Field of Invention:
The present invention belongs to evolution of efficient and innovative design technic for portal frame and connections by discretising into geometric ally most complicated and heavy weight precast elements with thrust on minimum number of elements and joints. This invention of system made the execution process very simple, fast and safe. The invention relates to a precast portal structure having precast elements with dry connections.
Description of invention:
To develop unique and world largest cricket stadium, the architectural design intent was created with intricate geometric al shape portal frames in bowl structure of stadium. Though the precast system design and construction is very c ommon in industrial practice, the pres ent design technique adopted is unique and not practiced. The present design is developed with elements having larger size, heavier weight, complicated geometry and asymmetrical shape with dry connections in addition to attain good f orm finish, faster construction and economical cost.
The innovative design techniques adopted for a portal are developed by discretisation of portal structure into minimum number of precast elements with dry connections. Due to this, precast elements became very large in size with as ymmetric geometric al shape and heavier in weight. This complicated the casting of elements at yard, transportation, lif ting, tilting and er ecti on of precast elements to f inal positi on.

This necessitated to develop innovative construction techniques for handling the elements during various stages of casting, transporting and erection stages. In each stages, the precast elements are meticulously analys ed, designed and detailed accordingly.
T he prec ast port al (in one plane) af ter dis cretiz ation consists of 2 numbers Y-Shaped columns (named as HY and GY Columns) connected with 2 numbers of inclined precast beams at the top in radial direction. In circumferential direction, the precast portal is connected with precast beams at beam-column junction to get 3 dimension frame action.(Refer figure 1 – figure 3)
The details of dry joint precast connection is elaborated herein:-The development of simple and construction friendly connection detail is the main objective for evolution of dry joint connection of precast elements. Unique and innovative design technic is adopted for connection design for large forc es and moments.
Various type of dry connections like c ast in anchors are readily available in practice. These joints are not suitable for connecting the precast beam and Y shape columns with large forces. The option of casting with wet j oints is n ot suit able as pl ac ing of joint r einf orcement is a cumbersome task and time-consuming activity due to rebar congestion at the junction and also risk of safety due to working at greater height.
The proposed dry connection detail has been developed using structural steel. This connection is very useful for easy construction with requir ed er ection t oler anc e for inserting the structural steel pr oj ecti on in

to the other precast element at joints and saf ely transfer the huge force and moments between two elements. The final appearance of the joint provides the aesthetic appearance required by architect along with structural strength, ductility and durability. The allowance of field adjustment, accessibility of j oint loc ation, r epetit ive d et ail, r obustness are considered in the design to create precast connections.
The details of Y-columns is elaborated herein:-Figure 1 illustrated as typical bay of upper bowl framing without seating. Figure 2 illustrated as typical bay of upper bowl framing without seating indicating the element weight.
Figure 3 illustrat ed as typic al p ort al f rame with discretizat ion l ocati on. Figure 4 i llustrat ed as t ypic al dr y conn ection j oint detail in First bay. HY1 : Rear column in first bay HY2 : Rear column in second bay HY11 : Top end of strong arm of HY1 in first bay HY12 : Top end of slender arm of HY1 in first bay HY21: Top end of strong arm of HY2 in second bay HY22 : Top end of slender arm of HY2 in second bay
GY1 : Front column in first bay
GY2 : Front column in second bay
GY11 : Top end of horizontal arm of GY1 in first bay
GY12 : Top end of vertical arm of GY1 in first bay
GY21 : Top end of horizontal arm of GY2 in second bay
GY22 : Top end of vertical arm of GY2 in second bay

PCHB1 : Circumferential beam connecting two top ends of slender arm
of HY columns in two bays.
PCHB2 : Circumferential beam connecting two top ends of strong arm
of HY columns in two bays.
PCGB1 : Circumferential beam connecting two top ends of vertical arm
of GY columns in two bays.
PCGB2A : Circumferential beam connecting near the two top ends of
horizontal arm of GY columns in two bays.
PCGB2B : Circumferential beam connecting near the two top ends of
horizontal arm of GY columns in two bays.
PRB1 : Primary Radial Beam connecting the four top ends of HY & GY
column in first bay.
PRB2 : Primary Radial Beam connecting the four top ends of HY & GY
column in second bay.
SRB : Seconday Radial Beam
The architectural intent demanded for aesthetic appearance and larger open space at concourse level. The structure intent required optimum number of supports for transferring the forces. Additionally, the HY column shall also be utilised for supporting cantilever staircase which is formed around the column to access upper bowl seating.
In the pres ent portal invention, the HY c olumn has as ymmetric and intricate shape, weighing about 235 MT, with one long slender arm (having cross section of 1mx1m with 18m long) and the other short strong arm (having cross section of 1mx2.5m with 9.4m long) is considered. The development of design techniques are ver y complicated part of design. The inclination of the arm is defined based on the optimum forces at all beam-column joints and permissible

