scholarly journals Impact of the fire on the bearing capacity of the ordinary concrete used in reinforced concrete structures in Burundi. History and architecture

Vestnik MGSU ◽  
2021 ◽  
pp. 1567-1572
Author(s):  
Emmanuel Mikerego ◽  
Donatien Nduwimana
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Negative Impact ◽  
Heating Temperature ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Ordinary Concrete ◽  
The Impact

Introduction. This paper presents the results of an assessment of the impact of fire on the bearing capacity of the ordinary concrete, to be taken into account in the rehabilitation of fire-damaged reinforced concrete structures in Burundi. Materials and methods. Experimental samples of the ordinary concrete made respectively of coarse river aggregates and crushed coarse quarry aggregates were prepared and subjected to different heating temperatures (250, 350, 450, 600 and 900 °C) simulating the fire. After natural cooling, experimental samples were subjected to compression test; and diagrams showing the loss of the load-bearing capacity of the ordinary concrete used in reinforced concrete structures in Burundi were drawn. Results. Negative impact of the fire on the load-bearing capacity of the ordinary concrete occurs above of 350 °C of heating temperature. Concrete made of crushed coarse quarry aggregates loses 50 and 78 % of its bearing capacity at around 525 and 900 °C of heating temperature, respectively. Similarly, concrete made of coarse river aggregates loses 50 and 70 % of its load-bearing capacity respectively at 600 and 900 °C of heating temperature. An evaluation curve of the after-fire bea­ring capacity of the concrete used in reinforced concrete structures in Burundi is established. Conclusions. The negative impact of the fire on the load-bearing capacity of the ordinary concrete occurs above of 350 °C of heating temperature. Concretes made of crushed coarse quarry aggregates and concrete made of coarse river aggregates lose 50 % of its bearing capacity at around 525 and 600 °C of heating temperature respectively. Knowing the heating temperature that the fire-damaged reinforced concrete structure has undergone is indispensable in deciding on its demolition or rehabilitation.

scholarly journals DETERMINATION OF THE CRITERIA OF DEFORMATION IN A SPECIAL LIMITING STATE

2021 ◽  
Vol 17 (1) ◽  
pp. 108-116
Author(s):  
Nikolay Trekin ◽  
Emil Kodysh ◽  
Sergey Shmakov ◽  
Tere Terekhov ◽  
Konstantin Kudyakov
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Rational Design ◽  
Progressive Collapse ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Load Bearing Capacity ◽  
Limiting State ◽  
Load Bearing

Constructive measures taken to ensure the integrity of the entire building or its part in emergency situations with design based on the existing criteria of the limiting state method leads to a significantincrease of the construction cost. One of the ways to reduce additional costs of construction while the protection design against progressive collapse is the possible use of additional reserves of deformability of load-bearing elements. It leads to redistribution of loads and the use of non-destroyed structures. It also leads to possible changes of limiting states in non-standard emergency design situations, taking into account the peculiarities of the operation of structures in a special limiting state at a stage close to destruction. In the GOST 27751-2014 «Reliability for constructions and foundations. General principles» calculated states of the firstand second groups of limiting states are given, and for a special limiting state only the area of its permissible application is indicated. The work of reinforced concrete structures at the stage close to the depletion of the load-bearing capacity is little reflectedin the scientificand technical literature; the work of reinforced concrete structures at the unloading stage due to the redistribution of forces is represented in single publications. The article presents theoretical studies based on experimental data on the deformation of bent reinforced concrete beam elements at a stage close to the maximum load-bearing capacity and at the stage of unloading up to the transformation of a structural element into a mechanism. The influenceof the longitudinal reinforcement, the class of reinforcement, prestressing and the concrete strength on the deformation of reinforced concrete bending elements is considered in the article. The research of the behavior of structural elements continuation at this stage is relevant and contributes to the development of economical and rational design solutions for protection against progressive collapse and in the design of earthquake-resistant buildings.

