Slab Buildings Research Articles

Investigation of optimization techniques on structural-acoustical shaped concrete slabs in buildings

Computational tools have become integrated into design practice at the building scale and component scale. While there has been a resurgence of optimization techniques in room acoustics, research has been limited on utilizing optimization techniques on building components, such as a building's structural floor. Quality design solutions must be found at the component scale to accommodate for increased urbanization, environmental concerns, building utilization, and the well-being of the occupants, especially in relation to the tenants' acoustic environment. This presentation will discuss the use of several design space exploration and optimization approaches to generate and consider multiple permutations of shaped concrete floor designs. The shape of the ribbed slab will be varied in order to improve both the embodied energy of the concrete slab, which is proportional to mass, as well as the sound transmission class (STC). Three computational techniques (Latin Hypercube Sampling, multi-objective evolutionary optimization and constrained optimization) will be used to determine trade-offs in the design. The advantages and disadvantages of each technique will be highlighted with respect to the trade-off between reduced mass and improved STC. Finally, the importance of model resolution will be discussed in early design space exploration and optimization procedures.

SEISMIC ANALYSIS OF FLAT SLAB BUILDING ON SLOPING GROUND.

In a developing country like India urbanization and industrialization has accelerated real estate development which leds to scarcity of land. This started the construction of multistorey buildings on sloping ground. Buildings constructed on sloping ground are very irregular and unsymmetrical in vertical and horizontal plane as compared to the buildings on level ground. Also, these buildings on sloping ground require great attention for seismic analysis. The present work studies the behavior of flat slab buildings on sloping ground. For this, G+8 storey 36 different building models with square plan area on sloping ground are considered. The total plan area and mass of the building is kept constant for all models. The sloping angles 0°, 16°, 21° are considered for square plan. The corner and core columns of some models are replaced with shear wall by keeping the mass constant. The response spectrum analysis of all models is carried out using software Etabs17. The study concludes that flat slab building with shear wall at outer periphery of building is preferable than the discontinuous shear wall at core of the building.

Çekme Düzensizliği Bulunan Betonarme Binaların Geçiş Kat Döşemelerinin Modellenmesi

Döşemeler, katlara etkiyen deprem yüklerini düşey taşıyıcılara aktaran, bu elemanlarının birlikte çalışmasını sağlayan yatay taşıyıcı sistem elemanlardır. Düşey taşıyıcılara oranla yüksek düzlem içi rijitliğe sahip olan döşemeler, rijit diyafram olarak modellenirler. Rijit diyafram modeli, taşıyıcı sistemi düzenli betonarme binalar için uygun çözüm sunmaktadır. Ancak normal katlardan perdelerle çevrili bodrum kata geçiş döşemeleri ile düşey doğrultuda plan alanlarının aniden değiştiği çekme düzensizliği bulunan binalardaki geçiş kat döşemeleri için rijit diyafram kabulünün dikkatle irdelenmesi gerekmektedir. Türkiye Bina Deprem Yönetmeliği (TBDY-2019)’nde geçiş kat döşemelerinin sonlu elemanlarla modellenmesi ve yeterli rijitliğe sahip olduğunun hesapla gösterilmesinin gerekliliği belirtilmektedir. Bu nedenle çalışmada çekme düzensizliğine sahip betonarme bina modelleri üzerinde, rijit diyafram modeli ile döşemelerin esnek davranışını (düzlem içi şekil değiştirmelerini) göz önüne alan sonlu eleman modeli arasındaki farklar incelenerek rijit diyafram modelinin uygulanabilirliği araştırılmıştır. Bu amaçla modellerde, döşemeler rijit diyafram modeli ve iki boyutlu sonlu eleman modeli olmak üzere iki farklı şekilde modellenmiş, mod birleştirme yöntemi kullanılarak analiz edilmiştir. Modeller, modal katkılar, geçiş kattaki yatay ötelenme değişimi, ve gerilme dağılımlarındaki değişimler dikkate alınarak incelenmiştir. Analizler neticesinde sonlu eleman modelinin, incelenen sistemler için rijit diyafram modeline oranla büyük değerler verdiği, ancak aradaki farkın kabul edilebilir limitler arasında olduğu görülmüştür. Analiz süresinde sağladığı avantaj dikkate alındığında yeterli döşeme kalınlığı alınarak rijit diyafram kabulünün incelenen sistemler için uygun olacağı kanaatine varılmıştır.

