Flat Slab

Flat slab is a reinforced concrete structural system supported directly by concrete columns without the use of beams reinforced that includes either drop panels or column capitals at columns to resist heavier loads and thus permit longer spans. By that large Bending Moment & Shear Forces are developed close to the columns. These stresses bring about the cracks in concrete & may provoke the failure of slab, thus there is a need to provide a larger area at the top of column recognized as column head/capital. Flat slab is defined as one sided or two-sided support system with shear load of the slab being concentrated on the supporting columns and a square slab called ‘drop panels’.

Punching shear is a conspicuous phenomenon of fracture mechanism in R.C Flat slab. To meet high shear and flexural demand at critical shear zones of column supports or point loads of flats slabs, the design codes proposed to construct Column heads (capital) and Slab drops against punching shear failure. But this may lead to decrease head clearance and increase of construction cost. To optimise the slab geometry at critical sections of punching shear zones, an experimental programme conducted on three full scale R.C flat plate slabs (NSF, WSF1, WSF2) constituted with different shear resistant elements(steel fibres and headed shear studs) used in punching shear zone. The flat slabs configurated by NSF is "Flat slab using conventional shear reinforcement bars, and WSF1 is "Flat slab using steel fibre concrete in shear zone and the rest of slab with conventional reinforcement" and WSF2 is "Flat slab with combination of steel fibre reinforcement and shear studs used in punching shear zone only and the rest of slab with conventional reinforcement. Random oriented hooked steel fibres of 1.5% volume fraction used for implicit strengthening of concrete at critical punching shear zone. The test parameters considered in this study are shear performance, load capacity, stiffness degradation, energy dissipation, and crack pattern. The test results indicated that, use of steel fibres and shear studs in critical punching shear zone of flat slab is significantly improves punching resistance mechanism, and load carrying capacity of flat slab (WSF2). Further the punching shear failure at ultimate load was observed by ductile mode with good energy dissipation.

Flat slabs system of construction is one in which the beams used in the conventional methods of constructions are done away with. The slab directly rests on the column and load from the slab is directly transferred to the columns and then to the foundation. To support heavy loads the thickness of slab near the support with the column is increased and these are called drops, or columns are generally provided with enlarged heads called column heads or capitals. A flat slab is a one-way or
two-way system with thickenings in the slab at the columns and load bearing walls called ‘drop panels’.
Drop panels act as T-beams over the supports. They increase the shear capacity and the stiffness of the floor system under vertical loads, thus increasing the economical span range. This form of construction has become less popular in recent years because of the limit on economical spans of about 9.5 m for reinforced slabs and about 12 m for pre-stressed slabs.

Reinforced flat slabs may need to be sensibly pre-cambered (not overdone) to control deflection. Absence of beam gives a plain ceiling, thus giving better architectural appearance and also less vulnerability in case of fire than in usual cases where beams are used. Plain ceiling diffuses light better, easier to construct and requires cheaper form work. As per local conditions and availability of materials different countries have adopted different methods for design of flat slabs and given their guidelines in their respective codes.

The aim of this project is to try and illustrate the methods used for flat slab design using ACI - 318, NZ- 3101, and EUROCODE2 and IS: 456 design codes. For carrying out this project an interior panel of a flat slab with dimensions 6.6 x 5.6 m and super imposed load 7.75 2 / KN m was designed using the codes given above.

In the present study the regular Block type layout of plan is taken into consideration with two types of slab system i.e. Flat slab and post tensioned slab are compared with each other. Considering zone 2 and zone 3 of seismicity according to Indian codes. Various types of Buildings with G+9, G+11, G+14, G+19 and G+24 storeys are considered with difference in geometrical properties and material properties. From past published journals and papers optimization is done in choosing different variety of placement of shear walls, their corresponding height and thickness were given due consideration with accordance to Indian codes. The method used for analysing the model is Linear Time history analysis considering Locc-North seismic condition using software namely ETABS 2015. And conclusion are drawn from various factors with respect to each structural member behaviour during the action of forces on them and differences have been highlighted.

Recent earthquakes have shown that the irregular distribution of mass, stiffness and Strengths may cause serious damage in structural systems. The present study is aimed at understanding the effects of earthquake forces on buildings that are irregular in plan i.e. L-shaped. The effect of wing lengths and their aspect ratios on performance of the structure is studied. Unequal orthogonal lengths are taken to study its effects on response of the building. Buildings are modelled with Flat Slab with and without shear walls and their results compared to determine which shear wall configuration gives the best resistance to seismic forces. Seismic analysis is done using Linear Time History Analysis method. The analytical results show that maximum amount of base shear, roof displacement, drifts occur in models that have equal wing lengths. As the length of one wing is shortened the values of the said parameters also come down i.e., base shear variation is19% and 34% in x and y direction respectively. Roof displacement also reduces by 19% as orthogonal length ratio is reduced. Story drift values also show a reduction of 18%. The presence of shear walls and their positioning impacts the performance of the structure and also the presence of torsion in the buildings.

