Er. Inki Choi, Head, Design (Bridges), Heavy Civil IC, L&T Construction is a structural engineer from South Korea and has 23 years' experience in bridge design. He has international experience in bridge design and delivery of projects in South Korea, Middle East, UK, Australia and India. His key experience areas are in design of iconic bridges such as cable-stayed bridge, arch and suspension bridges. The major projects in India include Trans Harbour Link Project (Mumbai) and Durgam Cheruvu Iconic Bridge (Hyderabad).
Er. Inki Choi presented an overview of the iconic bridges in India using precast prestressed segments and design challenges associated with the construction of such bridges. He briefly explained about the advantages of casting structural components in controlled environment which include quality control, speed, safety and environmental friendliness. The basic principles behind prestressed and post tensioned concrete bridges was also highlighted. He broadly discussed about the technical aspects and key challenges faced during construction of extradosed bridges like 2nd Vivekananda Setu (Kolkata), 3rd Narmada Bridge (Gujarat), Barapullah Elevated Road Project (New Delhi), 2nd Iswar Gupta Setu (West Bengal), New Ganga Bridge (Patna), Durgam Cheruvu Bridge (Hyderabad ) and cable stayed bridge - Mandovi Bridge (Goa). He detailed about the structural aspects like foundation, deck cross-sections adopted and various stages of construction.
He briefed about various loads acting on bridge and analysis techniques. According to him the main design challenges associated with construction were geometry control and camber control. He concluded with the note on how to overcome the closure errors which could be horizontal, vertical or both.
Theme Speaker - Professor Vellore S. Gopalaratnam, Department of Civil and Environmental Engineering, University of Missouri-Columbia. He is a Fellow of the American Concrete Institute and is a registered Professional Engineer in Missouri, USA. He has also been active in other professional organizations including the American Society of Civil Engineers and American Academy of Mechanics. His research interest includes prestressed concrete, high performance and fiber reinforced cement composites, polymer concrete, experimental mechanics and stress analysis of bridges and other structures, and field instrumentation and monitoring of structures.
Prof. Gopalaratnam gave an overview about high performance concrete prestressed bridge construction in US by briefing about first Missouri HPC Bridge and discussed in detail about internal instrumentation in bridges. The various laboratory tests conducted to obtain fundamental material properties and to compare field results with laboratory studies were discussed in detail. The study and working of embedded instrumentation of the pavement comprising of a joint base and other panels was also explained. He broadly discussed about the early age thermal loading and its influence on girder performance. Professor explained the various aspects of prestressed bridges like end zone stress due to prestress transfer, unrestrained creep, shrinkage response, service strains and service temperatures response. The load testing response was also briefed. In his view, instrumentation for automated remote monitoring of critical bridges has become technically reliable and economically affordable. Residual stresses from casting/curing operations may need to be explicitly considered and stresses due to thermal loading under service conditions and continuity detailing at diaphragms require more attention in design. He encouraged team work between industry and academic institutions in promoting thoughtful implementation of precast prestressed technology in India. He concluded his lecture by stating that complete system optimization of High Performance Concrete can result in greater benefits which includes size and shape optimization of girders.
a) OMKAR 1973, Worli – Mumbai. It is one of the tallest structures in India with 400-plus sky bungalows, ranging from 2,500 sq. ft. to 18,200 sq. ft. area with a height of over 300 meters and an area of about 5,000,000 sq. ft. and consisting of three towers. The project is scheduled for completion by Dec-2020. The consultant for the project is Buro Happold Engineering India Pvt Ltd. Utracon Structural Systems has been appointed by the project Developer for Post-tensioning design & execution of Podiums for Tower 1 & 2. Utracons’s specialist PT Design experts from India & Singapore assisted the Structural consultants to come out with optimum design solutions and faster cycle time as well. The best achieved time cycles in this project is 4 days per slab. 7 Floors were cast in one month (March 2017). In the recent periods, stringent Government norms demand better parking areas and PT provides a better solution through Post Tensioned Transfer Girders / Transfer Slabs, which normally acts as an elevated foundation. Podium level columns are ideally located in 10 to 13 m spans to accommodate more vehicles. After Podium levels, PT Transfer girder / slab will be constructed and over that typical level columns and walls will be placed at a spacing of 4 to 6 m. The analysis and design was carried out using the ‘ADAPT FLOOR PRO’ software.
b) KOHINOOR SQUARE - MUMBAI – It is considered as the tallest commercial tower in India. It is a special project as the transfer girder is constructed at 45th floor of the structure. The design aspects of PT – Transfer Girder & Slab was also elaborated. The supply and installation of Post – Tensioning component for the PT transfer Girder & Slab structure was by UTRACON Structural Systems. A brief introduction to transfer plates were also given.
