scholarly journals Analysis of Key Elements of Truss Structures Based on the Tangent Stiffness Method

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1008
Author(s):  
Jian Feng ◽  
Changtong Li ◽  
Yixiang Xu ◽  
Qian Zhang ◽  
Fang Wang ◽  
...  
Keyword(s):  
Stiffness Matrix ◽  
Progressive Collapse ◽  
Truss Structures ◽  
Specific Information ◽  
Tangent Stiffness ◽  
Collapse Resistance ◽  
The Matrix ◽  
Support Conditions ◽  
Global Stiffness Matrix ◽  
Progressive Collapse Analysis

In recent years, the topic of progressive structural collapse has received more attention around the world, and the study of element importance is the key to studying progressive collapse resistance. However, there are many elements in truss structures, making it difficult to predict their importance. The global stiffness matrix contains the specific information of the structure and singularity of the matrix can reflect the safety status of the structure, so it is useful to evaluate the key elements based on the global stiffness matrix for truss structures. In this paper, according to the tangent stiffness-based method for the element importance, the square pyramid grid was chosen as an example, and the distribution rules of key elements under different support conditions, stiffness distributions, and geometric parameters were studied. Then, three common symmetric grid forms, i.e., diagonal square pyramid grids, biorthogonal lattice grids, and biorthogonal diagonal lattice grids, were selected to investigate their importance indices of elements. The principle in this work can be utilized in progressive collapse analysis and safety assessment for spatial truss structures.

Static Analysis of Fe Discretized Structures With Bounded Uncertainties via Interval Method

2009 ◽  
Author(s):  
Nicola Impollonia ◽  
Giuseppe Muscolino
Keyword(s):  
Static Analysis ◽  
Interval Analysis ◽  
Stiffness Matrix ◽  
Probabilistic Method ◽  
Probabilistic Approach ◽  
Great Accuracy ◽  
Truss Structures ◽  
Interval Model ◽  
Global Stiffness Matrix ◽  
Bounded Uncertainties

The uncertainty presents in many engineering analysis is usually modeled by probabilistic approach. It is now largely recognized that the probabilistic approach often cannot be applied to describe structural uncertainty; indeed, it requires a wealth of data, often unavailable, to define the probability density function of the uncertainties. Alternatively non-probabilistic method can be adopted. In this framework, the interval model seems today the most suitable analytical tool. The interval model is derived from the interval analysis, in which the number is treated as an interval variable with lower and upper bounds. However, the application of the interval analysis in classical form can result in a severe overestimation of the uncertainty of the output. In this paper the limit of interval analysis is overcome by deriving an alternative solution, in the framework of linear static analysis of finite element modeled structures with uncertain-but-bounded parameters. The proposed procedure is based on the factorization of the elemental stiffness matrix following the unimodal components concept, which allows a non conventional assembly of the global stiffness matrix, and on the inversion of the assembled stiffness matrix by an interval-valued Sherman-Morrison formula. Numerical results on truss structures evidence the great accuracy of the proposed approach.

Progressive Collapse Analysis of CFST Frame with Semi-Rigid Connection

2014 ◽  
Vol 578-579 ◽  
pp. 779-783
Author(s):  
Yang Ma ◽  
Lai Wang
Keyword(s):  
Progressive Collapse ◽  
Joint Stiffness ◽  
Static And Dynamic Analysis ◽  
Numerical Result ◽  
Collapse Resistance ◽  
Rigid Connection ◽  
Alternate Path Method ◽  
Nonlinear Static ◽  
Resistance Performance ◽  
Progressive Collapse Analysis

A finite element method was developed to investigate the semi-rigid connection mechanical behaviors in the process of CFST structures progressive collapse, and different semi-rigid connection joint stiffness were taken into consideration and compared to rigid connection. Nonlinear static and dynamic analysis were carried out with alternate path method. The numerical result shows that the increase of joint stiffness would evidently enhance the structural progressive collapse resistance performance, and CFST structures have excellent characteristic to prevent progressive collapse, the great deformation capacity and energy dissipation ability of semi-rigid connections are advantageous to progressive collapse resistance.

scholarly journals Progressive Collapse Safety Evaluation of Truss Structures Considering Material Plasticity

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5135
Author(s):  
Sheng-En Fang ◽  
Chen Wu ◽  
Xiao-Hua Zhang ◽  
Li-Sen Zhang ◽  
Zhi-Bin Wang ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Progressive Collapse ◽  
Safety Evaluation ◽  
Truss Structures ◽  
Stiffness Matrices ◽  
Collapse Analysis ◽  
Importance Coefficient ◽  
Analytical Research ◽  
Progressive Collapse Analysis ◽  
The Impact

