COUPLING BEAM TO COUPLED SHEAR (HOLLOW) WALL CONNECTION

SYSTEM TECHNICAL FIELD

The Innovation is for a connection system related to coupled shear walls on coupling beams with main carrier system consisting of cross reinforcements, vertical reinforcements, horizontal reinforcements, joints, connection points and additional points in which shear and bending reinforcements are meant to be used.

PRIOR ART

In carrier systems in which the shear walls are used, coupled shear (hollow) walls are formed due to the gaps which are left for functional reasons such as doors, windows or transitional systems. These types of shear walls are named as coupled shear walls or shear walls with coupling beams. The positioning of hollows together with their numbers and sizes along the wall affect the activity of construction and the distribution of internal forces in coupling beams and shear walls. When the hollows which are left in shear walls are relatively smaller than the size of walls, the effect of hollows are neglected and the system is known to be a shear wall without hollow. However when the hollows left in shear walls are relatively bigger, their effect on the system is taken into account and alternatively the system is designed and constructed as coupled shear (hollow) wall. In this type of constructions the positioning of hollows in shear walls and the effects of hollows on structural system should be taken into consideration. When the coupling beams and coupled shear walls are designed appropriately, they can act ductile enough.

Shear walls and coupled shear walls systems are frequently found in buildings. Higher shear walls and coupled shear walls which have higher rigidity according to columns are preferred mainly for compensation of horizontal forces such as earthquake and wind. Coupled shear walls come into existence when hollows like doors, windows, corridor e.t.c are left on structural walls. These types of systems which are special types of structural wall systems are named as coupled shear wall. When the coupling beams of coupled shear walls in multi storey reinforced concrete buildings are designed and constructed in a ductile way, they act more ductile than shear walls without hollows.

Due to the effect of the lateral forces on the coupled shear wall system; while shear forces and bending moments occur in coupling beams; axial forces, shear forces and bending moments occur in coupled shear walls. Because of horizontal forces which affect coupled shear wall system, the overturning moments which is formed in the system is carried by two separate force groups. These consist of bending moments which are formed in shear wall system and reaction moments which are formed by reverse marked, equal valued axial pair of forces in shear walls. The intensity of axial forces in pair of shear walls depend on the ability of coupling beam to transfer the shear force which is formed on them without losing its capacity. When the rigidity of coupling beams increases, the walls would work together effectively. On the contrary, the normal force in walls will increase due to the shear force in coupling beam. The shear force coming to coupling beams increase, with the decrease of bending moments to the walls and the increase of rigidity of coupling beam.

The main aim of coupling beams is to maintain the transfer of shear forces between coupled shear walls that are formed from horizontal forces affecting the system. Coupling beams are exposed to reversed cyclic reversed loading. In coupled shear walls, earthquake effects is primarily concentrated on coupling beams. In cases where these effects exceed the capacity in coupling beams; bending damages are observed at the bases of the walls. According to scientific experiments that were made on coupled shear walls, it was found that the conventional beam details had a negative effect on activity of the system. Short span coupling beams equipped with classic flat reinforcements and stirrups, become weak due to the tension and pulling forces that occur without reaching their bending capacity of the cross sections. In short span coupling beams, equipped with classic flat reinforcements and stirrups; even though the stirrups are properly arranged and shearing capacity is well maintained by increasing rate of shearing capacity, short span coupling beams do not show functional activity due to weakening of adherence under reversed cyclic loading, joining of bending cracks on two sides and power exhaust in shearing forces at the edges. Scientific experiments indicated that reinforcements placed direction of diagonal especially in short and deep coupling beams showed positive results in terms of functional activity. The details of diagonally reinforced coupling beams have been involved in many current regulations such as Turkish Earthquake Regulation (ABYYHY 2007), European Earthquake Regulations (Eurocode8 2004), and U.S.A Concrete Institution (ACI 2008) e.t.c. Joining of this kind of diagonal reinforcements to concrete in coupled shear walls is important. By writing balance of a coupling beam you can easily find sufficient reinforcement force and area required. When seismic force affects coupling beam to coupled shear wall connection system in one direction, cross reinforcement bars which shows extension and lifts pulling force stays in concrete pressure area as seismic force changes its direction. If there is elastic extension exceeding limit in reinforcement, it carries most of pressure even without enclosing the cracks in concrete.