Progressive collapse behaviour of reinforced concrete flat slab buildings subject to column failures in different storeys

Abstract The progressive collapse of buildings could result in significant financial losses and casualties, and it is therefore of the utmost importance to reduce the risks of such occurrences. Flat-slab buildings are much more prone to progressive collapse than moment-frame buildings, since as there are no beams for redistributing the loads that the lost column initially resisted. Even more consideration should, therefore, be given to assessing the progressive collapse of flat-slab buildings. The current analytical research assesses the progressive collapse behaviour of eight-storey R.C flat slab building, with and without perimeter beams, by conducting linear static progressive collapse analysis as per the GSA guidelines (2016). This research explores the column removal situations for various typical positions on each storey, unlike earlier studies where only certain typical columns on the first storey are removed. The results are analyzed for each scenario in terms of joint vertical displacement and chord rotation at column removal locations, and thus the susceptibility of the building to progressive collapse is calculated in compliance with the relevant accepted criteria laid down in the DoD Guidelines (2009). The results showed that the incorporation of perimeter beams in flat slab buildings improved the progressive collapse resistance as it reduces joint displacement and chord rotation at column removal locations by providing sufficient stiffness and load paths for increased gravity loads.

Comparative Study on Progressive Collapse of An Irregular (Lshaped) Flat Slab Building by Linear Static Analysis using ETABS

Concrete and steel structures influences the construction of multi-storey structures. The aid of progressive collapse increases when there is a failure of one or more load bearing structural elements. Thereafter, this case study is carried out to determine the prospective of the progressive collapse of an irregular (L shaped) building due to the failure or removal of two adjacent columns at a time present in the ground floor. Failure may occur because of the natural or manmade accidental loads like explosion or seismic loads, collision of vehicles, etc. Columns at different locations were removed and the slab loads had been increased as per the General Services Administration (GSA) guidelines and the results in terms of Demand Capacity Ratios (DCR) are compared for all the cases. The Demand to Capacity Ratios were calculated for the interested columns. It is observed that when the interior columns were removed then the possibility of progressive collapse is more. This study has been made for the case or earthquake forces for corresponding zone II and zone V.

Analytical assessment of restraint forces and crack widths in end-restrained building slabs

This paper deals with the analytical assessment of restraint forces and crack widths in end-restrained building slabs. The analysis concentrates on the service limit state (SLS) and the challenge is hereby the appropriate consideration of the combined effect of axial restraint due to imposed deformations and bending cracking due to loading. As for the imposed deformations, the paper regards the drying shrinkage of concrete under indoor conditions, although any other temperature deformation or combination of shrinkage and temperature could be included accordingly.A deformation-based approach is presented, in which imposed deformations are made compatible with the released deformations of the slab due to opening of loading-induced bending cracks. The solution aims an appropriate inclusion of the most relevant effects while still providing a practicable and verifiable solution for the complex problem of assessing the restraint forces as well as the crack widths in end-restrained building slabs.The result of this approach is an analytical quantification of restraint forces to be transferred in the restraining members. In addition, the presented approach enables the determination of crack widths in the restrained conditions. An important asset of the analytical nature of this approach is the explicit correlation between individual system parameters, especially concrete properties and surrounding conditions, member dimensions and provided reinforcement, loading in the SLS and restraining condition.The paper includes the presentation of the general idea of a deformation-based assessment of end-restrained building slabs; the demonstration of this approach with an example from the literature; and the comparison of the analytical design solution with experimental results on the combined effect of bending and axial restraint in slab-like specimens.

Evaluation of Interactions Between Thermal Piles Integrated in Building Foundations

Abstract This paper investigates the impact of thermal interactions between heat exchangers integrated within building foundation piles to meet space heating and cooling needs of buildings. Specifically, a three-dimensional transient numerical model is developed to evaluate the thermal performance of the foundation piles. The model is used to estimate the temperature variations within the soil medium under various operation conditions of thermo-active foundation (TAF) systems. Then, a series of parametric analyses is carried out to evaluate the influence of design parameters of the piles on the performance of TAF systems, including the interactive effects between piles as well as the impact of these piles on the building slab heat transfer. Then, the parametric analysis results are utilized to develop simplified calculation methods to assess the thermal impacts of the geometric features for the piles on both the performance of TAF systems as well as the building slab heat losses and/or gains. The developed simplified calculation methods are suitable to develop design guidelines in order to enhance the performance of thermal piles to heat and cool buildings.

