scholarly journals Experimental Investigation of Impact Response of RC Slabs with a Sandy Soil Cushion Layer

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Jianli Wu ◽  
Guotao Ma ◽  
Zhenhua Zhou ◽  
Xuefeng Mei ◽  
Xiewen Hu
Keyword(s):  
Layer Thickness ◽  
Sandy Soil ◽  
Failure Modes ◽  
Impact Force ◽  
Concrete Slab ◽  
Failure Process ◽  
Impact Response ◽  
Rc Slabs ◽  
Cushion Layer ◽  
The Impact

The impact response of reinforced-concrete (RC) slabs covered with a sandy soil cushion layer was investigated using an outdoor rockfall impact test platform. Impact tests were carried out by releasing rockfalls with different weights from different heights to impact a combined structure. Test data included the acceleration duration curve of the rockfall, strain of the concrete slab at multiple measuring points, and midpoint displacement duration curve of the slab. The test results showed an exponential relationship between the impact force acting on the cushion layer surface and cushion layer thickness. An empirical formula was used to calculate the maximum penetration, and the result was in good agreement with the test value. In addition, the attenuation rate of the impact force acting on the cushion layer increased exponentially with the increase in the cushion layer thickness, and the peak impact force could be attenuated by approximately 70% at a thickness of 0.6 m. Finally, the failure process and failure modes of the RC slabs were investigated.

Effect of long-term moisture exposure on impact response of glass-reinforced vinylester

2021 ◽  
pp. 147509022199616
Author(s):  
Fatemeh Alizadeh ◽  
Navid Kharghani ◽  
Carlos Guedes Soares
Keyword(s):  
Water Uptake ◽  
Failure Modes ◽  
Sea Water ◽  
Composite Plates ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Water Type ◽  
Interfacial Damage ◽  
Impact Properties ◽  
The Impact

Glass/Vinylester composite laminates are comprehensively characterised to assess its impact response behaviour under moisture exposure in marine structures. An instrumented drop weight impact machine is utilised to determine the impact responses of dry and immersed specimens in normal, salted and sea water. The specimens, which had three different thicknesses, were subjected to water exposure for a very long period of over 20 months before tested in a low-velocity impact experiment. Water uptake was measured primarily to study the degradation profiles of GRP laminates after being permeated by water. Matrix dissolution and interfacial damage observed on the laminates after prolonged moisture exposure while the absorption behaviour was found typically non-Fickian. The weight of the composite plates firstly increased because of water diffusion up to month 15 and then decreased due to matrix degradation. The specimens with 3, 6 and 9 mm thickness exhibited maximum water absorption corresponding to 2.6%, 0.7% and 0.5% weight gain, respectively. In general, the results indicated that water uptake and impact properties were affected by thickness and less by water type. Impact properties of prolonged immersed specimens reduced remarkably, and intense failure modes detected almost in all cases. The least sensitive to impact damage were wet specimens with 9 mm thickness as they indicated similar maximum load and absorbed energy for different impact energies.

Response and failure modes of biaxial warp-knitted flexible composite subject to low-velocity impact

2021 ◽  
pp. 152808372110154
Author(s):  
Ziyu Zhao ◽  
Tianming Liu ◽  
Pibo Ma
Keyword(s):  
Impact Energy ◽  
Linear Density ◽  
Failure Modes ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Minor Effect ◽  
Low Velocity ◽  
Velocity Impact ◽  
Flexible Composites ◽  
The Impact

In this paper, biaxial warp-knitted fabrics were produced with different high tenacity polyester linear density and inserted yarns density. The low-velocity impact property of flexible composites made of polyurethane as matrix and biaxial warp-knitted fabric as reinforcement has been investigated. The effect of impactor shape and initial impact energy on the impact response of flexible composite is tested. The results show that the initial impact energy have minor effect on the impact response of the biaxial warp-knitted flexible composites. The impact resistance of flexible composite specimen increases with the increase of high tenacity polyester linear density and inserted yarns density. The damage morphology of flexible composite materials is completely different under different impactor shapes. The findings have theoretical and practical significance for the applications of biaxial warp-knitted flexible composite.

