Advances in Lightweight, Deployable and Steel Composite Structures

Transcription

1 Structural Steel Research Group Annual Seminar (SSRG ) Advances in Lightweight, Deployable and Steel Composite Structures Organised by Centre for Construction Material and Technology Sponsors: Corus International Asia and Continental Steel Pte Ltd The National Stadium (Bird's Nest), P.R. Chin

2 Agenda One-Day Seminar (Free Admission) The main objective of this seminar series is to provide a forum for research staffs and industrial engineers to exchange ideas. Academic and technical topics covering the following board areas will be presented and discussed. 1) Deployable Space Frame Structures Research members: Vu Khac Kien; Tran Chi Trung; Song Jianhong; Li Ya 2) Lightweight and Composite Materials and Structures Research members: Wang Tongyun; Chia Kok Seng; Dai Xuexin; Kazi Md. Abu Sohel; Lee Siew Chin; Xiong Dexin 3) Risk and Hazard Mitigation of Blast and Fire Research members: Kang Kok Wei; Yu Hang Each 25-min presentation will be followed by 5-min question-and-answer session. Your attendance and comments are very much appreciated. DETAILS: Date: 1 st, March, 2007, Thursday Venue: Blk E5, 03-19, Faculty of Engineering, 4 Engineering Drive 4, National University of Singapore, Singapore Time: 09:00 hrs 17:45 hrs Organized by SSRG - CCMT,, National University of Singapore Sponsored by Corus International Asia and Continental Steel Pte Ltd ENQUIRIES: For technical enquiry, please contact: Programme Director of Hazards, Risks & Mitigation Associate Professor Liew Jat Yuen, Richard Tel: ; cveljy@nus.edu.sg For registration, please contact: CE Office, Ms Juliana Bte Miswan: Tel: ; cvejulia@nus.edu.sg For further details, please contact: Coordinator, Mr. Dai Xuexin: Tel: ; Dai@nus.edu.sg i

3 Agenda Programme Time Event 9:00 9:15 Registration 9:15 9:30 Opening Speech Prof. J. Y. Richard Liew 9:30 10:00 Design and Analysis of Pre-tensioned Deployable Structures Vu Khac Kien (Ph.D. candidature) 10:00 10:30 Robustness of Novel Deployable Membrane Structures Tran Chi Trung (Ph.D. candidature) 10:30 11:00 Tea Break 11:00 11:30 Simplified Procedure for Estimating The Maximum Earthquake Responses of Radially Arranged Cable Truss Song Jianhong (Ph.D. candidature) 11:30 12:00 Linkages Between Today and The Future of Deployable Booms Li Ya (Ph.D. candidature) 12:00 13:00 Lunch 13:00 13:30 Development of Ultra-Lightweight Concrete for Applications in Steel-Concrete- Steel Composites Chia Kok Seng (Research Fellow) 13:30 14:00 Comparison of Fiber-Reinforced Lightweight Aggregate Concrete for Sandwich Composite Structures Dai Xuexin (Ph.D. candidature) 14:00 14:30 Steel-Concrete-Steel Sandwich System Subject to Static and Impact Load Kazi Md. Abu Sohel (Ph.D. candidature) 14:30 15:00 Tea Break 15:00 15:30 Novel Shear Connectors for Composite Construction Wang Tongyun (Research Engineer) 15:30 16:00 Numerical Modeling of Sandwich Composites Panels Subject to Impact Lee Siew Chin (Research Fellow) 16:00 16:30 Concrete-Filled Tubular Columns- Potential Applications for Multi-storey Buildings Xiong DeXin (Research Engineer) 16:30 17:00 Steel and Composite Members Subject to Blast Loading Kang Kok Wei (Ph.D. candidature) 17:00 17:30 Behaviour of Multi-storey Frame Structures under the Combined Effect of Blast and Fire Yu Hang (Research Engineer) 17:30 17:45 Closure Prof. J. Y. Richard Liew (Each presenter has 25-min presentation followed by 5-min Q&A session) ii

