List of Symbol Definitions

Transcription

1 List o Symbol Deinitions a long dimension or a section subjected to torsion (in, mm); acceleration (t/sec 2, m/sec 2 ); acceleration due to gravity, t/sec 2, 9.81 m/sec 2 (also see g) unit area (in 2, t 2, mm 2, m 2 ); distance used in beam ormulas (t, m); depth o the eective compression block in a concrete beam (in, mm); equivalent square column size in spread ooting design (in, t, mm, m) a area bounded by the centerline o a thin walled section subjected to torsion (in 2, mm 2 ) A area, oten cross-sectional (in 2, t 2, mm 2, m 2 ) A b nominal cross section bolt area (in 2, t 2, mm 2, m 2 ) A e net eective area, equal to the total area ignoring any holes and modiied by the lag actor, U, (in 2, t 2, mm 2, m 2 ) (see A net ) A g gross area, equal to the total area ignoring any holes (in 2, t 2, mm 2, m 2 ) A gv gross area in shear, equal to the total area ignoring any holes (in 2, t 2, mm 2, m 2 ) A net net eective area, equal to the gross area subtracting any holes (in 2, t 2, mm 2, m 2 ) (see A e ) A nt net area in shear o a bolted connection subject to shear rupture (in 2, t 2, mm 2, m 2 ) A nv net area in tension o a bolted connection subject to shear rupture (in 2, t 2, mm 2, m 2 ); net shear area or a masonry member (in 2, t 2, mm 2, m 2 ) A p bearing area (in 2, t 2, mm 2, m 2 ) A throat area across the throat o a weld (in 2, t 2, mm 2, m 2 ) A s area o steel reinorcement in concrete beam design (in 2, t 2, mm 2, m 2 ) A s area o compression steel reinorcement in concrete beam design (in 2, t 2, mm 2, m 2 ) A v area o concrete shear stirrup reinorcement (in 2, t 2, mm 2, m 2 ); seismic coeicient or acceleration A web web area in a steel beam equal to the depth x web thickness (in 2, t 2, mm 2, m 2 ) A 1 area o column in spread ooting design ((in 2, t 2, mm 2, m 2 ) A 2 projected bearing area o column load in spread ooting design ((in 2, t 2, mm 2, m 2 ) ASD b b E b Allowable Stress Design width, oten cross-sectional (in, t, mm, m); narrow dimension or a section subjected to torsion (in, mm); number o truss members (also see n); rectangular column dimension in concrete ooting design (in, mm, m); distance used in beam ormulas (t, m) eective width o the lange o a concrete T beam cross section (in, mm) width o the lange o a steel or concrete T beam cross section (in, mm) b o perimeter length or two-way shear in concrete ooting design (in, t, mm, m) b w width o the stem o a concrete T beam cross section (in, mm) 1

2 B B s B 1 c c 1 c 2 spread ooting dimension in concrete design (t, m); dimension o a steel base plate (in, mm, m) width within the longer dimension o a rectangular spread ooting that reinorcement must be concentrated within or concrete design (t, m) actor or determining M u or combined bending and compression distance rom the neutral axis to the top or bottom edge o a beam (in, mm, m); rectangular column dimension in concrete ooting design (in, mm, m); the distance rom the top o a masonry or concrete beam to the neutral axis (in, mm, m) (see x) coeicient or shear stress or a rectangular bar in torsion coeicient or shear twist or a rectangular bar in torsion CL, q center line C C a C b C d C D C F C u C H C i C L C m C M C p C r C s C v C V C t compression label; compression orce (lb, kips, N, kn); dimension o a steel base plate or concrete ooting design (in, mm, m); seismic design coeicient dependent on the building period o vibration; constant or moment calculation o plates with respect to boundary conditions; coeicient or eccentrically loaded bolt groups constant or moment calculation o plates with respect to boundary conditions modiication actor or LRFD steel beam design; constant or moment calculation o plates with respect to boundary conditions pressure coeicient or wind orce calculation load duration actor or wood design size actor or wood design lat use actor or wood design shear stress actor or wood design incising actor or wood design beam stability actor or wood design modiication actor or combined stress in steel design wet service actor or wood design column stability actor or wood design repetitive member actor or wood design seismic design coeicient based on soil, response and acceleration web shear coeicient or steel design glulam volume actor or wood design temperature actor or wood design; seismic coeicient based on structural system and number o stories to determine building period 2

