```python
import numpy as np
import os
from mpi4py import MPI
from tacs import TACS, elements, constitutive, functions

# Load the structural mesh from a BDF file
bdf_file = "path/to/your/mesh.bdf"
comm = MPI.COMM_WORLD
struct_mesh = TACS.MeshLoader(comm)
struct_mesh.scanBDFFile(bdf_file)

# Set constitutive properties
rho = 2700.0  # density in kg/m^3
E = 70e9  # elastic modulus in Pa
nu = 0.3  # Poisson's ratio
kcorr = 5.0/6.0  # shear correction factor
ys = 350e6  # yield stress in Pa
t = 0.01  # thickness in m

# Loop over components of the mesh, creating stiffness and element object for each
num_components = struct_mesh.getNumComponents()
for i in range(num_components):
    descriptor = struct_mesh.getElementDescript(i)
    if descriptor == "CQUAD4":
        stiff = constitutive.isoFSDT(rho, E, nu, kcorr, ys, t, i)
        element = elements.Quad4Shell(stiff)
        struct_mesh.setElementObject(i, element)

# Create a TACS assembler object from the mesh loader
assembler = struct_mesh.createTACSAssembler()

# Create a KS function and get the design variable values
ks_weight = 50.0
ks_func = functions.KSFailure(assembler, ks_weight)
dv_vals = assembler.createDesignVec()
assembler.getDesignVars(dv_vals)

# Get the node locations and create the forces
num_nodes = assembler.getNumNodes()
node_locs = np.zeros((num_nodes, 3))
assembler.getNodes(node_locs)
forces = assembler.createVec()
forces.set(1.0)  # Example: Set all forces to 1.0

# Set up and solve the analysis problem
res = assembler.createVec()
ans = assembler.createVec()
assembler.zeroVariables()
assembler.assembleJacobian(1.0, 0.0, 0.0, res, ans)
assembler.factor()
assembler.solve(res, ans)

# Evaluate the function and solve for the adjoint variables
funcs = np.zeros(1)
assembler.evalFunctions([ks_func], funcs)
adjoint = assembler.createVec()
ks_func.addAdjointResProducts([adjoint], [1.0], 1.0)
assembler.applyBCs(adjoint)
assembler.solveTranspose(res, adjoint)

# Compute the total derivative
dfdx = np.zeros(dv_vals.size)
assembler.addDVSens([ks_func], [dfdx])
assembler.addAdjointResProducts([adjoint], [dfdx], 1.0)

# Create a random direction along which to perturb the nodes and compute the total derivative
perturb = np.random.rand(num_nodes, 3)
assembler.setNodes(node_locs + 1e-6 * perturb)

# Set the complex step and compute the perturbed solution
assembler.zeroVariables()
assembler.assembleJacobian(1.0, 0.0, 0.0, res, ans, TACS.COMPLEX_STEP)
assembler.factor()
assembler.solve(res, ans)

# Evaluate the function for the perturbed solution and compute the projected derivative
perturbed_funcs = np.zeros(1)
assembler.evalFunctions([ks_func], perturbed_funcs, TACS.COMPLEX_STEP)
projected_derivative = (perturbed_funcs - funcs) / 1e-6

# Output the results for visualization
viewer = TACS.ToFH5(assembler, TACS.SHELL_ELEMENT, write_flag=TACS.ToFH5.NODES)
viewer.writeToFile('output.f5')
```