Documents published in Scipedia

• Beyond bending: tension. Membrane structures II

  J. Llorens

  membranes2023.

  
  

  Abstract

  Jürgen Hennicke [1] challenged the designers of structural membranes stating that "Structural membranes, if not designed as such, require an imposing steel structure". Responding to this challenge, a comparative study has been launched to assess the impact on the design efficiency of considering or not the structural principles of membranes, that are: only tension, funicularity, curvature and pre-stress. In a previous paper (J.Llorens, 2023 [2]) the general approach of the research and the first results have been presented. This paper shows more cases to complete the most usual repertoire.

  Abstract
  Jürgen Hennicke [1] challenged the designers of structural membranes stating that "Structural membranes, if not designed as such, require an imposing steel structure". [...]

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• HydroSKIN: Climate-resilient Membrane Façade Prototyping

  C. Eisenbarth, W. Haase, L. Blandini, W. Sobek

  membranes2023.

  
  

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• Main Canopy of Islamic Complex, Putrajaya, Malaysia – A Testimony to Excellent Performance of PTFE Membrane under Tropical Climate

  M. Sing, K. Choong, A. Che Malid, C. Ng

  membranes2023.

  
  

  Abstract

  This paper describes a landmark membrane structure where the surface appearance has been able to be maintained after years in service. The membrane structure is the main canopy structure located at the courtyard of Islamic Complex, Putrajaya, Malaysia. It is made using PTFE membrane which is known for its excellent durability. The construction process of the main canopy together with the mini canopy which consists of a group of four funnel-shape membrane structure made using PVDF membrane will be presented in this paper. The paper will also touch on the performance of PTFE membrane in humid tropical weather condition like Malaysia.

  Abstract
  This paper describes a landmark membrane structure where the surface appearance has been able to be maintained after years in service. The membrane structure is the main canopy [...]

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• Development of Air-inflated Lifting Equipment

  K. Hincz

  membranes2023.

  
  

  Abstract

  The research aimed to develop air-inflated equipment for lifting catamaran components during construction. The main structural parts of a newly developed catamaran are two hulls and three closed boxes. The three boxes connect the hulls and hold the deck. Different construction procedures were analysed to connect the main structural parts. One possibility is to float the hulls and the three boxes one by one on the water, lift the boxes to the required position with inflated tubes or pillows and connect the parts. Air-inflated tubes with various geometry and internal pressure have been analysed with the help of the Dynamic Relaxation Method. The deformed shape of the floating tubes, the membrane stresses, and the lifting forces were determined.

  Abstract
  The research aimed to develop air-inflated equipment for lifting catamaran components during construction. The main structural parts of a newly developed catamaran are two [...]

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• Structural Membrane of Levante Stadium Cable Roof

  E. Montes, A. Solar, I. Sánchez, J. Llanera, A. Bilbao

  membranes2023.

  
  

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• Tuning the incompatibility between recycled plastic aggregates and cement matrix with polymer-nano silica hybrids

  Q. Zeng, A. Al-Mansour

  DBMC 2023.

  
  

  Abstract

  Use of recycled waste plastics as the aggregates in construction materials has attracted increasingly gained attention for sustainable construction industry with great environmental benefits. However, the soft plastics and rigid cement matrix can naturally induce the great aggregate-matrix incompatibility, which results in the degradation of engineering properties of cement-based materials containing recycled plastic aggregates (RPAs). To overcome this shortage, this work reports a strategy of tuning the cement matrix with polymer-nano silica (P-nS) hybrids. Ethylene vinyl acetate (EVA) and recycled polypropylene (PP) were selected as the coating polymer and RPA, respectively. Density, strength, water sorptivity and carbonation resistance were measured to assess the physical and mechanical properties of the mortars with recycled PP particles. Microstructure was analyzed using scanning electron microscopy (SEM) with backscattered electron (BSE) and energy-dispersive X-ray spectroscopy (EDS). Results showed that the addition of P-nS hybrids into cement decreases density, mitigates strength reduction, obstructs water sorption, but have positive and negative effects on carbonation resistance of the cement mortars with RPA. The P-nS hybrids build the organic–organic links between the cement matrix and RPA, and coordinate their deformations. The findings of this work proof the proposed strategy of tuning the compatibility between soft aggregates and rigid matrix with the engineered microstructure towards enhancing the recyclability of waste plastics in construction materials.

  Abstract
  Use of recycled waste plastics as the aggregates in construction materials has attracted increasingly gained attention for sustainable construction industry with great environmental [...]

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• Recycling of Polypropylene Fibre Reinforced Concrete: Use of Recycled Aggregate and Recovered Fibre in New Concrete

  G. Liu, N. Tošić, A. de la Fuente

  DBMC 2023.

  
  

  Abstract

  The study aims at investigating the feasibility of using recycled aggregate (RA) and recovered fibres (RF) obtained from recycling of polypropylene fibre reinforced concrete (PPFRC) in new concrete production. The mechanical properties were compared between a parent concrete, polypropylene fibre reinforced recycled aggregate concrete (PPRAC), and recovered polypropylene fibre concrete (Re-PPRFC). All concretes were designed to have the same compressive strength and slump. The parent concrete was produced with 9 kg/m3 of polypropylene fibre. After recycling, the RA and RF were collected and new concretes with RA and RF, PPRAC and PPRFC, respectively, were produced with the same fibre content as the parent concretes. The strain-stress relationship in compression and residual tensile strength were tested. The results obtained for PPFRC, PPRAC and rePPRFC were compared. The results show that the RA and RF obtained by PPFRC recycling can benefit new concrete production.