Experimental and Numerical Study of Basalt FRP Strip Strengthened RC Slabs under Impact Loads

2020 ◽  
Vol 20 (06) ◽  
pp. 2040001 ◽  
Author(s):  
Wensu Chen ◽  
Thong M. Pham ◽  
Mohamed Elchalakani ◽  
Huawei Li ◽  
Hong Hao ◽  
...  
Keyword(s):  
Failure Modes ◽  
Shear Failure ◽  
Numerical Study ◽  
Impact Resistance ◽  
Basalt Fiber ◽  
Impact Behavior ◽  
Impact Loads ◽  
Quantitative Measurements ◽  
Rc Slabs ◽  
The Impact

Basalt fiber-reinforced polymer (BFRP) has been applied for strengthening concrete structures. However, studies on reinforced concrete (RC) slabs strengthened by BFRP strips under impact loads are limited in open literature. This study investigates the efficiency of using BFRP strips with various strengthening layouts and anchoring schemes on the impact resistance of RC slabs. A total of 11 two-way square slabs were prepared and tested, including one reference specimen without strengthening and ten slabs strengthened with BFRP strips and/or anchors. The RC slabs were impacted by a drop weight with increasing height until slab failure. The observed failure modes include punching shear failure, BFRP sheet debonding and reinforcement fracture. The failure modes and the effects of using various strengthening schemes on the impact resistant capacity of RC slabs were examined. The quantitative measurements, such as impact velocity, indentation depth and diameter, were compared and discussed. In addition, numerical studies were carried out by using LS-DYNA to simulate the impact tests of RC slabs with and without BFRP strengthening. With the calibrated numerical model, the impact behavior of slabs with various dimensions and strengthening layouts under different impact intensities can be predicted with good accuracy.

Vibration Analysis of Different Micro-Beams with Laser Ablation

2013 ◽  
Vol 462-463 ◽  
pp. 428-431
Author(s):  
Liang Cai Xiong ◽  
Quan Sheng Zhou ◽  
Peng Chen
Keyword(s):  
Laser Ablation ◽  
Dynamic Response ◽  
Vibration Analysis ◽  
Laser Excitation ◽  
Impact Force ◽  
Laser Doppler Vibrometer ◽  
Impact Response ◽  
Vibration Velocity ◽  
Laser Shock ◽  
The Impact

The dynamic response of different micro-beams after laser excitation experiments have been investigated in this paper. The impact force that induces the vibration of micro-beams is the interaction of focused pulse laser and tested beams. The impact response of micro-beams after being excited is measured by Laser Doppler Vibrometer. Different beams such as cantilever beam, L-shaped beam are employed in our experiments. Comparisons of the vibration velocity and its frequencies of different beams have also been performed. Experimental results show that the mechanical effects of laser shock do really exist and can be utilized.

scholarly journals Experimental study of the impact response of geocells as components of rockfall protection embankments

2009 ◽  
Vol 9 (2) ◽  
pp. 459-467 ◽  
Author(s):  
S. Lambert ◽  
P. Gotteland ◽  
F. Nicot
Keyword(s):  
Experimental Study ◽  
Numerical Model ◽  
Boundary Conditions ◽  
Composite Structures ◽  
Impact Force ◽  
Impact Response ◽  
Rigid Base ◽  
Transmitted Force ◽  
The Impact ◽  
Rockfall Protection

