Hydro-Mechanics Coupling on Rammed Earth Material: Drying Experiment at Structural Scale

Rammed earth structures are very sensitive to hydric conditions. Experimental studies have been undertaken to understand the link between liquid water transfer and mechanical behavior at structural scale. This study was done on a prismatic rammed earth sample of 15cm x 15cm x 45cm, structured as a wall element with several layers. Samples were subjected to one dimensional drying in an indoor environment. Humidity and temperature sensors were placed on each layer inside the sample. The kinetic of drying was monitored by continuous weighing the sample and humidity measurement at a regular interval. Results of water content evolution suggest that samples dry in two stages; the first stage is associated with relatively high evaporation flux of 13.88 g m-2h-1 while the second stage has very low flux of moisture evaporation. Unconfined compressive strength was performed in drying samples after 0, 2, 6 and 8 weeks of drying. In parallel, digital image correlation was used to determine the stiffness of samples. Results show an increase in compressive strength by the rate of 98 kPa per week in the first two weeks, then this rate reduces to 23 KPa per weeks after 8 weeks. These experimental results will allow to enhance the 3D hydro mechanical numerical model developed in the laboratory.

Mechanism and Integrated Control of “Rib Spalling: Roof Collapse—Support Instability” Hazard Chains in Steeply Dipping Soft Coal Seams

The hazard chain of rib spalling, roof collapse, and support instability occurring in steeply dipping coal seams (SDCSs) significantly threatens the safety and productivity of underground mining. A three-dimensional coal wall model was established considering the damage to the coal wall from the abutment pressure based on the new concept of the main control weak surface (MCWS) defined by the authors. Then, a support mechanical model under the conditions of a dynamic load induced by a sliding roof was constructed. Integrated control measurements based on the models above were developed and taken for the dangerous area of hazard chains in working faces. The results indicated that the dimensions of rib spalling were dominated by the shape, dimensions, and friction angle of the coal wall element. In detail, the order of the importance of the element failure factors, based on their sensitivities, was the roof load (6.33), the dip of the panel (−5.03), the friction angle of the coal (−3.24), the cohesion of the coal (−3.02), and the sidewall protecting force (−0.087). Additionally, the order of importance of the frictional sliding factors of the slip body was the MCWS cohesion (−0.293), roof load (0.213), and MCWS friction angle (−0.079). Equations for the threshold forces between supports under the support dumping and sliding limit states were obtained; the knowledge of these forces ensured support stability under a sliding roof. The support work resistance varied synchronously in different parts of the working face and remained within 2200–4000 kN, indicating that the proposed models and control measurements considered instrumental in hazard chain control in SDCSs were reliable.

New technical device for traction tests of autotractor equipment

Advanced agricultural production is based on innovative scientific developments. The priority direction is given to the technical support of the agro-industrial complex, which makes it possible to significantly increase labor productivity in this sector of the economy, including the quality of products. Autotractor equipment is not an exception in this regard. Its correct operation largely de-pends on its timely and qualified maintenance, including tests. Traction tests of machinery make it possible to establish and test their traction characteristics, economy, high-quality performance indi-cators of the main units, as well as control systems. A new technical means (load support) for trac-tion tests of auto-tractor equipment is proposed. It includes a base, a support and brake plate in-stalled on it for placing the tested equipment on it and a traction-braking device. The design of the support and brake plate is made in the form of a treadmill. The base is made with the possibility of mounting a traction-braking device in it and is made in the form of a recess with a small ledge in the bottom part. Traction-braking device consists of two bracings and support boards made in the form of parallelepiped. Front bracing is secured from base front wall element. The rear bracing is mounted on a small ledge on the side of the rear wall of the base. The structures of the lower part of the front pillar, as well as the upper part of the rear pillar, are firmly attached to the spar by braces. To the left and to the right of the installed bracings there are locks in the form of bars. The advantages of the new technical device for traction tests of autotractor equipment are expressed in the improvement of operational properties through reduced weight and size characteristics, simpler design, as well as small amount of preparatory work.