deflection criteria for beams. The column is a single, joint free element with c onnections only at the top of twin arm connected to beams and bottom of single arm c onnected to foundation.
There are various stages (few stages were briefed below) which the precast Y c olumns must undergo before being erected to its final position to achieve the portal action. Each stage was analysed criticall y and micro level planning and detailing were done for successful executi on of the port al.
Lifting Stage: This is the initial stage where the cast Y element which is yet to achieve its full strength had to be shifted out of the casting bed to stack yard, t o facilit at e c asting of next element. T his is achieved b y carefully choosing the lifting points on the element such that stresses are within the permissible limits at the time of lifting.
Transporting Stage: At this stage the element is lifted at 2 points which makes the element behave as a cantilever beyond the lifting point. The cantilever behaviour of strong arm is managed by rebar itself. The slender arm its elf is not adequate for sustaining the cantilever moments in the out of plane direction and hence provided with temporary strong back support, a specially fabricated structural steel member, fixed on top of the slender arm for the full length to act as a composite member. The Y element is loaded on the trailer with supports at 2 locations and shif ted to r equir ed loc ation.
Erection Stage: T his is the m ost critical p art of the er ection. The specially made C shaped clamp is fixed just above the CG of Y element which is supported on trailer. The Y element is simultaneously lifted b y

lifting crane about its CG and by the rear tailing crane. The C clamp f acilitates the rot ati on of th e element f rom h ori zont al t o vert ical position. Once the element is rotated and made vertical, the behaviour of slender arm is changed from deflecting out of plane to in-plane direction with 18m cantilever length. This movement of slender arm is controlled by connecting the slender arm with strong arm with temporary truss tie frame, which is plac ed in Y precast element while casting at ground bef or e the el em ent is tilt ed.
Post Erection: Upon tilting t o vertic al positi on, the element is p osition ed over the foundation by inserting the prefixed corrugated sleeves into foundation dowels and grouted. The grout material used is a special purpose high strength grout which attains the required strength in less than 24 hours thereby reducing the crane handling time. After the grout had achieved required strength, the element is released from crane and provided with lateral temporary truss supports to overcome free standing 35m cantilever span. The lateral trusses are provided in both directions at intermediate levels and connected to adjacent HY columns which are erected sequentially. The Y-column is then connected to precast beam in both directions at top and intermediate levels to achieve the portal acti on. Af ter f ixit y of the port al is achieved, tempor ar y supports are removed.
The HY column is provided with cantilever staircase on the periphery for accessing the upperbowl. The staircase compris es of Precast flight slab simply supported on Precast landing slab with cantilever steel beams. The inserts for fixing the staircase is embedded inside the HY column during casting. After HY column attains the portal action, the cantilever steel beam with landing slab is welded to the embedded insert plate.

The description of precast beam is elaborated herein:-The upperbowl structural system consists of two numbers of precast radial beams (PRB1A & PRB1B of span 14m and 26 m weighing 70 MT and 115 MT respectively) supported on GY and HY Columns. The beam column joints are laterally supported with circumferential beams. The force transfer from the radial beam to the column is achieved by fabricated structural steel which is partly embedded inside and partl y projected outside the column during casting. The radial beam is provided with two pockets (for each beam-column joint) at the bottom of the element. The size of the pockets is defined as per the size of structural steel embedment, required erection tolerance and space for grout to fl ow.
The beams are shifted from the casting yard to respective location in horizontal position using trailers. The loading points on the trailers are chosen in such a way that the design section satisfies the supporting boundary condition. The beams are then tilted to the required angle using specially made spreader beams and lifted to the nec essary height by positioning the pockets over the structural steel member and carefully lowered till the steel member is completely embedded into the pocket . W hile the element is still held by the crane, the pocket is grouted with high strength grout. The element is released from crane af ter the gr out at tains suff icient strength.
The description of dry joint connection is elaborated herein:-

