Research on Ground Liquefaction and Structural Force Characteristics of Underground Utility Tunnels Under CLC Stratigraphic Model

Damages to underground structures due to liquefaction of the soils caused by cyclic loads such as earthquakes have always been an important issue in geotechnical underground engineering practices. This paper presents a numerical study of the utility tunnels at different burial depths in "Coh-Liq-Coh" horizontally layered liquefiable grounds using the finite-difference program FLAC3D. "Finn-Byrne" cyclic load volumetric strain increment model simulates the fluid-solid coupling of saturated sand and the increase in pore water pressure during vibration. The numerical model was loaded using an acceleration sine wave for dynamic calculations. The numerical results showed that the burial depths have a strong influence on the liquefaction of the soil beneath the utility tunnels and on the forces and deformations of the structures. Under the numerical simulation conditions in this paper, the greater the burial depth, the greater the liquefaction of the soil beneath the structure, the greater the shear stress on the side walls and the smaller the settlement difference between the structure and the surrounding soil. In the numerical simulations in this paper, a reasonable burial depth for utility tunnels was 0.8 to 1.1 times of the structure height.

Energy-based Design Method for Passive Energy Dissipative Bracing Systems

In this study an energy-based method for the design of passive Energy Dissipative Bracing (EDB) systems is presented, as a retrofit technique for existing reinforced concrete (RC) buildings. A comprehensive literature overview concerning the design of hysteretic bracing systems based on various design philosophies, such as force-, displacement- or energy-based, is provided. The efficiency of the proposed method is validated by comparing the proposed methodology with two design procedures selected in the literature, applied to three RC frames. The results showed that the proposed method is more effective in avoiding the damage concentration at a single story and in distributing the additional strength provided by the EDBs proportionally to the hysteretic energy demand along the structure height. The validity of each procedure is compared based on non-linear static and non-linear dynamic analyses.

Self-Compacting Concrete and Concreting Technology for Foundation Block Using 9000 Cubic Meters of Concrete

. The paper presents the results of the development and implementation of the technology of self-compacting heavy structural concrete and the technology of concreting with its use of the largest foundation slab in Belarus (concrete volume ~9100 m3) of a high-rise building at the facility “Construction of a multifunctional complex in Minsk within the boundaries of Filimonova Street – Avenue Nezavisimosty – Makayonka Street”. The results of research are shown, which ensured the production of self-compacting concrete of class C35/45 with water resistance up to W20 (with the required W12 according to the project) from concrete mixtures of the maximum cone expansion of the PK6 (RK6) grade for three zones of the foundation slab different in degree of reinforcement: lower, middle and upper, with a total structure height of 3.5 m and plan dimensions ~(83´34) m. The technology of continuous (seamless) concreting has been developed and implemented, which made it possible to lay ~9100 m3 of concrete into the structure without defects within 42 hours of continuous operation, and a system of technological measures that prevented temperature cracking in concrete. The homogeneity of the physical and mechanical properties of concrete, confirmed by control tests, is ensured due to the uniform supply of the concrete mixture (from six concrete pumps at the same time) in layers 200–300 mm high with a distance between the supply points of about 5–6 m and the vertical arrangement of the “trunks” of the concrete pipes during delivery of concrete to each point, as well as the fact that the time for feeding the next volume of concrete was significantly less than the setting time of the previously laid concrete (with a total concreting speed £0.1 m/h). Standardized and original test methods for concrete mixtures, hardening kinetics and properties of hardened concrete have been used during the development, research and implementation of the project. Control tests of physical and mechanical properties and characteristics of concrete, carried out at BNTU together with authorized organizations controlling the progress of construction, as well as in independent (third-party) organizations, have confirmed their compliance with the design requirements.

UJI MODEL FISIK RAYAPAN GELOMBANG PADA REVETMEN BUIS BETON

Buis Beton (Precast concrete pipe) revetment is a common coastal structure to protect the shoreline from erosion. However, it is common that this type of structure face high wave run up. A continuous wave run up on the slope of the structure may reduce the life service of Buis Beton revetment. The objective of this research is to create scientific based guidance to design an efficient Buis Beton revetment against wave run up. A physical modelling test is conducted to understand the relationship between wave run up and Buis Beton revetment. The test scenario is based on the slope of the structure (θ), structure height (L), buis beton diameter (φ), incoming wave height (Hi) and wave period (T). The physical modelling is conducted in 2D wave flume with laboratory scale of 1:10 with regular wave simulation. Wave run up is observed using a video camera which is later processed digitally to acquire the wave run up data. This research shows that the relative wave run up has a reciprocal functional relationship with the Iribarren Number parameter. In general, wave run up height on Buis Beton revetment is less than or equal to 2.64 the wave height, Hm0.Keywords: Revetment, buis beton, wave run-up, physical modelling

Effect of Soil Structure Interaction on Seismic Behaviour of Pile Supported Frame Buildings

Experiences from past earthquake disasters clearly shows that the ground motion was highly responsible for majority of property and life loss. Excessive damage was occurred to pile supported bridges, towers, chimneys, high rise structures, etc among the collapsed structures. A numerical study is carried out to understand the dynamic soil structure interaction of a high rise structure in a visco elastic half space in the presence of nearby pile supported structures. For understanding the seismic response of group of high rise structures supported on pile foundations a two dimensional study is carried. Framed structures which are assumed from the linear structures of different dynamic characteristics are supported on group of piles. Some studies related to group effect of structures supported on piles are considered like group of two identical structures, group of three identical structures and group of three different structures, secondly the effect of variability in structure height is considered like 5 storey structure, 10 storey structure and 15 storey structure and the third one in which the effect of variability in structure shape is considered. Above all case the effect of structure soil structure interaction on seismic response is compared with fixed base response.