Theoretical or numerical progressive collapse analysis is necessary for important civil structures in case of unforeseen accidents. However, currently, most analytical research is carried out under the assumption of material elasticity for problem simplification, leading to the deviation of analysis results from actual situations. On this account, a progressive collapse analysis procedure for truss structures is proposed, based on the assumption of elastoplastic materials. A plastic importance coefficient was defined to express the importance of truss members in the entire system. The plastic deformations of members were involved in the construction of local and global stiffness matrices. The conceptual removal of a member was adopted, and the impact of the member loss on the truss system was quantified by bearing capacity coefficients, which were subsequently used to calculate the plastic importance coefficients. The member failure occurred when its bearing capacity arrived at the ultimate value, instead of the elastic limit. The extra bearing capacity was embodied by additional virtual loads. The progressive collapse analysis was performed by iterations until the truss became a geometrically unstable system. After that, the critical progressive collapse path inside the truss system was found according to the failure sequence of the members. Lastly, the proposed method was verified against both analytical and experimental truss structures. The critical progressive collapse path of the experimental truss was found by the failure sequence of damaged members. The experimental observation agreed well with the corresponding analytical scenario, proving the method feasibility.

scholarly journals Progressive Collapse Analysis of multi-story building under the scenario of multi-column removal

2019 ◽  
Vol 136 ◽  
pp. 04050 ◽  
Author(s):  
M. Nassir ◽  
J. Yang ◽  
S. Nyunn ◽  
I. Azim ◽  
F.L. Wang
Keyword(s):  
Static Analysis ◽  
Progressive Collapse ◽  
Analysis Procedure ◽  
Collapse Resistance ◽  
Collapse Analysis ◽  
Column Removal ◽  
Concrete Building ◽  
Column Removal Scenario ◽  
Progressive Collapse Analysis ◽  
Story Building

Recent studies regarding progressive collapse resistance of buildings considered only single critical column removal scenario. However, limited investigations have been conducted so far to assess multi-column removal scenarios. Hence this study is made to compare progressive collapse resistance of a multi-story building under both single and multi-column removal scenarios. An eight-storey reinforced concrete building was analyzed by using linear static analysis procedure and DCR values of the members are calculated to investigate the potential of progressive collapse as per GSA guideline. The values of DCR are compared for different cases. Comparisons of single and multi-column removal scenarios reveal that later scenarios are more critical because of their higher demand capacity ratios, and it is more critical when both corner and exterior columns are removed.

An Algorithm to Study the Elastodynamics of Parallel Kinematic Machines With Lower Kinematic Pairs

2012 ◽  
Vol 5 (1) ◽  
Author(s):  
Alessandro Cammarata ◽  
Davide Condorelli ◽  
Rosario Sinatra
Keyword(s):  
Stiffness Matrix ◽  
Rigid Bodies ◽  
Parallel Kinematic Machine ◽  
Element Analysis ◽  
Stiffness Matrices ◽  
The Matrix ◽  
Parallel Kinematic ◽  
Global Stiffness Matrix ◽  
Local Stiffness

In this paper, an algorithm to help designers to integrate the elastodynamics analysis along with the inverse positioning and orienting problems of a parallel kinematic machine (PKM) into a single package is conceived. The proposed algorithm applies concepts from the matrix structural analysis (MSA) and finite element analysis (FEA) to determine the generalized stiffness matrix and the linearized elastodynamics equations of a PKM with only lower kinematic pairs. A PKM is modeled as a system of flexible links and rigid bodies connected by means of joints. Three cases are analyzed to consider the combinations between flexible and rigid bodies in order to find the local stiffness matrices. The latter are combined to obtain the limb matrices and, then, the global stiffness matrix of the whole robotic system. The same nodes coming from the links discretization are considered to include joint masses/inertias into the model. Finally, a case study is proposed to show some feasible applications and to compare results to commercial software for validation.

