Slab Buildings Research Articles

A Review on Progressive Collapse of Reinforced Concrete Flat Slab Structures

The reinforced concrete flat slab structures are highly susceptible to punching shear failure. This occurs due to the transferring of shear force and due to the bending moment between the slab and the column. The initial local failure and the following redistribution of load can lead to punching failure of the slab in the adjacent column locations. This issue can collapse an entire building or a huge portion of a structure. Hence, an alternate load path method is necessary for preventing the catastrophic failure of the buildings. Compared to the moment frame buildings, flat slab buildings are more prone to the progressive collapse. Thus, the designing of flat plate structures demands more attention and study. Due to higher construction costs and limitations in the test set up, the researchers have adopted scale down structures for the experimental studies. The progressive collapse behavior of the prototype structures is usually analyzed using both analytical and numerical simulations. This paper discusses the existing researchers on the analytical study, experimental study, and numerical simulations of flat slab structures along with various load resisting mechanisms to mitigate progressive collapse. Further, various strengthening techniques available in the literature for the flat slab structures have been discussed. A parametric study and comparison of different strengthening techniques are also performed in this work.

Effect of using column capital on the punching shear strength of flat slab-edge column connection under eccentric loading

The influence of column capital on punching resistance at the edge column is virtually not fully studied. This is a significant omission, as column capital under eccentric loading can arise in flat slab buildings under lateral loading from wind and earthquakes. This paper deals with the effect of using reinforced concrete column capital on the punching shear strength of the flat slab-edge column connection under eccentric loading. The study involves testing experimentally six reinforced concrete flat slab-edge column models with dimensions (1000×1600×100 mm) with two different dimensions of column capital (300×400 mm, and 500×800 mm) in addition to reference model without columns capital (column dimension 200×200mm). Two specimens as a control without columns capital where the first specimen under axial load according to column section but another under eccentric loading with eccentricity (e=half width of column). The effect of size of the column capital and were studied experimentally. We observed an increase in punching resistance by (17.02% and 27.66%) respectively over that of the reference specimen under axial load, and about (18.18% and 25%) respectively over that of the reference specimen under eccentric loading.

Experimental Study on Two-Hour Fire Resistance Performance of Slabs in Modular Buildings under Loads

For a floor of a building with no less than four stories and no more than twelve stories, the two-hour fire resistance performance should be satisfied. In the case of slabs with steel studs, no two-hour fire resistance performance has been proposed in Korea. In this study, the two-hour fire resistance performance of slabs with steel studs performing as structural elements of modular buildings was evaluated. These specimens were redesigned based on the typical slab used in Europe and North America by modifying the 45 mm fire-resistant board to achieve two-hour fire resistance. The experimental results showed that the FR-001 specimens with 140 mm mineral wool applied to the lower slab and the FR-002 specimens containing 100 mm lower-slab glass wool and 150 mm upper-slab mineral wool did not satisfy the two-hour fire resistance performance, owing to the rapid deformation of the specimens after 75 and 110 min, respectively. However, the FR-003 specimens containing 100 mm glass wool, 150 mm mineral wool in the upper slab, and concrete in the slab satisfied the two-hour fire resistance performance requirement.

Https://www.acapublishing.com/dosyalar/baski/CEBACOM_2021_196.pdf

The compressive strength of concrete could be evaluated during and after construction because of a weakness in a reinforced concrete structural member appeared. Quality control of concrete in existing and new constructions can be evaluated by several methods. If the compressive strength did not comply with the design requirements, core samples from the low strength structural members are usually taken to evaluate the structural capability. In the construction sites, compressive strengths of columns and shear walls are the most important. Also, the preparing of quite simple reports for the quality control analyses of a construction is common especially in slab and beam analyses. Hence, in this paper, a new sightseeing assessment is recommended to this analysis. In this study, in-situ non-destructive and destructive investigations in newly constructed building slabs and beams were performed because of the weakness of concrete. With this scope, non-destructive and core sampling examinations were performed on slabs and beams according to the TS EN 13791. Building was constructed by using ready-mixed concrete with CEM I 42.5R and CEM II/B-S 42.5N type cement. As a result of this study, it is thought that the TS EN 13791 contains limited information for the evaluation of newly constructed building for concrete because of its varied ingredients. Compressive strength of concrete produced with granulated blast furnace slag like pozzolanic materials instead of cement needs more time to reach required strength if it is not designed for early strength.

