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Side Mounted Bridge Rail

Background

Caltrans is constantly faced with Right-of-Way issues and other limitations that eliminate the option of mounting a standard bridge rail on top of a bridge deck. The Caltrans Division of Engineering Services and the Highway Safety Features New Products Committee (HSFNPC) recognized the need for a crashworthy side-mounted bridge rail usable in areas where the posted speed limit exceeds 70 km/hr (45 mph). Crash testing will be performed according to current crash test guidelines, Manual for Assessing Safety Hardware 2009 (MASH) Test Level 4 for longitudinal barriers.

Development of the Side Mounted Bridge Rail

The California ST-70SM Side Mounted Bridge Rail was constructed two stages. A typical cross-section of each stage is shown in Figure 1 and 2.

Cross Section of Stage 1

Figure1. Cross Section of Stage 1

Cross section of Stage 2

Figure 2. Cross Section of Stage 2

A 76 ft. test section of the bridge rail with 8 posts was constructed at the Caltrans Dynamic Test Facility. The barrier was constructed in two separate concrete pours with rebar for anchoring. The 6 inner posts were held in place with 5 anchor bolts per post. Two stacked disc springs were installed on each anchor bolt, on the outside of the barrier post. The discs were retained with a flat washer and nut torqued to provide 10,000 lbs. of preload. The discs allow the barrier to have some controlled deflection, reducing the peak load on the rail and providing some energy dampening during impact. The reduced peak load provides a lower maximum stress on the top anchor bolts and a slightly lower peak deceleration of the impacting vehicle.

Early Construction of Barrier
Construction		 Close-up of Barrier Posts
Post Close-up
Close-up of Barrier Spring
Spring Close-up		 Completed Barrier
Completed Barrier
Mash Test Number 4-11
MASH Test No. 4-11		 MASH Test Number 4-10
MASH Test No. 4-10
MASH Test Number 4-12
MASH Test No. 4-12

Impact Conditions

Test 110MASH3P15-01 (MASH Test 4-11)
Vehicle: 2005 Dodge RAM 1500 Quad Cab Pickup
Impact Speed: 98.9 km/h
Impact Angle: 25.0°

Test 110MASH4C15-02 (MASH Test 4-10)
Vehicle: 2008 Kia Rio
Impact Speed: 104.1 km/h
Impact Angle: 25.0°

Test 110MASH4S16-03 (MASH Test 4-12)
Vehicle: 2004 Freightliner M2
Impact Speed: 90.6 km/h
Impact Angle: 15.8°

High Speed Crash Test Video

Test 110MASH3P15-01 Test 110MASH4C15-02 Test 110MASH4S16-03
110MASH3P15-01 Across 110MASH4C15-02 Across 110MASH4S16-03 Across
110MASH3P15-01 Upstream 110MASH4C15-02 Upstream 110MASH4S16-03 Upstream
110MASH3P15-01 Downstream 110MASH4C15-02 Downstream 110MASH4S16-03 Downstream
110MASH3P15-01 OH Downstream 110MASH4C15-02 OH Downstream 110MASH4S16-03 OH Downstream
110MASH3P15-01 OH Upstream 110MASH4C15-02 OH Upstream 110MASH4S16-03 OH Upstream
110MASH3P15-01 Post 4 Connection 110MASH4C15-02 Post 4 Connection 110MASH4S16-03 Post 3 Connection

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