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Abstract
The present research studies the effect of adding sugar factory waste sugarcane molasses as an alternative to chemical inhibitory additives manufactured on concrete cast during hot weather in the summer of Iraq. The current study includes a study of the setting time for cement paste and workability for fresh concrete and some mechanical properties of hardened concrete with sugarcane molasses using percentage 0–0.3% of cement weight. The study also included studying the value of pH of concrete to investigate the effect of sugarcane molasses on reinforced concrete. The results showed that the sugarcane molasses can be used by about 0.1% of cement weight for medium projects and between 0.1 and 0.2% for large projects. It was also found that the compression strength increased by about 11.5% and the indirect tensile strength increased by about 7.5 and 7.4% for splitting and flexural test, respectively for concrete mixtures containing 0.2% of sugarcane molasses.
Abstract
Helical concrete columns are a new type of structural members which arose in new twisted buildings to satisfy architectural purposes. Helical concrete columns have a unique geometry which depends on the values of twist angle (ϕ) and the tilt distance of the center of rotation. According to the ACI T1.1R-01:2001 guidelines, a combined effect of axial load and lateral cyclic displacement protocol was applied to twelve specimens. Nonlinear finite element method was used to conduct the analysis and the numerical simulation for the helical reinforced concrete columns. The findings of the study revealed that the value of the buckling load, lateral displacement and the drift angle of helical concrete columns are significantly affected by the tilting distance of the rotation center and the twist angle.
Abstract
Design flood hydrographs are often used to project safe and cost-effective hydraulic structures. This study proposes a system based on a combination of empirical and statistical approaches for constructing synthetic design flood hydrographs, that practitioners can easily apply. The system uses scaled observed seasonal flood hydrographs and respects the dependence structure among the flood peaks, volumes, and durations deduced from the set of seasonal flood hydrographs observed. The method was developed and tested based on data from the Horné Orešany reservoir in Slovakia.
Abstract
In the post-pandemic period, cities are committed to creating healthier and more healing urban environments. In high-density urban environments, urban complexes are increasingly assuming the function of enriching the external space and activating the vitality of cities, and their architecturally oriented public spaces have great potential for the promotion of residents' health. However, current research on public space and health has focused on green spaces and neighborhoods, and has not yet systematically sorted out the pathways that influence how building-oriented public space can contribute to health. In order to fill the gap, this study attempt to establish a model of health-promoting architecturally oriented public space, which can provide a reference for the similar projects.
Abstract
In the last two decades, the utilization of timber in construction has gained increasing attention among researchers and sustainable building designers. Therefore, studies of climate impact on timber structures have been conducted, many of them focusing on the moisture content caused changes in timber. In the present study, four-point bending tests have been performed on three testing groups, containing 30 samples each. The first group has been tested under its natural conditions, while the second and the third groups were fully saturated with water. The third group was glazed with a protection material. The results show the changes in the modulus of elasticity and the modulus of rupture caused by the moisture content increase. In the same time the material behavior changed from brittle to semi-ductile or ductile for some samples.
Abstract
This paper is dedicated to the memory of Dr. Miklós Iványi, who instilled in the authors an appreciation for experimental investigations, which are foundational to understanding material and structural behavior. Timber-concrete composite structures are increasingly adopted for new buildings due to their favorable sustainability parameters and the increased availability of cross laminated timber. For larger spans, however, solid timber floors lead to higher timber volumes and the use of glulam beams may become necessary for a more efficient use of wood. This paper presents laboratory tests of glulam-concrete composite beams and is the first in a series of two papers on investigating the associated failure mechanisms. Three full-scale glulam-concrete beam specimens were studied. The glulam and concrete are monolithically interconnected using a continuous layer of adhesive. Shear reinforcement was added to the glulam beams to allow for failure mode control. Static load tests to failure were conducted along with acoustic emission monitoring to track the progression of the failure. The results indicate that the shear reinforcement of the glulam layer affects the load capacity of the composite beam through shifting the failure from a shear to a tension failure mode. Similar glulam-concrete beams can enable larger span applications for buildings and bridges while maintaining an attractive sustainability performance.
