Effect of BRBs on the Seismic Resistance of Single-Layer Reticulated Domes

Xudong Zhi,Feng Fan,Feng Shi,Zhiwei Yu 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.1

This paper considers the seismic resistance of buckling restrained braces (BRB) in single-layer reticulated domes and their substructures. The method of tracing the full-range dynamic response is used to analyze the seismic response of dome structures with different embedded braces. Based on results relating to critical responses, such as displacement, development of plastic deformation and ultimate load, the effect of BRBs on key design parameters, including core area, yield stress, installing forms etc., is examined. The effect of a dome’s rise-span ratio on the structure is also investigated. It is concluded that BRBs between supporting columns can effectively improve a structure’s seismic performance.

Cost-effectiveness of Protective Measures for Single-layer Reticulated Domes subject to Impact Loading

Xudong Zhi,Duozhi Wang,Feng Fan 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.3

Many spatial structures, including some public buildings, were built in the last thirty years, but considerable uncertainty remains with respect to their structural performance under impact loading. This paper focuses on single-layer reticulated domes because they encounter significant safety hazards when subject to terrorist attack. Three kinds of protective measures are proposed for mitigating the probability of global structural collapse under impact loads. The risk reduction measures include Lighter Roofs, Whole Member Strengthening and Strengthening of Key Members. These measures are compared and evaluated with respect to risk reduction. A technique is then used for assessing the cost-effectiveness of these measures. An example of a single-layer reticulated dome subject to airplane impact is used to illustrate when the protective measures are cost-effective,with quantifying costs being useful in the decision-making process.

Sensitivity of Seismic Response and Fragility to Parameter Uncertainty of Single-Layer Reticulated Domes

Jie Zhong,Xudong Zhi,Feng Fan 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.5

Quantitatively modeling and propagating all sources of uncertainty stand at the core of seismic fragility assessment of structures. This paper investigates the eff ects of various sources of uncertainty on seismic responses and seismic fragility estimates of single-layer reticulated domes. Sensitivity analyses are performed to examine the sensitivity of typical seismic responses to uncertainties in structural modeling parameters, and the results suggest that the variability in structural damping, yielding strength, steel ultimate strain, dead load and snow load has signifi cant eff ects on the seismic responses, and these fi ve parameters should be taken as random variables in the seismic fragility assessment. Based on this, fragility estimates and fragility curves incorporating diff erent levels of uncertainty are obtained on the basis of the results of incremental dynamic analyses on the corresponding set of 40 sample models generated by Latin Hypercube Sampling method. The comparisons of these fragility curves illustrate that, the inclusion of only ground motion uncertainty is inappropriate and inadequate, and the appropriate way is incorporating the variability in the fi ve identifi ed structural modeling parameters as well into the seismic fragility assessment of single-layer reticulated domes.

Simlating the Stability and Pre-stressed Tension of a Single-Layer Spherical Reticulated Shell Supported by Cable

Zhang Zhonghao,Zhi Xudong,Li Qixun,Fan Feng 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.2

Along with other developments that have occurred in this era, building requirements include not only function and practicality but also encompass architectural elegance such as lighting and light-weight structures. Conventional latticed shell triangulation creates a poor architectural eff ect as well as mediocre lighting and excessive and cluttered componentry. A latticed shell with quadrilateral meshing is light and has excellent lighting properties, but it also has low rigidity and inferior stability. This study addresses this problem by deploying in-plane stayed cables and horizontal and vertical cables out-of-plane via a strut, and by developing a new single-layer spherical latticed shell system supported by cables. The eff ects that various parameters have on the mechanical properties of this structures such as the rise-span ratio, asymmetric load distribution, strut length, initial defects and cable pre-stress, are investigated based on mechanical responses such as structural displacement, internal force, critical bearing capacity and the instability modal. The basic rules of structural stress are summarised and examples of 100 m and 150 m large span latticed shell structures are used to verify and analyse the rules for the mechanical properties of this structure, and to investigate how applicable this type of architecture is in a large-span structure. Based on the sequence used to tension the cable(s) during construction, several plans for pre-stressing in-plane and out-of-plane cable(s) are also proposed. The eff ect that this pre-stressing sequence has on structural properties such as maximum displacement and critical bearing capacity is investigated at each stage of construction via a numerical simulation of the structure. A proper procedure for constructing this structure is also proposed to provide theoretical support for an actual project.

Failure Mechanism of Single-layer Saddle-curve Reticulated Shells with Material Damage Accumulation Considered under Severe Earthquake

Zhiwei Yu,Xudong Zhi,Feng Fan,Chen Lu 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.1

This paper presents the study on failure mechanism of single-layer saddle-curve reticulated shells subjected to severe earthquake. Failure mode of single-layer saddle-curve reticulated shells is illustrated with the consideration of material damage accumulation. The effects of different parameters on failure characteristics of single-layer saddle-curve reticulated shells are discussed. The influence of substructure upon failure behaviors of single-layer saddle-curve reticulated shells is particularly investigated. It is observed that dynamic strength failure is the failure mode of single-layer saddle-curve reticulated shells. The substructure has great influence on failure characteristics of single-layer saddle-curve reticulated shells subjected to the severe earthquake.

