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01
Dr. A.N.S.Kulasinghe

INNOVATIONS

INNOVATIVE PROJECTS

  • The method of assembling thin precast concrete cylinders of short length to form long cylinders to be sunk into the sea bed for the substructure of jetties, quay walls and mooring dolphins and the method of floating them for transport to the construction site. Developed in 1951 and acknowledged by the Institution of Civil Engineers Committee on Piling as an original contribution.
  • The use of an air lift pump with built in percussion soil cutter for excavation and removal of the soil inside the prestressed concrete cylinders and hollow piles. Introduced in 1952.
  • The use of a vibrating roller to compact concrete, with a low water cement ratio, which could not be compacted by vibration. First used in compaction of ‘in situ’ concrete of shallow depth in composite deck slabs in jetties using inverted T prestressed concrete beams placed side by side in 1949. The process of compaction of lean dry mixes with vibrating rollers, now known as ‘Roll Crete” is used widely in the construction of dams and roads.
  • The construction of large span roofs, in 1956, using pitched post tensioned beams with a high ratio of centre depth to depth at ends, which cannot be lifted at the ends due to instability, or from the middle due to failure by cantilever bending. The problem was solved by installing the roof purlins joining the upper flanges of an adjacent pair of beams and connecting their bottom flanges with a few struts! ties, resulting in a stable space frame at ground level. The roof structure was erected by jacking up using jacks at the ends and guided by the columns. The first roof structure built in 1956 had a span of 100 ft. and subsequent roofs have spans up to 130 ft.
  • The construction of cylindrical concrete shell roofs by the assembly of small thin concrete slabs by means of an orthogonal system of post tensioning to form the shell surface. Shuttering for the shell, steel placing and ‘in situ’ concreting are avoided in addition to ensuring water tightness and protection against steel corrosion without the necessity for external water proofing treatment. The shells were built at ground level and jacked up to required height. Port Warehouses of 100 spans were built in 1962 where three thin shells forming a total width of 100 ft. were built and jacked up at a time. The development of the technique was on a shell of 50 ft. span and 20 ft. wide, described in ‘Concrete and Constructional Engineering’ of May 1957.
  • The precasting of long prestressed concrete hyperbolic paraboloid shells using the long line system of prestressing, in 1961. These shells were used for roofing a number of structures in the Port of Colombo and outside. Described in the paper “Precasting of long saddle shaped hyperbolic paraboloid shells on the long line” presented to the World Conference on Shell Structures, San Francisco 1962.
  • The solution of the “corner droop” in umbrella type Hyperbolic Paraboloid Shells, by applying a prestress varying along the length of the edge beams. Shells constructed in 1958 and described in paper “Umbrella shaped hyperbolic paraboloid shells with prestressed edge beams” presented at the International Symposium on shell structures, Madrid 1959.
  • The method of construction of the conical shell of 1 36 ft. diameter base by assembling tapered prestressed concrete folded plates using a novel method of erection. Described in paper “Design and Construction of the Planetarium Building in Colombo”. Spanish translation published in REVISTA, Journal of the Institute. Mexicano del Cemento y del Concrete, March / April 1968.
  • Method of construction of 200 ft. /hemispherical shell at Kotmale, Sri Lanka where false work was avoided by assembling the reinforcement to form a skeletal shell of the required shape and concreting the shell in rings with the formwork being supported by the skeletal shell, Described in paper “Design and Construction of the Mahaweli Maha Seya Stupa as a Thin Shell” presented at the International Symposium on Innovative Applications of Shell and Spatial forms, Bangalore, India 1988.
  • The method of constitution of the tension shell of 100 ft. diameter and one inch thickness for the roof of the Kulasinghe Auditorium of the National Engineering Research and Development Centre of Sri Lanka. An outer ring of 100 ft. diameter and a concentric inner ring of 10 ft. diameter were connected with radial tensioned cables at ground level and the outer ring jacked up resulting in the inner ring sagging below the level of the outer ring. Transverse reinforcement was then placed and a one inch thick concrete was cast to form the shell. Removal of temporary weights placed on the inner ring induced a radial and circumferential prestress in the thin shell. Described in paper “Conical Shell as a tension structure for long spans” presented at the International Symposium on Innovative Application of Shells and Spatial Forms, Bangalore, India, 1988.
  • Prestressed concrete Vierendeel truss with parallel chords where the loads are carried by a parabolic prestressing cable in the plane of the truss and passing through the vertical members of the truss. First application was in the 100 ft. span, 10 ft. deep trusses for the North Light Roof of the Lanka Leyland Bus Assembly Plant in Sri Lanka in 1968. It has been applied to other structures, including bridges, resulting in considerable economy.
  • A method of constructing slip-formed walls for buildings without the reinforcement that is normally used to prevent horizontal cracking of the walls due to the tractive effect of the slipform. Spreading the jack reaction on to the wall itself and preventing the bulging of the walls immediately below the slip-form due to the vertical force on the wall by incorporating chopped vegetable fibers into the lean cement crusher dust mix having a low water cement ratio, were the innovative features contributing to the success of the method of construction.
  • The ‘Kulasinghe-CPC” system of post tensioning for prestressed concrete patented in 1956 incorporating several innovative features. They are, the construction of the twelve wire anchorages in mild steel, the arrangement of the wires to give maximum grout space and the hydraulic de-wedging device to release the wires from the jack after tensioning and anchoring them.
  • The method of constructing rectangular liquid storage tanks in which the thin wall panels are formed to the shape of ‘Prandt membranes’ to eliminate bending stresses in the panels, the loads being carried by tension. Patented in 1974.
  • The construction of pumps for cutter suction dredgers, where the volute casings of the centrifugal pumps are moulded in abrasion resistant rubber with a thin metal casing on the outside in place of rubber lining of pump casings made of metal which has the disadvantage of the lining peeling off. This novel arrange ment results in increased durability and lower costs. Several such pumps were constructed and operated in 1970 – 1971. The same method was extended to sewage pumps to provide resistance to corrosion.
  • The use of “Turgo” Impulse water turbines to power the cutter and winches on board cutter suction dredgers in place of more expensive electric or hydrostatic motors normally used the water under pressure to operate the turbines was supplied by an engine driven centrifugal pump on board the dredger (l 970-1971)
  • The use of linear induction motors for the cross and longitudinal travel of electric overhead traveling cranes – 1970.
  • The use of linear induction motors to provide a variable speed drive for the drawing rollers of a spinning machine -1970.
  • The use of very small reluctance-type synchronous motors running on gas bearings to drive individual spindles in a spinning machine. The motors ran at 9000 rpm on an ISO Hertz power supply (1969-1970).
  • A hoisting winch providing a very low speed, an intermediate speed. And a high speed, for lifting and lowering loads on electric overhead travelling cranes. Without variable speed gears or variable speed motors. Two drums with a small difference in diameter are driven by individual reversible motors. Each end of the rope, running through the pulley block of the crane hook is attached to a drum. Hoisting with the larger drum and lowering with the smaller drum 2ives a slow lifting speed, lifting with one drum with the other stopped gives the intermediate speed and lifting with both drums gives the high speed. Lowering speeds are obtained in a similar manner. Developed in 1970.
  • The Semi-Dry Batch Process of Anaerobic Digestion for bio-degradable material like straw, weeds, vegetable and fruit waste, and the biodegradable component of urban waste. This was patented in 1990 and won a silver medal at an exhibition in Switzerland. This technology provides a solution to the problem of urban waste disposal.