Conceptual Design in Structural System Development
- 1. Dr. Naveed Anwar Conceptual Design in Structural System Development Design of Tall Buildings: Trends and Achievements for Structural Performance Bangkok-Thailand November 7-11, 2016 Naveed Anwar, PhD
- 2. Dr. Naveed Anwar 2 The Tussle Can design be based on “Engineering Judgment” and “Intuition” Or It must be controlled by explicit computations and, restrictive limits and fully rational approaches
- 3. Dr. Naveed Anwar 3 It is by logic we prove, but by intuition we discover
- 4. Dr. Naveed Anwar 4 What a Structural Engineer Says ! Hardy Cross, 1885-1959
- 5. Dr. Naveed Anwar 5 Structural Engineers are “trained” to follow the procedures and equations and rules and be conformists Whereas Architects are encouraged to dream and be “defiant”
- 6. Dr. Naveed Anwar 6 Most structural engineer should be able to do Determine the wall thickness and reinforcement (6x2x3m) Design the most cost effective water tank to hold 36 Cum of water Most Structural Engineers would not know what to do (Will need a “Structural Designer”)
- 7. Dr. Naveed Anwar 7 Design the most cost effective, beautiful, and amazing water tank to hold 36 Cum of water Performance + Cost + Aesthetes Will need “Structural Artist”
- 8. Dr. Naveed Anwar 8 Structural Engineering and Art • Structural Engineering in Art • Application of structural engineering in creating works of art in architecture and sculpture • Art of Structural Engineering • Taking the structural design to the level of an Art
- 9. Dr. Naveed Anwar 9 The Rational Design Process Architectural Requirements Structural System Development Preliminary Sizing, Modeling and Analysis Response and Design Checks Detailed Modeling, Analysis and Design Performance Based Design Can we speed up this part
- 10. Dr. Naveed Anwar Learning from Experience 10 Architectural Layout Preliminary Sizing Modelling Analysis Design Structural Response And Design To make design preliminary decisions without explicit calculations
- 11. Dr. Naveed Anwar 11 Learn From Experiance A Master Thesis in AIT, based on the Tall Buildings designed by Sy^2 and PBD carried out by AIT Solutions
- 12. Dr. Naveed Anwar 12 Using Artificial Neural Networks
- 13. Dr. Naveed Anwar 13 Learn From Experience
- 15. Dr. Naveed Anwar 15 Using Trained Network for New Design or Quick Check
- 18. Dr. Naveed Anwar 18 A Swing Towards the AI • Rich Pictures • Analytical Hierarchy Process (AHP) • Artificial Neural Networks (ANN) • Genetic Algorithms (GA) • Expert Systems (ES) • Fuzzy Logic • Deep Thinking • Big Data and Data Mining
- 19. Dr. Naveed Anwar The Role of Computers and Software 19 • Initially, computers were used to program the procedure we had • Now, we develop procedures that are suited for computing
- 20. Dr. Naveed Anwar 20 Historical Prospective • In nature, the structures of organisms differ according to their size. For example, the structure of a large animal such as an elephant is radically different from that of a dog or a mosquito. • However, in spite of these obvious differences, until about the middle of the seventeenth century, scientists believed that it was possible to build larger structures simply by duplicating the form and proportion of a smaller one. • The prevailing opinion was that if the ratios between structural elements in the larger structure were made identical to the ratios in the smaller structure, the two structures would behave in a similar manner.