The effect of the stress distribution of anchorage and stress in the textured layer on the durability of new anchorages

Abstract The paper estimated the effect of the distribution of edge and shear stresses occurring in the façade texture layer of three-layer walls of large slab panel buildings, as well as the variability of these stresses depending on the anchorage strength of the anchorage. Bonded anchors with seven different diameters M8 ÷ M30, selected based on catalogues, were analysed. The traction stress was determined based on the destructive force, which is determined by the catalogues of manufacturers of bonded anchors. Depending on the choice of the method of repairing the connections between the textured layer and the structural layer, we give the three-layer walls a new character of work. One of the methods of strengthening the textured layer is the popular COPY-ECO system in Poland. It is a system of two anchors (horizontal and diagonal), reflecting the shape of the work of existing hangers. The article also analyses the variants of oblique anchorages for the M12 anchor with inclination angles of 30∘, 45∘ and 60∘. The extent to which the anchorage inclination angle has been assessed influences the higher parameters of the anchor’s bearing capacity due to the shearing of the textured layer.

Seismic Behavior of Flat Slab Buildings of Varied Heights Considering P-Delta Effect

Seismic Behavior of Flat Slab Buildings of Varied Heights Considering P-Delta Effect

Macro modeling of slab-column connections in progressive collapse with post-punching effect

In this paper, macro-modeling methods of the slab-column connections were suggested to predict their post-punching behavior. These modeling techniques can be used to evaluate the potential for progressive collapse of flat slab buildings. It is acknowledged that structural damage is primarily focused on the flat slabs at their slab-column connections. In the suggested model, shell elements were used to simulate the plate and beam connector components to simulate punching failure. Six load-deformation curves were implemented with linear and nonlinear behaviors to simulate bending, shear, torsion, and axial force of the beam connector components to model the inner forces transfer between the slab and the column and to study the action of the connections. Two methods of macro modeling for simulating post-punching behavior were presented: rebar-modeling, link element modeling. The rebar or link element is placed vicinity to the connector beam element and activated after the punching failure. A bilinear load-deformation curve for the link element is defined to simulate post-punching behavior. Some of the parameters used to introduce these curves are calibrated with the test results. Test specimens validated the proposed methods. The results show that both post-punching behavior modeling techniques have acceptable accuracy in predicting post-punching strength, post-punching stiffness, and deformation capacity.

A Novel Integrated Approach to Solve Industrial Ground Floor Design Problems

The ground floors of buildings usually have high loads from racks and other storage equipment in industrial buildings and logistics centers. Such types of buildings commonly require lift trucks. Therefore, there are special requirements for flatness tolerance across and along the driving track of truck lifts. Structural design solutions must be optimized and sustainable. The article reviews the behavior of soils and the importance of the actual behavior assessment of soils during the design of the ground floor on the elastic subgrade. The behavior of the ground floor’s areas above pile foundations that support the building’s columns is essential. Calculation results show the impact of subgrade stiffness on the behavior of reinforced concrete (RC) floor slab, especially in areas above pile foundations, where the stiffness of subgrade is much higher. The research provides a solution to achieve the required level of settlement dissimilarity in areas where there are piles underneath a building slab under the columns. The paper proposes a new integrated method for the evaluation of the subgrade reaction coefficient above the pile cap. The proposed method optimizes design time and eliminates the need for specialized geotechnical software. Obtained results confirmed the efficiency of the proposed design method.

The hot summer-cold winter region in China: Challenges in the low carbon adaptation of residential slab buildings to enhance comfort

The UK-China research project Low carbon climate-responsive Heating and Cooling of Cities (LoHCool) investigates enhanced indoor summer comfort in the 9 Billion m2 of building stock of the challenging Hot Summer and Cold Winter (HSCW) zone of China. The HSCW region lies South of the Huai River-Qin Mountain line below which central heating and cooling are deemed 'not required'. If this central government direction is relaxed, a significant carbon penalty could arise if the existing building stock is sealed and air conditioned to Western standards. LoHCool investigates the alternative strategy of increasing the existing stock's resilience to climate through low energy, low technology adaptation. The approach is applied here to typical slab building forms in Hangzhou and Chongqing in the East and West of the HSCW zone. Internal thermal conditions are simulated using the dynamic thermal model EnergyPlus calibrated using field data. Insofar as ventilation is a critical component of the adaptation schemes proposed, the local wind environment of the case study buildings is simulated using an advanced large eddy simulation model, Fluidity. Out of these diagnostic analyses, adaptation schemes are configured, specified and modelled, and found to significantly increase comfort with viable payback periods although supplementary cooling will be required as the century advances.