Screens surrounding openings in floor slabs of public buildings

Introduction. Screens often surround openings in the floor slabs of atrium buildings to prevent the spread of fire hazards to higher floors and to improve the efficiency of smoke ventilation systems. In this article, the co-authors assess the expediency of installing screens around openings in the floor slabs and identify the best screen height values. In this article, the co-authors perform a quantitative analysis of the ability of screens to prevent the propagation of hazardous fire factors, to identify general regularities typical for a multi-level space, and to develop recommendations for the installation of screens inside public buildings. The co-authors suggest that screen height should be a solution to the following tradeoff problem: the use of screens reduces acceptable evacuation time for the floor that has screens installed and rises the evacuation time for higher floors.Rational screen height selection algorithm. The co-authors propose the following algorithm for the two-stage selection of the rational screen height. At the first stage, the evacuation problem is resolved. As a result, evacuation completion time is determined for emergency exits. Further, acceptable evacuation time and the time needed to block emergency floor exits are identified for a particular type of a fire alarm system.At the second stage, the dynamics of hazardous fire factors in building rooms is assessed for various screen heights. As a result, the rational height of screens is established for the evacuation time to remain positive.Conclusions. Screen height values cannot be determined in advance. Each case requires an individual approach that entails the resolution of evacuation problems and the tracking of the dynamics of hazardous fire factors in buildings that have multi-height spaces. These ideas are in line with the concept of flexible regulation of fire protection systems designated for construction facilities.

Seismic response of reinforced concrete wall buildings with nonlinear coupling slabs

Reinforced concrete (RC) structural walls are widely used in high-rise buildings as the lateral force resisting system because of their inherent economy, stiffness, and strength. The floor plan configuration of residential buildings in Chile consists mainly in assemblies of large longitudinal walls and shorter transverse walls coupled by floor slabs. The coupling effect of the slabs has affected the response and the observed damage of RC buildings in recent earthquakes. The main objective of this article is to assess the seismic response of a RC structural wall building with coupling slabs. Additionally, the effect of the amount of slab reinforcement on the seismic response of the building is evaluated. To achieve the proposed objectives, seven three-dimensional models of a case study building were developed using shell-type elements in DIANA. The first four models aim to evaluate the effect of using elastic slabs with reduced (i.e. cracked) moment of inertia. The last three models consider nonlinear behavior for both walls and slabs. The response of the building was estimated using nonlinear static analysis and the seismic performance is evaluated from the results of roof displacement and shear, moment, and axial forces of the walls. Additionally, the seismic performance is evaluated from the strain demands of concrete and steel in both walls and slabs. Relevant conclusions about the building behavior, slab demands, and failure mode are drawn.

Improved progressive collapse resistance of irregular reinforced concrete flat slab buildings under different corner column failures

As the flat slab building with irregular geometric configurations is commonly designed to advance urban development and for architectural demands, its behaviour to resist progressive collapse must be examined. The building's progressive collapse occurs when one or more vertical structural load-bearing elements such as columns are removed due to an extreme load caused either by natural or manmade hazards. The present analytical research examines the failure criteria and improvement in the progressive collapse resistance of five and ten-storey irregular R.C flat slab building by incorporating perimeter beams along with strengthened perimeter columns in the building. The progressive collapse study is conducted by removing different corner columns on the ground floor as per the GSA guidelines (2003) and assessing the spread of damage. Static analysis is performed using the structural analysis program ETABS 2016. For each case, the results have been taken in terms of demand capacity ratio (DCR) at critical sections and, chord rotation and joint displacement at locations of removal of columns. The results showed that the presence of strengthened columns provides sufficient stiffness and the perimeter beam provides load paths for the building's gravity loads, thus making it resistive to progressive collapse under column failure.