Calculating the Dynamic Impedances of Foundations and their Effect on the Seismic Response of Structures: Analytical and Numerical Study

This study evaluates the movement of a frame built on soft soil under seismic excitation taking into account soil-structure interaction. First, the study was evaluated using the finite element method, then, by using a substructure method which modelled the soil using springs and dampers in a linear and nonlinear study. Rheological models were determined using impedance functions, calculated using a numerical program CONAN. These dynamic impedances are shown in the displacement vector of a three-degrees-of-freedom frame, which was calculated on the basis of lateral forces distributed over the structure height using the equivalent static method. In this regard, two different calculation norms were chosen; RPA2003 and UBC97. Finally, a parametric study was carried out, based on the effects of soil densification and the foundation geometry on the response of the RC frame.

Analysis of Pavement Structures. By Animesh Das. CRC Press: Boca Raton, FL, USA, 2014; 194p; ISBN 978-1466558557

Significant differences exist between pavement and building structures, particularly with respect to the type and mode of loading conditions: structural elements, beams and columns of buildings are subjected to static loads and pavement to dynamic loads. However, the design of structural members for buildings might need to address temporary dynamic loads due to wind, earthquake or other factors depending on building or structure height and application. In contrast, pavements are subjected to the moving loads of vehicles as well as to further loads due to temperature gradients. Since the layers of various materials used in pavements may vary in thickness and the statically indeterminate nature of pavement (due to the full contact with the bed soil layer or the lower layers), any deformation caused by changes in the moisture content and temperature can result in internal stresses in pavement structures. Consequently, analysis of pavement structures can be very complicated, requiring skills in material characterization, mathematics and modeling. In this regard, a useful book that covers various subjects in the pavement design and analysis was reviewed. Th details of each chapter were briefly explained. This book is recommended for consultant engineers and pavement researchers.

Simulation and Experimental Study on Improving Electrochemical Machining Stability of High Convex Structure on Casing Surface by Using Backwater Pressure

Casing parts are regarded as one of the key components in aero-engine components. Most casing parts are attached with different shapes of convex structures, and their heights range from hundreds of microns to tens of millimeters. The use of profiling blocky electrodes for electrochemical machining of casing parts is a widely used method, especially in the processing of high convex structures. However, with the increase of convex structure height, the flow field of machining areas will become more complex, and short circuits may occur at any time. In this study, a method to improve the flow field characteristics of machining area by adjusting the backwater pressure is proposed, the simulation and experiment are carried out respectively. The simulation results showed that the back-pressure mehtod can significantly improve the uniformity of the flow field around the convex structure compared with the extraction outlet mode and the open outlet mode, and then the optimized back-pressure of 0.5 MPa was obtained according to simulation results. The experimental results showed that under condition of the optimized back-pressure parameters, the cathode feed-rate increased from 0.6 mm/min to 0.8 mm/min, and the convex structure with a height of 18 mm was successfully machined. This indicated that the back-pressure method is suitable and effective for the electrochemical machining of high convex structure with blocky electrode.

ACTIVE, PASSIVE AND STABLE SHORES OF THE SEA OF AZOV

The purpose of this work is to comprehensively study the ecological and geological conditions and the results of monitoring studies of the coastal territories of the Taganrog Bay and the Sea of Azov to identify the degree of manifestation of dangerous coastal processes (DCP). The subject of the study is to assess the degree of manifestation of DCP under the influence of various natural factors, both constant in time (geological structure, height of the coastal cliff), and changing (dynamics of the level, waves, wind regime) and the impact of man-made causes. The performed factor analysis allows us to assert that the main natural factor of the intensification of DCP is the extreme surge levels (adverse end dangerous events: AE and DE). The types of shores are constant, but with different degrees of manifestation of DCP, they change significantly. As a result, according to these studies, maps were constructed for the average long-term (1980), intensive manifestation (2013–2014) and the period with a relatively calm manifestation of the intensity of DCP (2018–2020). According to the activity, the manifestations of DCP are divided into 4 types: type I – with a very high c (>4 m/year), type II – with a high (2–4 m/year), type III – with an average (1–2 m/year), type IV – with a weak rate (<1 m/year) of abrasions, which include subtypes of banks formed by exogenous processes (abrasive, abrasive-landslide, accumulative), indicating the conditions of their formation and the reasons for the isolation of the danger of coastal processes.

Base shear variation for irregular G+6, G+9 and G+12 structures in seismic zones IV and V for three soil types

It is attempted to expand upon the understanding on the structure’s behaviour when the seismic force, which is one of the predominant lateral forces, is applied on the structure. The base shear is calculated and compared for various variable parameters. For the three soil types the base shear is contrasted while varying the building heights of an irregularly planned structure in the seismic zones: IV and V. The structures’ heights are taken as follows: G+6, G+9, G+12 and storey height as 3m. Concluded observations talks about the amount of the variation in the base shear when the structure height and soil types are altered. While the G+9 and G+12 structures behaved identically, the G+6 structures in the medium and the soft soils fetched same results.