Twelve slabs, 11 of which contained double-headed studs as shear reinforcement, were tested supported by central column and loaded concentrically. Their behavior is described in terms of deflections, rotations, strains of the concrete close to the column, strains of the flexural reinforcement across the slab width, and strains of the studs. All failures were by punching, in most cases within the shear reinforced region. The treatments of punching resistance in ACI 318, Eurocode 2 (EC2), and the critical shear crack theory (CSCT) are described, and their predictions are compared with the results of the present tests and 39 others from the literature. The accuracy of predictions improves from ACI 318 to EC2 to CSCT—that is, with increasing complexity. However, the CSCT assumptions about behavior are not well supported by the experimental observations.

Surabaya adalah kota terbesar kedua di Indonesia setelah Jakarta. Menurut Dinas Kependudukan dan Pencatatan Sipil kota Surabaya pada awal tahun 2019 jumlah penduduk mencapai 3,095 juta jiwa dan akan terus meningkat, Dengan banyaknya jumlah penduduk yang ada dan terus meningkat, maka kebutuhan akan sarana prasarana untuk memfasilitasi penduduk seperti pembangunan gedung tingkat tinggi yang semakin banyak layaknya apartemen dan perkantoran. Maka dari itu dibutuhkan inovasi konstruksi yang relatif cepat, dan efisien tanpa mengurangi kualitas dari struktur. Seiring dengan perkembangan teknologi pada saat ini, sebuah bangunan juga tidak hanya membutuhkan kekuatan struktur yang kuat saja, tetapi memerhatikan dari segi arsitektural dan keindahannya.
Apartemen Amega Crown Residence menggunakan material beton bertulang dengan total 12 lantai dan 2 tempat parkir dan dibangun dengan metode cor ditempat. Untuk mengefisiensi biaya penggunaan material dan waktu tanpa mengurangi kualitas dan mutu beton, penulis akan memodifikasi Struktur Gedung Apartemen Amega Crown Residence menggunakan U-Boot untuk menghemat material dan metode pracetak serta dimodifikasi menjadi 14 lantai.
Pada perhitungan struktur gedung agar kuat terhadap beban lateral layaknya gempa, gedung ini didesain dengan sistem ganda yakni gabungan antara sistem rangka pemikul momen dan sistem dinding struktural (shearwall). Beban lateral yang disebabkan oleh gempa dipikul oleh kedua sistem tersebut. Dengan digunakannya U-Boot, membuat berat struktur gedung menjadi lebih ringan dan lebih indah secara estetika. Dari hasil analisis yang dilakukan, digunakan U-Boot tipe Single H-16 dan Single H-13.
Kata kunci: U-Boot, Beton Pracetak, Sistem Ganda

Graphical abstract Abstract A 3D finite element analysis was carried out to study the behavior of slab-column connections in a flat slab structure under combined gravity and cyclic lateral load. Prior to simulating the behavior of the proposed model, the slab-column connection specimen by using standard orthogonal stud rail from the previous study was modeled with the purpose of verifying the results using finite element tool. Given that numerical simulation was undertaken using ABAQUS to predict the structural behavior of the above-mentioned structure. With regard to providing an accurate result, a sensitivity analysis was performed by changing different parameters, such as dilation angle, viscosity parameter, and damage parameter-strain on both in tension and compression. After gaining the close resemblance to the previous study, the proposed models were then simulated using the similar technique. In the proposed model, drop panel element was used as a replacement of stud rail. Additionally, the engineered cementitious composite material using polyvinyl alcohol fibers (PVA-ECC) was also employed due to its strain capacity of 3-5% under tension compared to 0.01% of conventional concrete. Through this study, the results showed that the effect of utilizing the PVA-ECC material could significantly improve the specimen behavior and damage tolerance.

Twelve slabs, 11 of which contained double-headed studs as shear reinforcement, were tested supported by central column and loaded concentrically. Their behavior is described in terms of deflections, rotations, strains of the concrete close to the column, strains of the flexural reinforcement across the slab width, and strains of the studs. All failures were by punching, in most cases within the shear reinforced region. The treatments of punching resistance in ACI 318, Eurocode 2 (EC2), and the critical shear crack theory (CSCT) are described, and their predictions are compared with the results of the present tests and 39 others from the literature. The accuracy of predictions improves from ACI 318 to EC2 to CSCT—that is, with increasing complexity. However, the CSCT assumptions about behavior are not well supported by the experimental observations.

