Structural Engineering Portfolio (2021) by Aditya Tiwari

Portfolio of Work Aditya Tiwari

Structural Engineer – Tata Consulting Engineers Ltd

PROFESSIONAL WORK

AKG GRIDSHELL, NY Albright Knox Gallery in Buffalo, New York has commissioned Studio Olafur Eliasson to design a new grid shell roof in the open courtyard space. The double curved shell spans about 25 meters in plan. It rests on the walls and columns of the existing building, and also funnels down to meet the ground in its interior region. The structure works primarily as a grid shell, with axial forces dominant in the members. The unique hexagonal nodes, primarily coming from the artistic intent, add secondary bending to the individual members. A ring truss takes the horizontal thrust coming from the shell, so that only vertical loads are transferred to the old walls and columns of the existing structures.

2 Structural Design Fig : Global FE Model of the Gridshell

Fig : Typical hex node

Fig : Gh. Script for applying non uniform snow loads

My tasks and responsibilities -

Finished conceptual design iterations with designers.

Prepared grasshopper scripts for application of irregular wind and snow loads on the gridshell.

Finished geometrically non-linear analysis, stability and collapse analysis of the gridshell.

Finished elastic design of members and plastic design of nodes (using shell FE)

Optimized node reinforcements leading to marked savings in fabrication and welding time.

Prepared schemes for breakdown of structure into transportable pieces and their transport.

Fig : Shell FE model of the node

Fig : Non-linear (plastic) analysis of the node

Fig : Snow loads as applied on projected areas of the gridshell

FIFA STADIUM, BISC For the upcoming FIFA in 2022, the Bahrain International Sports City (BISC) has commissioned a new football stadium. Spanning 64 m on the longest side, the stadium roof is a lightweight cable structure resting on a concrete grandstand. The stadium roof is based on the spoked wheel structural system, with an outer compression ring and two inner tension rings, connected by radial cables in tension. The radial cables maintain a parabolic profile with floating struts connecting them. A roof membrane spanning between the outer and inner rings makes the shelter. As all the major structural elements of this system are primarily under axial loads, it is a lightweight and structurally a very efficient system.

4 Structural Design Fig : Global FE Model of the Roof

Fig : FE model of column base plate

Fig : Grasshopper to SOFiSTiK workflow for generating starting membrane panel forms

Fig : Rhino model with membrane boundaries (cables), one panel highlighted

Fig : Form Finding and analysis for one panel of roof membrane with FE

My tasks and responsibilites

Fig : Analysis of membranes – principal forces in local x.

Prepared grasshopper to Sofistik (FE analysis) workflow for generating starting membrane forms.

Finished form finding and analysis of roof membrane panels of the stadium using non linear FEA.

Finished analysis and design of base plates of the stadium

Finished Linear analysis of the global roof for unit load cases.

Fig : Analysis of membranes – principal forces in local y.

DONUM GRIDSHELL, CA The Donum estate in California has commissioned Studio Olafur Eliasson for designing a grid shell as a part of the development scheme. Primarily an outdoor structure, the shell spans about 16 m in plan diameter. The shell surface is developable, making it singly curved in principle. Nevertheless, it still exerts horizontal thrusts at the ring, and develops high bending moments in this region like double curved shells. The shell consists of two sets of members – the longitudinal beams which are primarily in tension, and the curved spirals primarily in compression. The outer ring beam takes the horizontal thrust of the shell. The shell is particularly flexible near the top opening. Additional stiffness near this opening was provided by a hidden ring beam, which was achieved by invoking a truss action between the mullions and the curved spirals near the opening.

6 Structural System Fig : Global FE Model of the Gridshell

Fig : Type A node transferring all forces

My tasks and responsibilites Fig : Type B node, a pinned connection

Fig : connection between the column and ring beams – assembled view

Planned the project – prepared deliverable list and timeline of delivery. Prepared budget of the project, and monitored the progress.

Finished conceptual design studies with designers.

Finished a geometrically non-linear analysis and stability analysis of the gridshell.

Finished elastic design of beam members, solid nodes (using brick finite elements) and design of connections.

Finished CAD modelling of connections for preparing fabrication data.

Prepared schemes for breakdown of structure into transportable pieces and their transport.

Fig : connection between the column and ring beams – exploded view

bLink, SE The city of Gothenburg has commissioned Studio Katharina Grosse for designing a large scale artwork to signify the new railway network being laid out in the city. The artwork – bLink, would be built on the edge of one of the railway bridges, as seen in the visualization. It approximately fits the volume of 14 m x 11 m x 10 m. The form of the object would be realized from aluminum panels. A steel structure inside the volume provides for the necessary strength, serviceability and stability of the object. Details between the aluminum panels and the steel structure ensure free thermal movements of the panels, without disturbing the aesthetics.

Structural Design My tasks and responsibilites -

Fig : Cutting pattern on the object

Conceptual structural design of the supporting structure – a two tier strategy of a secondary structure and a primary structure was developed and implemented.