  Abstract
  The study aims at investigating the feasibility of using recycled aggregate (RA) and recovered fibres (RF) obtained from recycling of polypropylene fibre reinforced concrete [...]

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• Numerical Simulation on the Influences of Wind Pressure on Jet Characteristics of Shotcrete

  S. Zhang, Y. Zhang, K. Wu, X. Kong

  DBMC 2023.

  
  

  Abstract

  A gas-liquid two phases model of shotcrete was developed to simulate the whole process from the spouting of concrete from nozzle, the scattering in the flow field to its colliding with a wall based on computational fluid dynamics theory, in which concrete was regarded as a Bingham fluid. The influences of wind pressures、 pumping speeds、 air incident angles and rheological parameters on five characteristic parameters including spouting velocity, jet velocity, jet trajectory, collision velocity and distribution of shotcrete on the wall were analyzed in depth. Results showed that concrete was gradually mixed well with air in the nozzle with an increasing average velocity, and the increase of velocity was most pronounced in the contraction section of nozzle. With the increases of wind pressures and pumping speeds, the spouting velocity and spouting mass of concrete both increased. Higher wind pressure and pumping speed led to larger jet velocity and more concentrated distribution, resulting in significantly longer jet distance, higher collision velocity and larger distribution area. The collision velocity and volume fraction of concrete on the wall were distributed symmetrically along Y axis, shifting towards the direction of gravity. With the increases of air incident angles, the spouting velocity and spouting mass of concrete both decreased, the shifting to gravity is weakened and the volume fraction decreased first and then increased. When plastic viscosity decreased, the spouting velocity and spouting mass of concrete both increased, accompanying with a higher jet velocity, a longer spraying distance and a larger distribution area.

  Abstract
  A gas-liquid two phases model of shotcrete was developed to simulate the whole process from the spouting of concrete from nozzle, the scattering in the flow field to its colliding [...]

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• Effect of Pre-calcination of Lead-zinc Tailings on the Activation of Blast Furnace Slag

  J. Ou, Z. Luo, Y. Mu

  DBMC 2023.

  
  

  Abstract

  Blast furnace slag and lead-zinc tailings (LZTs) are solid wastes from the iron-making and mining industries, respectively. In order to reuse these solid wastes, the LZTs were pre-calcined at different temperatures and then explored whether it is capable of being the activator of slag. The effects of pre-calcination on the phase composition of LZTs were elucidated by XRD. The compressive strength of LZTs-activated slag pastes was investigated, and the mineral composition and microstructure of the pastes were detected by XRD and SEM. The results imply that with the elevating of heating temperature from 500 ℃ to 1000 ℃, the dolomite in LZTs decompose into CaO and MgO, and the oxidation of pyrite resulted in the formation of Fe2O3 and gaseous SO3, then SO3 reacted with a part of formed CaO to produce CaSO4. The resulting CaSO4 and CaO can become the sulfate activator and alkaline activator of slag, respectively. The LZTs-activated slag pastes prepared with the LZTs preheated at 800 ℃ exhibit the highest strength at 90 d, which yield 24 MPa. The hydration products of LZTs-activated slag were ettringite and calcium silicate hydrates (C-S-H gel). Large amounts of dense C-S-H gel bond together, connecting most of the ettringite networks into a whole, thus forming a dense structure and effectively improving the strength of LZTs-activated slag. The outcome of this study provides a potential disposing or reusing approach of the large amounts of LZTs.

  Abstract
  Blast furnace slag and lead-zinc tailings (LZTs) are solid wastes from the iron-making and mining industries, respectively. In order to reuse these solid wastes, the LZTs [...]

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• Probability Durability Assessment of Existing Concrete Structures in Carbonation Environment

  H. Gu, J. Yao, Z. Meng

  DBMC 2023.

  
  

  Abstract

  In a particular service environment, the calculation models used to determine the durability of existing concrete structures differ from those employed in the design phase. This paper presents a methodology for assessing the probability durability of existing structures, taking into account the nondestructive testing results and the target reliability index. The initial step involves introducing a correction coefficient into the carbonation and corrosion development theory model. This coefficient is necessary to account for the correction associated with the corrosion monitoring of steel. The values of this coefficient should be determined based on the actual testing results, specifically considering the presence of reinforcing steel corrosion. Next, a probability expression is proposed using the measured results of probability characteristics and the target reliability index. This approach takes inspiration from the design-value method and the existing theory of structure reliability. It also takes into account the specific variables of concrete protective cover thickness and the compressive strength as the fundamental random variables. The residual working life can be calculated as the outcome of a durability assessment through quantitative analysis. This calculation can serve as a valuable reference for the maintenance program.

  Abstract
  In a particular service environment, the calculation models used to determine the durability of existing concrete structures differ from those employed in the design phase. [...]

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