3 d diameter o a circle (in, mm, m); depth, oten cross-sectional (in, mm, m); perpendicular distance rom a orce to a point in a moment calculation (in, mm, m) ; eective depth rom the top o a reinorced concrete beam to the centroid o the steel (in, mm); eective depth rom the top o a reinorced masonry member to the centroid o the steel (in, mm); critical cross section dimension o a rectangular timber column cross section related to the proile (axis) or buckling (in, mm, m); symbol in calculus to represent a very small change (like the greek letters or d, see & ) d eective depth rom the top o a reinorced concrete beam to the centroid o the compression steel (in, mm) d b d d x d y D DL e E E c E s a depth o a steel wide lange section (in, mm); bar diameter o concrete reinorcement (in, mm) depth o a steel column lange (wide lange section) (in, mm) dierence in the x direction between an area centroid and the centroid o the composite shape (in, mm) dierence in the y direction between an area centroid and the centroid o the composite shape (in, mm) diameter o a circle (in, mm, m); dead load or LRFD design dead load dimensional change to determine strain (in, mm) (see s or ); eccentric distance o application o a orce (P) rom the centroid o a cross section (in, mm) modulus o elasticity (psi; ksi, kpa, MPa, GPa); earthquake load or LRFD design modulus o elasticity o concrete (psi; ksi, kpa, MPa, GPa) modulus o elasticity o steel (psi; ksi, kpa, MPa, GPa) symbol or stress (psi, ksi, kpa, MPa); symbol or unction with respect to some variable, ie. (t) calculated axial stress (psi, ksi, kpa, MPa) b c c cr m m n p r calculated bending stress (psi, ksi, kpa, MPa) calculated compressive stress (psi, ksi, kpa, MPa) concrete design compressive stress (psi, ksi, kpa, MPa) calculated column stress based on the critical column load P cr (psi, ksi, kpa, MPa) calculated compressive stress in masonry (psi, ksi, kpa, MPa) masonry design compressive stress (psi, ksi, kpa, MPa) natural requency o a suspended cable (sec -1, Hz) calculated bearing stress (psi, ksi, kpa, MPa) calculated radial stress or a glulam timber (psi, ksi, kpa, MPa) 3

4 s t calculated steel stress or reinorced masonry (psi, ksi, kpa, MPa) calculated tensile stress (psi, ksi, kpa, MPa) v x y F F a F b F b F c F cr F c F connector calculated shearing stress (psi, ksi, kpa, MPa) combined stress in the direction o the major axis o a column (psi, ksi, kpa, MPa) yield stress (psi, ksi, kpa, MPa) orce (lb, kip, N, kn); capacity o a nail in shear (lb, kip, N, kn); hydraulic luid load or LRFD design allowable axial stress (psi, ksi, kpa, MPa) allowable bending stress (psi, ksi, kpa, MPa) allowable bending stress or combined stress or wood design (psi, ksi, kpa, MPa) allowable compressive stress (psi, ksi, kpa, MPa) critical unactored compressive stress or LRFD steel design lexural buckling (column) stress in ASD and LRFD (psi, ksi, kpa, MPa) allowable compressive stress perpendicular to the wood grain (psi, ksi, kpa, MPa) resistance capacity o a connector (lb, kips, N, kn) F ce intermediate compressive stress or ASD wood column design dependant on material (psi, ksi, kpa, MPa) F cr F c critical column stress due to buckling (psi, ksi, kpa, MPa) allowable compressive stress or ASD wood column design (psi, ksi, kpa, MPa) * F c intermediate compressive stress or ASD wood column design dependant on load duration (psi, ksi, kpa, MPa) F e F EXX F horizontal-resist F n F nv F nt F p F r F sliding F t F v F vm F vs elastic critical buckling stress is steel design yield strength o weld material (psi, ksi, kpa, MPa) resultant rictional orce resisting sliding in a ooting or retaining wall (lb, kip, N, kn) nominal stress (psi, ksi, kpa, MPa) nominal shear stress (psi, ksi, kpa, MPa) nominal tensile stress (psi, ksi, kpa, MPa) allowable bearing stress parallel to the wood grain (psi, ksi, kpa, MPa) allowable radial stress or a curved glulam (psi, ksi, kpa, MPa) resultant orce causing sliding in a ooting or retaining wall (lb, kip, N, kn) allowable tensile stress (psi, ksi, kpa, MPa) allowable shear stress (psi, ksi, kpa, MPa); allowable shear stress in a welded connection (psi, ksi, kpa, MPa) allowable shear stress in the reinorced masonry (psi, ksi, kpa, MPa) allowable shear stress in the reinorcement or masonry (psi, ksi, kpa, MPa) 4