Abstract
Cement and concrete are the most crucial and dominating engineering materials in the construction sector. Cement serves as an excellent binder for concrete and when it is treated under unusual conditions either to satisfy accelerating or retarding requirements by the construction industries, admixtures role comes into the effect. The construction industry has been searching for retarding admixtures and the optimal dosage level, particularly for ready mix concrete applications. Generally the retarding admixtures such as organic retarders (lignosulphonates, hydroxycarboxylic acids and their salts, phosphonates, sugars) or inorganic retarders (phosphonates, borates) were generally used to reduce the speed of the reaction between cement and water by altering the growth of the hydration products and/or limiting the rate of water penetration to the cement particles. The research was still in its infancy stage in terms of determining not just the appropriate dosage amount, but also the ideal retarder materials for the aforementioned uses. In considering this industrial need, an attempt was made on utilizing the usage of sugar in the concrete to study the retarding effect without affecting the strength properties of cement. The sugars usage levels were at 5, 10, 15, and 20% of the usage of cement to investigate consistency, setting time, compressive strength and micro structure properties at the curing age of 7, 14 and 28 days on the mortar specimens. The conclusions of the study reported that setting time was extended with increase of the dosage levels of sugar. However in considering the strength property, less than 5% of sugar dosage level can be better for the application as retarding agent in the industry applications.
Abstract
This paper presents an investigation on a battery-less voltage of Piezoelectric (PZT) V-shape cantilever beam Energy Harvester (EH) using human body vibration. The frequency ranges are walking (0–5 Hz), running (6–10 Hz) and motions (11–15 Hz) for human movement. Pacemaker devices typically require a lower resonant frequency with higher voltage which is powered by batteries. The battery has a limited duration during its working process and the battery is difficult to replace in the human body. To address the aforementioned issue, a V-shape cantilever beam EH has been developed as a solution to overcome these limitations. The cantilever beam was designed in COMSOL Multiphysics software 5.5 version using the Finite Element Analysis (FEA) method for experimental investigations followed by three categories of frequency ranges of the human body. The simulation results showed that the generated battery-less higher voltage was 269 mV (AC) at the resonant frequency of 14.37 Hz in the motion range of 11–15 Hz. Later, an Ultra Low Power (ULP) electronic circuits will be designed and simulated in the LTSPICE software to convert and boost-up from 269 mV (AC) to DC voltage attained. The estimated output power of the energy harvester system can be powered up (4.7 µW) for modern pacemaker applications.
Abstract
Aim
The occlusion of the teeth is affected due to the appearance of micro-cracks resulting from maximum stresses in the contact zones between the wire and the bracket under normal and tangential loading. The objective of this study is to evaluate the surface and volume constraints in the presence of bonding and partial sliding zones on the contact surface between wires and supports. Knowledge of these stress fields will make it possible to better limit the surfaces where most of the micro-cracks occur. Indeed, the evaluation of the stress will facilitate the modelling or application of established micro crack models on this subject, because the initiation of micro-cracks often appears on the contact surface or just below it.
Materials and methods
In this study, the two most common situations of contact between the wire and the bracket were studied; the first corresponds to the situation where the wire is positioned in the center of the support (classic friction), and the second corresponds to the situation where the inclined wire touches the ends of the supports (critical contact angle).The MATHCAD software was used to simulate the damage zones for normal loading in the two cases studied (classic friction, critical contact angle). We proposed a Hertzian loading for the first case and a linear loading for the second case. Also, the effect of the additional load during wire tightening applied by the orthodontist was studied.
Results
The charge concentration is located above the contact zone, of the order of 0.3P0 (pressure per unit of arbitrary normal length), according to Mathcad simulation results. The adhesion zone/micro-slip zone contact generates the largest tangential load, which is directed towards the side experiencing the most stress. We also observed that the stick area shifts towards the recessed side when the additional load is applied. Additionally, comparing the configurations, the critical contact angle resulted in a higher maximum shear stress.
Abstract
The dog clutch offers advantages in mass and efficiency, but faces challenges in mismatch speed synchronization, which affects its shiftability. Face impact between dog teeth also reduces its lifespan. Our previous work introduced the kinematical shiftability condition that ensures impact-free gearshift but had limitations due to analysis assumptions. This study eliminates those assumptions, but uses a similar approach. Based on our previous work for dog clutch engagement dynamics, we develop the dynamical shiftability condition. Validation with full dog clutch dynamics showed an agreement. Employing another previous work that introduced shiftability map and parametric study method, we study system parameters impact on shiftability but based on the dynamical shiftability condition.