SEISMIC PROGRESSIVE COLLAPSE ANALYSIS OF CONTROLLED STEEL FRAME STRUCTURES

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Tantely Jeriniaina Sitraka ◽  
Zheng He
Keyword(s):  
Progressive Collapse ◽  
Plastic Hinge ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Collapse Resistance ◽  
Element Loss ◽  
Concentrically Braced ◽  
Collapse Analysis ◽  
Steel Frame Structures ◽  
Progressive Collapse Analysis

Any element loss in the concentrically-braced frames (CBF) system significantly affects its seismic performance. The research presented in this paper aimed to understand the behavior of this system against seismic progressive collapse due to the failure of a column. A collapse of this magnitude may lead to the entire collapse of the structure, or else it could avoid or even localize the disaster by redistributing the released load to the surrounding structure. The progressive collapse phenomenon was investigated through analyzing a building equipped with CBF system during a seismic event. Four cases of failed beams were considered, depending on the location of the column loss and the configuration of the braces surrounding them. Through OpenSees simulation, the results showed the seismic and gravity loads increased and rapidly reached the ultimate state of the structure from 0.6 sec after the time of failure. The model for each scenario, regardless of the direct collapse of the structure due to the column loss, indicated the CBF system limited the plastic hinge formation around the failed element. Finally, the results showed the braces working in tensile are more reliable in terms of collapse resistance than those working in compression.

scholarly journals Applications of stiffness-based evaluation method to element importance of truss systems

2017 ◽  
Vol 23 (5) ◽  
pp. 562-572 ◽  
Author(s):  
Jianguo CAI ◽  
Wenwen JIA ◽  
Jian FENG ◽  
Fang WANG ◽  
Yixiang XU
Keyword(s):  
Stiffness Matrix ◽  
Evaluation Method ◽  
Progressive Collapse ◽  
Structural Performance ◽  
Load Path ◽  
Specific Element ◽  
Performance Indexes ◽  
Collapse Analysis ◽  
Progressive Collapse Analysis ◽  
Space Trusses

Two structural performance indexes, making use of eigenvalues of stiffness matrix, are presented in the study for the evaluation of element importance in the progressive collapse analysis of space trusses. Both indexes are based on the consensus that the element transferring higher loads in the load path is generally more important in the structural sys­tem. The first index is formulated as change of the smallest stiffness after removal of specific element, and the second in­dex is defined as determinant of the stiffness matrix. Several simple numerical examples are presented to investigate per­formance of the proposed indexes; and finally, a square pyramid space grid system is studied as an illustrative example.

Effects of Braces on Progressive Collapse Resistance of Steel Frame

2014 ◽  
Vol 578-579 ◽  
pp. 369-373
Author(s):  
Li Chang Dong ◽  
Lai Wang
Keyword(s):  
Axial Force ◽  
Progressive Collapse ◽  
Nonlinear Dynamic Analysis ◽  
Vertical Displacement ◽  
Steel Frame ◽  
Frame Structure ◽  
Collapse Resistance ◽  
Failure Point ◽  
Steel Frame Structure ◽  
Progressive Collapse Analysis

In order to carry on the progressive collapse analysis more properly, nonlinear-dynamic analysis method is used to analyze five-storey of steel frame structure. Four structure schemes have been established, namely frames, frames with horizontal braces, frames with vertical braces and frames with horizontal cross braces. According to analyzing with different position of failure column on the first floor, the curves of displacement-time of column failure point and axial force of failure column’s neighboring are obtained. The results indicate that horizontal braces can reduce the vertical displacement above damaged column and the axial force of the columns on the first floor evidently. The vertical displacement of horizontal cross braces is less than which of horizontal braces.

Progressive Collapse Resisting Capacity of RC Flat Slab Buildings with Varying Spans and Storey Heights

2021 ◽  
Vol 894 ◽  
pp. 115-120
Author(s):  
Suyash Garg ◽  
Vinay Agrawal ◽  
Ravindra Nagar
Keyword(s):  
Urban Growth ◽  
Progressive Collapse ◽  
Flat Slab ◽  
Collapse Resistance ◽  
Collapse Analysis ◽  
Column Removal ◽  
Vertical Displacements ◽  
Instantaneous Removal ◽  
Chord Rotation ◽  
Progressive Collapse Analysis

With no beams, reinforced concrete flat slab buildings are typically built to advance urban growth and to meet the architectural needs of large spans and low storey heights. Its behaviour to avoid a progressive collapse must therefore be investigated. In this research, the progressive collapse resistance of six-storey RC flat slab buildings with varying span lengths and floor heights is assessed by subjecting the building to three different instances of instantaneous removal of columns in the first storey, performing dynamic progressive collapse analysis as per GSA guidelines, and comparing the evaluated joint displacements and chord rotations at column removal locations with the permissible chord rotation for flat slab buildings as per DoD guidelines. The results have shown that the studied flat slab building with all different span lengths and floor heights is prone to progressive collapse. It is also observed that the vertical displacements and chord rotations at column removal positions increase as the span lengths and storey heights are increased alternately.

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