Need For Formwork Research Articles

Revolutionizing Construction Safety with Geopolymer Composites: Unveiling Advanced Techniques in Manufacturing Sandwich Steel Structures Using Formwork-Free Spray Technology

The article discusses the fabrication of sandwich steel and geopolymer structures using spray technology without the need for formwork. In the article, the effects of high temperatures on geopolymer materials are analyzed and their mechanical properties and durability are examined. The importance of geopolymer coatings for steel protection is also highlighted, and specific features such as the setting time, application process, attachment strength, fire testing, and production costs are analyzed. The materials and methods used in the study are described, including the composition of geopolymer binders and the process of applying geopolymer coatings to steel plates. The research includes test methods such as strength tests, density tests, thermal conductivity tests, accelerated aging tests, microstructure analyses, pore size analyses, and fire resistance tests. The research section concludes with a summary of the chemical and phase composition of the materials and a discussion of the fire resistance of the geopolymer composites (GCs). The results show that GC foams offer excellent thermal insulation, providing up to 75 min of fire resistance with a 6 mm coating, reducing temperatures by 150 °C compared to uncoated steel. GC foams have a density of 670 kg/m3, a thermal conductivity of 0.153 W/m∙K, and a cost effectiveness of USD 250 per cubic meter.

The stiffness and elasticity of polymer-coated pumice a potential method for reinforcing concrete 3D printing structures

Pumice has been used successfully as a lightweight aggregate concrete replacement (LWAC). Pumice, on the other hand, absorbs a lot of water during the mixing process, which might impair the strength of the concrete. This research examines the influence of coated pumice in concrete mixes on beam flexural strength and stiffness in order to avoid excessive water absorption and acknowledges concrete extrusion-based 3D printing's potential to revolutionize the construction sector. By getting rid of the need for formwork, 3D printing is expected to cut the cost of building civil engineering structures, speed up construction, and make working conditions better. Because of the layer-by-layer additive manufacturing process, it is necessary to alter the way concrete buildings are constructed and strengthened, particularly in areas subject to stress loads. The findings reveal the flexural strength of coated pumice was compared to that of untreated pumice and was found to be 2.58 percent higher. In addition, it also reveals that inclined nails may be utilized in a variety of orientations to provide printing materials with flexural strength.

Engineering properties of factory manufactured paving blocks utilizing steel slag as cement replacement

Vibropressing compaction of dry mixed concrete has increased the production rate of paving blocks, as it eradicated the need of formwork to hold the fresh concrete mixture in shape after molding. This technique also optimized the cost-benefit ratio as it helps in achieving high strength blocks with the minimum utilization of water and cement. In this study, effect of steel slag powder (SSP) was studied as the cement replacement material on the physical and mechanical properties of paving blocks. The cement was replaced with SSP as 5%, 10%, 15%, 20%, 25% and 30% by mass. Incorporation of SSP improved the finishing of paving blocks. The results of compression testing revealed that paving blocks incorporating 5–15% SSP as the cement replacement showed higher strength than the control paving block. This improvement is entirely credited to the better packing of constituent particles caused by the filling effect of SSP. The increase in ultrasonic pulse speed also confirmed that 5–15% SSP improved the density of paving blocks. However, the impact toughness of paving blocks reduced with the rise in SSP percentage beyond 5%.

Comparative Study on Axial Compressive Behaviour of CFST and Externally Wrapped CFRP Columns

Concrete column fails by crushing or bucking due to axial load in order to resist failure of confinement, concrete filled steel tubular column (CFST) and carbon fibre reinforced polymer (CFRP) wrapping are used. CFST member has its consecutive progression in the construction industries due to its high load carrying capacity upgraded ductile performance, need for form work is minimized and has greater confinement effect. CFRP wrapping provides resistance towards corrosion, light weight exceptional durability, increases strength over confinement. In this work, an experimental investigation between stunt and slender concrete filled steel tubular column is compared with conventional pcc strut and slender column externally wrapped by single and double layer of CFRP. Total of 8 specimen were tested under axial compression. The parameter varied is height (750mm, 1050mm). The diameter of the column is 75mm. M30 grade concrete is cast. End support condition is hinged. For short column slenderness ratio is 40, L/D is assumed to be 10 and for slender column slenderness ratio is 60 and L/D is assumed to be 14. From this study, the influence of slenderness ratio over an effect of confinement is observed. Maximum axial compressive strength of the column is recorded and it is compared with eurocode4, AS/ACI code, IS516:1959 code. The behaviour of column both experimental and analytical results is observed.