In the coupling beam shear wall systems, coupling beams with shear walls are aimed to work together. According to the Turkish Earthquake Regulation (ABYYHY 2007), if these two equations provided below balance, special shearing reinforcement which will be placed in coupling beam will be determined by methods which have scientific proof or cross reinforcements will be used so as to compensate bending moment and shearing force formed by coupling beam.

Vd > 1.5xbwxdxfctd

In the formula above;

(n : free open space range between surfaces of structural walls of coupling beam, hk : coupling beam height,

bw \ coupling beam body width,

d : coupling beam utility height,

fctd : concrete design pulling endurance

According to Turkish Earthquake Regulation (ABYYHY 2007), the total reinforcement area clustered by each of the cross reinforcement will be determined according to the formula below.

Asd = Vd / (2xfydxsiny)

In this formula; Asd : Total area clustered by each of the cross reinforcement

Vd : Shearing force calculated under companion of earthquake forces and horizontal forces multiplied with force coefficients,

fyd : longitudinal yield strength of the reinforcement,

γ : The angle made by cross reinforcement bars with horizontal.

According to the Turkish Earthquake regulation (ABYYHY 2007), at least four reinforcement's bars must be ready in cross cluster reinforcements in order to compensate shearing force and bending moment formed by it in coupling beam. Similarly these reinforcements must be lengthened at least one and a half times more into the shear wall. Reinforcement's bars will be surrounded with special earthquake stirrups of diameters not less than 8 mm with the distance range not exceed 100 mm and will not larger than 8 times diameter of cross reinforcement bar. In addition to cross reinforcements, minimum amount of stirrup and horizontal reinforcement will be placed in coupling beam.

According to the European Earthquake Regulation (Eurocode8 2004), in order to compensate the seismic effects reinforcements, both equations given below must be balanced and will be used throughout each of diagonal under conditions provided below.

l < 3x h

In the formula above;

/ : free open space range between surfaces of structural walls of coupling beam, h : coupling beam height,

Ved : design shear force in coupling beam

bw : coupling beam thickness,

d : coupling beam utility height,

ctd : concrete design pulling endurance .

a) According to Eurocode8 2004, the equation below must be balanced in coupling beams having cross reinforcement bars

In the formula above;

VEd : design shear force in coupling beam

Asi : total area of each diagonal direction to reinforcements in coupling beam fyd : longitudinal yield strength of the reinforcement.

a : the angle made by cross reinforcements used in coupling beam with horizontal b) Diagonal reinforcements must be equipped in such a way that their wideness are at least 0.5 ^χ b _w as part of column.

c) Stirrups must be used in order to prevent the buckling of longitudinal reinforcements which are equipped like columns.

d) Vertical and horizontal reinforcements must be placed on both sides of coupling beam and minimum conditions emphasized in European Earthquake Regulation (Eurocode 2004) must be maintained. Cross reinforcements surrounded by tight stirrups must be constructed in a way to surround each other and to pass in the middle of coupling beam as illustrated in the regulations. Similarly these cross reinforcements must be installed at edges of shear walls. Construction of such cross reinforcements is nearly impossible. The density in cross equipments in coupling beams and at edges of the shear wall; has generated many difficult problems in preparation of reinforcements, placing in between them, arrangement and installation. Moreover, it causes cross equipments to be different from the original structure emphasized in project thus making the construction impossible in most cases.

As a result of the construction technique, firstly construction of coupled shear walls require constructing shear wall's edges which are surrounded with tight stirrups and which have densely longitudinal reinforcements followed by construction of cross reinforcements surrounded with tight stirrups installed at edges shear walls and anchor them to the shear walls body. Due to the impossibility in construction and installation of cross reinforcements passing through each other with tight stirrups, these type of cross reinforcements find no place when it comes to the application. These cross reinforcements are not practical for placement and installation under conditions of construction site. Different types of coupling beam reinforcements were presented to literature due to the difficulties in application and installation of cross reinforcements. As per coupling beam reinforcement literature; after placing H profile horizontally into the coupling beam and anchoring bearing walls, a new composite beam type is established. Here H profile is installed horizontally to the coupling beam as a single piece. Steel plates are welded to H profile in order to delay the profile's bending and corrugation in coupling beam. This Steel H profile produced as a single piece also create problems in installation and anchoring.

