Question 1

What method does AXIS use to analyze continuous beams?

Accepted Answer

AXIS uses the stiffness (matrix) method to solve multi-span continuous beams, which handles any combination of span lengths, support conditions, and loading patterns exactly.

Question 2

What is the moment distribution method for continuous beams?

Accepted Answer

The moment distribution method iteratively distributes unbalanced fixed-end moments to adjacent spans using distribution factors (DF = relative stiffness EI/L). It converges to the exact solution for prismatic members.

Question 3

How does support settlement affect a continuous beam?

Accepted Answer

Support settlement induces additional moments proportional to EI × δ/L², where δ is the settlement. For a two-span beam with equal spans, settlement at the center support causes hogging moment at that support.

Question 4

What is the pattern loading concept for continuous beams?

Accepted Answer

Maximum negative moments at supports occur when adjacent spans are loaded and alternate spans are unloaded. Maximum positive moments occur when only the span of interest is loaded. Critical combinations must be checked per ASCE 7-22.

Question 5

How are support reactions calculated for a continuous beam?

Accepted Answer

Once moments at supports are found (by stiffness method or moment distribution), reactions are calculated from free-body diagrams of individual spans using statics: RA = (wL/2) + (ML – MR)/L.

Step	Formula	Substitution	Result
M0	support moment	0	0 kN·m
M1	support moment	-126.7	-126.7 kN·m
M2	support moment	-126.7	-126.7 kN·m
M3	support moment	0	0 kN·m

Step	Formula	Substitution	Result
M+1	span moment	98.2	98.2 kN·m
M+2	span moment	91.9	91.9 kN·m
M+3	span moment	98.2	98.2 kN·m

Step	Formula	Substitution	Result
R0	reaction	90	90 kN
R1	reaction	195	195 kN
R2	reaction	195	195 kN
R3	reaction	90	90 kN

Step	Formula	Substitution	Result
M0	support moment	0	0 kN·m
M1	support moment	-126.7	-126.7 kN·m
M2	support moment	-126.7	-126.7 kN·m
M3	support moment	0	0 kN·m

Step	Formula	Substitution	Result
M+1	span moment	98.2	98.2 kN·m
M+2	span moment	91.9	91.9 kN·m
M+3	span moment	98.2	98.2 kN·m

Continuous Beam

Continuous Beam

Spans

Loading

End Conditions

Continuous Beam Analysis

Support Moments

Span Moments

Reactions

Continuous Beam

Continuous Beam

Spans

Loading

End Conditions

Continuous Beam Analysis

Support Moments

Span Moments

Reactions