3D Printed Concrete Habitat on the Moon: Potential and Challenges

3D printing technology has grown exponentially since its inception, positioning itself as one of the most competitive manufacturing techniques. Recently, it has been suggested that 3D printing might make a long-lasting dream come true by building a permeant human habitat on the Moon. The use of 3D printing for this application offers great potential while being bound by numerous challenges. For instance, with 3D printing, the need to transport building materials from the Earth to the Moon can be eliminated, making significant cost savings. All it would require is for the 3D printers to be sent to the space and for a construction ink mix design to be used on the Moon. Furthermore, structures built on the Moon will be lighter due to the low gravity of the moon compared with Earth, and thus small structural elements will be required to withstand loads. However, the Moon observes extreme environmental conditions including temperatures ranging from -233 to +123 ̊C, vacuum atmosphere, and radiation. 3D printed habitats on the moon will need to withstand such harsh environmental conditions and protect residents from radiation. Our team at UNM started examining the use of 3D printed concrete as a potential material for the Moon habitat. The impact of gravity loads on the behavior of 3D printed concrete is being examined. Also, the difference between cement and polymer binders on the mechanical characteristics of 3D printed concrete incorporating Moon like aggregate is being studied. Our research work contributes to paving the road for building the first human habitats on the Moon

A nouvelle approach for predicting the shear cracking angle in RC and PC beams using artificial neural networks

The truss model for predicting shear resistance of reinforced concrete beams has usually been criticized because of its underestimation of the concrete shear strength especially for beams with low shear reinforcement. Two challengers are commonly encountered in any truss model and are responsible for its inaccurate shear strength prediction. First: the cracking angle is usually assumed empirically and second the shear contribution of the arching action is usually neglected. This research introduces a nouvelle approach, by using Artificial Neural Network (ANN) for accurately evaluating the shear cracking angle of reinforced and prestressed concrete beams. The model inputs include the beam geometry, concrete strength, the shear reinforcement ratio and the prestressing stress if any. ..

Investigation of The DGs Effect on The Coordination Between Protective Elements in Distribution Network

Addition of Distributed Generators (DGs) to the electric network have more advantages to the network. It improves the voltage profile and the power flow in the network. In the last decade, DGs is used in power system, especially the distribution system. Coordination study for protective devices must be performed on the distribution network with DGs to reach selectivity with minimum clearance time of fault. Due to DG insertion to the electric system, the short circuit level is changed and coordination between protective elements should be done. This paper presents a technique to avoid the miscoordination problem between protective devices due to the impact of DG units insertion without any additional costs. The proposed technique depend on activating and updating the setting of network relays to achieve correct coordination. Also, it doesn\u27t need any additional costs or any additional equipement to be installed in the electric network. This paper make studies on a real radial system of power transformer with its feeders of a 66kV utility substation before and after adding DGs. ETAP software is used to simulate the network under study

Extracting Concrete Thermal Characteristics from Temperature Time History of RC Column Exposed to Standard Fire

A numerical method to identify thermal conductivity from time history of one-dimensional temperature variations in thermal unsteady-state is proposed. The numerical method considers the change of specific heat and thermal conductivity with respect to temperature. Fire test of reinforced concrete (RC) columns was conducted using a standard fire to obtain time history of temperature variations in the column section. A thermal equilibrium model in unsteady-state condition was developed. The thermal conductivity of concrete was then determined by optimizing the numerical solution of the model to meet the observed time history of temperature variations. The determined thermal conductivity with respect to temperature was then verified against standard thermal conductivity measurements of concrete bricks. It is concluded that the proposed method can be used to conservatively estimate thermal conductivity of concrete for design purpose. Finally, the thermal radiation properties of concrete for the RC column were estimated from the thermal equilibrium at the surface of the column. The radiant heat transfer ratio of concrete representing absorptivity to emissivity ratio of concrete during fire was evaluated and is suggested as a concrete criterion that can be used in fire safety assessment

