報告書番号

N08060

タイトル（和文）

送電用鉄塔の耐風信頼性設計法に関する検討（その２）－風向特性を考慮した荷重・耐力係数法に基づく設計式の提案－

タイトル（英文）

Wind Resistant Reliability Design method for Overhead Transmission Tower Part 2 -Development of Design Equations in LRFD Format considering Wind Direction Effect-

概要 （図表や脚注は「報告書全文」に掲載しております）

前報では，送電用鉄塔の台風シミュレーションを用いた高精度の耐風信頼性解析コードと風向特性を考慮した等価再現期間およびモデル不確定性の評価法を提案した．本研究では，前報告の結果に基づき送電用鉄塔の風向特性を考慮した信頼性設計法を開発する．まず，日本全国を対象に様々なタイプの送電用鉄塔の信頼性解析を行い，前報で提案した等価再現期間を評価した．その結果，全風向一律の設計風速とする場合は14.6年，風向別に設計風速を定める場合は88.3年であること明らかにした．また，設計式の評価に必要な統計情報を整備するとともに，現在の設計法による平均的な信頼性指標を把握した．次に，信頼性解析に基づく統計量を用いて，1次近似2次モーメント法により部分係数を決定し，風向特性を考慮できる荷重・耐力係数形式の設計式を提案した．最後に，提案式と現行の風向特性を考慮しない設計式による評価値を比較により，提案式の合理性と有用性を確認した．以上の研究により，送電用鉄塔の風向特性を考慮できる実用的な信頼性設計法を確立した．

概要 （英文）

The previous paper has presented a high accurate reliability analysis code using a typhoon simulation, and an estimation method of an equivalent return period of design wind speed and a modeling uncertainty in a directional design procedure for overhead transmission tower. In this paper, the author discusses the design equations in load and resistance factor design (LRFD) format considering wind direction effect. First, non-exceedance probabilities of annual maximum load effect and reliability indices were calculated using the developed code for various kinds of overhead transmission lines in several areas. Using the calculation results, equivalent return periods and modeling uncertainties were estimated for two alternatives; directional independent design wind speed and direction dependent design wind speed. As a result, the return period was estimated as 14.6 years for direction independent design wind speed and as 88.3 years for direction dependent design wind speed, respectively. In addition, other statistical information such as distributions and distribution parameters of wind load effects were estimated to evaluate the design equations. Second, partial factors were determined based on the statistic information by the first order second moment method and the author developed the LRFD design equations for two alternatives. Finally, from comparison of the design value by the proposed method with by the current design method, the validity and usefulness of estimated equations were confirmed. In conclusion, the author established a practicable and reasonable reliability design method for an overhead transmission tower.

報告者

キーワード