本研究呈現一大型鋼構廠房的完整建模與動力分析流程，使用結構設計分析軟體SAP2000進行建模與分析，建立的模型包括一舊有鋼構架模型及一補強工程後的鋼構架模型。透過觀察該兩種鋼構架模型局部與整體之動力反應特徵，可對其受振動時的動態行為有完整瞭解，並比較補強工程對整體鋼構架反應行為造成的影響，進而探討補強工程於振動抑制效果的優劣，最終達到防範工安災害於未然的目的。分析結果指出，無論於靜態安全檢核亦或動力反應分析部份，補強後模型皆呈現出優良的反應降低成效。補強後各段構架依其補強程度之不同，檢核未過桿件比例有5 % ~ 10 %的下降水準，而各段的模態頻率亦達到5 % ~ 50 % 不等的提升量。補強後模型有較高的結構自振頻率，其原因在補強工程有效的提高了支撐構架的整體勁度，且其提高的百分比與補強後構架應力比檢核未過桿件比例下降程度呈現正比趨勢。
單段構架的模態性質於合併後依舊呈現於整體構架的模態特徵中，其原因在構架的組合形式為縱(長)向的連接，合併後對於主要振動方向(橫向)的影響並不明顯，故合併後局部構架自有的模態特徵仍明顯的表現於整體構架中，此特徵亦造成了振態參與質量呈現零散的分佈現象。於動力分析的結果中，當頻率較為分散的載重作用時，各段模型的模態頻率特徵於反應行為中表現較不明顯，相較於頻段集中的外力函數激勵，局部的頻率特徵明顯為非主要影響分析結果的控制因素，補強所增加的勁度即表現出良好的動力行為反應，達到有效的振動抑制目的。

Dynamic Simulation and Strengthening Analysis of Large Steel Frame Structure
Tsung - Hsuan Lee
Tsung - Chin Hou
Department of Civil Engineering, College of Engineering
SUMMARY
The aim of this paper is to demonstrate model building and dynamic analysis of steel frame factory. The finite element models contained original and reinforced models are built up and analyzed by finite element software SAP2000. Dynamic response comparison of those two models generally presents dynamic behavior of steel frames during vibration and the effect caused by reinforcement. By doing so, the result of vibration mitigation caused by reinforcement could achieve the disaster prevention purpose. The reinforced model shows that both of the static bearing capacity and dynamic response improve obviously. The number of element exceeding design strength decreases from 5% to 10% and the modal frequency increase from 5% to 50% in each part of the model. The main reason of modal frequency increment is that reinforcement effectively improves the stiffness of the supporting structure. Besides, the ratio of modal frequency increment and ratio the decrement of elements exceeding design strength are in direct proportion.The modal properties of the each model still appear in the whole model. Due to horizontal connection between each model, this connective way has little effect on the vertical vibration. Thus, modal traits of each model appear in the whole model that makes mass participation of the whole model apparently scattered. The result on dynamic analysis shows that the traits of each model appear seems unclear when distribution load applies. Comparing to the frequency Centralized External excitation function, partial frequency trait is not the control factor. Stiffness increased by the reinforcement reflect reasonable dynamic behavior that successfully reduce vibration

Keyword: Large Steel Frame Structures, SAP2000, Dynamic Simulation
INTRODUCTION
Petrochemical industries in Taiwan not only an essential role in whole industry development but also contribute to economy. Moreover, disaster prevention evaluations on refinery factory necessary to ensure them work steadily. This paper mainly discusses vibration caused by the newly installed 2m" discharge vents line in naphtha cracking plant and the reinforcement of the original steel structure. The purpose of 2m" discharge vent line is to transporting the huge amount of waste effluent and gas during annual maintains. The beneath supporting steel structure is induced vibration by the vent line when it transports waste; however, this phenomenon is unexpected in original design. In order to prevent structural damage, the insufficient stiffness part should have been improved. By static and dynamic simulation on discharge vent line and steel structure, the reinforcement effect can be evaluated and the result will be the example for the other part of steel structure to avert industrial disasters.
METHODS
The study method consists two parts. First part is to utilize SAP2000 to build up the FEM model of steel structure before and after reinforcement and check structure static loading by allowable stresses ratio. Second part is to simulate the vibration behavior of steel structure by apply five types of accelerated history on the upper structure and support of 2m" discharge vent line to demonstrate each effect. Adjust ion of application types and modes of accelerated history would yield corresponding dynamic traits. Besides, applying three types of earthquake acceleration time history simulates seismic effect on the steel structures. By doing so, dynamic behaviors would be evaluated clearly and demonstrate the result of vibration reduction.
RESULES
This section can be separated into to parts based on the SAP2000 analyze result. One part is static loading check and the other part is dynamic analysis. By conducting static and dynamic analysis, the influence of upper newly installed vent lines on whole structure can be clearly demonstrated to evaluate the reinforcement effect.
1. Static loading check
It is a safety issue that upper newly vent line installed on the original steel structure. Based on result of static loading check, the weakness of the original steel structure can be evaluated and improved. The analysis results show that the ratio of steel element not meeting standard decrease obviously because of reinforced steel structure. It means that reinforcement effectively enhance static allowable loading of whole structure.

2. Steel structure dynamic characteristic
This paragraph summary the reinforcement effects on reduce vibration which includes forced vibration on upper area and basement vibration. By doing so, natural disasters can be prevented that is the major purpose of this thesis.
(i) Structural modal parameter
From the modal analysis result, reinforcement enhances natural frequency of steel structure which means that its vibration period reduces. From stiffness aspect, lower period of structure are somehow equal to higher stiffness. From energy aspect, higher vibration frequency means structure has better ability to dissipate energy and resist more loading. That is the effect of reinforcement on whole steel structure.
The local modes characteristic mostly stay in whole steel structure after connection each local part FEM model. Modal parameter and mode shape of whole structure variations appear unobvious because its connecting direction is horizontal which is different from main vibration direction (vertical). Therefore, the local structural traits stay in the whole steel structure and lead modal parameters to distribute scattered.
(ii) Time history dynamic loading
From the result of five types of loading, the frequency of local parts did not appear obvious compared to relatively concentrate function when structure applied with irregular loading. Therefore, variation among different loading types influent analysis results merely. Besides, stiffness enhancement demonstrates the effect of reinforcement significantly.
By altering loading direction combination, x-axial vibration replaced by y-axial and the result is nothing different. The consequence of above means that x-axial vibration is not the major factor in the dynamic analysis.
(iii) Earthquake time history simulation
Under powerful earthquake simulation, the structure vibrates apparently. The displace wave function of reinforced structure displays gentle when earthquake wave arrive peak. The relationship between frequency domain of earthquake function and structural reaction is intimate which corresponds to the result of energy dissipation.
CONCLUSION
It is a safety problem that original bearing capacity is insufficient for newly installed 2m diameter vent lines on the original steel structure. Hence, structural reinforcement is necessary. From static loading check result, reinforcement effectively improves the weakness of steel structure and the ratio of element meeting standard increases greatly. The other safety problem caused by newly installed construction on steel structure can be improved by the reinforced structure.
Dynamic analysis result shows that local mode traits are not obvious when steel structure applied with loading whose main frequency is scattered. The steel structure behavior is affected by reinforcement which successfully reduces vibration.
To sum up, the result of static loading check and dynamic analysis shows that reinforcement construction improved structural stability positively. Furthermore, based on the analysis result, the reinforced construction can be viewed as the model of structural improvement and expected to reduce the risk of industrial disasters.

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