Abstract. Rockfall protection embankments are ground levees designed to stop falling boulders. This paper investigates the behaviour of geocells to be used as components of these structures. Geocells, or cellular confinement systems, are composite structures associating a manufactured envelope with a granular geomaterial. Single cubic geocells were subjected to the impact resulting from dropping a spherical boulder. The geocells were filled with fine or coarse materials and different boundary conditions were applied on the lateral faces. The response is analysed in terms of the impact force and the force transmitted by the geocell to its rigid base. The influence on the geocell response of both the fill material and the cell boundary conditions is analysed. The aim was to identify the conditions resulting in greatest reduction of the transmitted force and also to provide data for the validation of a specific numerical model.

scholarly journals A Design Method to Induce Ductile Failure of Flexural Strengthened One-Way Reinforced Concrete Slabs

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7647
Author(s):  
Huy Q. Nguyen ◽  
Tri N. M. Nguyen ◽  
Do Hyung Lee ◽  
Jung J. Kim
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Shear Failure ◽  
Design Method ◽  
Concrete Slab ◽  
Ductile Failure ◽  
Reinforced Concrete Slabs ◽  
Failure Loads ◽  
Ultimate Failure ◽  
Rc Slabs

Strengthening existing reinforced concrete (RC) slabs using externally bonded materials is increasingly popular due to its adaptability and versatility. Nevertheless, ductility reduction of the rehabilitated flexural members with these materials can lead to brittle shear failure. Therefore, a new approach for strengthening is necessary. This paper presents a methodology to induce ductile failure of flexural strengthened one-way RC slabs. Ultimate failure loads can be considered to develop the proposed design methodology. Different failure modes corresponding to ultimate failure loads for RC slabs are addressed. Flexural and shear failure regions of RC slabs can be established by considering the failure modes. The end span of the concrete slab is shown for a case study, and numerical examples are solved to prove the essentiality of this methodology.

scholarly journals Impact of rockfalls on protection measures: an experimental approach

2015 ◽  
Vol 15 (4) ◽  
pp. 885-893 ◽  
Author(s):  
J. K. Yuan ◽  
Y. R. Li ◽  
R. Q. Huang ◽  
X. J. Pei
Keyword(s):  
Impact Velocity ◽  
Impact Force ◽  
Incident Angle ◽  
Drop Height ◽  
Current Standard ◽  
Protection Measures ◽  
Buffer Material ◽  
Cushion Layer ◽  
Study Laboratory ◽  
The Impact

Abstract. The determination of rockfall impact force is crucial in designing protection measures. In the present study, laboratory tests are carried out by testing the weight and shape of the falling rock fragments, drop height, incident angle, platform on the slideway, and cushion layer on the protection measures to investigate their influences on the impact force. The test results indicate that the impact force is positively exponential to the weight of rockfall and the instantaneous impact velocity of the rockfall approaching the protection measures. The impact velocity is found to be dominated not only by the drop height but also by the shape of rockfall and the length of the platform on the slideway. A great drop height and/or a short platform produces a fast impact velocity. Spherical rockfalls experience a greater impact velocity than cubes and elongated cuboids. A layer of cushion on the protection measures may reduce the impact force to a greater extent. The reduction effects are dominated by the cushion material and the thickness of the cushion layer. The thicker the cushion layer, the greater the reduction effect and the less the impact force. The stiffer the buffer material, the lower the buffering effect and the greater the impact force. The present study indicates that the current standard in China for designing protection measures may overestimate the impact force by not taking into consideration the rockfall shape, platform, and cushion layer.

scholarly journals Theoretical Analysis of Rockfall Impacts on the Soil Cushion Layer of Protective Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Xing Wang ◽  
Yongxu Xia ◽  
Tianyue Zhou
Keyword(s):  
Numerical Simulation ◽  
Energy Conservation ◽  
Penetration Depth ◽  
Impact Force ◽  
Theoretical Method ◽  
Cavity Expansion ◽  
Rockfall Hazards ◽  
Protective Structures ◽  
Cushion Layer ◽  
The Impact