Prefabricated girders (precast) were presented as coupling beams to the literature before. Tie girders and their reinforcements are prepared as precast in other words poured concrete coupling beam is brought to construction site. Anchor reinforcements are stretched from coupling beam reinforcements. Precast beams are prepared under factory conditions and they are delivered to the construction site, installed reinforcements are inserted into coupled shear walls and placed then coupled shear wall is poured and single piece system is created. In such case, reinforcements emerged from precast coupling beams, create problems when they are placed to bearing walls.

Previously, in literature H profiles as coupling beam reinforcements are welded to each other in a cross style then with this one piece cross reinforcement was created and tested. At the ends of H profile, which will remain into coupled shear walls, cut parts are welded in order to extend the size of anchor. Installing and placing H profiles, which are welded to each other as one piece, into wall and coupling beam is nearly impossible. BRIEF SUMMARY OF THE INNOVATION

It is related to connection system of coupled shear walls with coupling beams which stem from the hollows which are left for functional reasons like doors, windows or transition systems.

Coupling beam reinforcements which were presented in literature previously are constructed as monolithic (single piece).

It is not practical to apply monolithic cross reinforcements due to their difficulties in installation and anchoring into structural walls. I brought forward a technique and a new reinforcement type in order to solve the problems mentioned above. The technique includes using functional steel equipments (L profiles, U profiles, T profiles, H profiles, box profiles, pipe profiles or L, U, I, T, H, box and pipe segment metal sheet) to create new type of equipment constructed with double, cross, horizontal steel parts which are surrounded by welded stirrups. Production of sectional systems under factory conditions eases installation phase, however connection of coupling beams to coupled shear (hollow) wall facilitate installation process. Thanks to the system , which I developed that enables connection of coupled shear (hollow) walls to coupling beams, installing phase will be more easier when rigid connection is provided without the sections which are to be placed into coupled shear (hollow) wall in order to provide anchoring. When we take into consideration that this connection phase is done under hard circumstances and very crucial for building survival, I understand that providing easy and healthy connection is obligatory. DESCRIPTION OF FIGURES

Figure 1. View of installed connection system of coupling beam to the coupled shear (hollow) walls.

Figure 2. Perspective view of installed connection of coupling beam to the

system

Figure 3. Overview of receiving gap apparatus

Figure 4. Exploded view of coupling beam with connection system

Part numbers on the figures with their corresponding names are provided below.

1 . Coupled shear (hollow) wall

2. Coupling beam

3. Connection plate

4. Space-taking apparatus

DETAILED DESCRIPTION OF THE INNOVATION

The Innovation is integrated with element as vertical reinforcement of two composite coupled shear (hollow) wall (1 ) facing each other through edges which are (L profiles, U profiles, T profiles, H profiles, box profiles, pipe profiles or L, U, I, T, H, box and pipe segment metal sheet) connected with at least one connection plate (3) and combined with screws, bolts, high strength bolts, rivets, smart screw, welding or other connecting elements. Subsequently coupling beam (2) is integrated with at least one connection plate (3) on both two sides welded, smart screwed, fasten, high endurance bolted, bolted, screwed or any other means resembling to these. With the connection plate (3) connected at the end of coupling beam (2) rigid connection is provided to vertical reinforcement of two composite coupled shear (hollow) walls (1 ) facing each other through their end points as far as they are connected together. The small gaps which may result during connection between two connection plates (3) can be taken by using appropriate simple space-taking tools (4). Thus the connection of coupled shear (hollow) wall with coupling beam can be done easily at the construction site besides the working hours will be decreased as well as the chances of work risks emerging at the time of installation are reduced.

Through coupled shear (hollow) wall connection system and coupling beams created in this way by developing a standard; a durable and resistive to seismic force and loads residential buildings may be created which are more safe and economical.