Abstract
Objectives It is known that the moisture content of wood has a significant effect on the joint strength of elements of wooden structures. However, there has been little research in establishing a specific relationship between the moisture content of wood and the nailed joint strength of wooden elements. The aim of the study is to determine the influence of capillary (free) and bound (hygroscopic) wood moisture on the strength of nailed connections during pull-out. Methods Conducting experimental studies. Results Three series of samples were tested. For each sample the maximum nail pulling force was determined, with the ultimate pulling resistance calculated according to the formula supplied by the appropriate Rules and Regulations. The samples of the first series were tested with wood having low moisture content. The samples of the second series were moistened prior to the test by being immersed in water for 24 hours to gain capillary moisture. The samples of the third series were moistened prior to the test hygroscopic moisture absorption by being placed in a desiccator above water for a long time without direct contact. Conclusion In the course of the study, it was found that both capillary and hygroscopic moisture significantly affects the strength of nailed connections, and that the effect on the maximum pulling force is not determined by the type of moisture, but by its value. The samples of the first series indicated the greatest nail pulling resistance. The samples of the second series had nail pulling resistance less by 48%. In the third series, the strength of the nailed connection was reduced by 31% as compared to the dry wood. The results of the study confirm the necessity of taking into account the humidity during the design and operation of nailed connections.
Highlights
For each sample the maximum nail pulling force was determined, with the ultimate pulling resistance calculated according to the formula supplied by the appropriate Rules and Regulations
The samples of the first series were tested with wood having low moisture content
In the course of the study, it was found that both capillary and hygroscopic moisture significantly affects the strength of nailed connections, and that the effect on the maximum pulling force is not determined by the type of moisture, but by its value
Summary
ВЛИЯНИЕ ВЛАЖНОСТНОГО СОСТОЯНИЯ ДРЕВЕСИНЫ НА ПРОЧНОСТНЫЕ СВОЙСТВА ГВОЗДЕВЫХ СОЕДИНЕНИЙ. Влажностное состояние древесины оказывает значительное влияние на прочность соединений элементов деревянных конструкций. Целью исследования является определение влияния капиллярной (свободной) и связанной (гигроскопической) влажности древесины на прочность гвоздевых соединений, работающих на выдергивание. Образцы первой серии испытывались при сухом состоянии древесины. Образцы второй серии перед испытанием были увлажнены. Образцы третьей серии перед испытанием были увлажены путем набора гигроскопической влажности. В ходе исследования было установлено, что капиллярная и гигроскопическая влажность существенным образом влияют на прочность гвоздевых соединений, причем влияние на максимальное выдергивающее усилие оказывает не тип влажности, а еѐ значение. Образцы первой серии показали наибольшее сопротивление выдергиванию гвоздя. Образцы второй серии имели сопротивление выдергиванию на 48% меньше. У образцов третьей серии прочность гвоздевого соединения была снижена на 31% относительной сухой древесины. Результаты исследования подтверждают необходимость учета влажности при проектировании и эксплуатации гвоздевых соединений.
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