During the Wenchuan Earthquake, with a magnitude of 5.12, collapses and rockfall hazards persisted for a long time after the initial investigations carried out by research fellow S. M. He and his team at the scene of the disaster in October 2008. It is possible that additional incidents of rockfalls in large quantities may continue in the same areas over the next ten to fifteen years. Furthermore, in the vast mountainous region of western China, the topographic relief is evident, and earthquakes occur frequently. Therefore, it is difficult to effectively defend against rockfall hazards. When designing protective structures, the key issue is the analysis of the mechanical response mechanism of the soil cushion layer of the upper cushion when subjected to the impact of rockfall. As such, a theoretical method was used to perform such an analysis. The cavity expansion and energy conservation model were adopted. Analytical solutions for the impact force and penetration depth were then derived. Furthermore, the impact force and penetration depth of rockfall were studied with the LS-DYNA software to obtain values for the impact forces and the penetration depth. Finally, the reliability of the theoretical method was evaluated using the cavity expansion, energy conservation, numerical simulation, Hertz, Japanese, Swiss, Australian, B. S. Guan, tunnel manual, and subgrade methods based on an engineering model. The results show that the cavity expansion and the energy conservation methods yielded consistent results. Meanwhile, the cavity expansion and the energy conservation methods also yielded consistent results with the numerical simulation, Japanese (obtained by laboratory experiment), Swiss (obtained by laboratory experiment), and Australian (obtained by field experiment) methods. The relevant methods and conclusions shall therefore be applied to the design of rockfall protection structure in future investigations.

Impact Response Spectrum for Design of Ship-Bridge Collisions

2014 ◽  
Vol 587-589 ◽  
pp. 1547-1553 ◽  
Author(s):  
Jun Jie Wang ◽  
Zhi Ran Yu
Keyword(s):  
Impact Force ◽  
Response Spectrum ◽  
Degree Of Freedom ◽  
Impact Response ◽  
Amplification Effect ◽  
Spectrum Method ◽  
Time Histories ◽  
Dynamic Amplification ◽  
Force Time ◽  
The Impact

Due to the complexity involved and limited study on the topic, the equivalent static method, adopted in the current codes for structural design of bridges under ship collisions, does not take into account the dynamic amplification effect correctly. An accurate assessment of impact force based on refined numerical simulation is time consuming and is normally too complex for ordinary design procedure. Herein, with reference to the earthquake response spectrum method, an impact response spectrum method, which considers the dynamic amplification effect and is efficient for design, is proposed. Through refined numerical simulations of ship-rigid wall collisions, 81 impact force time histories associated with 9 typical ships under 9 velocities are obtained. The dynamic magnification factor (DMF) of single-degree-of-freedom (SDOF) systems with different periods and damping ratios experiencing the 81 impact force time histories are then studied. The relationship of DMF and period under different damping ratios, i.e. the DMF spectrum, is yielded by statistical analysis, based on which the impact response spectrum is obtained. Finally, the design combination method for multi-degree-of-freedom based on the impact response spectrum of SDOF is discussed for a continuous beam bridge.

Research on Impact Response and Failure Modes of H Section Steel Frame Columns Subject to Blast Loads

2012 ◽  
Vol 204-208 ◽  
pp. 3094-3098
Author(s):  
Yun Fei Liu ◽  
Hong Gang Lei
Keyword(s):  
Failure Modes ◽  
Shear Failure ◽  
Plate Thickness ◽  
Steel Frame ◽  
Impact Response ◽  
Blast Loads ◽  
Steel Columns ◽  
Steel Column ◽  
Impulse Load ◽  
The Impact

Using finite software ANSYS LS/DYNA for simulating the impact response and failure modes of H section steel frame columns subject to blast loads，and loading different load conditions, changing column boundary conditions and web plate thickness. Conclusion: the failure model of steel columns changes with the change of load form,steel columns will be easy to occur shear failure in the end by the dynamic load, and the flange will be easy to occur bucking failure in local by impulse load; In the case of same size and web thickness, increase the web thickness can reduce the deformation of column effectively, improve the capability of H section steel column resist the blast load.

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