Comparison of theoretical and analytical investigation on axial compressive behaviour of concrete filled steel tubular columns

Concrete filled steel tubular (CFST) members has its successive footprints in the construction industry, owing to its high load carrying capacity, improved ductile performance, large energy absorption capacity etc. CFST column has its own advantages like maximizing the useable floor area and minimizing the need of formwork. In this research work, experiments are carried out on 8 circular CFST columns with 60 mm diameter and 2.5 mm thickness. The parameters varied are height (960 mm, 900 mm, 840 mm and 750 mm) and the in-filled materials like normal strength concrete and high strength concrete. The study mainly focused on analysing the codal provisions like Eurocode4, ACI and AS codes with the experimental results. From the study, the influence of slenderness ratio over effect of confinement is observed and evaluated. As the codal provision seems to be too conservative in predicting the compressive behaviour of CFST columns, a modified approach is derived. The analytical expression predicted by this simplified method is applicable for CFST columns with L/D ratio varies from 13 to 16.

The effect of slenderness ratio on modification of compressive strength of AISC code for composite columns (CFT) T-shaped with numerical (FEM) and experimental analysis

Today, the use of CFT columns is increasing worldwide, due to the confinement of concrete and steel, speed of build, and no need of formwork, In these columns, the circular sections produce the most confinement effect for the core concrete That’s why these columns are mostly made in circular and square shapes. But sometimes other geometrical shapes such as (T) are used, which provide less confinement for core concrete than circular and square sections. The AISC Code for the Calculation of compressive strength (Pn), considers the capacity reduction factor of concrete (C2) only for circular and square sections. The Code provided the value of this coefficient for circular sections due to greater confinement in core concrete 0.95 and square sections 0.85 but did not provide a coefficient for (T) shape. So in this study, 12 specimens in three groups of experimental, numerical and theoretical were used to calculate the reduction coefficient of concrete strength (C2) and to investigate the effect of slenderness ratio on this coefficient. Finally, it was found that the reduction coefficient of concrete (C2) for (T) shape due to lower confinement of core concrete was on average 31.69% less than a circular section and 23.13% less than square section. Also with a 64% increase in slenderness ratio, the reduction coefficient of concrete strength (C2) decreased by 14.82%.

Experimental and numerical assessment of the flexural behaviour of semi-precast-reinforced concrete slabs

Semi-precast-reinforced concrete slab system offers more economic method of construction as it minimises the need of formwork at site. The assembly of semi-precast slab system involves two steps: (1) casting of semi-precast slab at the yard and (2) overtopping of concrete at the site. One of the main factors that influence the performance of such slab system is the interface bonding between precast and overtopping concrete. Therefore, in order to better understand the performance of this slab system, a research was carried out to investigate the influence of surface treatment methodologies to the overall flexural behaviour through experimental and numerical studies. In total, five representative semi-precast slabs were constructed and tested to assess the flexural performance with different surface preparation methods and concrete overtopping. Further small-scale precast with overtopped concrete couplets and triplets were casted and tested as the representative semi-precast concrete slab types to examine the interface shear and tensile bond strength characteristics with those different surface treatments. The experimental results revealed that the surface treatment methods have influenced the flexural behaviour of the slabs, where the interface shear bond strength exceeds more than 1.0 MPa and the slab system behaves monolithically under flexural action. Moreover, numerical modelling technique for this slab system was developed based on the finite element framework to further analyse the overall flexural behaviour. Subsequently, good agreements between experimental and developed numerical model results were found. Finally, parametric analyses were performed to further assess the influences of concrete strengths, spans and reinforcement ratios on the safe imposed pressure applicable for this slab system.