Optimization of Object-oriented 3D CAD Pre-processing System for Steel Structure of High-rise Buildings

In this paper, the object-oriented method is used to study the pre-processing system of 3D high-rise building steel structure CAD. For the high-rise building steel structure design optimization system, users mainly contact with the functions of modeling, analysis, design checking and drawing. In fact, all these functions are carried out around the data stored behind. Three-dimensional high-rise building steel structure CAD pre-processing subsystem mainly integrates three-dimensional entity construction module, node design and editing module, construction drawing, processing drawing and CNC data output module. In this paper, the wall element is used to simulate the shear wall element, and the wall element can be automatically refined into a shell element composed of quadrilateral membrane element with rotational degree of freedom and generalized conforming bending plate element for thick and thin plate, which improves the speed and accuracy of analysis and calculation of shear wall. Various loads of high-rise building are calculated, especially the wind load of space action. It provides a new idea for wind load calculation of high-rise buildings. It is better to put forward a practical system optimization model, which can deal with the objective function, variables and constraints in a large number of engineering processing, and consider the actual constraints as fully as possible, which has strong practicability.

Development of a Reinforced Concrete Sheet Pile Wall Element

In the forthcoming years intensive renovation and reconstruction works can be expected on the banks’ freshwaters of Hungary. For the rehabilitation of the shores of Lake Velence works are starting in 2020. To support these investments there has been a demand for prefabricated reinforced concrete sheet pile walls. Realizing the opportunity, a major player in the market of pre-fabricated reinforced concrete elements for water way construction, CSOMIÉP Ltd. decided to develop a reinforced concrete sheet pile wall. In this study the development and complex structural and geotechnical design concept are shown through the major structural behaviors and useable geometries.

Combined neural networks and predictive control for heat exchanger networks operation

Optimal operation of integrated heat exchangers is a challenging task in the field of process control due to system nonlinearities, disturbances and adequate model identification. This paper describes the design of an advanced neural network predictive control (NNPC) applied to a heat exchanger network. A case study with two hot and one cold streams, through three counter-current heat exchangers is used to test the proposed strategy. A lumped dynamic model is built based on the concept of multi-cells topology (mixed tanks), where the hot and cold cells are connected by a wall element throughout the heat exchanger length. Each cell is assumed perfectly mixed and all physical properties are constant. A distributed behavior is achieved by increasing the number of cells. The main assumptions of the lumped model are constant temperature in each cell, heat exchanger volume and area equally distributed between cells and negligible heat loss to the environment. The predictive controller relies on a neural-based model of the plant that is used to identify the system and to predict future performance over a predefined horizon. Results were compared to a traditional controller, and the control performance was improved when compared to the Ziegler-Nichols tuning method.

Mathematic model for describing the stress-tension behavior of an autoclave with integrated heating element

This paper describes a mathematical model and the method for determining the thermal stress fields in a cylindrical wall element of a pressure vessel with a built-in heating element and a layer of heat insulating material. The method presented is based on the calculation of contact pressures.

THE GUEST’S PREFERENCES OF THREE-STAR HOTEL ROOMS BASED ON VISUAL AND PHYSICAL PERCEPTION

ABSTRACT The development of the tourism industry in Indonesia needs to be supported by appropriate facilities and infrastructure. Hotel as one of the supporting tourism in Indonesia has to be properly expanded. According to the data from Central Bureau of Statistics (BPS), the occupancy rate of star-rated hotels continues to increase over time. One of the factors affecting the customer's decision in choosing a hotel is its interior design. Interior elements consist of floor, wall, ceiling, and furniture. The wall element is one of the interior elements that are attractive to visitors. To find out the perception of hotel visitors, the author surveyed five three-star hotels in Jakarta. The five hotels are Maxone hotel in Matraman, Yellow Hotel in Harmoni, Lynt Hotel in Gambir, Park 5 Hotel and Swissbellinn both are located in Simatupang. The method used in this study is a mixed-method with a visual perception approach in the form of direct interviews and distributed questionnaires to 40 respondents. The results of the research show that several wall criteria of the hotel that are suitable for visitors among others are: bright wall colors and walls with soothing color schemes. Keywords: Guest’s preferences, hotel rooms, visual perception, wall design