inRange
inRange
RISA-3D
Lattice Tower, Built-Up C-Channels, Antenna Mounts, Anchor Connections
2025
Perched 23 ft above the busy streets of Queens, NYC Rooftop Lattice Tower Retrofit reimagines an 88.5 ft lattice tower that has supported two wireless carriers for decades. Rather than relying on traditional field measurements, the engineering team used a Pointivo digital twin to capture every splice, bolt line, and rust spot in millimeter detail. The scan revealed urgent structural concerns, including a corroded catwalk with minimal remaining strength and an access ladder already operating at 96.9% of its capacity—while still needing to accommodate new AT&T and T-Mobile equipment. The challenge was clear: integrate the 2022 NYC Building Code, ASCE 7-16, and TIA-222-H ice and wind provisions into a retrofit that maintained public safety, operational uptime, and cost efficiency. By bringing the digital twin into RISA-3D, engineers could evaluate every component—steel, anchors, and antennas—under 127 mph gusts, 1 in. ice glaze, and 20 psf snow. The result was a precise “remove-or-reinforce” strategy that extended the tower’s service life without a costly rebuild—proving how digital engineering workflows and RISA modeling can deliver safer, more efficient outcomes.
Originally designed decades ago, the rooftop lattice tower had seen numerous retrofits as wireless technology evolved. Its unique leg configuration—twin C-channels connected with laced diagonals—added complexity when assessing torsional and biaxial behavior. Alongside corrosion and fatigue, the structure now needed to meet modern design standards that account for ice, wind, and snow loads under TIA-222-H. Using photogrammetry as the foundation, the team built a detailed RISA model to replicate real-world boundary conditions—such as rooftop fixity, dynamic antenna loads, and connection flexibility. This hybrid approach ensured each retrofit decision was accurate, code-compliant, and backed by transparent analysis.
RISA-3D transformed the photogrammetry data into a fully functional analytical model where nodes represented actual joints and boundary conditions mirrored the rooftop environment. With RISASection, the team recreated the tower’s built-up leg sections, capturing their torsional and biaxial stiffness properties often missed in standard shapes. External spreadsheets were used for ASCE 7 and TIA-222-H load generation, with results imported into RISA-3D for comprehensive analysis. The software combined hundreds of LRFD load cases, tracked drift for antenna alignment, and clearly identified overstressed members through intuitive visual outputs. The findings were clear: the catwalk required demolition, select W-beam legs needed reinforcement, and anchor reactions were seamlessly exported to Hilti PROFIS for adhesive checks. With the digital twin and RISA model working together, engineers could instantly test “what-if” scenarios—ranging from new carrier loads to extreme ice storms—and deliver confident, code-compliant results.
Images 1, 2, 3, & 4: Walter Cevallos