INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 1 – MAY 2015 - ISSN: 2349 - 9303
Numerical Optimization of Shoring Towers for Slab Formwork Systems Suresh Naidu M 1 1
2
VIT University, Graduate Student, School of Mechanical and Building Sciences, maddineni.suresh2013@vit.ac.in
Ramesh Kannan M 2
VIT University, Assistant Professor, School of Mechanical and Building Sciences, rameshkannan.m@vit.ac.in
Abstract— The usage of Shoring Tower for slab formwork is getting increased due to not only because of flexibility in the assemble and construction over Prop-Supported Slab Formwork but also the capacity to withstand maximum construction working loads. The Shoring Tower is generally used for the construction of heavy structures like Bridges, Culverts, staging of Retaining walls, etc. However a comprehensive scale down of the shoring tower design goes well with the large span and increased slab thickness of conventional buildings. This research focuses primarily on Analysis, Modelling, Design and Adaptability of shoring tower for slab formwork through computer models and optimized. The different models are made from the combination of diameter of tubes with slab thickness and also with plywood thickness in Solid Works. Periodic analysis is done in ANSYS for different load combinations with the variations of slab thickness and plywood thickness will gives the optimized results for the slab formwork systems.
Index Terms— conventional buildings, modelling, static analysis, shoring towers, slab formwork systems —————————— ——————————
1 INTRODUCTION
TO
serve the needs of area for the developing population, the best arrangement is the vertical advancement which is the development of tall structures, for example, Bridges, Culverts, staging of Retaining walls and so on. Therefore to accommodate the future developing population, there ought to be diminishment in the horizontal development and rather vertical advancement is advanced. Be that as it may, the execution of vertical improvement is not all that simple following the development of tall structures are exceptionally too complex and requires higher level of development techniques and types of equipment’s and subsequently it couldn't be attained to by the present standard development routines and supplies. For the development of tall structure structures, numerous discriminating variables must be viewed as and the most critical component is the formwork operation, which impact highly on the decrease of construction time, cost and provide economical for the projects. Formwork plays an important role in construction industry on both economy and also execution time. Formwork is commonly based on multitier shoring tower for large and having high clearance concrete construction like commercial, industrial, residential, public and civil engineering projects all over the universe. Shoring towers are regarded as conventional formwork, made up of hand carried elements and are assemble in construction site a new and used as large number of times. Their manufacturing nature has only distinct features like they are module, they are made up of steel or aluminium, they are erected to greater heights as well as for lower heights and also often make up the vertical shoring of industrialized table forms. This shoring towers are preassemble in short module on the ground and they are lifted to required final location using cranes very easily when compare from the other formwork systems which are available now. Shoring towers will increase the quickness in the construction work and also flexibility in assemble and construction which will come on the prop-supported slab formwork system. This can also
increase the capacity to withstand maximum working loads which are coming from construction work. This shoring towers was modelled in Solid Works based on our requirements of the projects and periodic analysis was made with boundary conditions and loading by using ANSYS. The results were discussed carefully in order to get the optimized model from all other.
2 LITERATURE REVIEW In 2000, L.B. Weesner and H.L.Jones explain the experimental and analytical capacity of frame scaffolding. The similarities between the estimated and measured ultimate loads in frames with four different scaffolding, commercial software does indeed provide a reasonable upper bound prediction of ultimate capacity. This paper gives the maximum capacity which can resist the scaffolding. In 2006, I.Puente explains about shore-slab interaction in multistory reinforced concrete buildings during construction. This paper gives the zones were the shore-slab interaction in tall structure to be considered and also way of application of loading on it. In 2010, Hongbo and Wabg explain the experimental and analytical studies on the stability of structural tube and coupler scaffolds without X-bracing. From the full-scale tests and FEM analyses, it is specified that the global flexural buckling along the length of weak axis is the crucial failure section of STCS's.
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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 1 – MAY 2015 - ISSN: 2349 - 9303
3 MODELING OF SHORING TOWERS USING SOLID WORKS
Shoring towers are modeled by using Solid Works with 30 mm dia, 40 mm dia, 50 mm dia and 60 mm dia steel hollow sections with different variations of slab thickness. In this modeling, shoring tower height is taken as 3m and also consists of head of height 15cm and base screw of height 30cm. The components which are used to design the shoring tower in solid works are bottom base screw, connectors with varying diameters, frames 1m, frames 0.35m and head to withstand standard H-beams on it. The following shows some of the details of the shoring towers parts.