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5 Design and Analysis of Pre-tensioned Deployable Structures Vu Khac Kien Ph.D. candidate Deployable structures set a new level of construction in terms of speed and time savings due to their deployability. Most of deployable structures for civil engineering applications require pre-tensioning to stabilize their deployed forms. Therefore, the design of these pre-tensioned deployable structures involves various engineering aspects, including advanced non-linear analysis to account for pre-tensioning effects, joint designs to allow deployment of the structure, and experiments and testing. Furthermore, there is always a need to answer the question is there any alternative solutions? In the presentation, all of the above issues will be addressed and illustrated with the case studies of deployable tension-strut structures. KEYWORDS: Pre-tensioning, Deployable Structure, Advanced Non-linear Analysis, Structural Form Variations 1

6 Robustness of Novel Deployable Membrane Structures Tran Chi Trung Ph.D. candidate Two innovative deployable membrane structures, namely the Deployable struttensioned membrane structures (DSTMS) and the Butterfly-wing structures, have been proposed for rapid erection of large span enclosures. Since the membrane material is vulnerable to damage, it is important to ensure the safety of supporting components of the structures in the event of membrane failure. There are several threats to membrane, in which, vandalism and fire are the most critical hazards. This report investigates the robustness of DSTMS and Butterfly-wing structures against these two hazardous scenarios. In the vandalism scenario, membrane is considered as totally damaged, and thus progressive analysis is performed to assess the robustness of DSTMS and Butterfly-wing structures subjected to total membrane removal. Dynamic impact due to the sudden loss of membrane tension is also taken into account of the robustness study. It was found that both DSTMS and Butterfly-wing structures remain robust even in the event of the entire membrane damage due to vandalism. In the fire scenario, the robustness of DSTMS and Butterfly-wing structures subjected to internal fire occurring at critical locations is assessed in accordance with Eurocode 1&3 Part 1:2. The characteristics of membrane materials as well as the behaviour of membrane structures subjected to fire are discussed and explained. The study also presents an approach of determining the structural fire resistance of large space membrane structures according to their performance in real fire. Interestingly, it was found that none of structural members of either DSTMS or Butterfly-wing structures exposed to fire was damaged. This implies that both DSTMS and Butterfly-wing structures have enough robustness against the fire hazard without the need of costly fire protection. KEYWORDS: Butterfly-wing Structures, Deployable Strut-tensioned Membrane Structures, Fire, Hazards, Robustness, Vandalism 2

7 Simplified Procedure for Estimating the Maximum Earthquake Responses of Radially Arranged Cable Truss Song Jianhong Ph.D. candidate Though the finite element method has been a dominating analysis tool for structural design, simplified analysis method is still desired by many engineers. Simplified analysis method can be used for estimating responses and initializing member sizes in preliminary design as well as checking finite element solution in detailed design. A simplified procedure is proposed in the presentation for estimating the maximum earthquake responses of radially arranged cable truss which has been widely constructed around the world. The procedure is based on a hand-calculation formula derived according to some important findings: first, the vertical response is dominated by the first vertical symmetrical mode. Secondly, the vertical component is the main contributor of total earthquake response. Thirdly, the mode shape of the first vertical symmetrical mode is similar in shape to static deflection curve and thus can be modeled by deflection function. Numerical verification suggests that the proposed formula can be adopted in the design of such structure. KEYWORDS: Earthquake Responses; Band-calculation Formula; Mode Shape; Radially Arranged Cable Truss; Simplified Procedure 3

8 Linkages between Today and the Future of Deployable Booms Li Ya Ph.D. candidate Deployable structures are structures capable of large configuration changes in an autonomous way. Normally, these structures are used for easy stowage and transportation. And deployable boom structures are normally folded or unfolded in one dimension, which can be regarded as linear deployment device. An overview of various deployable boom structures, consisting of tubular booms, tensegrity booms, pantographic booms as well as other booms, is given. Challenges in form-finding and configuration refining as well as terrestrial applications are discussed. The emphasis will be on the possibility of using intuitive design method in this field and the trends of application on earth. Design targets relating to safety, serviceability and deployment speed are outlined and the module design concept for boom structures in the future are briefly described. Possibility of the application based on earth of the deployable booms is concerned with relative design concept. KEYWORDS: Deployable Booms, Form-finding, Intuitive Design 4