Case study on strengthening methods for progressive collapse resistance of RC flat slab buildings

The progressive collapse of buildings may result in major financial losses and fatalities, so reducing the chances of such occurrences is of paramount importance. Due to the absence of beams for redistribution of gravity loads that were initially resisted by the missing column, flat slab buildings are more prone to progressive collapse than moment frame buildings. Thus, flat slab buildings should necessarily be assessed for progressive collapse and strengthened accordingly in order to avoid the likelihood of progressive collapse. This study evaluates the efficacy of three different strengthening methods for reducing the potential for progressive collapse of a validated 3-bay by 3-bay 4-storey flat slab building simulation model, subject to alternate, simultaneous and sequential removal of columns in the first storey. Corner, edge and interior columns of each building model are statically and instantaneously removed and the static and dynamic response of the building is compared for different removal sequences. The three strengthening strategies investigated are the addition of perimeter beams, the addition of shear walls and the addition of both perimeter beams and shear walls. The results are evaluated in terms of the vertical displacements at the top of the removed columns and the DCR of the sectional forces of critical adjacent columns, for which the acceptance criteria provided for DCR by the GSA is used to assess the vulnerability of the studied building to progressive collapse. The results show that perimeter beam, shear wall and combination of both perimeter beam and shear wall improve the progressive collapse resistance of the studied building by reducing DCR of critical columns by up to 67.0% and reducing the vertical displacements at top of the removed column by up to 81.0% depending on the different column removal cases.

Evaluation of the deformability of balcony plates of monolithic residential buildings

The calculation and design solutions of balconies of modern monolithic residential buildings are considered. Such balconies are part of a monolithic floor slab, which relies on internal supporting vertical structures. They have a larger extension, and when using brick walls to fence balconies -and more loading. The experience of operating monolithic residential buildings with balconies with their removal of 1.2 … 2.5 m and a brick balcony railing with a two-chamber stained-glass window showed the possibility of increased deformations of the balcony cantilever sections of the floor slabs of such buildings. If for such balconies the maximum deflection provided by the project for the balcony cantilever sections of the slab will be close to the maximum permissible values, then deviations from the design that were allowed during the construction of the building (reducing the class of concrete versus design, changing the location of the working reinforcement of the slab during concreting) can lead to increased deflection of balconies. Computer modeling allows you to accurately reflect the real work of the structure, and performing calculations in a nonlinear setting -to obtain an adequate deflection of the console balcony slab. The main approaches to modeling the design scheme of a flat floor slab with a balcony part are considered for determining plate deformations taking into account non-linear deformation of materials, as well as taking into account plate reinforcement.

Prospects for the development of stay in plase formwork for low-rise buildings in cramped conditions

The article considers existing and promising systems for the construction of slabs in low-rise buildings using stay in place (SIP) formwork. The main conditions for using these formwork systems are described and the disadvantages of existing structures are highlighted. Using the example of previously patented inventions, various trends in the development of formwork systems are revealed. The article deals with precast concrete structures of fixed formwork, modular structures of fixed formwork, various types of connections. Variants of fixed formwork with different types of installation and delivery of concrete mix, made of different materials and shapes are considered. The main individual features of each type of invention are highlighted, on the basis of which assumptions are made for the development of these systems. Based on the results of the analysis, the article offers technical requirements and a brief description of a promising formwork system for the construction of floors of low-rise buildings in cramped conditions.

Cost Evaluation of Post-tensioned Slabs in Multi-storey Buildings Considering Seismic Effect

Currently, many owners and consultants prefer to use post-tensioned PT slab systems in multi-storey buildings due to their considerable savings in materials, labor, and time. On the other hand, many contractors still use the traditional RC flat slab systems due to their simple construction process. This research focuses on the comparison between the two systems taking into consideration: cost, time, and structural behavior. Detailed cost and time analysis is performed for each system considering all construction resources. The analysis and design of the buildings are conducted using many structural and project management computer programs. These include ETABS, SAFE, RAM, REVIT, and Primavera. The results indicated that, PT systems provide significant savings for spans larger than 6 m. The structural analysis of both systems also showed that PT slabs are more effective in resisting seismic straining actions.