Fig 3: 3d base plate
model of
3.4 H-Beam
3.1 Tube Steel hollow section is designed with inner dia as 40mm and outer dia as 50mm. These tubes are used to place vertically on base plate or on bottom base jack and also in horizontal directions of the frames to connect with each.
This are arranged on the top of the head as primary and Secondary beams on which plywood and slab will rest.
Fig 4:
3d model of H-Beam
3.4 Combination of Models Fig 1: 3d model of tube with 50mm dia
3.2 Head This heads are designed to carry girders, e.g. H12, H16, H20 or steel girders. It can be used as a single or double stringer.
Different models are made in solid works with varying diameters for tubes and also for slab and plywood thickness which are placed above the standard plywood HBeams.
Fig 2: 3d model of head with 50mm dia of tube below
3.3 Base Plate This item is placed in the starting phase of the assembly, according to the layout of the project’s drawings. It provides a stable support to the shoring. It is also useful to extent the structure by inserting base jack on the top of it.
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Table 1: different combinations of tubes with slab and plywood
INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 1 – MAY 2015 - ISSN: 2349 - 9303
The 3D model of shoring tower for the structural slab formwork systems in this research is modelled in solid works with dimensions 3mx3mx3m and also with standard H-Beams, top plate, base plate and tubes of 1m as shown in Fig
Fig 7: Connections (bonded) for parts in shoring towers
4.2 Meshing Fig 5: 3D model of shoring tower with slab and plywood
4 ANALYSIS OF SHORING TOWERS USING ANSYS The 3D model of shoring tower for the structural slab formwork systems in this research is modelled in solid works with dimensions 3mx3mx3m and also with standard H-Beams, top plate, base plate and tubes of 1m as shown in Fig
Division of the domain into elements is called mesh. Discretization is the process of subdividing a problem domain into series of smaller regions called as finite elements. It is the first step in the finite element analysis of a system basically involves the Discretization of irregular domains into smaller and regular subdomains. The meshing is done with mesh tool menu which has global set containing the size of the element divisions which defines the size of the element which is formed. As the size of the elements decreases the elements are increased in number which the results obtained are too accurate. As the elemental number increases the time consuming for solving a problem for the particular load increases thereby requires more memory space in the computer. Each element is assumed to be connected to the neighboring elements only at finite number of discrete points called nodes.
Fig 6: 3D model of shoring towers in ansys file
4.1 Geometry and Connections Shoring tower model is created for slab formwork systems by using Solid Work software. The model consists of 3mx3m with height of 3m and each tube is connected at placing of 3m clear span. The contact regions for the individual’s parts are taken as bonded one and selection of materials like structural steel, concrete, plywood, etc., for individual’s parts are also selected.
Fig 8: Coarse type of meshing for model
4.3 Loads and Boundary conditions A building has to perform many functions satisfactorily. Design of building should be structurally safe from loads being acted upon. Indian Standard (IS: 875 part 2-1987) provided a loading standard for buildings to save from hazards of life and property caused by unsafe structures. Generally the weight of concrete with reinforcement is taken as 25KN/m2, self-weight of
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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 1 – MAY 2015 - ISSN: 2349 - 9303
formwork for ordinary concrete varies between 0.5KN/m2 to 0.75KN/m2 and imposed load of 1.5kN/m2 uniformly distributed load are calculated and applied on the top of the slab. The fixed supports are to be applied at the bottom of the base plates.
Fig 9: Application of pressure on the top of the model
Structural steel tube of hallow section with outside diameter of 40mm and inside diameter of 30mm with different variations of slab thickness and also with plywood thickness are shown in table Table 3: Different combinations for 40mm diameter tubes
Fig 10: Fixed support given at bottom of the base plate
5 RESULTS AND DISCUSSIONS Analysis of the shoring towers was done with different loading conditions. Based on these conditions, we obtained the total deformation, Von-Misses stress and elastic strain. The total deformation values are decreases from 30 mm diameter tubes to 60 mm diameter tubes when they are made combinations with different variations of slab thickness and also with plywood thickness. Finally we plot a graph between loads vs. Deformations.