Seismic Performance of Single-Layer Lattice Shells with VF-FPB

Dewen Kong,Feng Fan,Xudong Zhi 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.4

Friction pendulum bearings (FPB) are recognized as a kind of effective isolation device for protecting and retrofitting anexisting structure, but they are not adaptive to different seismic inputs due to the constant friction coefficient and constant radiusof curvature. A new isolation bearing called variable-friction friction pendulum bearings (VF-FPB) was proposed which couldovercome this limitation while retaining all the advantages of an FPB. Unlike a conventional FPB, the sliding surface of a VFFPBwas divided into several parts with different surface materials which allowed the coefficient of friction to change whenthe slider went across different parts. This means that the stiffness of a VF-FPB changed as the relative displacement betweenthe slider and the sliding surface changes. In the current paper, the isolation mechanism of a typical VF-FPB was analyzed. The numerical model of a single-layer lattice shell was developed and the effect of VF-FPB installation on the structure wasstudied. The VF-FPBs used in the study had their surfaces divided into two parts, and it was found that an ‘optimal range’ existsfor the dimensions of two component parts for the best earthquake isolation effect. It was concluded that VF-FPBs couldimprove the seismic performance of a single layer lattice shell more effectively than conventional FPBs.

Comparion of Seismic Response of Single-layer Reticulated Dome under Unform and Incoherence Three-directional Excitations

Feng Fan,Yugang Li,Xudong Zhi,Lu Li 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.4

Seismic ground motions at structural supports are spatially varying and incoherent. The spatial incoherency effects shouldbe considered for structures with large span and multiple supports. Two single-layer reticulated domes of 120m span, with andwithout substructures under incoherent multiple supports and uniform excitations were modeled and analysed in this study. Time-history responses of structures are obtained and compared for simulated ground motion records. For the simulation, useof existing phase difference spectrum models and coherence models were considered, and three-directional excitations (twohorizontal directions and vertical direction) are considered. The analysis results show that the spatial coherency effect caninfluence the seismic responses of reticulated domes. The results also indicate that the seismic spatial coherency of all threedirections can be important, especially for structures without flexible substructures.

Failure Pattern of Singe-layer Reticulated Dome under Severe Earthquake and Its Shaking Table Test

Gui-Bo Nie,Xudong Zhi,Feng Fan,Jun-Wu Dai 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.2

Based on the constitutive model with considering material damage accumulation, the influence of material damageaccumulation on the responses of the structure is investigated in detail through the incremental dynamic analysis method (IDAanalysis). The failure pattern of single-layer reticulated dome under dynamic loading is obtained using IDA analysis throughmultiple sets of seismic load records and harmonic loading, which is identified to be the dynamic instability failure caused bythe geometric nonlinearity and the dynamic strength failure resulted by the material nonlinearity. The shaking table tests ofsingle-layer reticulated dome are exploited to verify the failure pattern of the structure under seismic load records. Experimentalresults show that the plasticity of the model develops and the deformation increases, as well as the mechanical propertiesweakens continuously with the increasing of the loading value, which indicates that the failure pattern of the structure isdynamic strength failure.

Infl uence of Multiple Earthquakes on Single-Layer Reticulated Dome and Its Shaking-Table Test

Ying-Nan Zhang,Xudong Zhi,Feng Fan 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1

In this paper, a primary dataset of mainshock–aftershock sequences is constructed from the Pacifi c Earthquake Engineering Research Center. This is followed by the collection of 342 groups of mainshock–aftershock ground motions for the dynamic time history analysis of a single-layer reticulated dome in the full process domain. According to the change curves between the characteristic factors and acceleration amplitudes, four diff erent levels of infl uence (i.e. no infl uence, slight infl uence, signifi cant infl uence and collapse under aftershocks) of multiple earthquakes on the seismic responses of a single-layer reticulated dome are defi ned. On this basis, a shaking-table test of a single-layer reticulated dome model, taking aftershocks into consideration, is conducted to obtain the full failure history under multiple earthquakes intuitively. Spherical joints are located accurately, using total station surveying equipment and lead screws during model processing. Experimental results verify the above four levels of infl uence of multiple earthquakes and provide a dependable reference for seismic design.

Artifi cial Neural Networks (ANN) Based Compressive Strength Prediction of AFRP Strengthened Steel Tube

Abderrahim Djerrad,Feng Fan,Xudong Zhi,Qi-jian Wu 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1

The use of FRP composites as external confi nement has recently become a very important system to consider when reinforcing concrete and steel structures. Many constitutive models have been proposed to design such structures. However, the emergence of artifi cial neural network off ers a better alternative with a strong prediction capability. In this research, an artifi cial neural network (ANN) based model is used to estimate the compressive strength, maximum stresses and strains of AFRP strengthened circular hollow section steel tubes under axial compression. A database of 129 cases of fi nite element model (FEM) was analyzed using ANSYS Workbench 19.0 and ACP Tool. The FEM was validated with a previously done experimental test. Diff erent geometric criteria have been taken into account to better address the complexity of the problem. Using this FEM database, ANNs have been trained using two approaches. The fi rst approach was using the neural network toolbox in MATLAB. The second approach was using a built-in neural network tool in ANSYS Workbench. The successfully trained ANN is further used to predict the new cases, as an alternative to FE Analysis. Following, a parametric study and a sensitivity analysis were also carried out to investigate the eff ect of diff erent parameters on the load capacity. The predicted results of the ANN models show a good correlation with the experimental and FEM results. Moreover, comparative analysis of performance result reveals that the ANSYS-ANN had better accuracy in terms of mean squared error and regression value (R 2 ) compared to MATLAB-ANN. The ANN is quite an effi cient tool in determining the strength of the AFRP strengthening steel tubes. Such a technique can be used to reduce computation time and labor.