Reinforced concrete voided slabs., Assignments of Civil Engineering

Download Reinforced concrete voided slabs. and more Assignments Civil Engineering in PDF only on Docsity! College of Engineering كلية الهندسة Department of civil engineering قسم الهندسة المدنية Reinforced concrete Reinforced concrete voided slabs. Prepared By: Shahad Salim Qata’ Supervised By Dr. Hussain Askar 1 Voided Biaxial Slabs Abstract. A bubble deck slab is a technique of realistically disposing the concrete in the center of the slab, which does not perform any structural role, thus significantly reducing the dead weight of the structure. High-density hollow voids of polyethylene replace the actual concrete in the middle of the slab, as a result reducing the dead load and productivity of the slab will be increased .This paper reviewed the numerous studies have been prepared on voided biaxial slab system. conventional Slab are a standout amongst the most widely recognized parts in present day building development devouring a large portion of the concrete .The Advantages are lower power as comparison consumption than conventional slab - in both production, transport, emissions gases especially CO2 and reducing materials, load, cost reduction and it is ecological structure element. A range of recycled plastic bubbles allows columns spacing of 50% without any symptoms. This offers a wide range of benefits and construction cost. The bubble system usually combines the benefits of the industrial elements in the controlled conditions with the completion of the final concrete site, leading to a finalized floor slab. 1. Introduction In any construction, slab has greatest significant role, utilized for docking resolution and for conveying the loads to different structural components. Biaxial voided slabs are reinforced concrete slabs in which the voids allow concrete to be reduced. The creation of the voided slab was invented in the 19th century. But using it unique in one-way spanning structure, and necessity be sustained by beams and fixed walls. The clue was to produce a voided deck with the similar volumes as a conventional concrete slab, however with significantly less weight because of the removal of the extra concrete [1]. In general, the slabs are divided into two parts in terms of load distribution as one-way slab and two-way slab. Slabs that tend to carry loads to one side is called one-way. The two-way slab is also called a "slab spanning" in two directions because bending occurs in mutually directions, when we observe slabs in general, while the overload increases, subsequently deflection of the slab will be increased. Thus, the thickness of the slab increases. Increasing the thickness of the slab makes it heavier because of the self- weight of the slab rise too, and will increase the other elements columns, foundations. Therefore, it makes constructions consume additional materials such as reinforced concrete and steel reinforcement [2] The new manufactured construction technology utilizing Bubble Deck slab is newly practical in several industrial projects. Bubble Deck slab also called a biaxial voided slab that is created by Jorgen Bruenig in 19th century. A biaxial voided slab is a new system of construction utilizing plastic balls in slab which replace the concrete in the middle of a slab to decrease the dead load of the structure [3]. The usage of sphere-shaped balls to fill the voids in the mid of a slab reduces 35%-50% of a slab self-weight compared to solid slab having same thickness without affecting its deflection behavior & bending strength [2]. 4 3.1 Concrete The concrete is composed of water, standard Portland cement and aggregates. Further, self-compressive concrete is typically used, either for pre-casting slabs, or for filling the joint in site. Also, the extreme dimension of aggregate is the thickness of bubbles deck slab and the dimension of aggregate must be fewer than 15mm.Therefore, must use the Grade M30 and above[7]. Figure 2. Standard Stress Block [8] 3.2 Steel reinforcement The steel reinforcement has numerous review, for example, Fe60 or Fe 40 or more. The reinforcement consists of two layers at the top and the other at the bottom for lateral supports. In addition, the separation in the middle of the bars relate to the measurements of voided be used and the amount of reinforcement of the cross ribs of the slab [7]. 3.3 Plastic spheres The bubbles (Fig.3) are prepared utilizing high intensity of polypropylene or HDPE. These are frequently made of impermeable materials that do not interact chemically with concrete reinforcement. The plastic spheres have sufficient strength and strong enough stiffness to sustenance the loads applied safely in the stages during and before the concrete casting. The diameter of the bubbles ranges from 180 mm to 450 mm. Contingent on this; depth of voided slab is 180mm to 600mm. The distance among a plastic ball and another plastic ball should be greater than 1/9th a plastic ball diameter. The insignificant diameter of the holes might be 180, 225, 270, 315, or 360 mm. The plastic spheres could be spherical, oval or square [3]. 