Empirical equation and experimental validation of shear parameters for high strength concrete (HSC)

With many benefits of the High Strength Concrete (HSC) the more brittle behavior which leads to sudden failure makes it important for proper understanding of its behaviour and safe and efficient estimation of capacities. Research on the behavior of HSC has been extensively carried out since last decade. High strength concrete has higher tensile strength hence a higher cracking shear can be expected. This paper analyses the different international standards available for estimating concrete’s component of shear strength for RCC beam. Different important factors mainly strength in compression, steel reinforcement (dowel action), ratio of shear span and depth, size effect i.e. depth along with the aggregate type (density of concrete) contributing to shear stress (Tc) of concrete has been also analyzed and thereafter, an equation has been proposed to compute or predict Tc value for concrete of both normal and higher grade or strength. The proposed equation has been validated by experimental results wherein 12 RCC beams (with and without reinforcement for shear) were cast and tested to fail in shear. The experimental results validated the proposed equation with considerable factor of safety keeping in view the sudden and brittle nature of failure in concrete in case of shear.

Empirical equation and experimental validation of shear parameters for high strength concrete (HSC)

With many benefits of the high strength concrete (HSC) the more brittle behaviour that leads to sudden failure makes it important for proper understanding of its behaviour and safe and efficient estimation of capacities. Research on the behaviour of HSC has been extensively carried out since last decade. HSC has higher tensile strength hence a higher cracking shear can be expected. This paper analyzes the different international standards available for estimating concrete’s component of shear strength for reinforced cement concrete (RCC) beam. Different important factors mainly strength in compression, steel reinforcement (dowel action), ratio of shear span and depth, size effect i.e. depth along with the aggregate type (density of concrete) contributing to shear stress (Tc) of concrete has been also analyzed and thereafter, an equation has been proposed to compute or predict Tc value for concrete of both normal and higher grade or strength. The proposed equation has been validated by experimental results wherein 12 RCC beams (with and without reinforcement for shear) were cast and tested to fail in shear. The experimental results validated the proposed equation with considerable factor of safety keeping in view the sudden and brittle nature of failure in concrete in case of shear.

UTILIZATION OF GRAPHENE OXIDE IN BUILDING MATERIALS

Cement-based materials (CBM) is one of the most commonly used building materials. Due to their brittle nature (sudden failure, low tensile strength, low resistant to crack), CBMs were modified through the addition of various traditional fillers/ reinforcement such as fibres and supplementary cementutious materials. Advanced modifiers/fillers such as Graphene-based nanomaterials (GBM) were utilized due to their superior properties in upgrading properties of CBM. GBM have been firstly used to enhance various polymeric matrices for storage energy, sensors and bio-applications. Following that, GBM were utilized in CBM with remarkable improvements in properties. In the current paper, an overview on the synthesis and structure of one type of GBM; namely graphene oxide (GO) was presented. The impact of GO on properties of CBM was addressed. One of the most observations from the highlighted published work was that the enhancements in CBM properties were linked to the uniform dispersion of functionalized GO and template effect of GO in CBM. Although GO with its attractive properties in upgrading properties of CBM, the usage of GO in construction industry is still not at the same demand level as in other applications and further investigations are needed in this regard.

SUDDEN FAILURE OF VENTILATION BY ANAESTHESIA WORK STATION DURING SURGERY: A CASE REPORT

We encountered a case with sudden and complete interruption of fresh gas ow in anesthesia workstation. On inquiry, it was found out that there was water in the medical gas pipeline system and a simultaneous malfunction of the dryer mechanism that lead to this condition. This case report emphasizes the importance of understanding the capabilities and limitations of the drager machine as well as of any anesthesia workstations being used to administer anaesthesia. In addition, this demonstrates the importance to being able to provide immediate backup ventilation in case of 1 ventilator failure.

Effects of Using Corn Cover Fibers on Some Mechanical Properties of Concrete

This investigation aims to use corn cover as natural fibers in concrete mixes to improve some mechanical properties like compressive strength, tensile strength, and flexural strength. using any type of fiber in concrete, in general, can improve the tensile and flexural strength of concrete. Concrete is weak in tension, so using fibers such as natural fibers like trunk fibers or industrial fibers such as steel fibers can improve tensile, the flexural strength of concrete and that may be decreasing the use of steel reinforcement in concrete, and also fibers can improve toughness and ductility of concrete because of its work inside the concrete that can reduce the propagation of cracks under loading. This study shows slight improvement on compressive strength by using fibers, but high increments in flexural strength, the optimum ratio of corn cover fibers was 2.5% by weight of cement which gives the highest values in compressive strength and flexural strength. compressive strength increased from (31.2 to 35.9) MPa (about 15% increment), increment for flexural strength was 70.6% for the optimum fibers content and the failure by using corn fibers was a ductile failure compared with plain concrete that gives sudden failure under flexure load, also tensile strength increased by using fibers, more fibers content beyond or more than 2.5% give lower values for the mechanical properties.

A new warranty policy for heterogeneous items subject to monotone degradation processes

A new renewable warranty policy is suggested that increases the probability of its success and can decrease the corresponding costs for certain ranges of parameters. It deals with heterogeneous populations of items from two subpopulations (‘weak’ and ‘strong’) and is aimed at elimination and further replacement of weak items after screening at some optimal time. This elimination is performed when degradation described by the corresponding mixed degradation process reaches some optimally predetermined level. Probabilistic and cost analyses of the model are performed and the illustrative example is presented. It is shown that the proposed warranty policy with inspection outperforms the conventional one in a probabilistic sense. Furthermore, the proposed policy becomes economically beneficial especially when the additional penalty cost caused by a sudden failure is large.