5 F x F y F yw F u F.S. orce component in the x coordinate direction (lb, kip, N, kn) orce component in the y coordinate direction (lb, kip, N, kn); yield stress (psi, ksi, kpa, MPa) yield stress in the web o a steel wide lange section (psi, ksi, kpa, MPa) ultimate stress a material can sustain prior to ailure (psi, ksi, kpa, MPa) actor o saety (also see SF) g acceleration due to gravity, t/sec 2, 9.81 m/sec 2 (also see a) gage spacing o staggered bolt holes (in, mm) G h shear modulus (psi; ksi, kpa, MPa, GPa); gigapascals (10 9 Pa or 1 kn/mm 2 ); relative stiness o columns to beams in a rigid connection (see ) depth, oten cross-sectional (in, t, mm, m); sag o a cable structure (t, m); height (in, t, mm, m); eective height o a wall or column, (see e ) h c height o the web in a wide lange section (in, t, mm, m) (also see t w ) h h n H H A depth o a lange in a T section (in, t, mm, m); height o a concrete spread ooting (in, t, mm, m) building height or determination o period or seismic design hydraulic soil load or LRFD design; height o retaining wall (t, m) horizontal load rom active soil or water pressure (lb, k, N, kn) I moment o inertia (in 4, mm 4, m 4 ); seismic importance actor based on building occupancy I moment o inertia about the centroid (in 4, mm 4, m 4 ) I T moment o inertia about the centroid o a composite shape (in 4, mm 4, m 4 ) (also see Î ) Î moment o inertia about the centroid o a composite shape (in 4, mm 4, m 4 ) (also see I c ) I c moment o inertia about the centroid o a composite shape (in 4, mm 4, m 4 ) I min minimum moment o inertia o I x and I y (in 4, mm 4, m 4 ) I net moment o inertia o plate area excluding bolt holes (in 3, mm 3, m 3 ) I o moment o inertia about the centroid (in 4, mm 4, m 4 ) I transormed moment o inertia o a multi-material section transormed to one material (in 4, mm 4, m 4 ) I x moment o inertia with respect to an x-axis (in 4, mm 4, m 4 ) I y moment o inertia with respect to a y-axis (in 4, mm 4, m 4 ) j number o connections in a truss (also see n); multiplier by eective depth o concrete or masonry section or moment arm, jd (see d) J, J o polar moment o inertia (in 4, mm 4, m 4 ) 5

6 k kg kips (1000 lb); shape actor or plastic design o steel beams, M p /M y; eective length actor or columns (also K); distance rom outer ace o lange to the web toe o illet o a wide lange section (in, mm); spring constant (lb/in, N/mm); multiplier by eective depth o masonry section or neutral axis, kd kilograms kn kilonewtons (10 3 N) kpa K K A K ce kilopascals (10 3 Pa) eective length actor with respect to column end conditions (also k); masonry mortar strength designation empirically derived coeicient based on soil properties material actor or wood column design length (in, t, mm, m); cable span (t, m) d development length o concrete reinorcement (in, t, mm, m) dc development length o compression reinorcement in concrete ooting design (in, t, mm, m) l dh development length or hooks (in, t, mm, m) e eective length that can buckle or wood column design (in, t, mm, m) n eective clear span or concrete one-way slab design (t, m) lb L pound orce length (in, t, mm, m); live load or LRFD design; spread ooting dimension in concrete design (t, m) L b unbraced length o a steel beam in LRFD design (t, m) L c clear distance between the edge o a bolt hole and the edge o the next hole or edge o the connected steel plate in the direction o the load (in, mm) L d development length o reinorcement in concrete (t, m) L e eective length that can buckle or column design (t, m) L m projected length or bending in concrete ooting design (t, m) L p L r maximum unbraced length o a steel beam in LRFD design or ull plastic lexural strength (in, t, mm, m) roo live load in LRFD design; maximum unbraced length o a steel beam in LRFD design or inelastic lateral-torsional buckling (in, t, mm, m) L length o the one-way shear area in concrete ooting design (t, m) LL live load LRFD Load and Resistance Factor Design 6