Anti-Seismic Bracing in a Hollow-Core Slab of Formwork-Free Shaping for The Possibility of Creating a Rigid Disk in a Building Floor Slab

Building codes and regulations for construction in seismic regions of many countries (including Uzbekistan) require that the floors slabs and elements of a building should possess resistance to seismic impacts, have such functions that not only distribute seismic load between the supporting elements of the building (walls, crossbars and frame columns), but also ensure the spatial operation of the building as a result of reliable bracing of these elements. Therefore, floor slabs made of reinforced concrete prefabricated elements must present rigid horizontal diaphragms (disks) that uniformly distribute seismic loads between load-bearing structures. To fulfill the above requirements, the building standards of Uzbekistan KMK 2.01.03-96 “Construction in seismic areas” oblige designers to provide the strength and rigidity of floors slabs of buildings (structures) by installation the anti-seismic bracings in inter-slab joints between the side surfaces of adjacent slabs; between the end supporting sections of slabs and the frame elements or the anti-seismic belts of stone buildings. The same standards require the presence of free lengths of reinforcement bars or concrete inserts at the ends of slabs for connecting floor slabs with each other and with an anti-seismic belt (or a framing beam); these requirements apply to the production of floor slabs using the aggregate-flow technology. An installation of bracing elements for hollow-core slabs of formwork-free shaping with adjacent structures is not provided since the slabs of a set length are fabricated on a production line by cutting a molded monolithic tape on the line. In this regard, hollow-core slabs of formwork-free shaping must have anti-seismic joint units that provide the bearing capacity of building structures of various systems at the stages of their life cycle. Typical solutions of such units for hollow-core slabs of formwork-free shaping have not been developed. An anchor node with a unit in the void at the end section of the slab has been developed for the anti-seismic bracing of a hollow-core floor slab of formwork-free shaping with adjacent building structures (through a seismic belt or a framing beam). For anti-seismic bracing in inter-slab joints between the lateral surfaces of adjacent floor slabs, a constructive solution is proposed for the cross section of a hollow-core slab of formwork-free shaping with a widened lower flange relative to the upper flange to install a reinforced concrete framing beam in the inter-slab joints. This creates a rigid disk in the building floors. Tests for pulling out anchor rods from nodes arranged in voids at the end sections of a hollow-core slab of formwork-free shaping assessed the strength and serviceability of the proposed antiseismic coupling units. The pulling out of the anchor rods in all tested units occurred before the loss of cohesive strength in the contact zone “concrete of the body of anchor unit - concrete of the slab”. The use of hollow-core slabs of formwork-free shaping with a widened lower flange relative to the upper flange greatly simplifies the installation of reinforced concrete framing beams in the inter-slab joints of buildings. A useful model was patented in the Intellectual Property Agency of the Republic of Uzbekistan; a constructive solution was proposed for a hollow-core slab of formwork-free shaping with a widened lower flange relative to the upper flange, application number FAP20180174 with priority date 11/08/2018. The proposed solutions for the anti-seismic ties of a hollow-core slab of formwork-free shaping with a building structure meet the requirements of the building codes of Uzbekistan KMK 2.01.03-96 “Construction in seismic areas” for transforming a floor slab made from prefabricated plates into a continuous beam slab to create a rigid horizontal diaphragm. The arrangement of the proposed anti-seismic connecting units in a hollow-core slab of formwork-free shaping does not change the manufacturing technology of this type of slabs, and allows the creation of a wide range of products for buildings and structures with various architectural, planning and structural solutions that increase the possibilities of housing, civil and industrial construction in seismic areas.

Performance of P-Delta Analysis of Flat Slab and R C Framed Buildings

Two-way slab directly rests on column known as flat plates, in flat slab building formwork is simple as compare to normal slab (that means slab rest on beam column frame building) and reinforcement layout are also simple and storey height decreases. In flat slab building check second order effect (second order effect known as p-delta effect). P-delta analysis means laterally displacing structures (for high rise building) with gravity loads will deflect. In P-delta analysis when lateral force act on member then it will deflect at delta distance and create secondary moments. For stability design of a building P-delta analysis is required. In the present work seismic analysis (consider zone V & soft soil) of a multi storey flat slab building with and without P-delta effects is analysed by using ETAB software. The seismic zone factor of 0.36 is considered. From the analysis check displacement and drift of flat slab building at different storey (G+9, G+19, and G+ 29) of flat slab building.

