Stiffness of Post-Tensioned Girderless Floor With Different Column Grids

The paper considers models of monolithic flat floor slabs with five spans in both directions. The cell sizes are 6×6m, 6×9m, and 6×12m. The calculation method is based on the application of temperature load and rope modeling of rod elements. It is shown that post-stressing should be used for slab side lengths over 7 m, as the installation of pre-stressed reinforcement for shorter lengths is less feasible and causes high economic costs.

Research and development support of the spacer system for the foundation pit constructed by the Moscow method

The article presents the results obtained during the research and development support for the construction of the foundation pit for a projected hotel near the Kursky railway station in Moscow using the truss spacer system fixed in the diaphragm wall. This construction technique, called the “Moscow method” ensures the gradual soil excavation between the pit walls along tiers reinforced by steel spacer trusses to be performed simultaneously with installation of floor slabs. The developed and approved at TsNIISK named after V.A. Kucherenko method for determining stresses (deformations) in elements of metal structures using mechanical strain gauges with a removable indicator was applied to monitor the construction of a unique structure. During the monitoring, emergency situations, requiring extra measures for eliminating the identified unacceptable stresses in the structures, were identified. The provided example demonstrates the research and development support to a prerequisite for the construction of unique buildings and structures.

Analysis of the structure of liners used for the modernisation of brick collectors

Brick sewers were designed as egg-shaped, pear-shaped, bell-shaped, vaulted, and even rectangular (sometimes with granite ceilings and floor slabs). In exceptional cases, circular sections were also made of brick. Efforts were made in order to ensure optimal flow conditions, and also that the cross-section was adapted to the shape of the rock mass pressure line. This is due to the fact that the most advantageous shapes for masonry collectors are shapes in which no tensile stresses will occur in any part of the cross-section under the influence of external loads. Nevertheless, sewage conduits degrade over time. The boundary conditions of their use also change, which affects the magnitude of mechanical and hydraulic loads. Further use of a sewer in such a case requires its renewal, and less frequently, modernization that results from the necessity to change its function. This is usually done by introducing a new conduit into the interior of the renovated or modernized sewer, which in literature is called a liner. The aim of the analysis was to determine the thickness of the liners that strengthen the structures of brick channels with an inverted egg cross-section and with dimensions of 1050 × 700 mm, which are intended for gravitational sewage systems. The analysis included the performance of variant static and strength calculations for the assumption that the conduit after its modernization will be replaced with a conduit operating in the pressure system, which is a very rare requirement. It was assumed that the best solution would be to use a CIPP (Cured In Place Pipe) liner.

Modeling of joint work of steel beam constructions with reinforced concrete ribbed floor slabs

Traditional methods of calculation of beam constructions of floors and coverings of industrial buildings assume their consideration when calculating separately from the frame structures, in particular, reinforced concrete slabs, without taking into account their joint work, which leads to a significant margin of safety. Today in Ukraine there is a significant number of industrial buildings and structures that need strengthening and reconstruction. In this regard, of particular importance are studies of the actual load-bearing capacity of the frames of single-storey and multi-storey industrial buildings, and both in the reconstruction and in new construction, the results of which will significantly reduce costs and more rationally design structures. At the same time, one of the most relevant areas is the study of the joint work of metal load-bearing structures with prefabricated reinforced concrete structures of rigid disks of coatings and floors in their calculation. Moreover, in the national building codes, as well as in the educational and methodological literature, the calculation methods of taking into account the joint work of such constructions are not fully covered. The purpose of this work is to estimate the reduction of mass of the metal beam structure in its calculation in bending, taking into account the joint work with the rigid disk of the floor consist of precast concrete. As part of the study, the calculation of the floor beam according to the traditional calculation scheme - without taking into account the joint work with the floor slab, the calculation of its cross-section taking into account the joint work with floor slabs and experimental numerical study of the floor by the finite element method. Modeling of the floor fragment was performed in the software packages "SCAD Office" and "LIRA CAD 2019". Numerical research is aimed at verifying the feasibility of using the calculation methodology of DBN B.2.6-98-2009 to determine the effective width of the shelf when calculating the T-sections for prefabricated reinforced concrete slabs, which are included in the joint work with the floor beams. A comparative analysis of the obtained cross-section of the beam with the beam which was previously calculated by the traditional method of calculation in stresses in the most dangerous cross section and the total mass of the beams. According to the results of the analysis, the correctness of the application of the above normative method for determining the effective width of the shelf of T-bending reinforced concrete elements was confirmed.

Full-Scale Blast Tests on a Conventionally Designed Three-Story Steel Braced Frame with Composite Floor Slabs

This paper summarizes the findings of two full-scale blasts tests on a steel braced frame structure with composite floor slabs, which are representative of a typical office building. The aim of this research study was to experimentally characterize the behavior of conventionally designed steel braced frames to blast loads when enclosed with conventional and blast-resistant façade. The two tests involved a three-story, steel braced frame with concentrical steel braces, which are designed to resist typical gravity and wind loads without design provisions for blast or earthquake loads. During the first blast test, the structure was enclosed with a typical, non-blast-resistant, curtainwall façade, and the steel frame sustained minimal damage. For the second blast test, the structure was enclosed with a blast-resistant façade, which resulted in higher damage levels with some brace connections rupturing, but the building did not collapse. Observations from the test program indicate the appreciable reserved capacity of steel brace frame structures to resist blast loads.

