隨著橋梁設施普遍運用於現代，如何在經濟的考量下做最佳設計，本案透過以研究高雄港聯外高架道路的預力箱型橋樑為例，討論在不同道路平整度、各種車速影響之下的變位與衝擊係數，研究透過模擬橋梁以車輛載重的動力試驗，來深入了解這座橋梁的特性，本案預力箱型橋樑以40.6m 的連續跨橋段分析研究，而衝擊係數公式(I)可看出，當L 越小時，I 值越大，但隨著未來趨勢，為降低橋墩數量，採大跨距的鋼橋，I值越降低，雖然大跨距橋梁強度已於設計時考量提升，但想了解I 值與現場衝擊產生的效應是否貼切，需透過車載試驗取得數據，但因為現場
車載受限經費、環境與時間條件較不易試驗，故可透過程式建立各種模型，比較不同跨距、各種形式之橋梁事先模擬，討論DA 值(Dynamic Amplification)與衝擊係數I 值之合理性，做為未來設計參考之依據，提升橋梁公共工程品質與經濟性。
關鍵字:衝擊係數、動態放大、變位、ASSHTO

SUMMARY
With the bridge facilities are widely used in present, It is a issue how to be the best design in the economic. The study is about the case of Kaohsiung Harbor network road of viaduct line. Discuss the displacement and impact coefficient due to different road roughness and various vehicle speeds. We can simulate dynamic vehicle loads test and see the characteristics of the bridge by using computer program. This study is about analyzing the pre-stressed concrete box girder bridge of continuous spans with 40.6m length. By studying the formula of impact fraction, it can be found that reducing span length cause increasing of impact fraction. In order to decrease the number of pillars, it is the trend to design large span of steel bridges in the future. It is more difficult to get impact fraction of the bridge by dynamic vehicle load test, so we can execute computer program to get the simulation of DA vale (Dynamic Amplification) compared with impact fraction according to ASSHTO deign code for the promotion of public bridge construction with quality and economy.
Key words: Impact fraction, Dynamic Amplification, displacement, ASSHTO

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