Structural steel tube of hallow section with outside diameter of 50mm and inside diameter of 40mm with different variations of slab thickness and also with plywood thickness are shown in table
5.1 Tabular Columns for different diameters of Tubes Structural steel tube of hallow section with outside diameter of 30mm and inside diameter of 25mm with different variations of slab thickness and also with plywood thickness are shown in table Table 2: Different combinations for 30mm diameter tubes
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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 1 – MAY 2015 - ISSN: 2349 - 9303
Table 4: Different combinations for 50mm diameter tubes
Fig 11: Total deformation variations obtained for model
Structural steel tube of hallow section with outside diameter of 60mm and inside diameter of 50mm with different variations of slab thickness and also with plywood thickness are shown in table
5.3 Von-Misses Stress
Table 5: Different combinations for 60mm diameter tubes
Fig 12: Von-Misses Stress for model
5.4 Equivalent elastic Strain
5.2 Total deformations The maximum and minimum deformation for shoring tower is obtained by static analysis in ANSYS. The maximum deflection happens at the centre of the concrete slab and minimum deflection i.e., zero, at the fixed support
Fig 13: Equivalent Elastic Strain for model
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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 5 ISSUE 1 – MAY 2015 - ISSN: 2349 - 9303
Fig 14: Deformations vs. Loads for 30mm dia steel hallow section tubes Fig 17: Deformations vs. Loads for 60mm dia steel hallow section tubes
Fig 15: Deformations vs. Loads for 40mm dia steel hallow section tubes Fig 18: Strain vs. Stress for 30mm dia steel hallow section tubes
Fig 16: Deformations vs. Loads for 50mm dia steel hallow section tubes Fig 19: Strain vs. Stress for 40mm dia steel hallow section tubes
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development of design guidelines. Eng. Struct 1996;18:258 67. [5] Chan SL, Zhou ZH, Chen WF, Peng JL, Pan AD. Stability analysis of semirigid steel scaffolding. Eng. Struct 1995;17:568 74. [6] Peng JL, Pan ADE, Chan SL. Simplified models for analysis and design of modular false work. J Constr Steel Res 1998;48:189 209. [7] Yu WK, Chung KF, Chan SL. Structural instability of multi-storey doortype modular steel scaffolds. Eng. Struct 2004;26:867 81. [8] Hurd, M.K., 2005. Formwork for Concrete, Special Publication No.4, Seventh Edition, American Concrete Institute (ACI), Michigan, U.S.A. [9] Goyal, J., 1992. R.C.C. Structure Construction Through Slip-Forming, CBS Publishers & Distributors, New Delhi. [10] Austin, C.K., 1960. Formwork to Concrete, Cleaver-Hume Press, London. [11] Peurifoy, R.L., and Oberlender, G.D., 2011. Formwork for Concrete Structures, McGraw Hill, U.S.A. [12] Rupasinghe, R., and Nolan, E., 2007. Formwork For Modern, Efficient Concrete Construction, BRE press. [13] Kannan, M.R., and Santhi, M.H., 2013. Automated Construction Layout and Simulation of Concrete Formwork Systems Using Build-ing Information Modelling Proceeding of the 4th International Conference of Euro Asia Civil Engineering Forum on Innovations in Civil Engineering for Society and the Environment, National University of Singapore, Singapore, pp. [14] Chi, S., Hampson, K., Biggs, H., 2012. Using BIM for smarter and safer scaffolding and formwork construction: a preliminary methodology. Modelling and Building Health and Safety, Singapore.
Fig 20: Strain vs. Stress for 40mm dia steel hallow section tubes
Fig 21: Strain vs. Stress for 40mm dia steel hallow section tubes
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CONCLUSION
From the static analysis, the model with 60 mm diameter with variations of slab thickness has less total deformations compare to all other models. Von-Misses stress are also decreases from 30mm diameter tubes to 60mm diameter tubes while Equivalent elastic strain also decreases from 300mm diameter tubes to 60mm diameter tubes. The model with 60mm diameter with slab thickness 100mm has lesser deformation, lesser stress and also lesser strain. These will gives optimized results compare all other models.
REFERENCES [1] Milojkovic B, Beale RG, Godley MHR. Determination of the factors of safety of standard scaffold structures. In: Proceedings of international conference on advances in steel structures. vol. 1. 2002. p. 303 10. [2] Vaux S, Wong C, Hancock G. Sway stability of steel scaffolding and formwork systems. In: Proceedings of international conference on advances in steel structures. vol. 1. 2002. p. 311 19. [3] Peng JL, Pan AD, Rosowsky DV, Chen WF, Yen T, Chan SL. High clearance scaffold systems during construction-1: Structural modelling and modes of failure. Eng. Struct 1996;18:247 57. [4] Peng JL, Pan AD, Rosowsky DV, Chen WF, Yen T, Chan SL. High clearance scaffold systems during construction-2: Structural analysis and
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