A Non-Linear Finite Element Modelling of Composite Beam to CFST Column Connection

The use of steel and concrete composite structure is increasing day by day especially the use of CFST columns in multistory composite building frames due to the reason that they can significantly reduce overall construction time by eliminating the need of formwork and sometimes even reinforcing bars. However, creating an ideal joint between composite beam and CFST column is quite challenging task from design, analysis and construction point of view. This connection behaviour can best be understood by its moment-rotation curve. So, here attempt has been made to model this composite connection numerically with the software which uses Finite Element Methods as a tool and results are validate. The composite connection possesses all three kinds of non-linearity, that are, geometric, material and boundary/contact nonlinearities. It is known that composite connection is nothing but the combination of bare steel connection and reinforced concrete slab with proper shear transfer mechanism and so first a bare steel connection and reinforced concrete beam is modelled. An explicit representation of connection is not necessary as long as the adequate features are captured. So attempt has been made to optimize the connection where ever it is possible. Usually design engineers design composite structure while neglecting the “composite action”in during the analysis. Sometimes these composite actions contribute much in resisting the applied load.

Thixotropy and interfacial bond strengths of polymer-modified printed mortars

3D concrete printing is an emerging construction technique for building structures layer-by-layer based on digital computer models without the need of formwork. The monitoring of interlayer bonding is crucial to ensure durability and structural integrity. This investigation aims at proposing a new methodology to assess the concurrent effects of material structural build-up (thixotropy), time gap between successive filaments, and incorporation of styrene-butadiene rubber (SBR) polymers on bond strengths of deposited layers. Four mortar series prepared with 450–750 kg/m3 binder and effective water-to-binder ratio of 0.35–0.55 are tested; the resulting thixotropy rate ranged from 0.16 to 1.1 Pa/s. Results showed that mixtures exhibiting moderate thixotropy levels (i.e., about 0.48–0.64 Pa/s) yielded the best performance regarding interfacial bonding. The incorporation of SBR proved efficient to enhance the bond strength as well as attenuate its rate of drop over the time gap between successive layers. This was related to the polymer films that coalesce in the cementitious system, thus binding the cement hydrates together and causing increased tensile strength properties. The bond strengths recorded on specimens exposed to hot temperature of 45 °C were consistently lower than those determined in standard curing conditions. The methodology proposed was successfully validated using 3D laboratory printing machine.

Tile vaults as integrated formwork for reinforced concrete: Construction, experimental testing and a method for the design and analysis of two-dimensional structures

Tile vaults are traditional, unreinforced masonry structures made of thin bricks (tiles), mortar and fast-setting cement or gypsum. They can be constructed without the need for a formwork, except at the boundaries, making them inherently economic. Tile vaults have historically provided a solution for the efficient construction of vaulted structures. Today, they can be used as permanent formwork for concrete shells, allowing for a significant reduction of the construction cost and waste produced, due to the possibility of reducing or even eliminating the need for traditional formwork. The concrete can be poured directly onto a tile-vaulted formwork to form a composite structure.This paper presents a technique for the construction of single-curvature shells consisting of a composite structure combining tile vaulting and reinforced concrete. A method for the design of these composite vaults and the assessment of their strength and stability against external loading is also presented. This method is based on limit analysis but takes into account the reinforcement’s contribution to the composite cross-section’s bending capacity.The equilibrium method is implemented computationally to provide fast results for the user. It provides graphical and intuitive results and opens the possibility for the future extension to fully three-dimensional problems. The design and structural analysis method is called Extended Limit Analysis for Reinforced Masonry (ELARM).Both the proposed construction technique and the computational method have been validated through experimental research. The feasibility of the building technique has been validated by the construction of two full-scale prototypes. In addition, the prototypes have been load-tested to failure to compare the results with those predicted by ELARM.

Time gap effect on bond strength of 3D-printed concrete

ABSTRACTAn advancing technology that combines the concrete extrusion with a motion control to create structures with complex geometrical shapes without the need for formwork is known as 3D concrete printing. Since this technique prints layer by layer, the time taken to reach the same position in the subsequent layer is important as it will create an anisotropic property that has a weaker tensile strength at the bond interface of the two printed filaments. Through rheological measurement, which reveals the material deformation and flow behaviour, it is possible to examine the material structural build-up due to time-gap effect by measuring at different time delay. This paper focuses on investigating the time-gap effect on the printed filament with rheological and observation at macroscopic-scale to understand the material behaviour of the initial and subsequent printed layer during its fresh phase. Rheological experiment findings reveal that the tensile strength of the printed specimen is correlated to the material modulus at the initial layer.