Multi-storey building for the commercial complexes is major requirement for the current scenario. For this large span and free space is required as per the need of the users. Due to this, these structures become challenges for structural engineer because large obstacle free space means less columns and greater spans which can result in a catastrophe. For this problem, a widely accepted concept has been introduced in the form of flat slab structures or beam less structures. To provide extra support column heads are introduced. Structural behaviour of these structures become complex under dynamic earthquake loading. Stability of this type of structure under such lateral loading must be checked before designing and construction of the building. In this articles deals with the different flat slab structures i.e. Flat slab structures with drop panels and without perimeter beams, Flat slab structures with drop panels and with perimeter beams uses fast non-linear time history analysis method. For this a regular commercial building having G+8 (32 m) is taken. Storey with a plan area 37.5 m x 37.5 m. is untaken for analysis in CSI-ETABSvr.2016 Software. The commercial building under taken in the earthquake Zone-IV for the city Rajkot in Gujarat. The non-linear dynamic analysis i.e. Time History approach used of Seismic response of the building. From the results it can be concluded that model 2 flat slab with perimeter used as optimized structure in the lateral stability under earthquake response.

It is known that the Greek codes allow flat-slab structural systems, however they provide specific compliance criteria. In the present study an extended parametric investigation was carried out in order to identify the seismic response of structural systems consisting of α) slabs-columns b) columns-perimetric beams c) columnsshear walls-slabs d) columns-shear walls-slabs and perimetric beams. The aforementioned systems were studied for all possible storey heights in Greece by means of F.E.M. Code SAP2000 ver.9. The compliance criteria provided by the Greek Code for earthquake resistance are related to second order effects, torsional flexibility, capacity design and the sensitivity of masonry infill. Conclusions were extracted concerning the number of storeys which can be applied to each case.

Punching shear of pre-stressed concrete flat slab is an undesirable mode of failure that occurs without warning and can lead to progressive collapse of large areas of the slab or even complete structures. Mod-eling the punching shear strength of pre-stressed concrete slabs is conceptually difficult as the tendons can be bonded or unbonded, the tendon passing through the columns or not, the stress in tendons at the punching failure is indeterminate, the tendons can be banded and the tendons can be draped resulting in beneficial vertical components of the vertical pre-stressing force. The purpose of this study is to predict punching shear resistance of pre-stressed concrete slab-column connection from physical analytical model, that includes integration of the vertical component of concrete tensile strength along the inclined surface of the inverted cone which represents the punching shear cracks, the dowel forces of supplementary bonded reinforcement and the pre-stressing force from pre-compression and vertical component of pre-stressing calculated by yield line theory. The comparisons of the present proposed equation with ECP 203, ACI 318, BS8810, and EC2 code provisions and Gardner equations for the previous experimental scaled studies indicated that the proposed equation is less conservative. Finally from the proposed equation the contribution of concrete tensile force, dowel force and pre-stressing force in the punching shear resistance of pre-stressed concrete flat slabs can be calculated. Poinçonnement du béton précontraint dalle est un mode de défaillance indésirables qu'elle se produit sans avertissement et peut conduire à l'effondrement progressif de vastes zones de la dalle ou même des structures complètes. Modélisation de la résistance au cisaillement de poinçonnage de précontrainte des dalles de béton est conceptuellement difficile que les tendons peuvent être collées ou non liée, le tendon peut passer à travers les colonnes ou non, le stress dans les tendons à la rupture par poinçonnement est indé-terminée, les tendons peuvent être bagués et les tendons peuvent être drapées entraînant bénéfique com-posante verticale de la force verticale de précontrainte. Le but de cette étude est d'étudier la prédiction de la résistance au cisaillement de poinçonnage de béton précontraint connexion dalle-colonne du modèle d'analyse physique, y compris l'intégration que de la composante verticale de la résistance à la traction en béton le long de la surface inclinée du cône inversé qui représente les fissures de poinçonnement, les forces de la cheville renforcements liés complémentaires et la force de précontrainte de la pré-compression et une composante verticale de la précontrainte du calcul de la théorie de la ligne du rende-ment. Les comparaisons de l'équation proposée présente avec ECP 203, ACI 318, BS8810, et les disposi-tions du code EC2 et les équations Gardner pour les études expérimentales échelle rapportés dans la litté-rature, ce qui indique que l'équation proposée est moins conservatrice. Enfin à partir de l'équation propo-sée la contribution de la force de traction en béton, la force de serrage et de précontrainte vigueur dans la résistance au cisaillement par poinçonnement du béton précontraint dalles peuvent être calculée.

Flat-Slab building is very popular from the aesthetic and architectural point of view. From functional aspect a flat-slab building is more efficient than a R.C. frame building. So, construction of Flat-Slab building is increasing also in high seismic zone. Sometimes international building codes remain silent about the seismic response of flat slab buildings. In this paper the response of Flat-Slab building and a normal symmetric R.C. frame building of same dimension have been studied for varying seismic intensities. Static, Response Spectrum, Pushover, and Time history analysis have been performed to assess the performance of the two buildings. The costs of construction for these two buildings have also been compared. An extensive study on lumped plasticity model as per FEMA 356 with varying position of plastic hinge and its effect on pushover curve has also discussed in the paper. The paper also comments on the plastic hinge pattern.

