ABSTRACT

A timber bridge constructed in 1815 was renovated in 2018, wherein the load-bearing system was reinforced with beech laminated veneer lumber (LVL) elements. Beech LVL is primarily found in dry and heated structures (Service Class 1). Although the material of this bridge would not be directly exposed to weather, it would be exposed to outdoor relative humidity ranging between 50% in spring and 90% or higher in autumn (Service Class 2). Thus, the moisture content development in the reinforcements was monitored to observe the response of the material under such conditions. The moisture content was measured using both sorptive and electrical resistance methods. The relationship between the electrical resistance of the material to moisture content and sorption isotherms was determined through laboratory experiments. Thereafter, the derived relationships were used to determine the moisture content measured on the bridge over a period of two years. Consequently, the two measurement methods resulted in overlapping of moisture content values, which remained within safe levels and are expected to be maintained in future. The overlapping moisture content measurements validated that either of the monitoring methods could be independently deployed to obtain reliable results.

摘要

一座建于 1815 年的木桥于 2018 年进行了翻新，其中的承重系统使用山毛榉单板层积材 (LVL) 元件进行加固。山毛榉 LVL 主要用于干燥和加热的结构（服务等级 1）。虽然这座桥的材料不会直接暴露在天气中，但它会暴露在春季 50% 和秋季 90% 或更高的室外相对湿度下（服务等级 2）。因此，监测增强材料中水分含量的变化，以观察材料在这种条件下的反应。使用吸附法和电阻法测量水分含量。材料的电阻与水分含量和吸附等温线之间的关系是通过实验室实验确定的。此后，派生的关系被用来确定两年期间在桥梁上测量的水分含量。因此，这两种测量方法导致水分含量值重叠，但仍保持在安全水平内，并有望在未来保持。重叠的水分含量测量验证了任何一种监测方法都可以独立部署以获得可靠的结果。