Study on Collapse Resistance of RC Frame under the Corner Column Removal Scenario

The progressive collapse of buildings induces a variety of catastrophic consequences, such as casualties and property loss over the past few decades. The corner column is more prone to abnormal load events compared to the inner column and outer column; thus, it is easier to trigger progressive collapse. By considering the effects of floor slabs and adjacent bays on progressive collapse behavior, the pseudo-static loading method was used to study the progressive collapse test of a 1/3 scaled, one story, 2 × 2-bay cast-in-place reinforced concrete frame substructure under the removal condition of a corner column. The test results show that the flexural deformation principally concentrates upon the components of a directly affected part (DAP), and compressive arch actions are observed in members of the indirectly affected part (IAP). Moreover, the slab adjacent to the removed column and periphery elements contributes great resistance to a progressive collapse.

A Study of Sandwich Reinforced Concrete – Foamed Concrete Floor Slabs

The development of housing construction demands an application of building materials which ensure necessary functional performance of structures, have high heat-insulating properties, are environmentally friendly and their use is economically appropriate. Simultaneous ensuring of mentioned indices is possible because of complex combined joining of building materials with different physical-mechanical properties. This article presents experimental determination of useful load for sandwich reinforced concrete – foamed concrete floor slabs. Sandwich reinforced concrete – foamed concrete floor slabs are the floor slabs which are composed of normal concrete, non-autoclaved foamed concrete and spatial reinforcement frame. Experimental determination of useful load was carried out on series that compose of four sandwich reinforced concrete – foamed concrete floor slabs. Experimental test of sandwich reinforced concrete – foamed concrete floor slabs was carried out under condition of pure bending that was achieved by applying to floor slab in one third of its span two concentrated forces equal in magnitude. Useful load for sandwich reinforced concrete – foamed concrete floor slabs was 33.23÷77.87 kN/m2. Sandwich reinforced concrete – foamed concrete floor slabs are proposed to be used in construction of housing and social structures.

Construction Technology and Management of Unilateral Support Formwork for 16M-High Concrete Outer Wall of Complex Deep Foundation Pit

Shanghai Grand Opera House, which is under construction in Shanghai, China, includes two relatively large opera halls, which are named as the large opera hall and the middle opera hall. Below the stages of these two opera halls are two deep stage pits where the mechanical equipment will be arranged after construction, therefore, the structure of these stage pits is designed to be basically hollow with only a small amount of floor slabs on the edges. For the most sections of the stage pits, the depth is 16m, and the arrangement of horizontal supports and lattice columns in the stage pits during the construction period is extremely complicated. To prevent the outer walls of the stage pits from leaking and further guarantee the quality of the structure, the unilateral support formwork, which is composed of multiple steel components as load bearing members, is applied to construct the 16m outer wall of the stage pits. In this paper, first, the specific working principle of the unilateral support formwork and numerical analysis of its construction steps are introduced. Then focus on explaining that through establishing detailed digital 3D models of the complex stage pits during construction period, the practical construction sequence and construction technologies are designed and formulated, meanwhile, the on-site staff can also be guided directly through digital 3D models, which guarantee the visualization of the complex technology and the convenience of on-site construction as well. The construction of the deep stage pits is currently in progress, and part of the outer wall has already been constructed successfully. The cost of the technology is certainly more than common construction methods, but it is still acceptable since most of the formwork members can be recycled and re-use, while the advantages are obvious. Finally, the main characteristics of the construction technology of the unilateral support formwork for 16m-high concrete outer wall is summarized and discussed, which can provide a reference for the construction of similar structures.

STATE OF THE ART OF TANK STRUCTURAL EVALUATION REVIEW: A CASE STUDY OF AN ELEVATED CONCRETE WATER TANK CONCERNING CRACK INITIATION

This study aims at the structural evaluation of the elevated concrete water tank condition, including crack initiation, through nondestructive testing. The growing demands for environmental quality have resulted in a rise in the design and construction of tanks and reservoirs in the construction industry. Cracks for water line leakage were found during watertight testing in concrete tanks. Long-term liquid leaking may permanently damage the tank and can contaminate the groundwater. Given the critical existence of leaked cracks in tank serviceability and durability, the contribution examines the triggers and effects of their occurrence. An inspection of the existing water tank system is conducted to ascertain its condition. The investigation included structural design checks, concrete compressive strength tests, visual assessments, hammer inspections, and Ultrasonic Pulse Velocity (UPV) testing with Portable Ultrasonic Non-Destructive Digital Indicating Tester (PUNDIT). This observation is made at many elevations on various sampling points on the tank structure's elements, including columns, beams, tank floor slabs, and tank wall shells. The results indicate the presence of flexural type cracks in the main beam's middle span and diagonal beams. Additionally, cracks attributed to long-term drying shrinkage were discovered on the diagonal of the floor slab and cracks of the same pattern on the main beam's middle span. The deflection estimated by structural remodeling was larger than the deflection estimated by design. The computed crack width in the main and diagonal beam exceeds the acceptable crack width.