Development of Computational Models and Input Sensitivity Study of Polymer Reinforced Concrete Masonry Walls Subjected to Blast
Development of Computational Models and Input Sensitivity Study of Polymer Reinforced Concrete Masonry Walls Subjected to Blast

Author:

Publisher:

Published: 2004

Total Pages: 170

ISBN-13:

DOWNLOAD EBOOK

Computational models were developed and used to simulate polymer reinforced masonry walls subjected to blast loading and the models were used to understand the response of the structure. LS-DYNA, a nonlinear finite element solver, was used. Model development challenges were considered, and appropriate input parameters were determined. With these pedestal values, a baseline model of one unit width of concrete masonry block was developed, and the response under two load conditions was studied. Dimensional and mechanical variants involved in the system were varied to study their effect on wall behavior. The effects of door and window openings on the performance of the polymer reinforcement were evaluated. This report also presents an analysis of strain rate that occurs in the polymer coating and results were compared to theory-based closed form solutions. Finally, the static nonlinear capabilities of LS-DYNA were used to describe the static resistance of the system, and a theoretical description of a simply supported membrane subjected to pressure load is provided and compared with nonlinear finite element results.

Concrete Solutions 2014
Concrete Solutions 2014

Author: Michael Grantham

Publisher: CRC Press

Published: 2014-08-18

Total Pages: 838

ISBN-13: 1138027081

DOWNLOAD EBOOK

The Concrete Solutions series of International Conferences on Concrete Repair began in 2003 with a conference held in St. Malo, France in association with INSA Rennes. Subsequent conferences have seen us partnering with the University of Padua in 2009 and with TU Dresden in 2011. This conference is being held for the first time in the UK, in association with Queen’s University Belfast and brings together delegates from 36 countries to discuss the latest advances and technologies in concrete repair. Earlier conferences were dominated by electrochemical repair, but there has been an interesting shift to more unusual methods, such as bacterial repair of concrete plus an increased focus on service life design aspects and modelling, with debate and discussion on the best techniques and the validity of existing methods. Repair of heritage structures is also growing in importance and a number of the papers have focused on the importance of getting this right, so that we may preserve our rich cultural heritage of historic structures. This book is an essential reference work for those working in the concrete repair field, from Engineers to Architects and from Students to Clients.

Blast Simulator Wall Tests
Blast Simulator Wall Tests

Author: Michael G. Oesterle

Publisher:

Published: 2009

Total Pages: 655

ISBN-13:

DOWNLOAD EBOOK

Loads generated in explosions that result from terrorist attacks and industrial accidents create devastating hazards for buildings and their occupants. The objective of this dissertation is to develop design guidelines and methodologies for protective/hardening strategies used to mitigate blast hazards in reinforced concrete and concrete masonry walls. Commonly, guidelines and methodologies are developed from experimental data. Field testing with live explosive is a reliable experimental method for demonstrating the performance of blast resistant concepts, but it is expensive, time consuming, and often produces low quality data. Static testing is another experimental method that allows researchers to clearly observe behavior and failure modes of structural components; however this too is limited because it cannot account for the rate effects associated with blast loads. The UCSD Blast Simulator was developed to offers an alternative method for testing structures to loads generated in an explosion without the difficulties and limitations associated with field and static testing. For this dissertation, tests were conducted with the blast simulator to study reinforced concrete walls protected with frangible panels, concrete masonry walls strengthened with carbon fiber reinforced polymer composite, and unreinforced masonry walls retrofitted with polyurea catcher systems. The objective of the dissertation was achieved through a succession of tasks that included; the development of a test protocol, validation and implementation of numerical models to predict loads delivered to specimens during blast simulator tests, development of method to correlate blast simulator loads to air blast loads, generation of high quality data on specimens with mitigation strategies for validation of numerical models to predict response of hardened/protected reinforced concrete and concrete masonry walls, and investigation of design variables with parametric studies. The investigation of concrete masonry walls demonstrated that the addition of carbon fiber reinforced polymers can increase the resistance to blast loads, but may result in a brittle failure mode. The study of reinforced concrete walls showed that frangible panels can improve the response by adding mass to the system. Finally, the research performed on unreinforced masonry walls with polyurea catcher emphasized the need for proper connection detailing.

Simplified Analytical Tools for Impact and Impulsive Loading Analysis of Reinforced Concrete Structures
Simplified Analytical Tools for Impact and Impulsive Loading Analysis of Reinforced Concrete Structures

Author: Andac Lulec

Publisher:

Published: 2017

Total Pages:

ISBN-13:

DOWNLOAD EBOOK

The analysis of reinforced and prestressed concrete elements under blast and impact loading is drawing the interest of many researchers due to increasing number of natural or human-made hazards that require attention. The analysis methods used are mainly based on either simplified single degree-of-freedom methods or highly sophisticated and complex hydrocodes. Although single degree-of-freedom methods are commonly used by designers for practical reasons, they are incapable of providing detailed results such as deformed shapes and crack maps. Additionally, since they require simplification of the structure to a single degree-of-freedom system, they are difficult to apply to complex geometries. On the other hand, hydrocodes overcome the limitations associated with the simplification of the structure. However, they require highly detailed models which require significantly increased modelling and computational time. Moreover, the accuracy of blast and impact analyses with hydrocodes heavily relies on the material input parameters which are not commonly known. Thus, there remains a need for accurate, simplified and reliable tools for analysis of reinforced and prestressed concrete subjected to blast and impact loading. The VecTor family of nonlinear finite element programs, using a macro-element smeared rotating crack approach, has been shown to be accurate in predicting the response of shear-critical structures under quasi-static conditions. In this study, two members of this suite, VecTor3 and VecTor6, were adapted for the blast and impact analyses of reinforced and prestressed concrete structures in 3D and axisymmetric conditions, respectively. The results obtained from the simulations were close to those experimentally observed. Additionally, a semi-analytical formula for the prediction of perforation velocity from missile impact was developed. The formula, which is based on the Modified Compression Field Theory, considers the influence of longitudinal and shear reinforcement in the target differently from other commonly used empirical formulae. The formula was validated with numerous missile impact data available in the literature, and good accuracy was found.

Statistically-based Air Blast Load Factors Based on Imprecised Parameter Statistics for Reinforced Concrete Wall
Statistically-based Air Blast Load Factors Based on Imprecised Parameter Statistics for Reinforced Concrete Wall

Author: Tanit Jaisa-ard

Publisher:

Published: 2015

Total Pages:

ISBN-13:

DOWNLOAD EBOOK

The determination of acceptable air blast load factors for Load and Resistance Factor Design (LRFD) is complicated due to highly variable loads and to non-linear and rate dependent material and structural response that can result. This has resulted in the use of blast load factors that are set equal to unity since load uncertainty, which is typically used as a probabilistic basis for developing LRFD load factors, is not considered. A precise distribution of random variables also has been required for load and resistance factor determination in LRFD. However, in the case where their distributions are uncertain due to insufficient data, such as for blast events, assumptions will be made that overlook uncertainties that should be accounted in the derivation. In this study, a combination of Response Surface Metamodels (RSM), Monte Carlo Simulations (MCS), and Probability Box (P-Box) that incorporate nonlinear finite element models were used to derive statistically-based blast load factors for LRFD. Load factor development centered on a case study involving a reinforced concrete (RC) cantilevered wall subjected to free air blasts. The resulting load factor was found to be 1.41 when precise parameter statistics were assumed. This blast load factor was then used to design a new RC cantilevered wall and this new wall was found to have its reliability close to the target value. However, when parameter uncertainty was considered, the resulting load factors based on P-Box representation were found to be a range between 1.16 and 1.74, indicating that there was a possibility that the load factor of 1.41 obtained from precise parameter statistic assumptions could be unreliable.

Pressure-impulse Diagrams Using Finite Element Analysis for Reinforced Concrete Columns Subjected to Blast Loading
Pressure-impulse Diagrams Using Finite Element Analysis for Reinforced Concrete Columns Subjected to Blast Loading

Author: Rasekh Rahim Zadeh

Publisher:

Published: 2011

Total Pages: 138

ISBN-13:

DOWNLOAD EBOOK

Reinforced concrete is one of the prime building materials widely used to construct protective structures. One of the purposes of this project is to study the non-linear response of reinforced concrete structures when subjected to impact and blast loading. The study is conducted at two levels: material level and structural level. At the material level, the strength enhancement of three material models of LS-DYNA subjected to high strain rates is studied. The effects of strain rate and lateral inertial confinement on the strength enhancement are investigated. Recommendations are made to improve the accuracy of the results of future numerical simulations for reinforced concrete structures subjected to loads having high strain rates. At the structural level, Pressure-Impulse diagrams for reinforced concrete columns that have four configurations of transverse reinforcement are developed. Finite element modeling in LS-DYNA is used to analyze the structures and calculate the damage level for each blast event. The developed Pressure-Impulse diagrams are used to study the effect of confinement on the reduction of damage level at impulsive, dynamic, and quasi-static loading conditions.