Improving the manufacturability of floor slabs by pre-installing elements that partially replace reinforced concrete and formwork

The article discusses well-known and perspective constructive and technological systems for the installation of monolithic and precast-monolithic floor slabs of civil and industrial buildings. It shows examples and expediency of using all kinds of inserts made of plastic and other light materials and products for replacing a part of heavy monolithic reinforced concrete. An original resource-saving method for the installation of precast-monolithic floor slabs with a simultaneous increase in the degree of their construction readiness is proposed. This effect is achieved by reducing their own weight and the use of permanent formwork. Reduction in own weight of the precast-monolithic floor slab is ensured by the use of volumetric lightweight trapezoidal or rectangular inserts, preferably made of expanded polystyrene, during its installation. The use of permanent formwork will eliminate the need for the subsequent performance of labor-intensive finishing and insulation works. To confirm the effectiveness of using the proposed method of precast-monolithic floor slab installation, the operation of two floor slabs was modeled in the LIRA SAPR computing complex - the proposed reinforced concrete innovative slab and a solid reinforced concrete slab. Having analyzed the calculated forces, deformations and the corresponding consumption of reinforcement and concrete, comparative indicators were obtained for the proposed innovative slab and for a typical solid floor slab. As a result, significant savings in material and cost have been proven.

Strength of cast-in-place slabs for rectangular cross-section columns punching

Flat slabs in contemporary buildings are most commonly supported by rectangular cross-section columns. Research of slabs supported by rectangular cross-section columns for punching is rather narrow. The purpose of this work was the experimental research of slabs punching by rectangular cross-section columns and adjustment of their design method. Reinforced concrete slabs 6 cm in thickness without transverse reinforcement were used as testing specimens. During tests load on the slab was transferred using stamps. Side ratios for stamps varied from 1 to 5 in experiments. Strength and strain properties of concrete were determined before slabs testing for punching. Ultimate loads, that resulted in slab punching, were acquired from test results. Formulae for punching load are suggested for rectangular cross-section columns punching based on obtained results. Generalized analysis of experimental research results shows that slab strength for punching is also influenced by short side of rectangular cross-section to slab thickness ratio.

Modeling of foundation slabs of buildings on complex foundations

The paper considers the problem of calculating the strength of foundation slabs under seismic and wind loads. As an example, a numerical model of a hotel building to be built on bulk islands is presented. The calculation of the foundation slab model is performed using the STARK ES software package. The results of the calculation are analyzed and recommendations for strengthening the foundation are given.

Sustainability assessment of methods to prevent progressive collapse of RC flat slab buildings

Previous studies have shown that RC flat slab buildings are highly vulnerable to progressive collapse because no beams could help redistribute the loads previously carried by the lost columns. The necessary strengthening methods should, therefore, be adapted to reduce the occurrence of progressive collapse. In this paper, the progressive collapse behaviour of five-storey R.C flat slab building is assessed by removing columns from the first-storey and dynamic analysis is conducted in compliance with GSA guidelines (2016). The results are analyzed in terms of vertical displacement and chord rotation at the location of removed columns and compared with the allowable limits as specified in DoD guidelines (2009). Different sized perimeter beams are used as strengthening methods to increase the progressive collapse resistance of the studied flat slab building. Since building strengthening uses structural elements that consume natural resources, sustainability criteria should be explicitly included in the strengthening requirements. These performance enhancement methods are then evaluated from structural, cost and environmental aspects and the results are examined. A strengthening alternative is then proposed which not only satisfy the progressive collapse code requirements but also requires less cost and emits less CO2 gas.

Analysis of the causes of defects in ground floor systems of residential buildings

The objective of this research is to analyse the interactions among the causes of defects in ground floor systems of low-rise residential buildings, and on that basis, to identify the most significant causes. The data used in this study was extracted from engineering inspection reports of 250 residential buildings in Melbourne, Australia. Association rule mining technique was used to investigate the relationships among the causes of the defects in the ground floor slab systems and to generate support, confidence and lift values. social network analysis was then carried out using the confidence values and the most significant causes of the ground floor slab defect were identified. Inadequate site drainage and soil drainage, with the out-degrees centrality of 4.84 and 4.56, respectively, were found to be the two main causes of distress in ground floor slabs of the residential buildings. On the other hand, landscaping related problem was found to have the lowest out-degree centrality value (1.60) which implies that the occurrence of poor landscaping on certain residential premises might not be the major cause for defects in the slab. The output of this research can provide useful information regarding the causes of cracks in ground floor slab systems of residential buildings. Understanding the causes of the defects, in turn, can help developers and contractors to take appropriate corrective actions or to develop strategies to reduce the occurrence of defects in newly constructed houses.