Structures with a large degree of indeterminacy is more to one with less indeterminacy, if yielding takes place in any one of them and members are monolithically connected to each other, then a redistribution of forces takes place. So it is necessary to study analysis of seismic behavior of building. Flat slab building structures are significantly flexible than traditional concrete wall structures or frame structures (beam-column-slab), thus becoming more vulnerable to seismic loading condition. Therefore, the characteristics of the seismic behavior of flat slab buildings suggest that guiding the concept and design of these structures in seismic regions are needed. Flat-slab have high degree of structural efficiency, therefore it is most widely used systems in reinforced concrete construction. It uses simple formwork arrangement and reinforcing arrangement, and requires the least story height. Five different models (conventional slab, flat slab, flat slab with drops, flat slab with column head and flat slab with column head & drop) are used in linear static analysis and Response spectrum method, analyzed in ETABS.

For reinforced concrete flat slab structures, column failure due to unexpected extreme loading may significantly
increase the moment and shear force at adjacent slab–column connections, which can trigger punching shear failure
at these connections and result in progressive collapse of flat slab structures. To determine the possible load-resisting
mechanisms developed in flat slab structures in resisting progressive collapse, three multi-panel flat slab substructures
are tested in this study. A flat slab substructure is tested as a control specimen. The remaining two specimens
are strengthened by adding drop panels or post-installed shear bolts. Punching shear failure is observed in the
control specimen and the specimen with post-installed shear bolts after reaching their yield loads. However, even the
control specimen without any strengthening exhibited considerable post-failure resistance and deformation capacity
mainly due to sufficient integrity reinforcement, which had been installed in the bottom of the slab. Test results
indicated that drop panels not only increase the flexural resistance but also raise the punching shear resistance of
the connections significantly. Thus, no obvious punching shear failure is observed in the specimen with drop panels.
However, post-installed shear bolts can only increase the punching shear resistance. For post-failure behaviour, this is
not very effective. The test results demonstrated that flexural failure dominates the performance of test specimens,
as relatively low slab reinforcement ratio but high span/thickness ratio was designed.

It is known that the Greek codes allow flat-slab structural systems, however they provide specific compliance criteria. In the present study an extended parametric investigation was carried out in order to identify the seismic response of structural systems consisting of α) slabs-columns b) columns-perimetric beams c) columns-shear walls-slabs d) columns-shear walls-slabs and perimetric beams. The aforementioned systems were studied for all possible storey heights in Greece by means of F.E.M. Code SAP2000 ver.9. The compliance criteria provided by the Greek Code for earthquake resistance are related to second order effects, torsional flexibility, capacity design and the sensitivity of masonry infill. Conclusions were extracted concerning the number of storeys which can be applied to each case.

It is known that the Greek codes allow flat-slab structural systems, however they provide specific compliance criteria. In the present study an extended parametric investigation was carried out in order to identify the seismic response of structural systems consisting of a) slabs-columns b) columns-perimetric beams c) columns-shear walls-slabs d) columns-shear walls-slabs and perimetric beams. The afore-mentioned systems were studied for all possible storey heights in Greece by means of F.E.M. Code SAP2000 ver.9. The compliance criteria provided by the Greek Code for earthquake resistance are related to second order effects, torsional flexibility , capacity design and the sensitivity of masonry infill. Conclusions were extracted concerning the number of storeys which can be applied to each case.

Featured Application: An optimization method, based on Simulated Annealing, is developed for the design of reinforced concrete slab. Abstract: Flat slabs have several advantages such as a reduced and simpler formwork, versatility, and easier space partitioning, thus making them an economical and efficient structural system. When producing structural components in series, every detail can lead to significant cost differences. In these cases, structural optimization is of paramount relevance. This paper reports on the structural optimization of reinforced concrete slabs, presenting the case of a rectangular slab with two clamped adjacent edges and two simply supported edges. Using the yield lines method and the principle of virtual work, a cost function can be formulated and optimized using simulated annealing (SA). Thus, the optimal distribution of reinforcing bars and slab thickness can be found considering the flexural ultimate limit state and market materials costs. The optimum result was defined by the orthotropic coefficient k = 8, anisotropic coefficient g = 1.4, and slab thickness H = 11.8 cm. A sensitivity analysis of the solution was developed considering different material costs.

Flat-Slab building is very popular from the aesthetic and architectural point of view. From functional aspect a flat-slab building is more efficient than a R.C. frame building. So, construction of Flat-Slab building is increasing also in high seismic zone. Sometimes international building codes remain silent about the seismic response of flat slab buildings. In this paper the response of Flat-Slab building and a normal symmetric R.C. frame building of same dimension have been studied for varying seismic intensities. Static, Response Spectrum, Pushover, and Time history analysis have been performed to assess the performance of the two buildings. The costs of construction for these two buildings have also been compared. An extensive study on lumped plasticity model as per FEMA 356 with varying position of plastic hinge and its effect on pushover curve has also discussed in the paper. The paper also comments on the plastic hinge pattern.