9 Development of Ultra-Lightweight Concrete for Applications in Steel-Concrete-Steel Composites Chia Kok Seng Research Fellow This paper presents an experimental study on the development of ultralightweight concrete (ULWC) for use in steel-concrete-steel (SCS) composites for offshore and marine applications. Conventional construction of steel structures usually involves a large number of stiffeners welded to the main steel plates to increase stiffness and prevent buckling. The process entails complex detailing that demands tight quality control, and is often labor intensive and time consuming. Appropriate design with SCS composite structures can eliminate stiffeners, thereby reducing the welding job and steel consumption, and improving fabrication processes. This is especially desirable with increased steel price over recent years. In using SCS composites for floating structures, it is essential that the materials used is light so that structural dead load may be reduced for economical and engineering reasons. ACI 213 defines structural lightweight concrete as those with a minimum 28-day cylinder compressive strength of 17 MPa and an equilibrium density (unit weight) between 1120 and 1920 kg/m 3, made with lightweight aggregates or a combination of lightweight and normal-weight aggregates. With careful selection of ingredient materials and optimization of mixture proportions, ULWC with 28-day cube compressive strength of 20 MPa and air-dry unit weight close to 1100 kg/m 3 are produced. KEYWORDS: Lightweight Aggregates, Steel-Concrete-Steel Composites, Ultra- Lightweight Concrete 5

10 Comparison of Fiber-Reinforced Lightweight Aggregate Concrete for Sandwich Composite Structures Dai Xuexin Ph.D. candidate Composite structures are gaining tremendously increased applications in aerospace and naval engineering. Many attempts have been made to employ composite structures in marine and offshore structures, e.g. ship double-hull. This may be an effective way to reduce consumption of longitudinal stiffeners, thus decreasing welding volume and eliminating fatigue problem. Lightweight aggregate concrete (LWAC) have been developed as infill material in steel-concrete-steel sandwich composite to be employed in double-hull construction. However, concrete is one type of brittle material in which fiber is essential to mitigate its brittleness and enhance its ductility, strength and fatigue resistance. Thus, three types of generally used and commercially available fibers are investigated for comparison study: 30 mm hook-ended steel fiber, 13 mm straight steel fiber and 30 mm straight PVA fiber. The objective is to select one type with best performance as infill material for sandwich panel to be employed in double-hull construction. The main parameters that are investigated are fiber types and fiber volume fraction. From the test results, it is concluded that fiber reinforced LWAC using hookended steel fiber with 2% volume fraction shows the best performance on static flexural strength, toughness and fatigue. If cost is taken into consideration, fiber reinforced LWAC using hook-ended steel fiber with 1% volume fraction is the best choice by Performance/Cost index. KEYWORDS: Steel-Concrete-Steel, Double-hull, Lightweight Aggregate Concrete (LWAC), Hook-ended Steel Fiber, Fatigue 6

11 Steel-Concrete-Steel Sandwich System Subject to Static and Impact Load Kazi Md. Abu Sohel Ph.D. candidate The Steel-concrete-steel Sandwich system comprising steel faceplates acting compositely with a compact fibre reinforced concrete core can replace stiffened steel plate, precast and reinforced concrete in deck-like structures. The innovative J-hooked shear connectors are the basic structural component of Steel-Concrete-Steel Sandwich system. In SCS sandwich system, the J-hook plate connections, embedded in concrete, are subject to tension, shear and bending. A series of static and impact tests has been carried out to evaluate the performance of steel-concrete-steel (SCS) sandwich beams subject to low velocity hard lateral impact and three point static load. Test also carried out to evaluate the performance of J-J shear connector subject to direct shear force. A specially designed 64-kg drop hammer with a hemispherical head, dropped from a height of 4.0 m, was used to produce the required impact force. Following the impact, for all specimens, the impact force history and permanent deformation were measured. The J-J shear connector performs well to resist the impact force and it helps to prevent the separation of outer steel skins during impact. KEYWORDS: Steel-Concrete-Steel, Sandwich System, J-J Shear Connector, Impact 7

12 Novel Shear Connectors for Composite Construction Wang Tongyun Research Engineer Steel-concrete-steel sandwich composite system has advantages over conventional stiffened plate construction. The key is the composite action between steel and concrete. To make these two materials working compositely and efficiently, it is critical to ensure successful shear transfer mechanisms. Conventional shear studs, and previously J-J shear connectors are examined. Direct bonding between steel face plates and concrete core has also been tested. However, intrinsic problems still exist. After discussion on these issues, this presentation will demonstrate the insight evolution of the development of the proposed novel shear connector. The corresponding construction procedure of the sandwich plates will also be demonstrated. Based on the preliminary numerical simulation results, the unique characteristics of the proposed shear connectors will be discussed to give a preliminary recommendation. KEYWORDS: Composite Structure, Shear Connector, Adhesion 8

