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International Concrete Abstracts Portal

Showing 1-5 of 259 Abstracts search results

Document: 

SP-347_09

Date: 

March 1, 2021

Author(s):

Quanquan Guo, Chengwei Guo, Xuqiang Dou,Chuanchuan Hou

Publication:

Symposium Papers

Volume:

347

Abstract:

In the past, the study of low-velocity impact response of steel-concrete composite panels (SC) mainly focused on the overall flexure failure mode. To study the impact dynamic response of SC panels under the local punching failure mode, a drop hammer impact test of ten SC panels was carried out in this paper. The influence of the impact energy, impact momentum, and axial compression ratio was investigated. With the increase of impact energy, five damage patterns appeared in turn under the local punching failure mode. And the whole response process could be divided into five stages. It was found that the change of impact momentum had little influence on SC panels, but axial compressive preload could improve the stiffness and the impact capacity of SC panels to a certain extent. A finite element (FE) model based on LS-DYNA was then established and it could simulate the test process reasonably well. A mechanical analysis of the dynamic response process was carried out with the numerical model, including a parametric study on the influence of the axial compression ratio.


Document: 

SP-347_13

Date: 

March 1, 2021

Author(s):

Girum Urgessa and Robert Sobeski

Publication:

Symposium Papers

Volume:

347

Abstract:

This paper presents qualitative and quantitative assessment of material flow response during projectile penetration of concrete targets using outputs from the finite element analysis. The assessment included two parts. First, the movement of the comminuted concrete was analyzed by examining the normal expansion of meshless particles using NECM (Normal Expansion Comparison Methodology). Second, the expansion of finite element nodes adjacent to meshless particles was analyzed by observing direction cosines and velocity profiles of the nodes using SECM (Spherical Expansion Comparison Methodology). This assessment is important to re-examine simplified assumptions used in analytical penetration depth equations that were developed without providing adequate insight into material flow.


Document: 

SP-348_08

Date: 

March 1, 2021

Author(s):

Tim Hogue, David Kerins, and Matthew Brightman

Publication:

Symposium Papers

Volume:

348

Abstract:

The “Notional Pile” formulation is developed for modeling a group of piles in a foundation. It is a new procedure for foundation modeling for dynamic analysis in conformance with ACI 351.3R. It is an augmentation of the well-known Novak procedure. Foundation stiffness is represented as a set of notional pile elements. This differs from conventional procedures in which the pile group stiffness is represented by a set of springs lumped at one point. With notional piles and finite element modeling of the cap, flexible-cap modes of vibration can be extracted. With conventional procedures, only lower-frequency rigid body modes can be extracted. Notional piles distribute stiffness more realistically and enable cap-pile interaction. A specific case is used to illustrate the new procedure. For that case, the cap did not have a regular distribution of mass or stiffness. Dynamic loads were applied with considerable eccentricity, at multiple locations and with multiple frequencies. Notional piles accommodated these irregularities. The notional pile formulation was validated by comparing measured to computed foundation responses. The comparison was good but not great. The foundation was to be reconfigured for new machinery. The retrofit design was modeled using notional piles. Responses were computed and compared to applicable limits.


Document: 

SP-347_14

Date: 

March 1, 2021

Author(s):

Seong Ryong Ahn and Thomas H.-K. Kang

Publication:

Symposium Papers

Volume:

347

Abstract:

Impact resistance of concrete panels has been researched since the 19th century. Studies therein primarily focused on conventionally reinforced concrete and steel fiber-reinforced concrete. Little research on the impact resistance of prestressed concrete exists. This paper investigated the impact resistance of prestressed concrete panels subject to hard and soft/hollow projectiles and under an assortment of prestressing levels. Damage mode, velocity change, impact force, and internal energy were measured and analyzed. A total of twelve finite element analyses, which considered high strain rate effects, were performed, as well as preliminary analyses with different mesh sizes. It is observed that level of prestressing tends to improve perforation resistance of concrete panels. Additionally, large deformation at soft projectiles occurred during impact, consuming the greater internal energy of the projectiles, unlike hard projectiles. As a result, soft projectiles caused a smaller degree of local failure on the concrete panels than hard projectiles with the same mass and velocity.


Document: 

SP-348_02

Date: 

March 1, 2021

Author(s):

Hongchun Liu, Jaspal S. Saini, Gang Zhao, Sushil Chauhan, Namgyu Park, Mahi Galagoda, Steven Wu

Publication:

Symposium Papers

Volume:

348

Abstract:

This paper discusses an innovative retrofit that stabilized a Steam Turbine Generator (STG) pedestal foundation undergoing unexpected differential settlements during construction. The innovative solution involved driving steel H-piles around the STG foundation perimeter. A new concrete bracket (a.k.a. corbel) was added around the STG foundation perimeter to fully engage and integrate the H-piles with the existing pedestal foundation. The pile layout was established and optimized based on dynamic and static performance analyses of the modified foundation geometry using finite element (FE) software ANSYS, considering bounding pile and soil dynamic impedances. The frequency-dependent dynamic pile impedances were calculated using DYNA6. The continuous settlement monitoring of the STG foundation demonstrated that the retrofit effectively seized the ongoing settlements and stabilized the foundation enabling the subsequent machine installation.


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