Development of connection strategy between aluminum panels and steel structure which incorporates thermal movements.

Geometricially non-linear analysis of the strucutre, and elastic design of steel members.

Coordinated with bridge engineers to establish safety of the structure against excessive vibrations.

Fig : Object assembly – panels, secondary structure and primary structure mounted on steel profiles at the bridge

Fig : Secondary structure designed with offset lines

Fig : Primary structure inside the volume

Fig : FE model of the assembled structure

Fig : Connection scheme for one panel (L), slotted and oversized connections (R)

P. V. TRACKER Solar Trackers have recently gained a significant market share in the renewables sector. Trackers are movable structures mounted with PV panels, tracking the movement of the sun through the day. The tracking significantly increases the efficiency of PV panels. A typical tracker consists of a series of PV panels fixed on longitudinal beams, together mounted on a movable supporting structural system. This tracker system has beams mounted on an X-arrangement of the posts. The tracker is driven on either sides by a cable system, which is driven by a main motor. In contrast, a conventional tracker system consists of panels and beams mounted on a single rotating tube. This system, along with the table bracing, the X-posts and the cables helps in developing an in-plane stiffness at the panel level of the system, making it stiffer than a torque-tube system.

10 Structural System Fig : Global FE Analysis considering Support Imperfections. The displaced support causes local concentrations.

Fig : Pulley encased in beams – first movement of the tracker.

My tasks and responsibilites -

Fig : Pulley at tracker foot – movement transferred to the main engines.

Fig : Rotating pin joint at ends of posts.

Finished peer reviews of PV tracker systems.

Finished conceptual design studies of PV tracker – from technical and economic perspectives.

Finished a geometrically non-linear analysis of the structure, with a special focus on effects of imperfections and support displacements. Finished elastic design of members based on these analyses.

Finished conceptual design of connections, and coordinated with mechanical engineers in development of movable connections.

Fig : FE model of a connection for peer review of a tracker.

CONTROL BUILDING The control building is “brain” of a power plant, housing equipment which continuously monitor all the processes and systems of the plant. Every major system can be controlled from this building via cables or “nerves” running across the plant. The circuits of these cables have regulating gears housed in switchgear rooms of the control building, which help in controlling the systems. The plan on the left shows the overall layout of the turbine buildings and the control building. The control building is sandwiched between the two gas turbine buildings in this project. Equipments, Switchgear rooms, Cable ducts, Computing devices etc. become the primary residents of this building, and the planning for various floors, services etc. is done by a team of architects, structural engineers, mechanical engineers, electrical engineers and instrumentation engineers.

12 Structural Design My tasks and responsibilites -

Fig : Conventional bracing v/s global bracing

Fig : The global braced frame shows more even distribution of loads

Fig : Diaphragm action stabilizing the unbraced frame

Prepared master list of deliverables calculations, drawings and reports

Coordinated with architects, mechanical, electrical and electronic engineers to establish overall constraints and requirements for the main control building .

Finished conceptual studies – evaluation of structural concepts for main control building.

Finished linear analysis, seismic analysis and elastic design of steel members.

Finished design of concrete block foundation for heavy machinery, using shell finite elements.

Fig : FE model of the building

SECOND VEHICLE ASSEMBLY BUILDING Second Vehicle Assembly Building (SVAB) is a rocket assembly facility for the Indian Space Research Organization located in Sriharikota, Andhra Pradesh. The houses a mobile launch pedestal, on which the rocket is assembled. This pedestal then transports the rocket over a railway track to the launch pad for lift-off. The structure houses foldable floors, rotating platforms and many other niche technological assets, making it one of the most rigorous planning and structural design endeavors. SVAB a massive 50m x 70m structure with a height of 96m. Being located in a cyclone prone region and because of the high importance of the structure, the structural system chosen is one with adequate reserve strength, to a point where it might be considered overly conservative for a regular 100m tall structure. The tubular structural system consists of columns on the periphery connected by beams, and continuous shear walls on 3 faces.

Structural Design of Shear Walls

Fig : Design of shear walls, step 1 - discretization

Fig : Design of shear walls, step 2 – combining resultant force resultants.

Fig : Design of shear walls, step 3 – plotting safety envelope.

My tasks and responsibilites -

Fig : FE model of SVAB

Finished material estimation (BOQ) preparation for beams and columns.

Finished ductile design of beams and columns.

Finished design of shear walls based on plate element results, using the Wood-Armer method.

Finished conceptualization and QA checks of reinforcement drawings for beams and columns.