The Timber-Precast UHPC Composite Connection

This paper deals with the connection of timber beams and precast concrete slabs. The connection of timber and concrete has many advantages associated with the efficient use of both materials, not only in terms of their stress. Timber is a natural renewable material. It can be achieved some savings of volume of the concrete by its application and thereby also reducing of the environmental burden. By the combining of the timber and ultra-high performance concrete (UHPC), it can be designed very subtle, bearable, aesthetic and durable structures. The conventional timber-concrete composite structures are most often realized by joining of the timber beams and the cast in-situ reinforced concrete slabs. However, the cast in-situ slab is not very suitable for UHPC application and it has some structural disadvantages, in particular the need to protect the timber beams against moisture penetration from the fresh concrete mix, the need for formwork, etc. The prefabrication eliminates some disadvantages of the cast in-situ design, increases the quality of the structure and speeds up the construction process. In the case of the timber-concrete composite structures, the prefabrication has a positive impact on the reduction of the concrete shrinkage projections as the development of deflections and the redistribution of internal forces between the connected parts of the cross-section. Some special coupling elements must be used for connection in the case of precast slabs. This paper summarizes the research findings in the field of development of special coupling elements for composite timber-precast concrete structures. The development of the new coupling elements for pedestrian and cyclist timber-UHPC composite footbridges is presented.

DigDesFab15 Research Pavilion

This full-scale research pavilion exercises the application of timber and polymer concrete in architectural production (Fig. 1). It attempts to develop and test a new hybrid construction technique using composite joints (as introduced in Schober, 2014) within a modular geometric system and no need for formwork. The structure was designed and erected by students and instructors of the Digital Design and Full Scale Fabrication seminar taught at the University of Applied Arts Vienna. CNC milled, 3-layer spruce laminated timber boards are used for construction, which are temporarily fixed, then rigidized with polymer concrete. The cured composite node proves high structural capabilities, as polymer concrete withstands both pressure and tensile forces, and the bond between the materials is as strong as the wood itself. Compared to traditional timber construction, no metal bolting is needed for the creation of the node, while at the same time the node geometry becomes more flexible, meaning any three-dimensional layout can be produced, as long as a temporary containment and fixation can be implemented until the chemical curing process is completed (Becker, Schober, Weber, 2016). The geometry is developed as an interpretation of the Zollinger (Menges A. et al., 2016) grid, where members originally are of twice the grid length (Fig. 2) and reciprocally reliant on each other (Fig. 3). Instead, every second grid cell is made a joint node when cast out with concrete, making the structural members a lost formwork at the same time (Fig. 4). Double-layering each makes it possible to cast all 122 nodes of the pavilion structure separately and flat-bolt them together on-site with metal screws. The software plugin RhinoVault is used as a design tool to produce an efficient, compression only basic shell surface, although the subsequent imposition of the grid system introduces eccentricities and local imperfections. A parametric model in Rhinoceros and Grasshopper tests various subdivision densities and node sizes, and evaluates the overall performance with the structural analysis tool Karamba. The different heights of the lamellas in the structure arise from the analysis and parametric interpretation of stresses under vertical and horizontal loading.

STUDIES ON REINFORCED HOLLOW CONCRETE BLOCK MASONRY

Masonry may be defined as the assemblage of building units joined with the help of cementitious material or any accepted joining material to perform required function. It has its own reputation and performs multi-functions in load bearing structures such assupporting loads, dividing spaces, thermal and acoustic insulation, weather and fire protection etc, but it has to be provided separately in framed structures. In present scenario, there is a great demand for construction of Multi-storied residential buildings in urban area because of needful requirements. Most of such buildings are constructed using RC-framed structure. On the other hand RC-framed structures are expensive and relatively difficult to construct because of the need for formwork. Masonry has a great benefit since it does not need form work. If moderate to High strength Engineered hollow concrete blocks are available, one can think of providing reinforcement through the core of such Hollow blocks. In this project an attempt has been made to obtain the load carrying capacity of Reinforced Hollow Concrete Block Masonry through experimental investigation by considering two different percentages of steels for this totally four number of Reinforced hollow concrete block masonry prisms (RHCBM) using 12 mm diameter bar and six number of Reinforced hollow concrete block masonry prisms (RHCBM) using 8 mm diameter bar were casted and tested. Further, an attempt has been made to compare the experimental load carrying capacity with the conventional mechanics based approach used for analyzing short columns. There was a fairly good corelation between the analysis and experiments.

