Artificial Intelligence stands as a pivotal technology reshaping the engineering and construction industry, altering the very fabric of professional workflows. With the exponential growth of AI model capabilities, it is imperative for the AEC industry to not only adapt but also strategically align this technology for enhanced productivity and sustainability. This presentation outlines the latest work conducted by Thornton Tomasetti's CORE Studio R&D team, focusing on the development of bespoke AI-driven tools, particularly in structural steel design. The session will highlight how CORE.AI models are refactoring engineering processes, enabling reduced embodied carbon footprints in design and facilitating rapid prototyping and optioneering. In this presentation, we share insights into Thornton Tomasetti's journey in building responsible AI for the AEC industry, reflecting on our experiences and lessons learned."