Energy Absorbing Concrete for Impact Loading

Energy Absorbing Concrete for Impact Loading

R. Sri Ravindrarajah  and M. C. Lyte

Abstract
Two structural grades, compressive strength of 30 and 45MPa, normal weight concrete and lightweight polystyrene concrete were tested for their impact response under 75kg weight test through 462mm drop. The impact response was monitored through load-time plot and the results were used to characterise the concrete for its impact response. Peak load and contact time are considered as important measurable quantities in identifying the energy absorbing capacity of concrete. The results showed that polystyrene aggregate concrete outperformed the normal weight concrete in its impact resistance due to inherent energy absorbing quality of embedded expanded polystyrene beads. Under the tested impact loading condition, polystyrene concrete having the compressive strength of 30MPa showed 28% increase in the contact time and 18% reduction in the peak load compared to the similar grade normal weight concrete

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Design of concrete structures to resist accidental impact

Design of concrete structures to resist accidental impact

Introduction-problems
Civil engineers encounter impact problems on a greavta riety of occasions
vehicle impact against bridgep iers and columns
rockshelter structures over roads in mountain areas
ship impact on sea platforms
aeroplane crashes on nuclear power plants
gas explosions in buildings Civil engineers are very often not familiar with structural dynamichse nacned such problems usually cause them great difficultiesIt. was, therefore, one of the author's intentions, during thlaes t 7 years of impact research,t o presenthis findings in a way that civil engineers can easily handle Because of the inherent non-linearities which result from the constitutive laws governing reinforced concrete, the need for rather exact predictions
compared with experiments does not necessarily lead to simple dynamics

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Behaviour of high-strength concrete plates under impact loading

Behaviour of high-strength concrete plates under impact loading

S. Murtiadi and H. Marzouk

Abstract
This research programme was carried out to investigate the behaviour of high-strength concrete plates subjected to impact loading. The research includes an experimental investigation on 16 concrete plates. A rigid projectile was used to apply the impact load to the tested reinforced concrete specimens. The rigid projectile consisted mainly of a solid steel cylinder with 220 kg mass and 304´5 mm dia. contact area, dropped at variable heights of up to 4 m. The structural behaviour with respect to deflection, concrete and steel strains, failure mode and energy absorption was examined. The effects of dynamic loading, concrete strength, reinforcement ratio and support pattern were the test parameters. Based on the experimental test results, it has been found that at a test velocity of 4±7 m=s the impact load is about twice the static punching shear capacity estimated from code provisions

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CONCRETE FLOOR SLABS ON GRADE SUBJECTED TO HEAVY LOADS

CONCRETE FLOOR SLABS ON GRADE SUBJECTED TO HEAVY LOADS

Purpose
This manual prescribes the criteria for the design of concrete floor slabs on grade in buildings for heavy loads and is applicable to all elements responsible for military construction. Heavy loads in buildings such as warehouses include moving loads, stationary live loads, and wall loads.

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A New Drop-Weight Impact Machine for Studying Fracture Processes in Structural Concrete

A New Drop-Weight Impact Machine for Studying Fracture Processes in Structural Concrete

X. X. Zhang, G. Ruiz† and R. C. Yu

ABSTRACT:
 This paper describes the main characteristics of a new drop-weight impact machine that has been specifically designed for studying the dynamic mechanical behaviour of structural concrete samples. Such a type of equipment has been used to generate simple and measurable fracture processes under moderate-to-fast loading rates, contrary to blast chambers, which produce complicated crack patterns that are difficult to analyse. The machine consists of two main parts, the mechanical structure and the data acquisition system. The former is just a hammer, guided by two robust columns, which can impact the specimen with energy up to 7860 J. The latter consists of piezoelectric force sensors, accelerometers and optical fibre photoelectric sensors plus oscilloscopes and signal conditioners. The paper also presents the results of some preliminary tests on plain-notched specimens that show the sensitivity of the work of fracture of a high-strength concreteto the loading rate

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Investigation and Analysis of Ogive-Shape Nose Steel Projectile into Concrete Target

Investigation and Analysis of Ogive-Shape Nose Steel Projectile into Concrete Target

Khodadad VAHEDI, Mohammad LATIFI

Abstract
Penetration of projectile into concrete target is of high interest to both civilian as well as applied scientist.The penetration process is highly complex and due to it interdisciplinary nature, most of the works in this respect are experimental. High cost of experimentation has forced many of the investigators to rely on simple analytical and engineering models. Recent investigations rely heavily on simulation processes using available software tools.The aim of this paper is to simulate the penetration of a high velocity ogive-shape nose steel projectile into concrete target. The crater depth is also obtained using analytical formula developed by Forrestal. The
results of the analytical as well as LS-DYNA simulation are compared with the experimental results of valid sources and a very good agreement is recorded

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Impact Response of Reinforced Concrete Beam and Its Analytical Evaluation

