Smart Construction Research RESEARCH ARTICLE Spatial Three-dimensional Technology of Special-shaped Pier Based on BIM YU Hongli, LONG Wenliang,QINA Jia,XIONG Yuangu No.1 Engineering Co., LTD. Of FHEC of CCCC Abstract: The development of society pushes people to pay increasing attention to the appearance of bridges apart from their quality and safety. It turns to be an inevitable trend of the emergence of bridges with novel forms and unique shapes, which could not only meet traffic demand, but also effectively integrate with their surrounding environment to form a beautiful landscape. However, complicated structure and unique shape make it difficult of the bridge construction. As the basic part of construction, pier model affects the construction of pier formwork and pier reinforcement. Currently, BIM has been widely used in the construction industry in China. Nevertheless, there has not been any cases of the formwork design nor reinforcement processing of spatial three- dimensional special-shaped pier. And it is the first time for the construction of spatial three-dimensional special-shaped bridge. So it is of great significance of the analysis on spatial three-dimensional technology of special-shaped pier based on BIM to promote the development of construction industry. Keywords: spatial three-dimensional; BIM; formwork; reinforcement 1. Introduction Cit at ion : YU Hongli (2017). Project Standard Design and Spe cial Research Report Takeunder ground commercial design of AB block in YU Hongli Central International Plaza as an example, vol. 1: 29 32. doi:// dx.doi.org/10.18063/scr.20 17.01.277. Copyright: 2017 YU Hongli This is an Open Access art icle distributed under the terms of the Creative Commons Attribution- NonCommercial 4.0 International License (http://creativecommons. o r g / l i c e n s e s / b y - n c / 4. 0 / ), permit- ti n g al l non -comme rc i a l u s e, d i s t r i b u t i o n, a n d repro du cti on in any medium, pro vided t he orig in al wor k is p r o p e r l y c i t e d. Xuzhou CSocial economy growth turns the quality, safety and function only to be the basic requirements of constructions. Instead, people pay more and more attention to their landscape and multi-functionality. Therefore, it becomes an inevitable trend of the emergence of special-shaped constructions. Nevertheless, the more complicated the structure models are, the more difficult their construction and the higher their cost are. So it is extremely important to decrease the construction difficulty of spatial threedimensional special-shaped framework and reinforcement to increase their processing accuracy. However, there are several defects of the normal construction technology: ( 1) The normal formwork design adopts CAD and 3D-Max. CAD modeling is based on polygon principle, therefore, it is impossible for it to accurately simulate and calculate numerical values of hyperboloid model. And 3D-MAX pays more attention to model and rendering, but lacks accuracy of surface model data. So it can not guide the block blanking. In all, the period of formwork design and processing is longer but the accuracy is lower if spatial three-dimensional special-shaped framework is designed by the above softwares. ( 2 ) The normal reinforcement technology could only process reinforcement with twodimensional plane. However, jig frame is required for the reinforcement with threedimensional plane. At the meantime, reinforcement bending test should be performed repeatedly. So it costs more materials, human resources and longer time. But the accuracy is relatively lower. 2. Construction Profile Xinggang Street Overpass is located in CBD Suzhou Center, western Jinji Lake, Suzhou Industrial Park,And it is an important part of Suzhou Central Landscape Project and its 33
TSpatial Three-dimensional Technology of Special-shaped Pier Based on BIM supporting projects. Its structural bridge design is performed by LERA Corporation (America), its landscape plan is designed by SWA Corporation and its construction plan is completed by Architects & Engineers Co., LTD. of Southeast University. The Overpass includes 26 piers, among which there are 15 in the form of spatial curved surface. And they look like calla. The spatial curved pier could be divided into three gradients: in the first part, the spatial curved pier is in a circular format; in the second part, the circle gradually turns upward into ellipse; and in the third part, the pier section gradually moves upward to connect with the beam bottom. Fig. 2.1-2 3-dimensional picture of pier column Fig. 2.1-2 3-dimensional picture of beam 3. Problems of Forwork Design and Reinforcement Processing Affected by pier model, formwork and reinforcement of the overpass are in the form of spatial curved surface. According to the construction plan, self-compacting concrete is required for the project, which should realize the effect of fair-faced concrete. And it directly points out that the processing of formwork and reinforcement should not apparently transform the straight line into a curve line. In addition, the panel of the formwork is made from 8mm steel, and the main reinforcement of the pier column is Φ40 steel bar. During the preliminary test, many problems of formwork without block optimization emerged, including multi-joints, not smooth joint seams, less accurate surface precision and longer processing period. Moreover, the steel bar is with less accurate precision, making it difficult to match with the formwork but extending the processing period. 