Development of an Efficient Steel Beam Section for Modular Construction Based on Six-Sigma

Table 3

Correlation analysis between the required qualities and quality characteristics.

Customers’ required quality	Quality characteristic
	Price of beams		Contribution to competitiveness of modules								Structural performance of bema			Quality of manufacturing		Absolute priority	Priority ratios	Ratings
	Surface area per unit length	Welding length per unit length	Span length	Thickness of webs	Diameter of web opening	Number of webs	Thickness of flanges	Number of openings	Height of ceiling and floor beams	Weight of floor beams per unit area of plan	Moment of inertia per sectional area of beam	Section modulus per sectional area of beam	Lever arm of bolts at the end plate	Number of axes of symmetry	Radius of curved section
Low cost of beams
Small steel quantity				○		○	△			◎	◎	○				7.7	10%	2
Low manufacturing cost	○	◎			○			○								13.1	17%	1
Easy design of modular building
Easy structural design			◎								◎	○	◎			4.3	5%	7
Easy architectural design	◎		◎		○			○	○	◎				○	○	4.3	5%	7
Easy fabrication and transportation
Easy connection				◎			◎						◎		○	4.3	5%	7
Transportation with low-bed trailer									◎				○			4.7	6%	5
Transportation with cargo truck									◎				○			3	4%	15
Easy installation of plumbing equipment					◎			◎								4.4	6%	6
Short time for stocking
A short time for stocking after order	○	◎						○								6	8%	4
The stock is secured in advance			◎													4.3	5%	7
High quality of manufacturing
Small manufacturing deformation		○				◎								◎		7.4	9%	3
Less surface defects															○	4	5%	12
Easy application of high-strength steel	◎									◎					○	3.3	4%	14
Structural performance
Structural safety											◎	◎				4	5%	12
Small floor vibration									○		◎					4.2	5%	11
Absolute priority	126	194	116	62	92	90	46	110	95	138	182	72	101	80	48		100%
Priority ratios	8.1%	12.5%	7.5%	4.0%	5.9%	5.8%	3.0%	7.1%	6.1%	8.9%	11.7%	4.6%	6.5%	5.1%	3.1%
Ratings	4	1	5	13	9	10	15	6	8	3	2	12	7	11	14