Development of Analytical Models for RC Columns under Blast loading Considering Strain Rate Effects

One of the most important examples of transverse excitation of beam-columns is structural reinforced concrete (RC) columns under blast loading. Under accidental or intentional explosions next to the buildings, external columns are the most critical and vulnerable structural elements. In this paper, tow analytical approaches are used to predict the first maximum dynamic response of rectangular RC column under simultaneously effect of axial force and transverse blast loading. The first analytical model is based on continuous formulation of Euler-Bernoulli beam theory and the second model is a single degree of freedom (SDOF) approach. Both of the approaches consider strain rate effects on nonlinear behavior of materials (concrete and steel reinforcement) and secondary effects of P-δ. Results of proposed models for predicting the first maximum lateral response of column under impulsive, dynamic and quasi-static loading regimes are compared to the results of nonlinear finite element analysis. The outcomes indicate undesirable discrepancies under high levels of axial force and quasi-static loading conditions. Nevertheless, in the impulsive and dynamic regimes  and moderate and low axial load ratio, the differences in the results are acceptable. Afterward, the analytical models are used to evaluate Pressure-Impulse (P-I) diagram for RC column under blast loading and effective factors on it

EPIDEMIOLOGY OF VIRAL GASTROENTERITIS IN IRAN

Viruses are prominent causative agents of acute gastroenteritis in children <5 years of age per year.(1) In the present review, all viral gastroenteritis studies in Iran were assessed, and the mean prevalences of rotaviruses, noroviruses, enteric adenoviruses, sapoviruses and astroviruses associated with acute gastroenteritis were 39.9%, 6%, 5.7%, 4.2% and 2.7%, respectively. In 2 studies, human bocavirus and human parechovirus were detected in 21.8% and 23.7% of children with acute gastroenteritis, respectively

Laboratory Study of High-Resistance Laterite-Based Geopolymer Bricks

A high amount of energy is required to produce different types of clay and sand-lime bricks, and a huge amount of carbon dioxide is released into the atmosphere. Also, brick waste from the destruction of dilapidated buildings pollutes the environment. Application of pozzolanic sources containing aluminosilicate and alkaline activators can be beneficial in production of geopolymer bricks, which do not need to be baked in a furnace and can be recycled. A laterite-based geopolymer brick mix design was introduced in this study as an environmental-friendly material. This type of brick is produced using available and cheap raw materials without the need for high furnace heat. The raw materials included laterite soil as aluminosilicate, laterite aggregate filler passed through sieve No. 8 and an alkaline activating solution with different concentrations. The effect of sieve size for laterite soil screening on the compressive strength of these brick samples was investigated. The results showed that the compressive strength of the prepared bricks here was much higher than the recommended standards for construction bricks and was similar to those of high-resistance bricks. The size of laterite soil sieves had a significant effect on the compressive strength of geopolymer brick samples. The percentage of water absorption of the bricks with different concentrations of alkali activating solution was also within the recommended range for construction bricks

A Predictive Model for the Strength of a Novel Geopolymer Construction Material Produced by Autoclaved Aerated Concrete Waste

Carbon dioxide emission and consumption of large amounts of natural resources are the environmental hazards observed in the production process of various commonly used construction materials, like Portland cement and clay bricks. Also, debris from the demolition of old buildings and disposing of the waste of construction material factories also cause environmental pollution. Producing environmentally friendly geopolymer materials with recycling construction wastes containing aluminosilicate resources and alkaline activators could be an effective method for reduction of environmental hazards. This paper is an innovative feasibility study of geopolymer material production using the waste autoclaved aerated concrete (AAC) powder. Here, a mix of AAC powder together with activator solution containing sodium hydroxide and sodium silicate at different concentrations was used to prepare the geopolymer mortar samples. The specimens were oven-cured at different temperatures. The effects of sodium hydroxide concentration and curing temperature on the compressive, tensile, and flexural strengths, as well as water absorption of the samples, were investigated. The main contribution of this study is the feasibility of the successful fabrication of geopolymer material based on AAC waste powder with desirable mechanical properties. Namely, the compressive strength of the base AAC blocks used here was 3 MPa and the maximum strength of the produced geopolymer material using the AAC powder was about 21 MPa. The test results were used to develop a model to predict the compressive strength of the proposed geopolymer AAC material to the effective parameters by Gene Expression Programming. The model predictions were confirmed using an extra series of test results implemented by the authors

Intra-peritoneal and intra-rectal immunogenicity induced by rotavirus virus like particles 2/6/7 in mice

We previously developed virus like particles of rotavirus (RV) with VP2, VP6, and VP7 proteins (VLP2/6/7) using stable High-five cell line. To evaluate the immunogenicity of our construct, we assessed the humoral and cytokine responses induced by VLP2/6/7 in BALB/c mice immunized intra-peritoneally and intra-rectally. Enzyme-linked immunosorbent assay (ELISA) and Relative quantitative (RQ) Real-time PCR were used to evaluate the antibody (IgG and IgA) levels in serum and mRNA levels of IL-6, IL-10 and IFN-gamma in spleen cells, respectively. Our results showed that VLP2/6/7 is capable of intra-peritoneal (I.P.) and intra-rectal (I.R.) induction of serum IgG and IgA responses. IgA was detected in fecal samples of immunization groups by I.P. and I.R. routes. Interestingly, I.R. route induced higher IgA titer compared with I.P. route which was statistically significant. Moreover, mRNA levels of IL-6 and IFN-gamma were significantly elevated in mice immunized intra- peritoneally with VLP2/6/7 compared to control group. As such, the mean change was 7.4 (P < 0.05) and 14.8 (P < 0.001) for IFN-gamma and IL-6, respectively. Likewise, the same pattern was found when mice were immunized intra-rectally. Although elevated, the difference in the mean change for IL-10 was not statistically significant when compared to control group. Our findings indicated that VLPs constructed via a stable insect cell line are able to induce both humoral and cellular responses, a similar pattern as observed after immunization with live RVs. (C) 2014 Elsevier Ltd. All rights reserved