In this paper, the effectiveness of textile-reinforced mortar (TRM) and fiber-reinforced polymer (FRP), as a means of improving the punching behavior of reinforced concrete flat slabs were numerically investigated. Finite element (FE) model using ABAQUS computer program was developed to analyze eight half-scaled slabs, in terms of load-carrying capacity, ductility, stiffness, and crack patterns. These eight specimens were divided into two groups (G1 and G2) with four specimens for each of them. Specimens of G1 was similar to that of G2 in all details but differ in the eccentricity of the applied load. Specimens of G1 were tested with concentric load, while these of G2 were tested with 150 mm eccentricity. For each group, one specimen was built as control (unstrengthened), one was strengthened by FRP-sheet, and the other two was strengthened by TRM-jacket with two different mesh opening (10 and 20 mm). The results obtained from FE analysis showed that the efficiency of TRM in increasing the punching shear capacity of strengthened slabs was less than that of FRP. In addition, the slabs strengthened by TRM showed stiffer behavior than that strengthened by FRP, but lesser ductile. TRM effectiveness was sensitive to the mesh size of the textile. When the mesh size decreased, stiffness was increased and ductility was decreased.

In this paper, the effectiveness of textile-reinforced mortar (TRM) and fiber-reinforced polymer (FRP), as a means of improving the punching behavior of reinforced concrete flat slabs were numerically investigated. Finite element (FE) model using ABAQUS computer program was developed to analyze eight half-scaled slabs, in terms of load-carrying capacity, ductility, stiffness, and crack patterns. These eight specimens were divided into two groups (G1 and G2) with four specimens for each of them. Specimens of G1 was similar to that of G2 in all details but differ in the eccentricity of the applied load. Specimens of G1 were tested with concentric load, while these of G2 were tested with 150 mm eccentricity. For each group, one specimen was built as control (unstrengthened), one was strengthened by FRP-sheet, and the other two was strengthened by TRM-jacket with two different mesh opening (10 and 20 mm). The results obtained from FE analysis showed that the efficiency of TRM in increasing the punching shear capacity of strengthened slabs was less than that of FRP. In addition, the slabs strengthened by TRM showed stiffer behavior than that strengthened by FRP, but lesser ductile. TRM effectiveness was sensitive to the mesh size of the textile. When the mesh size decreased, stiffness was increased and ductility was decreased.

This paper presents results of tests on 18 one-way reinforced concrete slabs under point loads having as main variable the transverse flexural reinforcement ratio, the loading position and the width of the slab. The response of the slabs is described and discussed in terms of deflections, strains of the concrete and of rebars, cracking pattern, failure modes and failure loads. Experimental results are also used to discuss and evaluate theoretical treatments presented by American Concrete Institute 318 (ACI, 2014) and Eurocode 2 (Comité Européen de Normalisation [CEN], 2005). All slabs failed by punching shear and results indicate that the recommendations presented by the codes are conservative, especially those related to the prediction of one-way shear resistance of reinforced concrete flat slabs. Resistência à punção de lajes de concreto armado com cargas concentradas assimétricas RESUMO. Este trabalho apresenta resultados de ensaios em 18 lajes unidirecionais de concreto armado sob carregamento concentrado, tendo como variáveis a taxa de armadura de flexão transversal, a posição de carregamento e a largura da laje. Seu comportamento é descrito e discutido em termos de deslocamentos, deformações do concreto e das armaduras, padrão de fissuração, modos e cargas de ruptura. Os resultados experimentais também são usados para discutir e avaliar as recomendações apresentados pelas normas ACI 318 (2014) e Eurocode 2 (CEN, 2005). Todas as lajes romperam por punção e os resultados indicam que as recomendações normativas são relativamente conservadoras, especialmente aquelas relacionadas com a previsão da resistência ao cisalhamento unidirecional de lajes lisas de concreto armado.

► SUMMARY:

♦ The Resilient Composite Systems (R.C.S.) could be counted as "The Methodically Reinforced Nonlinear Porous Materials", also having the high specific modulus of resilience in flexure. They are the compound materials, with some particular structural properties, in which, contrary to the basic geometrical assumption of the flexure theory in Solid Mechanics, the strain changes in the beam height during bending is typically "Nonlinear". The Resilient Composite Systems are made by expediently creating the disseminated suitable hollow pores and/or by distributing the appropriate lightweight aggregates throughout the methodically reinforced, fibered conjoined matrix so that; "the strain changes in the beam height during bending" is typically "nonlinear". Thereby, by applying the mentioned method to make the said composite systems, "considerably increasing the modulus of resilience and the bearing capacity in bending" together with "the significant decrease of the weight" and "the removal of the beam fracture possibility of primary compressive type" have been feasible. Through making these particular consistently functioning systems, the above-stated paradoxical virtues have been concomitantly fulfilled in "one functioning unit" altogether.

