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Design Loads

2 tools in the Civil and Geotechnical area.

Wind, Snow and Seismic Loads

Design-load generator in the ASCE 7 framework with every coefficient an entered input: wind velocity pressure q_z = 0.00256 K_z K_zt K_d K_e V² with K_z from the exposure constants and K_zt from the hill parameters, main wind-force pressures p = q G C_p − q_i (GC_pi) on the windward, leeward and side walls and the roof zones, story wind forces, components-and-cladding pressures q_h [(GC_p) − (GC_pi)], loads on a solid sign and on rooftop equipment; flat-roof snow p_f = 0.7 C_e C_t I_s p_g with the minimum load, the slope factor curves for warm and cold roofs, unbalanced snow on gables, leeward and windward drifts on a lower roof, sliding snow and the rain-on-snow surcharge; the equivalent lateral force procedure from S_s and S_1 with the site coefficients of the NEHRP tables, the design spectrum, the seismic design category, T_a = C_t h_n^x, C_s with its bounds, V = C_s W, the vertical distribution with story shears, overturning moments and allowable drifts, and the simplified procedure; and the strength and allowable-stress load combinations on entered load effects with the governing one. The default is an illustrative two-story 100 by 60 ft building (Exposure C, V = 115 mph, p_g = 30 psf, S_s = 1.0, S_1 = 0.4, Site Class D) for which the page gives q_h = 27.9 psf, p_f = 21 psf with a 63 psf drift surcharge, S_DS = 0.733 (SDC D) and V = 97.8 kips.

1 worked example reproduced, listed on the tool page.

Lifting and Rigging Loads

Lift-plan arithmetic from the public-domain rigging standards (DOE-STD-1090 Hoisting and Rigging, USACE EM 385-1-1, NAVFAC P-307, Army TM 3-34.86): the tension in every leg of a 1-, 2-, 3- or 4-leg bridle by statics from the lift-point layout, the hook height and the centre-of-gravity offset (four legs by the DOE two-leg-carry rule with the three-leg-carry and equal-share alternatives beside it), the sling angle and its load-angle factor 1/sin θ against the DOE Figure 11-7 table, vertical, choker and basket hitch factors with the choke-angle and D/d reductions, the required rated capacity and breaking strength of each leg with the design factor; the share of a load between two cranes or unequal legs by the centre of gravity with the hoist-line inclination; a spreader bar in compression with its Euler-Johnson column check or a lifting beam under its hanger loads with the shear and moment diagrams; a plate lifting lug checked in net tension, bearing, shear-out, Hertz pin pressure, base plate and base welds; shackle, hook and eyebolt rated loads reduced for side loading; the crane chart check with the percent of capacity and the 75 % critical-lift threshold; and the tilt and stability of a four-point lift from the hook height and the centre of gravity. Design factors are entered with the DOE values as defaults; ASME BTH-1 and B30 are cited, their tables not reproduced. The default case is an illustrative 20,000 lb load on a 4-leg bridle at about 60° with an offset centre of gravity.

1 worked example reproduced, listed on the tool page.

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