Probabilistic Analysis of a Hospital Building Slab Foundation

This paper deals with the design of a five-storey hospital building, in which we focus on the deterministic and probabilistic analysis of its slab foundation. The hospital building bearing structure was modeled as a reinforced concrete skeleton. The Boussinesque model was selected for the subsoil under the plate foundation, which was a model of the elastic half-space, where properties of individual layers of the subsoil were entered according to the geological survey. The geological topology consisted of clay gravel and also included a layer of clay sand. In the stochastic solution, the variance of values was considered for individual mechanical properties of different types of soil. We analyzed the influence of the variance of input values on the resulting deflections, strain, and stress state of the plate foundation. Two variants of the solution were considered on the given numerical example. Probability calculations confirmed the probability of failure, which was allowed for the second limit state.

Designing of the module envelope of a hybrid modular building to meet the passive house standards in Luxembourg

To face the challenges of climate change, new buildings need to be further greener while being able to ensure a minimum comfort to the tenants. Nonetheless, extensibility and flexibility could be added to buildings. In this context, the architect jointly with the team of this research project have designed a hybrid modular construction called “slab building” which is composed of a permanent concrete structure and several removable wooden modules. A module offers 27 m2 of living space but larger housings can be realized by combining two up to four modules. The aim of this paper is to design the walls of the modules to meet the criteria of nZEB. The thicknesses of the studied thermal insulations, namely rock wool, wood wool, polyurethane and aerogel, have been determined in accordance with the passive house requirements in Luxembourg. The embodied energy of the building materials has also been considered in the designing of the modules. Steady state calculations revealed that a wall thickness of 40 cm, comprising 31 cm of insulation is sufficient but according to the LCA outcomes, there is no environmental benefit in having the modules comply with the AAA energy class requirements at reasonable wall thicknesses.

BIM Approach for Sustainable Design of Flat Slab Buildings: A Review

Building Information System (BIM) is a potential digital tool with the Architecture, Engineering, and Construction (AEC) industry that is used to represent the projects in three-dimensional models. It provides a central unified database that can be queried, filtered, manipulated and/or changed for analysis, thus providing a collaborative tool for all the stakeholders in the project throughout the life cycle of the project. Positive returns on investments are acceded by the contractors adopting BIM while it helps detect clashes of intersecting building components early in the design stages. BIM is proving of utmost importance while focusing on the development of sustainable buildings and to develop the cities smarter and intelligent. Environmental concerns warrant more and more sustainable buildings to be designed and implemented. BIM has an intrinsic role to play in building design to address the growing environmental concerns such as to reduce carbon footprint, to cut construction and demolition waste, selection of green material, quality of the indoor environment, water conservation, and health factors of inhabitants, etc. In the current practices, the simulation and environmental performance analysis follow the design phase of the project, thus not getting incorporated into the decision making at this stage. Some models of flat slab buildings are generated by some studies where required parameters were assigned to different elements of the building. This paper makes an effort to review the literature regarding the BIM approach to sustainable construction of buildings considering the flat slab models.

Summertime Overheating Risk Assessment of a Flexible Plug-In Modular Unit in Luxembourg

Modular buildings offer faster construction process, provide better construction quality, allow reducing construction waste and are potentially flexible. Frames of modular units can be made of metal, timber, concrete or mixed materials but lightweight structures do not always allow erecting high-rise buildings and generally present a higher risk of overheating and/or overcooling. To reconcile these pros and cons, a typology of modular building called Slab was designed by a group of architects. The building is composed on the one hand of a permanent concrete structure named shelf-structure and on the other hand of several flexible removable timber modular units, also known as modules. The shelf-structure will host the common utility rooms and will serve as docking infrastructure for the housing modules. To provide high flexibility, the Slab building was designed to adapt to any orientation and location in Luxembourg. An energy concept and a HVAC systems design has been developed for the Slab building. Furthermore, a two-fold sustainability analysis was carried out. The first part of the analysis regards the determination of the minimum required wall thicknesses of the modules in accordance with Luxembourgish regulatory requirements, although the current regulation does not yet consider the Slab building typology. The second part, which is the subject of this paper, is thermal comfort assessment, more precisely, summertime overheating risk assessment of these modules, in compliance with Luxembourgish standard. In this regard, dynamic thermal simulations have been realized on two module variants; the first fulfills the passive house requirements, and the second—the current requirements for building permit application, which in principle corresponds to low energy house requirements. Simulations showed that with adequate solar shading and reinforced natural ventilation by window opening, overheating risk could be avoided for the normal residential use scenario for both module variants.