♦ The RCS (with the mentioned general structural properties and specific functional criteria) whose cement materials include the "C-S-H (Calcium Silicate hydrate) crystals" have been termed "Elastic Composite, Reinforced Lightweight Concrete (E.C.R.L.C.)".

♦ The RCS and ECRLC as a kind of RCS could be used in many cases. For instance, "Constructing Lightweightly and Consistently", also with practically utilizing the RCS and ECRLC in particular, can be counted as the pivotal and practical tactic to effectively increase the resistance & safety of the constructions against "earthquake" and lateral forces, in the large extent. For example, using some lightweight and insulating, "non-brittle", reinforced sandwich panels or 3D-panels, "with the high modulus of resilience and appropriate behavior against the bending loads and impacts", for construction could be taken into consideration according to the case... [It is worth remarking that; contrary to the ECRLC, the usual reinforced lightweight concretes, especially in the very low densities, are dramatically brittle; they do not have the appropriate behavior and resistance against the high bending loads and impacts.]
.
● "Resilient Composite Systems (RCS)":

♦ "Resilient Composite Systems" (RCS) are the compound materials, having some particular structural properties, in which, contrary to the basic geometrical assumption of the flexure theory in Solid Mechanics, the strain changes in the beam height during bending is typically "Nonlinear". The RCS could be counted as "The Methodically Reinforced Nonlinear Porous Materials", also having the high specific modulus of resilience in flexure. (Elastic Composite, Reinforced Lightweight Concrete; ECRLC is a type of RCS with the mentioned specifics.)

♦ Generally, the Resilient Composite Systems comprise these components as the main, necessary elements:
• 1) Mesh (Lattice);
• 2) Fibers or strands;
• 3) Conjoined matrix, having the disseminated suitable pores and/or the disseminated appropriate lightweight aggregates beads or particles. [Here, the general term of "lightweight aggregate" has a broad meaning, also including the polymeric and non-polymeric beads or particles.]

♦ The Resilient Composite Systems are made by creating the disseminated suitable hollow pores and/or by distributing the appropriate lightweight aggregates throughout the reinforced, fibered conjoined matrix so that; "the strain changes in the beam height during bending" is typically "nonlinear". Thereby, by applying the mentioned method to make the said particular composite systems, "considerably increasing the modulus of resilience and the bearing capacity in bending" together with "the significant decrease of the weight" and "the removal of the beam fracture possibility of primary compressive type" have been feasible. Through making these particular consistently (unitedly, integratedly) functioning systems, the stated paradoxical virtues have been concomitantly fulfilled in one functioning unit altogether.

♦ Generally, in these consistently functioning units, the amount and the use manner of the mentioned components in the organized system are so that; the reciprocal interactions among the components finally lead to the "typically nonlinear strain changes in the beam height during bending" (as the "basic functional character" of these systems with the specific testable criteria and indices) and the functional specifications fulfillment of the system.

♦ In the RCS in general, the main strategy to raise the modulus of resilience in bending is "increasing the strain capability of the system in bending" within the elastic limit.

♦ Here, the main tactic to realize the stated strategy is: "creating the suitable hollow pores and/or using the appropriate lightweight aggregates, all disseminated throughout the methodically reinforced conjoined matrix", to provide the possibility for occurring of the expedient internal deformities in the matrix during the bending course, which could lead to the more appropriate distribution of the stresses and the strains throughout the system and the more strain capability of the beam in flexure. On the other hand, only creating the hollow pores and/or using the lightweight aggregates in the matrix, by itself, not only cannot lead to the mentioned goals but also brings about weakening of the matrix and its fragility. Hence, concomitantly, the matrix should be well supported and strengthened. Here, this essentially ameliorating and strengthening the matrix are performed by giving attention to "the internal consistency of the matrix" and also via "employing the expedient reinforcements in two complementary levels": 1) Using the fibers to the better distribution of the tensile stresses and strains in the matrix, and to increase the matrix endurance and the modulus of resilience in tension and bending; 2) Using the mesh or lattice to better distribution of the tensile stresses and strains in the system, and to increase the system endurance and the modulus of resilience in tension and bending.

♦ In these systems, the presence of the mentioned hollow pores and/or lightweight aggregates disseminated throughout the conjoined matrix (which has been ameliorated through making "an integrated, reticular structure") provides the possibility for occurring of the expedient internal deformities in the matrix during the bending course. By the way, this can lead to the less accumulation of the internal stresses in the certain points of the matrix during bending, the better absorption and control of the stresses, and providing the more strain capability of the beam, especially within the elastic limit.