7 m mm M M a M A M B M C M m M n mass (lb-mass, g, kg); meters; moment per unit width (lb-t/t, kn-m/m); edge dimension in a steel base plate (in, mm) millimeters moment o a orce or couple (lb-t, kip-t, N-m, kn-m); bending moment (lb-t, kip-t, N-m, kn-m); masonry mortar strength designation required bending moment in steel ASD beam design (uniied) (lb-t, kip-t, N-m, kn-m) moment value at quarter point o unbraced beam length or LRFD beam design (lb-t, kip-t, N-m, kn-m) moment value at hal point o unbraced beam length or LRFD beam design (lb-t, kip-t, N-m, kn-m); nominal moment capacity o a reinorced concrete beam at the balanced steel ratio ( b ) or limiting strains in both concrete and steel (lb-t, kip-t, N-m, kn-m) moment value at three quarter point o unbraced beam length or LRFD beam design (lb-t, kip-t, N-m, kn-m) moment capacity o a reinorced masonry beam (lb-t, kip-t, N-m, kn-m) nominal moment capacity o a reinorced concrete beam based on steel yielding and concrete design strength (lb-t, kip-t, N-m, kn-m) M overturning resulting moment rom all orces on a ooting or retaining wall causing overturning (lb-t, kip-t, N-m, kn-m) M p M resist M u M ult M y M 1 M 2 internal bending moment when all ibers in a cross section reach the yield stress (lb-t, kip-t, N-m, kn-m) (also see M ult ) resulting moment rom all orces on a ooting or retaining wall resisting overturning (lb-t, kipt, N-m, kn-m) actored moment calculated in concrete design rom load actors (lb-t, kip-t, N-m, kn-m) internal bending moment when all ibers in a cross section reach the yield stress (lb-t, kip-t, N-m, kn-m) (also see M p ) internal bending moment when the extreme ibers in a cross section reach the yield stress (lb-t, kip-t, N-m, kn-m) smaller end moment used to calculate C m or combined stresses in a beam-column (lb-t, kip-t, N-m, kn-m) larger end moment used to calculate C m or combined stresses in a beam-column (lb-t, kip-t, N-m, kn-m) MPa megapascals (10 6 Pa or 1 N/mm 2 ) n n.a. number o truss joints or members, nails or bolts; modulus o elasticity transormation coeicient or steel to concrete; edge dimension in a steel base plate (in, mm) neutral axis (axis connecting beam cross-section centroids) n equivalent edge dimension in a steel base plate or design (in, mm) 7

8 N Newtons (kg-m/sec 2 ); bearing-type connection with bolt threads included in shear plane; normal load (lb, kip, N, kn); bearing length on a wide lange steel section (in, mm); dimension o a steel base plate (in, mm, m); masonry mortar strength designation N N o.c. O p meridional in-plane internal orce per unit length in a shell (lb/t, N/m, kn/m) hoop in-plane internal orce per unit length in a shell (lb/t, N/m, kn/m) on-center point o origin; masonry mortar strength designation pitch o nail spacing (in, mm) (also see s); pressure (lb/in 2, lb/t 2, kip/in 2, kip/t 2, Pa, MPa): unit weight o soil or determining active lateral pressure (lb/t 3, kn/m 3 ) p A active soil pressure (lb/t 3, kn/m 3 ) p r P P a P c P cr P e1 P n P o P r P u internal pressure (lb/in 2, lb/t 2, kip/in 2, kip/t 2, Pa, MPa) orce, concentrated (point) load (lb, kip, N, kn) required axial orce in ASD steel design (uniied) (lb, kip, N, kn) available axial strength or steel uniied design (lb, kip, N, kn) critical (ailure) load in column calculations (lb, kip, N, kn) Euler buckling strength in steel uniied design (lb, kip, N, kn) maximum column load capacity in LRFD steel and concrete design (lb, kip, N, kn); nominal axial load or a tensile member or connection in LRFD steel (lb, kip, N, kn) maximum axial orce with no concurrent bending moment in a reinorced concrete column (lb, kip, N, kn) required axial orce in steel uniied design (lb, kip, N, kn) actored column load calculated rom load actors in LRFD steel and concrete design (lb, kip, N, kn); actored axial load or a tensile member or connection in LRFD steel (lb, kip, N, kn) Pa Pascals (N/m 2 ) q shear low (lb/in, kips/t, N/m, kn/m) ); soil bearing pressure (lb/t 2, kips/t 2, N/m 2, Pa, MPa) q allowed allowable soil bearing pressure (lb/t 2, kips/t 2, N/m 2, Pa, MPa) q h q net q u static wind velocity pressure or wind orce calculation (lb/t 2, kips/t 2, N/m, Pa, MPa) net allowed soil bearing pressure (lb/t 2, kips/t 2, N/m, Pa, MPa) actored soil bearing pressure in concrete design rom load actors (lb/t 2, kips/t 2, N/m, Pa, MPa) Q irst moment area used in shearing stress calculations (in 3, mm 3, m 3 ) Q connected irst moment area used in shear calculations or built-up beams (in 3, mm 3, m 3 ) Q x irst moment area about an x axis (using y distances) (in 3, mm 3, m 3 ) 8

