Outrigger Trusses Research Articles

Nonlinear Seismic Analysis and Structural Performance Evaluation of a Complex High-Rise Building

The height of a complex supertall building is 250m. The central RC tube and peripheral SRC frame with two outrigger trusses are employed to resist vertical and lateral loads. It is classified as B grade complex tall building due to the structural characteristic. Due to the over-restriction and complexity of the super tall-building, Pushover Analysis is carried out in order to find it’s behaviors under rare intensity earthquakes. The analytical results demonstrate that the SRC supertall building with high level transfer story possesses good energy-consuming capacity, ductility and ideal yield failure mechanism under rare seismic excitation. Seismic performance of the SRC supertall building is evaluated through Capacity Spectrum Method and good results are obtained.

A comparison study of conventional construction methods and outrigger damper system for the compensation of differential column shortening in high-rise buildings

The outrigger and belt truss system is commonly used as one of the structural systems to effectively control the excessive drift due to lateral load and minimize the risk of structural and non-structural damage. However, this prominent structural system has a demerit of excessive stressing to structural and nonstructural members during construction due to differential column shortening. In this paper, several potential construction methods managing the outrigger to perimeter column joints experiencing differential column shortening are discussed. These methods include fixed joint without any adjustment, delayed joint, delayed joint with shim plate adjustment, and outrigger damper (or lock-up-device) installed joint. Based on our research through computer analysis, large scale laboratory test, shake table test and real installation of the apparatus to a high-rise project, the building with outrigger damper or lock-up-device system has many advantages in terms of building performance, construction convenience, quality control and cost reduction.

Finite Element Analysis on Joint of Ultra-High Steel Columns and Steel Core Barrel Outrigger Truss

The elastic and plastic characteristics of the Y-joint of frame-core tube structures with steel pipe column and steel pipe outrigger truss is studied in this paper. The finite-element method is adopted in the numerical study. To avoid the damage of the joint, controlling the relatively convex-concave deformation of the column wall through adding internal stiffener plate is discussed. Through the comparison of numerical study of the Y-joint with different shape of stiffener plate, a feasible design of the Y-joint is given.

Shaking table model test and numerical analysis of a supertall building with high‐level transfer storey

SUMMARYThe seismic behaviour of a 53‐storey tower with the height of 250 m is investigated in this paper. This supertall building is composed of a reinforced core, two outrigger trusses (a strengthened storey at 20th ∼ 21st floor and a high‐level transfer storey at 37th ∼ 38th floor) and eight composite (steel‐encased concrete) mega‐columns below the high‐level transfer storey in the exterior perimeter of the building. Due to the discontinuity of the eight composite mega‐columns, they are replaced by 33 upper‐close columns at the 37th ∼ 38th level. This paper describes tests performed on a 1/30 scaled model of the building to study its dynamic characteristics and to evaluate its earthquake resistant capacity. The model test results indicate that the prototype structure is able to withstand an earthquake of intensity 7 without severe damage. In addition, a 3D finite element analysis of model structure was carried out and the analytical results were compared with the experimental ones to gain a better understanding of the structural behaviour. Copyright © 2010 John Wiley & Sons, Ltd.

Seismic performance of a 55‐storey steel plate shear wall

AbstractThe Los Angeles Convention Center Hotel is a 55‐storey steel‐framed steel plate shear wall high‐rise building that takes full advantage of many of the performance‐based design approaches and philosophies. The primary lateral resistance system consists of thin steel plates (3/8–1/4 in. thick) within fully welded WUF‐W moment frames. Additional system stiffness is provided by several storey‐high outrigger trusses at the mid‐height and top of the tower while using buckling‐restrained braces (BRBs) as fuse elements to control the maximum force that the outrigger trusses can develop. Full nonlinear time history record analyses were performed using a suite of seven paired ground motions scaled to a 2475‐year event. Modelling methods were developed for the expected model system behaviour that correlated well with observations from independent research tests. While an essential part of the alternate design verification process, the nonlinear modelling needed to be carefully scrutinized at every step to ensure that unanticipated results of the verification were true behaviours rather than artificial artefacts of model limitations that were not indicative of actual system performance. Extensive analysis and design were performed for the diaphragms of the tower for building set‐back 26th level, as well as the ground floor podium transfer slab. A bounding analysis was performed to ensure essentially elastic behaviour for the backstay of the tower in the concrete basement wells and reinforced concrete mat. Copyright © 2009 John Wiley & Sons, Ltd.