4. Properties of bubble deck slab 4.1 Flexural Strength The slab roof is designed to omit great importance capacity of the concrete (contrasted to the concrete solid mortar) in the middle of slab where the slab is essentially UN stressed in flexure [6]. In the slabs, the depth of compression in the concrete is a small part of the depth of the slab. In other words, its effect includes concrete only between the ball and the surface. Therefore, there is no sensible difference between the behavior of a solid slab and Bubble Deck [11]. According to A. M. Ibrahim, N. K. Ali, and W. D. Salman (2013), studied flexural capacities of two-way bubble deck slabs of spherical voids. It has been confirmed the flexural performance of this biaxial voided slab such as strain, crack pattern, concrete 5 compressive, ultimate load and deflection, using special frame for testing two- dimensional flexural tests. It watches that the split shape and flexural conduct be dependent upon the void measurement to thickness of slab proportion. Figure 3.Hollow spherical and elliptical bubbles [3] Figure 4.Cracks in bubble deck [12] A definitive load capacity with respect to voided deck section having bubble measurement to deck thickness of (0.51 and 0.64) were the same of strong pieces, while when bubble size to deck thickness of (0.80) a definitive limit were lessened by around (10%)[12]. as shown in figure 4. 4.2Shear strength At somewhat flat slab, the resistance of shear the outline is frequently basic close to the sections of columns. The shear swings from the sections of columns and moves rapidly and outside the segment territories. Shear has been affirmed by testing and plotting the longitudinal and transverse weights inside the scope of the surface plate framework. Shear quality of biaxial voided piece is 0.6 times the shear quality of a customary solid slab of a similar thickness [11]. Valivonis, Skuturna, Daugeviius, & Šneideris(2017)studied the punching shear strength of reinforced concrete slabs with plastic void formers. In respect of increasing the punching shearing ability of the flat slabs, the concrete ribs provide shear 6 reinforcement at voids. Sections of slabs with void edging increments situated in the whole slab zone, bubble deck chunks with conventional slab cross shapes and voided biaxial deck piece chunks with conventional slab heads were investigated in this examination. A technique to register punching shear limit made on EC2 code has been anticipated. The outcomes accomplished for the punctured shear quality of the test pieces were affirmed with the EC2 system, and a procedure to decide the length of the punching shear outskirt has been projected [13]. 4.3 Durability The durability of the voided slab does not differ significantly from conventional slab. Concrete is a standard grade and mutual with an appropriate bar cover provides most of the durability control equal to the normal standards of conventional slabs [11]. In addition, the design of slabs is modern, the reinforcement part and balls are shaken into cement and create institutionalization of pressure, so a thickness of surface cement is delivered that is in any event safe and strong. The joints might be on the surface of the voided biaxial slab within edges to guarantee that the concrete surrounding every bar does not permit coordinate airflow from the strengthening steel superficial. This is basically fusion for imperviousness to fire yet in addition identified with sturdiness [2]. 4.4 Fire resistance As a voided biaxial slab performance like a conventional slab, the imperviousness to fire is simply a question of the measure of concrete layer. The imperviousness to fire is reliant on the temperature in the bars and subsequently the transport of the heat. As the bottom and top of the biaxial slab is conventional slab , and the rebar's are set in this solid portion, the imperviousness to fire can be planned by requests[14]. As indicated by Nasvik J. (2011) inspections did as per ISO 834 also, demonstrated that imperviousness to fire endures 60 180 minutes and the imperviousness to smoke is 1.5 times the imperviousness to fire[15]. 5. The tests of hollow-core slabs The consequences of Andersen and Lauridsen (1999) began an open deliberation on the resistance to fire of voided slab into Denmark, yet nonconformities of the figured outcome were not instantly clarified. Danish who is the minister of trade demanded another tests ought to be made. The Institute of Danish for Technology of Fire made on 1.2 m wide and two 265 mm thick expelled voided deck as found in Fig 5. Components ought to a traverse of 6min the middle of the supports. The furrow in the middle of components were thrown out[16]. When the element is lifted from the oven, it has been shown that the base was spine somewhat dropped down, wide cracks have been created to alternate canals in fig 6. No indication of shear disappointment be realized, the deflection showed that a disappointment mode of shear may have been bending. Be that as it may, as clarified in the accompanying, the disappointment methods of shear, berth, bending and overlay might be consequences of a similar decay of the slab [17].