Domain: Engineering — Structural Engineering
Target concept: Effect of the Number of Supports on the Lateral Stiffness of the Structure

Video generation prompt: Three steel frame models of the same height (unbraced / single-bay braced / multi-bay braced) are placed side by side on the shake table, and the same horizontal force is applied to all three simultaneously.

Evaluation guide:
(i) Target concept: Lateral stiffness of steel frames scales with bracing redundancy; minimum mechanism: diagonal braces provide axial load paths that resist lateral displacement, and adding more bays increases global frame rigidity without altering member sizes or material.
(ii) Storyline: Frame 0–1s: Static shot showing three aligned steel frames on shake table, bracing configurations clearly visible. Frame 1–2s: Horizontal force initiates synchronously (e.g., actuator extends or push rod contacts all frames at once). Frame 2–8s: Continuous lateral sway develops. Unbraced frame leads in amplitude, multi-bay lags visibly; all sway remains parallel, planar, and reversible. Frame 8–10s: Force withdraws; sway decays uniformly with no residual offset. Perspective: Fixed frontal orthographic view, centered on table, full-frame inclusion of all three models and their bases; no occlusion; lighting from upper-front fixed source casting consistent shadows.

Manual:
Experimental Procedure
1. Place three identical-height steel frame models side-by-side on a single shake table.
2. Configure left model as unbraced (no diagonal braces), middle as single-bay braced (one diagonal brace in one vertical bay), right as multi-bay braced (diagonal braces in ≥2 vertical bays).
3. Apply identical horizontal force simultaneously to all three models.
Observation of Experimental Phenomena
Unbraced model sways laterally the most; single-bay braced model sways less; multi-bay braced model sways the least — all swaying in same direction, starting only after force application.
Summary of Experimental Principles
Lateral stiffness increases with number of braced bays due to enhanced load path continuity and reduced lateral deflection under horizontal loading.

Prompt Grounding rubric:
level_1: No steel frame models are visible; or no shake table is shown; or the three models are not lined up next to each other; or none of the three bracing types (no diagonal braces / one diagonal brace / diagonal braces in multiple bays) can be identified; or no horizontal force or actuator contacting the frames is shown.
level_2: At least one steel frame model appears, but fewer than three are present; or the three models are not lined up next to one another on a single shake table; or the bracing types cannot be told apart (e.g., all three frames show no diagonal members, or the diagonal braces don't match the labeled unbraced/single-bay/multi-bay scheme); or no simultaneous force application to all three frames is shown.
level_3: Three steel frame models of the same height stand side by side on one shake table; each has the gray, metallic look of steel; at least two of the three bracing types are visually distinct: for example, one frame with zero diagonal braces, one with a single diagonal brace confined to one bay, and one with diagonal braces spanning two or more bays; a horizontal force (e.g., a push rod or shake-table actuator) is shown acting on all three frames at the same time.
level_4: Everything at the 3-point level holds, plus: the unbraced model shows no diagonal braces at all, the single-bay model shows exactly one diagonal brace confined to one vertical bay, and the multi-bay model shows diagonal braces spanning two or more vertical bays; all three models share the same base width, number of columns, and story height; the onset of force application looks synchronized across all three models within the same starting frame.
level_5: Everything at the 4-point level holds, plus: no model is partly hidden behind another; the camera's perspective does not distort or hide any frame's bracing layout; none of the three models starts moving noticeably later than the others; lighting and shadow direction stay the same across all three models so the bracing geometry remains clearly visible; the background behind the shake table stays static and uncluttered.

Scientific and Causal Correctness rubric:
level_1: None of the three models visibly sways sideways when the force is applied; or all three models sway by the same amount in the same direction; or a model sways before the force reaches it; or the stiffness order is backwards (e.g., the unbraced frame sways the least while the multi-bay frame sways the most).
level_2: At least one model visibly sways, but in an implausible way: e.g., a column compresses vertically instead of the frame swaying sideways; or a frame starts swaying before the applied force reaches it; or the full stiffness ranking is reversed (multi-bay sways the most, unbraced the least).
level_3: All three frames sway horizontally in the direction the force is pushing; the unbraced frame shows the largest sway amplitude, the multi-bay braced frame shows the smallest, and the single-bay braced frame falls visibly in between; none of the three frames begins to sway before the force is applied.
level_4: Everything at the 3-point level holds, plus: the three sway amplitudes are clearly separated with no overlap, keeping the strict order unbraced > single-bay > multi-bay at every moment during loading; none of the frames twists or buckles (only side-to-side sway/rocking is seen); no frame keeps swaying with a leftover offset once the force stops; none of the frames unexpectedly lifts or sinks vertically while swaying.
level_5: Everything at the 4-point level holds, plus: each frame's sway grows and decays smoothly with no sudden jerks or skips; the unbraced > single-bay > multi-bay ordering of sway amplitude never reverses or crosses over at any point in the video; no frame shows a hinge-like kink forming at a beam-column joint; all three frames sway strictly in the same plane as the applied force, without any of them drifting diagonally or twisting out of that plane.

Spatiotemporal Consistency rubric:
level_1: A model or the shake table vanishes and reappears; a model's size or orientation suddenly changes; the scene's lighting jumps from one look to a completely different one with no transition; part of a frame (a column, beam, or brace) flickers or disappears mid-sway; the camera view pans, tilts, or zooms during the video.
level_2: A model disappears for two or more consecutive frames and then reappears; the shake table's surface texture or shadow looks inconsistent from frame to frame; a brace visibly detaches from its frame during the sway; a column or beam stretches or compresses unnaturally rather than staying rigid; shadows point in a direction inconsistent with a fixed light source.
level_3: All three models stay continuously visible on the shake table for the whole video; no model disappears, teleports, or changes shape; there is no abrupt lighting change such as a flash or sudden dimming; no brace detaches and no column or beam separates from the frame; the camera stays fixed with no panning, tilting, or zooming; the background stays static and evenly lit.
level_4: Everything at the 3-point level holds, plus: each model's sway starts and stops smoothly with no sudden jump between frames; no model overlaps or passes through another model or the edge of the shake table; brace and column alignment stays geometrically consistent given the camera's fixed viewpoint; motion blur never obscures which frame has more or less bracing or which one is swaying more; every frame's columns and beams stay rigid and straight during the sway, with no visible bending at the joints or flexing that real steel members would not show.
level_5: Everything at the 4-point level holds, plus: none of the three models shows small unrelated shaking or vibration beyond the applied sway; the repeating diagonal-brace patterns on each frame stay clean and stable, without flickering, shimmering, or breaking up as the frames move; no brace or beam appears to float without a visible connection point; the perspective stays consistent throughout so the three frames' bracing layouts remain directly comparable; every joint keeps its visible angular connection without wobbling or shearing apart.