Field Retrofit and Testing of a Corroded Metal Culvert Using GFRP

One of the current pressing problem for all DOTs is the corrosion-oriented deterioration of the existing metal culverts. These metal culverts typically are designed for a life of 50 years. However, corrosion is making them last no longer than 30years. Here we propose use of Glass Fiber Reinforced Polymers (GFRP) pipe section as a fit-in GFRP profile liner for complete repair and rehabilitation of the corroded metal culvert with an expected life of 75 years. This is mainly because of the corrosion free nature of the GFRP material. In the current study, the design method for using glass fiber-reinforced polymer (GFRP) slip liner to retrofit CMP culvert is presented. Furthermore, this report presents field implementation of retrofitting of a 24 in corroded corrugated metal pipe embedded that is 25 ft span and buried below 18 of soil. The corroded corrugated metal pipe was retrofitted with a 22 in diameter GFRP slip liner. Load testing before and after the retrofitting proves the efficiency of the proposed retrofitting system and its ability to extend the service life of the retrofitted pipe

A nouvelle approach for predicting the shear cracking angle in RC and PC beams using artificial neural networks

The truss model for predicting shear resistance of reinforced concrete beams has usually been criticized because of its underestimation of the concrete shear strength especially for beams with low shear reinforcement. Two challengers are commonly encountered in any truss model and are responsible for its inaccurate shear strength prediction. First: the cracking angle is usually assumed empirically and second the shear contribution of the arching action is usually neglected. This research introduces a nouvelle approach, by using Artificial Neural Network (ANN) for accurately evaluating the shear cracking angle of reinforced and prestressed concrete beams. The model inputs include the beam geometry, concrete strength, the shear reinforcement ratio and the prestressing stress if any. ..

Flexural Strengthening of RC Slabs Using a Hybrid FRP-UHPC System Including Shear Connector

A polymeric hybrid composite system made of UHPC and CFRP was proposed as a retrofit system to enhance flexural strength and ductility of RC slabs. While the effectiveness of the proposed system was confirmed previously through testing three full-scale one-way slabs having two continuous spans, the slabs retrofitted with the hybrid system failed in shear. This sudden shear failure would stem from the excessive enhancement of the flexural strength over the shear strength. In this study, shear connectors were installed between the hybrid system and a RC slab. Using simple beam, only positive moment section was examined. Two full-scale RC slabs were cast and tested to failure: the first as a control and the second using this new strengthening technique. The proposed strengthening system increased the ultimate load carrying capacity of the slab by 70%, the stiffness by 60%, and toughness by 128%. The efficiency of shear connectors on ductile behavior of the retrofitted slab was also confirmed. After the UHPC top is separated from the slab, the shear connector transfer shear load and the slab system were in force equilibrium by compression in UHPC and tension in CFRP

Fit-in GFRP Liner for Retrofitting Corroded Metal Culverts

Corrugated metal pipes (CMPs) have been used as culverts in North America since the 1950s. Today, corrosion of CMPs is a major problem that requires an urgent and efficient solution to retrofit thousands of corroded CMPs across the country. One potential solution gaining wide acceptance is to use a fit-in Glass Fiber Reinforced Polymer (GFRP) liner inside the old CMPs and to connect them using polymer grout. In this paper, a methodology to retrofit corrugated metal culvert using a fit-in GFRP profile liner was developed and implemented. First, material characterization of the GFRP material and the epoxy grout were carried out for proper design of the retrofit system. Second, full-scale CMP-GFRP composite section was tested under three-point bending configuration to observe the retrofitted culvert behavior to failure. The new CMP-GFRP section develops full composite action and shows failure capacity of 75 kip with a deflection of 3.52 in at the end of the test. Post failure of the polymeric grout, GFRP pipe failure was observed at mid-span location starting on the tension side. A finite element model was developed to understand the behavior of the CMP-GFRP composite pipe and to allow for the efficient design of the proposed retrofitting system