The junction of the beam and column is developed using structural steel of grade E350. The fabricated steel section with studs/ribs is designed to r esist the entir e f orces on its own and trans fer the forces saf el y t o th e connecting prec ast elements.
The structural steel fabricated section is placed in position during casting of precast Y columns with required Embedment length.
The shape and size of fabricated structural steel is detailed in such a way that the longitudinal rebar in Y column does not obstruct the steel member and has sufficient gap in between f or concrete to flow. The embedment zone in precast Y column is confined with sufficient reinforcement to withstand heavy shear forces in concrete.
The connecting beam at the top is provided with through pockets with size considering r equired site tol er ance to r ec eive structural steel projection above the Y columns. There are no confinement reinforcement required around the pocket in precast inclined radial beams at top as the joint has perpendicular circumferential beam. The embedment length of structural steel member is calculated by limiting the bearing strength of concrete around the pocket provided in the beam.
At the intersection point between the Y columns and Radial Beams, the structural steel member resists the entire force (Axial + Shear + Bending). The axial compression is transferred as bearing from the beam above to the Y columns. The shear and bending force is transferred through bond between structural steel and concrete.

The joint connection is achieved by erecting the precast radial beams over Y-columns. The pockets in beam are inserted in to the projected structural steel in the precast column. After aligning the beam the pockets are grouted with high strength grout. The fixity of the joint is achieved after the grout attains its full design strength. (Refer figure 4).
The advantageous of the invention are:-
1. Is applicable for unconventional large span, complicated asymmetric shape and heavier sections.
2. Provides simpler connection detail to resist huge forces and
moments.
3. Results in faster construction and hence less time consuming.
4. Provides better form finish and henc e no further surface finish is requir ed post er ection.
5. Provides safe working environment as majority of work is done at ground and only connection involving minimal man power is required at greater heights.
With reference to figure 1,2,3 and 4, it is clearly illustrated an invention which a frame structure formed with an array of portal structures. Each port al is two b ay p ortions.
a) A first bay portion has a pair of Y columns (HY1 and GY1) spaced radially and are supporting a primary radial beam (PRB1),
b) A second bay portion has a pair of Y column (HY2, GY2) spaced radially and are supporting a primary radial beam (PRB2), and

c) A set of circumferential beams (PCHB1, PCHB2, PCGB1, PCGB2A, PCGB2B) are supported onto the columns of the two bays with three beams arranged at beam-column junctions and two beams arranged proximate to beam-column junctions.
In another aspect, the invention has a frame structure formed with an array of portal structures. Each portal is two bay portions with two intermediately portion. The first bag is described herein. A first bay portion with a first Y column GY1 and a second larger Y column HY1 which is spaced radially away from the first column GY1. The first column GY1 having a horizontal arm terminating at a top end GY11 and a vertical arm terminating at top end GY12. The second column HY1 having a slender arm terminating at a top end HY12 and a strong arm terminating at top end HY11, and arrangement is such that strong arm of GY1 is proximate to the strong arm of HY1. There is a primary radial beam (PRB1) extending along the four top ends (GY11, GY12, HY11, HY12) of the two columns (GY1, HY1) in the first bay thereby forming four column-beam junctions at ends (HY11, HY12, GY11, GY12). The second bay is described herein. A second bay portion is having a first Y column GY2 and a second larger Y column HY2 which is spaced radially away from first column GY2. The first Y column GY2 the first Y column GY2 having a horizontal arm terminating at a top end GY21 and a vertical arm terminating at top end GY22. The second column HY2 having slender arm terminating at a top end HY22 and a strong arm terminating at top end HY21, and arrangement is such that vertic al arm of GY2 is proximate to the strong arm of the H Y2. There is a primar y radial beam (PRB2) extending along the four top ends (GY21, GY22, HY21, HY22) of the two columns (GY2, HY2) the second bay thereby

forming four column-beam junctions at ends (HY21, HY22, GY21, GY22). The intermediate portion is described herein.
A first intermediating portion is arranged between the two bays with a first circumferential beam (PCHB1) extending across the first bay and second bay and between the top end of slender arm (HY12) which is beam-column junction of HY1 column in first bay and top end of strong arm (HY22) which is beam-column junction of HY2 column in second bay. There is also a second circumferential beam (PCHB2) extending across the first bay and second bay and between the top end of strong arm (HY11) which is beam-column junction of HY1 column in first bay and top end of strong arm (HY21) which is beam-column junction of HY2 column in second bay. There is also a third circumferential beam PCGB1 extending across the first bay and second bay and between the top end of vertical arm GY12 which is beam-column junction of GY1 column in first bay and top end of vertical arm (GY22) which is beam-column junction of GY2 in second bay. There is a pair of spaced fourth and fifth circumferential beams PCGB2A and PCGB2B extending across the first bay and second bay and proximate to the top end of horizontal arm (GY11) which is beam-column junction of GY1 column in first bay and proximate to top end of horizontal arm (GY21) which is beam-column junction of GY2 column in second bay with one beam on either side of the top ends of the horizontal arms (GY11, GY21) which are beam column junctions of GY1 column and GY2 column. The second intermediating portion has a sec ondary radial precast beam (SRB) arranged between the columns in the two bays and extending parallel to and in-between the primary radial beams (PRB1, PRB2) linearly across the said five circumferential beams (PCHB1, PCHB2, PCGB1, PCGB2A, PCGB2B).