Investigation of Axial Strengthened Reinforced Concrete Columns under Lateral Blast Loading

Different factors can affect blast response of structural components. Hence, experimental tests could be the best method for evaluating structures under blast loading. Therefore, an experimental explosion loading has been done on RC members by the authors. Four RC components, with identical geometry and material, with and without axial load were imposed to air blast. Observed data of the members’ response under blast loading was used for validation of finite element modeling process using ABAQUS software. With respect to complexity, limitations, and high costs of experimental tests, analytical studies and software modeling can be good alternatives. Accordingly, in this paper, the behavior of 6 different models of normal and strengthened RC columns under blast loading was evaluated using ABAQUS. Strengthening configurations considered here were designed for enhancing axial capacity of RC columns. Therefore, we can investigate the effectiveness of axial strengthening of column on its blast resistance capacity and residual axial strength. The considered strengthening methods were different steel jacket configurations including steel angle, channel, and plate sections. The results showed that retrofitting significantly improves blast performance of the columns. Moreover, residual strength capacity of the columns strengthened with steel channel is higher than the other models

Estimation of RC columns’ response under the effect of lateral blast loading by SDOF method and comparison with FEM

In most of the structural blast-resistant designs and analysis single degree of freedom (SDOF) method is used. Generally, for this method flexural response of the structural members is considered but in axial loaded members, secondary moments (P-δ effects) are also very important. In the case of columns of building structures, which mostly bear significant axial loads, ignoring P-δ effects under lateral blast loading can be very risky. This paper describes a simple way for taking into account P-δ effects and also the effects of high strain rates (which is very important in severe dynamic loading) in SDOF analysis of reinforced concrete columns under simultaneous axial load and lateral blast loading. The resulting responses are compared with explicit finite element analysis using LS-DYNA hydro-code. Proposed SDOF equation of motion is numerically calculated and secondary moment and high strain rate effects are included within the calculation procedure. Secondary moments due to P-δ effects have been considered as equivalent lateral load and strain effects are introduced to the model by dynamic increasing factors for concrete and steel materials. Based on the main results, estimated response of RC column under blast loading using SDOF method has acceptable accuracy compared to LS-DYNA analysis results

Laboratory Study of High-Resistance Laterite-Based Geopolymer Bricks

A high amount of energy is required to produce different types of clay and sand-lime bricks, and a huge amount of carbon dioxide is released into the atmosphere. Also, brick waste from the destruction of dilapidated buildings pollutes the environment. Application of pozzolanic sources containing aluminosilicate and alkaline activators can be beneficial in production of geopolymer bricks, which do not need to be baked in a furnace and can be recycled. A laterite-based geopolymer brick mix design was introduced in this study as an environmental-friendly material. This type of brick is produced using available and cheap raw materials without the need for high furnace heat. The raw materials included laterite soil as aluminosilicate, laterite aggregate filler passed through sieve No. 8 and an alkaline activating solution with different concentrations. The effect of sieve size for laterite soil screening on the compressive strength of these brick samples was investigated. The results showed that the compressive strength of the prepared bricks here was much higher than the recommended standards for construction bricks and was similar to those of high-resistance bricks. The size of laterite soil sieves had a significant effect on the compressive strength of geopolymer brick samples. The percentage of water absorption of the bricks with different concentrations of alkali activating solution was also within the recommended range for construction bricks

Investigation of Behavior of Masonry Walls Constructed with Autoclaved Aerated Concrete Blocks under Blast Loading

Autoclaved aerated concrete (AAC) blocks have widespread popularity in the construction industry. In addition to lightness, these materials have other advantages, including fire resistance, low acoustic and thermal conductivity, ease of cutting and grooving, and simple transportation. Since the behavior of AAC under severe dynamic loading conditions such as blast loads has not been adequately studied in the literature, in the current paper, the behavior of masonry walls constructed with AAC blocks was evaluated under blast loading. In this study, after performing experimental testing on materials and obtaining their compressive, tensile, and shear strength values, the finite element (FE) models of AAC-based masonry walls were created in the ABAQUS/Explicit nonlinear platform. Three different wall thicknesses of 15, 20, and 25 cm were simulated, and the models were analyzed under a lateral explosion caused by 5 and 7 kg of TNT at the stand-off distances of 2, 5, and 10 m from the wall face. The stress distributions, displacement responses, adsorbed energy, and crack propagation pattern were investigated in each case. The results showed the inappropriate behavior of these materials against explosion loads, especially at shorter distances and on walls with less thickness. The outcome gives valuable information to prioritize these walls for possible blast strengthening.Applied Science, Faculty ofNon UBCCivil Engineering, Department ofReviewedFacult