Seismic Response of Multistory Flat Slab Building with and without Shear Wall

Seismic Response of Multistory Flat Slab Building with and without Shear Wall

A CASE STUDY ON PRE-TENSIONING & POST TENSIONING SYSTEMS OF A PRESTRESSED CONCRETE

In Present days the pretensioning and post tensioning systems are very popularly using in the major constructions of a structure. The Pre-tensioning and Post-tensioning both methods are used under pre-stressing process. In which has few edges over the orthodox non-stressed structures like greater span to depth ratio, higher moment and shear capacity. These methods are generally adopted in the making of PSC girders, sleepers, Bridges, Slabs in buildings, Concrete Pile, Repair and Rehabilitations, Nuclear Power Plant etc.

Large-scale experiment on the behaviour of concrete flat slabs subjected to standard fire

The use of concrete flat slabs in multi-storey buildings is increasing, and the current fire design guidelines for flat slabs are based on research carried out a few decades ago. Since then, material properties of concrete and construction techniques have changed, which require new experiments to be carried out to assess the fire performance of concrete flat slabs. In this work, the fire resistance of flat slabs was investigated at a large scale (3.78 m × 4.75 m) under structural loading and exposed to ISO 834 fire conditions. The boundary conditions were partially fixed, compared to previous tests where they were free to expand. These modified boundary conditions simulate closer to the actual conditions and capture the effects of membrane action on punching shear behaviour. No spalling occurred during the 3-h duration of the test. The test was also extended to investigate the behaviour during the cooling phase, as it is critical with restrained support conditions. Results show that the duration of fire resistance is significantly higher than that of similar tests with no lateral restraint. Heat propagation and deformation recovery during the cooling phase were also measured. Improved fire resistance duration suggests that the punching shear resistance is enhanced by restrained support conditions.

Seismic Analysis of Flat Slab by using ETABS

The flat slab is a two-way reinforced concrete slab that usually does not have beams and girders, and the loads are transferred directly to the supporting concrete columns. ETABS automates several slab and mat design tasks. Specially, it integrates slab design moments across design strips and designs the required reinforcement; it checks slab punching shear around column supports and concentrated loads; and it designs shear link and shear stud if needed. The actual design algorithms vary based on the specific design code chosen by the user. This manual describes the algorithms used for the various codes. Recent earthquakes in which many concrete structures have been severely damaged or collapsed, have indicated the need for evaluating the seismic adequacy of existing buildings. About 60% of the land area of our country is susceptible to damaging levels of seismic hazard. Many existing flat slab buildings may not have been designed for seismic forces. Hence it is important to study their response under seismic conditions and to evaluate seismic retrofit schemes. This system is very simple to construct, and is efficient in that it requires the minimum building height for a given number of stories. Unfortunately, earthquake experience has proved that this form of construction is vulnerable to failure, when not designed and detailed properly, in which the thin concrete slab fractures around the supporting columns and drops downward, leading potentially to a complete progressive collapse of a building as one floor cascades down onto the floors below. Although flat slabs have been in construction for more than a century now, analysis and design of flat slabs are still the active areas of research and there is still no general agreement on the best design procedure. To study the effect of drop panels on the behavior of flat slab during lateral loads, flat plate system is also analyzed. Zone factor and soil conditions- the other two important parameters which influence the behavior of the structure, are also covered. Software ETABS is used for this purpose. In this study relation between the number of stories, zone and soil condition is developed.

Seismic Behaviour of Flat Slabs in Multi-Storey Buildings

Seismic Behaviour of Flat Slabs in Multi-Storey Buildings

Transmission of Railway Induced Vibrations in Buildings

This paper presents the problem of vibration transmission in building structures, which is induced by rail transport, and it discusses the effect of acoustic isolation used at the foundation. The vibration sources generate acoustic waves which are transmitted to the foundation and propagate trough the floors and slabs of the building. The transmission coefficients of the acoustic waves induced by metro trains and trams were determined in the building foundation and slabs. It was shown that mechanical resonances have a significant influence on the vibrations of the slabs. The characteristics of vibration propagation through vibration-insulated floors were found. Using the data obtained in this study, vibration effects in buildings located near vibration sources can be estimated, vibration protection measures can be developed.