Vol 17, No 4 (2021)

The theoretical prerequisites for justifying the development of two rapid assessment programs for road bridges to quickly determine the possibility of passing heavy vehicles on road bridge structures of a split and non-split system, made of wood, metal, steel-reinforced concrete, reinforced concrete with stressed and non-stressed reinforcement, according to the measured angle of rotation of their support sections, taking into account their actual operational condition, are presented. The programs implemented an experimental and analytical method for assessing the technical condition of road bridges for reliability. The features, conditions of application, positive and negative aspects of each version of the program are revealed. The creation of two variants of programs is due to, on the one hand, the need to ensure the safety of the driver of the vehicle and the bridge structure, and on the other hand, the need to guarantee the possibility of safe passage of heavy vehicles, both under the conditions of the load-bearing capacity of superstructures and the load-bearing capacity of road bridge supports, taking into account their actual operational condition. Both developed calculation programs were implemented by using a personal computer and certificates of state registration of computer programs were obtained. The developed programs will be used as part of the modernized IR-AM measuring complex.

Relevance. In the construction of buildings and structures, driven piles with a square cross section are most widely used. To install them in the working position, the percussion method is used. However, in cramped conditions, shock loads can lead to dangerous conditions and destruction of structures of nearby buildings. In such a situation, it is necessary to use rammed piles, since technological solutions for their construction are not associated with shock effects on the soil. One such solution is the new rammed cone-shaped pile design, which is installed without excavation. The aim of the study is to analyze the influence of the geometric parameters of the pile on its bearing capacity under the action of external loads, in particular, the angle of its taper. Methods. The results of a numerical analysis of the stress-strain state of a pile operating in a soil massif were obtained by the finite element method. Results. In the computational study, a comparative analysis of the state of piles of different lengths and geometries under the action of external loads was carried out. The influence of the angle of inclination of the lateral surface of the pile on its bearing capacity is considered. Rationalization of the pile design was carried out taking into account the total costs of building materials. Variants of geometric and design solutions for piles with a length L from 1 to 10 m are proposed. In subsequent articles, it is proposed to consider the effect on the bearing capacity of the pile of the geometric parameters of the crushed stone shell and the lower crushed stone spherical expansion, as well as to carry out a comparative analysis of the numerical results with experimental data obtained in laboratory and field conditions.

The building structure with infill wall shows higher global stiffness along with the uncertain behaviour during 2015 Gorkha earthquake. It significantly increased the collapse rate of structures during earthquakes. The response of buildings with different infills during seismic excitations is not completely accounted by current seismic codes in the region. On the other hand, due to the different geological region, availability of infill materials for reinforced concrete building also differs on region to region. In most of the situations the burnt clay brick, concrete blocks and stone block are used as infill materials during building construction. In this scenario, this study explores the importance of selection of right infill material for better seismic performance during earthquakes. For this, building constructed at Pokhara Metropolitan City is considered for case study. The structural model is prepared with and without considering infills. The solid, hollow concrete block and clay brick masonry are taken as infill material during analysis. The structural behaviour during earthquakes is studied with non-linear static pushover. The result shows that the hollow concrete block masonry infill (INHB) shows better structural performance compared to other infill types.

Relevance. This work is the first in a series of publications on the selection of a suitable analytical surface for implementation as a self-supporting structure for a thin shell footbridge. The study on the influence of concrete strength, live load position and support types on the stress-strain state of a hyperbolic paraboloid (hypar) shell is presented. Objective - to define the initial design parameters such as the appropriate concrete strength and the support type that generates the best structural behaviour to perform the subsequent structural design of a thin shell footbridge. Methods. The static finite element analysis was performed for 4 compressive strengths of concrete (28, 40, 80, 120 MPa) which correspond normal, high and ultra-high resistance concrete, 5 different live load arrangements and 3 different support conditions. Results. The shell model with pinned (two-hinged) supports shows the same vertical displacements as the model with fixed supports (hingeless). For the studied shell thickness, in terms of stress behaviour, the model with pinned ends is more efficient. The combination of two-hinged supports with 80 MPa concrete strength shows a better structural performance.

If a circle rolls around another motionless circle then a point bind with the rolling circle forms a curve. It is called epicycloid, if a circle is rolling outside the motionless circle; it is called hypocycloid if the circle is rolling inside the motionless circle. The point bind to the rolling circle forms a space curve if the rolling circle has the constant incline to the plane of the motionless circle. The cycloid curve is formed when the circle is rolling along a straight line. The geometry of the curves formed by the point bind to the circle rolling along some base curve is investigated at this study. The geometry of the surfaces formed when the circle there is rolling along some curve and rotates around the tangent to the curve is considered as well. Since when the circle rotates in the normal plane of the base curve, a point rigidly connected to the rotating circle arises the circle, then an epihypocycloidal cyclic surface is formed. The vector equations of the epihypocycloid curve and epihypocycloid cycle surfaces with any base curve are established. The figures of the epihypocycloids with base curves of ellipse and sinus are got on the base of the equations obtained. These figures demonstrate the opportunities of form finding of the surfaces arised by the cycle rolling along different base curves. Unlike epihypocycloidal curves and surfaces with a base circle, the shape of epihypocycloidal curves and surfaces with a base curve other than a circle depends on the initial rolling point of the circle on the base curve.

To create aesthetically expressive and functional small architectural forms, it is advisable to use reinforced concrete umbrella type shells in the shape of surfaces that can be specified in an analytical form. Hard landscaping is a suitable field of application for insufficiently studied and tested structures, in contrast to large structures of high importance class. The paper gives an example of a trial variant design of a small garden and park structure in the form of an umbrella type shell, during which different types of umbrella surfaces were analyzed and three variants were selected. Among the studied forms are the following surfaces: a paraboloid of rotation, an umbrella-type surface with a sinusoidal generator, an umbrella-type surface with radial waves based on cubic parabolas (with central flat point). The calculation of stress-strain state of three shells under their own weight was carried out using the finite element method and the peculiarities of working under load of each type of structures were revealed, recommendations are given when designing similar structures.

At the objects of space infrastructure and at nuclear power facilities there are industrial structures, the main task of which is to protect a person, equipment or machinery from emergencies such as, for example, explosions, falling of various objects, fragments. In accordance with the requirements of the Federal Law “On the Protection of the Population and Territories from Natural and Technogenic Emergencies”, when calculating such structures, all types of loads corresponding to their functional purpose must be taken into account. So, for structures located in the area of a possible accident and the fall of space rockets, it is necessary to calculate for the fall of the destroyed parts of the rocket engine. For nuclear power plant facilities, such accidents occur when containers and other heavy objects fall on the ground, affecting underground structures located in the ground, and for civil defense protective structures built into the basement floors of buildings, it is necessary to consider situations in which the overlying floors of a building collapse when exposed to there is an air shock wave on them. Therefore, this problem is relevant, and in this study, a finite-element method for calculating an underground structure in a non-linear dynamic setting has been developed when a large overall object collides with the ground.