Numerical study of dynamic responses of reinforced concrete infilled frames subjected to progressive collapse

2020 ◽  
pp. 136943322096527
Author(s):  
Jun Yu ◽  
Yi-Ping Gan ◽  
Jun Liu
Keyword(s):  
Dynamic Loading ◽  
Load Transfer ◽  
Progressive Collapse ◽  
Dynamic Responses ◽  
Infill Walls ◽  
Composite Effect ◽  
Infilled Frames ◽  
Load Paths ◽  
Macro Modeling ◽  
Peak Resistance

Recently, the contribution of infill walls on progressive collapse resistance of reinforced concrete (RC) structures attracts a great many research attentions, but the research interests are mainly concentrated on the static resistance and the macro-modeling approaches, which require predefined one-dimensional load paths through two-dimensional walls. However, the load transfer paths in dynamic loading regime are still not fully understood. To this end, high-fidelity finite element (FE) models of multi-story RC infilled frames are built and validated through quasi-static experimental results. Then the FE models are used to investigate the dynamic responses of infilled frames under different single and double CRS as well as the effect of the number of stories on the load transfer paths of full-height infill walls (FHIW) and infill walls having opening (IWHO). The results indicate that the load paths along the infill walls in static and dynamic loading regimes are similar prior to the peak resistance but different in post-peak resistance for single infilled story frames. Such difference results from the loading distribution pattern, in which the static loading is typically represented by a concentrated load whereas the dynamic loading involves the uniformly distributed load. Moreover, increasing the number of infilled stories with FHIW, trans-story load paths due to composite effect always exist to enhance resistance and such paths are scenario-dependent. In comparison, the load paths for multi-story frames with IWHO are relatively scenario-independent with minor composite effect. Therefore, to generalize the macro-modeling, it is conservative to ignore the trans-story load paths.

Pore Pressure Build-up of Silt Soft Clay under Dynamic Loading at Zhoushan Islands

2012 ◽  
Vol 594-597 ◽  
pp. 460-464
Author(s):  
Qian Shi ◽  
Kui Zhou ◽  
Qiang Li
Keyword(s):  
Pore Pressure ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
Soft Clay ◽  
Test System ◽  
Dynamic Responses ◽  
Minor Effect ◽  
Consolidation Pressure ◽  
Anisotropic Consolidation ◽  
Pore Pressure Build Up

The mechanism of dynamic tri-axial test is introduced in this paper and the dynamic responses of silt soft clay at Zhoushan are studied using a dynamic tri-axial test system. The laws of pore pressure build-up of the silt clay are obtained which are affected by the consolidation pressure and dynamic load. The greater the consolidation pressure and the dynamic loading is, the more the build-up of pore pressure is. However, the dynamic load has minor effect on pore pressure build-up under the anisotropic consolidation.

Experimental study on the progressive collapse mechanism in the braced and tied-back retaining systems of deep excavations

2020 ◽  
Author(s):  
Gang Zheng ◽  
Yawei Lei ◽  
Xuesong Cheng ◽  
Xiyuan Li ◽  
Ruozhan Wang
Keyword(s):  
Large Scale ◽  
Large Deformations ◽  
Load Transfer ◽  
Progressive Failure ◽  
Progressive Collapse ◽  
Collapse Mechanism ◽  
Bending Moments ◽  
Failure Path ◽  
Transfer Mechanisms ◽  
Very High

Collapses of braced or tied-back excavations have frequently occurred. However, the influence of the failure of some retaining structure members on the overall safety performance of a retaining system has not been studied. Model tests of failures of retaining piles, struts or anchors were conducted in this study, and the load transfer mechanisms underlying these conditions were analysed. When failures or large deformations occurred in certain piles, the increasing ratios of the bending moments in adjacent piles were much larger in the braced retaining system than in the cantilever system and more easily triggered progressive failure. When the strut elevation was lower or the excavation depth was greater, the degree of influence and range of pile failures became larger. When certain struts/anchors failed, their loads transferred to a few adjacent struts/anchors, possibly leading to further strut/anchor failure. The influence mechanisms of strut or anchor failure on piles were different from those of pile failure. As the number of failed struts or anchors increases, the bending moments of the piles in the failure zone first decrease and then increase to very high values. Therefore, the progressive failure path extends from struts/anchors to piles and will lead to large-scale collapse.

