Study and Analysis of Post Tension Flat Slab for Different Tendon Layouts

The main purpose of this paper is to study of post tension flat slab and study of their various tendon profiles. In this paper the analysis of various different tendon layouts with different sizes is done. In this paper different sizes of slab is considered and analysis is done with the help of SAFE software. With help of analysis we know the deflection of PT slab for different layouts. In this paper tendon layouts are as banded tendons in main direction, banded tendons in both directions, distributed tendons in both directions, banded and distributed tendons in both directions are considered with different sizes. This paper also includes PT strip stress diagram and layouts.

BEHAVIOR OF NON-BRITTLE ROCKS UNDER BENDING CONDITION

Experimental results of determining the bearing capacity of a marble beam are presented. A significant influence of plastic properties on the strength characteristics of the beam is noted. On the basis of a model of strength-different materials, an elastoplastic profile of stresses in a beam is constructed. It is proposed to use elastic stress distribution in the compression zone for rocks and similar heterogeneous materials with different compressive and tensile strengths, and elastic-plastic distribution in the tensile zone. Such a stress diagram makes it possible to explain the high values of bending strength in comparison with the tensile strength of the presented materials.

THE CHANGE IN THE BEARING CAPACITY IS CORROSIVE-DAMAGED FLOOR SLABS DEPENDING ON THTHE CHANGE IN THE BEARING CAPACITY IS CORROSIVE-DAMAGED FLOOR SLABS DEPENDING ON THE DEPTH OF DAMAGE TO THE STRETCHED ZONE CONCRETEE DEPTH OF DAMAGE TO THE STRETCHED ZONE CONCRETE

In this work, the influence of the depth of tensile concrete deterioration on the load-bearing strength and deflections of precast reinforced concrete slabs were determined experimentally. The momenta determination and measurement of deflections was carried out by loading the structure stepwise. Analysis of the results of the study indicated the following: as the plates are damaged, with the increase in the height of tensile concrete deterioration, the stress diagram gets gradually filled in the compressive sectional area and its height decreases, which can lead to the destruction of the structure. At the same time, the shear and bending moment diagram of sectional deformation gets curved. As the slab deflections increase, its load-bearing strength decreases.

РАСЧЕТНЫЕ МОДЕЛИ ЖЕЛЕЗОБЕТОННЫХ ПЛИТ ПОКРЫТИЯ АВТОМОБИЛЬНЫХ ДОРОГ

В статье приведены методики расчета нормальных и пространственных сечений при действии изгибающего момента, а также при совместном воздействии изгибающего и крутящего моментов. Неравномерные деформации основания и несимметричность приложения нагрузки приводят к возникновению в сечениях дорожных плит изгибающих и крутящих моментов. В общем случае плиты работают на поперечный изгиб с кручением, в частности на поперечный изгиб. Выполнены расчеты прочности нормальных сечений и расчеты прочности пространственных сечений для плит участка дороги с пороговыми неровностями испытательного полигона РУПП БелАЗ ППН-1, ППН-2, ППН-3, ППН-4, ПДТ-1, а также для железобетонных плит покрытий временных (2ПП30.18-30) и постоянных (1ПП30.18-30) дорог по серии Б3.503.1-1. При расчетах были рассмотрены четыре основные расчетные модели: альтернативная модель (эпюра напряжений в виде прямоугольника), упругопластическая модель (билинейная эпюра напряжений), линейно-параболическая и нелинейная с ниспадающей ветвью. Определение предельных усилий в нормальных и пространственных сечениях производилось с учетом следующих предпосылок: для средних деформаций бетона и арматуры считается справедливым линейный закон распределения по высоте сечений в качестве расчетного принимается сечение со средней высотой сжатой зоны, соответствующей средним деформациям сопротивление расчетного сечения будет исчерпано, если напряжения в растянутой арматуре достигнут предела прочности fyd. Проведен сравнительный анализ данных методик расчета, который показал незначительное расхождение (до 5 ) в несущей способности плит покрытия автомобильных дорог, вычисленной по различным методикам.The article presents methods for calculating normal and spatial cross-sections under the action of a bending moment, as well as under the combined action of bending and torque. Unequal deformations of the base and asymmetric load application lead to the appearance of bending and torque moments in the sections of road slabs. In the general case, the slabs work for transverse bending with torsion, in particular for transverse bending. Strength calculations of normal sections and strength sections of spatial sections for slabs of the road section with threshold irregularities of the BelAZ test site were performed: PPN-1, PPN-2 PPN-3, PPN-4 PDT-1 as well as for reinforced concrete slabs of coverings of temporary (2PP30.18-30) and permanent (1PP30.18-30) roads according to the B3.503.1-1 series. In the calculations, four main calculation models were considered: an alternative model (stress diagram in the form of a rectangle), an elastoplastic model (bilinear stress diagram), linear-parabolic and non-linear with a falling branch. The determination of ultimate forces in normal and spatial sections was carried out taking into account the following prerequisites: for medium deformations of concrete and reinforcement, the linear law of distribution over the height of the sections is considered fair as the calculated section is taken with the average height of the compressed zone corresponding to the average deformation the resistance of the design cross section will be exhausted if the stresses in the tensile reinforcement reach the ultimate strength fyd. A comparative analysis of the data of calculation methods was carried out, which showed a slight discrepancy (up to 5) in the bearing capacity of road paving slabs, calculated by various methods.