Concrete-Filled Steel Tubes for Accelerated Bridge Construction

Concrete-filled steel tubes (CFSTs), which are steel tubes with concrete infill, have increased strength, stiffness, and deformability relative to comparably sized reinforced concrete columns. The steel is at its optimal location and thus maximizes strength and stiffness while minimizing weight and material requirements and providing confinement to the concrete infill. In turn, the infill delays local and global buckling of the tube. In addition to their high resistance and stiffness properties, CFSTs are easily and rapidly constructed and eliminate the need for formwork and reinforcement. In bridge design, CFSTs may be used for bridge piers, shafts, caissons, and columns. However, the use of these tubes is limited in part because AASHTO design specifications for CFSTs are dated and in part because few validated, constructible connections exist. The American Institute of Steel Construction (AISC) includes more recent updates to CFST design provisions than does AASHTO. This paper compares current CFST design provisions with experimental results, noting limitations and deficiencies. Proposed provisions to improve the AISC provisions are introduced. These improved provisions are used as the basis of new AASHTO specifications for use of CFSTs in bridge design. Connections, which are a second limitation in CFST design, are also discussed. A foundation connection capable of developing the composite capacity of a CFST was evaluated experimentally and resulted in design expressions. A preliminary study of CFST column–to–cap beam connections using numerical simulation is introduced. This paper presents significant advancement and practical methods for the use of CFSTs in bridge design.

The Vaults of St. John the Theologian at Ephesos

E ver since the first excavation of the remains of the church of St. John the Theologian on the hill of Ayasoluk, the reconstruction of the vaulted, sixth-century phase of the monument has been a major challenge in the field of early Byzantine architecture. This is partly due to the historic significance of the building. According to the contemporary account of Procopius, the church, rebuilt and enlarged under the auspices of Justinian, constituted the Ephesian counterpart to the Constantinopolitan church of the Holy Apostles.1 It was later to become the heart of medieval Ephesos and one of the most important pilgrimage churches in Asia Minor.2 Besides its historical interest, the reconstruction of St. John’s has a great significance for the study of early Byzantine vaulting technology. Indeed, reconstruction offers the only opportunity to recapture the form of the enormous brick vaults of the church, which are now lost. These sophisticated vaults, which seem to have survived in an earthquake-prone area for more than eight centuries, constitute a remarkable feat of structural engineering.3 They must have been a highly innovative structure, erected at a time when most churches were timber-roofed. The task of accurate and reasoned reconstruction through the scrutiny of archaeological evidence is more demanding than it may initially appear, in spite of the systematic exploration of the monument since its discovery in 1921. Eight decades of excavation and survey have made the ground plan of the aisled cruciform church as well as the footprint of its atrium, baptistery and skeuophylakion mostly clear (Figure 1).4 Some parts have even become the object of full-scale physical reconstruction (Figure 2). In addition to this, Hans Hormann, Mustafa Buyukkolanci, and Andreas Thiel have shed light on the building phases that preceded Justinian’s vaulted church.5 Still, in spite …

Robotic Construction by Contour Crafting: The Case of Lunar Construction

Contour Crafting is a digitally controlled construction process invented by Professor Behrokh Khoshnevis that fabricates components directly from computer models, using layered fabrication technology. By obviating the need for formwork used in traditional concrete construction, CC can reduce costs and construction times significantly. The technique has great potential as a robotic form of construction reliant on relatively minimal human labor as a form of construction in relatively hazardous environments, such as the Moon with its radiation levels that can prove highly damaging. Current research funded by NASA has been exploring the potential for using CC on the Moon to build structures making use of readily available regolith that is found in great abundance on the surface of the Moon. This article offers an overview of this research and evaluates the merits of using CC on the Moon.