- 21. Dr. Naveed Anwar 21 4 Commandments of Tall Buildings Design 1. Resist overturning forces due to lateral loads by using vertical elements placed as far apart as possible from the geometric center of the building 2. Channel gravity loads to those vertical elements resisting overturning forces 3. Link these vertical elements together with shear- resisting structural elements that experience a minimum of shear lag effects such that the entire perimeter of the building resists the overturning moments 4. Resist lateral forces with members axially loaded in compression rather than those loaded in tension due to overturning
- 22. Dr. Naveed Anwar A Quick Look at Structural Systems
- 23. Dr. Naveed Anwar 23 The Building Structural System - Conceptual Gravity Load Resisting System (GLRS) • The structural system (beams, slab, girders, columns, etc.) that act primarily to support the gravity or vertical loads Lateral Load Resisting System (LLRS) • The structural system (columns, shear walls, bracing, etc.) that primarily acts to resist the lateral loads Floor Diaphragm (FD) • The structural system that transfers lateral loads to the lateral load resisting system and provides in-plane floor stiffness
- 24. Dr. Naveed Anwar 24 Vertical Load Resisting Systems • Supported on stiff beams or walls • One-way and two-way slabs • Main consideration is flexural reinforcement Slabs supported on long rigid supports • Supported on columns directly • Flat slab floor systems • Main consideration is shear transfer, moment distribution in various parts and lateral load resistance Slab-system supported on small rigid supports • Slabs on grade: light, uniformly distributed loads • Footings, mat, etc. Heavy concentrated loads Slabs supported on soil
- 25. Dr. Naveed Anwar 25 Lateral Load Bearing Systems PURPOSE • “To transfer lateral loads applied at any location in the structure down to the foundation level” SINGLE SYSTEM 1. Moment Resisting Frames 2. Braced Frames 3. Shear Walls 4. Tubular Systems DUAL SYSTEMS and Multiple 1. Shear Walls-Frames 2. Tube + Frame + Shear Walls
- 26. Dr. Naveed Anwar 26 Lateral Load Resisting Systems Moment Resisting Frame Shear Wall and FrameShear Wall – Frame Coupled
- 27. Dr. Naveed Anwar 27 Lateral Load Resisting Systems Braced Frame Tubular Structure Braced Tube Systems
- 28. Dr. Naveed Anwar 28 Lateral Load Resisting System Frame System Rigid Frame Frame with Haunch Girder Flat Slab-Frame System Wall System Couple Shear Walls Core Supported Shear Walls Spinal Wall System Outrigger and Belt Wall System Flat Slab Frame with Shear Wall Tubular System Tube Systems with Widely Spaced Columns Frame Tube System Irregular Tubes Exterior Diagonal Tube Bundled Tube Miscellaneous System Steel Structure Systems
- 29. Dr. Naveed Anwar Wall Systems
- 30. Dr. Naveed Anwar 30 Coupled Shear Walls • A system of interconnected shear walls exhibits a stiffness that far exceeds the summation of the individual wall stiffness. • The system is economical for buildings in the 40-story range as Walls behave as if they are connected through a continuous shear-resisting medium. • Placement of walls around elevators, stairs, and utility shafts is common because they do not interfere with interior architectural layout. • Resistance to torsional loads must be considered in determining their location.
- 31. Dr. Naveed Anwar 31 Coupled Shear Walls Coupled Shear Walls Representation of coupled shear wall by continuum model: (a) Wall with openings, (b) Analytical model for close-form solution
- 32. Dr. Naveed Anwar 32 Core-supported Structures • Shear walls placed around building services such as elevators and stair cores can be considered as a spatial system capable of transmitting lateral loads in both directions. • The shape of the core is typically dictated by the elevator and stair requirements and can vary from a single rectangular core to multiple cores. • Floor framing around the core typically consists of systems such as cast- in-place mild steel reinforced or post tensioned concrete
- 33. Dr. Naveed Anwar 33 Core-supported Structures
- 34. Dr. Naveed Anwar 34 Core-supported Structures Full depth interior shear walls acting as giant K-brace. (a) Plan and (b) schematic section
- 35. Dr. Naveed Anwar 35 Spinal Wall System • Well Suited for ultra tall residential towers • Shear walls are placed along both sides of corridor. • Spine walls run through the floors to resist lateral loads • Loads in perpendicular direction are resisted through cross wall placed in orthogonal direction Burj Dubai, Schematic Plan
- 36. Dr. Naveed Anwar 36 Outrigger and Belt Wall System • External moment is resisted through the combination of core and exterior columns connected through outriggers. • Effective depth of structure for resisting bending is increased when core flexes as vertical cantilever Outrigger and belt wall system with centrally located core
- 37. Dr. Naveed Anwar 37 Optimum Location of a Single Outrigger Wall Deflection index vs. belt wall and outrigger locationsDeflection index verses outrigger and belt wall location
- 38. Dr. Naveed Anwar 38 Wall Systems - Flat Slab- frame with Shear Walls Frame action from flat slab–beam and column interaction is generally insufficient to provide the required strength and stiffness for tall buildings A system of shear walls and flat slab- frames may provide an appropriate lateral bracing system. Coupling of walls and columns solely by slabs is a relatively weak source of energy dissipation.