The Concrete Diagrams Integral Parameters in the Calculations of Reinforced Concrete Elements by Limiting States

The paper proposes a method for calculating the reinforced concrete elements strength according to the deformation model using the deformation diagrams of concrete and reinforcing steel materials, which eliminates the complicated procedure of numerical integration of stresses in the element section during the transition to generalized internal forces. Integral parameters of diagrams are introduced into the energy model for calculating the strength of reinforced concrete elements along with the deformations and stresses normalized values at the base diagrams’ points. The integral parameters are calculated for the element cross section, the strain at the stress diagram gravity center in the compressed concrete zone and the coordinates of force in the concrete and reinforcement are relative to the neutral axis from the condition of the stress profile shape compliance in the element compressed zone, and the concrete diagram is used in the calculations. The integral parameters calculated dependences for the compressive strength concrete classes. The recommendations on the concrete diagrams integral parameters values rationing and their use in the complex sections and statically indeterminable systems calculations are given.

Forming Limit Stress Diagram Prediction of Pure Titanium Sheet Based on GTN Model

In this paper, the initial values of damage parameters in the Gurson–Tvergaard–Needleman (GTN) model are determined by a microscopic test combined with empirical formulas, and the final accurate values are determined by finite element reverse calibration. The original void volume fraction (f0), the volume fraction of potential nucleated voids (fN), the critical void volume fraction (fc), the void volume fraction at the final failure (fF) of material are assigned as 0.006, 0.001, 0.03, 0.06 according to the simulation results, respectively. The hemispherical punch stretching test of commercially pure titanium (TA1) sheet is simulated by a plastic constitutive formula derived from the GTN model. The stress and strain are obtained at the last loading step before crack. The forming limit diagram (FLD) and the forming limit stress diagram (FLSD) of the TA1 sheet under plastic forming conditions are plotted, which are in good agreement with the FLD obtained by the hemispherical punch stretching test and the FLSD obtained by the conversion between stress and strain during the sheet forming process. The results show that the GTN model determined by the finite element reverse calibration method can be used to predict the forming limit of the TA1 sheet metal.

Energy Model in Calculating the Strength Characteristics of the Reinforced Concrete Components

The article proposes applying energy from law deformation mechanics of the rigid body to deformation method for calculating the strength of reinforced concrete constructions with the use of diagrams illustrating the deformation of concrete and reinforcement. In terms of the energy theory of strength, concrete and rebar accumulate potential energy in the section of the construction component under stress; based on the contours of the diagram used in calculation it is possible to distinguish a stress diagram for concrete of the compressed zone. The value of the strains is equivalent to the force used for the deformation of the concrete specimen under stress (prism-or cylinder-shaped); the force is equal to the area used in the calculation of the normable diagram. The resolving balance equations are deduced with the use of the flat section hypothesis. The conditions of the stress balance in the section of the construction component are tested with the method of the successive approximation. The variable parameter of approximation is the construction component bending. General deformations (deflections) of the construction components are significantly higher than their limit stress values permitted for safe operation.

Comparison between resistant load contours generated considering the parabolic-rectangular (DPR) and the rectangular (DR) stress-strain diagrams for rectangular sections under combined axial compression and biaxial bending

The aim of this study is to compare the load contour diagrams generated for rectangular RC cross-sections under combined axial compression and biaxial bending obtained by the two forms of analysis allowed by NBR 6118:2014 [1]: the first using the parabolic-rectangular stress-strain diagram (DPR) and the second using the rectangular (constant stress) diagram (DR). In order to compare the load contours generated, a reference cross-section was adopted for which the concrete strength class (from C20 to C90) and the deformation domains (4, 4a and 5) were varied for the study. It was studied whether the use of the different diagrams (DPR or DR) would provide greater (or smaller) resistant efforts for the same section. The results show that the use of the DR is only acceptable when the section is working up to the 4th domain. Above this domain, it was observed that the use of this diagram shows resistant efforts inferior to those calculated by the DPR. In addition, it was found that, for concretes with resistance class above C50, in oblique loading directions, the use of the DR presents higher resistant efforts than those calculated using the DPR.