Impact Response of Reinforced Concrete Beam and Its Analytical Evaluation

Kazunori Fujikake; Bing Li; and Sam Soeun

Abstract:
This paper examines the impact responses of reinforced concrete beams through an experimental study and presents an analytical model developed to predict the maximum midspan deflection and maximum impact load, which aids as an important performance index to evaluate the damage levels of RC beams when subjected to impact loadings. The experimental study involves a drop
hammer impact test and investigates the influence of drop height and the effect of the amount of longitudinal steel reinforcement contributes to the response of RC beams. The RC beam specimens used in the experiment comprised of under-reinforced sections provided with sufficient amount of transverse reinforcements to allow for an overall flexural failure. The experimental impact responses
of the RC beams were simulated with two-degree-of-freedom mass-spring-damper system model, in which the loading rate effects were duly considered. The analytical results are in good agreement with the experimental results for the RC beams that exhibited overall flexural failure

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STATIC AND IMPACT BEHAVIOR OF FABRIC REINFORCED CEMENT COMPOSITES IN FLEXURE

STATIC AND IMPACT BEHAVIOR OF FABRIC REINFORCED CEMENT COMPOSITES IN FLEXURE

Mustafa GENCOGLU  and Barzin MOBASHER

Abstract:
Fabric-cement composites developed using the pultrusion production process have
demonstrated impressive tensile and flexural properties. AR Glass and PE fabric reinforced
composites exhibit strain-hardening behavior in addition to tensile strength in the range of 20-
25 MPa and strain capacity of the order of 2-5%. Impact properties were investigated under
three point bending conditions using an instrumented drop weight system. Test parameters
include the fabric type, specimen orientation, and drop height of hammer. Preliminary results
indicate that for the same drop height, the vertical type (beam) specimens are stiffer; however,
they have a lower ultimate deflection and higher load carrying capacity than the horizontal
(plate type) specimens. By increasing the impact energy beyond 5 Joules, the impact strength
of the horizontal specimens made with glass fabrics sharply decreased, while there was no
incremental change in the impact strength of the vertical specimens. Results are compared
with the static flexural tests conducted under closed loop deflection controlled tests.

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Impact Analysis of Concrete Structural Components

Impact Analysis of Concrete Structural Components

A. Rama Chandra Murthy*, G.S. Palani, and Nagesh R. Iyer

Abstract:
This paper presents an overview on the concrete structural components subjected to impact loading. The review includes empirical formulae, analytical models, and numerical simulations. Various empirical formulae on penetration depth, perforation, and scabbing limits as well as their ranges of application have been provided. It has been observed that the information available on the validation of these models is limited. There is wider scope to study the performance of well known empirical formulae. Penetration resistance function play an important role in any analytical model. It has been observed that the major limitation is rigid projectile assumption. There is scope to develop new/improved analytical models to represent projectile characteristics.
The numerical simulation of concrete structural components subjected to impact loads is a complex phenomenon. From the review, it is observed that employing appropriate material model for concrete, equation-of-state, contact algorithm and definition of yield surface plays significant role in the accurate simulation of concrete structural components. There is ample scope to develop improved methodologies in terms of development of material models and contact algorithms, which can be employed in nonlinear explicit finite element analysis of concrete structural components subjected to impact loading

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Instrumented drop weight impact test set-up design and assessment

Instrumented drop weight impact test set-up design and assessment

Bilal El-Ariss

Abstract:
Instrumented impact tests are useful to characterise the dynamic
behaviour of materials as they provide continuous load, strain and deflection
histories of an impact test. When these tests are used for low strength-to-weight
ratio materials like concrete, considerable parasitic effects of inertial loads are
manifested in the test records. With proper choice of the test parameters these
parasitic effects can be minimised. Even with proper choice of the test
parameters, one needs to understand the mechanics of such test set-up in order
to evaluate and isolate inertial effects from the true material response. It is with
this motivation that this paper outlines an analytical model to analyse the
mechanics of an instrumented impact test set-up including damping and inertial
effects associated with the tests and provides guidelines for proper selection of
test parameters for testing tension-weak brittle materials. Good agreement was
found between the test and proposed model analytical results

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Impact properties of steel fibre reinforced concrete in bending

Impact properties of steel fibre reinforced concrete in bending

A. E. Naaman* and V. S. Gopalaratnam f

 

SYNOPSIS
The effects of strain rate of loading including impact on the bending properties of steel fibre reinforced mortar are studied using an instrumented drop-weight impact machine. Particular emphasis is put on clarifying the influence of the fibre reinforcing parameters and matrix strength. The parameters investigated in the experimental programme include three volume fractions of fibres (1%, 2% and 3%), three fibre aspect ratios (47, 62 and 100, two mortar mixes and four strain rates of loading ranging from 0.5 x 10 -5 to 1.2 strains per second. It is found that depending on the fibre reinforcing parameters the energy absorbed by the composite at static loading rates can be one to two orders of magnitude higher than that of the unreinforced matrix. Moreover, up to a three-fold increase is observed in the modulus of rupture and the energy absorbed by the composite when the strain rate increases from 0.5 x10-5 to 1.2 strain per second

 

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