Mr. G. Sreenivasa Rao is an instrumentation technology graduate with 20 years of rich experience in Business management, Marketing & sales management, Project Management, Strategic Planning, Business Development, Key Account Management, System Engineering & services.
In his presentation the history and future of precast pavements were discussed. Precast Pre-stressed road pavement technology offers increased durability while substantially decreasing construction time and cost. He explained the need for precast pavements. In view of the limited capacities of the construction industry, prefabrication and pre-cast pavements methods seem to offer the sustainable, cost effective and suitable solutions. In precast concrete pavement construction, adjacent panels are assembled sequentially and tied together onsite through post-tensioning or cast-in-load transfer systems. Precast concrete pavement systems can be used for single-lane replacements, multiple-lane replacement (an additional lane may be needed to accommodate materials and equipment) or full-width road construction. The key advantages of precast pavement is the ability to open to traffic immediately after installation of precast panels. The other advantages are reduction of pavement thickness and savings in material. Also modular panels make the construction process safer and more efficient because roadwork can be completed during off-peak hour’s thus faster pace of construction to cut time of traffic flow limitation.
He described the main characteristics of Precast Pre-stressed Concrete Pavement (PPCP) and Jointed Precast Concrete Pavement (JPCP). He explained about the typical panel layout, characteristics, joint load transfer, support considerations and stages of installation of precast prestressed pavements. He concluded with the hope that public demand for quality and comfortable highway travel will make the highway administrations exploit the potential of the precast pre stressed pavement method.
Er. Topintzis D Tryfon has more than 21 years of structural design experience for variety of Civil Engg. projects such as, low-rise and high-rise buildings (cast-in-place or precast-prestressed), repairs and straightening of buildings damaged by earthquakes. He was head of the Structural Design Department of the M.E.C.S. Ltd Management and Design firm and is highly specialized on the design of multi-storey cast-in-place and precast-prestressed projects under seismic situations. In India recently he is head of the structural design team of the KEF Katerra Company
In his presentation, KEF – KATERRA's precast construction methods/systems with the main principles of the emulative design and the corresponding connection details were presented together with examples from projects executed in India. It was shown as how and why precast technique is the most appropriate construction method to meet the market expectations. The major difference between traditional monolithic cast in-situ R.C. structures and prefabricated ones were discussed. The construction method of KEF KATERRA system was described together with the main precast elements [Floor system with reference to Hollow Core Slabs (HCS), Beams (Shapes and detailing), Columns, Walls (Solid walls, Double walls) ] which constitute the system. The connection details of wall to wall connections, wall to foundation connections, column to column connections, column to foundation connections, beam to column connection (moment resisting – hinged connection) were presented. A brief discussion was given on code compliance – materials i.e. concrete grades and steel categories which are usually used for the production of the precast elements. The reference was also made to codes applicable in India.
Er. Subir Das - Chief Engineering Manager (Bridges), Heavy Civil IC, L&T Construction is having 26 years of experience in leading and managing design of bridges (rail and road) and other civil / structural engineering projects including some major infrastructure projects in India, Malaysia and UK. He is also conversant with various Design Standards viz., BIS, IRC, IRS, BS & Euro.
Er. Subir Das elucidated about the pre-cast full span method of construction (FSLM) which is one of the fastest techniques used in construction of bridges / viaducts. The FSLM technique consists of 3 main stages - casting of whole span at yard, transportation and erection.
The Dedicated Freight Corridor (DFC) is a corporation run by the Ministry of Railways (India) to undertake planning & development, mobilisation of financial resources and construction, maintenance and operation of the Dedicated Freight Corridors. Such freight corridors are expected to adopt world class and state-of-the-art technology with significantly higher design features that will enable it to withstand heavier loads (32.5T Axle Load) at higher speed of 100 kmph. The topography in select location of WDFC necessitated construction Viaduct which covers a distance of 2.76 km of length. Viaduct - Design philosophy was discussed in detail. He explained about the components of viaduct – superstructure and sub structure. He also explained about the PSC box girder detailing. The main reasons for adopting FSLM for Viaduct construction were shorter construction period, avoiding laborious process involving large number of workmen, formworks over undulated bed profile & crossings and reduced safety hazards due to working at higher elevation. The details of few international projects like Riyadh Metro, Saudi Arabia and Incheon Bridge, Korea were also highlighted. He also briefed about the construction process and challenges faced during the construction of such projects.
