurate FE models. The corresponding collapse risks are calculated through Incremental Dynamic Analysis and fragility theory. The results show that the structural collapse risk increases with the increased frame-tube stiffness ratio. Therefore，the stiffness and bearing capacity of peripheral frames should be strengthened to ensure the structural collapse margin. On the other hand, the collapse resistance capacity gradually decreases with the increasing of the mega brace stiffness. Thus, the stiffness proportion of mega braces should be recommended to meet the basic lateral stiffness requirements, which shall not exceed 35 % of the overall structural stiffness. Moreover, the distribution feature and ideal arrangement of the energy dissipation components are proposed. The seismic design recommendation based on the uniform collapse risk is also proposed for the BMFCT system, which serves a reference for the structural design of super high-rise buildings.

Seismic Design of Large-Span, Heavy-Load Transfer Truss for Zhanjiang Bay R&D Building

The Zhanjiang Bay Laboratory R&D Building project aims to create a favorable working, research, and living environment. Zone II of the Zhanjiang Bay Laboratory R&D Building is equipped with a large-span, heavy-load transfer truss to obtain a large space on the ground floor. The overall structure adopts a steel frame-core tube structure system. In order to reduce the deflection of the large-span, heavy-load transfer truss, eight diagonal pull rods are installed between the large-span, heavy-load transfer truss and the core tube. The Q235 cross-shaped replacement section can consume construction load energy. Adopting replacement methods can reduce the stress and damage of diagonal pull rods caused by construction loads. The structure adopts a performance-based seismic design method for seismic calculation and analysis. In addition, a special analysis was conducted on the single frame structure. The major results can be summarized as follows: during small earthquakes, all structural components are in the elastic stage; during large earthquakes, frame beams yield first, but frame columns and core tubes do not yield; even without considering out-of-plane constraints, the structure can still meet the requirements.

Numerical Investigation on the Pulling Resistant Capacity of Steel Beam-Concrete Wall Joints with T-stub Connectors

The steel frame-reinforced concrete core tube structural system is widely used in mid-rise and high-rise buildings due to its good seismic behaviour and high construction efficiency. Since the steel frame and the reinforced concrete core tube are supposed to deform synergistically under earthquake action, the steel beam-concrete wall joint (SBCW joint for short) will be subjected to a significant pull-out force. Therefore, the pulling resistant capacity of the SBCW joint is quite important for the seismic performance of the overall structure. In response to the shortages of the existing SBCW joint types, a new SBCW joint with a T-stub connector was proposed and studied. The experimental and analytical research has indicated that there are different failure modes and force mechanisms of the SBCW joint under pull-out load, and further studies are required for the pulling resistant capacity. On the basis of recent research findings, a numerical investigation on the pulling resistant capacity of the joint is conducted in this study. An elaborate 3D finite element model of the SBCW joint is proposed, and the load performance, strain and stress development, deformation characteristics and failure modes are analysed in detail. Then, a series of parametric analyses are carried out based on the finite element model, indicating that the length and the web height of the T-stub connector, the number of shear studs on the connector and the reinforcement ratio of stirrups have an obvious effect on the pulling resistant capacity. Finally, the critical value of the embedded depth of the connector, which is found to be one of the most important parameters for the failure mode and pulling resistant capacity of the joint, is determined, and design recommendations are proposed for the SBCW joints with T-stub connectors.

Comparative Seismic Analysis of High Rise Buildings with Different Structural Framing

Now a day it has been observed that modern trend is towards taller and slenderer structures both residential and commercial increasing rapidly. As the height of structure get increases, the building acts as cantilever and get deflected because of its slenderness. For such structure the effects of lateral loads like winds loads, earthquake forces have become more effective which increasing importance for every designer to face with the problem of providing adequate strength and stability against lateral loads with economic consideration. From the previous studies, it has been concluded that there was not much problem in drift failure particularly in lower seismic zones. But as we go to higher zones than the ordinary multistory buildings also face the problem of drift more than the prescribed by the IS code 1893-2002 which become critical limit causing sudden collapse during earthquake. This study focuses on the various provisions to reduce the drift of building and make it more stable. Some of them are providing shear wall, tube structural system and base isolation system. The analysis has performed using ETABS for G+42 multistoried building in zones III.

Comparative Analysis on Inclined Column by Using Staad Pro under Lateral Loads at Different Positions

Abstract: Advances in construction technology, materials, structural systems and analytical methods for analysis and design facilitated the growth of high-rise buildings. Structural design of high-risebuildings is governed by lateral loads due to wind or earthquake. Lateral load resistance of structure is provided by interior structural system or exterior structural system. Usually shear wall core, braced frame and their combination with frames are interior system, where lateral load is resisted by centrally located elements. While framed tube, braced tube structural system resists lateral loads by elements provided on periphery of structure. It is very importantthat the selected structural system is such that the structural elements are utilized effectively while satisfying design requirements. Recently Inclined columns structural system is adopted in tall buildings due to its structural efficiency and flexibility in architectural planning. Compared to closely spaced vertical columns in framed tube. Inclined column should be placed at the exterior surface of the building. Due to inclined columns lateral loads are resisted by axial action of the diagonal compared to bending of vertical columns in framed structure. Inclined column structures generally do not require core because lateral shear canbe carried by the diagonals on the periphery of building. Analysis and design of G+9 storey building is presented. A regular floor plan of 36 m × 36 m size is considered. Staad pro software is used for modelling and analysis of structural members. All structural members aredesigned as per IS 456:2000 considering all load combinations. Dynamic along wind and across wind are considered for analysis and design of the structure. Load distribution in system is also studied for G+9 storey building. Similarly, analysis and design of G+9 storey vertical column structures is carried out with and without weak storey. Comparison ofanalysis results in terms of time period, top storey displacement and inter-storey drift will be presented in this study with or without inclined column in frame structure.

Wind Pressure Distribution on the Façade of Stand-Alone Atypically Shaped High-Rise Building Determined by CFD Simulation and Wind Tunnel Tests

The investigation of wind pressure distribution on a façade of an atypically shaped 162 m tall building is discussed in this paper. The horizontal cross-section was changed with the height of the structure (the square in the bottom part and the polygon in the top). The surface of the structure was smooth. A structural system was created using a combination of the tube structural system and exoskeleton structure. The building was stand-alone, located in urban terrain. In this case, the information in standards were not sufficient for its design. Therefore, other available tools had to be used for the determination of required input parameters (mean external pressure coefficients). At first, wind tunnel tests (WT) were performed on a reduced-scale model (1:300). Then, the obtained results were compared with data from a computational fluid dynamics (CFD) simulation. The accuracy of the simulation was evaluated by the method of three metrics. Short descriptions of the reduced-scale model, boundary layer wind tunnel, used measuring devices, and the methodology of tests are mentioned. The aim of this research was to identify the influence of the shape modification on the values of mean external pressure coefficients (in the comparison with the original shape, which was the cuboid). In the case of the cuboid, good agreement between the values determined by the CFD and the values from Eurocode was achieved. Larger discrepancies occurred on the roof. The modification of the total shape of the structure from the cuboid to atypical structure had the positive effect on the mean values of external pressure coefficients cpe. These values were smaller (at some levels significantly). Mainly, this effect was noticeable on the leeward side. For the wind directions 0° and 180°, the changes of the values were relatively large. For the other two wind directions (45° and 67.5°), the values on the windward sides were similar. The large advantage of this atypical structure is that the negative pressures on side walls and leeward side are smaller in the comparison with the cuboid. This is very useful for the fixing of façade components, where the values of negative pressures are larger than the positive pressures on the cladding in the larger heights.

Research on damping performance and parameter influence of new frame-MRD-core tube composite structural system

The position of the plastic hinge is uncertain due to the design and construction of the frame-core tube structural system, causing problems such as reduced collapse resistance and difficulty in repairing after an earthquake. To address these problems, this paper proposes a new type of frame-magnetorheologicaldamper (MRD)-core tube composite damping structural system. In this system, the frame and the core tube are two independent structures connected by MRD. Based on the instantaneous optimal control algorithm, the semi-active control strategy of MRD is designed. The relative motion between structures is used to provide damping force, and the vibration control equation is established. In this paper, a 10-story reinforced concrete frame-MRD-core tube composite structural system is taken as an example, and the El Centro (NS, 1940) ground motion with the peak acceleration of 220 cm· S-2 is used as the lateral load for horizontal seismic time-history analysis. MATLAB is employed to perform numerical simulation calculations to investigate its damping effect and related influence parameters. Compared with the traditional frame-core tube structural system, the new system can reduce the top floor displacement and the maximum interstory drift by more than 50% and reduce the top floor acceleration of the frame and core tube by 65% and 40%, respectively. Furthermore, reasonably optimizing the position of the control floor can reduce the number of dampers. When the interstory control is implemented, the total control force of dampers can be reduced by 18% compared to the full-story control. This article provides a new damping idea and theoretical reference basis for the engineering design and application of the frame-core tube composite structural system.

