Study Of Thermal Effects For Crack Control On Concrete Small Hollow Block Building

Concrete Small Hollow Block (CSHB) is an environment-protected building material with a series advantages such as saving of energy and no consuming of clay soil, however, the thermal cracks in Concrete Small Hollow Block Building (CSHBB) is badly restricted its development. By this reason, it is necessary and significant to study the thermal cracks problem in CSHBB. The cracks are caused by a lot of reasons, by the same time, they can be controlled by much measures. This paper is mainly focused on thermal field analysis, field tests of CSHBB, thermal effects analysis and combination of thermal effects and load effects.By the analysis of influencing factors and heat-transfer modes, it was concluded that solar radiation was the main influencing factor to temperature field of CSHBB and the conduction was the main heat-transfer mode. By the field tests and finite element analysis, the temperature field of CSHBB was deduced that it was necessary to distinguish walls and roofs in different orientation to calculate their temperature fields respectively.Field tests were done in CSHBB nearly one year in hangzhou. By analysis the test data, the law of temperature variation in day and temperature variation in month was got; moreover, the probability statistics mode of day temperature difference with its statistic parameter was got too. At the same time, the year temperature difference data of walls and roofs were obtained. Through the field tests, the law of thermal cracks, displacement and stress in CSHBB was summarized.Based on the experiment of full-sized CSHB walls under lateral and vertical loads, initial crack-resisting stiffen formula was deduced by considering the influence of concrete beams, concrete core columns, structural columns, vertical pressure and window (or door). The results calculated from the formula were fit well with the experimental results. By the analysis of displacement at initial crazing, probability statistical mode and its parameters of relative displacement angle were presented. The control criterion of relative displacement angle was deduced.Three analysis methods for thermal effects of CSHBB were presented. Since the temperature difference was most important parameters in thermal effects calculation, a combined temperature difference method considered year temperature difference and day temperature difference was put forward. With the combined temperature difference obtained from field tests, a lot of calculations have been done by finite element method (FEM), considering of different structural measures. The law ofdisplacement and stress in CSHBB was presented and a relative displacement formula was deduced.Equation was deduced on normal use ultimate state for CSHBB based on displacement control method, whose statistical parameters of load item were got from field tests and statistical parameters of resist item were got from indoor experiments. Reliability analysis was also done based on the equation.Different structural measures for thermal crack control have different effects. Quantitative research has been done to see the effects of thermal crack control by slope roof in CSHBB. Control measures for design and construction were also presented.It was introduced that the masonry structure design method and loads combined method. By the comparison of calculation result with the tests result, it was concluded that the method to calculate the year temperature difference and day temperature difference from weather data was feasible. By this method, it was got that the statistic parameters of combined temperature difference in base period and the reliability to different anti-crack index was calculatedThe combination of thermal effects and load effects was considering in this paper. Since the common loads had little effects to the relative displacement of top floor in CSHBB, so it was unnecessary to considering them in normal use ultimate state. Thermal effects had no influence to the resist compression bearing capacity and resist shear bearing capacity, but had great...