1. Thrust arch bridges utilize hangers in compression rather than tension
2. Thrust arch bridges transmit horizontal thrust forces to their foundations rather than containing them within the superstructure
3. Thrust arch bridges are always constructed with a higher rise-to-span ratio
4. Thrust arch bridges do not require expansion joints due to their flexible foundations

Explanation

Explanation: In a thrust arch bridge, the horizontal thrust forces generated by the arch action are transmitted directly to the foundations rather than being contained within the superstructure. Unlike tied arch bridges that use a tie girder to resist these horizontal forces internally, thrust arch bridges rely on substantial abutments or foundations capable of resisting the significant lateral forces. This fundamental difference dictates many aspects of thrust arch bridge design, including foundation size and cost, abutment design, and suitable site conditions. Thrust arch bridges are particularly appropriate for locations with solid rock foundations that can efficiently resist these lateral forces. The arch itself is typically in compression throughout its length, transferring both vertical and horizontal components of force to its supports, which must be designed to handle these combined forces without excessive movement.

1. 4,160 kN
2. 4,880 kN
3. 6,100 kN
4. 7,830 kN

Explanation

Solution:

1. Factored uniformly distributed load = (1.25 × 50) + (1.7 × 35) = 62.5 + 59.5 = 122 kN/m
2. For a parabolic arch with uniform load, the horizontal thrust H = wL²/(8f) Where: w = factored load, L = span, f = rise
3. H = 122 kN/m × (80m)²/(8 × 16m) = 122 × 6,400/(128) = 6,100 kN
4. Since there are two abutments and each resists the full horizontal thrust: Horizontal thrust force at each abutment = 6,100 kN

Explanation: In a thrust arch bridge, the horizontal thrust is transferred directly to the abutments rather than being contained within the structure as in a tied arch bridge. The horizontal thrust depends critically on the arch geometry (particularly the rise-to-span ratio) and the applied loads. For a uniformly loaded parabolic arch, the formula H = wL²/(8f) calculates the horizontal thrust, which must be resisted by the abutments through a combination of passive earth pressure, friction, and structural resistance. This calculation demonstrates why thrust arch bridges typically require massive abutments or solid rock foundations, as these horizontal forces can be substantial. A smaller rise-to-span ratio results in significantly larger horizontal thrust forces, which is why many thrust arch bridges historically featured higher rises. In addition to these static loads, designers must also consider the effects of thermal expansion, creep, shrinkage, and dynamic loading, as these can all modify the thrust forces over time.