Study on seismic behaviour of a new hybrid structure with shaking table test and numerical analysis

AbstractThis paper presents a study on a hybrid high‐rise structure that has two structural systems: the main one is a mega‐frame consisted of mega‐columns, strengthened floors and the outrigger truss on the top; the secondary one consists of typical floors between the strengthened floors. Because of the complexity and innovation of the structural system, a detailed study, including shaking table test and numerical analysis, is needed to research the seismic property of the hybrid structure. First, a 1/50 shaking table model was tested by the State Key Laboratory for Disaster Reduction in Civil Engineering of Tongji University to obtain the frequencies of the free‐vibration modes and dynamic property of the model. Second, this paper used 3D finite element analysis software, named MIDAS, to build the numerical models. Two kinds of models were made to simulate the shaking table model and the prototype structure, respectively, and then a comparison between the analytical and experimental results was presented in this paper to verify the numerical models. In addition, the seismic behaviour of the prototype was analysed by the MIDAS. Finally, the structural system of the new hybrid structure was verified to be valid and applicable. Copyright © 2009 John Wiley & Sons, Ltd.

An analytical model for high‐rise wall‐frame structures with outriggers

AbstractIn this paper, the governing equations of wall‐frame structures with outriggers are formulated through the continuum approach and the whole structure is idealized as a shear–flexural cantilever with rotational springs. The effect of shear deformation and flexural deformation of the wall‐frame and outrigger trusses are considered and incorporated in the formulation of the governing equations. A displacement‐based one‐dimensional finite element model is developed to predict lateral drift of a wall‐frame with outriggers under horizontal loads. Numerical static results are obtained and compared with previously available results and the values obtained from the finite element package MIDAS. The proposed method is found to be simple and efficient, and provides reasonably accurate results in the early design stage of tall building structures. Copyright © 2007 John Wiley & Sons, Ltd.

Shaking table model test on Shanghai World Financial Center Tower

AbstractThe height of 101‐storey Shanghai World Financial Center Tower is 492m above ground making it possible the tallest building in the world when completed. Three parallel structural systems including mega‐frame structure, reinforced concrete and braced steel services core and outrigger trusses, are combined to resist vertical and lateral loads. The building could be classified as a vertically irregular structure due to a number of stiffened and transfer stories in the building. Complexities related to structural system layout are mainly exhibited in the design of services core, mega‐diagonals and outrigger trusses. According to Chinese Code, the height 190 m of the building clearly exceeds the stipulated maximum height of for a composite frame/reinforced concrete core building. The aspect ratio of height to width also exceeds the stipulated limit of 7 for seismic design intensity 7. A 1/50 scaled model is made and tested on shaking table under a series of one and two‐dimensional base excitations with gradually increasing acceleration amplitudes. This paper presents the dynamic characteristics, the seismic responses and the failure mechanism of the structure. The test results demonstrate that the structural system is a good solution to withstand earthquakes. The inter‐storey drift and the overall behaviour meet the requirements of Chinese Design Code. Furthermore, weak positions under seldom‐occurred earthquakes of seismic design intensity 8 are found based on the visible damages on the testing model, and some corresponding suggestions are proposed for the engineering design of the structure under extremely strong earthquake. Copyright © 2006 John Wiley & Sons, Ltd.

Shear wall with outrigger trusses on wall and column foundations

AbstractA graphical method of analysis is presented for preliminary design of outrigger truss‐braced high‐rise shear wall structures with non‐fixed foundation conditions subject to horizontal loading. The method requires the calculation of six structural parameters: bending stiffness for the shear wall, bending and racking shear stiffnesses for the outrigger, an overall bending stiffness contribution from the exterior columns, and rotational stiffnesses for the shear wall and column foundations.The method of analysis employs a simple procedure for obtaining the optimum location of the outrigger up the height of the structure and a rapid assessment of the influence of the individual structural elements on the lateral deflections and bending moments of the high‐rise structure. It is concluded that all six stiffnesses should be included in the preliminary analysis of a proposed tall building structure as the optimum location of the outrigger as well as the reductions in horizontal deformations and internal forces in the structure can be significantly influenced by all the structural components. Copyright © 2004 John Wiley & Sons, Ltd.

Analysis of high‐rise braced frames with outriggers

AbstractSummaryA graphical method of analysis for the preliminary design of tall building structures comprising braced frames with outrigger trusses subjected to horizontal loading is presented. For this method of analysis it is necessary to determine five stifnesses for the uniform structure: bending and racking shear stiffnesses of the braced frame and outriggers in addition to a stiffness parameter representing the axial lengthening and shortening of the exterior columns. The analysis allows a simple procedure for obtaining the optimum location of the outrigger up the height of the structure and a rapid assessment of the impact of the outrigger on the behaviour of the high‐rise structure. It is concluded that all five stiffnesses should be included in the preliminary analysis of a proposed tall building structure as the reductions in horizontal deflections and bending moments of the braced frame are influenced by all stiffness parameters. Copyright © 2003 John Wiley & Sons, Ltd.