إستشاري الهندسة المدنية
- 22 سبتمبر 2008
- مجموع الإعجابات
تصف الورقة المرفقة اعمال رفع بلاطة الجسر المنشأ عام 1925 في استراليا Ashgrove Avenue bridge واستبدال المخدات bearings التالفة فوق الكتف abutment الغربي للجسر . ومن الجدير بالذكر ان هذه المخدات المستبدلة كان الجسر قد صمم دون ان اي اعتبار لإمكانية ان يتم استبدالها إطلاقاً. حاليا فان السائد مثلا ان يتم تغيير المخدات للجسور بعد عمر افتراضي معين يختلف حسب نوع تلك المخدة وبالنسبة للمخدات الاكثر شيوعا وهي المسماة elastomeric bearing pads فان عمرها الافتراضي يتراوح ما بين 20-25 سنة وقد يطول أكثر من ذلك أو يقل.
Abstract: Detailed condition assessments of a 96-year-old, 5 spans continuously reinforced concrete road bridge showed that the structure was still in serviceable condition but bearings on the western abutment were at risk of failure. Over the course of 2 years, assessments and designs were developed including a very detailed methodology based on site samples, laboratory testing and jacking trials to determine how these bearings could be replaced, as they had not originally been designed as renewable. The construction and design of this structure meant that considerations and special allowance needed to be made when compared to traditional modern remediation to preserve the original function of the bridge. The in-situ materials encountered included, 18MPa concrete, 230MPa reinforcing steel, fully carbonated concrete cover, cast iron bearing brackets and bronze phosphor bearings. Perhaps unsurprisingly this work may have been avoided had the local drainage and road water been managed more effectively during the bridge’s earlier years. This is because while working in Council much of my work managing existing assets involves the management of moisture and water to maintain the asset. Some steps of the bearing replacement and jacking project were performed twice due to insufficient curing time of one of the components with no alternative engineering solution available. While the investigation and design proved correct, a slight change during the construction execution resulted in most of the program float being utiliئed not allowing repair product to properly cure, proving that the construction method and timing should be followed precisely when bespoke construction works are undertaken