Technology Of Elimination Damage And Deformation In Construction Structures

2021 ◽  
Vol 03 (05) ◽  
pp. 224-228
Author(s):  
Mirzaakhmedova Ugiloy Abdukhalimjohnovna ◽  
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Maintenance Work ◽  
Formation Of Cracks

The study found that the necessary maintenance work should be carried out in the first 7 days after the completion of concreting in reinforced concrete structures, which significantly increases the penetration in concrete, the formation of cracks, decreased strength, load bearing capacity of structures.

scholarly journals Impact of impurities of local construction materials on the bearing capacity of the concrete used in structures in Burundi

Vestnik MGSU ◽  
2021 ◽  
pp. 1357-1362
Author(s):  
Emmanuel Mikerego ◽  
Nestor Niyonzima ◽  
Jean Claude Ntirampeba
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Concrete Structures ◽  
Construction Materials ◽  
Reinforced Concrete Structures ◽  
Ordinary Concrete ◽  
Average Decrease ◽  
Local Construction ◽  
The Impact ◽  
Mixing Water

Introduction. The article is about an assessment of the impact of impurities contained in the local construction materials on the mechanical characteristics of the concrete used in reinforced concrete structures in Burundi. Materials and methods. The methodology of the study consisted in varying the quantity of impurities for the manufactu­ring of the concrete experimental cubic samples. The grain sizes of the studied ordinary concrete were in the favourable zones according to the recommended granulometry for standard concretes. Simulation of impurities was made by adding in the mixing water solid particles taken from a local rock called “red earth”. The particles were composed by (24 %) of clays, (38 %) of silts and (38 %) of sands. As for the used cement in this study, it was the type CEM I (32.5). The quantities of impurities were expressed in grams per litre of mixing water (g/l) and were varying from (0 g/l) to (100 g/l) with a step of (20 g/l). The prepared experimental concrete samples were stored in the laboratory of materials at the University of Burundi and were subjected to compression testing under hydraulic press after 28 days. Results. The impact of impurities consisting of (24 %) of clays, (38 %) of silts and (38 %) of sands is identified. Each increase of (20 g) of impurities in a litre of mixing water induces an average decrease of (4 %) on the compressive strength and the Young’s modulus for an ordinary concrete. Conclusions. The impact of impurities contained in the local construction materials used in the manufacturing of the concrete for reinforced concrete structures in Burundi is studied. Each increase of (20 g) of impurities in a litre of mixing water induces an average decrease of (4 %) on the compressive strength and the Young’s modulus of an ordinary concrete. For Burundi, a curve for the approximation of the bearing capacity of the concrete used in reinforced concrete structures according to the quantity of impurities contained in the local construction materials was established. Hence, it is advisable to start by the specification of the quantity of impurities contained in the construction materials before making the concrete for reinforced concrete structures in order to predict the mechanical performances of the concrete used in reinforced concrete structures.

scholarly journals Lubrication of Rough Short Bearing on Shliomis Model by Ferrofluid Considering Viscosity Variation Effect

2019 ◽  
Vol 4 (4) ◽  
pp. 982-997
Author(s):  
Mohmmadraiyan M. Munshi ◽  
A. R. Patel ◽  
G. M. Deheri
Keyword(s):  
Bearing Capacity ◽  
Reynolds Equation ◽  
Negative Impact ◽  
Random Variable ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Realistic Situation ◽  
Transverse Roughness ◽  
The Impact ◽  
Positive Effect

This study aims to explore the impact caused by change in viscosity and the roughness of a bearing surface on a ferrofluid lubrication of Shliomis model for short bearing. Based on this model and the Tipei (1962) model, a new resultant Reynolds equation has been found that shows thermal variation. The Christensen and Tonder models have been taken to derive the transverse roughness stochastically. An assumed mean has been taken for the probability density function with a non-zero value. This value is assigned to a random variable that measures the bearing’s surface roughness. This creates a more realistic situation that can have a lot of field applications. The model defines the problem mathematically while defining boundary conditions. It also uses the Simpson’s method to derive a conclusion. The results thus obtained are discussed in terms of pressure distribution and load bearing capacity. The graphical results obtained suggest that in the presence of magnetization, there is a significant enhance in the load bearing capacity. This positive effect can easily nullify the negative impact of the thermal effect. The short bearing approximation shown here is an example of the probable applications. Ferrofluids in the presence of magnetic fields significantly enhance the performance of a short bearing.

scholarly journals Influence of Different Fiber Dosages on the Behaviour of Façade Anchors in High-Performance Concrete

CivilEng ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 556-579
Author(s):  
Szymon Grzesiak ◽  
Matthias Pahn ◽  
Milan Schultz-Cornelius ◽  
Nora Susanne Bies
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
High Performance ◽  
High Performance Concrete ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Anchor Systems ◽  
The Impact

