BRJ – Volume 61, Number 2, 2014
P. Stanak, A. Tadeu, J. Sladek, V. Sladek:
meshless . . 67-84
Vladimír Živica, Martin T. Palou, Martin Križma:
Geopolymer cements and their properties: a review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85-100
Hadad S. Hadad, Ibrahim M. Metwally, Sameh El-Betar:
Cyclic behavior of braced concrete frames: experimental investigation and numerical simulation . . . . . 101-114
Chen Wang, Faizul Azli Mohd Rahim, Nurul Safwah Mohd Yusoff, Hamzah Abdul Rahman, Vili How:
Critical view on daylighting through solar bottle bulb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115-128
Longitudinally invariant elastic structures analyzed by the meshless mlpg method using 2.5D approach
P. Stanak, A. Tadeu, J. Sladek, V. Sladek
This paper presents a general 2.5D meshless MLPG methodology for the computation of the elastic response of longitudinally invariant structure subjected to the incident wave field. A numerical frequency domain model is established using the Fourier transform in time and longitudinal coordinate domains. This allows for significant reduction of computational effort required. In the MLPG method the Moving-Least Squares (MLS) scheme is employed for the approximation of the spatial variation of displacement field. No finite elements are required for the approximation or integration of unknowns. A small circular subdomain is introduced around each nodal point in the analyzed domain. Local integral equations derived from the governing equations are specified on these subdomains. Continuously non-homogeneous material properties are varying in the cross-section of the analyzed structure. A simple patch test is introduced to assess the accuracy and the convergence of developed numerical model. At the end of the paper, numerical examples illustrate the applicability of the proposed numerical formulation.
Keywords: meshless method, 2.5D modeling, wave propagation, FGM materials
Geopolymer cements and their properties: a review
Vladimír Živica, Martin T. Palou, Martin Križma
Concrete is the world’s most versatile, durable and reliable construction material. Next to water, concrete is the second most used substance on earth and it requires large quantities of Portland cement. The industrial sector is the third largest source of man-made carbon dioxide emissions after the transportation sector as the major generator of carbon dioxide, which pollutes the atmosphere. Ordinary Portland cement (OPC) production produces the largest amount of carbon dioxide amongst all industrial processes. In addition to that a large amount of energy is also consumed for the cement production. The production of OPC not only consumes a huge amount of the natural resources i.e. limestone and fossil fuels but also produces almost 0.9 t of CO2 for 1t of cement clinker production. Thus, the world cement production generates 2.8 billion tons of man-made greenhouse gas annually. Hence, it is inevitable to find an alternative material to the existing most expensive, most resource and energy consuming Portland cement.
Geopolymer cements are innovative binders which can be produced by the chemical action of aluminosilicate materials plenty available worldwide. They are rich in silica and alumina reacting with alkaline solution and producing aluminosilicate gel that acts as the binding material for the concrete. Geopolymers are synthesized by polycondensation reaction of geopolymeric precursor and alkali polysilicates.
The paper presents data on the important engineering properties of geopolymer cements showing that these cements offer an alternative to, and potential replacement for, OPC. Geopolymer technology also has the potential to reduce global greenhouse emissions caused by OPC production. Due to the high level of mechanical properties of geopolymer cements and their environmentally beneficial technology they appear as a prospective construction material for the future.
Keywords: geopolymer cement, ordinary Portland cement, technology, properties
Cyclic behavior of braced concrete frames: experimental investigation and numerical simulation
Hadad S. Hadad, Ibrahim M. Metwally, Sameh El-Betar
RC shear walls have been widely used as the main lateral-load resisting system in medium and high-rise buildings because of their inherent large lateral stiffness and load resistance. But, in general, the energy dissipating capacity of RC shear walls is not very good and it has been found that using the bracing system gives good results. The main purpose of this paper is to study the effect of different types of bracing on the lateral load capacity of the frame. Also, the research contains a comparison between the braced and infilled frames to decide on the best system. The research scheme consists of four frames; the bare frame, two frames the first of which was braced with concrete, the second was braced with steel bracing and the fourth frame was infilled with solid cement bricks. All the specimens were tested under cyclic loading. The results gave some important conclusions; braced and infilled bare frames increased the lateral strength of the bare frame depending on the type of bracing and infill. Also, the different types of bracing and the infill increased the initial stiffness of the bare frame by a reasonable value. The energy dissipation for the braced and infilled frames is always higher than that for the bare frame up to failure. Also, numerical modeling was carried out with the nonlinear software platform (IDARC). The numerical results obtained with the calibrated nonlinear model are presented and compared with the experimental results. Good agreement was achieved between the numerical simulation and the test results.
Keywords: bracing, infilled frame, cyclic loading; IDARC
Critical view on daylighting through solar bottle bulb
Chen Wang, Faizul Azli Mohd Rahim, Nurul Safwah Mohd Yusoff, Hamzah Abdul Rahman, Vili How
Daylighting is often integrated into a building as an architectural statement and for energy savings. However, the benefits from daylighting extend beyond architecture and energy savings. Solar bottle bulb is an invention that is highly effective and cost effective enough to be used in huge numbers for those without sources of interior lighting. This invention is very easy and excessively cheap, requires only a bottle, some roofing materials, water and minimal amount of regularly found chemical and no electricity is needed. This paper reviews the critical retrospect of daylighting through the solar bottle bulb perspective. It highlights the need for solar bottle bulbs use within the underprivileged areas of the world and the importance of this invention as a pathway towards sustainability. This paper presents a review on the designs, principles and applications of the invention that have brought the poor people into a new way of life. The review consists of the assessment of journals, books, newspapers, reports and online sources in the field of daylighting and solar bottle bulb.
Keywords: solar bottle bulb; daylighting, sustainability; underprivileged