13 Numerical Modeling of Concrete Sandwich Composites Panels Subject to Impact Lee Siew Chin Research Fellow Three-dimensional Finite Element (FE) models of lightweight concrete sandwich composite panels subjected to low-velocity drop-weight impact is presented in this seminar. The objective of the FE models is to predict the local damage of the sandwich panels and to capture the impact force time history of the hammer upon impact. The commercial LS-DYNA FE package was utilized for analysis and material model 72 was applied to model the lightweight concrete core. In this study, the high mass impact was achieved by dropping a 58 kg cylindrically shaped steel hammer, which has a hemispherical tip of 100 mm, from a height of 4 m onto the 300 mm x 300 mm sandwich panels. From the comparison to experimental data, it was shown that the FE models gave a reasonably good prediction of the penetration depth of the panels as well as closely predicted the impact-force time history of the drop-weight hammer. KEYWORDS: Drop Weight; Low-velocity Impact; FE Model; Local Damage; Impact- Force 9

14 Preload Effect on the Capacity of Axially Loaded Concrete- Filled Columns Xiong Dexin Research Engineer Concrete-filled steel tubular (CFST) columns are often used for high-rise construction. The hollow steel tubes are usually installed first with steel floor beams and metal floor decking, and they are connected to the bracing structures. The floor decks are then cast and concrete is pumped into the hollow steel tubes after several floors have been constructed. Therefore, before the infilled concrete has been hardened, the tubes are usually pre-loaded by the weight of unsolidified core-concrete, self-weight of steelwork and floor slabs, working load, etc. The preload produces initial stresses and deformations in the steel tubes and will affect the stiffness and strength of the composite columns. A modified Eurocode approach is proposed to evaluate the axial resistance of concrete-filled column subjected to preload. Finite element (FE) analyses are carried out on CFST with various preload ratio, eccentricity ratio, column length, material strength, etc. The FE analysis results together with other published test data are used to validate the proposed design method. It is showed that the proposed method could give good estimation of the preload effect on the capacity of CFST. KEYWORDS: Buckling; Concrete Filled Tube; Composite Column; Initial Stress; Preload; Eurocode 4 10

15 Section Classification of Steel Members Subject to Blast Loading Kang Kok Wei Ph.D. candidate This paper provides an interesting view point into the classification of steel members when they re subjected to blast loading. Being one of the preliminary steps in the design of steel structures, it is critical to correctly assess the section classification of the steel members. Due to the high strain rate effects, steel will exhibit a different stressstrain response when they are being subjected to blast loading. The yield strength, which will increase under such situations, will in turn affect the classification of the member. This difference will usually require the steel members to be reclassified to one with a lower resistance. A review of the current approach in determining the section classification will be provided and some shortcomings will be highlighted. Finally, numerical simulations, with the use of an explicit solver LSDYNA, will simulate 3 beams and 3 columns subjected to both near and far field blast loadings to determine the effects of strain rate on the steel members. Through these tests, the current approach in section classification of the members will be verified. KEYWORDS: Blast, High Strain Rate Effects, Section Classification, Steel, Yield Strength 11

16 Behaviour of Steel Frame Structure under the Combined Effect of Blast and Fire Yu Hang Research Engineer Since the terrorist attack is becoming more and more severe, the structural resistance of hazards caused by terrorist attack has gradually attracted the researcher s attention. According to the observation of 911incident in United States, it is the combination effect of impulsive load and fire load caused the collapse of the WTC tower. A steel frame structure is studied under the combination effect of impulsive load and fire load in this presentation. The effects of different parameters are discussed, such as the intensity of blast, location of hazard and so on. The response of structure under fire load is also compared with the response of structure under combination hazard of blast and fire. It is observed that the fire resistance of structure is greatly reduced when it is subjected to impulsive load. Besides, the fire hazard after explosion may also cause structural collapse even though the structures survive after an explosion hazard. Moreover, different strategies of simulating the structural response with commercial software LS-DYNA are also discussed. Further research should be concentrated more on the quantitative analysis of the structural response under the combination effect of blast and fire. KEYWORDS: Blast, Fire, Steel Frames, Combination Effect 12