When diamniotic twins suddenly become monoamniotic twins: spontaneous septostomy of the dividing membrane

In twin pregnancies, amnionicity and chorionicity are crucial as they strongly determine prenatal and perinatal management. First trimester ultrasound allows a highly reliable diagnosis of amnionicity and chorionicity, making it an internationally accepted standard in antenatal care. However, in rare cases, amnionicity can change from diamniotic to monoamniotic throughout pregnancy, substantially impacting perinatal management. We report the case of a confirmed monochorionic diamniotic twin pregnancy with a diagnosis of spontaneous septostomy of the dividing membrane (SSDM) at 28 weeks of gestation, resulting in a pseudomonoamniotic pregnancy. Even though SSDM is a rare condition and its sonographic diagnosis might be challenging, it should be considered if, in a known diamniotic pregnancy, there is a sudden failure to visualise the intertwin membrane truly separating both twins.

The Role of Action Potential Waveform in Failure of Excitation Contraction Coupling

Excitation contraction coupling (ECC) is the process by which electrical excitation of muscle is converted into force generation. Depolarization of skeletal muscle resting potential contributes to failure of ECC in diseases such as periodic paralysis, ICU acquired weakness and possibly fatigue of muscle during vigorous exercise. When extracellular K+ is raised to depolarize the resting potential, failure of ECC occurs suddenly, over a range of several mV of resting potential. While some studies have hypothesized the sudden failure of ECC is due to all-or-none failure of excitation, other studies suggest failure of excitation is graded. Intracellular recordings of action potentials (APs) in individual fibers during depolarization revealed that APs do not fail in an all-or-none manner. Simultaneous imaging of Ca2+ transients during depolarization revealed failure over a narrow range of resting potentials. An AP property that closely correlated with the sudden failure of the Ca2+ transient was the integral of AP voltage with respect to time. We hypothesize the close correlation is due to the combined dependence on time and voltage of Ca2+ release from the sarcoplasmic reticulum. The quantitative relationships established between resting potential, APs and Ca2+ transients provide the foundation for future studies of depolarization-induced failure of ECC in diseases such as periodic paralysis.

Improving the navigational preparation of a bridge crew for entering/leaving a port, including activities in case of emergency

Statistical analysis of the causes of ship accidents showed that 10 % of accidents are due to the influence of irresistible force, about 15 % are the result of technical imperfection and sudden failure of ship equipment, and the remaining 75 % account for the «human factor» regardless of the cause of the accident. A detailed analysis of the causes of accidents reveals that they are caused by the actions of individuals, dominated by organizational errors by a group of operators in the preparation and execution of the maneuvering control process. At the same time, there is a gap between the complexity of modern equipment and the psychological capabilities of the human operator as an element of the human-machine system. Analysis of accidents in the Bugsky-Dnestrovsky Liman Canal over the past 20 years has shown that 58.5 % of accidents occurred in the dark and under conditions of limited visibility. There were two causes of accidents: grounding and allision, 84.3 %; collisions, 28.8 %. This indicates the insufficient preparation of bridge crews for navigating the canal. This paper has considered a procedure of bridge crew navigation training for planning safe motion coordinates while entering/leaving a port along the trajectory points, as well as actions in case of a pre-emergency and techniques to predict it. The coordinates of the travel points are determined at the intersection of rectilinear segments of the recommended safe rectilinear path on a chart. It is a relevant task to use new methods of planning the path and controlling the movement along it, taking into consideration the area for maneuvering, maneuverable properties of the vessel, as well as external influences, for timely detecting the deviation of parameters from those planned. The calculation of the planned coordinates is performed for the center of gravity of the vessel for the characteristic points of the path of movement (the beginning and end of a turn, the onset of braking) and trajectory points (rectilinear segments of the path through 0.2 cables, and curvilinear sections through 10 degrees). Coordinates of the assigned path are represented in the form of the linear matrices of the path rectilinear and curvilinear sections. The navigational motion control system consists of the devices to automatically determine deviations from planned coordinates and decision support systems to correct deviations detected. The proposed method to plan and control motion was investigated by computer simulation, the test was carried out under natural settings. Their results showed that the calculated optimal assigned trajectory enables accident-free guidance of the center of gravity along the predefined path by ship’s control means and meets the established criteria of optimality. The proposed method could be used in the development of controls for automated vessels and is the only possible one for vessels with unattended operation

The Research on Delay Propagation of Urban Rail Transit Operation under Sudden Failure

With the increase and extension of urban rail transit lines, networked operation has become an inevitable trend of rail transit operations. Once an emergency occurs, it will cause operational delays; in serious cases, it may further lead to group safety incidents. Firstly, the sudden failure of rail transit is defined, statistical calculation is made according to the accumulated failure data, and then the sudden failures and average processing time are quantitatively calculated. Secondly, the time delay and propagation under the state of sudden failure are analyzed, on the basis of which the propagation and dissipation of time delay based on the single station failure cellular automata model and SIR model network based on multistation fault delay propagation are constructed. Finally, the reliability and accuracy of the model are verified by a case of rail transit in a city. The scheme in this paper can be used to estimate the scope of time and space delay under the sudden failure of rail transit and can provide the basis for the adjustment of traffic organization scheme and evacuation of passenger flow under the sudden failure.