- 39. Dr. Naveed Anwar Tubular Systems
- 40. Dr. Naveed Anwar 40 Tube System with Widely Spaced Columns Tube System with Widely Spaced Columns for 28-story building constructed in New Orleans
- 41. Dr. Naveed Anwar 41 Frame Tube System Frame Tube Building. (a) Schematic plan and (b) isometric view
- 42. Dr. Naveed Anwar 42 From Frame to Tube Tube Frame
- 43. Dr. Naveed Anwar 43 Shear Lag Effects in Frame Tube System (a) cantilever tube subjected to lateral loads, (b) shear stress distribution (c) distortion of flange element caused by shear stresses.
- 44. Dr. Naveed Anwar 44 Irregular Tubes Secondary frame action in an irregular tube; schematic axial forces in perimeter columns
- 45. Dr. Naveed Anwar 45 Exterior Diagonal Tube • Adding diagonal bracing improves the efficiency of frame tube in tall buildings by eliminating shear lag in flange and web frames. • Allows greater spacing between columns. • By applying structural principles, it is possible to visualize a concrete system consisting of closely spaced exterior columns with blocked-out windows at each floor to create a diagonal pattern on the building facade. • The diagonals carry lateral shear forces in axial compression and tension, thus eliminating bending in the columns and girders.
- 46. Dr. Naveed Anwar 46 Bundled Tube
- 47. Dr. Naveed Anwar Selection of Structural Systems
- 48. Dr. Naveed Anwar 48 Latest Techniques Genetic Algorithms (GA) Artificial Neural Networks (ANN) Fuzzy Logic Expert Systems (ES) Linear/Nonlinear Programming Value Engineering Analytic Hierarchy Process (AHP)
- 49. Dr. Naveed Anwar 49 Rich Pictures Try to consider as many factors as possible Take “Bird’s Eye” View
- 50. Dr. Naveed Anwar 50 Knowledge Model for System Selection • Architecture • Building Services • Construction Engineering • Value Engineering • Aesthetics • Ergonomics Engineering • Structural Engineering • Knowledge Engineering • Economics • Artificial Intelligence • System Engineering • Common Sense
- 51. Dr. Naveed Anwar 51 Rich picture Diagram for System Selecteion A Master Thesis at AIT: Sudiksha Amatya Naveed Anwar
- 53. Dr. Naveed Anwar 53 Rich Pictures Different professionals involved and their interrelationship with structural engineer during the selection of structural systems
- 54. Dr. Naveed Anwar 54 Structural System Suitability using AHP • The Analytical Hierarchy Process • A weighted importance and suitability value analysis to determine the comparative value of a system or option Value of an Option Global Importance Weights and Scores Sub Importance Weights and Scores Suitability Value and Score ijk p k ijklij n j iji m i il SCSBSAV 111
- 55. Dr. Naveed Anwar 55 Evaluating System Suitability Slab Systems Criteria Weights and Scores System Value (V) Main Criteria Ai Am Sub Criteria Bij Sub Criteria Bin Bmn Item k Item p Item k Item p Item Wt Score Wt Score Wt Score Wt Score p Score System – 1 System – l Cijkl Sijkl Cijnl Sijpl Cinkl Sinkl Cinnl Sinpl Smnpl System - q Using the Suitability Equation
- 56. Dr. Naveed Anwar 56 Assigning Suitability Values Score or Weight Representation of Suitability 10 Most important, most suitable, most desirable, essential 8, 9 Very important, very suitable, very desirable 6, 7 Important, suitable or desirable 5 May be or could be important, suitable or desirable 3, 4 May not be important, suitable or desirable 1, 2 Not important, not suitable, not desirable 0 Definitely not required, definitely not suitable, ignore
- 57. Dr. Naveed Anwar 57 To do a Good Conceptual Design Develop the “Concept” at a higher level Identify the challenges and find solutions Compare value of alternatives Use previous experience Be innovative, be defiant, think outside the box
- 58. Dr. Naveed Anwar 58 It is by logic we prove, but by intuition we discover
- 59. Dr. Naveed Anwar 59 View publication statsView publication stats