An Analytical Study of Flat Slab and Convention Slab with Framed Tube System by Performing Time History Analysis

Abstract: To study seismic demand for regular reinforced concrete frame of flat slab with drop and conventional slab structure by using framed tube structural system by performing time history analysis. The performance of these slabs on 30 storey building will be studied for the analysis, seismic zone (v) will be considered. It is a type of linear dynamic analysis, in which the strength of the structure is tested within the elastic limit of the structure. In this project, high rise building of 30 of area 1296sq.m along with framed tube subjected to earthquake loading are analysed by time history analysis using ETABS software. The dynamic parameters such as base shear, story displacements, and story drift and time period of flat slab building with framed tube is being studied and compared to conventional slab. Keywords: High-rise building, Framed tube, Time history analysis

Shaking table test of a supertall building with hinged connections connecting a gravity load resisting system to a lateral force resisting system

ABSTRACT Considering a common practical engineering structure, namely, a concrete-filled steel tube (CFST)-steel frame-core tube structure, the rigid connections between the steel beams and the columns/core are modified into hinged connections. In this manner, a 1:40 reduced scale specimen representing a real supertall building that consists of 68 storeys and four underground storeys is constructed for a shaking table test to study the seismic performance of the structure. Numerical simulations are performed to analyse the time history responses of a CFST-steel frame-core tube structural system with three different connection configurations: hinged joints, rigid joints and strengthened layers (which are defined as storeys equipped with outrigger and belt trusses to limit inter-storey drift). The results indicate that the earthquake damage to the structure mainly occurs in the lower storeys at the connections and the corners of the core tube. The seismic response of the structure under the long-period ground motion is significant. The largest inter-storey drift ratio of the core tube reaches 1/26, which exceeds the threshold of the frame-core tube structure system in the Chinese Code by a factor of 3.8. Both the rigid joints and the strengthened layers can reduce the inter-storey drift ratio of the structure.

Dynamic Time Analysis of the Composite Shear Wall on the Grid-tube-type Double Steel Plate Wall with Infilled Concrete

In this paper, based on a 30-story building with frame-core tube structure system, three comparative schemes are established of reinforced concrete core tube construction, steel-reinforced concrete core tube construction and the combined shear wall core tube structure with the grid-tube-type double steel plate wall with infilled concrete are established, and the dynamic elastoplastic time history is analyzed. Research shows that under the influence of a severe earthquake, the lateral strength degradation and stiffness degradation are slow on the Joint structural system of concrete filled steel tubular frame and composite shear wall core tube structure with the grid-tube-type double steel plate wall with infilled concrete, so interlayer shear force and bottom shear force increase, structural lateral stiffness increased significantly, interlayer displacement angle reduces significantly, and it improves the seismic performance of tall building.

Structural analysis of a multi-tower building with a large chassis in a business district

A business district building consists of two tower structures with basements and common podium and is a multi-tower structure with large chassis. The structural layout of the two towers is identical, both adopt the frame-core tube structure system with a total structural height of 156.85m. The seismic response characteristics of multi-tower structure with large chassis were analyzed through comparing the calculation results of single-tower model by SATWE software and multi-tower model with large chassis by MIDAS software.The results show that the seismic shear force of the podium significantly reduces and the seismic shear force of the towers up the podium increases. The vibration mode of the two-tower structure contains the vibration of two single towers, but it is not a simple superposition of dynamic characteristics, which is more complex.

Parametric Analysis of the Shear Lag Effect in Tube Structural Systems of Tall Buildings

Horizontal loads such as earthquake and wind are considered dominant loads for the design of tall buildings. One of the most efficient structural systems in this regard is the tube structural system. Even though such systems have a high resistance when it comes to horizontal loads, the shear lag effect that is characterized by an incomplete and uneven activation of vertical elements may cause a series of problems such as the deformation of internal panels and secondary structural elements, which cumulatively grow with the height of the building. In this paper, the shear lag effect in a typical tube structure will be observed and analyzed on a series of different numerical models. A parametric analysis will be conducted with a great number of variations in the structural elements and building layout, for the purpose of giving recommendations for an optimal design of a tube structural system.