The behaviour of façade anchors in high performance fiber reinforced concrete (HPFRC) has not been investigated in sufficient detail in recent years. The regulations in the European Technical Approvals also do not fully describe the load-bearing capacity of anchor systems. Due to the increase in the production of HPFRC elements, it is necessary to analyse the impact of added fibers in the concrete composition on the behaviour of anchors. In particular, the behaviour of anchors in filigree façade elements, which is one of the main application areas of the programme of polypropylene (PP) fiber-reinforced concrete, is therefore analysed. With a sufficient content of PP fibers surrounding the steel anchors oriented in an optimal direction, the fibers may enhance both the load-bearing capacity of anchors and the ductility of concrete. However, unfavourable effects on the installation process or even on the load-bearing capacity may also occur due to unfavourable fiber orientation. Therefore, tensile and punching tests were carried out in uncracked concrete with different types of anchor systems containing a tension anchor and an adjustable spacer bolt. The PP fiber content of the concrete component varied during the tests.

Experimental and numerical investigation on the vertical bearing behavior of discrete connected new-type precast reinforced concrete floor system

2020 ◽  
Vol 23 (11) ◽  
pp. 2276-2291
Author(s):  
Rui Pang ◽  
Yibo Zhang ◽  
Longji Dang ◽  
Lanbo Zhang ◽  
Shuting Liang
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Cover Plate ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Concrete Floor ◽  
New Type ◽  
Vertical Bearing ◽  
Floor System ◽  
Bearing Behavior

This article proposes a new type of discrete connected precast reinforced concrete diaphragm floor system that consists of precast flat slabs and slab joint connectors. An experimental investigation of discrete connected new-type precast reinforced concrete diaphragm under a vertical distributed static load was conducted, and the effect of slab joint connectors on the load-bearing capacity was evaluated. Then, a finite element analysis of discrete connected new-type precast reinforced concrete diaphragm, precast reinforced concrete floors without slab connectors, and cast-in-situ reinforced concrete floor were performed to understand their working mechanism and determine the differences in load-bearing behavior. The results indicate that the load-bearing capacity and stiffness of discrete connected new-type precast reinforced concrete diaphragm increase considerably as the hairpin and cover plate hybrid slab joint connectors can efficiently connect adjacent precast slabs and enable them to work together under a vertical load by transmitting the shear and moment forces in the orthogonal slab laying direction. The deflection of discrete connected new-type precast reinforced concrete diaphragm in orthogonal slab laying direction is mainly caused by the opening deformation of the slab joint and the rotational deformation of the precast slabs. This flexural deformation feature can provide reference for establishing the bending stiffness analytical model of discrete connected new-type precast reinforced concrete diaphragm in orthogonal slab laying direction, which is vitally important for foundation of the vertical bearing capacity and deformation calculation method. The deflection and crack distribution patterns infer that the discrete connected new-type precast reinforced concrete diaphragm processes the deformation characteristic of two-way slab floor, which can provide a basis for the theoretical analysis of discrete connected new-type precast reinforced concrete diaphragm.

scholarly journals Load Bearing Capacity Calculation of the System “Reinforced Concrete Beam – Deformable Base” under Torsion with Bending

2019 ◽  
Vol 97 ◽  
pp. 04059 ◽  
Author(s):  
Alexey Dem’yanov ◽  
Vladymir Kolchunov ◽  
Igor Iakovenko ◽  
Anastasiya Kozarez
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Cross Sections ◽  
Concrete Beam ◽  
Equations Of State ◽  
Reinforced Concrete Beam ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Deformable Base ◽  
The Relationship

It is presented the formulation and solution of the load bearing capacity of statically indeterminable systems “reinforced concrete beam – deformable base” by spatial cross-sections under force and deformation effects. The solution of problem is currently practically absent in general form. It has been established the relationship between stresses and strains of compressed concrete and tensile reinforcement in the form of diagrams. The properties of the base model connections are described based on a variable rigidity coefficient. It is constructed a system of n equations in the form of the initial parameters method with using the modules of the force (strain) action vector. The equations of state are the dependences that establish the relationship between displacements which are acting on the beam with load. Constants of integration are determined by recurrent formulas. It makes possible to obtain the method of initial parameters in the expanded form and, consequently, the method of displacements for calculating statically indefinable systems. The values of the effort obtained could be used to determine the curvature and rigidity of the sections in this way. It is necessary not to set the vector modulusP, the deformation is set in any section (the module is considered as an unknown) during the problem is solving. This allows us to obtain an unambiguous solution even in the case when the dependence M–χ has a downward section, i.e one value of moment can correspond to two values of curvature.

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