In his presentation, precast pre-and post-tensioned pavement panels for rapid implementation in urban intersections and highways with reference to US were discussed. The primary objective in panel construction for highways was to evaluate the performance of precast prestressed panels subjected to severe environmental conditions. He explained about the various construction stages of precast prestressed pavement. He briefed about the laboratory tests to be conducted to obtain the fundamental material properties. Prediction models for pre and post-tension losses were successfully developed based on creep and shrinkage measurements. He also discussed about the embedded instrumentation procedure and positioning of the gauges for crack surveys and joint performance. He also briefed about the long-term durability issues. The session was concluded with a note that the pilot instrumentation project offered a wealth of performance data that was useful to optimize precast prestressed pavement designs.
Er. Tsoukantas G Spyros shares his professional activities between experimental research, academic teaching and consulting work on the design and behavior of R.C. Precast structures under seismic situations. He is author of numerous technical papers and co-author of books for University students. He was the introducer with Prof. Tassios of the Greek Precast Code (1999), which is still valid in Greece. He was convenor of the 6.10 task group of fib (Bulletin 78 “Precast Concrete Buildings in Seismic areas”). He has designed and supervised a great number of R.C. and precast structures. Currently he serves as Head of the Education and R & D department, KEF KATERRA.
In this presentation, the main principles and philosophy of seismic design were briefly reviewed. Performance requirements, seismic actions, design concept etc., with emphasis on precasting and relevant ductility properties of precast structures was also discussed. The capacity design process was explained in detail. He explained the seismic behavior based on configuration and also seismic behavior of large panel of precast concrete walls. He also explained about precast frame systems, wall systems – large panel systems, wall frame systems (dual systems), floor framing systems, precast cell systems. He also gave an insight to the advantages and disadvantages of the precast cell systems and shared the views that indicate how these requirements drives the designer towards the most appropriate and cost effective choice of flooring systems.
Er. Shreedhar R. Revankar, Technical Service Manager, BASF India Limited, discussed the requirements of various global construction companies and addressed the challenges faced by the precast industry and offered solutions for the same. He also discussed the need for zero energy systems.
In his presentation he introduced two main concepts - Zero energy system and crystal speed hardening techniques for high quality design and material optimization resulting in energy efficient designs. The zero energy system takes into consideration all aspects of production process of precast elements. The energy efficiency is obtained by achieving higher strength at early ages.
The crystal speed hardening techniques will be able to save money and time while reducing CO2 emission. This is achieved by using Master X- SEED, a new hardening accelerator. It consists of synthetically produced nanoparticles suspended in liquids and boosts the hardening properties of the concrete mix. Master X- SEED can enhance the concrete strength and can double early strength and performance with increase in productivity in concrete production without affecting other performance characteristics of concrete. The science behind Master X- SEED is the addition of CSH nanoparticles to stimulate the formation of CSH nuclei during very early stage of cement hydration, which will accelerate CSH formation during the continuing process of hydration of cement.
Er. Sathiyaseelan, Principal Structural Manager, Teemage Precast IN, presented about main features to be considered in a precast structural systems. The main factors such as production, transportation and erection were also discussed. The real life problems faced by engineers at site which includes legal issues and time management was also discussed.
Er. Surya Prakash P., SatyaVani Projects and Consultants, Hyderabad, discussed the limitations on high investment involved in construction of precast concrete and technical labour skill required. He rendered his views about the common difficulties and challenges faced in precast technologies. He also expressed his future vision of making precast houses available for purchase at ecommerce websites like amazon, etc.
The seminar concluded with expert panel discussion on ‘Logistical and policy-related opportunities and challenges facing precast prestressed construction in India’ which was chaired and moderated by Er. Surya Prakash P., MD, SatyaVani Projects and Consultants, Hyderabad. The panel members were Er. Tsoukantas G Spyros (KEF Katerra), Ar. Vasanth (Ishan Foundation), Coimbatore), Er. V. Senthur (PWD, Tiruppur), Er. S. Sathiyaseelan (Teemage).
Er. Surya Prakash P. summarized the outcomes of the panel discussion into three categories as Opportunities, Challenges and Way forward:
Potential follow-up tasks: