AU2021102873A4 - A system and a method to provide ductile detailing in reinforced concrete wall–flat slab joint - Google Patents

A system and a method to provide ductile detailing in reinforced concrete wall–flat slab joint Download PDF

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AU2021102873A4
AU2021102873A4 AU2021102873A AU2021102873A AU2021102873A4 AU 2021102873 A4 AU2021102873 A4 AU 2021102873A4 AU 2021102873 A AU2021102873 A AU 2021102873A AU 2021102873 A AU2021102873 A AU 2021102873A AU 2021102873 A4 AU2021102873 A4 AU 2021102873A4
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slab
reinforcement
joint
wall
core
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AU2021102873A
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K.P. Jaya
Surumi Rasia Salim
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    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/38—Connections for building structures in general
    • E04B1/41—Connecting devices specially adapted for embedding in concrete or masonry
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/02—Structures consisting primarily of load-supporting, block-shaped, or slab-shaped elements
    • E04B1/04—Structures consisting primarily of load-supporting, block-shaped, or slab-shaped elements the elements consisting of concrete, e.g. reinforced concrete, or other stone-like material
    • E04B1/043—Connections specially adapted therefor
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/16—Structures made from masses, e.g. of concrete, cast or similarly formed in situ with or without making use of additional elements, such as permanent forms, substructures to be coated with load-bearing material
    • E04B1/165—Structures made from masses, e.g. of concrete, cast or similarly formed in situ with or without making use of additional elements, such as permanent forms, substructures to be coated with load-bearing material with elongated load-supporting parts, cast in situ
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B2/00—Walls, e.g. partitions, for buildings; Wall construction with regard to insulation; Connections specially adapted to walls
    • E04B2/84—Walls made by casting, pouring, or tamping in situ
    • E04B2/86—Walls made by casting, pouring, or tamping in situ made in permanent forms
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
    • E04C2/02—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials
    • E04C2/04—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres
    • E04C2/044—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres of concrete
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
    • E04C2/02—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials
    • E04C2/04—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres
    • E04C2/06—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres reinforced
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
    • E04C5/012—Discrete reinforcing elements, e.g. fibres
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/16—Auxiliary parts for reinforcements, e.g. connectors, spacers, stirrups
    • E04C5/162—Connectors or means for connecting parts for reinforcements
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/02—Structures consisting primarily of load-supporting, block-shaped, or slab-shaped elements
    • E04B1/04—Structures consisting primarily of load-supporting, block-shaped, or slab-shaped elements the elements consisting of concrete, e.g. reinforced concrete, or other stone-like material
    • E04B1/043—Connections specially adapted therefor
    • E04B1/046—Connections specially adapted therefor using reinforcement loops protruding from the elements
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/16—Structures made from masses, e.g. of concrete, cast or similarly formed in situ with or without making use of additional elements, such as permanent forms, substructures to be coated with load-bearing material
    • E04B1/167—Structures made from masses, e.g. of concrete, cast or similarly formed in situ with or without making use of additional elements, such as permanent forms, substructures to be coated with load-bearing material with permanent forms made of particular materials, e.g. layered products
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B2/00—Walls, e.g. partitions, for buildings; Wall construction with regard to insulation; Connections specially adapted to walls
    • E04B2/84—Walls made by casting, pouring, or tamping in situ
    • E04B2/86—Walls made by casting, pouring, or tamping in situ made in permanent forms
    • E04B2/8652—Walls made by casting, pouring, or tamping in situ made in permanent forms with ties located in the joints of the forms
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B2/00—Walls, e.g. partitions, for buildings; Wall construction with regard to insulation; Connections specially adapted to walls
    • E04B2/84—Walls made by casting, pouring, or tamping in situ
    • E04B2/86—Walls made by casting, pouring, or tamping in situ made in permanent forms
    • E04B2002/8676—Wall end details
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B2/00—Walls, e.g. partitions, for buildings; Wall construction with regard to insulation; Connections specially adapted to walls
    • E04B2/84—Walls made by casting, pouring, or tamping in situ
    • E04B2/86—Walls made by casting, pouring, or tamping in situ made in permanent forms
    • E04B2002/8688—Scaffoldings or removable supports therefor
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
    • E04C2/02—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials
    • E04C2/04—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres
    • E04C2/044—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres of concrete
    • E04C2002/045—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres of concrete with two parallel leaves connected by tie anchors
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/16—Auxiliary parts for reinforcements, e.g. connectors, spacers, stirrups
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04H—BUILDINGS OR LIKE STRUCTURES FOR PARTICULAR PURPOSES; SWIMMING OR SPLASH BATHS OR POOLS; MASTS; FENCING; TENTS OR CANOPIES, IN GENERAL
    • E04H9/00—Buildings, groups of buildings or shelters adapted to withstand or provide protection against abnormal external influences, e.g. war-like action, earthquake or extreme climate
    • E04H9/02—Buildings, groups of buildings or shelters adapted to withstand or provide protection against abnormal external influences, e.g. war-like action, earthquake or extreme climate withstanding earthquake or sinking of ground
    • E04H9/021—Bearing, supporting or connecting constructions specially adapted for such buildings

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  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Reinforcement Elements For Buildings (AREA)

Abstract

The present disclosure relates to a system and a method to provide an enhanced ductile detailing for reinforced concrete wall-flat slab joint. Provision of Core shear reinforcement in the void joint core can make a significant contribution to the ultimate resistance of the wall-slab joint region. The experimental results showed a significant increase of the slab positive bending moment of 35.9 % and slab negative bending moment of 21.5 % under lateral reverse cyclic loading of the wall-slab joint unit. The increase in slab resistance due to the core shear reinforcement increased the wall shear demands by 28.7 % on average in both directions of loading under lateral reverse cyclic loading of the wall-slab joint unit. The ductility of the specimen with core shear reinforcement was significantly increased. It was observed that the displacement ductility is enhanced for the specimen with core shear reinforcement by 55.9%. The specimen with core shear reinforcement was also found to be effective in improving the energy dissipation of the joint. An increase of 153 % was observed in cumulative energy dissipation capacity for the proposed detailing. The joint shear capacity was found to be enhanced by 36% by using the core shear reinforcement in place of the conventional detailing. 13 fin t t DII t I~I I~I IiI a a rt~

Description

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A SYSTEM AND A METHOD TO PROVIDE DUCTILE DETAILING IN REINFORCED CONCRETE WALL-FLAT SLAB JOINT FIELD OF THE INVENTION
The present disclosure relates to a system and a method to provide an enhanced ductile detailing in reinforced concrete wall-flat slab joint.
BACKGROUND OF THE INVENTION
Earthquake forces are inertia forces related to the mass of the structure which causes time dependent response. They induce oscillations causing stress reversals and if the structure is not provided with enough energy dissipation capacity, it would fail. For energy dissipation, it is necessary that the structure develop inelastic deformations leading to adequate warning before failure. It is imperative that a number of plastic hinges should be formed before the collapse of the structure. The hinges generally do form near to the joints of different structural elements supporting the structure.
Therefore, the ductility and energy absorption capacity of the joints are of paramount importance in seismic resistance of structures. In order to avoid failure within the joint core, special confinement and detailing of reinforcement are necessary which may lead to congestion of reinforcement. By modifying the joint detailing pattern, seismic performance of the joint can be improved to a great extent. The connection between shear wall and slab is an essential link in the lateral load resisting mechanism of wall-slab systems. However, despite the significance of the joints in sustaining large deformations and forces during earthquakes, specific guidelines regarding the detailing of reinforced concrete wall-slab connection are not explicitly included in the codes of practice.
In one prior art patent application (TW367385B) a forming material for mould board which is (a) in order to assembly a plurality of formed object on the side of concrete; and (b) in order to maintain the spaces and positions of formed objects and form the connections between them is disclosed.
In one prior art patent application (W2005019549A1) a mixed construction system which combines traditional or non-structural construction with structural construction, whereby concrete is used in both walls and slabs is disclosed.
In one prior art patent application (EP1669503A1) a mixed construction process combines traditional or non-structural construction with structural construction, concrete participating therein both in the walls and floor framing is disclosed.
In order to overcome the aforementioned drawbacks, there is a need to develop a system and a method to provide an enhanced ductile detailing in reinforced concrete wall-flat slab joint. SUMMARY OF THE INVENTION
The present disclosure relates to a system and a method to provide an enhanced ductile detailing for reinforced concrete wall-flat slab joint. Provision of Core shear reinforcement in the void joint core can make a significant contribution to the ultimate resistance of the wall-slab joint region. The experimental results showed a significant increase of the slab positive bending moment of 35.9 % and slab negative bending moment of 21.5 % under lateral reverse cyclic loading of the wall-slab joint unit. The increase in slab resistance due to the core shear reinforcement increased the wall shear demands by 28.7 % on average in both directions of loading under lateral reverse cyclic loading of the wall-slab joint unit. The ductility of the specimen with core shear reinforcement was significantly increased. It was observed that the displacement ductility is enhanced for the specimen with core shear reinforcement by 55.9%. The specimen with core shear reinforcement was also found to be effective in improving the energy dissipation of the joint. An increase of 153 % was observed in cumulative energy dissipation capacity for the proposed detailing. The joint shear capacity was found to be enhanced by 36% by using the core shear reinforcement in place of the conventional detailing.
In an embodiment, a system 100 to make an enhanced ductile detailing for reinforcing a concrete wall-flat slab joint comprises: a reinforcement cage 102 is made of steel; an additional core shear reinforcement is connected at the joint region in order to modify the void joint core of conventional reinforcement detailing, the additional core shear reinforcement comprises: U-hooks 104, used to connect a slab and a shear wall in the reinforcement cage; and stirrups 106, used at the joint region as core shear reinforcement; a concrete mix 108 which is designed and added to a wooden mould 110 with the correct placement of a reinforcement cage; a slump 112, used in the concrete mix to accommodate any steel congestion in the joint region; and the exterior shear wall and the flat slab 114, monolithically framed into the wall on one side.
In an embodiment, a method 200 to make an enhanced ductile detailing for reinforcing the concrete wall-flat slab joint, the method comprises the following steps: at step 202, preparing the reinforcement cage; at step 204, adding U-hooks to connect the slab and shear wall in the reinforcement cage; at step 206, adding stirrups at the joint region as core shear reinforcement; at step 208, preparing the wooden mould for the reinforcement cage; at step 210, preparing a concrete mix to be poured into the wooden mould; at step 212, pouring the concrete mix into the wooden mould containing the reinforcement cage; and at step 214, curing the slab after removing the wooden mould.
To further clarify advantages and features of the present disclosure, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.
BRIEF DESCRIPTION OF FIGURES
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Figure 1 illustrates a system to make an enhanced ductile detailing for reinforcing a concrete wall-flat slab joint in accordance with an embodiment of the present disclosure.
Figure 2 illustrates a method to make an enhanced ductile detailing for reinforcing a concrete wall-flat slab joint in accordance with an embodiment of the present disclosure.
Figure 3 illustrates (a) Comparison of displacement ductility of specimens; (b) Joint Shear Stress; (c) Details of prototype structure under lateral loading; (d) Exterior wall-slab subassembly model; (e) Reinforcement details of shear wall; and (f) Reinforcement details of slab in accordance with an embodiment of the present disclosure.
Figure 4 illustrates an (a) Reinforcement details of U type joint and A type joint; (b) Schematic representation of construction of U type joint and A type joint; (c) View of reinforcement cage of specimens; and (d) Joint reinforcement of U specimen and A specimen in accordance with an embodiment of the present disclosure.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present disclosure. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
DETAILED DESCRIPTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.
Embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings.
Referring to Figure 1 illustrates a system to make an enhanced ductile detailing for reinforcing a concrete wall-flat slab joint in accordance with an embodiment of the present disclosure. A system 100 to make an enhanced ductile detailing for reinforcing a concrete wall-flat slab joint comprises: a reinforcement cage 102 is made of steel; an additional core shear reinforcement is connected at the joint region in order to modify the void joint core of conventional reinforcement detailing, the additional core shear reinforcement comprises: U hooks 104, used to connect a slab and a shear wall in the reinforcement cage; and stirrups 106, used at the joint region as core shear reinforcement; a concrete mix 108 which is designed and added to a wooden mould 110 with the correct placement of a reinforcement cage; a slump 112, used in the concrete mix to accommodate any steel congestion in the joint region; and the exterior shear wall and the flat slab 114, monolithically framed into the wall on one side. Figure 2 illustrates a method to make an enhanced ductile detailing for reinforcing a concrete wall-flat slab joint in accordance with an embodiment of the present disclosure. A method 200 to make an enhanced ductile detailing for reinforcing the concrete wall-flat slab joint, the method comprises the following steps: at step 202, preparing the reinforcement cage; at step 204, adding U-hooks to connect the slab and shear wall in the reinforcement cage; at step 206, adding stirrups at the joint region as core shear reinforcement; at step 208, preparing the wooden mould for the reinforcement cage; at step 210, preparing a concrete mix to be poured into the wooden mould; at step 212, pouring the concrete mix into the wooden mould containing the reinforcement cage; and at step 214, curing the slab after removing the wooden mould. In an implementation, the mould may be made of any other material such as iron, copper, metal alloys and is not limited only to wood.
Figure 3 illustrates (a) Comparison of displacement ductility of specimens; (b) Joint Shear Stress; (c) Details of prototype structure under lateral loading; (d) Exterior wall-slab subassembly model; (e) Reinforcement details of shear wall; and (f) Reinforcement details of slab in accordance with an embodiment of the present disclosure.
The prototype structure considered was 12 m long, 7.5 m wide and six storeys high as shown in Figure 3c. Slab of dimensions 4 m x 2.5 m x 0.25 m was connected to a shear wall of cross section 2.5 m x 0.3m. The typical first storey exterior subassembly- JS, illustrated in Figure 3c, was considered for the experimental investigation. The deformed shape of the shear wall building under lateral loading is shown in Figure 3d. Due to the lateral loading, the exterior shear wall-slab subassembly is subjected to in plane moment at the slab-wall joint. The same moment is simulated at the joint by twisting the slab ends as shown in Figure 3d.
Seismic analysis of the prototype structure was performed using Equivalent lateral force method as per IS 1893:2002 Part 1. The structure was designed for seismic zone III and founded on medium soil profiles. As per IS 1893:2002, the Indian subcontinent is divided into four seismic zones (Zone 2, 3, 4 and 5). In which, Zone V expects the highest level of seismicity whereas Zone II is associated with the lowest level of seismicity. The study is carried out on a building located in Chennai, India which is in Zone III as per the zoning map.
The design moment, shear and axial force at the base of the shear wall obtained from the analysis was 4568.89 kNm, 358.32 kN and 1560.85 kN respectively. The shear wall was designed for these forces as per IS 13920:1993 and slab was designed based on the provisions given in IS 456:2000. M30 grade concrete and Fe 415 grade steel were used for design.
The test specimen U has the conventional reinforcement i.e., without core shear reinforcement whereas the test specimen A consists of core shear reinforcement along with the regular reinforcement. Given below are the experimental results derived from the comparison of specimen U and A using different tests.
The two test specimens represent 1/4 scaled down models. Each specimen consisted of an exterior shear wall and a flat slab monolithically framed into the wall on one side. The specimens were 625 mm wide with shear wall of thickness 75 mm and slab of thickness 62.5 mm. The length of the slab was 500 mm which is up to the midspan. The clear storey height was 875mm and the total height of the subassembly was 1.375 m. The geometry and reinforcement details of the test specimens are shown in Figure 3e and 3f. At the top of each specimen, the shear wall is bent sideways to form a projection of 500 mm in order to simulate out of plane bending moment in the shear wall.
The ductility is generally measured in terms of displacement ductility, which is calculated as per ASCE guidelines (ASCE 31- 03, 2002) and is presented in Figure 3a. Even though both type of specimens behaved in a ductile manner, the ductility of the specimen with core shear reinforcement was significantly increased. It was observed that the displacement ductility is enhanced for specimen A by 55.9% when compared with specimen U. A connection subjected to cyclic loading is considered to be ductile if sufficient amount of energy is dissipated without a substantial loss of strength and stiffness. The stirrups in the core region could take care of the joint shear demands by arresting the tensile forces (45o) due to shear. The stirrups also would provide increased confinement of the joint core region. The effect of such confinement of concrete joint core and better anchorage provides increased overall capacity of the connection (in strength and deformation). The ability to deform more without losing strength makes the subassembly ductile.
The area enclosed by the hysteretic loop in a given cycle represents the energy dissipated by that specimen during that cycle. The cumulative energy dissipated was computed by summing up the energy dissipated in the consecutive cycles throughout the test. The cumulative energy dissipated by the specimens were evaluated and compared.
Cumulative energy absorbed during each cycle of loading is plotted against corresponding drift for both the specimens. It is observed that the specimen A with core shear reinforcement was effective in improving the energy dissipation of the joint. Specimen A exhibited higher energy dissipation of 300.5 kNmm when compared with that of specimen U (118.7 kNmm). Thus an increase of 153 % was observed in cumulative energy dissipation capacity for A type of detailing when compared with U type detailing.
It was observed that the U hooks of the conventionally detailed specimen (specimen U) at the joint region had strained to some extent thereby developing cracks at the interface between slab and shear wall. As the drift increased, all reinforcement bars experienced a continuous increase in the strain. In specimen A, the core shear reinforcement provided resisted the shear thereby reducing the yielding of slab reinforcements. Therefore, it is clear that the effect of core shear reinforcement participation to slab strengths and joint shear demands increase with the increase of the drift levels.
It was observed that the specimen U just failed short of the predicted theoretical strength. Therefore the increase in ultimate load in specimen A can be attributed towards the provision of additional shear reinforcement in the joint core. Specimen A has exhibited improved load carrying capacity of 24.6 kN, which is an increase of 35.9% when compared with that of U type specimen.
Stiffness degradation was faster after 0.2% drift cycle due to the commencement of concrete cracking. The specimens showed similar initial stiffness, though the specimen U, without core shear reinforcement degraded in a faster rate when compared with the specimen A, with core shear reinforcement.
The ultimate value of joint shear stress induced in the joints is lesser than the values recommended in IS 13920-1993 (1.0fck MPa=6.1MPa). It can be observed from figure 3b that the shear resisting capacity is more for the specimen with core shear reinforcement than the conventional specimen. The shear capacity was found to be enhanced by 36% for A specimen when compared with U specimen.
Figure 4 illustrates an (a) Reinforcement details of U type joint and A type joint; (b) Schematic representation of construction of U type joint and A type joint; (c) View of reinforcement cage of specimens; and (d) Joint reinforcement of U specimen and A specimen in accordance with an embodiment of the present disclosure.
The two specimens had the same size and reinforcement detailing for the shear wall and slab. The first subassembly labeled "U" was constructed with conventional reinforcement detailing at the wall slab joint region, i.e. the provision of U shaped hooks connecting the shear wall and the slab for a lap length equal to development length of the bar (Ld), from the inner side of the wall. While the second subassembly labeled "A" has been constructed with proposed non-conventional reinforcement detailing, viz. additional core shear reinforcement at the joint region. In order to modify the void joint core of conventional reinforcement detailing, stirrups are provided in the joint core connecting the U hooks. The joint reinforcement details of the test specimens are shown in Figure 4a. The construction of the joint detailing is schematically shown in Figure 4b.
The concrete mix was designed according to IS 10262:1982 in proportion of 1:1.27:2.39 by weight of cement, fine aggregate and coarse aggregates respectively. Portland cement of 53 grade conforming to IS 12269:1987 was used for casting the specimen. River sand passing through 4.75 mm IS sieve and having a fineness modulus of 2.73 was used as fine aggregate. Crushed granite stone of maximum size not exceeding 10 mm and having a fineness modulus of 6.09 was used as coarse aggregate. A slump of 100 mm was used to accommodate any steel congestion in the joint region. The mechanical properties of the constituent materials, namely concrete and steel, were determined. The average compressive strength of concrete cubes after 28 days of curing was 37.76 N/mm2. Regarding steel, 6 mm diameter bars were subjected to tensile tests thus determining the mean yield stress of steel as 432 N/mm2.
The reinforcing steel bar bending was carried out to obtain the detailing of the shear wall - floor slab joint as discussed earlier. The views of reinforcement cages are shown in Figure 4c and 4d. Strain gauges were fixed onto critical points of the reinforcement cage in order to measure the strain experienced by the reinforcement during loading. The reinforcement cage is placed in the wooden mould into which the concrete is poured in order to get the desired shape and size of specimen. The concrete is mixed in a mechanical mixer. Needle vibrator is used to compact the concrete, and tamping is also done to prevent the aggregates from getting stuck between the rebars. Curing was done for 28 days with fully soaked gunny bags.
The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.

Claims (9)

WE CLAIM
1. A system to make an enhanced ductile detailing for reinforcing a concrete wall-flat slab joint, the system comprises:
a reinforcement cage, made of steel; an additional core shear reinforcement is connected at the joint region in order to modify the void joint core of conventional reinforcement detailing, the additional core shear reinforcement comprises: U-hooks, used to connect a slab and a shear wall in the reinforcement cage; and stirrups, used at the joint region as core shear reinforcement; a concrete mix which is designed and added to a wooden mould with the correct placement of a reinforcement cage; a slump, used in the concrete mix to accommodate any steel congestion in the joint region; and
the exterior shear wall and the flat slab, monolithically framed into the wall on one side.
2. A method to make an enhanced ductile detailing for reinforcing the concrete wall-flat slab joint, the method comprises:
preparing the reinforcement cage;
adding U-hooks to connect the slab and shear wall in the reinforcement cage;
adding stirrups at the joint region as core shear reinforcement;
preparing the wooden mould for the reinforcement cage;
preparing a concrete mix to be poured into the wooden mould;
pouring the concrete mix into the wooden mould containing the reinforcement cage;and
curing the slab after removing the wooden mould.
3. The method as claimed in claim 2, wherein, the concrete mix is designed according to IS 10262:1982 in proportion of 1:1.27:2.39 by weight of cement, fine aggregate and coarse aggregates respectively.
4. The method as claimed in claim 2, wherein, the shear wall was designed as per IS 13920:1993 and slab was designed as per IS 456:2000. M30 grade concrete and Fe 415 grade steel were used for design.
5. The method as claimed in claim 2, wherein, preparing the concrete mix, concrete is mixed in a mechanical mixer.
6. The method as claimed in claim 4, wherein, when preparing the concrete mix, a needle vibrator is used to compact the concrete, and tamping is also done to prevent the aggregates from getting stuck between the rebars.
7. The method as claimed in claim 2, wherein, curing of the concrete mix in the wooden mould along with the reinforcement is done for 28 days with fully soaked gunny bags.
8. The method as claimed in claim 6, wherein, after curing the slab, the average compressive strength of concrete cubes was found to be 37.76 N/mm2
9. The method as claimed in claim 2, wherein, regarding steel reinforcement cage, 6 mm 2 diameter bars, the mean yield stress of steel as 432 N/mm .
Preparing the reinforcement cage 202 Adding U-hooks to connect the slab and shear wall in the reinforcement cage 204 Adding stirrups at the joint region as core shear reinforcement 206 Preparing the wooden mould for the reinforcement cage 208 Preparing a concrete mix to be poured into the wooden mould 210 Pouring the concrete mix into the wooden mould containing the reinforcement cage 212 Curing the slab after removing the wooden mould 214 Figure 2
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117647451A (en) * 2024-01-19 2024-03-05 中国电建集团西北勘测设计研究院有限公司 Device and method for testing shearing strength of undisturbed loess multi-group shearing surfaces

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117647451A (en) * 2024-01-19 2024-03-05 中国电建集团西北勘测设计研究院有限公司 Device and method for testing shearing strength of undisturbed loess multi-group shearing surfaces
CN117647451B (en) * 2024-01-19 2024-04-12 中国电建集团西北勘测设计研究院有限公司 Device and method for testing shearing strength of undisturbed loess multi-group shearing surfaces

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