♦ The occurrence of the remarked internal deformities in the said methodically reinforced matrix during the bending course also means; the occurrence of the deformities in the said hollow pores and/or lightweight aggregates well disseminated throughout the conjoined matrix, in two different forms. Indeed, we have the internal deformities in the fibered lightweight matrix of the system throughout the bending course, in two main different forms, leading to: A) The comparative increase of the thickness (height) of the in-compressing layers (particularly in the upper parts of the beam) and the conversion of some internal compressive stresses to the internal tensile stresses (on the axis perpendicular to the mentioned internal compressive tensions) in the in-compressing layers; B) The comparative decrease of the thickness (height) of the in-tension layers (particularly in the lower parts of the beam) and the conversion of some internal tensile stresses to the internal compressive stresses (on the axis perpendicular to the mentioned internal tensile tensions) in the in-tension layers.

♦ In the under-bending sections of the "Resilient Composite Systems", the deformities occurring in the "conjoined layers perpendicular to the applied load direction" during the bending course are so that; "the initially plane sections perpendicular to the beam axis" typically shift from "the plane status" to "the curve status" during the bending course. Thereby, the basic geometrical assumption of the flexure theory in Solid Mechanics ("linearly" being of the strain changes in the beam height during bending) and the respective trigonometric equations & equalities are mainly overshadowed in these systems.

♦ This way, through occurring of the remarked internal deformities in the strengthened matrix during the flexure course, the stresses are more distributed and absorbed, and the rise rate of the internal stresses in the matrix ... reduces.  ...
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► [sites.google.com/site/newstructure1]

The economy of the structural design of reinforced concrete buildings is usually evaluated by comparing
the concrete volume per unit area and rebar weight per unit volume with certain empirical values depending on the type
of the structure and the past experience of the judging engineer. The aim of this paper is to refine those empirical values
and give that past experience the required scientific base. In order to achieve that goal, simplified methods of design
that stated in most of reinforced concrete design codes are used to figure out the required quantities of concrete and
reinforcement steel for different structural elements and types. Some reasonable assumptions are used to facilitate the
mathematical formulas to be usable and presentable. Produced formulas are accurate enough to be used in rough
estimation of concrete and rebar quantities, check quantity surveying results and evaluate the economy of the structural
design.

Flat-Slab building is very popular from the aesthetic and architectural point of view. From functional aspect a flat-slab building is more efficient than a R.C. frame building. So, construction of Flat-Slab building is increasing also in high seismic zone. Sometimes international building codes remain silent about the seismic response of flat slab buildings. In this paper the response of Flat-Slab building and a normal symmetric R.C. frame building of same dimension have been studied for varying seismic intensities. Static, Response Spectrum, Pushover, and Time history analysis have been performed to assess the performance of the two buildings. The costs of construction for these two buildings have also been compared. An extensive study on lumped plasticity model as per FEMA 356 with varying position of plastic hinge and its effect on pushover curve has also discussed in the paper. The paper also comments on the plastic hinge pattern.

One of the lateral load opposing frameworks in multi-storey structures is Steel brace frame. The resistance of the structure which enhances against horizontal forces by expanding its stiffness and stability is Steel bracing system in RC multi-storey building is conservative, simple to set up, involve less space and give obliged quality and inflexibility. Flat slab reinforced buildings have exhibit many dominances over conventional type of beam column building. However, the effectiveness of structure in flat slab construction is inferior in performance under earthquake loading. Flat slab requires the simple formwork which usually result in an economical construction. In present study, a G+9 storey building is analysed for seismic zone IV as per IS 1893: 2002 using ETABS software. Flat slab is used by providing drop panels and peripheral beam. For all models parameters are kept constant. The effect of the distribution of the steel bracing along with the flat slab RC frame on the seismic performance of the building is studied. The performance of the building is evaluated in terms of storey displacement, storey shear, story drifts and slab stresses. The percentage reduction in lateral displacement along X direction is tabulated. By providing drop panels the slab stress is reduced on structure compared to RC bare frame. Hence it is concluded that the use of steel bracing with flat slab in construction resists the lateral forces for many vulnerable conditions.

The slab is the main component of the structure. There are different types of slab used in different structure and gives better appearance to the structure. In this project, three type of slab to be used. The comparative study of Conventional slab, flat slab, and waffle slab under seismic condition to be analyzed. An effort has been made to evaluate the study between Conventional slab, flat slab, and Waffle slab for G+10 story building. This type of slab has been analyzed and designed by ETABS software. The plan of waffle slab plan is done in such a way in order to accomplish better burden dispersion. The near investigation of waffle slab with flat Slabs and conventional slab and features the benefit waffle slab have over flat Slabs and conventional slab. The parametric studies comprise maximum lateral displacement, story drift, and axial forces generated in the column due to slab.

A computing modeling approach has been carried out to understand the rigid frame structural behavior of eight storied commercial building due to incorporation of edge beams and shear walls into the flat plate structure. In this study, numerical analysis based on finite element method for reinforced concrete building materials and static lateral loading conditions has been conducted The lateral loads including earthquake and wind loads were applied using ETABS software package to the building model along both long and short direction as per Bangladesh National Building Code 2006 (BNBC). Based on computing modeling output data, a comparative study has been performed to understand the effect of edge beam and shear wall on the structural behavior of flat plate buildings. The results show that lateral displacements as well as lateral drifts are found smaller in case of edge beam and the smallest for shear walls while compared to flat plate building only. It is also found that in case of ...