Fig : FE model of SVAB

ITECH RESEARCH DEMONSTRATOR The ITECH Research Demonstrator was conceptualized, designed, analyzed and fabricated by the ITECH class of 2019. Our intent was to create a movable lightweight structure, capable of adapting to and interacting with the users. The structure is mounted with sensors and touch pads, capable of responding to changing weather conditions and explicit user inputs. The motion of the structure was achieved with biomimetic principles of origami and fold lines. The structure was made with thin carbon and glass fiber laminates, their high strength and less weight making them ideal for folding. The actuation was achieved with cushions inserted in pockets in the fold lines. The design process was augmented with computational processes in each stage. An initial design intent, with its movements inspired from biomimetic principles, was specified. Simulations enabled in design exploration, setting formation limits and evaluating structural performance. The results of the simulations also informed the material choice and layup, which was then used to program the industrial robot to fabricate the modules. Prepared modules were assembled to create the prototype.

16 Development

Fig : Computational design process of the demonstrator

Fig : Simulation methods in the design process

Some of the work finished -

Fig : Local Model to study stress concentrations

Prototyping of fiber composites using various methods (wet laying and heat pressing of prepregs)

Programmed custom goals for Kangaroo with C# to simulate plate bending for design explorations in the kinematic skeleton stage.

Derived formation rules and constraints of the structure based on kinematic and structural principles.

Finished finite element analysis for calculation of strength and movement of the pavilion.

Participated in physical assembly of the demonstrator.

Fig : Kangaroo (left) and FE (right) simulations to establish formation rules.

ITECH MASTER’S THESIS The master’s thesis, “Digitized Elasticity – Freeform Architectural Surfaces with Flexible Building Blocks”, was aimed at developing a computational design-to-production workflow for generating freeform architectural surfaces. The process would enable a designer to design freeform architectural surfaces in a context, for ex. creating or recreating indoor spaces, or repurposing outdoor spaces. A kit-of-parts approach was chosen – standardized and flat building components would be formed using a custom build actuation/forming machine. The module ends and connector elements were detailed in a way to enable creation of a range of freeform surfaces.

The design process consists of 5 stages. First the environment would be scanned, to give the designer the context to design in. The designer would then model a target surface. This surface would then be discretized into standardized triangles. Geometric information from the triangles would then be used to generate module formation information. Finally, the modules would be formed on the station and assembled on site. This final experience helped in establishing the overall scheme from computational design to digital production, and firmly established in me the abilities to see the larger goals of design, and develop individual computational processes to be able to realize the design.

18 Development

Fig : Computational design scheme developed in thesis

Work finished -

Fig : Forming of individual modules using actuations. Limits of formation derived from FE studies.

Schematic development of the conceptual design process.

Developed methods for discretization of freeform surfaced into triangles of fixed sizes.

Finished FE based form finding of modules, to derive formation rules and constraints.

Extracted parameters from the freeform geometry to generate inputs for the Arduino code for forming the modules.

Finished laser cutting of modules and assembly of the prototype.

Fig : FE studies for accurate form finding and establishing limits of formation.

19 Fabrication

Fig : Detailing of joints to achieve desired local and global form.

Fig : Digital fabrication of actuation station

Fig : Typical module assembly

Fig : Fabricated and formed modules before assembly

ITECH – DIGITAL FABRICATION The ITECH digital fabrication prototype is a double curved surface built out of identical modules, connected to each other using principles of shingled connections. The exercise was done to expose the students first hand to the design-to-production workflow – an introduction to the Modern Methods of Construction (MMC). We were exposed to the various stages of digital fabrication, and participated hands-on in each step. Starting with discretizing a target surface into modules, and refining the module geometry, we went on to program the robot’s tool path for milling the panels. Following the milling, the modules were sandpolished and manually assembled by the team. With this experience, concepts like the robot co-ordinate systems and rotation limits, programming the tool path in KRL, identifying potential milling issues etc. were solidified for me.

21 Fabrication

Fig : Back view of the connections

Fig : Digital fabrication in progress with the 6-axis KUKA robot.

Fig : Fabricated and sand polished modules

Fig : Close up view of the assembled prototype

Marina Tower is a proposed G+54 storied mixed usage (residential and commercial) structure. The plan dimensions are 35m x 30m and the height with the crown is 245m. The structure is proposed in Mumbai, where tall building structures are becoming increasingly important due to the population density. Architects and Engineers worked together since the conceptual design phase, leading to a harmonious organization of space and an economical structural system. The structure consists of shear walls rising from the basement up to level 12, where they terminate into a transfer girder, one floor deep. Peripheral columns rise from this level up to the roof level, connected by beams. Structure is clearly articulated in the massing, and this involvement of structure as an integral element of architecture rather than mere technology adds to the functional and aesthetic richness of the design.

23 Structural System

My tasks and responsibilites Fig : Tubular action

Finished conceptual design study of the framed tubed structural system with outriggers for tall buildings.

Finished modelling the structure in ETABS.

Finished 2nd order analysis of the structure.

Finished response spectrum analysis of the structure.

Fig : Meshing of the slabs, lift core and outriggers

Fig : Story Shear plot for Seismic loads

Fig : FE model of the Tower

Aditya Tiwari atiwari751@gmail.com