By calculating large quantity of examples , this text studies earthquake resistant behavior of tapered portal frame with pined bases and analyzes its natural frequency , natural period of vibration and vibration mode . by comparing interior forces of pillar top , beam end and span midpoint in two conditions that seismic action effect participates combination of forces and not when portal frame is n ' t changed , ensure conditions that combination of seismic action effect has controlling f unction during tapered portal frame design , and tapered portal frame demands anti - earthquake design
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