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

# Load a structural mesh from a BDF file
comm = MPI.COMM_WORLD
rank = comm.Get_rank()
bdf_file = "path/to/your/mesh.bdf"
if rank == 0:
    print("Loading BDF file:", bdf_file)
loader = TACS.BDFLoader(comm)
loader.scanBDFFile(bdf_file)

# Set constitutive properties
rho = 2500.0  # 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
prop = constitutive.MaterialProperties(rho=rho, E=E, nu=nu, ys=ys)
stiffness = constitutive.IsoShellConstitutive(prop, t=t, tNum=0)

# Loop over components of the mesh, creating stiffness and element object for each
num_components = loader.getNumComponents()
for i in range(num_components):
    descriptor = loader.getElementDescript(i)
    if descriptor == "CQUAD4":
        shell_element = elements.Quad4Shell(stiffness)
        loader.setElement(i, shell_element)

# Create a TACS assembler object from the mesh loader
assembler = loader.createTACS(6)

# 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
Xpts = assembler.createNodeVec()
assembler.getNodes(Xpts)
forces = assembler.createVec()
forces.set(1.0)  # Example: Set a uniform load

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

# Evaluate the function and solve for the adjoint variables
fval = assembler.evalFunctions([ks_func])
adjoint = assembler.createVec()
assembler.evalSVSens([ks_func], [adjoint])

# Compute the total derivative with respect to material design variables and nodal locations
dfdx = assembler.createDesignVec()
assembler.evalDVSens(ks_func, dfdx)
dfdu = assembler.createNodeVec()
assembler.evalXptSens(ks_func, dfdu)

# Create a random direction along which to perturb the nodes and compute the total derivative with respect to nodal locations
perturb = assembler.createNodeVec()
perturb.setRand()
assembler.addXptVec(Xpts, perturb, 1e-6)

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

# Evaluate the function for the perturbed solution and compute the projected derivative
fval_perturbed = assembler.evalFunctions([ks_func])
projected_derivative = np.dot(dfdx.getArray(), perturb.getArray())

# Output the results for visualization
if rank == 0:
    print("Function value:", fval)
    print("Perturbed function value:", fval_perturbed)
    print("Projected derivative:", projected_derivative)
```