Volume 116 (2019): Issue 7 (July 2019)

Turbulence affects the human perception of wind, the wind-induced damage to buildings, the values of wind speeds measured by 3-cup anemometers, and so on. The wind environment assessment criterion proposed by the Wind Engineering Institute Co., Ltd. is based on the relationship between the mean wind speeds measured by 3-cup anemometers and the condition of surrounding terrain. This criterion does not consider the influence of turbulence. Considering the significant urbanization of large cities and the change in anemometers used for wind speed measurements, a new criterion of wind environment assessment that considers the effect of turbulence is required. The present study discusses such a criterion based on a wind tunnel experiment, the observation at various locations, and a questionnaire survey on the wind environment that was conducted with for the residents and pedestrians in Tokyo.

In this paper, the authors present an engineering method to identify the transmission paths of structure-borne sounds. The method is based on the use of a standardised impact sound source with an insulation case. The advantage of this approach is the possibility of obtaining repeatable results because the method allows the separation of structure-borne and airborne sounds; the latter do not interrupt the measurement even in the case of loose connections or elements of low acoustic insulation. The research on the verification of the method was performed on the façade of the Cracow Philharmonic building; the main structure-borne sound transmission paths were determined successfully. Knowledge of the sound transmission paths allows the subsequent design of efficient vibroacoustic protection.

Road noise constitutes one of the most adverse impacts of road traffic on the environment. Noise that is particularly annoying for local inhabitants is recorded in the vicinity of engineering structures where various types of expansion joints are used [1–3]. There are currently many road connections being built in Poland, including a total of almost ten thousand expansion joints. The authors of this article attempt to determine the noise differences of several of the most commonly used expansion joints – single-, double-, and multi-module, block and finger expansion joint described as one of the most advantageous from the acoustic point of view. This study also attempts to determine the im-pact of expansion joint types on the noise level in comparison to the road section not equipped with these devices, which was adopted as the base noise level.

This article presents description and results of an investigation using PIV for measuring wind velocity fields in front of and behind bulkheads made from nets of different solidity ratios. The basic aim of the work is to determine the characteristic features of the wind velocity field on the windward and leeward sides of nets of different solidity ratios and to present an example of the usage of a PIV system in tests in an aerodynamic tunnel. The tests were performed in a mini aerodynamic tunnel especially prepared to test the PIV system. In the work, the regulations of measurement by means of a PIV system are presented, the main elements of the system are characterised and the main advantages and difficulties of realising measurements using this type of technique are described.

This paper describes model tests conducted at the Wind Engineering Laboratory of Cracow University of Technology as the first stage of studies on dynamic action on the atmospheric boundary layer in order to reduce the effects of air pollution and smog. It focuses on the cooperation between a series of ventilation towers placed one by one (or row by row) in order to generate a continuous airstream with sufficient velocity to aid the natural ventilation of urban areas. The tests were conducted for three different terrain categories with varying roughness. Also tested were different wind speeds, different spacing between the towers and different configurations of the towers in each row. As a preliminary set of tests, this enabled verification of the feasibility of the solution and its effectiveness on a rough terrain that simulates urban areas.

A new photovoltaic system combining electrical power production with snow mitigation intends to reduce the snow load on flat roofs. Applying electrical power to PV modules causes heat production on the module surface, allowing the ablation of snow. This study combines measurements and theoretical analysis to investigate which conditions are favourable for snow load reduction and discusses the system’s feasibility to perform a controlled snow load reduction in a heavy snow load scenario for buildings with flat roofs. Both melting and sublimating of snow are investigated as means to reduce the load. The results show that the potential for load reduction is highly dependent upon weather conditions and snowpack characteristics during system operation. The refreezing of meltwater and water saturation of snow are identified as phenomena potentially preventing sufficient load reduction in cold conditions. Due to such temperature sensitivity, the system is likely to be more suitable for warm climates occasionally experiencing heavy snow loads than for climates with long and cold winters.

Following global trends, Polish regulations on human exposure to vibration in buildings were changed and new Polish guidelines were published in June 2017. In accordance with international trends, two methods of assessment have been added to the regulations: basic RMS method and ad-ditional VDV method. For more clarity of RMS method, the human vibration perceptivity ratio (HVPR) was introduced to new Polish regulations. In the appendix to the Polish standard, the vi-bration dose value (VDV) method is presented. The third important change in the new version of the Polish standard is measurement equipment that should be used for human perception evaluation. New regulations have precisely described what kind of equipment should be used for low-frequency recording and a new measurement disc for the human perception of vibration on floors has been introduced to the Polish standard.

This paper describes model tests conducted in the Wind Engineering Laboratory of Cracow University of Technology on dynamic action on the atmospheric boundary layer in order to reduce the effects of air pollution and smog in urban areas. The paper focuses on vertical exhaust (ventilation chimney) and cooperation between a concentric system of ventilation towers and a ventilation chimney. The tests were conducted for different shapes and heights of ventilation chimneys, different diameters of the concentric system and different wind speeds provided by the ventilation towers. A heavy smoke visualisation was performed in order to qualitatively evaluate the efficiency of different solutions. The performed tests confirmed a sufficient level of efficiency of cleaning an area where the circular system is located.

Wind loads on cylindrical free-standing canopy roofs were investigated in a wind tunnel. First, the overall aerodynamic forces and moments were measured using a force balance. The distributions of net wind pressures provided by the difference between wind pressures on the top and bottom surfaces of the roof were then measured along two representative arc lines. Based on the results, the net wind-pressure coefficients for designing such roofs are proposed as a function of the rise-to-span ratio for two representative wind directions: one perpendicular to the eaves, the other inclined at an angle of 45° to the eaves. The roof is divided into three zones and constant net wind-pressure coefficients are specified for these zones. Two load cases providing the maximum tension and compression in the columns supporting the roof are considered as the most important load effect for discussing the design wind loads.