As seen above the arrangement encompasses arrangements of columns and beams extending across bays with intermediating bays wherein the beams and columns are so arranged uniquely which was unknown in prior art. The arrangement can be seated up and scaled down without much obligation to analyse.
The examples and embodiments are provided only for the purpose of understanding and none of them shall limit the scope of the invention. All variants and modifications as will be envisaged by skilled pers on are within the spirit and scope of the in venti on.

WE CLAIM:
1. A frame structure formed with an array of portal structures, each
portal c omprising of:-
a) a first bay portion with a pair of Y columns (HY1 and GY1)
spaced radially and supporting a primary radial beam (PRB1),
b) a second bay portion with a pair of Y column (HY2, GY2) spaced radially and supporting a primary radial beam (PRB2), and
c) a plurality of circumferential beams (PCHB1, PCHB2, PCGB1, PCGB2A, PCGB2B) supported onto the columns of the two bays with three beams arranged at beam-column junctions and two beams arranged proximate to beam-column junctions.
2. A frame structure formed with an array of portal structures, of
each portal comprising of:-
a) a first bay portion with a first Y column GY1 and a second
larger Y column HY1 spaced radially away from the first column GY1, the first column GY1 having a horizontal arm terminating at a top end GY11 and a vertical arm terminating at top end GY12, the second column HY1 having a slender arm terminating at a top end HY12 and a strong arm terminating at top end HY11, such that strong arm of GY1 is proximate to the strong arm of HY1; a primary radial beam (PRB1) extending along the four top ends (GY11, GY12, HY11, HY12) of the two columns (GY1, HY1) in the first bay thereby forming four column-beam junctions at ends (HY11, HY12, GY11, GY12). b) a second bay portion having a first Y column GY2 and a second larger Y column HY2 spac ed radially away from first column GY2, the first Y column GY2 having a horizontal arm

terminating at a top end GY21 and a vertical arm terminating at top end GY22, the second column HY2 having slender arm terminating at a top end HY22 and a strong arm terminating at top end HY21, such that vertical arm of GY2 is proximate to the strong arm of the HY2; a primary radial beam (PRB2) extending along the four top ends (GY21, GY22, HY21, HY22) of the two columns (GY2, HY2) the second bay thereby forming four column-beam junctions at ends (HY21, HY22, GY21, GY22).
c) a first intermediating portion between the two bays with a first circumferential beam (PCHB1) extending across the first bay and second bay and between the top end of slender arm (HY12) which is beam-column junction of HY1 column in first bay and top end of strong arm (HY22) which is beam-column junction of HY2 column in second bay; a second circumferential beam (PCHB2) extending across the first bay and second bay and between the top end of strong arm (HY11) which is beam-column junction of HY1 column in first bay and top end of strong arm (HY21) which is beam-column junction of HY2 column in second bay; a third circumferential beam PCGB1 extending across the first bay and second bay and between the top end of vertical arm GY12 which is beam-column junction of GY1 column in first bay and top end of vertical arm (GY22) which is beam-column junction of GY2 in second bay; a pair of spaced fourth and fifth circumferential beams PCGB2A and PCGB2B extending across the first bay and second bay and proximate to the top end of horizontal arm (GY11) which is beam-column junction of GY1 column in first

bay and proximate to top end of horizontal arm (GY21) which is beam-column junction of GY2 column in second bay with one beam on either side of the top ends of the horizontal arms (GY11, GY21) which are beam column junctions of GY1 column and GY2 column. d) a second intermediating portion with a secondary radial precast beam (SRB) arranged between the columns in the two bays and extending parallel to and in-between the primary radial beams (PRB1, PRB2) linearly across the said five circumferential beams (PCHB1, PCHB2, PCGB1, PCGB2A, PCGB2B).