It is common practice to use a flat slab system not just in new construction buildings but also for adding extra stories like mezzanine floors for existing buildings. As such, non-monolithic connections are used, however, few literature either experimentally or numerically, addresses the behavior of such connections. In this respect, this paper numerically investigated the behavior of two non-monolithic connection (using dowel and weld systems) validated against experimental work conducted in the concrete laboratory of the Faculty of Engineering, Ain Shams University. In this context, a parametric investigation for the influencing parameters is presented. The investigated parameters were related to dowels number, diameter, impeded length inside the slab, the height difference between the dowels in X & Y directions, welding length, and slab thickness. The results illustrate the impact of the tested parameters on the performance of the proposed connections. This paper is considered a gate opening for a numerical database that facilitates the formulation of design equations for the proposed non-monolithic connection

This paper examines the feasibility of replacing natural aggregate with recycled crushed ceramics in R.C flat slabs. Nowadays, many researchers are trying to use recycled ceramics as coarse aggregate in manufacturing concrete structures to decrease waste construction materials, and save raw materials. The experimental work was carried out on six slabs measuring 1650 x 1650 x 150 mm with a connected central column tested for punching shear. One slab was control without recycled ceramics aggregate; five slabs with recycled ceramics aggregate with different ratios of 20%, 35%, 50%, 60% and 70% were used.

The economy of the structural design of reinforced concrete buildings is usually evaluated by comparing the concrete volume per unit area and rebar weight per unit volume with certain empirical values depending on the type of the structure and the past experience of the judging engineer. The aim of this paper is to refine those empirical values and give that past experience the required scientific base. In order to achieve that goal, simplified methods of design that stated in most of reinforced concrete design codes are used to figure out the required quantities of concrete and reinforcement steel for different structural elements and types. Some reasonable assumptions are used to facilitate the mathematical formulas to be usable and presentable. Produced formulas are accurate enough to be used in rough estimation of concrete and rebar quantities, check quantity surveying results and evaluate the economy of the structural design.

Most methods for the design and analysis of reinforced concrete slabs for punching are based on experiments on slab-column connections, reflecting the situation in building slabs. Slab-column connections with unbalanced moments have also been studied in the past. Experiments indicate that the accuracy of models for asymmetrically loaded slabs is lower than for symmetrically loaded slabs. In this paper, the difference in accuracy between test predictions for symmetrically and asymmetrically loaded slabs is tackled. A plastic model, the Extended Strip Model, is proposed. The results of maximum loads according to this model are compared to experimental results of symmetrically and asymmetrically loaded slabs. The comparison between the proposed Extended Strip Model and the experimental results shows that the model has a consistent performance for both symmetrically and asymmetrically loaded slabs. Moreover, the model has as an advantage that it combines the failure modes of flexure, sh...

It is known that the Greek codes allow flat-slab structural systems, however they provide specific compliance criteria. In the present study an extended parametric investigation was carried out in order to identify the seismic response of structural systems consisting of α) slabs-columns b) columns-perimetric beams c) columns-shear walls-slabs d) columns-shear walls-slabs and perimetric beams. The aforementioned systems were studied for all possible storey heights in Greece by means of F.E.M. Code SAP2000 ver.9. The compliance criteria provided by the Greek Code for earthquake resistance are related to second order effects, torsional flexibility, capacity design and the sensitivity of masonry infill. Conclusions were extracted concerning the number of storeys which can be applied to each case.

In this paper, the effectiveness of textile-reinforced mortar (TRM) and fiber-reinforced polymer (FRP), as a means of improving the punching behavior of reinforced concrete flat slabs were numerically investigated. Finite element (FE) model using ABAQUS computer program was developed to analyze eight half-scaled slabs, in terms of load-carrying capacity, ductility, stiffness, and crack patterns. These eight specimens were divided into two groups (G1 and G2) with four specimens for each of them. Specimens of G1 was similar to that of G2 in all details but differ in the eccentricity of the applied load. Specimens of G1 were tested with concentric load, while these of G2 were tested with 150 mm eccentricity. For each group, one specimen was built as control (unstrengthened), one was strengthened by FRP-sheet, and the other two was strengthened by TRM-jacket with two different mesh opening (10 and 20 mm). The results obtained from FE analysis showed that the efficiency of TRM in increasing the punching shear capacity of strengthened slabs was less than that of FRP. In addition, the slabs strengthened by TRM showed stiffer behavior than that strengthened by FRP, but lesser ductile. TRM effectiveness was sensitive to the mesh size of the textile. When the mesh size decreased, stiffness was increased and ductility was decreased.