Construction Sequence Analysis of Tube in Tube Structural System Building

The effect of applying loads sequentially is an important factor and should be considered whileanalyzing multistoried frame structure. It is observed that the effect of the formationsequence increase with the increase in storeys is very important. Therefore, the effect of a construction sequencecannot be neglected and a precise analysis should be conducted.In this paper the construction sequential analysis has been studied on tube in tube structure. For this purpose, a tube in tube structural system building with different heights (G+35, G+40, and G+45) has been considered forcomparative study. The plan dimensions of the building are 45 m x 72 m. The structures were modelled and analyzed by using ETABS finite element software.Construction sequence is considered for dead load only. Also, the structure is analyzed for linear static analysis in order to check the stability of the structure as per Indian standards and then the structure is analyzed for construction sequence analysis. The variation in Storey displacements, Column axial forces, bending moments andShear forces were compared to know the construction sequence analysis effect on tube in tube structural system building.

Seismic design and elastic-plastic analysis of the hengda group super high-rise office buildings

The Hengda Group super high-rise building in Jinan City uses the frame-core tube structural system. With a height of 238.3 m, it is above the B-level height limit of 150 m for buildings within 7-magnitude seismic fortification zones. Therefore, it is necessary to apply performance-based seismic design to this super high-rise building. In this study, response spectrum analysis and comparative analysis of the structure are conducted using two software applications. Moreover, elastic time-history analysis, seismic analysis under an intermediate earthquake, and elastic–plastic time-history analysis under rare earthquakes are performed. Based on the analysis results, corresponding strengthening measures are implemented at weaker structural locations, such as corners, wall ends connected to framed girders, and coupling beams connected to framed girders. The failure mode and failure zone of major stress components of the structure under rare earthquakes are analysed. The conclusions to this research demonstrate that weaker locations and important parts of the structure satisfy the requirements for elastic–plastic deformation in the event of rare earthquakes.

Structure selection and analysis of tower 6a and 6b in weihai civic center

Weihai civic center covers an area of 193,100 square meters and consists of four high-rise buildings and large podium buildings. The building is divided into two parts through structural joints, with two towers forming a frame-core tube structural system and the lower podium as a frame structure. Through the selection of different structural systems, the selection and structure of the structural system are analyzed.

TEST-BASED PROBABILITSTIC SEISMIC FRAGILITY ANALYSIS OF DIAGRID-CORE TUBE STRUCTURES

By utilizing an external diagrid frame and an inner reinforced concrete core-tube, the diagrid-core tube structure forms a tube-tube structure with strong lateral stiffness. This structure form has been widely used in super high rise building structures. The seismic response results of the model structure with different seismic fortification levels have been obtained by the simulated earthquake shaking table test. Based on the empirical and analytical methods for the seismic reliability analysis of structures, the failure probabilities of the structure with different seismic fortification levels were analyzed, and the seismic performance and reliability of the diagrid-core tube structure system are studied. The shaking table test results show that the inclined columns in the layer where the section sizes of the structural members of the diagrid are changed were damaged before the inclined columns in the substructure. Furthermore, a shaking table test-based probabilistic seismic fragility analysis method was put forward. The damage probabilities of the prototype structure under different seismic fortification levels have been studied. The probabilistic seismic fragility level of the diagrid-core tube prototype structure system is obtained.

Application of Progressive Collapse Analysis in a High-Rise Frame-Core Tube Structure

Frame-core tube structure system is commonly adopted in high-rise office buildings and landmarks, which will cause a large range of damage and serious loss of life and property once the progressive collapse occurs. To analysis the progressive collapse resistance of a high-rise frame-core tube practical project, numerical simulation analysis based on alternate path method and explicit dynamics theory was conducted to study the dynamic response of the remain structure after removing a key member. In addition, large-scaled tests for the frame-core tube structure under static and dynamic loads were carried out to study the behavior and damage situation of the structure. The numerical simulation and test results proved that progressive collapse would not occur when local damages occurred in the bottom corner column, and the structure still has a good seismic performance under dynamic actions. And the feasibility and reliability of the selected numerical simulation method of progressive collapse analysis is proved according to the test results.