Numerical investigation on load transfer mechanism of bonded post-tensioned concrete beam-column substructures against progressive collapse

2020 ◽  
pp. 136943322098165
Author(s):  
Kai Qian ◽  
Hai-Ning Hu ◽  
Yun-Hao Weng ◽  
Xiao-Fang Deng ◽  
Ting Huang
Keyword(s):  
Prestressed Concrete ◽  
Load Transfer ◽  
Numerical Models ◽  
Progressive Collapse ◽  
Load Resistance ◽  
Catenary Action ◽  
Parabolic Profile ◽  
Arch Action ◽  
Column Removal Scenario ◽  
Post Tensioned

This paper presents the high-fidelity finite-element-based numerical models for modeling the behavior of prestressed concrete (PC) beam-column substructures to resist progressive collapse under column removal scenario. After careful calibration against data, the validated numerical models are further employed to shed light on the influence of bonded post-tensioned tendons (BPT) with a parabolic profile on the load transfer mechanisms of PC frames against progressive collapse. The effects of parameters, including initial effective prestress, profile of tendon and lateral constraint stiffness at the beam ends, are also investigated. The study shows that, due to the presence of prestressed tendons, the mobilization of compressive arch action in the beam at small deflections demands stronger lateral constraints, and the ultimate load resistance of PC beam-column substructures depends on combined catenary action from non-prestressed reinforcement and BPT at large deflections. For a given constraint stiffness, the initial effective prestress of BPT has less significant effect on the overall structural behavior. For prestressed tendon, a straight profile usually employed in structural strengthening can improve the initial structural stiffness and yield strength, but is less effective in enhancing the ultimate resistance against progressive collapse than the parabolic profile.

scholarly journals CASCO: a simulator of load paths in 2D frames during progressive collapse

2020 ◽  
Vol 2 (9) ◽  
Author(s):  
Enrico Masoero
Keyword(s):  
Progressive Collapse ◽  
Structural Topology ◽  
Matlab Simulation ◽  
Concrete Frames ◽  
Dynamic Simulations ◽  
New Approach ◽  
Load Paths ◽  
Collapse Resistance ◽  
Simplifying Assumptions ◽  
Damage Tolerant

Abstract Modern structural design software can simulate complex collapse dynamics, but the main physical processes driving collapse propagation are often hidden among structure-specific details. As a result, it is still unclear which structural geometries and material properties should be preferred when approaching the design of a damage-tolerant structure. This manuscript presents a new approach to explore the relationships between structural geometry, local mechanical properties, and collapse propagation. The insight comes from a unique ability to trace the evolution of load paths during collapse, achieved by combining energy conservation with local mechanisms of plastic failure and a few simplifying assumptions. The method is implemented in a new simulator of collapse of 2D frames, called CASCO and programmed in MATLAB. Simulation results for reinforced concrete frames predict collapse loads and mechanisms in agreement with fully non-linear, dynamic simulations, while also providing a graphical description of the evolving structural topology during collapse. A first application of CASCO to mechanically homogeneous and heterogeneous frames, indicates certain evolutions in number and density of load paths during collapse that may be targetted to improve collapse resistance.

Dynamic responses of two blocks under dynamic loading using experimental and numerical studies

2015 ◽  
Vol 49 ◽  
pp. 72-82 ◽  
Author(s):  
H.K. Cihan ◽  
A. Ergin ◽  
K. Cihan ◽  
I. Guler
Keyword(s):  
Dynamic Loading ◽  
Dynamic Responses ◽  
Numerical Studies

Dynamic analysis of laterally loaded pile groups in sand and clay

2002 ◽  
Vol 39 (6) ◽  
pp. 1358-1383 ◽  
Author(s):  
Yasser E Mostafa ◽  
M Hesham El Naggar
Keyword(s):  
Dynamic Loading ◽  
Dynamic Load ◽  
Load Transfer ◽  
Pile Group ◽  
Nonlinear Behaviour ◽  
Single Pile ◽  
Offshore Platforms ◽  
Group Effect ◽  
Pile Groups ◽  
Pile Head

Pile foundations supporting bridge piers, offshore platforms, and marine structures are required to resist not only static loading but also lateral dynamic loading. The static p–y curves are widely used to relate pile deflections to nonlinear soil reactions. The p-multiplier concept is used to account for the group effect by relating the load transfer curves of a pile in a group to the load transfer curves of a single pile. Some studies have examined the validity of the p-multiplier concept for the static and cyclic loading cases. However, the concept of the p-multiplier has not yet been considered for the dynamic loading case, and hence it is undertaken in the current study. An analysis of the dynamic lateral response of pile groups is described. The proposed analysis incorporates the static p–y curve approach and the plane strain assumptions to represent the soil reactions within the framework of a Winkler model. The model accounts for the nonlinear behaviour of the soil, the energy dissipation through the soil, and the pile group effect. The model was validated by analyzing the response of pile groups subjected to lateral Statnamic loading and comparing the results with field measured values. An intensive parametric study was performed employing the proposed analysis, and the results were used to establish dynamic soil reactions for single piles and pile groups for different types of sand and clay under harmonic loading with varying frequencies applied at the pile head. "Dynamic" p-multipliers were established to relate the dynamic load transfer curves of a pile in a group to the dynamic load transfer curves for a single pile. The dynamic p-multipliers were found to vary with the spacing between piles, soil type, peak amplitude of loading, and the angle between the line connecting any two piles and the direction of loading. The study indicated the effect of pile material and geometry, pile installation method, and pile head conditions on the p-multipliers. The calculated p-multipliers compared well with p-multipliers back-calculated from full scale field tests.Key words: lateral, transient loading, nonlinear, pile–soil–pile interaction, p–y curves, Statnamic.

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