4 Technology Principle 4.1 Principle of Formwork Design and Processing The three-dimensional special-shaped hyperboloid formwork is collectively modeled by ribbed panels and simulated on a 1:1 scale. And the formwork division is performed based on principles of symmetry and aesthetics as well as less joints (to keep the curved surface smooth). Surface deviation is controlled by block refinement based on surface curvature and camber. And the panel block is equidistant from the rib. So the number of surface blocks could be possibly reduced, and the symmetry and aesthetics of the formwork could be guaranteed. In addition, the adjustability of the curved surface and the quality of the joint between different curved panels would be improved. Moreover, the bending quality of the curved panel could be guaranteed because the length of the double-layer ribs in and out of the curved panel as well as the double diagonal of the small block panel could directly affect the curvature changes of the curved panel. According to the demands of easy processing, adjustabililty, aesthetics and smoothness of joint and the quantification ratio of the curve surface, the pier formwork is divided into 4 blocks vertically to gain 4 boundary lines to serve as the starting vertical control rib in the outer layer. Taking the two ribs along the bridge as the basic curve edge, vertical to which create the surface line on the panel as the horizontal section line. Based on this, create the control rib in the outer layer to control the direction of curve deformation. Set vertical tool in the curve plane to guarantee the extend direction of the curve plate to improve the accuracy of factory processing. To reduce the adjustment range of the curve panel during 34
the process of welding, it is required to perform the compression bending to the curved plane along the single direction (the direction with larger bending). And then the second bending would be performed based on double diagonal of the curved plane to make it primarily bi-directional bending. At last, it will be accurately located by the three-node control rib and tool during the process of welding. After welding, the control tool could be removed and transferred to the outer layer of the curved plane to secure the stability of the control rib and plane. 4.2 Principle of Reinforcement Processing The three-dimensional model of reinforcement is created by Rhino, an associated software of BIM. The file is transformed through IGES conversion station. And the two-dimensional decomposition of the spatial three-dimensional special-shaped pier would be performed. Extract the parameter from the decomposed dwg file to gain the parameter of the coordinate angle of the control point on reinforcement linear segment. As a result, it is easier to parameterize the bending of the reinforcement and refine its processing to secure the accuracy of the curved line processing of the reinforcement. 5 Technological Process and Points 1 Create accurate model of concrete facing of pier column in Rhino Model. And upload it into solidworks (a drawing software of structural steel model). Furthermore, benchmark and tool are determined by zebra diagram to improve the accuracy of the formwork. Fig. 5-1 Rhino Model of Pier Column Fig. 5-2 Zebra Diagram of Model Fig. 5-3 AUTOCAD of Tool Position Fig. 5-4 Model of Tool Position 2 To make it more convenient for formwork installation and dismantlement, segment and approximately symmetrically cut the formwork. Fig. 5-5 Segmentation of Formwrok 35
TSpatial Three-dimensional Technology of Special-shaped Pier Based on BIM 3 The plane is created with the lowest point of the formwork and wholly lofted upward by 50mm. After benchmark selection, transform the curve line into a straight line of the surface with lower curvature. In addition, the elevation of each node is measured. See below: Fig. 5-6 Benchmark Formwork Fig. 5-7 Completion of Benchmark and lofting 4 Rib Formwork Determination. According to the position and size of the grid in the simulated force analysis, the minimum distance (i.e. 400mm) of rib at easy deformation section could be determined. Moreover, the selection of ribs should be vertical to the panel. Fig. 5-8 Simulated Force Analysis of Curved Formwork Fig. 5-9 AUTOCAD of Rib Position 5Upload the position map into the model to perform the cutting process. And simulate and thicken the theoretical one-side model (the thickness of the steel is 8mm). Fig. 5-10 Position Model of Ribs Fig. 5-11Processing of Thickening 8mm According to the width of the ribs and steel, the steel plate is thickened outward of 140mm. And the position and number of the setting tools and ribs are determined by the design principle and the force analysis of the formwork. In addition, the rib plates and tools are created through the sheet metal function. Fig. 5-11 Tooling Block(1) Fig. 5-12 Tooling Block(2) 36 35