9 Q y irst moment area about an y axis (using x distances) (in 3, mm 3, m 3 ) r radius o a circle or arc (in, mm, m); radius o gyration (in, mm, m) r o polar radius o gyration (in, mm, m) r x radius o gyration with respect to an x-axis (in, mm, m) r y radius o gyration with respect to a y-axis (in, mm, m) R orce, reaction or resultant (lb, kip, N, kn); radius o curvature o a beam or radius o a shell (t, m); rainwater or ice load or LRFD design; seismic response modiication based on structural type; calculated reduction in live load limited to 60% (in percent); generic load quantity (orce, shear, moment, etc.) or LRFD design R a required strength (ASD-uniied) (also see V a, M a ) R n concrete beam design ratio = M u /bd 2 (lb/in 2, MPa) nominal value or LRFD design to be multiplied by (also see P n, M n ) nominal value or ASD design to be divided by the saety actor R u design value or LRFD design based on load actors (also see P u, M u ) R w R x R y s s.w. seismic response modiication based on structural type reaction or resultant component in the x coordinate direction (lb, kip, N, kn) reaction or resultant component in the y coordinate direction (lb, kip, N, kn) strain (=change in length divided by length) ( no units); displacement with respect to time (t, m); length o a segment o a thin walled section (in, mm); pitch o nail spacing (in, mm) (also see p); longitudinal center-to-center spacing o any two consecutive holes (in, mm); spacing o stirrups in reinorced concrete beams (in, mm) sel-weight S section modulus (in 3, mm 3, m 3 ); snow load or LRFD design; allowable strength o a weld or a given size (lb/in, kips/in, N/mm, kn/m) seismic soil proile; masonry mortar strength designation S net section modulus o plate area excluding bolt holes (in 3, mm 3, m 3 ) S required section modulus required to not exceed allowable bending stress (in 3, mm 3, m 3 ) S x section modulus with respect to the x-centroidal axis (in 3, mm 3, m 3 ) S y section modulus with respect to the y-centroidal axis (in 3, mm 3, m 3 ) SC SF S4S t slip critical bolted connection saety actor (see F.S.) surace-our-sided thickness (in, mm, m); time (sec, hrs) 9