5.1.5 Since the single control ribs are set at the same surface, it is easier to extract linear factors to perform CNC plasma cutting and blanking. According to the curved plate which is divided, the size of the surface could be accurately extracted by flattening of curved surface. And the bending processing could then be performed. Fig. 5-13 Material Extraction of Segments Arrange the layout based on the flattening figure of the model. And the corresponding small parts are cut by CNC plasma cutting machine on 8 mm steel. Once completed, each part should be identified and deposited according to the construction design. Fig. 5-14 Panel cutting with CNC Plasma Cutting Machine Fig. 5-15 Completed Rib Fig. 5-16 Semi-finished Processing of Panel Blanking and Bending 37 Fig. 5-17 Connection of base plate and rib
Project Standard Design and Special Research Report Fig. 5-18 Welding of Panel and Horizontal Rib Fig. 5-19 Completed Formwork 6. Installation Process of Special-shaped Pier Reinforcement Measure the plane coordinate and top elevation of the embedded main reinforcement at the construction site and transform the data identifiable to Rhino Model. Decompose the Rhino Model and upload the data of the construction measurement into it. Fig. 6-1 Integral Model of Pier Column The reinforcement of the pier column should be drawn based on pier column model and the rules of reinforcement in the Rhino Model. Fig. 6-2 Reinforcement Model of Single Pier Column Each reinforcement of the pier column is transformed from three-dimensional spatial position to the plane coordinate, the result of which is saved as.dwg format. And number clockwise with the longest axis setting as 1#. Fig. 6-3 Extraction of D40mm Reinforcement Fig. 6-4 Extraction of D40mm Model of Pier Column (1) Reinforcement Model of Pier Column (2) 38
Open the resulting graphics in AutoCAD. Affected by domestic technology and cost, it is impossible to accurately process the non-uniform curve reinforcement. And according to the construction design, the thickness deviation of the reinforcement layer of the pier column is ±1cm. Therefore, this project transforms the curve line of the reinforcement into a straight line after setting the maximum value of the camber for each segment at 5mm. To meet the accuracy requirements, take points at the reinforcement axis every 20cm, 40cm or 80cm and extract the relative position of the adjacent points (the length of the segments and the turning angle between the segments). Fig. 6-5 Marked Reinforcement The angle of compensation and rebound angle of Φ40 steel bar could be tested and calculated after the modification of the host of CNC bending machine. According to the data extracted, mark and unload the reinforcement. Process the reinforcement successively by CNC bending center and put it in order. Fig. 6-6 Reinforcement Bending Extract and process the data of reinforced hoop reinforcement. To make it more convenient for the vertical installation of the main reinforcement, the corresponding positions should be marked of the numbered reinforcing bars. The spatial location of the reinforced hoop reinforcement should be measured and lofted at the construction site, following which the other steel bars should be installed successively. 39 Fig. 6-7 Pier Reinforcement Installation (1) Fig. 6-8 Pier Reinforcement Installation (2) 7. Conclusion Social demands promote the development of technology. To guarantee the success of special-shaped construction, it is required to improve construction technology and optimize
TSpatial Three-dimensional Technology of Special-shaped Pier Based on BIM its innovation, which could also make enterprises to survive from the severe industrial competition. It is obvious that the cost rises of special-shaped concrete constructions. It is the first time to perform formwork design and reinforcement processing with BIM. By spatial three-dimensional technology, the formwork design and reinforcement processing of special-shaped pier is completed to reduce the construction difficulty and time. At the same time, the accuracy of formwork and reinforcement processing increases due to the simulation on a 1:1 scale. References 1. Huang Shaogang. Rhino 3D Industrial Modeling and Design, 2011, Tsinghua University Press. 2. Cui Fengkui. Solidworkds Machine Design, 2011, Machinery Industry Press. 40