10 t thickness o the lange o a steel beam cross section (in, mm, m) t w thickness o the web o a steel beam cross section (in, mm, m) T tension label; tensile orce (lb, kip, N, kn); torque (lb-t, kip-t, N-m, kn-m); throat size o a weld (in, mm); eect o thermal load or LRFD design; seismic building period (sec); depth in web o wide lange section rom illet to illet (in, mm) U shear lag actor or steel tension member design (see A e and A net ) U bs v V V a V c V n V s V u V u1 V u2 w reduction coeicient or block shear rupture velocity (t/sec, m/sec, mi/h); shear orce per unit length (lb/t, k/t, N/m, kn/m) (see q) shearing orce (lb, kip, N, kn); seismic base shear orce (lb, kip, N, kn) required shear in steel ASD design (uniied) (lb, kip, N, kn) shear orce capacity in concrete (lb, kip, N, kn) nominal shear orce capacity or concrete design (lb, kip, N, kn) shear orce capacity in steel (lb, kip, N, kn) actored shear calculated in concrete design rom load actors (lb, kip, N, kn) actored one-way shear calculated in concrete ooting design rom load actors (lb, kip, N, kn) actored two-way shear calculated in concrete ooting design rom load actors (lb, kip, N, kn) load per unit length on a beam (lb/t, kip/t, N/m, kn/m); load per unit area on a surace (lb/t 2, kip/t 2, N/m 2, kn/m 2 ) (see w ); width dimension (in, t, mm, m) w c weight o reinorced concrete per unit volume (lb/t 3, N/m 3 ) w u actored load per unit length on a beam rom load actors (lb/t, kip/t, N/m, kn/m); actored load per unit area on a surace rom load actors (lb/t 2, kip/t 2, N/m 2, kn/m 2 ) w load per unit area on a surace (lb/t 2, kip/t 2, N/m 2, kn/m 2 ) (see w); W x x xˆ X weight (lb, kip, N, kn); total load rom a uniorm distribution (lb, kip, N, kn); wind load or LRFD design; seismic building weight (lb, kip, N, kn); wide lange shape designation (i.e. W 21 x 68) a distance in the x direction (in, t, mm, m); the distance rom the top o a masonry or concrete beam to the neutral axis (in, mm, m) (see c) the distance in the x direction rom a reerence axis to the centroid o a shape (in, mm) the distance in the x direction rom a reerence axis to the centroid o a composite shape (in, mm) bearing-type connection with bolt threads excluded rom shear plane; design constant or steel base plate design based on concrete bearing capacity 10

11 y y y T ŷ a distance in the y direction (in, t, mm, m); distance rom the neutral axis to the y-level o a beam cross section (in, mm) the distance in the y direction rom a reerence axis to the centroid o a shape (in, mm) the distance in the y direction rom a reerence axis to the centroid o a composite shape (in, mm) (also see ŷ ) the distance in the y direction rom a reerence axis to the centroid o a composite shape (in, mm) (also see y T ) z the distance rom a unit area to a reerence axis (in, t, mm, m) (also see d x and d y ) Z plastic section modulus o a steel beam (in 3, mm 3 ); seismic geographic actor based on zone ' symbol or eet " symbol or inches # symbol or pounds = symbol or equal to symbol or approximately equal to symbol or proportional to symbol or less than or equal to c 1 symbol or integration coeicient o thermal expansion (/C, /F); angle, in a math equation (degrees, radians) angle, in a math equation (degrees, radians) ratio o long side to short side o the column in concrete ooting design coeicient or determining stress block height, a, based on concrete strength, c elongation (in, mm) (see e) P elongation due to axial load (in, mm) s T shear deormation (in, mm) elongation due to change in temperature (in, mm) beam delection (in, mm); story drit (in, mm); an increment LL beam delection due to live load (in, mm) max maximum calculated beam delection (in, mm) TL beam delection due to total load (in, mm) T change in temperature (C, F) strain (no units) 11

12 t y thermal strain (no units): strain in the steel = strain at the yield stress diameter symbol; angle o twist (degrees, radians); resistance actor in LRFD steel design and reinorced concrete design; angle deining the shell cuto (degrees, radians) limit o timber slenderness or intermediate length columns (no units) design constant or steel base plate design Poisson s ratio (also see); coeicient o static riction Poisson s ratio (also see ) speciic gravity o a material (lb/in 3, lb/t 3, N/m 3,kN/m 3 ); angle, in a math equation (degrees, radians); shearing strain (no units); load actor in LRFD design D dead load actor in LRFD steel design L b g live load actor in LRFD steel design angle, in a trig equation, ex. sin (degrees, radians); slope o the delection o a beam at a point (degrees, radians) pi (180) radial distance (in, mm); radius o curvature in beam delection relationships (t, m); reinorcement ratio in concrete beam design = A s /bd (or possibly A s /bt, A s /bh) (no units) balanced reinorcement ratio in concrete beam design reinorcement ratio in concrete column design = A st /A g maximum reinorcement ratio allowed in concrete beam design or ductile behavior max c engineering symbol or normal stress (axial or bending) engineering symbol or shearing stress shearing stress capacity in concrete design (psi; ksi, kpa, MPa); load per unit length on a beam (lb/t, kip/t, N/m, kn/m) (see w); load per unit area (lb/t 2, kips/t 2, N/m 2, Pa, MPa) load per unit volume (lb/t, kip/t, N/m, kn/m) (see ) summation symbol saety actor or ASD o steel (uniied) relative stiness o columns to beams in a rigid connection (see G) 12